Pallet having impact resisting plastic top

Abstract

A thermoplastic pallet has a top frame which comprises bridge parts that span the openings between columns into which forks may be inserted for lifting. The plastic bridges are designed for absorbing horizontal impact loads. Each bridge has several lengthwise impact absorber zones of differing compliance to horizontal loads. The zones are comprised of vertical ribs which define open or closed cells. The edge of the pallet deck, which is preferably corrugated metal, is spaced apart from the outer edge of the bridge. It is alternatively fastened to the inner edge of the bridge or to a subframe which spaced apart from the inner edge of the frame.

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, having edges which are inset from the outside edges of the frame, for receiving goods placed on the pallet; and,    deck support means, for attaching the deck to the top;    wherein each bridge has at least one impact absorber comprising a zone running lengthwise along the bridge in proximity to the outer edge thereof, for absorbing horizontal impacts on the edge.    
     
     
         2 . The pallet of  claim 1  wherein the impact absorber zone extends across substantially the whole width of each bridge.  
     
     
         3 . The pallet of  claim 1  wherein each bridge has a multiplicity of parallel lengthwise impact absorbing zones, each zone having a different compliance to a horizontal impact force.  
     
     
         4 . The pallet of  claim 3  wherein the compliances of the multiplicity of impact absorber zones change progressively and step-wise across the width of the bridge.  
     
     
         5 . The pallet of  claim 1  wherein the unit section modulus of the impact absorber zone about its horizontal midpoint axis is several times greater than the unit section modulus of the impact absorber zone about its vertical midpoint axis.  
     
     
         6 . The pallet of  claim 1  further comprising: a metal stay extending lengthwise in proximity to the outer edge of the bridge, the stay positioned between the impact absorber zone and the outer edge.  
     
     
         7 . The pallet of  claim 1  wherein the impact absorber zone is comprised of a multiplicity of open cells bounded by a combination of straight and arcuate ribs.  
     
     
         8 . The pallet of  claim 1  wherein said impact absorber zone is comprised of a multiplicity of closed cells.  
     
     
         9 . The pallet of  claim 8  wherein said closed cells are bounded by vertical ribs and top and bottom plates  
     
     
         10 . The pallet of  claim 9  wherein each bridge has a multiplicity of parallel lengthwise impact absorbing zones, each zone having a different compliance to a horizontal impact force; and, wherein the cell shapes in a zone are different from the cell shapes of an adjacent zone.  
     
     
         11 . The pallet of  claim 10  further comprising: a multiplicity of vertically open cells spaced apart amongst said closed cells.  
     
     
         12 . The pallet of  claim 8  wherein each bridge has a multiplicity of parallel lengthwise impact absorbing zones; wherein said zones are comprised of a multiplicity of essentially rectangular closed cells bounded by vertical ribs running both lengthwise and transversely; and wherein the cells of the impact absorber zone proximate the outer edge are smaller and have greater vertical corner radii than do the cells of an impact absorber zone further from the outer edge.  
     
     
         13 . The pallet of  claim 1  wherein there each side of the pallet has a column at the midpoint of the side; wherein each side of the frame comprises two adjacent bridges, each bridge extending from the midpoint column to an outer column at a corner of the pallet; and wherein there is no continuity between the impact absorber zones of the two adjacent bridges where the frame overlies the midpoint column.  
     
     
         14 . The pallet of  claim 1  wherein the impact absorber zone is proximate the outer edge of each bridge; wherein the lengthwise portion of each bridge which proximate the inner edge of the bridge is free of impact absorber; and wherein the deck support means comprises attachment of the deck said lengthwise portion of the bridge which is proximate the inner edge.  
     
     
         15 . The pallet of  claim 14  wherein each bridge comprises at least a second parallel lengthwise impact absorber zone located intermediate said outer edge zone and said portion where the deck is attached; the second zone having a different compliance from the compliance of the first zone.  
     
     
         16 . The pallet of  claim 1  wherein the top of the pallet further comprises a subframe spaced apart from the inner edge of the frame; wherein the deck support means comprises attachment of the deck to the subframe.  
     
     
         17 . The pallet of  claim 16  wherein each bridge comprises at least a second parallel lengthwise impact absorber zone located intermediate said outer edge zone and the inner edge the second zone having a different compliance from the compliance of the first zone.  
     
     
         18 . The pallet of  claim 17  wherein the compliance of the outer edge zone is lower than the compliance of the second zone.  
     
     
         19 . The pallet of  claim 1  wherein the base comprises outer rails connected in the form of a rectangle, cross rails connecting opposing side center points of the outer rails, wherein eight outer columns; and, wherein there is one center column to which the deck is attached.  
     
     
         20 . The pallet of  claim 1  wherein the deck has less compliance to horizontal impact load than does the impact absorber.  
     
     
         21 . The pallet of  claim 20  wherein the deck is made of corrugated metal.  
     
     
         22 . The pallet of  claim 21  wherein the deck is made of thermoplastic material.  
     
     
         23 . In a 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; and    a lengthwise impact absorber zone proximate the outer edge of each bridge.    
     
     
         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 24  wherein each bridge comprises a multiplicity of parallel lengthwise impact absorber zones, each zone having a different compliance to a horizontal impact load.  
     
     
         26 . In a predominately thermoplastic pallet of the type used with fork lifting devices, wherein the pallet has 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, wherein bridge portions of the top span adjacent columns, the improvement which comprises: a rectangular deck having edges which are spaced apart from the outside edges of the top; and, bridges which comprise impact absorbers, for absorbing the impact of horizontal loads on the top.