US 3868915 A
The invention relates to a pallets and particularly to pallets having an upper part and a lower part made from a synthetic plastics material and adjacently disposed spacer pieces on the upper part and lower part, the upper part and lower part being rigidly connected to each other and the spacer pieces having mutually corresponding and inter-engaging projections and recesses or depressions.
Description (OCR text may contain errors)
United States Patent 1191 1111 3,868,915 Hafner Mar. 4, 1975  PALLETS 33.677201 71197;. svhadlbtliurne 108/58 ,680,496 8 19 esta'e. Jr. 108/58  lnvemor- 4811 Leopoldslmhe, 3,699,901 10/1972 Cook 108/58 Doktorkamp 11, Germany  Filed: Dec. 27, 1972 Primary Examiner-Roy D. Frazier Assistant Examiner-William E. Lyddane [2H Appl' 312082 Attorney, Agent, or FirmPo1l0ck, Philpitt & Vande  Foreign Application Priority Data S d Dec. 29, 1971 Germany 2165341 57 ABSTRACT  US. Cl. 108/51, 108/53, 108/58 51 1m. (:1 865d 19/32 The Invention relates to a pallets and particularly to 58 Field of Search 108/51. 52. 53, 56, 57. pallets having an pp P and a lower P made 103 53 54 55; 34 34 from a synthetic plastics material and adjacently disposed spacer pieces on the upper part and lower part. 5 References Cited the upper part and lower part being rigidly connected UNITED STATES PATENTS to each other and the spacer pieces having mutually corresponding and inter-engaging projections and re- 2.420,625 5/1947 Stalnaker et a1 .1 108/53 X 2,699,912 1/1955 Cushman 1. 108/53 x or depressons' 2,955,791 108/56 5211133; 1:11;: 1331?; 190mm, 5 vw fi m 3,667,403 6/1972 Angelbeck, Jr 108/58 1 i K 1:1 1:1 [3 c: 1:: :1 [II] [:1 1:1 1:
PALLETS BACKGROUND OF THE INVENTION In the case of a pallet of the prior art, spacer pieces are provided which are constructed as inter-engaging cylindrical columns which are distributed between an upper part and a lower part. This known solution is however a purely theoretical solution which cannot be used in practice because suitable plastics materials are not available. The known pallet can only be produced from plastics material having virtually no shrinkage differential, otherwise, the upper part of the pallet and lower part of the pallet will not fit on each other. A plastics material which satisfies this requirement is however unsuitable for pallet manufacture on the one hand because it is very expensive and on the other hand because it is brittle and cannot cope with the mechanical demands made of it. Such unsuitable plastics materials could for example be polystyrene, acryl-butienestyrene and glass fibre reinforced plastics materials. These plastics are sensitive to impact, and therefore, they require considerable wall thickness, which makes the cost correspondingly high. Such pallets are therefore not competitive with cheap wooden pallets.
SUMMARY OF THE INVENTION The present invention is based on the problem of providing a pallet made from a plastic material having considerable shrinkage differential.
It is an object of this invention to provide a pallet made from a thermoplastic material such as polyethylene and, in order that the mutually corresponding recesses can also fit the matching projections when there is a considerable difference in the shrinkage between the upper part and lower part, special structural measures must be adopted.
According to this invention, a pallet comprises an upper part and a lower part, at least one of the parts including spacing pieces maintaining the parts in spaced relation, the upper part having a plurality of surfaces each of which interengages with one of a corresponding plurality of surfaces on the lower part. Each of the said inter-engaging surfaces extends in a direction parallel to or coincident with a radial line emanating from an axis essentially normal and common to the upper and lower part so as to restrain relative movement of the two parts in a direction transverse to the surfaces, and means for connecting the two parts together.
Preferably, one of each of the said plurality of interengaging surfaces comprises first locating means and the other surface comprises second locating means which locate along a path extending in the direction of the said radial line.
In one form, the first means comprises an elongate projection, wherein the second means comprises an elongate depression, the longitudinal axes of the said projection and depression being coincident with the said radial line and wherein the projection engages with and locates in the depression.
