Patent GB-1220359-A (GB)
Title: A bicycle hub having a three ratio gear mechanism
IPC: B62M11/16
Filed: 1968-08-12
Abstract: 1,220,359. Change speed gear; ratchet clutches. SHIMANO KOGYO K.K. 12 Aug., 1968 [11 Aug., 1967], No. 38431/68. Headings F2C and F2D. In a three ratio cycle hub planet gear wherein ratio shifts are effected automatically by input and output driven governors 33, 44, a manual over-ride control 66 selects low, intermediate and high ratio ranges respectively providing fixed low, automatic shifts between the lowest two ratios and automatic shifts between all three ratios. The gear has planet pinions 17 on a carrier 20 meshing a fixed sun gear 16 and a ring gear 12 on a carrier 15. The planet carrier 20 and ring gear carrier 15 are selectively connected to a block 8 fast with a driving sprocket 11 by ratchet clutches 25, 22 and to a driven hub 2 by ratchet clutches 28, 31. The ratchet clutches 25, 31 are held disengaged by the centrifugal governors 33, 44 when the input and output speeds are below predetermined values. When the manual control 66 is moved left against the bias of springs 62, 63 it acts through pins 60, 61 and sleeves 58, 59 to push balls 69, 70 radially outward to a position in which they prevent inward movement of the tails 35, 46 of the pawls of the ratchet clutches 25, 31 which are thus held disengaged irrespective of the speeds of rotation of the governors. Operation.-With the manual control 66 in the high ratio range, as shown, and at low speed (e.g. during starting) the ratchet clutches 25, 31 are held disengaged by the governors 33, 44 for low ratio in which the block 8 drives the hub 2 through the ratchet clutch 22, ring gear carrier 15, planet gear 12, 17, planet carrier 20 and ratchet clutch 28. When the speed of the hub 2 exceeds a predetermined value the governor weights 44a, 44b pivot outwardly against the bias of a spring 54 to release the pawl of the ratchet clutch 31 whereupon the gear up-shifts to direct-drive with the block 8 driving the hub 2 through the ratchet clutch 22, ring gear carrier 15 and ratchet clutch 31. The ratchet clutch 28 overrunning. When the speed of the block 8 exceeds another predetermined value the governor weights 33a, 33b pivot outwardly against the bias of a spring 43 to release the pawl of the ratchet clutch 25 whereupon the gear upshifts to overdrive ratio with the block 8 driving the hub 2 through the ratchet clutch 25, planet carrier 20, planet gear 17, 12, ring gear carrier 15 and the ratchet clutch 31. The ratchet clutches 22, 28 overrunning. When the input and output speeds fall below the predetermined values downshifts are prevented until a torque reversal occurs to bring the pawls of the ratchet clutches 25, 31 into positions in which they are held disengaged by the governor weights. Alternatively the manual control 66 may be moved left momentarily to disengage the ratchet clutches 25, 31. Intermediate range.-Leftward movement of the manual control 66 initially acts through the pin 60, sleeve 58 and ball 69 to hold the ratchet clutch 25 disengaged. Upshift to overdrive ratio is thus prevented whilst permitting automatic ratio shifts between the lowest two ratio in the manner described above. Low range.-On further leftward movement of the control 66 the sleeve 59 and ball 70 additionally hold the ratchet clutch 31 disengaged to enforce low ratio. Modification.-The governors 33, 34 may be adjusted so that the ratchet clutch 25 is engaged before the ratchet clutch 31 in which case the block 8 drives the hub 2 through the ratchet clutch 25, planet carrier 20 and ratchet clutch 28 for direct drive. The other ratios being as above described. In this case leftward movement of the manual control 66 disengages the ratchet clutch 31 before the ratchet clutch 25.