| 摘要 |
<p>The manhole frame has a central circular opening and three housings spaced at 120 degrees in its edge, while the removable circular cover has three matching peripheral tenons. The bottom face of each tenon has a section that can slide on a housing engagement ramp (10) during cover placing, the section having a spur (14) that extends radially towards the central vertical axis. The spur end (15) abuts, in the locked position, against the locking surface of a counter slope (11) that extends from one wall to another in the housing but not parallel to the lateral walls (8a,8b) or longitudinal axis (XX) of the housing.</p> |
