EP1845023A1 - Plastic palette with foamed cover plate - Google Patents

Abstract

The palette (1) has even and rectangular single piece cover plates (2, 3) and a set of carrier units (4) that is arranged on a lower edge of the plate and arranged to facilitate interference of fork-lift tooth. The cover plates are made of a foamed plastic material. The carrier units have a cross section structure, where thickness of each cover plate is 30 millimeters. An independent claim is also included for a method for producing a carrying body or a container with carrier or cover plates.

Description

The patent application relates to a pallet for storage and transport of goods according to the preamble of claim 1, and a method for producing such a pallet according to the preamble of the independent method claim.

Pallets for storage and transport of goods and goods of all kinds are known per se. Such a pallet consists essentially of a cover plate and a plurality of support elements, for example. In the form of support feet or support runners, which are arranged below this cover plate and form a defined distance of the cover plate to a support surface. These support elements are arranged on the underside of the cover plate such that the engagement of forklift tines o. The like. Is made possible. In addition to these single deck pallets, so-called double deck pallets are also known from the prior art, which comprise an upper cover plate (upper deck) and a lower cover plate (lower deck), wherein the support elements serve as a kind of spacer of the two cover plates and at the same time a cavity for the engagement of Form forklift tines between these two cover plates. Such double deck pallets offer the advantage that they can be used on both sides (also referred to as reversible).

The cover plates of the pallets described above are either multipart z. B. in the form of several on the support feet or support skids supporting slats or integrally formed. Common materials for pallets are wood, metals and increasingly also plastics. Plastic pallets offer the advantage that they are relatively light and weather-resistant. Other advantages of plastic pallets are their easy cleaning and disinfection options, which is why such pallets are also very popular for cleanrooms or in the food industry.

In plastic pallets with integrally formed cover plates, these are not made solid but ribbed for weight reasons, wherein the support ribs are arranged on the underside of the cover plate. To form the support ribs in the manufacturing process corresponding contours in the tool, eg. An injection mold, provided.

As a result of material concentrations in the foot areas of the support ribs and at the crossing points of support ribs, uneven shrinkage or voids formation occurs in the manufacturing process during cooling of the liquid polymer melt, which reduces the strength and thus significantly the load capacity of the pallet and / or poses as a geometry error the flat and smooth top of the cover plate is visible (for example, in the form of craters or furrows), which areas are then also correspondingly difficult to clean. In double-deck pallets furthermore has the disadvantage that they can not be produced in one operation, but the upper and lower cover plate made separately because of their support ribs as a partial body and then must be welded together.

The object of the invention is to provide a plastic pallet, which has improved strength properties, and to provide a simplified method for producing such a plastic pallet.

The object is achieved by a pallet according to claim 1 and a manufacturing method according to claim 13. The respective dependent subclaims indicate advantageous development of the pallet or the manufacturing process.

In which at least one cover plate and preferably both cover plates are formed in a double deck pallet made of a foamed plastic material, a lightweight but nevertheless stable and sustainable construction results. By using different propellants for the foaming process, the porosity and thus the load capacity of the cover plates can be quasi adjusted. As such out Cover plates formed of a foamed plastic material can do without support ribs completely, also eliminates the associated problems and disadvantages (as explained above). In particular, a pallet according to the invention has flat and smooth tops of the cover plates, which are free from geometrical errors.

In an advantageous embodiment, the cover plates are surrounded by a plastic skin, so to speak enclose the foamed plastic material, so that there is a closed and preferably smooth surface that is easy to clean or disinfect and on which the goods and goods to be transported very well put up or hang up. The plastic skin is advantageously formed of the same material as the plastic foam and connected by material connection with this. The surface of the cover plates can be roughened to increase the coefficient of friction μ.

To save weight, the support elements (or support feet or the support skids) are provided with holes extending in the height direction, advantageously such that there is a honeycomb-like cross-sectional structure of the support elements. The shape of the individual honeycombs is advantageously rectangular, but can also be other forms z. B. be circular or polygonal. The holes are suitably designed to extend over the entire height of the pallet, i. H. through the cover plate or cover plates and their surfaces. An advantageous thickness for such cover plates is a value of 10 to 50 mm, preferably 20 to 40 mm, in particular the thickness of the cover plate is 30 mm, possibly plus a tolerance of +/- 5 mm.

