US3087619A - Method and apparatus for concentration of ores - Google Patents

Description

April 30, 1963 M. KRAUT 3,087,519

METHOD AND APPARATUS FOR CONCENTRATION OF ORES Filed Nov. 27, 1959 7 Sheets-Sheet 1 INVENTOR; MA X KRA U T M. KRAUT 3,087,619

METHOD AND APPARATUS FOR CONCENTRATION OF ORES 7 Sheets-Sheet 2 M 0 m R. A v .n RI A 0 Y l a: w m m %w u l l I 1| m WT M l m w. w a E w m z W v i I n M 0 v 7- k M w n m n n t m "FIFE u ..I\M A E w W A #m a m v Z o "M Z I l! w WG- II. I Pyl hu w w J I ll v q E E 8 it 6 1 April 30 1963 Filed Nov 27, 1959 April 30, 1963 Filed Nov. 27, 1959 M. KRAUT METHCD AND APPARATUS FOR CONCENTRATION OF ORES 7 Sheets-Sheet 3 April 30, 1963 M. KRAUT METHOD AND APPARATUS FOR CONCENTRATION OF ORES Filed Nov. 2'7, 1959 7 Sheet 5 4 VENTOR I ATTORNEY April 30, 1963 M. KRAUT 3,0

METHOD AND APPARATUS FOR CONCENTRATION OF ORES Filed Nov. 2'7, 1959 '7 Sheets-Sheet 5 INVENTOR 4/41 AZ PAWT ATTORNEYJ M. KRAUT 3,087,619

METHOD AND APPARATUS FOR CONCENTRATION OF ORES April 30, 1963 '7 Sheets-Sheet 6 Filed NOV. 27, 1959 IHHHIH ATTORNEYS April 30, 1963 M. KRAUT 3,087,619

METHOD AND APPARATUS FOR CONCENTRATION OF ORES Filed Nov. 2'7, 1959 '7 Sheets-Sheet 7 United States Patent 3,087,619 METHOD AND APPARATUS FOR CONCEN- TRATION 0F ORES Max Kraut, San Francisco, Calif., assignor to Western Machinery Company, San Francisco, Calif., a corporation of Utah Filed Nov. 27, 1959, Scr. No. 855,597 27 Claims. (Cl. 209-456) The present invention relates to improvements inmethods of an apparatus for separating fine mineral particles of a high density from fine particles of lower density'in a fluid or liquid medium. The present invention is of particular utility in the separation of suspensoids which as the term is herein used are particles which are too fine to settle in a specific medium within a practical time limit allowable under operating conditions.-

This application is a continuation in part of my copending application Serial No. 674,266, filed July 15, 1957, which was a continuation in part of my application Serial No. 601,924, filed August 3, 1956, both now abandoned. 7

Conventional methods such as jigging and apparatus for performing these methods have no effect on suspensoids and can not effect their separation. Jigging and other similar methods can only effect separation on relatively coarse particles by stratification, wherein the particles readily settle in a pulsating medium with the heavier particles displacing lighter particles by gravity. 7

Examples of prior devices and methods are disclosed in United States Patents No. 2,242,020, issued May 13, 1941, to Wood, for Concentrating Cell; No. 2,271,650, issued February 3, 1942, to Kraut, for Jig; No. 2,523,364, issued September 26, 1950, to Glover, for Ore Concentrating Jig; No. 2,570,035, issued October 2, 1951, to Laughlin, for Means of Wet Screen Sizing; No. 2,638,220, issued May 12, 1953, to Schneider, for Underwater Screening; No. 2,708,032, issued May 10, 1955, to Heyman, for Mica Flake Classifying Device and Method; and No. 2,765,911, issued October 9, 1956, to Vissac for Fluidized Pulsating Jig.

In the present invention particles of differing size and density are discharged at substantially equal velocity into a fluid body. Particles of equal mass (volumexdensity) will have equal momentum (mass velocity) as they approach the fluid body but the more dense smaller particles, having a smaller exterior surface, will encounter lower resistance to movement through the fluid and will thus penetrate the fluid body more readily and deeply than particles of equal mass but lesser density. Particles of equal volume but differing densities when discharged toward the fluid' body at equal velocities will have differing momenta proportional to their respective densities as they approach the fluid body so that the more dense particles will have greater power of penetration into the fluid body than equal volume particles of lesser density and likewise penetrate the fluid body more deeply.

The present invention utilizes these principles by a1- ternately discharging a high velocity jet of intermixed particles of varying volume and density into a stationary body of fluid of predetermined density and viscosity and subsequently imparting a substantially slower counter movement to the fluid body at a velocity sufficient to overcome the momentum of the less dense suspended particles. In this manner the more dense particles continue moving through the fluid body to a first point of removal and the less dense particles are returned toward the jet to a second point of removal. I

The method, according to the present invention, is based on the principle of imparting to the particles greater momentum or kinetic energy to overcome the resistance 3,087,619 Patented Apr. 30, 1963 of the medium (viscosity resistance) whereby particles of equal diameter but of greaterdensity acquire greater energy than lighter particles and thereby have greater penetrating power in the medium. Applying this principle toa slurry carrying suspensoids by injecting the slurry at high velocity into a vessel carrying a liquid medium, particles with greater kinetic energy will penetrate the medium to greater depth than particles with lesser energy. Small particles of greater density may acquire equal momentum with larger particles of lesser density, but in that case the larger particles meet a larger viscosity resistance due to their larger surface which lessens their penetrating power. A counter current applied to the medium will readily carry back or reverse the direction of motion of particles of lighter density and greater surface area. The combined alternate action of jet and reversing counter current effect a positive separation of the heavier from the lighter susp'ensoids within certain size limits and thereby elfect the desired concentration of suspensoids of greater density. These suspensoids of greater density are usually mineral particles which are recovered for further processing.

The following description of the present invention will proceed first with a description of several jigs constructed in accord with and utilizing the method of the present invention and then with a description of the utilization of the present method in other apparatus to illustrate the broad applicability of the principles of the present invention.

Briefly described, the apparatus and the method, as employed in jigs, are such to impart alternately and successively to the mass of the pulp or slurry induced relatively slow upward movements through a suitable supporting screen having floatable objects thereon of substantially the same specific gravity as the slurry followed by an induced greatly accelerated downward movement through the screen. The objects, preferably balls, rise with upward fluid movement to open the screen orifices and fallto partially close the screen orifices on the high velocity downward fluid movement. The downward movement of the fluid below the screen and the orifice restricting movement of the objects is sufliciently rapid that a vacuum suction space is created under the screen and a high pressure differential between the top or the fluid above the screen and the underside of the screen which provides a large number of high velocity downward jets discharging into the fluid body beneath the screen. The high velocity of the slurry in the downward jets imparts to the suspended particles therein high kinetic energies or momenta in proportion to their respective masses. Relatively large gangue particles of low density acquire equally high kinetic energy and momentum as fine equal mass mineral particles of high density, but due to their larger volume and exposed surface area encounter greater resistance to movement through the fluid body into which the are discharged than more dense particles of equal mass. Likewise, as between the particles having equal volume, high density particles will have higher kinetic energy and momentum and can penetrate the fluid body beneath the screen more readily and can overcome the resisting upward slow currents of slurry and water heneath the screen and continue on their downward path, whereas having lesser kinetic energy and momentum of the less dense small ganglle particles will be overcome and the less dense particles will be carried along with the up ward current of slurry and water through the screen.

If the kinetic energy of any coarse low density gangue particles is not completely overcome by the upward movement of the fluid body through the screen, then in a second step of treatment, such as any well-known jigging or tabling operation, the relatively coarse or large gangue particles of low density which are recovered together with the fine mineral particles of high density can be readily separated from each other, resulting in a relatively high grade final concentrate of the fine mineral particles.

For definition purposes it is to be understood that the method step of screening and the structure which, for lack of a more descriptive term, is referred to herein as a screen, does not contemplate .a screen member having openings or mesh which separates components of the slurry by flow therethrough, but rather contemplates openings in the screen which are sufiiciently large at all times to permit passage therethrough in either direction of all component particles of the slurry, the separation being accomplished by the relatively slow upward movement of the slurry through relatively large orifices followed by relatively fast downward movement through orifices which have been reduced in size, the downward movement including inducing a vacuum below the screen.

Exemplified forms in which a suitable apparatus and method of the invention may be embodied are described herein, the apparatus of the invention being illustrated in the accompanying drawings which are made a part hereof, and the method being also described by reference to said drawings:

In the drawings:

FIGURE 1 is a vertical transversely central view in section of the apparatus of the invention, on line 11 in FIGURE 2;

FIGURE la is an enlarged fragmentary section taken substantially along lines 1a1a of FIGURE 1;

FIGURE 2 is a horizontal transverse view on line 22 of FIGURE 1;

FIGURE 3 is an enlarged fragmentary longitudinally transverse detailed view of a portion of FIGURE 1;

FIGURE 4 is an enlarged fragmentary laterally transverse detailed view of a portion of FIGURE 1;

FIGURE 5 is an enlarged fragmentary plan view of a portion of FIGURE 1, the view being partly broken away;

FIGURE 6 is an enlarged fragmentary vertical section of a portion of tank and supporting screen or grille shown in FIGURE 1;

FIGURE 7 is an enlarged fragmentary plan view of a modified form of supporting screen or grille means;

FIGURE 8 is an enlarged fragmentary centrally transverse vertical section of another modified, and preferred, form of supporting screen unit, including portions of the tank structure;

FIGURE 9 is a fragmentary plan View of a portion of FIGURE 8;

FIGURE 10 is a fragmentary plan view of still another modified form of supporting screen structure, reduced in size in relation to FIGURE 6;

FIGURE 11 is a fragmentary transverse vertical section of the screen structure shown in FIGURE 10;

FIGURE 12 is a vertical cross-section viewed from the front of the apparatus and illustrating a further embodiment according to the present invention;

FIGURE 13 is an enlarged fragmentary elevational view substantially along the line 13-13 of FIGURE 12;

FIGURE 14 is an enlarged fragmentary section substantially along the line 1414 of FIGURE 12;

FIGURE 15 is an enlarged fragmentary section along line 15-15 of FIGURE 12 more clearly illustrating the pocket grid screen with the pocket recessed flow retarding balls removed;

FIGURE 16 is a cross-sectional view in elevation similar to FIGURE 12 but showi g a modified form for removing the heavier concentrates;

FIGURE 17 is a cross-sectional view in elevation similar to FIGURE 12. but showing another modified form [for removing the small less dense particles;

FIGURE 18 is a section substantially along line 18-418 of FIGURE 17;

FIGURE 19 is a diagrammatic view illustrating still another embodiment of the present invention.

