METHODS, AND PRODUCTS PRODUCED BY SUCH METHODS

Technical Field

The present invention relates to methods and products manufactured using such methods. In particular, the present invention relates to thin layers of material and methods of processing such layers of material for improving properties of products manufactured using the processed layers of material.

Background

Thin layers of material is commonly used to produce thicker and more robust products. For example in the woodworking industry plywood is a product manufactured from thin layers of wood veneer that are glued together with adjacent layers to form the final product. Another example of using thin layers of material in product manufacturing is described in WO2019/151933A1 by the same applicant, where individual cones of veneer are joined by means of an adhesive to form a robust cone-shaped product. The final product using such technology has proven to exhibit superior properties in terms of mechanical strength thus making it suitable to form light-weight, yet robust, furniture parts.

While the cited prior art provides a great advantage compared to previously known techniques there is still a need for improving robustness of the final product, as well as reducing material cost and production cost. Having this in mind, it would be desired to provide further improvements to methods and products using thin layers of material.

Summary

It is an object of the invention to at least partly overcome one or more of the above-identified limitations of the prior art. In particular, it is an object to provide a method for manufacturing a product of thin sheets of material, where at least one sheet is provided with punctures. When attaching the thin sheets by means of an adhesive, the inventors have surprisingly realized that the punctures assist in improving the adherence between the sheets, resulting in significant increase in terms of robustness and load bearing capabilities of the final product.

According to a first aspect a composite product is provided. The composite product comprises a plurality of material sheets attached to each other in a multi-layer structure by means of adhesive, wherein at least one material sheet is provided with punctures or perforations. Preferably, the composite product is obtaining its final shape during attachment of the sheets to each other. The at least one punctured sheet may be made of paper, paperboard, veneer, high-density fibreboard, medium-density fibreboard, plastic, metal, non- woven, textile, or any natural or synthetic fibre material.

The punctures or perforations may be extending entirely, or at least to some extent, through the sheet from at least one side of the sheet. Preferably, for certain products the material sheet forming the exterior side of the product may have no punctures or perforations extending to the outer surface of the material sheet. It should be noted that throughout this specification the terms “puncture” and “perforation” are used interchangeably, both meaning a minute depressions extending partly or entirely through the sheet.

The width of the punctures may be 20 mm or less, such as 10 mm or less, or such as 5 mm or less.

The punctures may be distributed in a perforation pattern across the at least one material sheet, and the centre-centre distance between two adjacent punctures may be in the range of 1-20 mm, preferably in the range of 1-10 mm, even more preferably in the range of 1-5 mm. The distance between two adjacent, or successive punctures may be greater than the dimension, such as the diameter, of a single puncture.

The adhesive may be a carbamide glue, or melamine glyoxylic acid / glyoxal resin glue.

The composite product may comprise a plurality of material sheets forming a core, and an outer material sheet arranged on an exterior side of said core, wherein at least one of the material sheets of the core is provided with punctures.

The outer material sheet may have an exterior surface, wherein no punctures are exposed on said exterior surface of the material sheet.

The composite product may be planar thus forming a board or a beam, or tube-shaped thus forming a furniture leg, a cylinder, a lamp shade, or similar. The final shape of the composite product is preferably obtained as the sheets are attached to each other, such that no shaping is required after composite product is manufactured.

The total number of material sheets may be in the range of 2-100, preferably in the range of 4-15, even more preferably in the range of 5-12.

According to a second aspect, a material sheet is provided for use to form part of a composite product according to the first aspect. The material sheet is provided with punctures. The material sheet may further comprise an adhesive arranged at least to fill said punctures.

According to a third aspect, a method for manufacturing a composite product is provided. The method comprises i) providing a plurality of material sheets, ii) providing at least one of said material sheets with punctures, and iii) attaching said material sheets to each other in a multi-layer structure by means of adhesive.

The method may further comprise iv) shaping the material sheets to form a non-planar composite product. Preferably, shaping is performed simulatenously as attaching the material sheets to each other.

The method may further comprise v) applying the adhesive to the punctured sheet(s), wherein attaching the material sheets to each other is performed by a pressing action such that the adhesive is distributed inside said punctures.

