provided with seal ring elements, i.e. elements of generally circular and tapered shape for preventing the back flow of the melt

Full Title

Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor (extrusion blow-moulding B29C49/04) > Component parts, details or accessories; Auxiliary operations > Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die > Details of extruders > Screws > provided with seal ring elements, i.e. elements of generally circular and tapered shape for preventing the back flow of the melt