Patent ID: 6786072
Filing Date: 2004-09-07
Classification: B21C,F28F,Y10T

Abstract:
A method for the manufacture of a metallic heat transfer tube, the steps comprising:a) supporting a plain tube on a mandrel oriented inside thereof; b) roll forming helically extending and radially outwardly extending fins so that flank surfaces on mutually adjacent fins are axially spaced from one another to define a primary groove therebetween having a bottom wall laterally bordered by roots providing a transition surface between the bottom wall and the respective flank surfaces; and c) roll forming the mutually facing flank surfaces and the roots bordering the bottom wall into a reformed bottom wall having a reformed juncture with the mutually adjacent fins and at least one re-entrant secondary groove having a width less than an axial spacing between the junctures between the reformed bottom wall and the mutually adjacent fins.