GB2395185A

GB2395185A - Reinforced plastic pallets

Info

Publication number: GB2395185A
Application number: GB0226300A
Authority: GB
Inventors: Alain Marcel Wambeke
Original assignee: D W Plastics Nv
Current assignee: D W Plastics Nv
Priority date: 2002-11-11
Filing date: 2002-11-11
Publication date: 2004-05-19
Also published as: GB0226300D0

Abstract

A pallet (1 Fig 1) formed of a plastics material comprises a substantially planar upper deck (2), a substantially planar lower deck (3), and support elements (4) extending between the upper deck and the lower deck. The upper deck, the lower deck and the support elements constitute a single part. Reinforcement elements (8) preferably containing pultruded profiles are accommodated in channels (5) formed in the lower surface (6) of the lower deck. Preferably the reinforcements are of glass fibres and polyester or polyamide and inserted whilst the pallet is still hot from moulding. The channels can be formed as openings in ribs and can have the reinforcements clamped therein eg by clamping members (9). The pallet can be of high density polyethylene.

Description

2395 1 85

Reinforced pallets The present invention relates to pallets or like platforms, with or without side walls, for supporting loads to be liPced or lowered. More in particular, the present 5 invention relates to a pallet formed of a plastics material, the pallet comprising a substantially planar upper deck, a substantially planar lower deck, and support elements extending between the upper deck and the lower deck.

Pallets are widely used for transporting goods such as crates, kegs, boxes etc. The traditional wooden pallets are being replaced with more durable and more I O hygienic plastic pallets. These plastic pallets are typically made of HDPE (high density polyethylene) or similar materials. It has been found, however, that such plastics materials have a smaller bending strength than wood. In many applications it is therefore desirable to reinforce the plastic pallet.

British Patent GB 1 571 190 (Wavin) discloses a plastics pallet comprising 15 rigid reinforcement elements removably accommodated in channels, the reinforcement elements being solid bars of metal. Although using solid metal reinforcement bars results in a strong structure, the resulting pallet is relatively heavy. In addition, most metals are prone to corrosion which shortens the effective life span of the pallet.

20 British Patent Application GB 2 209 321 (Paul Craemer) discloses a multipart plastics pallet in which the lower part is provided with grooves which are open towards the mating plane with the upper part. The reinforcing sections are preferably made from metal but may also be made from an unspecified plastics material. This two-part pallet structure has the disadvantage that it requires assembly which adds to 25 the cost of the pallet. In addition, dirt may collect in any gaps or seams between the two parts.

International Patent Application WO 97/33798 (Wavin) discloses a plastic pallet having embedded reinforcement profiles of plastic material. The reinforcement profiles are accommodated in ribs constituting the top deck. The profiles may be 30 fibre-reinforced and may contain thermoplastic plastic material containing chemically linked glass fibres. This known one-part pallet is manufactured by first placing the reinforcement profiles in a mould and then moulding the pallet in that

mould, thus embedding the profiles. The disadvantages of this known pallet are that the ribs containing the reinforcement profiles are necessarily wide, and that placing the profiles in the mould before the moulding process significantly increases the production cycle time, thus increasing manufacturing costs.

5 European Patent EP l 021 346 (Orbis) discloses a reinforced plastic pallet provided with reinforcement elements which are preferably composite structural members of a fibreglass reinforced plastic formed by a pultrusion process. The reinforcement elements are positioned on the upper surface of the lower deck about its peripheral edges. This known pallet is assembled by positioning the reinforcement 10 elements within their respective channels in the lower deck, and then positioning the upper deck over the lower deck. The pallet of EP 1 021 346 therefore consists of at least two parts. This has the disadvantages of requiring an additional assembly step, as well as creating seams between the parts in which dirt may collect.

It is therefore an object of the present invention to provide a one-part 15 reinforced pallet which is strong yet economical.

It is another object of the present invention to provide a reinforced pallet which can be readily assembled.

It is a further object of the present invention to provide a reinforced pallet which can be readily recycled.

20 Accordingly, the present invention provides a pallet formed of a plastics material, the pallet comprising a substantially planar upper deck, a substantially planar lower deck, and support elements extending between the upper deck and the lower deck, wherein the upper deck, the lower deck and the support elements constitute a single part, and wherein channels for accommodating reinforcement 25 elements are formed in the lower surface of the lower deck, at least one reinforcement element being accommodated in a channel.

By providing a single part structure, the assembly of pallet parts is avoided and the manufacturing costs are reduced. In addition, the integral structure is strong and seams between the parts are avoided.

