GB738338A - Improvements in or relating to epicyclic change speed gears - Google Patents

Abstract

738,338. Variable-speed gearing. STURMEY-ARCHER GEARS, Ltd. April 20, 1954 [May 9, 1953], No. 12983/53. Class 80 (2). A four-speed epicyclic changespeed gear particularly for the hub of a cycle comprises a primary sun gear 1a formed on a fixed axle 1 and engaging planet pinions 2 on a carrier 4 which are also in mesh with a primary annulus 5. Secured to the primary carrier 4 is a secondary annulus 4b meshing with planet pinions 23 on a carrier 25 which also meshes with a secondary sun gear 20. A sliding clutch member 15 is adapted to couple prongs 11a of an input member 11 either to dogs 4a on carrier 4 or to splines 5c on an extension of annulus 5. In a further position as well as engaging splines 5c it disengages driving pawls 6 on the annulus 5 from teeth 8a on the driven hub 9. The secondary carrier 25 is also in engagement through pawls 26 with teeth 27a on the hub 9. The secondary sun 20 is rotatably mounted and can be slid axially to engage teeth 25b on the carrier 25 and to thereby rotate therewith or to engage a toothed ring 30 engaged with the primary sun gear la to be held stationary. The sliding of clutch member 15 and sun gear 20 is effected through a selector rod 31 passing through a hole in the axle and acted upon by springs 34, 36. With the parts in the positions shown the clutch 15 couples driving member 11 to the annulus 5 for a direct drive to hub 9 through pawls 6, the pawls 26 being over-run. For an increased ratio drive, clutch 15 is moved to the left to couple carrier 4 to driving member 11 so that annulus 5 is driven at an increased speed to drive again through pawls 6. A first reduced ratio is obtained by moving clutch 15 to the right where it is coupled to annulus 5 but also disengages pawls 6 from teeth 8a. Annulus 5 therefor drives, through planets 2 and carrier 4, the secondary train 4b, 23, 20, 25 solid since sun 20 is coupled to teeth 25b of carrier 25, and the pawls 26 transmit the drive to hub 9. A second reduced ratio is obtained by moving sun 20 to engage toothed ring 30 which holds it stationary. In this case a further reduction is obtained through the secondary train from annulus 4b to carrier 25 and pawls 26 drive as before.