| 摘要 |
<p>The shaft of manhole cover is readily adaptable to a different road level in the event of application of new layer of bitumen and has a fixed outer frame, and an inner frame carrying the lid. The inner frame has a complete vertically aligned serration profile, with teeth alternately terminating on two different parallel rising planes(1, A, B, C, D). The outer frame, with corresponding negative indentations, only completely bears the upper mounting plane(2, C, D). According to turning and height-setting of the inner frame, the outer one first accommodates this upper plane, and the lower one is gradually brought to bear. With load-bearing capacity maintained, the outer frame's width and weight are reduced.</p> |
