| 摘要 |
1,161,861. Extrusion apparatus for making tubular films. FMC CORP. 24 Jan., 1968 [2 May, 1967], No. 3772/68. Heading B5B. An apparatus for making tubular blown films by melt extruding thermoplastic material and including an extruder, a centre-feed die having an annular extrusion orifice and a feed elbow positioned between the extruder and the die is characterized in that the elbow has a flow passage including frusto-conical inlet and outlet sections and a 90 degree angular section extending between the smaller ends of the frustoconical sections. The diameter of the angular section may be from 25 to 95%, preferably from 30 to 75% of the diameter of the elbow flow passage at its inlet and outlet ends and may be of uniform size throughout its length. The radius of curvature of the angular section may be from 1 to 5 times, preferably 2 to 4 times, its diameter. The frusto-conical sections of the elbow flow passage may each have included angles of from 5 degrees to 60 degrees, preferably 7 degrees to 30 degrees. As shown in the drawing, a conventional extruder having a barrel 7 and a feed screw 9 has an adapter 11 bolted at 13 to the barrel 7, with a breaker plate 15 positioned between the adapter and the barrel in the usual manner. A feed elbow 17 is bolted to the adapter 11 and on the opposite end of the elbow is mounted a conventional centre-feed annular die 21 having an outer sleeve 23 and a mandrel 25. Spacers 27 are provided for supporting the mandrel in desired position relative to sleeve 23. A conduit 29 extends through the mandrel 25, one of the spacers 27 and the sleeve 23 and is connected by a pipe 31 to a source of air or other gas under pressure. Molten thermoplastic material is fed by the extruder through the flow passage 33 of the feed elbow 17 to the die 21 and is extruded therefrom as a tubular film 37 which is inflated by air or other gas under pressure delivered by the pipe 31. As in conventional apparatus, a ring 37 is provided for directing a stream of cool air or other gas on to the film as it issues from the die 21. Nip rolls 39 and 41 are provided for collapsing the tubular film 35 and withdrawing the film from the die in the usual manner. The elbow passage 33 includes frusto-conical inlet and outlet sections 43 and 45 connected at their smaller ends by a 90 degree angular section 47.
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