NL1042771B1 - Structural panel and method for providing such a panel - Google Patents

Abstract

The present invention pertains to a structural panel comprising at least one two- dimensional supporting layer and attached thereto a rigid structure that covers the supporting layer, which structure extends from one side of the supporting layer, wherein the rigid structure is a polygon structure made of pressed wood particles. The invention also pertains to a method for producing such a panel. (Fig. 1042771

Description

FIELD OF THE INVENTION

The present invention pertains to a structural panel, i.e. a panel having sufficient rigidity to be used as self-supporting building element, for example as a wall of a housing, it truck, boat, etc., and having the capacity to act as an insulating barrier for heat and optionally sound.

BACKGROUND OF THE INVENTION

Structural panels are known since the 1930’s of last century and commercially since the 1970’s. A huge advantage of such panels is that they can be made remote from an actual building site (i.e. a site where the ultimate construction is assembled, which construction could for example be a building or a mobile unit such as a container, truck or boat) under controlled circumstances to allow good and consistent quality, where after they are used to build a construction at an actual building site under less favourable circumstances. Nowadays, structural panels are commonly used in the

Ö 25 construction industry. In particular insulated panels, commonly in the form of a so-called sandwich panels, wherein a layer of an insulating material is sandwiched between two opposing two-dimensional supporting layers of a structural board material, are widely used in the construction industry for making buildings and other constructions. In such panels, also denoted as SIP-panels, the rigidity as well as the insulating properties comes about due to the central layer of a foamed material. Such panels in fact share the same structural properties as an I-beam or l-column. The rigid insulation core of the structural panel acts as a web, while the outer board or boards fulfill the function of the flanges.The board typically consists of sheet metal, plywood, cement, magnesium oxide board (MgO) or oriented strand board (OSB) and the core either expanded polystyrene foam (EPS), extruded polystyrene foam (XPS), polyisocyanurate foam, polyurethane foam or composite honeycomb (HSC. In the latter material innumerable thin aluminum hexagonal columns are gathered in a honeycomb form and bonded in a sandwich manner to metal or resin plates.

OBJECT OF THE INVENTION

It is an object of the invention to provide an alternative structural panel. It is a further object of the invention to provide for a method to produce such a panel.

SUMMARY OF THE INVENTION

In order to meet the first object of the invention a structural panel has been devised comprising at least one two-dimensional supporting layer and attached thereto a rigid structure that covers the supporting layer (providing structural rigidity to the panel), walls of which structure extend from one side of the supporting layer (not excluding that a second rigid layer may extend from the other side of the layer), wherein the rigid structure is a polygon structure made of pressed wood particles.

, In the present invention, the function of providing rigidity and insulation has been separated, contrary to the combined function a prior art foam material has in typical sandwich panels. This provides a higher degree of freedom to construct such panels.

The polygon structure which is made of pressed wood particles provides for the rigidity of the structural panel, and the open space in the polygon structure can be filed with an insulation material. This material may be as simple as gas (e.g. under vacuum), but can of course be any known or to be discovered insulation material. The polygon structure provides the opportunity to obtain maximum rigidity while using a minimum of material, still leaving a large open space. Honey comb panels are known as such, but typically with paper (cardboard), metal (typically aluminium) or plastic (3D printed) polygon structures. Applicant is the first to recognise that pressed wood can advantageously use for this purpose. The reason for this is clear: a polygon structure is a 3D structure of which the height is very large with respect to the thickness of the wall. Pressing of wood particles is used for producing articles that have completely contrary properties: typically such articles are relatively thin plate-like items such as panel board to replace wood planks or boards. There is an obvious reason for this: the height an article may have in the direction of pressing when fabricating this article from pressed wood particles is at most a few centimeters, otherwise an uneven strength throughout the bulk of the article may arise. Therefore, producing high end articles from pressed wood particles has been 5 almost exclusively used for plate like articles. It is noted that it is known to produce low end non plate like articles, such as toys, ornaments and pallets of pressed wood particles, but not hollow (polygon) like structures. These articles do not need to full fill the mechanical demands of structural panels, i.e. being light but still have sufficient rigidity to act as self-supporting walls of a building, while at the same time being capable 10 of providing adequate heat insulation, thus having a thickness of more than at least 10 cm. Maximum height of pressed wood products in the pressing direction is typically a few centimeters up to one decimeter. For structural panels this is considered too low, in particular to meet current insulation standards. Applicant found that by constructing the panel by using a polygon structure of pressed wood particles, high end structural panels, even having a thickness of up to 30 cm (or more) can be produced from pressed wood particles without needing to compromise any of the current mechanical demands for such panels.

