Valve control valve circuit for operating a single acting hydraulic cylinder

摘要

A system for operating a single acting hydraulic cylinder includes a directional valve that has one extreme position in which a workport is connected to a tank return conduit, another extreme position where the workport is connected to a pump supply conduit, and a closed intermediate a position where the workport is disconnected from both the pump and the tank. The directional valve is pilot operated and is biased toward the one extreme position by a spring. An electrically operated primary applies pilot pressure to the directional valve alternately from the pump supply conduit and the tank return conduit. A pilot operated check valve has a first state which restricts fluid flow only from the workport toward the chamber and a second state in which fluid can flows from the chamber to the workport. The system has a pressure compensation that also provides self priming of the directional valve.

主权项

1. A system for operating a hydraulic cylinder by selectively controlling flow of fluid between a chamber of the hydraulic cylinder and each of a pump and a tank, the system comprising:
a directional control valve including a workport, and a spool that has a first position in which the workport is connected to the pump, a second position in which the workport is disconnected from both the pump and the tank, and a third position in which the workport is connected to the tank, wherein the second position is between the first and third positions; a selective check valve operably connected to control fluid flow between the workport and the chamber of the hydraulic cylinder, and having a first state in which fluid can flow only from the workport toward the chamber and a second state in which fluid can flow from the chamber to the workport, wherein the selective check valve changes states in response to a control signal applied to a control port; the directional control valve having a fourth position in which the workport is disconnected from both the pump and the tank, wherein the third position is between the second and fourth positions, and a spring biases the directional control valve into the fourth position; and the directional control valve in the second, third, and fourth position provides a path between the pump and the tank.