US2410326A - Combined vibratory scrubber, stratifier, and screen for minerals - Google Patents

Description

@Ci- 29, 1946- W. L. zElGLl-:R ET AL 2,410,326

COMBINED VI/BRATORY SCBUBBER, STRATIFIER, AND SCREEN FOR MINERALS Filed Nov. 12, 1943 7'2 sheets-sheet .1

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Oct. 29, 1946. W. L ZEIGLER ET A1.

COMBINED VIBRATORY SCRUBBER, STRATIFIER, AND SCREEN FOR MINERALS Filed Nov. 12, 1943 2 sheets-sheet 2 Snoentor WLLLLAM Lamm-ER c; LAL/Ds Y. GARBBR Patented Oct. 29, 1946 -COI^YBINED VIBlXtA'IQRY SCR'UBBER, STRAT- -IFKER, AND SCREEN-FOR MINERALS lWilliam L. Zeiglen'Wallace, and Claude Y. Garbei', Kellogg, Idaho, assignors to The 'Sink & Float-Corporation, New York, N. Y., a corpora- Application November 12, 1943, Serial No. 509,982

3 Claims. l

This invention relates to a combined vibratory scrubber, stratierand screen for minerals useful in mineral particle treatment processes, and, more particularly, to a method of screening .ore particles and a stepped-pool Washing screen for treating such multi-size mineral particles for screening and desliming or decolloiding of the material or for .the separation and sorting of extraneous materials that may therewith be included.

.In the `art of mineral separation, a common practice is to Vgrind ore in the presence of water to reduce its size to particles that maybe treated by sink and float, jigging, tablingor other related processes. Objects of grinding-are theliberation of mineral particles, sizing for subsequent treatment, and to meet commercial requirements in an end product. .It appears to loe-an inescapable result of Wet grinding that there is createdslimes or colloidal materials to the detriment Aof the subsequent `treating processes. In the -case of crushed materials .slime coatings will make the material untreatable and reduce the eiciencyof the sink and float steps.

It has been our observation that when crushed ore contaminated-with slimes or colloids is .passed to conventional screens for removal vof the lines from the coarser particles the Whole volume Atends to agglomerate linto a mass in which `the slimes are plastered in a gel-like state upon the particles to thereafter travel with them into subsequent sink and iioat or recovery steps to the detriment of these later operations. Such occurs rather than the more desirable screening, desliming or decolloiding which we have found possible vto perform with a maximum output ,of clean valuable material at high speed and in `great volume by the use of our invention more'fully described herein.

Another diiculty that is encountered in screening and desliming operation arises from ascarcity of water for use in spraying the material to eliminate the colloids or slimes. This clifliculty is particularly prevalent in the desert mining districts, as are common-in California, where the .amount of Water that may be apportioned to desliming must be cut to the absolute minimum since slime is not readily dewatered or thickened.

In the art of mineral recovery all of the problems mentioned above are focused into one large problem making for real trouble vin .the Imilling operations. For example, it appears to be common for minerals when ground to be accompanied bylarge quantities of fines, slimes and ...colloids which must be removed if `a Asink and oat recovery is to be economically practical or even possible. The prior treatments of minerals, therefore, according to conventional practices of screening and desliming, require large volumes of water to produce satisfactory results. It appears to be a quirk of nature rthat minerals must be found in dry areas where such quantities of Water are not always available for use in the crushing and-sorting stages of the milling operations.

A fairly recent innovation in the more modern mills has been the adoption and use of vibratory screens for medium, coarse and fine sorting. In such devices a rapid and low amplitude `positive vibration is imparted lto move the screens in Various horizontal, oblique or vertical motions, with or without the screen being supported truly horizontal. Such vibrations are employed to produce screening as well as forward feed of the material. These screens are recognized as having good volume but, as we have learned in our wide experience in mineral recovery, are accompanied by the problem mentioned above of agglomeration of the fines, slimes and colloids with the minerals in a highly detrimental manner by altering in an undesirable Way the specific gravity and viscosity of the sink and float medium as well as through the tendencies of the slimes to contaminate the medium and consequent impairment of the sink and floatprocess. In all cases, even where water supply is no problem, high velocity spraying does not result/infill] or satisfactory screening or desliming.

