Tandem diaphragm brake booster

摘要

A tandem diaphragm brake booster includes a housing, first and second diaphragms disposed in said housing, a partition wall disposed between said first and second diaphragms within said housing for defining four pressure chambers. The housing is composed of a cup-shaped shell section having a broad cylindrical outer wall and a flange shaped rear shell section. A bead of the first diaphragm is situated between the inner surface of the front sell section and a securing member of the partition wall for defining the first and second chambers. The second diaphragm has inner and outer beads and through-holes at its periphery. The inner bead is compressed between the peripheral edge of the partition wall and the inner surface of the rear shell section and the outer bead is air-tightly secured between both peripheral edges of the front shell section and rear shell section. The partition wall and the second diaphragm define the third chamber and the second diaphragm and the rear shell section define the fourth chamber. The second and fourth chambers are connected through the cylindrical space formed between the inner surface of the cylindrical outer wall of the front shell section and the outer surface of the partition wall and through-holes of the second diaphragm.