More specifically, the invention relates above all to moisture-proof locking systems for floors of the type having a core and a decorative surface layer on the upper side of the core.

Field of Application of the Invention The present invention is particularly suited for use for floating floors, which are made of floor panels which on the one hand are joined mechanically with a joint sys- tem which is integrated with the floor panel, i. e. fac- tory mounted, and, on the other hand, are made up of one or more preferably moisture-proof upper layers of a deco- rative laminate or decorative plastic material, an inter- mediate core of fiberboard-based material or plastic material and preferably a lower balancing layer on the rear side of the core. The following description of the state of the art, problems associated with known systems and the objects and features of the invention will there- fore, as a non-restricting example, focus first of all on this field of application and, in particular, on laminate flooring made of rectangular floor panels, intended to be mechanically joined on both long sides and short sides.

However, it should be noted that the invention can be used in optional floor panels with optional joint systems where the floor panels have a core and are given their final shape by cutting. The invention can thus also be applicable to homogeneous wooden flooring and wooden flooring having two or more layers of wood or fiberboard- based material and a decorative surface layer of wood.

Thus, the invention may be applied to floor panels comprising any woodfiber-based material, such as solid wood, plywood, particle board, fiberboard, MDF, HDF etc.

The invention mainly discusses problem areas which are related to moisture penetrating into the joint system from the front side of the floor panel. The systems and methods that are indicated to solve these moisture prob- lems are also applicable to the case of preventing mois- ture from penetrating into the joint system from the rear side of a floor panel.

Background of the Invention Laminate flooring is usually composed of a core of a 6-9 mm thick fiberboard, a 0.2-0. 8 mm thick upper deco- rative surface layer of laminate and a 0.1-0. 6 mm thick lower balancing layer of laminate, plastic, paper and like material. The surface layer provides appearance and durability to the floor panels. The core provides stabi- lity, and the balancing layer keeps the panel plane when the relative humidity (RH) varies during the year. The RH can vary between 15% in winter and 90% in summer. The floor panels are usually laid floating, i. e. without glu- ing, on an existing subfloor which need not be entirely smooth or plane. Any irregularities are eliminated by means of underlay material in the form of, for instance, board or foam which is arranged between the floor panels and the subfloor. Traditional hard floor panels in float- ing flooring of this type are as a rule joined with the aid of glued tongue-and-groove joints (i. e. joints with a tongue on one floor panel and a tongue groove in an adjoining floor panel) on long side and short side. When laying, the panels are joined horizontally, a projecting tongue along the joint edge of one panel being inserted into a tongue groove along a joint edge of an adjoining panel. The same method is applied to long side as well as short side.

In addition to such traditional floors, which are joined by means of glued tongue-and-groove joints, floor panels have recently been developed which do not require the use of glue and instead are joined mechanically by means of so-called mechanical joint systems. These sys- tems contain locking means which lock the panels horizon- tally and vertically. The mechanical joint systems can be made by machining the core of a panel. Alternatively, parts of the locking system can be made of a separate material which is integrated with the floor panel, i. e. joined with the floor panel even in connection with the production thereof.

The main advantages of floating floors with mechani- cal joint systems are that they can be easily and rapid- ly laid by different combinations of inward angling and snapping-in. They can also easily be taken up again and be reused in another place. A further advantage of the mechanical joint systems is that the edge portions of the floor panels can be made of materials which need not have good gluing properties. The most common core material is wood in parquet flooring and in laminate flooring fiber- board of high density and good stability usually refer- red to as HDF-high density fiberboard. Sometimes MDF- medium density fiberboard-is used as core.

Laminate flooring and also many other floorings with a surface layer of plastic, wood, veneer, cork and the like are produced by a surface layer and a balancing layer being applied to a core material. This application can take place by gluing of a previously manufactured decorative layer, for instance when the fiberboard is provided with a decorative high pressure laminate which has been made in a separate operation where a plurality of impregnated sheets of paper are compressed under high pressure and at a high temperature. The currently most common method in producing laminate flooring, however, is direct laminating which is based on a more modern principle where both production of the decorative lami- nate layer and the attachment to the fiberboard take place in one and the same step of production. Impregnated sheets of paper are applied directly to the board and are compressed under pressure and heat without gluing.

In addition to these two methods, a number of other methods for providing the core with a surface layer are used. A decorative pattern can be printed on the surface of the core, which is then, for instance, coated with a wear layer. The core can also be provided with a surface layer of wood, veneer, decorative paper or plastic film, and these materials can then be coated with a wear layer.

As a rule, the above methods result in a floorboard element in the form of a large panel which is then sawn into, for instance, some ten floorboards, which are then machined to floor panels. In some cases, the above methods may result in completed floorboards and then saw- ing is not necessary before machining to completed floor panels is carried out. Production of individual floor- boards usually takes place when the boards have a surface layer of wood or veneer.

In all cases, the above floorboards are individually machined along their edges to floor panels. Edge machin- ing is carried out in advanced milling machines where the floorboard is exactly positioned between one or more chains and bands mounted so that it can be moved at high speed and with great accuracy past a number of milling motors which are provided with diamond cutting tools or metal cutting tools which process the edge of the floor- board. By using a plurality of milling motors which ope- rate at different angles, advanced joint geometries can be formed at speeds exceeding 100 m/min and with an accu- racy of 0. 02 mm.

Definition of Some Terms In the following text, the visible surface of the completed, mounted floor panel is called"front side", while the opposite side of the floor panel facing the subfloor is called"rear side".

The sheet-shaped starting material that is used is called a"core". By"fiberboard core"is meant a core material containing wood fibers such as homogeneous wood, MDF, HDF, particle board, flake board, plywood and the like. When the core has been coated with a surface layer closest to the front side and preferably also a balancing layer closest to the rear side, it forms a semi-manu- facture, which is related to as a"floorboard"or a "floor element".

A"floorboard"is generally of essentially the same size as the floor panel which is to be produced from the floorboard. Thus, the floorboard is generally formed into a floor panel.

The"floor element", on the other hand, is typically so large that at least two floor panels may be produced from it. Thus, the floor element is usually divided into several floor boards, which are subsequently formed into floor panels.

Hence, when the edges of the floorboards have been machined so as to give the floorboards their final shape, including the joint system, they are related to as"floor panels". By"surface layer"are meant all layers that are applied to the core closest to the front side and that cover preferably the entire front side of the floorboard.

"Decorative layer"relates to layers that are essentially intended to give the floor its decorative appearance.

"Wear layer"relates to layers that are above all intended to improve the durability of the front side.

The outer parts of the floor panel at the edge of the floor panel between the front side and the rear side are related to as"joint edge". As a rule the joint edge has several"joint surfaces"that can be vertical, hori- zontal, angled, rounded, beveled, etc. These joint sur- faces are to be found on different materials included in the floor panel and the joint system, e. g. laminate, fiberboard, wood, plywood, plastic, metal (especially aluminum) or sealing material. "Joint edge portion" relates to joint edge and part of the floor panel por- tions closest to the joint edge.

By"joint"or"joint system"are meant cooperating connecting means which join the floor panels vertically and/or horizontally.

Laminate flooring and also wooden flooring are often laid in kitchens, hallways and public rooms where they are continually exposed to water, for instance in the form of people walking on the floor with wet shoes and when cleaning the floor with water and the like. In recent years, laminate flooring is being used in bath- rooms as well. Laminate and wooden flooring are being sold all over the world and installed in humid climates where the relative humidity may exceed 90%.

When water penetrates into a material or when eva- porated or condensed water is to be found on or in mate- rials, it is generally related to as"moisture".

By"moisture-proof material"are generally meant materials which to a limited extent absorb moisture or materials that are not damaged by moisture.

Moisture in Floors When a laminate floor with a fiberboard-based core is exposed to moisture to a limited extent in the rooms mentioned above, the moisture can penetrate, via the joint between neighboring floor panels, into the upper parts of the joint system closest to the front side and thus penetrate into the core and its wood fibers. If the amount of moisture supplied is small, the water usually evaporates after some time, but, as a result, a permanent swelling of the joint edge portion, rising of the edge of the upper joint edge portion and cracks in the surface layer may arise in particular if the quality of the core is not high and if the laminate is thin. Rising of the edge also causes great wear on the surface layer round the joint edges. In a wooden floor, the joint edges may also swell at a high relative humidity and cause damage to the joint edges.

If the supply of moisture is extensive or if it takes place regularly for a long time, moisture may also penetrate through the entire joint system and into the subfloor and cause considerable damage such as in the form of mold. This may take place even if the floor panel is made of a moisture-proof core since this moisture- proof core as a rule merely counteracts swelling of the joint edge portions or prevents moisture from spreading into the core. The moisture-proof core cannot prevent moisture from spreading through the joint system and into the subfloor. This moisture migration through the joint system is reinforced if the geometry of the mechanical joint contains many joint surfaces on a floor panel, which do not have contact with corresponding joint sur- faces on the neighboring floor panel. Such a geometric design facilitates, for instance, manufacture and facili- tates displacements of a floor panel in its locked posi- tion along the joint edge of a neighboring floor panel, but such a geometric form is not advantageous in coun- teracting the possibility of moisture penetrating through the joint system.

A common misconception is that mechanical joint sys- tems are more sensitive to moisture than traditional joint systems with glue since glue is considered to pre- vent moisture from penetrating into the joint system.

Glued floors with environment-friendly water-based glue systems, however, cannot prevent moisture from penetrat- ing into the joint system. One reason is that as a rule glue is to be found only in parts of the joint system.

Another reason is that moisture that comes into contact with the glue layer dissolves the glue joint. The mois- ture penetrates through the joint system and the panels come loose in the joint.

Laminate floors and wooden floors could take a con- siderably greater market share, especially from plastic floors and tiled floors, if they could resist in a better way the effect of high relative humidity and of water on the surface.

Prior-Art Technique and Problems thereof When a laminate floor is exposed to water on its surface, a moisture-proof surface layer will counteract that moisture penetrates through the surface and into the core. The limited amount of moisture penetrating through the surface layer and into the core will as a rule not cause any damage. In the joints, moisture will pene- trate between the upper joint edges of neighboring floor panels, and as the moisture passes the moisture- proof surface layer and reaches the significantly more moisture-sensitive core, the moisture will spread into the core and at the same time continue towards the rear side of the floor panel. If the core contains wood fibers, these will swell. As a result, the thickness of the floor panel within the joint edge portion increases and the surface layer rises. This vertical swelling in turn causes damage to the floor. If additional moisture is supplied, the moisture will spread downwards to the rear side until it has passed the joint system and reaches the underlay board and the subfloor. This may cause even greater damage.

Various methods have been used to counteract these problems. Attempts have been made to prevent moisture from penetrating into the floor panel from the joint edge by coating the joint surfaces with a moisture-sealing material, for instance wax or silicone. This type of solution is described in, inter alia, W09426999 (Valinge Aluminium AB) and EP0903451 (Unilin Beheer B. V. ). One has tried to counteract moisture migration from the front side to the rear side of the floor panels along the joint by inserting elastic sealing means between neighboring floor panels. Such solutions are disclosed in, inter alia, W09747834 (Unilin Beheer B. V.).

Thus use has been made of several methods in order to improve in various ways the possibilities of the joint systems withstanding the effect of water and moisture.

The most common method is to make the core of the floor panel of a HDF panel of high quality as regards e. g. density and protection against moisture. The core's protection against moisture can also be improved by add- ing specific binders, in many cases in combination with use of special wood fibers when making the core. This method can significantly reduce, but not entirely elimi- nate, swelling as moisture penetrates. The main disadvan- tage of this method is the cost. The entire floor panel will have the same high quality although these specific properties are only utilized in a limited part of the floor panel in connection with the joint edge. Another disadvantage is that this method does not afford protec- tion against moisture migration through the joint system from the front side to the rear side of the floor.

It is also known that it is possible to counteract penetration of moisture into the core of the floor panels by spraying on, or otherwise applying to, the joint edges special chemicals which impregnate or reinforce the wood fibers in the joint system. This application of chemicals takes place after the joint by machining has been given is final shape and geometric form. As a rule, the impreg- nation takes place immediately in connection with the machining of the edges of the floor panels since it is desirable to use the condition that in this step of pro- duction the panel is held in the correct position by drive chains or belts in the machining equipment.

The impregnating materials can be applied in the joint system using different methods which can involve application by spraying, rolling, spreading and the like.

The most common impregnating materials are melted wax and liquids of different kinds such as oils, polyurethane- based impregnating agents and a number of other chemi- cals which all contribute to counteracting penetration of moisture from the joint edge into the core so as to reduce the risk of swelling as moisture penetrates between the upper joint edges.

