| 摘要 |
A front derailleur for a bicycle, for shifting a drive chain to one sprocket wheel of a multispeed front gear, has a fixing member, two parallelogrammatic linkage members, a chain guide, and return springs for restoring the chain guide. The fixing member is pivoted to an arm securing one terminal of a Bowden wire. A transmitting member for transmitting swinging motion of the arm to one of the linkage members is provided between the arm and the one linkage member, is supported at its one end to one of the arm and linkage member, and abuts at the other end against the other of both the members by being imparted with an elastic force greater than that of the return springs, so that when the chain guide is subjected to resistance within a given range the transmitting member transmits without displacement the arm motion to the chain guide to be laterally moved for changing the bicycle speed. On the other hand, when the resistance exceeds the given range, the transmitting member transmits no motion of the arm to the chain guide but is displaced to be energized, whereby it can, when the resistance becomes less than the given range, carry out the speed change by forcibly moving the chain guide using the stored elastic energy in it.
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