Hydraulic control for injection moulding machine - having hydraulic reservoir to give smooth change from injection to holding pressure

摘要

The device has a screw axially loaded by a piston. A pressure-limiting valve can be connected into the hydraulic circuit of the piston by a two-way valve when the holding pressure is to be applied. The hydraulic line leading from a pressure source to the chamber behind the piston is connected to a hydraulic reservoir. The reservoir becomes charged during the injection stage, and is then discharged during the holding stage. Pref. the two-way valve has one position which connects the pressure line supplying the piston to the hydraulic reservoir and another position connecting the hydraulic reservoir to the line leading from the pressure-limiting valve to the piston.