Vacuum servo-motor

Claim 1

A vacuum servo motor comprising, a housing having a first and a second chamber therein defined by a partition member, deflection means having finger plates adapted to be deflected when a force imparted to the partition member by a differential pressure between the pressure within both said chambers is transmitted to the outer ends of said deflection means, an input shaft, a socket responsive to movement of said input shaft for displacing the inner ends of said finger plates, an air valve operable according to the degree of deflection of said deflection means to selectively maintain or cut off communication between said fiRst chamber and atmosphere, a vacuum valve operable according to the degree of deflection of said deflection means to selectively maintain or cut off communication between said first chamber and said second chamber, a fulcrum plate for transmitting a boosting force created on said deflection means by said differential pressure and the input force to an output shaft, said partition member comprising a piston disposed in air-tight contact with said housing and a diaphragm air-tightly fixed at its one end to said housing and at the other end to said piston, each outer end part of said finger plates engaging in said piston and each inner end part of said finger plates being swingably supported on said socket to respectively open or close said air valve and said vacuum valve, said deflection means comprising three finger plates and two annular supports, said finger plates being received in notches equidistantly spaced on said supports, a sealing plate adhered to said supports and operable in response to the degree of deflection of said deflection means to selectively maintain or cut off communication between said first chamber and atmosphere, and between said first and second chambers, said sealing plate comprising a part of said air valve and said vacuum valve.