Patent Publication Number: US-11040799-B1

Title: Pallet with impact resistance

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     (Not Applicable) 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     (Not Applicable) 
     BACKGROUND 
     The invention relates to a pallet construction and, more particularly, to a pallet construction with a built-in energy absorption feature to accommodate loads by impact in the leading edge or feet of the pallet. 
     It is desirable to increase the impact resistance of a welded pallet foot and leading edge. In use, plastic molded pallets support stacks of product and are typically moved using a forklift. It is not uncommon for a forklift operator to impact the side or feet of the pallets with the tines of the forklift. Improving the impact resistance of a welded pallet will expand the useful life of the pallet. 
     SUMMARY 
     The described embodiments include a built-in energy absorption feature in the form of a sharp and narrow recess or fault in the lower deck of a pallet and surrounding the feet of the pallet. This recess or fault allows for an engineered region of lower stiffness in line with the loads seen during impacts in the leading edge or feet of the pallet. A portion of the fault may have a thinner wall thickness that acts as a flexure in the case of a foot or leading-edge impact. This flexure region will bend rather than buckle or otherwise deform axially. Load transfer into members that are parallel to the impact vector will create axial compressive loads that result in very little deformation for relatively high stress. High stress causes failure, and more deformation means more energy absorbed. The described embodiments utilize bending mechanics to allow for high deformation with relatively low stress. In the case of an impact in the leading edge or foot, the normal compression loading seen in the pallet structure is instead converted into bending loading. 
     Similarly, in the case of a foot impact, the typical critical loading is the tension stress created. This is once again transformed with the described embodiments into a bending scenario. In a typical plastic pallet, the foot bends back upon impact creating a region of high tensile stress in the radius that connects the foot to the rest of the pallet. This radius is a weak point that concentrates the stress that often causes failure at the radius. Typically, the rest of the pallet is too stiff to absorb the impact, so the stress cannot be distributed to surrounding areas. The fault around the feet defines a bending region that will bend and distribute the load among more material rather than concentrate the tensile stress to the radius. It is beneficial to extend the fault around the entire foot so that the compression stress seen on the back side of the foot is also converted into bending. 
     In an exemplary embodiment, a pallet includes an upper panel with a plurality of openings, a lower panel secured to the upper panel, and a plurality of feet aligned with the plurality of openings in the upper panel. A plurality of ribs are disposed between the lower panel and the upper panel, and a perimeter fault in the lower panel extends adjacent a perimeter of the lower panel. 
     The perimeter fault may be continuous adjacent an entirety of the lower panel perimeter. 
     The perimeter fault may extend from foot to foot among the plurality of feet. The perimeter fault between respective ones of the plurality of feet may include two straight sections that join at a vertex. 
     The pallet may also include a plurality of surrounding faults in the lower panel, where each of the surrounding faults extends around a respective one of the plurality of feet, and the plurality of feet extend from a surface defined by the surrounding faults. In this context, the perimeter fault may be partially contiguous with the surrounding faults. The surrounding faults and the perimeter fault may be three-sided in cross-section. The three-sided cross-section of the perimeter fault may include an outermost wall, a connecting wall, and an innermost wall, and the outermost wall may be more flexible than the connecting wall and the innermost wall. The three-sided cross-section of the surrounding faults may include an outer circumferential wall, a joining wall, and an inner circumferential wall, and the joining wall may be more flexible than the inner and outer circumferential walls. 
     In another exemplary embodiment, a pallet includes a lower panel, a plurality of feet, and a plurality of surrounding faults in the lower panel, where each of the surrounding faults extend around a respective one of the plurality of feet, and where the plurality of feet extend from a surface defined by the surrounding faults. 
     In still another exemplary embodiment, a pallet includes an upper panel including a plurality of openings, a lower panel secured to the upper panel, and a plurality of feet aligned with the plurality of openings in the upper panel. A plurality of ribs are disposed between the lower panel and the upper panel. A perimeter fault in the lower panel extends adjacent a perimeter of the lower panel, and a plurality of surrounding faults in the lower panel each extend around a respective one of the plurality of feet, with the plurality of feet extending from a surface defined by the surrounding faults. The perimeter fault extends between the surrounding faults among the plurality of feet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects and advantages will be described in detail with reference to the accompanying drawings, in which: 
         FIGS. 1 and 2  are perspective views of an assembled pallet; 
         FIG. 3  is a top view of the lower panel; 
         FIG. 4  is a bottom view of the lower panel; 
         FIG. 5  is a cross-sectional view of the perimeter fault; and 
         FIG. 6  is a cross-sectional view of the surrounding fault. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  are perspective views of an assembled pallet  10 . The pallet  10  generally includes an upper panel  12  with a plurality of openings  14 . The pallet  10  is also shown with various handles and grommets. A lower panel  16  is secured to the upper panel  12 . With reference to  FIG. 1 , a plurality of feet  18  are aligned with the plurality of openings  14  in the upper panel  12 . In some embodiments, the feet  18  are tapered and are hollow to facilitate stacking/nesting with an adjacent pallet. That is, in order to stack/nest empty pallets, the feet of an adjacent pallet can fit through the openings  14  of a pallet below into a nested configuration. 
