Abstract:
Support structures, systems, and methods are disclosed. Among the support structures are pallets designed especially, although not necessarily exclusively, for cold-weather environments such as commercial refrigerators and freezers and refrigerated transport carriers. Such pallets may include non-skid materials and optionally are recyclable, have improved stacking and load-bearing attributes, and incorporate recycled materials.

Description:
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 shocks caused by times or other equipment impacting the foot. 
     Connected to the lower surfaces of the feet in some embodiments of the invention are one or more removable and recyclable bottom boards or bases. Rather than forming such bases integrally with the platforms (as contemplated, for example, in the Ishida patent), methods and systems of the present invention usually create them separately for any of multiple reasons. Creating such bases separately obviously permits their use to be optional, unlike the integral base of the pallet of the Ishida patent. They additionally may be made to be more flexible than the platforms of the pallets, allowing them both to conform somewhat to uneven surfaces and to bend or flex, rather than break, in response to certain impacts. Should a bottom board nevertheless break in use, it may merely be removed from the pallet and replaced, without having to replace the remainder of the pallet. 
     The bottom boards or bases additionally function to distribute loads more evenly. Their lower surfaces too may have non-skid material, as mentioned earlier, incorporated therein or thereon if desired. Alternatively, (removable) rubber grommets or other components or mechanisms may be used to increase the friction available to retain the lower surfaces of the bases in place. In some embodiments, the upper surfaces of the bases additionally are bevelled to guide times or jacks and facilitate their use. 
     Further features of structures of the present invention include their ability to nest in pairs, thus diminishing the volume required for their storage in advance of use, and provision of four-way entry for times or jacks. Because adapted to be formed from a single sheet of material, the platforms of the invention may include holes in their sections between ridges permitting fluid to drain through them. This drainage reduces the possibility of fluid stagnating on the platforms and having potentially undesirable effects. Glass and recycled material (as noted above), finally, may be incorporated into the structures of the present invention, with the former acting as rebarring material and reducing creep of any HDPE present therein. As thus constructed, single sheet pallets of the invention have sufficient strength to be used as rack storage platforms for foodstuffs and other objects. 
     It is therefore an object of the present invention to provide pallets and other support structures and methods and systems for forming and using such structures. 
     It is also an object of the present invention to provide pallets designed for improved performance in environments, including commercial refrigerators and freezers and refrigerated transport carriers, frequently subjected to low temperatures. 
     It is another object of the present invention to provide pallets with improved stacking and load-bearing attributes and optionally which may incorporate recycled materials and themselves be recyclable. 
     It is a further object of the present invention to provide structures made of thermoformable material into or onto which a non-skid material is incorporated, in some embodiments on both upper and lower surfaces and on associated bottom boards. 
     It is yet another object of the present invention to provide such a non-skid material whose chemical constituency is functionally compatible with that of the thermoformable material from which other portions of the structure may be made. 
     It too is an object of the present invention to provide a pallet having a platform which may be formed of a single sheet of the thermoformable material, with the sheet being contoured to create ridges. 
     It is an additional object of the present invention to provide a platform having double-walled edges to reduce adverse effects of impact-related breakage of the outer edge. 
     Objects of the present invention also include providing feet and bottom boards separate from the pallet platforms and attaching the feet to the platforms so as to enhance their collective ability to avoid impact-related breakage. 
     Further objects of the present invention comprise providing the bottom boards with some flexibility and bevelling the boards for facilitating guiding times or jacks. 
     Other features, objects, and advantages of the present invention will be apparent with reference to the remainder of the text and drawings of this application. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a pallet or other structural support of the present invention. 
     FIG. 2 is a perspective view of a pallet similar to FIG.  1  and omitting any bottom boards or bases. 
     FIG. 3 is a perspective view of the underside of the pallet of FIG.  2 . 
     FIG. 4 is a plan view of a corner portion of the pallet of FIG.  1 . 
     FIG. 5 is a plan view of a portion of the underside of the pallet of FIG.  1 . 
     FIG. 6 is a diagrammatic representation of some elements o an exemplary method of manufacturing the pallet of FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a structural support in the form of pallet of the present invention. Included in pallet  10  of FIG. 1 are platform  14 , feet  18 , and (optional) bottom boards or bases  22 . Any pair or all of these components may be integrally formed; preferably, however, they are created separately and connected in manners including those described herein. Pallet  10 , consequently, may be particularly (although not exclusively) useful in situations where flexibility of its components may be needed to avoid impact-related damage. 
     Shown in FIG. 1 is upper surface  26  of platform  14 , whose edges as formed into outer walls  30 . Also detailed in FIGS. 1 and 4 is the ridged nature of upper surface  26 , with channels  34  spacing adjacent ridges  38 . If, as in some embodiments of platform  10 , outer walls  30  are approximately one and three-quarters inches high, the height of ridges  38  is approximately one and one-half inches. Such absolute and differential heights are not critical to the present invention, however, and may be changed as necessary or desired. 
