| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic circuit of a hydraulic telescopic boom of high operability, in which an attachment driving hydraulic actuator is expanded and contracted by the same operation as for expanding and contracting a boom expanding and contracting cylinder by an operator without feeling the sense of discomfort. SOLUTION: In this hydraulic circuit of the hydraulic telescopic boom comprising: a boom expanding and contracting hydraulic cylinder; the attachment driving hydraulic actuator for operating the attachment; an operation valve for expanding and contracting a boom; an expansion and contraction switch valve; a boom-attachment switch valve; an attachment expansion and contraction switch valve; a boom- attachment switching operation means; and an attachment expansion and contraction control means for interlocking and switching the expansion and contraction switching valve and the attachment expansion and contraction switch valve. The attachment driving hydraulic actuator is expanded when the operating valve for expanding and contracting the boom, is operated to an expansion side, and the attachment driving hydraulic actuator is contracted when the operation valve for expanding and contracting the boom is operated to a contraction side, in operating the attachment driving hydraulic actuator. COPYRIGHT: (C)2003,JPO
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