WO2004041516A1

WO2004041516A1 - Vacuum form covered structural elements

Info

Publication number: WO2004041516A1
Application number: PCT/AU2002/001515
Authority: WO
Inventors: John Richard France
Original assignee: France (Qld) Pty Ltd
Priority date: 2002-11-07
Filing date: 2002-11-07
Publication date: 2004-05-21
Also published as: AU2002336820A1

Abstract

A vacuum form covered structural element including a plurality of shape defining elements spaced from one another; one or more shape defining interjacent elements extending between the spaced elements across at least some of the space therebetween; and a covering vacuum formed onto the external surface or surfaces of the spaced and interjacent elements wherein at least some of the spaced elements are formed from stronger material than the interjacent elements or wherein the interjacent element or elements include ribs or channels extending substantially in the direction across the space between the spaced elements.

Description

"VACUUMFORM COVERED STRUCTURALELEMENTS"

FIELD OFINVENTION

THIS INVENTION relates to vacuum form covered structural elements. Although the invention has particular application to a structural beams, the invention is not limited to this field of use.

BACKGROUNDART

The technique of vacuum forming plastics elements has been practised in the art for at least about fifty years, and vacuum forming a covering onto a former has been practised in the art for nearly as long to form vacuum form covered elements. The technique involves heating a thermoplastics sheet alongside a shape defining interior member or bringing the heated thermoplastics sheet alongside the former after so heating, applying a fluid pressure differential such that the fluid pressure is higher on the side of the sheet remote from the former to a pressure differential sufficient to conform the sheet to the shape of the interior member and make contact with at least some of its surface. The pressure differential is maintained whilst cooling the thermoplastics sheet until the thermoplastics sheet is substantially non-plastic. In most instances, the fluid pressure differential has been applied by creating a relative lower pressure or partial vacuum to a chamber containing the interior former with vents to the chamber on the side of the sheet remote from the former being open to atmospheric pressure to supply the fluid to displace the plastics sheet when in its plastic state, and it is this aspect which has given the process the name by which it is commonly known. The firms HI SCH Maschinenbau GmbH & Co K.G. and Klemm & Damm GmbH are two examples of firms which have used this technique for moulding vacuum form covered elements since at least 1984. It has been found that vacuum formed covered elements exhibit superior strength when compared with either the separate skin or the shape defining interior element separately. It is possible that this may be due to the assembly possessing a monocoque or similar type of construction, although such elements also exhibit other advantages. However, the strength of such elements is limited and is not, for example, usually sufficient for such elements to perform as structural elements such as beams or girders .

The present invention aims to provide a vacuum form covered structural element which alleviates one or more of the disadvantages of the prior art or provides a vacuum form covered element which is stronger than those known in the art. Other aims and advantages of the invention may become apparent from the following description.

DISCLOSURE OFTHE INVENTION

With the foregoing in view, this invention in a first aspect resides broadly in a vacuum form covered structural element including:

a plurality of shape defining elements spaced from one another;

one or more shape defining interjacent elements extending between the spaced elements across at least some of the space therebetween; and

a covering vacuum formed onto the external surface or surfaces of the spaced and interjacent elements;

wherein at least some of the spaced elements are formed from stronger material than the interjacent elements. In a second aspect, the present invention resides broadly in a vacuum form covered structural element including:

a plurality of shape defining elements spaced from one another;

wherein the interjacent element or elements include ribs or channels extending substantially in the direction across the space between the spaced elements .

In one form, the vacuum form covered structural element is in the form of a composite beam wherein the spaced elements are formed from timber or metal, such as rolled-hollow-section steel, of elongate form, and the interjacent element or elements are in the form of an integral block of plastics foam bonded to the elongate members and of appropriate shape to perform as a web between the elongate members . In such form, the covering is vacuum formed onto the assembled part-formed composite (referred to hereinafter as a composite skeleton) to form a composite beam or girder.

In another form, the vacuum form covered structural element is in the form of a platform, panel or pallet wherein the spaced elements are arranged in spacial relationship with one another to form a frame-like assembly. In such form, some of the spaced elements may intersect with one another and be bonded to one another at the intersections. The interjacent element or elements are provided in between the spaced elements to form the composite skeleton which is covered with the vacuum formed skin or cladding to form the vacuum form covered element.

