Abstract:
A pallet assembly includes an upper deck and a lower deck spaced by a plurality of columns. In one embodiment, the columns are snap-fit into the upper deck and the lower deck. The weight of the pallet is reduced without significant reduction in strength by providing only a single cross beam in each of the upper and lower reinforcement members and orienting them perpendicular to one another. The reinforcement members are minimized for weight reduction and for improved performance in heat tests. The peripheral rail of the upper reinforcement member is reduced such that it rests on only an inwardly open recess on an inner corner of each of the corner columns. This reduces the size and weight of the upper reinforcement member, while still providing support to the upper deck. Additionally, the peripheral rails of both the upper and lower decks are reduced in length such that either ledge does not directly support them while the pallet is stored on a rack. As a result, in the case of sufficient heat source on the pallets, the pallets will eventually collapse without interference from the reinforcement members and at least partially smother the heat source.

Description:
This is a continuation-in-part of U.S. patent application Ser. No. 10/426,338, filed Apr. 29, 2003. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to a pallet assembly and more particularly to a plastic pallet with reinforcement members. 
   Pallets are often used to store and transport goods. Pallets maintain the goods at a distance above the floor such that they can readily be lifted and moved by a forklift. Plastic pallets are lighter and more durable than wooden pallets. Elongated metal or composite reinforcement members have been used in some plastic pallets in order to increase the stiffness and load-bearing capacity of the pallet. 
   Some pallets comprise upper and lower decks separated by a plurality of columns that maintain the space between the upper and lower decks. The pallets may have reinforcement bars sandwiched between two layers in the upper deck or the lower deck. Traditionally, the reinforcement bars were straight bars inserted into the upper deck. One pallet previously developed by the assignee of the present invention includes reinforcement members with a frame or peripheral rail extending continuously and completely about the outer periphery of the deck and a pair of perpendicular cross beams connected to the peripheral rail. The cross beams are centered on the columns for support and the peripheral rail is also either centered on the columns or positioned outwardly of center of the columns. 
   It is desirable to minimize the number of components of the pallet and minimize the weight of the pallet while retaining the rigidity of the pallet. Additionally, some plastic pallets are evaluated for their performance under Underwriters Laboratories, Inc. (UL) Standard 2335, which, in part, evaluates the heat release performance of plastic pallets while stored on racks having inwardly extending ledges upon which the pallets are supported. Ways have been sought to manufacture the pallets of fire-retardant materials. 
   SUMMARY OF THE INVENTION 
   The present invention provides a reinforced pallet assembly with fewer components, increased strength, reduced weight and improved performance under UL standard 2335. 
   The pallet assembly of the present invention includes an upper deck and a lower deck spaced by a plurality of columns. In a first feature described below, the weight of the pallet is reduced without significant reduction in strength by providing only a single cross beam in each of the upper and lower reinforcement members and orienting them perpendicular to one another. 
   In another feature according to the present invention, the size of the reinforcement members are minimized for weight reduction and for improved performance under UL standard 2335. The reinforcement members each include a frame or peripheral rail. The peripheral rail of the upper reinforcement member is minimized such that it rests on only an inwardly open recess on an inner corner of each of the corner columns. This reduces the size and weight of the upper reinforcement member, while still providing support to the upper deck. Additionally, the peripheral rail of lower deck is reduced in length such that neither ledge directly supports it while the pallet is stored on a rack. Similarly, the length of the peripheral rail of the upper deck is also less than the distance between the ledges. The reinforcement members are spaced from the pallet outer edges of the pallet by a distance greater than the width of the ledges. In one embodiment, the outer dimensions of the reinforcement members are less than the distance between an inner edge of one ledge to the inner edge of the opposite ledge. As a result, in the Commodity Classification test portion of UL standard 2335, the pallets will eventually collapse without interference from the reinforcement members and at least partially smother the heat source. 
   In one embodiment, the columns are snap-fit into column mounts in the upper deck and the lower deck. The snap-fit columns provide for ease of assembly. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying scale drawings wherein: 
       FIG. 1  is a perspective view of the pallet assembly according to the present invention. 
       FIG. 2  is a perspective view of the lower deck and lower reinforcement member of the pallet of  FIG. 1 . 
       FIG. 3  is a plan view of the lower deck and lower reinforcement member of  FIG. 2 . 
       FIG. 3A  is an enlarged view of a portion of the lower deck and lower reinforcement member of  FIG. 3 . 
       FIG. 3B  is a section view of the lower deck and reinforcement member taken along line  3 B- 3 B of  FIG. 3A . 
       FIG. 4  is a perspective view of the lower reinforcement member and columns of  FIG. 1 . 
