Hydraulic master cylinder

摘要

A tandem master cylinder for a vehicle split hydraulic braking system which has disc brakes in one part of the system and drum brakes in the other half. One of the pistons in the master cylinder is prevented from developing a substantial pressure until a predetermined pressure is developed by the other piston by virtue of a control piston working in a blind bore in one of the pistons. Hydraulic fluid is trapped in a control chamber formed by the blind bore and the control piston by a first valve means and released by a second valve means at the predetermined pressure. The arrangement allows pressure to the disc brakes to be delayed while pressure to the drum brakes is overcoming the effects of the usual pull-off springs.