Compressing screws separate solid matter from liquidity. They work continuously and fully-automatic. Thin as well as viscid mixtures can be separated. The mixture of solid matter or liquidity comes through the inlet into the conical screw shaft which conveys it through the horizontal sieve. Part of the water flows through the sieve due to gravity. The screw transports the remaining water containing the solid matter into the press zone in the last section of the sieve. There, a compact stable cake is formed which permanently reforms itself and is pressed out of the outlet when dry. Compression screws are e.g. used to drain grass or the waste of an extraction.