EXTRUSION SCREW FOR EXTRUSION OF POLYMERIC MATERIALS

摘要

The screw (1) is rotatably accommodated in a cylinder and comprises at least in one of compressing (E) and metering (F) zones thereof: main flights (C) of a constant height having the top faces thereof disposed in a small gap relation with the inner surface of the cylinder (2); at least one thread (A, B) of eccentric flight formed between the main flights (C) in parallel relation therewith and having a height alternately reduced and increased gradually through a predetermined angle on the screw; and at least a couple of grooves (a, b, c) formed between the main and eccentric flights, one of the grooves having a depth alternately reduced and increased gradually through an angle on the screw corresponding to that of the variation in height eccentric flight (A, B) and the other one of the grooves having a depth alternatively reduced and increased with a phase lag from the first-mentioned groove.