Patent ID: 6928920

Claim:
In a brake booster having a first shell that is joined to a second shell to create a housing with an interior cavity that is divided by a movable wall into a first chamber and a second chamber, said first chamber being connected to receive fluid having a first pressure while said second chamber is selectively connected to receive fluid having the first pressure and a second pressure as a function of an input force applied to a valve to create a pressure differential across the movable wall and develop an output force for effecting a brake application, said movable wall being characterized by a diaphragm, a backing plate and a hub member, said diaphragm having a disc with an peripheral and an axial bead, said peripheral bead being retained between said first and second shells while said axial bead is located in a groove in a cylindrical body of said hub member, said groove having a front face separated from a rear face with an arcuate transition surface located between a bottom of said groove and said front face, said axial bead having a profile corresponding to said groove and an arcuate lip that extends from a rear surface, said lip being connected by a convolute to a radial section of said disc, said backing plate having a profile that essentially substantially corresponds to said disc of said diaphragm with a radial annular surface that engages said front face of said groove, said axial bead engaging said backing plate to urge said radial annular surface into engagement with said front face of said groove to separate said front chamber from said rear chamber, said convolute allowing said movable wall to move in response to an input force being applied to said valve without creating a radial force in said diaphragm that may cause said axial bead to move out of contact with the bottom of said groove.