| 摘要 |
PROBLEM TO BE SOLVED: To secure high safety by preventing fluctuation of turning speed due to wrong operation of a hydraulic actuator, while improving productivity and profitability of a device by using a hydraulic pump to be commonly used to drive a turning motor and to drive other hydraulic actuator. SOLUTION: A turn control valve 42 and an actuator control valve 44 are provided along a bypass flow passage 56 formed from the hydraulic pump 40 to a tank. When operating the turn control valve 42, a selector valve 70 is switched to hold the condition wherein the operating fluid is bypassed on a downstream side of the control valve 42 regardless of operation of an actuator operating lever 65, and a sudden change of the amount of the operating fluid to be supplied to the turning motor 18 due to operation of an actuator 24 during the drive of the turning motor 18 can be thereby prevented to prevent a sudden change of the turning speed. COPYRIGHT: (C)2007,JPO&INPIT
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