Servo booster

Claim 1

A servo-booster comprising: a shell casing; a piston plate and a diaphragm cooperating therewith and extending across said shell casing for defining two chambers therein and for receiving a differential pressure produced between said two chambers, said piston plate having a non-circular opening therethrough; a cylindrical valve body having therein a valve mechanism for controlling the pressure across the two chambers, said valve body having a head portion with a non-circular configuration at one end thereof, said head portion having a radial shoulder at a location spaced from said one end and facing in the direction toward the other end of said valve body, the configuration of said head portion being the same as that of said non-circular opening in said piston plate and said head portion being insertable through said opening in said piston plate when said head portion is in a predetermined angular relationship with said opening, said valve body and said piston plate being connected with one another by inserting said head portion through said opening in said piston plate and rotating said valve body and piston plate relative to each other for engaging said radial shoulder with said piston plate; and a retaining plate non-rotatably mounted on said piston plate and having a portion bent out of the plane of said retaining plate, said head portion having a recess therein for engagement by said bent out portion in projection-and-recess engagement when said valve body is rotated relative to said piston plate for holding said piston plate and said valve body in engagement for preventing only relative rotation of said valve body and said piston plate.