STEEL STRIPS WITH FOLDED EDGES TO FORM LOAD BEARING

FIELD OF THE INVENTION

The invention relates to the construction of load bearing structures, and is particularly applicable to the construction of pallets for use in the transport of goods. BACKGROUND TO THE INVENTION

Pallets, used in the transport of goods, are traditionally manufactured from timber. They are cheap and easy to produce, but deteriorate in use through shrinkage, warping, and splitting. Deteriorated pallets may be unable to support a desired load. Additionally, deterioration of a pallet may lead to the exposure of sharp points of fasteners such as nails. Timber pallets are also now subject to stringent export quarantine regulations and are a fire risk in ships, aircraft and warehouses. Plastic and fibre reinforced pallets are also available. They are lightweight, but have load bearing limitations, as well as suffering from lack of dimensional stability in heat. Plastic and fibre reinforced pallets may become brittle when exposed to UV radiation or to low temperatures, such as in coolrooms. Metal pallets, particularly steel pallets, have been in existence for many years but have tended to be both heavy and expensive. An attempt to address some of these issues is described in US Patent 5,507,236. The specification of this patent describes the fabrication of a horizontally positioned corrugated sheet or sheets sandwiched between top and bottom dished panels. The drawings show that the corrugated panel is not fixed to the side walls, thus the structure is not unitized. The present invention seeks to overcome, at least in part, some of the above identified problems of prior pallet constructions.

This application claims priority to Australian provisional application no. 2007904798 filed 4 September 2007, the entire contents of which are incorporated herein by this reference thereto. SUMMARY OF THE INVENTION

A first aspect of the present invention provides an elongate strip for use in a load bearing structure, the strip having longitudinal upper and lower edges

wherein at least one of said edges is folded or rolled whereby said elongate strip is stiffened.

Advantageously, this stiffens the elongate strip. Advantageously this also results in the blunting of an otherwise thin, sharp edge, and also allows for the easier attachment or bonding of a flat deck to a surface of a load bearing structure formed from a plurality of strips. Preferably, both the upper and lower edges of said strip are folded or rolled. Preferably, the strip is aluminium, steel or stainless steel.

Advantageously, a plurality of strips can be assembled to form a load bearing structure. The plurality of assembled strips are preferably fixed to each other by connection methods such as a fastener, adhesive, welding or other fixing means.

A strip edge may be folded between 90° to 180°, or may be rolled. This may be done by folding or rolling the strip at either longitudinal edge to the same side, to form a cross-section of an approximate "C" shape, or to alternate sides, to form an approximate "S" shape.

The folding or rolling of the strip edges may be achieved by a roll-former, folder, press or other suitable means.

The strips may be formed with bends along their length. These bends may be angular or may consists of sinusoidal or semi-circular undulations or mixtures thereof, so as to enable a plurality of said elongate strips to be bonded together in tessellations.

In an alternative embodiment, said strip has a plurality of slots extending inwardly from at least one of said edges, and preferably each said slot is wider at said respective edge than at an inward end of said respective slot.

Advantageously, a plurality of first strips can be interlocked with a plurality of second strips, using said slots, to form a load bearing structure. Slots on the first strips may receive the second strips. In use, the wider portions of said slots receive the folded or rolled edge of a respective interlocking strip. The strips may be slotted and interlocked to form a square or rectangular tessellation.

A second aspect of the present invention provides a load bearing structure including a plurality of strips as described herein, arranged in an array extending in a horizontal plane such that respective longitudinal axes of said strips are

aligned in a regular order or array relative to each other, the upper edges of said strips forming the upper surface of the array.

Preferably, the assembled array has a square, rectangular, hexagonal or sinusoidal pattern. Even where said strips have one or more bends along their length, the assemblage of said strips are arranged to form a regular order or array. In some cases, this may be achieved by arranging the longitudinal axes of said strips parallel to each other, whether or not said strips have bends. Said strips may be fixed to each other by fasteners (including rivets), adhesives, welding (including laser welding), clinching or other fixing means. By forming strips with bends along their lengths, a plurality of strips can be arranged to form for example, a hexagonal pattern or tessellation. The tessellation may have regular sided hexagons (a honeycomb) or may have irregular sided hexagons in which the hexagon sides have differing lengths. Such a variation can improve strength in a particular direction if required. Tessellations of other polygons, curves or plane figures are possible.

In another preferred embodiment, the load bearing structure includes a plurality of first strips each having a plurality of slots extending inwardly from at least one of said edges, and preferably each said slot is wider at said respective edge than at an inward end of said respective slot. The structure advantageously includes a plurality of second strips arranged to be received by respective slots to thereby form an interlocked structure. Advantageously, the reception of a folded or rolled edge in a respective slot reduces the propensity for rotation of the first strips relative to the second strips. The assembly may be further strengthened by use of additional connection methods such as fasteners, adhesive, welding, riveting, clinching or other fixing means. The present invention advantageously can be welded using laser welding.