`Having in mind the'defects of the v prior lart of screening, it is an object of our invention to .provide a method .and means of handling particle materials in a manner to produce accurate separations or sorting in great capacity with a marked delineation between various products of the feed mass. Y

Another object of our invention is to provide a sorting screen .and operating means therefor .that will fully perform the steps of our method vof particleseparation without including the prior art defects of such similar mechanisms.

Still another obiect .of this invention .is the :provision, in a sorting screen of .the type mentioned, of a stratifying and scrubbing .pool which will rapidly and accurately .produce separation of mixed and multi-size particles in any of several desired. manners, while also preventing or breaking up agglomeration.

A still further Yand more specific object ofthis invention is .the provision .of a vibratory tscreen having stepped pools in 'sequence for vparticle treatment in a series of stages at a high volume feed without slime contamination of those particles most sought by those least sought.

The foregoing objects and others ancillary thereto we prefer to accomplish as follows:

According to a preferred embodiment of our method of particle separation, we feed crushed ore or similar granular material into a pool of nuid that is under the effect of reciprocatory or gyratory vibration. During such cycles of vibration the material is subjected to the mechanical forces in the presence of the water in a pool and without screening and is then passed across a screen for sorting and the elimination of certain of the mixture therethrough and the passage forward of that which does not go through the screen. In the specific embodiment of the invention shown here, we arrange that these steps be performed in repetition several times for subsequent retreatment either to variously grade the material into several sizes or to repeatedly subject the material to the same action for the elimination of one content from the remainder of the feed mass. In the former case, screens having varying characteristics are included in the sequence while in the latter case the screens are identical so that al1 the undersized material is the same and the coarse will be uniform and merely have been repeatedly retreated. The screens are supported in incline so that a wedge shaped pool may be created with the pointed end directed with the feed of the material.

That portion of the screen plate forming the bottom of the pool is imperforate while that portion that lies under the tapering end of the pool and forward thereof is perforate for the downward passage of particles that are to leave the mass along with a portion of the uid. Water or other fluid supply means are provided to flood the same into a pool in low pressure slow velocity streams. Likewise material feed means are employed for supplying material to the rear end of the pool in a constant manner. The screen is supported in its preferred angularity in a frame that is in turn resiliently supported upon springs so that it is free to move under the effect of a shaker mechanism 'associated therewith for that purpose. In the case of a desliming operation wherein the slime passing through .the screen tends to stick to and travel along the underside of the screen throughout its length means are provided for damrning such flow and for directing that material downward away from the screen and to free it from the mechanism. In certain instances a dam may be provided across the upper face of the screen to retard stratification and fluid movement in a forward direction to meet conditions sometimes encountered wherein it is desirable to lengthen the period that the particles are inthe fluid pool.

The novel features that we consider characteristics of our invention as set forth with particularity in the appended claims. The invention itself, however, both as to its organization and the method of its operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawings, in which Figure 1 is a longitudinal vertical sectional view of a vibratory screen that performs our method and embodies our invention,

A Figure 2 is an enlarged view of a portion of the screens of Figure 1,

Figure 3 is a plan view of the frame and its screens,

Figure 4 is a vertical sectional view on the plane suggested by lines 4 4 of Figure 1,

Figure 5 is a perspective View of a portion of a screen,

Figure 6 is an enlarged fragmentary sectional view of a portion 0f the screen and the dam used thereon, and

Figure 7 is a fragmentary View in cross section showing the manner of applying the method to the ordinary fiat screen,

A separation method and means for use herein to overcome the defects hereinbefore enumerated must have at least two totally distinct characteristics; th'e method must be capable of performance with a high capacity output coupled with high efficiency of separation of various particles in the feed material; and the mechanism must be capable, in a constant manner, of performing the process with a maximum of efficiency and a minimum of wear under hard usage. Accordingly, a preferred embodiment of my invention, referring .to Figure 1 of the drawings, is constituted by a resiliently supported frame which has as the principal bottom member thereof a perforate and imperforate screening plate. The frame comprises upright side Walls I0 and I2 joined at the feed end by wall I4 and at the tail end by wall I6 which is slotted at I8 for the outward passage of tailing materials from the inside the frame. Near the middle of the side walls a cross beam 20 is secured therebetween to stiffen the frame and to form a support for the shaker head 2I shown in Figure 1. This shaker head includes case 22 in which is journalled for rotation parallel shafts 24 and 2E to the former of which is secured drive means to which power is supplied in a conventional manner to produce rotation of shaft 24 and through gears 30, 3I to driven shaft 26. Each of these shafts have unbalanced rotor members which operate to unbalance each other and create vibration.

