Openable hatch apparatus for a skylight

An openable hatch apparatus for covering an opening through a surface of a structure, said opening having a raised curb defining the perimeter of said opening, said raised curb including an external curb surface extending substantially perpendicularly away from said structure surface, said hatch assembly comprising:

• covering means having a geometric shape and size suitable for substantially covering said opening;
• a frame assembly surrounding the periphery of said covering means and having a depending skirt portion, said depending skirt portion opposing and being spaced from said external curb surface when said hatch assembly is joined to said raised curb;
• a stem extending from said depending skirt and a bearing joined to said stem, said bearing having a periphery that includes a convex surface and at least one chordal flat surface, said stem and said depending skirt defining a junction therebetween;
• and
• a flange adapted to be connected to the curb and including a cradle in which said bearing can be rotatably mounted, said cradle defining an arc greater than 180.degree. and having an opening which faces outwardly from the external curb surface, the shape of the bearing being such relative to the cradle that it can be (a) placed horizontally into the cradle through said opening when the frame assembly is in a predetermined position, and (b) rotated within said cradle to a position in which it cannot be removed from the cradle, whereby substantially the entire weight of the frame assembly may rest on the stem or bearing and be supported by the cradle after the bearing has been inserted into said cradle.