arc particularly for use in lining of tunnels, for example, tunnels of coal mines

摘要

The invention relates to arches for use in tunnels such as underground mine tunnels. These arches are composed of a bent metal beam often of "H" or "T"-section. Problems have previously arisen in accurately bending the beams to the required shape. The apparatus of the invention includes a D-shaped former which is rotatable relative to a roller. The beam is clamped to one end of the former and on rotation of the former relative to the roller, the beam is bent around the former so that it assumes the required shape, the ends of the beam being clamped to the former. A cutting device may be employed to cut the beam, while bent around the former, into three or more sections.