Patent ID: 8567788

Claim:
Master cylinder for a hydraulic braking circuit, comprising a piston ( 2 ) sliding axially in a body ( 4 ) and collaborating with an annular seal ( 1 ) placed in a housing ( 6 ) of the body ( 4 ), this seal comprising an internal dynamic sealing lip ( 14 ) surrounding the piston, the internal dynamic sealing lip ( 14 ) fitting into an annular groove ( 20 ) of the piston when this piston is in a rear rest position, and an outer static sealing lip ( 10 ) pressing against a first wall of the housing, the outer static sealing lip ( 10 ) having a top surface, characterized in that the seal comprises an additional static sealing lip ( 16 ) which extends primarily radially from the top surface toward the first wall and also presses against a second, generally radially extending wall of the housing, wherein the outer static sealing lip ( 10 ) and the additional static sealing lip ( 16 ) define a concave groove therebetween that defines a small closed volume (V) of liquid between the outer static sealing lip ( 10 ), the additional sealing lip ( 16 ) and the first wall of the housing.