| 摘要 |
PROBLEM TO BE SOLVED: To improve the safety of a ladder for manhole to be set at a manhole of an underground structure such as conduit line system and set the ladder freely. SOLUTION: A ladder body consisting of two vertical side supports 21, 21 and a plurality of rungs 24, 24 is fixed on a bottom panel 11 of an underground structure 10 through lower end fixing parts 25, 25, while the ladder body is fixed to an interior wall 12 (or underside of upper panel 13) through upper side fixing members 28, 28, whereby the body is set under a manhole 14. Handrail members 26, 26 are slidably mounted to the top ends of the supports 21, 21, respectively, so that each of the members 26 is protruded from the manhole and retracted therefrom. An engaging groove comprising a vertical part and a horizontal part and an engaging means having an engaging protrusion which is slidably engaged in the engaging groove are provided in each of the members 26 and the corresponding support 21 respectively so that the handrail member 26 is engaged in its lowered state or in its lifted state.
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