Control valves for heating and cooling systems

An actuator for opening and closing a globe valve. The globe valve has a stem through which positioning of the globe valve is achieved. The globe valve is normally biased to open position. The actuator comprises an electric motor which drives a worm and pinion arrangement. The pinion drives an output gear which gear is movable between a base and a raised position within a frame and held in the base position by a compression spring with a similar compression rating to that of the required valve shutoff. The output gear drives a worm stem bearing against the stem of the globe valve to move it against its bias in one direction to close the globe valve. The output gear and worm stem are arranged so that, when the globe valve is fully closed, the worm stem is at its extreme position in that one direction and the output gear then begins to move within its frame from its base to its raised position. A shoulder on the output gear simultaneously moves a first leaf spring to break contact with a first switch and turn off the electric motor with the valve in closed position. In the opposite direction, the output gear returns to its base position and then moves the worm stem in an opposite direction to a position where the worm stem moves a second leaf spring to break contact with a second switch to turn off the electric motor with the valve in open position.