PLASTICS PALLETS AND MOULDING APPARATUS FOR PRODUCING PLASTICS PALLETS AND OTHER PLASTIC ARTICLES

Abstract: A pallet of moulded construction comprising a load-carrying surface supported by underlying support structure configured to permit the insertion of the tines of the fork-lift, the load-carrying surface being reinforced at its underside by a celular reinforcing structure comprising cells the axes of which extend perpendicularly to the load-carrying surface.

Description: PLASTICS PALLETS AND MOULDING APPARATUS FOR PRODUCING PLASTICS PALLETS AND OTHER PLASTIC ARTICLES The present invention relates to pallets and more particularly to pallets of moulded plastics construction, and to moulding apparatus for producing such pallets and other plastics articles. The present applicants and their successors in business have devised a range of plastics pallets of one-piece moulded plastics construction formed by an injection moulding technique using either wholly or partially post-consumer recycled plastics. While these pallets are effective in use, the applicants have determined that it would be of advantage to construct a pallet of lighter weight whilst achieving similar strength characteristics to those of their earlier pallets. More particularly there is disclosed in International Patent Application No. PCT/AU97/00382, the disclosure of which is hereby incorporated by reference, a load- carrying pallet moulded in one piece in a suitable plastics, for example post-consumer recycled plastics. International Patent Application PCT/AU95/00690 also discloses a load- carrying pallet formed as a one-piece plastics moulding. We are now proposing to produce a pallet of the type disclosed in the aforesaid applications but using less plastics material. This will be achieved by using thinner sections for the load carrying platform, the beams beneath the platform, and the ground-engaging struts at the underside of the pallet. However in order to achieve adequate rigidity of the overall structure we are proposing to reinforce the load-carrying platform by moulding a multiplicity of intersecting webs into the underside of die load-carrying platform whereby the ribs intersect to define a cellular structure with the cells distributed throughout the exposed parts of the underside or at least in those parts subject to maximum loading. For example, the cellular structure may be of honeycomb form or alternatively the cells may be of rectangular or diamond shape. In each case, the axis of each individual cell will extend perpendicularly to the plane of the load-carrying surface and each cell will be open at its underside. According to one aspect of the present invention, there is provided a pallet of moulded construction comprising a load-carrying surface supported by underlying support structure configured to permit the insertion of the tines of the fork-lift, the load-carrying surface being reinforced at its underside by a cellular reinforcing structure comprising cells the axes of which extend perpendicularly to the load-carrying surface. Advantageously, the underlying support structure comprises a series of parallel beams of hollow construction comprising opposed side walls, the beams being internally reinforced by webs defining a cellular structure extending to the underside of the load-carrying platform, and the axes of the cells of the reinforcing structure within the beams being substantially perpendicular to the load-carrying platform. Advantageously, the beams have transverse apertures to permit insertion of the tines of a fork-lift laterally to the beams, and the cellular reinforcement of the load-carrying platform in the zone of the platform adjacent die lateral apertures in the beams has a smaller cell size than that in other zones of the load-carrying platform. Advantageously, the entire pallet is constructed in a single moulding operation and me mould incorporates a retractable core for forming the cellular reinforcement at me underside of the platform in the zones thereof adjacent d e lateral apertures in the beams. Advantageously, the cellular reinforcing structure in the beams extends to die underside of the beams, and me load-carrying platform is configured to define a pattern of upstanding projections and lands around me projections whereby when two like pallets are arranged in stacked relationship, me lower edges of the reinforcing cells of me beams of the upper pallet will engage with the lands on in me load-carrying platform of die lower pallet whereby to prevent slippage between the two pallets. According to another aspect of die present invention mere is provided an injection - mould having a retractable mould core structure, said mould core structure comprising a retractable core configured to form cellular or omer reinforcing structure at an inner surface of an article being moulded, and means for retracting said core in a direction substantially at right angles to said surface, said retracting means comprising at least one driving member mounted for reciprocatory movement in a direction at right angles to die direction of retraction, and means linking said driving member and core to translate said movement of the driving member into die required movement of me core. In a preferred embodiment of the invention the linkage provided between die core and the driving member is provided by one or more cooperating cams and cam tracks. Advantageously, the driving member comprises a strip having a series of driving cams, said strip cooperating with a corresponding strip