Patent ID: 6138836
Filing Date: 2000-10-31
Classification: D21D

Abstract:
A blade arrangement for a pulp screening apparatus comprising a screen cylinder (7) provided with apertures, the pulp to be screened being fed to one surface of the screen cylinder, and blades (11; 11a to 11c) that rotate round the axle of the screen cylinder (7) close to the surface whereto the pulp to be screened is fed, and which blades (11; 11a to 11c) comprise a portion that creates a pressure change for removing material that is clogged in the screen cylinder (7) apertures, and in which screening apparatus the pulp is fed to the screen from one end and the rejected pulp fraction is discharged from the opposite end in the axial direction of the screen cylinder, characterized in that in the blade arrangement, the cross section of the blade (11; 11a to 11c) in the vertical direction of the screening apparatus changes according to the consistency of the pulp screened in such a way that the blade comprises on its trailing side a sloping section (11"") creating a suction pulse, that the sloping section (11"") is short and steep at the upper end of the screening apparatus where the consistency of the pulp screened is lower, and, correspondingly, at the lower end of the blade where the consistency of the pulp screened is higher, the sloping section (11"") creating the suction pulse is longer and slightly inclined.