In the case of a single-deck pallet, this included a plurality of support elements, which are designed as support skids or as support feet. Conveniently, three rows of three support feet are arranged on the underside of the cover plate. Two rows extend advantageously along parallel longitudinal edges of the cover plate and the third row is for this purpose arranged substantially centrally. Of course, more than three rows of support elements may be included or only two rows. Similarly, a set of support feet can be more be formed as three support feet or only two support feet. In a particularly advantageous embodiment of the pallet is provided that a support foot is arranged in the region of the center of gravity of the cover plate, resulting in a particularly good support for the cover plate in this often critical area.

In an advantageous development of the pallet according to the invention, this has two cover plates, which are designed as upper cover plate (upper deck) and lower cover plate (lower deck) and which are spaced from each other by the support elements. The two cover plates include, together with the support elements, a cavity open to the side surfaces of the pallet, which is provided for the engagement of forklift tines or the like.

In a particularly advantageous embodiment, the double-deck pallet has identically formed cover plates which are mirror-inverted to an imaginary vertical plane of the pallet (i.e., a plane which extends parallel between the two cover plates, which are also parallel (surface-parallel) to one another).

Conveniently, the support elements are formed of the same plastic material as the cover plates. It is particularly advantageous if the pallet as a whole is integrally formed from this plastic material. As plastic materials are polyethylene (PE) or polypropylene (PP) are used, wherein the plastic materials with one or more additives such. As dyes, foaming agents, blowing agents, etc. may be provided.

The production method according to the invention, which is preferably to be used to produce the previously described pallets, provides that the molten plastic material, in particular propellant, is introduced into a casting mold to form the cover plates, this casting mold comprising at least two tool plates which at the same time form part form the shape contour (cavity). After the introduction of the molten plastic material in the mold contour, it comes to these advantageously cooled tool plates, which form the surface and the lower surface of the cover plate for solidification of the plastic material, so that a skin forms around the still liquid plastic melt around. In a second method step, the distance between these two tool plates is increased, whereby the still liquid plastic melt as a result of the propellant and now provided Aufschäumvolumens foams existing in the mold cavity and thereby forms the cover plate, while maintaining the already formed skin. Of course, it is also possible to use more than two tooling plates to produce a cover plate of the type described above.

By evacuating the contour of the mold substantially simultaneously with the increase in the spacing of the tool plates, the foaming effect can advantageously be enhanced.

By foaming the plastic, in particular the heat energy contained in the melt is converted into mold energy, whereby the cooling effort for the tool is reduced, and also an advantageous short production cycle time is achieved.

Conveniently, the distance of the tool plates during the moving apart by ten to twenty times, preferably increased by fifteen times. With these numerical values, particularly stable cover plates could be created in preliminary tests.

It should be noted at this point that the manufacturing method of the invention provides only the foaming of the cover plates, while the support elements are made non-foamed, but with the honeycomb structure described above. For the production of this honeycomb structure corresponding known from the prior art cores are advantageously used, which are introduced into the tool at the designated places.

It is envisaged that the manufacture of the pallet will essentially take place by means of an injection molding process developed further in the above sense.

A significant advantage of the manufacturing method described above is that in particular the double deck pallets can now be produced in one operation. By eliminating the rib structure, the use of ordinary cores, which form the cavity for the engagement of the forklift tines between the cover plates, is now sufficient. This results in a total over the prior art, a significant simplification of the manufacturing effort.

Fig. 1:

eine Doppeldeckpalette in einer perspektivischen Ansicht auf die obere Deckplatte,

Fig. 2:

die Doppeldeckpalette der Fig. 1 in einer perspektivischen Ansicht auf die untere Deckplatte und

Fig. 3:

einen Schnitt durch eine Deckplatte einer Palette gemäß der Fig. 1 oder 2.

Further features and advantages will become apparent in a non-restrictive manner from the description of an embodiment with reference to the figures. Show:

Fig. 1:

a double deck pallet in a perspective view on the upper cover plate,

Fig. 2:

the double deck pallet of Fig. 1 in a perspective view of the lower cover plate and

3:

a section through a cover plate of a pallet according to the Fig. 1 or 2.

