| 摘要 |
A variable-speed bicycle comprises a multi-stage freewheel 6 with two or three sprockets mounted on a rear wheel hub 9, a rear derailleur 10 adapted to cooperate with the freewheel for switching over a chain 8 from one sprocket onto another, and an action converter 44 for converting a tension force of direction P into a thrust force of direction S, the derailleur comprising a horizontal support shaft 11 mounted to a bracket 13, a tensioner 35 mounted on the shaft, and a helical spring 29 surrounding the shaft and interposed between the tensioner and the bracket, the tensioner being axially siidable on the shaft as well as rotatable about the shaft under functions of the spring, the action converter comprising a push arm 50 disposed operatively in contact with the tensioner for imparting the thrust force thereto, all of the above constituent elements being housed within a gear case 1.
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