GB527837A - Improvements in or relating to epicyclic change speed gears - Google Patents

Abstract

527,837. Variable-speed gearing. STURMEY-ARCHER GEARS, Ltd., and BROWN, W. April 11, 1939, No. 10904. [Class 80 (ii)] A four-speed gear for a bicycle hub comprises two sets of epicyclic gear trains 19, 21, 25 and 11, 15, 23, the annulus 19 and the planet carrier 22 of the first train being fixed respectively to the planet carrier 17 and the sun wheel 23 of the second train. The annuli 11,19 are connected to the hub casing 33 by ratchet clutches 12, 20. A dog 40 rotatable on a sleeve 34 slidable on the axle 24 is driven by the driving member 31 and can engage successively dogs 18 on the carrier 17 and splines 13, 14 on the annulus 11 by movement of the chain 37. In the position shown, the sun wheel 25 is held fixed by dogs 50 thereon engaging a sliding dog 51 splined to the axle 24. The annulus 11 is thus driven at a greater speed than the carrier 17 and the drive is taken to the hub casing through the clutch 12 giving a close ratio over drive for high gear. When the dog 40 is moved to engage the splines 13 a direct drive through the clutch 12 is obtained. The splines 14 are angularly displaced in relation to the splines 13 and when they are engaged by the dog 40 the clutch 12 is rendered inoperative and the drive is taken through the annulus 11 and carrier 17 to the ratchet clutch 20. This gives a close ratio low gear. Further movement of the chain 37 causes compression of the spring 56 and a shoulder 54c on the rod 54 abuts a key 61 and moves the dog 51 away from the dogs 50 and into engagement with dogs 53 on the planet carrier 22. The gear train 19, 21, 25 is thus inoperative and a second low gear of wider ratio from the normal is obtained. In a modification, giving a fifth speed ratio, the dog 51 is controlled by a second chain so that it may engage the dogs 53 when the dog 40 engages the dogs 18. In another modification the part of the carrier 22 forming the sun wheel 23 is separated from the part carrying the planetating gears 19, and the gear 25 is permanently keyed to the axle 24. A slidable dog may clamp the two parts of the carrier together, or lock the sun portion 23 to the shaft 24, leaving the other part free. Specifications 483,992 and 519,945 are referred to.