Classifying – separating – and assorting solids – Sifting – With liquid treatment
Patent
1992-10-13
1993-12-21
Dayoan, D. Glenn
Classifying, separating, and assorting solids
Sifting
With liquid treatment
209303, 209306, B07B 104
Patent
active
052715035
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention is directed to apparatus for separating impurities, such as coarse particles (e.g., knots and other undefibered materials) from pulp suspensions. More particularly, the present invention is directed to such apparatus for screening through gaps in which the surfaces defining those gaps are relatively movable with respect to each other.
BACKGROUND OF THE INVENTION
The types of screens which are designed for screening through gaps in which the surfaces defining the gaps are relatively movable with respect to each other, or so-called gap-screens, are usually designed so as to have a cylindrical housing with an inlet for the injected pulp suspensions and outlets for both the reject and accept portions of the pulp suspensions, respectively. Within these housings, a stator and a rotor are generally located, which between them define one or more gaps through which the pulp suspension is intended to pass. In this manner, coarse material, which cannot pass through the gaps, is separated from the pulp suspensions in the form of a reject.
A gap-screen comprising several gaps can be formed with concentric rings, every second one of which is stationary and thus alternates with rotary such rings. The gaps are then located at alternating spaces with respect to the center of rotation. This, in turn, implies that the flow conditions are different at the different gaps. Furthermore, the number of gaps is restricted by the fact that the diameter of the screen must be limited by factors such as the circumferential speed thereof.
If, instead, the gaps were located radially, i.e., the rings defining the gaps were located sequentially in the axial direction, the diameter of the screen can be limited even with a larger number of such gaps. Problems arise, however, with the mounting and dismounting of the rings defining the gaps, because these rings must be mounted and dismounted individually and sequentially, which becomes both complicated and tedious. At the same time, it is difficult to maintain a definite gap width, because an improper dimension of one ring can affect the size of all of the gaps.
SUMMARY OF THE INVENTION
In accordance with the present invention, the aforesaid problems are solved, and at the same time additional advantages in the screening of pulp suspensions are achieved. In accordance with this invention, the stator and the rotor comprise a plurality of annular elements arranged in a mutually spaced relationship. The rotor is thus located radially outside the stator, so that the rotor elements are located directly in front of the spaces between the stator elements, and the axial length of the rotor elements is greater than the spaces between the stator elements and the rotor elements. In view of this design, the stator and the rotor can be mounted and dismounted as separate units. Furthermore, a definite gap width can be obtained for all of the gaps, since it can be defined by the radial distance between the annular elements of both the stator and the rotor.
In accordance with the present invention, apparatus is provided for screening a pulp suspension comprising a housing including an inlet for the pulp suspension, screening means for screening the pulp suspension, a reject outlet for removal of a portion of the pulp suspension which does not pass through the screening means, and an accept outlet for removal of a portion of the pulp suspension which does pass through the screening means, the screening means comprising a stator rigidly mounted within that housing, and a rotor rotatably mounted within the housing radially outward from the stator, the stator including a plurality of annular stator elements axially spaced along the stator whereby the plurality of stator elements alternate with a plurality of stator spaces therebetween, and the rotor including a plurality of annular rotor elements axially spaced along the rotor, whereby the plurality of rotor elements alternate with a plurality of rotor spaces therebetween, the plurality of rotor elements being a
REFERENCES:
patent: 3400820 (1968-09-01), Nelson
patent: 3452875 (1969-07-01), Rich et al.
patent: 3677402 (1972-07-01), Holz
patent: 4287055 (1981-09-01), Holz
patent: 4749474 (1988-06-01), Young
patent: 4836915 (1989-06-01), Frejborg
Dayoan D. Glenn
Sunds Defibrator Industries Aktiebolag
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