Druckmittelbetriebener Stellantrieb

摘要

A device for operating a servo drive having a positioning element controlled by a pressure medium. The device includes an electrical control unit generating a control signal based upon the position of the positioning element, a pre-control system connected to receive the control signal through an electrical control path and a main control system controlled by the pre-control system to operate the servo drive by moving the positioning element. A switching element is positioned between the electrical control unit and the pre-control system and opens the electrical control path prohibiting the transmission of the control signal upon detecting operation malfunction. Upon opening of the control path, the pre-control system acts to switch the main control system into a deventilation mode and said positioning element is moved into a predetermined "fail safe" position deventilating the positioning volume of the drive.