In preferred embodiments of the invention, selected one(s) or selected groups of the plurality of strips can be cut to have a greater width than other strips. When assembled into a load bearing structure such as a pallet, these selected strips will thus have a greater "depth" or "height" than other strips. The selected strips can be arranged in a load bearing structure such that the upper edges of the selected strips are level with the upper edges of the other strips (resulting in the selected strips projecting below the other strips).

Use of the wider selected strips advantageously provides projecting 'feet', 'legs' or 'beams', which support the remainder of the structure above ground level. Use may also advantageously increase the rigidity of the pallet.

In a preferred embodiment a pallet formed according to the invention has feet, which could be integrally formed by providing some strips of a greater width where feet are required, (such that they protrude below other strips). Preferably, the feet define a gap under the load bearing structure allowing either two and/or four way tine access for a forklift or hand trolley. These feet may additionally be joined together at their base to provide additional strength and preferably are joined by a section of sheet metal. Alternatively, these feet may additionally be connected to another planar array, integrally or otherwise, to form a double sided pallet.

Additionally the load bearing structure may be bonded to top and/or bottom decks along the edges of the strips when such decks are required. This advantageously further stiffens the load bearing structure.

Such a load bearing structure is capable of spanning across a space such as encountered in pallet racking and provides a void beneath the array for insertion of forklift and pallet truck tines.

In a preferred embodiment, the selected one(s) or groups of wider strips may be fixed to two arrays of other strips. For example, a pallet may have an upper array and a lower array, the two arrays spaced apart and each fixed to the selected strip(s). The configuration may be an T cross section, a square or rectangular section, two adjacent rectangular sections or other configurations.

In a preferred embodiment, the selected one(s) or groups of wider strips may be shorter than other strips, forming 'feet' or 'legs' rather than 'beam' protrusions. A pallet having nine such legs or posts and accessible to forklift tines from 4 directions ("nine post, four way pallet") can be configured in such a manner.

Advantageously, the base of the selected strips may be fixed together with strips or sheets of (eg) sheet metal, preferably in a direction orthogonal to the longitudinal axes of the strips forming the array. This can increase structure strength and rigidity.

A third aspect of the present invention provides a method of manufacturing a load bearing structure strip including the steps of: i) cutting a strip from a planar sheet; and ii) folding or rolling at least one edge of said strip; and iii) forming bends in said strip.

The strip may be cut from the sheet by any suitable means, including punching, guillotining, laser etc. The planar sheet may be provided in coil or roll form, and the cut strip may be stored in coil or roll form if desired, prior to folding or rolling. The strip may be folded or rolled by any suitable means, including rollforming. The bends may be formed in the strip by any suitable means including rollforming, rotary forming, folding or punching.

Optionally, one longer strip may be cut into several shorter sections before assembly into a load bearing structure. A fourth aspect of the present invention provides a method of manufacturing a load bearing structure including the steps of: i) manufacturing a plurality of strips according to the third aspect of the invention; and ii) arranging said plurality of strips in an array extending in a horizontal plane such that respective longitudinal axes of said strips are aligned in a regular order or array relative to each other, the upper edges of said strips forming the upper surface of the array; and iii) fixing said plurality of strips in position relative to each other.

In one embodiment, the strips are arranged in array before being fixed. In another embodiment, the array is arranged by fixing each strip in position as the array is created, for example, each strip is fixed to an adjacent strip as it is added to the array.

Suitable fixing means include fasteners (including rivets), adhesives, welding (including laser welding), clinching or other fixing means. In one preferred embodiment, the plurality of strips are fixed in position relative to each other through use of a frame. Preferably, a U-channel frame member receives a plurality of strips. Further U-channel frame members are used to create a

bounding frame surrounding the strips, holding or trapping the strips in a fixed position relative to each other.

In a preferred embodiment, a top and/or a bottom deck may be fixed to said structure. Optionally, beams or posts may be fixed to said structure. A fifth aspect of the present invention provides a method of manufacturing a load bearing structure strip including the steps of: i) folding or rolling an edge of a planar sheet; and ii) cutting a strip, including said sheet edge, from said sheet; and iii) cutting a plurality of slots in a cut edge of said strip; and iv) optionally folding or rolling the cut edge of said strip.