Fig. 1 shows a designated double deck pallet 1 in a perspective view from a viewing direction obliquely from above. The pallet 1 has an upper cover plate 2, which is also referred to as upper deck and a lower cover plate 3, which is also referred to as lower deck. The cover plates 2 and 3 are each formed with a flat and closed top, with their undersides are formed substantially flat and closed. Both cover plates 2 and 3 can be used as support plates for goods or goods (reversible pallet). The two cover plates 2 and 3 are arranged substantially surface parallel to each other and connected by a total of nine support members 4 and spaced apart. These mirror-image formed support plates 2 and 3 and the support elements 4 define a cavity in the form of engagement slots 5a and 5b on the side surfaces of the pallet 1, which are provided for the intervention of forklift tines o. The like. And formed over the entire length or width of the pallet continuously are. Of course, more or fewer than nine support elements 4 may be provided in an alternative embodiment. In the case of a single-deck pallet, the support elements 4 correspond to the support feet or support skids.

In the illustrated embodiment, the support elements 4 are arranged in three rows of three support elements, wherein the support elements in the outer areas flush with the side edges of the cover plates 2 and 3 complete. Of course, in an alternative embodiment, the support elements can also be set back in relation to these outer edges. A single support element 4 is arranged in the centroid of the cover plates 2 and 3, resulting in a particularly advantageous support in this area, especially since often the largest load forces occur at this point in the loading case. The support elements 4 have a kind of honeycomb-like structure through holes, these holes in and over the entire pallet height d. H. also extend through the cover plates 2 and 3 and their closed tops. This honeycomb-like structure is designated 6 in FIGS. 1 and 2 and serves primarily to save weight, but also to avoid material concentrations which can lead to the problems of voids formation already described above.

As shown in FIGS. 1 and 2, the pallet 1 is made in one piece. As materials preferably polyethylene (PE) or polypropylene (PP) are used, wherein the plastic material may be mixed with a color additive. By the way, all the plastic materials used are very easy to recycle.

The cover plates 2 and 3 are formed of foamed plastic material. Fig. 3 shows a cross section through an upper cover plate 2, wherein subsequent Designs apply equally to the lower cover plate 3. The cover plate 2 has inside a foamed and denoted by 7 plastic material, which is surrounded by a plastic skin 8 of the same plastic material, the skin 8 is materially connected to the foamed plastic material 7. Despite its low weight, such a sandwich construction has a high rigidity and strength, so that the cover plate 2 as a whole is made stable and has a high load-bearing capacity. Only the cover plates 2 and 3 are formed of foamed plastic material, but not the support elements 4, which have the honeycomb-like structure. In Fig. 3, a support member 4 with the honeycomb structure 6 (dashed lines) is shown in the left image area.

The pallet shown in FIGS. 1 and 2 has by way of example a length of 1200 mm, a width of 1000 mm and a height of 165 mm.

Preferably, the pallet described above is to be produced by means of the manufacturing method described below, for which protection is also desired. According to this production method, it is provided that the liquid plastic melt, which may be mixed with additives such as dyes or foaming propellants, is introduced into a mold contour (cavity), this mold contour having parallel tool plates which form the top and bottom of a cover plate 2 or 3 depict. For the production of a double deck pallet, the production tool accordingly has four such tool plates. The significantly defined by the two mold plates part contour for a cover plate 2 or 3 is filled in a first step mold filling with the plastic melt, wherein the liquid plastic melt solidifies on the cooled mold plates and around the still liquid melt around the skin 8 is formed.

In a second step, the distance between these two tool plates and thus the volume of the part contour is increased, wherein the propellant contained in the plastic material foams the still liquid phase melt until the enlarged part contour completely filled with foamed plastic material is, without prejudice to the skin 8, which has already formed on the cooled mold plates. The foaming effect can be promoted by the application of a vacuum (evacuation), wherein corresponding vacuum pumps are connected to the tool and the partial mold contours for the cover plates 2 and 3. After solidification, preferably within the tool, a dimensionally stable sandwich structure according to FIG. 3 has formed, wherein the skin 8 has formed a closed, smooth surface around the foamed plastic material 7.

The plastic material has a temperature of about 220 ° C when introduced into the mold contour. During the foaming process no plastic material is usually tracked. The distance between the two tool plates is increased by about fifteen times when moving apart. If the distance between the two tool plates when introducing the molten plastic material, for example, realistic 2 mm, the distance to foaming is increased to about 30 mm, which then also corresponds to the thickness of the cover plate.