All methods of application are complicated, expen- sive and give an unsatisfactory result. It is particular- ly difficult to provide moisture-proof corners. If appli- cation by spraying on a moving floor panel, for instance, starts too late, part of the edge closest to the corner will have no impregnation. If spraying is terminated too late, impregnating liquid will reach the open air, and this will cause undesirable smearing of equipment and also spreading of undesirable solvents or impregnating materials in the air and the room where production takes place. It is also difficult to impregnate the core at the joint edge immediately under the surface layer without simultaneously causing smearing of the surface of the floor panel closest to the joint edge. It is also diffi- cult to obtain deep and even impregnation in the areas immediately under the surface layer which are most expos- ed to moisture and swelling. Everything is made worse by the fact that machining and thus subsequent impregnation take place at very high speeds and with the surface layer of the floor panels facing downwards. Further disadvan- tages are that the impregnation, especially if it is water-based and environment-friendly, may cause fibers to swell or a layer of solidified impregnating agent to settle in the joint system in such manner that the geo- metry of the joint is changed in an uncontrolled manner.

Besides the above methods do not result in a reliable seal against moisture migration from the front side of the floor panels along the joint surfaces down to the rear side of the floor panels. Nor can they solve the problem of swelling of upper joint edge portions in wooden floors.

It is also known that is possible to use core mate- rials of plastic which do not swell and do not absorb moisture. This gives a perfect seal against moisture migration horizontally away from the joint between two joined floor panels. Plastic is disadvantageous since panels of plastic material are considerably more expen- sive than fiberboard and since it is difficult to glue or directly laminate a decorative surface layer on a panel of plastic material. Moreover machining of plastic is much more difficult than machining of fiberboard-based material for making said connecting means of the floor panels along all four edges. An example of a floor panel having a plastic core is provided in EP1045083A1. An example of a floor panel having connecting means made of plastic materials is provided in US6101778.

The above-mentioned publication W09426999 (Valinge Aluminium AB) discloses a system for counteracting mois- ture penetration into the floor panels from the joint edges and for counteracting moisture migration from the front side of the floor panels to their rear side. This publication suggests the use of silicone or some other sealing compound, a rubber strip or some other sealing device which is applied in the joint system before installation. The system according to W09426999 (Valinge Aluminium AB), i. e. sealing against moisture using a sealing compound or a sealing device, which is applied in the joint in connection with manufacturing, also has drawbacks. The drawbacks are essentially the same as in edge impregnation by spraying or spreading. It is also difficult to handle panels with a smeary sealing com- pound. The properties of the sealing compound can also change in course of time. If the sealing compound is applied in connection with laying, laying will be diffi- cult and expensive.

One way of providing impregnation of floor panels is disclosed in DE20002744U1.

One possibility of establishing a seal against pene- tration of moisture is to insert, in connection with lay- ing, a sealing device in the form of e. g. a sealing strip of rubber into the joint. Also this method is difficult and expensive. When the sealing means is applied in the joint in connection with manufacture, it is not known how the sealing means is to be designed for optimal func- tions, how the application should take place in a rational manner and how the corners should be designed so that the seal can function along the joint edge of the entire floor panel both on the long sides and on the short sides. The above-mentioned publication W09747834 (Unilin Beheer B. V. ) shows in Fig. 10 how sealing means have been applied in a visible manner between the upper joint edges, so that a narrow gap is to be seen between the neighboring floor panels.

The use of inserted elastic sealing means in joints is known also in connection with the joining of story- high wall elements. This is shown in for instance GB2117813 (Ostrovsky) disclosing a joint system, which, however, is not suitable for floor panels that are to be laid without great visible joint gaps.

Furthermore, it is known to apply a sealing paste or a water resistant glue in a joint between the floor panels as is shown in EP 0665347A1. However, such a procedure would require the seal to be applied at the time the panels are installed. Furthermore it would be associated with most of the drawbacks inherent in floor panels which are connected by means of glue.

It is also known (according to WO 9966152, Valinge Aluminium AB) that it is possible to provide the edge of the core on the long side or the short side with separate materials which are attached to the core and which are then machined to achieve specific functions in the lock- ing system, such as strength, protection against moisture or flexibility. However, it is not known how these mate- rials are to be applied and formed in order to solve the moisture problems described above in an optimal manner.

A specific problem, which is related to moisture penetration in floor panels from the joint edges, arises in connection with wooden floor panels which have several wooden layers with different directions of fibers since wood swells to a greater extent transversely of the direction of fibers than along the direction of fibers.

This means that in a wooden floor, which has a surface layer with its direction of fibers in the longitudinal direction of the floor panel and a core having a diffe- rent direction of fibers, for instance transversely of the floor panel, and which is installed in an environment which is moist or has a high relative humidity, the sur- face layer will swell to a greater extent in the trans- verse direction of the floor panel than does the core. As a result, the upper joint edge portions and especially the parts closest to the joint surface will swell and expand parallel with the surface of the floor panel and move the floor panels apart whereas the joint system made in the core largely retains its form. This may cause damage, for instance, by the decorative layer (surface layer) being compressed, the joint system breaking or the locking function of the locking system being wholly or partly lost.

It may therefore be established that moisture prob- lems in connection with joined floor panels are associat- ed essentially with > vertical and horizontal swelling of the joint edge por- tions D moisture penetration through the joint system.

Summing up, it can be said that as regards the pro- viding of a seal against moisture migration in the floor panels from the joint edges, there are a plurality of known methods, none of which provides a result which is satisfactory as regards quality as well as cost. As regards sealing against moisture migration along the joint from the front side to the rear side of the floor panels, there are no known solutions which allow an inte- grated design where the panel even in connection with manufacture is provided with a seal that counteracts such moisture migration.

Brief Description of the Invention and Objects thereof The invention is based on the understanding that several types of seals may be involved, which are necessary above all in a moisture-proof locking system for floor panels which can be joined together, viz. material seal"which counteracts swelling of joint edges, >"material seal"and"joint seal"which counteract swelling and moisture penetration through the joint system, "compensation seal"which compensates for swelling and shrinkage of joint edges.

By"material seal"is meant a seal which prevents or counteracts spreading of moisture from the joint edge of a floor panel into the floor panel. By"joint seal"is meant a seal which prevents or counteracts migration of moisture through the joint along the joint surfaces. By "compensation seal"is meant a seal which adjusts to material movements caused by moisture in a floor panel (swelling and shrinkage) owing to changes of the moisture content, for instance by changes in relative humidity in the ambient air, and which counteracts stress under compression and the arising of a visible gap between the upper joint edges of neighboring floor panels owing to such material movements caused by moisture.

As is evident from that stated above, the known solutions to problems caused by the moisture in connec- tion with floor panels and floor materials are not quite satisfactory. Some of the solutions are insufficient as regards the intended effect, others have deficiencies which cause difficulties in connection with manufacture or laying, whereas others are unsatisfactory from the viewpoint of cost.

Therefore an object of the present invention is to eliminate or significantly reduce one or more of the remaining problems associated with moisture sealing in connection with manufacture and use of floor panels. A further object of the invention is to provide a rational and cost-efficient manufacturing method for manufacturing floor panel cores, floorboard elements, floorboards and floor panels.

These and other objects are achieved by floor panels, floors and manufacturing methods having the features that are stated in the independent claims. The dependent claims and the following description define embodiments of the invention.

The invention is especially suited for use in floor panels with mechanical locking systems and in floor panels which are made from board elements which are divided into a plurality of boards before machining.

However the invention can also be used for floors with a joint system that is glued and for floor panels that are produced directly as separate floorboards for machining to floor panels and which are thus not manufactured by dividing large board elements before subsequent machining of the individual floorboards.

Thus, according to a first aspect of the invention, there is provided a floor panel, comprising a body having a wood fiber-based core, in which floor panel at least two opposite parallel joint edge portions are provided with connecting means for mechanical joining of the floor panel in the horizontal direction with similar floor panels, the connecting means having active locking surfaces for cooperation with corresponding active locking surfaces of adjacent floor panels after the floor panel has been joined therewith. The floor panel is distinguished in that at least one of the active locking surfaces wholly or partly is made of an elastically deformable material, other than that of the body of the floor panel.

According to a second aspect of the invention, there is provided a system for forming a joint between two adjoining edges of floor panels, the floor panels having a core and a surface layer applied to an upper side of the core, the surface layer consisting of at least one layer, said floor panels, at their adjoining joint edge portions, being provided with connecting means for joining the floor panels with each other in the vertical direction, and whose upper adjoining joint edges meet in a vertical joint plane. The system is distinguished in at least one of the opposite joint edge portions of the floor panels, when the floor panels are joined together, is provided with a joint seal for counteracting penetration of moisture along the vertical joint plane between adjacent floor panels, and that this joint seal is made of an elastic sealing material which is secured in at least one of the floor panels, formed in connection with the forming of the joint edges (82,83) of the floor panels, and adapted to be compressed when neighboring floor panels are joined together.

According to a third aspect of the invention, there is provided a floor panel comprising a core and a surface layer applied to an upper side of the core, the surface layer consisting of at least one layer, the floor panel at opposite joint edge portions having connecting means for joining the floor panel with similar floor panels in the vertical direction, so that joined floor panels have upper joint edges which meet in a vertical joint plane.

The floor panel is distinguished in that at least one of the opposite joint edge portions of the floor panels is provided with a joint seal for counteracting penetration of moisture along the vertical joint plane between adjacent floor panels, and that this joint seal is made of an elastic sealing material, which is secured in the floor panel, formed in connection with the forming of the joint edges (82,83) of the floor panels and which is adapted to be elastically deformed when the floor panel is joined with a similar floor panel.

Thus, according to the first, second and third aspects of the invention, the core can be provided with inserted and fixedly secured elastically deformable materials, which may act as a sealing means and/or as compensation means for swelling or shrinking of the floor panels. The elastically deformable materials are applied in portions that will later will be machined for making the connecting means of the completed floor panel. The elastically deformable material will thus be machined simultaneously as or in connection with the machining of the remaining parts of the joint system. As a result, the elastically deformable material can be made into accurately positioned and accurately dimensioned seals for forming the above-mentioned joint seals or compensation means.

According to a fourth aspect of the invention, there is provided a method of making a core for production of a floor board or a floor element that is to be divided into at least two floor boards, the method comprising making the core from a sheet shaped material, from which a part of a locking system for vertical locking of the floor boards is to be formed. The method is distinguished by making a groove in the sheet-shaped material, and inserting an elastic sealing material in the groove.

According to a fifth aspect of the invention, there is provided a method for use in manufacturing a floor panel, the method comprising the steps described above in connection with the fourth aspect of the invention. The method is distinguished in that the elastic sealing material is formed into a joint seal in connection with the forming of the locking system.

By suitable methods, such as sawing or milling, the core can, before application of the surface layer (for instance a decorative surface layer), be pretreated so that, for instance, one or more grooves are formed in the surface in the areas where edge machining of the joint system will later take place. Subsequently, a suitable sealing material is applied in the groove, suitably by impregnation or extrusion or any other suitable method.

The sealing material may form a material seal and/or may have the property of changing into a solid, moisture- proof and elastically deformable material which could be formed to a joint seal. The surface layer can then be applied to the surface of the core over the groove with the sealing material. According to this aspect of the invention, the sealing material can also be applied in a similar way after the application of the surface layer.

The groove is then made in the floor element or the floorboard in the surface layer and in the core, or merely in the core of the floorboard. When the floor element is sawn up in floorboards, the edges will contain the sealing material. If the sealing material is applied in a groove or a machined edge part of the floorboard it is preferred that a reference surface is machined in connection with the application of the sealing material.

This reference surface could be an outer portion of the edge of the floorboard. The final machining of the locking system and the joint sealing could then be made in a second production step, where the reference surface could be used to position the floorboard in relation to the machining tools. With this method it is possible to position sealing material with a tolerance of about 0,01 mm in relation to the joint surfaces, and the surface of the floor panel. It is possible to position and form a joint sealing in the core and in the lower part of a 0,1 - 0, 5 mm thick surface layer. The joint sealing will protect the wood fiber core and prevent moisture from penetrating trough the locking system. This method makes it possible to apply and form a seal in all types of laminate floors that could be produced with the sealing material. It is obvious that the method could be used for thicker surfaces of, for instance, 1-3 mm plastic and linoleum surfaces. Such a sealing will not be visible from the surface and it will protect the wood fiber core under the moisture proof surface layer. If the sealing material is flexible, it may also prevent moisture from penetrating trough the locking system.

To form a joint sealing it is possible, in principle, to use any known sealing material, which can be applied in liquid form or in semi-liquid form by extrusion, such as foam or the like, and which after application are formable, elastically deformable and moisture-proof. It is an advantage if the sealing materials have properties which allow adhesion to the core. Such adhesiveness, however, is not necessary since the sealing material can also be attached mechanically in, for instance, undercut grooves.

The subsequent machining in the production of the floor panels is carried out in such manner that the seal- ing material is only partly removed or reshaped. For instance, the sealing material can be formed by cutting into an elastically deformable joint seal which will be exactly positioned along the entire long side and the entire short side and in the corners and also exactly positioned in relation to the surface layer.

The joint seal and especially its active part, which provides the moisture seal, can be formed with an optional outer geometry by cutting which can be made with very narrow tolerances in connection with the rest of the joint system being formed.

If the joint system between the decorative layer and the joint seal also has a material seal, the result will be a floor with floor panels which all have moisture- proof joints on the long sides and the short sides and in the corners. If the floor is also provided with moisture- proof baseboards made of e. g. plastic material which in connection with the floor have a suitable sealing mate- rial or sealing strip, the floor will be quite moisture- proof in all joints and along the walls.