A sixth aspect of the present invention provides a method of manufacturing a load bearing structure including the steps of: i) manufacturing a first and a second plurality of strips with slots as herein described; and ii) arranging said first plurality of strips in an array such that respective longitudinal axes of said first strips are aligned parallel to each other, with the cut edge of said first strips having slots forming the upper edge of each first strip, respective slots on each first strip aligned with respective slots on each next first strip in the array; and iii) arranging said second plurality of strips in an array such that the slots in said first strips receive respective second strips and the slots in said second strips receive respective first strips whereby said first and second strips are interlocked; and iv) optionally welding the junction between said first and second strips. It is envisaged that the present invention will be advantageously applied in the construction of pallets, with the elongate strips being formed of a suitable metal such as aluminium, steel, or stainless steel.

A seventh aspect of the invention provides an elongate strip when used in a load bearing structure, the strip having longitudinal upper and lower edges wherein at least one of said edges is folded or rolled whereby said elongate strip is stiffened.

An eight aspect of the invention provides a load bearing structure elongate strip when used in a load bearing structure, the elongate strip having longitudinal

upper and lower edges wherein at least one of said edges is folded or rolled whereby said elongate strip is stiffened.

Advantageously, use of sheet metal such as aluminium, steel or stainless steel is easy to work with during manufacture, easy to refurbish in use and easy to recycle. As the load bearing structure has open space between strips, the average density of the structure is relatively low when compared to other structures of similar strength. The invention enables provision of a high weight-to- strength load bearing structure. BRIEF DESCRIPTION OF THE DRAWINGS It will be convenient to further describe the invention with reference to the accompanying drawings which illustrate preferred embodiments of the load bearing structure of the present invention. Other embodiments are possible, and consequently, the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention. In the drawings:

Figure 1 is a perspective view of an elongate strip according to one embodiment of the invention;

Figures 2a to 2f are cross-sectional views of elongate strips according to various embodiments of the invention; Figure 3 is a partial plan view of a load bearing structure according to another embodiment of the invention; Figure 4 is a partial plan view of a load bearing structure according to another embodiment of the invention;

Figure 5 is a partial plan view of a load bearing structure according to another embodiment of the invention; Figure 6 is a plan view of a load bearing structure according to another embodiment of the invention;

Figure 7 is a perspective view of two elongate strips, prior to interlocking, according to an embodiment of the invention;

Figure 8 is a perspective view of two interlocking elongate strips according to another embodiment of the invention;

Figure 9 is a partial perspective view of a load bearing structure according to another embodiment of the invention;

Figure 10a is a perspective view and 10b a side view of a pallet according to an embodiment of the invention;

Figures 11a-c are side views of load bearing structures according to alternative embodiments of the invention; and Figure 12 is a partial perspective view of a double sided pallet according to an embodiment of the invention; DESCRIPTION OF PREFERRED EMBODIMENT

The preferred embodiments of the load bearing structure herein described are goods pallets. This does not thereby limit the scope of the invention claimed. Referring to the drawings, Figure 1 shows an elongate strip 10 having a longitudinal upper edge 12 and a longitudinal lower edge 14. The upper edge 12 has been folded 22, thereby stiffening the strip 10 and blunting what would otherwise be a thin and possibly sharp edge. Preferably, the strip 10 is cut from sheet metal such as aluminium, steel, or stainless steel. Figures 2a to 2f show cross-sectional views of alternative embodiments of an elongate strip, wherein both the upper and the lower edges are folded (Figures 2a to 2c), twice folded (Figure 2d), or rolled (Figure 2e) or one edge is folded and the other rolled (Figures 2f). Other variations or combinations are possible, to form various "C", "S", "Z" or other cross-sectional shapes. The use herein of directional terms such as upper, lower, vertical or horizontal is for the purpose of relative orientation and is not to be taken as limiting the invention claimed herein. For example, an edge described as 'upper' may, in use, form a right or left hand side edge, depending on the direction of orientation in actual use. In use, elongate strips 10 are positioned in an array such that each strip 10 has a substantially vertical portion extending between upper and lower edges 12, 14. The vertical portion, in use, carries a load applied to one of said edges, for example, where the array forms a pallet for carrying goods. Advantageously, an elongate strip (of a given thickness and height) according to the present invention, will have a higher second moment of area (and hence be stiffer) than an elongate strip (of the same thickness and height) not having a rolled or folded edge.

Examples of some suitable arrays are shown in Figures 3-5.

Figure 3 shows an array having hexagonal tessellations. Each strip 10 is bent at 60° angles along its length and arranged adjacent similar strips. The array could be varied by having irregular hexagons. Figure 4 shows an array of strips each extending approximately sinusoidally about its longitudinal axis. Figure 5 shows a lattice array of hemispheres. The array could be varied to square, diamond, triangle or other polygonal shapes.