30 By providing channels in the lower deck, a better reinforcement is obtained as an uneven loading and/or supporting of the pallet results in higher material stress in the lower deck than in the upper deck.

By providing channels in the lower surface of the lower deck, the channels are easily accessible and reinforcement elements can be inserted after the moulding of the pallet. In addition, the inserted reinforcement elements may easily be removed for recycling or other purposes.

5 It is desirable that the reinforcement elements have a bending strength exceeding the bending strength of the plastics material. According to a further aspect of the present invention, the reinforcement elements have an elasticity modulus between approximately 30,000 and 45,000 MPa, preferably between 35,000 and 40,000 MPa. These ranges provide an excellent reinforcement of the pallet while 10 preserving some resilience which decreases the risk of cracks forming in the plastics material. It will be understood that the elasticity modulus is a well-known measure of the bending strength of an object or a material.

Although reinforcement elements having the above-indicated bending strength can be achieved in various ways, it is preferred that the reinforcement 15 elements comprise glass fibres, preferably unidirectional glass fibres. Additionally, or alternatively, it is preferred that the reinforcement elements comprise polyester and/or polyamide.

In a preferred embodiment, the reinforcement elements comprise pultruded elements. That is, fibres (e.g. glass fibres) which are subjected to a pultrusion (pulled 20 extrusion) process. In this way, particularly strong reinforcement elements are obtained. The reinforcement elements can be held in their respective channels in various ways. In a particularly advantageous embodiment the reinforcement elements are dimensioned so as to be clamped by the walls of the channels. That is, the 25 reinforcement elements fit tightly in the channels. Alternatively, or additionally, the channels may be provided with clamping members for clamping the reinforced elements. These clamping members are preferably constituted by retainer lips which partially close the channel so as to retain the reinforcement elements.

The present invention further provides a method of manufacturing a pallet 30 according to any of the preceding claims, the method comprising the steps of: À moulding a pallet provided with channels in a lower surface of its lower deck, and

accommodating reinforcement elements in said channels.

The moulding step can be carried out using a well-known moulding technique such as injection moulding. The accommodating step of the separately manufactured reinforcement elements can be carried out manually or by a robot. Alternatively, the 5 reinforcement elements can be accommodated in the channels by overmoulding, that is, by moulding the elements directly in the channels after the moulding of the pallet itself. Preferably, the reinforcement elements are accommodated in the channels immediately alter the moulding of the pallet while the pallet is still hot. In this way, 10 the natural shrinkage ofthe plastics material when cooling down is used to securely clamp the reinforcement elements in the channels.

The present invention additionally provides a kit-of-parts for forming a pallet as defined above, the kit-of-parts comprising a pallet body and at least one reinforcement element as defined above.

The present invention will further be explained below with reference to exemplary embodiments illustrated in the accompanying drawings, in which: Fig. I schematically shows, in perspective, a pallet according to the present invention. 20 Fig. 2 schematically shows, in perspective, part of the pallet of Fig. 1 in more detail. Fig. 3 schematically shows, in plan view, the lower surface of the lower deck of a pallet according to the present invention.

Fig. 4 schematically shows, in perspective, channels formed in ribs which 25 constitute a surface of a deck.

Fig. 5 schematically shows, in perspective, how reinforcement elements may be inserted in a pallet of the present invention.

Fig. 6 schematically shows, in perspective, a first method of clamping reinforcement elements in a pallet according to the present invention.

30 Fig. 7 schematically shows, in perspective, a second method of clamping reinforcement elements in a pallet according to the present invention.

Fig. 8 schematically shows, in plan view, a third method of clamping reinforcement elements in a pallet according to the present invention.

Fig. 9 schematically shows, in plan view, the arrangement of Fig. 8 seen from below The pallet 1 shown merely by way of non-limiting example in Fig. 1 (as well as subsequent embodiments according to the present invention) is preferably formed of a thermoplastic or other polymeric material and is preferably, but not necessarily, formed by an injection moulding process. Engineered materials may be used, as well I O as a synthetic resin such as polyethylene or polypropylene with a filler added to stiffen the resin. It is contemplated that the pallet disclosed herein may be manufactured by various other moulding techniques and manufacturing processes applicable to the design and material selected, including but not limited to blow moulding, thermoforming, vacuum moulding, etc. It is further contemplated that the 15 material from which the pallet according to the present invention is formed may include materials other than plastics and polymer blends, and may include metallic materials, such as aluminium or tin.

