Method and apparatus for producing tubular bodies, particularly for packaging tubes

Abstract From the Canadian patent

A foil sheet comprising a plurality of layers is continuously rolled up around a shaft extending in its longitudinal direction to form a tubular body in such a manner that the two edges overlap. For welding the, overlapping edges are pressed together between two belts driven such that they rotate in the longitudinal direction. The inner belt traveling inside the tubular body has a longitudinal groove, which at least partly receives the area of the overlapping edges. The longitudinal groove shapes the inwardly oriented region of the seam of the tubular body and prevents plastic material that has been liquefied for welding purposes from stretching uncontrollably as a result of the pressing …