The material seal between the surface layer and the joint seal can, in addition to the above-described impregnation, be provided in many different ways, for instance: The core can be made of a moisture-proof material.

In a direct-laminated floor, the upper part of the core can immediately under the decorative layer be impreg- nated, e. g. according to what is described below.

Impregnating material can also be applied in the grooves of the core where also the joint seal is applied.

In a floor of high pressure laminate, the laminate's reinforcement layer of phenol-impregnated kraft paper under the decorative layer can constitute a material seal.

Another alternative is that a moisture-proof plastic layer is applied between the core and the decorative surface layer in the entire panel.

In the same way as the joint seal is applied, also materials with other properties, for instance non-com- pressible materials, can be applied in order to protect the joint edge and form a material seal.

The material seal can consist of one or more mate- rials which cover the entire core surface and which are also resilient and sound-reducing. The advantage is that it is possible to obtain, at the same cost, a moisture seal, sound reduction and a softer floor. Parts of the joint seal may also constitute a material seal. Finally, the entire joint seal, or parts thereof, can also constitute a material seal. This means that the joint seal may also serve as a material seal with or without impregnation of the core.

As is evident from that stated above, this aspect of the invention is suitable for core materials which are wood fiber-based, e. g. fiberboard-based, but also for moisture-proof core materials, such as plastic and various combinations of plastic and fiberboard-based materials.

As non-limiting examples of materials that can be used to provide a joint seal, mention can be made of acrylic plastic-based materials, elastomers of synthetic rubber, urethane rubber, silicone rubber or the like, or polyurethane-based hot-melt adhesive.

In one embodiment, the floor panels may have a mechanical joint system which for a long time and during swelling and shrinkage of the floor panels holds together the joint edge with the sealing material in close contact with another sealing means or with the other joint edge. The method and the system may also function in a traditionally glued tongue-and-groove joint, but it is considerably more expensive and more difficult to provide a tight joint than with a mechanical joint system.

In connection with laying, it is possible to add glue, sealing material and the like to the above- described joint system for the purpose of, for instance, additionally reinforcing the strength or moisture resistance of the joint in parts of the floor or in the entire floor.

Within the scope of the invention, long sides and short sides can be formed in various ways. The reason may be that the connecting method during laying can be different at long sides and short sides. For instance, the long side can be locked by inward angling and the short side by snapping-in, and this may necessitate dif- ferent material properties, joint geometries and seal geometries, where one side is optimized for inward angl- ing and the other for snapping-in. Another reason is that each square meter of floor contains considerably more long side joint than short side joint if the panels are elongate. An optimization of the material cost can give different joint designs.

Impregnation and edge reinforcement of the core in certain areas before application of surface layer and balancing layer can also be used on the rear side in order to, for instance, reinforce that part where the lower parts of the joint system are formed. This can be used, for instance, to make a strong and flexible strip or lower lip and a strong looking element when the strip or the lower lip is formed integrally with the core. If, for instance, the strip is made of a material other than that of the core, for instance aluminum, impregnation from the rear side can be used to reinforce critical parts, where the strip is secured or where the panel cooperates with the locking element.

The above described manufacturing methods can also be used to produce a mechanical joint system, which contains elastic locking means. These elastic locking means can be pressed together as adjoining upper joint edges swell and can expand as they shrink. In this way, the horizontal swelling problems and the arising of visible gaps in a dry floor can be counteracted. Since this swelling problem is mainly related to the long side, the corners are not involved in this respect. The elastically deformable material can therefore also be mechanically applied in solid form in the groove for instance by snapping-in or pressing-in into undercut grooves of by gluing to the edge of the groove. Thus these elastic locking means will serve as an"elastic compensation seal".

The above-described manufacturing method of provid- ing a partial material seal in predetermined areas in a core can also be used in connection with manufacture of the sheet-shaped core. Impregnating material is then applied either in the compound of wood fiber and binder which is formed to a core or in connection with the core getting its final shape in the manufacturing process.

According to a sixth aspect of the invention, there is provided a rectangular floor panel comprising long sides, short sides, a core and a surface layer which is arranged on a surface of the core, said surface layer comprising a wear layer and a decorative layer (35), the floor panel, adjacent to opposite joint edge portions, being provided with a locking system for joining the floor panel with similar floor panels in the vertical direction and in the horizontal direction along the long sides and short sides, said locking system being at least partly formed from the core. The floor panel is distinguished in that it further comprises a portion constituting a material seal for counteracting penetration of moisture from the joint edge of the floor panel into the core, said material seal being located between - the surface layer, and - an elastically deformable joint seal which is is fixedly secured in the floor panel and which, when the floor panel is joined with a similar floor panel, counteracts penetration of moisture along the joint surfaces of the joint edges between the adjacent floor panels.

According to a seventh aspect of the invention, there is provided a floor element for use in forming at least two floor boards, the floor element comprising a wood fiber-based core and a surface layer that is attached to a surface of the core. The floorboard is distinguished in that a groove is provided in the surface of the core and/or in the surface layer, said groove being arranged in a portion of the board where a mechanical locking system is to be formed, and said groove being provided with an elastically deformable material and/or an impregnation agent. The elastically deformable material may be formed into the joint seal described above at least partly in connection with the forming of the connecting means.

According to an eight aspect of the invention, there is provided a floorboard for use in forming a floor panel, the floorboard comprising a wood fiber-based core and a surface layer that is attached to a surface of the core. The floorboard is distinguished in that a groove is provided in an upper edge portion of the floorboard, where a mechanical locking system is to be formed, said groove being provided with an elastically deformable material and/or an impregnation agent.

According to a ninth aspect of the invention, there is provided a ethod for forming a joint between two adjoining edges of floor panels, the floor panels having a core, a surface layer applied to an upper side of the core, the surface layer including at least one layer, and a locking system at adjoining joint edge portions for joining the floor panels with each other in at least a vertical direction and whose upper adjoining joint edges meet in a vertical joint plane. The method is distinguished by securing an elastic sealing material in at least one of the floor panels, forming a joint seal simultaneously with forming the joint edge of the floor panel, the joint seal formed in at least at one of the adjoining joint edge portions of the floor panels and adapted to be compressed when adjoining floor panels are joined together. According to the method, the joint seal is adapted to counteract penetration of moisture along the vertical joint plane between adjoining floor panels.

Brief Description of the Drawings Figs la-d illustrate different steps in the production of a floor panel.

Figs 2a-e show the composition of a laminate floor with a surface of high-pressure laminate and direct laminate.

Figs 3a-c illustrate examples of different mechanical joint systems and moisture migration.

Figs 4a-d illustrate impregnation of an edge according to prior-art technique.

Figs 5a-c show impregnation to form a material seal according to the invention.

Figs 6a-c show impregnation of upper joint edges according to the present invention.

Figs 7a-d illustrate an embodiment of a material seal according to the invention.

Figs 8a-e illustrate the making of a joint seal in a mechanical joint system according to the invention.

Figs 9a-d illustrate the making of a mechanical joint system with material seal and joint seal as well as edge reinforcement of parts of the joint system according to the invention.

Figs 10a-c illustrate compression of a joint seal according to the invention.

Figs lla-g illustrate alternative embodiments of mate- rial and joint seals according to the inven- tion.

Figs 12a-b illustrate alternative embodiments of mate- rial and joint seals according to the inven- tion.

Figs 13a-c illustrate floor panels with a joint seal on two sides according to the invention.

Figs 14a-e illustrate mechanical locking systems, Fig. 14a illustrating prior-art technique and Figs 14b-e illustrating mechanical locking systems with a compensation seal in the form of an elastic locking means according to the invention.

Figs 15a-e illustrate an embodiment of the invention.

Figs 16a-f illustrate a joint system which is formed according to the invention and has high strength.

Figs 17a-d illustrate sealing of corner portions of neighboring floor panels.

Description of Embodiments of the Invention Figs la-d illustrate in four steps the manufacture of a floor panel. Fig. la shows the three main components surface layer 31, core 30 and balancing layer 32. Fig. lb shows a floor element 3, where the surface layer and the balancing layer have been applied to the core. Fig. lc shows how floorboards 2 are made by dividing the floor element. Fig. Id shows how the floorboard 2 after edge machining obtains its final shape and becomes a completed floor panel 1 with a joint system 7, 7'on the long sides 4a, 4b, which joint system in this case is mechanical.

Fig. 2a shows manufacture of high pressure laminate.

A wear layer 34 of a transparent material having a high wearing strength is impregnated with melamine with addi- tion of aluminum oxide. A decorative layer 35 of paper impregnated with melamine is placed under this layer 34.

One or more layers of reinforcement layers 36a, 36b made of paper core and impregnated with phenol are placed under the decorative layer 35, and the entire packet is placed in a press in which it is caused to cure under pressure and heat to a surface layer 31 of high pressure laminate having a thickness of about 0.5-0. 8 mm.

Fig. 2c shows how the surface layer 31 and a balanc- ing layer 32 are then glued to a core 30 so as to form a board element 3.

Figs 2d and 2e illustrate direct lamination. A wear layer 34 in the form of an overlay and a decorative layer 35 of decoration paper are placed directly on a core 30, after which all three parts and, as a rule, also a rear balancing layer 32 are placed in a press where they are caused to cure under heat and pressure to a board element 3 with a decorative surface layer 31 having a thickness of about 0.2 mm.

Figs 3a-c illustrate prior-art mechanical joint sys- tems and how moisture, according to studies made by the inventors, affects the joint systems.

In Fig. 3a, the floor panel 1 consists of a direct- laminated surface layer 31, a core 30 of fiberboard-based material (HDF) and a balancing layer 32. The vertical locking means which locks the panels 1 and 1'in the D1 direction, consists of a tongue groove 9 and a tongue 10.

The horizontal locking means which locks the panels parallel with the surface layer 31 in the D2 direction consists of a strip 6 having a locking element 8 which cooperates with a locking groove 12. The strip is made by machining of the core 30 of the floor panel and is there- fore in this embodiment of the invention formed integral- ly with the core 30. Dashed arrows MPM indicate how mois- ture can penetrate from the joint edge into the core 30 as moisture penetrates into the joint system from the front side or upper side of the floor.

Fig. 3b illustrates an embodiment where both the vertical and the horizontal locking means are formed as a tongue groove 9 with a locking groove 12 and a tongue 10 with a locking element 8. The dashed arrow MPJ illu- strates how moisture can penetrate through the parts of the locking system.

In Fig. 3c, the floor panel is provided with a sur- face layer 31 of high pressure laminate, a core 30 of HDF and a balancing layer 32 of high pressure laminate. Also in this embodiment, the vertical locking means consists of a tongue groove 9 and a tongue 10 which are made from the core 30 of the floor panel. The horizontal locking means consists of a strip 6 and the locking element 8, which are made of aluminum and mechanically attached to the core 30.

In all the above cases, the joint systems are inte- grated with the core, i. e. formed or mounted at the fac- tory, and at least part of the joint system is always made by cutting of the core 30 of the floor panel. The locking systems can be joined by angling, horizontal snapping or snapping in an upwardly angled position.

Figs 4a-4c illustrate impregnation of joint edges 82,83 according to prior-art technique, the machined joint being impregnated by an impregnating material 24 being applied sideways by spraying.

To facilitate the understanding, the floor panels are in all figures illustrated with their surface layer directed upwards. In the actual production, the floor panels are however, as a rule, oriented with their front side (upper side) directed downwards in the processing machinery and in the subsequent impregnation.

In the prior-art type of impregnation, the floor panel is moved passed a stationary spray nozzle 40. It is difficult to direct the jet of impregnating material 24 so that the edge of the jet is placed immediately under the surface layer 31 in connection with the upper adjoining joint edges 16 with a view to making a material seal 20.

Even if the application can take place using pro- tective plates 43 which protect the surface, it is diffi- cult to provide an efficient protection. The strip 6 and the locking element 8 are in many cases an obstacle, and it is difficult to apply the impregnating material 24 with sufficient accuracy and to obtain sufficiently deep penetration into the area immediately under the surface layer 31 at the upper adjoining joint edges 16. Thus the impregnating depth varies and is smaller immediately under the surface layer and furthest away from the sur- face layer, as is evident from Figs 4a-4d.

Figs 5a-5c illustrate impregnation to make a mate- rial seal according to the invention. The impregnating material 24 is applied in a suitable fashion in band- shaped areas 44 on the core surface 33, before the remaining layers, i. e. the decorative and the wear layer are applied. The application can take place, for instance, by being sprayed, rolled on etc. conveniently first in the longitudinal direction L in zones where the long sides of the floorboard are later to be formed.

Suitably one long side 4 of the core 30 is used as a guide surface which is then also used as guide surface to facilitate the positioning in connection with applica- tion of the surface layer 31, sawing up and machining. In this way, it will be easier to ensure that the material seal 20 is correctly positioned in relation to the com- pleted joint edge.

