| 摘要 |
PROBLEM TO BE SOLVED: To operate a tooth and a mainbody of a working attachment for a construction machine to be opened/closed and swung, respectively, with a common hydraulic system. SOLUTION: A construction machine in which a working attachment with a tooth opened/closed by a hydraulic cylinder 10 and a mainbody swung by a hydraulic motor 3 is mounted at the end of an arm includes a branch feed pipe 13 and a branch return pipe 14, each branching from an oil feed pipe 11 extending to the hydraulic cylinder 10 and a return pipe 12, connected to a hydraulic motor 3 and a sequence valve 16, open when oil pressure exceeding that at the beginning of swing is applied, provided in the branch feed pipe 13. The branch return pipe 14 is provided a check valve 17 to carry oil only in the direction of return and counter balance valves 7 are laid between the hydraulic motor 3 and each of the branch feed pipe 13 and the branch return pipe 14.
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