Brief Description of the Drawings

The present invention will hereinafter be further explained by means of non-limiting examples with reference to the appended schematic figures where;

Fig. 1 is an isometric view of a planar product according to an embodiment;

Fig. 2a is an isometric view of a tube-shaped product according to an embodiment;

Fig. 2b is a cross-section of the product shown in Fig. 2a;

Fig. 3 is an isometric view of a product according to an embodiment;

Fig. 4 is an isometric view of a product according to a further embodiment;

Fig. 5a is a top view of a sheet forming part of a product according to an embodiment;

Fig. 5b is a top view of another type of sheet forming part of a product according to an embodiment;

Fig. 5c is a top view of yet another type of sheet forming part of a product according to an embodiment;

Figs. 6a-d are cross-sectional views of a sheet forming part of a product according to an embodiment;

Fig. 6e is a top view of a sheet forming part of a product according to an embodiment; Fig. 7a is a side view of a process for forming a multi sheet product according to prior art;

Fig. 7b is a photograph showing a fracture of a prior art product;

Fig. 8a is a side view of a process for forming a multi sheet product according to an embodiment;

Fig. 8b is a photograph showing a multi sheet product according to an embodiment;

Fig. 8c is a photograph showing a fracture of a product according to an embodiment;

Fig 9a is a side view of a perforation plate for use in manufacturing a sheet forming part of a product according to an embodiment;

Figs. 9b-c are side views of different manufacturing devices for producing a sheet forming part of a product according to an embodiment;

Figs. lOa-c are top views of examples of sheets for forming a tubular product according to an embodiment;

Fig. lOd is an isometric view of a manufacturing method for forming a tubular product using the sheets shown in Figs. lOa-c;

Fig. 11 is a side view of a manufacturing method for forming a tubular product according to an embodiment;

Figs. 12a-b are side views of a manufacturing method for forming a tubular product according to an embodiment;

Fig. 13a is an isometric view of a manufacturing method for forming a tubular product according to an embodiment;

Fig. 13b is a top view of a plurality of sheets for use with the manufacturing method shown in Fig. 13a

Fig. 14a is a top view of a sheet for forming a product according to an embodiment;

Fig. 14b is a top view of the sheet shown in Fig. 14a in an expanded state; and

Fig. 15 is a schematic view of a method according to an embodiment.

Detailed Description

Starting in Fig. 1 a first example of a composite product is shown. The composite product is in the form of a board la being formed by gluing several material sheets 10, or plies, in a layered structure. In the shown example five material sheets 10 are used to form the composite product la. In Fig. 2a another example of a composite product is shown, here in the form of a tubular furniture leg lb. The furniture leg lb is actually cone-shaped, as will be further explained with respect to Figs. lOa-d. The furniture leg lb is preferably hollow, whereby the robustness of the furniture leg lb is provided by the cone body. A cross-section of the furniture leg lb is shown in Fig. 2b. Eight material sheets 10 are arranged in a layered structure to form sufficient rigidity. As indicated in Fig. 2b, the exterior material sheet 10’ may be made of a material being different from the interior material sheets 10 in order to obtain a desired pattern or look of the furniture leg lb.

In Fig. 3 another example of a composite product is shown, here in the form of a lamp shade lc. The lamp shade lc is made by a cone-shaped multi layered structure formed by multiple material sheets 10. In the shown example, five material sheets 10 are used to form the rigid lamp shade lc. As for the furniture leg lb, the exterior material sheet 10’ of the lamp shade lc may be chosen to have a material which fits with the desired looks of the lamp shade lc.

In Fig. 4 another composite product is shown, here in the form of a beam Id. The beam is formed by multiple plies, or material sheets 10, bonded by means of adhesive to form a rigid product Id with specific load bearing capability. It should be realized that the rigidity of the beam Id is dependent on the number of plies 10 used, as well as the material and physical properties of each ply 10.

