FIELD OF THE INVENTION

This invention relates to the international transport and warehousing industries and in particular to a high-performance light-weight plastic pallet, capable of supporting heavy loads for use in those industries.

BACKGROUND TO THE INVENTION

The international transportation and warehousing industries have historically used wooden pallets for transporting and storing goods. Due to the danger of transporting bacteriological growth and/or other pathogens within wooden pallets there is now an international drive to replace wooden pallets with plastic pallets.

Plastic pallets of different sizes, weights and configuration are essentially used to carry loaded goods of various sizes and weights on their upper surface or deck which is mostly found to be predominantly flat.

Both wooden and plastic pallets have a tendency to deflect when carrying heavy loads across a variety of transportation and weight loading scenarios. There is also a large variety of pallets that are designed to meet the transportation spectrum from lightly structured light-weight pallets for light loads to heavily structured heavy-weight pallets containing metal elements that are designed for extremely heavy loads.

The various pallet sizes, types and configurations that are currently available can conveniently be divided into three main "classes" of pallets. The information below in respect of each of the three classes is based on a 1200x1000mm plastic pallet.

Light weight, disposable, one-way, single-use pallets are at the one end of the pallet spectrum. This class of pallet typically weigh between 4 and 7kg and they are not considered to be structurally robust and while they might be able to carry dynamic loads (on a fork lift) of between 300 to 500kg they are not generally designed to withstand loads above about 200kg without excessive deflection and accordingly, they are not considered to be "rack compatible". They are not designed to be placed within a warehouse racking system where they would deflect excessively if loaded beyond about 200kg and the pallet would be in danger of falling through the racking system potentially destroying the load and causing danger to those working below. These pallets are often used for transporting items such as flowers where a typical load could weigh about 100kg. These light-weight, lightly loaded pallets are often transported by aircraft. Light-weight, single-use pallets do not usually contain metal sections. Light-weight pallets are not considered to be "stackable" where loaded pallets are placed one upon another - often to heights of 6 meters or more.

Medium weight pallets are essentially multiple-use pallets designed to move a large variety of goods, with loads typically weighing up to 1 ,200kg. Medium weight pallets are generally of robust design and would typically weigh 16kg to 20kg. They are designed for the general transportation of goods which would encompass refrigerated and frozen goods or dry goods such as tinned items as typically sold by the larger retailers. Medium weight pallets are considered to be partially rack-compatible and can be used in warehouse racking systems where their safe load carrying / racking limit is generally considered to be about 700 to 800kg. Medium weight multiple-use pallets do not usually contain metal sections. Medium weight pallets are considered to be "stackable" and the total weight carried by the bottom pallet could be as high as 4,000kg.

Heavy weight pallets are essentially multiple-use pallets designed to move a large variety of goods weighing as much as 1 ,200kg or more. Heavy weight pallets are generally of robust design and typically weigh 24 to 27kg or more. Like medium weight pallets, they are designed for the general transportation of goods which could include refrigerated and frozen goods or dry goods such as tinned items as typically sold by the larger retailers. Heavy weight multiple-use pallets usually contain metal sections and are considered to be "fully rack-compatible" within warehouse racking systems where their safe load carrying / racking limit is generally considered to be 1200kg or slightly more than this. Heavy weight pallets are considered to be "stackable" and the total weight carried by the bottom pallet could be as high as 4,000 to 6,000kg.

5 Most pallets can be placed in a warehouse racking system where the pallet is typically only supported along two opposite edges with the pallet body being unsupported and depending on the loaded weight, the pallet body will deflect downwardly to a lesser or greater extent where some are considered safe and "partially or fully rack-compatible" and others are found to be dangerous and "not rack-compatible".

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Heavily structured heavy-weight plastic pallets typically contain a large volume of plastic material and incorporate metal elements (usually these are steel inserts in the form of steel tubes, square or rectangular steel sections or small "I" beams which are usually purpose made). Metal elements are added to, or installed within the pallet body after 15 the pallet body has been manufactured.

Plastics material used to manufacture pallets are generally not very stiff, yet pallets often carry loads of 1 ,000 kg or more and under such high loads, plastic pallets tend to distort excessively. The distortion typically includes an outward splay of the lower 10 extremities and the pallet body tends to deflect downwardly along the top deck and the base or lower extremities of the pallet body. This deflection is especially pronounced when a pallet is placed in a warehouse racking system where the pallet body is not fully supported across the base - as would be the case if the loaded pallet were supported on a flat level surface such as a warehouse floor.