A material made from pressed wood particles is so-called engineered wood, also called 20 composite wood, man-made wood, or manufactured wood. This broad category of engineered wood includes a range of derivative wood products which are manufactured by binding or fixing the strands, particles, fibres, or veneers or boards of wood, together with adhesives, or other methods of fixation to form composite materials. The subcategory of pressed wood from wood particles is material made wood particles (made from the same hardwoods and softwoods used to manufacture lumber) such as sawmill scraps and other wood waste. Oriented strand board can use trees from the poplar family, a common but non-structural species. The use of wood particles is contrary to the use of whole logs for veneers, plywood and other engineered wood that dos not use wood particles.

In order to meet the second object of the invention a method of producing a structural panel is devised, the method comprising producing a two-dimensional supporting layer, producing a polygon structure of pressed wood by mixing wood particles with a binder and pressing the mixture in a mould to form the polygon structure, and attaching the 35 polygon structure to one side of the supporting layer. These steps can be combined in one or two or more separate process steps that take place at a different time and place •Λ.

(i.e. they do not need to take place as separate consecutive process steps).

DEFINITIONS

Δ polygon structure is a structure consisting in essence (for more than 50%; in particular for more than 60, 70, 80, 90, 95% up to 100%) out of, preferably regular, polygons, such as triangles, squares, pentagons, hexagons etc.

A honeycomb structure is a structure consisting in essence (for more than 50%; in particular for more than 60, 70, 80, 90, 95 up to 100%) out of regular hexagons.

A structure made of pressed wood particles is a structure made of a mixture of wood particles such as chips, sawmill scraps and other wood waste, and a binder, which mixture is pressed under high pressure and optionally high temperature to form a rigid structure. Pressed wood from wood particles is different from engineered wood made form pressed sheets of wood such as plywood, laminated timber, laminated veneer, parallel strand, laminated strand etc.

A two dimensional item means that the item extends in essence in 2 dimensions, i.e. having a length and width far greater (more than 10 times, preferably more than 15, 20, or even 25 times) than its thickness.

A one dimensional item means that the item extends in essence in one dimension, i.e. having a length far greater (more than 10 times, preferably more than 15, 20, or even 25 times) than its height and width.

To extend in essence in a direction perpendicular, means to divert no more than 5° from 30 a perpendicular direction, in particular no more than 4°, 3°, 2°, Γ or 0°.

To fill an open space with material is to put the material in the space such that at least 50% of the open space is taken by the material, preferably at least 60, 70, 75, 80, 85, 90, 95, 96, 97, 98, 99 or up to 100% of the open space.

EMBODIMENTS OF THE INVENTION

In an embodiment of the present invention the walls of the polygon structure extend in essence in a direction perpendicular to the plane in which the supporting layer extends.

Although such a constitution is known for polygon structures of other materials such as paper, aluminium and plastic, it is not known for pressed wood products. This is because pressing typically takes place in a direction perpendicular to the wall of the product to be made, which might seem to prevent that a polygon can be made wherein 10 the walls extent in essence perpendicular to the supporting layer. However, applicant found that it is possible for example by leaving the common production techniques of making the polygon in one go, but assembling the polygon out of separately made smaller structures. Other options are to leave the common pressing process of pressing in the moving direction of the die, but using a die that can expand in lateral direction for 15 exerting the required pressing force. Although this might make the initial production costs somewhat higher, given the low cost materials and the greater freedom in other aspects, this is believed to be compensated in the end.

In a second embodiment the thickness of the polygon structure is at least 15 cm, 20 preferably at least 20 cm. This provides the option of having a greater volume available for an insulating material. In the art, no 3D objects have been made of pressed wood particles having a depth greater than about 10 cm. In the current invention, by using a pressing direction parallel to the supporting layer, any height (depth) can be created for the polygon structure.

