Patent GB-602512-A (GB)
Title: Improvements in variable speed gearing
IPC: F16H61/02
Filed: 1946-05-03
Abstract: 602,512. Change-speed gear. WINTHER, M. P., and WINTHER, A. May 3, 1946, No. 13476. Convention date, May 11, 1945. [Class 80 (ii)] [Also in Group XXXIV] A variable speed-gear of the electromagnetic type is controlled by an auxiliary shaft driven at a speed proportional to the engine and having means for successively operating switches in electrical circuits to actuate the speeds, the timing of the operation of the switches being governed by inlet manifold pressure. Journalled in the rear and front ends respectively of a crank-shaft 9 and a driven shaft 25 is a low-speed shaft 19 which has a one-way clutch connection 17 with the bore of the flywheel 11 and is splined at 107 to receive the hub 103 of a clutch plate 105. The rear end of the low-speed shaft carries rigid therewith a sun gear 75 meshing with planet gears 71 carried by a support 67 integral with the driven shaft 25, the planet gears 71 meshing in turn with an annulus gear 73 rigid with a bell-shaped housing 35, journalled in the main casing by the bearing 45, carrying the spindles of a second set of planet gears 81 and being prevented from anti-clockwise (viewed from the left of the drawing) by a one-way detent 55. The planet gears 81 mesh with an annulus 79 rigid with the support 67, and with a sun gear 85 fixed to the rear end of a sleeve, or intermediate shaft 87 to which is splined at midlength a brake drum 91 and at the front end the hub 95 of a clutch plate 99. The driven shaft 25 carries a gear 65 for driving a governor used in the selector system described below. Attached to the fly-wheel 11 is a clutch ring 123 co-operating respectively at its front and rear faces with the clutch plates 105, 99 and clutch pressure plates 115, 125 which are normally urged apart by a series of springs 129. Engagement of the clutch comprised of plates 123, 105, 115, hereinafter known as clutch A, is effected by clockwise movement of the levers 147 pivoted at 149 on the clutch cover 133 and acting through the knife edge 155 and drawbolt 117. Similarly, engagement of the clutch 123, 99, 125 is effected by clockwise movement of the levers 130. These movements are produced by axial movement of the control tube 163, which is attached by a bell housing 165 to the outer race of a ball bearing 167, and of the pins 139 which are likewise attached to the ball bearing 145. Axial movement of the ball bearings 145, 167 is produced by the interaction of ball bearing screw-threads 176, 174 and 180, 178, the latter threads being formed on a sleeve 173 rigid with the clutch cover 133 and the former threads in the bores of brake drums 181, 183 attached to the inner races of the ball bearings 145, 167 and forming the magnetic eddy-current conductive rings of electric brakes. The brake control means for the drum 181 comprises a peripheral magnetic coil 185 in a two-piece magnet housing 187 having alternating pole-forming teeth 189, 191 which extend within the coil. When current is applied to the coil windings a toric flux field is formed as shown dotted at 193 causing the teeth to become alternately north and south, which flux field also passes through the drum 181 and causes retardation by the interaction of the flux field 193 and the flux field of the induced eddy currents. The axial movement of the tube 163 is similarly controlled by the current in the coil 195, return motion to free the clutches A and B being provided, when the coils 185, 195 are de-energized, by the springs 129, the ball screw-threads having insufficient friction to prevent the return of the drums 181, 183 to abut the fixed stop 175 on the sleeve 173. The brake drum 91 co-operates in a similar manner with alternating polepieces 223, 229, 235 which are energized by two coils 219, 221 producing two toric flux fields producing eddy-currents in the drum 91. A friction brake band 233 is provided around the periphery of the drum 91 and is arranged to be manually controlled for use when the vehicle is started by turning without energization of the electric brakes. The periphery of the bell housing 37 is formed with teeth 243 for co-operation with positive detent controlled by the rod 252 pivoted on the manual forward-reverse lever 292 (Fig. 12). The gear ratios are obtained by the engagement or energization of the clutches A and B and the brake 91 together with the one-way detent 55. Low speed is obtained by energizing the brake 195 and engaging the clutch A which transmits the drive from the engine to sun-wheel 75 which, as annulus 73 is prevented from backward rotation by the detent 55, causes the rotation of the support 67 and hence the driven shaft 25, the epicyclic train 79, 81, 85 and the intermediate shaft 87 