US1449604A - Apparatus for separating solid materials of different specific gravities - Google Patents

Description

Mar. 27, 1923.

M. HOKANSON.

APPARATUS FOR SEPARATING SOLID MATERIALS OF DIFFERENT SPECIFIC GBAVITIES.

2 SHEETS-Emil l.

ORIGINALFILED JULY 17, 1918- /9 FIE.1.

INVENTOR WITNESSES Mar. 27, 1923. 1,449,604. M. HOKANSON.

APPARATUS FOR SEPARAHNG SOLID MATERIALS OF DIFFERENT SPECIFIC GRAVITIES.

ORIGlNALHLED JULY 17, 1918- 2 SHEETSSHEET 2.

FISH;

WITNESSES wzsrww. 9 64 m Patented Mar. 27, 1923.

UNITED STATES PATENT OFFICE.

MARTIN HOKANSON, OF DULUTH, MINNESOTA.

APPARATUS FOR SEPARATING SOLID MATERIALS OF DIFFERENT SPECIFIC GRAVITIES.

Application filed July 17, 1918, Serial No. 245,296. Renewed June 29, 1922. Serial 1T0. 571,794.

To all whom it may concern:

Be it known that I, MARTIN HOKANSON, a resident of Duluth, in the county of St. Louis and State of Minnesota, have invented a new and useful Improvement in Apparatus for Separating Solid Materials of Different Specific Gravities, of which the following is a specification.

This invention relates to apparatus for separating and concentrating solid granular materials of different characteristics. One purpose of the invention is to provide apparatus for separating the valuable part of ore from gangue, by Sub ecting the material, in a finely crushed condition, to the action of an upwardly flowing current of Water in a series of vertical chambers, and controlling the water flow so that its velocity in each chamber is just sufiicient to carry therethrough the particles of a particular material, the velocit in the next higher cylinder not being su cient to carry the sa1d heavier particles therethrough, but sufficient to carry the next lighter particles therethrough. That is, each cylinder has a velocity which will not support granular solid material which has been carried through the preceding cylinder. Consequently, at the top of each cyl nder the heaviest particles of material carrled therethrough are dropped out of the upwardly flowing stream, the other particles being carried on through the next cylmder, the heaviest particles of the remaining mixture being separated out at the top thereof, and so on.

Fig. 1 shows a vertical central section through the apparatus (diagrammatic) Fig. 2 shows a horizontal sectlon on the line 2-2 of Fig. 1; Fig. 3 shows a partial vertical section on an enlarged scale of a portion of the apparatus shown in Fig. 1; Fig. 4 shows a modification of the feed arrangement; and Figs. 5 and 6 show modifications of a supplementary water supply system. I

If particles of matter of the same sizes but different weights are exposed to an upward flow of water of decreasing velocity, light particles will be carried farther than heavy particles, and the distance to Wh1(ll the individual particles are transported will vary quite accurately accordin to their respective specific gravities. somewhat similar principle is that particles of matter of the same specific gravity, but of different sizes, will be graded by an upward current of water of decreasing velocity, the smaller particles being carried to the greater distance. This principle has been applied to the grading of sand. In the present case, the first of these principles only is used, namely, an upward current of water is applied to a mixture in which the particles are all substantially of the same size but are of different specific gravities.

The present apparatus is particularly concerned with the separation of the gangue, such as silica, alumina, etc., from iron and other ores. The silica sometimes occurs in a coarse sandy state, sometimes in a very finely divided state, in some forms of ores being so fine that it is necessary to crush the ore so that it will pass a one hundred mesh sieve, or smaller, before the silica particles, etc), will be detached from the iron oxide particles. The ordinary hematite ore when free from silica, has a specific gravity of about two to three. The silica particles having a specific gravity of somewhat less and the alumina is still lighter. Therefore, when particles of ore, and particles of gangue, etc., of the same size are subjected to a vertical current of water, the particles of gangue will be raised by a current of lesser velocity than that required to carry the particles of ore, and this furnishes a very accurate means for separating the one from the other.

It is a known principle that water moving through a pipe under pressure attains its greatest velocity at the center of the pipe, and that near the walls of the pipe the rate of flow is considerably less than at the center. Where a current of water in a pipe is carrying a mixture of uniformly sized particles, there is a tendency for the heavier particles to be thrown outward toward the walls of the pipe into the slower current, and if the particles are of the same specific gravity,

but different sizes, the larger particles will be thrown out first.

