Background Art Such material is inexpensive and easy to fabricate and has found widespread applications in cardboard boxes to hold a wide variety of goods. Such boxes are stacked on a pallet (normally formed from timber or some other structurally strong material) to be transported, for example by truck.

It has long been a commercial desire of cardboard box fabricators to also manufacture a pallet from cardboard, however, despite many attempts hitherto none has found commercial acceptance.

The present invention utilizes the ARMACEL (Registered Trade Mark) process. That process basically involves partially, or substantially completely, encapsulating an article with a layer, or a plurality of layers, of thermoformable plastics material.

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/AU00/00250 (WO 00/59709) entitled"An improved method of forming structural articles"-the contents of all three of which are hereby incorporated into the present specification by cross reference.

These specifications disclose forming structural articles from a shape defining interior member and at least one external skin. The basic steps of the method comprise : 1. heating a thermoformable sheet intended to form the external skin, 2. bringing the heated sheet alongside the interior member, 3. applying a fluid pressure differential between opposite surfaces of the interior member and the sheet to conform the sheet to the shape of the interior member and mutually engage same, and 4. maintaining the fluid pressure differential until the sheet has cooled.

The application of a fluid pressure differential is normally brought about by evacuation of the gas (normally air) between the heated sheet and the interior member or article.

Object of the Invention The object of the present invention is to provide a structural article which can be manufactured from cardboard and which can be utilized in such a cardboard pallet.

Summary of the Invention In accordance with a first aspect of the present invention there is disclosed a structural article fabricated from paper, cardboard or like inherently weak laminar material and shaped to be subjected to a mechanical load in a preferred orientation, wherein said laminar material is formed into a plurality of parallel and abutting layers each of which includes parallel arranged corrugations and each of which are like aligned, said corrugations extending in substantially said preferred orientation, and said article is vacuum encapsulated in sheet plastics material.

In accordance with a second aspect of the present invention there is disclosed a method of fabricating a structural article from paper, cardboard or like inherently weak laminar material, the article being shaped to be subjected to a mechanical load in a preferred orientation, said method comprising the steps of :

(i) forming said laminar material from a plurality of parallel and abutting layers each of which includes parallel arranged corrugations and each of which are like aligned, (ii) orienting said laminar material so that said corrugations extend in substantially said preferred orientation, and (iii) whilst maintaining said orientation vacuum encapsulating said laminar material in sheet plastics material.

Description of the Drawings Embodiments of the present invention will now be described with reference to the drawings in which: FIG. 1 is a perspective view of a prior art sheet of cardboard in widespread use, FIG. 2 is a perspective view of a portion of a known prior art cardboard arrangement but not in widespread use, FIG. 3 is a side elevational view of a prior art structural member fabricated from a plurality of cardboard layers such as those illustrated in Fig. 1, FIG 4 is perspective view of a structural article fabricated in accordance with a first embodiment of the present invention, and FIG. 5 is a perspective view of a pallet fabricated in accordance with a second embodiment of the present invention.

Detailed Description As seen in Fig. 1, a prior art sheet 1 of cardboard is fabricated from an upper face 2, a lower face 3, and a corrugated layer 4 interposed between the two faces 2,3.

Many articles are fabricated from cardboard utilizing the sheet 1, in particular, packaging materials such as boxes for a wide variety of goods. The sheet 1 is inexpensively fabricated utilizing a corrugating machine which applies glue to hold the corrugated layer 4 in position between the faces 2,3. The material is not structurally strong and many ingenious methods of folding blanks, for example, have been developed in order to provide boxes with appropriate strength formed from various layers, be they interengaged or glued. In general, sheet 1 is regarded as being a packaging material and not a structural material.

Turning now to Fig. 2, it is also known to provide multiple corrugated layers 41,42, 43, etc each of which is normally interposed between a corresponding pair of facing sheets 21,22, 23, etc so as to build up by gluing the adjacent layers into a relatively large block of cardboard material. Such material is sometimes used to fill voids such as the interior void created when a door is fabricated from a rectangular frame of timber and two plywood sheets which cover opposite sides of the frame.

Such material is normally provided for sound transmission, heat transmission, or like properties but does not contribute in any substantial way to the structural strength of the article. Because of the expense of the large quantity of glue used in the fabrication of the material of Fig. 2, this style of cardboard fabrication has not found widespread commercial acceptance.

It is also known to form articles from multiple layers of the sheet 1 of Fig. 1 so as to form an article which in side elevation appears as illustrated in Fig. 3. Typical of such articles are retention devices used to hold irregularly shaped products within a regularly shaped cardboard box. Thus, for example, say, five or ten layers of the sheet 1 of Fig. 1 are stacked one above the other and held in position, for example by gluing, so as to form a thick rectangular slab. The outer perimeter of such a slab is formed, or if necessary cut, to match the interior (normally rectangular) profile of the box. In addition, a central opening is cut in the stacked sheets which has a shape corresponding to the shape of the irregularly shaped product. Thus such a retention device can be located within a cardboard box in order to hold the irregularly shaped article in position and insulated from mechanical shocks which it may experience during transport. Again, such a retention device is structurally weak and is not regarded as a structural article in its own right.

In particular, it will be appreciated that when the device formed from the stacked sheets as illustrated in Fig. 3 is subjected to the forces indicated by arrows F1, F2, and F3 in Fig. 3, the device is particularly weak having a low stiffness or resistance to bending. The device is easily initially bent, and then easily subsequently kinked, leading to permanent deformation so that the initial shape is forever lost.

Turning now to Fig. 4, in the first embodiment of the present invention a structural article in the form of a beam 10 has corrugated layers 41,42 etc arranged as in Fig. 2 and interposed between sheets 21,22, 23 etc. Then the beam 10 is vacuum encapsulated with sheet plastics material in the manner described in prior art specifications WO 95/23682; WO 97/09166 and WO 00/59709 the disclosure of which is hereby incorporated by a cross reference. Utilizing the abovementioned encapsulation technique, the beam 10 is covered with a layer (not apparent in Fig. 4) of preferably transparent APET. Furthermore, each of the corrugated layers 41,42 etc defines a plurality of passageways which each open onto the upper surface of the beam 10 as illustrated in Fig. 4. Preferably the encapsulating sheet plastics material is partially drawn into the open ends of each of these passageways so as to tightly bind all the sheet material within the beam 10 together. Indeed, it has been found that such binding is so tight that it is not necessary for the sheet materials 21,22... 41,42... to be glued prior to encapsulation. Instead, it is only necessary that the sheet materials be temporarily held in a jig during the initial stage of the encapsulating process.

Experimental results to date indicate that when forces F1, F2 and F3 are applied to the beam 10 in the same manner as are applied in the prior art of Fig. 3, an improved result (by several orders of magnitude) is able to be achieved.

In particular, Fig. 5 illustrates a pallet 15 having a load bearing deck 16 and support bearers 17,18 which are spaced apart by a distance sufficient to enable the prongs of a forklift truck to be located under the load bearing deck 16. The entire pallet 15 is fabricated from cardboard which is arranged as illustrated in Fig. 5 in the same manner as in Fig. 4, both for the load bearing deck 16 and the support bearers 17,18. With the cardboard so arranged, and without the need for any gluing, the entire pallet 15 is then encapsulated using the processes described in the abovementioned patent specifications.

The result is an extremely strong pallet 15 which is waterproof and reusable, yet is fabricated at extremely low cost from very inexpensive materials.

The foregoing describes only some embodiments 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'.