US2277817A - Classification - Google Patents

Description

I Mrch 1942' T. B. couN CLASSIFICATION Filed 1939 2 Shee 1 tlvrfr mm M 64 R m MW March 31, 1942. T. B. COUNSELMAN CLASSIFICATION Fil ed NOV. '7, 1959 2 Sheets-Sheet 2 INVENTOR.

' 171/000,?! 5. damn/M ATTORNEY.

Patented Mar. 31, 1942 cmssn rca'rron Theodore B. Counselman, Evanston, 111., assignor to The Dorr Company, Inc., New York, N. Y., a corporation of Delaware Application November 7, 1939, Serial No. 303,207

Claims.

This invention relates to classifiers that are used in the art of classification, that is, in the treatment of suspended solids making use of their different settling rates to effect a separation thereof into at least two fractions divided in so far as possible,in accordance with a predetermined particle size. An ideal arrangement would be to have all particles over a critical size go into one fraction, with all particles under that size going into another fraction. Classifiers, as most frequently used in metallurgy, comprise a tank that holds liquid-solids mixture or pulp being treated. The tank is generally provided with an inclined partially-submerged floor along which the fraction of larger and more readily set'tleable of the suspended solids, called sands, is conveyed upwardly to emergence and discharge. The fraction of finer solids that remain in suspension is overfiowed from the other or deep end of the classifier.

Classifiersof this type are often used-in what is called closed circuit grinding. In this operation, ore after being crushed is supplied to a grinding mill, the discharge from which has particles fine enough to be treated for the recovery therefrom of metal values, but also has particles too large for such treatment.- Therefore, it is the function of a classifier to receive this conglomerate discharge and by the classifiers size selective or fractionating functions, overflow of fine particles or fines on their way to valuerecovery treatment, while emerging to discharge all particles larger than the usable sizes. These large particles or sands, are returned to the mill for regrinding until they are reduced to usable However, the selectivity or fractionating ability of a classifier is important when it is used in other industries, such as in the washing and classifying of sand for use in concreteand the like. So a major object of this invention is to devise a classifier and a method of operation therei:

of that will attain efilcient control of particle.- size separation.

Present-day classifiers, as now designed and operated, are incapable of making efilcient coarse classifications; that is, in the range from 4 to 28 mesh or so. It is possible to make these coarse classifications or segregations, but with the limitations of the machines now available, it is necessary to do this at a very high density, namely, in a very thick pulp The reason why this is so is that the mechanical limitations of the mechanism used for removing the oversize fromthe classifier are'such that the size of unit is so great that the overflow capacity of the machine is out of all proportion to the raking capacity, with the result that if an attempt ismade to make a coarse separation in a dilute pulp, the particles settle so fast that the desired size cannot be overfiowed. As a result of this, it is customary to thicken up the pulp until the settling rate has been retarded to such an extent as to adjust the overflow capacity to the dimensions dictated by the mechanism. 7

Elfecting the classification at a high density or in a thick pulp has the very definite objection that it results in .a very ineificient classification. The reason for this is that in addition to the contamination of the oversize product, resulting from the simultaneous settlement of fine particles along with the coarse particles, there is an additional contamination resulting from the pulp .that fills the voids .between the particles of oversize product. This pulp must contain at least as many fine particles as are contained in the pulp overflow, since the overflow is the most dilute pulp in the machine.

An idea of the magnitude of this contamination of oversize product with material that should have overfiowed, is indicated in the following table, compiled and interpolated from analyses of active classifier operations:

At 3:1 circulating load.

It might be pointed out that in the coarseseparation range being dealt with here, present practice is to make the separations at from to solids; whereas it is possible with this chine that would make coarse separations at high dilutions. To do this, I found it advantageous to use relatively small classification or overflow areas compared with the dimensions required to accommodate a raking or discharging mechanism capable of handling the very tremendous tonnage of sand that will settle out in this small overflow area. I conceived the idea of trying to divorce the two functions of the machine. This I do in a tank which can accommodate the necessary raking or sand-dewatering mechanism, and associating with it a classifying chamber that contains a pool of small but adjustable dimensions. The area or overflow velocity can be ad- Justed to give the desiredseparationwithout regard to the size of tank required to accommodate the discharging and dewatering device.

In the preferred embodiment the two compartments are in constant hydraulic communication through a slot of relatively small area. Classification is effected in the pool of the top compartment. The sand discharged from the pool through the slot is removed without any further classification. The raking mechanism does a dewatering job, and the surplus water rises through the slot to overflow from the pool.