Fig. 5b illustrates the corresponding impregnation of the parts that will later constitute the short sides 5 of the floorboards. In this impregnation, the core is moved in the transverse direction W perpendicular to the longitudinal direction L. Also in this case, one short side 5 of the core 30 can be used as guide surface in the subsequent manufacture.

Fig. 5c shows an enlargement of a portion that will constitute corners of the floor panel and that will be fully impregnated parallel with the long side to be as well as the short side to be. The parting lines 45 indicate the saw cuts along the long side and the short side for dividing the board element into floorboards.

Figs 6a-6c illustrate in greater detail how the impregnation is carried out and penetrates into the core and how the impregnating area is positioned relative to the connecting means to be, which are indicated by dashed lines in Figs 6a and 6b. Fig. 6c shows the edges of two floor panels which are made of the board element after this has been cut into individual floorboards by sawing along the line 45.

Fig. 6a shows how the impregnating material 24, when being applied by means of a spray nozzle 40, will pene- trate into the core 30 from the core surface 33 and towards the central portion of the core in order to form a material seal 20.

The penetration of the impregnating material 24 into the core 30 can be facilitated by establishing a vacuum on the underside of the core by means of a vacuum device 46. The vacuum device 46 may consist of, for instance, a stationary vacuum table or moving vacuum bands. If the core 30 is stationary during the application of the impregnating material 24, for instance moving spray nozzles 40 are used.

Fig. 6b shows how the impregnating material 24 is positioned in the core 30 of the board element 3 after application of the surface layer 31. The impregnating material then constitutes a material seal 20. The part- ing line 45 indicates the intended saw cut.

Fig. 6c shows the joint edges 82,83 of the floor panels 1, 1'after machining. In order to simplify the illustration, the floor panel has a mechanical joint along one side only. The material seal 20 will be exactly positioned along the two perpendicular sides and in the corner, and in the shown embodiment it is to be found in the upper joint edge portions 80,81.

A fiberboard-based core 30, e. g. HDF, is produced by ground wood fibers being mixed with a binder, such as melamine, after which a panel is formed by means of pres- sure and heat. Alternatively, the impregnating material 24 can be applied to the panel in connection with this production, the application taking place within special portions which will later constitute joint portions in the floor panel.

Figs 7a-7d illustrate in detail the different pro- duction steps to produce a material seal 20 in a mecha- nical joint system.

According to Fig. 7a, impregnating material 24 is applied from the core surface 33 in the portions 86,87 (dashed) which in the completed floor panel will consti- tute joint edge portions which are generally designated 86 and 87 and in which the joint system 9,10 is formed.

A considerable part of the upper joint edge portions 80, 81 is impregnated so as to form a material seal 20.

Fig. 7b shows the floor element 3 with a surface layer 31, a balancing layer 32 and a material seal 20 in the core 30 under the surface layer 31. The Figure also shows the intended saw cut 45 and the contours of the final connecting means by dashed lines.

Fig. 7c shows the edges of the floorboard 2,2' after sawing up. The sawing tolerance does not affect the final position of the material seal 20 closest to the joint edge. In the subsequent machining, no additional equipment is required to provide a material seal 20 in the upper joint edge portions 80,81 of a locking system since this material seal has been provided even before the application of the different surface layers to the core 30.

Fig. 7d illustrates the machined joint with a mate- rial seal 20 immediately under the surface layer 31. HP designates a horizontal plane parallel with the surface layer of the panel. The joint edges of the floor panel 1, 1'are generally designated 82,83 and can have an optional joint system. In the shown embodiment, the joint edges are formed as a mechanical tongue-and-groove joint which can be locked by inward angling and snapping-in. VP designates a vertical plane (joint plane) which extends perpendicular to the horizontal plane HP at the upper joint edges 80,81 closest to the surface layer. T indicates the thickness of the floor panel. The largest amount of impregnating material 20 is to be found in the upper joint edge portions 80,81 immediately under the wear layer 31, i. e. within the area which is most critical in the viewpoint of moisture. This concentration of impregnating material immediately under the wear layer 31 is obtained as a result of the impregnating material being caused to penetrate into the core from the core surface during impregnation.

The upper joint edge portions 80,81 are thus char- acterized in that the material seal 20 is not only to be found in the core surface 31 closest to the surface layer 31 between the vertical plane or joint plane VP and a lower plane at a distance P2 from the core surface 33, but also all the way in the horizontal direction from the vertical plane VP to a plane at a distance P1 from the vertical plane VP. This entire volume of the core 30 under the core surface 33 is thus impregnated so as to form the material seal 20. Such a location and extent of a material seal cannot be provided by means of the known impregnating methods in which impregnating material 24 is applied to or sprayed onto the upper joint edges 84,85 at the vertical plane VP when these upper joint edges are already provided with a surface layer 31 and machined to their final shape.

Since the impregnating material 24 penetrates from the core surface 33, the concentration of the impregnat- ing material will be particularly high closest to the core surface 33. In the normal case, the concentration of impregnating material decreases downwards from the core surface 33, as shown schematically in Figs 4a-4d.

The material seal 20 should, above all because of the expense, be limited to a part of the floor panel 1 where the intended connecting means are formed, and should therefore preferably not cover the entire core surface 33.

This method makes it possible to provide under the surface layer 31 a material seal 20 in a considerable portion of the parts of the joint system. Regarding the extent of the material seal in the transverse direction, i. e. transversely of the joint plane VP and along the horizontal plane HP, it can be mentioned that P1 may exceed 0.2 times the floor thickness T and, without dif- ficulty, may amount to 1 time the floor thickness T or more. In many embodiments, the distance P1 can be so great that all parts of the joint edge portion which contain parts of the connecting means of the floor panel are impregnated with the material seal 20.

The impregnating depth, i. e. the distance P2, can conveniently be 0.1-0. 3 times the floor thickness T. How- ever, it is many times preferred for the impregnating depth to be such that at least upper parts of the con- necting means will consist of impregnated core material.

According to the invention, the joint system is characterized in that the material seal 20 is located in the core surface 33 at the vertical plane VP and at a distance P1 from VP and that the sealing properties within this area are essentially equivalent or homoge- neous, i. e. the core surface 33 has been coated with essentially the same amount of impregnating material 24 per unit of volume of core material 30. This is a signi- ficant difference compared with prior art when applica- tion takes place from the vertical plane VP, in which case the concentration of impregnating material, as illu- strated in Figs 4a-4d, decreases from the joint edge at the vertical plane VP and inwards to the panel parallel with the surface layer 31 at the distance PI and where the impregnating depth in the horizontal plane will be smaller closest to the core surface 33 and greater at a distance therefrom.

Figs 8a-8e illustrate a different embodiment of the invention. In this case, a groove 41 is formed in the core surface 33, for instance in the area where the upper and inner part of the tongue 10 will later be formed. In the groove 41 a sealing material 50 is then applied, which has the property that after application it will have a solid form, be moisture-proof, be elastically deformable and may be shaped by cutting.

As shown in Fig. 8b, the core 30 with the groove 41 and the sealing material 50 is then coated with a surface layer 31 and preferably also with a balancing layer 32 to form a floor element. Then the floor element 3 is sawed up in floorboards by cutting along the line 45 and is machined to floor panels 1, 1'with joint systems. These floor panels are shown in Figs 8c-8e, and the joining of the floor panels according to this specific embodiment will be described in more detail below.

As described above, the groove 41 could also be formed in a floor element or floor board which comprises a surface layer 31,32 that is bonded to the core 30.

This means that the groove 41 may be formed both in the surface layer 31,32 and in the core 30. This groove 41 could be impregnated and/or provided with a sealing material 50. This method offers the advantages that a standard floor element could be used and impregnation materials could be applied, which may be difficult to use in connection with gluing or lamination of the surface layer 31,32 to the core 30.

The sealing material 50 is formed to a joint seal 55, preferably by cutting by means of tools which are especially adapted to form elastically deformable syn- thetic materials.

As mentioned above, a large number of sealing mate- rials that can be used are available on the market. As a non-limiting example, materials having the following pro- perties can be used.

A sealing compound based on acrylic plastics, elas- tomers of synthetic rubber, silicone rubber or the like, which have the properties that they can be applied in the groove 41 as a compound by extrusion, that they can adhere to the core material (optionally after applying a primer layer thereto), that they have good heat resis- tance, that they are moisture-proof, that they can resist detergents, and that after application they can be cured or dried and change into a solid, elastically deformable form. The properties of the materials should be optimized in such manner that they are both sufficiently elastical- ly deformable and preferably at the same time can be machined rationally by means of cutting tools.

Different types of polyurethane-based hot-melt adhe- sives that are applied by being heated and extruded can also be used to form the joint seal. When such materials solidify, they change into a solid, elastically deform- able form. These materials can later be formed by cutting but also by using heated rolls or drag tools of a suit- able form, which are moved along and in contact with the sealing material 50 to shape this to a suitable geometry.

Combinations of cutting rough machining and final forming by means of hot scraping or rolling tools are also possible as is also a two-step application, where the first application is carried out with a highly liquid material that penetrates into the core, and where the subsequent second application takes place with a mate- rial which is more viscous and has good adherence to the former material. It is also possible to use different types of primer system to improve the adhesion of the joint sealing material to the floor panel.

Different materials, methods of application and methods of forming can be used on opposite joint edges and respectively on the long side and the short side for the purpose of optimizing function and cost.

Fig. 8c shows the machined joint edge with a mecha- nical locking system 9,10, 6,8, 12 and an elastically deformable joint seal 55. As is evident from this Figure, the joint seal 55 is compressed in connection with the laying of the floor panel. In this embodiment, which shows inward angling, the compression and the deformation begin only when the locking element 8 is already in ini- tial engagement with the locking groove 12 and when the tongue 10 is already in engagement with the tongue groove 9. Both the vertical and horizontal locking functions in the mechanical locking system are thus active as the compression proceeds. As a result, the compression in connection with laying can take place by applying an extremely small amount of force, and the need for com- pression therefore does not render laying difficult.

Fig. 8d shows how two floor panels 1, 1'are joined by snapping-in, where compression of the joint seal 55 can take place in the same manner as described above by interaction between a tongue groove 9 and a tongue 10 and where lateral displacement along the joint plane has been facilitated and where a flexible strip 6, a locking ele- ment 8 and a locking groove 12 cooperate in the compres- sion of the joint seal and therefore will compress the joint seal in connection with snapping-in.

It is advantageous if the joint seal 55 is formed so that the compression can start when the guide part 11 of the locking element 8 engages the guide part 13 of the locking groove 12. This engagement will be facilitated if the guide part 11 of the locking element is formed as a rounded or beveled part in the upper portions of the locking element. The guiding as well as the compression will also be facilitated if the locking groove 12 is formed with a correspondingly rounded guide part 13 in the lower part of the locking groove 12 closest to the joint edge.

In connection with laying, the joint seal 55 is pressed against an opposite cooperating joint surface 56 in the joint system. In the embodiment illustrated in Figs 8a-8e, this joint surface 56 has an inclination of 45° to the horizontal plane HP of the panel. This is illustrated in Fig. 8e. The pressure applied by the joint seal 55 will therefore be uniformly distributed on the vertical 9,10 and horizontal 6,8, 12 locking means of the joint system. This is advantageous since it is desirable to reduce the pressure both in connection with laying and in the locked position. Excessive pressure horizontally in the locked position may result in the floor panels separating and the joint obtaining an undesired joint gap at the adjoining upper joint edges 16. Excessive vertical pressure in the locked position may result in rising of the joint edge portion 80 in the upper part of the tongue groove 9.

Figs 9a-9d show how the material seal 20 and the joint seal 55 can be combined to a moisture-proof locking system. In this case, a groove 41 has been formed in the upper side of the core 30 after impregnation to form the material seal 20.

In this embodiment, both the tongue groove side 9 and the tongue side 10 have been provided with sealing material 50a, 50b. The embodiment is also characterized in that the impregnating material 24 serves as binder and increases the strength of the core 30. In this embodi- ment (see Fig. 9a) the impregnating material 24 has been applied in several areas on the core 30. These areas will constitute a material seal 20 and also a material rein- forcement of the upper joint edge portions 80,81. The impregnation will also provide an edge reinforcement 21a, 21b in the portions where the strip 6 is attached and in an area 21c in the core 30 adjacent to the locking groove 12 where the locking groove 12 cooperates with the lock- ing element 8.

Fig. 9b shows how the sealing material 50a, 50b can be applied in the groove 41. Once the core 30 has been provided with a surface layer 31 and a balancing layer 32 (Fig. 9c), the joint edge and the sealing material 50a, 50b are formed to a joint seal 55a, 55b (Fig. 9d). As mentioned above in connection with Fig. 8b, the sealing material could be provided in a groove that is made in both the surface layer 31,32 and in the core 30.

The strip 6 can be formed and fixed to the core 30 in different ways [for instance as shown and described in EP1061201 (Valinge Aluminium AB) or W09824995 (Valinge Aluminium AB)], so that the mechanical locking system for locking together the floor panels 1, 1'in the vertical and horizontal directions will comprise the tongue 10 and the tongue groove 9; the joint seals 55a and 55b; the material seal 20; the strip 6 with its locking element 8; the edge-reinforced fixing parts 21a, 21b for the strip 6; and an edge-reinforced locking surface 14 in the lock- ing groove 12.

