Patent GB-783519-A (GB)
Title: Improvements in or relating to the production of filamentary material by melt spinning
Inventor: DICKIE WILLIAM ALEXANDER
IPC: D01D1/04
Filed: 1954-04-09
Abstract: <PICT:0783519/IV (a)/1> Apparatus for melt spinning comprises a vessel having two internal annular concentric surfaces converging downwards towards one another to form a narrow annular slit between them, and means for supplying heat to the outer of the surfaces to melt filament-forming material retained by the surfaces above the slit. The fused material runs down through the slit to the bottom of the vessel, whence it can be drawn away and extruded in the form of filaments.  Preferably only the outer of the two surfaces is heated, and is in the form of a downwardly converging truncated internal cone, having an opening at the bottom below which the vessel increases in diameter, leaving the edge of the opening as a downwardly projecting lip from which the fused material can drip into the lower part of the vessel.  The surface may terminate, immediately above the lip, in a narrow annular portion extending upwards and inwards to form a weir by which fragments of unmolten material small enough to have passed through the annular slit may be retained until they are molten.  The narrow annular portion and the lip may be integral and constituted by a separate ring lodged within the inner edge of the downwardly converging cone. The heated outer surface may be the inner wall of an annular vessel through which a heating fluid is circulated, or may be the inner surface of a substantial annular block of metal provided with electrical heating elements, e.g. wound round the outside. As shown in Fig. 1, chips or flakes of filament forming material are charged continuously into the upper part 3 of a melting vessel and fall on to the inner conical surface 15 of a heavy metal block 12 which is heated by a flexible blanket 21 strapped round the outer surface of the block and containing electrical heating elements.  The material is retained until it is molten in contact with the surface 15 by the outer surface 34 of the downwardly flared stainless steel cone 23 of which the lower edge 24 is internally bevelled and is spaced at 35 about 1/16 inch from the conical surface 15.  The cone 23 is supported by four horizontal legs 25 resting on cleats 26 on the inner surface of the upper part 3. The fused material runs down the surface 15 and passes through the annular slit 35 between the surface 15 and the edge of the cone 23, solid material being retained at the slit and by the weir 19 constituting the upper surface of the stainless steel ring 17.  The fused material drops from the downwardly extending lip 18 of the ring 17 and collects as a pool at 33 in the bottom of the lower part 4 of the vessel, whence it is drawn away through the duct 5 by the spinning pump 6 for extrusion.  The vessel and the blanket 21 are heavily lagged with heat-insulating lagging 22.  Inert gas such as nitrogen is supplied to the conical lower part 4 by a pipe 29 which is coiled round the wall of the conical part 4, passes through the wall, and then turns vertically upwards.  Inert gas is also supplied, together with the filamentforming material, through the flange 11, and reaches the draw-off pipe 28 by way of a gap 30 between the cone 23 and a hood 27.  Extending through a tube 31 which passes through the wall of the upper part 3 is an insulated level-indicating electrode 32 in the form of a conductor electrically connected to the walls of the vessel through a circuit giving a reading depending upon the electrical resistance between the walls and the electrode 32 and indicating the depth of immersion of the tip of the electrode in the pool of molten material 33.  The level of this pool may be maintained constant by arranging that the current supplied to the heating blanket 21 is controlled by the level indicating circuit.  In another very similar form of apparatus the inner cone 23 and separate hood 27 are substituted by a single closed hollow member having a cylindrical lower part integral with a conical upper part supported by radial legs in the same manner as the inner cone 23. The bottom of the integral hollow member is closed by a plate having a central insulating gland through which the electrode 32 extends.  Immediately above the plate the cylindrical part is pierced with a ring of perforations.  A pipe entering the conical upper part of the hollow member and corresponding to the pipe 28 of Fig. 1 is not used to draw off inert gas but to supply it, the gas escaping from the interior of the hollow member by way of the perforations and being drawn off from the top of the melting vessel by means of a draw-off pipe passing through the flange 11. Inert gas is supplied to the lower part 4 of the melting vessel as in Fig. 1, and is drawn off through a second vertical pipe located in the lower part 4.