| 摘要 |
PROBLEM TO BE SOLVED: To provide a locking device for a manhole cover which resists a quite inadequate use environment exposed to rainwater and muddy water and in which a security function is reinforced largely because a lock unit is used in an upper-lower two-stage structure. SOLUTION: The locking device for the manhole cover is composed of a rod-shaped housing fixed onto the cover, a first lock unit being installed to the lower-side section of the housing and locking the cover at a closing place to a fixed receiving frame for a manhole and a second lock unit mounted on the upper side of the housing and closing a passage for a key for the first lock unit. The second lock unit is extracted from the housing by a key for the second lock unit, and the locking of the cover to the fixed receiving frame is released by the key for the first lock unit. COPYRIGHT: (C)2004,JPO
|
