GB2030066A - Casting foam plastics material - Google Patents

Abstract

Foam plastics material, is formed with a plurality of through holes by dispensing the foam forming materials into a mould pierced by a plurality of rods, which are withdrawn after the foam has set around them. This can be done with batch production in a pot mould (1), the lid (2) having an array of rods (3) depending from it, or with continuous production. In this case the ingredients are dispensed onto a conveyor (4) forming the floor of a tunnel (5). The rods (11) depend from an overhead loop (9), almost meeting the conveyor at an upstream zone (10) and being diverted away over a downstream zone, where the foam (6) will have set. The cushioning effect of the foam is improved by the reduction in density. <IMAGE>

Description

SPECIFICATION Improvements relating to foam plastics material This invention relates to foam plastics material.

It is primarily concerned with resilient foam plastics material in which the chemical interaction of the ingredients causes expansion to the final foamed state. The most common material in this field is polyether foam, but PVC and polyester foams are also produced in considerable quantities. The invention is also applicable to semi-rigid material such as foamed polystyrene.

These materials have many fields of application, one of the largest being the furniture industry. However, they are also needed for padding and packaging, for acoustic purposes, and for sponges.

It has long been the aim to reduce the density of such materials, but the approach hitherto has been almost entirely chemical.

But the best results from this still leave polyether foam, for example, with a density of about 1 4or per cu. ft. The aim of this invention is to reduce this density substantially without noticeably impairing the performance of the material, and indeed enhancing it in many respects. It will reduce material costs, increase the resilience, aid certain manufacturing processes, and improve the permeability to water or other fluids.

According to the present invention there is provided a method of making foam plastics material wherein the ingredients are mixed and solidify in an enclosure pierced by a plurality of rods subsequently removable from the solidified mass.

This method is readily applicable to the use of pot moulds, by which individual blocks of foam plastics material are produced. The pot mould is preferably provided with a lid or cover from the underside of which the rods depend. This enables existing moulds to be used. However, alternatives are possible and the rods could be upstanding from the floor of the mould, or extend through the sides, or there could be a combination of these arrangements. It is possible to have sets of different sized and shaped rods, perhaps at different spacings as well, so that a variety of hole patterns in the foam can be produced.

This method can be used both for "original" foam production, in which the ingredients are poured in a liquid state into the pot mould and chemical reaction causes them to expand around the rods, and also in the formation of reconstituted foam, in which the ingredients are fragments of previously foamed material and an adhesive.

For large production runs of a single type of foam material, the mixing, expansion and solidifying are generally done on a continuously moving substantially horizontal conveyor. In this technique, the ingredients are delivered by a mixing head moving back and forth across a moving web of paper. As the paper moves on the chemicals react and the material foams up until it achieves its ultimate expansion. It does this in the upstream section of a tunnel, and to shorten this section the foam is often laterally confined between non-adherent belts providing walls moving at conveyor speed. The paper is then pared away from underneath but the block of foam material continues down a further stretch of tunnel while the gases released by the chemical reactions are ducted away, possibly to be reused. As the block emerges from the tunnel, suitable lengths are cut off.

To produce such foam with pierced holes, the rods move with the conveyor over the section where the foam expands. They will then be withdrawn over a downstream section and returned upstream for re-use. The rods may be mounted on a movable belt, and during their working run they may simply hang vertically to terminate just above the moving paper, the gap being no more than an inch. The withdrawal may be achieved by guiding the belt up at a shallow angle over a run sufficient to lift the most downstream rods clear of the block. The slope must not be steep, for that would substantially alter the horizontal spacing of the rods, which is then determined by the foam material in which they are partially embedded. However, its resilience is such that it will tolerate the very small rod spacing difference engendered by a shallow sloping run.Alternatively, the block conveyor and the rod belt may both slope down over the foam expanding and setting zone, and over the rod withdrawal zone the block conveyor will continue down at the same slope while the rod belt reverses to incline upwards at the corresponding angle.

This will keep the same rod spacing throughout. When the rods are clear, they are carried back by the belt, lying substantially horizontally until they reach the ingredients' delivery zone, when they will be carried down and flop over to resume the vertical hanging position.

Alternatively, or even in addition, a moving block under formation may be pierced by rods entering laterally from one or both sides. Such rods will have to be mounted on carriers that travel with the conveyor, and which are diverted laterally away from the moving block downstream of the expansion zone. They will then be returned to the ingredients delivery zone and moved back over the conveyor.

For a better understanding of the invention some embodiments will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a diagrammatic vertical section through a pot mould, Figure 2 is a diagrammatic vertical longitu dinal section through apparatus for producing a continuous block of foam, and Figure 3 is a plan view of another continuous process apparatus.

In Fig. 1, a pot mould 1 has a lid or cover 2 from the underside of which depend a plurality of parallel steel rods 3. When the cover is properly placed, these rods extend virtually to the bottom of the mould. The ingredients for the foam material are either poured in with the cover open, and the cover is then closed over before any substantial expansion has occurred, or the mould or cover could be equipped with ducts and nozzles for dispensing the ingredients while the cover is closed.