In present-day classifiers there are provided in the tank, and over the inclined bottom floor, three general types of conveyors for urging settling. sands upward along the floor, namely, a spiral screw conveyor, flights carried by endless belts or chains travelling unidirectionally, and reciprocating rakes, the. latter being frequently referred to as the Dorr type. material to be classified is supplied to the tank, from which all of the suspended solids must be gotten out, whereas it is a feature of this invention to subject the material to be classified to a particle-size selective or fractionating treatment comprised in a relatively small pool outside of and exterior to the tank proper, with the area of the pool being adjustable. This is done by rapidly flowing through said pool the feed material to be classified at a rate whereby a substantial percentage of the liquid with the finer solids suspended therein will pass substantially horizontally over a submerged slot in a covered top section of the classifier tank. When safeguarded by suitable mechanical and hydraulic controls, the

fines in the feed tend to hurdle the slot while the quicker-settling coarser-sized particles drop through the slot into the classifier tank from which they are dewatered by being raked to emerged discharge as is usual. It is the keeping of the major portion of the fines out of the bath in the classifier tank proper that constitutes the foundation upon which this invention is built, and the-arrangement and control of the hurdle constitutes an important feature of the invention.

Whether any particular particle in suspension in the feed sinks through the slot into the classifier bath, or instead flows rushingly past the submerged slot and thus avoids entering the classifier, is determined by certain control features that relate to the pool on the covered top or deck of the classifier. These features comprise generally the correlating of the pool area or velocity of overflow therefrom, and the dimensions of the submerged slot, to the end that finer solids are discouraged from passing th'erethrough. More spethrough the submerged slot. Other factors that In such classifiers, all of the .efilcient and satisfactory manner.

might be used to control the selectivity of the pool are (l) to dilute the bath in the tank by" adding water; (2) to vary the rate of movement of the rakes in the classifier bath; and (3) to change the rate of feed; but the last two of these are not ordinarily desirable practically.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description. In the accompanying drawings, for the purpose of example, there has been illustrated the best embodiment of the invention now known to me, but such embodiment is to be regarded as typical only of many possible embodiments, and the invention is not to be limited thereto.

In the drawings:

Fig. l is a vertical section through the lower or fines discharge end of a classifier of the Dorr type having and embodying the features of the present invention;

Fig. 2 is a perspective view at larger scale looking down on the end of the classifier of Fig. 1;

Fig. 3 is a fragmentary section taken on the line 3--3 of Fig. 1;

Fig. 4 is a diagrammatic view somewhat similar to Fig. 1 but showing the manner in which the invention operates to effect the desired classification.

As has been previously mentioned, the mechanical classifiers of the prior art make use of a relatively large tank within which operates conveying means which serves to urge settled material to a point of emergence and which also causes a certain amount of turbulence in the classifier bath, thus discouraging settling of the fine particles which overflow a suitable weir. These prior classifiers are quite efiicient in making what are commonly known in the art as fine separations wherein the product that is desired is an overflow containing as much as possible of the finest size materials and as little as possible of coarser sizes. However, these classifiers have been generally incapable of producing efficiently at high dilution what is commonly termed as a coarse separation (say 4 to 28 mesh).

The classifier of the present invention is particularly adapted to perform the act of making what is known as a coarse separation in a highly Generally speaking, the arrangement of the classifier of the present invention comprises a relatively large tank having a sloping bottom or fioor up which the settled sands are conveyed to emergence and dewatered by suitable conveying mechanism. The lower or discharge end of the classifier tank is covered and provided with means for the formation of a relatively small pool on the upper surface of the cover or deck so that all material treated by the machine must enter and flow through the small pool. The cover or deck is provided with a slot or opening communicating with the main tank. All feed entering the pool rushes through it in a rapid flow and the coarsest particles drop from the pool through the slot into the classifier tank, while substantially all other particles are carried by the rapid fiow over and the finer solids therein is from an upper portion of the deeper section of the compartment or pool therein. Thus,- the small pool of initial liquid body is in substantially vertical hydraulic communication with an underlying portion of a secondary liquid body that is in the classifier tank I and performs functions of classification or segregation so that the tank itself serves primarily as a thickener or dewaterer wherein the coarse solids which have dropped through the slotted deck settle to the bottom and are conveyed upwardly to emergence by the conveying mechanism. In this embodiment apparently little classification or segregation takes effect within the classifier tank and substantially all particles once dropping through the slot become a part of the ultimately emerged sands or so-called raked product.

