FORMING OF TUBULAR METAL DUCTING

摘要

Apparatus for forming spiral lock seamed ducting from flat strip metal material, the apparatus employing or adapting a machine having at least one pair of driven lock forming rollers with co-operating peripheries and which are capable of drawing flat metal strip from a supply source and shaping opposite longitudinal edge portions of said strip so that one edge portion is capable of being interlocked with the other. In the present invention a circular forming head is provided at the output end of the lock forming machine and wit its axis transversely of and angled to the feed path of lock formed strip fed from the machine so that strip fed through an aperture in the forming head will follow a helical path in such forming head to emerge from one open end of the forming head as spiral formed tubular ducting, the angle of the forming head relative to the strip feed path determining the pitch of the helical path and providing that the leading edge portion of one circumvolution and the trailing edge portion of a preceding circumvolution will overlap. The forming head is provided with an inner curved forming member adjacent the strip inlet to the forming head and co-operating with an inner circumferential bearing surface of the forming head and disposed so that the strip passes between the forming member and the said bearing surface. A tuck-in member extends partly into the forming head adjacent the strip inlet thereto and is arranged to tuck or fold one edge portion of the strip into the opposite complementary shaped edge portion of the next circumvolution; in addition there is provided a compression means which can be in the form of a pair of co-operating rollers disposed so that overlapping edge portions of adjacent circumvolutions are passed therebetween and can be compressed to form a locked seam to the tubular ducting formed by the apparatus.