carried by die core and providing a series of cam tracks which cooperate with me respective cams such that movement of the driving strip in one direction causes retraction of me core and movement in die opposite direction causes extension of die core into an operative position for moulding. Preferably mere are two or more such driving strips arranged in parallel relation and each cooperating with a respective strip carried by the core. Preferably, the or each driving strip is driven by a fluid cylinder. Advantageously, me cams and cam tracks cooperate when the core is in its operative moulding position to lock me core in that position against the pressure of the material being moulded. The present invention also provides a me od of injection moulding plastics articles using a retractable core structure as defined above. The present invention also provides a moulded plastics article when produced by use of a mould incorporating a retractable core structure as defined above. - An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a pallet in accordance witii a preferred embodiment of the invention; Figure 2 is an underneath perspective view of the pallet; Figure 3 is an undernea perspective view from a more oblique angle in order to better illustrate the underlying cellular reinforcing structure; Figure 4 is a schematic section through two such pallets arranged in stacked relationship in order to illustrate me relationship between the lower edges of the reinforcing cells of the upper pallet and the load-carrying platform of the lower pallet; Figure 5 is a plan view of a retractable mould core for use in the production of the pallet; Figure 6 is a side view of the core; Figure 7 is an end view of me core; Figure 8 is an end view of me core guide; and Figure 9 is a schematic section showing me core and its cooperation widi driven and driving cam strips respectively carried by me core and core guide. There is shown in the accompanying drawings a pallet of one-piece construction formed by injection moulding. The pallet may be formed wholly from post-consumer recycled plastics, a mixture of post-consumer recycled plastics and omer plastics, or virgin plastics material. The pallet comprises a load-carrying platform 2 provided wifh multiplicity of upstanding projections 4 distributed over its entire surface, me projections 4 being separated by a grid-like pattern of longitudinal and transverse lands 5. As shown die projections 4 are of rectangular shape wim a substantially planar upper surface. The projections act to prevent slippage of goods carried on me pallet while permitting the load- carrying surface easily to be cleaned, for example by hosing or steam cleaning. The projections 4 also provide a strengthening function for the platform 2 and a stacking function as will be described. - The load-carrying platform 2 is supported by an underlying support structure consisting of a series of parallel beams comprising two outer beams 6 defining opposed outer side walls of the pallet and a central beam 8. The beams 6,8 are spaced to define an access for the tines of a fork-lift truck from either of me two open ends of die pallet. The beams 6 defining the outer side walls of the pallet are also apertured at 10 to permit entry of the fork- lift tines from either of the two opposed sides thereby providing so-called four-way entry for the tines. The central beam 8 is also apertured in alignment witii the apertures 10 in d e outer beams 6 to permit passage of the fork-lift tines across the underside of die platform. In order to provide a rigid structure of relatively light weight, each of die beams 6,8 is of hollow construction consisting of parallel side walls reinforced internally by webs 12 which extend from the base of die beam 6 or 8 to me underside of the platform 2 at right angles thereto, except in those sections of the beams 6,8 provided with the apertures for entry of the fork-lift tines. In die case of die two outer beams 6, die webs 12 extend transversely between die longitudinal walls of die beams, whereas for the central beam 8 which is of greater width man the outer beams 6, there is also a central longitudinal reinforcing web 14. The web reinforcement not only reinforces the beams 6,8 but also reinforces the platform 2 whereby the platform 2 can also be of reduced diickness. In addition to reinforcement by the beams 6,8 and me webs 12, 14 within the beams 6,8, the load-carrying platform 2 is reinforced by a series of longitudinal and transverse webs 16, 18 in me zones between die outer beams 6 and central beams, the webs 16, 18 being perpendicular to the plane of me platform and extending respectively parallel to, and at right angles to, the axis of the beams 6,8. It will be noted mat die web reinforcement of the platform 2 is, in the zones of the lateral apertures for the fork-lift tines in the outer and central beams, of reduced depth and in these zones in order to achieve effective reinforcement the longitudinal and transverse reinforcing webs 16a, 18a are more closely spaced than elsewhere at the underside of the platform. For similar reasons, me parts of each of the outer and central beams 6,8 beneath the apertures for passage of the fork-lift tines have longitudinal and transverse reinforcing webs 14a, 12a of closer spacing than in the remainder of the beams. Widi a reinforcing structure as described above, die wall thickness of die pallet can be thinner dian in the earlier pallets discussed at the outset, resulting in a substantial weight saving but