Referring to the drawings in which like reference characters indicate corresponding parts in the several views, 10 indicates a supporting frame which is preferably rectangular in plan, at one side of which is a source of power for operating the apparatus, herein illustrated as any suitable motor generally indicated 11 for providing a differential of a relatively slow upward and a relatively fast downward motion to a hutch of the concentrating apparatus, the motor preferably being of the type illustrated and described in my United States Letters Patent No. 2,766,735, dated October 16, 1956.

Supported upon the upper portion of the frame 10, as at L2, is securely mounted a tank 13 for containing a slurry, illustrated as an open top boxlike receptacle preferably in this embodiment squarely rectangular at its upper portion, though it may equally well be circular in plan if desired.

At one port-ion of its peripheral wall adjacent the up- .per edge, the wall of the .tank has an overflow opening 14 adjustably regulated by a suitable gate 15 which may open into any suitable discharge launder (not illustrated).

Suitable feed means are provided for feeding ore pulp into the tank comprising a feed hopper 16 adjacent the upper edge of the tank, having suitable communication with the interior of the tank through feed chute 18, the feed opening 17 into the tank being preferably below a supporting screen structure generally indicated 19, to be further described.

While in FIG. 1 the feed for the ore pulp is shown below the screen as the preferred form of the invention, it is to be understood that with certain types or fineness of ground ore containing no sandy material, the ore pulp may be fed above the supporting screen.

The screen structure is supported in the upper portion of the tank, preferably above the feed opening 17, by a screen-supported channel member 20 extending around the interior wall of the tank and providing a groove 21 into which the screen structure sits with a suitable packing seal 22. Depending into the tank below the channeled support member 20 and extending transversely across the tank there may be a plurality of relatively spaced baffle partitions 23.

The lower portion of the tank comprises an inverted frusto-conical wall member or vessel 24 having a relatively arge opening 25 at its bottom which, in turn, is closed by an inverted conical hutch 26 having sealed cona flexible diaphragm 27, such as rubber, by means of which the hutch may be vertically reciprocated relative to said opening 25 of the conical lower wall of the tank, manifestly to provide said upward and downward movements of the slurry. At the vertex of its cone the hutch has an outlet opening 28 to which is connected a valve member 28a, to be further described.

The supporting screen structure 19 which is mounted within the upper portion of tank 13 comprises a peripheral supporting side wall 29 fitting conveniently and slidably removably within the tank wall, the lower edge of said side wall of the screen structure resting in the groove 21 and being sealed by the rubber packing 22.

The supporting screen may be any suitable mechanical form which may effectively provide for carrying out the invention, several modifications thereof being exemplified herein. In FIGS. 1 to 6 the screen structure comprises screen-supporting bars 30 and 31 mounted transversely within the confines of the side wall 29, being suitably supported at ends, as by a bracket 33 connected to the side wall. The support bars 30, 31 are preferably in pairs in which the bars in each pair have overlying relation, the opposed faces of the bars in each pair being spaced and mounting between the opposed faces thereof a suitable supporting screen member 34 which may be made of relatively spaced parallel slats 35, providing openings or orifices 35a, therebetween, the slats being exemplified as spaced apart substantially 6 mm. (about 7 inch). Suitable supporting cross bars or .tie members 36 may also be employed to support and maintain the spacing of the screen slats. The lower tier 30 of the support bars may be fixedly welded in place as at 37 and preferably the upper tier is removable for cleaning or replacement of the screen slats 35.

On the upper face of the screen slats 35 are loosely deposited a plurality of small objects of relatively light weight and susceptible to up and down movement with the pulsations or movements of the slurry. Such objects in order not to pass through the screen, manifestly should be of slightly greater diameter than the spacing or slot openings 3511 between the slats 35, and they should have a slightly, almost minutely, greater specific gravity than the slurry, so that such objects and the slurry are substantially in balance by the same order of specific gravity, whereby such objects may be raised with the slightest upward movement of the slurry through the screen. As an example, if the slurry be of the order of 1J1 the specific gravity of such objects may be 1.2. An example of such objects may be cited as polyethylene or vinyl pellets or balls 39, the diameter or which may, for example, be 7 mm. if the slots 35:: between the screen bars are 6 mm. A suflicient number of these balls are placed upon the screen openings to provide a plane thereof illustrated herein as one ball deep. In FIGS. 1 to 6, the balls are closely spaced, to be substantially in relative contact at the opposed portions of their circumferential faces, and provide a layer of balls which may rise with the upward movement of the slurry to provide relatively large screen openings, and tall with the downward movement of the slurry body, whereby, when they are levelled out upon the screen openings, they provide orifices 39a of reduced size through which induced accelerated high velocity downward jets of slurry may flow. An example of such reduced area of opening may be one-third to one-fourth of the area of the Ifiull opening. Because of the slow up ward movement of the slurry, they are not excessively displaced, though, as a precaution against such displacements, any suitable guide means may be provided for the balls in their said movements. The screen and balls thereon may best be described as a floating check valve portion of the screen with return by-pass of slurry as downward jets through the reduced orifices 39a. As a further precaution against suchupward movement of the balls to an extent that they might be permanently carried out of the screen structure and be discharged at outlet 14, a retaining guard screen 38 of a mesh that will not pass the balls may be placed over the compartments in which the .balls operate, a 6 mm. screen being satisfactory for this purpose if the balls are 7 mm.

The density of the slurry is determined by the relative contents of solids, sands and slime in water. Therefore, means are provided for introducing water into the slurry for the purpose of independently regulating its density and controlling the quantity of water which may be introduccd, such regulation and control preferably being at or adjacent to the annular opening 25 of the conical portion 24 adjacent to the diaphragm 27. Such a means is herein exemplified by conduit pipe 45 which cornmunicates at its upper end with a source of water supply 46 through an elbow 47. The conduit pipe 45 is co-axial with the conical vessel portion 24, and at its lower end the conduit passes through the apex of, and thereby comniunicates with, the interior of a hollow conical hood valve 48 which is fixedly mounted thereto as at 49, by a suitable sealing body 51}. Fluid connnunieation between the interior of pipe 45 and the interior of valve 48 may be established by any suitable passage means such as a port 48a ("FIGURE-S l and 1a) formed in pipe 45. At the base of its cone the outwardly flared tapered wall of water therebetween.

ti the conical hood is of a diameter substantially similar to the diameter of the opening 2 5 so as to snugly fit said opening for selectively and adjustably opening and closing said opening, as shown by broken lines in FIG. 1. For purposes to be described, the conical hood 48 may have a ring 51 internally adjacent to its base edge.

At its opposite or upper end the water conduit 45 has an adjustment means whereby it may be raised and lowered and thereby raising or lowering the hood 48 and thus selectively determining the area of annular opening between the base edge of hood 48 and the wall of opening 25 whereby the quantity of water flowing into the lower portion of the conical vessel at the opening 25 may be controlled and adjusted relative to the slurry, the means for such adjustment comprising a rotatable hand wheel 52 at the upper end of the water conduit which may be supported on a cross bar 53 at the top of the tank. If desired, a tubular sleeve 54 may enclose said water conduit and extend from the under side of said cross bar to the upper face of screen structure 19. Since the water conduit is vertically adjustable, manifestly, it has a sliding relation in such a sleeve. 7

Means for regulating the quantity of water discharged into the slurry includes a secondary hood valve 55 within the hood valve 48. Preferably it is also conical con- ;Eorming generally to the form of the interior of the conical hood 48, with relation to which it is spaced, and of lesser diameter at its base, providing for a flow of This secondary hood valve 55 is mounted at the lower end of a control rod 57 which is mounted longitudinally through the conduit 45, the lower end of the rod being stabilized at the vertical axis of the cone 4 8 by a bracket 58 transversely of the opening 25 of the conical vessel 24, the rod '57 extending through and beyond the opposite upper end of the conduit 45 :whereat it is longitudinally adjustable by a threadedly mounted hand wheel 59 to raise and lower the secondary hood valve. The base peripheral edge of this secondary hood valve thus opens and closes relative to the annular ring 5-1 of the conical hood and thereby regulates the quantity of the flow of water into the slurry.

Valve 28a mounted at the outlet opening 28 of the hutch 26 preferably is an upwardly retroverted goose-neck tube 60 communicating with said outlet opening 28, and having a check valve 61 therein which opens upon the .upward movements of the hutch to permit outward flow through the tube and closes against reverse or backflow into the hutch upon the downward suction stroke of the hutch, since it is undesirable to have air drawn into the hutch on the downward or suction stroke which creates a vacuum suction under the screen,

Since the structure and operation of .the apparatus contemplates a vertical reciprocation of the hutch relative to conical member 24, by flex-ore of the resilient diaphragm 27, means are provided for such vertical reciprocation of the hutch comprising the prime mover or motor 11 which, by suitable connection 65, vertically reciprocates a cross arm 66 of a jig yoke having spaced parallel arms 67 which are pivoted at opposite ends as at 68. Transversely between the two pivoted arms 67 of the jig yoke is a rocker shaft69 which extends centrally through the inclined conical wall of the hutch with sufficient pivotal action so that the hutch may be vertically reciprocated on its Manifestly the hutch may ride up and down with the rocker shat-t relative to opening 25 responsive to the flexure of the resilient diaphragm 2,7 and provide upward and downward movement of the slurry. For conservation of motive power the jig yoke may be CQUIllIGI'ebfllfiIlCfid ly a3; suitable means, such as the balancing weight and ar The prime mover or motor 11 is, as stated, preferably of the structure disclosed in my aforesaid United States patent, but Whether of this or other type, it has the characteristics of imparting to the hutch a relatively slow upward movement followed by a rapid downward movement, the upward movement forcing the slurry mass relatively slowly upwardly toward and through the screen, and the rapid downward movement setting up a vacuum suction below the screen, the purpose of which is to be explained in connection with the operation of the method which may be carried out by the apparatus as herein described.

