Cae Screenplates Inc.

Cae Investments B.v.

Frank Aaltonen

Frey A Frejborg

Timo Alajaaski

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. Contoured surfaces typically include grooves, and variables that may be changed to affect the turbulence include the depth of the grooves, the angle of inclination of the downstream wall of the grooves, the spacing between the grooves, the radius of curvature of the opening (holes or slots) edges, the frequency of openings in grooves, and the dimensions of the openings (holes or slots) in the grooves. The screen cylinder is mounted in a pressure screen housing.

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Lisse, Netherlands

Frank Aaltonen