Four-Flight Screw Elements for Self-Cleaning Extruder Mixing

The patent applies asymmetry by designing screw elements with non-uniform flight geometries where adjacent flights have different crest angles and gap dimensions. Specifically, the first and second flights have different crest angles (first crest angle ≠ second crest angle) and different gap dimensions, creating an asymmetric profile that enables effective self-cleaning while maintaining mixing and dispersing performance. This asymmetric design allows each screw element to clean its counterpart effectively during rotation.

The patent implements local quality by varying the geometric parameters of different flights along the screw element. Each flight has locally optimized crest angles and gap dimensions tailored to its specific position and function. The first flight has a first crest angle and first gap dimension, while the second flight has a second crest angle and second gap dimension, creating localized variations that enhance mixing efficiency and shear quality while maintaining manufacturability through systematic geometric progression.

The patent applies parameter changes by systematically varying the gap dimensions and crest angles of different flights according to a defined progression pattern. The gap dimensions follow a geometric progression where adjacent flights have different gap sizes optimized for their specific cleaning and mixing functions. This parameter optimization allows effective self-cleaning with controlled energy input, as the varying parameters create efficient material shearing and mixing without excessive energy consumption.