In FIG. 7 there is shown a modified form of supporting screen member in which a plate 70 has relatively closely spaced circular openings 71 and through which the slurry may flow upon the upward and downward movements thereof, small objects such as cubes 72 larger than the openings 71 serving the same purpose and function, relative to the openings in the plate, as the balls 39 in FIGS. 1 to 6 of the drawings, the upward movement of the slurry raising the cubes and the downward movement reseating the cubes in the openings and leaving a portion 73 of the openings free for downward flow of jets of slurry through orifices of reduced area as previously described.

FIGS. 8 and 9 illustrate a second modified and preferred form of screen structure. In this modification the screen structure is generally indicated 80, which includes a peripheral side wall 81, supported in the sealing seat 22 of the tank, and in which the side wall may be of greater height than in FIGS. 1 to 6 for purposes to be described. In this modification transverse screen supporting bars 82 support a transversely horizontal screen plate 83 comprising a plurality of side-by-side or juxtaposed downwardly tapered recesses 84 which are examplified as inverted frusto-pyramidal pockets substantially squarely rectangular at their open top and having side walls convergingly tapered downwardly, preferably at an angle of substantially 60 degrees, to a squarely rectangular opening 85 at the bottom. The objects or balls 86 have characteristics similar to the balls 39 previously described and have substantially the same specific gravity as the slurry, and therefore function in the same manner, rising and falling within the recessed pockets. Each ball is guided within a pocket by the side walls thereof, the balls being retained in the recessed pockets by an overlying retaining screen 87 mounted upon the upper face of the screen plate 83, and supported upon the upper edge of the tapered walls. It may again be pointed out by way of example that if the balls 86 are of 7 mm. diameter the rectangular opening 85, at the bottom of the recessed pockets, as Well as the mesh of the retaining screen 87, may be 6 mm. Upon relatively slow upward movement of the slurry the balls rise to provide relatively large open orifices of the lower screen openings 85 and fall with the vacuum-induced relatively fast downward movement of the slurry, eifectively reducing the fluid flow area of the rectangular screen openings 85, and providing the orifices 85a of reduced open area through which high velocity vacuum-induced jets of slurry are projected downwardly upon the downward movement of the hutch, as indicated by the broken lines in FIGURE 9 showing the seating area of the balls relative to the rectangular openings 85.

The screen structure may be further modified by a deposit of a relatively thick layer 88 of loosely and miscellaneously disposed objects on the upper face of the retaining screen 87, a layer thickness of six inches being stated as a practical and efiicient example. These loosely disposed objects are preferably polyvinyl cubes having substantially the same specific gravity as the slurry (previously stated as 1.1), and dimensioned in size so as to be suporpted above the retaining screen 87, that is, substantially 7 mm. if the retaining screen is 6 mm. mesh. The inclusion of the layer 83 may make it desirable to appropriately increase the height of the side Wall of the screen structure and correspondingly raise the overflow discharge outlet 14. A grill 89 may be mounted across said overflow discharge outlet to prevent the objects or Q cubes 88 from being carried out of the tank with the overflow waste slurry. It is to be understood that these loosely disposed particles deposited above the retaining screen may be similarly employed in relation to all forms of the supporting screens and balls described in the several exemplifications of the supporting screen structure.

In FIGURES 10 and 11, another modified form of screen is disclosed in which there are transverse supporting bars 90 which support a ball-supporting screen 91 of relatively spaced screen slots 92 triangularly normal in vertical section, providing elongated rectangular orifices 93. Balls 94 in this modified form of screen operate in the same manner as the balls 39 in FIGURES l to 6 to open the screen orifices 93 upon upward movement of the slurry and partially close said openings 93 to provide the reduced openings 93a upon downward movement of the slurry as previously described.

In this modification of FIGURES l0 and 11, the balls are guided in such vertical movement in pockets 95 formed by the slot members 92 and vertical partitions 95 upstanding from the screen 91. A retaining screen 97 may overlie the supporting screen and balls, and have superimposed thereupon a layer of miscellaneously and loosely disposed objects 98 having characteristics as previously described. The guide members or pockets thus provide three vertical Walls substantially perpendicular to the plane of the screen, and the fourth wall is divergingly inclined upward and outward at substantially a 30 degree angle, whereby the pockets are downwardly tapered from a relatively large upper open area to a smaller lower area in which the openings 93 are positioned, whereby the freedom of space for upward movement of the slurry is increased and the balls 94 are guided to seat rapidly :and accurately in the openings 93 responsive to the downward movement of the slurry to provide the orifices 92a of reduced area.

The operation of the method and apparatus may be basically described with reference to FIGURES 1 to 6, supplemented by further references appropriate to the modifications of the supporting screen structures of FIG- URES 7 to 11.

In operation, the ore pulp enters the slurry mass in tank 13 as indicated by hopper 16 and the feed opening 17 in the drawing. It is preferred and is believed to be important for most eflicient operation that the ore pulp enter the slurry below the supporting screen for the reason that if it is fed above the screen the slow upward current would not maintain the relatively large gangue sand particles in suspension above the screen whereupon these rapidly settle, choking the openings and thus form a matting on the screen, which would prevent the most efficient functioning of the method and apparatus. By feeding the ore pulp below the supporting screen structure 19 these larger gangue sands settle downwardly in the slurry toward the bottom of the vessel 24.

With the slow upward current of the slurry, the light layer of balls or spheres on top of the screen openings, being substantially the same specific gravity as the slurry, are raised thus opening the full area of the orifices of the entire screen free for the rising current of the slurry to pass at a slow upward velocity through said openings. The slow upward motion of the slurry through the fullsized screen openings carries in suspension the fine and light gangue particles together with fine mineral particles of high specific gravity, but not the sands of larger gangue particles. By successively repeated slow upward pulsations, the slimes and the fine light gangue particles gradually work to the upper stratum of the slurry above the screen and are discharged in the overflow at outlet 14. The slow upward current of the slurry is, however, insuflicient to carry with the current to said waste overflow the fine mineral particles, since, because of their high specific gravity, they do not flow upwardly as readily as the slirnes and fine gangue and, secondly, because the upward motion imparted to the slurry through the full 9 openings of the screen is followed by an accelerated very rapid downward motion through screen openings of reduced size responsive to a vacuum suction below the screen, as will be further described.

On the following rapid downstroke of the hutch, responsive to the motor as aforesaid, the hutch drops quickly and with it the pulp level beneath the screen, which causes a downward vacuum suction under the screen. The balls on top of the screen openings. settle rapidly responsive to the vacuum suction, whereby the balls close the screen openings only partly, leaving a large number of small openings 39a between the balls and through the screen, whereby high velocity jets of the slurry are induced through these small openings by the high differential pressure across such openings between the top and bottom of the screen due to the vacuum suction under the screen and the weight of the slurry trapped above the screen augmented by atmospheric pressure. These jets carry with them the mineral particles which are thus invested with high kinetic energy. The jets, upon striking the slurry level below the screen, are resisted by the next succeeding up-current of slurry and hutch water, permitting only particles with high kinetic energy to continue downward against the slowly rising current. The preconcentrate thus for-med below the screen is a composite of the fine mineral particles of high specific gravity and the relatively large gangue particles of lower specific gravity. The smaller and lighter gangue particles and the slimes with low kinetic energy and relatively small surface area are carried along with the rising current of the pulp through the screen and eventually are discharged over the discharge tailings lip 14.

The preconcentra-tes, in successive cycles of pulsations continue to work down into the hutch and are discharged from the bottom of the conical hutch through the automatic valve 28a which opens on the upward or pressure stroke of the hutch and closes on the downstroke or suction stroke of the hutch and thus prevents an intake of air which may destroy the vacuum and would have a deleterious effect on the operation of the method. The velocity of the current in the annular space around the circumferential base of the hood 48 is regulated and controlled by the position of said conical hollow hood relative to the circumference of opening '25, and the quantity of hutch water admitted is controlled by the hollow cone valve 55 within said hood, thereby affecting the grade of concentrates of the slurry being processed.

Having described the method of operation in relation to the structures shown in FIGURES l to 6, the modified screen structures shown in FIGURES 8 to 11, provide for guiding of the balls in the upward and downward movement thereof, which is especially advantageous in relatively fast operation of the method. In other respects the operation is the same.

Referring to the layer of objects or cubes 88, as shown in FIGURES 8 and 9, this ancillary miscellaneously and loosely disposed layer of objects may be employed above the retaining screen with any or all of the forms of ballsupporting screens illustrated and described. The phenomena effected by such layer is to more completely separate the fine mineral particles from the slimes and fine gangue particles in the slurry that passes upwardly through the ball-supporting screen. The said objects above the retaining screen, being relatively light in weight and of the same order of specific gravity as the slurry, rise and fall with the respective slow upward and fast downward movements of the slurry, and because of their miscellaneous positioning they do not obstruct the normal currents of such flow. The employment of such layer above the retaining screen has an appreciable effect of maintaining the fine mineral particles of high specific gravity at r the lower level of the body of slurry above the ball-supporting screen, but permitting the lighter slimes and gangue to rise to the discharge level. In actual operation, the inclusion of such an ancillary layer above the sup- It porting screen unit has increased the overflow of slime waste by twenty percent, and correspondingly decreased the content of slimes and fine gangue particles in the preconcentrate drawn off from the hutch.

The velocity of the slurry operative over the entire screen area is a function of the volume of the feed intake of the slurry and the quantity of the hutch water added.

The preconcentr-ates discharged at the outlet valve 28a consisting of relatively coarse gangue particles and fine mineral particles are then readily separated from each other by any well-known jigging or tabling operation whereby there is produced a final relatively high grade concentrate of fine mineral particles.

The recovery of fine mineral particles may be further promoted by taking advantage of mass action by adding to the ore slurry in the tank *a quantity of finely ground material of high specific gravity, such as ferro-silioon, magnetite, metallic iron, which may then be readily separated magnetically or by gravity concentration from the concentrates and returned to the tank feed in a closed circuit.

