Patent ID: 7318455

Claim:
A metal pipe comprising a bent metal plate having parallel first and second edge sections in opposed and engaged position; a male portion formed on said first edge section and having a pair of divided pieces; and a female portion formed on said second edge section and having a space with a back portion and broadened toward the back portion from an open end of said space, a projection projecting toward said open end from the center of the back portion, and a pair of engaging walls formed on said open end; wherein said pair of divided pieces are inserted in said space through said open end and are deformed in a mutually spaced direction by insertion of said projection between said divided pieces, with clearances between said divided pieces and said projection and with said pair of engaging walls engaging said pair of divided pieces; wherein convex engagement sections projecting from said second edge section are provided on said pair of engaging walls, and concave engagement sections opposing said convex engagement sections are provided on said male portion; and wherein said pair of engaging walls are deformed to pinch said pair of divided pieces from both sides thereof due to engagement of said concave and convex engagement sections.