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This excessive distortion and deflection causes the loaded goods to take up some of the stresses with the potential for damage to the loaded goods and it is also possible for the pallet and its load to slip through the racking system and fall to the ground - with the possibility of causing other racked and loaded pallets also to fall. Additionally, there is a 30 risk that such a falling pallet may damage objects below or expose warehouse personnel to danger. In attempts to stiffen and strengthen pallet bodies to reduce distortion and deflection, pallet manufacturers have increased the plastic volume contained within their pallets. Where extra-heavy loads are to be carried by the pallet, they have additional reinforcing elements - typically in the form of metal elements, which are usually housed within apertures in the pallet body that are designed to accept these metal elements.

The metal elements bear much of the weight and stresses imparted by the load and these are spread across the pallet body in manners intended to reduce distortion and deflection of the pallet body.

Due to the use of additional plastic material and metal elements to bear the heavy loads applied to the pallet deck, plastic pallets have become heavier and more expensive to produce to the point that it is now common to find "fully rack compatible" plastic pallets that are capable of carrying heavy loads, containing in excess of 23kg of plastic within the pallet body structure and with the addition of the metal elements, have a total weight in excess of 26kg.

The addition of metal elements that essentially become part of the pallet body is problematic at the end of the usable life of the pallet when the metal elements need to be removed before the plastic content of the pallet body can be recycled.

Further, corrosion of the metal elements is an additional problem during the life cycle of the pallet and if the pallet is overloaded during use, the metal elements tend to deform permanently with a deflected shape. This deformation creates stress within the pallet body, it potentially alters the shape of the pallet, it potentially damages the plastic in the immediate vicinity of the deformed metal elements and the deformed metal elements often prove difficult to remove for maintenance or pallet scrapping purposes, prior to reclaiming the plastic content of the pallet.

Plastic pallets are considerably more expensive than wooden pallets. The present invention seeks to provide plastic pallets that can be produced at low cost and still have a high load bearing ability, while preferably being rack compatible and without a need to recover parts of the pallet before recycling its polymeric body.

SUMMARY OF THE INVENTION

According to the present invention there is provided a pallet which comprises:

a pallet body of a plastics material, said pallet body including a load deck and a plurality of pillars extending from an underside of the load deck;

characterised in that said pallet includes at least one flexible tensile element extending in a continuous loop, generally around the pallet body, generally along the load deck and generally between undersides of the pillars.

The term, "generally around the pallet body" is not limited to situations where the tensile element extends around the entire pallet body, but it includes the tensile element being slightly recessed or embedded in the pallet body, i.e. in close proximity to the periphery of the pallet body and still extending around the bulk of the pallet body. Similarly, the terms "generally along the load deck" and "generally between undersides of the pillars" include situations where the tensile elements extend in close proximity to the load deck or the undersides of the pillars, respectively.

The tensile element may be fixedly attached to the pallet body, e.g. the pallet body may include an insert and the tensile element may be fixedly attached to the insert, e.g. by being welded to the insert.

The pallet body may include a bottom structure that extends between the undersides of at least some of the pillars.

The pallet may include a plurality of said tensile elements and the tensile elements may be parallel to one another, may extend transversely to one another, and/or may extend in any direction. Each tensile element may be received in a groove defined in the pallet body and the grooves may be covered, at least in part, with lids. Instead, the covered grooves may be integrally formed in the pallet body or the tensile elements may be moulded in situ in the pallet body.

The tensile elements may be straps and may be of a plastics material such as nylon, or any other material suitably resistant to elongation.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show how it may be put into effect, the invention will now be described by way of non-limiting example, with reference to the accompanying drawings in which:

Figure 1 shows a three-dimensional view of a first embodiment of a pallet according to the present invention;

Figure 2 shows a detail three-dimensional view of a strap groove of the pallet of Figure

1 ;

Figure 3 shows a three-dimensional view of a second embodiment of a pallet according to the present invention;

Figure 4 shows a detail three-dimensional view of two intersecting strap grooves of the pallet of Figure 3;

Figure 5 shows a detail three-dimensional view of two intersecting strap grooves of a third embodiment of a pallet according to the present invention;

Figure 6 shows a three-dimensional view of part of a fourth embodiment of a pallet according to the present invention;

Figure 7 shows a sectional view of the pallet of Figure 6, taken at VII-VII;

Figure 8 shows a three-dimensional view of a fifth embodiment of a pallet according to the present invention'

Figure 9 shows a sectional view of the pallet of Figure 8, taken at IX-IX; and

Figure 10 shows a detail, exploded view of an insert and a length of a strap of the pallet of Figures 8 and 9. DETAILED DESCRIPTION OF THE DRAWINGS

Referring to the drawings, a pallet according to the invention is generally identified by reference number 10, with suffixes referring to the particular embodiment of a pallet according to the invention.

