Patent ID: 11009076

Abstract:
A side lip has an intermediate thick portion. An inner circumferential side surface of the side lip has a side surface shape of a cone. An outer circumferential side surface of the side lip includes a first outer circumferential portion having a side surface shape of a cone in which the thickness gradually increases from a small diameter side toward a large diameter side, and a second outer circumferential portion having a side surface shape of a cone or a column in which the thickness gradually decreases. A thickness T1 of a distal end portion of the side lip is 0.5 T to 0.7 T, and a thickness T2 of the intermediate thick portion is 1.2 T to 1.5 T, relative to a thickness T of a base end portion of the side lip. An angle A of the distal end portion of the side lip is 10° to 30°.