Patent GB-1471238-A (GB)
Title: Classifying apparatus for fibrous suspensions
IPC: D21D5/02
Filed: 1975-03-19
Abstract: 1471238 Vortex cleaner; wet screening apparatus HERMAN FINCKH BETEILIGUNGS H H BURKHARDT and H M KURTZ GmbH [trading as HERMANN FINCKH METALLTUCHUND MASCHINENFABRIK] 19 March 1975 [20 March 1974] 11435/75 Headings B1D, B2H and B2P A classifier for fibrous suspensions, e.g. waste paper stock, comprises a vertically disposed, stationary screen cage 68, Fig. 3, and a rotor 70 provided in an upper portion of a housing, the rotor being arranged for rotation inside the screen cage, a lower portion of the housing forming a vortex cleaner 12 with its bottom portion 16 provided with an outlet 22 for heavy material separated from the suspension and its upper portion provided with an outlet for the remainder of the suspension arranged to communicate with the inside of the screen cage 68; an inlet 20 to the lower portion of the housing for suspension to be classified arranged in proximity to the lower end of the rotor 70; a first outlet 30 in the upper portion of the housing arranged above the screen cage for a reject fraction of the remainder of the suspension; a second outlet 28 in the upper portion of the housing for an accept fraction of the remainder of the suspension which has passed through the screen cage; the rotor 70 having the shape of a hollow cylinder which is closed at least in its circumferential portion and at the bottom, the circumferential portion being provided with at least one stirring element 86; and means 82 on the rotor to  circulate the suspension to be classified. The conical portion 16 of the vortex cleaner is pivotable about an axis 18, Fig. 1, in order to provide access to the interior of the classifier. The outlet 22 is provided with a slide valve 26 operable by a pneumatic cylinder 24. The rotor 70 is mounted on a shaft 36 rotatably supported in a bearing housing 34 and driven through a V-belt drive 40 by an electric motor 42. Three suspension-accelerating ribs 82 are secured to the conical bottom 80 of the rotor and their inclination correspond to that of the tangential inlet pipe 20. Two stirring strips 86 are secured to the rotor shell 76 and are inclined at an angle to the vertical, Fig. 5, the cross-section of each strip being wedge-shaped with its leading edge 86a being thicker than its trailing edge. The function of the strips is to prevent clogging of the screen cage apertures and to force the suspension being classified to flow upwardly towards the outlet 30. Dilution water may be introduced through a valved inlet 74. The rejects-outlet 30 is provided with a slide valve 32, Fig. 1, which is actuated by a reciprocable pneumatic cylinder 44 connected to a source of pressure air through a four-way valve 48 actuated by a magnet 54. The electric circuit of the magnet includes a timer 56 and a switch 58 which is controlled by a switching ammeter 60 incorporated in the circuit of the electric motor 42. The timer provides periodical opening and closing of the circuit of the actuating magnet 54 and hence reversal of valve 48 and periodical opening and closing of slide valve 32. When the load on the rotor 70 exceeds a predetermined value due to clogging of the space between the rotor and the screen cage 68, the switching ammeter 60 opens the switch 58 causing the slide valve 32 to open and to stay opened until the strong flow thus created in the said space removes the clogging. The ammeter then closes the switch 58 back and the slide valve 32 is thus closed.