The floor panels 1,1'according to this embodiment will then have upper joint edge portions 80,81 which in the vertical plane VP have a reinforced material seal 20 immediately under the surface layer 31 and joint seals 55a, 55b in connection with the material seal 20. The material seal 20 and the joint seals 55a, 55b together with the moisture-proof surface layer 31 counteract that moisture penetrates into the core 30 and that moisture penetrates through the joint system. This results in a moisture-proof floor. As mentioned above, the vertical 9, 10 and horizontal 6,8, 12 locking means should be designed in such manner that they can hold the elastically deformable joint seals 55a, 55b compressed and elastically deformed during the life of the floor without the locking means being deformed. It is particu- larly important for the tongue groove 9 not to be too deep in the horizontal direction and for the upper part or lip 15 of the tongue groove to be rigid so as not to rise. Moreover the locking element 8 and the strip 6 should be designed in such manner that they can resist the pressure applied by the joint seals 55a, 55b without the floor panels 1, 1'separating while forming a visible joint gap adjacent to the upper joint edge portions 81, 82. The sealing material 50a, 50b should also be selected so that during the entire life of the floor it exerts a pressure and prevents moisture migration through the joint system.

As appears from Fig. 9d, the core 30 is impregnated and reinforced in the areas 21a, 21b and 21c where the strip 6 is fixed and where the locking element 8 locks against the locking groove 12. This allows use of less expensive core material 30, which can be of lower quali- ty and which by means of impregnation is reinforced to obtain greater strength in the critical areas. In this manner, high quality can be combined with low cost.

A plurality of variants of this moisture-proof lock- ing system are conceivable. The joint seals 55a, 55b can be optionally arranged in the joint system, but it is advantageous if the joint seal is arranged invisibly from the surface close to the surface layer 31. They can be optionally arranged on the tongue groove side 9 or on the tongue side 10, and they can, like in the embodiment shown, be found in both joint parts. Of course, several joint seals 55 can be arranged on each joint part above and beside each other. Moreover, the contact surface between the joint seal 55 and the opposite part in the joint system can be designed in an optional manner with geometries that are, for instance, toothed, triangular, semicircular and the like. Basically all the forms that are normally used when designing sealing strips of elas- tic synthetic material or rubber can be used.

Using vacuum technique as described in connection with the embodiment according to Fig. 6b, the entire joint system from the surface layer 31 to the balancing layer 32 can be provided with a material seal and edge reinforcement 20. This can increase the joint's strength and protection against moisture, give the machined strip better flexibility, enable machining to obtain smoother surfaces and enable a reduction of the frictional forces when displacing one floor panel relative to another in the locked position. It is also possible to impregnate wood fibers with plastic material in such manner that the wood fibers, together with the impregnating material, will have such properties that they can be formed to a joint seal.

As described above, the sealing material 50a, 50b and/or 20 can alternatively be arranged in grooves which can also be made in the floor element 3 or in the floorboard 2 before the connecting parts are made. The groove 41 can then be made in both the core 30 and the surface layer 31.

Sealing material 50a, 50b can also be arranged at the edge of the floorboard 2 or the floor panel 1 when the entire joint system or parts thereof have been made, and the final forming of the joint seal 55a, 55b can also take place in a separate manufacturing step when the floor panel 1 has already obtained its final shape.

By changing the angle of the pressure surfaces between the elastically deformable joint seals 55a, 55b, the direction and distribution of the compression pres- sure can be adjusted between fully horizontal and fully vertical direction. It is an advantage if the pressure surfaces are not perpendicular but are inclined in rela- tion to the horizontal plane HP, so that the pressure is distributed with vertical and horizontal components, so that the distribution of pressure is optimized in rela- tion to the possibilities, afforded by the combinations of materials, of forming a rigid upper tongue groove part 15 and a strong horizontal joint 6,8, 12.

Figs lOa-lOc illustrate in detail how compression can be achieved in connection with inward angling. The active part 54 of the joint seal 55 is formed with a con- vex outer part which starts to be compressed when the locking groove 12 engages the locking element 8. Such a position is shown in Fig. lOb. In connection with the final downward angling and locking, the final compression of the joint seal takes place against an opposite coope- rating joint surface 56. The joint surface 56 can be coated with, for instance, wax or other similar materials after the joint system has been formed. This can facili- tate displacement along the joint edge in the locked position and contribute to improving the functions of the material seal and the joint seal.

As is evident from Fig. 10c, the joint system can have one of more expansion spaces 53a, 53b where the joint seal 55 can swell when being pressed together. The joint seal 55 can thus be formed to have some excess, and if the joint system has been formed with appropriate expansion spaces 53a, 55b, the joint seal 55 can be formed with lower tolerance requirements and maintained function.

The material seal 20 in the upper joint edges has in this embodiment been made with a considerable depth from the core surface 33, which means that the entire area from the upper parts of the joint seal 55 to the core surface 33 is moisture-proof. In this embodiment, the major part of the joint edge portion between the tongue groove 9 and the core surface 33 will constitute a mate- rial seal 20.

Figs lla-llc illustrate different embodiments of the invention. Fig. lla shows an embodiment according to the invention where the joint seal 55 has been formed to minimize edge rising and separation of the joint edges.

The contact surface of the joint seal 55 with the oppo- site cooperating joint surface 56 has a small angle to the plane of the panel, which means that the major part of the compression force will be directed essentially vertically in the direction of the arrow A. The joint edge above the tongue, however, is rigid and the risk of edge rising is small.

In the embodiment in Fig. lib, the elastically deformable joint seal 55a, 55b is arranged immediately under the surface layer 31, which surface layer thus covers the joint seal. The upper part of the seal 55a, 55b can constitute the material seal which prevents moisture from penetrating into the core 31, while the lower parts of the seal 55a, 55b can constitute the actual joint seal. The sealing 58a, 58b may also cover part of the surface layer 31,32 closest to the core.

The embodiment according to Fig. lie is character- ized in that separate materials 58a, 58b, which can con- stitute a material seal, are arranged above the elasti- cally deformable joints seals 55a, 55b. These separate materials 58a, 58b can also be used for the purpose of decoration by the surface layer 31, for instance, being a beveled portion 60, so that the separate materials 58a, 58b will be visible in the joint. Such a decorative material may also be applied in a grove formed in the core 30 and in the surface layer 31,32 of the floorboard before the final machining of the edges of the floor panel.

The principles of sealing function also without the mechanical joint system if glue is applied between the tongue groove and the tongue 10.

Fig. lld shows an embodiment where one edge of a floor panel has a material seal 20 and the other edge a joint seal 55a. The joint seal covers the lower part of the surface layer 31. Figs llf and llg show how the sealing material 55a and 20 may be applied in groves 41a and 41b, which are made in the floor board. The advantage of this method is mainly that the sealing material may be applied with great accuracy. Furthermore, application on the surface may be avoided, a considerable amount of impregnation could be applied, and the locking system may be formed to its final shape with great accuracy in a second machining operation where a reference surface such as lOa may be used to position the floor board. It is obvious that the application of a material seal and a joint seal could be combined in several ways. Both sides could, for example, have material seal and joint seal, or only join seal or material seal, etc. In this embodiment, a considerable amount of impregnating material 20 is to be found in the upper joint edge portions, immediately under the wear layer 31, i. e. within the area that is most critical in the viewpoint of moisture. This concentration of impregnating material immediately under the wear layer 31 is obtained as a result of the impregnating material being caused to penetrate into the core, from the groove 41b closest to the surface during impregnation. No protection of the surface closest to the final edge is necessary, since the surface is protected by the remaining part 31a of the surface layer and since a considerable amount of impregnation material could be applied. The core part which is closest to the surface could be impregnated to a horizontal depth of about 1 mm or more and the impregnation could be made with this depth over substantially the whole edge of the floor panel. The vertical concentration of impregnating material 20 under the wear layer 31 is higher at the joint surface than in the core. Naturally, the procedure above, which was described with reference to the upper surface 33 of the floor panel, may also be applied to the lower surface of the floor panel.

Fig. 12a shows an embodiment according to the inven- tion where the core 30 has been coated with three diffe- rent surface layers having different functions. The sur- face of the floor panel 1, 1'comprises a transparent, hard and durable wear layer 34 of plastic material, an intermediate decorative layer 35 of plastic film and a reinforcement layer 36 which is made of an elastic mate- rial and which can be both moisture-proof and sound- absorbing. The decorative layer 35 of plastic film can be replaced with decorative patterns which are printed directly on the underside of the transparent wear layer 34 or on the upper side of the elastic reinforcement layer 36. This embodiment could also be produced without a seal and may then constitute a floating floor panel with a wood based core such as HDF/MDF, a resilient surface and a mechanical locking system for locking the floor panels horizontally and vertically at its long and short sides through angling and/or snapping. The seal could even in this embodiment be applied in a grove that is formed in the core and in the surface layer of the floor board.

The joint seal 55a on the tongue side has an active part 54 in the form of a convex bulge which presses against the opposite elastic cooperating joint surface 56. The active part 54 of the joint seal 55a has been made small, and this contributes to reducing the fric- tion in connection with lateral displacement when the short sides of the floor panels are to be locked by snap action. Friction can also be reduced by the joint seals 55a, 55b being coated with different types of friction- reducing agents.

Fig. 12b shows an embodiment with the same surface layer 31 as in Fig. 12a, but the joint seals 55a, 55b have been formed in the elastic and deformable reinforce- ment layer 36 closest to the core 30. If the wear layer 34 is harder than the reinforcement layer 36, on the one hand the deformation of the joint seal 55b will essen- tially take place in the lower part 57 of the joint seal closest to the core 30 and, on the other hand, no signi- ficant deformation of the wear layer 34 will take place.

This results in a moisture-proof and sound-absorbing floor. Also in this embodiment, the sealing means in the form of material seal and joint seal can be designed in many different ways as described above.

It is obvious that the above-described embodiments according to Figs 6-12 can be combined. For instance, the sealing means according to Figs 12a and 12b or 10a and lOb can be arranged in same joint system. The strip 6 can be made of aluminum etc.

Fig. 13 shows a floor panel 1 with a mechanical joint system on the long sides 4a, 4b and on the short sides 5a, 5b and with a joint seal 55a and 55b on one short side 5a and one long side 4b. When the floor panel 1 is connected with other similar floor panels 1'on both long sides 4a, 4b and on both short sides 5a, 5b to form a floor, there will be a joint seal on all sides.

If, besides, the joint edges have a material seal 20 according to the embodiments described above, the joint system of the floor panels will counteract penetration of moisture into the joint system on all sides 4a, 4b, Sa, 5b and in all corner portions 38a, 38b, 38c, 38d.

Linear machining of long sides and short sides makes it possible to design the corner portions 38a, 38b, 38c, 38d with the same narrow tolerances as the sides 4a, 4b, 5a, 5b of the floor panels 1. The joint seal in the cor- ners 38a, 38b, 38c, 38d will have an exact fit, and the angular displacements between the short sides 5a, 5b and the long sides 4a, 4b as well as the deviations from parallelism between the long sides 4a, 4b that may appear can be compensated for if it is ensured that the possibi- lity of the joint seals 55a, 55b being deformed when the floor panels have been joined, will exceed these manufac- turing tolerances.

Fig. 14a is a cross-sectional view of conventional- ly designed floor panels 1, 1', transversely of a joint along one long side of a wooden floor. The floor panels 1, 1'have a surface layer 31 of wood with a main direc- tion of fibers parallel to the long side and a core 30 having a different direction of fibers essentially per- pendicular to the long side. The longitudinal side edges of the floor panel 1, 1'have a mechanical joint system 9,10, 6,8, 12. In moist surroundings, the upper joint edge portions 80, 81 swell transversely of the direction of fibers (i. e. transversely of the joint between the neighboring floor panels 1, 1') more than does the core 30. This means that the floor panels 1, 1'along the long sides are pressed apart and that the strip 6 is bent backwards. This involves a risk of the upper joint edge portions 80,81 or the cooperating locking surfaces 14, 18 being compressed or damaged. As the floor panels 1, 1' dry and shrink in winter (when the relative humidity falls), this may in turn result in a joint gap arising between the upper joint edge portions 80,81.

Figs 14b-14e show how it is possible to compensate for this risk of joint gaps arising by utilizing accord- ing to the invention an elastic compensation seal 52 which is inserted into the horizontal locking means 6,8, 12 for counteracting the effects of swelling and shrink- ing of the upper joint edge portions 80,81.

Fig. 14b shows an embodiment of a floorboard 2' which is suitable to form a joint system with a compensa- tion seal according to the invention. The contour lines of the joint system to be have been indicated by dashed lines in Fig. 14b. The surface layer 31, the core 30 and the balancing layer 32 are laterally offset on both the tongue groove side 9 and the tongue side 10 to minimize the waste when machining the joint edges. In the under- side of the floorboard 2 a groove 40 is formed in the core 30. An elastic material 51 is arranged and fixed in the groove 41 by, for instance, extrusion or the like according to the previously described methods or alterna- tively by gluing or mechanical fixing by, for instance, pressing material into a groove.

