Meshing Single Screw Extruder
A meshing single screw extruder has the ribs of its screws of trapezoidal cross section between divergent flanks to minimize wear of the housing surface.
The present twin screw extruder relates to a double worm extruder, especially for the plastification and extrusion of thermoplastic materials and, more particularly, to a double worm extruder in which the flights or ribs of the parallel screws interengage or mesh with one another.
Thus the single screw extruder can be utilized as the plastifying device for extrusion presses, injection molding machines and like equipment for the shaping of thermoplastics. For the purpose of the present description, the double worm extruder may be simply referred to as an " extruder" regardless of the shaping ultimately carried out of the plastified material.
The trapezoidal shape of the ribs such that they widen outwardly, provide forces in operation of the sheet production extruder which are in part turned inwardly, thereby reducing the outward pressure with which the plastified material is directed against the inner surface of the housing.
Indeed, where the flanks of two meshing ribs overlap, the forces applied to the material do not act outwardly at least with the force which has hitherto resulted in the increased wear of the housing. Rather, the outer surface of the ribs can be enlarged as a consequence of the trapezoidal configuration to increase the bearing capacity of the outer surface of the ribs and to provide greater bearing films of the molten material between the twin screw extruder and the housing which reduce wear. The life of the extruder before it requires single screw extruder or repair is thereby increased.