Improvement connected with Ventilating Manhole Covers of Sewers and Drains.

摘要

23,282. Ham, F. G. S. Oct. 28. Manhole covers; ventilating.-A manhole cover B, for drains and sewers, is provided with a closing- tray E having an annular channel D forming a water lute, and supported by lugs F in bayonet slots G. To allow ventilation, the tray is turned down into the position shown in dotted lines.