       FIG. 3  is a plan view of the lower panel  16  without the upper panel  12 . To increase structural rigidity, the pallet  10  includes a plurality of ribs  20  between the lower panel  16  and the upper panel  12 . The ribs  20  may extend up from the lower panel  16  into engagement with the upper panel  12 , or the ribs  20  may extend downward from the upper panel  12  into engagement with the lower panel  16 . In some embodiments, corresponding ribs extend from both the lower panel  16  and the upper panel  12 , and the ribs  20  are connected by via hotplate welding or the like to permanently connect the ribs  20  between the lower panel  16  and the upper panel  12 . The ribs  20  shown in  FIG. 3  are formed into a honeycomb configuration, although other configurations may be used. Additionally, cylindrical ribs or posts  22  may also be provided to facilitate alignment, control weld parameters, and/or add to structural rigidity. In some embodiments, the cylindrical ribs or posts  22  are weld stops that are not welded and are used facilitate alignment. 
     The lower panel  16  also includes a perimeter fault or recess  24  extending adjacent a perimeter of the lower panel  16  and/or a plurality of surrounding recesses or faults  26 , each extending around a respective one of the plurality of feet  18 . In this manner, the feet  18  extend from a surface defined by the surrounding faults  26  rather than from the lower panel  16 . As shown in  FIGS. 3 and 4 , the perimeter fault  24  may be continuous adjacent an entirety of the lower panel perimeter. The perimeter fault  24  generally extends foot to foot among the plurality of feet  18 . The perimeter fault  24  between respective ones of the plurality of feet  18  may include two straight sections that join at a vortex as shown. The perimeter fault  24  may alternatively be curved, straight or angled. In some embodiments, the perimeter fault  24  is segmented to avoid being parallel. The perimeter fault  24  may be partially contiguous with the surrounding faults  26 . 
       FIG. 5  is a cross-sectional view of the perimeter fault  24  defining a downwardly opening channel. The perimeter fault  24  may be three-sided in cross-section, including an outermost wall  28 , a connecting wall  30  and an innermost wall  32 . One or more of the walls  28 ,  30 ,  32  may be configured to be more flexible. For example, in some embodiments, the outermost wall  28  has a thinner wall thickness than the connecting wall  30  and the innermost wall  32 . 
       FIG. 6  is a cross-sectional view of an exemplary surrounding fault  26  defining a downwardly opening channel. The surrounding fault  26  is similarly three-sided in cross-section, including an outer circumferential wall  34 , a joining wall  36  and an inner circumferential wall  38 . One or more of the walls  34 ,  36 ,  38  may be configured to be more flexible. For example, in some embodiments, the joining wall  36  has a thinner wall thickness than the inner  38  and outer  34  circumferential walls. 
     The perimeter fault  24  and the surrounding faults  26  define an engineered region of reduced stiffness in line with the loads seen during impacts in the leading edge (via the perimeter fault  24 ) or feet (via the surrounding faults  26 ) of the pallet  10 . The more flexible wall of the faults acts as a flexure in the case of a foot or leading-edge impact. This flexure region will bend rather than buckle or otherwise deform axially. Load transfer into members that are parallel to the impact vector will create axial compressive loads that create very little deformation for relatively high stress. High stress causes failure, and more deformation means more energy absorbed. The faults  24 ,  26  enable the pallet  10  to utilize bending mechanics to allow for high deformation with relatively low stress. In the case of an impact in the leading edge, the normal compression loading seen in existing pallet structures is instead converted into bending loading. 
     Similarly, in the case of a foot impact, the typical critical loading is the tension stress created. With the surrounding faults  26 , this is once again transformed into a bending scenario. In a typical plastic pallet, the foot bends back upon impact creating a region of high tensile stress in the radius that connects the foot to the lower panel  16  and the rest of the pallet. This radius is concentrating the stress and may cause failure at the radius. As the rest of the pallet is too stiff to absorb the impact, it cannot spread to surrounding areas. With the surrounding faults  26  around the feet  18 , the flexible straight section of the joining wall  36  becomes a bending region. This region will bend and distribute the load among more material rather than concentrate the tensile stress. It is beneficial to extend the surrounding faults  26  around the entire foot so that the compression stress seen on the back side of the foot is also converted into bending. 
     It is desirable that the deck be minimally constrained axially, i.e. allow bending. In some embodiments, this may be achieved by utilizing bent ribs  20  to induce the ribs to buckle easier than a straight rib. The bent ribs may include two straight sections that join at a vertex at an obtuse angle. See  FIG. 3 . This structure induces the ribs  20  to buckle at a lower stress than a straight rib in compression loading. This feature is described in commonly-owned U.S. Pat. No. 9,714,116, the contents of which are hereby incorporated by reference. 
     The basic mechanics as to why bending and buckling absorb more energy than direct compression or tension loading is that energy can be described as the product of force and displacement:
 
Energy=Force×Displacement
 
     An impact is exerting a discrete amount of energy into the pallet, and allowing the pallet to deform increases the displacement, thus reducing the force (loading) in the ribs. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.