Abstract: A screen cylinder (125) used for screening cellulosic fibrous material pulp in the pulp and paper industry incorporates first (66) and second (67) downstream surfaces (16) having contoured slopes that form a funnel entrance of the grooves (13) at the screen cylinder slots (17). The contoured construction of the screen cylinder (125) effects greatly enhanced utility compared to conventional milled and discrete element screen cylinders, including substantially avoiding the Coanda effect.

Abstract: A screen cylinder (125) used for screening cellulosic fibrous material pulp in the pulp and paper industry incorporates first (66) and second (67) downstream surfaces (16) having contoured slopes that form a funnel entrance of the grooves (13) at the screen cylinder slots (17). The contoured construction of the screen cylinder (125) effects greatly enhanced utility compared to conventional milled and discrete element screen cylinders, including substantially avoiding the Coanda effect.

Abstract: The differences in performance of a screening cylinder during screening of a fiber suspension (e.g. low consistency paper pulp) at the inlet end compared to the reject end is accommodated by constructing the feed side surface of the screening cylinder so that it induces greater turbulence in the vicinity of the screen cylinder surface adjacent the reject end of the screen than adjacent the inlet end. Typically this increase in turbulence is at least about 10% (preferably at least about 40%, and typically greater than 100%). The turbulence increase can be provided by a substantially smooth screening medium surface at the inlet end and a contoured screening medium surface adjacent the reject end, or by first and second contoured surfaces of different aggressiveness.

Abstract: An apparatus for screening pulp comprises a vessel, a cylindrical screen within the vessel, a rotor moving in the vicinity of the screen at a predetermined speed, an inlet for the unscreened pulp, an outlet for the screened pulp in the vessel. The rotor is non-cylindrical, for instance, elliptical, triangular, and in general, is multi-cam. The rotor has a contour surface which is achieved by attaching bars of the contoured shape to the surface of the rotor, for instance by welding. According to one embodiment, the contour surface of the rotor is discontinuous. The bars form a plurality of spaced protrusions instead of a single protrusion along the entire axial length of the rotor.

Abstract: An apparatus for screening pulp comprises a vessel, a cylindrical screen within the vessel, a cylindrical rotor moving in the vicinity of the screen at a predetermined speed, an inlet for the unscreened pulp, an outlet for the screened pulp in the vessel. The rotor has a contour surface which is achieved by means of a plurality of protrusions of contoured shape on the surface of the rotor, for instance by welding. The protrusions are spaced and are arranged along the entire axial length of the rotor.

Abstract: An apparatus for screening pulp comprises a vessel, a cylindrical screen within the vessel, a rotor moving in the vicinity of the screen at a predetermined speed, an inlet for the unscreened pulp, an outlet for the screened pulp in the vessel. The rotor is non-cylindrical, for instance, elliptical, triangular and, in general, is multi-cam. The rotor has a contour surface, for instance grooves formed of a first bottom plane parallel to the envelope surface, an inclined plane, an upper plane and a side plane, the side plane being essentially perpendicular to the first bottom plane, the inclined plane forming an angle between 5 degrees and 60 degrees with the first plane, the upper plane being parallel to the first plane. The contour surface of the rotor may also be achieved by attaching bars of the contoured shape to the surface of the rotor, for instance by welding.

Abstract: The pulp screening apparatus comprises a housing having an inlet for allowing fibrous stock to be introduced into the interior, a first outlet for allowing the accept screened stock to be removed, a second outlet for the reject, a screen having a contour surface within the housing, a rotor moving in the vicinity of the screen at a predetermined speed and forming together with the screen an annular screening chamber. The rotor has at least the surface facing the screen partially contoured and is provided with a plurality of perforations along at least a portion of the length of the screening chamber to allow fibrous stock to be introduced into the screening chamber and to prevent the undesired debris of the stock from entering the chamber. Both sides of the rotor may have a contoured surface with grooves.

Abstract: An apparatus for screening paper stock comprises a vessel, a cylindrical screen cylinder within the vessel, a rotating element moving in the vicinity of the screen cylinder at a predetermined speed, an inlet for unscreened stock, an outlet for the screened stock, and an outlet for the stock fibers and unwanted rejectable material which does not pass through the screen cylinder. The rotating element has a contour surface with grooves formed of a first bottom plane parallel the envelope surface, an inclined plane, an upper plane, and a side plane, the side plane being essentially perpendicular to the first plane, the inclined plane forming an angle between 5.degree.-60.degree. with the first plane, the upper plane being parallel to the first plane. The rotor element may be either a rotor or blade type segments. Also the screen cylinder has a contour surface. The inclined plane of the contour surface of the rotor may be the upstream or the downstream side plane. The method is also described.

Abstract: An apparatus for screening pulp comprises a vessel, a cylindrical screen within the vessel, a rotating element moving in the vicinity of the screen at a predetermined speed, an inlet for the unscreened pulp, an outlet for the screened pulp in the vessel. The rotating element has a contour surface, for instance grooves formed of a first bottom plane parallel to the envelope surface, an inclined plane, an upper plane and a side plane, the side plane being essentially perpendicular to the first bottom plane, the inclined plane forming an angle between 5 degrees-60 degrees with the first plane, the upper plane being parallel to the first plane. The rotating element may be a rotor or blade type segments. The rotor is located on the inlet side of the screen but the contour surface of the screen may be the outer or the inner surface of the screen drum. Also the screen has a contour surface which may have different configurations.

Abstract: An apparatus for screening pulp comprises a vessel, a cylindrical screen within the vessel, a rotating element moving in the vicinity of the screen at a predetermined speed, an inlet for the unscreened pulp, an outlet for the screened pulp in the vessel. The rotating element has a contour surface with grooves formed of a first plane parallel to the envelope surface, an inclined plane, an upper plane and a side plane, the side plane being essentially perpendicular to the first plane, the inclined plane forming an angle between 30.degree.-60.degree. with the first plane, the upper plane being parallel to the first plane. The rotating element may be a rotor or blade type segments.

Abstract: A screen drum and a method for its manufacture is disclosed wherein the screen drum comprises at least two cylindrical screen members spaced apart, between which a stiffening ring is disposed. The stiffening ring has two cylindrical surfaces which guide the ends of the cylindrical screen members, and a projecting part between them. The cylindrical screen members and the stiffening ring are attached to each other by a weld joint connecting the projecting part of the stiffening ring and the ends of the cylindrical screen members and filling the gap between them.