Patent GB-923479-A (GB)
Title: Improvements in or relating to hydrostatic power transmissions
IPC: F16H47/04
Filed: 1961-11-17
Abstract: 923,479. Tractor power take-off. FORD MOTOR CO. Ltd. Nov. 17, 1961 [Nov. 18, 1960], No. 41204/61. Class 79(2) [Also in Group XXIV] A hydromechanical transmission particularly for driving the ground wheels and power take-off shaft of a tractor, comprises a planet carrier 100 fast with a gear 108 meshing a gear 110 fast on an input shaft 14, a ring gear fast with a shaft 148 carrying gears 150, 152 constantly meshing gears 126, 128 which are selectively clutchable to an output shaft 18 by an internally toothed clutch sleeve 132, and a sun gear 106 fast on a shaft 66. The cylinder-carrying rotor 42 of a variable displacement swash-plate unit 36 is fast with the input shaft 14, and is in a closed hydraulic circuit with a second variable displacement swash-plate unit 38 having a rotor 44 fast on the shaft 66. A power take-off shaft 140 is fast with the planet carrier 100. In operation, for starting in a low speed range, the gear 128 is clutched to the shaft 18, the hydraulic unit 36 is adjusted to its maximum displacement position, and the hydraulic unit 38 is adjusted to have a displacement 89% of that of the unit 36 which is such that with the output shaft 18 stationary on the shaft 66 is driven at the same speed through the hydrostatic and planetary gears. The shaft 18 thus remains stationary. On increasing the displacement of the unit 38 the shaft 66 is driven more slowly through the hydrostatic gear and the shaft 18 begins to rotate in the same direction as the input shaft 14. When the unit 38 is given its maximum displacement the speed of the shaft 18 may be further increased by reducing the displace-. ment of the unit 36 down to zero, and then increasing its displacement in the negative direction thus driving the unit 38 and hence the sun gear 106 in reverse. When the hydraulic unit 36 reaches its full negative displacement the output speed can be increased still further by decreasing the displacement of the unit 38. For reverse unit 36 is given a positive displacement and the unit 38 is adjusted to -have a displacement less than 89% of that of the unit 36. The unit 38 and sun gear 106 are driven forwardly faster than under forward starting conditions, and the ring gear and shaft 18 are driven in reverse. For operation in the high speed range the gear 126 is clutched to the output shaft 18. For a fully mechanical reverse the hydraulic units are adjusted for zero delivery and a clutch' sleeve 82 is slid to the left to clutch a gear 78 to the input shaft 14. The gear 78 meshes a gear 92 fast on the shaft 66 so that the sun gear 106 is driven forwardly to give reverse rotation of the shaft 13. For fully mechanical forward drive, the hydraulic units are adjusted to their zero delivery position, gear 78 is clutched to the input shaft 14 by the clutch sleeve 82, and an internally toothed clutch sleeve 122 is slid to the left to clutch the outer race 120 of an overrunning coiltype clutch to the shaft 66. The inner race 116 of the overrunning clutch is fast with the planet carrier 100, and under these conditions the outer race becomes locked to the inner race by the clutch spring 118, thus rotating the carrier 100 at the same speed as the sun gear so that the planet gear is locked solid. Two speed ratios are obtained according as gear 126 or 128 is clutched to the output shaft.