US2355851A - Classifier - Google Patents

Description

Patented Aug. 15, 1944 CLASSIFIER John H. V. Finney and Arthur C. Daman, Denver, 0010., assignors to Mining Process and Patent Company, Denver, 0010., a corporation of Delaware Application November 4, 1941, Serial No. 417,776

12 Claims.

with and more or less suspended in the liquid carrying medium.

This pulp is introduced into the classifier which ordinarily has an inclined tank so that the pulp forms a pool at the lower end of the tank. Means are provided for elevating the larger and heavier particles of divided solids, called sands, upwardly from the pool along the inclined bottom of the tank, while the finer solids, together with the liquid carrying medium, are passed ofi H by overflow as the slime from the classifier to go to the next stage of recovery operations, such as, for instance, the flotation cells. Thus the sands are classified and separated from the rest of the pulp. The sands are ordinarily returned to the reducing mill for further grinding.

In the type of classifier as herein illustrated, that is provided with a rotary screw-type elevator, there has always been an inherent problem in providing a suitable bearing for the lower end of the conveyor shaft, which normally is submerged in the pool of pulp. This problem arises from the fact that it is difficult to lubricate such a bearing so placed in the pool of pulp, which situation is particularly aggravated by the fact that the pulp has a deleterious abrasive effect on the bearing and the shaft journalled therein.

A further desideratum is that the helical or screw-type elevating conveyor must be so journalled that the lower end thereof can be raised when desired, particularly during a shutdown of the machine or immediately before starting operation of the classifier following a shutdown. One reason for this is that the solids contained in the pulp naturally will settle to the bottom of the tank during a shutdown and unless the conveyor is raised from the solids prior to starting again, it may be damaged by being stuck in the settled solids.

invention to provide in a classifier having an inclined helical or screw-type elevating conveyor,

improved means for journalling the shaft of said conveyor, which means are so designed and located as to eliminate the difficulty of lubrication and overcome the danger of damage to the bearing and shaft by the abrasive effect of the pulp.

Another object is to provide in a classifier of this kind, improved means for elevating the conveyor if and when desired.

A further object is to provide in a classifier, improved means for feeding and discharging pulp, in order to establish an optimum liquid level in the tank, and to create a controllable flow of the pulp across the tank.

Other objects and advantages reside in details of design and construction as will become apparent hereinafter, which tend to improve the all-around operating efficiency of a classifier.

In order to disclose an operative reduction to practice of the present inventive concepts, the accompanying drawings which illustrate a typical example will be described in some particularity.

In the drawings wherein like parts have been similarly designated,

Figure 1 is a plan view, partially in section, of a classifier built according to this invention;

Figure 2 is a side elevation, partially in section, of the classifier illustrated in Figure 1;

Figure 3 is a cross sectional view taken approximately along the line 3-3 of Figure 2, and drawn to a somewhat larger scale;

Figure 4 is a cross sectional view as indicated by the line 4-4, Figure 2, and drawn 'to a larger scale; and

Figure 5 is a diagrammatic illustration of a detail of Figure 1.

Referring to Figures 1 and 2, reference character l2 denotes an inclined tank, the lower end of which is closed so as to permit fluid pulp introduced thereinto to form a pool as indicated at l3.

A hollow shaft l4 carries helical or screw conveyor flights shown fragmentarily at 15, it being understood that these flights comprise the conveyor which in entirety extends substantially :from end to end of the tank l2, and which is positioned on an incline that normally corresponds with the angle of inclination of said tank 12.

-These flights, two in number, extend from upposite ends of shaft I4 and terminate at a bearing 22 intermediate the ends ofthe shaft.

The upper end portion Me of the shaft M, which is preferably of a reduced size, is suitably journalled as at It and", on a yoke-like structure l8, which in turnis pivotally mounted at IS on the general tank-supporting structure 20.

veyor I5, without interrupting power input to the I conveyor.

In order further to journal the conveyor shaft I4, another bearing 22 is provided for the shaft adjacent the longitudinal center thereof, well above the liquid level of the pool. This positioning of the lower bearing near the center of the.

shaft is in advanced contradistinction from the ordinary practice of journalling the lower end of the conveyor shaft down in the pool of pulp. This improved positioning of the lower bearing is of great importance in overcoming the difficulties and obtaining the objectives hereinbefore pointed out.

As well illustrated in Figures 2 and 3, the bearing 22 is provided with lifting rods 23, which in turn are secured to a cross head 24, the ends of which are positioned between arcuate guides 25 carried upon superstructure 26.

A lubricator tube I2! is also connected with the bearing 22 and is supported in the cross head 24 where it is readily accessible for the introduction of suitable lubricant. I

In order to provide means for angularly lifting the entire shaft and conveyor assembly about the pivotal axis I9, chains 21 are attached to the cross head 24 and are also secured to spiral sheave-lik cams 28, which in turn are carried .upon a shaft 29 that is suitably journalled for rotation upon said superstructure 26.

