WO1998057860A1

WO1998057860A1 - A pallet and a method of its manufacture

Info

Publication number: WO1998057860A1
Application number: PCT/SE1998/001126
Authority: WO
Inventors: Karl Johan Back
Original assignee: Karl Johan Back
Priority date: 1997-06-18
Filing date: 1998-06-11
Publication date: 1998-12-23
Also published as: AU8049698A; SE9702324D0; SE9702324L; SE510634C2

Abstract

The invention relates to a method of producing a pallet that comprises an upper, load-supporting part (11), a lower part (13) spaced from said upper part (12) with the aid of spacers (15). The invention is characterised by gluing to a first, elongated sheet-like core (13) of predetermined thickness a surface covering of liquid-proof sheet material (12) so as to form a load-supporting upper part (11), and gluing to the mutually opposing side surfaces of a second, elongated sheet-like core (14) of predetermined thickness a liquid-proof covering sheet (12), such as to form a bottom part (14). The bottom part consisting of said core and said liquid-proof covering material is worked to form spacing blocks (15) of predetermined height. The top and bottom pallet-parts (11, 12) can be packed together while using the material obtained from the cutting process and from which spacing blocks are formed, and said spacing blocks are fitted so as to provide a finished pallet (10).

Description

A PALLET AND A METHOD OF ITS MANUFACTURE

The present invention relates to a method of producing pallets, preferably standardised and stackable pallets, that include a load-supporting upper part and a bottom part which is spaced from said upper part and disposed parallel therewith in the same vertical plane, and which further includes a plurality of mutually spaced spacer elements which are attached to the upper and the lower part of said pallet such as to form between said upper and lower pallet-parts and on all sides of the pallet openings through which the forks of a fork-lift truck or fork-lift wagon can be inserted .

The invention also relates to a system for packaging, transporting and/or storing pallets produced in accordance with the method.

Pallets of this kind are usually made of wood and are therewith an homogenous product. However, such pallets are relatively heavy, causing shifting of empty pallets difficult and strenuous. Such pallets are also bulky, which incurs high transportation costs when transporting empty pallets from the pallet manufacturer to the pallet consumer. This is one of the reasons why a large number of pallet manufacturers are spread throughout the country, so as not to be too far from a consumer. The manufacture of such pallets also entails a relatively large number of working steps and is relatively expensive. Millions of such pallets are manufactured annually, consuming very large quantities of wood and placing high demands on natural resources. Disposable pallets made of corrugated fibreboard have also been suggested. Although corrugated fibreboard is beneficial with respect to weight, fibreboard pallets are unable to withstand successfully the harsh handling to which they are often subjected by forklift trucks or forklift wagons. It is also necessary to cover or coat corrugated fibreboard with a liquid-resistant material, which is an expensive process.

Examples of corrugated fibreboard pallets are described in GB 2 284 592 and EP 0 283 799 Al . WO 93/21076 teaches a pallet that includes a load-supporting surface comprised of a sheetlike material that is folded to form a frame structure.

These latter known pallets have the advantage of being light in weight, i.e. a weight which is markedly less than a typical wooden pallet. The drawback with these known pallets is that they are unable to withstand the often harsh handling to which they are subjected. The corrugated fibreboard must be surface-treated to make it waterproof, therewith increasing production costs. Furthermore, the pallets are still relatively bulky and therefore entail relatively high unit transport costs.

The object of the present invention is to provide a method of producing a pallet on the principle of prefabricated parts, with which ^"commercially available material can be used to an optimum and with the minimum of material waste. The inventive method enables pallets to be produced in large quantities with the aid of simple means, and to be transported and/or stored in a space-friendly fashion. The pallet can be assembled quickly to a finished product, with the aid of simple mechanical aids. Such a pallet is obtained by the method steps set forth in the characterising clause of Claim 1.

The dependent Claims define advantageous method steps.

