Patent GB-1467418-A (GB)
Title: Multiple speed range transmission
IPC: F16H47/04
Filed: 1974-02-27
Abstract: 1467418 Hydromechanical variable speed gear GENERAL ELECTRIC CO 27 Feb 1974 [2 March 1973] 8941/74 Heading F2D An hydrostatic - mechanical transmission, which provides, in a stepless sequence, low, intermediate and high ratio ranges and one reverse range, comprises an input shaft 10, output shaft 60 and an intermediate shaft 36 connected to input 10 in part through an hydrostatic gear 24, 26, and to output 60 by planetary gear trains 38, 40, 42, introduced by selective brakes 44, 46, 48 and a clutch 65 to transmit forward drive torque from the intermediate shaft 36 to the output shaft 60 in some but not all of the ranges, and in the low speed range (as well as in the reverse range) the output shaft 60 is driven solely by the intermediate shaft 36. The intermediate shaft 36, which carries the suns 38, 40, 42 of the intermediate, reverse and low range trains, is driven by the planet carrier 35 of a torque-combining input planetary train 28, a sun 30 of which is invariably driven by the input shaft 10 through meshed wheels 12, 14, whilst its ring gear 32 is input driven through meshed wheels 18, 20 and an hydrostatic gear with variable displacement pump-motor units 24, 26, which may exchange function. The output planet carrier 53 of both low and reverse trains 48, 46 is connected directly to the output shaft 60 by meshed wheels 56, 58, whilst the output ring gear 64 of the intermediate high train 38 drives (or is driven) through meshed wheels 67, 71, the ring gear 70 of a torquecombining output train 73, the planets of which are carried by the output shaft 60, whilst its sun 74 is variably driven by the input shaft 10 through meshed wheels 18, 80, 78. Low ratio range is established by braking at 48a ring gear 52 of the train 42, the planet carrier of which then drives the output shaft 60 through the wheel pair 56, 58. Initially the stroke of the pump 24 of the hydrostatic gear is set for maximum displacement and the motor 26 drives the ring gear 32 at the input train 28 reversely at a speed less than sufficient to hold the intermediate shaft 36 stationary, at which time a neutral condition is established. Output speed is then increased by reducing pump stroke through zero and increasing to a forward maximum, terminating low range, whereupon the low brake 48 is released and intermediate range brake ## synchronously engaged, to hold a planet carrier 66 of the intermediate train 38 so that its sun 38 is connected reversely to its ring gear 64 and thence, through the wheel pair 67, 71 to the ring gear 70 of the torque-combining output train 73. Pump stroke is now decreased back to zero and then increased to a reverse maximum, to reduce the speed of the intermediate shaft 36 finally to zero, and-throughout this range the direction of torque flow is not forward from the intermediate shaft 36 to output, but in the reverse direction, the unit 26 now acting as a pump and 24 as a motor to regenerate torque. At the end of the intermediate range the intermediate brake 44 is released and clutch 65 engaged synchronously to lock together the sun 38 and ring gear 64 of the intermediate train, introducing high range, in which the pump displacement is decreased through zero to a forward maximum. For reverse, the planet carrier 84 of the reverse train 40 is braked at 46, whereupon the common ring gear of the low reverse trains is reversely driven and combines with the forward driving sun 42 to drive the output shaft 60 reversely through the planet carrier 53 and wheels 56, 58, by-passing the torque-combining output train 73.