Pallet

Abstract

A pallet is constructed of a thin-walled, resinous shell filled with a foam core bonded to the inside surface of the shell. The shell includes integral support beams spaced appropriately to accommodate a forklift for warehousing operations. Materials of construction are selected to meet strength requirements at minimum cost.

Description

BACKGROUND OF THE INVENTION

1. Field

This invention relates to pallets used in warehousing and transportation for the storage and relocation of goods.

2. State of the Art

A major expense in warehousing and shipping arises from the use of pallets. Although pallets have traditionally been constructed of low-cost wood, the initial investment in labor and materials to construct an adequate supply of pallets for a warehousing operation is considerable; the procurement expense of pallets is sufficient that they are customarily reused rather than being discarded. It is often necessary to ship goods on pallets and then return the empty pallets to their point of origin. Because wooden pallets are heavy, their transport, whether loaded or unloaded, adds appreciably to shipping costs.

Many replacements for conventional wooden pallets have been suggested, but none of these has gained general commercial acceptance. Various pallets constructed of resinous materials have been tried but these generally have one or more disadvantages from the standpoint of initial investment costs or physical properties. The plastic or resinous pallet structures of the prior art generally either lack sufficient strength for large loads or, if they do possess sufficient strength, are unduly expensive for general use. Thus, there remains a need for a general purpose, low cost, lightweight pallet.

SUMMARY OF THE INVENTION

The present invention provides an inexpensive pallet of light weight but with sufficient strength to support large loads. The novel pallet structure of this invention makes it possible to form inexpensive resinous materials by conventional, low-cost, manufacturing techniques, into pallets of adequate strength at less cost than typical wooden pallets. Besides conserving on material and manufacturing costs, the claimed pallet effects a significant savings on transportation costs compared to presently available pallets.

In general, the pallet of this invention comprises an exterior shell element formed from thin, lightweight, resinous sheet material and a core element of lightweight, rigid, resinous foam, conforming in shape and substantially filling the interior of the shell to form an approximately flat, upper bearing surface for the pallet. The core is bonded by appropriate adhesive or bonding agent to the inside surface of the shell.

The shell, which constitutes the exterior of the claimed pallet, is shaped in the general configuration of a conventional pallet, although conventional wooden pallets often contain structural reinforcing members which are unnecessary for the pallet of this invention. Thus, the shell includes an open, or hollow, rectilinear body portion with depending hollow support beams openly communicating with the interior of the body of the shell. The body portion of the shell element may be considered to include a bottom member which forms the base of the body portion in its normal position of use. The aforementioned parallel support beam members are each formed by approximately parallel support beam walls depending from the bottom member and connected at their distal ends to form a beam base. The interior of each beam member openly communicates with the interior of the body portion of the shell. Support beam members depend from two opposite sides and at least one intermediate location of the bottom member. According to some embodiments, the shell is completed by side members extending upward from rigid attachment to the outermost beam walls at opposite sides of the bottom member so that the ends of the pallet normal the beam walls are open. According to other embodiments, end caps are provided to connect corresponding edges of the body portion and support beams so that the complete shell is formed as an enclosure. The core element substantially fills the entire interior of the shell to provide a bearing surface flush with the top edges of the side members. If desired, a platform element of resinous sheet material may be mounted atop the bearing surface of the core element to provide additional strength and to protect the core element from abrasion in use. More often, the shell is open-topped and the pallet load is placed directly on the bearing surface of the core element.

Shell elements and platform elements for the claimed pallet may be formed from thin, resinous sheets by conventional vacuum forming, shell molding, casting, or other techniques. By "thin" is meant of small dimension relative to the body portion and support beams of the pallet structure. Thus, a shell element formed from a thin, resinous sheet will have an interior volume many hundreds of times greater than the volume of material in the shell. The support beams, for example, typically have hollow interior volumes to accommodate a rigid foam core at least about 10 times as thick as the resinous sheet material defining the beam walls and beam base. Although it is possible to construct the pallets of this invention from sheet materials as thick as one-eighth to one-fourth inch or more, such heavy material is ordinarily not required. The preferred sheet material for use is the least expensive available which has sufficient strength and toughness to give satisfactory performance in use. Thus, contrary to suggestions of the prior art, the resinous sheet materials most often employed for the production of pallets according to this invention are less than about one-sixteenth of an inch thick. Materials as thin as about one thirty-second of an inch or less are satisfactory for many applications.

The shell material may be selected from a broad range of resinous sheet materials. Any resinous organic material susceptible to conventional forming techniques and which is solid and noncrystalline at ambient temperatures may be used. The material selected for use in a particular instance may depend upon the environment in which the pallet is used. For example, if extreme climactic or load conditions are to be encountered, a material with suitable properties to withstand these conditions is preferred over more susceptible materials, particularly when the pallet is intended for reuse. By way of example, suitable resinous sheets may be selected from the condensation polymers, such as the polyesters, including cellulose esters, polyamides, phenol aldehydes, and urea and/or melamine formaldehydes; vinyl polymers, such as polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, acrylates, methacrylates, and polystyrenes; polyolefins, notably polyethylene, polypropylene, or other copolymers of ethylene and/or propylene with unsaturated esters; cellulose ethers; polyurethanes; indenecoumarone; and various epoxide-type resins.

