Tandem master cylinder with valved hydraulic power booster fluid passage

Abstract

A hydraulic braking system having an auxiliary piston disposed between an input piston and a presser piston, so as to define a first power chamber between the auxiliary and presser pistons, and a second power chamber between the input and auxiliary pistons. The presser piston cooperates with a housing to define a pressure chamber connected to a first braking arrangement. The first power chamber is connected to a second braking arrangement and supplied with a power pressure from an external hydraulic source through a control valve and the second power chamber. The system includes a connecting mechanism connecting the auxiliary and presser pistons such that the two pistons are normally placed in a spaced-apart state but are abuttable on each other. The system also includes a valve device disposed in a passage formed through the auxiliary piston, so as to inhibit a fluid flow from the first power chamber to the second power chamber when the input and auxiliary pistons are advanced as a unit in abutting relation with each other, and permit fluid flows in both directions between the two power chambers when these pistons are placed in other conditions. The system is capable of activating the first and second braking arrangements by an operating force acting on the input piston through a manually operated mechanism, in the event of a power failure in the second power chamber or external hydraulic source.