| 摘要 |
PROBLEM TO BE SOLVED: To provide a manhole structure having fall prevention ladder performing derricking motion and locking automatically uninclinably and securely fixing it in a state leaving little room in oscillation. SOLUTION: This manhole structure is provided with the lid receiving frame 1, a manhole lid 2, the fall prevention ladder 6, and a first locking structure for locking and holding the locked ladder 6. The fall prevention ladder 6 includes a side frame 10, a crosspiece body 11, a bracket 12, and a supporting shaft 13. The fall prevention ladder 6 can rise, and fall to the horizontally lying position and the rising position around the supporting shaft 13. The first locking structure includes a lock frame 32 guided slidingly by the fall prevention ladder 6, a lock recessed part 21 provided in the bracket 12, a lock spring 33 energizing the lock frame 32, and a lock releasing body 34. When the fall prevention ladder 6 is raised, the lock frame 32 is automatically engaged with the lock recessed part 21 to fix the fall prevention ladder 6 so as to prevent it from tilting and falling down. COPYRIGHT: (C)2008,JPO&INPIT
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