Patent GB-449536-A (GB)
Title: Improvements in or relating to variable speed transmissions
IPC: F16H15/50
Filed: 1934-12-22
Abstract: 449,536. Variable-speed friction gearing. CHILTON, R., 26, Midwood Road, Ridgewood, New Jersey, U.S.A. Dec. 22, 1934, No. 36873. [Class 80 (ii)] A variable-speed gear comprises a planetary member, consisting of two sets of drivably connected radial rollers 10, 10c, Fig. 3, in driving contact with coaxial driving and driven members 16, 18 and preferably also a reaction member 15, at least one of such contact-points, e.g. that with the driven member 18, being shiftable axially along the rollers to vary the speed. The Specification explains, with the aid of diagrammatic reference to a gear with a single set of rollers, that as the contact with the driven disc 18 shifts from the axial line 14a through the point of contact with the driving member 16, to the parallel line 13a through the reaction contact-point, the speed-ratio progressively changes from one - to - one, to one - to - zero. Beyond these points overdrive and reverse can be obtained. In the one-to-one position, the reaction-member 16 is relieved of contact-load and the planetary member is entrained in the one-to-one drive. The contact-points with the members 15, 16 lie on different fixed pitch-cone angles, and in a modification are constituted by toothed bevel gears at the inner end of each roller set. Contact-shift is obtained either by tilting the rollers or by use of a deformable disc. Either or both the discs and rollers may be convex, or one member may be convex and the other concave, the radii of curvature being different. In this last case, contact-shift may be effected by movement of the rollers along their own axes. End-thrust may be provided by a torque-responsive cam-and-ball arrangement, which may be acted upon by hydraulic pressure. In a construction described with reference to Fig. 6, not shown, the speed-ratio is automatically controlled by the load, there being a pair of opposed driven discs constituted by Belleville plate-springs which deform under the torque-responsive end-thrust. The deformable discs may be backed by ribs, connected to specially arranged struts for obviating backlash, and may also be connected to a control collar. Fig. 10 shows a simple form of manual hydraulic control. Torque-responsive end-thrust means act independently on the driving member 16 and reaction-member 15, to cause contact-shift, and comprise hydraulic plungers 53, with loose balls 52 bearing on cam inclines 51 on the members 15, 16. Each member 15, 16 has two sets of staggered inclines 51, the balls 52 being staggered radially to engage inner and outer inclines alternately and in different phase. A small pump supplies pressure oil to both sets of cylinders, and control is effected by varying the relative leakage between the sets, whereby the differential thrust on the members 15, 16 causes tilting of the rollers and contact-shift over the driven disc 18. Exhaust valves 58 leading from each set of plunger-cylinders lead to relief valves 59, 60, the relative opening of which is controlled by the position of a hand lever 62 acting on the valves through a loose rocking-beam 61, for which the control-lever forms a variable fulcrum, thus, controlling the proportionate pressure on the plungers 53. A mechanical variant of this control, Fig. 9 (not shown), uses toggle-levers acting on mechanical plungers which replace the pistons 53, the toggle levers being each pivoted on three loose balls, arranged in transverse bores in their centre-parts, and being connected at their inner ends by a ball thrust-bearing. Each individual roller may, as shown in Fig. 10, have a part-cylindrical cap 50 at each end, engaging a guide in a cage 49, or each pair may have one such cap at each end engaging a partcylindrical guide in the cage. In the construction shown in Fig. 11, controlled manually and automatically by the load, for use on a motorvehicle the sets of planetary rollers 157 are separated by a composite loose ring 167, formed as an outer annular piston-and-cylinder arrangement 167, engaging each roller at an outer contact-point, and an inner piston-and-cylinder arrangement 170, engaging them at an inner point. The piston areas may be the same or different and the controlled pressure difference between the inner and outer pistons determines the tilting of the rollers 157, and so their contact-point with convex discs 127, 145, carried by a cage secured to the driven member 128. The driving shaft 111 is driven through a one-way roller clutch 109 by the engine crankshaft 100, and drives a rear large-angle bevelwheel 133 meshing with bevel planets 164, universally connected to the rear rollers 157. A non-rotary small-angle reaction bevel-wheel 136 is similarly connected with the front rollers 157. Both sets of rollers 157 are mounted for tilting movement in radial planes only, in cages 162 connected by external clutch dogs 165. The outer and inner pressure cylinders 167, 170, controlling the tilting of the rollers 157, are supplied with pressure oil by separate gear-pumps 184, 183 respectively, driven by a spiral gear 181 on the driving shaft 111. The delivery-pressure of the pump 184, leading to the outer cylinder 167, is controlled by the torque in the gear, acting through the reaction bevel-wheel 136, which is connected by clutch-dogs to a flanged sleeve 140, having cam-recesses co-operating with a fixed ball 142, to move the sleeve axially under torque, and close a valve seat 186 communicating with the pump 184. The delivery-pressure of pump 183 supplying the inner cylinder 170, is controlled by a leakage plunger 197 acted on by a rocking- beam 203, subjected also to the pressure of the pump 184 through a non-leaking plunger 189. A hand control-lever 204 constitutes a variable fulcrum for the rocking-beam 203, its position along the beam serving to determine the pressure-difference between the inner and outer cylinders 170, 167. The outer piston 166 is also subjected to the action of a centrifugal device, comprising masses 175 which tend to urge the piston inwards with speed increase, and so counterbalance the centrifugal hydraulic pressure. The driving shaft 111 carries a bevel wheel 116 which drives a pair of massive transverse flywheels. To provide an axial adjustment for the mean position of the inner piston and cylinder 170 and also to provide for equal and opposite movements thereof, these members are connected together by clutch dogs 172 and are both helically splined to a double helical wheel 210 located axially on the driving shaft 111. The latter is itself located axially in the gear by an end-bushing 216 which can be screwed inside an axially located driven bushing 124, to adjust the shaft axially, taking with it the wheel 210 and so adjusting the piston and cylinder 170. The bevel planets 164 are universally connected to the rollers 157 by loose toothed couplings and have spherical seatings on bushings in the rollers.