System for amplyfying manual operating force transmitted to a functional device of a bicycle.

摘要

A roller brake mechanism having an operating force amplifying device includes a cam (7) rotatable about an axis of an axle, a plurality of rollers (8) displaceable with rotation of the cam, a roller case (9) for displaceably retaining the rollers, a brake drum (5) extending from a wheel hub (2), and a brake shoe (10) disposed between the rollers and brake drum for contacting the brake drum with displacement of the rollers. The amplifying device is formed as a clamping ring (18) having one end thereof operatively connected to a brake lever (100) through an interlocking wire (150), and the other end operatively connected to the cam. An intermediate portion of the ring is wound around a peripheral surface of the brake drum. Based on a primary operating force applied from the brake lever, the clamping ring clamps the brake drum, which produces a frictional force for allowing the clamping ring to take power from the brake drum, i.e. the wheel hub. The power thus taken is used as an amplified or supplemented operating force for operating the cam of the roller brake mechanism. The cam under the amplified operating force presses the brake shoe upon the brake drum. Thus, the brake is operable by a great force obtained by taking power from the wheel hub, which allows the primary operating force to be small.