Bicycle chain-shifting device

Abstract

In a chain-shifting device for a bicycle or the like a switch unit is to be attached to the bicycle frame. The switch unit comprises a switch frame, a switch member and an operating member. Both the switch member and the operating member are swingable about a swinging axis with respect to the switch frame. Transmission means extend between the operating member and a movable chain mover unit. In view of facilitating the shifting of the chain between different sprockets associated thereto it is desired to temporarily move the chain mover unit beyond the desired position adjusted to the respective sprocket and to return it hereupon into said desired position. For automatically obtaining such go and back movement of the chain mover unit when being brought to a desired position corresponding to a respective sprocket it is proposed that releasable locking means are operationally provided between the switch member and the switch frame, said releasable locking means being releasable by a releasing torque acting onto said switch member; abutment means are provided in part on said operating member and in part on said switch member for defining two angularly offset terminal positions of said operating member with respect to said switch member. The operating member is biased by a biasing torque towards a rest position with respect to said switch member; said biasing torque resists against deflection of said operating member from said rest position towards at least one of said terminal positions. The biasing torque is smaller than the releasing torque.