Patent GB-1054920-A (GB)
IPC: B29C49/06
Abstract: 1,054,920. Injection-blow moulding apparatus. E. P. MOSLO. Dec. 30, 1963, No. 51218/63. Heading B5A. An injection-blow moulding apparatus comprises a parison mould located between two blow moulds and a pair of cores or mandrels carried by a support which reciprocates between two positions in which one of the mandrels is in the parison mould and the other in one of the blow moulds. The injection apparatus includes compressing means actuable to subject the plastics material to pressure and valve means responsive to electrical control means to prevent injection of the plastics for a predetermined time after actuation of the compression means. As described the apparatus comprises a horizontally disposed injection moulding unit 80, Fig. 30, movably supported on a guideway 81. On its forward movement the ram 88 feeds the plastics material into the heating unit 87 and through an adjustable lostmotion linkage actuates a pusher rod 320 which feeds material from the hopper 82 to the funnel 84. The heating unit 87 is surrounded by resistance heating coils 331 and is connected via a pre-compression unit 89 (Fig. 33, not shown), to four nozzles 340, the feeding of the material being controlled by a valve 346 in a manifold 342 having heater elements 362. Two groups of four cores or mandrels 75 (Fig. 1, not shown), extend from holders 73, 74 to co-operate with a four-cavitied parison mould 62 and two four-cavitied blow moulds 64, 66. Each core 75, Fig. 7, has a bore 183 and carries a hollow valve stem 184 biased by a spring 193 to close the valve element 194 on the seat 195, 196. Within the valve stem 184 is a coolant circulating tube 198. The valve element 194 is located in the open position during blowing and also during ejection of the article, ejection being assisted by the action of a stripper bar 178. A bracket 222 co-operates with a nut 198 to retain the valve 194 open during closure of the blow mould. The cores 75 may be modified (Fig. 11, not shown) so that the blowing air passes via a plurality of radial passages. The parison mould is moved between open and closed position by a hydraulic motor and is clamped in the closed position by a piston actuated toggle mechanism which moves wedge blocks apart to be wedged below wear blocks and exert a downward pressure on the upper mould halves. The arrangement is such that the clamping mechanism is moved under low pressure and is held closed under a high pressure. The electric, hydraulic and pneumatic control and actuating circuitry is described and includes a plurality of timers and limit switches tripped by machine parts to actuate safety interlocking means. A lamp and flasher unit is actuated by a thermal relay if the moulds do not close within a predetermined time because of an obstruction and also if the low clamping pressure is maintained after mould closure, the machine being stopped in both events. The control circuitry admits of three modes of operation viz. manual, one cycle or repeated cycles. Among the timers is an injection delay timer which holds back the injection so that it finishes with the finish of blowing and another timer controls the length of time during which injection takes place. The injection ram 88 moving forward under low pressure and after opening of the valve 346 under high pressure a low injection pressure being maintained to prevent shrinkage back out of the mould. In operation the ram 88 moves over a short distance a number of times as set on a counter to pack the heating unit 87.