FR2711618A1 - Pallet made of plastic material and its method of manufacture - Google Patents

Abstract

The invention relates to a pallet made of plastic material. It consists of the combination of an upper element (1) comprising a substantially flat panel (2), possibly having openings (3), which supports on its lower surface a system of stiffening ribs and a plurality of open-bottomed blocks (4, 5, 6, 7, 8) constituted by an assembly of vertical walls which are open at the bottom, with hollow longitudinal members (9, 10, 11) made by extrusion and fastened, for example by welding or gluing, to the bottoms of a series of aligned blocks (6, 7, 8). The invention also relates to the method of manufacturing such a pallet.

Description

 The present invention relates to a new plastic pallet and its manufacturing process.

 We know that pallets are kinds of trays intended to support various goods in particular for their transport and storage.

 These trays are provided with feet or studs, generally nine in number, leaving between them spaces intended to receive the forks of a forklift or one of a pallet truck in order to allow movement from one place to another of the pallet and the goods it supports.

 It is also known that there are standards which define the different dimensions of the pallets as well as the resistance which they must present with respect to the different forces which are applied to them.

 The most commonly used pallets are wooden pallets which have the advantage of a low cost price, but which have the disadvantage of having a limited lifespan, a high weight and soiling quickly so that they are difficult to use in certain industries such as the food or medical industries.

 Plastic pallets are also known which have the double disadvantage of being of a much higher price than that of wooden pallets, and of not being able to meet the standards in force, that is to say that they do not have mechanical strength sufficient, either that their plate or their studs do not meet the requirements of the standards.

 Following numerous studies, the applicant company has imagined a new plastic pallet which makes it possible to meet the standards in force and which has the advantage of being simple and inexpensive to manufacture, which allows it to be economically competitive with wooden pallets, without having the disadvantages.

 The present invention relates to a plastic pallet, characterized in that it is constituted by the combination of an upper element comprising a substantially flat plate, possibly hollowed out, which comprises on its lower face, a network of ribs of stiffening and a plurality of studs constituted by a set of vertical walls and open at their lower part with hollow longitudinal members produced by extrusion subject for example by welding or gluing to the lower part of a series of aligned studs.

 The upper element of the pallet according to the invention has the particularity of being constituted by a substantially flat plate which is extended perpendicularly downwards by a plurality of stiffening ribs connected laterally to each other as well as partitions also connected laterally together to form studs.

 This upper element can be easily produced by a conventional injection molding process which consists in sending the plastic material in the pasty state under high pressure in a mold of corresponding shape.

 This upper element can also be produced by an injection-compression process which consists in injecting the plastic material under a relatively low pressure into a half-opened mold, then in closing the mold, which has the effect of strongly compressing the plastic material to inside the mold and give it the shape it should have.

 The upper element of the pallet can also be produced by a similar process known as extrusion-compression, according to which the elements of the mold are separated from one another, the extruded plastic material is deposited in the part bottom of the mold, then the mold is closed by applying its upper part to its lower part so as to compress the plastic.

 According to the invention, the side members are obtained by continuous extrusion of a hollow plastic profile which advantageously comprises at least one vertical rib which contributes to its stiffening.

 The beams that are used for the realization of the pallet are sections cut to the desired length in the extruded profiles in question.

 It can be seen that these beams can be obtained in a simple and economical manner.

 According to a preferred embodiment of the invention, the side members comprise at least one vertical partition which makes them more rigid.

 In addition, it is very easy to considerably increase their mechanical characteristics by placing inside one or more of their internal cavities, a reinforcing element such as for example a tube, a metal profile or a bar of wood.

 The welding or bonding of the beams under the studs of the upper element of the pallet according to the invention is easily carried out while having excellent mechanical characteristics.

 Indeed, the lower end of the studs which is formed by the edge of the partitions of the latter comes to bear without difficulty on the upper face of the beams, which allows easy welding and avoids any problem of precise positioning.

 Thus, for example, the welding of the side members on the lower surface of the studs can advantageously be carried out according to the invention by vibration welding.

 It is known that this welding process is implemented by vibrating one of the parts to be welded while it is applied against the other so as to cause a local rise in temperature which causes the plastic of the two parts to melt and thus allows to weld them.

 This process can be easily implemented in the case of the invention because the welding can be carried out by slight relative displacements between the lower edge of the partitions constituting the studs, and the upper smooth surface of the side members.

