Twin sheet pallet

Abstract

A twin sheet plastic pallet comprising an upper plastic sheet and a lower plastic sheet selectively fused to the upper sheet. The lower sheet has a generally rectangular configuration, including sidewalls and end walls, and includes a plurality of separate parallel upwardly opening longitudinally extending U-shaped grooves extending from end to end of the sheet and a plurality of downwardly opening U-shaped grooves interspersed between the upwardly opening grooves and opening in the end walls of the sheet. The upper sheet defines a top wall, defining the platform surface of the pallet, and a plurality of upwardly opening U-shaped protrusions extending downwardly from the top wall and sized to nest within the upwardly opening grooves of the lower sheet, whereby with the upper sheet positioned over the lower sheet and the protrusions positioned in the upwardly opening grooves, the sheets may be fused together to form double thickness U-shaped wall structures at the interfaces of the protrusions and the upwardly opening grooves. The pallet further includes a pair of longitudinally extending metallic beams positioned between the upper and lower sheets, and laterally aligned slots are formed in the U-shaped wall structures to allow passage of the forks of a forklift truck.

Description

BACKGROUND OF THE INVENTION

This invention relates to shipping and storage pallets and more particularly to plastic pallets embodying a twin sheet construction.

Whereas twin sheet pallets have in general proven to be superior to the wooden pallets previously in use, the undersurfaces of the pallets tend to be irregular so that movement of the pallets over irregular transfer surfaces and over various transfer devices such as conveyors is difficult and sometimes impossible. Further, the prior art twin sheet pallets fail to make provision to preclude tipping of the pallet off of the forks of a forklift truck in the presence of an unbalanced load on the pallet. Further, the prior art twin sheet pallets have tended to creep or sag after extended periods of use.

SUMMARY OF THE INVENTION

This invention is directed to the provision of an improved twin sheet pallet.

More specifically, this invention is directed to the provision of a twin sheet plastic pallet which moves readily over transfer surfaces or transfer devices, which is resistant to tipping of the pallet off of the forks of a fork lift truck in the presence of an unbalanced load, and which is resistant to creepage or sag even after extended periods of usage.

The invention pallet is of the plastic twin sheet type comprising a generally rectangular upper plastic sheet and a generally rectangular lower plastic sheet selectively fused to the upper sheet, to form the pallet.

According to an important feature of the invention, the lower plastic sheet includes parallel, alternate, upwardly opening grooves and downwardly opening grooves extending from end to end of the sheet, and the upper plastic sheet has a generally planar top wall and a plurality of upwardly opening protrusions extending downwardly from the top wall and nestingly and fusedly received in the upwardly opening grooves in the lower sheet. This arrangement provides a simple, sturdy construction which resists creepage and provides a footprint facilitating smooth movement of the pallet over transverse surfaces or transfer devices.

According to a further feature of the invention, the lower sheet includes end walls and the downwardly opening grooves in the lower sheet open in the end walls. This specific construction further simplifies the construction of the pallet and further clarifies the smooth, continuous footprint of the pallet.

According to a further feature of the invention, each downwardly opening groove in the lower sheet is defined in part by a top wall; a series of upstanding knobs is provided on each groove top wall; the protrusions in the upper sheet are arranged in longitudinally extending rows; and portions of the top wall of the upper sheet between the rows are fused to the knobs. This specific arrangement provides a sturdy, simple twin sheet construction between the upper and lower sheets.

According to a further feature of the invention, laterally aligned slots are provided in sidewalls of the grooves and the protrusions to allow passage of the forks of a fork lift truck. This arrangement provides firm receipt of the forks of a forklift truck to discourage tipping.

According to a further feature of the invention, two longitudinally spaced protrusions are provided in each upwardly opening groove to provide longitudinally spaced laterally aligned sets of protuberances, and laterally aligned slots are provided in each set of protrusions and in the associated upstanding walls of the upwardly opening grooves and the downwardly opening grooves. This specific construction further facilitates the firm positive receipt of the two forks of the forklift truck.

According to a further feature of the invention, the lower sheet includes generally parallel upstanding side walls, generally parallel upstanding end walls, and a plurality of separate, flat, laterally spaced, parallel bottom walls extending from end wall to end wall, and the underfaces of the bottom walls define a pallet footprint comprised solely of a plurality of separate, flat, laterally spaced, parallel surfaces extending from end wall to end wall of the sheet. This specific construction further facilitates the movement of the pallet over transfer surfaces or transfer devices.

