Head for coextruding a thermoplastic parison

An extruder head having

• inner, middle, and outer annular outlets centered on a common axis and immediately adjacent one another;
• a flow splitter on the axis;
• first and second inlets axially upstream in an axial flow direction of the splitter;
• a third inlet between the splitter and the outlets;
• a tubular inner passage centered on the axis and extending in the direction from the first inlet around the splitter to the inner outlet;
• a tubular middle passage centered on the axis and extending axially in the direction from the second inlet around the splitter to the middle outlet;
• a separating element upstream of the splitter between the inner and middle passages;
• and
• an outer passage having an upstream portion axially downstream of the splitter and extending transversely of the axis and a tubular downstream portion also axially downstream of the splitter extending coaxially around the inner and middle passages from the upstream portion to the outer outlet.