Patent ID: 7347140

Claim:
A screw press, for separation of liquid from solid-liquid mixtures, comprising: a perforated casing having a plurality of perforations; a screw shaft disposed within the perforated casing, the screw shaft defining an axis, the screw shaft extending axially to a shaft end and including a drum having an outer circumference and at least one helical blade mounted on the drum, the drum outer circumference and the perforated casing defining a gap adapted for receiving the solid-liquid mixture, the gap having a substantially circular cross section and extending axially in a conveying direction of the solid-liquid mixture to a discharge end, the drum also having a discharge area proximate to the discharge end of the gap, the discharge area having a tapering diameter; a ring-shaped counter pressure device disposed proximate to the discharge end of the gap, the counter pressure device including a counter pressure surface having a radius that decreases in the conveying direction of the solid-liquid mixture; a plurality of pressure cylinders, the pressure cylinders applying a force substantially uniformly over a circumference of the counter pressure device for displacing the counter pressure device in the axial direction of the screw shaft; and inner and outer circular ring surfaces disposed between the outer circumference of the drum and the shaft end.