Manhole cover has ridge formed to recess on manhole opening frame to engage lateral projection of cover and prevent cover from accidentally closing from upright open position

摘要

A ridge (7) is formed to a recess (3) on a manhole opening frame (1) to engage the lateral projection (4) of a cover (2) and prevent the cover from accidentally closing from an upright open position. The ridge also allows play or tilting of the cover hinge about its axis, with the hinge inserted into hinge holes (5,6) on both sides of the recess.