Patent ID: 7191875

Claim:
A disc brake comprising: a seal groove located on an inner surface of a cylinder of a caliper for a brake, the seal groove consisting of five surfaces, the five surfaces consisting of: first and second chamfered parts respectively provided on opposite peripheral edges of the seal groove, a first side wall extending radially outward from an outer edge of the first chamfered part, a second side wall extending radially outward from an outer edge of the second chamfered part, and a bottom side of the seal groove extending between the first side wall and the second side wall, and forming one inside corner having an acute angle, and forming another inside corner having an obtuse angle, the corner with the obtuse angle being on a side of hydraulic pressure; a piston seal with a cross-section consisting of six contiguous surfaces fitted into the seal groove, two of the surfaces of the piston seal being flat surfaces facing and contacting the two side walls of the seal groove, and two other surfaces being chamfered surfaces on outer peripheral edges of the piston seal in order to provide a closed annular space in each of the bottom inside corners of the seal groove; and a brake piston, said brake piston and the cylinder are sealed by the piston seal wherein substantially no clearance is provided between the piston seal and the seal groove in a direction in which the brake piston is slid, wherein peripheral clearances are formed between inner portions of the piston seal and the first and second chamfered parts respectively provided on the opposite peripheral edges of the seal groove.