PANELS

Abstract: A building panel (10) comprises a pair of facing sheets (12, 14) and a core (16), the core comprising an open cell structure (22) having walls extending between the facing sheets and a foam filling (26).

Description: TITLE: Panels DESCRIPTION This invention concerns panels, especially building panels for use in constructing walls and roofs. Building panels are known which comprise metal facing sheets and a core of polyurethane foam. Whilst having good insulation properties, these panels do have some disadvantages. One disadvantage is that they have a limit on their load bearing capacity even when made relatively thick because polyurethane foam is not particularly strong. Another disadvantage arises simply from the use of polyurethane foam which gives off toxic fumes in fire situations. Increasingly, therefore, there is a movement away from using such wall panels. An object of this invention is to provide useful panels. According to this invention there is provided a panel comprising a pair of facing sheets and a core, wherein the core comprises an open cell structure having walls extending between the facing sheets and a foam filling. The facing sheets may be of metal, especially of steel, more especially of galvanised steel. One or both of the facing sheets may be profiled. Preferably outer faces of the or each facing sheet is covered or coated with a corrosion protection layer. Profiling is preferably in the form of longitudinal internal channels protruding from the outer face of a facing sheet of a panel. Typically, the channels are trapezoidal in section having a narrower base than open side. In a finished panel the profile channels will be filled with the foam material but the open cell structure will not necessarily extend thereinto. That means that in a fire situation, the profile channels can provide passages for escape of fumes from the foam unhindered by the open cell structure. The fumes can, therefore, be directed upwards out of top edges of panels and away from the interior of the building. The facing sheets may alternatively be made of non-metallic materials and as such are preferably rigid boards. Examples of suitable rigid boards for use in the invention include particle boards, cement particle boards, glass fibre reinforced cement boards, cellulose reinforced gypsum boards, crushed slate boards and resin boards. Wooden facing sheets or composite wooden facing sheets may also be used in forming panels of the invention, including, for example, plywood and chipboard. Preferably facing sheets used in the invention are able to offer some fire resistance due to their composition, the addition of fire resistant materials or coating thereof with fire resistant materials. The open cell structure forming part of the core of a panel according to the invention is preferably a honeycomb structure, wherein lengths of material are bonded together at intervals or are formed into a lattice by being interwoven. There are two principle ways of producing a honeycomb structure suitable as a core. The first way is the expansion process, in which sheets of material, having adhesive applied in strips, are cut and stacked on top of each other and then the adhesive is cured, usually under pressure and at elevated temperature. Slices are then cut to the required thickness and expanded to give the honeycomb structures. The other way of making honeycomb structures is to corrugate sheets of material, apply adhesive to nodes and stack the sheets in an oven to cure. The material used to form the open cell structure may be metallic or non-metallic. Aluminium is a preferred metal for forming the open cell structure. Suitable non-metallic materials for forming the open cell structure include paper and cardboard impregnated with a stiffening material, such as a resin, especially a phenolic resin, thermoplastic polyurethane sheets, fibreglass, carbon fibre in a resin, such as phenolic, epoxide or polyumide resin, and polypropylene or polyester sheets. The honeycomb structure may be of a conventional hexagonal cell type or may be reinforced by flatsheets between each node to form trapezoidal cells. The foam filling for the core of panels of the invention is preferably a synthetic foam, suitable examples of which include polyurethane, polyisocyanate and phenolic foams. Opposed panel ends may be shaped or provided with complementary formations for engagement with ends of adjacent panels, such as in tongue and groove fashion or by provision of overlapping rebates. Panels according to the invention may be fabricated in the following manner. One facing sheet is laid out and the open cell structure laid out thereon. The foam filling is poured into the open cell structure in uncured or partially cured state and the other facing sheet laid on top. As the foam cures the foam bonds with the facing sheets to form a cohesive structure. Advantage of panels according to the invention may also include improved strength against impact damage as well as dimensional stability. Panels of the invention are suitable as building panels and as such may be used, for example, as wall panels, roof panels, floor panels (decking) and for making doors, especially fire doors or roller shutter doors. This invention will now be further described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 shows a first panel according to the invention; Figure 2 shows a second panel according to the invention; and Figure 3 shows a third panel according to the invention. Referring to Figure 1 of the accompanying drawings, a wall panel 10 comprises inner and outer facing sheets 12 and 14 respectively sandwiching a core 16. The outer facing sheet 12 is of embossed galvanised steel with spaced, parallel, alternate wide and narrow trapezoidal section profiles 18 and 20 respectively. The inner facing sheet 14 is also of embossed, galvanised steel. Both sheets 12 and 14 have on their outer faces coatings for protection against corrosion. The core 16 comprises a honeycomb structure 22 with its cells 24 bridging to the facing sheets and a filling 26 of polyurethane or polyisocyanate foam. The honeycomb structure 22 may be of aluminium or of phenolic resin impregnated paper. Turning to Figure 2 of the accompanying drawings, a wall panel 100 comprises inner and outer substantially flat facing sheets 102 and 104 respectively and a core 106. Ends of the facing sheets are bent and shaped to from at opposite ends of the panel tongue and groove jointing profiles 108 and 110 respectively for joining panels end to end. The core 106 comprises a honeycomb structure 112 of aluminium or phenolic resin impregnated paper and a polyurethane or polyisocyanate foam filling 114. The panels illustrated in Figures 1 and 2 of the accompanying drawings may be made in the following way. One facing sheet is load down and the honeycomb structure load thereon. Uncured or partially cured polyurethane or polyisocyanate foam in flowable form is poured onto the honeycomb structure, the underlying facing sheet acting as a tray. The other facing sheet is laid on top and the foam cured. As the foam cures it bonds to the two facing sheets. Figure 3 of the accompanying drawings illustrates an embodiment of the invention not based on use of metal facing sheets. A panel 200 comprises inner and outer flat facing sheets 202 and 204 of cement particle board and a core 206. Alternative materials for the facing sheets include particle boards, glass reinforced cement boards, cellulose reinforced gypsum boards, crushed slate boards and resin boards. The core 206 comprises a honeycomb structure 208 of aluminium or phenolic resin impregnated paper and a polyurethane or polyisocyanate foam filling 210. The honeycomb structures used in each of the illustrated embodiments may, of course, be substituted by a honeycomb structure made of any other suitable material such as of sheets of polyurethane, fibreglass. carbon fibre, polypropylene or polyester. Panels of the invention may have several advantages over prior art panels. The open cell core provides strength enhancing load spanning characteristics of the panels and the overall flatness of the panels can be improved relative to prior art panels. The panels perform better in fire situations in the respects of structural integrity and control of spread of smoke. The open cell core structure can retain smoke and hence delay its escape. Panels having an outer profiled facing sheet also provides a means for venting smoke to the exterior of a building upwards along the profiles.

