GB2277751A

GB2277751A - A structural element and a method for its production

Info

Publication number: GB2277751A
Application number: GB9308241A
Authority: GB
Inventors: Dale Mccrea
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-04-21
Filing date: 1993-04-21
Publication date: 1994-11-09
Also published as: GB9308241D0

Abstract

The structural element comprises at least one board member 1 and a binding medium 5, wherein the binding medium fills in about the board member or members to complete the element. The board member(s) may comprise cardboard waste and the binding medium may comprise a polyurethane resin; the element may be a beam or panel. An adhesive 2 may coat board 1; where board 1 is corrugated cardboard it may be spiked to assist penetration by adhesive 2 and/or binder 5. <IMAGE>

Description

A STRUCTURAL ELEMENT AND A METHOD FOR ITS PRODUCTION DESCRIPTION The present invention relates to a structural element and a method of forming such an element. In particular, the present invention relates to elements which are suitable for use in the construction of temporary shelters and furnishings.

Structural elements suitable for the first such application should satisfy a number of criteria. They should be strong, rigid, weatherproof, lightweight for ease of transportation and construction, inexpensive and made of readily available materials to ensure adequate supplies, insulated to provide warmth, and easily assemblable into a final edifice by unskilled labour. In addition to the above requirements, suitable elements should also be capable of receiving simple retaining brackets and fixtures for holding them together in a structure. It would be desireable if smaller elements of the same material could also be used for the manufacture of simple furnishings for these temporary shelters, such as beds, chairs, tables, shelves, cupboards and the like.

Traditional construction materials, such as brick, timber or metal do not meet all of the above requirements, being, in the main, too expensive, too heavy or too difficult for unskilled labour to work with under emergency conditions.

Cardboard is relatively inexpensive and readily available. A commercial product is available under the Trade Mark Tri-wall and comprises three sheets of corrugated cardboard glued back to back to form a reinforced cardboard approximately 15 mm thick.

However, "Tri-wall" and other commercially available cardboards have not proven suitable for use in the construction of temporary shelters for several reasons.

"Tri-wall" is not weatherproof or rigid enough to provide a load bearing structure. Furthermore, since "Tri-wall" comprises three layers of corrugated cardboard, with the channels formed by the corrugations running the length of each sheet, it is susceptible to damp penetration or infestation by insects or mould.

It is an object of the present invention to provide a structural element which is suitable for use in the construction of temporary shelters and furnishings and which does not suffer from the aforementioned disadvantages of traditional materials and of "Tri-wall".

Accordingly, in a first aspect, the present invention provides a structural element having a predetermined shape comprising at least one board member and a binding medium, wherein the binding medium fills in about the board member or members to complete the element.

In a second aspect, the present invention provides a method of forming a structural element having a predetermined shape comprising moulding at least one board member with a binding medium, wherein the binding medium fills in about the board member or members to complete the element.

In an embodiment of the invention in its first aspect, the board members are arranged to form a laminated assembly within the structural element. In this specification, the term "laminated assembly" is understood to mean that the board members form a layer structure within the structural element, and is not limited merely to the case where each board member has the same dimensions of length and width as the composite element. It is envisaged that a structural element according to the invention may be constructed from oddments of cardboard waste material, irrespective of their shape or size. Thus, in a preferred embodiment, the structural element comprises board members which are not all of a uniform shape or size.

In the present invention, a board member can be formed from a low density material. A low density material is understood to mean one which has residual air pockets in its structure and includes fibrous or cellular materials, such as cardboard, chipboard and any kind of fibre-board, boards made of fabric, felt, paper or any kind of pulped material. In an especially preferred embodiment, the board member or members are made of cardboard, and, most preferably, are made of corrugated cardboard. The use of low density materials for the board members of the invention allows a lighter weight of the completed structural element.Also, in embodiments where the broad members are in the form of corrugated cardboard sheets and these do not run the entire length of the structural element, the latter is less susceptible to damp penetration or infestation by insects or mould than single (extensive) sheets of "Tri-wall" or like corrugated materials.

