Actuator device for a hydraulic spool valve

摘要

There is disclosed an actuation device for operating a hydraulic spool valve. The device includes a d.c. electric motor and a high-ratio gearbox. The output of the gearbox connects with the spool of the valve through a segmented rack and pitman pin or a rack and pinion arrangement. A control circuit for the electric motor includes position feed-back to permit accurate positioning of the spool. Further, spring means are included to bias the spool to its neutral position in the absence of a control signal or on occurrence of a fail condition.