The system Claims 13 and 14 define how the novel method can be utilised to pre-pack, transport and/or store a pallet produced in accordance with the invention, in a practical and cost-saving manner.

So that the invention will be more readily understood and further features thereof made apparent, the invention will now be described with reference to two selected embodiments thereof and also with reference to the accompanying drawings, in which

Fig. 1 illustrates a first embodiment of an inventive pallet in perspective and from above;

Fig. 2 illustrates the pallet shown in Fig. 1 in perspective and from underneath, wherein the broken lines indicate ultimate openings to be cut from the material;

Fig. 2a shows the underside of the pallet, wherein the the material removed to provide said openings is used to form separate blocks;

Fig. 3 shows a piece of material cut from the underside of the pallet;

Fig. 4 shows four pieces of the material shown in Fig. 3 mutually stacked and glued together to form said spacer elements;

Fig. 5 is an enlarged view of one corner of the pallet shown in Fig. 1 or Fig. 2; and Figs. 6 and 6a illustrate respective respectively the under part and the bottom part of a second embodiment of an inventive pallet.

Figs. 1 and 2 illustrate an inventive pallet generally designated 10. Fig. 1 illustrates in perspective the flat load-supporting upper part 11 of the pallet 10, this upper part consisting of a waterproof outer covering sheet 12 glued to a sheet-like core material 13. As indicated in Figs. 1 and 2 in broken lines, the sheet-like outer covering 12 may conveniently project outwardly from the core material 13, as shown at 12'. These outwardly projecting parts of the outer covering sheet 12 can be folded either upwards or downwards along fold lines or weakenings to a configuration that will enable a plurality of such assemblies to be stacked together. The opposite bottom surface of the core material 13 is also provided with a similar waterproof surface covering sheet 12 (12'), therewith forming a sandwich construction.

The core material 13 is preferably a lightweight material, for instance an expanded polystyrene material, e.g. cellular plastic. The skilled person, however, will understand that the core 13 may be comprised of other suitable materials. An expanded plastic-type of material has been chosen partly because of its lightness and partly because of its resistance to liquids,^' since said material consists of about 98% air and .2% solid material.

In one preferred embodiment of the invention, the two outer covering sheets 12 are comprised of so-called liquid board, i.e. board that is comprised of a number of compressed paper sheets that are glued to respective opposing surfaces of the core 13. One such surface sheet 12 may conveniently have a thickness of about 1-2 mm. The core 13 will suitably have a thickness of about 20 mm.

Fig. 2 is a perspective view of the underside of the pallet 10 in Fig. 1, i.e. its bottom plate or bottom part 14. This bottom plate or bottom part 14 is produced in the same way as the load-supporting upper part 11, i.e. it comprises core material 13 that has a waterproof covering sheet 12 (12') on both main surfaces thereof. Reference numeral 15 identifies respective spacer elements which are disposed at intervals and conventionally fastened to the bottom surface of the upper part 11 and to the upper surface of the bottom part 14 such as to space said upper part 11 and said bottom part 14 a given distance apart and such as to provide between said spacer elements openings through which the forks of a forklift truck can be inserted for lifting and moving a loaded pallet. These spacer elements are comprised of material that has been cut from the underside, or bottom part 14, of the pallet 10 in Fig. 1, i.e. material having the sandwich structure of the core 13 and opposing waterproof surface covering sheets on opposite sides of said core material.

In accordance with the invention, the underside, or bottom part 14, -of the pallet 10 includes four apertures of predetermined size that have been punched or otherwise cut from said bottom part, these apertures being referenced 16 in Fig. 2. The apertures are disposed about a central solid cross such as to form a supporting surface whose area corresponds to two-thirds of the area of the pallet as a whole. The inventive pallet can be further strengthened by providing corner straps and side straps 17 in the manner shown in Figs. 1 and 2. These straps may conveniently be made of the same material as that from which the cover sheets 12 are made.

