Patent GB-190408140-A (GB)
Title: Improvements in Variable Ratio Gearing for Motor Driven Vehicles and other similar purposes
Inventor: MITCHELL FRANK
Filed: 1904-04-09
Granted: 1905-04-06
Abstract: 8140. Mitchell, F. April 9. Motor road vehicles.-Relates to variable speed and reversing friction and worm gearing specially applicable to motor road vehicles. The drive takes place through a worm which can be made to rotate so as to diminish, and further, to rereverse, the speed of the driven member. In the arrangement shown in Figs. 1 and 3, a driving-sleeve a is secured to a disc d and a casing g, the former carrying brackets f and worms e the latter, which may also serve as a beat pulley, supporting in bosses the outer ends of two spindles l, the inner ends of which are supported by cross-pieces on the brackets f. Friction wheels o sliding on keyways on the spindles l gear with a stationary friction face disc h, the boss of which forms a bearing for the driven shaft b. Each spindle l carries a pinion n, which gears through an idle pinion m with a pinion k on the axle of a worm e in engagement with a wormwheel c on the shaft b. The wheels o have collars p, straps in which are engaged by forked ends of arms q pivoted to the disc d at r. Links s connect the arms q to a sliding collar t movable by a lever u. For the highest speed, the wheels o are moved inwards until they clear the disc h by coming opposite a recess i ; the gear revolves as a whole. On moving the wheels o outwards, the worms e rotate so as to retard, stop, and ultimately to reverse the wheel c. A modification of the operating device consists of a chain x, Fig. 6, for each wheel o. Each chain is secured at both ends to one of two slides v working in guides in the bracket f and carrying the operating-straps. Each chain x passes through holes in the disc d and over a pulley y on the sleeve a. One part of each is fastened at z to a lever n while the other passes freely. In Fig. 6 the lever is shown pivoted to a link 2 and the disc h secured to a standard 4. The toothed wheels n, m, k are shown outside this disc h. A loose pulley 7 is shown riding on the sleeve a held by a collar 8. An extra grip is produced for reversing by providing wheels 10 on the backs of and slightly smaller than the wheels o. These wheels 10 are provided with leather or like surfaces adapted to engage a raised ring 9 at the edge of the disc h. In one modification, three worms are operated by separate wheels o, and in another there are four worms geared in pairs through bevel and crown wheels and operated by two wheels o. The wheels o may be arranged between pairs of oppositely-moving discs 18, 21, Figs. 10 and 11, and the worms e may be arranged on the spindles l with the wheels o. A ball bearing 15 may be arranged between the driving- casing g and a fixed disc 14, which carries pinions 17 meshing with teeth on a ring 16 on the casing g and with a toothed wheel 19 which is driven at increased speed in the reverse direction and carries with it the loose disc 18. Toothed wheels 20 loose on the spindles l make the discs 18, 21 move with equal and opposite speeds relatively to the casing g, the disc 21 running on a ball bearing 22. The brackets f support worm-wheels 23 meshing with the worms e. The axles 24 of the wheels 23 carry pinions 25 gearing with a toothed wheel 26 on the driven shaft b. A positive grip is arranged for the greatest reverse speed by providing clutch members 27, 28 on the wheels o, 20 respectively. In the device shown in Fig. 12, the movable wheels o are replaced by face wheels 29 fixed to the spindles l, and the fixed disc h, Fig. 1, is replaced by a wheel 30 which is prevented from rotating and engages the wheels 29, causing them to rotate, and can be moved axially to vary the speed by a handle u and links 31, 2. The wheels 29 may be provided with conical faces and pressed inwards upon the wheel 30 by springs. The worm-wheels c might be replaced by wheels with rollers on their edges ; they might also be fitted with one-way clutches. In Fig. 17 is shown a conical worm 36, which may be used with or instead of one of the worms e. In Figs. 1 and 6, the disc h might be made conical, in which case the spindles l would be inclined, and in place of the wheels n, m bevel gearing might be used. In the Provisional Specification, it is stated that tapered pulleys may be used to rotate the worms, aud that each friction wheel may be operated by pressure in one direction against a sprmg. Also, that when the friction disc is made conical it might be traversed axially against spring action and caused to operate the friction wheels. It is stated, further, that the outer ends of levers working the friction wheels may be operated by an axially. moving cone, and that links directly attached to a sleeve on the shaft may be used instead of levers.