US 3603272 A
A two part die for injection molding an integral plastic pallet having a load carrying top portion and a supporting bottom portion each formed by transversely spaced ribs of U-shaped cross section, the die comprising two die sections having each a plurality of spaced webs tapering toward free ends thereof and arranged with respect to each other so that when the die is closed the webs of one section will intermesh and engage without play plane side faces of the other section and so that at the free ends of the webs hollow spaces of U-shaped cross sections are formed for molding the U-shaped ribs.
Claims available in
Description (OCR text may contain errors)
United States Patent Inventor Ermt Ditges Herzebroek, Westialen, Germany Appl. No. 785,812 Filed Dec. 20, 1968 Patented Sept. 7, I971 Assignee Pres-Und Stmswerk Paul Craelner KG Hern'brock (Westtalen), Germany Priority Dec. 20, I967 Germany P 15 56 151.0
PLASTIC PALLET AND DIE FOR PRODUCING THE SAME 12 Claims, 7 Drawing Figs.
Int. Cl. 865d 19/04 FietdotSea l08/5l,52, 53, 58
[5 6] References Cited UNITED STATES PATENTS 2,615,661 l0/l952 Cushman 108/53 X 3,404,642 10/1968 Belcher et al. 108/58 X 3,481,285 12/1969 Yellin 108/58 Primary Examiner-Bobby R. Gay Assistant Examiner-Peter A. Aschenbrenner Attorney-Michael S. Striker ABSTRACT: An integrally formed plastic pallet from an injection molding die. The top portion of the pallet for carrying the load is separated from the bottom portion through which the pallet is supported, by spacing portions. The top and bottom portion have rib portions arranged with recesses between them. The top and bottom ribs are displaced from each other in conjunction with their recesses, so that the top ribs lie above the bottom recesses, whereas the bottom ribs lie beneath the top recesses. The recesses are at least as wide as their respective ribs.
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PLASTIC PALLET AND DIE FOR PRODUCING THE SAME BACKGROUND OF THE INVENTION Flat pallets used in materials handling have, heretofore, been constructed of wood. These flat pallets have a top surface for loading purposes or upon which the load is placed, and a bottom or placement surface which is equally flat. Spacing members are situated between these two top and bottom or placement surfaces, and the design and combination of these elements have been constructed, in the past, of different designs and of wood. Wooden pallets, however, become easily damaged during severe handling and heavy loading, and as a result such wooden pallets have only a relatively short lifespan. Wooden pallets, in addition, are susceptible to the cf fects of acids, alkalines, salts, and humidity. Wood, furthermore, is a good nutrient for the growth of bacteria. In view of the disadvantage from the bacterialogical viewpoint, wooden pallets are not desirable for use in processes involving the transfer and processing of food supplies. The same situation and reasoning also applies to pallets made of steel, since they are readily susceptible to rust, even though their surfaces may be coated or plated.
In recent times, accordingly, flat pallets made of synthetic materials such as plastic, have been considered. The plastics preferably used for this purpose are polyethylene or polystyrene. Such conventional pallets as used in the art, however, have the disadvantage that they are assembled from a number of parts. As a result, such pallet assemblies are costly to produce. The load carrying capability and stability of the conventional plastic pallets, furthermore, leave must to be desired.
Accordingly, it is an object of the present invention to provide a flat plastic pallet which does not have the aforementioned disadvantages, residing in conventional pallets. It is an object of the present invention to provide a flat plastic pallet of high strength and rigidity and thereby of long lifespan. It is also an object of the present invention to provide a flat plastic pallet which is not affected by acids, water, alkalines and salts. It is furthermore intended, to provide pallets of the preceding character which is not a nutrient base for bacteria growth and is thereby adapted for use in conjunction with food supplies. In addition, it is a specific object of the present invention to produce a plastic pallet which may be produced in a relatively simple manner.