     Platform  14  typically is made of a thermoplastic material comprising HDPE. It thus may be created from a solid sheet of material thermoformed into the ridged shape shown in FIG.  1 . Ridges  38  function in many respects as reinforcing ribs, enhancing the load-bearing strength of platform  14 . Forming platform  14  of a solid sheet of material additionally avoids creating a shell having a hollow internal structure into which liquid or solid matter can be admitted. This avoidance may in some cases be particularly important in commercial food-storage areas, where pallet breakage is significant (which may allow admittance of foreign matter into the interiors of hollow pallets) and hygiene may be important. Because platform  14  is typically formed of a solid sheet, furthermore, one or more holes  42  may be created quite easily in channels  34  to allow liquid to drain away from its upper surface  26 , permitting the platform  14  to be steam-cleaned relatively easily. 
     As illustrated especially in FIGS. 1 and 4, ridges  38  need not extend to outer walls  30  of platform  14 . Creating ridges  38  in this manner defines a (nominally) transverse channel  46  partially bounded on one side by edges  50  of ridges  38 . Bounding the opposite side of each transverse channel  46  is an inner wall  54 , which together with a corresponding outer wall  30  forms a boundary ridge  58 . Inner and outer walls  54  and  30  additionally serve as the double-walled edges of platform  14 ; should an outer wall  30  break or crack (as, for example, when impacted by a fork-lift time), the presence of a corresponding inner wall  54  minimizes degradation in performance of the pallet  10 . 
     Similar (nominally) longitudinal boundary channels  62  may be present in platform  10 . Such boundary channels  62  are bounded by a side  66  of each outermost ridge  38 A and by inner wall  70 , with each inner wall  70  and corresponding outer wall  30  again functioning as the double-walled edges of platform  14  described in the preceding paragraph. Each of the four sides of platform  14  consequently includes protection against performance degradation should integrity of an outer wall  30  be impaired. 
     FIG. 5 details a portion of underside  74  of platform  14  together with an exemplary foot  18 . Each of ridges  38  forms a corresponding channel, or slot  78 , in underside  74  in which one or more feet  18  may be placed. Such feet  18  thus typically are oriented parallel to ridges  38  as shown in each of FIGS. 1-3 and  5 . If placed in a slot  78 A defined in underside  74  by inner wall  70  and outer wall  30 , a foot  18  could provide further protection against degradation in performance should the outer wall  30  be broken or cracked. 
     Illustrated in FIG. 5 is foot beam or structure  82 , which includes one or more feet  18  integrally formed with (or bonded to), depending from, and spaced along beam or rail  86 . Rail  86  may be fitted into a slot  78  and fixed therein with adhesive, using mechanical fasteners (if removable for recycling), or by ultrasonic welding or any other suitable material or mechanism. A preferred attachment material  90  is low density polyethylene (LDPE), which following application and cooling can bond structure  82  to underside  74 . Using LDPE maintains recyclability of pallet  10  while providing some flexibility to the connection between structure  82  and platform  14 . This flexibility may be important should a foot  18  be impacted by an object in use, as it allows some bending of structure  82  relative to platform  14  before breakage of the connection occurs. 
     Rail  86  need not necessarily be present as part of pallet  10 . If present, moreover, it need not necessarily extend substantially the entire length of the slot  78  into which it is fitted. Using an elongated rail  86  may be disadvantageous in some cases, as it effectively requires the length of the corresponding platform  14  to be at least its length, which may not always be preferred. 
     FIG. 5 further illustrates a protrusion  94  in underside  74  caused by extension of transverse channel  46  beyond inner walls  70 . Such protrusion can provide an interference fit with rail  86  (which is deformable by contact with protrusion  94 ), thus facilitating its retention in slot  78 A. Some or all of protrusions  94  need not necessarily be present in platform  14 , however, as should be understood by those skilled in the art. 
     Three structures  82  (each containing three feet  18 ) are shown in FIG.  1 . Spacing feet  18  in this manner defines a pair of openings  98  underneath each outer wall  30  of platform  14 . Openings  98  are adapted to receive, for example, times of a fork-lift truck or walker-rider equipment, making pallet  10  accessible from any of its four sides. Unlike many plastic pallets, pallet  10  is capable of providing this “four-way” entry while retaining sufficient load-bearing capacity, even when edge racked, to be useful in many circumstances. 
     Bases  22 , when present, may provide significant features to pallet  10 . Typically extruded from polymeric material (such as but not limited to polyethylene) in the form shown in FIG. 1, each base  22  may comprise upper and lower surfaces  102  and  106 , respectively, whose central portions are separated by internal ribs  110 . Edges  114  of upper surface  102  may, however, be bevelled, functioning to guide times or similar equipment into openings  98  without damages the corresponding base  22 . 
     In some embodiments of pallet  10 , bases  22  are connected to feet  18  with screws or other mechanical fasteners, which must be removed before a pallet  10  is recycled. Other connection means or materials may, of course, be used instead. Bases  22  additionally may have grommets or other devices protruding from lower surfaces  106  to increase their frictional contact with, for example, a floor or storage rack. 
     By not integrally forming bases  22  with either or both of feet  18  and platform  14 , such bases  22  indeed may be employed only when desired. Should a base  22  become damaged in use, moreover, it need merely be detached from feet  18  and replaced, thus avoiding one having to replace the entire pallet  10 . Base  22  additionally made be made of less-rigid material than platform  14 , allowing it to conform somewhat to an uneven surface and to bend or flex, rather than break, in response to certain impacts. 
