| 摘要 |
A hydraulic control device for a working machine includes control valves (1-6); hydraulic actuators controlled by corresponding control valves and divided into groups (A,B); unified bleed-off valves (27,28) disposed on discharge lines of first and second hydraulic pumps (7,8); central bypass paths provided in the control valves, the central bypass paths of each group being connected in tandem so as to form a central bypass line (24); and bypass-cutting valves disposed on the central bypass lines, the bypass-cutting valves (35,36) being automatically switched so as to open the central bypass lines when the unified bleed-off valves are not operated.
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