The strips may be fixed to each other to form a unitized structure using fasteners, adhesives, welding or other suitable fixing means, which could include fixing each of the strips to a bar, plate or deck rather than directly to each other. Alternatively, the strips may also be fixed in a unitized structure by being contained or bounded by an outer frame 30 having, for example, a "C" channel section as shown in Figure 6, as well as fixed to each other. In another suitable arrangement, the strips 10 are not bent along their length, but extend linearly and substantially parallel to each other. Figure 7 shows an alternative elongate first strip 10 having upper and lower edges 12, 14 and an elongate second strip 50 having upper and lower edges 52, 54. The upper and lower edges 12, 14, 52, 54 of the first and second strips 10, 50 are folded.

The first strip 10 has a plurality of slots 16 extending inwardly from lower edge 14. Said slot 16 is wider 18 at edge 14 than at an inward end of the slot 16.

Similarly, the second strip 50 has a plurality of slots 56 extending inwardly from upper edge 52. Said slot 56 is wider 58 at edge 52 than at an inward end of the slot 56.

A plurality of first and second strips 10, 50 may be positioned such that respective first strips 10 are received in respective second strip slots 56 and respective second strips 50 are received in respective first strip slots 16. This forms an interlocking lattice of first and second strips which may be used as a load bearing structure.

The length said slots 16, 56, extend inwardly from respective edges 14, 52 determines whether upper edges 12, 52 and lower edges 14, 54 of strips 10, 50 are horizontally aligned with each other.

Slots 16, 56 have wider portions 18, 58 at the edges 14, 52. These wider slot portions 18, 58 receive the folded edge of the respective strip received by

slots 16, 56. Slot width is preferably matched to the strip to be received by the slot. Where both first and second strips 10, 50 have both upper and lower edges 12, 14, 52, 54 folded or rolled, the interlocking surface area between a given first and second strip at intersection 70 is increased. As shown in Figure 8, the "internal" surface area of a slot extending through a folded or rolled edge is greater than a slot of the same length through a non-folded or non-rolled edge. Indeed, as shown in the cross-sections of Figure 2a to 2f, not only is the surface area greater, but an arrangement of greater stiffness and stability is obtained where the "C", "Z" or other cross-section of a first strip 10 is placed perpendicularly to the face of a second strip 50. Relative twisting between the first and second strips 10, 50 is prevented, as the folded or rolled edge of first strip 10 comes into contact with second strip 50 along a greater longitudinal length (of second strip 50) when compared to an unfolded or un-rolled edge. This increases stability at each intersection 70. Figure 9 is a partial perspective view of a pallet according to an embodiment of the invention.

By altering slot length (where a slotted arrangement is used), or by altering overall height of strips (whether or not a slotted arrangement is used), the strip edges may be aligned or proud as required. This may be useful to provide, for example, protruding feet, legs or a beam, for a pallet, such that a fork lift or hand trolley may insert tines beneath the remainder of the pallet. Figures 10a and 10b show a pallet 60 having such an arrangement, using a hexagonal tessellation of strips. Figures 11a to 12 show alternative arrangements using strips of differing heights. Providing some second strips 50 of greater depth than first strips 10 allows said second strips 50 of greater depth to function as legs. In a non-slotted embodiment of the invention, selected one(s) of the strips may be of greater height than other strips, resulting in an arrangement similar to that shown in Figures 10a to 12. Optionally for greater stiffness, a decking or flat plate 62 may be applied of sheet metal or similar between said second strips 50 of greater depth as shown in Figure 10b. Where of sheet metal, the sheet thickness is minimal in comparison to a wooden stiffener such as often used on the base of wooden pallets.

Where a hand trolley or jack is used, it takes extra effort and is a potential health and safety hazard to push the trolley over a wooden bar in order to locate the tines. In comparison, the sheet metal is barely noticeable.

Preferably, elongate strips 10 are manufactured from sheet materials by cutting a strip from the sheet and then folding or rolling one or both edges. Where slots are to be formed on an edge, the slots are preferably cut, punched or otherwise formed prior to the folding or rolling process. However, elongate strips may be cut and subsequently folded or rolled along either or both edges.

Preferably, robot laser cutting or a rotary die is used to cut slots and to cut strips from sheets. Preferably, the strips are arranged in an array and robot laser welded together. The embodiment of Figure 7 may be assembled by aligning a plurality of second strips 50 parallel to each other and with slots 56 aligned with respective slots on adjacent second strips 50, and inserting into respective said slots a plurality of first strips 10 having slots 16 such that respective slots 16, 56, receive respective strips 10, 50, to form an interlocking lattice having intersections

70.

Desirably, in the embodiment of Figure 9, welding occurs at the intersection 70 to prevent relative vertical movement of first and second strips 10, 50, and may occur at upper and/or lower edges, or on vertical portions, folded or rolled portions of the strips.

Advantageously, load bearing structures for use as pallets and fire doors are easily manufactured from sheet materials such as sheet steel to create a light weight, high strength and durable structure.