Patent ID: 6022284
Filing Date: 2000-02-08
Classification: B62M

Abstract:
Apparatus for changing bicycle gear ratio comprising pedals (1) to a first shaft (3) of which a group of coaxial overdrive gears is fixed, with at least an overdrive gear (20) of larger diameter and at least an overdrive gear (2) of smaller diameter; a plurality of sprockets (4) of different diameter, pack-like disposed close to each other and mounted on a second shaft (40) of a rear wheel; a roller chain for the transmission of motion from one of the overdrive gears (2; 20) to one of the sprockets (4); means for shifting the chain (5) from one to another of said sprockets (4), with a cyclist-operated lever-and-wire driving means for driving said means for shifting the chain; and means for guiding the deviation of the chain (5) from one to the other of the overdrive gears (2; 20) in cooperation with the means for shifting the chain (5) over the sprockets (4) of the rear wheel, characterized in that teeth of each overdrive gear exhibit, in correspondence of a respective sector (M, N), reduced height and thickness with respect to other teeth, said sectors (M, N) being angularly offset and cascade disposed with respect to the direction of rotation of the overdrive gears and with the sector (N) of said at least one overdrive gear (20) of larger diameter being moved forward with respect to that (N) of said at least one overdrive gear (2) of smaller diameter, and in that between each pair of overdrive gears are disposed solid to the larger gear of the pair and fixed thereto, in order to guide the deviation of the chain (5) from the smaller overdrive gear to the larger one.