The frame formed of walls I0, I2, I4 and I6 is spring suspended by resilient links 34 from suitable overhead supports 33 and, when the vibrator head 2l is attached and caused to operate, will receive from said head vibration which causes .the frame and its screens to move in gyration preferably at an -angle oblique to the generally horizontal plane in which the frame is disposed.

Near the lower edges of the walls forming the frame in cups 35 is mounted a plurality of cross bars 36 which are shown to be canted forward so that the upper forward edge of each overhangs the lower edge on the forward face. The upper and lower faces of each bar 36 is substantially horizontal. These bars form the primary supports for the sorting screens 38, 38a, 38h, 38e and 38d each of which have end flanges 39 and 4i! that are inclined at an acute angle to the screen and oppositely to each other for engagement of the screen to adjacent bars 36. The rear ange 39 is hooked over the lower edge of the rearmost bar 36 of an adjacent pair and the forward flange 40 similarly engages over the upper edge of the forwardmost bar of such a pair. The rear edge of screen 38 which is the first of the series is hooked under the flange of anchor clip 42 mounted on the frame and is held there by the retainer bar 44 through the instrumentality of bolts d5. A spring leaf 4B presses the upper face of the screen 38. The most forward end of screen 38d, the last in a series, is engaged by anchorA clip 48 and drawn taut by the bolt 50. Since the intermediate cross bars 36 are loosely seated in cups 35 the whole serrated assembly is movable slightly under the urgence of the end anchor take-up means, `the screens may be tensioned to a degree after assembly.

I lEach of the screens comprises imperforate vportion A and perforate portion B as suggested walls of the frame, and the portion A -o'f each screen forms a wedge-shaped pocket which will contain fluid and material during operation of the machine. This fluid in the pool P is wedgeshaped since it has an upper generally horizontal face which converges with the rising bottom formed by the imperforate portion of the screen inl tangentiality with the perforate portion B.

Beneath each screen on suitable cross bars 52 we mount resilient buffer supports 54 in contact with the under face of the screen.

On occasion a dam 55 is attached to the mid upper Space of the screen to alter the fluid level in the pool P and to retard feed material in the pool for purposes of stratification or to prolong the scrubbing treatment in any one pool. These dams are preferably formed of rubber and are usually attached to the screen along the line of demarcation between the perforate and imperforate zones A and B.

Feed material is delivered to the left end of the screen as shown in Figure 1 by a conduit 58 having a discharge end 60. This material being largely fluid flows readilyonto and across the screen 38.

Water or other treating fluid is delivered to the screens through a primary conduit 62 that runs longitudinally of the frame above the screens and has several lateral headers 64 from which depend the spigots 65. The incoming water is preferably not under a great head, it being primarily intended that it fiow freely under the natural effect of gravity to discharge smoothly rather than jet-like as has previously been conventional practice.

The method In practice our separation process comprising the treatment of a fluid mass composed of liquid and solid particles to effect a separation of a po-rtion of the particles from others thereof. As has been said before, such separation can be desirable in selective separation of several types or sizes of particles from a mass such as sand and gravel or, as we have more particularly applied the invention, to the separation of slimes or colloids from oversize mineral particles in mineral treatment processes. In either case the basic function of the method is the same and comprises the imparting of vibration to a fluid mass but without permitting screening of the same during a scrubhing and stratification period and then, subsequently, screening and decanting a portion of the stratified mass to remo-ve a selected portion or stratum from the remainder. Therein lies an important distinction from prior conventional practices wherein screening takes place simultaneous with scrubbing and stratifying since by postponing the screening operation until adequate stratification takes place we facilitate the scrubbing and desliming (in the case of mineral separation) vand produce cleaner overflow oversize than has .heretofore beenk possible.

