US2189418A - Material classifier - Google Patents

Description

Feb. 6, 1940. J, H, v, FINN Y. 2,189,418

MATERIAL OLASSIFIER Filed Oct. 18, 1957 2 Sheets-Sheet 1 (JbHN HIZ ENNEY Gummy.

Sheets-Sheet 2 J. H. v. FINNEY MATERIAL CLASSIFIER Filed 001;.- 18, 1937 Feb. 6 1940.

No NR Q Q so EVA/9W JOHN H IZF /N EY Patented Feb. 6, 1940 i s I UNITED STATES PATENT OFFICE MATERIAL CLASSIFIEB John H. V. Finney, Denver, Colo., assignor to Homer 0. Hirsch, El Paso, Tex.

. Application October 18, 1937, Serial ,No. 169,586

6 Claims. (01. 209-18) The present invention is concerned generally size, so that only the fines will be discharged with material classifiers such as are used chiefly with the fine traction and only the oversize matein handling ores during metallurgical operations, rial will be discharged with the oversize or coarse and especially with classifiers of the type wherein fraction. It is also preferable that a classifier the solid particles are suspended in a body of be capable of adjustment so that the separation 5 liquid, usually water, from which the particles can be made at any particular particle size asmay settle out according to size and density. It is be desired according to the further treatment to customary to obtain the desired classification of be given or according to the ore being handled. the particles by allowing only a portion of the These operating characteristics have not been 10 solid particles to settle out, this settled portion found to a satisfactory degree in prior devices; 10

i being then removed from the liquid and the finer and it has been a shortcoming of prior devices particles left in suspension. that, although they may operate satisfactorily as The uses to which classifiers may be put are to one characteristic, all these characteristics varied and include other uses than those involved are not found in any one machine. For example,

16 in ore dressing or metallurgical operations, so in the early type mechanical classifiers using a that although I describe my invention and the drag conveyor to remove the oversize, separation advantages thereof in connection with handling between the fines and oversize is generally very ore, it will be realized that I am not necessarily poor, since a large percentage of the fines are limited thereto. The most common use of mefound lightly cemented or plastered on to the 20 chanical classifiers is with grinding mills oplarge particles, and in this type of classifier the erating to crush or reduce ores. Usually the fines settle and are removed with the coarse par practice is to connect the classifier in a closed ticles, since there is no agitation or washing accircuit with the mill in such a way that the mill tion that frees the fines from the larger pardischarge flows to the classifier where the solid ticles to which they are attached.

particles are divided into a coarse or oversize This condition has been materially improved 5 fraction, which is returned to the mill for reby the introduction of classifiers using mechangrinding, and a fine fraction, which is removed ical rakes having a reciprocal motion for conveyfrom the closed circuit and taken to a point of ing the settled particles out of the classifier. further treatment. The oversize which is re- The reciprocating rakes introduce sufilcient agiturned to the mill is termed the circulating load tation into the liquid to wash the fine particles 30 and, in order to keep the mill operating under off the settled coarse particles, and the separaconditions of high efliciency, amounts to several tion is, as a result, much cleaner. However, the times the weight of fin'es which represents the agitation developed depends upon the speed of recovery from the mill. Thus, it has become a the rakes and when the rakes operate too rapidly common practice for the circulating load often the overflow carries with it an undesirable per- 35 .to be twelve to sixteen or even more times the centage of oversize particles. Of course, the caamount ground and recovered as fines; that is, pacity of the classifier, as measured by the quanfor every ton of sufiiciently ground material retity of coarse output, is determined by the speed covered from the mill, there are twelve to sixteen of the rakes; and with the high circulating loads 40 tons of insufllciently ground material flowing in now coming into general use it has been neces- 40 the circuit from the mill to the classifier and back sary to design rakes with deep blades and long to the mill for regrinding. strokes, which, while they increase the capacity For best efficiency in further treatment of the of the classifier, also introduce excessive agitag'round material separated as fines by the classition and the problem of keeping the overflow her, it is desirable that the ratio of fine solids to 4 free of oversize material is becoming increas- 45 liquid in the classifier output be kept substaningly acute. It will be realized that in this type tially constant within certain definite. limits. classifier a sharp separation producing a clean Also, the classifier coarse product returned to the rake product ,or oversize is brought about by a 'mill tor further grinding should contain a minimaximum of agitation, while a clean overflow or 5 mum of liquid to obtain the best grinding ef-' fines product requires a minimum of agitation,

ficiency. These conditions establish certain so that with the rake construction it is impossible definite requirements for the nature of the classito operate under conditions which produce both fier products. It is obvious that a satisfactory products in the most desirable condition. classifier should be capable of making a clean, Other mechanical classifiers use a screw consharp separation between the fines and the overveyor for removing the oversize particles from 55 the classifier tank. The screw conveyor construction has the advantage of providing large place is also affected to some extent by the.

amount of agitation in the liquid contained within the classifier, since separation is determined primarily by settling effects, and agitation infiuences the rate of settlingand often prevents proper settlimg from taking' place. reason that undue agitation not only causes a relatively large amount of coarse material to pass out with the fines, but also has a tendency to increase the particle size in the fines.

