EP0082685A1

EP0082685A1 - Packaging cushions and method of making cushioning material

Info

Publication number: EP0082685A1
Application number: EP82306737A
Authority: EP
Inventors: Clifford Malcolm Rawlinson
Original assignee: STAKEHILL ENGINEERING Ltd
Current assignee: STAKEHILL ENGINEERING Ltd
Priority date: 1981-12-16
Filing date: 1982-12-16
Publication date: 1983-06-29

Abstract

A packaging cushion consists of a soft flexible slab 1 of, for example, foamed pvc which can be held in place by pieces of magnetic rubber 2 included in the cushion. Moulding techniques are described which overcome practical difficulties of manufacture.

Description

The invention relates to packaging cushions for protecting finished steel articles from damage in transit and storage. The invention also includes a method of making cushioning material.
Pressed steel articles which may or may not be painted, such as motor-car panels, refrigerators, cookers, etc are easily scratched during handling and some form of protective packaging is generally employed. Often, the articles are packaged in cardboard boxes and supported and separated by polystyrene blocks. Such packaging is time-consuming and can be expensive. Furthermore, the packaging volume required to protect complex shapes can be excessive. Generally, padding is required only over protruding parts of the articles. Therefore, it is desirable to be able to apply cushioning pads at selected parts only. The present invention seeks to provide a packaging cushion material which may be applied selectively to finished steel articles without damage to the finish.
. According to one aspect of the invention there is provided a packaging cushion comprising a slab of soft flexible plastics material forme to include one or more magnets arranged to allow the cushion to flex and adhere by magnetic attraction to a ferromagnetic surface.
The material of the magnet or magnets may be of magnetic rubber, by which is meant material which is flexible and magnetic; generally composed of natural or synthetic rubber which binds particles of magnetized ferrite. It is necessary that the magnetic effect should be distributed across the cushion. Thus, if magnetic rubber is used, a single magnetic strip may be employed. Generally, however, there will be a plurality of magnets in the cushion, distributed in a matrix. With such an arrangement the magnets may be pieces of magnetic rubber or may be solid magnets of, for example, ceramic ferrite material.
Whereas magnetic rubber may be disposed at the surface of the slab, it is preferred that if solid magnets are employed, they should be contained wholly within the plastics material, or at least held in recesses therein. The word "include" as used herein is to be interpreted accordingly.
The plastics material employed may be a cold- cured material such as polyurethane, ir a heat-cured material such as polyvinylchloride (pvc). The latter material has the advantage that it is relatively inexpensive and free of fire-hazards. Also, it can be foamed to give a particularly effective cushion. However, one serious disadvantage was found in practice. This was that the integrity of the moulding was damaged during heat-curing. Experiments showed that this was due to the unexpected effect of the emission of gases from the magnets when subjected to heat. This applied both to magnets made of magnetic rubber and magnets made of ceramic material. A second aspect of the invention takes account of this discovery.
According to a second aspect of the invention there is provided a method of making a packaging cushion material consisting in taking a mould with a ferro- magnetic base, placing one or more magnets on the base, to be held by magnetic attraction, either with or without a spacer between the or each magnet and the base, filling the mould with a heat-curing soft plastics material, heat-curing the material so that it includes the magnets by moulding, and taking measures to avoid the formation of gas bubbles in the material resulting from gases given off by the magnet or magnets during curing.
The measures above-mentioned may comprise (a) a preliminary de-gassing step whereby the magnet or magnets are held at an elevated temperature to drive off gases; and/or (b) the provision of vent holes to vent the gases as they are driven off during curing. The magnet or magnets themselves are provided with holes and/or channels for venting purposes.
The invention will further be described with reference to the accompanying drawings, of which:-

Figure I is a perspective view of a packaging cushion in accordance with the invention;
Figure 2 is a perspective view of another packaging cushion in accordance with the invention;
Figure 3 is a diagram illustrating the method of manufacture of the cushion of Figure 1; and
Figure 4 is a cross-sectional diagram illustrating the manufacture of another cushion in accordance with the invention.

