METHOD FOR MAKING BENT CLOSED SHAPES Russian patent published in 1999 - IPC

FIELD: pressure working of sheet material by means of specially profiled rolls, namely manufacture of bent closed shapes. SUBSTANCE: method comprises steps of successively bending up in rolls at first flanges, then lateral walls of shape relative to its web and finally simultaneously bending up flanges and lateral walls until making ready product. Flanges are bent up in such a way that to receive angle between flange and lateral wall exceeding by 5-30 degrees predetermined angle between them in ready shape. Then lateral walls are bent until joining flange edges. Simultaneous bending of flanges and lateral walls until making ready shape is realized due to successively upsetting joined flanges. At bending up lateral walls, predetermined width of shape web is temporarily made less than necessary one by value being no more than its tripled thickness. At upsetting flanges width of shape web is increased until preset value. EFFECT: enhanced closeness of abutting flange edges of closed bent shapes due to use of minimally allowed curvature radiuses no more than blank thickness in bending zones. 2 cl, 10 dwg, 1 ex