Horizontally supported planar surfaces – Industrial platform – Having plastic load-contacting surface
Reexamination Certificate
1999-07-26
2001-10-23
Chen, Jose V. (Department: 3624)
Horizontally supported planar surfaces
Industrial platform
Having plastic load-contacting surface
Reexamination Certificate
active
06305301
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods and systems for forming and utilizing support structures (including but not necessarily limited to pallets) and more particularly to such structures which optionally may be recycled, have improved characteristics for stacking, and have any or all of non-skid, glass, and recycled materials incorporated thereon or therein.
BACKGROUND OF THE INVENTION
Numerous designs of pallet-like support structures exist today. U.S. Pat. No. 3,490,583 to Cook, for example, illustrates in its FIG. 1 a shipping pallet (designated by the numeral “4”). Such pallet consists merely of a horizontal platform from which vertical legs depend at two opposed sides. Space underneath the horizontal platform allows entry of times of a fork-lift truck (or pallet jack) from the sides from which legs do not depend, permitting movement of the pallet when loaded with products.
Placement and use in a refrigerator or freezer of a pallet like that shown in the Cook patent is problematic for many reasons, however. Among difficulties involved in using this type of pallet in a cold environment is the low coefficient of friction of the wood or other material of which the pallet typically is formed. The Cook patent arguably attempts to address this difficulty at least partially by coating the undersides of load-containing trays, made of paperboard or wood, with a solution of synthetic latex.
Such latex coating, as described in the Cook patent, is intended primarily to prevent slippage between the trays of the load. It accordingly is not applied to the pallet itself, retaining the vulnerability of the pallet to sliding relative to the fork-life times when moved. Synthetic latex additionally is neither thermoplastic nor adequately recyclable in many circumstances. Recyclability is not expressed as an objective of the subject matter of the Cook patent, moreover, as in practice the types of pallets illustrated therein often are disposed of by chipping, shredding, burning, or dumping in landfills.
U.S. Pat. No. 5,685,233 to DeJean purports to describe a recyclable pallet assembly. Included in the assembly are support bars and stringers, all of which, according to the Abstract of the DeJean patent, “may be provided with an anti-skid surface for protecting a user walking on the pallet.” The DeJean patent thereafter refers to the anti-skid material as constituting “a coating consisting of sand grit, or other particulate, intermixed with an adhesive, such as an epoxy resin,” however, precluding the assembly from being recyclable and reextrudable. Again, moreover, no anti-skid material of any type is applied to the undersides of the assembly, retaining the vulnerability to sliding discussed above.
Yet another pallet is disclosed in U.S. Pat. No. 4,397,246 to Ishida, et al., which patent is incorporated herein in its entirety by this reference. Detailed in the Ishida patent is a pallet whose deck board surface is grooved so as to receive separate “slip preventing members” in the form of soft, deformable cords. Alternatively, the cords may be welded directly to the surface of the deck board. In either event, according to the Ishida patent, “each slip preventing member must project beyond the upper or lower surface of the deck board.”
To provide surfaces in which the grooves may be formed, the pallet of the Ishida patent comprises a hollow rectangular molded body. Accordingly, it has an integral support base or bottom, such as is shown beneath the rectangular openings of FIGS. 1 and 3 of the Ishida patent. By contrast with the soft, deformable material from which the cords are formed, this base has the same rigidity as the remainder of the pallet. Should it crack or break, the load-distribution characteristics of the pallet may change sufficiently to preclude its further beneficial use.
SUMMARY OF THE INVENTION
The present invention provides alternative pallets and other support structures and methods and systems for forming and utilizing them. Pallets of the invention are especially (although not exclusively) designed for improved performance in places, such as commercial refrigerators and freezers and refrigerated transport containers, subjected to decreased temperatures. They additionally optionally are recyclable, have improved stacking and load-bearing attributes, and incorporate recycled materials.
Certain embodiments of pallets consistent with the concepts of the invention may be made of thermoformable material such as high density polyethylene (HDPE). As well an olefinic rubber, or thermoplastic olefin such as a Kraton polymer available through Shell Chemical Company, 1415 West 22nd Street, Oak Brook, Ill. 60522-9008, may be incorporated into or onto portions of the pallets. Non-polar materials like these have many characteristics in common with, and thus bond well, to olefins including HDPE. By contrast, polarized materials such as urethanes can decrease the flexural modulus and tensile strength of predominately HDPE-containing support structures. Slickness of urethanes additionally increases at low temperatures, undermining their use as non-skid materials in refrigerators and freezers.
Although a Kraton polymer or other thermoplastic olefin may be brushed or sprayed onto or otherwise combined in any suitable manner with the remainder of the thermoformable material of the present invention, it preferably is co-extruded on portions of upper and lower surfaces of the structure. Similar shrink-rate characteristics of Kraton polymers and HDPE reduce tendency for warping and wrinkling during the co-extrusion process. Use of Kraton polymers additionally may diminish the instability inherent in exposure of pallets to ultraviolet radiation and increase material-compatibility for purposes of recycling the structures.
Embodiments of the platform portion of the present invention additionally may be formed from a single sheet of thermoformable material, with the sheet being contoured to create ridges (ribs) and, if desired, double- or parallel-walled edges. Inclusion of double-walled edges may avoid substantial degradation of performance should the outer wall break or crack, as can occur sometimes when the outer wall is impacted by, for example, a rapidly-moving fork-lift time. To maximize strength for particular pallet heights, preferred draw between the top of a ridge and top of a base portion of some pallets is approximately one and one-half inches. Those skilled in the art will, however, recognize that the invention is not limited to pallets having this particular draw amount and that other draw amounts may exist instead.
Further features of support structures of the present invention include use of separate foot beams and bottom deck boards or bases. These feet may be formed either individually or in groups and thereafter attached to the underside of the platform portion of a pallet. Creating feet in groups effectively fixes a minimum dimension of the platform, however, as it must be sufficiently long or wide to receive the group of feet. By contrast, utilizing individually-formed feet optimizes the ability to manufacture differently-dimensioned platforms, as the numbers of feet attached to particular platforms may be varied as necessary or appropriate.
In either circumstance, however, the feet (if present) may be attached to a platform by a low-density polyethylene (or other) material if desired. Typically the platform will be preheated in the area receiving the attachment material, which material will then be extruded or otherwise applied to the platform as molten plastic. Application of the attachment material may be automated as, for example, by having a heater, followed by at least one extruder, traverse the lengths of each foot. In one preferred method, two extruders are employed simultaneously, with each positionable along a longitudinal side of the tops of the feet. Regardless of application method, however, once cooled the attachment material effectively welds the foot to the platform, with the low density of the material providing it some flexibility to absorb shoc
Piper, Jr. Paul P.
Smith Leslie E.
Chen José V.
Kilpatrick & Stockton LLP
Piper Plastics, Inc.
Russell Dean W.
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