Patent ID: 7263924
Filing Date: 2007-09-04
Classification: F15B,Y10T

Abstract:
1. A hydraulic circuit comprising: a pump port that is communicated with a pump; a tank port that is communicated with a tank; a first actuator port and a second actuator port that are communicated with an actuator; a first supply and discharge port that is communicated with the first actuator port and a second supply and discharge port that is communicated with the second actuator port; a direction changing valve that is arranged between the pump port and the tank port and between the first supply and discharge port and the second supply and discharge port, and changes a supply and discharge direction of a hydraulic oil between the pump, the tank, and the actuator; a first pilot check valve that is arranged between the first supply and discharge port and the first actuator port; a first pilot path that activates the pressure of the hydraulic oil from the second supply and discharge port on the first pilot check valve as the pilot pressure; and a first overload relief valve that discharge the excess amount of the hydraulic oil in the first actuator port; wherein the direction changing valve has a neutral position to communicate the first supply and discharge port with the tank port; wherein the first overload relief valve is arranged in parallel with the first pilot check valve and is arranged between the first supply and discharge port and the first actuator port; and wherein the first overload relief valve serves as first valve opening means that opens the first pilot check valve when the pressure of the hydraulic oil from the first actuator port exceeds a predetermined relief pressure.