| 摘要 |
A pneumatically operated brake booster in association with the hydraulic master brake cylinder of motor vehicles comprises a housing, an annular diaphragm having its outer periphery sealingly attached to the housing and its inner periphery sealingly attached to an axially movable power piston, a valve mechanism mounted in the power piston and operated by a manually operable push rod, which includes an air valve, and a key inserted into a radial slot of the power piston to thereby engage the air valve. The diaphragm is provided at the rear wall surface thereof adjacent to the housing with a plurality of radial projections abutting the housing. The circumferential space between neighboring radial projections is made smaller than the width of the key thereby holding the key in position and preventing the radial withdrawl thereof from the power piston.
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