1. A hydraulic brake booster for use in a brake system having a housing with a first bore for retaining a power piston, a
second bore for retaining a control valve and an actuation chamber, said second bore being connected to a source of pressurized
fluid, a reservoir and said actuation chamber, said control valve including a first cylindrical member and a second cylindrical
member retained in said second bore, said first cylindrical member having a stepped bore that extends there through and a
first sleeve located in said stepped bore to control communication between an inlet port, a supply port and a relief port
in said housing, an actuator arrangement including a ball located in said stepped bore and a pin retained in said second cylindrical
member, said pin having a first end being located in said actuation chamber and connected with a first input member and a
second end that extends into said stepped bore to engage said ball, said first end on receipt of a first input force initially
moving said pin and ball from a position of rest to interrupt fluid communication between said actuation chamber and said
reservoir through said relief port and thereafter moving said first sleeve to selectively initiate communication of pressurized
fluid presented to said inlet port to said actuation chamber that acts on said first piston as a function of said first input
force to effect a first brake application of a wheel brake, said pin and ball returning to said position of rest on termination
of said first input force, said actuator arrangement being further characterized by a second sleeve that surrounds said pin
with a lip on a first end that engages said second cylindrical member to position a second end thereof in an auxiliary actuation
chamber in said second cylindrical member, said second sleeve responding to a second input force derived from pressurized
fluid being presented to said auxiliary actuation chamber as a function of a second input and acting on said second end of
said second sleeve to move said first end into engagement with said ball and move said ball from a position of rest to interrupt
fluid communication between said actuation chamber and said reservoir through said relief port and thereafter moving said
first sleeve to selectively initiate communication of pressurized fluid presented to said inlet port to said actuation chamber
that acts on said first piston as a function of said second input to independently effect a second brake application of a
wheel brake, said ball returning to said position of rest and said second sleeve returning to engagement with said second
cylindrical member on termination of said second input force.
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