Patent GB-410168-A (GB)
Title: Improvements in extrusion apparatus
IPC: B29C48/08
Filed: 1932-11-10
Abstract: <PICT:0410168/IV/1> <PICT:0410168/IV/2> <PICT:0410168/IV/3> <PICT:0410168/IV/4> <PICT:0410168/IV/5> Apparatus for the extrusion of sheets, films, foils and similar products comprises a solid body, which is adapted to form a rigid support for the jaws of an extrusion slit, running longitudinally of said body, and which is formed with a longitudinal passage communicating with said slit to distribute the material for extrusion along the slit, any tendency of the jaws to be forced apart by the pressure of extrusion being counteracted by said passage either communicating with said slit by a series of smaller passages in said body or being formed eccentrically in the body so that there is a generally increasing thickness of material from the slit side of the passage to the side remote from the slit.  A square section block 21 is formed with an internal passage 22 which communicates by openings 23 with a manifold 24 supplied by a pipe 25. The block carries plates 28 which form a slit 27, the width of which is adjustable by the micrometer screws 29 each of which has two parts 30, 31 of different pitch which engage with trunnions secured one to a bracket 34 on the block 21 and the other to a bracket 35 on the plate.  The edges of the plates are bevelled to form a chamber 39 preceding the slit 27.  The chamber 39 communicates with the passage 22 by a number of passages 40. Plates 41 close the ends of the passage 22, and plate 42 the ends of the chamber 39 and slit 27. Passages 46 in the block permit it to be heated or cooled by fluid entering at 47 and leaving at 48. The slit 27 may be formed as shown in Fig. 4 with a throat 51 and a small chamber 52 to cause the solution to flow smoothly. Trunnions 50 are provided at each end of the nozzle for its support.  In a modified form of the apparatus, the block may be triangular in section.  To prevent any "stream lining" effect due to the passages connecting the longitudinal passage with the slit, a roll of fine wire gauze may be placed immediately before the slit, or the actual jaws of the slit may be suitably formed in a manner specially adapted to produce a smooth extrusion or a perforated plate may be supported on ledges within the block just before the slit.  In another modification a block 106 is eccentrically bored at 107 so that a greater thickness of material lies above the passage 107 than beneath it.  This passage communicates with the slit 108 formed between the two plates 109, 110 carried on the underface of the block 106 and having suitably shaped jaws 111, 112.  The ends of the passage 107 and slit 108 are closed by end plates 114, integral with trunnions 123 flanged at 124 and secured to a flange 125 on a hollow trunnion 126 in a fluid tight bearing 127.  Spinning solution is fed through these trunnions to the passage 107, if desired from both ends.  Passages for heating or cooling fluid and thermometer pockets may be provided in the block. In a further modification, a block of roughly circular cross section has an eccentrically disposed passage flats being worked on the block to support the plates constituting the jaws of the slit.  The material may be forced to the slit by a pump, e.g. a gear pump, suitable means being provided for filtering the material and ensuring a uniform flow. The extrusion may take place into coagulating baths, or evaporative atmospheres or on to drums or bands.  According to the Provisional Specification the invention may be applied to a nozzle in the form of a circle adapted to produce seamless tubes which may either be used as tubes or slit to form sheets. Specifications 182,154, 293,325, [both in Class 102 (i)], 396,723, 400,589, and 400,597 are referred to.