In the subsequent machining, the elastic material 51 is removed or reshaped only partially and is formed to an elastic compensation seal 52 which constitutes the active locking surface in the locking groove 12 and which is operative in the horizontal direction D2. This is illu- strated in Fig. 14c.

As the joint edge portions 80,81 swell, the elastic compensation seal 52 will be compressed by its locking surface 14 pressing against the locking surface 18 of the locking element 8. As a result, the mechanical look- ing system can compensate for the great movements due to moisture in the upper joint edge portions 80,81 without the joint system being damaged or a visible joint gap appearing in winter when the floor has dried and shrunk.

The problem with the upper joint edges swelling will be greater if the thickness WT of the surface layer 31 is considerable and if this thickness is more than, for instance, 0.1 times the floor thickness T.

A joint system according to the above embodiment is especially suitable for use together with underfloor heating and in surroundings where the relative humidity varies significantly during the year. The elastic locking means or compensation seal 52 can be arranged optionally on the locking element 8 (as in Fig. 14d) or in the lock- ing groove 12 (as in Figs 14c and 14e) or in both these parts, and it can be formed with many different geome- tries having different angles and radii which can facili- tate inward angling and displacement. The elastic locking means or compensation seal 52 can also be combined with a material seal 20 and a joint seal 55 according to the previously described embodiments of the invention.

Fig. 14d illustrates an embodiment where the elastic locking means or compensation seal 52 also serves as a joint seal, sealing against moisture. In this case, the seal 52 will, when compressed, also take up the movements that are caused by swelling and shrinking of the upper joint edge portions 80,81. The compression and, thus, sealing capacity of the elastic seal 52 will thus increase when the floor panels are located in moist surroundings. In this case, there is a material seal 20 which, however, has not been illustrated specifically in this Figure but which extends down to at least the upper parts of the connecting means in the same way as shown in, for instance, Fig. 7d.

Fig. 14e illustrates an embodiment where the elastic compensation seal 52 is compressed by a locking element 8 which is made of a material other than that of the core 30. In this embodiment, the strip 6 and the locking ele- ment 8 can be made of aluminum or some other convenient metal. This construction has a flexibility which is greater than in the case where the strip 6 is formed integrally with the core of the floor panel. The inven- tion can also be used in this embodiment. One of the advantages of this embodiment is that the friction is low during lateral displacement in the locked position.

Figs 15a-15e illustrate a embodiment of a joint system with a joint seal 55 which has been arranged in the groove 41 in the core 30 adjacent to the upper and inner part of the tongue 10 and which has been formed using a tool 70.

Figs 15a and 15b show the critical tolerance which lies in the position of the tool 70 when forming, for instance, a groove 41 in the core 30 or the board ele- ment relative to the vertical plane VP to be in the floor panel 1'. The innermost position of the tool 70 is defin- ed by a plane TP1. Fig. 15b shows the outer position of the tool 70 which is defined by a plane TP2 outside the vertical plane VP. As is evident from these two Figures, the contact surfaces of the joint seal 55 for contact with the opposite cooperating joint portion 56 can be formed with great accuracy although the manufacturing tolerance TP1-TP2 for the horizontal positioning of the groove 41 relative to the joint edge to be at the ver- tical plane VP is fairly great and may exceed 0.2 times the floor thickness T. Using modern production equipment it is possible to manage a horizontal lateral positioning with these tolerances in the entire production chain from production of the surface layer 31 and the board element 3 to the completed floor panel 1'. The positioning of the tool 70 in the vertical direction is less critical since the tolerance mainly depends on the thickness tolerances of the materials and since these as a rule are small in relation to the tolerances in connection with the lateral positioning.

In this embodiment, it is also possible to use the core surface 33 or the surface of the surface layer 31 as reference surface. The groove 41 and the sealing material 50, which is then formed into the joint seal 55, can therefore be positioned with great accuracy in the verti- cal direction. The active contact surfaces of the joint system and the joint seal 55 can therefore be made with very narrow manufacturing tolerances, which may be below 0.01 times the floor thickness T although the original positioning of the sealing material 50 is effected with significantly lower tolerance requirements.

Such an embodiment is characterized in that the manufacturing tolerance between the active part 54 of the joint seal and the upper adjoining joint edges 16 will be significantly lower than the tolerance between another part of the joint seal which is not active, and the above-mentioned upper adjoining joint edge 16. This facilitates rational manufacture and enables high quality manufacture.

If the groove is formed in the core of the floor board and in the surface layer 31,32, the outer part of the tongue 10 could be formed in the same machining step and this part of the tongue or some other parts of the floor board could be used as a reference surface when forming the locking system and the seal 55. In this case, the vertical and horizontal tolerances could be reduced to as little as 0,01 mm.

Fig. 15c shows the joint seal 55 in its compressed state with expansion spaces 53a and 53b on both sides of the joint seal.

Fig. 15d shows how the joint seal 55 can be formed to facilitate machining of the surface layer 31 when this consists of a laminate. When machining the upper joint edge 80 using a diamond cutting tool 71 which operates horizontally, i. e. perpendicular to the vertical plane VP according to the arrow R, great wear arises at the point 72 on the diamond cutting tool that works on the laminate wear layer 35 which contains aluminum oxide. In order to utilize a greater part of the active surface of the dia- mond cutting tool, the tool is moved from its starting position 71, for example, step by step downwards in the direction of the tongue 10. The starting position of the tool is indicated by the position 71 and its end position by the position 71'. If the joint seal 55 is located adjacent to the upper and inner part of the tongue 10 in the shown groove 41 and if its upper boundary UP is located at a distance SD from the surface of the surface layer 31 that exceeds, for instance, 0.2 times the floor thickness T, it is possible to provide a joint seal 55 which is designed in such manner that the machining of the joint edge adjacent to and under the surface layer 31 will be facilitated. This form and location of the joint seal 55 at a distance from the surface layer 31 also makes it possible to form, by simple machining of the tongue 10 using the tool 73 (see Fig. 15e) and the opposite and cooperating joint portion 56 on the opposite joint edge, the locking system with radii and angles in a manner that facilitates a snapping-in and/or inward angling function of the locking system.

Figs 16a-16e show locking systems that have a plura- lity of horizontal locking means. These locking systems can be used in connection with moisture-proof locking systems but also merely as ordinary mechanical locking systems to provide a locking system with great horizontal strength. The basic principles can be used in locking systems which are joined by inward angling or snapping-in and using strips 6 which are optionally formed integrally with the core 30 or made of a separate material, such as aluminum, and then secured to the core.

Various combinations of the systems can be used on the long and short sides. The locking elements 8a, 8b, 8c and the locking grooves 12a, 12b, 12c can be made with different angles and radii of, for instance, wood, fiberboard-based materials, plastic materials and like panel materials with strips which are machined from the core or which consist of separate materials, and the locking elements can be designed for installation of the floor panels by angling or snapping-in.

The locking system according to Fig. 16a has two strips 6a and 6b, two locking elements 8a, 8b and two locking grooves 12a, 12b. The locking element 8a and the locking groove 12a enable locking with great strength as well as good guiding in connection with, for example, inward angling. The locking element 8b results above all great in strength and can significantly increase the horizontal locking force. The locking element can be designed so as to be operative when the horizontal ten- sile force is so great that the upper joint edges begin to move apart, for instance when a joint gap of 0.05 mm or 0.10 mm arises.

Fig. 16b illustrates a locking system with three horizontal locking means with the locking elements 8a, 8b, 8c and the locking grooves 12a, 12b, 12c which can be made according to these basic principles. This embodiment consists of a locking means with good guiding capacity 8a, 12a, and two locking means 8b, 12b and 8c, 12c which contribute to increasing the strength of the joint system in connection with horizontal tension load. This joint system can hold together the joint edges during compres- sion of the joint seal 55. Several locking elements can be formed according to this method in the upper and lower parts of the tongue 10 and in the strip 6, and they can be adjusted to facilitate inward angling, snapping-in and guiding and to increase strength.

Fig. 16c illustrates that a separate locking means 8b, 12b and/or 8c, 12c, for example, can be used to limit separation in a joint system where parts of the locking groove 12a can consist of an elastic locking means 52.

The locking systems according to Figs 16a and 16b are mainly intended for snapping-in but they can be adjusted, with minor changes of the angles and radii of the locking system, so as to be easier to angle.

Fig. 16d shows a locking system with two horizontal locking means 8a, 12a and 8b, 12b which are convenient for e. g. the long side which may be laid by inward angling.

Fig. 16e illustrates a locking system for e. g. the short side which may be laid by snapping-in. The locking system according to Fig. 16e differs from that in Fig.

16f among other things by the locking element being smaller and having a greater inclination in relation to the surface layer, the strip 6a being longer and more flexible, the tongue groove 9 being deeper, and the upper locking element 8b having a locking surface which is more inclined in relation to the surface layer.

The locking grooves 12b and 12c can be made to have advanced forms by means of tools which need not neces- sarily rotate. Fig. 16f illustrates manufacture of the undercut groove 12c in a joint system according Fig. 16b.

The panel can, according to prior-art technique in metal working, be moved past a stationary grooving tool 74 which in this embodiment has teeth 75 which operate per- pendicular to the surface layer 31. When the floor panel 1 moves in the direction of the arrow B, the floor panel will pass the grooving tool 74 which is inserted into the tongue groove 9 and the teeth of which make the final forming of the undercut groove 12 with its locking sur- face. The major part of the tongue groove 9 is formed in a conventional manner using large rotating diamond cutting tools before the panel comes to a such a position that the grooving tool 74 is operative. In this manner, essentially all geometric shapes can be formed in the same way as in extrusion of plastic or aluminum sections.

This technique can also be used to form the groove 41 in the core where the sealing material is arranged.

Figs 17a-17d illustrate an enlargement of the corner portion 38a of the floor panel, which has previously been illustrated in Fig. 13, and show a joining of three floor panels 1, 1'and 1". Precisely the corner portions con- stitute one of the critical parts in a moisture-proof floor. To counteract penetration of moisture into the joint system through the corner, it is a great advantage if the joint seal 55a, 55b is unbroken in at least one corner 38a according to Fig. 17a. Moreover, the joint seal in the corner 38d of the floor panel 1'should be positioned and formed in such manner that its active part 54 is not completely removed in connection with the machining of the different parts, specifically the tongue groove 9, of the joint system.

Figs 17c and 17d illustrate the joint system in a cross-sectional view along the line C1-C2 in Fig. 17b, i. e. the short side and the corner portion 38a of the panel 1'are shown in an end view whereas the panel 1 is shown in cross-section along this line C1-C2. In this embodiment, the active part 54 of the joint seal is intact in the panel 1'at the outer end of the upper lip of the tongue groove 9b. This is due to the fact that the active part 54 is placed in a plane SA which is position- ed between the surface layer 31 and the upper part of the tongue groove which in this case is an undercut groove 9b. The active part 54 of the joint seal will thus in this plane be in contact with an opposite cooperating joint surface 56 of the third floor panel lu.

This embodiment makes the corner 38a have an area SA where the sealing material 55a is positioned in one or more planes and where the joint seal 55a is unbroken.

There will thus be no gaps or hollows where moisture can penetrate from the surface and spread in the joint sys- tem. This embodiment is thus characterized in that the floor panel has two corners 38b, 38d where the joint seals 55a, 55b are in unbroken contact with the opposite cooperating joint surface. The active part 54 of the joint seal 55 is thus continuous along one entire long side and one entire short side as well as in the corners between these long and short sides.

Hence, a system has been described, for forming a joint between two adjoining edges 4a, 4b; 5a, 5b of floor panels 1, 1'which have a fiberboard core 30 and a surface layer 31 applied to the upper side 53 of the core and consisting of at least one layer, and which at their adjoining joint edges 82,83 have connecting means 9,10 for joining the floor panels with each other in the vertical direction Dl, the upper adjoining joint edges 16 of said floor panels 1, 1'meeting in a vertical joint plane VP. In the system, adjoining joint edge portions 80,81 of the floor panels 1, 1'have a material seal 20 for counteracting penetration of moisture into the cores 30 of the floor panels from the joint edges 82,83, said material seal 20 comprising an impregnation of the core 30 within said joint edge portions with a moisture- sealing agent and/or an agent counteracting or significantly reducing swelling caused by moisture, from the upper side 33 of the core 30 and at least a distance down towards the connecting means 9,10.

In the system, the concentration of the moisture- sealing agent in the joint edge portion may be higher at the core surface 33 than at a distance therefrom.

In the system, the impregnation of the core 30 may extend down to a depth P2 which is at least 0.1 times the thickness T of the floor panel.

In the system, the impregnation of the core 30 may extend down to a depth P2 which corresponds to at least half the distance between the surface 33 of the core and the upper surfaces of the connecting means 9,10.

In the system, the impregnation may extend down to at least upper parts of the connecting means 9,10.

In the system, the impregnation may extend from the joint plane VP inwards in the core 30 a distance Pi which is at least 0.1 times the thickness of the floor panel.

