US 5,178,055 AGranted

Vacuum booster

AssigneeNissin Kogyo Co., Ltd.

InventorsTakayoshi Shinohara, Toshiyuki Suwa

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Abstract

A vacuum booster includes a booster piston having a front surface facing a vacuum chamber, a diaphragm superposed on the rear surface of the booster piston and having a rear surface facing a working chamber adapted to be selectively put into communication with the vacuum chamber or the atmosphere, a piston boss carried on a central portion of the rear wall of the booster shell for a longitudinal reciprocal movement and provided with an annular step with which an inner peripheral bead of the diaphragm engages from the rear, and an annular stopper retained on the piston boss to abut against the inner peripheral bead from the rear. The stopper includes an annular retaining portion at an outer periphery thereof to project forwardly which has a curved front end, and the inner peripheral bead of the diaphragm is formed into a ring shape projecting rearwardly to have its outer periphery engaged with the stopper retaining portion. The curved front end of the retaining portion serves as a center about which the diaphragm is deflected toward the working chamber and thus avoids any damage to the diaphragm. When the diaphragm is deflected toward the working chamber, its inner peripheral bead can be urged radially inwardly by the retaining portion, thus reducing a load imposed on the bead to separate it away from the step of the piston boss, thereby improving the reliability of the stopper.

Claims5

Dependent claims

A vacuum booster comprising:

a booster shell;
a piston boss carried on a central portion of a rear wall of said booster shell for a longitudinal reciprocal movement;
a booster piston contained in said booster shell for a longitudinal reciprocal movement and having a front surface facing a vacuum chamber connected to a vacuum pressure source;
a diaphragm superposed on a rear surface of said booster piston and having a rear surface facing a working chamber selectively communicated, through a control valve operatively connected to an input rod, with said vacuum chamber and the atmosphere;
said diaphragm having an outer peripheral bead coupled to said booster shell, and an inner peripheral bead which engages, from the rear, an annular step on said piston boss;
an annular stopper retained on said piston boss and including a base plate portion formed into a flat ring shape to come into close contact with a rear surface of said inner peripheral bead of said diaphragm, a plurality of pawls projecting rearwardly from an inner peripheral edge of said base plate portion at circumferentially spaced locations so as to engage said piston boss, a plurality of flat portions extending radially inwardly from said inner peripheral edge of said base plate portion at positions between adjacent pawls to be put into close contact with said rear surface of said inner peripheral bead, a slit provided between a base end of each pawl and each flat portion, and retaining portions projecting from an outer peripheral edge of said base plate portion;
and
said inner peripheral bead of said diaphragm being formed into a ring-like configuration projecting rearwardly so as to engage at its outer periphery with said retaining portions.

5 more elements

Dependencies are inferred from the claim text.