Each embodiment of the pallet 10 comprises a pallet body 1 1 which includes a rectangular load deck 12 and feet or pillars 14 extending downwards from the underside of the load deck at each corner of the load deck and midway along each edge of the load deck. Each pallet 10 further includes a central pillar 15 that is not shown in the drawings, apart from Figure 9. Each pallet 10 also includes a base or bottom structure 16 that extends between the undersides of the pillars 14 and the bottom structure can be a bottom deck, any number of runners, a part or complete "picture frame", any number of "skids", or any other formation, but in the illustrated embodiments, the bottom structure comprises a number of runners. The load deck 12, pillars 14 and bottom structure 16 together form a pallet body and are all made of a plastics material, e.g. high density polyethylene (HDPE). They may be integrally made, e.g. by being injection moulded, or they may be assembled or attached together and they may be of different materials, but these parts of the pallet 10 can normally be recycled without a need for dismantling or stripping. The size of the pallet 10 can vary, but it is typically of a standardised size, e.g. it has a length of 1200mm and a width of 1000mm.

Referring to Figures 1 and 2, the first embodiment of a pallet 10.1 has three strap grooves 18 that extend generally parallel across its load deck 12, aligned with the pillars 14 and the strap grooves extend continuously along the outsides of the pillars and along the underside of the bottom structure 16. In each of these strap grooves, a tensile element, preferably in the form of a flexible strap (not shown) is received and each strap extends around the pallet 10.1 in a loop, along its strap groove. The straps are fitted after the pallet body 1 1 has been manufactured and are tensioned and their ends attached together, e.g. by welding or with clips, to form continuous loops around the pallet body. The straps are preferably taut, even when the pallet is not loaded and they are preferably made of a material that is resistant to elongation, e.g. nylon, polyethylene terephthalate (PET) or similar straps, steel strapping, steel wire, steel wire cable or strapping, or any other strapping that is capable of bearing substantial tensile loads, while resisting elongation.

If the straps are made of PET or similar polymeric strapping material, the straps would be light in weight, inexpensive, non-corrosive and generally resistant to damage by water or the elements and, it would be easy to remove and replace the straps if any maintenance is required and also easy to remove and reclaim the straps when it is time to scrap the pallet 10.1 and reclaim the plastic material within the pallet body 1 1 .

The strap grooves 18 cause the straps to be recessed from the top of the load deck 12, the outer peripheries of the pallet's edges and from the underside of the bottom structure 16, so that the straps are protected against abrasion or similar wear to which these parts of the pallet 10.1 are exposed, from loads, warehouse floors, handling, etc.

The strap grooves 18 also ensure that the straps remain in their correct positions.

The strap grooves 18 are preferably deep enough to ensure that the straps are recessed as described above, with some additional depth for a margin of safety and with sufficient depth to accommodate any attachment means of the straps - e.g. buckles or clips.

When the pallet 10.1 receives a load on its load deck 12, the load causes bending stresses in the load deck 12 and if the load deck is only supported at its periphery (e.g. when it is supported on opposing edges in a racking system), the bending stresses would tend to cause the load deck to deflect downwards and the deflection would cause the pillars 14 at the pallet's periphery to splay or distort outwards. However, if the pallet 10.1 is supported at opposing edges, with the straps extending between the supports (i.e. if the front edge 20 and rear edge 22 are supported), the deflection and distortion mentioned above will exert tension on the straps and the straps will resist the deflection - effectively by absorbing a substantial portion of the stresses caused by the load and bearing it as a tensile stress in the straps. The result is that the pallet 10.1 deflects substantially less than it would have deflected, if it did not have the straps, or put differently, the pallet 10.1 is capable of carrying a substantially higher load, without deflecting unacceptably and accordingly, by adding the straps to the pallet 10.1 , its load carrying capacity has been increased markedly.

The straps are preferably taut to the extent of being lightly pre-stressed, when the pallet 10.1 is un-loaded. The initial light positive tension in the straps may cause the load deck 12 to deflect slightly upwards (depending on the class of the pallet - e.g. whether the bottom structure 16 is sturdy enough to resist such deflection), but this would flatten out once under weighted load. It is not essential to the operation of the invention, that the pallet 10.1 should have a bottom structure 16 and in the event that it does not have a bottom structure, it will be more prone to upward deflection when un-loaded, but this does not affect its performance adversely.

Referring to Figures 3 and 4, the second embodiment of the pallet 10.2 is identical to the pallet shown in Figures 1 and 2, except that instead of the straps housed in three parallel strap grooves 18, the pallet 10.2 has three additional strap grooves 18 that extend in an identical manner to the first three strap grooves, except that they extend transversely to the first strap grooves (i.e. between the left edge 24 and right edge 26 of the pallet).