In another embodiment additional water is supplied to the classifier tank preferably by means of sprays directed upon the settled material near the point where it emerges from the classifier bath. In this embodiment, depending upon the amount of water supplied, there may be some upfiow of liquid upwardly through the slot, thus assisting in the classification action and carrying up any fines which may have passed downwardly through the slot.

Referring particularly to the drawings, in Fig. 1 there will be seen the lower or overfiow end of a classifier of the well-known Dorr type. This classifier comprises a tank having an upwardly inclined bottom or fioor 5, end wall 6 and side walls 1. Raking blades 8 attached to stringers 9 are operatively supported in the tank by means which include the hanger I0, linkage II and bell crank l2. These details, and the supporting and driving arrangement at the upper end of the raking assembly, and their operation, are well known in the art and are thoroughly described and illustrated in the patent'to J. V. H. Finney No. 1,997,379, so further description thereof is deemed unnecessary. Furthermore, according to the broader aspects of the invention, it will be understood that any other suitable type of conveying and dewatering mechanism may be utilized instead of the reciprocating rakes herein illustrated, for example, a spiral screw conveyor, a bucket elevator, sand wheel or endless belt or chain conveyor equipped with suitable blades.

In the present invention the lower end of the classifier tank is completely decked over or covered by. means of a sloping roof or deck I3 which preferably, although not. necessarily, parallels the inclined bottom or floor 5. The deck l3, at the discharge end of the classifier, preferably is extended beyond the end wall 6 and turns slightly downward as indicated at It to form a discharge lip for the classifier overflow. The deck l3 extends longitudinally and upwardly from the end wall 6 to a vertical transverse parti ion I 8 extending the full width of the tank. The deck 13 is impervious and continuous except for a slotted area or region left at 26. The deck 13 and the vertical transverse partition l8 effectively separate the liquid holding section of the tank from the regions above thedeck except there is constant hydraulic communication through the slotted area between that portion of the liquid that is within the tank and underlying the inclined deck and the liquid-solids mixture flowing through and undergoing classification in the pool that is maintained on the inclined deck. The

deck-has a lower section i3a terminating at a suitable distance from the end wall 6 and is provided with a substantially vertical ballie or deflecting plate l5 extending downwardly into the tank and transversely of the tank. The deck also has an upper section l3?) and side sections I30. The transverse edges of the slot or slotted section 26 are defined by the upper and lower edge portions respectively of the lower deck section Ilia and the upper deck section I311. The longitudinal edges of the slot are defined by inwardly disposed edge portions of the side sections I I30 of the deck.

A feed receiving space or section I7 is provided at the upper end of the deck between'transversely spaced vertical walls 56. These vertical walls l6 extend from the partition l8 longitudinally the full length of the inclined deck i3 and are disposed at opposite sides of the slot, or slotted portion 26. Secure and water-tight joints are provided at the lower edges of the wall it and the inclined deck 13 and at the vertically extending higher end portions thereof with the transverse partition 68. Thus, there is provided a longitudinally extending trough of progressively increasing depth. This trough is closed at its upper or feed receiving end by the transverse partition [8 and is left with the slotted area or section 26 I intermediate its ends.

Each side i of the tank extends upwardly a substantial distance, to wit, to an elevation higher than that of the high end of the deck I3 whereby a liquid level may be maintained in the tank which is substantially higher than that of the flowing pool or body undergoing classification in what may be referred to as the primary classifying zone 28 that is located within the space provided by the U-shaped trough construction just referred to. This trough is functionally divided into three regions, zones, or areas disposed in serial arrangement as follows, to wit. into a feed receiving pocket or section ll immediately over the high end of the inclined deck and therefore referred to as the high feed well section; a primary or initial liquid holding or classi fying pool, zone or area 28 immediately over the intermediate section of the inclined deck wherein the slot or slotted portion 28 is located and therefore referred to as the intermediate zone, or area and which may be viewed as a zone lower than I the feed receiving zone; and a sluice-way launder or slimes discharge fiume immediately over the lower section of.the inclined deck, and which is therefore properly ,referred to as the low efliuent launder or liquid discharge section leading from the apparatus. These three sections, zones; or areas are realized and established as follows:

A longitudinally extending and longitudinally positionable U-shaped member 35 is disposed within the trough, the exterior of this member is of such contour and size as to provide a sliding and nesting'fit with the interior of the trough. This longitudinally positionable U-shaped member has at the high end thereof a'vertically and transversely extending wall 2| which extends from the top portion of the member downwardly close to but so as to be vertically spaced from the higher edge portion of the bottom section 21 of said member whereby a feed discharge area or passageway is left or provided at 22 for subable wall of a feed receiving member or feed well I! of which the other walls thereof are provided by the fixed or main transverse partition I3 and by said upper sectionsof the longitudinally ex- I tending trough walls IS. The area which is left open along the lower edge of the longitudinally adjustable transverse positionserves as a horizontally and transversely extending feed discharge area leading from the high feed well to the high shallow end of the succeeding classifying pool or zone 28 and which is located on the opposite side of, and which is adjustable as to length by, the longitudinally adjustable transverse partition 2|.

