A length of flexible metal piping includes an interlockably shaped metal band spirally formed into a plurality of winding groups wherein each group includes a plurality of interlocked windings. Each of the winding groups are connected to each other by at least one free winding wherein the leading portion...http://www.google.com/patents/US4197728?utm_source=gb-gplus-sharePatent US4197728 - Flexible piping method and apparatus of producing same
