Patent ID: 7476824
Filing Date: 2009-01-13
Classification: B23K

Abstract:
1. A welding apparatus comprising: a) a resistance-welding first electrode having a central longitudinal axis and a longitudinally endmost and tube-contacting electrode surface substantially coaxially aligned with the central longitudinal axis and adapted to physically contact an outward end fold of a heat-exchanger tube which is disposed in an orifice of a heat-exchanger tubesheet with the outward end fold contacting an outward-facing side of the tubesheet; and b) a resistance-welding second electrode having a longitudinally endmost and tubesheet-facing-and-contacting electrode surface substantially coaxially aligned with the central longitudinal axis and adapted to physically contact the outward-facing side of the tubesheet, wherein the first electrode is disposed longitudinally and transversely within the second electrode during welding, wherein the tube-contacting electrode surface of the first electrode and the tubesheet-contacting electrode surface of the second electrode are substantially parallel and face substantially in a same direction, wherein the electrode surface of the first electrode is a circularly annular electrode surface, wherein the electrode surface of the second electrode is a partially or completely annular electrode surface which has a circular inside diameter and which is radially outwardly spaced apart from the circularly annular electrode surface of the first electrode, and wherein the annular electrode surface of the second electrode has a fluted outer perimeter to avoid physical contact with any adjacent additional heat-exchanger tube.