Thus, the present invention provides a method for the production of a structural element which may be easily followed by persons who are unskilled in conventional manufacturing processes, and which can make use of an inexpensive and readily available starting material.

Cardboard is especially suitable for use in the present invention. Furthermore, it is not necessary to employ newly manufactured cardboard in the invention and use can be made of waste cardboard. Since large amounts of cardboard are produced as packaging waste, it can be significantly less costly than new products, such as "Tri-wall" and, its reuse in the present invention is highly desirable in terms of conservation of the environment.

Any suitable binding medium may be used in the present invention, provided that it is capable of filling in about and, preferably, between and within board members to complete the structural element. In a preferred embodiment, the binding medium fills in gaps between adjacent board members, or gaps between the assembly of board members and the periphary of the element. Thus, in the case where the binding medium occupies the space between two board members arranged on top of one another, the binding medium can be laminated together with the board members. In a most preferred embodiment, the binding medium is capable of forming a a matrix wherein the board members are set.

The term "matrix" in this specification is used in its mineralogical sense, namely that the binding medium forms a material in which the board members are fixed or held in place.

In an embodiment of the invention, the binding medium comprises a synthetic resin, preferably, an expanded synthetic resin, and most preferably a foam. This permits a smaller quantity of resin to be used, thus allowing a reduction in the final weight and cost of the completed structural element. In a preferred embodiment, the foam is formed from a moisture curing precursor. In the case where the board members are made of waste cardboard, the use of a moisture curing precursor may permit the cardboard to be used whilst still damp. In a most preferred embodiment, the synthetic resin is a polyurethane resin. Such polyurethane resins are well known in the art, and can be cured by ambient or added moisture; on curing, residual isocyanate groups in the polyurethane are hydrolysed by moisture and release carbon dioxide, causing the adhesive to foam. Suitable polyurethane resins are widely available, such as that sold under the Trade Mark "National 074-0005" by National Starch & BR< Chemical Limited, Slough, Berks., U.K. The polyurethane resin may be either filled or unfilled, depending upon the physical properties required for the structural element. For example, the polyurethane resin may contain a fire- retardant additive, such as melamine, if desired.

In a yet further embodiment, the binding medium also comprises an adhesive. The adhesive may be applied to each board member as it is added to form the structural element together with a sufficient quantity of the resin to fill in any gaps between board members.

Preferably, the adhesive is a fast-setting synthetic resin emulsion adhesive, and, most preferably, a polyvinyl acetate adhesive. Suitable polyvinylacetate adhesives may be obtained under the Trade Marks "National 833-1173E" and "National 240 0007" from National Starch & Chemical Limited, Slough, Berks., U.K.

In an especially preferred embodiment, the structural element according to the invention is in the form of a panel. The size of the panel will depend upon the specific application for which it is intended, but, by way of illustration only , in the construction of a temporary shelter, a suitable panel size might be 2400 x 1200 x 75 mm. However, the structural elements according to the invention are intended to have a wide range of applications besides the construction of shelters, and the size or shape of the element may be varied accordingly. In order to achieve the desired shape of element, it may be necessary to construct the element from a plurality of separate laminar arrays of board members, each of which arrays may have a different spatial orientation. Thus, in an embodiment, the structural element comprises a plurality of laminar arrays of board members.In a further embodiment, the structural elements are in the form of a beam or similar load bearing structure. Such a beam might be of rectangular, square or "I-shaped" cross-section, as required. In a still further embodiment, the structural element comprises at least one other component in addition to board members and binding medium. This component is preferably fabric or woven material, particularly waste fabric or woven material. However, other compounds such as strengthening struts, fillers, resins or other additives may also be present.

