EXTRUSION OF THERMOPLASTIC TUBE

摘要

A machine has a nozzle formed with an annular passage centered on an axis and having at an outer axial end an annular mouth. A plastic mass is introduced under pressure into the inner axial end of the passage at two diametrally opposite locations and mixes and passes outwardly along the passage to emerge from the mouth as a tube. The axial outward flow of the mass along the passage is impeded upstream of the mouth to pressurize the mass with a pressure substantially greater than atmospheric. Such flow is impeded either by restricting the passage or by allowing the volume of the passage to increase against a predetermined counterforce. The mass will form when it leaves the nozzle a tube of almost perfectly uniform wall thickness.