The present invention is directed to bicycles and, more particularly, to a bicycle derailleur that includes a threaded member for mounting the derailleur to a bicycle frame.
A bicycle rear derailleur engages a driving chain on one of a plurality of sprockets mounted on the rear wheel hub. A conventional derailleur comprises a base member detachably fastened to the back end the frame, a chain guide for guiding the chain onto the plurality of sprockets, a movable member that pivotably supports the chain guide, and a link mechanism that movably supports the movable member relative to the base member. Rear dropout portions are formed at the back end of the frame for installing the rear wheel hub and the rear derailleur. The base member sometimes is mounted to the rear wheel hub axle and secured by a nut that screws onto the hub axle. Such a derailleur is shown in laid-open Japanese Patent Publication No. H1-136,888, for example.
The chain guide has a pair of vertically aligned pulleys that guide the chain onto one of the plurality of sprockets, wherein the chain guide is pivotably coupled to the moveable member so that the chain guide pivots around an axis that is substantially parallel to the hub axle. The chain guide is biased relative to the movable member in a direction that also produces tension on the chain (typically clockwise when viewed laterally outwardly from the derailleur). The link mechanism may comprise a four-point link mechanism having a pair of links that move the movable member in the direction of the hub axle and diametrically outwardly as the chain guide moves closer to the sprockets. The inner cable of a Bowden cable assembly is fastened to the link mechanism such that pulling or releasing the inner cable using a shifter disposed on the handlebar causes the link mechanism to move the movable member and chain guide to engage the chain with a desired sprocket.