Machine for the manufacture of helically wound metal duct or pipe

Abstract

A machine for manufacturing metal duct or pipe having improved efficiency, reliability, and speed of operation. A continuous, thin metal strip is corrugated, helically wound and seamed to form a durable yet bendable duct or pipe. The corrugation of the strip along its longitudinal axis is achieved by passing the thin metal strip through a plurality of synchronously driven (same RPM) corrugating strip roller die stands, each stand having progressively larger diameter rollers such that as a point on the metal strip passes from one corrugating strip roller stand to the next, the next stand rollers have progressively higher circumferential surface speed than the last, creating a pull on the strip material emerging from the preceeding roller stand, the pulling force at each stand preventing wrinkling or buckling of the strip as it passes through the corrugating operation. The corrugated strip is then helically wound into a bendable duct having a circular cross section by passing adjacent edges of the strip through novel, nonfouling front and rear strip lock tucking fingers which act to quickly but reliably interlock adjacent strip edges. The interlocked seam is then passed through and between compression rollers which have, peripherally disposed, a modified gear tooth pattern about their circumference forming a plurality of ridges and furrows along the seam. The bottom compression roller is ball-bearing mounted for free and unrestrictive rotation. All of the machine rollers, including the strip corrugating die rollers and the compression seam forming rollers are synchronously driven in rotation by a common drive motor through an endless drive chain. The continuously formed metal pipe may be cut to any desired length through the use of a cam-actuated moveable cut-off saw blade which severs the finished pipe perpendicular to the longitudinal axis of the pipe.

Dependencies are inferred from the claim text.