Operating mechanism for rotating the shaft 29 to turn the spiral sheave-like cams 28 to impart upward angular motion to the shaft I4 and the conveyor I5, comprises a hand-crank 30 connected to operate a worm 3I, which in turn meshes with a worm-wheel or gear 32 that is securely keyed or otherwise fastened to said shaft 29.

The guides 25 are provided with cooperating inner guide surface, between which the ends of the cross head 24 are positioned. These guiding surfaces are arcuate and positioned on a true radius from the pivotal axis. I9 of the entire angular movement of the shaft and conveyor.

The design of the sheave-like spiral earns 28' is such that as the chains 21 are wrapped thereupon, the direction of the lifting force applied to the mechanism will constantly be in substantially tangential relationship to the arc of angular movement of the bearin 22. The guides 25 and the cams 28 cooperate to provide this tangential relationship of the direction of lifting force, which is an important advantage in that the lifting force as transmitted from the lifting mechanism will constantly be substantially perpendicular to the bearing 22 and the shaft I4. Obviously, this perpendicular lift on the bearing 22 and the shaft I4 is an optimum arrangement.

sheave-like spiral cams 28 provide another important advantage because the effective length of the lever arm of the lifting force transmitted from the shaft 29 to the chains 21, varies as the cams rotate. The shortest and therefore the most in the lower end of the tank I2.

advantageous lever arm is effective at the beginning of the lift, where the greatest force normally will be required because the flights of the helical conveyor may be buried in settled solids Obviously, in order to pull the conveyor out of such settled solids and overcome the static inertia thereof, greater lifting force will be required to initiate upward movement of the shaft I4 and the conveyor flights I5, than will be required after upward angular movement thereof is progressing.

As the spiral cams 28 rotate in the direction of the arrow shown in Figure 2, the effective length of the lever arm will gradually increase from minimum at the beginning of the lift, to maximum at the end of the lift.

Another important improvement in the present classifier resides in the feed launder 33, Figures 1, 2 and 4, in cooperative combination with the overflow weir 34. The feed launder 33 is attached to the main tank I2 by means of a plurality of bolts 35 which engage in slots 36 in the launder, providing for relative angular movement of the launder. This provision for selective angular positioning of the launder is important because the main tank I2 may be positioned at different angles of inclination, and further, because the nature of the pulp being fed to the tank requires difierent angles of the feed launder depending upon circumstances.

The tank is further provided with a plurality of deflectors 31, which can be angularly moved and positioned about their pivotal fastenings so that as pulp is fed into the launder, it may be deflected and directed into the tank I2 as desired.

Across the tank I2 from the launder 33 is positioned the overflow weir 34. This weir 34 comprises one or more weir boards and it is manifest that the level of the liquid in the pool may be selectively governed by the height of the upper edge of the board. Furthermore, as illustrated in Figure 4, the overflow weir board may be provided with a cut-out 34a of a selected depth, shape and length, so that the cut-out provides another factor of selective control of the lever of the liquid in the pool, and the exact place of overflow therefrom.

These features embodied in the feed launder and the overflow weir cooperate to provide a definite and controllable cross-current flow of the liquid in the pool. As best shown in Figure 4, the direction of rotation of the conveyor I5 is preferably as indicated by the arrow 38. Rotation in this direction prevents undue turbulence adjacent the overflow weir, and at the same time facilitates the cross flow from feed to overflow.

Another improvement, which is optional, is best illustrated in Figure 1 wherein a conduit 40 has a swivel connection M with the end of the shaft I 4a whereby fluid, such as air under pressure, water or any other fluid, may be introduced into the interior of the shaft I la-I4 which is hollow, to

be discharged through a plurality of ports 42 adjacent the lower portion of the shaft I4 into the pool of pulp in the tank I2. This feature may or may not be used, depending upon circumstances, but it provides means for aerating the pool of pulp or for diluting it, either of which may be desirable under certain circumstances.

The various improved features herein illustrated and described may be used in selected combinations as desired, according to circumstances, the nature of the material being classified, and the operating results wanted.

-" Furthermore, certain features, such as the improved feed launder and discharge weir positioned across from each other may well be incorporated into classifiers other than the screw conveyor type.

What we claim and desire to secure by Letters Patent is:

- 1. In a classifier inclusive of a tank for liquid pulp, the improvement which comprises a feed launder at one side of the tank, an overflow weir at the other side of the tank positioned opposite to the feed launder, a rotary conveyor positioned in the tank between said launder and said overflow weir with its upper surface at a higher elevation than said weir, and mechanism for rotating said upper surface of the conveyor away from the launder and toward the weir.

2. In a classifier having an inclined tank and having an inclined rotary conveyor mounted for angular movement, the improvement which comprises arcuate guides for said conveyor positioned intermediate its ends and on a radius from the axis of angular movement, and cam mechanism connected with said conveyor by means of a flexible element for applying force for said angular movement from a fixed point and in a constantly changing direction so as to continually exert such force in a direction which is substantially perpendicular to the axis of rotation of the conveyor.

