| 摘要 |
A metal container has a seam which comprises two continuous groups of concentric circular arcs having a center angle of 180 degrees or 180 degrees and under 180 degrees and centered on two points separated from each other by a distance equal to 1/2 of the sum of the thickness of two metal sheets making up the seam. The axis of the seam is a straight line passing through the two centers that can be inclined at any angle with respect to the axis of the container. The seam has a cross-sectional shape that is mostly point-symmetrical with respect to a center that is the mid-point between the two centers. The seam is formed by an apparatus which comprises a seaming roll and a chuck ring, each of which has a forming groove comprising, in cross-section, two continuous circular arcs centered on two points that are separated from each other by the distance equal to 1/2 of the sum of the thickness of the metal sheets making up the seam. The seaming roll and chuck ring are disposed in such a manner that at least one of the center-to-center distances between one of the centers of curvature in the forming groove of the seaming roll and one of the centers of curvature in the forming groove of the chuck ring becomes equal to 1/2 of the sum of the thicknesses of the metal sheets making up the seam upon completion of seaming. The flanges of the body and end closure sheets are seamed together into two continuous groups of concentric circular arcs, without relative displacement in their extreme edges, after placing the extreme edges of both flanges into such relative positions as are occupied at the center of the completed seam.
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