Mixing and extrusion machine with self-cleaning twin screw and method of use

A mixing and extruding machine for manufacturing a rubber mixture, the machine comprising:

• an introduction hopper;
• and
• a mixer, the mixer being a convergent conical twin-screw mixer including:
• sleeves in which two screws are inclinedly mounted between an opening and an outlet, each screw of the two screws including a thread having a thread tip and a channel defined between adjacent portions of the thread, the channel including a core surface, the opening being disposed upstream of the sleeves and connected to the introduction hopper for the introduction hopper to feed the two screws, the outlet being disposed downstream of the sleeves to discharge the rubber mixture at the end of a mixing cycle;
• one or more motors coupled to the two screws to rotate the two screws in the sleeves during the mixing cycle;
• and
• one or more movable doors provided at the outlet and movable to allow, during the mixing cycle, the evacuation and shaping of the rubber mixture,
• wherein the two screws are mounted in the mixer such that the thread tips of each screw tangentially contact the core surface of the opposite screw in order that the two screws remain substantially in contact with each other when rotating the two screws with a constant predetermined angle and center distance that facilitates self-cleaning, and
• wherein an inner surface of each sleeve is predefined in order to determine a predetermined distance between each of the thread tips and the inner surface of a corresponding sleeve such that the thread tips of each of the two screws remain in tangential contact with the inner surfaces of the sleeves and preventing the retention of the rubber mixture on the inner surfaces.