Actuating apparatus for adjusting a movable element, particularly the closure member of a valve

Claim 1

A valve assembly, comprising a housing defining an inlet and outlet and a valve opening therebetween, said housing defining a central tube section having communication with said outlet and a surrounding annular section having communication with said inlet, said tube and annular sections having inner and outer openings defined in a common plane, said housing defining a main chamber above said common plane, a flat circularly shaped diaphragm forming a movable wall for said main chamber and having an unstressed position in said plane in closing relation to said openings with the periphery thereof being attached to said housing in proximity to the periphery of said annular section opening, a bellows in said main chamber defining with said housing an expansible control chamber, said bellows having a movable end engaging said diaphragm and a fixed end attached to said housing, a liquid/vapor type filling for said control chamber biasing said diaphragm in an expanding direction, electric heating means in said control chamber, electric type temperature responsive feedback means in said control chamber, electric contact means extending from outside said housing to the interior of said control chamber connected to said heating means, and said feedback means, adjustable control means connected to said heating means and said temperature responsive feedback means via said contact means, for operating said heating means responsive to said feedback means to maintain a selected predetermined vapor pressure in said chamber, said liquid/vapor filling being pressurizable by heat to provide an oppositely acting counter-force relative to the pressures in said inlet and said outlet to cause said diaphragm to assume intermediate positions of stable equilibrium corresponding to a range of pressures in said control chamber.