| 摘要 |
<p>The manhole cover has a separate upper portion (1) with conical sides, while the diameter of the top of this part of the manhole cover is greater than that of its underside. The top part of the manhole has outward-sloping conical metal sides (2) matching the slope of the sides (3) of the manhole cover. A sealing ring (12) fits into the top of the space (8) between the cover and the manhole sides. This defines the width of the space and height of the cover with respect to the top of the manhole. An inwards-extending flange (5) at the bottom of the support, for the upper part of the cover, has a flexible sealing lip (14).</p> |
