PRESSURE OPERATED TEMPERATURE SENSOR ACTUATOR

Improvement in a system for controlling fluid temperature comprising a member movable between positions in which the temperature is respectively increased and decreased, and an actuator linked to the member and mounted to communicate with the fluid to adjust the position of the member in accordance with temperature changes in the fluid, the improvement being in the actuator, which comprises a housing; a diaphragm mounted in the housing to define a control chamber therein, the diaphragm having a valving portion and having a piston portion linked to the member and mounted to reciprocate in the housing, to move the member between its positions, the housing having an opening on one side of the diaphragm for connection to a source of regulating pressure, the valving portion being adjacent the opening and movable between sealed and unsealed positions with respect thereto; and a temperature sensitive element mounted to apply force to the valving portion dependent upon the fluid temperature, so that the balance of forces on the valving portion, including force attributable to the regulating pressure, will determine the position of the valving portion, and, in turn, the pressure in the chamber and the positions of the piston portion and the member.