According to a further feature of the invention, the pallet further includes at least one metallic beam positioned between the upper and lower sheets and extending substantially from end wall to end wall of a pallet. This beam construction augments the bending strength to the pallet.

According to a further feature of the invention, the spacer knobs are arranged in laterally spaced longitudinally extending rows and the metallic beam is positioned between a top wall section of the lower sheet and a portion of the top wall of the upper sheet and extends substantially from end to end of the pallet between adjacent spacer knob rows. This arrangement allows the spacer knobs to further function to locate and retain the metallic beam.

Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:

FIGS. 1 is a perspective view of the invention pallet;

FIG. 2 is an exploded perspective view of vacuum formed upper and lower sheets utilized to form the pallet;

FIGS. 3 and 4 are cross-sectional views taken respectively on lines 3-3 and 4-4 of FIG. 1;

FIG. 5 is a perspective view of the pallet with the pallet in an upside down orientation;

FIG. 6 is an end view of the pallet;

FIG. 7 is a side view of the pallet;

FIG. 8 is a bottom view of the pallet;

FIG. 9 is a top view of the pallet;

FIG. 10 is a perspective view of the lower sheet;

FIG. 11 is an end view of the upper sheet;

FIG. 12 is a side view of the upper sheet;

FIG. 13 is a perspective view of the upper sheet;

FIG. 14 is a fragmentary view of the lower sheet;

FIG. 15 is a fragmentary enlarged view taken within the circle 15 of FIG. 3;

FIG. 16 is a fragmentary perspective view showing a pallet beam; and

FIG. 17 is a cross-sectional view of a pallet beam.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In overview, the invention pallet 10 is formed of lower and upper plastic sheets 12 and 14, knitted or fused together, and a pair of reinforcing steel beams 13 positioned between the upper and lower sheets.

Sheets 12 and 14 may be separately molded in a vacuum forming process, may be formed of an organic polymeric material such as polyethylene, and may be knitted or fused together to form the pallet in a compression molding process. The molds for vacuum forming the sheets are not shown but may be constructed in accordance with known vacuum forming techniques.

Each of the upper and lower sheets is formed from a generally rectangular planar plastic sheet and the sheets are fused together utilizing the molds while the sheets are in a heated, moldable state so that fusion may occur between the upper and lower sheets at any point where an interface is defined between the upper and lower sheets.

Lower sheet 12 starts out as a generally rectangular sheet of polyethylene plastic material and is vacuum molded in known manner utilizing a suitable lower mold. Lower sheet 12 includes upstanding end walls 12a, upstanding sidewalls 12b, a longitudinally extending upwardly opening U-shaped side groove 12c proximate each sidewall 12b of the sheet, and a central longitudinally extending upwardly opening U-shaped groove 12d positioned between the side grooves 12c/12c. Each of the grooves will be seen to extend from a first end wall 12a to the other end wall 12a whereby each groove extends the full length of the pallet. Grooves 12c/12d all have substantially the same depth.

Each side groove 12a is defined by a respective upstanding sidewall 12b, a flat bottom wall 12e, and an upstanding inboard wall 12f. Central groove 12d is defined by spaced upstanding inboard walls 12g and a flat bottom wall 12e. Each inboard wall 12g of the central groove 12b is connected at its upper edge to the inboard wall 12f of a respective side groove 12c by a flat top wall 12h and a series of downwardly opening, upwardly extending hollow spacer knobs 12i are provided on the upper face of each top wall 12h. The knobs 12i are provided in laterally spaced rows along the entire length and width of the walls 12h. Knobs 12i have a circular truncated cone configuration except that the confronting faces 12j of the outboard knob rows on each top wall 12h are flatted to define a longitudinal channel for seating and locating of a respective beam 13. A row of downwardly opening upwardly extending locator knobs 12k are also provided in each top wall 12h between the rows of flatted outboard knobs. Locator knobs 12k are staggererd with respect to, and smaller than, spacer knobs 12i. It will be seen that upstanding walls 12f and 12g and top walls 12h coact to define a pair of downwardly opening grooves 12l interspersed between upwardly opening grooves 12c and 12d and opening in end walls 12a. Each upstanding sidewall 12b is generally planar with the exception of a pair of longitudinally spaced depressions 12m.