It also lies within the scope of the invention for the material cut from the bottom plate to form the spacer elements 15 between the top and bottom parts of the pallet 10.

An inventive pallet is manufactured by covering the mutually opposite main sides a first elongated, sheet-like core material 13 of given thickness with a waterproof covering sheet 12 (12') that covers at least the core material 13, covering the mutually opposite surfaces of a second, elongated sheet-like core material 13 of given thickness with a waterproof covering sheet 12 (12') that covers at least the core material 13, so as to form a bottom part 14, providing in said bottom part 14 a number of apertures 16 of mutually the same size, preferably four such apertures, and forming spacer elements from the composite material that was removed to form said apertures. The pieces may be cut from the bottom part by means of a water-jet cutting technique and the pieces thus removed then cut into a number of parts, e.g. nine parts, of equal size in conjunction with the same cutting process (Fig. 2), these pieces then being glued together to form a spacer block of given dimensions. For instance, four pieces of material can be glued together to form a spacer block. A standard pallet normally requires nine mutually spaced spacer elements. Such a spacer block will, for instance, include four covering sheets of core material 13 and eight waterproof paperboard covering sheets 12. Such a spacer block will be very load-resistant and have a very high bearing capacity. Such a method utilises the pallet material to an optimum, with negligible material waste. Optimal flexural rigidity of such a spacer element 15 can be achieved by placing the spacer element 15 upstanding on one edge, i.e. such that the core material 13 of the spacer element will be positioned perpendicularly to the core material 13 in the upper and lower plane 11 and 14 respectively. An additional advantage of this method of manufacture is that it is preferred to stack an upper part 11 and a bottom part 14 together and then fit the material that was removed to form said apertures back into the apertures so as to provide a flat pack having a thickness of about 25 mm, which can be readily transported to the consumer who himself assembles the spacer elements at the given positions.

When the apertures are cut from the bottom loading plane with the aid of a water jet, the material pieces 16 from which the spacer elements are formed will be cut with such precision as to enable said pieces to be retained in said apertures by friction, so as to require only a light knock to remove these pieces 16, whereafter an appropriate number of pieces are glued together to form said spacer blocks, which are then placed appropriately between the top and bottom planes 11 and 14 respectively.

An important benefit from the aspect of transportation is that two composite parts, namely parts 11 and 14, can be packed together to form a flat pack and then transported to a consumer at a cost which, at present, is a third of the cost of transporting a finished pallet. It will be understood that the inventive pallet can be mass- produced at a cost which is far less than the cost of a typical wooden pallet. No new machine constructions for manufacturing the novel pallet are required, since machinery and mechanical equipment herefor already exists .

The pieces of material taken from the sheet material 16 and glued together to form said spacer elements 15 can be fitted so that the core material extends perpendicular to the core material of the top and bottom part and therewith obtain optimum mechanical strength. When the material pieces are positioned in this way, an outer sheet or covering sheet 12 will conveniently face outwards and thereby make the spacer blocks more resistant to blows, knocks and like impact forces.

Figs. 6 and 6a illustrate another method of forming the bottom part of an inventive pallet.

Fig. 6 illustrates the bottom part of an inventive pallet, i.e. the part that corresponds to the bottom part 14 of composite construction shown in Figs. 1 and 2. This part has been referenced 14' in Fig. 6. As will be seen from this Figure, the bottom part 14' has been worked to provide a plurality of equally sized beam-like pieces 144-150. The embodimentillustrated in Figs. 6 and 6a is based on a pallet measuring 1200 x 800 mm, i.e. a so-called complete pallet. On this basis, the beam-like pieces or members 144-150 will be seven in number. Of these seven beams, the beams 144, 145 and 146 are intended to form the supporting beams of the pallet and are orientated at a predetermined distance apart, as shown in Fig. 2a. In practice, the beams 144 and 146 form respective pallet side-beams, while the beam 145 is placed centrally between the beams 144 and 146.