turning idly. When the coils 219, 221 are energized, the brake drum 91 and hence the sun gear 85 are held with the result that the rotation of annulus 79 causes forward rotation of the bell housing 35, through the planets 81, and thus forward rotation of the annulus 73 with resultant increase in speed of the driven shaft 25 for the intermediate speed. Deenergization of the brake 91 and engagement of the clutch B by energization of the brake 185 causes the two sun-wheels 75, 85 to rotate solid, and thus provide a direct drive from shaft 9 to driven shaft 25 for the high speed. Reverse is provided by locking the gear ring 243 on the bell housing with the detent, deenergizing brakes 91 and clutch A and thus leaving the drive to be transmitted through clutch B to sleeve 87 and sun gear 85 which, as the spindles of the planets 81 are held, drives the supports 67 and driven shaft 25 in the reverse direction. To start the engine by towing the vehicle, i.e. with all coils deenergized, the band brake 233 is operated manually and the free-wheel clutch 17 takes the place of the clutch A. Reverse rotation of the bell housing 37 and rotation of the sun gear 85 is prevented and the drive is then from shaft 25 through planets 71 to sun gear 75 and thence through the free-wheel 17. Lubrication is provided by suitable channels attached to the casings and the gears. Fig. 12 shows an arrangement for controlling the gear electrically with respect to engine speed through a governor 273 on a shaft 267 driven from the engine ; with respect to road speed by governor-controlled switches 305, 337 and 339 of which the first opens at 8 m.p.h. and closes at 12 m.p.h. and the latter two open at 8 m.p.h. and close at 20 m.p.h. ; with respect to engine suction through the capsule stack 321 ; and with respect to throttle opening through the switch 346 operated by the accelerator 303. In operation, the manually-operated lever 292 is placed in the forward gear position which closes the switches 329, 297 and 351 and opens the switch 367, the ignition switch 289 is closed and current from the battery 287 flows through wire 291 to carbon pile 283, through wires 293, 295, switch 297, coil 195 which energizes clutch A and thence to earth, as shown by solid arrows. As engine speed increases, the governor 273 acts on the pile 283 to decrease its resistance and thus allow the clutch A to engage smoothly at 12 m.p.h., the driven shaft governor closes the switch 305 and current flows as shown by dotted arrows, in wire 325 closed switch 327, biassed by spring 328, switch 329, switch 305 and switch 307, which will be closed if manifold pressure is low enough, wire 333, coils 219, 221 of the brake 91 and then to earth, thus engaging the intermediate speed. If, however, the throttle is wider open than normal, the intermediate speed is held out until engine speed is equivalent to throttle opening. To prevent intermediate speed being disengaged on higher manifold pressure, a switch 372 is connected across the switch 307 and is held in against the biassing spring 370 by a solenoid 368 connected across the coils 219, 221. As engine speed increases in intermediate speed, the manifold pressure decreases to close switch 316 and switches 337, 339 close at 20 m.p.h. so that current flows, as shown by the dashed arrows, through switch 337, wires 295, 343 normally closed throttle switch 346, wire 345, time delay choke 347, switches 351, 339, 316, holding coil 355 and coil 185 for clutch B, to earth. At the same time switch 327 is opened by current in the coil 360 which is across the coil 185, the choke 347 providing a slight time delay while the switch 327 is opened. Thus, high speed is engaged by clutch B as the brake 91 is freed. For reverse the manual switches 329, 297, 351 are opened and switch 367 closed bv movement of the lever 292 which also locks the bell housing 37 through the detent controlled by the rod 252, thus coil 185 is directly energized through the pile 283 and the control is similar to that obtained in low gear. Full travel of the throttle pedal against the spring 381 opens the switch 346 and thus causes intermediate speed to be engaged by the closing of switch 327, upon the de-energization of the coil 185, as soon as the engine speed increases sufficiently to allow the necessary closure of the manifold pressure controlled switch 307. A slight release of the pedal at speeds in excess of 20 m.p.h. will, if the manifold pressure is low enough, allow the re-engagement of high speed. If when the pedal 303 is fully depressed the rod speed is less than 8 m.p:h., then the three governor-controlled switches will be open and low speed will be engaged. In modifications, straight spur gears and bevel gears may be used in place of the helical gears shown in the epicyclic trains.