Claims: CLAIMS 1. A panel comprising a pair of facing sheets and a core, wherein the core comprises an open cell structure having walls extending between the facing sheets and a foam filling. 2. A panel as claimed in claim 1 , wherein the open cell structure is a honeycomb structure. 3. A panel as claimed in claim 2, wherein the honeycomb structure comprises lengths of material bonded together at intervals. 4. A panel as claimed in claim 2, wherein the honeycomb structure comprises lengths of material interwoven into a lattice. 5. A panel as claimed in any one of claims 1 to 4, wherein the open cell structure is of metal. 6. A panel as claimed in claim 5, wherein the open cell structure is of alumimum. 7. A panel as claimed in any one of claims 1 to 4, wherein the open cell structure is non-metallic. 8. A panel as claimed in claim 7, wherein the open cell structure is of paper or cardboard impregnated with a stiffening material. 9. A panel as claimed in claim 8, wherein the stiffening material is a resin. 10. A panel as claimed in claim 9, wherein the resin is a phenolic resin. 11. A panel as claimed in claim 7, wherein the open cell structure is of a material selected from thermoplastic polyurethane sheets, fibreglass, carbon fibre in a resin, polypropylene sheets and polyester sheets. 12. A panel as claimed in any one of claims 1 to 11 , wherein the foam filling is a synthetic foam. 13. A panel as claimed in claim 12, wherein the foam filling is selected from polyurethane, polyisocyanate and phenolic foams. 14. A panel as claimed in any one of claims 1 to 13, wherein the facing sheets are of metal. 15. A panel as claimed in claim 14, wherein the facing sheets are of steel. 16. A panel as claimed in claim 14 or 15, wherein one or both facing sheets is or are profiled. 17. A panel as claimed in claim 16, wherein profiling of the or each facing sheet is in the form of longitudinal channels protruding from the outer face of the facing sheet. 18. A panel as claimed in claim 17, wherein the channels are trapezoidal in section having a narrower base than open side. 19. A panel as claimed in claim 16, 17 or 18, wherein the profile channels are filled with the foam filling with the open cell structure not extending into the channels. 20. A panel as claimed in any one of claims 14 to 19, wherein outer faces of one or both of the facing sheets is or are covered with a corrosion protection layer. 21. A panel as claimed in any one of claims 1 to 13, wherein the facing sheets are of non-metallic material. 22. A panel as claimed in claim 21 , wherein the facing sheets are of rigid board. 23. A panel as claimed in claim 22, wherein the rigid board is selected from particle boards, cellulose reinforced gypsum boards, crushed slate boards and resin boards. 24. A panel as claimed in claim 21, wherein the facing sheets are of wood or a wood composite. 25. A panel as claimed in claim 24, wherein the facing sheets are of plywood or chipboard. 26. A panel as claimed in any one of claims 1 to 25, wherein facing sheets have fire resistant materials added thereto or are coated therewith. 27. A panel as claimed in any one of claims 1 to 26, wherein opposed panel ends are shaped or provided with complementary formations for engagement with ends of adjacent panels. 28. A panel as claimed in claim 27, wherein said complementary formations comprise a tongue on one end and a corresponding groove on the other end of the panel. 29. A panel as claimed in claim 27, wherein opposite ends of the panel are rebated oppositely whereby a rebate of one panel is overlappable with a rebate of an adjacent panel. 30. A panel substantially as hereinbefore described with reference to and as illustrated in any one of the accompanying drawings. 31. A method of making a panel comprising a pair of facing sheets and a core, wherein the core comprises an open cell structure having walls extending between the facing sheets and a foam filling, the method comprising the steps of laying out one facing sheet with the open cell structure thereon, pouring the foam filling in uncured or partially uncured state into the open cell structure, laying the other facing sheet on top of the open cell structure and curing the foam filling to form a cohesive structure.

Inventors: WOOD IAN PHILIP, WOOD, IAN, PHILIP
Applicants: ROBERTSON UK LTD H H, WOOD IAN PHILIP, H.H. ROBERTSON (U.K.) LIMITED, WOOD, IAN, PHILIP
Application year: 1996
Main classification: E04C2
IPC codes: E04C2