Hydraulic control device for the injection unit of a plastics injection moulding machine

摘要

A hydraulic control device (10) for the injection cylinder (12) of a plastics injection moulding machine is proposed. The hydraulic control device (10) with a low number of hydraulic main stages (24, 19) can be converted without intervention in the hydraulic power unit from an embodiment for open-loop injection moulding (Figure 1) to an embodiment (80) for closed-loop injection moulding (Figure 2). A 3/2 in-line valve (24) is connected into the supply line (15) to the injection cylinder (12), which 3/2 in-line valve is designed essentially as a pressure balance cartridge and, operated by a pressure control valve (68) via an open control loop (54), can either relieve the injection cylinder (12) via a non-return valve (31) to the tank (17) or connect the injection cylinder (12) to a variable displacement pump (16). In the open control loop (54) there is a switching pilot valve (55) which, when exchanged for a 4/4 directional control valve (81) and with the arrangement of a displacement sensor (86) on the 3/2 in-line valve (24) and of a pressure sensor (87), allows closed-loop control of pressure in the injection cylinder (12). <IMAGE>