Control apparatus having temperature compensating means

Claim 1

IN A TEMPERATURE RESPONSIVE CONTROL APPARATUS HAVING A POSITIONABLE OUTPUT MEMBER AND A VARIABLE VOLUME CHAMBER FILLED WITH A TEMPERATURE RESPONSIVE MEDIUM CONNECTED TO ACTUATE THE POSITIONABLE OUTPUT MEMBER AS A FUNCTION OF ONE OF TWO TEMPERATURES TO WHICH SAID CHAMBER IS EXPOSED OVER A RELATIVELY WIDE RANGE OF TEMPERATURE VALUES, THE COMBINATION OF PIVOT MEANS OPERATIVELY CONNECTED TO SAID POSITIONABLE OUTPUT MEMBER ABOUT WHICH SAID POSITIONABLE OUTPUT MEMBER IS ADAPTED TO PIVOT IN RESPONSE TO VOLUME VARIATIONS OF SAID VARIABLE VOLUME CHAMBER, A SECOND VARIABLE VOLUME CHAMBER FILLED WITH A TEMPERATURE RESPONSIVE MEDIUM AND EXPOSED TO THE OTHER OF SAID TWO TEMPERATURES, SAID SECOND VARIABLE VOLUME CHAMBER BEING OPERATIVELY CONNECTED TO SAID PIVOT MEANS AND OPERATIVE TO MODIFY THE POSITION OF SAID PIVOT MEANS AND THUS MODIFIED THE LEVER ARM LENGTH OF SAID POSITIONABLE OUTPUT MEMBER THROUGH WHICH SAID FIRST NAMED VARIABLE VOLUME CHAMBER ACTS TO THEREBY COMPENSATE FOR EXPANSION RATE VARIATIONS OF SAID FIRST NAMED VARIABLE VOLUME CHAMBER OCCURRING AS A RESULT OF VARIATIONS IN SAID ONE TEMPERATURE.