| 摘要 |
PROBLEM TO BE SOLVED: To open a lid for an underground structure by a comparatively small force even if an opening and closing structure of the lid is applied to a lid having a large thickness. SOLUTION: This opening and closing structure of the lid is provided with a receiving frame 2 forming an opening 14 and the lid 1 closing the opening, a first supporting point 3 is provided in a vicinity of the inside of a fringe part 10 of the lid, and a second supporting point 4 is provided on the receiving frame side at a position on more inner side of the opening and lower than a first supporting point position of the closed lid. The first supporting point and the second supporting point are mutually connected by hinge hardware 5, which opposes the approach of the first supporting point and the second supporting point exceeding a predetermined distance. The connection of the first supporting point and the hinge hardware enables turning in a horizontal face of the lid while the hinge hardware stands substantially straight by bringing the first supporting point onto the upper side, and the connection of the second supporting point and the hinge hardware allows the displacement of the hinge hardware in the direction in which the first supporting point leaves the second supporting point. The second supporting point is formed by a horizontal shaft 22, and the hinge hardware has an oblong hole 27 along the longitudinal direction to insert the horizontal shaft therein. The hinge hardware has a head part like a rugby ball, and the first supporting point can turn for the head part.
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