GB660230A - Improvements in or relating to variable gear mechanism for cycles - Google Patents

Abstract

660,230. Change speed gearing for cycles. HERCULES CYCLE & MOTOR CO., Ltd. Feb. 9, 1950 [Feb. 10, 1949], No. 3638/49. Class 80 (ii) A cycle gear of the Derailleur type consists of a fork plate 12 slotted to receive the rear wheel spindle 13, upon which the rear wheel carries three chain sprockets 14-16, engaged by the driving chain. The shifting of the chain from one sprocket to another is effected by a grooved roller or pulley 18, mounted on a spindle 19 slidable in the sleeve 20 fixed to the rigid bracket 21, the other end of this bracket being clamped by the wheel spindle nut 23. The axial sliding of the pulley 18 is motivated in one direction by a compression spring 31 and in the other by a head 27, rotatably anchored to the spindle 19, and having attached to it one end of a chain 28 connected through a Bowden cable to a controlling lever. To the spindle 19 is secured, by a locking nut 35 and tongue 36 in a keyway 37, an arm 34 having fixed to its other end a screwed spindle 38 clamped in the arm by a lock-nut 39. The spindle 38 carries a grooved roller or pulley 40 serving to tension the driving chain. The spring force on the arm 34 for tension is provided by the spring 31 of which one end is engaged with a flanged disc 25 locked to the bracket 21, and the other with a peg 41 on the arm, in such a way that the spring acts in torsion. The outer end 42 of the spring is cranked radially and can be inserted in one of a series of angularly spaced notches in the flange of the disc 25 so that the loading of the spring may be adjusted. The grooved rollers or pulleys 18 and 40 are identical, each having two spaced peripheral flanges 45, 45, leaving a groove of a radial depth substantially equal to the radius of the rollers of the driving chain, and the width between the flanges being slightly greater than the width of the chain. The outer edges of the flanges 45 are flared slightly in an outward direction to prevent the chain riding up them. In the centre of the groove is a shallow annular rib 46, or alternatively shallow angularly spaced projections corresponding in spacing to the pitch of the chain. The rollers 18, 40 are mounted on ball bearings comprising balls 47 in an internal groove 48 and races 49, 50. The bearings may also be of the needle-roller or other equivalent type.