Patent ID: 7748597
Filing Date: 2010-07-06
Classification: B21C

Abstract:
1. An apparatus for producing a tube of polygonal cross section from a flat strip, the apparatus comprising: tube-shaping and -welding means for bending the strip into a generally circular-section tube, welding edges of the strip together at a seam, and advancing the tube downstream in a travel direction; means including a first roll unit downstream of the tube-shaping and -welding means for rolling the circular-section tube and transforming it into a tube of generally polygonal section with a plurality of pairs of opposite and substantially parallel flat sides; means including a second roll unit having a plurality of pairs of barrel-shaped rolls downstream of the first roll unit, each barrel roll pressing against and inwardly bending a respective one of the opposite flat sides of the polygonal-section tube each barrel roll bearing on the respective side in a direction transverse to the respective side and to the travel direction; and respective guide means supporting each of the pairs of barrel rolls for floating free movement transversely of the direction and generally parallel to the respective side so that the barrel-shaped rolls exert substantially no transverse bending stress on the travel polygonal-section tube and can follow transverse movement of the tube and for shifting the respective barrel rolls in a direction transverse to the direction such that the barrel rolls do not exert any net force or only a minimum net force upon the tube.