DUCT MEANS FOR AN AIR FLOW OR A GAS FLOW AND A METHOD FOR MANUFACTURING, HANDLING AND MOUNTING SAID DUCT MEANS

TECHNICAL FIELD

The present invention relates to a ventilation duct comprising a fibre material and at least one fluid impermeable surface material, with an erect position with a polygonal cross section, and a flat storage position, wherein the walls are rigid enough to keep the duct open in its erect position, and there are fold lines provided for switching the duct between its erect and its folded positions respectively.

The invention also relates to a blank for forming a ventilation duct, comprising a web of a fibre material with at least one fluid impermeable surface material, wherein longitudinal fold lines are provided, making the blank foldable into a polygonal tube shape.

Finally, the invention relates to a method of manufacturing a ventilation duct including the step of laminating a fibre material with at least one fluid impermeable material.

BACKGROUND ART

The ventilation ducts used today are mostly made of galvanized steel. In said ducts air shall be transferred in an over pressure or an under pressure hardly exceeding 100 mm water column (i.e. 1 kPa). Considered from an environmental point of view, venting ducts made of steel is a very doubtful choice. Besides the fact that steel for use in venting ducts is galvanized, it is also very space demanding when transported.

The demands which must be met by ventilation ducts are:

- They must not influence the quality of the air.

- They must be possible to clean.

- They must fulfil the tightness standards.

- They must meet up to the fire classifications, which first of all are about not supporting any spreading of fire and flue gases.

- They must not act in such a way that they will hinder an escape during fire.

- The material in the ducts should meet up to the European fire standard A2sldO, where A2 stands for the material being practically unburnable, si that the material does not create too dark flue gases and dO that it does not drip when heated.

As a venting duct transfers heat, this must be compensated for when passing from one fire cell to another. This is often done by insulating the duct in such an extent that the temperature rise in the cell not exposed to fire is deemed to be acceptable.

A duct of steel is rigid and keeps its shape even at very high temperatures. This means, at the passage from one fire cell to the next, that a fire valve has to be installed which closes when smoke is detected. In such a way flue gases are prevented from spreading from one fire cell to another. These measures are expensive and for that reason never used e. g. in passing a wall within a fire cell, even if it would have been beneficial to do so.

Ducts of steel are relatively difficult to handle, to cut and to mount. A great amount of handcraft skill and often more than one person are needed in the handling and mounting process of a steel duct.

Further, US 3 818 948 discloses a duct the walls of which are made from an insulating blanket having laminated on both sides thereof inner and outer facing sheets. The facing sheets are made from a cloth backing laminated to a polyethylene film and the insulating blanket is made from glass fibres or any other suitable

insulating material. In the side walls of the duct there is provided stiffening elements in the form of short lengths of metal wire. The metal wires are bonded to the inner facing sheet and are surrounded by the insulating material.

This duct is flexible and could be flattened for compact transportation.

The duct according to US 3 818 948 is made in short lengths and is used as connectors or elbows. As it is flexible it is not self-supporting and could not be used in long conduits.

PROBLEM STRUCTURE

The main object of the present invention is to provide a duct for air or gas flows and a blank and a method for manufacturing said duct, thereby achieving a solution to the problems mentioned above concerning expensive materials, expensive transports and storing, negative impact on the environment, complicated handling and mounting. The invention also prevents fire from spreading.

In view of the prior art, the main object is to provide a duct which is both collapsible to a flat condition and rollable, and yet self supporting in a working position.

Yet another object is to obtain a duct allowing a reduced building height and a mounting directly in connection to a wall or to a ceiling.

Still another object of the present invention is to obtain a duct for air flows or for gas flows which may easily be cut to correct lengths using a knife or a pair of scissors.

A last object of the invention is to make mounting possible even to a single and inexperienced worker.

SOLUTION

The above mentioned objects of the present invention are obtained if the ventilation duct intimated by way of introduction is characterized in that it is reliable in its storage position and self-supporting in its erect position, by the provision of alternating soft and rigid portions in its walls.

Regarding the blank the objects are attained if it is characterized in that transverse, alternating soft and rigid portions are provided, making the blank reliable.

Regarding the method the objects are attained if it is characterized in that it includes the step of embossing rigid and soft areas on the blank, by selectively applying heat and pressure in different areas.

