| 摘要 |
An extrusion head ( 1 ) for blow moulding of hollow bodies comprises: a body ( 2 ) and a force plug ( 3 ) set within the body so as to define a cylindrical gap ( 4 ), through which the molten plastic material fed by an extruder can flow; a die opening ( 6 ) set at the bottom end of the body ( 2 ); a bottom part ( 30 ) of the force plug ( 3 ), set within the die opening ( 6 ) so as to define an annular gap ( 10 ) communicating with the cylindrical gap ( 4 ) for exit of the tubular parison; and a plunger ( 20 ) supporting at the bottom an ovalizing insert ( 40 ), slidably mounted within a chamber ( 32 ) formed in the bottom part ( 30 ) of the force plug. The plunger can pass from a retracted, resting, position, in which the bottom edge ( 48 ) of the ovalizing insert is located within the chamber ( 32 ), to an extracted, working, position, in which the bottom edge ( 48 ) of the ovalizing insert projects at the bottom with respect to the bottom edge ( 38 ) of the bottom part of the force plug.
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