Upper sheet 14 starts out as a generally rectangular sheet of polyethylene plastic material and is vacuum formed in known manner utilizing a suitable upper mold. Upper sheet 14 includes a generally planar top wall 14a and a plurality of upwardly opening U-shaped protrusions extending downwardly from the top wall. Specifically, a pair of elongated longitudinally extending and longitudinally spaced U-shaped protrusions 14b are provided proximate each side edge 14c of top wall 14a and a pair of elongated longitudinally extending and longitudinally spaced U-shaped protrusions 14d are provided in a central portion of the pallet. The protrusions all have substantially the same longitudinal extent and all have substantially the same depth. The protrusions in general have a size and cross-sectional configuration sized to nest snugly within the grooves 12c/12d and have a longitudinal extent and spacing corresponding to the depressions 12m. Each protrusion is defined by side walls 14e and a bottom wall 14f.

Each beam 13 has a length corresponding to the length of the pallet and, in cross-section, includes side walls 13a, a top wall 13b including a central “V” 13c, and spaced bottom wall sections 13d terminating in lips 13e defining a central slot 13f.

Following the vacuum forming operations to form the upper and lower sheets, and with the upper and lower sheets still in a heated moldable state, beams 13 are positioned between the outboard knob rows on each top wall 12h with side walls 13a of the beams seated against the confronting flatted faces 12j of the knobs and the locator knobs 12k protecting upwardly into slot 13f, and the molds are brought together in known fashion to compression press the upper sheet to the lower sheet to form the twin sheet pallet 10 with the beams encapsulated between the upper and lower sheets and specifically with each beam totally surrounded by upper sheet top wall 14a, a lower sheet top wall 12h, and knob flats 12j. As the upper and lower sheets, in a heated moldable state, are brought together the plastic material of the sheets fuses or knits together in known manner at all areas where the upper and lower sheets form an interface. Specifically, the periphery of the top wall 14a of the upper sheet fuses to the upper edge 12m of the lower sheet; the sidewalls 14e of each side protrusion 14b fuse to the inboard face of a depression 12m of the lower sheet and an inboard wall 12f of the lower sheet; the bottom walls 14f of the protrusions 14b fuse to outboard bottom walls 12e of the lower sheet; the sidewalls 14e of the central protrusions 14d fuse to sidewalls 12g of the lower sheet; the bottom wall 14f of each central protrusion 14d fuses to a respective portion of the central bottom wall 12e of the lower sheet; and the upper end of each hollow knob 12i fuses to the underface 14g of the top wall 14a of the upper sheet. As shown, the bottom wall 14f of each protrusion 14b/14d may be shaped to form a longitudinally extending downwardly opening groove 14h extending the entire length of the protrusion so that, as the upper and lower sheets are brought together, a void 16 is formed between each lower sheet bottom wall portion 12e and the bottom wall 14f of the associated protrusion. Further, and as noted, the protrusions 14b are sized such that the outboard wall 14e of each protrusion 14b actually seats against the inboard face of a respective indentation 12m so that a space 18 is formed between the upper and lower sheets above and along the extent of each indentation 12m. Further, the knobs 12i serve to define a space 20 between the upper and lower sheets in the pallet areas between the side grooves and the central groove. Spaces 16, 18 and 20 will be seen to define a twin sheet or double wall configuration for the pallet to provide structural rigidity for the pallet. Although the walls of the pallet where interfaced walls of the upper and lower sheets have been fused together are illustrated as having a thickness of twice the thickness of each interfaced wall, it will be understood that in most applications the final thickness of the interfaced and fused together walls will be less than twice the thickness of the separate walls.