The opposite longitudinal extremity or deeper section of the classifying zone or pool 28 is defined by a vertically adjustable transversely extending partition 4| of which the uppermost edge a defines an overflow weir past which liquid from the classifying area with the finer solids therein cascades and rushes over into the sluice-way or effluent launder on its way from the apparatus. The vertically positionable weir member 4| is adjustably secured in place in any suitable manner as by bolts Mb extending through slotted portions in the baffle members 15 heretofore referred to. It will here be remarked that the bafile members l serve to deflect solids engaging therewith in their downward path from the classifying zone into the liquid underlying the classifying zone whereby there is avoided a delivery of gravitating solids into the extreme lowermost end of the deep tank section. This baiiie or deflecting member I5 is shown in Fig. 2 as depending from the inclined deck l3 and as extending the full width of the tank, namely, from the longitudinal wall I at one side of the tank to the longitudinal wall I at the other side of the tank.

The adjustable U-shaped member 35 may be viewed as providing a bottom lining section 21 and side wall lining sections 29. As to said longitudinally adjustable member 35 it will be noted that the section 21 just referred to provides a floor portion immediately over and in substantial engagement with the inclined deck and this statement applies regardless as to its particular longitudinal position when disposed for the novel operation of the apparatus. From the lowermost edge of this adjustable fioor portion 21 there depends a transversely ext-ending lip 38 which extends downwardly through the slot of the inclined roof and it will be observed that by changing the longitudinal position of the U-shaped member 35 there is accomplished a corresponding change in the longitudinal dimensions of the slot.

Between this lip 38 and the adjustable vertical gate 23 which is thus provided by the U-shaped member, there is located, comparatively close to the gate 23, an upwardly extending fiow impeding or jump baffle 31 provided for ironing out inequalities of distribution from the feed discharge cpening referred to, whereby a more uniform transverse distribution will be efiected of the liquid-solids pulp as it enters the classifying zone.

It has recently been ascertained that the classification or fractionating of solids as to certain desired groupings of particle-size is attainable by a relatively fast fiow of liquid from the feed receiving pocket into and acrossthe classification pool holding zone during which time only a desired type of solids of relatively heavy character will pass from the pool downwardly through the slot into the underlying portion of the .tank while liquid with the finer solids therein will flow over and past the vertically positionable weir that controls the depth of the classifying pool.

It has also only recently been ascertained that desired classification is primarily a function of the area of the classifying pool or as otherwise expressed of the distance between the vertical plate or wall 2| that is between the feed receiving section I! and the classifying zone 28 on the one hand and the overflow weir a at the opposite end of the classifying zone on the other hand. Normally the U-shaped member 35 is secured in place relative to the trough through the medium of clamping means 35 comprising clamping screws that engage outwardly projecting flange portions disposed at and along the upper edges of the trough wall i6.- Primarily in order that the desired change in surface area or consequent length of flow across the classifying zone may be realized, the U-shaped member 35 and the parts thereof which are movable therewith, have been made so that longitudinal adjustment of all can be made preferably simultaneously. To attain a construction which will readily permit of the desired longitudinal adjustment there have been provided jack screws or lifting devices such as 39, which can be relied upon for forcibly effecting slight vertical movement of the U-shaped member relative to the U-shaped trough in which it is located. This vertical movement is sufficient to loosen-any sand or other solids matter which might otherwise tend to bind the adjustable U- shaped member in the position occupied therefor and to lift it from any sands which may have become lodged in the underside thereof on the deck immediately thereunder. There are also provided longitudinal forcing and adjusting means such as screws 34 having right and left hand threaded sections at opposite ends thereof of which one of the sections has threaded engagement with the nut or socket member 32 fixed to the main side wall 16 of the trough, while the other end has engagement with a nut or socket member 33 that is secured to a flange or wall portion of the U-shaped member 35. Of course, after longitudinal adjustment has been effected the jack screws 39 or equivalent operating device should be positioned whereby the U-shaped member 35 wil1-assume proper operative position therefor with respect to the underlying sections of the U-shaped member and whereby the screws of the clamping means 35 can be relied upon for securing the member 35 in its longitudinally adjusted position.

