Annular manifold for an extrusion head for producing a tubular moulding from a thermoplastic material

An annular manifold for an extrusion parison head for producing a tubular moulding from a thermoplastic material, comprising:

• an accommodation body with a first accommodation chamber with an inner surface and a second accommodation chamber with an inner surface,
• a first distribution sleeve with an outer surface having a distribution groove, wherein the first distribution sleeve is accommodated in the first accommodation chamber,
• a second distribution sleeve with an outer surface having a distribution groove, wherein the second distribution sleeve is accommodated in the second accommodation chamber,
• an annular first distribution chamber which is formed between the inner surface of the first accommodation chamber and the outer surface of the first distribution sleeve, and which opens into an annular gap opening,
• an annular second distribution chamber which is formed between the inner surface of the second accommodation chamber and the outer surface of the second distribution sleeve and which opens into the annular gap opening,
• wherein the outer surface of the first distribution sleeve has a single helical distribution groove with more than one winding and less than 1.25 windings around the first distribution sleeve, and the outer surface of the second distribution sleeve has a single helical distribution groove with more than one winding and less than 1.25 windings around the second distribution sleeve.

A method for producing a tubular moulding from an extrusion parison head of thermoplastic material, the method comprising:

• flowing molten plastic through an annular manifold, the annular manifold comprising:
• an accommodation body with a first accommodation chamber with an inner surface,
• a first distribution sleeve with an outer surface, which has a distribution groove, wherein the first distribution sleeve is accommodated in the first accommodation chamber, and
• an annular first distribution chamber, which is formed between the inner surface of the first accommodation chamber and the outer surface of the first distribution sleeve, and which opens into an annular gap opening,
• wherein:
• the outer surface of the first distribution sleeve has a single helical distribution groove with more than one winding and less than 1.25 windings around the first distribution sleeve,
• the molten plastic flows from the distribution groove of the first distribution sleeve into the annular first distribution chamber,
• the molten plastic flows from the distribution groove of the first distribution sleeve into the annular gap opening, and
• the molten plastic flows from the annular gap opening into an annular flow channel.