Patent ID: 7730754
Filing Date: 2010-06-08
Classification: B21C

Abstract:
1. A method of manufacturing a spiral duct comprising: supplying a metal band having two straight longitudinal edges extending in a longitudinal direction of the metal band; forming dual bent parts at each straight longitudinal edge of the metal band; cutting the metal band in the longitudinal direction into two cut metal bands by varying a horizontal rotation angle of a cutting roll such that each cut metal band has a cut edge extending substantially in the longitudinal direction and having straight and waved portions, and a straight edge corresponding to one of the two straight longitudinal edges of the metal band; forming single bent parts at the cut edge of each cut metal band; and coupling the single bent part with the dual bent part of each cut metal band while helically winding the cut metal bands to make continuous ducts having integrally formed curved and straight duct parts.