       FIG. 5  is a perspective view of the columns, lower reinforcement member and lower deck of  FIG. 1 . 
       FIG. 6  is a perspective view of the upper reinforcement member, columns, lower reinforcement member and lower deck of  FIG. 1 . 
       FIG. 7  is a plan view of the sub-assembly of  FIG. 6 . 
       FIG. 8  is a side view of the pallet assembly of  FIG. 1 . 
       FIG. 9  is a top view of the pallet assembly of  FIG. 1 . 
       FIG. 10  is a bottom view of the pallet assembly of  FIG. 1 . 
       FIG. 11  is a side view of the pallet assembly of  FIG. 1  positioned on a rack. 
       FIG. 12  is a perspective view of a broken-away corner section of the pallet of  FIG. 1  with an alternate column that is snap-fit into the upper deck and lower deck. 
       FIG. 13  is an exploded perspective view of the corner section of  FIG. 12 . 
       FIG. 14  is a side view of the exploded corner section of  FIG. 13 . 
       FIG. 15  is a perspective view of the column of  FIG. 14 . 
       FIG. 16  is a top view of the corner section of  FIG. 12 . 
       FIG. 17  is a section view taken along lines  17 - 17  of  FIG. 16 . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   A pallet assembly  10  according to the present invention is illustrated in  FIG. 1 . The pallet assembly  10  generally includes a molded plastic upper deck  12  and a molded plastic lower deck  14  spaced apart by a plurality of molded plastic columns  16 . A lower reinforcement member  20  is received within a channel  22  formed in the upper surface of the lower deck  14 . A tapered molded rail  35  extends around the entire periphery of the lower deck  14  to ease fork entry into openings defined between the columns  16 . 
     FIG. 2  illustrates the lower deck  14  and lower reinforcement member  20 . As can be seen in  FIG. 2 , the lower reinforcement member  20  comprises two laterally extending rail sections  26   a  and  26   b  at opposite ends of the lower deck  14  and three longitudinally extending rail sections  24   a ,  24   b  and  24   c  connecting the laterally extending rail sections  26   a  and  26   b . The two laterally extending rail sections  26   a ,  26   b  together with two of the longitudinally extending rail sections  24   a  and  24   c  are connected at rounded corners  28  to form a frame or peripheral rail, generally about the periphery of the bottom deck  14 . The center longitudinally extending rail section  24   b  connects the laterally extending rail sections  26   a  and  26   b . The central longitudinally extending rail section  24   b  generally bisects the opening defined by the peripheral rail of the lower reinforcement member  20  to create a first uninterrupted space  25   a  defined among the rail sections  24   a ,  24   b ,  26   a ,  26   b  and a second uninterrupted space  25   b  between rail sections  24   b ,  24   c ,  26   a ,  26   b . In the embodiment shown, there is no cross bar perpendicular to the center longitudinally extending rail section  24   b . All of the lower reinforcement member  20  is received within the channel  22  formed in the lower deck  14 . The channels  22  pass through column mounts  30  formed in the lower deck  14 . The column mounts  30  are molded recesses for receiving columns  16  (shown in  FIG. 1 ). As can be seen in  FIG. 2 , the channels  22  and the lower reinforcement member  20  pass through each of the column mounts  30 . The reinforcement member  20  may be formed of any material having the desired properties, including metal (such as steel) or composite material, and may have a tubular or I-beam cross-section or any known shape for reinforcement members. 
   The lower deck  14  further includes a plurality of molded pockets  32  alternating with molded protrusions  34  on either side of channels  22 . These provide reinforcement to the lower deck  14  and improve cleanliness because they do not create small cavities that entrap dirt as do typical, closely-spaced ribs extending in the same direction from a planar member that form many cavities opening in the same direction. Each molded pocket  32  and molded protrusion  34  forms a corresponding molded protrusion  34  and molded pocket  32 , respectively, on the underside of the lower deck  14 . A tapered molded rail  35  extends around the entire periphery of the lower deck  14  outside of the molded protrusions  34  and pockets  32 . The tapered molded rail  35  provides ease of fork entry and minimizes pallet damage by guiding the fork tines into the openings during fork entry. 
   As can be seen in  FIG. 3 , the laterally extending rail sections  26   a  and  26   b  are spaced from the outer edges of the lower deck  14  by a distance x. The longitudinally extending rail sections  24   a  and  24   c  are spaced from the outer edges of the lower deck  14  by a distance y. As will be explained below, the distances x and y may vary based upon the particular pallet size, or pallet standard, or particular application. In the embodiment shown, for a 40″ by 48″ pallet, x is preferably greater than two inches and more preferably approximately three inches. In the particular embodiment shown, x is three inches. The y dimension could differ from the x dimension, but in the preferred embodiment is similarly preferably greater than two inches and more preferably approximately two and a half inches. In the particular embodiment shown, y is two and a half inches. 
