EXTRUDING DEVICE

An extraction device for separating liquid from a liquid-solid mixture such as sludge or beet slices comprising a screw rotatably driveable in a barrel. The screw has a helical flight formed thereon defining a screw thread. The depth of the thread, in the axial direction of the screw, decreases in a direction opposite to the direction of conveyance of the material. A secondary helical flight formed on the screw defines a second thread for conveying extracted liquid in a direction to the direction of conveyance of the mixture. The two threads are adjacent one another. The second thread is closed at each of its ends, upstream, in the direction of conveyance of the mixture, of an outlet in the barrel for the solid components and downstream of an inlet for the mixture.