| 摘要 |
PROBLEM TO BE SOLVED: To provide a toothed wheel reduced in weight in comparison with a conventional toothed wheel. SOLUTION: This toothed wheel is provided with a peripheral portion that comprises a side projection at one or more teeth, projecting with respect to one of the sides of the toothed wheel. The projection provides the necessary guide for a chain and the stability of the coupling between chain and toothed wheel, without making heavier the toothed wheel itself with an excessive thickness in any of its parts. Such a wheel also allows the lack of material in the vicinity of the projection to be exploited to make the gear shifting operations in a group of many toothed wheels easier. A pair of toothed wheels is also provided wherein the wheel of greater diameter comprises a first specialized tooth for upward gear shifting, in which wheel the outer side of the peripheral portion comprises a substantially flat area without recesses, situated in front with respect to the specialized tooth and outside the teeth. COPYRIGHT: (C)2007,JPO&INPIT
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