In th'e practice of the present invention, iron ore, (or other ores or materials to be subjected to concentration as herein described) is crushed, if necessary, to reduce it to sufliciently small particles to free the gangue, resulting in a loose mechanical mixture. The mixture is graded into sizes, the number of grades depending upon #tlre nature of the material being handled. Each grade is then subjected to separation according to this invention.

The graded mixture of ore and gangue and water is supplied to 'a receptacle 1, from which it is introduced to the bottom of a vertical cylinder 2, the first of a series of similar separators. It will be understood that the mixture of anular materials and water must be force upward through the apparatus under ressure. This may be done by situating t e mixing receptacle 1 at a height greater than that of the separating apparatus, and connecting the bottom of cylinder 2 to it by a pi e 3. In this case the feeding is done entire y by gravity and is automatic so long as the tank 1 is properly supplied. Instead of this gravity feedin arrangement I mayuse a force pump, an carry the mixture from any convenient point. A desirable modification of the feeding means is illustrated in Fig. 4, and described below.

The pipe 3 has avertical extension 4 connected to an inverted conical portion 5, forming the lower end of cylinder 2. This first cylinder is of such length as to subject the mixture to the separating influence of the upward flowing current for suficient time to throw the heavy particles to the outside. This cylinder forms a chamber A.

Surrounding theupper end of cylinder 2 is an enlarged casing or jacket 6, the lower end of which is supported by the cylinder 2, and the upper end of which forms an aligned vertical cylinder 7. Thus an enlarged chamber B is formed around the upper end of cylinder 2, and below this, and surrounding the cylinder is an annular gocket, C. The cylinder 7 forms a chamber which in turn leads into an enlarged chamber E, formed by a casing or jacket 8, surroundin the upper end of cylinder 7 and supported t ereby just as the casin 6 surrounds and is supported by the cylmder 2. The casing 8 forms an annular pocket F about the to of cylinder 7, and extends upward as a t ird vertical aligned cylinder 9,

forming the cylindrical chamber G. The

upper end of this third cylinder is surrounded by an enlarged circular tank 10, which forms an overflow basin H, around the upper end of cylinder 9.

The bottom 11 of the annular pocket C formed by the junction of easing 6 and cylinder 2 13 provided with perforations 12. Fitted into these perforations are nozzles 13 having their upper ends flush with the bottom 11 and their lower ends curved and pointing in the direction of inclination of the bottom 14 of a draw-off chamber I which is situated immediately beneath the perforated bottom 11. 'The bottom 14 and walls of the chamber I are inclined in each direcinaaeoe tion around the chamber A so that said chamber I increases in size to the point Where it empties into a draw-oii port 15, which leads b a suitable pipe 16 to any desired point. lsirectly opposite the draw-off port 15, and at the smallest part of the chamber I, is an inlet port 17, to which is connected a pipe 18 controlled by valve 19.

The same arrangement of draw-oif chamber, perforated bottom, and inlet and outlet ports therefor are provided at the junction of casing 8 and cylinder 7, as illustrated in the drawing, and indicated by similar reference numerals having the letter It added, except for the annular draw oflt' compartment marked J.

The overflow compartment H is provided with a suitable drain pipe 20.

It will be understood that the pipes 16, 16, and 20 are'led to any suitable place for discharge of the material, and are provided pith the necessary valved connections there- In a former application Serial No. 207,- 001, filed December 13, 1917, I have described apparatus somewhat similar to this, and having similar objects, in which each of the succeeding cylindrical chambers corresponding to A, D, and C, is larger than its preceding cylinder. This was for the purpose of securing a decreased flow of liquid in each succeeding cylinder, so as to cause the throwing out of the heavier particles at the top of the first cylinder, and so on. I have found, however, thatwith certain mixtures, and materials of certain composition, a sufiicient quantity of water is drawn off around the top of the first cylinder 2, to secure the necessary decrease of velocity in the cylinder 7, for the purpose of separation. In theory, the apparatus is designed so that the heaviest particles will be just barely carried to the top of the chamber A, by the velocity of flow therein, and

y will be thrown out into theienlar ed chamber B, fallin into the pocket and removed throug li draw-off chamber I and pipe 16. Now, a certain amount of water is carried off with the heavier particles with this operation, and consequently the volume of water flowing upward through chamber D is less than that in chamber A. Since, theoretically, the velocity of chamber D should be just sufiicient to raise the particles of next greatest specific gravity to-the top of that chamber, it is essential that the velocity of flow in chamber D be less than in chamber A, but still it must be great enough to raise the second class of particles to the top there of. In order to compensate for the loss of water about the top of the first cylinder, I find that the second cylinder must often be as small as the first, or even smaller, in order to maintain the desired velocity therein. Consequently, in this apparatus, the succeeding cylinders are not necessarily larger, but may be made of approximately the same size, or of even smaller size successively, according to the circumstances and materials of each case.

