| 摘要 |
PURPOSE:To raise the efficiency of operations by a method in which a rising and falling boom to be freely operated by a boom cylinder is provided to an upper mobile slewing body and a bucket is attached through an arm to the tip of the boom. CONSTITUTION:A boom 6 and an arm 8 are turned by a boom cylinder 7 and an arm cylinder 10, and a bucket 14 is operated for excavation. When the excavating direction of the bucket 14 is changed, the extending and contracting amounts of the cylinders 7 and 10 are varied. The tip of the arm 8 is tilted toward the directions of arrows (a) and (b) according to the extending and contracting amounts of the cylinders 7 and 10, and the excavating direction of the bucket 14 is changed. Even when trenches of wider width than the width of the bucket 14 are to be excavated, the excavating operation can be continuously performed without the needs to move the upper slewing body.
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