Further advantages of the invention are presented in the sub-claims.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present embodiment will now be described in greater detail hereinbelow, with reference to the accompanying drawings. In the accompanying drawings:

figure 1 is a perspective view of a ventilation duct according to the invention in a mounted position;

figure 2 is a perspective view of the ventilation duct according to figure 1 ;

figure 3 is a close up view in cross section of a corner area of the ventilation duct according to figure 1 ;

figure 4 is a schematic view of the layer structure in the walls of the ventilation duct;

figure 5 is a perspective view of the ventilation duct in a storage position and partly rolled up;

figure 6a is a perspective view of a section of a blank for forming a ventilation duct according to another embodiment of the invention; and

figure 6b is a view in cross section of the blank.

DESCRIPTION OF A PREFERRED EMBODIMENT

In the following description, the invention will be described in connection to a use as ventilation duct which does not exclude other uses, e.g. for evacuating flue gases. Generally the duct is well suited for transporting a fluid, especially a gas.

In figure 1 a portion of a ventilation duct 1 according to a preferred embodiment of the invention is shown. The shown portion of the duct 1 has a rectangular cross section, and is mounted hanging from a building structure, such as a ceiling, by means of a suitable suspension means such as threaded bars or wires 2 and brackets 3.

The wires 2 are preferably of metal or any other suitable, fire resistant material. The brackets 3 are likewise manufactured from metal, in the preferred embodiment from sheet metal.

As can be seen in figure 1, the distance between two adjacent brackets 3 widely exceeds the length of each bracket 3. In the preferred embodiment the distance is up to approximately 2-3 m. Along the distance between the brackets 3, the duct 1 is rigid enough to be self-supporting. This means that a duct 1 hanging freely between two brackets 3 spaced apart 2-3 m will not hang down to any substantial degree. Also, although the brackets 3 support the duct 1, they do not assist in keeping it open. The rigidity of the duct 1 is sufficient to keep it open during normal conditions, i.e. in the absence of a fire.

Figure 2 shows a view where a number of rigid areas 10, acting as stiffening ribs, and soft areas 11 are visible on the outside of the duct 1. Both the rigid 10 and the soft areas 11 are formed integral with the walls 5, 6 of the duct 1. Also, there are fold lines 13 along the corner areas where adjacent walls 5, 6 meet. The fold lines 13 also have the function of longitudinal stiffening ribs.

The rigid areas 10 are preferably formed by pressing a fibre material, which is comprised in the duct walls 5, 6, to a high density with a small outer dimension in selected areas. The original material is preferably uniform in thickness and composition, but different areas will be compressed to a different extent. The ribs or rigid areas 10, which have been compressed to a high extent, are thus compact and has a high relative content by volume of fibres and binding agents, and a low relative content by volume of air. The rigid areas 10 are thereby resistant to deformation.

The soft areas 11 , on the other hand, have a higher relative content by volume of air and a lower relative content by volume of fibres and binding agents, as they have been less compacted, although both the rigid areas 10 and the soft areas 11 have been produced from a material with a uniform and much bigger original thickness. The content of the binding agent must not be so high that the fibres in the soft areas

11 are completely fixed mutually into a rigid structure, but they are to a high extent free to move in relation to one another.

As mentioned above the rigid areas 10, i.e. the stiffening means, are integral with the material of the duct walls 5, 6. This means that the stiffening means are constituted by the wall material itself, particularly the fibre material and the hinder therein. No separate stiffening means need to be inserted into the walls 5, 6.

The soft areas 11 are less compact, a fact which gives them several desirable properties. First of all, they are less rigid than the rigid areas 10, i.e. they are fairly easily deformable, taken by themselves. This allows for rolling of the duct 1, even though it has rigid areas 10 which are hard to bend or otherwise deform. By placing the rigid areas 10 and the soft areas 11 alternating on the duct 1, or a blank for a duct 1, the duct 1 as a whole will be possible to roll when in a flattened condition as seen in figure 4, particularly as the rigid areas 10 have a limited extension in the direction of rolling, i.e. the longitudinal direction A of the duct. In the roll, the soft areas 11 are at least partly deformed, while the rigid areas 10 remain substantially unbent.

The alternating rigid and soft areas 10, 11 also makes the duct 1 flexible to a certain degree in the directions mainly perpendicular to the walls 5, 6 of the duct 1. This flexibility makes installations between non-aligned points possible, without the need for angled connectors and multiple joints. The bends of the duct 1 must not be too sharp, but a bending radius of approximately Im and upwards is possible in the preferred embodiment. In this way, most ventilation openings at different heights, or openings that are laterally displaced, are easily connectable provided that the distance between them is long enough to allow smooth bends.