It is necessary to accurately measure the comparative specific gravities of the materials being separated, to determine the proportion of each constituent of the mixture, and to regulate carefully the velocities in the several cylinders in order to give the required velocities in the several cylinders to secure an eflicient separation.

For this purpose I prefer to provide cylinders of approximately the same size, and regulate the velocities of flow in each one by means of controlling the amount of water drawn off between cylinders.

This is done by means of valves 21 and 21 in the draw-01f pipes 16 and 16, and by supplying additional water to the draw-off compartments I and J by means of the pipes 18 and 18*. Manifestly, the rate of escape of water through the ports '12 and 12 is dependent upon the discharge of water from the compartments I and J. If the water introduced from the orts 18 and 18 is equal to the amount owing out the pipes 15 and 15*, then there can be no escape through 12 and 12*. Consequently, these supplementary supplies of water must be so regulated as to accurately control the discharge from the concentrating apparatus at each draw-off point. By this means, the velocity of flow in each of the chambers A and D can be accurately regulated, and varied to suit the proportions and weights of the materials being separated.

The operation of the apparatus is as follows: Any kind of ore from which the gangue is to be separated (or other mechanical mixture of fine materials of different specific gravities) is crushed and accurately graded to a uniform size. The required size varies according to the nature of the ore or other material to be separated. The graded mixture is then placed in the receptacle, 1, and mixed with water to carry it. This mixture flows by gravity through pipe 3 and upward through cylinder 2. The particles of greatest specific gravity will be thrown to the outside of the chamber A as the mixture passes therethrough, and upon reachin the enlarged chamber B, the heavier particles at the outside of the stream will be thrown outward. The rate of flow being suddenly decreased, the upward stream will not be sufficient to support the heavy particles and they fall into the annular chamber C, settle to the bot.- tom thereof and escape through the nozzles 13 into the draw-off chamber I and through the pipe 16. The constant outflow from the bottom of chamber C produces a slight downward current in said chamber, which assists in leading the heavy particles into said chamber and down, to the discharge orifices. The amount of Water, and the size of the chambers B and D are so related that all but the heaviest particles are carried on upward throu h the cylinder 7 and into the chamber Here again the heavier particles are no longer supported by the flow of water and fall outward around the top of cylinder 7 into the pocket F, and are drawn off just as above described. The very light material is again carried'on through the cylinder 9, and finally flows off by Way of pipe 20 to be discharged at any suitable place. Or a third separating arrangement can be used to clean the Water, so that it may be used over again, as in localities where water is scarce.

In my prior application above referred to I show a centrifugal pump for forcing the mixture through the separating apparatus. The mixture of ore and water has a'rapid wearing effect on the pump casing, and therefore I prefer to use the gravity feed above described. However, in some cases a pump feed may be desirable. By providing a tank 30, (Fig. 3) adapted to receive the mixture of ore and water, and connecting it to the bottom of cylinder 2 by a pipe 31, and leading a horizontalbranch 32 into the pipe 31, water may be pumped into the apparatus so as to give sufficient pressure and velocity to the mixture, regardless of the elevation of mixing tank 30. Any form of pump may be used, though I have illustrated a centrifugal pump 33.

In this modification it is better to introduce water from pump 33 in the form of a jet under high pressure, to get an injector action. To this end pipes 31 and 32 are reduced in size toward their meeting ends and an interior nozzle '34 is ledinto pipe 32 from pump The end of this nozzle extends nearly to the restricted portion lying at the junction of pipes 31 and 32. Consequently, the stream of clear water from nozzle 34 will carry the mixture from tank 30 into pipe 31 and into the separating apparatus, under suflicient pressure to move it through the apparatus.

In order to keep the mixture of Water and solid particles in tank 30 uniform, I may provide an agitator, comprising a vertical shaft 35 having lateral paddles 36 thereon, in the tank. This may be driven by any suitable means, such as by belt pulleys 51,

or operated intermittently by hand.

In order to supply water and solids in proper porportions I' provide a water supply pipe 50 having a control valve 37, and a granular supply pipe 38, having a control gate 39 therein.

