| 摘要 |
A relief valve for a reversible delivery pump includes a bore having two portions of different diameters and a pair of ports opening into the bore on either side of a valve seat located between the two portions. A spool is slidable in the bore to engage the seat and includes two piston parts engaged in the respective portions of the bore. A selector valve allows the smaller of the pistons to communicate with whichever of the ports is at the higher pressure. Opposite ends of the spool intercommunicate via restricted orifice, the flow through the orifice being regulated by pilot valve responsive to the higher pressure.
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