Driving device for opening and closing a valve

摘要

A driving device for opening and closing a valve comprises a cylindrical body, an actuating cylinder, a spindle, a piston member, a transparent plate and a stop means for controlling the rotation of the spindle. Said stop means comprises a ring gear, a spring and a stop bar having a wedge-shaped head, said wedge head having a pair of surfaces forming an included angle which is bisected by the axis of the stop bar such that rotation of the spindle by fluid pressure on the valve is prevented but manual rotation of the spindle in either direction is permitted.