Hydraulic boosters for vehicle hydraulic systems

摘要

A control valve for controlling the pressurisation of a power chamber of the booster comprises a spool working in a bore in a boost piston. The spool carries longitudinal spaced radial seals, a first one of the seals being disposed so as to prevent fluid from a radial high pressure supply port entering the power chamber through the spool at least when the booster is in an inoperative position. Movement of the spool in a forward operating direction, in response to an input force, causes the first one of the seals to uncover the port so that fluid can enter the power chamber through the spool. The other seal is adapted to uncover a radial return port connected to a reservoir when the input force is released.