Between the soft areas 11 and the rigid areas 10, there are narrow hinge zones 15 with a very limited thickness. Although they are very compact, regarding the fibre

content by volume, their limited thickness allows for bending in these zones during rolling, especially at the borders to the soft areas 11, respectively.

The thickness and higher content of air in the soft areas 11 contribute to good sound and heat insulation properties of the duct walls 5, 6.

As is disclosed in figs 1, 2 and 4, in the preferred embodiment, all the walls 5, 6 are of the same general design with alternating soft 11 and rigid 10 areas and hinge lines 15; they could even be fully identical. However, embodiments are also conceivable where the walls 5, 6 are of different design. Thus, it would be possible that two opposing walls in a square duct have no or a lower number of rigid areas 10 than the remaining walls. Also the opposite would be possible.

The corners 14 of the duct 1, having a polygonal cross section, e.g. square, are formed in particular areas, with fold longitudinal lines 13, where the thickness of the material is approximately the same as in the hinge zones 15. Still, the original thickness of the material was the same even in these areas, but the degree of pressure, that has been applied, has been adapted to obtain the minimum thickness. This thickness is low enough to allow bending of the material to form the corners 14 of the duct 1, while the formed corners 14 in the erect duct 1, due to their angles, act as stiffening ribs and increase the rigidity of the erect duct. Hence bending of the duct 1 is possible mainly perpendicular to the walls 5, 6. The folding lines 13 at the corners 14 also contribute to the self-supporting properties of the duct 1, i.e. its rigidity is high enough, in relation to its weight, to prevent the duct 1 from unwanted bending or sagging, even over considerable duct lengths.

The inside 16 of the duct 1 is impermeable for fluids, especially air; to provide a useful duct for ventilation purposes, where air has a certain positive or negative pressure in relation to the ambient air outside the duct 1. It is of course also possible to transport other fluids, especially gases, in the duct 1.

Further, the inside of the duct 1 is preferably smooth, without creases or nooks, in order to make the cleaning thereof as easy as possible. The use of a plastic film, e. g. manufactured from polyethylene or polypropylene as an inner layer 17, displays a combination of the required properties concerning impermeability and surface smoothness. Another suitable material is aluminium foil, which is mainly inorganic, and a good choice for reasons of fire prevention. Possibly, two or more materials may be combined in a laminated inner surface layer 17.

Further contributing to the smoothness of the inside 16 of the duct is an absence of joints of the duct 1 or the materials therein. Thus, the duct 1 is preferably manufactured from continuous webs of materials, and the duct 1 is cut into suitable lengths at the building site. Also, a reduced number of transverse joints will reduce the pressure drop in a ventilation system as a whole.

In order to obtain a maximum smoothness of the inside of the duct 1 at its corners 14, two fold lines 13 are provided a short distance from each other as is shown in figure 3. Instead of one single fold, where the inner angle would be approximately 90 degrees in a duct 1 with a rectangular cross section, two separate folds, with an inner angle of approximately 135 degrees respectively, will result at the fold lines 13. This reduces the risk of excess material at the folds forming undercut nooks, which would be hard to clean, at the inside of the duct 1. Another option is to arrange the fold lines 13 in groups of three, so that there will be three inner angles of 150 degrees respectively.

Figure 4 shows the structure of the walls 5, 6 of the duct 1. The inner layer 17 is thin, preferably a film. As mentioned above, the inner layer 17, which will be facing the inside of the duct 1, may be a polyethylene film or a polypropylene film, but may also be aluminium foil or a viscose layer, which is coated with silicone. For

some applications, antistatic properties of the material in the inner layer 17 are important.

Suitable materials for the main layer 18 of the duct lare fibre materials such as glass wool or mineral wool. There is preferably a binding agent in the fibre material, so that the fibre material may be pressed into a particular shape, but the content of the binding agent should not be so high that rigid fibre structures appear in the areas 11 that are intended to be soft.

An outer layer 19, which is optional, provides the duct 1 with a pleasant surface appearance. The surface should be easy to clean, but must not necessarily be impermeable, in order to let possible humidity and condensate in the main layer 18 evaporate into the ambient air. A suitable material for the outer layer 19 is a non- woven material of viscose etc.

The ducts will not transfer heat and they will preferably shrink if they are exposed to temperatures of 70 to 100 degrees centigrade or more, which means that the spreading of flue gases will be minimized even within a fire cell.