However, the primary factor in prior classifiers determining the size of separation between the fine and coarse particles is the velocity of flow through, the classifier tank. For any given tank, the velocity of fioW depends upon the quantity of water added to the classifier with the incoming particles and the depth of liquid in the tank, since the deeperthe liquid the lower the rate of flow. Since particle separation depends primarily upon l undered settling, the' higher the velocity the greater the hindrance to settling and consequently the larger the particle size carried out in the overflow. In the operation of these various known types of classifiers, the factors of washing or agitation, control of the size separation, coarse product capacity, and the density of fines in the overflow are all interdependent, since they are all affected by the same features of construction and consequently one cannot be varied without adversely affecting another of these qualities. The necessary result has been that in order to obtain the best operating conditions it has been necessary to make a compromise between the speed of the conveyor elements, the slope of tank bottom, the amount of water added, and whether the water was added with the feed or as a spray on the solids after they had been removed from the body of liquid within the tank.

It has thus become a general object of my invention to provide a mechanical classifier in which the factors of agitation, size of separation, capacity, and density of overflow are all independent of each other and are functions of separate and independent features of construction, so that the classifier is entirely flexible and may be adjusted to meet any condition of ore, size or quantity of product, and rate of feed.

It is also an object of my invention to provide a mechanical separator in which the size of separation may be selected at any point and is always clean and sharp so that all the fines and only fines are carried out in the overflow from the classifier.

Another object of my invention is to provide a classifier having a variable capacity in which the rate of oversize discharge can be varied to suit either changes in the rate of feed or changes in the percentage of oversize particles contained in a constant feed, and in which these changes in discharge rate may be effected without in any Way changing the other operating conditions within the classifier.

Another object of my invention is to provide a mechanical classifier in which all of the operating factors described are independently variable, and one portion of the classifier may be adjusted It is for this J to alter one factor without affecting the operation of the machine as to other characteristics, and thus there can be .obtained a maximum efficiency of the classifier for any conditions under which it may be used.

These objects of my invention have been attained in a classifier in which I provide a tank having an inclined bed and adapted to contain a body of liquid and the solid particles that are to be classified, an inlet means for admitting to the tank a constant flow of liquid and suspended particles, and the several independent means for conveying from the tank the oversize particles, for discharging the liquid and the suspended fine particles, for determining the particle size in the overflow, and for washing the oversize particles to free them of any fines. The conveying means for removing the oversize particles may take any conventional form, but is preferably a screw conveyor because of the large capacity of this type of construction'with minimum agitation, and above the conveyor is placed liquid agitating means which may conveniently take the form of a rotatable paddle wheel adapted to agitate a portion of the liquid above the conveyor. Interposed between the agitating means and the conveyor is preferably a baffle, so that the currents within the liquid are directed around and along the raking means in order to give a continued washing effect over the coarse particles and free them from any fines which they may carry. At the liquid outlet, the liquid and suspended fines pass through one or more vertically extending sorting columns of adjustable cross-section. The crosssection of the sorting column determines the outlet velocity of the liquid, and consequently determines the size of the particles which will be carried by the discharged liquid which overflows a conventional weir. forming the sorting column or columns, at the top of which are placed one or more weirs, includes one or more members which extend from a point above the liquid level in the tank to a point well below the liquid level so that all of the liquid leaving the tank is forced to pass through the sorting column or columns.

How the above as well as other objects and advantages of my invention are attained will be more easily understood from reference to the following specification and the annexed drawings, in which:

Fig. 1 is a vertical, longitudinal section through a mechanical classifier constructed according to my invention;

Fig. 2 is a vertical, transverse section on line 22 of Fig. 1;

Fig. 3 is a plan view of the classifier; and

Figs. 4 and 5 are fragmentary vertical sections showing variational constructions at the liquid outlet.

The classifier illustrated in the drawings has a body or tank generally indicated at In which .is adapted to contain a body of water or other liquid holding in suspension the solid particles which are to be classified. The side walls of one end wall ll of the tank are vertical, or generally so, and the bottom or bed I2 is inclined longitudinally of the tank, the bed sloping uniformly from the low end of the tank to a point at-its upper end which is normally above and beyond the liquid level maintained in the tank. The inlet meansfor the tank preferably, although not necessarily, ificludes a short transverse launder I5 into which the incoming fluid and suspended solids are emptied from inlet launder The wall means for I6 connected to agrinding mill or other source.

