Transmission device used between two relatively rotatable components

摘要

A transmission device is equipped with a flat cable (11) which has a winding direction reversal section (11a) at the middle, and three dummy cables (21A through 21C) which are wrapped over the flat cable, the winding direction reversal sections (11a and 21a through 21c) of the flat cable and dummy cables being arranged in the circumferential direction at approximately equal intervals. The winding direction reversal sections which produce elastic reaction forces are distributed in the circumferential direction at approximately equal intervals, and hence the slack of the flat cable is suppressed when an inner case or an outer case performs reciprocal rotation, thus securely preventing troubles caused by the slack in the flat cable, whereby the possible case revolution number can be increased with a shorter flat cable, and the operation stability of the transmission device can be improved.