Patent ID: 6539628
Filing Date: 2003-04-01
Classification: B21D,F28D,F28F,Y10T

Abstract:
A bending method of bending a metal strip from a flat shape into a folded shape having an approximately U-shaped cross section, the method comprising:a first bending step of compressing the metal strip between a wider concave roll having a circumferential rim formed with a wider V-shaped groove defined by left and right sloping surfaces forming a wider spread angle and a wider convex roll having a circumferential rim formed with a wider ridge projecting toward a middle of the V-shaped groove between the left and right sloping surfaces and having a left edge for pressing the metal strip at a first left pressing point against the left sloping surface and a right edge for pressing the metal strip at a first right pressing point against the right sloping surface, and a second bending step of compressing the metal strip between a narrower concave roll having a circumferential rim formed with a narrower V-shaped groove defined by left and right sloping surfaces forming a narrower spread angle smaller than the wider spread angle of the first bending step and a narrower convex roll having a circumferential rim formed with a narrower ridge projecting toward a middle of the narrower V-shaped groove between the left and right sloping surfaces and having a left edge for pressing the metal strip at a second right pressing point against the left sloping surface and a right edge for pressing the metal strip at a second left pressing point against the right sloping surface, the second left pressing point and the second right pressing point being located between the first left pressing point and first right pressing point.