1523809 Controlling flow through parison extrusion |head STANDARD OIL CO 22 July 1976 [28 July 1975] 30597/76 Heading B5A A cross-head die 1 for the extrusion of a tubular thermoplastics material parison for blow moulding into a biaxially apertured bottle, comprises a lateral inlet 15 for the material into a tubular passage 8, at a location where the flow of material is restricted by an insert 10 of the die head mandrel 2 and by an obstruction comprising a welded head 11 extruding around half the circumference of the downstream end of the insert, the flow of material along the passage 8 being thereafter further rendered uniform by heating by a plurality of independdently controlled electric heaters 18 which are circumferentially spaced apart, and extend longitudinally of the die head 1. The response of the heaters 18 may be rendered shorter by air cooling holes in the head, extending longitudinally, or by a liquid temperature controlled zone extending longitudinally. The parison is extruded from an outlet defined between a surrounding die 5, which is radially adjustable at bolts 6, and a mandrel part 4 which is axially displaceably adjustable through the remainder of the mandrel 2, to vary the thickness of the outlet. The heaters are controlled from means 19.
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