wimout sacrificing strengm and rigidity of die pallet. It will be noted diat die reinforcing webs 12, 14 which extend to die underside of die beams 6,8 define a structure consisting of open cells of rectangular form, the axes of which are at right angles to d e platform 2. The boundary walls of diese cells correspond to the rectangular pattern of lands 5 defined around die upstanding projections 4 (or groups of die projections 4) on the load-carrying platform 2 whereby when two such pallets are located in stacked relationship, the end edges of the reinforcing cells at the underside of die upper pallet will engage with the lands 5 of die load-carrying platform of the lower pallet in order to prevent slippage between die two pallets. This is illustrated schematically in Figure 4. As discussed above, me entire pallet is consttucted in one-piece in a single injection moulding operation. In order to form the cellular reinforcing structure at me underside of die load-carrying platforms in me zones of the lateral apertures in die beams 6,8, the mould incorporates retractable cores in these zones. The preferred form of these cores will now be described with reference to Figures 5 to 9. Figures 5 to 7 show a core or insert 32 for moulding a cellular structure at the underside of a section of die load-carrying platform 2 of the pallet described above. In die particular form shown, the core 32 produces a structure with rectangular cells, me size of the various cells changing throughout the structure in accordance widi me structural requirements of the load-carrying platform. The core 32 is mounted widiin the mould in a core guide 34 (Figure 8) of channel-like structure for movement in a direction at right angles to me plane of the load-carrying surface to permit retraction of me core 32 after moulding. The opposed sides 36 of die core 32 are in sliding contact witii die sidewalls 38 of die guide 34 and die opposed ends 40 of the core 32 are in sliding contact widi me adjacent surface of die mould, a close fit being provided to prevent seepage of incoming plastics material around me sides and ends 36, 40 of the core 32 and into me core guide 34. Two or more parallel cam strips 42 are attached to the underside of me core 32 and project into the interior of the core guide 34, preferably each strip 42 being located widiin a respective longitudinal slot 44 at me underside of die core 32. Each cam strip 42 is shaped to provide a plurality of cam tracks 46a, 46b which are inclined to me axis of movement of the core 32. Each of the cam strips 42, which constitutes a driven cam strip, cooperates widi a respective driving cam strip 50 which is mounted for sliding movement in a direction at right angles to me axis of movement of the core 32 in a groove 52 provided in me base of me core guide 34. Each driving cam strip 50 has a series of driving cams 54 having driving cam surfaces 54a, 54b which are shaped for cooperation with the respective cam tracks 46a, 46b of the adjacent driven cam strip 42. The driving cam strips 54 are coupled for co-joint movement to a fluid actuated cylinder. Figure 9 illustrates the position of the driving cam strips 54 in the extended, operative position of the core 32 at which moulding takes place. In this configuration an upper locking surface 54c of each driving cam 54 engages a corresponding surface 46c at me underside of the corresponding cam track, these surfaces extending at right angles to the direction of displacement of the core 32, to lock the core 32 in its operative position. In order to refract die core 32 after moulding to facilitate ejection of die moulded product, die fluid cylinder is actuated to displace die driving cam stiips 50 towards die left as viewed in Figure 9 whereby die inclined driving cam surfaces 54a of the driving cams 54 engage the correspondingly inclined cam tracks 46a of the driven cam strips 42 and mereby cause the core 32 to be rettacted out of engagement with die moulded cellular structure. The inclined cam surfaces and cam tracks enable substantial displacement to be achieved even although the available space for retraction is relatively restricted. To reset die core 32 in preparation for a subsequent moulding, me driving cam strips 50 are displaced in the opposite direction (to die right as shown in Figure 9) by actuation of the fluid cylinder whereby the inclined driving cam surfaces 54b of the driving cams 54 engage the correspondingly inclined cam tracks 46b of the driven cam strips and cause extension of die core 32 towards its operative position. Towards die end of die displacement of the driving cams 54, the upper locking surfaces 54c of the driving cams 54 move into engagement widi die surfaces 46c of the cam tracks to thereby hold die core 32 in its operative positions as previously described. Although die core structure has been particularly described witii reference to die production of reinforcing structure of cell-like form at the under side of me load-carrying platform of the pallet, the core may be configured to provide other reinforcing structure, for example, a series of parallel ribs or webs. It is to be understood mat d e core structure described herein is also applicable to the manufacture of articles other than pallets. The embodiment has been described by way of example and modifications are possible within the scope of die invention. Throughout this specification and claims which follow, unless me context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any omer integer or group of integers.

