| 摘要 |
PROBLEM TO BE SOLVED: To try to make a space required for housing small, and also to make a counter weight and the like small in size by providing an A-type frame with a folding type rear side part. SOLUTION: When an A-type frame 11 is to be housed in from its upstand position, its front side leg part 13 is revolved backward by a derricking cylinder 26, so that both a rear lower side leg part 20 and a rear upper side leg part 23 are thereby folded into a forward projected V-shape by way of a slide pin 22 and a slot 25. In this case, the slide pin is kept at the lower end side of the slot 25 until the halfway of a folding action using an energizing spring 27, and it is then folded while both the rear lower side leg part 20 and the rear upper side leg part 23 are being slid starting from the halfway of the folding action. This constitution thereby enables the Atype frame 11 to be compactly housed in without providing a large gap and the like for a counter weight 6.
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