By the use of low amplitude high frequency vibration during the stratifying period of our process we speed the layering effect without retardi-ng the capacity of our separation means because when separation takes place the portion of the material to lbe separated from the massleaves -rapidly and without requiring prolonged screening as has been necessitated before. An important phase of our method lies in the forming and maintenance of a pool of fluid containing particles of various sizes and natures which pool is then vibrated to stratify and scrub the same and to intermittently separate, decant and advance a portion of the mass over the screen in its highly stratified condition to permit the slimes, fines and fluid to drop out of the mass and away from the individual particles passing on over the screen.

Operation of the appawtus With the screen resiliently suspended and the shaker head operating to vibrate the screen, fluid gangue is fed to the screens near the left end as shown in Figure 1 lby the conduit 50 and additional treating liquid is supplied near the pockets in the screen assembly through the spigots 66. The mass being treated forms a pool on the lower rear end of screen 38, as well as on the others in the case of a sequential series, and is there momentarily retained while it is vibrated whereby the particles in the mass are scrubbed against each other in fluid and the walls of the pool to separate the slimes from the coarser particles and the mass is stratified. During the cycles of vibration of the mass a portion of the same is ad- Vanced up the inclined face of the screen from the imperforate zone A to the perforate zone B which permits the fines and slimes that have collected in the lowermost stratum as well as the fluid to drop through the openings in the screen while the oversize particles pass on forward to the lip at the upper corner of the support bar 36, whence it cascades into the next pool and is similarly retreated either in repetition or for the next largel` sizing and sorting operation.

Such slimes and fluid as descend through the screen openings often tend to cling to the underside of the screen and produce blinding thereof or to travel forward in an undesirable underfeed following the contours of the screen until it is returned to the coarser mass to recontaminate it. To defeat this-action we employ the' dams comprising members 52 and 54 which serve to supportV the screens from below. As the forwardly creeping slime contacts the rear sideof the dam it is deflected downward away from the screen and is caused to fall away by the vibration of those members.

The dam 56 on the upper face of the screen may or may not be used, but when it is used it serves to retard forward movement of increments in the pool P until proper stratification has taken place and the fiuid level has risen to permit an increment to pass over the apex of the darn.

Although we have shown and described a certain specific embodiment of our invention, we are fully aware that many modifications are possible to meet slightly altered conditions. This we have in mind throughout our description of our invention, which we claim as follows:

O-ur method and mechanism may be applied to existing flat top vibrating screens by fastening bars 68 across the screen as shown in Figure 7 to maintain liquid pools on the top of the screen plate or cloth. This apparatus consists of cross 'barsGBboth above and below the screen plate or cloth between which the screen is supported to maintain the liquid in the pool. VThe perfora- `tions -in the screen or cloth are stopped olf by a suitable plate as Hi which may be clamped between the bars for secure placement.

We claim:

'1. A vibratory separator, comprising: a serrated deck formed of inclined plates having risers `between adjacent plates, each said plate being forate and periorate portions to the apex, and

means for vibrating said deck longitudinally "thereof, whereby particle bearing fluid has the particles therein scrubbed and stratified and portions thereof intermittently decanted for the removal of a portion of the fluid and of particles of a size to pass through said screen.

2. A vibratom7 separator, comprising: a serrated deck formed of inclined plates having risers ybetween adjacent plates, said risers being canted forward, each said plate being perforate adjacent its apex and imperforate adjacent the root, said plates being characterized by being smooth from the root across the imperforate and perforate 4portions to the apex, and means for vibrating said deck longitudinally thereof, whereby particle bearing fluid has the particles therein scrubbed and stratified and portions thereof intermittently decanted for the removal of a portion of the fluid and of particles of a size to pass through said screen.

3.7A vibratory separator, comprising: a serrated deck formed of inclined plates having risers between adjacent plates, each-said plate being perforate adjacent its apex and imperforate adjacent the root, said plates being characterized by being smooth from the root across the imperforate and perforate portions to the apex, and means for vibrating said deck longitudinally thereof, whereby particle bearing fluid has the particles therein scrubbed and stratied and portions thereof intermittently decanted for the removal of a portion of the fluid and of particles of a size to pass through said screen, and defiectors in contact with the underside of said plates to prevent creeping of slimes and the like and to direct the same away from the screen.

WILLIAM L. ZEIGLER. CLAUDE Y. GARBER.

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