| 摘要 |
PROBLEM TO BE SOLVED: To provide a shaft for a pneumatic caisson, by which a vertical ladder can be lifted and lowered safely and rapidly without limiting the material passing range of excavated materials or the like. SOLUTION: A passage for the common use of the entrance and exit of the operators and the transport of materials is installed, and a hollow shaft body 11 constituted in a vertically extensible manner, the vertical ladder 12 mounted on the interior wall of the shaft body 11 and a foldable back rest 13 set up on the opening surface side of the vertical ladder 12 are secured.
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