GB1322288A - Two-stage injection moulding method and apparatus for making rubber-soled footwear - Google Patents

Abstract

1322288 Moulding rubber soles UNIROYAL INC 19 Nov 1971 [23 Nov 1970] 53825/71 Heading A3B [Also in Division B5] Injection moulding apparatus for forming a rubber midsole (60, Fig. 4-6) against a lasted upper 22 under a first pressure and for form ing a rubber outersole (68, Fig. 6) against the midsole under a second higher pressure includes a mould defined by the lasted upper 22, a pair of movable sidewalls 12 and a sole plate 24 reciprocated by a fluidically operated piston 34. To form the midsole (60), rubber is injected from a gun 48 through a port 14 into the mould and the sole plate 24 is advanced under the first pressure to spread the rubber over the upper 22. The midsole is incompletely cured and the plate 24 is retracted. Rubber of a lower modulus is then fed from a gun 54 through a port 16 into the mould and the plate 24 is advanced under the second higher pressure to spread the rubber of lower modulus over the midsole to form an outer sole which together with the midsole is subsequently fully cured using electrical heating elements 71. The second higher pressure may be retained throughout the curing cycle or may be decreased after a predetermined time to the first pressure which is then maintained for the remainder of the cycle. The movement of the plate 24 is controlled by switches 42, 42a actuated by the guns 48, 54 respectively. The operation of the fluidic circuit which includes a low-pressure conduit 205a, a high-pressure conduit 204a, a timer 203, a switching valve 200 and venting and connecting valves 38, 40 is described. Twelve moulds may be uniformly distributed around a turntable.