Patent ID: 8925439
Filing Date: 2015-01-06
Classification: A01B,F15B,Y10T

Abstract:
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.