Snap-action servo mechanism

Claim 1

In a servo mechanism having a first output member movable in response to a difference in servo fluid pressure thereacross, the improvement characterized by: a nozzle; a conduit providing fluid communication between said first output member and said nozzle, to accommodate a flow of servo fluid therebetween, thereby effecting a change in pressurization of said first output member; a nozzle closure for modulating said flow of servo fluid through said nozzle; a fluid pressure responsive actuator having a second output member mechanically connected to said closure for adjusting the position thereof, said second output member being biased toward a predetermined closure setting by a restoring force associated with said actuator, said restoring force varying with the position of said output member; an open chamber providing communication between said actuator and said nozzle for accommodating the application of said servo fluid flow through said nozzle to said actuator in opposition to said restoring force; and a first flow restrictor disposed in said chamber opening for restricting flow therefrom, thereby enhancing the pressurization of said actuator by said nozzle flow, whereby the rate of change of pressurization of said actuator by said nozzle flow as said closure is adjusted by said actuator is greater than the rate of change of said actuator restoring force thereby maximizing the rate of change of pressurization of said servo mechanism at said one reaction surface for snap-action type movement of said first output member.