It should be realized that while some specific examples of composite products are given with reference to Figs. 1-4, the herein presented products and methods could be used for a great number of additional composite products having various purposes. In principle, the described products and methods are advantageous for all composite products being formed by material sheets being arranged in a multi-layered structure. Such products may include boards, beams, tube-shaped or cone-shaped products e.g. forming furniture legs, cylinders, lamp shades, waste baskets, floor boards, bed slats, shelves, honeycomb structures, or similar.

Now turning to Figs. 5a-c, examples of material sheets 10 for use with the present invention will be discussed. When forming a composite product la-d, at least one material sheet 10 is provided with punctures 20, indicated by circular dots. The punctures 20 are preferably relatively small, and distributed across at least some area of the material sheet 10. Starting in Fig. 5a, a material sheet 10 is shown where punctures 20 are distributed evenly across the entire area of the material sheet 10. The punctures 20 are arranged in rows and columns, wherein the centre-centre distance between two adjacent punctures 20 is substantially constant for the entire material sheet 10.

In Fig. 5b another example of a material sheet 10 is shown. Here, the entire material sheet 10 is provided with punctures 20. However, in this example there is no constant distance between the punctures 20 but they are instead distributed in a more random pattern. The centre-centre distance between two adjacent punctures 20 may vary up to several 100 percent, as indicated in Fig. 5b.

In Fig. 5c the material sheet 10 is divided into sections lOa-c. A first section 10a is provided with punctures 20 in a first pattern. A second section 10b is provided with punctures 20 in a second pattern, while in section 10c there are no punctures. The punctures 20 of sections lOa-b are indicated as dotted areas. For example, the punctures 20 of the first pattern may have a relatively small centre-centre distance while the punctures 20 of the second pattern may have a relatively large, or non-constant, centre-centre distance. Alternatively, or in combination, the punctures 20 of the first pattern may have a first size, while the punctures 20 of the second pattern may have a second, or varying size.

The examples shown in Figs. 5a-c should be considered non-limiting; for example, a material sheet 10 may be divided into far more sections than three, wherein the punctures 20 are provided differently in at least some of the section. “Different” should in this context be interpreted as a measure for the punctures 20 per se, and/or the distribution pattern of the punctures 20 (i.e. how a puncture 20 is distributed with relation to other punctures 20 within the same section). Yet further, there is no need for a clear border between adjacent sections lOa-c. Instead, the puncture pattern of one section 10a may gradually change to the puncture pattern of an adjacent section 10b.

Preferably, the distance between two consecutive punctures 20 is greater than the diameter of a single puncture 20.

In Figs. 6a-d punctures 20 are shown. Starting in Fig. 6a, the puncture 20 is extending entirely through the material sheet 10. The cross-section of the puncture 20 is somewhat tapered.

In Fig. 6b the puncture 20 is also extending entirely through the material sheet 10, but the cross-section of the puncture 20 is substantially constant. Such puncture 20 may e.g. be provided by a punching action of the material sheet 10.

In Fig. 6c the puncture 20 corresponds to the constant-diameter puncture of Fig. 6b, but here the puncture 20 is not extending entirely through the material sheet 10, but the material sheet 10 is intact as seen from the underside. Shallow punctures 20 are shown in Fig. 6d, i.e. they do not extend entirely through the material sheet 20. The punctures 20 are tapered, similar to the puncture of Fig. 6a. In this embodiment punctures 20 are provided on each sides of the material sheet 10.

The examples given in Figs. 6a-d provides some alternatives for the configuration of the punctures 20. It should be noted that the embodiments could be combined for a single material sheet 10, i.e. a material sheet 10 could be provided with tapered punctures, constant diameter punctures, shallow punctures, and/or punctures extending through the entire material sheet 10, or any combination thereof.

In Fig. 6e puncture shapes are exemplified. Seen from above, the puncture 20 may be quadratic, triangular, circular, polygonal, elliptic, or rectangular. In fact, any suitable shape of the puncture 20 may be feasible as long as it allows for adhesive to flow into the puncture 20 during production of the composite product la-d.