Inspite of being self-supporting, the duct is soft to a certain degree, which means that fire tape, which expands when it is subjected to heat, can be used when passing through fire cells. In this way the duct may be sealed off by the expanded tape in case of a fire. This is less expensive than the corresponding necessary arrangements in ducts made of steel. Apart from that, the duct preferably includes more than 90% of inorganic material, which means that the amount of burnable material in the duct itself is minimized, which makes the duct itself fire resistant.

Thus an inorganic material is used at least in the main layer 18 in the preferred embodiment of the invention and such an inorganic material may very well be based on a volcanic mineral, but in the preferred embodiment nonwoven fibre cloth is

used in the walls of the duct. In the present case, an unburnable fibre of the type glass fibre and/or rock wool fibre are used. The core of the duct wall consists of either of these fibres or both fibres in combination and constitutes more than 90 % of the total weight of the final product. Thus the content of binders is less than 10 % of the total weight.

The duct may assume an erect position as well as a storage position. The erect position is shown in figures 1 and 2. In the storage position, which is shown in figure 5, the duct 1 is folded over along at least one of the fold lines 13, so that the inside surfaces of the duct 1 are in a face-to-face contact. In the flat storage position, the duct 1 may be rolled, in order to form a roll 20, which is compact and thus well suited for transport and storage. An outer package may be applied on the roll 20, according to processes which are known by the person skilled in the art.

As mentioned above, the rolling of the duct 1 in its storage position is made possible by providing hinge zones 15, as well as soft areas 11, which are bent or compressed during rolling.

The duct 1 has an air tight or fluid impermeable inner layer 17 and a conformed core in the fibre cloth so that the duct 1 will be isolated against condensate by its impermeable inner layer 17 or coating. The duct 1 will also be manufactured with a non-sealed outer layer and a conformed core in the fibre cloth in such a way that the duct 1 will insulate both regarding noise and regarding heat losses.

In cases where the duct 1 is transporting a flow of cold fluid through a humid environment at elevated temperatures it is essential that also the outer layer 19 is fluid impermeable to prevent condensation within the main layer 18 of the duct.

Thus, the duct 1 has a low weight, which makes it easy to transport and mount. The fibre material in the main layer 18 is of the same type as in heat and sound

insulation, and will thus improve the properties of the duct 1 in these respects, compared to the prior art. The inside of the duct 1 is easy to clean, due to its inner layer 17, and the arrangement of pairs of fold lines 13 in the preferred embodiment will further facilitate cleaning.

Three views of a section of a blank 21 for forming the duct 1 are shown in figures 4, 6a and 6b, where figure 6a refers to an embodiment with triangular cross sectional shape. In the preferred embodiment (figures 4 and 6b), the blank 21 is a continuous web, where the pattern of alternating rigid areas 10 and soft areas 11 is repeated. The rigid areas 10 and the soft areas 11 , as well as the hinge zones 15 between them extend mainly in the transverse direction of the blank 21.

Fold lines 13 extend in the longitudinal direction A of the blank 21 between the columns of repeated rigid areas 10 and soft areas 11. The fold lines 13 are substantially parallel with the lateral edges 22. As mentioned above, the fold lines 13 are arranged in pairs in the preferred embodiment, in order to obtain corners 14 according to figure 3 in the erect position of the duct 1.

The rigid areas 10 and the soft areas 11, and the hinge zones 15 between them are arranged in a single layer on the blank 21 , which has not yet been folded. Hence, the blank 21 is reliable to at least the same extent as the duct 1 in its storage position.

In order to obtain the duct 1 from the blank 21 , the blank is folded over, as shown in figure 5. The two lateral edges 22 of the blank 21 will be arranged next to each other. Any method known in the art for joining the lateral edges 22 may be used, such as gluing, heat lamination or the use of adhesive tape. Thereafter the blank 21 has been formed into the tube-shaped duct 1, in its storage position.

The method of manufacturing starts from a fairly thick web or mat of fibre material, which has been manufactured in a way which is well known for a person skilled in

the art. In the preferred embodiment the thickness of the web is approximately 50-100 mm, preferably 80-90 mm. If the web consists mainly of glass wool, a surface weight of 500-2000 g/m ² , and preferably 600-800 g/m ² has been useful in practical tests (at least for small ducts being about 12x12 cm).

First the outer layer 19 (if any) is laminated onto the main layer 18 in a conventional way, known to the person skilled in the art.

