| 摘要 |
1392326 Hydrostatic transmissions BERGENS MEKANISKE VERKSTEDER AS 30 March 1972 [31 March 1971] 15237/72 Heading F2D In a hydrostatic transmission, particularly for trawl winches of fishing boats, a pump 1, of fixed displacement, supplies a motor 2 through a reversing and throttling valve 13, the motor having a by-pass valve 6 and the return to the pump 1 a pressure reduction valve 4. When the pump is supplying the motor (position H of valve 3) the valve 4 is controlled by a spring and by the output pressure from the pump as well as the pressure of an expansion tank 5 so that the throttling by this valve is increased by an increased output pressure from the pump to slow the motor and reduce this pressure (and vice-versa on decrease of pressure) so that the pump output can be maintained at a desired value. When the motor 2 overruns the pump 1 (position L of valve 3) and is used for braking a pilot valve 8 opens the by-pass 6 at a predetermined pressure from the motor 2 so that the degree to which the motor drives the pump is controlled. The valve 4 here acts to prevent cavitation occurring in the motor. An operating handle (not shown) operates valve 3, and by means of this the throttling of the return from the motor can be made complete (position S of valve 3), the braking being limited by a by-pass valve 6 controlled by a pressure-operated pilot valve 7. A valve 9 can be operated which bleeds control fluid from the by-pass valve 6 to fully open this valve and allow the motor to turn freely. An alternative embodiment (Fig. 2, not shown) has a throttle valve preset for a maximum opening pressure in place of valve 6 and a further throttle valve preset for a minimum opening pressure connected in parallel across the pump between pump and valve 3, the valves 7 and 8 not being present in this embodiment. A further embodiment (Fig. 3, not shown) has a throttle valve adjustable in a range between maximum and minimum pressures in parallel across the motor (in place of valves 6, 7, 8) and a yet further embodiment has a spring seated non- return valve connected in parallel across the pump as the throttle valve opening at a minimum pressure of Fig. 2 (Fig. 4, not shown). |
