PROCESS FOR THE PRODUCTION OF A LARGE-CALIBRE PLASTIC PIPE AND AN EXTRUSION TOOL FOR PERFORMING THE PROCESS

摘要

Method of manufacturing a large-calibre plastic pipe, a hollow plastic profile of thermoplastic material which has a rectangular cross-section being extruded and close-together windings with adequate deformability being wound helically around the hollow plastic profile on a drum and, during the winding operation, the windings being welded to one another at the contact surfaces by means of a butt weld with axial pressure and heat being applied. The hollow plastic profile is shaped with an elongated, rectangular overall cross-section in an extrusion die as a multi-cell profile having profile outer walls and cell-forming cross-pieces. At the same time and/or thereafter, it is calibrated by internal cooling of the profile outer walls and of the cell-forming cross-pieces and provided with a dimensional strength which is stable up to a predetermined critical pressure. The calibrated and dimensionally stabilised multi-cell profile is again heated at the contact surfaces to the welding temperature of the thermoplastic material. The butt weld between the windings is welded under an axial pressure below the critical pressure for dimensional stability. - Extrusion dies for carrying out the method are also specified.