In the next step of the manufacturing process, there is a thin coating or inner layer 17, applied on that side of the blank which is to be the inside of the duct 1, which coating preferably consists of a product of pure hydrocarbon e.g. polyethene or polypropylene. It is impermeable and does not emit gases to the air and is durable enough to withstand cleaning. Preferably the inner layer 17 is in the form of a film, or an aluminium foil, which may be laminated onto the main layer 18. The lamination of the inner layer 17 may also take place at the same time as the lamination of the outer layer 19 or afterwards.

The outside of the duct 1 does not have to be covered by a specific coating. The outer fibres of the nonwoven fibre cloth in the outer layer 19 may be sprayed with a glue to create a proper outer surface. The outer layer 19 may, in fact, also be a woven material, and could e. g. comprise glass fibres and a fire retarding agent.

In the next step the pattern of alternating rigid areas 10 and soft areas 11, as well as the hinge zones 15 and the fold lines 13, are pressed, or embossed, into the outer surface and further into the main layer 18, which hinge zones 15 and fold lines 13 will be used as notches to make the duct 1 suitable for rolling, bending and mounting in a rational and simple way. Simultaneously with the application of the pressure, heat may be applied. During this process the inner layer 17 is supported on an even and smooth surface.

In a preferred embodiment, the pressure is kept constant during a time period of approximately 7 seconds or more, and the temperature is approximately 200 degrees Celsius. Other combinations of temperatures and pressure times are possible, and will be realised by the person skilled in the art. The heat may be applied by contact with heated elements, such as an embossing matrix or roll, but the heating could also be performed with hot air, microwaves etc.

An alternative to direct application of pressure and/or heat is the employment of needle-felting, for creating the rigid and soft areas 10, 11. Additional portions of fibre material are bonded to the web in selected areas, by repeated punching of a set of needles through the web and the additional portions, until they are joined by felting of the fibres.

The rigid areas 10 are pressed so as to assume a thickness in the range of 6-10 mm, preferably approximately 8 mm in the preferred embodiment, i.e. into a thickness of approximately 1/10 of the original thickness of the material. The hinge zones 15 are even thinner and have a thickness in the range of 1-4 mm, preferably approximately 2 mm in the preferred embodiment. This means that these zones 15 have been pressed so as to assume a thickness of approximately 1/40 of the original thickness of the material. Finally, the soft areas 11 are pressed to assume a thickness of about 12-16 mm or about 1/7 to 1/5 of the original thickness.

In order to facilitate the bending at the fold lines 13, the fibres are preferably pre-treated, or broken, by bending the blank 21 at the fold lines 13 over an edge or by applying a narrow roll along each fold line 13, which is arranged so as to be aligned with a corresponding recess.

In the finishing step the blank 21 is folded and glued, taped or melted along its longitudinal edges 22 to make a flat duct 1, which is cut into appropriate lengths, which are rolled up, and are ready to be delivered.

The recesses pressed into the outer surface are on one hand longitudinal, i.e. the fold lines 13, and on the other hand transversal, i.e. the hinge zones 15. The longitudinal recesses are four if the duct has a rectangular shape. For the preferred embodiment of figure 3, there will be four pairs of fold lines 13. Thus there may be more or less longitudinal grooves depending on the wanted shape of the final duct 1.

In a rectangular duct 1 the recesses are made in such a way that the duct 1 may be folded to a flat unit being reliable to a final package. The longitudinal recesses may also be used to facilitate the mounting of the ducts 1. The transversal recesses, or hinge zones 15, are necessary to make it possible to roll the duct.

The transversal recesses also act as reinforcements of the duct to give it an increased stability enabling its self-supporting properties.

On the building site where the duct 1 is to be installed, the duct 1 is first unrolled from the roll 20 in its storage position. Appropriate lengths of the duct 1 are cut from the roll 20. By separating the walls 5, 6 that are in surface contact with each other, and by making folds at the fold lines 13, which were previously not folded, the duct 1 is given the shape of a tube with a polygonal cross section, and its erect position is obtained.

The duct 1 is then mounted at the desired position in the building, and connected to suitable ventilation means, such as fans and the like.

Due to its hinge zones 15, and its soft areas 11, the duct 1 can be bent to a certain degree in a mounted, erect position, i.e. be allowed to be changed in direction, both sideways and between different levels, the bends having a minimum radius of about 1000 mm, as discussed previously.

The invention may be modified without departing from the scope of the appended claims.