| 摘要 |
An adjustable manhole cover frame suitable for mounting on a manhole basin has an outer ring, capable of resting on the top surface of the basin, and an inner ring engaging the outer ring by screw threads and having support for a manhole cover. The inner ring also has screw jacks having lower ends suitable for contacting the basin top and rotatable to lift the inner ring. The inner ring may be rotated within the outer ring to adjust the height of the manhole cover, and the screw jacks may be used both to stabilize the inner ring while the outer ring base remains close to or in contact with said top surface, and may also be used to lift both rings out of contact with the top surface when additional raising of the inner ring is required.
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