3. A classifier comprising an inclined tank for liquid pulp, a similarly inclined shaft pivotally journaled adjacent its upper end for rotation in the tank and for angular up and down movement with reference to said tank, rotary conveyin means carried on the shaft, another and lower bearing for the shaft positioned above the normal liquid level in the tank, superstructure above said lower bearing, rotary sheave-like spiral cams journalled in said superstructure, manually operable gears for transmitting rotary force to said cams, chains attached to the respective cams in a position to be wound thereon by rotation thereof, arcuate guides positioned on a radius from the axis of angular movement of the conveyor shaft, a cross head connected with said lower bearing and with said chains and positioned to be guided in an arcuate path of movement by said guides, a feed launder at one side of the tank, and an overflow weir at the opposite side of the tank.

4. In a classifier, a tank having upright walls, a feed launder mounted on one of said upright walls for angular movement to different vertical positions, means within said launder for dividing feed passing therethrough and into the tank, and an adjustable overflow weir on a wall of the tank opposite the feed launder cooperating with said feed launder to determine the rate and direction of flow between the point of feed introduction and the overflow.

5. In a classifier, a tank having upright walls, a feed launder mounted on one of said upright walls for angular movement to different vertical positions, means for holding said launder in selective angular positions on said wall, and an adjustable overflow weir on a wall of the tank opposite the feed launder cooperating with said feed launder to determine the rate of flow between the point of feed introduction and the overflow.

6. In a classifier, a tank having upright walls, a feed launder mounted on one of said upright walls for angular movement to different vertical positions to vary the rate of feed introduction, means for holding said launder in selective angular positions on said wall, and means within said launder for dividing feed passing therethrough and into the tank.

7. In a classifier, a tank having upright walls, a feed launder mounted on one of said upright walls for angular movement to different vertical positions to vary the rate of feed introduction, means for holding said launder in selective angular positions on said wall, and adjustable means withinsaid launder for selectively dividing feed passing therethrough and into the tank.

8. In a classifier, a tank for pulp enclosed on three sides and the bottom to form a lower pool and a therewith-associated inclined passageway having a sands discharge at a substantially higher elevation than the surface of the pool, rotary conveying means for moving sands settling in said pool to the elevated sands discharge, said means including a hollow shaft having one of its ends submerged in the pool and its opposite end terminating adjacent the sands discharge, and means associated with the elevated end of the shaft for delivering fluid thereinto, there being an opening in the shaft within the pool for the delivery of said fluid thereto.

9. In apparatus of the character described, a tank for pulp enclosed on three sides and the bottom to form a lower pool and an inclined passageway, said tank having a sands discharge at a higher elevation than the surface of the pool and a weir to determine the depth of the pool, rotary conveying means for moving sands settling in said pool to the elevated sands discharge, said means includingan inclined central rotatable member having its lower end free and at least partially below the top of said tank and its opposite end terminating adjacent the sands discharge, and a plurality of conveyor flights on said rotatable member, means outside the pool providing the sole support for said rotary conveying means and comprising a bearing at the sands discharge end of the tank and a second bearing between said first bearing and the free end of said member, said conveyor flights being so mounted that one of them extends along and is supported on the portion of said member extending between said bearings and another flight extends along and is supported on the portion of said member beyond said second bearing to extend into the pool, the ends of said flights adjacent said second bearing being closely spaced so as to substantially uninterruptedly move material toward said sands discharge, supports for said second bearing extending between the adjacent ends of the flights, and means to raise and lower said conveying means.

10. An apparatus of the character described in claim 9 wherein each of said conveyor flights comprises a ribbon element supported upon said central rotatable member by supports extending radially from said rotatable member.

11. An apparatus of the character described in claim 9 wherein said second bearing is positioned midway of the length of said inclined central rotatable member.

12. In apparatus of the character described, a tank for pulp enclosed on three sides and the bottom to form a lower pool and an inclined passageway, said tank having a sands discharge at an elevation at least as high as the surface of the pool and a weir to determine the depth of the pool, rotary conveying means for moving sands settling in said pool to the sands discharge, said means including an inclined central rotatable member having its lower end free and at least partially below the top of said tank and its opposite end terminating adjacent the sands discharge, and a plurality of conveyor flights on said rotatable member, means outside the pool providing the sole support for said rotary conveying means and comprising a bearing at the sands discharge end of the tank and a second bearing between said first bearing and the free end of said member, said conveyor flights being so mounted that one of them extends along and is supported on the portion of said member extending between said bearings and another flight extends along and is supported on the portion of said member beyond said second bearing to extend into the pool, the ends of said flights adjacent said second bearing being closely spaced so as to substantially uninterruptedly move material toward said sands discharge, supports for said second bearing extending between the adjacent ends of the flights, and means to raise and lower said conveying means.

JOHN H. V. FINNEY.

ARTHUR C. DAMAN.

Images