| 摘要 |
A gear changing mechanism is adapted to engage an endless chain in a chain drive. The mechanism includes a rotary shaft and a gear set located around the shaft. The gear set has a plurality of generally circular gears of different diameter adapted to mesh with the chain, and the gear set has a plurality of operating positions each corresponding to partial wrapping of the chain about a different one of the gears. Each gear is formed as a plurality of separate gear segments that align circumferentially to define the gear. The gear set also comprises a plurality of separately moveable supporting structures each of which has rigidly fixed thereto one gear segment from each of the gears. Mounting means are provided that mount each of the supporting structures to the shaft for rotation together with the shaft and for axial displacement along the shaft. Controls are provided that can axially displace the supporting structures in succession between one operating position and another as each of the supporting structures and the gear segments fixed thereto enter a zone of non-contact with the chain. During gear changes, the chain remains stationary and the gears are displaced relative to the chain.
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