Claims: CLALMS:- 1. A pallet of moulded construction comprising a load-carrying surface supported by underlying support structure configured to permit the insertion of the tines of the fork-lift, die load-carrying surface being reinforced at its underside by a cellular reinforcing structure comprising cells the axes of which extend perpendicularly to the load-carrying surface. 2. A pallet according to claim 1, wherein the underlying support structure comprises a series of parallel beams of hollow construction comprising opposed side walls, die beams being internally reinforced by webs defining a cellular structure extending to die underside of me load-carrying platform, and the axes of die cells of me reinforcing structure within the beams being substantially perpendicular to die load-carrying platform. 3. A pallet according to claim 2, wherein me beams have transverse apertures to permit insertion of the tines of a fork-lift laterally to the beams, the cellular reinforcement of the load-carrying platform in the zone of the platform adjacent die lateral apertures in the beams having a smaller cell size than mat in omer zones of d e load-carrying platform. 4. A pallet according to claim 2 or claim 3, wherein the cellular reinforcing structure in the beams extends to me underside of the beams, and die load-carrying platform is configured to define a pattern of upstanding projections and lands around die projections whereby when two like pallets are arranged in stacked relationship, the lower edges of me reinforcing cells of the beams of me upper pallet will engage widi die lands on in the load-carrying platform of the lower pallet whereby to prevent slippage between me two pallets. 5. A pallet according to any one of claims 1 to 4, wherein the entire pallet is constructed in a single moulding operation. 6. A method of making a pallet according to claim 3, comprising moulding me entire pallet in a single moulding operation in a mould incorporating a retractable core for forming the cellular reinforcement at die underside of me platform in me zones thereof adjacent die lateral apertures in the beams. 7. An injection mould having a retractable mould core structure, said mould core structure comprising a retractable core configured to form cellular or other reinforcing structure at an inner surface of an article being moulded, and means for refracting said core in a direction substantially at right angles to said surface, said refracting means comprising at least one driving member mounted for reciprocatory movement in a direction at right angles to me direction of refraction, and means linking said driving member and core to translate said movement of me driving member into die required movement of me core. 8. A mould according to claim 7, wherein the linkage provided between die core and die driving member is provided by one or more cooperating cams and cam tracks. 9. A mould according to claim 7, wherein the driving member comprises a strip having a series of driving cams, the driving strip cooperating with a corresponding driven strip carried by the core and providing a series of cam tracks which cooperate with the respective cams such that movement of the driving strip in one direction causes refraction of die core and movement in the opposite direction causes extension of the core into an operative position for moulding. 10. A mould according to claim 9, wherein there are two or more such driving strips arranged in parallel relation and each cooperating with a respective strip carried by d e core. 11. A mould according to claim 9 or claim 10, wherein the or each driving strip is driven by a fluid cylinder. 12. A mould according to any one of claims 9 to 11, wherein the cams and cam tracks cooperate when the core is in its operative moulding position to lock die core in that position against the pressure of die material being moulded. 13. A mould according to any one of claims 7 to 12 configured to produce a pallet according to any one of claims 1 to 4.

Inventors: BERELOVICH LAZER, SMORGON VICTOR, BERELOVICH, LAZER, SMORGON, VICTOR
Applicants: BERELOVICH LAZER, SMORGON VICTOR, VICFAM PLASTICS PTY LTD, BERELOVICH, LAZER, SMORGON, VICTOR, VICFAM PLASTICS PTY. LTD.
Application year: 1998
Main classification: B65D19
IPC codes: B29C33, B29C45, B29D31, B65D19