Method of manufacturing cylindrical tubes and apparatus for carrying out the method

A method of manufacturing cylindrical tubes in which a plastics-foil web (2) made of a heat-meltable plastics materials, and a first fibre web (4) are helically wound on a rotating, heated mandril (16) with the plastics-foil web in contact with the mandril, the surface of the fibre web facing the plastics-foil web being coated with a plastics layer which can be heated to a tacky state or to a molten state such as to be joined with the plastics-foil web, and in which an edge portion along one longitudinal edge of the plastics-foil web is heat-welded to an edge portion along the opposing longitudinal edge of the plastics-foil web during winding of the webs on the mandril, characterized in that there is used a plastics-foil web whose two longitudinally extending, parallel edge portions (2", 2'") extend beyond the two longitudinally extending parallel edge portions (4', 4") of the fibre web, and that the plastics-foil web and the fibre web are fed into the mandril at a common angle such that one free edge portion (2'") of the plastics-foil web will overlap the other free edge portion (2") outside of the adjacent edge portions (4', 4") of the fibre web;

• in that heat is applied to said overlapping edge portions of the plastics-foil web;
• and that a further, heated fibre web (17) is wound on the helically wound plastics-foil web and the first fibre web in a manner such as to press the overlapping edge portions (2", 2'"), against the cylindrical mandrel (16) and cause said edge portions to be welded together, so as to form a smooth, even cylindrical surface on the interior of the tube.