| 摘要 |
A manhole cover made of pig iron having a concrete filling has a trough-shaped shell (5), an outer support ring (13) and in between a circle of ventilation openings (23) between which radial inset ribs (11) run. To reduce the proportion of pig iron, the shell (5) is drawn to the outside to such an extent that the ventilation openings (23), in their upper area, lie partly inside the width of the support ring (13) and, as sloping shafts which are separated from one another only by the ribs (11) and are defined on the inside by the outer contour of the shell, run radially downwards to the inside in order to open out at the bottom inside the support ring (13). <IMAGE> |