     FIG. 3A  is an enlarged view of a portion of the lower deck  14  and lower reinforcement member  20  in which it can be seen that the rail section  26   a  of the reinforcement member  20  is positioned in the channel  22  between flex ribs  37  extending from either side of channel  22  toward the rail section  26   a . The flex ribs  37  can also be seen in  FIG. 3B . The flex ribs  37  serve two purposes. First, during manufacture the extent to which the ribs extend inwardly can be adjusted by modifying the mold more easily than modifying the mold in order to move an entire wall of the channel  22 . This adjustment feature can be used to accommodate manufacturing tolerances between the reinforcement member  20  and the lower deck  14 . Also, when in use, the flex ribs  37  provide some flexibility such that the different rates of thermal shrinkage and expansion between the reinforcement members can be accommodated by flexure of the flex ribs  37 . Additionally, the flex ribs  37  permit the plastic deck  14  to flex in relation to the rigid reinforcement member  20  during impact and/or loading. In general, the reinforcement member  20  is free floating within the channel  22  in the x and y directions and sandwiched in the z direction. 
     FIG. 4  illustrates the lower reinforcement member  20  and columns  16 . Each of the columns  16  includes cross-ribs  36  extending vertically through the columns. Formed in the cross-ribs  36  in each column is a lower channel  40  passing through the lower end of the column  16  and into which the lower reinforcement member  20  is received such that lower edges of the cross-ribs  36  abut the lower reinforcement member  20 . Each of the columns  16 , other than the corner columns  16 , also includes an upper channel  42  through an upper end of the cross-ribs  36  of the column  16 . At the upper end of each of the corner columns  16  is an inwardly open corner recess  44  for receiving a reinforcement member. 
     FIG. 5  illustrates the lower reinforcement member  20  and columns  16  with the addition of the lower deck  14 . As can be seen in  FIG. 5 , the columns  16  are secured to the lower deck  14  over the lower reinforcement member  20  and the column mounts  30  via snap-fit connections and/or heat staking, adhesive, hot-plate welding, or other known methods. 
     FIG. 6  illustrates the sub-assembly of  FIG. 5  with the addition of the upper reinforcement member  50 . The upper reinforcement member  50  comprises longitudinally extending rail sections  54   a  and  54   b  and laterally extending rail sections  56   a ,  56   b  and  56   c . The longitudinally extending rail sections  54   a  and  54   b  are joined with the outer laterally extending rail sections  56   a  and  56   c  at rounded corners  48  to form a peripheral rail with a single cross-bar  56   b  extending from longitudinally extending rail  54   a  to longitudinally extending rail section  54   b . The center laterally extending rail section  56   b  generally bisects the opening defined by the peripheral rail sections and defines an uninterrupted space  58   a  among rail sections  56   b ,  56   c ,  54   a ,  54   b  and an uninterrupted space  58   b  among rail sections  56   b ,  56   a ,  54   a ,  54   b . Each of the rail sections is received within a channel  42  in the cross ribs  36  in the upper end of the columns  16  such that the upper edges of the cross-ribs  36  abut the upper reinforcement member  50 . Each of the rounded corners  48  is received within the inwardly open corner recess  44  formed on each of the inner corners of each of the corner columns  16 . 
     FIG. 7  is a top view of the sub-assembly of  FIG. 6 . As can be seen in  FIG. 7 , the upper reinforcement member  50  is positioned inwardly of the lower reinforcement member  20 . In particular, the laterally extending rail sections  56   a  and  56   c  are positioned a distance y′ from the outer edge of the decks and are disposed completely inwardly of the laterally extending rail sections  26   a ,  26   b  of the lower member  20 . The distance y′ is preferably greater than two inches, more preferably greater than three inches and most preferable five and a half inches. The longitudinally extending rail sections  54   a ,  54   b  of the upper reinforcement member  50  are positioned at-a distance x′ from the outer edge of the decks and at least partially inwardly of the longitudinally extending rail sections  24   a  and  24   c  of the lower member  20 . The distance x′ is preferably greater than two inches and more preferably greater than three inches. In the embodiment shown, x′ is three and a half inches. 
     FIG. 8  is a side view of the completely assembled pallet assembly  10  of  FIG. 1 . As can be seen in  FIG. 8 , the upper deck  12  includes a plurality of cross-rib members  60  extending downwardly to provide increased support.  FIG. 9  is a top view of the pallet assembly  10  according to the present invention. 