In Figs. 5 and 6, I show modifications of the supplementary water supply means.

In Fig. 5, a water pipe controlled by valve 41 leads into the enlarged casings 6 just above the top of cylinder 2, and is connected to an annular ipe 42 extending around the chamber l as shown. The underside of pipe 42 is perforated, as shown, so that Water therefrom is forced downward, thus aiding the separating current above described in leading the heavy particles into chamber C. A similar arrangement may be provided for chamber E.

Near the bottom 11 of chamber C another pipe 43 having a control valve 44, leads through the casing to a circular perforated pipe 45 in chamber C. The perforations in pipe 45 are on the lower side thereof and are situated respectively just above nozzles 13, so as to aid in driving out the solids therethrough. A similar arrangement may be provided for chamber F.

Instead of placing pipe 42 inside the chamber B, I'may make an offset 45 in the wall of casing 6, as shown in Fig. 6, and place pipe 42 on the outside and lead small nipples 46 to the inside of chamber B.

Any desired combination of these modified features may be provided and used. Or they may all be attached to a standard apparatus, and used or not according to the particular circumstances of each case.

It will be obvious that the means pro-' vided allow ver accurate adjustment of the rate of flow in each chamber.

It will be understood that the drawings are merely illustrative of my apparatus, and the proportions of the various compartments are not intended to be fixed by the dimensions shown. For instance, the cylinder 7 may be longer than the cylinder 2, if desired, and larger or smaller in diameter than that cylinder. Likewise, the cylinder 9, which is here shown as very short, and in efiect merely an outlet from chamber E, may be prolonged, and provided with draw-0d connections and. compartments similar to those about the tops of cylinders 2 and 7 The apparatus is not limited to the separation of iron ore, but may be used for any mixture of ore and gangue, or in fact for any mechanical mixture of particles of different specific gravities, where the difference in specific gravities is large, and the size of the particles the same, or nearly so.

The method carried out by the above described process is not claimed herein but is claimed in my application Serial No.

272,327, filed Jan. 21, 1919.

I claim:

1. Apparatus for separating solid granular materials, comprising a vertical vessel, means for forcing the materials in a finely divided form mixed with water upwardly through said vessel, said vessel intermediate its height being provided with a portion of increasing diameter providing an annular maaeoa chamber in which the solids are deposited by radial separation from the vertical stream, sa d annular enlargement being provided w1th a series of outlets uniformly spaced around said vessel, an annular chamber receiving from said discharge openings, said annular chamber being or progressively increasmg dimensions from one side, and a controllable outlet from the largest point of said draw-01f chamber.

2. Apparatus for separating solid granu-' lar materials, comprising a vertical vessel, means for forcing the materials in a finely divided form mixed with water upwardly through said vessel, said vessel intermediate its height being provided with a portion of increasing diameter providing an annular chamber in which the solids are deposited by radial separation from the vertical stream, said annular enlargement being provided with a series of outlets uniformly spaced around said vessel, means for regulating the amount of water drawn off through said discharge openings, and means to introduce an additional supply 'of water to said vessel adjacent the withdrawal point.

3. Apparatus for separating solid granular materials, comprising a vertical vessel, means for forcing the materials in a finely divided form mixed with water upwardly through said vessel, said vessel intermediate its height being provided with a portion of increasing diameter providing an annular chamber in which the solids are deposited by radial separation from the vertical stream, said annular enlargement being provided with a series of outlets uniformly spaced around said vessel, an annular draw-off chamber receiving from said openings and being of progressively increasing dimension from one side, a withdrawal outlet from the largest point of said draw-off chamber, and an additional water supply connected to said draw-0d chamber.

4:. Apparatus for separating solid granular, materials, comprising a. vertical vessel, means for forcing the materials in a finely divided form mixed with water upwardly through said vessel, said vessel intermediate its height being provided with a portion of increasing diameter providing an annular chamber in which the solids are deposited by radial separation from the vertical stream, said annular enlargement being provided with a series of outlets uniformly spaced around said vessel, an annular drawofi' chamber receiving from said discharge openings and being of increasing dimensions from one side, an outlet at the largest point of said draw-ofi' chamber, and means for introducing an additional water supply adjacent to said draw-ofi' openings and so related thereto as to induce a current through said draw-off openings.

