GB859314A - Improvements in and relating to expanded plastic materials produced by moulding, andto the manufacture of articles from them - Google Patents

Abstract

859,314. Moulding expanded plastic materials. BOURGOIS, J. Nov. 4, 1957 [Nov. 9, 1956 ; Jan. 18, 1957 ; May 7, 1957], No. 34313/57. Class 87(2). [Also in Groups XIV and XXXI] Plastic material is expanded by heating it in an apertured mould whilst subjecting it to a stressing pressure controlled by means responsive to the internal pressure developed in a closed pilot mould which is subjected to the same conditions of heat as is the apertured mould, and which curtains a charge of the same composition. The plastic material, e.g. polyvinyl chloride, polystyrene, polyethylene, polyurethane, ethoxylinic resin, or silicone material, may be expanded in an autoclave 7, Fig. 3, in light-weight moulds having apertures communicating with the autoclave interior, whilst controlling the pressure by introducing air into the autoclave 7 through an electrically operated valve 34 in response to the increase in pressure in a pilot mould 30 containing a predetermined quantity of the plastic material. The expansion of the material in the pilot mould 30 causes a metal diaphragm 31 to engage an electrical contact 32 to energise a relay to open the valve 34. The resulting increase in pressure in the autoclave disengages the diaphragm 31 from the contact 32 until the pressure within the pilot mould 30 again rises above that in the autoclave. The pressure acting upon the light weight moulds is thus maintained substantially the same as that within the pilot mould. In applying the method to the manufacture of a padded arm rest comprising a perforated sheet metal plate covered with expanded plastic material the perforated plate 14, Fig. 7, is arranged as the top wall of a mould 18 having clamped thereto a peripheral inverted L-shaped member 19 forming a passage through which the charge 22 in the mould may expand. The parts 18 and 19 are coated with a plastisol before the charge 22 is introduced into the mould and expansion effected in the autoclave 7, so that the finished arm rest has an outer non-cellular skin 16, Fig. 8, covering the sponge material 15 anchored to the plate 14 at the perforations 17. The plate 14 may, alternatively, be embedded completely in the plastic material. A motor cycle saddle may be made in the same manner as the arm rest. There is also described the manufacture of a vehicle seat or back rest having springs embedded in expanded plastic material. The moulding of several other articles is referred to, including that of a toroid of resilient cellular material for replacing the inner tube of a pneumatic tyre.