By way of example of operation and not as a limitation, the timing of the relative up and down movements imparted to the slurry may be of a ratio of 40 or 50 to 1, such as an upward movement of four to five seconds and a downward movement of one-tenth :of a second, the desirable number of such two-Way strokes per minute depending on the fineness of the material of the ground ore, which may make it desirable to vary the length of the stroke and the number of such strokes between ten and sixty per minute.

By way of fiurther explanation of the operation of the exemplified supporting screens and the balls thereon it will be noted that the mode of operation is closely akin to a plate having perforated therein a number of small swing-check valves corresponding to the number of balls as herein exemplified, each of such valves having a relatively smal return by-pass operating in the same manner as the relatively small orifices 39a between the balls exemplified herein, whereby the slow upward movement of the slurry would open the entire valve for a relatively free flow therethrough and the accelerated downward movement, which creates a partial vacuum under the screen, as previously explained, would close the valve and provide the downward jets of high velocity through the small return by-pass orifices.

The recovery of fine mineral particles further may be economically promoted by improving the apparatus above described to eliminate preliminary sizing of the feed.

In the past, it has been the custom to first treat differ- I ent sizes of mineral and gangue particles in separate jigs to facilitate a more efficient subsequent separation of fine mineral particles of high density from its fine less dense gangue particles. In the fine or su-spensoid size particle ranges particularly treated by the present invention, preliminary sizing of the fines to separate large mineral and gangue particles from relatively smaller mineral and gangue particles, is costly and difficult.

Thus, in order to further improve the separation of high density particles of small volume from low density particles of varying volumes density, a further embodiment of the present invention is illustrated in FIGURES 12 to 15 for obtaining separation of the fine mineral particles having high density from relatively low density gangue particles of varying volumes over an exceptionally wide range of sizes, thereby obviating, or at least limiting to a large extent, the necessity of costly preliminary ore treatments involving fine screening and classification.

Referring now to FIGURES 12 to 15, and more particularly to FIGURE 12, wherein the further construction embodying the principles of the present invention is shown, the reference humeral designates a cylindrical slurry tank open at its ends and fixedly supported upon 11 the upper ends of angle iron corner posts 112 of a rigid generally rectangular structural frame 114.

The bottom end of slurry tank 110 is closed by an inverted conically shaped hutch 116 which is coaxially and flexibly attached in fluid tight relationship to tank 110 by means of a circumferentially extending diaphragm 118 made of flexible material such as rubber so as to permit vertical displacement of hutch 116 relative the rigidly supported tank 110. At the vortex of its cone, hutch 116 is provided with an outlet port 124 which is connected to a downwardly sloping pipeline 126 by means of a flexible coupling 128.

The lower end of pipeline 126 terminates in a flared portion 130 rigidly secured to a closed elevator casing 132 in communication with an opening 134 formed in the casing. Casing 132 houses a conventional upright continuous bucket-type elevator 136 having a series of material receiving buckets 138 suitably secured to a moving continuous belt 140. At the upper end of elevator casing 132, a material discharge opening 142 is provided for emptying the contents of buckets 138.

Referring now to FIGURES 12 and 13, the means for vertically reciprocating hutch 116 comprises any suitable hydraulic motor 144 having fluid inlet and outlet connections 145 and 146 respectively for imparting a differential of a relatively slow upward motion and a relatively fast downward motion to hutch 116. Motor 144 is preferably of the type illustrated in the embodiment of FIG- URES 1 to 6, being fully described in said United States Letters Patent No. 2,766,735, wherein the power member 147 is slowly raised by introduction of fluid pressure through inlet 145 and allowed to rapidly fall by gravity upon release of pressure fluid through outlet 146.

Motor 144 is mounted coaxially above slurry tank 110 on a base plate 148 rigidly supported on frame 114 by means of a series of inclined an'gle irons 149 secured at their lower outwardly extending ends to frame 114. As best shown in FIGURE 13, the reciprocable power member 147 of motor 144 carries at its upper end a cross arm 154 which is connected to and supports a jig cross arm 156 below motor 144 by means of a series of cables or rod and nut assemblies 158.

As clearly shown in FIGURE ating shaft 160 slidably extends through cross arm 156 coaxial with motor 144 and is resiliently suspended from cross arm 156 for reciprocable movement therewith by means of a coiled compression spring 164. Compression spring 164 is mounted on top of jig cross arm 156 between two guide covers 166 and 168 in surrounding relationship to shaft 160. The upper end of shaft 160 extending beyond spring guide cover 168 is threaded and receives a tightening lock nut assembly 170 bearing against the upper face of cover 168 which is urged upwardly by spring 164.

The lower end of shaft 160 a hub 171 rigidly fixed to hutch of radially extending structural brace members 172. The portion of shaft 160 extending downwardly beyond hub 1 71 is threaded to receive a tightening and lock nut assembly 173 which bears against the bottom face of hub 171 so as to resiliently suspend hutch 116 and shaft 160 from cross arm 156 in the position shown in FIGURE 12.

Also supporting hutch 116 is a series of equiangularly spaced heavy duty upright coiled compression springs 174 anchored at their respective bottom ends to frame 114 and aifixed at their upper ends to a rigid horizontal plate 175 fixedly secured to hutch 116. For a purpose as will hereinafter become apparent, compression springs 174 flexibly support only a predetermined par-t of the dead weight of hutch 116.

By this structure, it will be appreciated that hutch 116 is resiliently suspended from frame 114. When pressure fluid is introduced into motor 144 to uniformly and slowly raise power member 147, cross arm 156 is carried upwardly by movement of cross arm 154 so as to com- 12, an upright jig operslid-ably extends through 116 by means of a series press spring 164 and raise shaft 160. Since nut assembly 173 bears against hub 171 in the lowered or bottom position of shaft 160, vertical displacement of shaft 160 in an upward direction slowly lifts hutch 116 to Its upper or raised position. When the pressure fluid acting on power member 147 is released as described in said Letters Patent No. 2,766,735, the power member 147 falls rapidly under its own weight causing cross arm 156 to drop a corresponding distance by gravity. The sudden release of pressure on spring 164 allows the energy stored in the spring to be released so that it expands and follows cross arm 156 in its downward movement.

The portion of the weight of hutch 116 and its contents not supported by spring 174 now acts to cause the hutch to fall rapidly from its raised position, carrying with it shaft 160 which moves against the bias of spring 164 in its expanded condition. Hutch 116 continues to fall until spring 164 becomes sufiiciently compressed by the downward movement of shaft 160 to resiliently support from cross arm 156 the rest of the weight of hutch 116 and its contents not supported by springs 174.

In this manner, the downward movement of hutch 116 is cushioned and the hutch is shocklessly brought to rest in its lowered position without sudden or abrupt stopping to thereby preclude the occurrence of excessive strains and stresses in the other structural components of the apparatus that would otherwise occur. Since springs 174 only support a predetermined part of the dead weight of hutch 116, the gravitational force corresponding to the remainder of the weight of the hutch not supported by springs 174 overcomes the bias of spring 164 and the atmospheric pressure forces tending to hold the hutch as will be explained so as to facilitate the requisite rapid downward movement of the hutch.

A pipeline 176 for introducing either hutch water or heavy media into hutch 116, extends horizontally through the conical walls of hutch 116 and has a fluid outlet port 177 communicating with the interior of the hutch. Supported above outlet port 177 on pipeline 176 is a perforated inverted conical shaped hood 178 for evenly and uniformly distributing heavy media or water discharged for outlet 177 into the interior of hutch 116.

The opposed ends of pipeline 176 extending beyond hutch 116 respectively are connected to suitable heavy media and water sources (not shown) by means of valved pipes 179 and 180.

Supported within the upper portion of slurry tank by a ring 181 secured to tank 110, is a pocketed grid member 182 disposed in a generally horizontal plane but having its top face somewhat gradually and uniformly conically sloped downwardly from its peripheral outer edge toward the center of tank 110. A central opening is formed in grid member 182 through which shaft extends. Received through the central opening of grid member 182 and rigidly fixed thereto is a discharge tube 184 for discharging coarse gangue particles of light density into hutch 116 where they are removed together with the fine mineral particles of high density. With the present embodiment additional jigging treatment of the particles removed from the bottom of hutch 116 is required to separate the dense small mineral particles from the large light gangue particles. Slidably received in tube 184 is a sleeve 185 which is vertically adjustable and held rigid with frame 114 by means of bolts 18511. By this construction, sleeve 185 is readily adjustable to control the depth of concentrate formed above grid 182.

As best shown in FIGURES 12 and 14, and 15, memher 182 is provided with a series of upstanding projections 186 having inverted cone shaped cross sections to form a series of individual equidistantly spaced side-byside or juxtaposed downwardly tapered pockets 188 having substantially squared bottom openings 191) providing fluid communication between the top and bottom of the grid and side walls shaped to conform to inverted frustopyramids so as to be squarely rectangular at their open 13 top. Recessed pockets 188 are substantially identical to the shape of recesses 84 described in connection with the screen embodiment illustrated in FIGURES 8 and 9.

Freely received in each pocket 188 is a ball 192 identical to and having the same functional characteristics of balls 86 and 39 illustrated in the previously described embodiments. Balls 192 as hereinbefore described have substantially the same specific gravity as the slurry introduced into tank 110 and therefore function in the same manner, rising and falling within their individual recessed pockets 188. Each ball 192 is guided into a seated position over bottom opening 190 in its recessed pocket by the side walls thereof and are of such diameter with respect to the dimensions of the pocket opening 190 that they are retained within their pockets to prevent their falling through the pocket openings.

A's hereinbefore described, upon relatively slow upward movement of the slurry introduced into tank 110, the balls 192 rise to provide relatively large open orifices in grid member 182 and fall with the vacuum induced relatively fast downward movement of the slurry in tank 110 to seat over the pocket openings 190 and thereby reduce the effective fluid flow area of these openings, providing orifices with the side walls of the recessed pockets that are of reduced open area and through which high velocity vacuum induced jets of slurry are projected downwardly upon the downward movement of hutch 116.

A retaining screen 196 supported by grid member 182 and conically shaped to correspond to the conically shaped upper face of grid member 182 overlies the pocket recesses and retains balls 192 in their respective pockets. Retaining screen 196 is held firmly in place over grid member 182 by means of structural ring-shaped members 198 and 200 respectively urged downwardly in the abutting contact with the upper face of screen 196 by bolts 202 and 204 which are secured to frame 114.

