GB1338657A - Chain shifting means for derailleur speed changing devices - Google Patents

Abstract

1338657 Chain-shift change-speed gear M MORSE 29 June 1971 30335/71 Heading F2D In a derailleur-type chain-shift change-speed gear for cycles having a laterally shiftable carrier 80, supporting two jockey pulleys 101, 102, 102, mounted on a parallel linkage 50, 51, one end of which is privotally mounted at 66, 67 on a bracket 60, fixed adjacent the rear wheel spindle, and the other end 87, 72 of which carries a pivot block 52 on which the jockey pulley carrier 80 is laterally ajustable by a screw 75, for initial setting purposes, and torsionally spring biased, in a clockwise direction, by a spring 79 to effectively compensate for the difference in the working length of the chain and maintain correct chain tension during ratio change, i.e. shifting the chain into engagement with any one of a series of sprockets 11 to 15 having different radii of progressively increasing magnitude, the sprockets being formed with 9, 14, 20, 30 and 45 teeth respectively in goemetric progression with the increments in radii between each pair of adjacent sprockets thus increasing progressively from the smallest 11 to the largest sprocket 15, the arrangement is such that during each chain shift e.g. from sprocket 11 into engagement with the next larger sprocket 12, to obtain a lower ratio, the jockey pulley 101 is first caused by displacement of the carrier 80 to move closely adjacent the periphery of the next larger sprocket 12, and in alignment therewith (Fig. 1), whereby the chain 16 is constrained, i.e. pinched, to feed directly on to said next larger sprocket 12, whereupon the jockey pulley 101 is then caused to undergo an outwards radial displacement relative the hub axis to accommodate the winding of the chain 16 around said next larger sprocket 12 (Fig. 2), the radial displacement during each change to a lower ratio other than the lowest ratio being substantially equal to the increment in radius between the larger sprocket 12 to which the chain is shifted and the following larger sprocket 13 in the series. The derailleur shift is operated in the usual manner by a cable 39 acting on a bell-crank arm 88 of the parallel linkage 50, 51. In Fig. 10 (not shown) the jockey carrier (151) is connected to the fixed frame bracket by parallel link arms (147, 148) turnable through 90 degrees for the full range of chain-shift.