Servo booster mechanism

In a system having a servo booster mechanism through which an input signal is modified to produce a corresponding output signal for moving a linkage to supply a device with an operational input, said servo booster mechanism being characterized by

• a housing having a cavity therein;
• piston means located in said cavity for establishing first and second chambers therein, said piston means having a projection that extends through said housing, said projection having a first bore therein connected to a surrounding environment, said projection being connected to said linkage;
• a cylindrical member located in said first bore, said cylindrical member having a second bore therein for connecting said second chamber with the first bore, said cylindrical member having an annular seat that surrounds a central opening and a control orifice through which fluid from said second chamber flows into said second bore;
• conduit means connected to a source of fluid under pressure (P.sub.s) having a first branch connected to said first chamber and a second branch connected to said second chamber;
• first restrictor means located in said second branch to create a pressure drop in said fluid presented to said second chamber to create a fluid pressure (P.sub.x);
• valve means located in said second bore, said valve means cooperating with said cylindrical member to define a third chamber within said second bore, said control orifice being connected to said third chamber and said third chamber being connected to said first bore through said central opening, said valve means having a plunger with a second face exposed to a fluid pressure P.sub.h) in said third chamber and a first face exposed to the fluid pressure (P.sub.x) in said second chamber, the relationship of said first face and annular seat controlling the flow of fluid from said third chamber into said first bore for communication to said surrounding environment, said input signal moving said plunger to change the relationship between said first face and annular seat to allow fluid to flow from said third chamber and change the fluid pressure therein from P.sub.h to P.sub.h -1, said change in the fluid pressure P.sub.h in said third chamber producing a corresponding change in the fluid pressure P.sub.x in said second chamber to P.sub.x -1 to create a pressure differential (P.sub.s -P.sub.x -1) across said piston means, said pressure differential (P.sub.s -P.sub.x -1) acting on and moving said piston means to produce said output signal, said piston means on moving reestablishing the P.sub.x fluid pressure in the second chamber whereby the pressure differential (P.sub.s -P.sub.x) acts on and holds the piston means stationary to reestablish the relationship between said first face and annular seat whereby a substantially constant volume of fluid flows from said third chamber to the surrounding environment by way of said first bore.