Abstract: A screen assembly is provided for the dewatering of flowing suspensions. A screen body having a perforated wall has a first slide bearing mounted at a first end thereof, and a second slide bearing mounted to a second end thereof. The screen body is mounted in a generally cylindrical container through which suspension to be dewatered flows in a first direction, and the screen slide bearings engage first and second bearing surfaces mounted interiorly of the container. The bearing surfaces have different effective cross-sectional areas. The screen between the first and second ends thereof and the bearing surfaces define a screen cavity volume, and a rod attached to a linear actuator moves the screen in the first direction, and in a second direction opposite the first direction, so that the cavity volume changes during movement of the screen. The screen and bearings may have any desired configuration or cross-sectional area.