| 摘要 |
PROBLEM TO BE SOLVED: To set speed of an actuator to be primary operation speed responding to operation quantity of a control lever of an operation device, regardless of the magnitude of a load applied to the actuator, when the actuator is operated by the gravity of a structure. SOLUTION: This hydraulic device is provided with a hydraulic pump 2, a tank 8, a boom cylinder 6, a boom directional control valve 7 and the boom operation device 12. The boom directional control valve 7 blocks a pressure oil supply passage from the hydraulic pump 2 to the boom cylinder 6 when the boom cylinder 6 is contracted by the gravity of the predetermined structure such as a boom 50. On a main line 13 for returning oil in a bottom chamber of the boom cylinder 6 to the tank 8 when the boom cylinder 6 is contracted by the gravity of the structure such as the boom 50, a pressure compensation vale 14 operated in accordance with the pressure of the main line 13 is arranged in a portion positioned between the boom cylinder 6 and the boom directional control valve 7. COPYRIGHT: (C)2007,JPO&INPIT
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