Following the fusing together of the upper and lower sheets to form the pallet, and after allowing the material of the pallet to cool, a cutting or routing step is performed to form a pair of slots 22 extending laterally across the pallet to allow the entry of the forks of a forklift truck. Specifically, an oblong cut out 24 is formed in each depressed portion 12m of a side wall 12b, in the outboard sidewall 14e and the inboard sidewall 14e of the nested protrusion 14b, in an inboard wall 12f, in an inboard wall 12g, in the central protrusion sidewalls 14e, in an inboard wall 12g, in an inboard wall 12f, in the inboard and outboard sidewalls 14e of the nested protrusion 14b, and in the depressed portion 12m of the other side wall 12b. The laterally aligned cut outs 24 in the various walls of the pallet coact to define the respective fork slots 22 whereby to facilitate the handling of the pallet by a fork lift truck. In the completed pallet the planar top wall 14a of the upper sheet defines a generally planar platform surface for receipt of a pallet load and the bottom walls 12e of the lower sheet grooves 12c/12d coact to define a pallet footprint comprised solely of the flat parallel laterally spaced underfaces 26 of the bottom walls 12e.

The invention pallet will be seen to provide many important advantages. Specifically, the invention construction provides a continuous longitudinally extending footprint along the underface of the pallet so that the pallet can pass easily over barriers and irregular transfer surfaces and transfer devices such for example as conveyors.

The invention construction also provides firm entrapment for the forks of the fork lift truck so that the pallet, even if unevenly loaded, will not tend to tip off of the forks as the pallet is lifted and transported by the forks.

The invention construction also provides a very stiff and rigid pallet which resists creepage or sagging even over extended periods of use.

The invention pallet is also extremely simple in construction and therefore relatively inexpensive to produce and yet is extremely sturdy so as to provide an extremely long useful life.

The invention construction also lends itself to simple and effective cleaning operations between pallet usages.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, 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, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.

Claims

1. A plastic twin sheet pallet comprising an upper plastic sheet and a lower plastic sheet selectively fused to the upper sheet, characterized in that: the lower sheet has a generally rectangular configuration, including sidewalls and end walls, and includes a plurality of separate, parallel, upwardly opening longitudinally extending U-shaped grooves extending from end to end of the sheet and at least one downwardly opening U-shaped groove interspersed between the upwardly opening grooves and opening in the end walls of the sheet; and the upper sheet has a generally rectangular configuration and is positioned over the lower sheet and selectively fused to the lower sheet to define a platform surface for the pallet.

2. A pallet according to claim 1 wherein: the upper sheet defines a top wall defining the platform surface and a plurality of upwardly opening U-shaped protrusions extending downwardly from the top wall and sized to nest within the upwardly opening grooves of the lower sheet whereby with the upper sheet positioned over the lower sheet and the protrusions positioned in the upwardly opening grooves the sheets may be fused together to form double thickness U-shaped wall structures at the interfaces of the protrusions and the upwardly opening grooves.

3. A pallet according to claim 2 wherein: the pallet includes aligned slots in the opposite sides of the U-shaped wall structures to allow passage of the forks of a fork lift truck.

4. A pallet according to claim 2 wherein: the protrusions are arranged in longitudinally extending rows; and at least two longitudinally spaced protrusions are positioned in each upwardly opening groove.

5. A pallet according to claim 2 wherein: the at least one downwardly opening groove is defined by spaced upstanding walls and a flat top wall; the lower sheet further defines a series of knobs upstanding from each groove top wall; and portions of the top wall of the upper sheet overly the knobs and are fused to the knobs to define a double wall construction.

6. A plastic twin sheet pallet comprising an upper plastic sheet and a lower plastic sheet fused together at selected interfaces, characterized in that: the lower sheet has a generally rectangular configuration and includes generally parallel upstanding sidewalls, generally parallel upstanding end walls, and a plurality of separate, flat, laterally spaced, parallel bottom walls extending from end wall to end wall, the underfaces of the bottom walls defining a pallet footprint comprised solely of a plurality of separate, flat, laterally spaced, parallel surfaces extending from end wall to end wall of the sheet; and the upper sheet has a generally rectangular configuration and is positioned over the lower sheet and selectively fused to the lower sheet to define a platform surface for the pallet.

7. A pallet according to claim 6 wherein: each bottom wall comprises the bottom wall of an upwardly opening U-shaped groove; and the upper sheet defines a top wall defining the platform surface and a plurality of upwardly opening, U-shaped protrusions extending downwardly from the top wall and sized to nest within the grooves of the lower sheet.

8. A pallet according to claim 7 wherein: the grooves comprise a side groove extending along each sidewall of the lower sheet and a central groove; and each sidewall of the lower sheet constitutes a sidewall of a side groove.