In another form, particularly in relation to the second aspect of the invention hereinbefore described, the spaced elements and interjacent elements are formed integrally as a shaped block with the ribs or channels being provided in selected orientations according to the anticipated loading of the vacuum form covered structural element. It is preferred, however, that the spaced and interjacent elements are assembled to form the composite skeleton as hereinbefore described.

In third aspect, the present invention resides broadly in a method of forming a vacuum form covered structural element including:

providing a plurality of shape defining elements in spaced relationship to one another;

providing one or more interjacent elements such that the spaced elements are formed from stronger material than the interjacent elements;

bonding the one or more shape defining interjacent elements to at least some of the spaced elements across at least some of the space or spaces therebetween to form a composite skeleton; and

vacuum forming a covering onto the external surface or surfaces of the composite skeleton.

In a fourth aspect, the present invention resides broadly in a method of forming a vacuum form covered structural element including:

providing a plurality of shape defining elements in spaced relationship to one another; providing one or more shape defining interjacent elements having ribs or channels extending substantially in the direction across the spaced between the spaced elements;

bonding the one or more shape defining interjacent elements to at least some of the spaced elements across at least some of the space or spaces between the spaced elements to form a composite skeleton; and

Preferably, the spaced elements are formed from stronger material than the interjacent elements as hereinbefore described.

In a fifth aspect, the present invention resides broadly in a method of forming a vacuum form covered element including:

placing a shape defining former into operative disposition with respect to a first jig;

heating a first thermoplastics sheet;

bringing the heated first thermoplastics sheet alongside the former whilst in operative disposition with respect to the first jig;

and applying a fluid pressure differential across the heated first thermoplastics sheet such that the fluid pressure is higher on the side of the sheet remote from the former to a differential sufficient to conform the sheet to the shape of the former and make contact with at least some of its surface and such that some of the heated first thermoplastics sheet overlaps the former to cover at least part of the first jig; maintaining the differential whilst cooling the thermoplastics sheet until the thermoplastics sheet is substantially non-plastic;

removing the former and the cooled first thermoplastics sheet from it operative disposition with the first jig such that some of the first thermoplastics sheet extends away from the former such that the former and the first thermoplastics sheet forms a partially covered vacuum form covered element;

placing a the partially covered vacuum form covered element into operative disposition with respect to a second jig such that at least some of the former is exposed;

heating a second thermoplastics sheet;

bringing the heated second thermoplastics sheet alongside the at least some of the exposed portion of the former whilst in operative disposition with respect to the second jig;

and applying a fluid pressure differential across the heated second thermoplastics sheet such that the fluid pressure is higher on the side of the sheet remote from the former to a differential sufficient to conform the sheet to the shape of the former and make contact with at least some of the exposed surface and such that some of the heated second thermoplastics sheet is encapsulated by the extended edge of the first thermoplastics sheet to form a seam between the first and second thermoplastics sheets;

maintaining the differential whilst cooling the second thermoplastics sheet until the second thermoplastics sheet is substantially non-plastic.

The excess edge, if any, of the second thermoplastics sheet is preferably trimmed from the first thermoplastics sheet along its junction. If required, the first thermoplastics sheet is pierced or provided with penetrations to permit vacuum to be applied as the pressure differential hereinbefore described. Preferably, a bonding agent is provided on the surface of the spaced and interjacent elements to bond them to one another as well as to bond the covering to the former.

In a sixth aspect, the present invention resides broadly in a vacuum form covered element being covered with two thermoplastics having a seam extending along at least some of their respective adjoining edges.

BRffiFDESCRIPTION OFTHF, TfflAWTNftS

In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention and wherein: -

Fig. 1 is a pictorial view of a vacuum form covered structural beam according to the invention;

Fig. 2 is an end view of the beam of Fig. 1;

Fig. 3 is a sectional view of the beam of Fig. 1 along line 3-3 of Fig. 4;

Fig. 4 is a front elevation of the beam of Fig. 1;

Fig. 5 is a plan view of the beam of Fig. 1;

Fig. 6 is a sectional view of the beam of Fig. 1 along line 6-6 of Fig. 4;

Fig. 7 is a pictorial view of a vacuum form covered pallet according to the invention;

Fig. 8 is a front elevation of the pallet of Fig. 7; Fig. 9 is a plan view from below of the pallet of Fig. 7;

