US1319771A - Method and apparatus for grading finely-divided material - Google Patents

Description

H. K. HITCHCOCK.

METHOD AND APPARATUS FOR GRADING FINELY DIVIDED MATERIAL.

APPLICATION FILED AUG-9. I915.

1,319,771. Patented Oct. 28,1919.

3 SHEETSSHEET I.

FIELI.

V INVENTOR WITNESSES H. K. HITCHCOCK METHOD AND APPARATUS FOR GRADING FINELY DIVIDED MATERIAL.

I APPLICATION FILED AUG.9, 1915. 1,319,771. Patented 001;. 28,1919.

3 SHEETS-SHEET 2.

WITNESSES INVENTOR H. K. HITCHCOCK.

METHOD AND APPARATUS FOR GRADING FINELY DIVIDED MATERIAL.

APPLICATION FILED AUG-9,1915.

1,319,771. Patented 001:. 28,1919.

3 SHEETS-SHEET 3.

u II III! wn'nzssss INVENTOR ww wMM/WW ga /W 2g HALBERT K. HITCHCOCK, OF PITTSBURGH, PENNSYLTTANIA.

METHOD AND APPARATUS FOR Application filed August 9, 1915. Serial No. 44,625.

'7 0 all whom it may concern:

Be it known that I, HALBERT K. HITCH- COCK, a resident of Pittsburgh, in the county of Allegheny and State of'Pennsyl- Vania, have invented a new and useful Improvement in Methods and Apparatus for Grading Finely-Divided Material, of which the following is a specification.

This invention relates to method and ap-' paratus for grading or classifying finely divided material, such as sand, emery or other abrasive materials to 'be used, for example, in grinding or polishing plate glass, or as binders in ceramics, or any other finely d1- vided material. The invention is an im- ,provement upon that shown, described and claimed in my Patent No. 1,100,302, June,

' The object of the invention is to provide improved method and apparatus for producing a cleaner and more accurate separation or classification of thedifi'erent grades of material and avoiding contamination of one grade by any other grade; which more particularly produces a cleaner coarse. grade" or grades of the material; and which also automatically maintains a unlform or constant density of the mixture in the grading vessel, so that the grading or classifying 'opparticles are between definite upper and lower limits and no material having other characteristics. I

In the drawings, Figure 1 represents a diagrammatic sectional elevation of one form of grading apparatus embodying the invention; Fig. 2 is a similar view illustrat-' ing the application of the invention to grinding apparatus; Fig. 3 is a view corre-,

sponding to Fig. 2 and illustrating a diflerent form of the invention; and Fig. 4'is a detail sectional elevation of the lower portion of the grading vessel.

The method utilizes the general principles Specification of Letters Patent.

the finer grades are carried-upwardly by invention being shown herein.

GRADING FTNELY-DIVIDED MATERIAL.

Patented Oct.

set forth in my prior Patent 1,100,302, and grades or classlfies the material while in suspension in a liquid in a gradin vessel by the actlon of a current of liquid aving an upward flow or travel relative to a downward movement of the material, which separates and classifies the several grades in diflerent strata or zones in said vessel, the finer grades near the top and the coarser grades near the bottom. The material 'to be graded has heretofore beenintroduced into the grading vessel elther at its bottom, as in my Patent 1,100,302, or at the upper level of the liquid therein. When introduced at the bottom the upward flow or travel of the liquid relative to the material, and pass in turn the outlets through which the several coarser'grades are withdrawn. This gives practically clean grades 1n ordinary grinding apparatus but a small percentageof the fine material unavoidably passes out through the various openings when the apparatus is run c0ntinuously. On the other hand, when the material 1s introduced at the upper level Ofljqlid in'the grading vessel it is necessary to allow considerable time for the material to settle to the proper level before withdrawing the finer grades, or the finer grades withdrawn are contaminated by some of the coarser material, which has to pass downwardly through the finer grades to reach its proper level near the bottom of the vessel.

