GB715320A - Improvements relating to mine props and mine arch supports - Google Patents

Abstract

715,320. Mine arch supports and props. MURMANN, W. Feb. 8, 1951 [Feb. 8, 1950], No. 3112/51. Class 20 (2) Two parts, e.g. I or rail-sections, of a mine arch support or pit prop are secured together by clamps to yield under excess load and an elongated shearing member is interposed between the two parts, the arrangement being such that on relative movement of the parts towards each other, the shearing member is stressed in tension and is sheared by the clamps. As shown in Figs 1, 3 the arch support comprises arch members connected by links 1 and each formed of two rail-section parts 2, 3 connected at their overlapping ends by clamps 9, 10 each clamp being bolted to one of the rail parts and frictionally engaging the other. Between the overlapping ends of the parts 2, 3 there is arranged an e!ongated sheet metal shearing member 4 having a relatively narrow middle part 5, Fig. 6, and widened ends 6, the clamps 9, 10 being located in the region of the narrow part 5. On movement towards each other of the parts 2, 3, shearing edges provided on the clamps 9, 10 shear off the projecting edges of the parts 6 of the shearing member 4 whilst the middle part 5 is stressed in tension. Shearing need not take place at both ends of the shearing member 4. For example the shearing member may be of T-shape, the broader portion being sheared by the shearing edge of the clamp 10 whilst the narrow end is secured to the part 2 in the vicinity of the clamp 9, which would have no shearing edge. In a modification, Fig. 5 (not shown), a similar arrangement is applied to a pit prop.