In another form, the first means comprises two elongate projections, the longitudinal axes of which are spaced one on each side of the said radial line, and parallel to the said radial line, wherein the second means comprises two elongate depressions the longitudinal axes of which are also spaced one on each side of the radial line and parallel to the said radial line and wherein the two projections engage with and locate in the respective depressions.
In yet another form, the first and second locating means each comprise racks of elongate teeth, the teeth in one rack engaging with and locating in the tooth spaces in the other rack.
Preferably, the first and second locating means each comprise two racks of elongate teeth and the longitudinal axes of the two racks of teeth are spaced one to each side of the said radial line and parallel to the radial line. It has been found expedient for the axis to be a central axis common to both the upper part and lower part.
If the shrinkage in the upper part amounts for example to 4% and approximately 2/2% in the lower part, then the shrinkage differential is 1/2% and in the case of a pallet to cm in length, this results in corresponding points in the upper part and lower part diverging in their position by approximately 1 to 1.8 cm.
The result of this is that spacer pieces which are provided cannot match each other and bores for screws have to be made substantially larger than the screws themselves. Since the material has a high rate of cold flow, normal simple screwing is impossible, since the screws would become repeatedly slackened and by virtue of the relatively large holes required, there would always be a displacement of the upper part in relation to the lower part. The thrust forces acting on a pallet could therefore not be absorbed by such a construction. This problem is reliably resolved by the construction proposed according to the invention. If sufficiently large screw holes, for example elongated holes, are provided in the upper part or lower part of the pallet, then with such constructions, even should these screws become slack due to cold flow of the material, the thrust forces would be absorbed by the positively inter engaging first and second locating means.
The invention further suggests that the under part and upper part of the pallet be constructed differently in ribbing and structure. By virtue of the upper part and lower part being of different constructions as compared with the known two-part pallet, both parts can be adapted to their particular tasks. The upper part must have a half-closed and fairly rigid surface for the goods which are to be placed on it, while the lower part is so shaped that access for a fork-lift truck is possible.
Whereas according to a further suggestion of the invention, the upper part is constructed with inwardly directed reinforcing ribs, the lower part has an encircling frame, the inside of which has no troublesome projections which protrude beyond the contours of the inside. The virtually smooth construction of the inside of the frame therefore permits easy application of a fork lift truck.
It has been found expedient for the upper part and lower part to be bolted to each other, there being at least in the spacer piece of the upper part or lower part an elongated aperture, the longitudinal axis of which coincides with one of the radiatingly extending lines. The bolting together of the upper part and lower part has been found to be a particularly sensible solution from the point of view of expenditure and success. The presence of the elongated holes guarantees that no finishing work on the upper part or lower part is necessary after the injection moulding process, bolting together being possible without any further work.
The invention further proposes that the projections or recesses in the spacer pieces be ribs or grooves, respectively. Such ribs and grooves can be easily and reliably produced and they can easily be so dimensioned that they have large areas positively engaging one another. Such ribs and/or grooves, like other corresponding disposed projections and recesses, guarantee that the upper part and the lower part always fit each other even if, due to differing shrinkage, the two parts are of different sizes. The deviations must occur so that the upper part and the lower part are geometrically similar to each other, one of the two parts being larger than the other. The two parts have a common center which is constituted by the center of the radiating lines. Since, by virtue of the geometrically similar enlargement or shrinkage of one part in relation to the other, the now mutually corresponding projections and recesses, in other words particularly the grooves and ribs, can have become displaced essentially in the direction of radiation only, it is ensured that the upper part and the lower part always fit each other.
The invention further proposes that the outside of the upper part be constructed to fit positively the outside of the lower part.
