| 摘要 |
<p>PROBLEM TO BE SOLVED: To shorten total time required to bring the whole extension boom to a target expansion condition, in an expansion mechanism using one expansion cylinder. SOLUTION: This mechanism is constituted to be switched between an ordinary expansion oil passage 136 wherein a space between an extension side oil chamber 131 of the expansion cylinder and the first outlet port 132 of an expansion operation selector valve 103 communicates with an extension side oil passage 130, wherein a differential selector valve 133 is interposed between a contraction side oil passage 134 of the expansion cylinder and the second outlet port 135 of the selector valve 103, and which makes the contraction side oil passage 134 of the expansion cylinder communicate with the second outlet port 135 of the selector valve 103 by switching the differential selector valve 133, and a differential extension oil passage 137 for communicating the contraction side oil passage 134 of the expansion cylinder with the first outlet port 132 of the expansion operation selector valve 103.</p> |
