Brake actuator

Claim 1

A brake actuation assembly comprising: a master cylinder having a cylindrical body with a shoulder located between a first end and a second end and a bore therein, piston means located in said bore; a power assist booster having a front shell joined to a rear shell to define a housing, said front shell having an end plate fixed to said shoulder and a cylindrical body attached to said end plate, said cylindrical body having a flange that extends radially outward, said flange having a series of openings therein, said rear shell having a disc with a projection that extends through a first opening in a stationary bulkhead, said disc having a rib adjacent its periphery, said rib having a groove therein, said projection having a second opening therein, a movable wall for separating a first chamber from a second chamber in said housing, said movable wall having a hub member and a diaphragm member, said hub member having an annular projection that extends through said second opening and engages said projection on said rear shell, said hub having a bore therein, said first end of said cylindrical body of said master cylinder extending into said bore and engaging said hub, said hub having a series of grooves through which said first chamber is continually connected to said bore, said diaphragm member having a first bead located in said groove in said rib and a second bead attached to said hub, said first bead engaging said cylindrical body to seal said first and second chambers from the surrounding engagement and for resiliently positioning said cylindrical body in an axial plane with said pistons in said master cylinder, and a valve for controlling flow communication of fluid through said bore between said first and second chambers; fastener means extending through said opening in said flange to connect said front shell to said stationary bulkhead; an actuator responsive to an input signal for operating said valve to control the development of a pressure differential between said first and second chambers by interrupting fluid communication to said first chamber and initiating fluid communication to said second chamber with the surrounding environment, said pressure differential acting on and moving said wall to produce an output force, the engagement of said cylindrical body and projection on said rear shell holding said hub in said axial plane within said booster to allow said output force to move said piston means in said master cylinder without the development of any lateral forces, said piston means responding to said output force by developing a reaction force, said reaction force being transferred from said master cylinder through said front shell into said stationary bulkhead to substantially eliminate the creation of any axial deformation of said rear shell.