By my improved method the material to be graded is introduced into the grading vessel at a level intermediate its bottom and the upper level of liquid therein, thereby enabling the coarser material to travel downwardly against the rising current of liquid and the finer grades to travel upwardly with said current, so that all grades of material find their proper levels without contaminating one grade with material from another. The material to be graded maybe introduced into the grading vessel in any suitable. manner but preferably is in suspension in a liquid, being conducted to and introduced into the grading vessel in the form of a stream. of mixture which may flow or travel either upwardly or downwardly, both forms of the The upward flow or travel of the liquid relative to the material may be produced in any suitable manner,'such for example as described in by prior Patents, Nos, 934,441,

September 21, 1909, 1,056,415, March 12}, 1913, and 1,100,302, June 6, 1914, that 1s, 1t may be produced by the displacement of the liquid by the solid particles travellng downwardly, the displaced liquid rising to take the place of the falling particles and thereby creating an upward flow of travel of the liquid, or it may be produced by mtroducing a supply of liquid into or near the bottom of the grading vessel. Th1s l quid, for ex-- ample, may be that WlllCh carrles 1n suspension the particles of material to be graded, the liquid having an upward fiow or travel through the grading vessel to the overflow at the top, while the particles of material to be graded or classified have a downward movement relatively to the upward flow of the liquid and seek the levels of their proper grades in said vessel. The best results, however, are obtained when the upward flow or travel of the liquid is produced or augmented by introducing a separate supply of fresh liquid into the grading vessel at or near its bottom and preferably at a level below the level at which the material to be graded is introduced thereinto. This fresh liquid supplv has an upward flow or travel relative to the downward movement of the coarser particles of material to be classified and accurately separates or classifies the same into definite grades. The outlet or outlets for the coarsest grade or grades may be located at any suitable level, but are preferably located at a level between the inlet for the fresh liquid supply and the inlet for the material to be graded, so that they lie in a zone or stratum not traversed by any of the finer grades. Consequently, an extra clean coarse grade or grades can be withdrawn from this region of the grading vessel. The fresh liquid supply travels upwardly through the grading vessel with the liquid of the mixture containing the abrading material, but the velocity of the upward flow or travel of the liquid relative to the downward flow of the material at and near the inlet for the mixture is not sufiicient to carry any of the coarser particles upwardly, but is merely sufficient to lift the finer grades to their proper levels in the grading vessel.

The mixture of liquid and finely divided material to be classified is preferably introduced into the grading vessel in an upwardly traveling stream, but may be introduced in the form of a stream of mixture having a downward flow or travel relative to the upward flow or travel of the mixture in the grading vessel, and which stream of material is so handled as to be independent of the main body of liquid in the grading vessel, say for example, by introducing it through a downwardly extendingpipe or conduit dipping into the mixture in the grading vessel and having its lower end immersed therein to a level above the level of the outlet for the coarsest grade withdrawn therefrom. The density of the mixture in the grading vessel varies from time to time as the total quantity of material therein to be graded increases or diminishes, and the total quantity of material in the grading vessel varies with the supply thereto and the amounts of the various grades withdrawn at the different outlets. While the downwardly moving stream of mixture introduced into the grading vessel is independent of or separated from the body of liquid therein, nevertheless the density of the body of mixture in the grading vessel affects the velocity of the flow of the stream of mixture being supplied tosaid vessel. This is due to the fact that the column of mixture in v the pipe or conduit through which it is introduced into the grading vessel is balanced against a similar column of the body of mixture in the grading vessel. If the weight or pressure produced by the body of the mixture in the grader is less than that of the column of liquid in the pipe or conduit the preponderating weight of the mixture in the pipe or conduit produces a more rapid downward flow thereof, while, on the other hand, if the weight or pressure produced by the mixture in the grading vessel is greater than that in the pipe or conduit through which the mixture is introduced thereinto, then the preponderating effect of the body of liquid in the grading vessel tendsto .produce an upward flow of the mixture in the pipe 'or conduit. This effect partially or completely counteracts the normal downward flow of the mixture in the delivery pipe or conduit to replace the mixture being withdrawn from the grading vessel and causes more or less of the mixture being supplied to the grader to pass out through the overflow and back to the sump, thus shunting the superfluous material around the grader. Consequently the velocity of the downward flow or travel of the mixture through the delivery pipe or conduit varies inversely with the density of the body of the mixture in the grading vessel, increasing as the density decreases and decreasing as the density increases, and has a tendency to automatically govern or regulate the mixture being graded so that it is maintained at a practically uniform or fixed density.

Referring to the drawings, Fig. 1 repre sents the invention applied to apparatus for grading or classifying finely divided material. In many respccts the apparatus shown is similar to that of my rior Patent 1,100,302 before referred to. s illustrated, it comprises a primarygrading vessel or tank 10 provided with a bottom inlet pipe 11 through which a fresh liquid supply may be introduced for producing the upward flow or travel of the liquid for the grading operation, and also with an overflow outlet 12 through which the excess liquid. and mud and the material too fine for further use flow. to the sewer. In said primary'grader the particles of materialare distributed in'vari ous strata orzones'accordmg to the characto be collected for use or to be ground up into vessel.