In an embodiment of the present invention according to the invention in its second aspect, the board members may be coated with binding medium before being assembled in a mould. The term "coated" in this context is understood to mean that the binding medium is applied to at least a part of at least one board member, and does not mean that all exposed surfaces of all board members must be evenly coated. The binding medium can comprise a single component, which is used to coat the board members and to fill in about members.

In an embodiment, the binding medium used in each step is a polyurethane resin. However, the binding medium can comprise a plurality of components and the component used in each step can be different. In an especially preferred embodiment, the binding medium component used to coat the board members is a polyvinyl acetate adhesive, whilst the binding medium component used to fill the spaces between board members is a polyurethane resin.

In a most preferred embodiment of the inventive method, the board members are coated with binding medium, arranged in the mould, and then lightly compressed with a roller before addition of more binding medium. The roller serves to ensure intimate contact between the board members and thus facilitate adhesion; the degree of compression should be sufficient to ensure good contact between members but not so much that the air pocketed structure of the members is destroyed.

In an embodiment of the inventive method, the board members are punctured, preferably in addition to being compressed with a roller, in order to enable the binding material to penetrate into the board member and thereby block channels or corrugations within their structures. Thus, the structural elements can be less susceptible to damp penetration or infestation by insects or mould than commercially available cardboard materials. In a still further embodiment, the roller is a spiked roller, which randomly punctures the board members and thus aids penetration of the binding medium into any spaces within the board members. The method provided by the invention in its second aspect may be used to prepare a structural element as described in the first aspect of the invention, and in any embodiment thereof.

In a third aspect, the present invention provides an article made from a structural element as described in the first aspect of the invention, which element may be made by a method provided by the invention in its second aspect. As previously described, the article may be a temporary shelter or refuge, or an article of furniture, such as a bed, chair, table, shelf or cupboard or the like, or any other item which can be constructed from the inventive element, such as a toy, for example.

In a fourth aspect, the present invention provides a composite material comprising a cardboard reinforced synthetic resin. In a preferred embodiment of this aspect of the invention, the cardboard is in a matrix formed of the synthetic resin, which resin is most preferably a foam.

The nature of the invention and the manner in which it may be put into effect will be made more apparent from the embodiments now described, by way of illustration only, with reference to the accompanying drawings, wherein: Figure 1 shows a cross-sectional view of a panel according to the invention in situ in a mould; Figure 2 shows three views of a chair according to the invention (a) front view, (b) side view and (c) rear view; and Figure 3 shows a front perspective view of a temporary shelter according to the invention.

With reference to Figure 1, in a method in accordance with the invention, sheets of corrugated cardboard 1 of various size are coated with a polyvinyl acetate adhesive 2. The sheets of coated cardboard 1 are then arranged in layers in a mould 3 and compressed with a spiked roller (not shown), which leaves punctures 4 in the sheets 1. A polyurethane resin 5 is then poured into the mould 3 over the cardboard sheets 1. A lid 6 is placed on top of the mould 3 and the polyurethane resin 5 allowed to cure and expand to fill the mould, filling in the punctures 4 and any gaps between and about the sheets 1. The completed structural panel, comprising cardboard sheets 1, polyvinyl acetate adhesive 2, and cured polyurethane resin 5, is then removed from the mould.

With reference to Figure 2, an armchair according to the invention is constructed of structural panels prepared as described above. The panels comprise two side panels 7, a rear panel 8, a seat-forming panel 9 and strengthening panels 10. The panels are held in place by securing pins 11, made of recycled aluminium, melted and the re-set in barb shaped moulds.

With reference to Figure 3, a temporary shelter according to the invention is constructed from structural panels as described above, and from beams prepared in like fashion. Wall-forming panels 12 are joined together by flat metal brackets 13, which link the panels 12 to form a wall, and right angle metal brackets 14, which join together panels 12 at the corners of the structure. Floor-forming panels 15 are supported on feet 16, each foot comprising a cluster of four "tin" cans 17. A roof is provided by roof panels 18 supported on roofing beams 19.

The above examples are intended to be by way of illustration of the invention only and are not to be taken to limit the scope of protection as claimed.

