Impact-resisting pallet having metal stay

Abstract

The top of a thermoplastic pallet has a rectangular frame to which the pallet deck is directly or indirectly attached. The edge of the deck is spaced apart from the outer edge of the frame. The frame comprises bridge parts which span the openings between columns into which forks may be inserted for lifting of the pallet. The plastic bridges are designed for absorbing horizontal impact loads. Each bridge has several lengthwise impact absorber zones of differing cell configuration and thus differing compliance to horizontal impact loads. A metal stay runs along the outer edge of each bridge, for distributing impact forces, and for improving the resistance of the pallet top to impact loads. A stay may be anchored by its ends at the opposing ends of a bridge, and or along its length by engagement of perforations in the stay with plastic features distributed along the length of the edge of the bridge.

1 . A pallet comprised of: 
 a rectangular base;    a plurality of spaced apart outer columns extending upwardly from the periphery of the base;    a rectangular top, mounted on and attached to the outer columns, the top comprising a rectangular frame having inner edges and outer edges, the frame comprising bridges which span the spaces between the outer columns;    a deck, for receiving goods placed on the pallet; and,    deck support means, for attaching the deck to the top;    a stay, made of a material having a modulus of elasticity greater than that of the material of the frame, extending lengthwise along at least one bridge in proximity to the outer edge thereof; and,    means for anchoring the stay, to resist tension forces within the stay which result from horizontally impacts at the outer edge of the bridge.    
   
   
       2 . The pallet of  claim 1  wherein the deck edges are inset from the outside edges of the frame, wherein said at least one bridge comprises an impact absorber zone running lengthwise along the bridge, wherein the stay is positioned between the zone and the outer edge of the bridge.  
   
   
       3 . The pallet of  claim 1  wherein the stay runs along the surface of the outer edge of said one bridge.  
   
   
       4 . The pallet of  claim 1  wherein the stay is spaced apart from the outer edge of said one bridge by a layer of plastic material.  
   
   
       5 . The pallet of  claim 1  wherein the stay is one piece and extends along the length of two adjacent bridges; and wherein the stay is anchored to the frame where it overlies said outer columns.  
   
   
       6 . The pallet of  claim 1  wherein the stay is one piece and extends continuously around the entire periphery of the frame and the anchoring means comprises attachment of the stay ends to each other.  
   
   
       7 . The pallet of  claim 1 , for use with a forklift device, wherein the pallet has eight columns spaced around the periphery of the base and eight bridges spanning the spaces between the columns; and wherein each bridge has a stay.  
   
   
       8 . The pallet of  claim 1  wherein the stay has a rectangular cross section and is made of a metal selected from the group consisting of iron base alloys, nickel base alloys, and cobalt base alloys.  
   
   
       9 . The pallet of  claim 8  wherein the stay is made of 0.010 to 0.020 inch thick carbon steel having a hardness number of at least Rockwell B65.  
   
   
       10 . The pallet of  claim 5  wherein the stay has a substantially rectangular cross section and a height to width aspect ratio of at least 10 to 1.  
   
   
       11 . The pallet of  claim 1  wherein the stay has a substantially rectangular cross section; and, wherein the stay has section modulus about a horizontal midpoint axis which is at least 20 times the horizontal section modulus about the vertical midpoint axis.  
   
   
       12 . The pallet of  claim 1  wherein the means for anchoring the stay comprises engagement of the ends of the stay with portions of the frame which overlie columns.  
   
   
       13 . The pallet of  claim 12  wherein the stay ends are contoured in the plane of the deck and are engaged with mating contoured portions of the frame.  
   
   
       14 . The pallet of  claim 1  wherein the means for anchoring the stay comprises a multiplicity of anchor points spaced apart along the length of the stay.  
   
   
       15 . The pallet of  claim 14  wherein the stay has a multiplicity of spaced perforations and wherein said anchor points comprise plastic projections of the frame engaged with said perforations.  
   
   
       16 . The pallet of  claim 15  wherein said perforations are cut outs along the edge of the stay.  
   
   
       17 . The pallet of  claim 15  wherein the means for anchoring the stay further comprises engagement of the ends of the stay with portions of the frame which overlie columns.  
   
