| 摘要 |
1,214,273. Extrusion die heads. LAVORAZIONE MATERIE PLASTICHE S.p.A. 28 Feb., 1969 [4 March, 1968], No. 10954/69. Heading B5A. In a tube-forming extrusion die head, particularly intended for the production of tubes of foamed thermoplastics, e.g. polystyrene, the mandrel is of generally "pear" shape and incorporates a spider 4 in the region of its maximum diameter, the spider having at least thirty-six fins 4a which sub-divide the flow of material through passage P, the passage converging in the neighbourhood of the downstream ends of the fins as at 5a. Preferably the fins have wedge-shaped upstream and downstream ends (4d, 4e), Fig. 4 (not shown), are equally spaced within the passageway, and exceed forty-eight in number. Preferably the converging portion of passageway P is formed, as shown, in the outer wall thereof and extends downstream to the wedge-shaped ends (4e) see Fig. 3 (not reproduced), of the fins, although the convergence may continue to the downstream extremities of the fins. The extrusion orifice 25 of the die head is adjustable by rotation of combined parts 14 and 10, the former being rotated by a pinion 12a and the latter being screw-fitted to part 8 at F. A sizing mandrel 15 is cooled by water flow in channels 23 and the extrudate is cooled externally by air from cooling ring 26. Air from a further ring 27 on mandrel 15 inflates and cools the emerging extrudate and acts as a lubricant about the sizing mandrel. This mandrel is coupled to a double-walled extension (16), Fig. 2 (not shown), and the complete mandrel 15 (16) is slidable towards and away from the extrusion orifice on a fixed frame (19). The tube is longitudinally slit by a knife (30). |
