The present invention relates to the field of pallets useful in material handling, and more particularly, to a reinforced plastic pallet.
Pallets have been in wide use for many years to minimize the cost of handling products or articles that can be stacked or otherwise secured on them to thus enable large volumes of products or articles to be handled simultaneously and to be handled in mechanized fashion so as to minimize labor costs. Historically, fork-lift pallets have been constructed of wood, having a plurality of parallel stringers on which are nailed or otherwise secured one or more structural members defining a pallet platform. The pallet platform can be composed of multiple wood strips or unitary wood panels, such as plywood panels, to provide a generally planar support surface on which the goods or articles are appropriately arranged or stacked. The parallel stringers raise the product support platform above a floor surface and thereby permit the forks of a fork-lift truck to be inserted within spaces defined between the stringers. This enables a fork-lift truck to lift and move the pallet with all of its articles as a unit or package. Typically, the pallet will remain with the products or articles until such time as the articles are removed from the pallet for further handling, for use or for distribution.
Even though pallets are typically of low cost, they are sufficiently costly that they are used many times for shipment of products before they become sufficiently worn or damaged that replacement is necessary. Although wood has historically been a low cost commodity, thus enabling pallets to be manufactured of wood at low cost, of late, the cost of wood for products such as pallets has significantly increased, thus causing pallet manufacturers to seek other sources for materials. Pallets have been constructed of extruded or formed metal such as steel or aluminum.
With the growth of the plastics industry a wide variety of plastics have been investigated to determine their suitability for use in producing pallets. Plastic pallets can easily be molded and are stronger and lighter weight than wooden pallets. They can also be made with recyclable materials. Furthermore, plastic pallets are more durable than wooden pallets, however, may be subject to weakness as the amount of material is reduced to lower weight and cost.
To increase the durability of plastic pallets, various reinforcing elements or rods have been used. While the reinforcing elements have improved the strength of the pallets, many applications, referred to as clean applications, prohibit exposed reinforcing elements. Encasing the reinforcing elements within the pallet plastic has proven challenging as the difference in thermal coefficient between the plastic and the metal of the reinforcing elements has resulted in cracking or other adverse effects. Attempts to avoid the thermal effects have resulted in complex systems, for example, preformed, full length sleeves to separately encase the reinforcing elements. Such sleeves have added to the cost and complexity of manufacturing the pallets.
Briefly, the present invention provides a plastic pallet with a reinforcement assembly embedded within at least one of the decks and including reinforcement caps to accommodate the effects of thermal contraction or expansion.
In one aspect, the invention provides a pallet including top and bottom decks supported in spaced apart relationship by a plurality of post assemblies. A reinforcement assembly is encapsulated within at least one of the top or bottom deck. The reinforcement assembly includes at least one reinforcement rod having opposed ends and a plurality of reinforcement caps. Each reinforcement cap has an outer member defining a closed end and an open end and an inner compensation structure within the outer member and defining a stop surface spaced from the outer member open end such that an initial open area is defined within the outer cap member. A respective rod end is received in the initial open area. The inner compensation structure is configured to deform to accommodate a relative position change between the cap member and the reinforcement rod end.
In another aspect, the invention provides a method of forming a pallet including positioning a reinforcement cap on each end of at least one reinforcement rod; positioning the at least one reinforcement rod in a mold in a desired configuration; and molding top and bottom decks and the post assemblies of the pallet such that the at least one reinforcement rod and the reinforcement caps thereon are embedded within the top and/or bottom deck.
The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain the features of the invention. In the drawings:
In the drawings, like numerals indicate like elements throughout. Certain terminology is used herein for convenience only and is not to be taken as a limitation on the present invention. For example, the terms front, back, left and right are utilized herein to assist with understanding of relative positioning, but are not intended to be limiting to an orientation of use of the device. The following describes a preferred embodiment of the present invention. However, it should be understood, based on this disclosure, that the invention is not limited by the preferred embodiment described herein.
Referring to
The top deck 12 of the present embodiment includes a generally planar surface 14 supported by an interconnected rib structure 15. The top deck 12 may be a solid surface, but the rib structure 15 is generally preferred as it reduces weight and material cost. The surface 14 preferably includes a plurality of through holes 13 to facilitate passage of water, debris and the like through the pallet top deck 12. Optionally, one or more elastomeric grommets 16 may extend through the top deck 12. In the illustrated embodiments, the grommets 16 are aligned with the fork receiving openings 11 such that the lower portions of the grommets 16 reduce slipping between the pallet 10 and the fork tines (not shown). The grommets 16 may also extend above the top surface 14 to reduce slipping of items positioned on the pallet 10. The top deck 12 is not limited to the illustrated embodiments and may have various other configurations for accommodating and supporting various cargo and rack structures.
The bottom deck 30 preferably includes a first series of beam members 33 interconnected with a second series of beam members 35 extending orthogonal thereto to form a grid structure. While the illustrated structure is preferred, the bottom deck 30 may include more or fewer beams, or alternatively, be a planar structure similar to the top deck 12. The plank members 33, 35 again preferably include a supporting rib structure 37, but are not limited to such a configuration. In the preferred embodiment, the planks 33 and 35 are formed interconnected as a unitary grid structure 34.
Each post assembly 50 is defined by an outer post member 52 extending between the top deck 12 and the bottom deck 30. In the preferred embodiment, the outer post members 52 are formed integrally with both the top deck 12 and the bottom deck 30 such that the pallet 10 is generally a one-piece assembly. It is recognized that aspects of the invention may be utilized with multi-component pallets with separate top and bottom decks and with singular or multi-component posts. As with the top and bottom decks 12, 30, ribs 54 preferably extend within the outer post members 52.