As illustrated in Fig. 1, pallet 1 includes a top or upper deck 2 and a bottom or lower deck 3 which both have an upper surface and a lower surface. The decks 2 20 and 3 preferably have a rectangular shape with rounded corners, but may also take other shapes, including but not limited to a square, circular, triangular or other shapes as desired or required by the use and application. Pallet 1 is preferably and generally symmetrical about a centreline. The upper surface of top deck 2 is preferably a substantially planar surface on which articles (not shown) can be carried. However, 25 raised areas or ridges may be provided to position articles on the top deck.

Top deck 2 and bottom deck 3 are connected by support elements 4, which are integral with both decks. Such an integral, one-part structure is strong and inexpensive to manufacture. Apertures 7 provided between the support elements 4 are capable of accepting the prongs of a fork lip or similar device.

30 As can be seen, the upper "surface" of top deck 2 is constituted by a structure of interconnected ribs 10. This open structure is very strong yet light. The open character allows the pallet 1 to be thoroughly cleansed. Similarly, the lower deck 3

has a lower "surface" 6 comprised of interconnected ribs 10. The channels 5 are shown to be constituted by a series of openings in the ribs 10, as is shown more clearly in Fig. 4. A clamping member 9, which will later be explained in more detail, is shown to protrude from one of the channel walls. It is noted that in Fig. 4 the lower 5 surface (6)of the lower deck 3 is shown to be at the top of the drawing.

Although the pallet I of Figs. I and 2 is shown to have an open structure, resulting in open top and bottom "surfaces", pallets according to the present invention can also be provided with closed top and bottom surfaces as may be desirable for some application. In most embodiments having a closed surface the ribs 10 shown in Figs. 1 and 2 will still be present to provide structural rigidity.

The lower surface 6 of the lower deck 3 and the position of the reinforcement elements 8 is shown more clearly in Fig. 2. As can be seen, in the embodiment shown parallel, spaced apart reinforcement elements 8 are used. A preferred layout of the reinforcement elements 8 is shown in Fig. 3 which illustrates the lower surface 15 6 of the lower deck 3. As can be seen, several parallel channels 5 are provided (in the manner shown in Fig. 4) in which reinforcement elements (8 in Figs. 1 and 2) may be accommodated. To provide an even stronger structure while avoiding relatively wide reinforcement elements, pairs of parallel channels 5 are provided. It will be understood that various other layouts may be utilized and that pairs of channels may 20 be replaced by single channels. In addition, in some embodiments not all channels are provided with reinforcement elements, some channels being left open.

The reinforcement elements may be made of a plastics material. Preferably they contain fibre glass reinforced polyester and/or polyamide. Most preferably the reinforcement elements are pultruded profiles consisting of coated unidirectional 25 fibreglass. Such reinforcement elements are both strong and durable. However, embodiments in which aluminium reinforcement elements are used can also be envisaged. Aluminium has the advantage of being relatively light and, in contrast to other metals, its properties are not affected by corrosion, in particular when it has been suitably treated with anti-corrosive agents. Aluminium reinforcement elements 30 typically have an elasticity modulus of approximately 70,000 MPa.

The reinforcement elements have, in a preferred embodiment, a substantially rectangular cross-section, a width of approximately 5 mm and a height of

approximately 10 mm. However, other dimensions and/or cross-sections are also possible. Suitable cross-sections are, for example T-shaped, Ishaped, U-shaped, etc The reinforcement elements 8 may be inserted into the channels 5 in the manner shown in Fig. 5, resulting in the arrangement shown in Fig. 6. When 5 accommodated in the channels, the reinforcement elements may be held in their respective positions by e.g. gluing or welding. It is preferred, however, to clamp the reinforcement elements without the help of any external means or tools. In the embodiment of Fig. 6a, clamping members 9 are constituted by lips protruding from the edges of the channel 5 (see also Fig. 4). Some force will be necessary to insert the 10 reinforcement element 8, after which the clamping members 9 will maintain its position. The clamping members 9 are preferably alternatingly spaced along the respective channel, that is, pairs of clamping members protruding from opposite channel walls are preferably not located directly opposite each other but spaced apart in the direction of the channel. Such an arrangement allows an easier insertion of the 15 reinforcement element.

Alternatively, the natural shrinkage of the plastics material after moulding is used to clamp the reinforcement elements in the channels, as illustrated in Fig. 7. To this end, the reinforcement elements are introduced into the channels immediately after the moulding process or at least when the pallet is still relatively hot. Upon 20 cooling down, the channel will shrink slightly so as to clamp the reinforcement element. In this embodiment the clamping members shown in Fig. 6a may be omitted. In the embodiment of Fig. 8, elongate ridges I I prevent the reinforcement element X to be inserted into the channel from the lower side 6 of the lower deck.

