Mixer/extruder having selectively variable shearing action therein

An extruder, including an elongated rotor and a cylindrical barrel surrounding said rotor, said extruder having a feed zone, a metering zone and at least one mixing or working zone positioned between said feed zone and said metering zone;

• the rotor in said mixing or working zone including an upstream groove-forming flighted portion, a downstream groove-forming flighted portion and a substantially unflighted portion intermediate said upstream and downstream flighted portions;
• the barrel in said mixing or working zone including on an inner surface thereof upstream input grooves open to and at least in part overlaying the grooves in said upstream flighted portion of said rotor and downstream output grooves open to and at least in part overlaying the grooves in said downstream flighted portion of said rotor, said input grooves and output grooves of said barrel each including portions thereof which overlay said substantially unflighted portion of said rotor, the portions of said input and output grooves of the barrel which overlay the substantially unflighted portion of the rotor being circumferentially spaced from and interleaved with one another;
• cahnnel means intercommunicating said input and output grooves, said channel means comprising a plurality of circumferentially oriented passageways which overlay and face the substantially unflighted portion of the rotor and interconnect the interleaved, circumferentially spaced portions of corresponding input and output grooves of said barrel;
• throttling means positioned in said channel means for varying the cross-sectional area of said channel means to thereby vary the amount of shearing action and work performed on material passing through such channel means, said throttling means comprising a plurality of radially movable wedge members, there being one of said wedge members positioned in each of said passageways;
• camming means carried by said barrel for concurrently moving said wedge members to selected corresponding positions between their radially innermost positions and their radially outermost positions, said camming means including at least one camming ring rotatably positioned on said barrel, said camming ring including a plurality of camming slots therein, there being one of said camming slots for each of said wedge members, said camming ring further including gear tooth means fixedly positioned thereon, said wedge members each including a cam follower fixed thereto, said cam followers being in engagement with corresponding ones of said camming slots;
• and drive means including a worm gear in engagement with the gear tooth means on said camming ring for rotating said camming ring to thereby concurrently radially move said wedge members.