GB2063146A - Mould for the production of seat- cushions - Google Patents

Abstract

A mould for the production of seat-cushions from an expanded material comprises two mould halves (2,3) which, when brought together, define an enclosed cavity for the reception and moulding of the expanded material; at least one of the mould halves consists of at least one sheet (3) of a thermoplastics material having a configuration corresponding to that of one part of the cushion. The sheet (3) can be supported on a layer (9) of an insulating material within a box-like member (8). <IMAGE>

Description

SPECIFICATION Mould for the production of seat-cushions The present invention relates to a mould for the cold moulding of seat-cushions in an expanded material, i.e. for the production of a shaped block of expanded material which can be covered with a layer of a covering material, such as a fabric or a skin, to produce a seat component.

Known moulds for producing such seatcomponents generally consist of two mould halves made of a metal, in particular of aluminium, irrespective of the nature of the material to be moulded therein.

Such moulds have numerous disadvantages.

The main problem is the high cost of the metal moulds which, generally speaking, are made by means of a pressure die-casting or drawing process.

Consequently, their manufacture requires specialised, delicate manufacturing technology.

Moveover, this technology belongs to the mechanical engineering sector as opposed to the plastics materials technology sector.

This makes the manufacturers of cushions dependent on the mould manufacturers, with the result that even modest modifications in or alterations to the shape of the cushions, which require changes in the shape of the moulds, come up against two obstacles, viz. high cost (modification to the shape of the cushions means the construction of new moulds) and long processing times (due to the dependence of the cushion manufacturer on the mould manufacturer).

The result is a lack of flexibility on the part of the seat-cushion manufacturer in meeting the demands of a market which is continually asking for new shapes of cushion.

Afurther disadvantage of the known metal moulds is considerable production wastage due to the fact that the expanded material has a tendency to stick to the walls of the mould.

In order to overcome this problem, anti-adhesives have been used. These are sprayed on to the surfaces of the walls of the mould each time a cushion is to be produced. This in turn results in the introduction of other problems, e.g.: - the need to clean the moulds at frequent inter vals; - the cost of the anti-adhesive material; - unsatisfactory productivity due to the time re quired (for anti-adhesive operation and for clean ing the moulds); - the endangered health of the operator through inhaling the material sprayed as an anti-adhesive agent.

The aim of the present invention is to overcome the problems mentioned above and to provide moulds in respect of which it is possible to change the shape at will and in a simple manner, thereby increasing flexiblity of manufacture in relation to market demand and also increasing the productivity of the moulds.

Thus, the present invention provides a mould for the production of seat cushions from an expanded material, the mould comprising two mould halves which, when brought together, define an enclosed cavity for the reception and moulding of the expanded material, in which at least one of the mould halves consists of at least one sheet of a thermoplastics material having a configuaration corresponding to the shape of one part of the cushion.

The present invention will be illustrated, merely by way of example, in the following description and with reference to the accompanying drawings, wherein: Figure 7 is a cross-sectional view of the basic elements of a mould in accordance with the present invention; Figure2 is a cross-section of a complete mould in accordance with one embodiment of the present invention; Figure 3 is a cross-section of a mould in accordance with a second embodiment of the present invention, and Figure 4 is a cross-section of a mould in accordance with a third embodiment of the present invention.

As can be seen in Figure 1, a mould 1 consists of two mould halves 2 and 3 which can be brought into contact with each other. When broughttogether, the mould halves define a cavity 4 in which the cushion of expanded material is produced.

Mould half 2 consists of a flat sheet of rigid material. Mould half 3 consists of a sheet of a thermoplastics material, so shaped that its inner surface 5 has a configuration which corresponds to that required for the external surface of the moulded product.

Preferably, the sheet of thermo-plastics material which forms mould half 3 has anti-adhesive properties relative to the material to be moulded. For example, the thermo-plastics material which forms mould half 3 can consist of polyethylene or polypropylene.

