880,063. Hydro-mechanical variable speed gear. SVENSKA ROTOR MASKINER A.B. Nov. 6, 1957 [Nov. 8, 1956], No. 34594/57. Class 80 (2). [Also in Groups XXIX and XXXIV] Gearing for motor cars comprises an hydrodynamic torque converter having an impeller 20, a turbine 24, 28 and a reactor 26, a sun-gear 44 fast with the turbine meshing planet pinions 52 in a carrier 50 fast with the reactor and in turn meshing a ring gear 54, application of a brake 56 to the ring gear causing the reactor to be driven forwardly in the same direction as the turbine, but at a lower speed. The planet carrier 50 can be stationed by application of a brake 60 and is integral with a second sun gear 62 meshing planet pinions 64 in a second carrier 68 stationed by application of a brake 70, the planet pinions 64 in turn meshing a ring gear 72 fast with a driven shaft 48. The torque converter is filled, and servmotors 98, 102, 106 applying the brakes are energized, by oil supplied under pressure from a pump 74 driven through gears 77, 76, 78, 80 from the casing 12 of the torque converter. Oil under pressure is supplied to the torque converter from the pump 74 through a passage 82, a pipe 84 on the main axis of the gear, and passages 86 in the impeller housing. Oil is vented from the torque converter through passages 87, a passage 88 around the pipe 85, a port 89, a one-way pressure relief valve 90, and a cooler 91, whence it flows through a filter 92 back into a sump 94. Control of the engagement of the brakes 56, 60, 70 is effected automatically in accordance with the differences in the speeds of rotation of the torque converter impeller 20 and turbine 24, 28, under the control of an override valve 148, operative to produce neutral, and a fourposition ratio range selector valve 150. Two valves 120, 134 in the control circuit of the brake servos 98, 102, 106 are arranged to operate automatically at relative speeds between the turbine and impeller stated in the Specification. Each valve comprises at one end gears 78, 80, as already described, driven from the casing 12 of the torque converter, and in free sliding splined engagement with valve pistons 120, 134. At their opposite ends, the valve pistons 120, 134 carry freely threaded upon their tapped ends 124, 138 flanged and internally threaded sleeves 126, 140 biased by springs 128 into frictional engagement with the ends of hollow and meshing gears 118, 116. The gear 116 is fast for rotation with a gear 112 driven through gears 108, 110 from the output shaft 48 of the gearing. The arrangement is such that, when the gears 116, 118 rotate relatively slowly compared with the gears 78, 80, the valve pistons 120, 134 remain at their right-hand positions. When the gears 116, 118 begin to rotate more quickly, as the speed of the output shaft 48 increases and the motor car moves off from rest, first the valve piston 120 and then the valve piston 134 are screwed leftwards. With the car at rest and the ratio range selector valve 150 in the position shown in Fig. 6, movement of the override valve 148 rightwards to the position shown blocks the outlet of the pump 74, and all the brakeengaging servos 98 &c. are disengaged. By moving the ratio range selector valve 150 rightwards from the position shown, the two servos 98, 106 are energized to station both the planet carriers 50, 68, thus holding the turbine 24, 28 and the output shaft 48 stationary. This effect is obtained irrespective of the positions of the two ratio selector valves 120, 134. With the ratio range selector valve 150 moved back to the position 150a shown in Fig. 6, and the override valve 148 moved leftwards so that the pump 74 can energize the circuit, the gear is conditioned to initiate movement of the car. The servo 106 is energized to engage the brake 70 and hold the second planet carrier 66 stationary. The planet pinions 64 thereon, meshing the ring gear 72 on the output shaft, also mesh the sun gear 62 fast with the reactor 26, which is accordingly driven backwards as the car moves off. When the speeds of the impeller and turbine of the torque converter reach a predetermined ratio, the ratio selector valve 134 is screwed leftwards. The servo 106 is vented to exhaust to disengage the brake 70, the servo 102 stays vented as before, but the servo 98 is now energized to hold the planet carrier 50. As the reactor 26 is fast with the planet carrier 50, the reactor is held stationary, and the hydrodynamic torque converter functions in the normal way. On a still further increase in the ratio of the speeds of the impeller and turbine of the torque converter, the ratio selecting valve 120 is similarly screwed leftwards. This causes the servo 98 to be vented, the servo 106 remains vented as before, but the servo 102 is now energized to hold the ring gear 54 stationary. Accordingly, since the sun gear 44 is driven by the turbine 24, 28, the reactor 26 is also driven forwardly, but at a slower speed than the turbine. It is stated that at very high speeds an overdrive effect is now obtainable. Normal hydrodynamic braking is obtained when the car overruns the engine. To obtain increased hydrodynamic braking, the ratio range selector valve 150 is moved to a first leftwards position, causing the servo 102 to be vented and the servo 98 to be energized, thus engaging the brake 60 to station the planet carrier 50 and the reactor 26 of the hydrodynamic torque converter. Hydrodynamic braking by churning is now effected. On moving the ratio range selector valve 150 to a second leftwards position, the servo 98 is vented, and the servo 106 is energized to station the second planet carrier 66. The hydrodynamic torque converter reactor 26 is now rotated backwards at high speed, so that a considerably increased braking effect is obtained. In one modification, Fig. 14 (not shown), the brake 60 for the planet carrier 50 is omitted and the gearing is controlled by a simplified control system embodying a single ratio selector valve under the control only of a ratio range selector. Specifications 684,213, 700,342 and 880,062 are referred to.