Access covers for manholes

Claim 1

An access cover comprising an outer frame and a removable cover member which fits within said outer frame, the cover member comprising an inner frame with an appropriate filling, each said frame being shaped in plan to provide corners and being fabricated from a plurality of lengths of angle-section frame members, each comprising interconnected wall and ledge portions, mitred at their ends to facilitate being joined to each other by joints at said corners to define a substantially vertical wall, formed from said wall portions, and a substantially horizontal ledge, formed from said ledge portions, extending inwardly from the vertical wall, the joint at each corner including an angular corner member with limbs to which the frame members are connected, wherein said lengths of frame members are metal extrusions each formed with a longitudinally extending captive groove in its wall portion, each said angular corner member being shaped so that its limbs fit around the corner within said captive grooves of the associated wall portions, said captive grooves being coaligned, said corner members each defining at least one vertical groove in each of its limbs with a respective wall of each said vertical groove being angled to provide opposed sloping receiving faces in one limb relative to the other limb and, for each corner, the respective frame members being joined together by simultaneously piercing tongues from their wall portions and crimping said tongues directly into positive engagement against the slope of the receiving faces of the corner member to urge the frame members together at the corner concerned.