Fig. 10 is a detail view of detail E of Fig. 9;

Fig. 11 is a front elevation of the pallet of Fig. 7;

Fig. 12 is a sectional view of the pallet of Fig. 7 along line B-B Fig. 13;

Fig. 13 is a plan view from above of the pallet of Fig. 7;

Fig. 14 is a sectional view of the pallet of Fig. 7 along line C-C of Fig. 13;

Fig. 15 is a sectional view of the pallet of Fig. 7 along line A-A of Fig. 13

Fig. 16 is a detail view of detail D of Fig. 14;

Fig. 17 is a detail view of detail F of Fig. 9;

Fig. 18 is a plan view from below of an alternative pallet according to the invention;

Fig. 19 is a detail view of detail E of Fig. 18;

Fig. 20 is a plan view from below of another alternative pallet according to the invention;

Fig. 21 is a pictorial view of a further alternative pallet according to the invention;

Fig. 22 is a plan view from above of the further alternative pallet of Fig. 21;

Fig. 23 is a front elevation of the further alternative pallet of Fig. 21; Fig. 24 is a side elevation of the further alternative pallet of Fig. 21;

Fig. 25 is a plan view from below of the further alternative pallet of Fig. 21;

Fig. 26 is a sectional view of the further alternative pallet of Fig. 21 along line C-C of Fig. 25;

Fig. 27 is a sectional view of the further alternative pallet of Fig. 21 along line A-A of Fig. 25;

Fig. 28 is a detail view of detail B of Fig. 23;

Fig. 29 is a detail view of detail D of Fig. 25;

Fig. 30 is a detail view of detail E of Fig. 25;

Fig. 31 is a diagrammatic partial sectional view illustrating a first step of the method of the present invention;

Fig. 32 is a diagrammatic partial sectional view illustrating a second step of the method of Fig. 31;

Fig. 33 is a diagrammatic partial sectional view illustrating a third step of the method of Fig. 31;

Fig. 34 is a diagrammatic partial sectional view illustrating a fourth step of the method of Fig. 31;

Fig. 35 is a diagrammatic partial sectional view illustrating a fifth step of the method of Fig. 31.

DETAILED DESCRIPTION OFTHE DRAWINGS

The vacuum formed beam 10 shown in Figs . 1 to 6 has two square section timber members 11 spaced from and parallel to one another being separated by a web 12. The web is of slightly smaller thickness than the dimensions of the timber members. The web forms an interjacent element between the timber members which together form the spaced elements of the beam. The web includes a plurality of regularly spaced transverse channels shown typically at 14. Each channel extends transverse to the elongate direction of the beam and are of semi-circular cross section.

The front and back sides and the top and bottom edges of the beam are covered by a vacuum formed covering, but no covering is provided on the ends of the beam. The vacuum formed covering is posited in two stages in accordance with the method hereinbefore described with reference to the fifth and sixth aspects of the invention.

The pallet 20 shown in Figs. 7 to 17 has a square top panel 21 with rounded corners and an edge chamfer 25 and extending from the lower face thereof, nine feet, being four corner feet shown typically at 22, for edge feet shown typically at 23 and a centre foot 24. The corner feet are disposed under the corners of the square top panel and the edge feet are disposed half way along each edge of the panel, and the centre foot is located under the centre of the panel. The corner feet are substantially square in plan view with rounded corners as is the centre foot, and each of the feet taper from there emergence from the lower face of the top panel to a smaller dimension at their respective lower faces . The edge feet are rectangular in plan view with rounded corners, the shorter side of the edge feet being the same as the side of the corner feet, and the longer side of the rectangle being substantially the same dimension as the sides of the centre foot.

Extending between each corner foot and its adjacent edge foot there are provided six channels shown typically at 15, each channel ("edge channels") extending up the side face of each corner foot, from there across the under face of the top panel, and then down the side face of the adjacent edge foot. In a similar arrangement, there are 10 channels ("centre channels") extending between each edge foot and the centre foot in a regularly spaced pattern, but with a gap in the middle to provide space to allow a piercing jig to pierce the skin of the pallet to permit a vacuum to be used to vacuum form a covering in accordance with the fifth and sixth aspects of the invention hereinbefore described. The centre channels extend up the side of each centre foot, across the under face of the top panel and down the side faces of the centre foot. The channels are substantially semi-circular in cross section.

