Abstract: A mechanism for adjusting spring tension at a derailleur head mountable to a bicycle frame having a limiting stop, includes an orienting washer rotatably mounted to the bicycle frame and having a tail engaging the limiting stop. A coil spring has a first end fixed to the derailleur head and a second end rotatably mounted relative to the orienting washer. An adjusting sleeve in the head rotates the second end of the coil spring relative to the orienting washer, to adjust tension of the spring. A retaining arrangement releasably retains the second end of the spring at a desired angular position after the second end of the spring has been rotated. A bolt secures together the orienting washer, the spring, the sleeve and the retaining arrangement to assemble the mechanism and for mounting the assembled mechanism to the bicycle frame and the derailleur head.

Abstract: A reel drum is rotatably supported on a board, and a tensioner case is detachably mounted to the board in the vicinity of the reel drum. Wires are extended from the reel drum in directions opposite to each other. A pair of tension rollers pressed onto the respective wires and roller holders rotatably supporting the respective tension rollers are attached to the tensioner case to be allowed to move in directions substantially orthogonal to the respective wires when the wires are tensioned. Moreover, the tensioner case is provided with biasing means to bias the roller holders in directions that the tension rollers are pressed onto the respective wires. The biasing means is a torsion spring. A contact portion of each roller holder which a wire end extended portion of the torsion spring is in contact with has an angle shape with a ridge aligned in a direction orthogonal to the wire end extended portion of the torsion spring.

Abstract: Disclosed herein is a derailleur for a chain bicycle designed to move forward with either forward or reverse rotation of the bicycle's pedals. The chain bicycle comprises a single endless chain, first and second rear wheel sprocket assemblies, first and second one-way clutches to transmit power to a rear wheel hub in only a forward direction, and an idler roller. Any one sprocket of the second rear wheel sprocket assembly engages with the endless chain by using a pantograph linkage, and at the same time, any one sprocket of the first rear wheel sprocket assembly engages with the endless chain by using a chain hook member. The idler roller is coupled to a second base member via a plurality of joint shafts, so as to permit not only rotating, tilting and sliding motions thereof relative to any one joint shaft, but also elastic pivotal rotation in either clockwise or counterclockwise direction relative to another joint shaft parallel to a pedal shaft.