Thermally actuated valve with ambient temperature compensation

DETAILED DESCRIPTION The present invention employs a resilient poppet mounted on the end of a cantilevered bimetal blade arm which is spring biased to close the poppet against an annular valve seat provided about an outlet port in an electrically operated valve.
The root or base portion of the bimetal arm has an electrical resistance heater wrapped thereabout which, upon energization, causes warpage of the bimetal to deflect the arm and open the poppet from the valve seat.
The outboard or free end portion of the bimetal arm has the bimetal material reversed for deflection in an opposite sense for a given temperature change to thereby neutralize thermal response of the arm to changes in ambient temperature, or in other words to provide ambient temperature compensation.
The bimetal material employed for the base or active heated portion of the bimetal arm is composed of bimetal material having a substantially linear deflection response to changes in temperature up to 800.
degree.
F.
to provide control response to heating thereof by the electric resistance heater coil.
The outboard or compensator portion of the bimetal arm is composed of bimetallic material having a generally linear temperature response to temperatures up to 300.
degree.
F.
and a substantially non-linear response to changes in temperature above 300.
degree.
F.
The non-linear response of the compensator blade at temperatures above 300.
degree.
F.
thus produces minimal deflection due to heating of the compensator portion of the blade by heat transfer from the active portion of the bimetal arm.
The present invention thus provides for ambient temperature compensation of a bimetal operated thermally responsive electric valve, yet prevents overcompensation thereof by heating of the compensator due to energization of the actuation coil.