The decks 12 and 30 and post assemblies 50 can be manufactured from any suitable material, including, plastics and various other natural or synthetic materials. Various molding techniques, for example, but not limited to, injection molding or gas assist injection molding, may be utilized.
Referring to
In the embodiment illustrated in
Each reinforcement rod 62 is preferably a hollow cylinder extending between ends 64, 66. While the preferred rods are hollow, other rods including solid or partially filled rods may be utilized. Additionally, while the illustrated rods are cylindrical, they may have other shapes, for example, but not limited to, square, rectangular or I-beam. The reinforcement rods 62 are preferably metallic, for example, steel, but may be made from other metals and non-metals, for example, reinforced fiberglass.
A reinforcement cap 70 is positioned at each end 64, 66 of each reinforcement rod 62. The reinforcement caps 70 help to accommodate differentials in post mold shrinkage and also thermal expansion and contraction of the pallet beams 33, 35 relative to the reinforcement rods 62.
Referring to
To accommodate contraction or expansion of the pallet 10, an inner compensation structure is defined within each cap 70. In the present embodiment, the inner compensation structure is defined by a plurality of ribs 80 extending between the outer cap member 72 and the inner cap member 76 from the closed ends 73, 77 to a rib free end 82. Four ribs 80 are shown in the exemplary embodiment, however, more or fewer ribs 80 may be utilized. The length L3 of each rib 80 is less than the length L1 of the outer cap member 72 such that a hollow annular area 75 is defined within the outer cap member 72 between it and the inner cap member 76. The hollow annular area 75 is configured to receive the end 64, 66 of a reinforcement rod 62 as illustrated in
The reinforcement caps 70 may be manufactured from a plastic or other suitable material, including metals. Exemplary materials include, but are not limited to nylon 6/6 or die cast zinc. Additionally, different portions of the caps 70 may be manufactured from different materials. In exemplary pallet, the beam members 33, 35 are be manufactured from polypropylene, the reinforcement caps 70 are manufactured from nylon 6/6 and the reinforcement rods 62 are manufactured from steel.
Prior to molding, a reinforcement cap 70 is positioned on each end 64, 66 of each reinforcement rod 62 as illustrated in
The molded beam members 33, 35 have an initial position relative to the reinforcement assembly 60 when the pallet 10 is removed from the mold. This is illustrated in
In use, the pallet 10 may undergo further contraction when utilized in cold conditions or expansion when utilized in hot conditions. The reinforcement caps 70 will accommodate such contraction or expansion in a manner similar to the post-molding shrinkage.
Referring to
In the present embodiment, the inner compensation structure is defined by a series of steps 180, 184 defined on the outer surface of the inner member 176. Each step 180, 184 defines a respective open end facing stop 182, 186, respectively. The stop 182 is spaced from the open end 174 of the outer cap member 172 such that the initial hollow annular area 175 is defined within the outer cap member 172 between it and the inner cap member 176 from the stop 182 to the open end 174. The hollow annular area 175 is configured to receive the end 64, 66 of a reinforcement rod 62 during assembly as in the previous embodiment. The steps 180 and 184 may be formed as annular members or may be defined by spaced apart ribs. In operation, one or both steps 180, 184 will deform in response to a force from the respective rod end 64, 66 due to contraction of the pallet 10. As such, the reinforcement caps 170 help to accommodate differentials in post mold shrinkage and also thermal expansion and contraction of the pallet beams 33, 35 relative to the reinforcement rods 62.
Referring to
In the present embodiment, the inner compensation structure is defined by a plurality of ribs 280 extending radially inward from the outer cap member 272 inner surface. Four ribs 80 are shown in the exemplary embodiment, however, more or fewer ribs 280 may be utilized. Similar to the first embodiment, the length of each rib 280 is less than the length of the outer cap member 272 such that a hollow annular area 275 is defined within the outer cap member 272. The free ends 282 of the ribs 280 define a stop which limits initial positioning of the rod end 64, 66 within the outer cap member 272, but the caps 270 do not extend over a substantial length of the rods 62. The hollow annular area 275 may have a larger depth than in the first embodiment to receive more of the rod end 64, 66 since there is no inner member to extend into the rod 62. In the present embodiment, the ribs 280 have a rectangular configuration, but may be formed with a taper similar to the first embodiment. The caps 270 are utilized and operate in substantially the same manner as the caps 70.
Referring to
In the present embodiment, the inner compensation structure is defined by an elastomeric insert 380 positioned within the hollow area of the outer member 372. The elastomeric insert 380 has a width W which is less than the length of the outer member 372 such that a hollow annular area 375 is defined within the outer cap member 372 between the open end 374 and an end surface 382 of the elastomeric insert 380. The hollow annular area 375 may have a larger depth than in the first embodiment to receive more of the rod end 64, 66 since there is no inner member to extend into the rod 62. In operation, the elastomeric insert 380 will compress or otherwise deform in response to a force from the respective rod end 64, 66 due to contraction of the pallet 10. As such, the reinforcement caps 370 help to accommodate differentials in post mold shrinkage and also thermal expansion and contraction of the pallet beams 33, 35 relative to the reinforcement rods 62. It is contemplated that the outer member 372 may also be manufactured from an elastomeric material such that the entire reinforcement cap 370 is elastomeric. In such an embodiment, the outer member 372 and the insert 380 may be manufactured as separate components or as a unitary structure.
These and other advantages of the present invention will be apparent to those skilled in the art from the foregoing specification. Accordingly, it will be recognized by those skilled in the art that changes or modifications may be made to the above-described embodiments without departing from the broad inventive concepts of the invention. It should therefore be understood that this invention is not limited to the particular embodiments described herein, but is intended to include all changes and modifications that are within the scope and spirit of the invention as defined in the claims.