Patent GB-795835-A (GB)
Title: Hydrostatic gear
IPC: F16H47/04
Filed: 1956-05-18
Abstract: 795,835. Variable-speed gearing. EBERT, H. May 18, 1956 [May 23, 1955], No. 15604/56. Class 80 (2). A shaft 6, especially in a motor vehicle drive, is driven from a shaft 3 by a stepless variable-speed gear embodying two hydrostatic aggregates 26, 27, the gear ratio being varied automatically in accordance with the engine speed and displacement of the accelerator pedal 57. When the speed of the shaft 6 equals the speed of the shaft 3, a friction clutch 4, 7, 8 is engaged to connect the shafts 3, 6 to one another and the hydrostatic gear 26, 27 is rendered ineffective. A planet-wheel carrier 20 has pinions 22, 23. Pinions 22 mesh a fixed annulus 24 and a sun gear 17 free on the shaft 6, and pinions 23 mesh a sun gear 19 fixed to the shaft 6 and with an annulus 25 having a gear 31 geared to the shaft 33 of the hydrostatic aggregate 26. The shaft 34 of the other hydrostatic annulus 27 is geared to a gear 32 fixed to the shaft 6. The sun pinion 17 is rigidly connected by a casing member 16 to the driving-shaft 3. The gear aggregates 26, 27 are pivoted about fixed pivots 28, 29 and are interconnected by a link 30 so that their angular positions may be varied simultaneously by pressure fluid admitted to one side or other of a piston 37 through ducts 39, 40. A friction clutch 4, 7, 8 within the casing 16 may directly couple the shafts 3, 6 when pressure fluid is admitted via ducts 14, 15 into a space 13 of a slidable cylinder 13. The pressure and suction sides of the aggregates 26, 27 can be interconnected through ducts 43, 44. When so connected by a piston slide valve 45 the aggregates are rendered ineffective. The fluid pressure system includes a pressure line 61, Fig. 3, supplied by a gear pump 59 and controlled by a centrifugal pressure switch B. The fluid supply to the clutch 4, 7, 8 is controlled by a centrifugal governor C which is driven according to vehicle speed and by a slide valve D fixed to the piston 37. The fluid supply to the ducts 39, 40 is controlled by a speed governor A driven according to engine speed and the supply pipe 58 to the governor is controlled by a slide valve G. The speed governor A is affected by the position of the accelerator pedal 57. In the position shown, the clutch 4, 7, 8 is engaged pressure fluid passing through pipe 64, valve D, pipe 66, valve F and pipe 15 to the cylinder space 13. Pressure in a pipe 47 connected to pipe 15 holds the slide valve 45 in its left hand position to interconnect ducts 43, 44 and render the hydrostatic gear ineffective. Pressure in the pipe 47 also holds the slide valve G in its right hand position and disconnects pipe 58 from the pressure pipe 61. If the vehicle speed falls governor C interconnects pipes 64, 15, 47 to a pressureless pipe 65 so that (a) the clutch 4, 7, 8 is disengaged and (b) pipe 58 is connected to pressure pipe 61. The hydrostatic gear then functions. When the engine is idling the pressure in the pipe 46 acting on the valve 45 is insufficient to overcome the spring 50 so that the ducts 43, 44 are interconnected. Also the friction clutch is disengaged so that the vehicle is stationary and the piston 37 is in its left-hand position so that the hydrostatic gear is in its lowest gear position. As the speed increases the valve 45 is moved to the right to bring the hydrostatic gear into operation and the vehicle starts to move in low gear. The gear ratio will gradually increase until the piston 37 reaches its right hand position. The pipes 64, 66 will thus be interconnected so that the friction clutch 4, 7, 8 is engaged and the hydrostatic gear is disengaged. If, when a direct drive is in operation, a hill or like resistance is encountered, full depression of the accelerator pedal 57 will cause an arm 68 to move the valve F to the left to connect the pipes 15, 47 to a pressureless pipe 70. This will disconnect the direct drive and put the variable-speed hydrostatic gear into operation again.