The means for introducing feed into slurry tank 110 comprises a downwardly sloping duct 206 positioned above the tank and extending radially toward the center thereof. Feed duct 206 communicates at its inner end with a radial opening 208 formed in a sleeve 210 supported above retaining screen 196 on frame 114 coaxially with tank 110 and in surrounding concentric spaced apart relationship to jig shaft 160. Between sleeve 210 and jig shaft 160 an inverted conically shaped tube 212 is adjustably supported on frame 114 in concentric spaced relationship to sleeve 210 by means of bolts 214. The lower wide end of the conical tube 212 extends downwardly beyond the lower edge of sleeve 210 and forms a feed well space 216 with sleeve 210.

Tailings or light low density particles discharged over the peripheral edge of slurry tank 110 are collected in a peripherally sloped launder 222 surrounding the tank near the upper edge thereof.

Thus by the means above described for centrally feeding the ore into the slurry tank 110 and peripherally discharging the tailings, surface cross currents are minimized so as to permit the fine dense mineral particles to settle instead of being carried away over the tailings discharged by the cross currents. The inwardly sloping conical shape of screen 196 and grid 182 urges the layer of coarse heavy mineral particles towards the center discharge 184.

In operation of the above apparatus thus far described, fluctuations in the rate of ore feed and variations in the character of the feed correspondingly affects the density of the slurry in the hutch. Increases in the feed cause corresponding increases in the slurry density. Variations in the slurry density have been found to have a substantial effect upon the separation of particles. To this end, it will be appreciated that increases in the feed rate tend to increase the density of the medium in the slurry tank and a denser medium, while assisting in the removal of fine gangue particles, resists and decreases the settling velocity of the fine heavier mineral particles thereby re- 14 tarding the separation of these particles. Similarly, a reduction or interruption in the rate of feed tends to lower the density of the medium in the slurry tank and a less dense medium will not provide sufiicient fluid resistance to keep the fine gangue particles from settling with the fine heavier mineral particles.

In order to compensate for variations in the density of the slurry medium to thereby assure a more uniform and efficient separation of particles over a wide range of particle sizes and to prevent serious metallurgical losses, a speed control unit 226 is provided for hydraulic or air motor 144 and comprises a rotary valve 228 in motor inlet 145 for controlling the admission of pressure air or fluid to hydraulic motor 144. Actuation of valve 228 controls the speed at which power member 147 is raised from fully lowered position to fully raised position as is more fully described in said Letters Patent No. 2,766,735. Rigidly secured to the operating stem 230 of valve 228 is an operating lever 232 having a weight 234 attached to the free end thereof so as to bias the operating stem 230 to valve closed position. Secured transversely to operating lever 232 intermediate weight 234 and operating stem 230 is an arm 236 which carries at its lower end the inner telescoping member 238 of a conventional mercury dash pot 240 having a support base 242 rigidly secured to frame 114. By this structure, dash pot 240 resists movement of valve operating stem 230 in either direction and weight 234 tends to rotate stem 230 toward valve closed position.

With continued reference to FIGURE 12, the linkage for operating the lever 232 comprises a link 244 rigidly secured at one end to spring cover 168 and pivotally secured at its opposite end to the lower end of a generally upright link 246. The upper end of link 246 is pivotally connected to the left-hand end of a force multiplying lever 248 which is fulcrumed about a machine screw 250 threadedly secured in frame 114. At the opposite righthand end, as viewed from FIGURE 12, lever 248 carries a mounting block 252 which is adjustably secured to lever 248 by means of a screw 254. Mounting block 252 is formed with a tapped bore which threadedly receives a stud 256 adjustable in height to abuttingly engage operating arm 232 between valve stem 230 and dash pot cross arm 236.

By means of this construction, the admission of air or hydraulic fluid into hydraulic motor 144 is regulated by the height to which cover 168 and consequently shaft and hutch 116 are raised. As the density of the medium in hutch 116 increases, the force needed to raise the hutch to its normal raised position correspondingly increases. For a given hutch weight, when valve 228 is set in one position to admit pressure fluid into motor 144 at a predetermined flow rate, the power member 147, and consequently hutch 116, will be raised in a predetermined period of time corresponding to the rate at which fluid is being introduced into motor 144-. When the density of the slurry increases so as to increase the weight of the slurry in the hutch and valve 228 is held in its same setting, a longer period of time will be required to raise the hutch to its upper position. As a result, it will be appreciated that the time required for raising the hutch will therefore increase with corresponding increases in the weight of the slurry in the hutch for a single setting of valve 228.

In raising hutch 116 as hereinbefore described, a resistive countercurrent of fluid resists the settling of the particles in the slurry so as to urge particles of low density to the surface of the slurry; This resistive countercurrent of the slurry caused by raising hutch 116 also tends to resist to a lesser extent downward movement of the fine high density particles of small volume which are settling in the slurry for discharge through the hutch outlet 124. Thus when the upward movement of hutch 116 is prolonged, then the resistive counterforce' tending to restrain the fine high density particles from settling. is increased 1.5 in proportion to the length of time that it is required to raise the hutch, thereby tending to make the separation -of the fine dense particles more diflicult.

In accordance with the present invention, springs 174 are fully compressed when hutch 116 is dropped to its lowered position and are constructed to support only a predetermined part of the dead weight of the hutch when fully compressed. Thus, the loads carried by springs 174 in elongated and compressed positions corresponding to raised and lowered positions of the hutch, remain substantially constant irrespective of variations in the weight of the slurry in the hutch. Spring 164 accordingly supports a load equivalent to all of the remaining weight of the hutch and the slurry not supported by springs 174. Since the maximum load supported by springs 174 remains constant, variations in the weight of the slurry are therefore taken up by spring 164. When the weight of the slurry is increased, the magnitude of deflection of spring 164 is also increased to support the additional weight and when the weight of the slurry is decreased, the magnitude of deflection of spring 164 is correspondingly reduced. For example, if the total weight of hutch 116 and the slurry is 3000 pounds and the constant load carried by springs 174 when compressed is 2000 pounds, then the remaining 1000 pounds is carried by spring 164. .If the density of the slurry is increased so that the total weight becomes 3300 pounds, the load carried by springs 174 remains constant and the load taken up by spring 164 accordingly increases to 1300 pounds thereby causing a further increment of compression of spring 164. Thus the magnitude of deflection of spring 164 varies correspondingly according to changes in the weight of the slurry. Since spring cover 168 is subject to variations in the magnitude of deflection of spring 164 and since the operating arm 232 is connected through the system of linkage arms 244, 246 and 248 to the spring cover 168, then variations in the magnitude of deflection of spring 164 are transmitted to valve 228 to control the rate of ipre'ssure fluid flow being introduced into motor 144.

Thus, valve 228 is readjusted by speed control unit 226 at the end of each stroke of power member 147 and jig shaft 160 in accordance with variations in the density of the slurry. When the weight of slurry in hutch increases,

operating arm 232 rotates valve stem 230 between positions permitting an overall increased rate of pressure fluid flow into motor 144. As the rate of fluid flow is increased, the added pressure fluid force acting on the power member 147 to compensate for the additional Weight of the slurry in hutch 116 causes power member 147 and consequently hutch 116 to again be raised in a changed time period needed to effect efficient separation of the particles in the slurry.

Similarly, speed control unit 226 functions to decrease the rate of fluid flow into motor 144 as the density of the slurry is reduced. Thus, it will be appreciated that the speed control unit 226 controls the rate of pressure fluid flow into motor 144 in response to variations in the weight of the slurry. The time period for raising the hutch can therefore be changed to a value at which the most eflicient separation of particles occurs irrespective of changes in the density of the slurry.

In order to protect screen 196 which is generally of fine mesh from rapid wear, a thin layer of lead shot 260 is placed over screen 196 as shown in FIGURE 15. The density of the lead shot is substantially greater than that of the slurry so that the lead shot will not be readily shifted with the pulsations of the slurry caused by the jig action. The layer of lead shot 260 performs the function of a fine screen.

On top of the lead shot 260, a layer of relatively coarse bedding material 262 is placed. Bedding material 262 is selected to have about equal density as the minerals to be recovered.

In operation of the apparatus above described, the feed of mixed sizes enters through opening 208 into the feed well 216. Motor 144 sets in motion movable hutch 116 with a relatively slow upward stroke followed by a rapid downward stroke causing the pulsations of currents in the slurry which bring about the separation of light particles of low density from small heavier particles of high density. Above bedding 262 the slurry becomes stratified on the slow upstroke followed on the downstroke by the heavier coarse gangue particles displacing lighter particles thus forming a bed of coarse concentrates of heavier coarse particles on top of bedding 262 which is the common method of concentration in jigging. During this action the slurry containing the neo-suspensoids and very fine high density mineral particles and fine gangue particles of low density which do not stratify and cannot be concentrated above the screen by the jigging operation indicated, are drawn down through screen 196 and pocket grid 182 in the form of high velocity jets into the hutch and separation of the fine heavy mineral particles from the lighter fine gangue particles takes place as fully described in the operation of the previous embodiments. The layer of coarse concentrates formed on top of bedding 262 gradually moves with the pulsations of the slurry toward the center discharge tube 184 with its height adjustment sleeve 185. The movement of the concentrates toward the center is helped by the conical shape of grid 182 and screen 196. The discharge of the coarse concentrate into the hutch is principally effected by the difl'erential in pressures above and below grid 182 as created by the rapid downward motion of the hutch. Trailings or fine light particles of low density are discharged over the peripheral edge of the tank and collected in peripheral launder 222 surrounding the tank.

The separation of gangue particles from fine mineral particles may be effectually enhanced by the introduction of heavy media into the hutch through pipe 176 under the perforated conical hood 178. Heavy media at the bottom of the hutch promotes cleaning of the concentrates without interfering with free settling of mineral particles at the top .as would occur where heavy media is introduced with the ore due to increased viscosity.

The discharge of concentrates (gangue in the case of coal) may be effected and controlled in various manners depending largely on the kind and size of the material. In FIGURE 12 the discharge is illustrated as being controlled by means of elevator 136 which provides a wide discharge opening from the hutch and tends to maintain at all times a constant level in the hutch irrespective of load.