25 Instead, the reinforcement element is inserted lengthwise. To this end, the channel 5 runs all the way to the side of the pallet. As shown in Fig. 9, the channel may be closed offal the side of a pallet by a cap 12 which may be fixed to the pallet by welding or gluing. This cap 12 can preferably removed or broken to allow the reinforcement element 8 to be removed for recycling purposes.

30 Of course combinations of the embodiments discussed above are also possible, for example, embodiments in which the reinforcement elements can be inserted in more than one direction.

In an alternative embodiment, the plastic reinforcement elements are directly moulded into the channels, preferably in a separate mould which can be clamped over the pallet body ("overmoulding"). In this way, the insertion of separately manufactured reinforcement elements is avoided.

S The present invention is based upon the insight that the lower deck rather than the upper deck should be reinforced. The present invention is also based upon the further insight that reinforcement elements should be inserted into the pallet after it has been moulded, and that the channels accommodating the reinforcement elements should be readily accessible. Accordingly, the present invention provides a 10 one-part pallet in which the lower surface of the lower deck is provided with channels for accommodating reinforcement elements.

It will be understood by those skilled in the art that the present invention is not limited to the embodiments illustrated above and that many modifications and additions may be made without departing from the scope of the invention as defined 15 in the appending claims.

Claims

Claims

I. A pallet (l) formed of a plastics material, the pallet comprising a substantially planar upper deck (2), a substantially planar lower deck (3) , and support elements (4) 5 extending between the upper deck and the lower deck, wherein the upper deck, the lower deck and the support elements constitute a single part, and wherein channels (5) for accommodating reinforcement elements are formed in a lower surface (6) of the lower deck (3), one or more reinforcement elements (8) being accommodated in the channels (5).
2. The pallet according to claim 1, wherein the reinforcement elements (8) have an elasticity modulus between approximately 30,000 and 45,000 MPa, preferably between 35,000 and 40,000 MPa.

15
3. The pallet according to claim 1 or 2, wherein the reinforcement elements (8) comprise glass fibres, preferably unidirectional glass fibres.
4. The pallet according to claim l, 2 or 3, wherein the reinforcement elements (8) comprise polyester and/or polyamide.
5. The pallet according to any of the preceding claims, wherein the reinforcement elements (8) are dimensioned so as to be clamped by the walls of the channels (5).

25
6. The pallet according to any of the preceding claims, wherein the channels (5) are provided with clamping members (9) for clamping the reinforced elements (8).
7. The pallet according to any of the preceding claims, wherein the channels (5) are constituted by openings in ribs (10).
8. The pallet according to any of the preceding claims, wherein the reinforcement elements (8) have a width between 3 and 7 mm, preferably between 4 and 6 mm, and a height exceeding their width.

5
9. The pallet according to any of the preceding claims, made from high density polyethylene.
10. A method of manufacturing a pallet according to any ofthe preceding claims, the method comprising the steps of: 10 À moulding a pallet (1) provided with channels (5) in a lower surface of its lower deck (3), and À accommodating reinforcement elements (8) in said channels (5).
11. The method according to claim 10, wherein the reinforcement elements (8) 15 are accommodated in the channels (5) immediately after the moulding of the pallet when the pallet is still hot.
12. A kit-of parts for forming a pallet (1) according to any of claim 1-9, comprising: 20 À a pallet body formed of a plastics material, the pallet body ( I) comprising a substantially planar upper deck (2), a substantially planar lower deck (3), and support elements (4) extending between the upper deck and the lower deck, wherein the upper deck, the lower deck and the support elements constitute a single part, and wherein channels (5) for accommodating reinforcement 25 elements are formed in a lower surface (6) of the lower deck (3), and À reinforcement elements (8) for accommodating in said channels (5).
13. The kit-of-parts according to claim 12, wherein the reinforcement elements (8) have an elasticity modulus between approximately 30,000 and 45,000 MPa, 30 preferably between 35,000 and 40,000 MPa.
14. The kit-of-parts according to claim 12 or 13, wherein the reinforcement elements (8) comprise glass fibres, preferably unidirectional glass fibres.
15. The kit-of-parts according to claim 12, 13 or 14, wherein the reinforcement 5 elements (8) comprise polyester and/or polyamide.
16 A pallet substantially as described herein and illustrated in the drawings.
17. A method of manufacturing a pallet substantially as described herein and I O illustrated in the drawings.