Vacuum-operated brake power booster having diaphragm edge bead retention member

A vacuum-operated brake power booster comprising, a movable wall sealed relative to a vacuum housing, said wall defined by a diaphragm plate and a rolling diaphragm on said diaphragm plate, a piston rod adapted to be coupled to a brake pedal, and operatively connected to a control valve, said control valve connecting a first chamber of the brake power booster alternately to either a vacuum or to a higher pressure differential, said control valve including a control valve piston which is axially displaceable within a control valve housing and which acts through the intermediary of an interposed reaction element on the end of a master cylinder push rod, said rolling diaphragm including an edge bead sealingly engaged around the control valve housing in a peripheral groove in the control valve housing, a retaining element arranged in an annular chamber formed by a cylindrical surface of the control valve housing and a neck portion of the vacuum housing, said retaining element including a first ring surrounding the edge bead of the rolling diaphragm and lockingly securing the edge bead in said groove against the effect of a radial force on said edge bead, said retaining element being nondisplaceably affixed on the control valve housing and including a second ring coaxially arranged at a distance from said first ring, said first ring and said second ring being interconnected by a plurality of axially extending webs forming a plurality of bleed passages aligned with a vacuum passage of said control valve for bleeding the brake booster, an air filter provided on an external peripheral portion of the retaining element between said first and second rings and coaxial to said axially extending webs for reducing noises occurring during the rapid inflow of outside air to said first chamber.