The vertical positioning of the weir member can be relied upon in obtaining the desired settling conditions within the apparatus as a whole and thereby indirectly attaining the type of classification or fractionation desired. This adjustment, however, is only secondary to that which is accomplished by the longitudinal adjustment of the U-shaped member and the consequent and direct adjustment in a longitudinal direction of the partition 2| between the feed receiving well H on the one hand and the classifying area or zone on the other. It will also be' noted that the transverse partition 2| has associated therewith along the lower edge portion thereof the vertically adjustable gate 23 which can be relied upon for regulating or controlling to a certain extent the quantity of feed passing from the feed receiving chamber into the classifying zone. The gate 23 is securedby bolts 24.

Fig. 4 of the apparatus can now well be referred to as illustrative of the settling or sedimenting conditions existing within the classifier during the normal operation thereof. The incoming pulp is first delivered into the feed receiving pocket ll, rushes in a longitudinal direction therefrom to the adjustable feed passageway 22 into the classification zone 28. In this zone the baffle 31 provides a flow distributing wall on the opposite side of which there progressively form and collect bodies of solids that assume a shape or contour much after the order of the fine dots used on the drawings. They deposit longitudinally behind and ahead of the bafile 31. As the liquid flows through the classification zone, due to the controlled condltions therein, the larger and heavier solids sought to be separated pass downwardly in more or less sheet fiormation through the slotted area 26 left between the depending flange 38 and the overflow Weir. The pulp in the classification pool 28 has a relatively high density-substaritially higher than that of the liquid content in the underlying region of the tank, with the result that in the normal operation of the apparatus, the height of the level of the liquid Within the tank is at an elevation indicated by B of Fig. 4 which is relatively high as compared with the general surface level A of the liquid in the classification pool 28. The general height or elevation of liquid or pulp in the feed receiving chamber I1 is sufliciently high as compared with that in the classifying pool so that a relatively high velocity of flow will at all times exist across the classifying pool 28.

At the most there is relatively little classification of solids within the raking compartment. The operation of the apparatus in the raking compartment is primarily as a solids removing and dewatering instrumentality. There may be a slight upfiow of liquid from the raking compartment through the slot 26 upwardlyinto the classification zone 28 consequent to any supply of liquid which may be applied at the high end of the raking section for the purpose of further washing the sand and also consequent to any accumulation of water in the raking section incident to the dewatering operation performed therein. Because of the fact a relatively large part and in fact primarily the entire classifying operation is realized within and performed by the high flows of liquid as it passes through the horizontally adjustable classification pool 23; this is sometimes herein referred to as the primary or initial body of liquid, whereas the liquid of the tank is herein referred to as a secondary body of liquid.

In operating the classifier of the present invention it will be understood that the slidable trough 35 defined by the bottom member 21 and side walls 29 will be positioned by means of screws 34 at a suitable point so that the slot 25, actually measured by the distance from the baffle l to the lip 38, will be of a desired size or width. The vertically sliding gate 23 is also adjusted to provide a proper size or'height for the discharge opening 22 of the feed well or feed launder ll. The feed of suspended solids to be classified is continuouslyintroduce'i into the feed receiving section or launder I! by any suitable piping arrangement not shown, a suitable head of liquid being maintained within the launder. The feed suspension then flows through the opening 22 and across the jump baiile 31 in a relatively thin sheet, an object of the narrow opening 22 andthe jump baflle 31 being to impart an even spread to or distribution of the feed. The suspension will then flow down the inclined sluice-way or trough defined between the longitudinally adjustable walls 29 and the fixed trough side wall I6 and pass through the slot 26 filling the lower part of the tank to form what is known as the bath. Since no opening for the escape of liquid is provided in the tank, the same will soon become filled and the continued feed of suspension will form a relatively small pool confined by the dam or weir Ma, the upwardly extending just referred to side walls and the end walls of the slidable trough or U-shaped member 35 extending back as far as the jump bafile 31. The continued feed of suspension will, of course, cause liquid to overflow the dam or weir Ma from the pool just. referred to. The pool thus formed being relatively quite small compared to the volume or rate of feed, the suspension will rush through the pool at a relatively rapid rate. Only the largest and heaviest particles will drop out of this rush of suspension and passthrough the slot 26 down into the classifier bath, all other particles passing rapidly with the overflow across the weir Ma where the material will flow down the deck section l3a and off the discharge lip M to any suit- .in which it functions to produce a clean and coarse sand product and overflow all that is possible of the fine and intermediate sized particles.

