| 摘要 |
PROBLEM TO BE SOLVED: To provide an inner cover for underground structures which can be fitted in existing various kinds of underground structures with one operation freely to be removed and through which a worker can easily enter into a manhole for maintenance. SOLUTION: This inner cover for underground structures is formed of two frame parts 21 and 22 formed to be brought in contact with the inner wall of an opening by enlarging and to be separated from the inner wall of the opening by shrinking and plate-like inner cover members 23 and 24 respectively provided in each frame part 21 and 22 to cover inside of the opening 15. The two frames 21 and 22 are provided to be brought in contact or separated in a single operation, and the two cover members 23 and 24 are fitted to each frame part 21 and 22 so that they are opened only upward or downward, and formed so that an opening/closing ends thereof are overlapped with each other in the condition wherein both the inner cover members 23 and 24 are closed. COPYRIGHT: (C)2004,JPO
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