Patent ID: 7736253

Claim:
A gear-shifting apparatus which comprises: a chain; a plurality of gear-shifting sprockets arranged in an axis direction; and a changing mechanism for changing the chain from one of the plurality of gear-shifting sprockets to a selected other one of the plurality of gear-shifting sprockets in response to a gear-shifting operation, the changing mechanism comprising: a guide pulley which is movable in the axis direction and which is operable to guide the chain to the selected other one of the plurality of gear-shifting sprockets, and a pulley support member which rotatably supports the guide pulley to which the chain is wound, and which is movable in the axis direction by means of the gear-shifting operation, the pulley support member comprising: a first arm part disposed on a first side of the pulley, a second arm part disposed on a second side of the pulley, a spring-containing part operatively attached to the second arm part, and a pulley axle which extends through the first arm part, the second arm part, the pulley and the spring-containing part; wherein the pulley support member is provided with engagement recovery parts for causing a derailed portion of the chain, which has been derailed from an orbital plane of the guide pulley, to engage with the guide pulley, wherein the engagement recovery parts include a first extending part and a second extending part, which are arranged respectively on two sides in the axis direction of the orbital plane of the guide pulley, and which each extend in a respective direction away from the orbital plane of the guide pulley, the first extending part being integrally formed with the first arm part of the pulley support member, and the second extending part being integrally formed with the spring-containing part, the engagement recovery-guiding parts configured to be substantially symmetrical to one another as seen in cross-section, and to diverge outwardly away from one another at a distal end of the arm adjacent to the tension pulley; and wherein each of the extending parts is operable to guide a derailed portion of the chain, which has gone onto the extending part, in a way that the derailed portion of the chain slides on the extending part, moves towards the orbital plane of the guide pulley, and thereafter engages with the guide pulley, due to a tension force on the chain.