Such a construction ensures that the pallet according to the invention can be satisfactorily stacked. It is particularly advantageous for the outside of the upper part to have ribs disposed in the region of the edge, while the outside of the lower part has correspondingly shaped and disposed grooves. In addition to its stacking properties, such a pallet also has the advantage that the raised marginal zone can prevent goods placed on the upper part from slipping on the outside surface of the upper part. This is particularly convenient for the transportation of crates of bottles which, without the provision of an edge, could easily slip off the pallet, which they do in the case of the known pallet.
In order to facilitate entry by a fork lift truck, it is advantageous for the profile of the encircling frame and of the connecting crosspiece to be relatively flat and slightly convex.
The invention further proposes that the inwardly directed ribs of the upper part extend at least partially and substantially diagonally to the outer edge. Such an arrangement increases the stability of the pallet and its resistance to torsion.
Finally, the invention proposes that the lower part and the upper part of the pallet be at least substantially of the same size.
BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, of which:
FIG. 1 is a plan view of the upper part of the pallet;
FIG. 2 is a section on the line II-II in FIG. 1;
FIG. 2a is a section on the line Ila-lla in FIG. 1;
FIG. 3 is a side view of the assembled pallet;
FIG. 4 is a view of the underside of the pallet in the direction of the arrow IV in FIG. 3;
FIG. 5 is a side view of the lower part of the pallet;
FIG. 6 shows two inter-engaging spacing pieces of the upper part and lower part, in an exploded view;
FIG. 7 is a section through another form of embodiment of the spacer pieces;
FIG. 8 is a plan view of the surface of the lower spacer piece according to FIG. 7;
FIG. 9 is a plan view of the lower spacer piece according to FIG. 6;
FIG. 10 is a section through a further form of embodiment of the upper and lower spacer piece;
FIG. 11 is a plan view of the surface of the lower spacer piece according to FIG. 10;
FIG. 12 is a plan view of a construction of a frame piece of the lower part according to the arrow XII in FIG. 5;
FIG. 13 is a part of the edge according to the arrow XIII in FIG. 2;
FIG. 14 is a section along the line XIV-XIV in FIG. 12; and
FIG. 15 is a section along the line XV-XV in FIG. 13.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The pallet consists of two synthetic plastic parts, namely a lower part 1 and an upper part 2. The upper part 2 has spacer pieces 3 while the lower part has spacer pieces 4. By means of correspondingly disposed and shaped depressions and projections or inter engaging teeth, the spacer pieces 3 and 4 engage one another. FIGS. 6 to 11 show different embodiments of the positively inter-engaging corresponding spacer pieces 3 and 4.
In the common center 5 of upper part 2 and lower part 1 are spacer pieces, one of which carries a (not shown) cylindrical depression while the other carries a likewise not shown cylindrical stud which fits the depression. Thecenter 5 of these spacer pieces is at the same time the center of a number of radiatingly intersecting lines 6, 7, and 8. These lines pass through the spacer pieces 3 and 4 and form the lines of symmetry for the projections and depressions or inter-engaging teeth.
The upper part 2 of the pallet has an encircling edge 9 which is injection-moulded in one piece with connecting crosspieces 10. The areas between the edge 9 and the connecting crosspieces 10 are filled by means of a substantially diagonally disposed ribbed lattice II, the strengthening ribs 12 (see FIG. 2a) of which point into the interior of the pallet. A discontinuously encircling edge 13 is provided on the upper part of the pallet.
The lower part 1 (see FIG. 4) comprises an encircling frame 14 which is constructed in one piece with connecting crosspieces 15. Both the frame 14 and also the connecting crosspieces 15 have the slightly convex profile as shown at 16 in FIGS. 3 and 5. Externally encircling the underside of the frame 14 is a groove 17 (see FIGS. 12 and 14) which matches the edge 13 of upper part 2 in its shape and location. The groove 17, together with the edge 13, allow the stacking of empty pallet. To save on material, both the lower encircling frame 14 and also the connecting crosspiece 15 have apertures 18.
