GB1483741A - Injection moulding control system - Google Patents

Abstract

1483741 Control of injection moulding HUNKAR LABORATORIES Inc 23 July 1974 [19 Oct 1973] 32573/74 Heading G3N An injection moulding machine is of the type having a ram 16 which, when it advances (to the right in Fig. 1) injects plasticized material into a mould cavity 23 and when it retracts rotates to plasticize the material to be injected in the next advance phase. The invention consists in a control system for such a machine, the general organisation of which is broadly the same as in the system shown in Fig. 1 of Patent No 1411112 (which is referred to). The principal differences between the present system and that of the prior patent are the substitution of a single flow-divider valve 43B for two independent flow-control valves (45, 52) and the fact that, in the present case servo-control of the ram is continuous throughout each advanceretract cycle. Another difference between the present and the prior patent is that not only the advance but also the retract are limited by pressuresensitive control elements, the single pressure transducer (72) of the prior case being replaced by two such transducers 48, 101. A control system incorporating this two-pressure-transducer arrangement is claimed in Specification 1483742. Fig. 2 (not shown) is a block diagram illustrating the inter-relation of the control functions performed by the Fig. 1 apparatus in use. Figs. 3 and 4 (not shown) depict sub-systems whereby, during the retraction phase, appropriate variations in back pressure and rate of screw rotation are obtained.