 Such a weld would be very difficult, if not impossible, to be carried out if one wished to weld two pieces by their ends constituted by partitions or ribs, due to the fact that the vibrations would be such that the corresponding ribs of the two parts would cease to be opposite each other during vibration.

 In addition, the realization of the pallet according to the invention makes it possible to obtain an upper plate which can have at will a continuous surface or a surface in which orifices have been made, the surface and the number of which depend on the use that the 'we want to make the palette.

 In addition, the lower surface of the pallet, which consists of the lower faces of the longitudinal members, also has flat surfaces of sufficiently large width to be able to meet standards and which allow stacking of pallets loaded with fragile products such as for example liquids in plastic bottles.

 By choosing the number and the nature of the reinforcing elements which are engaged in the longitudinal cavities of the longitudinal members, it is possible without any difficulty to adapt the mechanical characteristics of the pallet to the use that must be made of it.

 Such reinforcing elements must simply be slid into the corresponding cavities, their section being slightly smaller than that of the cavities.

 These reinforcing elements are kept inside the cavities, for example using plastic end covers which are glued, welded or clipped to the end of the side members, which has the advantage of both immobilizing the reinforcing elements inside the side members and to prevent dirt from entering the inside of the side members.

 According to a particular embodiment of the invention, the side members are closed at their ends by an element, for example made of molded plastic, which has an upper cutting angle in order to facilitate the introduction of the forks of the handling machine.

 The pallets according to the invention can be produced with a very wide range of thermoplastic material, the strength of which can possibly be reinforced by fibers such as glass fibers.

 Thus, for example, the upper element and the side members of the pallet can be made of high density polyethylene.

 According to the invention, it is advantageous to produce cut sides on the upper corners of the side members so as to facilitate the introduction of the forks of the handling equipment between the studs.

 For the same reason, it is also advantageous to produce cut sides on the angles of the studs between which the forks of the handling equipment must be introduced.

 Always for the same reason, it is interesting to finish the reinforcement ribs which are below the upper plate by bevel cuts.

 To reinforce the solidity of the upper element, it is advantageous for the partitions and the ribs to be connected to the lower face of the plate by rounding in order to avoid too great a concentration of the stresses in the material.

 According to a particular embodiment of the invention, the peripheral partitions of the pads can have on at least part of their periphery a section in the form of Greek or corrugations so as to increase their resistance to crushing.

 Due to their method of manufacture, the pallets according to the invention finally have the advantage of allowing easy differentiation of the different models or of their users or of their owners by using upper elements combined with spars of different colors, which allows the very wide variety of identifications desired in logistics.

 It is even possible, thanks to the extrusion process of the side members, to make them in several colors, for example with strips of different colors.

 This possibility gives the pallets according to the invention the significant advantage due to the fact that in many cases they are rented pallets which are subjected to frequent movements and of which it must nevertheless be easy to identify the owner, which can be easily obtained thanks to the invention.

 Pallets, and in particular standard pallets, most often have a generally rectangular shape.

 According to the invention, it is advantageous to arrange the side rails parallel to the long sides of the pallet, so as to benefit in this direction from the rigidity which is imparted by the side rails with possibly the reinforcing elements which they contain.

 The mechanical strength required across the width can thus be more easily provided by the ribs located on the underside of the plate.

In order to better understand the invention we will now describe an embodiment taken as a non-limiting example and shown in the accompanying drawing in which
FIG. 1 represents a perspective view of an embodiment of a pallet according to the invention,
FIG. 2 is a top view of a quarter of the pallet in FIG. 1,
FIG. 3 is a view of a section along III-III of FIG. 2,
FIG. 4 is a section on IV-IV of FIG. 2 shown with the contiguous rib,
FIG. 5 is a view along VV of FIG. 2,
FIG. 6 is a diagrammatic partial perspective view on a larger scale showing the connection of a stud on its spar, and
- Figure 7 is a partial perspective view of the underside of the upper element of the pallet of Figure 1.

 We see in Figure 1 the upper element 1 of the pallet which is constituted by a plate 2, substantially planar, provided at its lower part with nine studs among which the peripheral studs 4, 5, 6, 7 have simply been shown and 8.

 We also see in Figure 1, how a beam 9 is secured to the lower part of the pads 6, 7 and 8.

