Patent ID: 7451542

Claim:
A method for the manufacture of a heat-exchanger tube, comprising integral outer fins and inner fins worked out of a tube wall which extend helically on an outside of the tube and extend axially parallel or helically on an inside of the tube, and the inner fins are intersected by secondary grooves, in which the following method steps are carried out: helically extending outer fins are formed by a first rotatingly driven rolling tool, which is mounted on an arbor, in a first forming area on the outside of a plain tube by fin material obtained by displacing material from the tube wall by means of a first finning step, and the finned tube which is being created is rotated by radial forces and moved axially corresponding with the helical fins which are being created, since the axis of the rolling tool is skewed with respect to the tube axis, whereby the outer fins are formed out of the otherwise nonformed plain tube; the tube wall is supported in a first forming area by a first profiled mandrel lying in the tube, which mandrel is rotatable and profiled, whereby the radial forces of the first rolling tool presses the material of the tube wall into grooves of the first profiled mandrel to form helically or axially parallel extending inner fins on the inner surface of the tube; the outer fins are further shaped by a second rolling tool during a second finning step in a second forming area which is spaced from the first forming area, wherein the second rolling tool is mounted on the same arbor as the first rolling tool and hence is rotatingly driven in the same direction as the first rolling tool, and the inner fins are provided with secondary grooves; whereby the tube wall is supported in a second forming area by a second mandrel lying in the tube, which second mandrel is also constructed rotatably and profiled, the profiling of which, however, differs from the profiling of the first mandrel with respect to the amount or the orientation of the helix angle.