Patent ID: 6928918

Claim:
Pneumatic brake booster comprising an envelope ( 101 ) of longitudinal axis (Y) formed of a dish ( 105 ) equipped with a rim ( 153 ) and a lid ( 103 ), said envelope ( 101 ) defining an interior volume ( 107 ) divided sealingly into a variable-pressure work chamber ( 109 ) and a low-pressure chamber ( 111 ) by a skirt ( 113 ) mounted to slide with sealing alone the longitudinal axis (Y) in the envelope ( 107 ), said skirt ( 113 ) being equipped with a central orifice ( 115 ) in which a pneumatic piston ( 117 ) is sealingly mounted, a three-way valve ( 123 ) mounted in the pneumatic piston ( 117 ) and actuated by an actuating rod ( 125 ) connected to a brake pedal, the said sealing between the variable-pressure work chamber ( 109 ) and the low-pressure chamber ( 111 ) is achieved by a first sealing means ( 156 ) arranged between a radially internal first end of the skirt ( 113 ) and a radially external end of the piston ( 117 ) and by a second sealing means ( 157 ) arranged at a radially external second end of the skirt and the internal surface of the rim ( 153 ), the skirt providing sealing between the radially external first end of the skirt and the radially internal second end of the skirt, the second sealing means being a sealing piece ( 157 ) of tubular shape fixed to the skirt ( 113 ) and bearing against the interior face of the rim ( 153 ) of the dish ( 105 ) and able to slide over said interior face, the said sealing piece ( 157 ) at a first longitudinal end ( 161 ) is fixed by trapping in a fold ( 165 ) made on an external radial end ( 163 ) of the skirt ( 113 ), characterized in that a low-pressure cavity ( 167 ) is produced in the fold ( 165 ), between the interior end of the fold ( 165 ) and the first end of the sealing piece ( 157 ).