 Similarly, longitudinal members 10 and 11 join the lower parts of the pads which are in alignment with the pads 4 and 5.

 Partially shown in FIG. 1 is how the plate 2 can be provided with orifices 3, the dimensions of which can be chosen as a function of the nature of the products which are intended to be placed on the pallet.

 The advantage of these orifices 3 is to lighten the pallet, but it is clear that when it is desired to put fragile products such as products in bags on the pallet, it is advantageous to limit the size of these orifices for avoid damaging them.

 FIG. 2 is a top view of the lower quarter of the pallet in FIG. 1.

 We find in this figure the plate 2 as well as the orifices 3.

 We see in broken lines the top of the stud 6 as well as half of the top of the studs 5 and 7.

 The pads 5, 6 and 7 are constituted by peripheral partitions 12, and central partitions 13, which are joined laterally to each other and which, at their upper part, are integral with the plate 2. The central partitions 13 could also be positioned according to radial directions, for example along diagonals.

 Alternatively, the peripheral partitions 12 may have, for example on their faces facing the outside of the pallet, sections in the form of Greek or corrugations to increase their resistance to crushing.

 Also shown in broken lines in Figure 2, the ribs 14 which are arranged parallel to the width of the pallet and the ribs 15 which are arranged parallel to the length of the pallet.

 A rib 16 which goes around the plate 2 has also been shown in broken lines.

 Like the partitions 12 and 13 which constitute the studs, the ribs 14, 15 and 16 are integral with the underside of the plate 2, of which they provide rigidity and mechanical solidity.

 Note in Figure 2 that according to a preferred embodiment of the invention the studs have cut sides 17 to facilitate the introduction between them of the forks of the forklift.

 There is shown in Figure 7 the upper element of the pallet according to the invention which has been turned over so that one can see the partitions which constitute the studs, as well as the ribs.

 This figure 7 clearly shows how the lower ends of the peripheral partitions 12 and of the internal partitions 13 which constitute the studs are made up.

 We also see the cut sides 17 which are made on the periphery of the studs to allow easier engagement of the forks of the forklift.

 Finally, we see in FIG. 7 the arrangement of the ribs 14 and 15 as well as the peripheral rib 16.

 It is understood that, taking into account this particular structure of the upper element of the pallet, it is possible to manufacture the latter without this posing any particular difficulty because the partitions and the ribs are all directed perpendicular to the plate 2.

 FIG. 3 represents a section along III-III of FIG. 2, on which we find the plate 2, the orifices 3, as well as the transverse ribs 14 and the peripheral rib 16.

 It is noted that the peripheral rib 16 as well as the last transverse rib 14a have a height less than the other transverse ribs 14 so as to facilitate the engagement of the forks of a forklift in the free spaces between the studs.

 Figure 4 is a section along IV-IV of Figure 2 which corresponds to Figure 3, except that there is shown in addition the longitudinal rib 15 and that the section was made outside the orifices 3.

 We see in Figure 4 how the longitudinal rib 15 is cut at a bevel at its end to join the rib 14a to the rib 14 which is adjacent to it.

 In FIG. 5 which is a section along V-V in FIG. 2, we find the peripheral partitions 12 as well as the central partitions 13 of the studs 5 and 6. We also find in this figure a longitudinal rib 15 as well as the transverse ribs 14.

 FIG. 6 is a perspective view of the lower part of the stud 6 which rests on its spar 9.

 In the embodiment shown, the spar 9 is constituted by a generally trapezoidal profile, comprising a lower face 18 intended to rest on the ground or on the products supported by another pallet and an upper face 19 intended to be connected with the lower part of the partitions 12, 13 and 17 which constitute the stud 6.

 The spar 9 has a generally trapezoidal shape which corresponds to the shape of the lower part of the partitions 12, 13 and 17 which constitute the stud 6, so as to ensure proper positioning of the stud on the spar.

 We also see in Figure 6, how the spar has four vertical partitions 20, 21, 22 and 23 which define five channels inside the spar.

 It can also be seen how, according to a preferred embodiment of the invention, a reinforcement element 24, constituted for example by a metal tube, is engaged in the central recess of the beam between the walls 21 and 22.

 The reinforcing element can be, if desired, immobilized in the beam, for example by a slight deformation or withdrawal of the plastic material or by the fact that the reinforcing element is supported on ribs or extra thicknesses present on the inner surface of the spar.

