| 摘要 |
<p>A manhole access cover comprises a removable cover member which fits within an outer frame, the cover member comprising an inner frame with an appropriate filling (44). Each of the inner and outer frames are fabricated from a plurality of lengths of angle-sectioned members (1, 21) mitred at their ends and joined to each other at the corners of the frame so that the frame comprises a substantially vertical wall formed from vertical (3, 33) limbs of the frame members and a substantially horizontal ledge extending inwardly from the vertical wall and formed from horizontal limbs (2, 22) of the frame members. The joint at each corner includes an angular corner member (9) extending around the corner on the vertical wall and to which the angle-sectioned members are crimped by piercing metal out of the angle-sectioned members (15) and crimping it into the corner members. The joint at each corner also includes an angular corner plate (8) which extends across the mitre between the horizontal limbs of the frame members towards their free edge.</p> |
