Patent AT-E40073-T1: [Translated] SCREW EXTRUDER.

An extrusion apparatus having a barrel (3) and a rotatable threaded screw (1) coaxially positioned therein is disclosed. The apparatus includes an upstream inlet section having an opening (13) therein for receiving material to be processed by the apparatus, a compression section (2) downstream of the inlet section, and a mixing or plasticizing section (7/8) downstream of the compression section. The interior surface of the barrel is provided with an undercut (12) therein which intercommunicates the feed opening with the compression section and has a portion thereof which extends downstream in the compression section about the interior surface of the barrel with a continuously decreasing cross-sectional area. The undercut may be formed in a cylindrical insert (9), carried within the barrel and, in an alternate embodiment, a second undercut cylindrical insert positioned about the first insert and rotatable relative thereto may be employed to vary the cross-sectional area of the undercut.