| 摘要 |
<p>A chain or belt drive system which automatically alters the effective gear ratio according to load requirements comprises a driving wheel (15) (conveniently in the form of a spider), a driven wheel having a driving connection (teeth 29) with a chain or belt for driving same, and means (23, 25, 27) providing a driving connection between the driving wheel and the driven wheel. The axis about which the driven wheel rotates is movable relative to the axis about which the driving wheel rotates. The movement gives rise to a change in the effective gear ratio and is opposed by a resilient biasing force. The means providing a driving connection between the driving wheel and the driven wheel comprises a plurally of driving elements (23) carried slidably by the driving wheel and cooperable sequentially with the driven wheel. The sliding connection allows relative movement of the driven wheel with respect to the driving wheel whilst maintaining the driving connection. A cam controls sliding movement of the driving element.</p> |
