Flexible piping method and apparatus of producing same

Abstract

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 of a first winding is separated from the leading portion of a corresponding subsequent winding and interlocking is prevented for at least one revolution. Each free winding, which constitutes one circumference of the piping, is formed by the insertion of a shaping tool into contact with the leading portion of the free winding prior to the point where this leading portion would normally interlock with the leading portion of a corresponding subsequent winding one revolution later. The shaping tool alters the cross-sectional arrangement of the metal band such that interlocking of that portion of this spiralling band which is contacted by the shaping tool is prevented. A timer controls the duration of the interval of time during which interlocked windings are spirally formed and the same time also controls the duration of the interval of time during which the shaping tool is inserted into contact against the leading portion of a winding when forming a free winding. Each free winding may be severed widthwise in order to separate adjacent winding groups into individual sections of piping. By the incorporation of the free winding concept, the area of burrs on the free end of each individual section is limited to the area of the widthwise cut.