Launder 15 has one or more openings IT in the sides, through which the incoming fluid is deliveredinto the tank.

The coarse particles settle out of the body of liquid in the tank onto inclined bed l2 and suitable conveying means are provided to convey the settled coarse particles out of the body of liquid and to a point of discharge from the tank. Although other suitable types of raking or conveying means can be used, it is preferred that there be provided one or more helical ribbon or screw conveyors 20 that are rotatably mounted at their upper and lower ends respectively by bearings 2| and 22. On the upper end of each conveyor shaft 20 there is secured a bevel gear 23 which meshes with another bevel gear 24 attached to driveshaft 25 that is driven by some suitable means, such as drive pulley 26. Only one each of gears 23 and 24 are shown as the driving arrangement for each shaft is the same, and it will be understood that two similar gears are provided for each conveyorused. The bevel gears and drive shaft are enclosed within housing 21 which is mounted on and between extensions of the vertical side walls'of tank Ill. The

--two conveyors are preferably separated by a vertical'division plate 28, as shown in Fig. 2, so that they form in effect two separate raking means, and launder opening I! is placed directly above the division plate so that liquid and suspended solids will be delivered equally at both sides of plate 28, although it will be understood that individual openings in the launder wall directly above each conveyor 20 could also be used. When two screw conveyors 20 are used as shown, it is preferred that shaft 25 rotate in sucha direction that the two conveyors move of screws 20 and before being-discharged from the tank at the upper end of the bed. After leaving bed H, the oversize material falls down chute 28 into a hopper or onto a conveyor or like means for return to the mill.

Each bearing 22 is preferably a sleeve mounted on a fixed post 20 suitably supported in end wall ll of the tank. Lubrication of the bearing is effected by means of pipe 3| that extends longitudinally of post 30 and is connected to oil reservoir 3la which is located at a point higher than the liquid level in the tank. The pressure head thus obtained forces oil to flow through pipe line 3| to the upper end of bearing 22" and then downwardly over the bearing surfaces. The lubrication pressure is sufllcient to keep water out of the bearing which, if it enters, carries with it abrasive particles that cause excessively rapid wear of the bearing surfaces, but by keeping the oil pressure higher than the water pressure, entry of abrasive particles into the bearing is prevented. The result is a greater increase in the useful life of the submerged bearings 22.

Liquid agitating means is provided in order to pendently of any motion of the conveying means.

Although this agitator may take other forms, it

on shaft 33 which is rotatably mounted in bearings 34 on the side walls of tank l0! At one end of shaft 33 there is attached sprocket wheel 36 which is driven by chain 31 from a second sprocket attached to drive shaft 25. Paddle wheel 32 is located above the conveyor means in a position to agitate. a portion of the body of liquid normally contained within tank Ill, and it is preferable, although not necessary, that there be provided baiile means in the form of plate 40, which is mounted on partition 28 and the sidewalls of the tank, in order to direct the currents in the liquid body around and along conveyors 20. It will be seen from Fig. 1 that when paddle wheel 32 is rotated in a clockwise direction, that the currents above baiile 40 move toward the left or the deep end of the tank, and that as a consequence there are currents beneath baffle 40 whichmove in the opposite direction or toward the shallow end of the tank, that is,in the same direction as the .conveying movement which moves the oversize particles along inclined bed I2. These latter currents produce a washing motion which frees the coarse particles of any attached fine particles and yet accomplishes this washing action without undue agitation that interferes with the normal settling of the coarse particles. Plate 40 may be slidably mounted on its supporting angles 4| for adjustment to modify the path of currents flowing around it. e

The outlet for the discharged liquid and fines carried in suspension therein is at the deep end of the tank. At this point the top edge of the end wall H of the tank forms an overflow weir 45 over which the liquid flows into outlet launder 46 which extends transversely of tank ID. A discharge pipe 41 is connected to the launder to take the discharged liquid to any desired place for further treatment. A second discharge launder 50 is also provided and is formed by the space between vertically extending plates 5| and 52 which are connected at their lower ends by a bottom member 53. Launder 50 extends transversely across the entire width of tank l0 and is provided with end walls which preferably lie against the side walls of the tank.

The top edge of plate 5| also forms an overflow weir, the fluid that passes over this weir falling into launder 5B and being discharged into launder 46 through a short connecting pipe 54 that is attached to plate 5| and has a sliding fit in an opening in end plate ll. Launder 50 .is preferably movably-mounted upon the side walls of tank It) and is provided with end brackets which rest upon the flanges of the angles 'at the top of the tank walls. The tank angle flanges are slotted as at 55 in Fig. 3, to receive bolts 56 passing through the brackets on the movable launder, so that sliding movement of the launder along theangle flange is permitted when bolts 56 are loosened. By tightening up bolts 56, the launder can be locked in any position to adjust the space between end wall H and plate 5!.

