Background Art Normally plywood is fabricated from timber veneer with the grain of adjacent layers being perpendicular. For example, traditional "three-ply" has three layers with the grain on the outermost layers running, say, north-south and the grain of the inner layer running east- west. Where additional strength is required further layers are added to the laminate so as to create five-ply, seven-ply, etc.

Although the present invention is predominantly concerned with timber veneers, there are substitutes for timber formed by adhering timber particles together, such as when sawdust is adhered to form particleboard, and the like. Such timber substitutes do not normally show the attractive timber grain visible in timber veneers, however, the term "timber" as used herein is intended to cover such timber substitutes as well as timber itself.

As alluded to above, in order to strengthen plywood the traditional approach has been to increase the number of layers forming a laminate and hence the thickness and weight of the plywood increases. A characteristic of such an approach is that the strength of the plywood increases roughly in steps, each corresponding to a corresponding additional layer of the laminate.

In general, the thermally insulative and/or acoustically insulative properties of plywood are not materially changed by increasing the number of layers from which the plywood is formed. For example the insulative properties of five-ply are essentially similar to those of three-ply. This substantially restricts the range of applications in which plywood can be utilised.

Furthermore, it is traditional for plywood to be provided with a decorative finish formed by enhancing the appearance of the grain of the timber. Traditionally this has been done by applying one or more coats of clear varnish or similar clear paint finishes. Not only is such painting time consuming, but it is not particularly hard wearing and generally the varnished surface must be re-varnished after a relatively short period of time.

Object of the Invention The object of the present invention is to, at least to some extent, ameliorate the abovementioned disadvantages by the provision of a plywood substitute which, in its preferred embodiment, utilises the ARMACEL process.

Summary of the Invention The ARMACEL process and apparatus for forming structural articles, especially from weak substrates such as polystyrene and cardboard, and articles so formed, are disclosed in the applicant's International PCT Patent Application No. PCT/AU95/00100 entitled "A method and apparatus for forming structural articles" (WO 95/23682), International PCT Patent Application No. PCT/AU96/00541 entitled 'Layered Structural Article" (WO 97/09166) and International PCT Patent Application No. PCT/AUOO/00250 (WO 00/59709) - the contents of all three of which are hereby incorporated into the present specification by cross reference. A further, specification unpublished as at the priority date of this application is that of International Patent Application No. PCT/AU2004/000826 (WO 2004/113053) which discloses the encapsulation of an interior member which is neither at least partially fluid permeable nor is perforated to become so. The disclosure of that specification is also hereby incorporated by cross-reference.

According to an aspect of the invention there is provided a timber substitute comprising an outer veneer or similar decorative layer of timber and an inner thickness defining layer of thermally insulating inherently weak material, said outer layer and inner layer being at least partially encapsulated by at least one sheet of transparent thermoformable plastics material which extends over said outer layer, said transparent encapsulating layer imparting to the observable surface of said decorative layer the appearance of a treated timber finish whereby said timber substitute has a thickness determined predominately by said inner layer, a strength determined predominantly by said encapsulating layer and an appearance determined by the interaction of said encapsulating and decorative layers. In preferred embodiments, the substitute includes a second decorative layer located adjacent said inner thickness defining layer but on the opposite side thereof from said (first)decorative layer.

Preferably, said inner thickness defining layer determines the thermally insulative and/or acoustically insulative properties of the substitute, and the inner thickness defining layer is formed from an expanded polymer. More preferably, either one or both of said decorative layers comprises a single layer veneer of timber.

In preferred embodiments, the inner layer is an expanded polymer such as expanded polystyrene, or paper, aluminium or recycled waste materials.

Preferably, said transparent encapsulating layer is formed from the group consisting of APET, PET, PETG, Polycarbonate, Polycarbonate/Polyester blends, ABS Polystyrene blends, HIPS Polystyrene blends, SAN Polystyrene blends, LDPE Polystyrene blends, HDPE Polystyrene blends, Polypropylene, Vinyl, PMMA Acrylic blends, Cellulose Acetate, PBT, PPE, Acetal, PVC, and NORIL.

In preferred embodiments, a decorative sheet is interposed between the outer side of one of said decorative layers and the adjacent encapsulating layer.

