Power driven valve actuator

An actuator responsive to a thermostat for controlling the flow of a heating fluid through a valve to a space to be heated, wherein the valve includes a casing, a valve element, a seat, a spring biasing the valve element against the seat, valve stem means for moving the valve element away from the seat against the bias of the spring, and an opening in the casing for permitting contact between the valve stem means and the actuator, comprising:

• a housing;
• means for releasably securing said housing to the valve;
• a thrust member for engaging the valve stem means of the valve;
• heat responsive means for moving said thrust member in a direction for moving the valve element away from the seat, said thrust member having a first end within said heat responsive means and a second end projecting from said heat responsive means for engagement with the valve stem means of the valve;
• heating means responsive to the temperature in the space to be heated for heating said heat responsive means;
• first circuit means for connecting said heating means to a source of energy, said first circuit means including a switch;
• means for supporting said heat responsive means for movement relative to said housing;
• an actuator spring in operative engagement with said heat responsive means for biasing said heat responsive means to a starting position;
• and
• means in engagement with said switch for tripping said switch in response to the movement of said heat responsive means to break said first circuit means and discontinue the flow of energy to said heating means.