'sels for each grade withdrawn.

smaller sizes if necessary, but preferably each grade is conducted in suspension in the liquid to an independent secondary grading vessel or tank 19, there being one of said yes- Said vessels 19 are each provided with a bottom 'inlet' 20 for a clear liquid supply, and with an overflow 21 to carry off the fine material either to the sewer or to a sump or pit to be later regradedf The secondary cones 19 are of the same construction shown in my prior-Patent 1,100,302, embodying a conical lower portion 22, a cylindrical intermediate portion 23 and a conical upper portion The upward velocity at the top of the comcal bottom should be slightly above the upward velocity in the primary grading cone at the point from which the material con; ducted to the secondary grader comes, while the.- upward velocity in the space in the cylindrical part of the grader should be'the same as the upward velocity at the point in the primary cone where the next finer grade is withdrawn. The opening to the outlet,

pipe or conduit 25 from each secondary grading vessel is at a level at or near the bottom of the cylindrical intermediate portion 23 of said vessel, so that a clean grade of material is withdrawn therefrom, said material being conducted to a storage tank 26, in which it may be held in suspension for use as desired, or may be allowed to settle for later use.

The material to be graded is supplied to the primarygrader from a mixing tank or lixivia-tor 30, in which. are located power driven paddles or stirrers 31 for mixing the material and putting it in suspension in the liquid. The liquid is introduced to said tank through a suitable pipe and the solid material to be graded may be shoveled in or delivered from a hopper, as desired. The material'in suspension in the liquid flows from he tank 30 through a pipe 32 into a mixin cone or funnel 33, from which it passes to the primary grader through a depending pipe or conduit 34 connected to the bottom of the cone 33 and extending down into the mixture in the primary grading The outlet from the lower' end of the pipe 34 may be atany suitable level intermediate the bottom of the grader 10 and the outlet" pipes. or conduits 13'and 14 maintaining a constant head of the mixture Preferably; suitable-means isprovided for Y shown as at a level between the openings beingsupplied to the primary grader, land 1 in the, form shown the supply of material to the cone 3 3 is. regulated by a ball 'float 3'5 in said cone, which controls a" valve 36 in the-plpe 32. This ball float. maintainsa definite level of liquid inthe mixing cone 33 and mcreases'the supply through the valve 36 as the level of liquid falls and decreases it as the level of liquid rises.

The depending delivery pipe34 automati cally maintains substantially a uniform den.-

sity of the mixture in the primary grading vessel with the several grades to-be withdrawn therefrom at substantially constant levels. As the density of the body of the mixture in the primary grading vessel increases there isan'increa'sing tendency to counteract or retard the downward flow or travel of the mixture being delivered to said primary grader through the pipe 34, and if an over supply of material collects in the D primary grading vessel further supply of' material from the lixiviator 30 is held back until turther material is withdrawn from theprimary grader through the several outlets therefrom. If the density of the material in the primary grading vessel decreases by insuflicient supply or too rapid withdrawal of the several grades therefrom'the oppositlon to the downward flow or-travel of'the mlxture through the pipe 34 decreasesand a greater supply of material passes through the lixiviator to the primary grading vessel.

This arrangement produces a senes. of very clean definlte grades of material with practlcally unvaryl'ng characteristics in each of the several grades as soon as the grader ,has operated long enough to reach a stable condition. I

F1g.,2 illustrates the invention applied for gradlng finely divided material, such as sand or the like, and supplying the same directly to a grinding apparatus. In the apparatus shown 40 represents the grinding table equipped with the usual runners 41 and surrounded by a gutter 42 leading to the ditch-.43 through which the used materlal flows to the .s'ump or pit 44, provided with the usual waste overflow 44 to the sewer, .for eliminating the excess water and 45 having a plurality of withdrawal pipes 46, 47, 48, the inlets to which are at different levels n sand vessel, said pipes being provided vwlth suitable valve mechanism enabling material to be delivered from any one or more of said pipes to a trough 49 through whlch 1t flowsto the grinding table. An

overflow pipe 39 conducts the waste material from the grader 45 to the ditch 42. So far whose bottom opening 1s immersed in the liquid in said vessel at a level intermediate the levels of the openings to the outlet pipes 46 and 47. The bottom of the grading vessel is provided with an inlet 51 for a clear liquld supply to produce or augment the upward flow or travel of the liquid relative to the material. The coarse partlcles in the material to be graded passing in through the pipe 50 fall downwardly against the rising current from the inlet 51, the velocity of said current being sufliclent to lift the finer particles of material before they have a chance to fall to the outlet for the coarsest grade. clean, coarse grade of material may be withdrawn from the pipe 46. The finer grades rise to the levels of the outlets for the finer grades, but no coarse material is carried up with the fine, so that the several finer grades are clean and free from contamination by the coarser grades.