The core material should have sufficient rigidity and resistance to compression to withstand compressive loads. Thus, a rigid foam is generally preferred. Many suitable rigid foams are known to the art, and the form employed in the pallet structure of this invention will generally be selected on the basis of cost and compatibility with the resinous sheet material selected for the shell element. Suitable materials may be selected from the various rigid polyurethane, polycarbonate, and polystyrene foams commonly used in the construction and appliance industries for noise and temperature insulation. Foam densities between about 2 and about 4 pounds per cubic foot are preferred, although foams of greater or less density may be used in particular instances.

The bonding systems known to the art for bonding the selected rigid foam to the resinous material of the shell may be employed to effect a high-strength, physical bond between the shell and the core. It is often possible to cast the core in the shell in the presence of the bonding agent so that the core solidifies in place, tightly bonded to the interior surface of the shell.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which illustrate what is presently regarded as the best mode for carrying out the invention:

FIG. l is a pictorial view from the top of one form of the invention;

FIG. 2, a similar view from the bottom; and

FIG. 3, a sectional view taken along the line 3-3 of FIG. 1.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The pallets illustrated include a shell element 10 comprising a body portion 11, having a bottom member 12 (FIG. 2); three support beam members 13-1, 13-2, and 13-3 depending from the bottom member 12, as illustrated; and side members 14-1 and 14-2, extending upward from attachment to the outside walls 13-1a, and 13-3b, respectively, of the beams 13-1 and 13-3. Each beam member 13-1, 13-2, and 13-3 is constructed of two beam walls a and b, respectively, connected at their distal ends by a beam base c. For example, referring to FIG. 3, support beam 13- 2 is formed by parallel beam walls 13-2a and 13-2b connected by beam base 13-2c.

In the illustrated instances, the shell element is vacuum formed as a unitary structure including end cap members 15 so that it forms an open-topped enclosure with a rectilinear upper perimeter. The support beams 13 are hollow and openly communicate with the interior of the body element 11.

In the specific embodiment of FIG. 2, slots 16-1, 16-2, and 16-3 are provided at about the center of the support beam 13-1, 13-2 and 13-3, respectively. Such slots are just sufficiently wide; e.g., about 10 inches, to accommodate pallet-moving means so that the pallet and its load may be withdrawn from a stored location even when its ends 15 are blocked. The support beams 13, are sufficiently spaced to accommodate conventional pallet-handling equipment, such as forklifts.

A core 17 of rigid polyurethane foam is cast in place in the shell to substantially fill the entire interior thereof and provide a flat bearing surface flush with the upper edges of the end caps 15 and sidewalls 14. If desired, a load-bearing platform element (not shown) of resinous sheet material similar to that of the shell element may be bonded to the top of the core member in the same fashion that the core element is bonded to the interior surface of the shell element.

Pallets, such as those illustrated, have been constructed of shells molded from 1/8-inch ABS-GSE polyethylene plastic sheets filled with 4 pound polyurethane rigid foam bonded to the shell with conventional polyester bonding agent. The shell walls of such pallets are less than one-eighth of an inch thick, yet are capable of withstanding static loads in excess of 9,600 pounds. They are nevertheless lighter in weight and cheaper to manufacture than conventional wooden pallets.

Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims which themselves recite those details regarded as essential to the invention. It is recognized, for example, that various structural modifications may be made to the embodiments illustrated to adapt them for specific uses or to enhance their strength properties. Although the illustrated beam members are of simple construction and provide good strength properties, it is recognized that other shapes and dimensions are possible.

Claims

I claim:

1. A pallet, comprising:

an exterior shell element formed from thin, resinous sheet material and including:

a body portion having a bottom member and parallel, support beam members, each of which is formed from approximately parallel, support beam walls depending from said bottom member and connected at their distal ends to form a beam base such that the interiors of said beam members openly communicate with the interior of said body portion, at two opposite sides and at least one intermediate location of said bottom member, and

side members extending upward from rigid attachment to the outermost beam walls at said opposite sides of said bottom member; and

a core element of rigid resinous foam, conforming in shape and substantially filling the interior of said shell to form an approximately flat, upper bearing surface for said pallet, bonded to the inside surface of said shell.

2. A pallet according to claim 1, wherein the shell element includes three support beam members depending from opposite sides and approximately the center, respectively, of the bottom member and extending the full length of said sides.

3. A pallet according to claim 2 wherein each said support beam member includes a slot at approximately its center to accommodate pallet moving means.

4. A pallet according to claim 1, including a platform element of thin, resinous sheet material mounted atop the approximately flat, bearing surface of the core element.

5. A pallet according to claim 1, wherein the shell element includes end-cap members connecting corresponding edges of said side elements, bottom element, support beam walls, and support beam bases.

6. A pallet according to claim 5, wherein the shell element is of unitary construction from resinous sheet material between about one thirty-second and about one-fourth inch thick.

7. A pallet according to claim 6, wherein the core element is of rigid foam having a density between about 2 and about 4 pounds per cubic foot.

8. A pallet according to claim 7, wherein the walls of the shell element are less than about one-sixteenth of an inch thick.

9. A pallet according to claim 8, including a platform element of thin resinous sheet material bonded on top of the core element.