AU675003B2 - Pallet construction - Google Patents

Description

I 1k r 1.

P/00/01i1 Regulation 3.2

AUSTRALIA

Patents Act 1 990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Pallet Construction 0 0* 0 0 0000 The following statement is a ful; description of this invention, including the best method of performing it known to me: 0000 *00000 0000 0 00 0 00 GH&CO REF: P21790-B:TJS:JM 41 1/21790-B 2 PALLET CONSTRUCTION Field of the Invention This invention relates to pallets for the support of articles, for example forklift pallets.

Background of the Invention Pallets for the storage and transportation of articles are in widespread usage. The most common example is a pallet which includes a solid platform with runners on the bottom to support the platform above some underlying surface or article, or a plurality of slats joined to the runners for the same purpose. The spacing between the runners and the underlying surface is defined by the thickness of the slats. In turn this thickness is determined by the situation in which the pallet is to be 15 used. If it is a forklift pallet, then the thickness must be at least as great as the thickness of the forklift blades. Another consideration is to provide adequate columnar strength to support the loads transferred from the slats or platform. Still another determinant, especially as to the slats, is that there be sufficient bending strength to resist bending forces applied by the load which generate a tensile stress in the bottom of the slat.

It is a simple matter to over design a pallet.

Reduced to absurdity, a heavy steel plate with thickwalled tubular steel runners could be expected to handle almost any load that would be manipulable by a forklift.

This absurdity illustrates two important aspects of forklift desijn: cost and weight.

PalleL_ are subjected to rough usage, and their useful life before repair, especially wooden pallets, is surprisingly short. It is common to use wooden slats and runners that are nailed together to form the pallet.

Wood is a relatively inexpensive material, and the cost of assembling the pallet is acceptable. So, in many uses, especially for closed circuit shipping, where the pallet is returned for re-use, this is an acceptable R construction. However, it is bulky, and it is heavy.

S:P21790B/8.11.96 3 For one-way pallets the situation is often very different. These frequently are used for air freight shipments, and in other transactions which are weightrelated as well as volume-related. When heavier pallets are used, it is not unusual for shipping capacity to "weigh out" before it "cubes out". This is to say that where the weight capacity is reached there still remains unfilled volume that cannot be utilised because the weight limit has been reached. The pallet weight therefore reduces the number of articles that could otherwise be shipped.

For example, an inexpensive wood pallet weighs about pounds and presently costs about US$4.85. In a routine shipment involving about 25 such pallets, weight savings V 0 15 attainable with the use of this invention (which weighs only about 63 pounds for many useful embodiments), enable the shipment to contain one more pallet full of articles.

The foregoing example relates weight and cubage.

.There is another even more pertinent example, namely the usage of pallets in air freight shipments. At the present time, airfreight from California to Australia costs about US$2.51 per pound, and this rate includes the pallets.

The articles must usually be palletised, and the weight of the pallet is a severe economic burden.

It follows from the above that a more expensive pallet which weighs less can be the most economical device to use. Obviously all of the parameters must be taken into account, but it is a fact that there are literally thousands of applications where a costlier pallet that will be discarded after one use will be on balance as the most economical choice. If for some reason the pallet can be reused or used for another purpose, the economy is even greater.

Accordingly, it is not the objective to produce the lowest priced pallet; it is to produce a pallet adequate for the intended purposes with a lesser tare weight to justify the increased cost and create net savings.

The term "adequate for the intended use" defines S:P2179B/8.11.96 4 another objective to provide just enough strength, and of course with the least practicable cost and weight.

It is an object of this invention to provide such a pallet, utilising a composite structure, and to the maximum extent to use commonly available materials such as are used in the building trades. Such materials themselves have long been subjected to intense scrutiny as to strength and economy of cost, and are ideally suited for use in structures such as pallets.

Brief Description of the Invention This invention is a pallet having a platform, either formed as a solid plate, or as a plurality of parallel slats, attached to a plurality of runners on their bottom faces. Although the platform and runners could be made 15 of different materials, best advantage is attained if all are made of the same composite material. That is, it makes little sense to have composite slats and wooden runners.

i:: *e The composite from which the platform and slats are formed is a corrugation of material which, when side supported, provides suitable columnar strength to resist crushing. Buttress material fills in the corrugations to provide side support and at least some columnar strength.

The supported corrugation is overlaid top and bottom with 25 a sheet of material having tensile properties to resist bending of the platform. A protective skin is formed over this sheet.

The sheets, the buttress material, and the corrugation, are bonded into a continuous structure.