5. Apparatus for separating solid granular materials, comprising a vertical vessel, means for forcing the material in a finely divided form mixed with water upwardly through said vessel, said vessel intermediate its height being provided with a portion of increasm diameter providing an annular chamber in which the solids are deposited by radial separation from the vertical stream, said annular enlargement being provided with a series of outlets uniformly spaced around said vessel, an annular drawofi chamber receivin from said discharge openings and being 0% progressively-increasing dimension from one side, a discharge outlet from the largest point of saiddrawoff chamber, and nozzles in said discharge openings projecting into the draw-off chamber and directed toward the dscharge opening therefrom.

6. Apparatus for separating solid granular materials, comprising a vertical vessel, means for forcing the material in a finely divided form mixed with water upwardly through said vessel, said vessel intermediate.

its" height being provided with a portion of increasing diameter providing an annular chamber in which the solids are deposited by radial separation from the vertical stream, said annular enlargement being provided with a series of outlets uniformly spaced around said vessel, an annular drawoif chamber receiving from said discharge openings and being of progressively increasing dimension from one side, a discharge outlet-from the largest point of said draw-off chamber, nozzles in said discharge openings projecting into the draw-ofi' chamber and directed toward the discharge opening therefrom, and a water supply connected to said draw-off chamber and directing the current in the direction of the nozzles.

7. Apparatus for separating solid granular materials, comprising a vertical vessel,

means for forcing the materials in a finely divided form mixed with water upwardly through said vessel, said vessel intermediate its height being provided with a portion of increasing diameter providing an annular chamber in which the solids are. deposited by radial separation from the vertical stream, said annular enlargement being provided with a series of outlets uniformly spaced around said vessel an annular draw-ofi chamber receiving from said openings and being of progressively increasing dimension from one side, a withdrawal outlet from the largest point of said draw-off chamber, an additional water sup 1y connected to said draw-off chamber, and further water supply to the upper portion of said annular enlargement.

3 8. Apparatus for separating solid granular materials, com rising a vertical vessel, means for forcing t e material in a finely divided form mixed with water upwardly through said vessel, said vessel ntermediate ats heightbe ng provided with a portion of mcreasm diameter providing an annular chamber-in which the solids are deposited by radial separation from the vertical stream, said annular enlargement being provided with a". series of outlets uniformly spaced around said vessel, an annular draw-oft said draw-off openings and so related thereto as to induce a current through said drawofi openings, and a further water sup ly to the upper portion of said annular enlargement.-

9. Apparatus for separating solid granular materials, comprising a vertical cylindrical vessel, means for-forcing the material in a finely divided form mixed with water upwardly through said vessel, a second vessel above the first vessel and having its lower end extending below and of larger diameter than the top ofthe first vesel, thereby providing an annular chamber in which the solids are deposited by radial separation from said annular chamber being provided with a series of outlets uniformly spaced around the vertical stream, the upper end of the first vessel curving progressively outwardly,

said vessel, an annular chamber receiving A from said discharge openings, said annular chamber being of progressively increasing dimensions from one side, and a controllable outlet from the largest point of said drawofi' chamber.

10. Apparatus for separating solid granular materials, comprising a vertical cylindrical vessel, means for forcing the material in a finely divided form mixed with water upwardly through said vessel, a second vessel above the first vessel and having its lower end extending below and of larger diameter than the top of the first vessel, thereby providing an annular chamber in which the sol-v terials to be separated to the bottom of the said cylinder, a casing surrounding the top of the said cylinder and attached to the outer wall thereof below thetop, drawwfi ports at the junction of the casing and cylinder wall, means to regulate the amount of water drawn from the apparatus through said ports, means to introduce a re ated amount of water above said draw-o and a second cylinder leading upward from the said casing.

12. Apparatus for separatmg granular materials of different characterist cs, comprising a storage receptacle for a mixture of water and the granular materials, means to force the mixture from the storage receptacle to the bottom of a vertical cylinder, an enlarged casing about the top of the said cylinder, means to draw off solid materlal deposited in said casing at the top of the first cylinder, means to regulate the amount of water drawn off with said solid material, means to introduce a supplementary supply of water to said casing, and a series of succeeding axially aligned cylinders and casings having similar drawing off and water supplying means.

13. Apparatus for separating a mixture of solids of different characteristics, comprising a vertical cylinder, means to introduce the mixture in a stream of water to the bottom of the cylinder, an enlarged casing about the top of the cylinder and connected to the outer wall thereof below the top, perforations in the casing wall at its bottom, an annular chamber surrounding the connections between the casing and the cylinder wall, an escape port from the draw-off cham ber, and a valved inlet pipe thereto connected to a water supply.