A composite product is thereby formed by arranging a plurality of material sheets 10 in a layered structure. At least one of the material sheets 10 is provided with punctures 20, as explained above. Combinations of punctured/perforated material sheets and non-perforated/non-punctured material sheets can be formed in various ways. In one example, all material sheets 10 except the exterior material sheet 10 of the composite product are provided with punctures. However, the exterior material sheet 10 may in some embodiments be provided with punctures, although the punctures do not extend to the outside surface of the exterior material sheet 10. In another embodiment, the exterior material sheet 10 is provided with punctures extending to the outside surface, such that the punctures will be visible on the composite product.

In Figs. 7a-b an example of a composite product lx according to prior art is shown, including the manufacturing process for such prior art composite product. For producing a tube-shaped product lx, a number of material sheets 10 are joined by applying an adhesive 30 onto the surfaces of the material sheets 10, and pressing the material sheets 10 towards each other as the adhesive is cured. Optionally, heat may be added during the pressing process in order to improve adherence between the material sheets 10. This is shown schematically in Fig. 7a, although only two material sheets 10 are shown. As can be seen in Fig. 7a to the right, the adhesive will penetrate to some extent into the material sheets 10 thereby improving the adherence between the material sheets 10. The exact level of penetration will depend on properties of the material sheets 10, as well as properties of the adhesive 30.

The composite product lx is formed by providing a large sheet of paper, and coating one side of the paper sheet with an adhesive. By winding the large sheet of paper, a tubular shape is accomplished. The paper tube, having eight layers of paper, is subsequently covered by a wood veneer. Importantly, none of the paper sheet or the wood veneer sheet is provided with any punctures.

For the current test, the paper was a 200gsm kraft liner resulting in a paper tube thickness of approximately 2.4 mm for the eight layers.

For testing the composite product lx it was subjected to an increasing load until the composite product broke. The resulting product lx, after breaking, is shown in the photograph of Fig. 7b. As is shown, the break is not a distinct cut but instead it can be seen that the paper has been subject to a delamination, especially visible in the encircled area of Fig. 7b. For the given test, the product lx broke at a load of 420 N.

An example of another composite product ly is shown in Figs. 8a-c, including the manufacturing process for composite product. For producing the tube-shaped product ly, also in this case a number of material sheets 10 are joined by applying an adhesive 30 onto the surfaces of the material sheets 10, and pressing the material sheets 10 towards each other as the adhesive is cured. This is shown schematically in Fig. 8a, although only three material sheets 10 are shown. Typically, the step of pressing the material sheets 10 towards each other is performed immediately after application of adhesive 30, i.e. no drying of the adhesive 30 is required prior to attaching the material sheets 10. Importantly, the material sheets 10 are provided with punctures 20. As can be seen in Fig. 8a, the adhesive will penetrate to some extent into the material sheets 10 in the normal direction thereby improving the adherence between the material sheets 10. The exact level of penetration will depend on properties of the material sheets 10, as well as properties of the adhesive 30. However, due the punctures 20 the adhesive will also flow into these cavities, and penetrate into the material sheet in substantially all directions. At locations where punctures 20 from different layers overlap, the adhesive will form an extended bond in the normal direction (which is the case for the upper two layers in Fig. 8a).

The composite product ly is formed by a method identical to the process described above with reference to Figs. 7a-b, i.e. by providing a large sheet of paper (however in this case the paper sheet is provided with punctures 20), and coating one side of the paper sheet with an adhesive 30. By winding the large sheet of paper, a tubular shape is accomplished. The resulting paper tube is shown in Fig. 8b. The small dots indicate that the adhesive has penetrated through the paper sheet, as explained above. The paper tube, having eight layers of paper, is subsequently covered by a wood veneer. For this example, no punctures 20 were provided on the exterior wood veneer.

For the current test, the paper was a 200gsm kraft liner resulting in a paper tube thickness of approximately 2.4 mm for the eight layers.

For testing the composite product ly it was subjected to an increasing load until the composite product broke. The resulting product ly, after breaking, is shown in the photograph of Fig. 8c. As is shown, the break is a much more distinct cut with substantially no delamination of the paper layers. For the given test, the product ly broke at a load of 600 N, i.e. an increase in load by almost 50% compared to the previous test of non-punctured paper.

