Tandem brake booster for automotive vehicle

摘要

A tandem brake booster for automotive vehicles comprises a housing the interior of which is subdivided into front and rear chambers by means of a partition wall, a front movable wall assembled within the front chamber to subdivide the front chamber into front constant and variable pressure chambers and being integrally provided at its inner peripheral portion with a front cylindrical hub member extending from the front chamber into the rear chamber across the partition wall, a rear movable wall assembled within the rear chamber to subdivide the rear chamber into rear constant and variable pressure chambers and being integrally provided at its inner peripheral portion with a rear hub member. The rear hub member is engaged with the rear end of the front hub member and is formed with a cylindrical portion which extends into the front variable pressure chamber across the partition wall and is arranged in surrounding relationship with the front cylindrical hub member. A cylindrical seal member is disposed between the front cylindrical hub member and the cylindrical portion of the rear hub member to connect the front and rear movable walls to each other and is formed in its peripheral wall with a first recess for providing a passage for communication between the constant pressure chambers and with a second recess for providing a passage for communication between the constant pressure chambers.