Method and apparatus for laser welding elongated workpieces

1. Apparatus for welding together two elongate workpieces moving along a track, said workpieces joined along a seam line which varies in vertical height above said track, said apparatus comprising a laser welding head mounted for both vertical and rotary movements relative to said track, and means for moving said laser welding head vertically and rotationally in response to changes in the height and slope of said portions of said seam line, and further comprising a pinch roller mounted for rotation about a horizontal axis which applies pressure to said workpieces and which moves vertically in response to changes in height or slope of said seam line, said laser welding head mounted for rotation about said horizontal axis.

2. Apparatus for welding together two elongate workpieces comprising a first, lower workpiece having a planar bottom surface and a non-planar top surface that is higher above said bottom surface at at least one location along the length of said first workpiece than at at least one other location along the length of said first workpiece, and a second, upper workpiece having a lower surface engageable with said top surface of said first workpiece along a nonlinear weld line extending along a seam line formed between said first workpiece and said second workpiece along a margin of said top surface of said first workpiece and said lower surface of said second workpiece and extending continuously along the length of at least one of said workpieces, said apparatus comprising: a track including rolls for supporting said lower one of said workpieces and moving said workpiece along a path extending through said welding machine; a guide assembly for engaging said second workpiece on said top surface of said first workpiece; three pressure-applying rolls comprising a central pinch roll mounted for rotation about a first, horizontal pinch roll axis, a first hold-down roll upstream of said pinch roll and rotatable about a second horizontal axis parallel to said pinch roll axis, and a second hold-down roll downstream of said pinch roll and rotatable about a third axis parallel to said pinch roll axis; means constantly biasing each of said three pressure-applying rolls into engagement with the top surface of said second workpiece as it passes beneath said pressure-applying rolls so that a seam is maintained between said first and second workpieces along a line of joinder between them; a laser welding beam aimed toward said seam as it passes adjacent said pinch roll at a weld point positioned on said seam on a line passing through the center of said pinch roll and perpendicular to an imaginary line passing through the axes of rotation of said first hold-down roll and said second hold-down roll.

3. A method for welding together two elongate workpieces comprising a first, lower workpiece having a planar bottom surface and a non-planar top surface that is higher above said bottom surface at at least one location along the length of said first workpiece than at at least one other location along the length of said first workpiece, and a second, upper workpiece having a lower surface engageable with said top surface of said first workpiece along a nonlinear weld line extending along a seam line formed between said first workpiece and said second workpiece along a margin of said top surface of said first workpiece and said lower surface of said second workpiece and extending continuously along the length of at least one of said workpieces, said method comprising the steps of: providing a track including rolls for supporting said lower one of said workpieces and moving said workpiece along a path extending through said welding machine; mounting said first workpiece on said track; engaging said second workpiece on said top surface of said first workpiece; passing said first workpiece and said second workpiece along said track under a sequence of three pressure-applying rolls comprising a central pinch roll, a first hold-down roll upstream of said pinch roll, and a second hold-down roll down stream of said pinch roll; constantly biasing each of said three pressure-applying rolls into engagement with the top surface of said second workpiece as it passes beneath said pressure-applying rolls so that a seam is maintained between said first and second workpieces along a line of joinder between them; pointing a laser welding beam to a part of said seam passing beneath said pinch roll at a weld point positioned on said seam on a line passing through the center of said pinch roll and perpendicular to an imaginary line passing through the axes of rotation of said first hold-down roll and said second hold-down roll.