The pool as can be seen is maintained bya weir or dam on one side and a sloping deck on the other. Therefore, since the point of intersection of the pool surface with the sloping deck can be varied by varying the height of the weir, the area can be changedby the adjustment of the weir, and this is the main adjustment for the separation.

Besides restricting the area lengthwise, the

area across the machine can also be restricted; in

other words, the classification pool can be narrower than the width of the main tank or even that of the raking blades. The slot must be small enough to prevent mixing of the material in the classification pool with the communicating large body of water in the raking or discharging compartment; in other words, there probably must be restriction at this point, but the degree of restriction does not seem to effect the general result. Narrowing the slot has given somewhat better classification, probably due to preventing such intermixing.

In this figure the apparatus will be assumed to be in continuous operation with the blades 8 being reciprocated in known manner to convey settled sands up to the inclined bottom of floor 5. Appropriate clearance is provided between the top deck I8 and the blade mechanism when in its uppermost position, a continuing supply of liquid containing solids of different sizes being introduced into the feed launder II. The suspension escapes from the launder through the opening 22 and rushes rapidly over the Jump baflie 31 which assistsin spreading the fiow into a thin and even sheet. This flow of solids and liquids into the pool established by the dam or weir member 4| causes a' rapid current through the pool which overflows the weir Ma and continues on down the deck section l3a. The classifier tank is, of course, filled with water. Since the rear end of the tank is closed, as the reciprocating rakes or raking blades move rearwardly or downwardly, the compression caused thereby produces a pulsation upward through the slot 26, and return motion of the blades produces an opposite pulsation. Thus a jigging action is produced in or through the slot, since the water has no other escape on the rearward stroke of the blades. They act like a plunger as they approach and depart from the lower vertical and wall 6 of the tank. The tank water level will have achieved somewhat of a super elevation over the level in the pool, the latter being indicated by the broken line A and the former by the broken line B. This condition prevails because of the higher specific gravity of the material in the pool over that of the liquid bath in the classifier tank. Since there is no outlet for liquid in the tank I manifestly only a small part of the liquid entering the superposed pool passes into the tank and the bulk of it will overflow the weir 41a. Because of the rapid flow through this pool only those particles will drop out of the flow whose size and weight is suflicient'to render them quickly settleable. Thus in this pool there is a very quick segregation or division of the fractions and only the very quickest settling materials will have an opportunity to drop out of the rapid flow. In other words, in this liquid flow, the particles of different sizes will naturally have different trational water may be continuously supplied to the tank bath in order to cause some upfiow through jectories from the point where they pass over the Jump bafiie 31 to the w eir Ma. All of those particles having a trajectory which clears the weir 4 la will naturally pass oiT with the overflow. On the other hand, those whose trajectory is more pronounced, causing them to impinge upon the weir providing member M and the baffie 15, will drop through the slot 26 and untimately settle within the liquid in the classifier tank to the bottom thereof.

In actual practice, there is generally built up I a bank of settled sands (indicated by dots on the drawings in Fig. 4) extending from the top of the jump bafiie 37 down to the free end of the member 21. When this condition is established it is found that the sands thereafter, even though settling upon the established bank, are carried by the rush of the current down to the lip 13 and fiow in sheet formation through the slot 28 into the tank.

Thus, by means of the present classifier apparatus, there is accomplished what may be termed a quick division or segregation of the feed suspension wherein only the heaviest, and therefore quickest settling particles are ejected from a rapidly flowing stream and collected and settled in the main classifier tank from whence they are conveyed as a relatively clean sand product or coarse material.

In a further modification of the invention addithe slot 28. This may be conveniently accomplished by means of a suitable liquid supply element which sprays water upon the sands at about the point where they emerge from the liquid in the classifier tank. To this end there is shown in Fig. 1 a pipe'or conduit 42 extending transversely through the classifier tank toward the rear thereof and somewhat above the normal liquid level. The pipe 42 is provided with one or more downwardly directed spray nozzles 43. Water under pressure is supplied through pipe 42 and ejected through nozzles 43 in the form of a spray directed upon the sands at about the point where they emerge from the liquid in the tank. As water is continued to be supplied through the conduit 42, since there is no other exit, it will naturally cause an up-current of water through the slot 26 and into'the superposed pool, ultimately passing out over the weir 4Ia. In some operations this upflow will function to carry up undesirable small and intermediate sized particles that may have strayed downwardly through the slot and may also assist, by dilution, the segregation taking place within the pool. In this embodiment the bafiie l5 and lip 38 serve to direct the upfiow through the slot and tend to establish a uniform flow.

