Abstract: An actuator has a fail-safe mechanism operable by a spring. The spring is normally held inoperable by electrical means so that the fail-safe mechanism is independent of the normal operation of the actuator. The fail-safe mechanism is rendered operative by failure of the electrical supply so that the spring rotates a cam plate which is coupled with the switch plate so as to move the output shaft to a predetermined fail-safe position by the stored energy of the spring force.

Abstract: A control unit responsive to axial movements of a motor shaft coupled to an actuator. The control unit provides torque and limit switches which are connected to disable the electric motor. The rotation of the output shaft of the actuator is used to operate limit switches in the control unit so that the motor will be deenergized when the actuator has moved to its full limit or when an excessive torque is encountered. Limits are established by connecting a counting mechanism to the electric motor output shaft. The actuator is controlled in first and second directions by first and second switches. A switch actuator is associated with each switch which is latched into position by the motion of the actuator members. The latch member prevents relative movement of the actuator until the motor direction is reversed, thereby preventing hammering and repeated actuation of said motor upon detection of the torque limit.

Abstract: This invention relates to an electrically operated actuator for quarter-turn valves, such as butterfly or ball valves.The actuator includes a single phase 2-pole dynamo-electric machine comprising a stator having three windings and a rotor having a plurality of short-circuited windings. The rotor is coupled directly with the output shaft and the windings of the stator are energised from a power supply through respective limit switches which are cam controlled by the output shaft.One of the stator windings controls the final movement of the actuator in each direction of travel and the limit switch for this winding is broken to de-energize the winding by an adjustable stop mechanism.

Abstract: The invention relates to a motor driven actuating mechanism which incorporates means of sensing torque and deriving a mechanical movement therefrom. The invention provides a mechanical brake which utilizes the mechanical movement of the torque sensing means to brake the mechanism if a preset torque is exceeded.In the preferred embodiment of the invention the mechanism comprises a worm and wormwheel in which the worm shaft is movable axially against a spring in response to torque reaction. The shaft movement is utilized to de-energize the drive motor and the mechanical brake comprises a brake disc attached to the worm shaft.