Thermopneumatic actuator

Claim 1

In an air conditioning apparatus for a space including a duct opening into the space, means for forcing air through the duct into the space, air conditioning means for regulating a temperature of air passing through the duct and a control member for controlling the air conditioning means, a thermopneumatic actuator comprising: a housing defining therein a pressure chamber, a valve chamber, a first temperature chamber communicating with the space and a second temperature chamber communicating with the duct; a first diaphragm hermetically sealing the first temperature chamber from the valve chamber; a second diaphragm hermetically sealing the second temperature chamber from the pressure chamber, the second diaphragm being equal in area to the first diaphragm; aspirator means for inducing air flow from the space through the first temperature chamber. means for inducing air flow from the duct through the second temperature chamber; a power diaphragm constituting a wall of the pressure chamber, the control member being operatively connected to and positioned by the power diaphragm; a diaphragm spring urging the power diaphragm and thereby the control member against air pressure in the pressure chamber; a valve having inlets communicating with an air pressure source and the space respectively, an outlet communicating with the pressure chamber and a movable valve element operatively supported by the first and second diaphragms for controlling communication between the inlets and the outlet; first and second thermally deformable springs disposed in the first and second temperature chambers respectively and being mechanically connected in parallel between the housing and the valve element; and a valve spring connected between the valve element and the diaphragm in such a manner that a force of the valve spring opposes parallel forces of the first and second thermally deformable springs.