GB777858A - Method of and apparatus for the extrusion of synthetic plastic sections and the like products of any desired length - Google Patents

Abstract

777,858. Extruding synthetic plastics. FAIGLE, H. Oct. 19, 1954 [Nov. 3, 1953; July 26, 1954], No. 30060/54. Class 87(2). As synthetic plastic material is extruded through a heated nozzle it is surrounded by a mould to give it the desired shape, and the mould is moved in the direction of and in unison with the extruded material. When the material has set sufficiently to be self-supporting the mould is returned to a position in readiness for re-use. Figs. 1 to 3 show a tubular mould 4 which slides on the extrusion nozzle 2 from the Fig. 1 position to the Fig. 2 position and then back to the Fig. 3 position, then forward, then back, and so on. A temporary stopper 6 is used in the initial stage. Long lengths of polyamide rod may be thus produced. The tip of the nozzle is heated by electrical means 3. The mould also has electrical heating means 5, which are used, when the mould has reached the Fig. 2 position, to re-melt the outer surface of the plastic section 8 and so allow the mould to retract. The mould may be moved by the pressure of the extruding material. Fig. 4 shows a modified apparatus for producing polyamide rods, the mould being in the form of half-tubes 9 which are linked together and trained around square pulleys 45, 45<SP>1</SP>, meet at the nozzle to form tubular moulds and slide over the nozzle. The pulleys 451 are driven by worm gear 48, 48<SP>1</SP>. The half-tubes may be held together by screw clamps, electromagnets or stationary rollers between which they run. As shown, the half-tubes form chains, but they may be joined by hooks, the front pair of half-tubes being in turn detached from the contiguous pair and joined on to the rear. Fig. 6 shows modified half-tubes 11 which form shaped contours on the extruded material and are moved by gears 53 having teeth which mesh with teeth 52 on the half-tubes (which are not joined together). By varying the speed of the driving-mechanism of Figs. 4 and 6 the mould may be moved at the same speed as the extruded material or faster or slower to reduce or increase the resistance to flow. Fig. 8 shows apparatus for extruding tubes, the core 16 having a heating element 19 and the mould 15 being in the form of separate rings. The core and mould are slid from the left to the rightward position shown, the core being then heated to free it from the material and slid back to the left and the rings being removed in turn from the solidified material. Fig. 9 shows an extrusion nozzle. through which the material passes from right to left, comprising an external tube 22 over which the moulds slide, an inner tube 21 through which the material passes, an electrical heater 23 and heat insulation 24 to prevent overheating of the inner tube. The inner tube may be surrounded by a heating bath of gas or liquid, Fig. 10 (not shown). Fig. 11 shows a nozzle comprising two annular chambers 34, 34a separated by insulation 31 disposed within tubes 32, 33, the outer chamber 34 being fed with heating medium and the inner chamber 34a with cooling medium. In Fig. 12 an outer electrical heating element 40 is separated from a cooling chamber 44a by insulation 41 and a tube 42. A nozzle may be heated by high frequency electrical means.