Abstract: A plastic tube has an inner tube, a stiffener layer, and an outer tube. The inner tube is arranged the support organ. A corrugated stiffener preform is formed with corner area walls shaped thinner than the other walls. The preform is fed upon the inner tube to form a stiffener layer that advances with a certain pitch upon the inner tube. The corner parts of every stiffener yield and the brush angle (?) between the lamellas of the outside gets greater than the corresponding brush angle between the lamellas of the inner side. The stiffener is joined to the inner tube with a melted plastic layer and fed upon the stiffener plastic tape joined to the stiffener with a melted plastic layer. Between the settled edges of the plastic tape a spiral weld joint is formed so that the plastic tape forms the outer tube.

Abstract: A method to produce plastic tube. The material of the plastic tube is fed around a core having a same diameter as the inside diameter of the tube. The material is fed as an uninterrupted material flow which, after having settled upon the core, goes forward following essentially the helical line in the side direction of the core inside a mold mounted on the core. The plastic tube is formed of the material ribbons and melted plastic material fed to the spaces between the ribbons. The round and rising sheet at the end of the mold directs the material flow to the side direction of the core and the head of the plastic tube gets welded and fixed to the starting tube that is used to draw the tube as the production process advances in the side direction of the core.