Mine roof supporting assembly

Claim 1

A MINE ROOF SUPPORT ASSEMBLY COMPRISING, IN COMBINATION, A SUPPORT PLATE HAVING AN UPPER ROOF ENGAGING SURFACE AND A LOWER OUTER FACE, SAID PLATE PROVIDED WITH A CENTRAL OPENING HAVING A DIAMETER NO LESS THAN THE DIAMETER OF A HOLE FORMED IN THE ROOF, AN OUTWARDLY PROJECTING ANNULAR OUTER AND INNER SIDE WALLS, SAID OPENING AND INCLUDING A OUTER AND INNER SIDE WALLS, SAID INNER SIDE WALL PROVIDING A CONCAVE SPHERICAL SEATING SURFACE SURROUNDING SAID OPERATION; THE UPPER EDGE OF SAID INNER SIDE WALL COPLANAR WITH THE UPPER ROOF ENGAGING SURFACE OF SAID PLATE AND PROVIDING A SECOND ROOF ENGAGING SURFACE SURROUNDING THE HOLE IN THE MINE ROOF STRUCTURE WHICH EDGE COMBINED WITH SAID FIRST MENTIONED ROOF ENGAGING SURFACE PREVENTS DISTORTION OF SAID PLATE WHEN SAID PLATE IS IN ASSEMBLED SUPPORTING POSITION, A FASTENING BOLT HAVING A SHANK PORTION INSERTABLE THROUGH SAID OPENING IN SAID PLATE AND ADAPTED TO EXTEND INTO A HOLE PROVIDED IN THE MINE ROOF STRUCTURE, MEANS ON SAID SHANK PORTION TO ANCHOR SAID BOLT IN SAID ROOF HOLE, SAID BOLT PROVIDED WITH A HEAD PORTION HAVING A CONVEX SPHERICAL SURFACE FACING SAID SHANK PORTION, THE RADII OF SAID PLATE AND BOLT HEAD SPHERICAL SURFACES BEING SUBSTANTIALLY EQUAL, WHEREBY, REGARDLESS OF THE RELATIVE ANGLE BETWEEN SAID BOLT SHANK AND THE UPPER SURFACE OF SAID PLATE, A POSITIVE FULL CONTACT ENGAGEMENT IS PROVIDED BETWEEN SAID BOLT HEAD AND THE SEATING SURFACE OF SAID PLATE.