| 摘要 |
The manhole has a stop (38) secured to a frame and perpendicular to rear end wall (3) of the frame, and a self-locking arm (30) whose end is pivotally mounted to the frame and is slidable in a fixed longilinear guiding groove (35) such that the end approaches a front end wall (3) of the frame during tilting of a rectangular shaped plug (8) towards a closed position of the plug. The end bearing on the stop during tilting of the plug causes the plug to withdraw towards the rear end wall adjacent to a hinged side of the plug such that the plug closes an opening of the frame. |
