Method and device for homogenizing and filtering a viscoelastic material using coaxial telescoping screws

Apparatus for extruding a viscoelastic material, comprising kneading-and-conveying screws arranged substantially coaxially within a housing;

• one of the kneading-and-conveying screws being of smaller diameter than another of the kneading-and-conveying screws and extending telescopingly within such larger-diameter other screw along a telescoping region;
• a screw flight of the larger-diameter screw defining a trough whose floor has orifices extending therethrough to fluidly interconnect a first space swept by the screw flight of the larger-diameter screw with a second space swept by the screw flight of the smaller-diameter screw;
• a stationary cylindrical tube arranged substantially coaxially with, and radially between, the first and second spaces;
• the tube including apertures extending generally radially therethrough;
• the first space being axially closed-off by a wall at a downstream end thereof wherein material being conveyed by the larger-diameter screw is forced through the orifices and then through the apertures to enter the second space;
• the housing including a selectively openable passage communicating with the first space adjacent the wall to enable the removal of substances in the material that have not passed through the orifices and have accumulated at the wall.