Improvements in or relating to yielding roof supports for mines

摘要

1,060,500. Hydraulic pit props. W. EGGEMANN and E. VON CAMPENHAUSEN. Dec. 18, 1963 [Dec. 24, 1962; Nov. 7, 1963], No. 49910/63. Heading E1E. A hydraulic pit prop comprises a piston tube 30 movable within a short cylinder 18 suspended, hingedly or otherwise, from the upper end of a guard tube 12, Fig. 2 (not shown), which may have a detachable extension piece (11) at its foot. The piston tube 30 is clamped against a piston head 27 by a threaded tube 35 rigid with a plate 38 seated on a shoulder therein. The tube 35 opens into the cylinder chamber 23, and its upper end carries a relief valve 41 exhausting into the upper end of tube 30, which may subsequently be emptied through bores 34. The prop may be released by opening the inlet ball valve 25. The outer surface of the piston tube 30 is chromed or otherwise hardened.