Patent ID: 8029073

Claim:
Brake booster comprising: a casing ( 2 ) of longitudinal axis (X), a skirt ( 6 ) and pneumatic piston ( 12 ) assembly mounted such that it can slide in a sealed manner in the casing ( 2 ) along the longitudinal axis (X), said skirt-piston assembly ( 6 , 12 ) dividing the interior space ( 4 ) of the casing ( 2 ) into a low-pressure front chamber ( 8 ) and a variable-pressure rear chamber ( 10 ), a three-way valve ( 26 ) actuated by a control rod ( 28 ) mounted in a longitudinal passage ( 34 ) pierced in the pneumatic piston ( 12 ), said control rod ( 28 ) being connected via a first longitudinal end to a brake pedal, a slide valve plunger ( 32 ) able to move, in said piston, along said longitudinal axis (X) under the control of a second end of said control rod ( 28 ), said slide valve plunger ( 32 ) allowing the force of the control rod ( 28 ) to be applied to a hydraulic piston ( 122 ) of a master cylinder, said skirt-piston assembly ( 6 , 12 ) transmitting a pneumatic boost force to the hydraulic piston ( 122 ) of the master cylinder, a sleeve ( 54 ) mounted such that it can slide in a sealed manner in the pneumatic piston ( 12 ) along said longitudinal axis (X) over a determined travel (C), said three-way valve ( 26 ) comprising a first ( 48 ) and a second ( 50 ) valve seat, and a valve shutter ( 46 ) intended to be pressed against the first and/or the second valve seat ( 48 , 50 ), said second valve seat ( 50 ) being borne by a first longitudinal end of the slide valve plunger ( 32 ), the first valve seat being borne by a first longitudinal end of said sleeve ( 54 ), characterized in that it also comprises: an elastic device ( 70 ) bearing, on the one hand, against a front face ( 72 ) of the piston ( 12 ) and, on the other hand, against a shoulder ( 71 ) of the sleeve ( 54 ) and having a tendency to apply a forward force on the sleeve relative to the piston, a device for transmitting the pressure of the master cylinder ( 120 ) to the sleeve ( 54 ) and tending to apply a rearward force to the sleeve ( 54 ).