Mould half 3 is produced by placing a flat sheet of a thermo-plastics material on a rigid surface (e.g. of wood) shaped according to the configuration which it is desired to impart to the mould half and heating the said sheet to a temperature which exceeds its softening temperature. The mould half 3 is provided with an edge portion 6, whereby its surface which is to abut mould half 2 is parallel to the surface 7 of the said mould half 2 in order to ensure a seal between the two mould halves when they are brought together to close the mould.

The mould shown in Figure 2 comprises, in addition to the elements present in the embodiment illustrated in Figure 1, box-type shell 8 containing the shaped sheet 3.

A thermo-insulating layer 9 consisting, for example of a mass of glass fibres, or a mass of an expanded material such as a rigid polyurethane or a phenolic resin, or a mass of compacted material such as an epoxy resin, a polyester or a polyether, is inserted between shaped sheet 3 and the box-type structure 8. The layer 9 is also adapted to support the shaped sheet 3 and to give it increased rigidity As stated previously, the sheet of thermo-plastics material comprising mould half 3 forms the entire mould half, including the edge portion 6 of the latter where mould half 3 is to contact mould half 2.

We have found that, in order to provide a sharp transition between the mould half 3 and the edge portion 6, it is preferable to make the two aforementioned elements separately and then to join them firmly together, for example, by glueing. The mould illustrated in Figure 3 is made in this way.

As can be seen in Figure 3, the edge portion 6 of mould half 3 comprises a member 10 made of a material which possesses a certain degree of adhesiveness relative to the expanded material to be moulded and is covered with a film of an antiadhesive material.

For example, member 10 can be made of a metal, for example steel, and covered with a film of polytetrafluoroethylene.

The shaped sheet of thermo-plastics material constituting mould half 3 is able to withstand the mechanical stresses which are generated as a result of pressure produced in the mould during the expansion of contents. The capacity of mould half 3 to withstand the mechanical stresses also depends on the thickness of the said shaped sheet and on the presence of the layer 9 of insulating material.

The mould illustrated in Figure 4 is to be used if the pressures produced inside the mould are relatively high or if it is desirable for the mould half 3 to be relatively thin, for optimum shaping of the said mould half, or to reduce the cost to a minimum, or both.

As can be seen in Figure 4, the mould is provided with a plurality of rigid support members 11 placed between the box-type structure 8 and the mould half 3.

By using a shaped sheet of thermo-plastics material for the mould half 3, the production of the said mould half can be carried out by the cushion manufacturer, who already possesses the relevant technology.

In addition, the possibilities of modifying mould half 3 are practically unlimited and extremely simple to carry out and therefore permits considerable flexibility for the cushion manufacturer in relation to market demand.

Also, with the mould in accordance with the present invention, cushions can be obtained with a surface which is much smoother than that which can be obtained by using known moulds. This is probably due to the fact that with the moulds in accordance with the present invention, the operation of applying an anti-adhesive to the mould is eliminated. Moreover, this improves the quality of the cushions themselves.

Finally, the cost of the mould is considerably reduced since it is limited to the cost of a pattern (male or female) in wood, the cost of the sheet of thermo-plastics material and the cost of the process of shaping the said sheet of thermo-plastics material.

Claims (7)

1. A mould for the production of seat cushions from an expanded material, the mould comprising two mould halves which, when broughttogether, define an enclosed cavity for the reception and moulding of the expanded material, in which at least one of the mould halves consists of at least one sheet of a thermo-plastics material having a configuration corresponding to that of one part of the cushion.

2. A mould according to Claim 1, in which the surface of the sheet of thermo-plastics material which is to face the cavity of the mould possesses anti-adhesive characteristics relative to the expanded material.

3. A mould according to Claim 1 or 2, in which the sheet of thermo-plastics material is attached to a box-type element and a layer of a thermo-insulating material is placed between the said sheet and the box-type element.

4. A mould according to Claim 3, in which the thermo-insulating material is a rigid expanded material.

5. A mould according to Claim 3, in which the thermo-insulating material is a rigid compacted material.

6. A mould according to Claim 3, in which a plurality of rigid support members are embedded in the thermo-insulating material between the sheet and the box-type element.

7. A mould for the production pf seat cushions, substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings.