| 摘要 |
In a bicycle a rear wheel hub 1 is driven by a chain from a pedal shaft and includes a clutch-brake combination 3,4,5. The chain is shifted to various rear wheel sprockets 6 to change the transmission ratio. A chain tensioner compensates for the differences in diameter of the various sprockets. To avoid loosening of the upper chain strand and belated brake effect in response to backward pedaling, a separate brake- actuating transmission line is provided between the pedal shaft and a driver member 2 of the rear wheel hub. This transmission line comprises a free- wheel unit mounted onto the pedal shaft and a disengageable drive unit 8 adjacent the rear wheel hub. The units are interconnected by a transmission member 12 separate from the chain. The disengageable drive unit 8 may comprise a pinion 7 fixed to the driver member 2 and a rack 9 formed by a series of pins 10 engageable with the pinion 7 on displacement of the rack 9 in direction F. <IMAGE> |