Additionally, the edge feet on the centre foot are hollow and each have a cavity, an edge foot cavity designated by reference numeral 26, and a centre foot cavity 27, each cavity being open to the under face of the pallet.

The corners and edges of the panel are provided with a radius. It will be appreciated that the radius of the composite skeleton prior to vacuum form covering is increased by the additional rounding afforded by the covering process.

The alternative pallet 30 shown in Fig. 18 is similar to the pallet shown in Figs. 7 to 17, except that top panel is rectangular, the corner feet are rectangular in plan view, two of the edge feet are replaced by narrower forms (narrow edge feet) and are not hollowed out, the smaller dimension of the rectangular planned section of the narrow edge feet being the same as the small dimension of corner feet, and there being only four channels extending between the corner feet and the narrow edge feet. In the other alternative pallet 40 shown in Fig. 20, the underside construction of the pallet is somewhat different from that shown in Figs. 7 to 19, there being two elongate edge feet 41 along the underside two of the edges of the top panel, and an elongate centre foot 42 disposed centrally between and parallel to the elongate edge feet, and being hollow with a bottom open cavity 43.

Between each elongate edge foot and elongate centre foot there are provided five sets each of three channels ("cross channels"), each set of three being regularly spaced channels shown typically at 44 and each set being separated by approximately the same width as the regular spacing of the channels in each set.

The further alternative pallet shown in Figs. 21 to 30 is similar to that shown in Fig. 20, but has two elongate side feet

52 which have a cavity 54 open to the underside, the centre foot

53 also having a cavity 56 open to the underside, and the ribs shown typically at 55 extending between each of the elongate side feet and the centre foot, up the sides of the edge feet nearer to the centre foot, across the under face of the top panel 51 and down the elongate side faces of the centre foot. The channels are provided in regularly spaced arrangement but with five gaps such that there are four sets of four ribs between two sets of three ribs to the outside of the four sets as shown. The slots for the pallet footings are the same dimension as the footing width to allow the pallets to stack on top of one another.

Referring to the diagrammatic Figs. 1 to 35, a first skin 61 is heated and brought into contact with a core 62 which is mounted into a first jig 63 as shown in particular in Fig. 31. In step two shown in Fig. 32, the core and first skin bonded thereto are removed from the first jig and inverted so that an edge portion of the first skin shown at 69 can be trimmed along a trim line 65. The first skin and its core are then inserted into a second jig 64 as shown in Fig. 3 with a portion of the first skin extending away from the core. As shown in Fig. 34, a second skin 66 is heated and brought into contact with the core, the edge of the first skin and the second jig and a vacuum applied to permit the second skin to be urged against the exposed face of the core, with part of the second skin being pressed into a fold under the edge of the first skin as shown at 70, the edge portion 68 of the second skin being trimmed along a trim line 67 as sown in Fig. 35. The heating of the first and second skins is typically sufficient to permit at least some fusion welding of the skin to the core and each skin to the other. Hot melt glue or the like may be used to assist in the welding process.

In use, vacuum form covered structural elements may be constructed in accordance with the invention and used in load bearing applications such as beams or pallets. Of course, the use of the invention is not limited to beams or pallets . Some of the spaced elements can be made from stronger material and the interjacent elements, and ribs or channels can be provided to enhance the strength and/or stiffness of the interjacent elements .

The vacuumed form cladding or covering of the vacuum form covered structural elements can be completed by following the two stage vacuum form covering process as described in relation to

Figs. 31 to 35. For example, the structural element may be a plastic composite structural beam having an inner core of wood and expanded polystyrene foam forming a composite skeleton. The inner core is made structurally stronger by encapsulating it in a plastic covering suitable thickness. The vacuum form covering can be polyvinyl chloride, high impact polystyrene, acrylonitrile butadiene styrene or a composite structure of two or more of these materials. Of course, other engineering plastics may be used of desired. Moreover, in the case of the beams of the present invention, rolled hollow section steel may be used for the spaced elements in place of the square section timber described in respect of Figs. 1 to 6.

The composite beam is believed to have structural load bearing capabilities achieved by the design of inner core that has a load bearing capacity without the use of a vacuum form covering in the form of a plastic membrane skin. The plastic membrane skin is believed to increase the load bearing capabilities and also allow for increased torsional rigidity.

