| 摘要 |
891,789. Extrusion machines. WELDING ENGINEERS Inc. July 28, 1958 [Aug. 15, 1957] No. 24190/58. Class 87(2). An extrusion machine comprises a pan of screws in parallel intersecting bores, the screws having flights of at least two dissimilar sections, the first section being non-positive with flight spaces appreciably larger than the flights and the second section being positive and having interpenetrating flights closely fitting the bores and having substantially equal flights and flight spaces. Two screws 35, 36 are located in casings 20,21 having liners 27,28, an inlet 31, a vent which may be under vacuum and a die 32 with orifices 33. The screws 35, 36 have five sections A to E. In section A the interpenetrating flights of one screw occupy a small portion of the flight space of the other screw allowing the material to partially rotate with the screws giving a non- positive forwarding action. The pitch of the flights gradually decrease towards section B where the flights of one screw have only a slight clearance in the flight space of the other screw allowing almost no rotation of the material with the screws and giving a positive forwarding action. In section C there is again a large clearance of the interpenetrating flights, which may have radial slots 59 and the pitch of the flights gradually decreases towards Section D where again the flights have only slight clearances in the flights of the other screw. Section E discharges the material through the die. Each section of the screw has a greater forwarding capacity than the section to which it discharges. In Fig. 2 (not shown), not all the sections have interpenetrating flights. Specification 733,911 is referred to.
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