Mechanism for hydraulic brake booster

Claim 1

In a hydraulic brake booster for use in a vehicle hydraulic system having a fluid reservoir and a pressure source: a housing defining a bore therewithin; a piston slidable in said bore defining a variable-volume chamber between one end of the piston and a corresponding end of the housing; valve means shiftable within said housing from a first position venting said chamber to said fluid reservoir to a second position communicating said chamber with said pressure source; operator-operated means engaging one end of the valve means for shifting the latter; a compartment defined within said valve means communicated to said pressure source as the valve means is shifted toward the second position; a plunger extending into said compartment for pressurizing the fluid contained therein as the valve means is shifted whereby fluid pressure developed in said compartment acts on said valve means to oppose movement of the latter; and a second bore defined within said housing; said valve means including a valve spool slidably mounted in said second bore; the other end of said spool valve cooperating with a corresponding end of said bore to define a variable volume cavity therebetween; said cavity being vented to said reservoir; said compartment having an open end and a closed end; one end of said plunger being slidably received within said open end; the other end of said plunger being adapted to engage said corresponding end of said second bore.