Actuator

An actuator in particular for a locking unit, an injection unit, slide or ejector of an injection molding machine or injection compression machine, comprising a hydraulic force translator with two piston units moving relative to each other with different effective areas which enclose a pressure chamber together with a spacer, wherein the smaller piston unit is preferably electrically driven and the spacer can be fixed relative to a stationary chassis of the machine by means of a hydraulically operated clamping device for applying a great axial force, and comprising a high-pressure reservoir (HD) and a low-pressure reservoir (ND) adapted to be connected via a valve arrangement to a chamber of the force translator, characterized in that the chamber is operatively connected to the small piston unit and is enlarged during the out-movement thereof and is connected to the low-pressure reservoir (ND) via the valve arrangement and, when reducing the chamber in size, is connected via the valve arrangement to the high-pressure reservoir (HD) so as to charge the same, and comprising a directional control valve by which the high-pressure reservoir (HD) can be connected to the clamping means.