The objects of the present invention areachieved essentially by constructing the top surface and the underside or placement surface of resistor plastic material such as hard polyvinylchloride or polyolefin such as polypropylene or low-pressure polyethylene. The pallet has parallel ribs between which are recesses, and the ribs and recesses of both surfaces are displaced with respect to one another. The ribs of the top surfaces extend beyond the recesses of the placement surface or standing surface which has ribs of at least the width of the ribs of the upper or top surface. At the same time, the ribs of the bottom or placement surface lie beneath the recesses of the top surface. The ribs of both surfaces are preferably of a U- shaped profile, and designed so that the side legs of the U profile are directed inward. Spacing and strengthening crossmembers or bridge members are, furthermore, provided between the top surface and the placement surface. These crossmembers run vertical or substantially vertical between these surfaces. The displaced openings formed through the dies, permit simple and thorough cleaning of the pallets.
The pallets designed in this manner, are produced, in accordance with the present invention, through injection molding. Through the use of a two-part construction, the pallet is made of integral or one-piece fonn. The two halves of the die are arranged so that their inner sides are spaced from each other, and form members with plane side surfaces project outward. The form members of the two die halves are displaced in relation to each other so that they reach into each other without play when the die is closed. At the outer ends of the form members, U-shaped hollow spaces remainfor the pur-,
SUMMARY OF THE INVENTION A flat plastic pallet of integral construction having a top portion upon which the load to be carried by the pallet is placed. A bottom portion through which the pallet is supported, is spaced from the top portion through spacing portions between them. The top and bottom portions of the pallet have ribs which are spaced from each other with recesses between them. The ribs and recesses are displaced relative to each other so that the ribs of the top portion lie across the recesses of the bottom portion. Similarly, the ribs of the bottom portion lie across the recesses of the top portion. The recesses are at least as wide as the corresponding ribs lying 0pposite the recesses. The pallet is made of plastic material such as hard polyvinylchloride or polyolefin such as polypropylene or low-pressure polyethylene. The ribs of the top and bottom portions run parallel to each other.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING FIG. I is a side view of the underside of the pallet, and is taken to one side of the axis of symmetry AA which is a central axis;
FIG. 2 is a sectional view taken along the line II-II in FIG.
FIG. 3 is a sectional view taken along the line III-III in FIG.
FIG. 4 is a sectional view taken along the line IV-IV in FIG. I;
FIG. 5 is a partial top view of the interior side of an injection molded portion for producing the pallet of the construction of FIGS. 1 to 4; and
FIGS. 6 and 7 show two different sections at right angles to the die form members used in a die for injection molding of the pallet of FIGS. 1 to 4, respectively taken along the line VI--VI and VII-VII ofFIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, FIGS. 1 to 4 show the top surface of a tray made of resistor or strong synthetic plastic material such as hard polyvinylchloride or polyolefin. A plurality of parallel profiled and U-shaped ribs 1 lie between rectangular recesses 2. At the underside or set-on surface are, similarly, a plurality of parallel profiled and U-shaped ribs 3 lying between rectangular recesses 4. The ribs 1 and 3, as well as the recesses 2 and 4 of both surfaces are displaced in relation to each other. The arrangement is such that the ribs 1 of the top surface lie about the recesses 4 which have a somewhat wider dimension than the ribs 1. The ribs 3, at the same time, on the set-on surface or underside or placement surface are, at the same time, beneath the recesses 2 which are similarly wider in width, to some extent, than the ribs 3. These dimensional relationships and arrangement may be seen by referring to FIGS. 3 and 4.
Between the ribs 1 and 3, and at right angle to them, are vertical flat bridges 5 which serve as spacers. In addition, flat bridges 6 are provided between legs of the U-shaped ribs I and 3 which lie substantially vertically opposite to each other outside of the external flat bridges 5. These flat bridges 6 also serve as spacers, and when functioning together with the vertical flat spacers 5 of the pallet, an exceptionally large amount of stability is realized.
The top surface, the placement surface and the flat bridges 5 and 6 are of integral construction and produced through injection molding as a one-piece unit, in accordance with the present invention.
The top surface has a frame 7 which extends beyond all of the sides of the placement surface. This frame 7 has a U- shaped profile similar to the ribs 1 and 3. As shown in FIGS. 3 and 4, angle or U structural members 8 may be injection molded into this frame. These structural members 8.serve to impart additional stability to the tray or pallet. It is also possi ble to injection mold similar such structural members into the ribs 1 and/or 3. These structural members may be made of iron or other metallic substance.
