| 摘要 |
A hydraulic tool is operable in an open center (OC) and a closed center (CC) mode and includes a cylinder and a piston within the cylinder. The piston defines a drive chamber and a retract chamber. A valve spool selectively supplies and exhausts hydraulic fluid to and from the drive chamber and the retract chamber. An oil tube is coupled to the valve spool and extends through the piston and is in communication with the retract chamber. The oil tube includes at least one hole that can selectively communicate the drive chamber and the retract chamber. A selector sleeve is provided for switching between the OC and CC modes. In the OC mode when the tool is in the neutral mode, the valve spool is configured to supply the hydraulic fluid through the oil tube to the retract chamber such that movement of the piston can allow communication between the retract chamber and the drive chamber through the at least one hole in the oil tube.
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