| 摘要 |
<p>Apparatus for modulating the fluid pressure directed to a load comprises a housing having an inlet port and an outlet port. A valve member in the housing is movable in a first direction to increase communication between the inlet port and the outlet port and in a second direction to decrease communication between the inlet port and the outlet port. A valve-positioning structure moves the valve member in the first and second directions. The valve positioning structure moves the valve member in the first direction (a) in a first stage of valve operation which causes an increase in the pressure in the outlet port at a first rate and (b) in a second stage of valve operation which causes an increase in the pressure in the outlet port at a second rate that is higher than the first rate. The valve positioning structure initially applies a force to the valve member that is proportional to the pressure desired in the outlet port and which urges the valve member in the first direction, and as the pressure in the outlet port increases applies a force to the valve member that is proportional to the pressure in said outlet port urging the valve in said second direction so that when the outlet pressure reaches the desired pressure the forces acting on the valve member are balanced.</p> |
