Improvements in or relating to steel arches used for underground supports, tunnelling, air raid shelters, or buildings requiring arch supports

摘要

539,467. Shelters; mine-roof supports. THOMAS, H. E. March 20, 1940, No. 5150. [Classes 20 (i) and 20 (ii)] Arched members for air raid shelters, tunnel supports, and the like, comprise two circular section members A, B, with an interfitting joint at the ridge, whereby the use of fishplates, bolts, spanners &c. usually employed in such constructions is eliminated. The joint is formed by a doubledovetail tapered-projection C on one part, entering a double dovetail recess D on the other part, and is locked by leader and follower rings E, F forced over the interfitting parts. A retainer projection G is provided on the ringed member A to prevent the loss of the rings.