Method of making a brazeable metal pipe having tube-insertion apertures

Abstract

A method of making a brazeable metal pipe which has elliptical tube-insertion apertures and guide lugs extending from at least one of the opposite edges defining the minor axis of each aperture, with the guide lugs extending in the direction of insertion of flat tubes. The method in an embodiment comprises the steps of: bending a part of a raw strip, which may be previously embossed to form recesses, so as to provide a bulged portion arc-shaped in cross section and connected to at least one unbulged flat portions; pressing inwardly to form inward swells; subsequently punching each inward swell to provide the tube-insertion aperture so that at least one of the opposite edges located at ends of the minor axis of said aperture remains unpunched; and finally bending the at least one unbulged portions to produce the finished pipe. Alternatively, the method may comprise the step of: punching raw apertures through the raw strip so that each aperture has protrusions; bending it to form the bulged portion; bending the protrusions to give the guide lugs; and finally bending the unbulged portions, thus any complicated die is not needed and the pipe wall is protected well from being collapsed or deformed.