Claims

1. A structural element having a predetermined shape comprising at least one board member and a binding medium, wherein the binding medium fills in about the board member or members to complete the element.

2. A structural element as claimed in claim 1, comprising a laminated assembly of board members.

3. A structural element as claimed in claim 2, wherein the binding medium fills in between adjacent board members, within a board member or between the assembly of board members and the periphary of the element.

4. A structural element as claimed in claims 2 or 3, wherein the board members are not all of a uniform size or shape.

5. A structural element as claimed in any of claims 2-4, wherein the binding medium is laminated with the board members.

6. A structural element as claimed in any of claims 2-5, wherein the board members are set in a matrix of binding medium.

7. A structural element as claimed in any of claims 2-6, wherein the board members comprise a low density material.

8. A structural element as claimed in any of claims 2-7, wherein a plurality of internal voids are defined within at least one board member.

9. A structural element as claimed in any of claims 2-8, wherein at least one board member is cardboard.

10. A structural element as claimed in claim 9, wherein the cardboard is "corrugated cardboard".

11. A structural element as claimed in any of the preceeding claims, wherein the binding medium comprises a synthetic resin.

12. A structural element as claimed in claim 11, wherein the resin is an expanded resin.

13. A structural element as claimed in claim 12, wherein the resin is a foam.

14. A structural element as claimed in claims 11-13, wherein the resin is formed from a moisture curing precursor.

15. A structural element as claimed in claims 11-14, wherein the resin is a polyurethane resin.

16. A structural element as claimed in any of claims 2-15, wherein the binding medium further comprises an adhesive.

17. A structural element as claimed in claim 16, wherein the board members are laminated with the adhesive.

18. A structural element as claimed in claims 16 or 17, wherein the adhesive is a polyvinyl acetate adhesive.

19. A structural element as claimed in any of the preceeding claims, wherein the element is a panel.

20. A structural element as claimed in any of claims 1-18, wherein the element is a beam.

21. A structural element as claimed in any of claims 2-20, wherein the element comprises a plurality of laminar arrays of board members.

22. A structural element as claimed in any of the preceeding claims, wherein the element further comprises fabric or woven material.

23. A method of forming a structural element having a predetermined shape comprising moulding at least one board member with a binding medium, wherein the binding medium fills in about the board member or members to complete the element.

24. A method as claimed in claim 23, wherein the element comprises a laminated assembly of board members.

25. A method as claimed in claim 24, wherein the board members are compressed prior to an addition of binding medium.

26. A method as claimed in claim 25, wherein the board members are compressed with a spiked roller.

27. A method as claimed in any of claims 24-26, wherein the board members are punctured so as to allow binding medium to penetrate the board members.

28. A method as claimed in any of claims 24-27, wherein the board members are fixed in a laminar array with binding medium.

29. A method as claimed in any of claims 24-28, wherein uncured binding medium is added to the laminar array of board members in a mould and the medium is then caused to expand to fill the mould.

30. A method as claimed in any of claims 24-29, wherein the board members are fixed in a laminar array using a first binding medium component, and a precursor for a second binding medium component is added to the laminar array in a mould and the precursor for the second component is then caused to expand to fill the mould.

31. A method as claimed in any of claims 23-30, wherein the structural element is as claimed in any of claims 1-22.

32. A method substantially as hereinbefore described in any of the foregoing examples.

33. A structural element prepared by a method as claimed in any of claims 23-32.

34. A structural element substantially as hereinbefore described with reference to the accompanying drawings.

35. An article made from a structural element as claimed in any of claims 1-22, 33 or 34.

36. An article made from a structural element prepared by a method as claimed in any of claims 23-32.

37. A composite material comprising a cardboard reinforced synthetic resin.

38. A composite material as claimed in claim 37, wherein the cardboard is in a matrix formed of the synthetic resin.

39. A composite material as claimed in claim 38, wherein the resin is a foam.