Patent ID: 6976417

Claim:
A pneumatic brake booster comprising an envelope ( 2 ) of longitudinal axis (X), a first, low pressure, chamber ( 10 ), a second, variable pressure, chamber ( 12 ), a skirt ( 4 ) delimiting the first and second chambers ( 10 , 12 ) and mounted sealed and slidable in the envelope ( 2 ), a pneumatic piston ( 8 ) rigidly attached to a central portion of the skirt ( 2 ), a three-way valve ( 20 ) mounted in a shank ( 14 ) of the pneumatic piston ( 8 ) and actuated by a brake control ( 33 ) comprising a control rod ( 22 ) of longitudinal axis (X) operated by a pedal at a first longitudinal end ( 25 ), a plunger ( 32 ) mounted in ball-joint fashion at a second longitudinal end ( 34 ) of the said control rod ( 22 ), the said three-way valve ( 20 ) comprising an equalizing valve ( 23 ) suitable for interconnecting the first and second chambers ( 10 , 12 ) at rest and an inlet valve ( 24 ) suitable for allowing the second chamber ( 12 ) to be supplied with pneumatic fluid at high pressure, the equalizing valve ( 23 ) comprising a first seat ( 26 ) supported by the body ( 14 ) of the piston and a blanking element ( 36 ), the inlet valve ( 24 ) comprising a second seat ( 28 ) supported by a first longitudinal end of the plunger and the said blanking element ( 36 ), the plunger ( 32 ) comprises at a second longitudinal end, the opposite end to the first end ( 54 ), a surface facing a first face of a reaction disk ( 55 ) bearing via a second face on a first longitudinal end ( 50 ) of a thrust rod ( 48 ) suitable for transmitting a braking force applied to the brake control and the brake boosting effect to a master-cylinder, the pneumatic piston ( 8 ) also comprising in its central portion a surface ( 56 ) bearing against the first face of the reaction disk ( 55 ), characterized in that the said booster comprises means ( 68 , 168 , 268 , 368 , 468 ) allowing to damp the relative and in particular oscillatory movement between the brake control ( 33 ) and the pneumatic piston ( 8 ) when no hydraulic reaction exists, said means ( 66 ) to damp is a friction coupling between the plunger ( 32 ) of the brake control ( 33 ) and the pneumatic piston ( 8 ), said means ( 68 ) to damp comprise an annular groove ( 74 ) made in an inner wall of a second cylindrical section ( 60 ) of the passage ( 18 ) of the piston ( 8 ) and an element ( 72 ) in a material with a high coefficient of friction mounted in the said groove ( 74 ) and intended to come into contact with a second cylindrical portion ( 58 ) of the plunger close to the control rod.