GB419998A - Improvements in two-speed pedal-crank driving-mechanism for cycles - Google Patents

Abstract

419,998. Change-speed gearing. WOODWARD, R. T. C., 69, Burns Road, Stoke, Coventry, and ADCOCK, J., 7, Greswolde Road, Sparkhill, Birmingham. March 7, 1934, No. 7207. [Class 80 (ii).] Two-speed gearing for cycles operated by momentary backpedalling comprises two driving- members 1, 2, Figs. 1 and 9, adapted to be turned at different speeds in the same forward direction and coupling means 15 for selectively clutching these members to a driven member 3. In Fig. 1, the members 1, 2 are sun gears driven from stepped planets 5, 6 rolling on a fixed annulus 7 so that both speeds gear up. In Fig. 9, the members 1, 2 are driven constantly through a fixed countershaft 30. A coupling ball 15 is slidable in a straight slot 18 in the member 3 every time speed is changed, being thrown over by the inclined faces 21, 23, Fig. 3, of channels 16, 17 in the members 1, 2, respectively. In the high-speed position of Fig. 2, the flat upward-driving face 19 of the channel 16 engages the ball 15 which drives steadily on to the opposite face 20 of the slot 18. To change speed, a short back-pedalling movement brings the members 1, 2 downwards relatively to the slot 18 to the position of Fig. 3, which shows the shifting inclined face 21 of channel 16 in the act of throwing the ball 15 over into the other channel 17. On resumed forward pedalling, the drive is picked up by the ball 15 held in the slot 18 and pushed steadily by the advancing straight face 29 of the member 2, the member 1 passing on idly at higher speed. The change to high speed may be effected by a single backpedalling movement, a shifting face 23 on the member 2 bringing the ball 15 back to and through the position of Fig. 3 as it is thrown leftwardly into slot 16. Too much backpedalling changes speed twice, that is back to low speed. The change to high speed is preferably therefore effected in two stages. To this end, the slot 18 is formed with a shoulder 24, Fig. 6, which stops the ball 15 midway as it is being thrown leftwardly by the descending inclined face 23. On resumed forward pedalling, a bevel 25 on the member 2 advancing upwardly strikes the ball 15 and completes the throw over to the left so that the following straight face 19 of the member 1 picks up the drive on high speed. In an arrangement described with reference to Fig. 10, not shown, there is an epicyclic train with three spur elements, and the change is between a 1 to 1 drive and an overdrive.