Pallet with a plastic platform

Abstract: The pallet comprises a platform (12) formed by a hollow, unitary body having two opposed major walls on which there are corresponding inwardly-extending ribs (16) which are welded together. Projecting portions (17, 18, 19) of the platform (12) are welded to corresponding base elements (13) which are also formed, in threes, by hollow unitary bodies. The resulting structure is particularly stiff and can advantageously be produced by an extrusion-blowing process with plastics material of high molecular weight.

Description: The invention relates to loading trays, commonly known by the term "pallets", which can be used for transporting containers of liquids and, more particularly, to a pallet with a plastics platform. A known palletized container for liquids or for granular materials is constituted substantially by a plastics vessel, by a cage made of profiled metal sections surrounding the vessel, and by a quadrangular steel or plastics platform on which the vessel bears and to which the cage made of profiled metal sections is fixed. The platform has stiffening ribs and, if it is made of plastics material, is formed by a moulding process, preferably by injection. Suitable support elements are formed on or applied to the four corners and to the centre of the lower surface of the platform. A plastics platform of this type, however, can be produced only with plastics material of relatively low molecular weight and therefore has inadequate mechanical characteristics for certain applications. Moreover, it is quite expensive since it requires specific manufacturing tooling, in particular, an injection mould. GB 1 202 353 discloses a pallet comprising a quadrangular plastic platform formed by a unitary hollow body having two major walls which are disposed opposite one another. One of the two major walls has protuberances which extend towards the interior of the hollow body so far as to contact the opposite major wall at a number of locations so as to form at each location a depression in the exterior of the pallet and a corresponding projection within the pallet. An object of the present invention is to propose a pallet with a plastics platform which is stronger and less expensive than known pallets. This object is achieved by the provision of the pallet defined and characterized in general in the first claim. The invention will be understood better from the following detailed description of an embodiment thereof, given by way of non-limiting example with reference to the appended drawings, in which: Figure 1 is a perspective view of a palletized container which uses a pallet according to the invention, Figure 2 shows a pallet according to the invention in perspective and with parts separated, Figures 3 and 4 are perspective views of the platform which constitutes the main part of the pallet according to the invention, from above and from below, respectively, Figure 5 is a section taken on the line V-V of Figure 3, and Figure 6 is a section taken on the line VI-VI of Figure 2. As is shown in Figure 1, the palletized container comprises a right-angled parallelepipedal vessel 10 with rounded corners, a cage formed by a peripheral framework 11 made of profiled metal sections arranged in a grid and welded at the points of intersection, and a pallet formed by a quadrangular plastics platform 12 on which the vessel 10 bears, and by base elements 13 fixed to the bottom of the platform. The body of the vessel 10 is preferably made of plastics material, for example, polyethylene, by a blowing process. In the centre of its upper portion, the body has a hole which, in the drawing, is closed by a lid 14 and, at the bottom of a side wall, the body has a hole in which an outlet valve 15 is fixed. The framework 11 is fixed to the platform 12 by suitable means, not shown, for example, by U-shaped bent sheet-metal strips extending around the lower peripheral section of the framework and fixed to the platform by bolts or by screws extending directly through the lower peripheral section and the underlying platform. Two cross-members 9 are fixed removably to the upper peripheral profiled section of the framework in order to hold the vessel in position. As can be seen in Figure 2 in particular, the upper surface of the platform 12 is shaped so as to have, in the vicinity of its edge, a seat 8 for the lower peripheral section of the framework 11. The platform 12 is constituted by a flattened, quadrangular, hollow body made of plastics material, for example, high-density polyethylene, preferably formed by an extrusion-blowing process. The blowing takes place in a mould shaped so as to create, in at least one of the main walls of the hollow body, protuberances which extend inwardly so far as to contact the opposite wall. In the embodiment shown, the protuberances are ribs which correspond to channels 16 in the outer surfaces of the hollow body, and which are formed in corresponding positions on both of the major walls. The ribs are preferably welded to one another throughout their length, inside the hollow body. The welding takes place during the blowing when the plastics material is still in the molten state. The ribs have the function of stiffening the structure and of distributing the load throughout the surface of the platform. In this embodiment, some of the ribs extend like rays from a central region of the platform; more precisely, four ribs extend along the diagonals and four ribs extend parallel to the sides of the platform; some ribs extend as branches of the diagonal ribs in directions parallel to the sides; the ribs could, however, be arranged in a different pattern which satisfies the structural stiffening requirements and those of the blowing process equally well. In order to stiffen the structure further, as shown in Figure 2, a strip 7 of sheet metal may be applied to the upper surface of the platform, the strip 7 having bent ends which can be fitted in corresponding seats 6 formed centrally on two opposite sides of the platform. The lower wall of the platform is shaped so as to have nine outwardly-projecting, that is, downwardly-projecting portions; more precisely, it has a central portion 17 (Figure 4), four portions, indicated 18, in the vicinity of the corners, and four portions, indicated 19, in the centres of the sides. These projecting portions form nine coplanar bearing surfaces. An area (indicated 20 in Figures 4 and 5) of the lower surface of the platform is defined within each projecting portion. The upper wall is shaped so as to have corresponding portions 21 projecting towards the interior of the hollow body and in contact with the above-mentioned areas 20. The contact areas are preferably welded together. In the embodiment shown, the contact areas defined by the peripheral projecting portions 18 and 19 are connected to the contact area defined by the central projecting portion 17 by diagonal and median ribs, respectively. Greater stiffness of the structure is thus achieved. According to the preferred embodiment of the invention, the base elements 13 (Figures 2 and 6) on which the platform 12 bears, are connected in threes by cross-members 30. Each set of three elements 13 is constituted by a hollow body formed by extrusion-blowing, that is, by the same technique which is used to form the platform 12. In fact, the hollow bodies for forming the base elements and that for forming the platform can be formed by the same extrusion-blowing cycle. As can be seen in Figure 6, each base element 13 is shaped so as to have a recessed region in which two opposite walls of the hollow body are welded to one another internally to ensure greater stiffness of the support structure. The base elements 13 can advantageously be fixed to the platform 12 by hot plate welding, that is, by placing the two portions on a plate heated to the softening temperature of the plastics and immediately afterwards bringing the surfaces to be welded into contact with one another. The outwardly-projecting portions 17, 18, 19 and the base elements 13 together define two channels 31 (Figure 1) for the insertion of the forks of a conventional lift truck. The cross-members 30, together with the lower surfaces of the base elements 13, define a stable support surface which is particularly suitable for the sliding of the pallet on roller conveyors of automatic plants. The lower surfaces of the peripheral base elements 13 advantageously have chamfers 35 (Figures 2 and 6) which define a peripheral seat in which the upper profiled section of the framework of a palletized container identical to that described can be fitted. This facilitates stable stacking of several containers. The pallet according to the invention is a structure which is light and at the same time strong and which can be produced by a blowing mould which, as is known, is much less expensive than an injection mould such as those required by the prior art. This structure is produced with the use of plastics material, possibly recycled material, with a high molecular weight and therefore stronger than the plastics material which has to be used with the injection-moulding technique, which is more fluid and hence weaker when in the solid state. A further important advantage is achieved when the pallet is intended for a palletized container in which the vessel is also made of plastics material. In this case, the overall economy permitted by the invention is particularly notable since the same apparatus which is used for the manufacture of the vessel can also be used to manufacture the pallet.

