| 摘要 |
A manhole cover frame (F) is moulded in one piece of a hardenable material such as concrete which is poured into a jig (1) and is actually moulded against those surfaces of a manhole cover (C) with which it is to interfit in use. When the frame (F) is matched to the cover (C) used to mould it, there results a perfect fit between the two. The surfaces of the cover (C) which are to seat against the frame (F) are machined prior to use of the cover (C) in the moulding process, so that a closely mated interface is obtained between the cover (C) and the frame (F). Alternatively, the cover surfaces are not machined but are coated with a low-frictional material. |