For the formation of the honeycomb structure 6 of the support elements 4 as well as for the formation of the engagement slots 5a and 5b corresponding cores are arranged in the tool, the use of such cores belongs to the prior art and is therefore known in the art. As already described above, the support elements are not made of foamed plastic material for reasons of strength.

As already described above, the pallet in question is manufactured in one piece in one operation, regardless of whether it is a single-deck or double-deck pallet. Due to the one-piece production in one operation, a substantially shorter cycle time and a higher output are achieved compared to the known production methods.

Advantageously, the manufacturing method described above is performed on a modified injection molding machine.

Claims (19)

Pallet comprising at least one flat and preferably rectangular and one-piece cover plate (2), and a plurality of arranged at the lower edge of this cover plate support members (4) which are arranged to each other to allow the intervention of forklift tines o. The like.,
characterized in that
this at least one cover plate (2) is formed from a foamed plastic material (7). Pallet according to claim 1,
characterized in that
the foamed plastic material (7) of the at least one cover plate (2) is surrounded by a plastic skin (8) and thus has a closed and preferably smooth surface. Method according to claim 2,
characterized in that
the plastic skin (8) is formed of the same material as the plastic foam (7) and is preferably connected by material connection with the plastic foam (7). Pallet according to claim 1, 2 or 3
characterized in that
the support elements (4) at least partially have a honeycomb-like cross-sectional structure (6). Pallet according to one of the preceding claims,
characterized in that
the thickness of the at least one cover plate (2) is 10 to 50 mm, preferably 20 to 40 mm and in particular 30 mm. Pallet according to one of the preceding claims,
characterized in that
the support elements (4) are arranged in three rows, each row preferably comprising two, in particular three support elements. Pallet according to one of the preceding claims,
characterized in that
a support element (4) in the centroid or in the region of the centroid of the at least one cover plate (2) is arranged. Pallet according to one of the preceding claims,
characterized in that
the pallet is designed as a reversible double-deck pallet (1), wherein two cover plates (2, 3) spaced apart by the support elements (4) are included which enclose a cavity intended for the intervention of forklift tines or the like and both cover plates (2 , 3) are formed from the foamed plastic material (7). Pallet according to claim 8,
characterized in that
the two cover plates (2, 3) are formed identically and the pallet (1) is constructed in mirror image. Pallet according to one of the preceding claims,
characterized in that
the support elements (4) are formed of the same material as the cover plates (2, 3). Pallet according to one of the preceding claims,
characterized in that
the pallet is integrally formed of a plastic material. Pallet according to claim 11,
characterized in that
the plastic material is polyethylene or polypropylene, preferably including several additives. Method for producing a supporting body or a container with a supporting or cover plate (2, 3) having a foamed plastic material (7), preferably a pallet and in particular a double-deck pallet (1) according to one of claims 1 to 12,
characterized in that
in a first step to form the support or cover plate (2, 3) the molten and mixed with additives plastic material is introduced into a mold contour with two spaced tool plates and solidifies to form a skin on these tool plates, said tool plates significantly the part contour for the Cover plate (2, 3) defined, and
in a second step, the distance between these two tool plates is increased, whereby the still liquid plastic material foams. Process for the preparation according to claim 13,
characterized in that
At the same time as enlarging the distance of the tool plates, a vacuum generated by means of vacuum pumps is formed in the mold contour to enhance the foaming effect. Process for the preparation according to claim 13 or 14,
characterized in that
the movable tool plates are cooled, preferably by means of a water cooling. Method for the production according to one of claims 13, 14 or 15,
characterized in that
the distance of the tool plates by ten to twenty times, preferably increased by fifteen times. Method according to one of claims 13 to 16
characterized in that
the object in question is manufactured in one piece in a sequence of operations. Process for the preparation according to one of claims 13 to 17,
characterized in that
Cores for shaping the honeycomb-structured support elements (4) and the engagement slots (5a, 5b) are provided in the corresponding casting tool. Process for the production according to one of claims 13 to 18,
characterized in that
the manufacturing process is performed substantially on a corresponding modified injection molding machine.

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