BOUDINEUSE A VIS A PAS SIMPLE REALISANT UN CISAILLEMENT AMELIORE

摘要

1352934 Extruder screw BARMAG BARMER MASCHINENFABRIK AG 19 April 1971 [13 April 1970] 24664/71 Heading B5A [Also in Division B1] The screw of an extruder for thermoplastics material, comprises one or more sections comprising a pair of co-extensive channels 6, 7, each of continuously but oppositely varying depths, and which are defined between a pair of constant pitch screw flights 2, 5, one 5 of which, Fig. 1, has a clearance (2s) with the barrel of at least twice that (s) of the other, to effect homogenizing shearing of particulate material passing thereover. The sum of the depths of the channels 6, 7, is constant, and the depths of each channel may vary over a section comprising a screw length of at least ¢D, 5D as in Fig. 1, 10D, 11D as in Fig. 2 (not shown), or 4À5D as in Fig. 3. Where more than one section of the channel depths varying between maximum and minimum are provided, the clearance of each land to the barrel may be altered to that of the other in the following section, e.g. as at 18, Fig. 3, to produce a shearing flow across the land clearance of 2s which is always in the downstream or in the upstream direction. Mixing means may be provided as radial projections from the screw core, or slot like openings in the screw flights.