Patent ID: 6423423
Filing Date: 2002-07-23
Classification: B21D,F28D,F28F,Y10T

Abstract:
A V-shaped metal strip having a V-shaped cross section for forming a metal tube having a closed elongated cross section, the V-shaped metal strip comprising:a U-shaped portion having a U-shaped curved inside surface and a U-shaped curved outside surface, only the inside curved surface being formed with a plurality of fold lines extending in a longitudinal direction of the V-shaped metal strip and arranged away from an imaginary median plane bisecting the V-shaped cross section, wherein said U-shaped curved inside surface is free of any fold lines on its surface at said imaginary median plane bisecting the V-shaped cross section, and wherein each of the fold lines is in the form of a vertex of an obtuse angle in the V-shaped cross section of the V-shaped metal strip.