Image Number 3 for United States Patent #4896562.
A valve actuator differential worm planetary gear drive provides forward or reverse motion to a valve stem, from an input from either a motor-driven worm or a handwheel driven worm, by using a plurality of planet gears to send motion to the sun gear. If the preference is to have the motor driven the valve primarily, the manual worm stays locked and the motor worm acts as a planetary arm. When it is desired to move the valve by hand, the motor gear is fixed and rotation of the handwheel worm gear transmits the power through the ring gear and the planet gears to the drive sleeve.
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