| 摘要 |
A demountable rear-wheel axle of a bicycle, carrying a set of sprockets of progressively decreasing diameters, is detachably held in a forked frame member next to a generally crescent-shaped stationary supporting element secured to that frame member, the supporting element having an arcuate edge generally paralleling about half the periphery of the adjoining smallest diameter sprocket. A guide bracket movable generally parallel to the wheel axle, engaging the driving chain of the bicycle, can be aligned not only with the several sprockets but also with the stationary supporting element to let the chain embrace that element when it is desired to remove the rear wheel; the movement of the guide bracket is controlled by a hand lever which normally is blocked by a releasable latch from aligning that bracket with the supporting element.
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