In another embodiment the panel comprises a second two-dimensional supporting layer that is attached to the polygon structure at a side of the panel opposite to the side of the first supporting layer. This way a sandwich panel can be formed.

In yet another embodiment of the structural pallet according to the invention, the open spaces in the polygon structure are filled with insulating material. In a further embodiment wherein the insulating material is pre-manufactured as a self-supporting material (e.g. a polymer foam material), the pre-manufactured insulating material is cut (e.g. in situ) to dimensions corresponding to the polygon structure to fill the open spaces.

In an embodiment of the method according to the invention the supporting layer and polygon structure are both made from pressed wood. This has the advantage that only one material needs to be used to make the basic construction of the panel. Assembling a panel from pressed would sub-articles is easier then assembling a panel out of different types of articles. Also, recycling of the panel is easier in this case. In a further embodiment the supporting layer and polygon structure are made as a unit construction in one pressing processing step. In this method, he attaching of the supporting layer to the polygon structure inherently takes place, but cannot be distinguished a separate process step.

In another embodiment walls of the polygon structure are pressed using a pressing direction that extends in a direction parallel to the supporting surface. The advantages of this embodiment have been explained here above.

In yet another embodiment the supporting layer and polygon structure are made as separate parts before they are assembled to form the panel. This greatly improves the freedom to operate for making the polygon structure. The strength of the assembly can be improved by making the separate parts such that mutual parts anchor or otherwise form a mechanical connection without the need to use an additional binder or glue, or for improving the strength of a connection in which a binder or glue is applied. In a further embodiment, walls of the polygon structure are pressed using a pressing direction that extends in essence in a direction parallel to the supporting surface. In yet a further embodiment multiple separate one dimensional polygon-in-part items are made, which are assembled in the panel to form the polygon structure.

In a further embodiment each one dimensional polygon-in-part item is made in a continuous press, e.g. a continues press using rotating platens or moulds. This way, the polygon-in-part items can be made using existing techniques that have been applied commercially successfully over the last 20 years, in particular fro manufacturing OSB,

MDF and other board material. Thereafter, it is only a small step to assemble a structural board by gathering the polygon-in-part items on a supporting layer to form a polygon structure.

In again a further embodiment each pair of abutting one dimensional polygon-in-part items has mutual mechanical elements that mate to form a mechanical connection between the two items. This further improves the rigidity, in particular the resistance against bending stresses, of the structural panel. In a particular embodiment one item of each pair has at one of its sides a perpendicular extending flat member that fits a slot in the corresponding side of the other member.

In still a further embodiment wherein in a first step two separate supporting layers are positioned in parallel at a distance corresponding to the height of the polygon structure to form the outer layers of the panel, in a second step the multiple separate polygon-inpart items are pushed in a consecutive order between the two layers from one side of the panel until the polygon structure is complete.

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The invention will now be explained in more detail using the following non-limiting examples.

EXAMPLES

Figure 1 schematically shows a structural panel according to the invention.

Figure 2 schematically shows multiple one dimensional polygon-in-part items, partly assembled into a honeycomb structure.

Figure 1

Figure 1 schematically shows a structural panel 1 according to the invention. This panel _λ as depicted consist of a two-dimensional supporting layer 2 (which in this case is assembled out of multiple plan-parallel sub layers) and a rigid polygon structure 3 (in this case a honeycomb structure), which extends from one side of the supporting layer. This rigid structure is made from pressed wood particles and has a height of 20 cm (but may of course be lower or higher). Typically, although not shown, the hollow spaces in the rigid polygon structure are filled with an insulating material, where after a second two-dimensional supporting layer is put on top of the panel to seal the honeycomb structure with its insulation. After that, depending i.a. on the mechanical properties of the panel, the panel can be used as a part in the construction of a building, e.g. as a wall, roof part etc.

In the shown embodiment, the honeycomb structure is assembled out of multiple onedimensional polygon-in-part items (which becomes more clear when looking at figure 2) positioned on a separate two-dimensional supporting layer. However it is also possible for example to press the honeycomb structure and supporting layer as one unit construction in one go. Since the pressing direction is most conveniently in the direction perpendicular to the direction in which the supporting layer extends, the walls cannot be 5 made too high, typically about 10-15 cm, and preferably extend from the supporting layer under an angle of about 75 to 80° (and not exactly vertical, i.e. under an angle of 90°). This way strong walls can be pressed, which would be harder if the walls would extend exactly vertically (using wood particles) and pressing in the same direction as the walls of the honeycomb extend.