FIGURE 16 illustrates a modified form of concentrate discharge generally indicated at 270 and basically consisting of an outlet pipe 272 having a downwardly facing sand bleed 274. Pipe 272 is connected to an upwardly sloping duct 275 communicating with an upright overflow duct 276 having a series of overflow outlets 278 at different elevations.

By this structure, the rate of discharge from hutch 116 is increased proportionally with respect to the head of the slurry in hutch 116, since as the level of the slurry in hutch 116 increases, the level of slurry in overflow duct 276 correspondingly increases to communicate with an increasing number of outlets 278.

In some cases it may be desirable to keep the coarse concentrates separate from the fine concentrates which later may require a subsequent treatment such as pelletizing in iron ores. That may be readily accomplished by placing a screen 290 underneath discharge tube 184 and connecting it to separate discharge duct 292 controlled by a rotary valve 294 as shown in FIGURE 16. The screen 290 functions to maintain pulsations of the slurry and suction in the tube 184.

When treating fine material by the apparatus described above, a problem is encountered in that the pulsating currents permit fine particles to pass through bedding 262, but the bedding will retain the relatively coarser but light sand particles of the ore which tend to accumulate on top of the coarse bedding forming a layer of fine sands indicated at 300, FIGURE 17. If this layer 300 is allowed to build up and increase in thickness, it eventually fills up to the mouth of feed well 216, preventing the further admission of feed and interfering with the proper operation of the apparatus. In treating fines, the jig motion, as hereinbefore described, must be kept relatively slow and uniform on the upstroke to prevent undue agitation of the slurry which would tend to keep fine mineral particles in suspension and prevent them from settling In order to maintain the slow motion of the upward slurry current it is preferable to remove the sand layer 300 and thereby maintain the apparatus in continuous operation. To accomplish the removal of sand layer 300, the side of slurry tank 110 is provided with an opening 302 of suitable width and height as best shown in FIGURE 17. Opening 302 is covered with an inclined shield 304 having closed sides 306 as clearly shown in FIGURE 18. Shield 304 is positioned adjacent to the peripheral overflow edge of tank 110 and slopes down into the bedding slightly below the level of fine sand layer 300. Slats 308, held by bracket 310, are removable to adjust the height and level of sand overflow. A slide 312 is shiftable in a slot 314 formed by bracket 315 to adjust the discharge overflow 318 between slats 308 and slide 312. With continued reference to FIGURES 17 and 18, the sand level is shown to be slightly raised above its normal level. As the level of sand layer 300 increases, the portion under shield 304 is subject to a squeezing action as a result of the inclination of the shield. By this action, the sand under shield 304 readily builds up and is discharged through opening 318 into launder 222. A series of shields 304 may be arranged around the edge of slurry tank 110 so that the sand level adjusts itself with the pulsations of the jig. In this manner an effectual sand discharge is obtained while maintaining a normal fine sand level.

By the above constructions of FIGURES 12 to 18, exceptionally wide ranges of particle sizes can be efiiciently separated to facilitate the recovery of mineral particles without requiring costly preliminary screening, classification or sizing operations. This is particularly accomplished in accordance with the present invention by means of the central feed 206 and peripheral discharge of tailings above the cylindrical tank 110, the maintenance of a slow and uniform upward movement of hutch 116 with sufficient speed to keep bedding 262 in fluid condition and to allow ample time for stratification of coarse particles above grid member 182, the provision of bedding 262 to retain the coarser fraction of less dense particles above grid 182, the provision of speed control unit 226 to compensate for changes in the density of the slurry, and the provision for uniform distribution of the high velocity fluid jets by means of grid member 182. By this construction, for example, particles ranging in size from approximately /2 inch down to sizes in a micron range can be effectively and efliciently separated.

While the foregoing descriptions have been largely concerned with the elements of the particular apparatus, it is obvious that the invention is not necessarily restricted thereto and that functional equivalents may be employed to carry out the method of particle separation. For example, different screens and motors for operating the hutch may be used.

To illustrate the broad applicability of the method of the present invention and to more clearly distinguish the action from known methods of jigging, a further embodiment is illustrated in FIGURE 19 wherein the reciprocal movement of structural parts that is representative of jigging methods is not present.

Refrering now to FIGURE 19, a slurry supply tank 330 is connected to a suitable feed pump 332 by means of a duct 334. Pump 332 is provided with a pressure outlet 335 connected by a duct 336 to a stationary pressure chamber 338 rigidly supported by any suitable means (not shown). Pressure chamber 338 is formed with a generally horizontal bottom wall 340 having a series of downwardly extending uniformly spaced orifices 342 and closed side walls 343. Disposed in spaced relationship beneath bottom wall 340 is a stationary receiving tank 346 rigidly supported by any suitable framework (not shown) and having an upper cylindrical wall portion 348 open at the top and closed at the bottom by a lower inverted conically shaped wall portion 350 rigidly secured to cylindrical wall 348 around the bottom peripheral edge thereof. At the vertex of wall portion 350a valved fluid outlet 352 is provided to permit discharge of fluid and particles from tank 346.

Adjacent to the bottom edge of cylindrical wall portion 348 is secured a circular generally horizontal plate 353 interfitting with tank 346 and having a series of uniformly spaced openings 354.

A peripheral lip 356 is secured to tank 346 adjacent the upper edge thereof to facilitate removal of fluid and particles overflowing the tank.

In order to supply fluid to tank 346 such as water or heavy media, a storage tank 358 is provided for and is connected to tank 346 by means of a duct 360. Duct 360 communicates with an opening 362 formed in tank 346 beneath plate 353.

The means for controlling the flow of fluid through ducts 336 and 360 comprises valves 362 and 364 respectively. Valves 362 and 364 are mechanically interlocked as by arm 366 so their operation is simultaneous. As shown in FIGURE 19, movement of arm 366 upwardly opens valve 362 and concomitantly closes valve 364. correspondingly, movement of arm 366 downwardly opens valve 364 and closes valve 362.

By this construction, it will be appreciated that with the exceptions of valves 362 and 364 and pump 332, the apparatus basically has no relatively movable parts for facilitating the separation of intermixed particles in the feed as will now be described.

Thus, in operation, tank 346 is filled with water or heavy media from tank 358. The slurry containing the intermixed suspensoids to be separated is stored in tank 330 and is pumped from tank 330 to pressure chamber 338 by pump 332 to fill chamber 338 with slurry under pressure. The slurry in pressure chamber 338 is discharged downwardly through orifices 342 in high velocity jets into the medium in tank 346.

Since equal velocities are imparted to the intermixed particles in the jets, those particles of equal mass will acquire equal momentum (massxvelocity) or kinetic energy. Small particles of greater density acquire equal momentum with larger particles of lesser density but the larger particles of lesser density owing to their relatively larger surface, meet with a greater viscosity resistance as they enter the fluid in tank 346 in comparison to the smaller particles of greater density. Thus for particles of equal mass and momentum, the smaller particles of greater density have a greater penetrating power than the larger particles of lighter density.

Small particles of equal volume but of differing densities acquire different momentums upon being discharged in the high velocity jets. Consequently, the particles of greater density have greater penetrating power than the particles of equal volume but of lesser density.

By reversing the position of valves 362 and 364 so as to open valve 364 and close valve 362, the high velocity jet flow from the pressure chamber is interrupted and water or heavy media is introduced into tank 346 adjacent the bottom thereof at a flow rate to provide for a slow upward current in the medium in tank 346 which is uniformly distributed by passage through plate openings 354. This slow upward current which is counter to the downwardly penetrating particles will readily carry back or reverse the direction of motion of particles of lesser penetrating power.

In this manner, the combined alternate action of jet and counter-current effectuates a positive separation of small particles of high density from less dense particles of equal or greater volume. The small dense particles are recovered from the bottom outlet in tank 346 and the remaining less dense particles are removed as tailings, overflowing the top edge of tank 346.

Thus, in accordance with the present invention, the method of separating intermixed suspensoids of particles of varying size and differing densities, basically consists of discharging a stream of a suspension of such intermixed particles at a first relatively high predetermined velocity into a fluid body of predetermined density and then imparting a movement to the fluid that is in countercurrent to the movement of the particles penetrating into the fluid and is of such velocity to overcome the momentum of low density particles irrespective of their size while merely reducing the momentum of the high density particles.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restric tive, the scope of the invention being indicated by the appended claims rather than by the foregoing descrip tion, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

l. A method of separating particles of varying size and differing densities in accord with their densities comprising the steps of discharging a stream of a suspension of such particles at a first predetermined velocity for penetration into a body of liquid medium having a predetermined density and imparting movement to said body which is counter to the movement of said stream and which is at a velocity sufiicient to overcome the momentum of the low density particles in the stream irrespective of their size while merely reducing the momentum of the high density particles in the stream, said first predetermined velocity being imparted to said particles prior to introduction into said body.

2. A method of separating particles of varying size and differing densities in a slurry body comprising the steps of moving said slurry body in a first direction at a first velocity to impart like velocities and differing momenta to said particles proportional in magnitude to their respective masses, and reversing the direction of movement of the lower density particles therein while merely retarding the rate of movement of the higher density particles therein in said first direction by applying a uniform current of viscous resistance to said particles only after the like velocities have been imparted to said particle.

3. A method of separating relatively high density fine particles from relatively low density particles in a slurry, said method comprising the steps of providing a confined body of such slurry, providing a member having a horizontally disposed orifice immersed in said slurry body, acting upon said slurry body beneath said member to produce vertical undulant movement of said slurry through the orifice, the upward movement of the slurry body being relatively slow and the downward movement being relatively rapid, and constricting said orifice immediately upon initiation of downward slurry movement to a degree to prevent downward movement of the portion of the slurry body above the member at the same rate as the portion thereof beneath said member to thereby create a void between the bottom of said member and top surface of said slurry body portion beneath said member and thereby induce the formation of downwardly directed jet discharge stream through the constricted orifice.

4. The method according to claim 1 comprising the steps of confining said body with at least an intermittent free surface, and emitting said stream at a predetermined distance from said free surface and in the direction of 20 said free surface to enable said said body.

