GB688782A - Improvements in steel roof-shoring devices in mines - Google Patents

Abstract

688,782. Mine roof support bars. ALLAIN, P. L. Nov. 9, 1950. No. 27412/50. Class 20(ii) Mine roof support bars 1A, 1B, Fig. 1, are connected end-to-end by means of male and female end portions 2, 3, the male end 2 having an arcuate upper surface 7 engaging a similarly formed top wall 10 of the female end 3 which has an open bottom and side walls 12 formed with slideways 13 for the side wings 16 of a wedge 15 adapted to bear against the under surface 9 of the male end 2. In assembling the roof support bars the rear end of the bar 1B is raised to insert the male end 2 through the open bottom of the female end 3 of the prop-supported bar 1A and to rest it on a nose 11, the forward end of the bar 1B being then raised and the wedge 15 inserted to hold the bar 1B as a cantilever. A further prop is then inserted under the male end of the bar 1B and flexibility imparted to the connection by removal of the wedge. On removal of the prop supporting the rearmost bar, the latter swings downwardly about the arcuate surface 7 of the adjacent bar and the angular extent of the surface is such that the female end is disengaged from the male end before the rearmost bar has touched ground. This facilitates the recovery of bars in seams of small thickness. As shown in Fig. 1, the arcuate surfaces 7, 10 are cylindrical about a transverse axis but in a modification shown in Fig. 7, the co-acting surfaces 7, 10 cf the male and female ends are bi-conical, the former having a cut-out portion 23 adapted to straddle a web 4 in the female end which is provided with a platform 24 for supporting the tip 22 of the male end during erection of the associated bar.