Pit prop designed to work in thin seam of coal - has projections with inclined surfaces allowing easy turning of cap

摘要

The face supporting device for use in mining comprises two extensible props (2) mounted on a base (1) and carrying a cap (3). Part-spherical heads (4) on the props engage in spherical bearings (5) in the cap and a part-spherical element (8) engages between each prop head (4) and a pair of resilient plates (7) mounted on the cap to restrict lateral tilting of the cap relative to the props. The elements are so arranged that they do not impede longitudinal angular displacement of the cap relative to the props due to the props being extended to different heights.