Figure 2

Figure 2 schematically shows multiple one dimensional polygon-in-part items 30, partly assembled into a honeycomb structure. Individual one dimensional polygon-in-part 15 items 30 and 30’are shown in the lower right part of figure 2. These part in essence extend in only one dimension and can be produced like a common OSB or MDF panel in a continuous press, e.g. using a press that comprises a rotating hot platen as is commonly known in the art. These parts, after having been made, can be assembled to form a polygon structure, such as the honeycomb structure as shown in figures 1 and 2.

In figure 2, four separate one dimensional polygon-in-part items 30, 30’, 30” and 30’” are shown to be assembled to form a polygon structure corresponding to the structure of figure 1.

As shown, in this embodiment each pair of abutting one dimensional polygon-in-part items has mutual mechanical elements 300 and 301 that mate to form a mechanical connection between the two items. Such elements can be as simple as mating ridges as shown in figure 2. Such mating elements have been to greatly increase the strength of the rigid polygon.

In practice, the polygon structure may be assembled as a stand-alone structure, optionally provided with insulating material in the hollow spaces, and with layers of protecting foil. This structure is then transported to a building site, at which site the foil is removed and the actual supporting layer is connected to the polygon structure, for example via wooden battens. This way, a cavity for guiding cables, pipes, tubes etc.

may be formed at the building site in between the polygon structure and the supporting layer(s).

Claims (17)

CONCLUSIONS A building panel comprising at least one two-dimensional support layer and attached thereto a rigid structure covering the support layer, walls of 5, which structure extends from one side of the support layer, characterized in that the rigid structure is a polygon structure made of pressed wood particles. A building panel according to claim 1, characterized in that the walls of the The polygon structure extends substantially perpendicularly to the plane in which the underlayer layer extends. 3. A building panel according to any one of the preceding claims, characterized in that the thickness of the polygon structure is at least 15 cm, preferably at least 20 cm. 15 cm. A building panel according to any one of the preceding claims, characterized in that the panel comprises a second support layer which is attached to the polygon structure on one side of the panel opposite to the side of the first 20 support layer. A building panel according to any one of the preceding claims, characterized in that the open spaces in the polygon structure are filled with an insulating material. 25 A method of producing a building panel comprising; - producing a two-dimensional support layer, - producing a polygon structure of pressed wood by mixing wood particles with a binder and pressing the mixture in a mai around the polygon 30 to form a structure, - fixing the polygon structure on one side of the support layer A method according to claim 6, characterized in that the support layer and the polygon structure are both made of pressed wood. A method according to claim 7, characterized in that the support layer and the polygon structure are made as a unit in one process step, A method according to any one of claims 6 to 8, characterized in that walls of the polygon structure are pressed while breaking a press 5 direction which extends in a direction parallel to the support layer. A method according to claim 6 or 7, characterized in that the support layer and the polygon structure are made as distinct parts before they are assembled to form the panel. A method according to claim 10, characterized in that walls of the polygon structure are pressed using a pressing direction that extends essentially in a direction parallel to the support layer. 15 A method according to any one of claims 10 and 11, characterized in that several separate one-dimensional polygon parts are made, which are assembled on the panel to form the polygon structure. A method according to claim 12, characterized in that the various 20 individual one-dimensional polygon parts together form a hexagon structure. A method according to any of claims 12 and 13, characterized in that each one dimensional polygon part is made in a continuous press. 25 A method according to any one of claims 12 to 14, characterized in that each pair of adjacent one-dimensional polygon parts have mechanical elements cooperating with each other and fitting together to disguise a mechanical connection between the two parts. 30 A method according to claim 15, characterized in that one part of each pair has on one of its sides a perpendicularly extending flat part that fits into a slot in the corresponding side of the other part. A method according to any of claims 12 to 16, wherein in a first step two 35 individual support layers are positioned in parallel at a distance corresponding to the height of the polygon structure so as to form the outer layers of the panel, characterized in that the various individual polygon parts are pushed between the two layers in a sequential order between the two layers side of the panel until the polygon structure is complete ,. ¹ ° 427 ₇₁

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