Brief Description of the Drawings Preferred embodiments of the present invention will now be described with reference to the drawings in which:

Fig. 1 is a schematic cross-sectional view illustrating in exploded form the bringing together of an inner layer and two decorative outer layers so as to form a laminate,

Fig. 2 is a view similar to Fig. 1 but showing the laminate in unexploded form,

Fig. 3 shows the laminate partially encapsulated by a first transparent encapsulating layer,

Fig. 4 shows the material of Fig. 1 inverted and encapsulated with a second transparent encapsulating layer, and Fig. 5 is a perspective view showing the finished encapsulated plywood substitute.

Detailed Description As seen in Figs. 1 and 2, a laminate is formed from an inner layer 3 of inherently weak material such as expanded polystyrene (EPS) and two outer layers in the form of a first outer layer 1 and a second outer layer 2. However, it will be appreciated that the expanded polystyrene can be replaced with any other suitable material such as corrugated or honey-combed paper, aluminium, recycled waste materials or any other relatively low cost bulk substitute.

The outer layers 1, 2 are preferably formed either from a single veneer of timber or from a multi-ply timber material such as three-ply. Preferably the outer surface of each of the outer layers 1, 2 has a well defined timber grain.

As seen in Fig. 3 the laminate of Fig. 2 is partially encapsulated by means of the application of the above described ARMACEL process so as to form a first encapsulating layer 5. Then the article is inverted and a second encapsulating layer 6 is applied as illustrated in Fig. 4. The encapsulating layers 5, 6 are formed from a thermoformable plastics material which is preferably selected from a class of materials consisting of APET, PET, PETG, Polycarbonate, Polycarbonate/Polyester blends, ABS Polystyrene blends, HIPS Polystyrene blends, SAN Polystyrene blends, LDPE Polystyrene blends, HDPE Polystyrene blends, Polypropylene, Vinyl, PMMA Acrylic blends, Cellulose Acetate, PBT, PPE, Acetal, PVC, and NORIL.

The final result is illustrated in perspective view in Fig. 5 from which it can be seen that the transparent encapsulating layer 5 or 6 allows the timber grain of the uppermost outer layer 1 or 2 to not only be visible but to be visible through a highly reflective surface on which reflections 8 readily form. That is, the encapsulating layer has an appearance similar to that of a highly polished varnished timber surface.

The above described embodiment can be modified in various ways. Firstly, rather than use plywood for the intended visible outer layer 1 (and the other outer layer 2 is desired) instead particle board, or similar, can be used. In order to achieve the desired timber grain finish, a layer of paper onto which is printed a timber grain pattern is located on the exterior surface of the outer layer 1, immediately prior to its being encapsulated by the layer 5 (as indicated in Fig. 3). Thus the timber grain visible through the transparent layer 5 is the grain of the paper sheet.

In a still further embodiment, it is known to provide some thermoformable plastic films, such as PVC, with an embossed or indented timber pattern profile on its upper surface. This pattern is retained by the plastics material, notwithstanding that it is heated during the ARMACEL process. This material enables a non-grain material, such as particle board, used as outer layer 1 to result in a grained appearance when encapsulated because the grain present on the outer surface of the encapsulating layer 5 is visible to the observer. Under these circumstances the encapsulating layer 5 need not be transparent but could be translucent or even opaque and coloured to represent a timber colour or finish.

A number of very desirable advantages flow from the above described procedures. Firstly, the plywood substitute is of very great strength, the strength being endowed by the encapsulating layers and, in particular, by the encapsulation utilising the ARMACEL process. Thus, in general, the strength of the article is not related to the number of layers and, in particular, is very much greater than one would expect from a consideration of the individual constituents from which the finished article is fabricated.

Secondly, the inner layer 3 very substantially increases the insulation of the finished article both in relation to heat and/or in relation to sound transmission. Indeed, a cavity or form of void can be created in the inner layer 3 to further increase the insulation values.

Thirdly, an exterior surface is achieved which is akin to that of a varnished timber surface, however, the durability of the surface is very much greater than that of varnished timber and, in practice, never needs to be replaced or re-coated. In addition, the surface of the encapsulating layers also very substantially resist scuffing, scratching, marking, and the like. The foregoing describes only one embodiment of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.

The term "comprising" (and its grammatical variations) as used herein is used in the inclusive sense of "having" or "including" and not in the exclusive sense of "consisting only of.