GB672667A - Improvements in machines for extruding plastic materials - Google Patents

Abstract

672,667. Mixing. ABBEY. A. (Dow Chemical Co.). April 22, 1948, No. 11158/48. Class 86 [Also in Groups V. XIII and XXVI] A machine comprises a pair of juxtaposed rotatably-mounted feed rolls, each roll working in a barrel. The working spaces of the barrels communicate with each other and one or both of the barrels has a spiral groove in the interior surface thereof. Figs. 1, 2 and 6 show such a machine, Fig. 2, being a sectional plan. Two smooth rolls 15, 15<1> co-operate with barrels 10, 10<1> having wide spiral grooves 11, 11<1> of right- and left-hand lead respectively. The barrels are formed by boring two blocks 1, 1<1>, and the grooves are cut in the walls of the bores. The blocks are held together by bolts 33, a plate 2 being interposed between them. The thickness of this plate determines the spacing of the rolls. The spacing may be varied by means of interchangeable plates of different thickness, or shims may be used. The grooves cut through the adjacent faces of the blocks and through the plate 2, as shown in Fig. 6, forming a series of windows 14 by which the barrel working spaces are joined. Fig. 6 shows specially cut edges E, which scrape the rolls; these edges may be omitted. The rolls are driven by separate drives through off-set chain sprockets 20, 20<1>. The rolls may be driven at the same or different speeds. If the operation is chiefly or solely one of extrusion, the rolls are driven at the same speed. If the operation involves mixing and compounding, the rolls may be driven at different speeds. The rolls .are hollow and heat transfer fluid is circulated therein by means of an annular tube 21. At its rear end each roll has a spiral groove 16<1> which prevents backward travel of the plastic material. Two conduits 26, 26<1> formed in face-plates 3, 3<1> lead to a passage 27 in an adaptor or nose-piece 7 and thence to an extrusion die 8. The adaptor may be dispensed with, in which case the material emerges as two strips. The face-plates 3, 3' and blocks 1, 1<1> are hollowed for heat transfer fluid each block having three separate spaces 28, 28' whereby three different temperature zones may be provided. A feed hopper 6 is formed by complementary parts of the blocks 1, 1<1>. In modifications (1) Figs. 7 and 8 (not shown). The blocks 1, 1<1> are subdivided horizontally and the ribs 12, Fig. 6. are cut away to form a continuous long slot (2) The rolls are grooved at the hopper end, to aid feeding of coarse granules. (3) Figs. 11, 12. An expansion chamber 137 is provided above the rolls over a portion of their lengths. This chamber permits escape of gas or vapour, which may be vented or drawn off by suction through a connection 138. Alternatively gas or liquid may be forced into the chamber and incorporated into the plastic material during working thereof between the rolls. At each end of the chamber is a control valve 140 for regulating flow of material into and out of the chamber. (4) The pitch of the grooves may be uniform or progressively increasing or diminishing. The depth of the grooves may be uniform or may vary. One of the barrels may be smooth and the other grooved. The rolls and barrels may be conical. Multiple pairs of rolls may be set in a single'casing. Specification 672,668 is referred to.