GB483992A - Improvements in or relating to epicyclic change speed gear - Google Patents

Abstract

483,992. Variable-speed gearing. STURMEY ARCHER GEARS Ltd., and BROWN, W. Sept. 26, 1936, No. 26139. [Class 80 (ii)] A close-ratio three-speed gear arranged in a cycle hub 32 comprises a pair of three-element epicyclic trains, the planet carrer 17 and sun wheel 23 of the primary train being coupled to the annulus 19 and planet carrier 22, respectively, of the secondary train, and the sun wheel 25 of the secondary train being formed on the fixed axle 24. Pivoted pawls 12 and 20, carried by the annuli 11 and 19 of the two trains, co-operate with ratchet teeth on the hub 32. The driving sprocket 41 is secured on a member 31 formed with dogs which are in constant engagement with dogs on a member 40 which is slidable on the axle by means of a cross-pin 35 under the action of a control chain 37 and a spring 38. An extension of the annulus 11 is formed with sets of internal splines 13 and 14, these sets being axially and angularly spaced. The pins 16 carrying the planet wheels of the primary train have projections 18. The proportions of the gears are such that the annulus 11 rotates somewhat faster than the annulus 19. When the member 40 occupies its intermediate position, in which its dogs engage the splines 13, direct drive through the pawls 12 results, the pawls 20 overrunning. When the member 40 is allowed to move to its left-hand position, in which its dogs engage the projections 18, an overdrive through the pawls 12 is obtained, the pawls 20 again overrunning. When the member 40 is moved to its right-hand position, its dogs tilt the pawls 12 to non- driving position and engage the splines 14, and an underdrive through the pawls 20 is obtained. The cycle can free-wheel in all speeds. The heels of the pawls 12 are chamfered on one side so as to permit the member 40 to move to the right during free-wheeling. The members of the gear are journalled on each other and in the hub.