| 摘要 |
PURPOSE: A manhole ladder with a locking device is provided to help a worker to climb down the ladder safely and prevent the approach of unauthorized persons. CONSTITUTION: The manhole ladder with a locking device is composed of: a vertical support(4) fixed to a wall by anchors(2); a couple of hinges(5) assisting a frame(7) provided with numbers of bars to be rotated; a locking device(10) provided with a polygonal bolt(8) attached to the frame bar and connected to a locking bar(9); a frame(7) used as a handle for a worker climbing down the ladder in safe. Workers lock the manhole with the locking device after finishing work, therefore only authorized persons are allowed to come into a manhole.
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