GB1416945A - Apparatus for extruding polymeric material - Google Patents

Abstract

1416945 Extruder screw B F GOODRICH CO 5 Oct 1973 46737/73 Heading B5A The transition zone 23-24, of a plastics extruder screw, Fig. 2, intermediate feed and metering zones 22-23 and 24-25, comprises adjacent co-extensive primary and secondary channels 38, 42, respectively of progressively increasing and decreasing volume in the extrusion directions, and defined between screw flights 32, 34 which are respectively of greater and lesser clearance from the extruder barrel surface. Particulate material within the primary channel 38 is melted in contact with the barrel surface and passes over the flight 32 into the secondary channel 42. The decreasing volume of channel 38 is achieved by a progressively decreasing depth, d<SP>1</SP>, at a constant width W 1 to enhance melting of the particles by contact with the barrel. The increasing volume of the secondary channel 42 is obtained by a progressively increasing width W 2 and depth d 2 . The melting of the particles is effected by a heated barrel, and by shearing contact with the barrel. The barrel is provided with a fluid, e.g. water, cooling jacket. The feed section 22-23 comprises a single flight 30 and the metering section 24-50 comprises either a pair of flights 26, 28 as shown, or a single flight. At the beginning 23 of the transition zone 23-24 the flights 32, 34 are formed by separation from the flight 30, and at the termination 24 of the transition zone the flights 32, 34 may merge, as in Fig. 2, with the depth of the channel 38 decreasing to the surface of the flight 32. Alternatively, Fig. 3 (not shown), the transition zone may terminate at a similar depth, but with the flights (32, 34) spaced apart, or may terminate as in Fig. 4, with a continued region 51-52 of constant depth.