Abstract: Centrifugal separator having a piston valve 3 for opening and closing of apertures adjacent the periphery of the drum for discharge of solids through passageway 19. The drum is provided with a ring 16 which in part defines the passageway, and which has a lip 15. The piston valve has a lip 13. When the piston valve 3 moves down, the apertures are open, and after a short interval the lip 13 strikes the lip 15 closing the passageway 19. Thereby discharge of solids is stopped. Thus, the piston valve need move in only one direction, up or down, for a discontinuous discharge of solids. That provides better control, since for a discharge, the piston need be accelerated in only one direction.

Abstract: Closing piston 5 can be lowered under the influence of the weight of solids in the separating chamber 4 so that solids are ejected through annular opening 19 and into annular gap 18. The closing piston 5 can then be raised to close the opening 19. Thereafter the pumping piston 7 can be raised to pump the ejected solids upwardly in the annular gap 18 for discharge of the solids over the lip 3a.