| 摘要 |
Three-position fluid valves for use in downhole environments are disclosed. An example valve includes first, second and third ports, a chamber coupled to the second port, a first sleeve to selectively couple the first port to the chamber and the second port, a second sleeve to selectively couple the third port to the chamber and the second port, and a piston that forms at least part of the chamber and is coupled to the sleeves. The piston moves between a first position in which the piston displaces the first sleeve to couple the first port to the chamber and the second port, a second position in which neither of the first or third ports is coupled to the second port, and a third position in which the piston displaces the second sleeve to couple the third port to the chamber and the second port.
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