Patent GB-585181-A (GB)
Title: Improvements in or relating to power transmission mechanism
IPC: F16H29/20
Filed: 1944-09-01
Abstract: 585,181. Variable-speed gearing. DAVIES, E. O. Sept. 1, 1944, No. 16720. [Class 80 (ii)] Variable-speed gearing comprises one or more gearwheels, e.g., 17, 18, Figs. 1 and 2 engaging circularly curved parallel rack-teeth 24 inside a transverse ring 23, which rotates round the gearwheels about its own axis, and also oscillates relatively to the wheels about an axis at right-angles thereto, the oscillatory movement serving to impart driving impulses to the teeth of the gear-wheels and the design being such that the impulses are always unidirectional. For this purpose two methods are used. In that shown in Figs. 1 and 2, (described more fully below) the rack-ring 23 is in one piece and the rack-teeth 24 extend over only one half of its inner circumference, so that rotation of the ring 23 causes the rack-teeth to leave contact with one wheel 17 and mesh with the other wheel 18 at the instant the direction of oscillation of the ring reverses, whereby the impulse imparted to the wheel-pair 17; 18 by the rack-teeth continues in the same direction. In the second method shown in Fig. 4 (described more fully below) the rack-teeth 153 are formed around the inside of a cylinder 131 split in an axial plane into two parts which are reciprocated in opposite directions by swash plates 138, and rotation of the cylinder causes the rackteeth of the two parts to mesh alternatively with opposite sides of a single gear-wheel 124 as the reciprocation reverses direction so that unidirectional impulses are imparted to the gear-wheel. In the diagrammatic form shown in Figs. 1 and 2 the wheel 18 of the meshing pair 17, 18, drives a wheel 1 on a final driven shaft 9 carrying a flywheel. The rack-ring 23 is pivoted on transverse trunnions 23a on a fork 22 secured to a driving shaft 4, and is connected by a link 30 to a collar 33, which, by means of a screw 38, can be adjusted axially along the shaft 4 to vary the inclination of the ring 23, and so its amplitude of oscillation and the speed of driven shaft 9. The wheel-pair 17, 18 is carried in a bracket 14 pivoted on vertical trunnions 12, 13, to allow the wheels to follow vertical pivotal movement of the rack-ring 23. The longitudinal ends of the rack-teeth 24 are bevelled to facilitate mesh with the wheels 17, 18 and correct phase-positioning of the wheel teeth for change-over of mesh with the rack is ensured by either making the rack-teeth helically inclined so that the rotation of the rack-ring effects the necessary phase displacement, or by providing one more tooth on one of the wheels 17, 18 than on the other. In the form shown in Fig. 4, split cylinderhalves 131 carrying the rack-teeth 153 are splined in a driving drum 111 in which they are reciprocated in opposite directions by a swash-plate 138 trunnioned at 140 on the driving- shaft and oscillated by engagement with an eccentrically adjustable ring 145 on the driven shaft 115. The rack-teeth engage alternately on opposite sides of a toothed wheel 124 on a transverse spindle 122 in a cage 119 secured to the driven shaft 115, and the wheel 124 meshes with a pinion 127 connected, by bevel gearing 128, 130 and a fast spindle 114, with the driving drum 111. In the non-inclined portion of the swashplate the rack-teeth lock the wheel 124 and a solid one-to-one drive results. In one adjusted inclined portion, the rotation imparted to the wheel 124 by the reciprocating racks 153 exactly neutralizes that imparted to the wheel by the driving spindle 114 through the bevel gearing, so that no drive is imparted to the driven shaft 115, this being a neutral position on each side of which intermediate forward and reverse ratios are obtained. In all the other modifications oscillation is imparted to the gear-wheels instead of to the rack. In Fig. 3 an internally spherical rack-member 53, with teeth over half its circumference, as in Figs. 1 and 2, forms part of a casing 51 secured to the driving shaft 49 of an electric motor 46. The rack-teeth engage gear-wheels 93, 94, which engage also a twostart worm 102 fast on the driving shaft, and are carried by a cage trunnioned at 104 on the enlarged end of an aligned driven shaft 57. Arms 105 secured to the shafts of the gearwheels 93, 94 are linked to a ring 90 carried in a ball-bearing ring 82 trunnioned at 83 in the driving casing 51 and adjustable to varying inclinations by means of a sliding collar 63 so that relative rotation between driving and driven shafts oscillates the cage of the gearwheels 93, 94 about its trunnions 104, thus rolling the gear wheels over the worm 102 and rack 53. In the non-inclined position shown the gear-wheels 93, 94 are locked to the worm and rack so that a solid one-to-one drive results. A neutral position is obtained when the inclination of the ring 90 is such that the rotation imparted to gear-wheels 93, 94 by their rolling in the rack neutralizes that imparted to them by the driving worm 102. Intermediate forward and reverse ratios are obtained on each side of this neutral position, which, in the case of a motor-vehicle, may be used to eliminate the usual main-clutch. In a modification of this form, Figs. 6 to 8 (not shown), the arms 105, Fig. 3, are secured to the gear-cage and are oscillated by engagement with a circular track carried by the driven shaft and adjustable eccentrically therein. Final drive is through epicyclic. gearing as described below with reference to Fig. 9. In Fig. 9 the gearwheels 258, 260, four of which are provided, are carried by slides 244, which are reciprocated in a driven cage 221 by swash-plates 227, 251 trunnioned at 229, 253 on the driving drum 210, so that the gear-wheels roll on the rack-ring 211 and on a four-start worm 262 both carried by the driving drum 210. The slide-cage 221 drives the driven shaft 215 through epicyclic gearing comprising a ring-gear 217 fast on the driven shaft 215, a sun 226 fast on an extension of the driving worm-shaft 218 and a planetcarrier on the slide-cage 221. Inclination of the swash-plate 227 is adjusted by sliding a collar 230, which turns a worm 238 engaging teeth on the swash-plate. Solid drive is provided in the non-inclined position and neutral, reverse and intermediate forward ratios are also obtainable in inclined positions.