Abstract: A valve actuator with manual override includes an input shaft for receiving input torque. The input shaft drives an epicyclic gear train sun gear and in turn is motor driven through a non-reversible gear set. The sun gear is in driving engagement with first, second and third planetary gears that in turn engage a first ring gear. Secured to each of the first, second and third planetary gears are fourth, fifth and sixth planetary gears. A second epicyclic ring gear engages the fourth, fifth and sixth planetary gears and is secured to an output shaft that in turn is secured to a valve shaft. The first ring gear engages a worm gear that may be manually actuated to operate the driven valve. The worm gear is slideably mounted on a shaft and biased by springs such that when the output shaft reaches a limit of rotation, or excessive load torque is applied, axial movement is transferred to the worm gear.

Abstract: A valve actuator utilizing a drive motor and a stored energy device to operate valves primarily in safety related applications is disclosed. The actuator operates on signal or loss of power to return a driven valve to a predetermined position. The actuator in particular utilizes unidirectional coupling between a driven shaft and an output shaft that is coupled to the driven valve. Specifically, the coupling utilizes a coiled spring having a unique diametral relationship with the driven shaft in order to insure reliable actuation and control of shaft wear. A fluid dampened device or dashpot is also utilized to provide controlled operation during the return cycle that is powered by the stored energy device.

Abstract: An electrically energized actuator for operating a valve has an output shaft for connection to a rotatable valve stem and is driven, via a gear train, by an electrically energized motor. A safety shut off mechanism is responsive to a predetermined resistance to rotation of the output shaft to operate an electric switch which prevents further operation of the drive motor.