With regard to FIGS. 7 and 8, the upper spacer piece 3 has, disposed parallel with the radiating line 6, elongate projections or ribs 19 which engage in corresponding depressions or grooves 20 in the lower spacer piece 4. Also provided in the lower spacer piece is an elongated hole 21 while a hole 22 is provided in the upper spacer piece 3. A screw is passed through the hole 22 and the elongated hole 21, washers are fitted and then the two parts are bolted rigidly to each other.
FIGS. and 11 show a different form of locating means comprising racks of elongate teeth or serrations, the teeth or serrations on one part engaging in and loeating in the tooth spaces on the other part. There are two racks on each spacing piece arranged one each side of the radial line in a similar manner to the elongate projection and depressions shown in FIGS. 7 and 8.
Finally, FIGS. 6 and 9 show a further embodiment. Where this embodiment is concerned, the lower spacer piece 4 has a projection 23 which engages in the depression 24 of the upper spacer piece 3 when the pallet is in the assembled position. In the position of assembly, the shoulders 25 and 26a of the spacer pieces 3 and 4 rest on each other. The projection 23 is constructed as a rib. The depression 24 extends so that its walls 25 extend parallel with the line 6. With this embodiment also, an elongated hole 21 is provided in the lower spacer piece 4, while there is in the upper spacer piece 3 a hole 22. The upper part and the lower part are connected by means of screws 26, nuts 27 and washers 28.
The projection 23, which is constructed as an elongated rib, and the depression 24 have obliquely extending lateral flanks of the same inclination with respect to the vertical plane extending jointly through the line 6.
What I claim is:
l. A pallet comprising an essentially flat upper part and an essentially flat lower part, said upper and lower parts having a common axis normal to the load bearing surface of the upper part and to the upper surface of the lower part, at least one of the parts including spacing pieces for maintaining the upper and lower parts in spaced relation, the upper part having a plurality of protrusions or depressions in a lower surface thereof each of which interengages with one of a corresponding plurality of depressions or'protrusions on an upper surface of the lower part, each of a first group of said pluralities of said interengaging protrusions or depressions having an elongated longitudinal axis extending in a direction essentially along one of a plurality of radial lines projected from said common axis, and each of further groups of said pluralities of said interengaging protrusions or depressions having longitudinal axes extending in directions essentially along others of said plurality of projected radial lines, whereby relative movement of the two parts in a direction transverse to said surfaces is restrained, and means joining said upper and lower parts for connecting the two parts together while allowing limited relative movement therebetween.
2. A pallet according to claim 1 wherein the longitudinal axes of said protrusions are spaced one on each side of the said radial lines and parallel to the said radial lines, and the longitudinal axes of said depressions are spaced one on each side of the radial lines and parallel to the radial lines, said protrusions engaging with and locating in the respective depressions.
3. A pallet according to claim 1, wherein the protrusions and depressions each comprise racks of spaced, elongated teeth, the teeth in one rack engaging with and locating in the spaces in the other rack.
4. A pallet according to claim 3 wherein the protrusions and depressions each comprise two racks of elongate teeth and wherein the longitudinal axis of the two racks of teeth are spaced one to each side of the said radial lines and parallel to the radial lines.
5. A pallet according to claim 1 wherein each of the two parts includes spacing pieces and wherein the inter-engaging protrusions and depressions comprise surfaces of the spacing pieces.
6. A pallet according to claim 1, wherein the said normal axis is a central axis common to both the upper and the lower part.
7. A pallet according to claim 1, wherein the means for connecting the upper part and lower part together comprise bolts which pass through apertures in the spacing pieces and wherein the apertures in the spacing piece on at least one of the parts are elongated and have a longitudinal axis which coincides with one of said radial lines.
8. A pallet according to claim 1 wherein a peripheral edge portion of the upper part is formed to receive positively a peripheral edge portion of the lower part to facilitate stacking of pallets.
9. A pallet according to claim 8, wherein the peripheral edge portion of the upper part is formed with ribs and wherein the peripheral edge portion of the lower part is formed with corresponding grooves in which the ribs locate.
10. A pallet according to claim 1, wherein said upper part includes an essentially rectangular outer edge and inwardly directed ribs which extend at an oblique angle