American Maplan Corporation

Wilhelm Hanslik

An apparatus for the laboratory testing of plastic compositions as to their extrudability comprises a housing with two mutually parallel, intersecting cylindrical bores occupied by two counterrotating plasticizing screws each having two sections with threads of mutually opposite pitch separated by a gap. The gaps of the two screws are relatively offset to define a recirculation zone in which a plastic mass to be tested, fed in axially by intermeshing thread sections of these screws, is transported in one axial direction by an extension of a thread section of one screw and in the opposite axial direction by an overlapping extension of a thread section of the other screw. In the recirculation zone, in which the turns of the overlapping thread-section extensions have the same pitch, clashing is avoided by reducing the sum of the radii of these turns to less than the spacing of their axes or providing the turns with discontinuities enabling them to pass by one another. The instrument continuously records pressure and temperature at the gaps as well as the torque applied to the screws by their drive.

Apparatus for testing plastic compositions

A double-worm press, especially an extrusion or plastifying press for thermoplastic materials and particularly high viscosity thermoplastics, has generally conical worms, at least the discharge zones of which are formed so that the material is treated generally adiabatically therein. For this purpose, the end of the discharge zone has a depth of the worm flight which is between 24 and 33% of the worm diameter, preferably between 26 and 30%, with the ratio of the depth of the flight (or height) to the diameter of the worm increasing progressively away from the discharge end, counter to the direction of feed of the material.

Double-worm extrusion press

An extruder for thermoplastic or elastomeric materials has a mastication stage with one or more feedscrews preceded by a preheating zone in which the incoming bulk material is circulated and possibly recirculated by two screw-type conveyor members or augers in a loop within a heated extension of the extruder housing. The augers may be counterrotatingly disposed in two juxtaposed cylindrical compartments or may be coaxially nested and corotating with opposite pitch.

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Vienna, Austria

Wilhelm Hanslik