| 摘要 |
A variable speed gear arrangement comprises a disc member 12, rotatable about a first axis 14, having rings 16 of gear teeth 18 which mesh with teeth 24 on a gear, eg spur gear 20, that is rotatable about a second axis 22. The gear 20 has a splined shaft 30, which engage with spines in a bush 36, which allows it to be slid along the second axis 22, whilst remaining in mesh with teeth 24, in order to change the transmission ratio. Between each gear ring 16 there is a gap, wider than the width of gear 20, which ensures that the gear 20 unmeshes from one ring 16 before engaging another. To facilitate meshing/unmeshing, the teeth 18 have tapers of opposite senses (see fig 5) wherein a top face (66, fig 5) narrows away from axis 14 and a base (70, fig 5) widens away from axis 14. At a datum level the teeth 18 have the same tooth thickness, pitch and pressure angle as the gear teeth 24. Taper angle # is calculated by dividing number of teeth n by 360‹. |
