| 摘要 |
A speed control and transmission vent valve (10) includes a first valve (12), a second valve (14) having first (64) and second inlets (66), an openable outlet (70) and a spool (62 or 62') movable in response to fluid in the inlets (64,66) between first, second and third positions, a passage (112) connecting the first valve (12) to the first inlet (64), and two-state switch means (16) for communicating fluid in the passage (112) to the second inlet (66) in response to one state of the switch means (16) to move the spool (62 or 62') from the first to the second position and for communicating fluid in the passage (112) to the first inlet (64) in response to a second state of the switch means (16) to move the spool (62 or 62') from the second position to the third position in which a fluid control signal is generated. The speed control and transmission vent valve (10) can be used in a tractor having a hydrostatic transmission, and is directed to reducing the operator skill and control needed to actuate the transmission to move the vehicle. |