When subjected to bending forces, the composite functions best when the axis of the corrugations is in the bending plane. Frequently it will be advantageous to reinforce the lower surface side, which will be convex, with reinforcement material to withstand resultant tensile forces which could crack the bottom of the structure. As a practical matter, the reinforcement material will be applied to both sides so that either side may be top or bottom. Strands such as glass fibres S:P2179B/8.11.96 may for this purpose be incorporated into the composite.

These have no function as to compressive strength, but do improve the resistance to bending. These are optional.

In addition to the strands in such alignment, cross strands can be provided, which can be laid in place, or woven together.

The bonding together may consist of adhesive bonds at the various interfaces. Preferably the material will all be porous so that a bonding material can penetrate the entire structure. The preferred embodiment is a structural foam used as the buttressing material which penetrates or envelopes the other members. This is a light-weight arrangement, and can be self-skinning as well.

15 The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings in which: 9. Brief Description of the Drawings Figure 1 is an isometric view showing the presently S 20 preferred embodiment of the invention; Figure 2 is an end view of Figure 1; Figure 3 is a side view of Figure 1; Figure 4 is a cross-section taken at line 4-4 in Figure 1; 25 Figure 5 is a cross-section taken similarly to Figure showing another embodiment of the invention; e9 Figure 6 is a fragmentary plane view of a material useful for the corrugation and reinforcement; Figure 7 is a fragmentary view of an alternative material of construction; and Figure 8 is a cross-section taken at line 8-8 in Figure 4.

Detailed Description of the Invention Figure 1 shows a pallet 10 having runners 11, 12, 13 and slats 14, 15, 16, 17, 18, 19 and 20. The runners underlay the slats. The slats are attached to the runners by an acceptable means (not shown), such as adhesives or mechanical fasteners. Acceptable mechanical f RAB nr7;a~F:~~S:P2179B/.11.96 C

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6 fasteners may include nails adapted to be driven into and retained by composite structures, expansion bolts, and nut-bolt combinations with head and nuts suitably recessed. These are exemplary of a wide range of alternatives.

The dimension of thickness 21 of the runners provides room for forklift tongues to be inserted beneath the slats. The span length 22 between the slats is a parameter to be considered in the design of the composite to be used.

The slats create a "platform" on which articles are to be placed. While from a weight and expense standpoint slats are to be preferred, it is within the scope of this invention to provide a unitary, single piece platform instead. The term "platform" includes both.

The slats and runners are preferably made form the same composite. If greater thickness is needed, it usually will be best practice to bond together a number of layers, rather than to scale up the dimensions of a 20 single layer.

Also, in the manufacture of an economically optimised pallet, the use of materials which are already produced in large quantities is advantageous. One such product may be used for certain layers and for the corrugation.

This material is a phenolicresin-bonder sheet of randomly-laid glass fibres used in the roofing trades.

It is porous with glass strands about 1 inch long. It weighs about 1.2 pounds per hundred square feet. It has a minor tensile strength about 30 pounds per inch, S 30 which is useful but sometimes not enough, and excellent columnar properties when side supported. It is commercially available from Conglas Inc. of Bakersfield, California under the mark "CONGLAS" Reinforcing glass fibres, usually about 16 microns in diameter, are useful for their tensile properties. These fibres are obtainable from a wide variety of commercial sources.

It is most convenient to form this composite in a 411/S:21790B

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7 continuous process rather than to make sub-parts and then bond them together. Accordingly the use of a single plastic material for filling and bonding is to be preferred. Also, although non-foamed plastic materials are useful, they will be heavier. Fcr this reason foams are to be preferred. The outside surfaces must resist at least minor abrasion, so a skin must be provided. The use of a self-skinning plastic material is preferred because it requires one less manufacturing step.

Urethane foams are self-skinning.

With the foregoing in mind, the composite structure in Figure 4 will be discussed. Slat 20 is shown. The other slats and the runners will preferably be made of similar material. In the illustration, the bending plane runs in the direction of length of the illustrated slats.

When the slats are loaded, they tend to deflect downward by, becoming concave at the top and there in compression, and convex on the bottom, and there they will be in tension. There is no problem with compression, but the 20 tension stress may cause the slat to crack at the bottom centre of the span if the tensile strength is exceeded.

To allow for greater load weight, glass fibres 45 as already described are laid as parallel strands atop the reinforcement sheet. These have substantial tensile strength and are provided in quality as needed. Usually they will be applied to the adhesive or foam surface *before it sets up so the strands are incorporated into the matrix, and then the matrix skins over to form skin 46.

