| 摘要 |
<p>A pulley comprises a hub (2), a crown wheel (5) designed to co-operate with an endless flexible element, a band spring (9) for coupling selectively in rotation the hub (2) and the crown wheel (5), a braking surface (27), and a controlled element (16) torsionally connected to the hub (2) at least via the band spring (9) and mobile between a first position, in which the hub (2) and the crown wheel (5) are fixed in rotation via the band spring (9), and a second position, in which the braking surface (29) contacts the controlled element (16) and determines a relative rotation between a first end portion (10) and a second end portion (11) of the band spring (9) for rotationally decoupling the crown wheel (5) with respect to the hub (2) when the latter is turning. The pulley further comprises a brake (20) set between the hub (2) and the second end portion (11) and configured for opposing the relative rotation between the hub (2) and the second end portion (11) when the controlled element (16) is in the second position.</p> |
