Classifying – separating – and assorting solids – Sifting – With liquid treatment
Patent
1994-12-12
1997-02-11
Terrell, William E.
Classifying, separating, and assorting solids
Sifting
With liquid treatment
209300, 209389, 210413, B07B 104, B07B 152
Patent
active
056011920
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a pressure sorter for fiber suspensions, in particular, for the preparation of fiber suspensions obtained from waste paper, with a housing in which a stationary screen is arranged rotationally symmetrical to a screen axis, this screen separating a supply chamber encircled by the screen from an accepts chamber lying outside the screen in the housing, as well as a rotor drivable about the screen axis by a motor, the circumferential surface of this rotor together with an inlet side of the screen limiting the supply chamber in radial direction, an inlet for the fiber suspension to be treated communicating with a first axial end of the supply chamber and a rejects outlet communicating with a second axial end of the supply chamber, wherein profiled elements are provided at the circumferential surface of the rotor for generating positive and negative pressure pulses in the fiber suspension.
BACKGROUND
In pressure sorters of this type, the fundamental problem is that when no suitable countermeasures are taken, the throughput of usable fiber suspension through the screen and into the accepts chamber is drastically reduced in that the screen openings or apertures are clogged on the inlet side of the screen by impurities contained in the fiber suspension to be prepared, but also by fiber conglomerations; additionally, during the operation of such pressure sorters, the fibers contained in the fiber suspension to be prepared are fundamentally inclined to form a fiber fleece on the screen inlet side by means of which a high throughput of usable fibers (long as well as short) desired per se through the screen openings into the accepts chamber is prevented and besides, at least in most cases, undesired fractioning of the fiber suspension is effected--this means a separation of the fiber content in the fiber suspension to be prepared into shorter and longer fibers, whereby such a fiber fleece prevents, in particular, longer fibers from passing through the screen and into the accepts chamber.
The most varied measures are found in the state of the art by means of which it was attempted to control all or a part of the precedingly stated problems, whereby in this connection it needs to be realized that in pressure sorters of the type described in the beginning, the screen openings are intended to be flushed back by means of the negative pressure pulses generated by the profiled elements, i.e. by generating underpressure phases in the supply chamber liquid is intended to be sucked back from the accepts chamber through the screen openings and into the supply chamber in order to flush out from the screen openings impurities and fiber conglomerations collected at the inlet side of the screen openings.
A first measure, which can be deduced from the state of the art, consists in the fact that the screen openings are designed such that they widen in the conveying direction (i.e. in the direction from the supply chamber to the accepts chamber) (see for example, U.S. Pat. No. 3,581,903), in order to decrease the danger of the screen openings clogging up.
In order to effect a backwashing of the screen openings as well as to prevent a fiber fleece resulting on the inlet side of the screen, another known pressure sorter (see for example, U.S. Pat. No. 4,276,159) was equipped with a rotor which has in the vicinity of the screen inlet side rotating cleaning vanes with airfoil-like profile in section vertical to the rotor axis for generating positive and negative pressure pulses as well as having its screen designed such that due to the widened screen openings on the inlet side, a "roughened" screen inlet side results in order to generate turbulences in the fiber suspension to be prepared at the inlet side of the screen and in its vicinity by means of the interaction of the rotating rotor vane with the fiber suspension located in the supply chamber and the inlet side of the screen profiled in this manner, these turbulences counteracting the formation of a fiber fleece on the screen inlet side.
Als
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Czerwoniak Erich
Hutzler Wilhelm H.
Hermann Finckh Maschinenfabrik GmbH & Co.
Nguyen Tuan
Terrell William E.
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