     FIGS. 2-3 illustrate the optional nature of bases  22 , showing a pallet  10  which has omitted them either permanently or temporarily. 
     Pallets  10  of either FIG. 1 or FIG. 2 may be nested in pairs for storage or transport. To create one such pair, a first pallet  10  is turned upside down, so that its feet  18  extend upward. A second pallet  10  may then be placed thereover so that two feet  18  of the first pallet  10  protrude upward into openings  98  defined by the second pallet  10 , while two feet  18  of the second pallet  10  protrude downward into openings  98  defined by the first pallet  10 . The result is a pair of pallets  10  whose height is not substantially greater than the height of one such pallet  10 , thus reducing the volume of space required to store or transport the pair. The length of the pair, while somewhat longer than the length of a single pallet  10  (because at least one foot  18  of each pallet  10  is not received by an opening  98  in the other pallet  10 ), is less than twice the length of a single pallet  10 . 
     Excepting, perhaps, any mechanical fasteners employed as components of pallet  10 , the pallet  10  is designed to be recyclable. Among materials useful for this purpose is polyethylene of which, if desired, the majority of pallet  10  may be made. Polyethylene tends to “creep,” or “droop,” under certain loading conditions, however, as its flexural modulus is relatively low. Pallet  10  hence may also include fiberglass or other substances for reinforcement. Usually, however, such pallet  10  will not include either wood (which as noted above is not readily recyclable) or thermosetting materials (as opposed to thermoformable thermoplastic materials such as HDPE). On the other hand, any or all of the thermoformable materials present in pallet  10  may, for example, be pre- or post-consumer or industrial waste, so that the pallet  10  includes recycled materials. 
     Each of upper surface  26 , underside  74 , and lower surface  106  (if present) of pallet  10  contacts another object in use. Upper surface  26  receives the load to be supported by pallet  10 , while lower surface  106  typically rests in contact with a floor or components of a rack. Times or a pallet jack contact underside  74  when pallet  10  is moved from one location to another. Maintaining frictional contact adequate to prevent (or at least limit) relative movement between pallet  10  and each of the load, times, and rack or floor (or another empty pallet) may thus be important to avoiding damage to the load. 
     Accordingly, non-skid material  114  may be included as part of pallet  10 . In certain preferred embodiments of the invention, such non-skid material  114  is co-extruded with a sheet of HDPE-containing material and then thermoformed together. Since both upper surface  26  and underside  74  may include non-skid material  114 , such non-skid material may be extruded onto both sides of the HDPE-containing sheet ultimately forming platform  14 . After having been heated and pressurized during the thermoforming process, the non-skid material  114  is integrated with the HDPE-containing sheet, whose rigidity is retained. There thus is no soft, deformable non-skid cord welded to or fitted into grooves of pallet  10 , unlike the pallet of the Ishida patent. Likewise, non-skid material  114  may be co-extruded onto lower surface  106  of base  22 . 
     Non-skid material  114  alternatively may be sprayed or otherwise applied to or incorporated into pallet  10 . Regardless of application method, it need not necessarily be applied to the entirety of any of upper surface  26 , underside  74 , and lower surface  106 . Instead, in many cases application of non-skid material  114  to only portions of these surfaces will produce satisfactory results. 
     Preferred constituents of non-skid material  114  are thermoplastic olefins such as Kraton polymer. Although many other compositions may be used as non-skid material  114 , urethanes are not preferred for most embodiments of the invention because of their diminished performance at low temperatures. Incorporated herein in their entireties are the following brochures of Shell Chemical Company, as they appeared on-line as of May 3, 1999, describing Kraton polymers: “Kraton Polymers Processing Guide,” “Kraton Polymers and Compounds Typical Properties Guide,” and “Shell Kraton Polymers for Modification of Thermoplastics.” Copies of these brochures are included with the Information Disclosure Submitted herewith. 
     FIG. 6 diagrams aspects of an exemplary method of creating a support structure of the present invention. As described in block  118 , HDPE is mixed with fiberglass as the primary components of platform  14 . The mixture is heated and extruded into a sheet as described in block  122 , with non-skid material  114  being co-extruded onto at least portions of the sheet (see block  126 ). The sheet containing non-skid material  114  may then be cooled and cut to an appropriate shape (block  130 ), following which it is thermoformed into platform  14  (block  134 ). 
     As shown in block  138 , formed separately (typically using an injection molding process) are (typically hollow) feet  18  (whether or not part of structure  82 ). One or more such feet  18  may then be inserted into appropriate slots  78  in the sheet forming platform  14  (block  142 ), after which LDPE polyethylene may be used to weld feet  18  in place (block  146 ). Separately extruded (or otherwise formed) bases  22  (see block  150 ), finally, may be attached to the feet as described in block  154 . 
     The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of the present invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of the invention. As but two of many examples of such modifications, platform  14  need not be rectangular if desired and the dimensions of pallet  10  may vary as appropriate for loads which it is to support.