Vacuum booster device

摘要

A vacuum booster device having a diaphragm the inner peripheral portion of which is rigidly clamped between the outer peripheral portion of a valve body and the central portion of a piston plate, wherein a rigid annular ring is attached to the diaphragm for preventing the radial outward movement of the material of the inner peripheral portion of the diaphragm when the diaphragm is compressed axially between the valve body and the piston plate.