Patent ID: 7677153

Claim:
A pneumatic brake booster ( 14 ) comprising: an axially movable control member ( 20 ) for controlling the booster and for receiving a control force applied by a user; a pneumatic enclosure ( 16 ) containing a rear chamber (CA) and a front chamber (CB), separated by a pneumatic piston ( 22 ); and means ( 42 ) for forming pneumatic valves comprising: a first balancing valve element (VE 1 ) and a second balancing valve element (VE 2 ) for placing the rear chamber (CA) in communication with the front chamber (CB) and a first intake valve element (VA 1 ) and a second intake valve element (VA 2 ) for placing the rear chamber (CA) in communication with a pneumatic pressure source, characterized: in that the control member ( 20 ) has a first part ( 20 A) that axially moves with respect to a second part ( 20 B), said first part ( 20 A) of the control member ( 20 ) receiving the control force applied by the user by way of the second part ( 20 B) of the control member ( 20 ); in that the means ( 42 ) for forming the valve comprise a tubular support ( 44 ) that is mounted in an axially floating manner in the pneumatic enclosure ( 16 ); in that said first balancing valve element (VEl) and said second balancing valve element (VE 2 ) are borne respectively by a balancing end ( 44 B) of the support and the pneumatic piston ( 22 ); in that said first intake valve element (VA 1 ) and said second intake valve element (VA 2 ) are borne respectively by the first part ( 20 A) of the control member ( 20 ) and an intake end ( 44 A) of said tubular support ( 44 ); in that said first part ( 20 A) and said second part ( 20 B) of the control member ( 20 ) are connected by means ( 52 ) for adjusting their relative axial position as a function of the power of the force applied to the control member ( 20 ); and in that a third intake valve element (VA 3 ), complementary with said second intake valve element (VA 2 ) is borne by the second part ( 20 B) of the control member ( 20 ), said second intake valve element (VA 2 ) selectively engaging with one of said first intake valve element (VA 1 ) or said third (VA 3 ) intake valve element depending on the relative axial position of said first and second parts of the control member ( 20 ).