Patent ID: 7036974

Claim:
A mixing device for extruders, comprising: a substantially cylindrical body to be terminally engaged with an extrusion screw having a shank and a transportation thread helically wound on the shank; at least one primary mixing thread helically wound at least partly around the substantially cylindrical body in a predetermined winding direction and having a predetermined crest diameter, said device further comprising at least one secondary mixing thread helically wound at least partly around the substantially cylindrical body in the same direction as said predetermined winding direction and having a crest diameter smaller than the crest diameter of the primary mixing thread; said at least one primary mixing thread delimiting at least one primary flow channel and at least one secondary flow channel that are substantially parallel; said at least one primary mixing thread further having at least one communication groove on its crest between the respective primary flow channel and the respective secondary flow channel; wherein said at least one secondary flow channel has an increasing depth from an inlet end to an outlet end of the substantially cylindrical body.