9. A twin sheet plastic pallet comprising: a generally rectangular lower plastic sheet including upstanding sidewalls and upstanding end walls and defining a plurality of separate, parallel, upwardly opening longitudinally extending U-shaped grooves extending from end to end of the sheet and a plurality of downwardly opening U-shaped grooves interspersed between the upwardly opening grooves and opening in the end walls of the sheet; and a generally rectangular upper plastic sheet defining a top wall providing a platform surface for the pallet and a plurality of upwardly opening U-shaped protrusions extending downwardly from the top wall and sized to nest within the upwardly opening grooves of the lower sheet whereby, with the upper sheet positioned over the lower sheet and the protrusions positioned in the upwardly opening grooves, the sheets may be fused together to form double thickness U-shaped wall structures at the interfaces of the protrusions and the upwardly opening grooves.

10. A pallet according to claim 9 wherein: the upwardly opening grooves and downwardly opening grooves laterally alternate and share common upstanding walls.

11. A pallet according to claim 10 wherein: the upwardly opening grooves comprise a side groove extending along each sidewall of the lower sheet and a central groove; and each sidewall of the lower sheet constitutes an upstanding wall of a side groove.

12. A pallet according to claim 11 wherein laterally aligned slots are provided in the upstanding walls of the upwardly opening grooves and the downwardly opening grooves and in the protrusions to accommodate the forks of a fork lift truck.

13. A pallet according to claim 12 wherein: the protrusions are arranged in longitudinally extending rows; and at least two longitudinally spaced protrusions are provided in each upwardly opening groove.

14. A pallet according to claim 13 wherein: two longitudinally spaced protrusions are provided in each upwardly opening groove to provide longitudinally spaced, laterally aligned sets of protuberances; and the laterally aligned slots are provided in each set of protrusions and in the associated upstanding walls of the upwardly opening grooves and the downwardly opening grooves.

15. A pallet according to claim 14 wherein: the upstanding walls of adjacent upwardly opening grooves are connected by top wall sections of the lower sheet which also form the top wall of the interspersed downwardly opening groove; a series of upstanding spacer knobs are provided on each top wall section; and portions of the top wall of the upper sheet between the rows of protrusions are fused to the upstanding knobs.

16. A twin sheet plastic pallet comprising: a generally rectangular lower plastic sheet having parallel, alternate upwardly opening grooves and downwardly opening grooves extending from end to end of the sheet; and a generally rectangular upper plastic sheet having a generally planar top wall and a plurality of upwardly opening protrusions extending downwardly from the top wall and nestingly and fusedly received in the upwardly opening grooves in the lower sheet.

17. A pallet according to claim 16 wherein: the lower sheet includes end walls; and the downwardly opening grooves in the lower sheet open in the end walls.

18. A pallet according to claim 17 wherein: each downwardly opening groove in the lower sheet is defined in part by a top wall; a series of upstanding knobs is provided on each groove top wall; the protrusions in the upper sheet are arranged in longitudinally extending rows; and portions of the top wall of the upper sheet between the rows are fused to the knobs.

19. A pallet according to claim 18 wherein laterally aligned slots are provided in side walls of the grooves and the protrusions to allow passage of the forks of a fork lift truck.

20. A pallet according to claim 19 wherein: the lower sheet further includes side walls extending between the end walls; the upwardly opening grooves comprise a side groove extending along each side wall of the lower sheet and a central groove; and each side wall of the lower sheet constitutes an upstanding wall of a side groove.

21. A pallet according to claim 2 wherein the pallet further includes at least one beam positioned between the upper and lower sheets and extending substantially from end wall to end wall of the lower sheet.

22. A pallet according to claim 5 wherein the pallet further includes at least one metallic beam positioned between a groove top wall and an overlying portion of the top wall of the upper sheet, extending substantially from end to end of the pallet, and positioned between upstanding spacer knobs.

23. A pallet according to claim 15 wherein: the spacer knobs are arranged in laterally spaced longitudinally extending rows; and the pallet includes at least one metallic beam positioned between a top wall section of the lower sheet and a portion of the top wall of the upper sheet and extends substantially from end to end of the pallet between adjacent spacer knob rows.

24. A pallet according to claim 23 wherein the pallet further includes upstanding locating knobs positioned between adjacent rows of spacer knobs and engaging an underface of the beam.

25. A pallet according to claim 24 wherein a beam is provided proximate each side edge of a pallet.