Abstract: 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 drive worm, by using a plurality of planet gears to send motion to the sun gear. If the preference is to have the motor drive 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.

Abstract: 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.

Abstract: A switch assembly for a geared limit switch for valve actuators is formed from aligned switch modules. The switch modules includes a pair of switch units, each switch unit having a plunger and a movable contact plate mounted between two springs. As the plunger is driven inward, a camming element on the plunger contacts an edge of an aperture in the movable contact plate, forcing the plate to move in a direction perpendicular to the line of plunger travel. The inward motion of the plunger and the camming action continue after the contacts have closed, wiping the contacts mounted on the movable plate across the surfaces of the stationary contacts. When the plunger is released, an outer edge of the movable plate engages a beveled inner wall of the switch unit housing, returning the movable contact plate to its original position.