   
       18 . The pallet of  claim 1  wherein the edges of the deck are inset from the outside edges of the frame; wherein, top of the pallet further comprises a subframe spaced apart from the inner edge of the frame; and, wherein the deck support means comprises attachment of the deck to the subframe.  
   
   
       19 . The pallet of  claim 1  wherein the deck support means comprises attachment of the edge of the deck to the subframe.  
   
   
       20 . The pallet of  claim 1  which comprises at least two of said stays, running in parallel.  
   
   
       21 . The pallet of  claim 1  wherein the pallet is predominately comprised of polyolefin thermoplastic material and the stay is made of metal.  
   
   
       22 . In a predominately thermoplastic pallet of the type used with fork lifting devices, having a rectangular top comprised of a deck for receiving goods placed on the pallet, wherein the top is supported on eight spaced apart columns extending upwardly from the periphery of a rectangular base, the improvement which comprises: 
 a top comprised of a thermoplastic frame which forms the outermost portion of the top;    the frame comprising bridges spanning spaces between the columns, having inner edges and outer edges;    each bridge comprising a lengthwise impact absorber zone proximate the outer edge of the bridge;    a stay, made of a material having a modulus of elasticity greater than that of the frame material, extending lengthwise along at least one bridge in proximity to the outer edge thereof; and,    means for anchoring the stay, to resist tension forces within the stay which result from horizontally impacts at the outer edge of the bridge.    
   
   
       23 . The pallet of  claim 22  where the edges of the deck are inset from the outer edges of the top;  
   
   
       24 . The pallet of  claim 23  wherein the exterior dimensions of the pallet are about 40 inches×80 inches; and, wherein and the pallet is a GMA type pallet.  
   
   
       25 . The pallet of  claim 23  wherein the pallet is predominately comprised of a material selected from the group which comprises polyethylene, polypropylene and combinations thereof.  
   
   
       26 . The pallet of  claim 23  wherein each bridge comprises a multiplicity of parallel lengthwise impact absorber zones, each zone having a different compliance to a horizontal impact load.  
   
   
       27 . A wood pallet for use with a forklift device for transporting goods which comprises: predominately thermoplastic leader board attached to the end of the top, the leader board comprising at least one lengthwise impact absorber zone in proximity to the outer edge of the board, for absorbing impacts at the edge of the board.  
   
   
       28 . The pallet of  claim 27  further comprising: a metal stay extending along the outer edge of the leader board, the stay closer to the edge than said impact absorber zone.  
   
   
       29 . The pallet of  claim 27  wherein the pallet top comprises a multiplicity of wood slats and one leader board at each end of the top.  
   
   
       30 . The pallet of  claim 27  wherein the leader board has two parallel impact absorber zones, each having a different compliance to horizontal impact loads.  
   
   
       31 . The pallet of  claim 27 , wherein the leader board has a lengthwise interior zone made of low rigidity material and an exterior of high rigidity material.  
   
   
       32 . The method of making the top of a thermoplastic pallet wherein the top is supported on a multiplicity of columns, wherein the top is comprised of a a rectangular frame having inner edges and outer edges, and the frame comprising bridges which span the spaces between the outer columns; wherein the at least on bridge has a stay made of a material having a modulus of elasticity greater than that of the thermoplastic, the stay extending lengthwise along the bridge in proximity to the outer edge thereof, which comprises: (a) forming a first frame part having lengthwise ribs defining a multiplicity of open cells, and having a cavity running lengthwise in proximity to the outer edge of the bridge portion of the frame; (a) forming a cover part shaped to fit the top of the frame and close the open cells, the top comprising a male buttress shaped to fit into the lengthwise cavity of the basic frame element when the two parts are mated; (c) placing a the stay along the buttress; and (d) joining the parts while heating the mating surfaces thereof sufficiently to cause the parts to weld together.  
   
   
       33 . The method of  claim 32  which further comprises: providing perforations along the length of the stay; providing a groove along the length to the buttress; and positioning the stay within the groove before mating the parts, wherein the heating and joining are sufficient to cause thermoplastic to flow from the mated parts into said stay perforations, to and thereby form distributed anchoring points for the stay.