14. Apparatus for separating granular materials of different characteristics, comprising a series of vertically arranged cylinders having enlarged chambers about the top of each cylinder, means to draw ofi' granular material from each enlarged chamber, and means to supply additional water at each draw-oft level to compensate for that drawn off with the granular material.

15. Apparatus for separating granular materials of different characteristics, comprising a series of vertically-arranged upward-flow cylinders, an enlarged settlement chamber connecting each cylinder to the cylinder next above, a series of perforations in the bottoms of said settlement chambers adapted to carry off granular material deposited there, an annular draw-off chamber beneath each settlement chamber and connected thereto by said perforations, an outlet from said draw-off chamber tocarry off granular material and water and an inlet thereto to supply water to compensate for the water discharged from the draw-off chamber.

16. Apparatus for separating granular materials of different characteristics, comprising a series of vertically-arranged upward-flow cylinders, an enlarged settlement ports,

chamber connecting each cylinder to the cylinder next above, a series of perforations in the bottoms of said settlement chambers adapted to carry off ranular material deposited there, an annu ar draw-ofi chamber beneath each settlement chamber and connected thereto by said perforations, an outlet from said draw-oil chamber to carry off granular material and water, an inlet thereto to supply water to compensate for the water discharged from the draw-ofi chamber, and means to control the amount of water supplied to the draw-off chamber.

17. Apparatus for separating solidmaterials comprisin in combination, a vertical casing, a second casing above the said first casing and having its lower end of larger diameter than the top of the first casing and extending below the top of the first casing and forming an annular chamber therearound, means for forcing the material in a finely divided form mixed with water upwardly through said casings, and a con- Iitantly open outlet from said annular cham- 18. Apparatus for separating solid materials comprising in combination, a vertical casing, a second casing above the said first casing and having its lower end of larger diameter than the top of the first casing and extending below the top of the first casing and forming an annular chamber therearound, means for forcing the material in a finely divided form mixed with water upwardly through said casings, and a series of constantly open withdrawal openings in the bottom of said annular chamber and entirely around the same.

19. Apparatus for separating solid materials comprising in combination, a vertical casing, a second casing above the said first casing and having its lower end of larger diameter than the top of the first casing and extending below the top of the first casing and forming an annular chamber therearound, means for forcing the material in a finely divided form mixed with water upwardly through said casings, the bottom of said annular chamber being provided with a series of withdrawal openings extending entirely around the same, an annular withdrawal chamber below said perforated bottom and receiving the discharge from said openings, and a constantly open draw-ofi' outlet from said last named chamber.

20. Apparatus for separating solid materials comprising in combination, a vertical casing, a second casing above the said first casing and having its lower end of larger diameter than the topof the first casing and extending below the top of the first casing and forming an annular chamber therearound, the bottom of said annular chamber being provided with a series of withdrawal openings extending entirely around the same, means for forcing the material in a finely divided form mixed with water upwardly throu h said casings, an annular draw-off cham er below said perforatedbottom andreceiving the discharge from said openings and being of progressively increasing dimension from one side in both directions to the other side, and an outlet from the largest point in the said draW-ofi' chamber.

21. Apparatus for separating solid materials comprisin in combination, a vertical casing, a second casing above said first casing and having its lower end of larger diameter than the top of the first casing and extending below the top of the first casing and forming an annular chamber around the first casing,'a third casing above the second casing and having its lower end of larger diameter than the top of the second casing and extendin below the top of the second casing and orming an annular chamber therearound, means for forcing the material in a finely divided formmixed with water upwardly throu h said casings, and constantly open oufiets from both of said annular chambers.

22. Apparatus for separating solid materials comprising in combination, a vertical casing, a second casing above the said first casing and having its lower end of larger diameter than the top of the first casing and extending below the top of the first casin and forming an annular chamber aroun the first casing, a third casing above the second casing and having its lower end of larger diameter than the top of the second casing and extending below the top of the second casing and forming an annular chamber therearound, means for forcing the material in a finely divided form mixed with water upwardly through said casings, the bottoms of each of said annular chambers being provided with discharge openings extending entirely around the same, an annular withdrawal chamber below each of said perforated bottoms and receiving the discharge therethrough and being of progressively increasing dimension from one side in both directions to the other side, and a draw-off outlet from the largest point of each of said draw-off annular chambers.

In testimony whereof, I have hereunto set my hand.

MARTIN HOKANSON.

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