| 摘要 |
1,174,102. Extrusion dies. NATIONAL DISTILLERS & CHEMICAL CORP. 3 Jan., 1967 [3 Jan., 1966; 14 Jan., I966], No. 374/67. Heading B8A. A die for the extrusion of multi-layer plastics tubes comprises interchangeable die plates 22, 23 each having similarly configured upstream and downstream surfaces. Between the plates is defined an annular plenum 59 which receives material via conduit 71 and delivers to an annular discharge orifice 62. Further plates 10, 13 and 24 complete the die casing and define further plenums 61 and 56 fed via conduits 82 and 80 respectively, and delivering to respective discharge orifices 63, 57. A mandrel 20 with cap 11 is provided having a support-air duct 21À Plate 10 is positioned by screws 16-19. Band heaters 43, 44 are provided. To increase the number of layers, further plates such as 22, 23 are added. In a second embodiment, Fig. 4 (not shown), a metal pipe (80a) is coated using a die comprising similar interfitting plates (60a- 62a) whose plenums (69-71) are defined by inserts (69a-71a). In the embodiment of Figs. 5-8, a die section is described particularly intended for use with a heat-sensitive material such as vinylidene chloride. Plates (91-93), Fig. 6 (not shown), define axially spaced plenums 95, 96, Fig. 7, which each extend over an arc of approximately 180 degrees, overlap to prevent the formation of weld lines and preferably taper in depth away from inlet 94. According to the invention such an arrangement decreases the residence time of the material in the die section. It may be fitted into the dies described above. |
