US Patent 7160051 Closure device

A fixed frame (4) and a covering element (6), the frame (4) defining a frame plane (P—P). A first latch (30) has two latch surfaces (32, 34) which cooperate and which are inclined relative to the frame plane (P—P). The covering element (6) and the frame (4) comprise cooperating stop surfaces (52, 56) which limit a displacement of the lid (6) within the frame (4) in the frame plane (P—P). The stop surfaces (52, 56) are inclined relative to the frame plane (P—P) by an angle of from 30° to 80° and they maintain the covering element flat on the frame. Application to manhole covers for closing manholes.