PROBLEM TO BE SOLVED: To ensure appropriate visibility even in the sprinkling operation in the fog or at dusk by coating the expansion boom with a fluorescent paint. ;SOLUTION: The expansion boom 20 is provided with a first-stage boom 22, a second-stage boom 23 and a third-stage boom 24 in this order from the base end toward the tip. The first-stage boom 20 is combined bendably with the tip of an oscillating boom 21 at the base end. Meanwhile, the second-stage boom 23 and third-stage boom 24 are slid toward the tip with respect to the first-stage boom 22 and second-stage boom 23 which are respectively only one stage closer to the base end to freely change the projecting amt. The first-stage boom 22, second-stage boom 23 and third-stage boom 24 are coated with a fluorescent paint 26. By such a constitution, the booms 22, 23 and 24 loom in the fog due to the fluorescent paint 26. Accordingly, the position and attitude of the booms 22, 23 and 24 are easily recognized by an operator.;COPYRIGHT: (C)1999,JPO
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