Mine roof expansion shell assembly

Claim 1

A shell segment for use in a mine roof expansion shell assembly formed by a second identical shell segment, a standard machine bolt and a standard nut, said shell segment including an upright generally semi-cylindrical base portion and two elongated finger-like side wall portions extending from said base portion and having exterior surfaces which lie generally in an extension of the curved side surface of said base portion, each of said side wall portions increasing in thickness from said base portion toward its distal end to provide a generally planar inner cam surface insecting chords of said extension of said curved side surface, each of said planar surfaces in combination with the other corresponding planar surfaces of said assembly being adapted to engage one side of said standard nut and thereby prevent turning of said nut within said assembly while providing a wedging action tending to separate said finger-like side wall portions at their distal ends, said semi-cylindrical base portion having a horizontal locking projection protruding from one of the opposite sides of its flat side wall surface at a location intermediate the opposite ends of said base portion, and said semi-cyliNdrical base portion also having a horizontal locking recess extending inwardly into the curved side thereof from the other of said opposite sides of said flat side wall surface at a location intermediate the opposite ends of said base portion, two of said shell segments mating together so that said horizontal locking projection on each segment projects into the horizontal locking recess of the mating segment whereby said mating segments are interlocked both axially and laterally.