Patent ID: 7921688
Filing Date: 2011-04-12
Classification: B21B,B21C,B21D

Abstract:
1. A forming roll device for successively forming a raw tube with a circular cross section into a square tube with a square cross section or rectangular cross section, comprising: at least an upper-lower forming roll pair and a left-right forming roll pair, each roll having a rotation axis, the rotation axis of each of said forming rolls is disposed within a plane that includes a cross section of said raw tube, wherein: a surface of each of said forming rolls in the direction of its axis of rotation has a plurality of curvatures, said curvatures of the surface of each of said forming rolls are structured so that straightening of raw tube locations adjacent to sections scheduled to be a corner portion of the square tube precedes straightening of raw tube locations adjacent to sections scheduled to be a side portion of the square tube, a curvature of the surface of each of said forming rolls that constricts a raw tube location adjacent sections scheduled to be a corner portion of said square tube is smaller than a curvature of the surface of each of said forming rolls that constricts a raw tube location adjacent sections scheduled to become the side portion center of the square tube cross section, and a curvature of the surface of any of said forming rolls in the direction of the rotation axis becomes continuously or consecutively smaller toward both outer sides from a position on the surface of an of said forming rolls for constricting a raw tube location to become a side portion center of said square tube cross section.