The remaining four beams 147, 148, 149, 150 are each separated into nine equally sized blocks a-i, thereby obtaining thirty-six blocks in total.

When a pallet of this design is intended for assembly by a receiver, e.g. a user, the pallet is left unassembled and can be packaged as a flat, rectangular pack that subsequent to being appropriately packaged can be readily transported to said receiver and there assembled on site.

When the bottom part of a pallet constructed in the aforedescribed manner shall be handled so as to provide a pallet ready for use, the following procedure is taken:

The beams 144, 145, 146 are placed on an underlying support surface in the manner shown in Fig. 6a, wherein because the bottom part 14' including the liquid-proof protective sheet has a given size, the four mutually stacked and mutually glued spacer blocks, e.g. blocks a, b, c and d, will form a single spacer block of predetermined height, wherewith a number of blocks thus formed are placed on top of the beam 144 at the position marked with reference numeral 1. The next group of four blocks is placed on the beam 144 at position 4, and finally a third group of four blocks is placed on the beam 144 at position 7. The two remaining beams 144 and 146 are provided with correspondingly placed groups of four blocks at the positions marked with reference numerals 2, 5, 8 and 3, 6 and 9 respectively. Each group of four blocks is glued firmly to a respective beam. The free end surfaces of respective blocks in each group are then coated with an adhesive and the top load-supporting pallet surface is then applied to said free end surfaces.

It is again emphasised that the bottom part of the pallet may be worked in a manner different to that described. Thus, the described and illustrated embodiments refer to a standard so- called complete pallet. The invention can be applied equally as well to other types of pallet, for instance to so-called half-pallets where the total number of spacer blocks is less than thirty-six, while employing the aforedescribed principle of working said bottom part although with the working process adapted to the size of the pallet concerned.

The inventive pallet has a number of advantages over conventional pallets. For instance,

- the pallet components are readily available and light in weight;

- unassembled pallets can be transported over long distances at reasonable cost, implying centralised mass-produced manufacture;

- the design of the bottom part provides bending strength in all directions;

- improved stability of mutually stacked pallets; - the waterproof sheet can be extended over the core material on the pallet surface, so as to enable said surface sheet to be folded up to form one or more collars; and

- although liquid-resistant paperboard would appear to be the best surface material at the present time, it will be understood that other material of good tensile strength may alternatively be used. It will be obvious to the person skilled in this art that the described and illustrated invention can be modified within the scope of the following Claims. It has earlier been mentioned that the core material may be material other than an expanded plastic material, although this latter material is preferred. The mutually opposing surface sheets embracing the core material may also consist of any appropriate plastic material. The inventive pallet is also environmentally friendly. The polystyrene used can be smelted down and recovered as fresh polystyrene, and the paperboard material from which the surface sheets are made can also be recycled.

The inventive method can thus be applied conveniently in a pallet packaging, transporting and/or storing system, by - placing the elongated, load-supporting upper pallet-part provided with said surface sheets on an underlying support surface;

- placing the second, elongated bottom pallet-part provided with said surface sheets directly on the top pallet-part, subsequent to working said bottom pallet-part; and

- providing the thus formed flat pallet-pack with a wrapping and transporting said pallet-pack to a receiver or to a storage location.

A plurality of pallets pre-fabricated in accordance with the invention can be stacked together to form an homogenous pack, in accordance with the following Claim 13.

The inventive pallet is based on the principle of constructing all pallet components from a single type of composite or sandwich material, for instance such components as the upper load-supporting plane, the bottom stabilising plane, and the spacing blocks of given height disposed therebetween.