The present invention provides the benefit of obtaining the final shape of the composite product already as the material sheets are attached to each other. Hence the composite product does not need to be an intermediate product for further processing and shaping.

In a preferred embodiment the adhesive 30 is applied to the material sheets 10 in a dry, or solid state. By using specific rollers or other applicators, a thin foil or layer of adhesive 30 may be applied to a material sheet 10. The material sheet 10, including a dry adhesive layer, can then be used for forming the composite product by the process described above, i.e. by arranging several material sheets 10 onto each other. For forming and attachment, the material sheets 10 may be heated such that the adhesive melts, and during this phase the composite product is formed to its intended shape. Thereafter cooling may be performed such that the composite product may maintain its desired shape.

Some examples of techniques used for perforation of the material sheets 10 will be discussed with reference to Figs. 9a-c. Starting in Fig. 9a, a general principle of providing punctures to a material sheet 10 requires the material sheet 10, and a perforation unit 40. Here, the perforation unit 40 is shown having a plurality of needles 42 projecting towards the material sheet 10. As the needles 42 engage with the upper surface of the material sheet 10 and is further pressed into the material sheet 10, the punctures will be formed. Although shown as sharp tips, the exact configuration of the projections 42 of the perforation unit 40 can be adjusted to create the desired punctures.

In Fig. 9b the perforation unit 40 is a perforation roller, rotating against an anvil roller to form a nip in which the material sheet 10 to be perforated is fed. The punctures will be provided as the material sheet 10 engages with the perforation roller 40.

In Fig. 9c the perforation unit 40 is a pressing unit moving downwards toward the material sheet 10. As the pressing unit 40 pushes into the material sheet 10, the punctures are formed.

Other examples of perforation techniques include punching, blasting, using suction or high pressure air, or using laser. In other embodiment the material sheet 10 can be provided with particles which upon removal leave punctures/perforations in the material sheets. Such particles may be solid particles which are mechanically removed, or the particles may be chemically removed by etching, dissolving, etc. For the case of punching, a combined process may be utilized where adhesive is injected directly into the punched holes/punctures, thereby providing a material sheet 10 having punctures 20, where the punctures 20 are pre-filled with adhesive.

Examples of manufacturing methods for producing tube-shaped composite products lb will now be described with reference to Figs. 10-13. Starting in Fig. 10, a first example is shown. In Fig. 10a a material sheet 10 is shown. The material sheet 10 has the shape of a truncated triangle. By bringing the long edges towards each other, a truncated cone is formed. Due to the straight upper and bottom edges, the final three-dimensional shape will not be a perfect cone.

A perfect truncated cone will instead be formed by a material sheet 10 as shown in Fig. 10b, however such pre-cutting of the material sheet 10 cause an increased material waste.

On this note, material waste is minimized by using a material sheet shape as shown in Fig. 10c. Two identical material sheets 10 may be formed by cutting a single material sheet at a non-perpendicular angle a, indicated in Fig. 10c.

When folding the resulting material sheet 10 to form a cone, the longitudinal joint between the long edges will twist along its length.

The tubular composite product lb is formed by arranging cones into each other, as illustrated in Fig. lOd. To the left a product lb is formed by four individual cones 3a-d, wherein each cone 3a-d is formed by folding a single material sheet 10. The outer surface of each inner cone 3b-d is coated by an adhesive so that the cones 3a-d adhere to each other. At least one cone 3a-d is formed by a perforated material sheet 10, i.e. a material sheet 10 being provided with punctures 20. Preferably, the inner cones 3b-d are formed by perforated material sheets 10, while the outer cone 3a is formed by a material sheet 10 having no punctures 20, or at least no punctures 20 extending to the outer surface of the material sheet 10. The outer cone may be formed by a sheet of wood veneer, while the inner cones 3b-d may be formed by perforated paper sheets 10.

To the right in Fig. lOd another example of a tube-shaped product lb is shown. Also here, the product lb is produced by joining cones 3a-b. The outer cone 3a may be identical to the outer cone 3a explained above, while the inner cone 3b may be formed by winding a sheet of perforated paper to a tubular, or slightly cone-shaped, structure. Adhesive may be applied between the cones 3a-b, as well as during the winding process to obtain the inner cone 3b.