 As indicated above, the upper element of the pallet can be produced for example by injection, by injection-compression or extrusion-compression.

 The number and dimensions of the ribs which are located on the underside of the upper element are chosen according to the mechanical strength which it is desired to impart to the pallet.

 Given their profile, the side members can be easily obtained by extrusion to then be cut to the desired length.

 The assembly of the beams on the studs can easily be carried out by a vibration welding process, which consists in applying the studs on the beam by vibrating one part with respect to the other so as to cause heating and melting partial of the two parts, which ensures their welding.

 There is shown in Figure 6, how it is possible to close the recesses of the spar using a plate 25 for example of plastic which can be easily glued, clipped or welded, for example to the mirror, at each end of the side members in order to keep the frame 24 in the side member and to prevent dirt from entering inside the latter.

 It is understood that the embodiment which has been described has no limiting character and that it may receive any desirable modifications without departing from the scope of the invention.

Claims (17)

 1. Plastic pallet, characterized in that it is constituted by the combination of an upper element (1) comprising a substantially planar plate (2) possibly hollowed out (3) which supports on its lower face a network of ribs stiffening (14,15) and a plurality of studs (4,5,6,7,8) constituted by a set of vertical walls (12,13) and open at their lower part; with hollow beams (9,10,11) produced by extrusion subject for example by welding or gluing to the lower part of a series of aligned studs (6,7,8).  2. Pallet according to claim 1, characterized in that the stiffening ribs (14,15) are connected laterally to each other and to the vertical walls (12,13) which constitute the pads (4,5,6,7 , 8).  3. Pallet according to any one of the preceding claims, characterized in that the network of stiffening ribs (14,15) comprises ribs parallel to at least one of the sides of the pallet.  4. Pallet according to any one of the preceding claims, characterized in that the hollow beams (9,10,11) are arranged at the lower part of the studs parallel to the long sides of the pallet.  5. Pallet according to any one of the preceding claims, characterized in that the longitudinal members (9,10,11) comprise at least one vertical partition (20,21,22,23).  6. Pallet according to any one of the preceding claims, characterized in that the longitudinal members (9,10,11) comprise in at least one of their longitudinal cavity a reinforcing element (24) constituted for example by a tube or a metal profile or a wooden bar.  7. Pallet according to any one of the preceding claims, characterized in that the ends of the side members (9,10,11) are closed by a plate (25), for example made of plastic, which is welded, glued or clipped on the side members.  8. Pallet according to any one of the preceding claims, characterized in that at least certain angles of the studs have a cutaway (17) to facilitate the introduction of the forks of handling equipment between the studs.  9. Pallet according to any one of the preceding claims, characterized in that the peripheral walls (9) of the studs have on at least part of their periphery a section in the form of Greek or corrugations to increase their resistance to l 'crushing.  10. Pallet according to any one of the preceding claims, characterized in that the longitudinal members (9,10,11) have a substantially trapezoidal section whose upper corners have a cutaway to facilitate the introduction of the forks of handling equipment between the studs.  11. Pallet according to any one of the preceding claims, characterized in that the reinforcing ribs (16,14a) disposed on the periphery of the pallet have a height less than the other reinforcing ribs so as to facilitate the introduction of handling equipment forks between the studs.  12. Pallet according to any one of the preceding claims, characterized in that the ends of the reinforcing ribs are cut at a bevel to facilitate the introduction of the forks of the handling equipment between the studs.  13. Pallet according to any one of the preceding claims, characterized in that the upper element (1) and / or the side members (9,10,11) are made using a plastic material containing fibers such as glass fibers or other reinforcing fillers.  14. A method of manufacturing a pallet according to any one of the preceding claims, characterized in that the upper element (1) is produced by injection, injection-compression or extrusion-compression of a thermoplastic material such as polyethylene of high density.  15. The method of claim 14, characterized in that the beams (9,10,11) are manufactured by extrusion and then cut to the desired length.  16. Method according to any one of claims 14 and 15, characterized in that the side members (9,10,11) are fixed to the lower part of the studs (4,5,6,7,8) of the upper element by vibration welding.  17. Method according to any one of claims 14 to 16, characterized in that the different parts of the pallet are made with plastics of different colors to identify them for logistical purposes.