| 摘要 |
A pump or other source supplies hydraulic fluid under pressure to a plurality of slave services which require a pre-selected priority of supply such as, e.g., brakes (first priority), power steering (second priority), and self-leveling device (third priority). A valve having a resiliently loaded spool is connected between the pressurized fluid source and the slave services, with the source pressure acting in opposition to the resilient loading on the spool so that the position of the spool is influenced by the source pressure. Accordingly, if the source pressure falls below a pre-determined value the resilient loading displaces the valve spool so as to cut off supply of fluid to the least essential service; if the source pressure falls below a second and lower value the spool is further displaced to cut off supply to the second priority service, and so on. Provision is made to leave the first priority service (e.g., brakes) always connected. A pressure accumulator may be connected between the fluid source and the valve. A Euler strut-type spring may be employed to provide the resilient loading so as to provide a "snap" spool displacement action to open or close the lower priority slave services in response to source pressure.
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