Classifying – separating – and assorting solids – Sifting – With liquid treatment
Patent
1983-10-07
1985-07-16
Miles, Tim
Classifying, separating, and assorting solids
Sifting
With liquid treatment
209380, 210393, 210404, 210408, B07B 122
Patent
active
045295093
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a screen machine, preferably for cellulose pulp and recycled pulp, including a screen rotor which is rotatable within a housing having an inlet for unscreened suspension, an outlet for accepts and a discharge opening for rejects.
From U.S. Pat. No. 1,429,707 is known a pulp screen of this kind having a cylindrical screen drum and self-clearing action. The pulp is fed into one end of the drum and is forced to rotate with the drum by means of blades. By the action of centrifugal force, fibers and water are forced radially outwards through the screen slots. The casing of the machine is elliptical, and thus at two points the casing is located closer to the drum than at other points. At these two points, therefore, the screened pulp located outside the drum and also rotating therewith will be "compressed" and cause a back-flow radially inward through the screen slots. Thereby these are cleared of oversize fibers, etc., which are discharged at the other end of the drum.
The screen machine according to the present invention also has a self-clearing action which, however, results from the utilization of centrifugal force.
The essential object of the invention, thus, is to clear screen holes in a screen rotor by means of centrifugal force immediately after each screen zone, within which screening takes place against the action of centrifugal force. Cylindrical as well as conical screen drums can be contemplated, as well as disc-shaped screen rotors; in the latter case, of course, the screen holes will have to be inclined against the axis of rotation in order to obtain centrifugal pumping action.
An embodiment of the invention will now be described with reference to the accompanying drawing, wherein
FIG. 1 is an axial section through a machine according to the invention, and
FIG. 2 is a section along line II--II of FIG. 1.
FIG. 1 shows a machine casing 10, in which a shaft 12 driveable by a pulley 11 is journalled in bearings 13, 14. In the other end of shaft 12 is mounted a screen rotor 15 for rotation with the shaft, said rotor being concentrically located within a substantially cylindrical screen housing 16.
In the example shown, the shaft 12 is horizontal and the screen housing 16 is provided with an inlet 17 for unscreened stock located at the top of the periphery, a central outlet 18 for screened stock (accepts) coaxial with the screen rotor 15, and a selectively openable discharge opening 19 for non-screenable goods (rejects). The screen rotor 15 has a tight hub disc 20 attached to the shaft 12 and an envelope plate 21 arranged at the periphery of the hub disc, the envelope disc being provided with a plurality of screen openings 22. Straight in front of the hub disc 20 the screen rotor 15 is open towards the wall 23 of the screen housing, in which the outlet 18 is disposed. Between the wall 23 and the edge of the envelope plate 21 there is an interspace 24.
The arrangement is such that the pulp suspension flows from the inlet 17, via the annular space 25 between the housing 16 and the rotor wall 21 through the screen openings, and to the outlet 18, whether the rotor is rotating or not.
The pressure of the stock at the inlet 17 and within the annular space 25 is thus so much greater than the pressure in the outlet 18 that a flow takes place radially inwards through the screen openings 22 in spite of rotation of the rotor. This flow is indicated in FIG. 2 by small arrows at approximately 12, 3, 6 and 9 o'clock positions.
According to the invention, within the rotor are arranged a number of fixed baffle plates 26, 27, 28, 29 shutting off one sector each of the interior of the rotor from the outlet 18. The baffle plates 26 to 29 thus extend from the wall 23 of the screen housing into the rotor, and terminate immediately adjacent the hub disc 20.
As mentioned above, there is an interspace 24 between the wall 23 and the open end of the rotor drum. Because of this interspace, the pressure of the annular space 25 exists also within the sectors defined by the rotor envelope 21 and the ba
REFERENCES:
patent: 1429707 (1922-09-01), Baker et al.
patent: 2352303 (1944-06-01), Young
patent: 2707905 (1955-05-01), Mathewson
patent: 3276584 (1966-10-01), Mathewson
patent: 3404065 (1968-10-01), Ingemarsson
patent: 3452875 (1969-07-01), Rich et al.
patent: 3616904 (1971-11-01), Aremaa
patent: 3627139 (1971-12-01), Burtsev
patent: 3750885 (1973-08-01), Fournier
patent: 4266413 (1981-05-01), Yli-Vakkuri
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