In use, the interjacent element is formed by cutting a length of expanded polystyrene with hot wire from a block molding process to the required dimensions of length, width and thickness . The length is then cut to the design to provide structure to the expanded polystyrene component. The length of wood is cut to the same length as the expanded polystyrene component, two lengths being required. The dimensions of the wood are selected to be such that the overall width is 10 millimetres wider than that of the expanded polystyrene element . The expanded polystyrene and wooden elements are joined together as shown in Fig. 3 using hot melt adhesives. The composite core is then placed into a vacuum form covering machine whereupon a plastic sheet is heated and then using a vacuum to create a pressure differential, the sheet is rapped around the core structure. Depending upon the level of automation involved, the core may be required to be covered a second time from its opposite side in accordance with the method of the present invention. The plastic composite beam may be produced in lengths of up to 20 metres and a range of selected cross sectional dimensions .

Prior, to the bonding of the expanded polystyrene to the timber, grooves are cut or formed into the polystyrene at right angles to the elongate direction. Hot melt adhesive is applied to the wood structure prior to vacuum forming a covering over the composite skeleton, the finished product being a fully encapsulated core.

Although the invention has been described with reference to specific examples, it will be appreciated by persons skilled in the art that the invention may be embodied in other forms which are encompassed within the broad scope and ambit of the invention as defined by the following claims.

Claims

1. A vacuum form covered structural element including:

a plurality of shape defining elements spaced from one another;

wherein at least some of the spaced elements are formed from stronger material than the interjacent elements.

2. A vacuum form covered structural element including:

a plurality of shape defining elements spaced from one another;

wherein the interjacent element or elements include ribs or channels extending substantially in the direction across the space between the spaced elements.

3. A vacuum form covered structural element according to Claim 1 or Claim 2 in the form of a composite beam wherein the spaced elements are formed from timber or metal, such as rolled- hollow-section steel, of elongate form, and the interjacent element or elements are in the form of an integral block of plastics foam bonded to the elongate members and of appropriate shape to perform as a web between the elongate members .

4. A vacuum form covered structural element according to Claim l or Claim 2 in the form of a pallet wherein the spaced elements are arranged in spacial relationship with one another to form a frame-like assembly.

5. A vacuum form covered structural element according to Claim 4, wherein some of the spaced elements intersect with one another and are bonded to one another at the intersections .

6. A vacuum form covered structural element according to Claim 4 or Claim 5, wherein the spaced and interjacent elements are assembled to form the composite skeleton having at least some of the spaced elements formed from stronger material according to Claim 1.

7. A vacuum form covered structural element according to Claim 4 or Claim 5, wherein the spaced elements and interjacent elements are formed integrally as a shaped block with the ribs or channels being provided in selected orientations according to the anticipated loading of the vacuum form covered structural element .

8. A method of forming a vacuum form covered structural element including:

9. A method of forming a vacuum form covered structural element including:

providing one or more shape defining interjacent elements having ribs or channels extending substantially in the direction across the spaced between the spaced elements;

10. A method according to Claim 9 including forming the spaced elements from stronger material than the interjacent elements according to Claim 8.

11. A method of forming a vacuum form covered element including:

heating a first thermoplastics sheet; bringing the heated first thermoplastics sheet alongside the former whilst in operative disposition with respect to the first jig; and

applying a fluid pressure . ifferential across the heated first thermoplastics sheet such that the fluid pressure is higher on the side of the sheet remote from the former to a differential sufficient to conform the sheet to the shape of the former and make contact with at least some of its surface and such that some of the heated first thermoplastics sheet overlaps the former to cover at least part of the first jig;

maintaining the differential whilst cooling the thermoplastics sheet until the thermoplastics sheet is substantially non-plastic;

heating a second thermoplastics sheet;

12. A method according to Claim 11, including trimming any excess edge of the second thermoplastics sheet from its junction with the first thermoplastics sheet.

13. A method according to any one of Claims 8 to 12 , including bonding the spaced elements and interjacent elements to one another.

14. A method according to any one of Claims 8 to 13 including providing a bonding agent on the surface of the spaced and interjacent elements to bond them to one another.

15. A method according to any one of Claims 8 to 14 , including providing a bonding agent on the surface of the spaced and interjacent elements to bond the covering thereto.