Tube corrugating apparatus and method

Abstract

A novel corrugating die for metal tubing is disclosed comprising a hollow die body having one or more die teeth positioned in the internal cavity thereof. The individual die teeth have a flat shape with a curved surface and extend diagonally into the die cavity providing a die corrugating tooth surface extending from the surface of the die cavity inward along a curved line. Preferred embodiments of the die utilize a plurality of die teeth spaced uniformly around the die cavity. The angular positioning of the die teeth is such that the teeth lie somewhat on a helical line. When a thin-walled, hollow tubing is inserted into the die at the end adjacent to the roots of the die teeth and held against rotation and the die body rotated relative to the tubing, the die teeth corrugate the tubing in somewhat the manner of a thread cutting die. When only one or two die teeth are used, the die teeth must be set at a very low helical pitch. As the number of die teeth is increased the helical pitch may be greater. Rotation of the die body causes the die teeth to corrugate the tubing to a substantial depth defined by the die teeth and shorten the tubing according to the depth and the width of the teeth. Tubing corrugated by this or other apparatus may be further reduced in size by passing through a stationary reducing draw die. The surface of the tubing is preferably pitted by shot or sandblasting or etching or the like. The product is a novel helically corrugated heat exchange tubing of high heat transfer efficiency.

Dependencies are inferred from the claim text.