In Fig. 11 another example is shown for producing a tubular product lb. Four material sheets 10 are provided, although any suitable number of material sheets can be used for spirally winding a tube. As the tube is rotated, preferably be means of a mandrel, continuous production is obtained. Preferably, the material sheet 10a forming the outer layer of the product lb is having no perforations, or at least no punctures 20 extending to the outer surface, while the remaining inner material sheets 10 are provided with punctures 20. Adhesive is applied before the material sheets are joined.

Another example is shown in Fig. 12a, illustrating a convolute winding process. A single material sheet 10 is convolutely wound for a plurality of turns about an axis R that is parallel to the longitudinal edges of the sheet 10. The material sheet 10 thus forms a tube having a plurality of layers defined by the sequential turns of the material sheet. As indicated in Fig. 12a, the material sheet 10 may have an end section 10a having no punctures, or at least no punctures extending to the exterior surface of the material sheet 10. The remaining part of the material sheet 10 may preferably be provided with punctures 20.

In Fig. 12b another variant of the method of Fig. 12a is shown. Here, the material sheet 10 is ring-shaped (see e.g. Fig. 10b) such that a perfect cone will be obtained as the material sheet 10 is wound. It should be noted that the material sheet 10 does not need to be perfectly ring shaped, but it may be cut at distinct angles instead of along a circular arc.

For all embodiments of a composite product described herein, it should be noted that even though it may be preferred to leave the outer or exterior material sheet without punctures extending to the exterior surface of the outer material sheet, it can still be advantageous to have adhesive penetrating to the exterior surface of the outer material sheet as it may improve adherence of paint or other substance being used for coating the final composite product. In Fig. 13a a linear process for forming a tube-shaped product lb is shown. A plurality of material sheets 10 are advanced linearly toward a mandrel such that they approach the mandrel in a direction substantially parallel to the mandrel axis. Forming tools (not shown) may assist in wrapping each material sheet 10 into a generally tubular shape around the mandrel. As indicated in Fig. 13b, preferably the material sheets are circumferentially staggered relative to one another so that the edges of one material sheet 10 are not circumferentially aligned with those of an adjacent material sheet. For improving robustness of the longitudinal joints, the material sheets 10 may have side sections 10a being provided with punctures 20. However, the entire material sheets 10 may be provided with punctures 20. Adhesive is applied to the material sheets 10 before joining.

The principle of providing material sheets 10 with punctures 20 can also be used with advanced forming of three dimensional forming, such as chair seats etc. In order to allow for more flexibility in forming, the material sheet 10 may be provided with slits 12 as indicated in Fig. 14a. When the material sheet 10 is rearranged in a non-planar shape, the slits 12 will allow the sheet 10 to expand in some directions as indicated in Fig. 14b. For creating a robust multi-layered product, the slitted material sheet 10 is provided with punctures 20.

When the material sheet 10 is bent or extended in some direction, the slits 12 will form spaces between rectangular parts 14 of the material sheet as indicated in Fig. 14b. The rectangular shape of the parts 14 is caused by the configuration of the slits 12, in this example being arranged in a cross-like pattern. However, it would also be possible to distribute slits 12 in other patterns, so as to form e.g. triangular parts 14 when the material sheet 10 is bent or extended in some direction.

So far, various aspects of the principle and use of perforated material sheets 10 have been described. As explained, the punctures 20 allow the adhesive to penetrate the material sheet 10 and form bonds between adjacent layers of the material sheets 10, as well as to create barriers for e.g. moisture. Yet further, as the material sheets 10 are preferably joined by a pressing action (possibly also adding heat to the pressing action), the punctures 20 will assist in removing excess air from the laminate, or at least to assist in evenly distributing the air thus preventing trapped air bubbles between the material sheets 10.

