US Patent 7121394 Hub assembly for a bicycle

A hub assembly for a bicycle includes a hub shell adapted to be rotatably mounted on a hub axle, and having a plurality of angularly displaced retreat bores for receiving pawls, respectively, a flywheel mounting cylinder rotatably mounted on the hub axle and having a tubular coupling wall confronting the retreat bores, and an annular drive member including a coupling segment which is coupled to and which is rotated with the tubular coupling wall, and a toothed segment which extends into an annular accommodation space between the hub shell and the hub axle to be coupled with the pawls radially so as to form a uni-directional mechanism for driving the hub shell to rotate in a clockwise direction.