In either form of the invention it will, ofcourse, be understood that the invention is not limited to the precise details of construction shown and described herein. In other words, the essence of the invention resides in providing a classifier apparatus which has means for conveying settled sands upwardly along an inclined bottom, with means in hydraulic communication with the classifier tank for establishing and maintaining a relatively small classification pool so that the feed suspension will pass rapidly through the pool and while so doing undergoes a quick and sharp segregation or fractionation, dropping into the tank only particles of a desired relatively coarse size as one fraction, with substantially all J of the finer and intermediate particles as another fraction overflowing from the pool and not being permitted to enter the tank at all. Thus the invention contemplates providing a classifier tank the lower end of which is decked over, the deck having means associated with it for the establishment 'of a relatively small classification pool. It then contemplates the provision of a slot or slotted opening through the deck reaching to the pool whereby quickly settling material may drop outof the pool, through the slot and into the classifier tank. It is also contemplated that there be means for varying the area of the pool (or the rate of overflow therefrom) in 7 order that adequate control may be exercised over and passes directly to overflow from the unitary classification pool that is outside of the main tank.

Much stress has been laid on the extent of the classifying pool so that it should be stated that in connection with a classifier that was six feet wide, a pool was used that varied from 17 inches in length to 28 inches and a slotwas used whose length was 3 feet but whose width varied from 4 to 12 inches. This classifier was used in classifying limestone, and was fed at rates from 55 tons of solids per hour up to over .100 tons per hour. In liquid measure, the feed amounted to about 300 gallons of liquid per minute.

The separation ranged from 6 to 14 mesh.

I claim:

1. In a classifying apparatus in operative combination. a sloping classifying basin adapted for receptio; of feed of solids in. suspension at an upstream entrance and for the discharge of slimes from the downstream exit, having a sloping deck over which there is an unobstructed classifying zone progressively increasing in depth and having an opening therethrough leading from th cross-stream overflow member upstanding from the deck and disposed downstream of the opening including vertically positionable weir means over which must flow substantially all of the liquid of the original feed having in suspension certain remaining smaller sized solids leaving the apparatus as slimes; a tank in hydraulic communication with the basin through the medium of said opening and having liquid-confining walls extending upwardly to elevations higher than that of said vertically positionable weir means whereby the tank is adapted for retaining liquid at a level that can rise higher than the elevation of said weir means; and means for removing sands from the tank.

2. An apparatus as defined in and by claim 1 in which the curtain baflie has a vertically adjustable lower portion whereby the flow space below the same can be regulated as to its height.

3. An apparatus as defined in and by claim 1 in which the'basin adapted for reception of solids in suspension is in the form of a sloping trough of which the bottom provides the deck over which there is th classifying zone that progressively increases in depth; in which the tank provided for receiving the sands has an inclined floor section sloping in the same general direction as that of the deck of the sloping trough; in which the means for removing the sands from the tank is a reciprocating rake structure operatively disposed over the inclined floor section of the tank; and in which there is a deflector plate depending from the trough deck in the immediate region of the downstream portion of the sand discharge opening and over a region in which rake structure operates.

4. An apparatus as defined in and by claim 1 in which there is a deflector balile extending downwardly from the bottom of the basin in the immediate region of the downstream edge of the sands discharge opening, and in which the means for removing sands from the tank embodies a sands conveying structure operatively disposed with respect to the tank floor and functionable for transferring sands to emergence from the region near the lower portion of said deflector baflle.

