Patent ID: 7061228

Claim:
An apparatus used for detecting the rotation of a bicycle part, wherein the apparatus comprises: a casing member comprising: a separate generally annular body structured to be mounted to a mounting boss of the bicycle part other than a wheel spoke so that the annular body is incapable of rotating relative to the bicycle part as the bicycle part rotates in opposite directions around a rotational axis, wherein the annular body includes a plurality of circumferentially disposed exposed magnet mounting portions that are concentric with respect to the rotational axis and are fixed relative to each other during rotation of the casing member; and a cover member detachably mounted to the annular body for blocking the plurality of magnet mounting portions; wherein the casing member further comprises: an inner peripheral surface to fit around an outer peripheral surface of the mounting boss; and a surface that extends radially inwardly relative to the inner peripheral surface and is nonrotatably connected to the inner peripheral surface to face an axially facing surface of the mounting boss.