Abstract: A plastication screw (1) comprises a shank (2) extending along a rectilinear axis (3), a feeding region (4) to supply a product to be plasticated, a plastication region (5) placed immediately downstream of the feeding region (4), relative to a main feeding direction (S) of the product along the axis (3) of the shank (2), at least one primary thread (7) extending in a helical development around the shank (2) at least in the plastication region (5), following a predetermined winding direction (V), and at least one secondary thread (10) extending in a helical development around the shank (2) in the same way as said predetermined winding direction (V), in at least part of the plastication region (5). The primary thread (7) and the secondary thread (10) each have a varying pitch (p1, p2). The pitch variation (p2) of the secondary thread (10) is greater than the pitch variation (p1) of the primary thread (7).

Abstract: A plastication screw (1) comprises a shank (2) extending along a rectilinear axis (3), a feeding region (4) to supply a product to be plasticated, a plastication region (5) placed immediately downstream of the feeding region (4), relative to a main feeding direction (S) of the product along the axis (3) of the shank (2), at least one primary thread (7) extending in a helical development around the shank (2) at least in the plastication region (5), following a predetermined winding direction (V), and at least one secondary thread (10) extending in a helical development around the shank (2) in the same way as said predetermined winding direction (V), in at least part of the plastication region (5). The primary thread (7) and the secondary thread (10) each have a varying pitch (p1, p2). The pitch variation (p2) of the secondary thread (10) is greater than the pitch variation (p1) of the primary thread (7).

Abstract: A mixing device comprises a cylindrical body (14) to be terminally engaged with an extrusion screw (2) and carrying at least one primary mixing thread (15) and at least one secondary mixing thread (16) having a crest diameter (d3) smaller than the crest diameter (d1) of the primary mixing thread (15). The primary mixing thread (15) has a helical extension in the same direction as that of the secondary mixing thread (16), to delimit at least one primary flow channel (17) and at least one secondary flow channel (18) that are substantially parallel. The primary mixing thread (15) further has, on its crest (19), communication grooves (20) between the primary (17) and secondary (18) flow channels.