| 摘要 |
596,527. Variable-speed epicyclic gearing. WATSON, C. D. July 30, 1945, No. 19381. [Class 80(ii)] Relates to free-wheeling two speed bicycle, winding engine or like gears of the kind having a centrifugally actuated pawl on the driven member alternatively engageable with inner and outer driving ratchet members revolving at different speeds, and provides locking means whereby speed changes can only occur upon free-wheeling. As shown, applied to a bicycle rear hub in place of the normal free wheel, a driving sprocket 1, Fig. 3, carries planet pinions 9 meshing a fixed sun 6 and a rotatable annulus 7. Direct drive external and overdriving internal ratchet teeth 10, 11, Fig. 2A, on the sprocket 1 and annulus 7 respectively are alternatively engageable by each of two diametrically opposed centrifugal pawls 3a pivoted on the driven hub 2. The pawl flyweights 4a tend to move the pawls into engagement with the teeth 11 against the pressure of springs 5a mounted in the flyweights. The free end of each spring 5a interferes with the free end of the opposite flyweight and the weights are thus prevented from moving outwards until the pawls are forced inwards on freewheeling and release the springs. In a modification, one pawl 3c, Fig. 2B, alone is centrifugally actuated, being connected by a spring 14 to linked flyweights 4c. The latter are prevented from moving outwards against springs 5c by a catch 13 on the other pawl 3d, which is spring pressed into engagement with the outer teeth and is forced inwards to release the catch on freewheeling. The gearing may be arranged to give direct drive and an underdrive. A number of two speed units may be arranged in series or parallel, friction or other means being provided in the former case to maintain the intermediate units at output speed during a long freewheeling interval. |