In Fig. 2, the apparatus comprises a conveyor 4 which travels along the base of a tunnel 5 and supports a block of foam 6 as it is continuously foamed and during the gas release period. The foam ingredients are dispensed in known fashion from a mixing head 7 onto a paper web 8 providing a temporary floor over the upstream section of the conveyor.

In the roof of the upstream section of the tunnel there is supported a continuously driven belt 9, travelling at conveyor speed. Its lower run has an upstream portion that moves parallel with the conveyor over the foam expanding and setting zone 10, and a downstream portion which diverges upwardly from the conveyor. The conveyor has a continuous downslope over this section, while the downstream portion of the belt slopes upwards at the corresponding angle. The belt 9 carries an array of steel rods 11 which hang vertically from the lower run, terminating just above the paper web 8 over the zone 10. Downstream of this they are withdrawn from the block 6 by the divergence of belt 9 and conveyor 4, the respective slopes ensuring that the same rod spacing is maintained. The foam expands around the rods, and is left with a corresponding array of substantially through holes.When the lower skin is subsequently removed for scrap, the holes extend right through the - block.

The belt 9 carries the rods 11 back to the upstream end of the conveyor, during which they lie flat. As they reach the end of the upper run, they flop over and hang vertically again.

Fig. 3 shows diagrammatically a system for piercing the block from the sides. The rods 12 cannot now be freely pivoted on a belt; they have to be firmly supported to extend horizontally over the upstream section of the conveyor 13. A possible arrangement is shown, in which the rods are divided into groups on respective carriers 14, which alternate on either side of the conveyor. This enables a continuous array of holes to be formed in the foam and one or more carriers to be returning to the upstream end while the others are piercing the expanding foam and being withdrawn.

Foam produced by these methods may have its overall density reduced by 20% or even more. It loses none of its effectiveness, and is indeed more resilient and comfortable as cushioning, not only because there is less material to offer resistance but also because of the freer air flow allowed by the holes. An added advantage is that, for buttoned cushioning, the holes are ready-made.

Claims (22)

1. A method of making foam plastics material wherein the ingredients are mixed and solidify in an enclosure pierced by a plurality of rods subsequently removable from the solidified mass.

2. A method as claimed in claim 1, wherein the enclosure is a pot mould.

3. A method as claimed in claim 2, wherein the mould lid is provided with the plurality of rods depending therefrom.

4. A method as claimed in claim 1, wherein the ingredients are dispensed onto a moving conveyor at the upstream end of a tunnel-like enclosure, and the rods are arranged to travel with the conveyor.

5. A method as claimed in claim 4, wherein the rods span the tunnel substantially completely over an upstream section thereof and are gradually withdrawn over a downstream section thereof.

6. A method as claimed in claim 5, wherein at least some of the rods are carried by a closed loop over the tunnel and suspend therefrom during their working run over said sections.

7. A method as claimed in claim 6, wherein the conveyor carries the expanding, setting and solidified foam in a substantially straight path with a downward incline, the working run of the rods carried by the loop being parallel to the conveyor path over the upstream section and divergent therefrom with a corresponding upward incline over the downstream section.

8. A method as claimed in any one of the claims 4 to 7, wherein at least some of the rods are mounted on carriers at the sides of the tunnel to project laterally into the foam.

9. A method as claimed in claim 8, wherein each carrier has a group of rods, and the carriers alternate on either side of the conveyor.

10. A method of making foam plastics material substantially as herebefore described with reference to Fig. 1, Fig. 2 or Fig. 3 of the accompanying drawing.

11. Foam plastics material produced by the method as claimed in any preceding claim.

12. Apparatus for making foamed plastics material, including an enclosure for receiving the ingredients of said material and a plurality of rods projecting into said enclosure and removable therefrom when the enclosure contains a solidified mass of foam.

13. Apparatus as claimed in claim 12, wherein the enclosure is a pot mould.

14. Apparatus as claimed in claim 13, wherein the mould lid is provided with the plurality or rods depending therefrom.

15. Apparatus as claimed in claim 12, wherein the enclosure is a tunnel whose floor is a moving conveyor, with despensing means for the foam ingredients at the upstream end thereof, there being means carrying the rods for travelling with the conveyor.

16. Apparatus as claimed in claim 15, wherein the rods span the tunnel substantially completely over an upstream section thereof and means are provided for gradually withdrawing them over a downstream section thereof.

17. Apparatus as claimed in claim 16, wherein the carrying means include a closed loop over the tunnel, the rods suspending therefrom during their working run over said sections.

18. Apparatus as claimed in claim 17, wherein the conveyor travels in a substantially straight path with a downward incline, and the working run of the rods carried by the loop is parallel to the conveyor path over the upstream section and divergent therefrom with a corresponding upward incline over the downstream section.

19. Apparatus as claimed in any one of the claims 15 to 18, wherein the carrying means include carriers at the sides of the tunnel, the rods being arranged to project laterally into the foam.

20. Apparatus as claimed in claim 19, wherein each carrier has a group of rods, and the carriers alternate on either side of the conveyor.

21. Apparatus as claimed in any one of claims 12 to 20, wherein the rods are replaceable by others of different size and/or their spacing can be varied.

22. Apparatus for making foamed plastics material substantially as hereinbefore described with reference to Fig. 1, Fig. 2 or Fig.

3 3 of the accompanying drawing.