Abstract: A hydrocyclone having an inlet opening toward its upper part. A hollow ro inside the upper part of the cyclone has a bottom end. An accepts removal tube has an entrance opening that projects up inside the hollow rotor and the bottom end portion of the rotor overlaps the accepts removal tube a short distance below the entrance opening. This defines sharp direction changes in the flow path of stock past the outside of the rotor to the entrance opening of the accepts removal tube. Conveyor ribs may be defined on the exterior and on the inner wall of the drum. Annular thickenings at the bottom of the drum and at the exterior of the accepts removal tube near the entrance opening constrict the pathway for the stock and enhance separation of heavy materials from the stock.