In the system, the impregnation may extend from the joint plane VP inwards in the core 30 a distance PI which corresponds to at least half the width of the connecting means 9,10, seen from the joint plane.

In the system, the impregnation may extend from the joint plane VP inwards in the core 30 a distance PI which corresponds to the width of essentially the entire connecting means 9,10, seen from the joint plane.

In the system, the core 3 within at least its joint edge portions may be impregnated with a property- improving agent also from its underside.

In the system, the adjoining joint edges 82,83 may also have connecting means 6,8, 12 for joining the floor panels 1, 1'with each other in the horizontal direction HP perpendicular to the joint plane VP.

In the system, the core 30 within at least said joint edge portions may be impregnated with a property- improving agent also from its underside and at least a distance up towards the connecting means 9,10, 6,8, 12.

In the system, the impregnation may extend up to at least lower parts of the connecting means 6-10,12, 14, 18.

In the system, the impregnating agent may be an agent improving the mechanical properties of the core 30.

In the system, the impregnating agent may be an agent improving the elasticity properties of the core 30.

In the system, the core 30 may be impregnated over less than half the distance between said opposite joint edge portions.

In the system, the core 13 may be impregnated within said joint edge portions within which at least parts of the connecting means 6-10,12, 14,18 are formed.

In the system, the connecting means 9,10, 6,8, 12 may be designed for mechanical joining of neighboring floor panels 1,1"at a vertical joint plane VP both perpendicular to the same and perpendicular to the front side of the floor panel.

In the system, the floor panels 1, 1'may be quadrilateral and have all their opposite joint edge portions impregnated.

In the system, the entire core surface 33 at the joint edge portion of the corner portions 38a-d may be impregnated.

In the system, the floor panels 1, 1'may be quadrilateral and have mechanical joint systems 9,10, 6, 8,12 for vertical and horizontal joining on all sides.

In the system, the connecting means 9,10, 6-8-12 may be designed for joining a floor panel 1 with a previously installed floor panel 1'by inward angling and/or snapping-in to a locked position.

In the system, the connecting means 9,10, 6,8, 12 may comprise a lower lip or locking strip 6 which may be formed integrally with the core and is included in the mechanical connecting means.

In the system, the lower lip or locking strip 6 is impregnated with an elasticity-improving agent.

In the system, the connecting means 9,10, 6,8, 12 may comprise an integrated locking strip 6 which is made of a material other than that of the core 30 and which is fixed to fixing elements 21a, 21b which are formed along one of the opposite parallel joint edge portions of each floor panel.

In the system, the fixing elements 21a, 21b made in the core 30 for the locking strip 6 may be impregnated with a property-improving agent.

In the system, the fixing elements 21a, 21b may be impregnated with a strength-increasing agent.

In the system, the connecting means 9,10, 6,8, 12 may be made by cutting.

In the system, the opposite joint edge portions 86, 87 of the floor panels 1, 1'may also have a joint seal 55 for counteracting penetration of moisture along the joint surfaces of the joint edges between neighboring floor panels when joined, and that this joint seal 55 is formed at the joint edge portions 86,87 and is made of an elastic sealing material 50,50a, 50b, which is secured in at least one of the floor panels 1,1'and which is compressed, when neighboring floor panels are joined together.

In the system, the joint seal 55 may be formed of parts of the connecting means 9,10, 6,8, 12 and/or por- tions of the floor panel parts above and/or below the connecting means.

In the system, the joint seal 55 may be designed in such manner that the tolerance within a floor panel and/or between different floor panels is smaller between the active part and the upper adjoining joint edges 16 of the joint seal 55 than between another part of the joint seal 55 and said upper adjoining joint edges.

In the system, the joint seal 55 may be made of parts of the vertical connecting means 9,10 and/or portions of the floor panel parts positioned above the vertical connecting means.

In the system, the joint seal 55 may be made by machining of the elastic sealing material 50,50a, 50b in connection with the designing of one of the joint edges 82,83.

In the system, the joint seal 55 may be made by machining of the elastic sealing material 50,50a, 50b in connection with the designing of one of the vertical connecting means 9,10.

In the system, the active part 54 of the joint seal 56 may be designed in such manner that the compression is begun essentially when the locking element 8 during inward angling comes into contact with the active locking surface of the locking groove 12.

In the system, the active part 54 of the joint seal 56 may be designed in such manner that the compression is begun essentially when the locking element 8a during snapping-in comes into contact with the active locking surface of the locking groove 12.

In the system, the floor panels may have a joint seal 56 with an active part 54 on a long side and a short side, and that this active part 54 is continuous and covers all these long sides and short sides as well as the corner portion between these long sides and short sides.

The system may further comprise an impact sound insulating layer 36 of plastic between the core 30 and the decorative and wear layer 34. Also, in the system, the free surface portions of the impact sound insulating layer 36 facing the joint VP may be designed by cutting in connection with the designing of the joint edge and are formed as joint sealing means 55a, 55b which are compressed when neighboring floor panels 1, 1'are joined together.

In the system, the joint sealing means 55,55a, 55b may be formed with contact surfaces which are inclined to the upper side of the floor panels 1, 1'in the joined state.

The system may comprise more than one locking means 8a, 8b, 8c for horizontal joining of neighboring floor panels 1, 1'.

In the system, the locking means 8a, 8b, 8c for horizontal joining, one may be placed on one side of the vertical joint plane VP and another on the other side of the vertical joint plane VP.

In the system, the locking means 8a, 8b, 8c for horizontal joining may be arranged at different levels relative to the front side of the floor panels 1, 1'.

Furthermore, a floor panel has been described, which has a fiberboard core 30 and at least one surface layer 31 applied to the upper side of the core and which at least at two opposite parallel joint edge portions 86,87 has connecting means 9,10 for joining of the floorboard in the vertical direction Dl with similar floorboards. In the floorboard, the core 30 within at least said upper joint edge portions 80,81 is impregnated with a property-improving agent all the way from its upper side 33 and at least a distance down towards the connecting means 9,10.

In the floor panel, the concentration of the property-improving agent in the joint edge portion may be higher at the core surface 33 than at a distance therefrom.

In the floor panel, the impregnation may extend to a depth which is at least 0.1 times the thickness of the floor panel.

In the floor panel, the impregnation of the core 30 may extend down to a depth P2 corresponding to at least half the distance between the surface 33 of the core and the upper parts of the connecting means 9,10.

In the floor panel, the impregnation may extend down to at least upper parts of the connecting means 9,10.

In the floor panel, the impregnation may extend inwards from the joint plane VP in the core 30 a distance which is at least 0.1 times the thickness of the floor panel.

In the floor panel, the impregnation may extend inwards from the joint plane VP in the core 30 a distance corresponding to at least half the width of the connect- ing means 9,10, seen from the joint plane VP.

In the floor panel, the impregnation extends inwards from the joint plane VP in the core 30 a distance PI corresponding to at least half the width of the con- necting means 9,10, seen from the joint plane.

In the floor panel, the impregnation may extend down to at least upper parts of the connecting means 9,10.

In the floor panel, the core 30 within at least said joint edge portions may be impregnated with a property- improving agent also from its underside and at least a distance up towards the connecting means 6-10,12, 14, 18.

In the floor panel, the adjoining joint edges 82,83 may also have connecting means 6,8, 12 for joining the floor panel 1 in the horizontal direction HP with another similar floor panel 1'perpendicular to the joint plane VP.

In the floor panel, the impregnation may extend up to at least lower parts of the connecting means 6-10,12, 14,18.

In the floor panel, the impregnating agent is an agent improving the mechanical properties of the core 30.

In the floor panel, the impregnating agent may be an agent improving the elasticity properties of the core 30.

In the floor panel, the impregnating agent may be a moisture-sealing agent and/or an agent counteracting or significantly reducing swelling caused by moisture and intended to form a material sealing means 20.

In the floor panel, the core 30 may be impregnated over less than half the distance between said opposite joint edge portions.

In the floor panel, the core 30 may be impregnated within said joint edge portions, within which at least part of the connecting means 6-10,12, 14,18 are formed.

In the floor panel, the connecting means 6-10,12, 14,18 may be formed for mechanical joining of the floor panel 1 with a neighboring similar floor panel 1'at a vertical joint plane VP both perpendicular to the same and perpendicular to the front side of the floor panel.

The floor panel may be quadrilateral and have all its opposite joint edge portions impregnated.

In the floor panel, the connecting means 6-10,12, 14,18 may be formed for joining a floor panel 1 with a previously installed floor panel 1'by inward angling and/or snapping-in to a locked position.

In the floor panel, the connecting means 6-10,12, 14,18 may comprise a lower lip or locking strip 6 which is formed integrally with the core 30 and is included in the mechanical connecting means 6-10,12, 14,18.

In the floor panel, the lower lip or locking strip 6 may be impregnated with an elasticity-improving agent.

In the floor panel, the connecting means 6-10,12, 14,18 may comprise an integrated locking strip 6 which is made of a material other than that of the core 30 and which is fixed to fixing elements 21a, 21b which are formed along one of the opposite parallel joint edge portions of the floor panel.

In the floor panel, the fixing elements 21a, 21b formed in the core 30 and intended for the locking strip 6 may be impregnated with a property-improving agent.

In the floor panel, the fixing elements 21a, 21b may be impregnated with a strength-increasing agent.

In the floor panel, the connecting means 6-10,12, 14,18 may be made by cutting.

In the floor panel, parts of the connecting means 6- 10,12, 14,18 and/or adjoining portions of the core 30 within the upper parts of the joint edge portions may be made of an elastic sealing material 50,50a, 50b, which is secured in the core 30 and designed by machining in connection with the designing of the connecting means 6- 10,12, 14,18 and which is made to form a joint sealing means 55,55a, 55b for counteracting penetration of moisture between neighboring joined floor panels 1, 1'.

In the floor panel, the joint seal 55 may be made of parts of the connecting means 9,10, 6,8, 12 and/or por- tions of the floor panel parts positioned above and/or below the connecting means.

In the floor panel, the joint seal 55 may be designed in such manner that the tolerance within a floor panel and/or between different floor panels is smaller between the active part of the joint seal 55 and upper adjoining joint edges 16 than between another part of the joint seal 55 and said upper adjoining joint edges.

In the floor panel, the joint seal 55 may be made of parts of the vertical connecting means 9,10 and/or portions of the floor panel parts positioned above the vertical connecting means.

In the floor panel, the joint seal 55 may be made by machining of the elastic sealing material 50,50a, 50b in connection with the designing of one of the joint edges 82,83.

In the floor panel, the joint seal 55 may be made by machining of the elastic sealing material 50,50a, 50b in connection with the designing of one of the vertical connecting means 9,10.

In the floor panel, the active part 54 of the joint seal 56 may be designed in such manner that the compression is begun essentially when the locking element 8, during inward angling, comes into contact with the active locking surface of the locking groove 12 when the floor panel is joined with a similar floor panel.

In the floor panel, the active part 54 of the joint seal 56 may be designed in such manner that the compression is begun essentially when the locking element 8, during snapping-in, comes into contact with the active locking surface of the locking groove 12 when the floor panel is joined with a similar floor panel.

In the floor panel, there may be a joint seal 156 with an active part 54 on a long side and a short side and that this active part 54 is continuous and covers the entire long sides and short sides as well as the corner portion between said long sides and short sides.

The floor panel, may comprise an impact sound insulating layer 36 of plastic between the core 30 and the decorative and wear layer 34. In that floor panel, the free surface portions of the impact sound insulating layer 36 facing the joint VP may be designed by cutting in connection with the designing of the connecting means 6-10,12, 14,18 and be made as joint sealing means 55a, 55b which are compressed, when neighboring floor panels 1, 1'are joined together.

Also described is a method of making a fiberboard core 30 which is intended for production of floorboards 2 or board elements 3 to be divided into floorboards 2 which have opposite joint edge portions 86,87. The method is characterized that said fiberboard core 30 is impregnated with at least one property-improving agent within defined band-shaped areas 44 which comprise joint edge portions 86,87 to be of the floorboards 2.

In the method, the impregnation of the wood-based panel may take place from its front side to be.

In the method, the impregnation may be carried out in such manner that the concentration of the property- improving agent in the joint edge portion is higher at the core surface 33 of the core than at a distance from the core surface.

In the method, the impregnation of the wood-based panel may take place from its rear side to be.

In the method, the impregnation may be carried out to a depth corresponding to at least 0.1 times the panel thickness T.

In the method, the impregnation may be carried out at least to such a depth that parts of the connecting means 9,10 to be of the floor panels will be impregnated.

In the method, the impregnation may be carried out by applying a liquid impregnating agent over the band- shaped areas 44.

In the method, the impregnation may take place with an agent improving the mechanical properties of the core 30.

In the method, the impregnation may take place with an agent improving the elasticity properties of the core 30.

In the method, the impregnation may take place with a moisture-sealing agent.

In the method, the impregnation may take place with a swelling-reducing agent.

In the method, the core 30 may be impregnated over less than half the distance between said opposite joint edge portions.

In the method, grooves 41 may be formed in the panel within the band-shaped areas 44 to a depth on a level with the connecting means 6-10,12, 14,18 to be of the floorboards, and an elastic sealing material may be inserted in said grooves.

