Elector beam welding apparatus chicorporating a hole center locating means

Claim 1

Apparatus for welding the ends of tubes along their line of adjoinment to the header plate of a heat exchanger which has been drilled with holes through its thickness and into which the ends of tubes to be welded to said header are inserted, comprising: a chamber, capable of being evacuated, which is formed with two open sides opposite one another; sliding carriage means mounted over one of said open sides; an electron beam welding gun comprising means for generating, focusing and deflecting an electron beam mounted on the said carriage; means for translating the said carriage along two mutually perpendicular lines which are parallel to a plane passing through the borders of the said open side; means for attaching the said chamber to the said header plate so that the second open side of the said chamber is covered by a portion of a surface of the said header plate which includes several of the said tube ends so that the space inside the said chamber and tubes may be evacuated; means for sealing off the said tubes at their ends opposite the header plate to which they are to be welded; means for directing the aforementioned electron beam essentially normal to a plane defined by the intersection of the edge of the hole in the header with the outer surface of the tube to be welded thereto so that at its rest position it is within an an area in the plane circumscribed by the said edge of the hole; means for deflecting the said beam out from and back to the at rest position of the beam sequentially along four separate radial paths along mutually perpendicular axes lying on said plane; means for generating an electrical pulse whenever the said beam strikes the inner edge of the said tube during each of said outward deflection; means for generating separate voltages by the action of each of said pulses, which represent the distance and direction from the rest position of the beam to the inner edge of the said tube along each of the said paths; electrical means for adding algebraically the voltages representing the said distances and directions on one of said axes and simultaneously adding alegebraically the voltages representing the said distances and direction on the other axis so as to obtain separate voltages which represent the deviation of the at rest position of the beam from the center of the tube along each of the said axes; and means for causing the beam to be deflected along the said axes through the action of the last mentioned voltages so that the beam passes through the geometric center of the said tube.