Zusammenbau eines mehrstufigen Kettenrades für ein Fahrrad.

摘要

A multi-stage sprocket assembly for a bicycle has a small sprocket (12), a large sprocket (13) disposed coaxially with the small sprocket and a shift assist projection (16, 18, 23, 24) provided to the large sprocket for assisting a shifting movement of a chain (3) from the small sprocket (12) to the large sprocket (13). The assembly includes a guide face (15', 17a', 17c') for guiding an outer side face of link plate of the chain. The guide face is formed in a side face of a second tooth (15a) of the large sprocket facing the small sprocket, the second tooth (15a) being forwardly adjacent, relative to a moving direction of the chain, a first tooth (15c) of the large sprocket which comes into engagement with a leading portion of the shifting chain (3). The shift assist projection (16) is so displaced toward the small sprocket that the projection comes into engagement with the shifting chain portion at a position forwardy distant from a position of the engagement between the leading end of the shifting chain portion (3) and the first tooth by a distance which is substantially an integer multiple of a disposing pitch of the large sprocket teeth (13). Also, the shift assist projection (16) has such a radial height as to prevent this projection from extending into a rotary drive-moving path of the chain as fully engaging the large sprocket for propelling the bicycle.