5. The method according to claim 4 comprising the steps of alternating the counter movement of said body relative to said stream with a concurrent movement that is in the same direction as the movement of said stream to produce an undulant movement of said body, and maintaining a predetermined timed relationship between the concurrent and counter current movements of said body and the discharging of said stream.

6. The method according to claim 5 comprising the step of producing a sub-atmospheric space above said free surface by said concurrent movement of said body to establish a pressure differential for causing emission of said stream.

7. A method of concentrating fine particles of high density from finely ground ore, including the steps of providing a generally horizontally oriented orificed screen embodying fluid flow responsive means for opening the orifices thereof in response to upward fluid flow therethrough and for substantially constricting the orifices in response to downward fiuid flow therethrough, immersing said screen in a confined body of slurry, inducing in said slurry below said orificed screen successive alternating flows of relatively slow upward movement followed by a relatively accelerated downward movement through the orifices of the screen, the rate of downward slurry movement being sufiiciently great to induce a vacuum suction space immediately below the screen substantially simultaneously with the commencement of and responsive to the rapid downward movement of the slurry and to thereby induce the formation of downwardly directed jets of slurry through the constricted orifices of the screen and through said space into the body of slurry therebelow whereby greater kinetic energy and momentum are imparted to fine particles of high density in said downward jets than to the particles of low density therein, the succeeding slow upward movement of the slurry being of such velocity that the lesser downward momentum of the particles of relatively lower density is overcome and the low density particles are carried upwardly through the screen open orifices to the upper surface of the slurry for discharge as waste while the relatively higher momentum and kinetic energy of the high density particles is merely reduced so that such high density particles continue downward movement, and drawing off concentrate portions of the slurry below the level of the screen.

8. The method for concentrating finely ground mineral particles in a slurry as defined in claim 7, including the steps of fully opening the orifices in the screen substantially immediately upon initiation of upward slurry movement and maintaining such orifices open during the upward movements of the slurry, and partly closing said orifices responsive to and substantially simultaneously with the commencement of the downward movement of the slurry.

9. Apparatus for concentrating finely ground particles in a slurry, including a tank for containing a slurry therein and having a slurry feed inlet, a discharge outlet for concentrates at a lower portion of the tank and a discharge outlet for waste at an upper portion of the tank, and means operative in said lower portion of the tank for successively pulsating said slurry at a differential of velocity respectively slowly upwardly and rapidly downwardly, the combination therewith of an orificed supporting pocket screen structure mounted transversely across said tank and dividing the tank into the said upper portion and lower portion said screen structure having spaced apart upper and lower faces and having its area divided into separate pockets open at both ends to provide fluid communication through said screen and adapted for separately seatingly receiving and holding a ball therein, the openings of said pockets at said lower face being of relatively smaller area than the openings at said upper face, at least one of the side walls'of each of said pockets being inclined upparticles to penetrate into 21 wardly and outwardly between the said respective upper and lower openings to permit movement of said balls in said pockets, and means overlying the pockets for limiting the upward movement of balls in the pockets beyond the confines of the pockets.

10. In an apparatus for concentrating finely ground particles in a slurry, including a tank for containing a slurry therein and having a slurry feed inlet, a discharge outlet for concentrates at a lower portion and a discharge outlet for waste at an upper portion, and means operative in said lower portion of the tank for successively pulsating said slurry at a differential of velocity respectively slowly upwardly and rapidly downwardly, the combination therewith of an orificed supporting screen structure mounted transversely across said tank and dividing the tank into the said upper portion and lower portion, said screen structure having separate pockets open at the top and each formed with an orifice disposed in the bottom thereof to provide fluid communication through said screen structure through which flows of slurry may be pulsated, a ball shiftably positioned in each pocket, being of a shape and area relative to the size of the balls whereby the balls in the respective pockets are adapted to be seatingly supported by the edges of said pocket forming said orifices and to maintain a portion of said lower orifices open for passage of slurry therethrough, and a guard grille overlying the pockets in sufiicient proximity thereto for confining said balls against movement out of pockets by the force exerted by the upward flow of the slurry.

11. In an apparatus for concentrating finely ground particles in a slurry, including a tank for containing a slurry therein and having a slurry feed inlet, a discharge outlet 'for concentrates at a lower portion and a discharge outlet for waste at an upper portion, and means operative in said lower portion of the tank for successively pulsating said slurry at a differential of velocity respectively slowly upwardly and rapidly downwardly, the combination therewith of a supporting screen structure mounted transversely across said tank and dividing the tank into the said upper portion and lower portion said screen structure having a plurality of orifices through which flows of slurry may be pulsated, a plurality of balls associated individually with said orifices, said orifices being of a shape and area relative to the size of the balls whereby the balls associated with the respective orifices may be supported by the edges of said orifices and maintain a portion of said orifices open for passage of slurry therethrough, and a guard grille overlying said screen in sufficient proximity thereto for confining said balls against the upward flow of the slurry.

12. In an apparatus for separating intermixed particles having varying size and differing densities in accord with their densities, a vessel confining a body of slurry having a free unconfined top surface; means for projecting at least one stream of a suspension of said intermixed particles at said free surface of said body of slurry with a sufficient predetermined first velocity to penetrate said body of slurry including a member having at least one orifice therein disposed over said free surfacein fluid communication therewith and supply means for delivering said suspension of intermixed particles to said orifice under a predetermined pressure; and delivery means separate from said supply means for introducing a fluid medium to said vessel at a point to cause an upward movementof said slurry in counter current to said stream.

13. The apparatus as defined in claim 12 wherein said member is fixed relative to said vessel.

14. The apparatus as defined in claim 12 wherein means are provided for controlling the delivery of said suspension and said medium in interlocked relationship so that the delivery of said suspension and said medium takes place in sequence.

15. The apparatus as defined in claim 12 wherein said supply means comprise means defining a pressure chamber with said member and fluid pump means having an outlet 22 in fluid communication with said pressure chamber and operative to establish a pressure differential across said orifice for producing said stream.

16. In an apparatus for separating intermixed particles suspended in a fluid, a tank open at least at its bottom end, a rigid closure member disposed beneath the bottom end of said tank, flexible means attaching said closure member in liquid tight relationship to said tank so that said closure member is at least vertically displaceable relative to said tank and encloses the bottom open end thereof, flexible means resiliently supporting only a predetermined portion of the dead weight of said closure member, and means resiliently supporting the remainder of the Weight of said closure member and the weight of the contents in said tank comprising motor means having a power member operably movable in opposed directions at difiering predetermined velocities, means including a resilient member operably coupling said closure member with said power member for transmitting motion of said power member to said closure member to reciprocate said closure member with a slow upward movement and a relatively rapid downward movement, said flexible means and said resilient member cushioning and shocklessly interrupting the downward movement of said closure member.

17. In an apparatus for separating intermixed particles suspended in a fluid, a tank for confining a body of said fluid and open at least at its bottom end, a rigid closure member disposed beneath the bottom end of said tank, flexible means attachingsaid closure member in fluid tight relationship to said tank so that said closure member is at least vertically reciprocable to said tank, drive means operably coupled to said closure member for imparting alternating and successive slow upward and rapid downward movement to said closure member, and means for controlling the magnitude of velocity at which said closure member is moved upwardly in response to variations in the density of said fluid.

18. The apparatus as defined in claim 17 wherein said drive means includes fluid operated motor means having a pressure fluid inlet, closure member support means operably coup-ling said motor means to said closuremember and including a movable member responsive to variations in the weight of fluid in said tank, valve means in said pressure fluid inlet for controlling the introduction of pressure fluid into said motor means, and means operatively connecting said movable member to said valve means to operate said valve means and control the rate of pressure fluid flow to said motor means in proportion to the changes in density of said tank.

19. In an apparatus for separating particles suspended in a slurry in accordance with their densities, a tank for containing a slurry therein and having a slurry feed inlet, a discharge outlet for concentrates at a lower portion and a discharge outlet for waste at an upper portion, movable means operative in said lower portion of the tank for pulsating said slurry, a grid structure mounted transversely across said tank in a predetermined position and dividing the tank into the said upper portion and lower portion, said grid structure having a plurality of orifices providing fluid communication between the upper and lower portions of said tank, motor means operatively coupled to said movable means for successively and alternately imparting slow upward movement and relatively rapid downward movement to said movable means whereby the slurry in said tank is alternately moved slowly upwardly through said orifices and above said grid structure and rapidly downwardly through said orifices and means cooperating with said orifices in said grid structure and operative by the pulsations imparted to said slurry to allow fluid flow through the entire cross sectional flow area of said orifices upon upward movement of said slurry but to effectively partially reduce the magnitude of the flow area through said orifices upon downward movement of said slurry to thereby temporarily trap a portion of said slurry above said grid structure and to establish a low pressure void immediately below said grid structure whereby slurry from above said grid structure is discharged through the eflectively reduced flow area of said orifices in the form of jet streams of predetermined velocity, said orifices being approximately vertically disposed so that said jet streams project toward the free surface of said slurry below said grid structure to penetrate said slurry, said inlet feed being centrally disposed above said grid structure and including a feed duct, means defining a feed well centrally above said grid structure and communicating with said duct, said discharge outlet for waste being disposed above said grid structure about the periphery of said tank whereby cross currents of slurry between said inlet feed and said discharge for waste are minimized.

20. In an apparatus for separating particles suspended in a slurry in accordance with their densities, :a tank for containing a slurry therein and having a slurry feed inlet, a discharge outlet for concentrates at a lower portion and a discharge outlet for waste at an upper portion, movable means operative in said lower portion of the tank for pulsating said slurry, a grid structure mounted transversely across said tank in a predetermined position and dividing the tank into the said upper portion and lower portion, said grid structure having a plurality of orifices providing fluid communication between the upper and lower portions of said tank, motor means operatively coupled .to said movable means for successively and alternately imparting slow upward movement and relatively rapid downward movement to said movable means whereby the slurry in said tank in alternately moved slowly upwardly through said orifices and above said grid structure and rapidly downwardly through said orifices and means cooperating with said orifices in said grid structure and operative by the pulsations imparted to said slurry to allow fluid flow through the entire cross sectional flow aera of said orifices upon upward movement of said slurry but to eifectively partially reduce the magnitude of the flow area through said orifices upon downward movement of said slurry to thereby temporarily -trap a portion of said slurry above said grid structure and to establish a low pressure void immediately below said grid structure whereby slurry from above said grid structure is discharged through the effectively reduced flow area of said orifices in the form of jet streams of predetermined velocity, said orifices being approximately vertically disposed so that said jet streams project toward the free surface of said slurry below said grid structure to penetrate said slurry, a centrally disposed discharge being provided to withdraw concentrates collected above said grid structure and the upper face of said grid structure being sloped downwardly toward said discharge from the periphery of said tank to enhance movement of concentrates toward said discharge.