     FIG. 10  is a bottom view of the pallet assembly  10 , showing the cross-rib members  60  on the underside of the upper deck  12  which also define a channel  62  into which the reinforcement member  50  is received.  FIG. 10  also shows the molded pockets  32  and protrusions  34  formed on the underside of the lower deck  14  and the molded rail  35  around the periphery of the lower deck  14 . Ribs  68  extend downwardly inside the molded rail  35 . The channel  62  of the upper deck  12  also includes flex ribs  69  similar to those described above with respect to the lower deck  14 . 
     FIG. 11  illustrates the pallet assembly  10  mounted in a rack  70  having ledges  72  extending perpendicularly from vertical supports  74 . For one known rack, the standard width for the ledges  72  is two inches. Thus, by ensuring that the distance, x and x′, from the outer edges of the pallet assembly  10  to the reinforcement members exceed the width of the ledges  72 , in the event that a heat source or other source causes the pallet assembly  10  to collapse. In other words, the distance z 1  between an inner edge of one ledge  72  to an inner edge of the opposite ledge  72  is preferably greater than the outer dimension z 2  of the reinforcement members  20  and  50 . The collapsing pallet assembly may in some circumstances assist in at least partially smothering the heat source that may be located below. 
     FIG. 12  is a perspective view of a broken-away corner section of the pallet  10 ′ of  FIG. 1  with an alternate column  16 ′ that is snap-fit into the upper deck  12 ′ and lower deck  14 ′. The other columns  16 ′ (not shown) in the pallet  10 ′ would be similar. Components that correspond to those in the first embodiment are given the same reference numeral with a prime designation. Except as otherwise indicated below and in the drawings, the pallet  10 ′ and its components are identical to those in the first embodiment. The column  16 ′ snap-fits into column mount  30 ′ over the channel  22 ′ and the reinforcement member  20 ′ in the lower deck  14 ′. The column  16 ′ includes a plurality of flexible snap-fit tabs  80  that snap into snap-fit receivers  82  on the upper deck  12 ′ and lower deck  14 ′ to secure the column  16 ′ to the upper deck  12 ′ and to the lower deck  14 ′. Alternatively, some or all of the snap-fit tabs  80  could be formed on the upper deck  12 ′ and the lower deck  14 ′ and be snap-fit into the column  16 ′. 
     FIG. 13  is an exploded perspective view of the corner section of the pallet  10 ′ of  FIG. 12 . As shown, the flexible snap-fit tabs  80  are aligned with snap-fit receivers  82  in the column mount  30 ′. The column  16 ′ may also include smaller, relatively inflexible snap-fit tabs  84  formed on lower and upper peripheral ribs  92 ,  94  of the column  16 ′.  FIG. 14  is a side view of the exploded corner section of  FIG. 13 . As shown, the snap-fit tabs  80  protrude only slightly below lowermost edges of lower peripheral ribs  92  of the column  16 ′ (i.e. portions of the column  16 ′ other than the snap-fit tabs  80 ) and are slightly recessed from a plane containing the uppermost edge of upper peripheral ribs  94  of the column  16 ′. 
     FIG. 15  is a perspective view of the column  16 ′ of  FIG. 12 . Each flexible snap-fit tab  80  includes a camming surface  86  opposite a shoulder  88  mounted at a free end of a cantilevered flexible finger  90 . The smaller, relatively inflexible snap-fit tabs  84  also include a camming surface  95  and adjacent shoulder  96 . 
     FIG. 17  is a section view taken along lines  17 - 17  of  FIG. 16 . The column  16 ′ is pressed into the column mount  30 ′, such that the camming surface  86  of each snap-fit tab  80  contacts a snap-fit flange  98  in the snap-fit receiver  82  and then flexes inward until the shoulder  88  of the snap-fit tab  80  snaps back behind the snap-fit flange  98 , thereby securing the column  16 ′ to the upper deck  12 ′. The column  16 ′ is secured to the lower deck  14 ′ in a similar manner. The column  16 ′ of  FIGS. 12-17  provides easy assembly of the pallet  10 ′. 
   The upper and lower decks  12 ,  14  of the pallet assembly  10  of the present invention are each preferably formed in one piece of polypropylene via an injection molding process, but of course can be formed of any type of plastic applicable for the desired use. The columns  16  are each preferably formed in one piece of polyethylene via an injection molding process, but of course can be formed of any type of plastic applicable for the desired use. The materials may be chosen and distributed in accordance with the teachings of commonly-assigned U.S. Pat. No. 6,807,910, entitled “Pallet Assembly,” filed Oct. 19, 2001, hereby incorporated by reference in its entirety. 
   While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. There are many different configurations for pallet assemblies and many variations in design, many of which would benefit from the present invention.