5. A classifying unit for dividing a flow-stream of liquid-solids mixture into slimes and sands and comprising in operativ combination a trough having a sloping bottom; meansproviding as an upstream member a feed-receiving well disposed at the high section of the sloping bottom and embodying a curtain bafile defining the top of a distributing flow passage leading downstream from the lowerportion of the feed-receiving well; a cross-stream jump bafile downstream from the feed-receiving well and providing an upper edge over which the flowing liquid-solids mixture trajectorily passes after leaving said sands distributing flow passage; which said bottom provides a substantial extent of floor area sloping downwardly and downstream from said jump baflle and has therethrough a sands discharge slot extending transversely of the trough and disposed at the low section of the trough bottom; a verti- 1 Cally-positionable weir extending upwardly from said bottom and disposed downstream with respect to said sands discharge slot and over which weir substantially all of the liquid of the mixture and certain solids thereof which have been classified as to maximum size rang must pass from the unit as slimes, the interior of the trough being unobstructed within the liquid-holding space between the jump balile and the vertically-positionable weir whereby there can follow a horizontal flow of surface liquid from the jump batlle region to and over the positionable weir; a tank having a liquid-tight connection with said trough but disposed so as to have constant hydraulic communication therewith through said sands discharge slot and constructed so as to comprise rising marginal walls reaching to elevations substantially higher than that of the overflow elevation of the vertically-positionable weir for thereby retaining liquid so that the level of such retained liquid can rise substantially higher than that of the slimes when overflowing said weir; and means for removing as sands from said tank th larger solids which have been passed'thereinto through the said sands discharge passageway.

6. An apparatus as defined in and by claim 5 in which the cross-stream jump baflie is longitudinally adjustable with respect to the downwardly sloping bottom section of the trough.

7. An apparatus as defined in and by claim 5 in which the cross-stream jump baffle and a movable section of the bottom of the trough are connected and are simultaneously adjustable lengthwise of the trough and in which said movable section has one edg arranged to overlie an edge of said sands-discharge slot in certain positions of adjustment whereby the area of the slot is adjusted according to the adjustment of the jump baflie.

8. An apparatus as defined in and by claim 5 according to which'th'e curtain baflle has a vertically adjustable lower member; the cross-stream of solids in suspension at the shallow upstream entrance end thereof, provided with a crossstream slot at a lower portion thereof, for the gravitational discharge of coarse solids as sands outflowing slimes from the upper portion of the deep end section thereof, and having a deck embodying a sloping floor section that is inclined downwardl in the direction of fiow and that extends horizontally in cross-stream direction; a cross-stream end member rising at the deep end of the trough and provided atthe top thereof with a slimes overflow weir; means providing a feedwell at the shallow end of the trough and embodying a cross-stream member providing a curtain baflie below which a flow passage leads downstream from the well; a flow distributing means embodying a cross-stream jump bafiie positionable along said sloping floor section and having a horizontally-extending upper edge providing a submerged distributing member disposed downstream from the curtain baflle but upstream from the sands discharge slot, the interior of the trough being unobstructed within the liquidholding space between the jump baiiie and the slimes overflow weir whereby there can follow a horizontal flow of surface liquid from the jump bafiie region to and over the slimes overflow weir; means for holding the jump baflle in its various adjusted positions with respect to said sloping floor section; a tank in hydraulic communication with the trough through the medium of said slot and having marginal walls rising to elevations substantially higher than that of the slimes overflow weir thereby adapting the tank for retaining liquid up to a level which may rise substantially higher than the elevation of the slimes overflow weir; and means for removing sands from the tank.

10. An apparatus for classifying solids in suspension comprising in operative combination a sloping classifying trough providing a high upstream end and a deep downstream and adapted for the reception of feed of solids in suspension at the upstream end thereof, provided with a crossstream slot at a lower portion thereof for the gravitational discharge of coarse solids as sands from the trough, and from which there is a discharge -of outflowing slimes from an upper portion of the deep downstream end thereof, the bottom of which trough embodies a fixed deck section sloping downwardly in the direction of flow, extending horizontally in cross-stream direction and over which there is a classifying zone that progressively increases in depth and also a movable deck section positionable with respect to said fixed deck section so as to adjustably define one of the long edges of the slot and thereby the effective area of the slot opening; a cross-stream end member rising within the trough from a region in the vicinity of the deep end of the deck and provided along the top thereof with a slimes overflow weir functionally disposed downstream with respect to the sands discharge slot; means providing a feedwell at the shallow end of the trough and embodying a cross-stream member providing a curtain battle below which a flow-passage leads downstream from the well; flow impeding and distributing means disposed downstream from the curtain bafile but upstream from the sands discharge slot; a liquid-holding tank in hydraulic communication with the trough through the medium of said slot and having rising liquid-confining structure extending to elevation higher than said slimes overflow weir and thereby adapting the tank for retaining liquid up to a level which may rise substantially higher than the elevation of the slimes overflow weir; and m:ans for removing sands from the tank, the upper interior portion of the classifying zone being left unobstructed whereby the classifying pool normally maintained therein has a continuous horizontal flat surface extending from the shallow upstream section of the trough to the slimes overflow weir.

THEODORE B. COUNSEIMAN.

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