In the illustrated case, the core material preferred is a moulded, expanded cellular plastic material. The reason for this is because the material per se is very light and consists of cellular spheres of different sizes which have been compressed to a given density and which is made liquid impenetrable by compressing the closed cells. By providing the mutually opposite main surfaces of this core material with sheet-like surface coverings in accordance with this application, a pallet constructed in accordance with the invention can be loaded with 2,500 kg + 10% deformation pressure, while having an intrinsic weight of only abut 5,000 g. In respect of weight and mechanical strength, it will be seen that no competitive pallet exists, among other things with regard to the readiness at which the pallet components can be obtained. Manufacture of the proposed pallets results in negligible waste.

Claims

1. A pallet comprising a load-supporting, preferably imperforate, upper part, and a bottom part spaced from said upper part, and further comprising a number of spacer elements disposed in spaced relationship between said upper and lower pallet-parts and fastened thereto, characterised by covering the mutually opposing main surfaces of a first, elongated sheet-like core (13) of predetermined thickness with at least one sheet of liquid-proof material (12) such as to form a load-supporting upper pallet-part (11); covering the mutually opposing side surfaces of a second elongated core (13) of predetermined thickness with a liquid-proof material, such as to form a bottom pallet-part (14); wherein the bottom pallet-part (14) consisting of said core and said liquid-proof covering material is worked so as to form spacing blocks (15) of predetermined height, and wherein the top and bottom pallet-parts (11 and 14) can be packed together with material removed in said working process, and wherein said spacing blocks (15) are fitted to provide a finished pallet.

2. A method according to Claim 1 , characterised by working said bottom pallet-part (14) consisting of said core and said liquid-proof covering material so as to form a number of closed apertures (16), and further working the material thus obtained to form said spacer blocks (15).

3. A method according to Claim 1 , characterised by working the bottom pallet-part (14) consisting of said core and said liquid-proof covering material so as to form a plurality of mutually identical beam-like elements (144-150); orientating preferably three of these beam-like elements to function as supporting beams (144-146) in mutually spaced relationship; working all remaining beam-like elements (147-150) to form a number of spacer blocks of predetermined dimensions; joining together a number of blocks to form a stack of such blocks (a-i), fastening one end of said block stacks at preferably three places to a supporting beam; and fastening the other end of respective stacks to the rear side of the top load- supporting part of the pallet.

4. A method according to any one of Claims 1-3, characterised in that a spacing element (15; a-i) is formed by gluing together two or more pieces of material obtained from the material (16) cut from the bottom pallet-part (14).

5. A method according to any one of the preceding Claims, characterised in that the core is comprised of a compression- moulded, expanded polystyrene plastic material, such as a cellular plastic material.

6. A method according to one or more of the preceding Claims, characterised by placing the load-supporting top pallet-part (17) and the bottom pallet-part (14; 14') on top of one another, and fitting the pieces (16) intended to form said spacing blocks (15) in the aperture or apertures formed in the bottom pallet-part such as to form an homogenous pack.

7. A method according to Claim 1, 2 or 3, characterised in that the first and the second cores (12, 13) are comprised of identical material and have mutually the same dimensions.

8. A system for packaging, transporting and/or storing a pallet produced in accordance with any one of Claims 2, 3, characterised in that a) the first elongated, load-supporting upper part (12) provided with said covering sheets is placed on an underlying support surface; b) the second elongated bottom part (13) provided with said covering sheets is placed directly on the top part, subsequent to working said bottom part (13); and c) the thus formed flat pack, optionally appropriately wrapped, is transported to a receiver or to a storage location.

9. A system according to Claim 8, characterised in that a) a desired number of load-supporting parts (12) provided with said covering sheets are stacked directly one upon the other; b) a corresponding number of bottom parts (13) provided with said covering sheets are placed above the upper parts (12), subsequent to forming apertures in said bottom parts (13) and forming said spacing elements (15); c) the apertures (14) formed in the overlying bottom parts are filled with the material pieces from which spacing blocks are produced; and' d) the finished rectangular pack, optionally provided with an appropriate wrapping, is transported to a receiver or to a storage location.