In the method, the elastic sealing material may be cast in said grooves 41.

There is also described a method of producing a floorboard 2 or a floorboard element 3 which is intended to be divided into floorboards, which have opposite joint edge portions 86,87, in which method a fiberboard core 30 is coated with a surface layer 31 on its front side and preferably also a balancing layer 32 on its rear side. The is characterized in that before the coating with the surface layer 31 and a possible balancing layer 32, the fiberboard core 30 is impregnated with at least one property-improving agent within defined band-shaped areas 44 comprising joint edge portions 86,87 to be of the floorboards.

In the method, the impregnation of the wood-based panel 30 may take place from its upper side to be.

In the method, the impregnation of the wood-based panel 30 may take place from its underside to be.

In the method, the impregnation may be carried out at least to such a depth that parts of connecting means 9,10, 6-8-12 to be of the floorboards will be impregnated.

In the method, the impregnation may be carried out by applying a liquid impregnating agent over the band- shaped areas 44.

In the method, the impregnation may take place with an agent improving the mechanical properties of the core 30.

In the method, the impregnation may take place with an agent improving the elasticity properties of the core 30.

In the method, the impregnation may take place with a moisture-sealing agent and/or an agent counteracting or significantly reducing swelling caused by moisture.

In the method, the core 30 may be impregnated over less than half the distance between said opposite joint edge portions.

In the method, grooves 41 may be formed in the panel 30 within the band-shaped areas 44 to a depth on a level with the connecting means 9, 10 to be of the floorboards and an elastic sealing material 50,50a, 50b may be inserted into said grooves.

There is also described a floorboard which is intended as semi-manufacture for producing a floor panel 1 and which has a fiberboard core 30 and a surface layer 31 applied to the upper side 33 of the core and which has at least two opposite parallel joint edge portions 86,87 which are intended for cutting to form connecting means 9,10 of the floor panel. The floorboard is characterized in that the core 30 within at least said joint edge portions 86,87 is impregnated with a property-improving agent all the way from its upper side 33 and at least a distance down towards the connecting means 9,10.

In the floorboard, the concentration of the moisture-sealing agent in the joint edge portion may be higher at the core surface 33 than at a distance therefrom.

In the floorboard, the impregnation may extend to a depth which is at least 0.1 times the thickness of the floorboard.

In the floorboard, the impregnation of the core 30 may extend to a depth P2 which corresponds to at least half the distance between the surface 33 of the core and the upper surfaces of the connecting means 9,10.

In the floorboard, the impregnation may extend down to at least upper parts of the connecting means 6-10,12, 14,18 to be.

In the floorboard, the core 30 within at least said joint edge portions may be impregnated with a property- improving agent also from its underside and at least a distance up towards the connecting means 6-10,12, 14, 18.

In the floorboard, the impregnation may extend up to at least lower parts of the connecting means 6-10,12, 14,18.

In the floorboard, the impregnating agent may be an agent improving the mechanical properties of the core 30.

In the floorboard, the impregnating agent may be an agent improving the elasticity properties of the core 30.

In the floorboard, the impregnating agent may be a moisture-sealing agent and/or an agent counteracting or significantly reducing swelling caused by moisture.

In the floorboard, the core 30 may be impregnated over less than half the distance between said opposite joint edge portions.

In the floorboard, the core 30 may be impregnated within said joint edge portions, within which at least parts of the connecting means 6-10,12, 14,18 of the floor panel are to be formed.

The floorboard may be quadrilateral and have all its opposite joint edge portions impregnated.

In the floorboard, the joint edge portions on the upper side of the floorboard may be impregnated with a moisture-sealing agent and/or an agent counteracting or significantly reducing swelling caused by moisture.

In the floorboard, the joint edge portions on the underside of the floorboard may be impregnated with a strength-increasing agent.

In the floorboard, the joint edge portions on the underside of the floorboard may be impregnated with an elasticity-improving agent.

The floorboard may comprise an elastically deformable sealing material 54, which is secured in the core in such positions thereof as, in machining the floorboard to a floor panel, will form parts of the connecting means 6-10,12, 14,18 of the floor panel and/or adjoining portions of the core 30 of the floor panel within the upper parts of the joint edge portions.

In the floorboard, the elastic joint sealing material 56 may be secured in the core 30 within areas which are intended to form a long side and a short side of a floor panel to be and which are continuous along the entire long sides and short sides as well as a corner portion between said long sides and short sides.

The floorboard may comprise an impact sound insulating layer 36 of plastic between the core 30 and the decorative and wear layer 34.

According to this embodiment, a system is provided for forming a joint between two adjoining edges of floor panels which have a fiberboard core and a surface layer applied to the upper side of the core and consisting of at least one layer, and which adjacent to their adjoining joint edge portions have connecting means for joining the floor panels with each other in the vertical direction and which meet in a vertical joint plane. According to this aspect of the invention, the adjoining joints edge portions of the floor panels have a material seal for counteracting penetration of moisture into the cores of the floor panels from the joint plane. This material seal comprises an impregnation of the core within said joint edge portions with a moisture-sealing agent and/or an agent counteracting or significantly reducing swelling caused by moisture all the way from the upper side of the core and at least a distance down towards the connecting means.

This impregnation may extend to a depth which is at least 0.1 times the thickness of the floor panel, seen from the upper side of the core. More preferably, the impregnation extends down to at least upper parts of the connecting means of the floor panels. The extent of the impregnation seen from the joint plane and inwards in the core is preferably also at least 0.1 times the thickness of the floor panel. More preferably, the impregnation, seen from the joint plane, extends a distance corresponding to at least half the width of the connecting means.

It is also preferred for the core to be impregnat- ed from its underside and at least a distance up towards the connecting means. The impregnation of the underside of the core can be effected using a property-improving agent, especially an agent which improves the mechanical properties of the core.

In some connecting systems, it is possible to choose to improve the strength and elasticity properties of the core for the core to better satisfy its function as starting material for mechanical connecting means.

Through this embodiment, the necessary properties of the core are obtained within those parts of the floor panels which are most exposed to influence, i. e. the edge portions. This causes great economic advantages since the impregnation of the core has been limited to precisely the portions that need be improved so as to obtain a floor having the desired properties as regards resistance to the influence of penetrating moisture. The impregnation of the core therefore preferably takes place to less than half the distance between the opposite edges of the core. Most advantageously, the impregnation is restricted to those parts of the edge portions within which at least parts of the connecting means are formed.

As mentioned above, the embodiment is particularly usable in connection with systems which are based on mechanical joining of neighboring floor panels, i. e. systems where the mechanical locking means join the floor panels at a vertical joint plane both perpendicular thereto and perpendicular to the front side of the floor panels. The connecting means can particularly advanta- geously be designed for joining a floor panel with a previously installed floor panel by inward angling and/or snapping-in to a locked position.

When utilizing the embodiment for floor panels with mechanical locking means, the connecting means may com- prise a lower lip or locking strip which is formed inte- grally with the core. In such a case, it is particularly advantageous, as mentioned above, to impregnate the lower parts of the core with a property-improving agent, espe- cially an elasticity-improving agent, so that this lower lip or locking strip obtains optimal properties for its intended function. Within the scope of the invention, however, such a locking strip can also be made of a dif- ferent material, for instance aluminum, and in that case the parts of the core which form the attachment for the separate locking strip can advantageously be impregnated with such a property-improving agent in order to further increase the core's capability of retaining the attached locking strip.

According to this embodiment, the problem of providing a material seal has thus been solved by the core, and thus not the completed joint edge, being impregnated in the areas where the joint system will later be formed. The impregnating agent can be caused to penetrate so that the upper part of the core closest to the front side will be impregnated in an area where the joint edge will later be formed. Then the core is coated with a surface layer on its front side and preferably also a balancing layer on its rear side. The board ele- ment or the floorboard will thus contain parts where the core under the surface layer is impregnated. The board element is sawn, where appropriate, into floorboards hav- ing edge portions within which the core under the surface layer is impregnated. The edges of the floorboards are then machined and the completed floor panels will have upper joint edge portions which are impregnated.

An impregnating agent can be applied to the surface of the core and/or in the parts of the core under the surface using methods which do not require the impregna- tion to take place from the joint edge of the machined joint systems.

The main advantage of a joint system made according to this manufacturing method is that the impregnating agent can be applied without actually requiring tole- rances. A further advantage is that the production line in the manufacture of board elements may have a high capacity although the impregnation is carried out at a relatively low speed since the impregnation takes place in connection with the production of the large board ele- ments which are later divided into a plurality of floor- boards, and not in connection with the individual edge machining of the floorboards. The impregnating material can also be allowed to penetrate into the core during a relatively long time.

Further advantages are that the method allows impregnating material to be applied directly under the surface layer in areas adjacent to the completed joint edge, i. e. in the upper joint edge portion, and to have a significantly greater extent horizontally from the joint edge towards the floor panel compared with what can be achieved by impregnation from the joint edge of the floor panel after this has been machined for making the connecting means. A further advantage is that all corners will have joint edge portions that are impregnat- ed. Since the joint is formed after impregnation, any swelling in connection with the impregnation will not affect the joint geometry, nor will there be any impreg- nating residues on the joint surfaces or on the surface layer closest to the joint edge.

One more advantage is that the impregnating result can be checked by measuring the swelling of the core, the board element or the floorboard in portions where the joint edge will be made and in another, not impregnated, part of the panel at a distance from this joint edge, for instance closest to the central part of the floor panel to be.

The impregnating result can be ensured before the final machining of the floor panels is made and this can result in a higher capacity and a considerable saving in costs in the form of a smaller amount of rejects.

This method of providing a material seal is suitable for all fiberboard-based core materials such as homoge- neous wood, plywood consisting of a plurality of veneer layers, materials consisting of wood blocks glued toge- ther, fiberboard of the type HDF and MDF, particle board, flake board (OSB) and the like. The method can also be used in other core materials which, for instance, do not contain wood fibers and which do not swell when exposed to moisture but where the intention above all is to obtain impregnation of certain parts with a view to pro- viding an edge reinforcement.

In principle, all impregnating material available on the market can be used which contribute to increasing the protection against moisture in wood or fiberboard- based materials. However, it should preferably be pos- sible to apply them in liquid form, and they should have such properties as to allow surface layers to be applied to the core using such prior-art application methods as gluing, direct lamination, varnishing, calendaring or coating of plastic films or the like by extrusion, optionally in connection with grinding or application of primer layers and the like with a view to improving adhe- sion. As non-restrictive examples of usable impregnating materials, polyurethane, phenol and melamine can be men- tioned. The impregnating liquid can be applied in diffe- rent ways, for example, by spraying. Other methods, which are very difficult to use in the systems that are used today for impregnating machined joint edges of a com- pleted floor panel, such as rolling, spreading, inject- ing and the like, function in an excellent fashion in connection with the present invention. The penetration of impregnating agent into the core can be facilitated by applying heat, vacuum, pressure or the like, optionally in combination with e. g. grinding of the surface of the core before application of the impregnating agent. Grind- ing of the impregnated core can also take place before applying the surface layer so as thus to remove any swollen surface parts before applying the surface layer.

Vacuum and grinding of surface parts cannot be used when impregnation is carried out from the joint edge, and several of the methods described above are also consider- ably more difficult to use when impregnating from the joint edge.

It is also possible to make grooves in the core in areas that will later constitute joint portions of the floor panel. The impregnating agent can then be applied both from the surface of the core and from the edges of the groove. Different layers having different properties can also be applied. Rolling or spreading is particularly advantageous in the cases where the impregnating agent contains substances, which are not environment-friendly such as polyurethane (PUR) with isocyanate. When rolling on the impregnating agent, it is possible to use, with- in valid limits, up to 10 times more isocyanate than if application takes place by spraying.

The impregnating method can also be used to rein- force the edge. Various chemicals, such as those mention- ed above, can be supplied in liquid form which after cur- ing or solidification reinforce the wood fibers and give the joint edge a higher compression, shearing or impact strength or elasticity. The preferred method is, parti- cularly suitable to provide a moisture-proof but also strong joint edge with the aid of e. g. thermosetting plastics such as melamine or phenol which as a rule require both heat and pressure to cure. Direct lamination of the surface layer in fact takes place at a high tem- perature and under high pressure, and in connection with this operation also the impregnating layer can be cured.

Hot-gluing of surface layers can also cause curing or drying. This method can be used in combination with mois- ture impregnation.

Different layers can also be produced by, for instance, a two-step impregnation where the first impreg- nating step is made with an agent that penetrates deep under the surface of the core and gives increased protec- tion against moisture, while the second impregnating step is carried out with an agent which, for instance, has a different viscosity or other curing properties and which results in a strong joint edge immediately under the sur- face layer. In this way, for instance direct-laminated floor panels can be produced which have reinforced joint edge portions, whose properties can be equivalent to or better than the considerably more expensive laminate floors which have a surface layer of high pressure lami- nate.

The embodiment above is intended to be used in order to change the properties of the core by adding different materials before application of the surface layer in those parts of the core which will constitute the joint edge portions of the floor panel.