30 As shown in Figure 7, glass fibre cloth 47 can be substituted for the randomly laid material preferred for the corrugation and for the reinforcement layer.

A corrugation 30 of the above described material is shown with crests 31 and troughs 32, which extend along a dimension of length 33. Buttresses 34 fill the troughs and are bonded to the corrugation. Preferably the corrugation is porous as described, so the buttress material not only bonds to the corrugation, but 411/S:21790B I 8 penetrates into it and becomes integral with it.

The buttresses are preferably made of closed-cell structural foam.

To the boundary 35 of the buttresses and to the crests of the corrugations there is applied a reinforcement sheet 40 of material having tensile properties. Preferably it is the sheet material already described. It is bonded at the boundary. Preferably the foam material penetrates the sheet and extends beyond it to cover it. For many structures this will be adequate, and the foam forms a skin, or a skin material is applied to it.

However, for many applications, more tensile strength is needed, running in the bending plane. In the illustration the bending plane runs in the direction of length of the illustrated slats. When the slats are °-*loaded they tend to bend downward, becoming concave at the top and therefore in compression, and convex on the bottom, and therefore in tension. There is no problem 20 with compression, but the tension load may cause the slat to crack at the bottom centre of the span if the tensile strength is exceeded.

Figure 5 illustrates that solid pre-prepared inserts can be fitted into the troughs of the corrugation and bonded to the corrugation. This will rarely be preferred. Also, non-foaming settable plastics may be *used throughout, but these involve a weight penalty.

The preferred embodiment of composite is the unitary formed construction of Figure 1. It is optimum for 30 weight, and sufficient for strength. The pallet shown can conveniently have over all deck dimensions of 42 x 48 inches and carry a load of 2,000 pounds, while weighing only about 6M pounds. This compares to a conventional wooden pallet of the same dimensions which weights about 61 pounds. The load carrying capacities can be made roughly equal.

While the pallet of this invention costs more than a wood pallet, the savings made in the course of its 411/S:21790B

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9 employment more than justifies the additional expense for many applications.

This invention is not to be limited by the embodiments shown in the drawings and described in the description, which are given by way of example and not limitation, but only in accordance with the scope of the appended claims.

o* e* a 411/S:21790B

Claims (10)

1. A load-carrying pallet comprising: a platform and a plurality of runners beneath said platform and attached to it, said platform and runners each being constructed of composite materials bonded together and comprising: a corrugation of sheet material, said corrugation having longitudinally extending crests and troughs; a plurality of buttresses, one each filling each of the troughs and abutting said corrugation so as to provide side support to the supported corrugation against collapse, said buttresses providing top and bottom boundaries facing away from said troughs; a reinforcement member overlaid on both the top and S 15 bottom boundaries of the supported corrugation, said V. reinforcement member being a sheet material having a tensile strength to resist bending; and a skin surface formed over the reinforcement members; the skin, reinforcement members, buttresses and 20 corrugation being bonded to form a unitary structure.

2. A pallet according to claim 1, wherein said *sheet material is arranged to have a substantial columnar e strength when side-supported.

A pallet according to claim 1 or 2, wherein said 25 sheet material comprises randomly-laid, bonded-together glass fibres. o:

4. A pallet according to claim 1, 2 or 3, wherein said buttresses are provided as an initially fluid plastic material which penetrates into said reinforcement member sheet material, and which subsequently solidifies.

A pallet according to claim 4, wherein said plastic material is an adhesive.

6. A pallet according to claim 4 or 5, wherein said plastic material is a foam.

7. A pallet according to claim 6, wherein said foam is a urethane foam. B. A pallet according to claim 4, 5 or 6, wherein said skin is also formed of said fluid plastic material.

S:P21790B/8.11.96 11

9. A pallet according to any one of claims 2 to 8, wherein a group of parallel glass fibres is laid upon the reinforcement member beneath the skin, said fibres being bonded to the reinforcement member.

10. A pallet substantially as hereinbefore described with reference to figures 1 to 6 and 8 or figures 1 to 7 and 8 of the accompanying drawings. Dated this 8th day of November 1996 ERICA F MOORE By her Patent Attorneys GRIFFITH HACK CO eo a S:P2179B/8.11.96 ABSTRACT A load carrying pallet having a platform and a larality of runners beneath the platform. The platform and all runners are made of composite comprising a corrugation of sheet material with crests and troughs. The throughs are filled with buttresses, and a skin layer of linear reinforcing strands is laid on this combination. All is bonded together to form a monolithic composite. *o ea. 411/S:21790B