Abstract: Pressure screening apparatus for paper making stock embodies a cylindrical perforated screening member which defines screening and accepts chambers on the inside and outside thereof respectively in a closed housing which is filled with liquid stock under pressure in operation. A rotor member which operates in the screening chamber to keep the screening perforations open is specially constructed to provide it with sufficient buoyancy to counterbalance its weight when the apparatus is in operation and the housing is therefore filled with liquid stock. In the preferred form, the housing is mounted with the rotor axis horizontal, but it can also be made with the rotor axis vertical.

Abstract: In froth flotation apparatus for separating solid particle impurities from a liquid suspension stock in a flotation cell, provision is made for aerating the stock flowing through the inlet conduit leading to the cell by positioning a drum-shaped rotor having an irregular outer surface in the conduit on an axis extending transversely of the conduit, directing a supply of air against the rotor surface on the upstream side of its rotational axis, and causing the rotor to rotate at a linear speed of its outer surface which is substantially higher than the linear flow rate of the stock in the conduit so that the rotor surface breaks up the air impinging thereon into bubbles and distributes those bubbles in the stock flowing therepast to create foam within the cell.

Abstract: Apparatus for thickening a suspension of pulp material employs a single pair of liquid-impervious rolls and a single loop of wire trained around both rolls which are spaced from each other in substantially the same horizontal plane. The pulp stock to be thickened is delivered into the wedge zone defined by the upper wire run approaching the top of one roll and the surface of that roll, so that the pulp is trapped between the wire and roll as it travels around the roll with the wire, and the rolls are driven at sufficient speed to develop centrifugal forces which cause liquid to be expressed through the wire from the pulp trapped against the roll.