Claims: A pallet comprising a quadrangular plastic platform (12), formed by a unitary hollow body having two major walls which are disposed opposite one another, at least one of said two major walls having protuberances (16) which extend towards the interior of the hollow body so far as to contact the opposite major wall, characterized in that said protuberances comprise: first ribs extending, from a central region of the platform, parallel to the sides of the platform and second ribs extending, from a central region of the platform, along the diagonal of the platform, each rib being welded, throughout its length, with the opposite major wall. A pallet according to claim 1, in which both of the major walls have protuberances (16). A pallet according to claim 2, in which at least some of the protuberances (16) of one major wall are in contact with protuberances (16) of the opposite major wall. A pallet according to any one of the preceding claims, in which the protuberances (16) are welded at the points of contact with the opposite wall. A pallet according to any one of the preceding claims, in which said first and second ribs are formed in corresponding positions of said two major walls, each rib of one of said two major walls being welded together, throughout its length, with the corresponding rib of the opposite major wall. A pallet according to any one of the preceding claims, in which ribs (16) parallel to the sides branch out from diagonal ribs. Pallet according to anyone of the preceding claims, comprising coplanar bearing surfaces defined by a plurality of peripheral outwardly-projecting portions (18,19) and a central outwardly-projecting portion (17), said ribs extending from the central outwardly-projecting portion (17) to a respective outwardly-projecting portion (18,19) of said plurality of peripheral outwardly-projecting portions. A pallet according to Claim 7, in which each of the outwardly-projecting portions (17, 18, 19) defines an area (20) of the respective main wall which is in contact with the opposite main wall. A pallet according to Claim 8, in which the opposite main wall has a plurality of inwardly-projecting portions (21) in the region of the contact areas (20) defined by the outwardly-projecting portions (17, 18, 19). A pallet according to Claim 9, in which the contact areas (20) are welded. A pallet according to any one of Claims 8, 9 and 10, in which, of the outwardly-projecting portions, one (17) is arranged centrally, and others (18, 19) are arranged peripherally and have their respective contact areas (20) connected to the contact area (20) of the central projecting portion (18) by means of respective ribs (16). A pallet according to any one of Claims 7 to 11, comprising base elements (13) in contact with bearing surfaces of at least some of the outwardly-projecting portions (17, 18, 19) of the platform (12). A pallet according to Claim 12, in which at least two base elements (13) are connected to one another by a cross-member (30). A pallet according to Claim 12 or Claim 13, in which the base elements (13) are welded to the bearing surfaces. A pallet according to Claim 13 or Claim 14, in which the base elements (13) connected by a cross-member (30), and the cross-member itself, are parts of the same hollow body. A palletized container comprising a plastics vessel (10), a cage (11) made of profiled metal sections which surrounds the vessel, and a pallet according to any one of the preceding claims, on which the vessel is supported and to which the cage made of profiled metal sections is fixed.

Inventors: CASSINA VIRGINIO, CASSINA, VIRGINIO
Applicants: DAVIPLAST SERVICOS DE CONSULTO, DAVIPLAST - SERVICOS DE CONSULTORIA, SOCIEDADE UNIPESSOAL LDA.
Application year: 2000
Main classification: B65D19
IPC codes: B65D19, B65D77