A variation on this embodiment of the invention (that is not illustrated), includes similar straps that extend diagonally across the load deck and intersect above the load deck and below the pallet to form an X. The invention is not limited to any orientation of the straps in relation to the load deck.

Referring to Figure 5, the third embodiment of the pallet 10.3 is identical to the pallet shown in Figures 3 and 4, except that the strap grooves 18 have shoulders 28 along their edges and can be covered with lids 30 (of which only one example is shown in Figure 5). The lids 30 can be attached in any suitable manner, e.g. their edges can be welded or adhesively attached to the shoulders 28, or the like. Preferably, the outer surfaces of the lids 30 are flush with the outsides of the pallet body 1 1 , to allow goods or other pallets to slide easily over the strap grooves 18 and to protect the straps.

Referring to Figures 6 and 7, the fourth embodiment of the pallet 10.4 is identical to the pallet shown in Figures 1 and 2, except that the straps 32 are not received in strap grooves, but are embedded in the pallet body 1 1 , e.g. by moulding the plastic material of the pallet body with the straps 32 already in situ. This method of manufacture holds the advantage of protecting the straps 32 against damage and it could be used to provide a first set of parallel straps 32, as shown, but also to provide a second set of straps in a transverse direction.

Referring to Figures 8 to 10, the fifth embodiment of the pallet 10.5 is similar to the pallet shown in Figures 1 and 2, with a pallet body 1 1 moulded from HDPE and PET straps 32 that are slightly recessed in grooves in the load deck 12 and bottom structure 16. However, the straps 32 are covered along the load deck and bottom structure, by lids 30 (as described with reference to Figure 5) and instead of the straps extending around opposing edges 24,26 of the pallet 10.5, they extend in close proximity to the edges, between the load deck and bottom structure.

The pallet body 1 1 is moulded with suitable recesses in its load deck 12 and bottom structure 16, at the pillars 14, to receive inserts 34 of PET. Each insert 34 has anchoring protuberances 36 that are received in the pallet body 1 1 to anchor them in position and that have rounded outer edges. The straps 32 are positioned around the inserts 34 and are welded end-to-end (preferably taut and more preferably under tension) and are welded to the inserts 34, before being covered by lids 30 on the load deck 12 and bottom structure 16. The attachment of the straps 32 to each of the inserts 34 prevents the straps from sliding around the pallet body 1 1 and increases the ability of each of the lengths of straps extending along the load deck 12 and bottom structure 16 to bear tensile loads and resist deflection of the pallet 10.5.

Referring to all the drawings, further to some of the advantages of the present invention mentioned above, the invention holds the advantages that it greatly enhances the performance of plastic pallets. A pallet 10 according to the invention requires less plastic material by volume for a given load carrying ability and is lighter, or can carry more load than other plastic pallets containing a similar volume of plastic material, it distorts less, including less outward splaying of the lower extremities of the pallet body 1 1 and less upward (when lifted with tines of a fork lift truck or the like) or downward deflection of the load deck 12 and bottom structure 16, it does not require metal elements to achieve "fully rack compatible" status, it is less expensive to produce and its plastic contents is fully recyclable. Tests have shown an improvement in excess of 100% in the ability of the pallet body 1 1 to carry a given load, when compared to use of the same pallet body, without the straps. The invention could negate the need for load-supporting metal sections. The invention will outperform current pallet designs based on a given volume of plastic in the pallet body. The invention provides a light-weight plastic pallet capable of being placed within a rack and supported only along two edges while carrying a heavy load with minimal distortion or deflection of the pallet body 1 1 . The invention thus provides the transportation and warehousing industries with a light-weight pallet of low plastic content by volume with no supporting metal sections, yet able to achieve a high stiffness / plastic material ratio, that is capable of carrying heavy loads with minimal outward splaying, distortion or downward deflection of the pallet body 1 1 .

Further to the embodiments of the invention described above, in other embodiments of the invention, instead of straps extending around the pallet body 1 1 as a loop, the straps can extend around the pallet body in part. In particular, the straps can extend across the top of the load deck or can extend across the underside of the pallet body 1 1 - typically extending between the undersides of pillars. In these embodiments of the invention, the pallet would include means for securing the straps to the pallet body and the means can be fixed or removable and can include welding the straps to inserts in the pallet body, as shown in Figures 9 and 10. Another example of suitable fixing means includes a small loop at the end of a strap and a short rod that can be slid through the loop and can be received in a suitable groove in the pallet body 1 1 . One such rod can pass through multiple loops on one side of the pallet body 1 1. The pallet body 1 1 could be placed in a jig or the like and can lightly be compressed and possibly flexed upwards at its centre, before positioning the straps between the pillars at the underside of the pallet body and securing the strap ends. The pallet is released from the jig so that the flexing is reversed and the strap is placed under tension - and is thus pre-stressed.