Patent ID: 7637135

Claim:
A method for producing from a flat metal sheet, a longitudinally slotted hollow profile with constant wall thickness comprising a plurality of transition segments having different cross sections, at least one transition segment of which becomes larger or smaller along its length, the method comprising: providing one piece of cut metal sheet comprising either concave or convex longitudinal edges to compensate for material shortage or material excess in each transition segment; forming the cut metal sheet as a U-shape in a central segment extending in a longitudinal direction; inserting the U-shaped metal sheet in a first half of a die corresponding to the hollow profile; bringing together, sides of the U-shaped metal sheet with a second half of the die using a core comprising a guide blade for longitudinal edges; forming the hollow profile comprising the plurality of transition segments, each transition segment having a substantially similar wall thickness to provide a constant wall thickness throughout the hollow profile; and releasing the hollow profile from the die.