21. In an apparatus for separating particles suspended in a slurry in accordance with their densities, a tank for containing a slurry therein and having a slurry feed inlet, a discharge outlet for concentrates at a lower portion and a discharge outlet for waste at an upper portion, movable means operative in said lower portion of the tank for pulsating said slurry, a grid structure mounted transversely across said tank in a predetermined position and dividing the tank into the said upper portion and lower portion, said grid structure having a plurality of orifices providing fluid communication between the upper and lower portions of said tank, motor means operatively coupled to said movable means for successively and al ternately imparting slow upward movement and relatively rapid downward movement to said movable means whereby the slurry in said tank is alternately moved slowly upwardly through said orifices and above said grid structure and rapidly downwardly through said orifices and means co-operating with said orifices in said grid structure and operative by the pulstations imparted to said slurry to allow fluid flow through the entire cross sectional flow area of said orifices upon upward movement of said slurry but to effectively partially reduce the magnitude of the flow area through said orifices upon downward movement of said slurry to thereby temporarily trap a portion of said slurry above said grid structure and to establish a low pressure void immediately below said grid structure whereby slurry from above said grid structure is discharged through the efiectively reduced flow area of said orifices in the form of jet streams of predetermined velocity, said orifices being approximately vertically disposed so that said jet streams project toward the free surface of said slurry below said grid structure to penetrate said slurry, said means co-operating with said orifices in said grid structure comprising a plurality of orifice closure members associated with said orifices and movable relative to said grid structure by the pulsations of said slurry, said orifice closure members being of a shape and size relative to the area and shape of said orifices so as to be supported by the edges of said orifices and maintain a portion of said orifices open for passage of slurry therethrough, a screen like guard grille overlying said grid structure in sufiicient proximity thereto confining said orifice closure members against upward flow but allowing limited free movement of said orifice closure members to permit fluid flow substantially through the entire flow area of said orifices, a centrally disposed dis charge being provided to withdraw concentrates collected above said guard grille and said guard grille being sloped downwardly toward said discharge from the periphery of said tank to enhance movement of concentrates toward said discharge.

22. In an apparatus for separating particles suspended in a slurry in accordance with their densities, a tank for containing a slurry therein and having a slurry feed inlet, a discharge outlet for concentrates at a lower portion and a discharge outlet for Waste at an upper portion, movable means operative in said lower portion of the tank for pulsating said slurry, a grid structure mounted transversely across said tank in a predetermined position and dividing the tank into the said upper portion and lower portion, said grid structure having a plurality of orifices providing fluid communication between the upper and lower portions of said tank, motor means operatively coupled to said movable means for successively and alternately imparting slow upward movement and relatively rapid downward movement to said movable means whereby the slurry in said tank is alternately moved slowly upwardly through said orifices and above said grid structure and rapidly downwardly through said orifices and means co-operating with said orifices in said grid structure and operative by the pulsations imparted to said slurry to allow fluid flow through the entire cross sectional flow area of said orifices upon upward movement of said slurry but to effectively partially reduce the magnitude of the flow area through said orifices upon downward movement of said slurry to thereby temporarily trap a portion of said slurry above said grid structure and to establish a low pressure void immediately below said grid structure whereby slurry from above said grid structure is discharged through the effectively reduced flow area of said orifices in the form of jet streams of predetermined velocity, said orifices being approximately vertically disposed so that said jet streams project toward the free surface of said slurry below said grid structure to penetrate said slurry, said means cooperating with said orifices in said grid structure comprising a plurality of orifice closure members associated with said orifices and movable relative to said grid structure by the pulsations of said slurry, said orifice closure members being of a shape and size relative to the area and shape of said orifices so as to be supported by the edges of said orifices and maintain a portion of said orifices open for passage of slurry therethrough, a screen like guard grille overlying said grid structure in sufiicient proximity thereto confining said orifice closure members against upward'flow but allowing limited free movement of said orifice closure members to permit fluid flow substantially through the entire flow area of said orifices, a layer of particles having individual densities substantially greater than the density of said slurry being disposed over said guard grille.

23. The apparatus as defined in claim 22 wherein a layer of coarse bedding material is disposed over the top of said layer of particles, the density of said bedding material having a density approximately equal to the minerals to be recovered from said slurry.

24. In an apparatus for separating particles suspended in a slurry in accordance with their densities, a tank for containing a slurry therein and having a slurry feed inlet, a discharge outlet for concentrates at a lower portion and a discharge outlet for waste at an upper portion, movable means operative in said lower portion of the tank for pulsating said slurry, a grid structure mounted transversely across said tank in a predetermined position and dividing the tank into the said upper portion and lower portion, said grid structure having a plurality of orifices providing fluid communication between the upper and lower portions of said tank, motor means operatively coupled to said movable means for successively and alternately imparting slow upward movement and relatively rapid downward movement to said movable means whereby the slurry in said tank is alternately moved slowly upwardly through said orifices and above said grid structure and rapidly downwardly through said orifices and means co-operating with said orifices in said grid structure and operative by the pulsations imparted to said slurry to allow fluid flow through the entire cross sectional flow area of said orifices upon upward movement of said slurry but to effectively partially reduce the magnitude of the flow area through said orifices upon downward movement of said slurry to thereby temporarily trap a portion of said slurry above said grid structure and to establish a low pressure void immediately below said grid structure whereby slurry from above said grid structure is discharged through the eiiectively reduced flow area of said orifices in the form of jet streams of predetermined velocity, said orifices being approximately vertically disposed so that said jet streams project toward the free surface of said slurry below said grid structure to penetrate said slurry, and means for introducing media of selected density into said tank comprising a duct adapted to be connected to a source of media and extending into the interior formed by said tank and said movable means and terminating in an outlet below said grid structure, and a perforated hood disposed over said outlet to uniformly distribute liquid introduced through said duct into said tank.

25. The apparatus as defined in claim 23 wherein means are provided for removing of sands accumulating on top of said bedding comprising means forming an opening in the side of said tank above sand bedding and a plate structure having closed sides and an inclined portion extending downward from said tank from above said opening between said sides and terminating a predetermined height above said bedding.

26. Apparatus for concentrating finely ground particles in a slurry, including a tank for containing a slurry therein and having a slurry feed inlet, a discharge outlet for concentrates at a lower portion of the tank and a discharge outlet for waste at an upper portion of the tank, and means operative in said lower portion of the tank for successively pulsating said slurry at a difierential of velocity respectively slowly upwardly and rapidly downwardly, the combination therewith of a planar orificed supporting pocket screen mounted laterally transversely across said tank and dividing the tank into the sa d upper portion and lower portion, said screen comprising a planar body having an upper face and a lower face which are relatively spaced by the planar body, said screen body having its planar area divided into separate pockets each adapted for separately receiving and holdmg a ball therein, the said separate pockets being open at said upper face and having an opening at said lower face of relatively smaller area than the upper opening, the side walls of said pockets being inclined upwardly and outwardly between the said respective upper and lower openings, and means overlying the pockets for limiting the upward movement of balls in the pockets beyond the confines of the pockets.

2 7. In apparatus for concentrating finely ground particles in a slurry, including a tank for containing a slurry therein and having a slurry feed inlet, a discharge outlet for concentrates at a lower portion and a discharge outlet for waste at an upper portion, and means operative in said lower portion of the tank for successively pulsating said slurry at a differential of velocity respectively slowly upwardly and rapidly downwardly, the combination therewith of a planar orificed supporting screen mounted laterally transversely across said tank and dividing the tank into the said upper portion and lower portions, said screen having separate pockets each provided with an orifice through which flows of slurry may be pulsated, a separate ball in each pocket, the said pockets being open at the upper planar portion and having the orifices thereof at a lower planar portion, said lower orifices of the pockets being of a shape and area relative to the size of the balls whereby the balls in the respective pockets may be supported by the edges of said lower pocket orifices and maintain a portion of said lower orifices open for passage of slurry therethrough, and a guard grille overlying the pockets in sufficient proximity thereto for confining balls in said pockets against the upward flow of the slurry.

References Cited in the file of this patent UNITED STATES PATENTS 1,078,520 Stromberg Nov. 11, 1913 2,138,810 Wood NOV. 29, 1938 2,199,091 Pardee Apr. 30, 1940 2,242,020 Wood May 13, 1941 2,271,650 Kraut Feb. 3, 1942 2,416,066 Phelps Feb. 18, 1947 2,708,517 Evans May 17, 1955

Claims (1)

12. IN AN APPARATUS FOR SEPARATING INTERMIXED PARTICLES HAVING VARYING SIZE AND DIFFERING DENSITIES IN ACCORD WITH THIER DENSITITES, A VESSEL CONFINING A BODY OF SLURRY HAVING A FREE UNCONFINED TOP SURFACE; MEANS FOR PROJECTING AT LEAST ONE STREAM OF A SUSPENSION OF SAID INTERMIXED PARTICLES AT SAID FREE SURFACE OF SAID BODY OF SLURRY WITH A SUFFICIENT PREDETERMINED FIRST VELOCITY TO PENETRATE SAID BODY OF SLURRY INCLUDING A MEMBER HAVING AT LEAST ONE ORIFICE THEREIN DISPOSED OVER SAID FREE SURFACE IN FLUID COMMUNICATION THEREWITH AND SUPPLY MEANS FOR DELIVERING SAID SUSPENSION OF INTERMIXED PARTICLES TO SAID ORIFICE UNDER A PREDETERMINED PRESSURE; AND DELIVERY MEANS SEPARATE FROM SAID SUPPLY MEANS FOR INTRODUCING A FLUID MEDIUM TO SAID VESSEL AT A POINT TO CAUSE AN UPWARD MOVEMENT OF SAID SLURRY IN COUNTER CURRENT TO SAID STREAM.

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