410,136. Variable - speed gearing; screw-and-nut mechanism. WHEATLEY, C. H. P., 21, Linton Crescent, Hastings, Sussex. Nov. 11, 1932, No. 31874. [Classes 80 (i), 80 (ii), and 80 (iii).] A positively-acting mechanism for producing infinitely variable linear or rotary motion is arranged so that the direction of the propelling force is substantially at right angles to the direction of possible slip between driver and driven members in rolling contact which produces relative motion, and means are provided to vary, either manually or according to load, the path of rolling contact on one or both of the members to vary the gear ratio of the mechanism. Screw-and-nut mechanism. A spiral 1, Fig. 1 (Comp), engages a spiral 6 of the same hand rotatable in a carriage 5. When the spiral 1 is rotated, the two spirals roll together and the carriage slides along the spiral 1. The velocity ratio may be varied by varying the interpenetration of the spirals, the cross-sections of the spiral tracks being as shown in Figs. 2 (Comp.) or 4 (Comp.). For effecting the adjustment, the bearings 7 of the spiral 6 are mounted on eccentric pins rotatable by a handle 9, which may be clamped at any desired point on a scale or is movable against a spring to effect automatic adjustment of ratio to load. Alternatively, the spirals may be of opposite hand and of the same pitch and radius so that when closely meshed the drive is in one direction while when they are slightly meshed it is in the opposite direction, and at some intermediate position there is no drive. In a further construction, the tracks on the member 1 may be circular. To increase the strength of the mechanism, three spirals 6 may be equally spaced round the spiral 1. Variable-speed gearing. In the form shown in Figs. 6 (Comp.) and 7 (Comp.) there is a variable drive from six rollers 16 to two spirals 20 mounted on carriers 22, 23 splined to the driven shaft 25 and urged towards the rollers by a spring 30. The rollers 16 are driven from the shaft 12 through a yielding gear-wheel 13, 14 and gears 17 rigid with the rollers. The common shafts of the rollers 16 and gears 17 are mounted in a disc 18 mounted with slight friction on the shaft 12 and prevented from rotating backwards by a pawl 19. On rotation of the driving-shaft, the disc 18 is carried round until one of the rollers 16 comes into contact with one of the spirals. The rollers 16 then revolve, the reaction of the disc 18 being taken by the pawl ; and the spiral tracks 20 are fed from one roller to the next in an undulating path, thus producing rotation of the carriers 22, 23 and driven shaft 25. Variation in the gear-ratio is brought about automatically by longitudinal movement of the carriers 22, 23 under the action of the spring 30, the spiral tracks engaging the conical rollers at varying radii. In the form shown in Figs. 9 (Comp.) and 10 (Comp.), a disc 39 is driven from a shaft 48 through a gear 47 which drives two conical wheels 43, 44 spring-pressed towards one another so as to grip alternately each of a pair of spiral tracks 31 formed on wheels 33, 34 journalled in brackets on the discs 39, and geared together by gears 41, 42. The wheels 43, 44 are mounted in a yoke 46, which is displaceable by a hand-lever 50 so as to drive the wheels with a variable gear ratio, the profile of the tracks being somewhat as shown in Fig. 2 (Comp.). In an automatically variable form, Fig. 11 (Comp.), the yoke 46 is arranged to move slantwise in the fixed member 49 and is biassed towards a position of higher gear ratio by a spring acting on the lever 50. In further forms, spirals of half a turn, or a plurality of spirals, or two circular tracks and a single spiral, may be employed. The mechanism shown in Fig. 9 (Comp.), 10 (Comp.) and 11 (Comp.) may be used for driving motor vehicles as shown in Fig. 15 (Comp.). One such mechanism is used for each wheel 74, the disc 39 being secured to the wheel. The conical wheels 43 are driven by chains 72 from sprockets 70 on the driving-shaft 69. The control lever 50 of each gear is connected by links 50<a>, 50b to a beam 76 mounted on a slide pulled along the axle by a spring 78 so as to urge the levers 50 constantly towards the high gear position. Further movement in the same direction gives a reverse drive, but such movement is normally prevented by a stop 80. The drive tends to raise the yokes 46 against the action of the spring 78 to decrease the gear ratio as the load increases, the beam 76 operating to give equal torque on each wheel and to allow differential movement. In the form shown in Figs. 13 (Comp.) and 14 (Comp.), a conical friction wheel 61, rotated by a flexible coupling 67 from a shaft 66, rolls round the circular gap between wheels 51, 52 so as to engage spiral teeth on each wheel alternately. The wheels 51, 52 are geared together to rotate in synchronism by bevel gears 55, 56 engaging a double bevel gear 57 on the driven shaft 58. The wheel 61 is mounted in a bearing 62 slidable during rotation in a frame 63 fastened to the shaft 64 so as to produce variable penetration of the wheel and a variable ratio. According to the Provisional Specification, four circular tracks 12, Figs. 6 (Prov.) and 7 (Prov.), are rotatably mounted in a spider 14 and carry pinions 17 engaging a sun 16 on the driving-shaft 22. The spider is freely mounted on the driving-shaft and is urged to the left by a spring 18 acting through a lever 19, so that the tracks 12 are forced into contact with spiral grooves 20 on a drum fixed to the driven shaft 21. As the spider rotates, the tracks 12 roll along the grooves 20 under the action of the gears 16, 17 and impart rotation to the shaft 21, each track entering the next groove to that engaged by the track before it. The grooves may be cut in the drum by substituting tools for the tracks 12. In the arrangement shown in Figs. 8 (Prov.) and 9 (Prov.), drive is transmitted from the shaft 24 through a conical track 23, and eight spirals 28 mounted in carriers 31 secured to the tubular driven shaft 29. As the track 23 rotates, it passes from one spiral to another, shocks being avoided by gearing the spirals together by worm-wheels 32, 33 engaging shallow spiral teeth 35 on the tips of the spirals. This worm gearing is reversible, but the gearing as a whole is irreversible for any position of track 23. The track may be moved, either manually, or automatically against a spring, to the dotted positions 26, 27 to give forward and reversed drive respectively. The spiral tracks may be cut by replacing the track 23 by a cutting tool. Four spirals and two tracks may be employed. A spiral driving-member may be employed, the penetration thereof with respect to the driven spirals being variable to vary the gear ratio, and also, if the spirals are of opposite hand, reversal. Also, the arrangement shown in Figs. 8 (Prov.) and 9 (Prov.) may be modified to give a differential drive. Each set of four spirals is driven by a separate track, and the carriers 30, 31 are geared to the driven shaft through a differential gear.