Abstract: In a servohydraulic actuator comprising a valve housing, a tandem cylinder, first and second servo valves operating synchronously and in axial alignment with one another in the valve housing and hydraulically connected to the tandem cylinder. Each of the first and second servo valves include an outer sleeve provided with inlet and outlet ducts and a control slide wherein one of the first and second servo valves are displaceable and the other servo valve is stationary. The displaceable valve includes a device for applying a resetting force acting against displacement of the valve. An intermediate sleeve separates the first and second servo valves and includes a coupling rod having an enlarged portion with a transverse opening which extends between and connects the control slides of the first and second servo valves. The actuator also includes an adjustment device for applying an externally controlled axial force against the resetting force to displace the outer sleeve of the displaceable servo valve.

Abstract: A hydraulic system having a high-pressure differential cylinder implemented as a servo actuator is hydraulically connected to a valve combination and an electro-hydraulic servo valve. The valve combination is a multi-functional valve including multiple interengaging valves and correcting elements all disposed within a housing. The valves and correcting elements are positioned and engaged along a functional axis of the multi-functional valve. This combination of valves provides for a single lightweight housing for the valve. The multi-functional valve is hydraulically connected via conduits with the servo valve and the differential cylinder. This device allows for the use of a single valve arrangement for controlling the numerous operating modes of the differential cylinder or servo actuator.