Hydraulic brake booster

Claim 1

In a hydraulic booster, especially for use in actuating a master cylinder arrangement of a vehicle braking system, a combination comprising: a main housing defining an elongated bore; a booster piston received in said bore for longitudinal displacement; an operating element mounted partially in said bore for selective translation relative to said housing between a rest position and a plurality of operating positions; means for defining a pressure chamber, said pressure chamber bounded at one end by a face of said operating element disposed in said bore, and bounded at the other end by a face of said booster piston; means for supplying a fluid at a controllable pressure into said pressure chamber, including: a control valve including a valve housing and a valve member movable therein, said valve housing having an elongated internal passage and at least one outlet and one inlet port communicating with said passage, means for admitting the fluid to one of said ports at a control pressure which differs by a predetermined amount from a nominal reference pressure at said other port, said control valve member accommodated in said passage for movement longitudinally thereof between an inactive position in which it establishes communication only between said outlet port and said pressure chamber and a plurality of active positions in which it establishes communication between said inlet port and said pressure chamber, and means for moving said control valve member between said inactive and active positions thereof relative to said control valve housing in dependence on the position of said operating element relative to said booster piston, said moving means including an elongated tubular element having two longitudinally spaced portions respectively secured to said booster piston and to a stationary guide within said main housing, and a deformable elongated force-transmitting body of substantilly constant length at least partially received in said tubular element for displacement relative thereto and operatively connected to said operating element and to said control valve member for joint movement therewith such that said control valve member is in said inactive position when said operating element is in said rest position.