Abstract: A mixing section (10,50,60) for mixing material in an extruder (8) having a barrel (32), The mixing section (10,50,60) includes a screw (14) having a central shaft (16), and a floating annular sleeve (12) located between the screw (14) and the barrel (32), and surrounding a portion of the screw (14). The sleeve (12) has mixing elements (28) protruding radially inward toward the screw (14). A portion of the central shaft (16) has mixing elements (18) protruding radially outward toward the sleeve (12). The mixing elements (18) on the screw (14) and the sleeve (12) create multiple regions of reorientation (2) in the material to be mixed which produce improved dispersive mixing.

Abstract: A screw extruder (10), including a barrel (18) having a bore (26) which defines an inner surface (24). At least one extruder screw (28) is positioned within the bore (26), each screw (28) further including a central shaft (34) and at least one screw flight (30). Each screw flight (30) further includes a front pushing face (36) and a rear face (38). The profile (40) of each front pushing face (36) acts with the inner surface (24) of the barrel (18) to form a progressively narrowing passage (46) through which material is forced into multiple regions of high elongational and shear stress (48) which act to break down agglomerates of material and thus dispersively mix the material.Also presented is a screw extruder (100) having a single screw (28) which includes dispersion disks (102) which are rotationally offset from one another and whose design is not constrained by interaction with a second disk, which provides improved distributive and dispersive mixing.

Abstract: A screw extruder (10), including a barrel assembly (12) having a central bore (36) which defines an inner surface (37). An extruder screw (38) is positioned within the barrel assembly's (12) central bore (36). The barrel assembly (12) has an input end (20) which includes a feed housing portion (25), the feed housing portion (25) having an opening for introduction of material into the central bore (36). There is a shaping die (18) situated at the output end (16) of the barrel assembly (12) to shape the extruded material. The feed housing portion (25) also has one or more groove channels (44) opening into the inner surface (37) of the feed housing portion (25) with a key (48) disposed in each of these groove channels (44). Contacting each key (48) are one or more independently activated actuators (28) which can be used to adjust the radial depths of the keys (48) in the groove channels (44) thus controlling the depth of grooves (46) formed between the keys (48) and the central bore (36) of the barrel (12).