Referring to Figure 1 there is shown a packaging cushion constituted by a slab 1 of soft, foamed polyvi^pylchloride. Moulded in to one face of the slab are four rectangular pieces 2 of magnetic rubber material. The cushion is flexible and will adhere by magnetic attraction to a ferro-magnetic surface. The cushion will shape itself to a curved surface and can be applied where necessary to protect a finished steel product against abrasion during storage or transit. Typically, the magnetic pieces 2 are lmm x 3cm x 4cm. The cushion in this example is 7mm thick. Clearly, other dimensions can be employed.
Figure 2 shows another embodiment in which instead of discrete pieces of magnetic rubber there is provided a continuous strip 3 at the surface of the cushion.
Figure 3 shows one stage in the manufacture of the cushion of Figure 1. A steel mould tray 4 is of such a size as to accommodate a number of such cushions. The tray may be 2m'x 1m, for example. Only one corner is shown in Figure 3. Through the base of the tray there are provided a number of pairs of vent holes 5. In the manufacture of the cushions, first the rubber magnets 2 are laid over the pairs of vent holes in the base of the tray, after being roughened and cleaned with a solvent. Then a pvc mixture including a foaming agent is poured into the tray and the whole is inserted into an oven for heat-curing at 200°C for 20 minutes. During this treatment gases are driven off from the magnets, but the gases can escape via the vent holes 5, and large bubbles do not form in the pvc. The moulded slab can then be cut into individual cushions.
As a preliminary step it may be preferable to stabilise the magnetic material by subjecting it to a temperature of 50 - 60°C for about 12 hours.
Figure 4 shows manufacture of another cushion in accordance with the invention. Here the magnets are of ceramic ferrite material. Only one magnet 6 is shown in Figure 4 but it will be appreciated that there are a number arranged in a matrix.
In this example the steel mould tray 4 has upstanding pads 7 formed in its base. The pads are of the same diameter as the magnets and the magnets are initially set in place on the pads, to which they are magnetically attracted. Then the pvc material 8 is poured into the tray and cured by heat as described above.
Each magnet has a central vent hole 9 which aligns with a similar hole 10 in the pad 7 to allow gases to escape. While the upper end of hole 9 is shown open, it may alternatively be a blind hole. Other vent holes 11 may be provided around the periphery of the pads 7.
It will be noted that the magnets are provided with a flange 12 to key them in to the pvc. The magnets will be held below the surface of the cushion, effectively in recesses, to prevent contact with the surface being protected.
It is to be understood that the invention is not restricted to the details of the embodiments described above. In particular, the invention may employ cold- cured plastics such as polyurethane. Injection moulding or extrusion moulding techniques may be employed.

Claims

1. A packaging cushion comprising'a slab of soft flexible plastics material formed to include one or more magnets arranged to allow the cushion to flex and adhere by magnetic attraction to a ferromagnetic surface.

2. A packaging cushion as claimed in claim 1 wherein there are a plurality of magnets arranged as a matrix across the slab.

3. A packaging cushion as claimed in claim 2 wherein the magnets comprise pieces of magnetic rubber material inset at or very near one face of the slab.

4. A packaging cushion as claimed in claim 2 wherein the magnets comprise ceramic magnets included wholly within the slab.

5. A packaging cushion as claimed in any of the preceding claims wherein the material of the slab is a heat-cured material.

6. A packaging cushion as claimed in claim 5 wherein the heat-cured material is polyvinly-chloride (pvc).

7. A packaging cushion as claimed in claim 6 wherein the pvc is foamed.

8. A packaging cushion as claimed in any of claims 1 to 4 wherein the material of the slab is polyurethane.

9. A method of making a packaging cushion material consisting in taking a mould with a ferro- magnetic base, placing one or more magnets on the base, to be held by magnetic attraction, either with or without a spacer-between the or each magnet and the base, filling the mould with a heat-curing soft plastics material, heat-curing the material so that it includes the magnets by moulding, and taking measures to avoid the formation of gas bubbles in the material resulting from gases given off by the magnet or magnets during curing.

10. A method as claimed in claim 9 wherein said measures comprise a preliminary de-gassing step whereby the magnet or magnets are held at an elevated temperature to drive off gases.

11. A method as claimed in claim 9 or claim 10 wherein said measures comprise the provision of vent holes to vent the gases as they are driven off during curing.

12. A method as claimed in claim 11 wherein the magnet or magnets themselves are provided with holes and/or channels for venting purposes.