This principle can be used for a wide range of composite products, and in the following some examples will be given. For all examples, a material sheet having no punctures would mean that there are no punctures extending to the exterior surface of the material sheet. Hence, even if a material sheet is mentioned as having no punctures, there may be punctures on the inside of the material sheet. Example 1 board

Material Number of layers Punctures

Upper layer Wood veneer 1 No Core Paper 2-20 Yes

Bottom layer Wood veneer 1 No

Example 2 board

Material Number of layers Punctures

Upper layer Wood veneer 1 No Core MDF/HDF 2-20 Yes

Bottom layer Wood veneer 1 No

Example 3 beam

Material Number of layers Punctures

Upper layer Wood veneer 1 No Core Paper 2-100 Yes

Bottom layer Wood veneer 1 No

Example 4 beam

Material Number of layers Punctures

Upper layer MDF/HDF 1 No Core MDF/HDF 5-100 Yes

Bottom layer Wood veneer 1 No

Example 5 tube

Material Number of layers Punctures

Outer layer Wood veneer 1 No Core Paper 2-20 Yes Inner layer Paper 1 Yes

Example 6 tube

Material Number of layers Punctures

Outer layer Textile 1 No Core Paper 2-20 Yes

Inner layer Paper 1 Yes Example 7 tapered tube (e.g. furniture leg )

Material Number of layers Punctures

Outer layer Wood veneer 1 No Core Paper 4-15 Yes

Inner layer N/A N/A N/A

Example 8 lamp shade/waste basket

Material Number of layers Punctures

Outer layer Wood veneer 1 No Core Paper 2-10 Yes

Inner layer N/A N/A N/A

For all examples above, different configurations of the punctures may be considered. The following table provides guidance on how to select appropriate dimensions/patterns for the punctures.

Shape Tapered Depth Diameter Average C-C distance Pattern

Circular Yes Full 1 mm 2 mm Constant

Circular No Partial 2 mm 10 mm Random

Triangular Yes Partial 5 mm 30 mm Constant

Elliptic No Full 1 mm 3 mm Random

It should be noted that the above parameters could be combined and altered in order to form other configurations of the punctures.

Now turning to Fig. 15, a method 100 for producing a composite product is schematically illustrated. In a first step 102, a plurality of material sheets is provided. In a subsequent step 104, which may be performed during production of the material sheets, at least one of said material sheets is provided with punctures. In a step 106, the material sheets are attached to each other in a multi layer structure by means of adhesive.

An optional step 108 may be performed by shaping the material sheets to form a non-planar composite product. Step 106 of attaching the material sheets to each other may be performed by applying the adhesive to the punctured sheet(s), and wherein attaching the material sheets to each other is performed by a pressing action such that the adhesive is distributed inside said punctures.

The sheets of material 10 may be selected from various type of construction material such as paper, paperboard, veneer, high-density fibreboard, medium-density fibreboard, plastic, metal, non-woven, textile, or any natural or synthetic fibre material such as hemp, bamboo, carbon fibre, etc.

Preferably the material sheets 10 used to form the composite product are relatively thin; a paper sheet may e.g. have a thickness of 0.05 - 0.2 mm, a medium density fibreboard sheet may e.g. have a thickness of 3 - 30 mm, and a wood veneer sheet may e.g. have a thickness of 0.4 - 1 mm. However, perforation may also be used for significantly thicker sheets/pieces, such as dimensional lumber pieces, when such is used to form layered composite products, e.g. glulam beams.

The perforated material sheet will, when used as a layer in a composite product, provide improved robustness due to the adhesive forming a bond between adjacent layers, as well as assisting in the removal of trapped air. Also, the inventors have surprisingly realized that the provision of punctures also improve drying of the material sheets. This is particularly advantageous for wood veneer sheets, where the punctures will reduce the drying time during manufacturing of the veneer sheets. The punctures may also improve drying of the material sheet after wetting, e.g. by means of the adhesive used to attach the material sheet.

A perforated material sheet can be used for various composite products. In one aspect, the punctures of a material sheet are filled with a specific substance, such as plastic, paraffin, adhesive, cork, etc. Such substances can be used to further improve properties of the final composite product; when using paraffin, this will provide impregnation of the final composite product. Using cork, this will improve sound absorbing properties.

It is apparent to a person skilled in the art that the basic idea may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.