Process and apparatus for forming a tube from a flat web

An apparatus for forming a tube from a flat web, comprising:

• means for supplying a flat web comprising cellulose and having longitudinal edges;
• means for providing an adhesive material to at least one of the longitudinal edges of said flat web;
• means for forming said flat web into a tube, wherein the edges of said web abut or overlap, said forming means comprising a forming body which includes an internal bore of substantially circular cross-section, the circumference of said internal bore being equal to the outer circumference of said formed tube, said internal bore extending at least in the region whereat said tube is completely formed, for supporting the outer surface of said formed tube, and wherein said forming body further comprises a substantially cylindrical internal mandrel having a circumference which is equal to or smaller than the internal circumference of said formed tube, for supporting the inner surface of said formed tube, at least a part length of said internal mandrel being arranged in the interior of said internal bore of said forming body;
• means for guiding at least one of said longitudinal edges of said web along a straight line parallel to the direction of travel;
• means for separating said edge zones at a distance from one another during tube formation, wherein said guiding and separating means comprises a flexible strip comprising a curved cross section adaptable to the circumference of said tube and at least one radially projecting edge providing for said parallel travel of said web, said flexible strip being fixed by at least one radially projecting edge to at least either one of the inner surface of said internal bore or the circumferential surface of said internal mandrel and extending upstream of said internal bore and said internal mandrel, for engaging said web as said tube is formed;
• means for contacting said edge zones with each other;
• and
• means for joining said edge zones to form said tube.