The material to be graded is supplied to the pipe 50 from a supply box or vessel 52, located at the upper end of the pipe 50 and provided with a suitable hand-operated valve 53 for allowing or shutting off the flow of material from said vessel to the pipe 50. Material is supplied to said vessel in any suitable manner,'such as by a centrifugal pump 54, the inlet to which dips into the sump or pit 44, and which pump supplies material to the vessel52 through the pipe 55. Vessel 52 is also supplied with an overflow pipe 56 delivering to the sump and connected to said vessel 52 at -a level above the valve 53, so that when said valve is open a constant head or level of liquid is maintained in the vessel 52 at the level of the overflow pipe 56. v

In operation of this system the valve 53 is open and the material delivered by the pump passes downwardly to the grading vessel 45 through the pipe 50, the excess flowing back to the sump through the overflow 56. The absolute density of the body of the mixture always depends upon the exact head of the overflow 56 above the level of liquid in the grading vessel, which head is constant and produces the downward flow of the supply of material to the grader.-

The vertical depending pipe 50 with its opening below the level of the liquid in the tank 45 automatically regulates the flow of material to the grading vessel in accordance lation of the supply of material to Consequently a very with variations in the density of the mixture in said vessel, as before described, and it also produces very clean grades of material at the different levels in the grading vessel. so that the grinding operation is more efi'ectlVe and may be carried on with greater rapidity. Throughout the grading operation material m' y be discharged to the grinding table with the several grades in any desired order or sequence and constantly in suspension in a liquid, and furthermore, the material flowing off from the grinding table passes back to the sump and-again up to the grading vessel, so that a complete cycle of circulation is going on during the entire grinding operation. Fresh coarse material is added from time to time to the sump, usually a new measured batch before each grinding operation.

Figs. 3 and 4 illustrate another arrangement for securing very clean grades of ma-' terial at the different levels in the grading tank, but which omits the automatic reguthe gradlng vessel in accordance with the density of the material therein. Tn this form the circulation of the material to and from the grinding table is the same as in the form before described, the material passing out from the grading vessel through the several outlets 46, 47, 48 to the grindin table, thence to the sump and thence back 1nto the grading vessel. The material is deliveredfrom the sump to the grading vessel 45 by a centrifugal pump 54, which discharges into the grading vessel through a'nozzle 60 at the bottom of said vessel and which extends part way up into the same, its outlet 61 being at a level above the level of the opening to the withdrawal pipe 46 for the coarsest grade of material. I The grading vessel is also provided at or near its extreme bottom, and at a level below the level of the outlet for the coarsest grade, with an inlet 62 for a supply of clear liquid. The .finer particles delivered to the grading vessel by the nozzle 60 pass directly upwardly to their various levels in the grading vessel, and as no coarse material passes through the levels of the finer grades the latter are withdrawn in a clean condition uncontaminated by the coarser material. The coarse material falls downwardly from the outlet 61 against the rising stream of clear liquid from the inlet 62. This rising stream prevents any of the finer grades from flowing through the outlets for the coarse grade or grades, so that a very clean, coarse grade of material is withdrawn from this region in the grading vessel. The auxiliary water supply also enables the operator to control the density of the grinding mixture without changing the velocity of flow from the pump or appreciably varying the grading velocity for the finer grades.

Inbothof thefsystem's shownrespectively in Figs; 2 and 3v the finishing operation is carried on with the finer grades collected in the upper strata of thegrading. vessel dur- 1. The method of grading finely divid r material mixed with a liquid, consisting in subjecting said material in a vessel to an upward flow or travel of the liquid relative to the material and thereby separatln the material into grades, withdrawin erent grades from said vessel indepen ently and from difi'erent' levels therein, introducing the material "to be graded into said vessel therefrom,

at a level above the level of the coarsest grade and below the level of the next finest grade withdrawn therefrom, and simultaneously introducing liquid into sa1d vessel below the level from which the coarse ma;- terial is withdrawn.

2. The method of grading finely divided material mixed with a liquid, consisting in subjecting said material in a vessel to an upward flow or travel of the liquid relative to the material and thereby separating the materialvinto grades, introducing sa1d material in suspension in a liquid into said vessel at a level intermediate the levelsof the' coarsest and useful finest grades withdrawn simultaneously withdrawing coarse useful material from a level below and fine material from a level above the level at which the material is-introduced to said vessel, and simultaneously introducing liquid into said vessel at a level below the level at which the material introduced thereto.

