| 摘要 |
PROBLEM TO BE SOLVED: To dispense with a round part and a cutout at a receiving frame and a flange part and to open a manhole cover by utilizing the principle of a lever. SOLUTION: This keyhole blocking device 75 for a manhole cover is provided with a receiving frame 31 having a flange part 35 at the inner periphery of an annular body 33; the manhole cover 43 supported at one end part by the receiving frame 31 and having a keyhole 47 at the other end part; a claw part 55 swingably provided at a lower face 43a of the manhole cover 43 through a rotating shaft 51 and locked to the flange part 35 from below; a locking body 49 having a top face part 57 for closing one end side of the keyhole 47; a weight body 59 additionally provided at the locking body 49 to impart rotational moment in a direction of locking the claw part 55 to the flange part 35; and a keyhole blocking plate 7 swingably provided at the locking body 49 through a support shaft 73 in the same direction as the rotating shaft 51 and making a base end on one end side abut against the top face part 57 from below to block the other end side of the keyhole 47.
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