Plastic moulding press with several injection pistons - in which each is connected via an adaptor to compensating pistons which moves up at cycle end to attain full pressure

摘要

A plastic moulding press has several injecting pistons coupled via an adaptor to a common drive. The rear end of each piston rests against a compensating piston and moves between fixed stops in the adaptor. During injection the injection pistons remain against the rear stops for the majority of the cycle and full injection pressure is attained at the end of the cycle by moving the compensating pistons forward in the fixed adaptor to force the injection pistons against the forward stops. Pref. a pressure sensor is positioned between the injection and compensating pistons and is connected to a data and control unit which controls cycle pressures. A further pressure sensor is mounted in the surface of the injecting piston. Each compensating piston is operated by a hydraulic circuit with a spindle drive piston driven by a stepper motor. In an alternative version the compensating piston is pushed against a stop by a coil spring when the piston is unloaded. When the injection pressure reaches a max. value the compensating piston draws back against the spring force until reaching a stop. USE/ADVANTAGE - For prodn. of plastic components, esp. semiconductor switching housings. Ensures complete filling of cavities and enables a pressure limit to be attained at the end of the cycle.