3. The method of grading finely divided material mixed with a liquid, consisting in subjecting. said material in a vessel to an upward flow or travel of the liquid relative to the material and thereby separating the material into grades, introducing said material under a constant head in suspension in a liquid into said vessel at a level intermediate the levels of the coarsest and finest grades withdrawn therefrom by a downwardly moving stream of mixture independent of the upward flow or travel of the liquid in said vessel, to thereby control the flow of said stream by the density of the mixture-in said vessel, and withdrawing several grades from said vessel separately and independentl L The method of grading finely divided material mixed with a liquid, consisting in subjecting said material in a; vessel to an upward flow or travel of the llquid relative the material and thereby" separating the materlal mto grades, introducing said ma- I i a;

terial under aconstant' hea'd. suspensionma l1qu1d mto said vessel at a level intermediate the levels, of the coarsest and finest grades withdrawn therefrom by a downwardly moving stream of mixture independent of the upward flow or travel-of the liquid 1n sa1d vessel, to thereby control the flow of sa d'streamdby the denslty o fthe mixture in sa1d vessel-,Etnd withdrawing coarse mater al from a level-below and fine material from a level above the level at which the material is introduced into said vessel. T

The method of grading finely divided material mixed with a liquid, consisting in 1 subjecting said material in a vessel toan upward flow or travel of the liquid relative to the' ma ter1al, and thereby separating'the material into grades, introducing the maintermediatethe levels of the coarsest and finest grades withdrawn therefrom, simultaneously withdrawing a coarse grade from said vessel at a level below the level at which tive to the material to separate the material into grades, means for independently withdrawing diflerent grades from -diflerent levels in sa1d vessel, means for introducing 'terial to be graded into said vessel at a level the material is introduced thereto, withthe material to be graded into said vessel at a level intermediate the level of the coarsest and next finest grades withdrawn therefrom, and means for simultaneously introducing liquid into said vessel below the level from which the coarse material is withdrawn.

7. Apparatus for grading finely divided material mixed with a liquid, comprising a grading vessel, means for producing therein an upward flow: or travel of the liquid relative to the material, means for withdrawing several different grades from dilferent levels in said vessel, a conduit for supplying material to be graded extending into said vessel and terminating at a level intermediate the levels of the coarsest and I finest grades withdrawn therefrom, and means for introducing a liquid. supply to said vessel at a level below. the level of the coarsest material withdrawn therefrom.

8. Apparatus for grading finely divided material mixed with a liquid, comprising a grading vessel, a conduit for supplying material to be graded in suspension in a liquidjto said, vessel, said conduit opening into rfiow, means for returning the material from said overflow to the vessel for regradmg, an

outlet for withdrawing the coarse material from the vessel at a level below that at which the material is introduced therelnto, and outlets for Withdrawal of the finer material at levels above that at which the material is introduced thereinto.

9. Apparatus for. grading finely divided material mixed with a liquid, comprising,

a grading vessel, a conduit, for supplying material to begraded in suspension in a liquid to said vessel, said conduit opening into said vessel at a level intermediate its bottom and the upper level of the liquid therein, said vessel being provided with an overflow, means for returning the material from said overflow to the vessel for regrading, outlets for withdrawing the coarse material from a level below, and outlets for withdrawing the fine material from levels above that at which the material is introduced into the vessel, and a liquid supply pipe connected to said vessel at a level below that at which the coarsest material is withdrawn.

10. Apparatus for grading finely divided material mixed with a liquid, comprising a grading vessel, means for producing therein an upward fiow or travel of -the liquid relative to the mate-rial, outlets for withdrawing the various grades from difierent levels in said vessel, an overhead supply reservoir for material to be graded mixed with water, a conduit extending downwardly therefrom into said reservoir and terminating at a level intermediate the levels of the coarsest and finest grades withdrawn therefrom, and a liquid supply to said vessel at a level below the level of the coarsest material Withdrawn therefrom.

11. Apparatus for gradin finely idivided material mixed with a liqui comprising a grading vessel, means for producing therein an upward flow or travel of the liquid rela tive to the material, outlets for withdrawing the various grades from different levels in said vessel, an overhead supply reservoir for material to be graded mixed with water, a conduit extending downwardly therefrom into said reservoir and terminating at a level intermediate the levels of the coarsest and finest grades withdrawn therefrom, means to maintain a constant head of liquid in said supply reservoir, and a liquid supply to said vessel at a level below the level of the coarsest material withdrawn therefrom.

In testimony whereof I have hereunto set my hand.

HALBERT K. HITCHCOCK. Witnesses:

ELBERT L. HYDE, GLENN H. LERESCHE.

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