GB813382A - Control means for metal die casting or plastic moulding machines - Google Patents

Abstract

813,382. Controlling injection-moulding machines. E.M.B. CO. Ltd. Sept. 3, 1956 [Sept. 19, 1955], No. 26699/55. Class 87(2). [Also in Group XXII] A platen-retraction controlling device for an injection-moulding machine comprises a hydraulic cylinder, a piston movable in the cylinder, a series of intercommunicating ports in the cylinder to permit the flow of fluid from one side of the piston to the other, adjustable throttles to control said flow, and means operated by the piston for actuating the mechanisms of the machine. A hydraulic cylinder a has an oil reservoir n, side ports al, a2, a3, a4, with an intercommunicating passage a5, throttle valves m1, m2, m3, in the passage a5, between the ports al, a2: a2, a3: and a3, a4, respectively, the port a1 leading directly into the reservoir n and the port a4 leading into the reservoir through a throttle valve m4. A piston b with a through port of ports bl sealed by a spring- loaded disc valve o, has a piston rod c extending through both end walls of the cylinder a, one end of the rod c having a rack f arranged to actuate cam followers k through cams j on a shaft i and pinion g, the movements of the cam followers k controlling the mechanisms of the press, and the other end of the rod c having a piston d in an air cylinder e attached to the cylinder a. In operation, with the platens and the mould closed and with a charge of material injected into the mould, air is admitted into the cylinder e causing the pistons d and hence b to move to the left (in relation to Fig. 1), the piston b displacing fluid which flows from the port a2 to the port al through the throttle valve m1. The rate of flow of the fluid and thus the rate of movement of the piston b is controlled by the throttle valve ml and the valve is adjusted so that during the movement of the piston b from port a1 to port a2 sufficient time is allowed for the material in the mould to set. Further movement of the piston b, past the port a2, causes fluid to flow through port a3, valve m2 to port a2, the adjustment of the valve m2 allowing sufficient time for the injection mechanism to be withdrawn and returned to its initial position. The final movement of the piston b, past the port a3, causes fluid to flow through the port a4, valve m3 to port a3, the adjustment of the valve m3 allowing the mould to be opened and the moulded article ejected. During this third stage of movement the throttle valve m4 may be opened, by-passing the port a3 and hastening the mould opening and article ejection. During the return stroke of the piston b fluid pressure opens the disc valve o. The cams may be arranged to close the mould and restart the process for a continuous cycle of operation.