| 摘要 |
979,453. Hydrostatic transmissions. DOWTY HYDRAULIC UNITS Ltd. Aug. 9, 1961 [Aug. 19, 1960]; No. 28812/60. Headings F2C and F2D. [Also in Division G3] Two separate hydrostatic transmissions each comprise a variable displacement pump driving a fixed displacement motor, a common control means being provided for simultaneously varying the displacement of the pumps and means also being provided for selectively varying the displacement of the individual pumps. Tractor engine 1 drives, through gears 2, 3 and 4, two variable displacement hydraulic pumps 5 and 6 which respectively drive hydraulic motors 7 and 12 which drive, through gear trains 8 and 13, sprockets 9 and 14 in driving engagement with endless tracks 11 and 15 respectively. The displacements of pumps 5 and 6 are adjustable by servomotors 16 and 17 (see Division G3), which include projecting control members 18, 19 respectively. A manuallyoperated speed control lever 25 is connected with members 18, 19 through a link 24, yoke 23 and springs 21, 22. Lever 25 also controls a rotary valve 26. Member 28 of the valve has two recesses 29, 31 which co-operate respectively with ports 32, 33, 34 and 36, 37, 38 extending into the bore 35 of the valve. Ports 32, 34, 36, 38 are fed with liquid from an auxiliary pump 42 through restrictors 43 to 46 respectively and are also connected, through pipes 47, 48, 49 and 51, to servomotors 17 and 16 for overriding control thereof. Ports 33, 37 are respectively connected to adjustable leak valves 39, 41. Thus if lever 25 is rotated counterclockwise port 33 is connected to port 34, and port 36 to port 37. Operation of leak valve 39 permits liquid flow from pump 42 through restrictor 44 and reduces pressure in pipe 48 relatively to pipe 47. Thus valve 39 is arranged to apply an overriding control to servo 17 in the direction to reduce the displacement of pump 6. Similarly, operation of valve 41 is arranged to reduce the displacement of pump 5. Thus the tractor speed is adjusted by lever 25 and steering is effected by operation of valves 39, 41. Specification 949,672 is referred to. |
