Abstract: To provide significant manufacturing and assembly cost savings in a rugged construction featuring a minimized number of simplified component parts, a thermostat is provided wherein an open-ended shell is mounted for movement toward and away from a fixed valve seat for controlling fluid flow responsive to a thermally responsive actuator, and a return spring assembly is provided for urging the shell in the direction of the valve seat which assembly includes means directly connected to the shell and providing a return spring seat for effecting transfer of the thermal actuator return spring load directly to the shell.

Abstract: A control valve assembly incorporates direct metal-to-metal engagement between a casing of a temperature-responsive valve actuator and a piston guide to promote ease and accuracy of calibration. In addition, a substantially frictionless override feature is incorporated in the assembly to effect pressure relief and to accommodate thermal excursion of the valve actuator beyond the travel required to effect the desired valve movement.