Electric fail safe valve actuator

摘要

A fail safe valve actuator is disclosed that is powered by an electric motor which drives through a wrap spring clutch and a centrifugal brake configured to absorb a portion of the energy released when the power fails and the valve stem is moved rapidly to its fail safe position by an actuator spring. The valve member is held in operating position by a solenoid. When power fails, a spring moves the valve stem in the other direction to move the valve member to its fail safe position. A torque limiting device is mounted adjacent the output end of a gear train to protect the gear train and the electric motor from the high torque created when the valve stem abruptly stops moving when the valve member reaches its operating position.