Fluid flow governing valve means

Claim 1

An electric circuit for governing the valve member of a fluid flow governing valve means including a housing enclosing a movable main valve member, a conduit for supplying pressure fluid to move said main valve member, valve means in said conduit and having a valve body for controlling the flow of pressure fluid acting upon said main valve member, said circuit comprising: (A) an electric resistance wire having heat expansion properties and connected to said control valve body, so its thermal movements will determine the position thereof, (B) a source for supplying electric current to said resistance wire, at an intensity higher than acceptable thereof during an extended exposure, (C) potentiometer means for monitoring the supply of current from said source and including a first manually adjustable resistor to indicate the desired input, a second adjustable resistor operable in response to the position of said main valve member and a comparator for evaluating possible differences between the resistance values at said first and second resistors, and (D) means governed by the thermal movements of said wire for causing an intermittent flow of the current allowed to pass on by said potentiometer means.