Holes 9 are provided in the ribs 3 of the placement surface. These holes prevent the accumulation of water or other fluids in the upper open profiles of these ribs.
The placement surface also has four large rectangular recesses 10 which are intended for receiving the running rollers of forklift trucks. When the fork thereof is in lowered position and inserted beneath the pallets to such an extent that the pair of rollers immediately rearwardly of the fork will enter into a corresponding pair of the recesses 10. The legs 3a of the U-shaped ribs 3 bordering the recesses 10 are maintained somewhat lower and have upper inclined edges 36, so that driving in and out of the pallets by forklift trucks is simplified. The dies for producing the pallets with the structure described above, consists of two parts 11 and 12, as shown in FIGS. 6'and 7. Both die parts have form members 13 or 14 with plane side surfaces at their inner surfaces and spaced from each other, while at the same time projecting to the exterior. The bridge members 13 and 14 are displaced in relation to each other so that when the die is closed, the bridge members reach into each other without play. Hollow spaces 15 and 16 only remain for the purpose of forming the plastic ribs 1 and 3. These hollow spaces 15 and 16 remain at the outer ends of reduced cross section of the members 13 and 14, and are U- shaped.
Between neighboring front surfaces of the members 13 and 14, free gaps 17 are provided for forming the vertical plastic bridges 5 which are at right angle to the ribs 1 and 3. These bridging members such as the member 5, for example, may
also be designated as crossmembers or flange members. A
number of members 13 and 14 lying outside of the outer gap 17, furthermore, are designed so that a free gap 18 remains for the purpose of forming the plastic crossmember 6, after the die parts 11 and 12 are brought together. The members 13 have, moreover, pins 19 on their outer surfaces, for the purpose of forming holes 9 in the plastic ribs 3.
The recesses 10 serving the purpose of receiving the running rolls of the forklift truck are rectangular, and are formed through the rectangular forming member 20 in the die part 12.
The flat pallets made of synthetic or plastic material, in accordance with the present invention, are preferably produced with dimensions of 1000 X1200 mm., 800 l200 mm., and
800 XlOOO mm. By using identical die elements, these sizes of pallets can be produced in integral or one-piece form through injection molding techniques.
it wili be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.
While the invention has been illustrated and described as embodied in plastic pallets and their dies, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.
What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.
1. A plastic pallet comprising, in combination, a top portion having a top surface for carrying the load to be ap lied to said pallet; a bottom portion having a bottom surface or supporting said pallet; spacing portions between said top portion and said bottom portion; rib portions on said top and bottom portions arranged with recesses between said'rib portions, said rib portions and recesses being displaced relative to each other so that the rib portions on said top portion lie over'the recesses of said bottom portion and the rib portions of said bottom surface lie beneath the recesses of said top portion.
2. The plastic pallet as defined in claim 1 wherein said recesses are at least as wide as said oppositely lying rib portions.
3. The plastic pallet as defined in claim 1 wherein said plastic is hard polyvinylchloride.
4. The plastic pallet as defined in claim 1 wherein said plastic is polyolefin. p
5. The plastic pallet as defined in claim 1 wherein said plastic is polypropylene.
6. The plastic pallet as defined in claim 1 wherein said plastic is low-pressure polyethylene.
7. The plastic pallet as defined in claim 1 wherein said rib portions are U-shaped the legs of said U-shaped rib portions being directed inward.
8. The plastic pallet as defined in claim 1 including cross portions arranged between said rib portions on said top per-- tion and on said bottom portion.
9. The plastic pallet as defined in claim 8 wherein said top portion, said bottom portion and said cross portion are of integral construction.
10. The plastic pallet as defined in claim 1 wherein said rib portions on said bottom portion have openings.
11. The plastic pallet as defined in claim 1, wherein said spacing portions comprise elongated strip portions connecting respective rib portions of said top and bottom portions and extending at least substantially normal to the elongation of said rib portions.
12. The plastic pallet as defined in claim 11, said spacing portions further comprising elongated reinforcing portions also connecting respective ones of said rib portions of said top and bottom portions but extending at least substantially normal to the elongation of said strip portions.