| 摘要 |
A vacuum type brake booster device comprising a booster shell, a booster piston accommodated in the booster shell, a piston diaphragm working together with the booster piston for dividing the booster shell into both front and rear working chambers, and tie rods extending through the piston and the diaphragm for connection of the front and rear walls of the booster shell. Circumferential positioning devices are arranged between the booster piston and piston diaphragm and between the piston diaphragm and booster shell, respectively, so that the piston can correctly be adapted to the shell. Accordingly, the booster piston can be operated freely from interference of the tie rods. Furthermore, the piston diaphragm can be prevented from unnecessary forces due to the pressure difference between both the working chambers by the aid of thin-wall portions arranged in the piston diaphragm.
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