Improvements in or relating to Concrete Props and Beams for Supporting the Roofs of Coal Mines and other Mines and for like purposes
115,539. Lewis, E. F., and Lewis, R. J. July 11, 1917. Mine props.-The prop or support comprises two side posts A and a cross-beam D, each made of reinforced concrete. Each post is recessed into the beam in some such manner as is shown at D', D , the joint being also curved from side to side, a...
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