Wall II and plate 5|, together with the side walls of the tank, form vertically extending plate means which define between them a vertically extending space 58 that acts as a sorting column at the top of which are the overflow weirs 45 and 5|. The upward velocity of the liquid flowing vertically through sorting column 58 determines the size of the particle which is carried over the weirs. Plate 52 extends from a point above the normal liquid levelto a point 7 below that liquid level to prevent liquid from reaching and overflowing the weirs except by passing through sorting column 58. Plate 52 is also interposed between the agitating means 32 and sorting column 58 in order that the zone of agitation may be separated from the relatively quiet zone of sorting incolumn 58.

Many variations in the form and arrangement of the parts constituting the liquid outlet means may be made without departing from the.

spirit of my invention. For example, only one weir may be used. This may be accomplished by extending end wall ll up above the liquid level so that only weir 5| overflowing into movable launder 50 is utilized as an .outlet. The same results may be obtained by combining plates 52 and 53 into a single member 50, as illustrated in Fig. 4.. With this latter arrangement, plate 60 performs the functions of plate 5| in defining the sorting column and the functions of plate 52 in guiding liquid into the sorting column and separating the sorting zone from the zone of agitation. Plate 60 is adjustably mounted on the tank sides for movement toward or away from wall II to vary the area of the sorting column as described in connection with launder 50.

With either of'these single weir arrangements there is used only one discharge launder, either launder 46 or launder 50.

Just as more than one weir and more than one outflow launder may be used, so may there be more than one sorting column. A construction of this nature is shown in Fig. 5 in which the end wall I l of the tank extends above the water level and a single U-shaped launder 6| is provided. The vertical side walls of launder 6| form two overflow weirs 62 and 63 over which the discharging liquid flows into launder 8|. Launder 6| is connected directly to discharge pipe 41' by means of pipe 54 provided with a sliding fit where it passes through wall ll. With the construction of Fig. 5, one sorting column is formed in the space between vertical wall 62 of the launder and end plate H, and a second sorting column is forined in the space between vertical wall 63 and plate 60. Both launder SI and plate 60 are movably mounted on the tank walls to permit suitable adjustment of the area of both sorting columns, plate 60 requiring twice the range of movement that launder 6| has.

From the various modifications of the liquid outlet means described, it will be seen that the broad aspect of my invention includes any arrangement of spaced, vertically extending wall means defining one or more vertically extending sorting columns with weir means at the top of each sorting column over which the liquid flows into one or more discharge launders. The Wall means includes a member so arranged, by extending above and below the liquid level, that the wall means deflects all liquid discharged from the tank through the one or more sorting columns and thus prevent unregulated flow into the discharge launders from the main body of water beyond the sorting columns. This latter flow would, of course, not be controllable as to velocity and consequently would not subject theparticles to the same sorting action as is found in the sorting columns 58.

The level of liquid and suspended solids in the tank is defined by the weirs and the depth of liquid is maintained approximately as indicated in the drawings. The feed consisting of solid particles of a wide range of sizes suspended in liquid, usually water, enters the classifier ,parts.

through launders l5 and I6 and is delivered into the tank through outlet I! which is preferably midway between the sides of the tank.

The agitation created by paddle wheel 32 causes the liquid in the tank to flow around baffle plate as indicated by the arrows, the fiow above the plate being toward the liquid outlet or overflow end of the tank and the fiow below the baffle being in the direction toward the solids discharge end of the tank. Consequently, these agitation currents rise at the upper end of the baflle at a point directly below the feed inlet. A primary separation of particles takes place in this rising stream of liquid, the largest particles settling down through this stream into the conveyor screws, while the fine and intermediate sizes are caught in the localized agitation flow which breaks up all of the flocks and frees the coarse particles of adhering fines.

Liquid leaving the classifier tank rises vertically in the sorting column and overflows at weirs and 5| into the discharge pipe. This outgoing flow carries fine and intermediate particles into the sorting column. At this point the intermediate sizes fall back in the slowly rising current and settle to the bottom of the classifier along the conveyor screws, while the fines are carried upwardly and out of the classifier with the overflowing liquid. The conveyors pick up all the particles settling out of the liquid at the sorting column or around the agitator or underneath the feed launder and move these coarse and intermediate particles up the inclined tank bottom to the end of bed l2, where they are discharged from the classifier. These coarse particles are dewatered by gravity drainage as they are moved up that portion of bed l2 which is above the liquid level. Also, they may be washed by overhead water sprays of any conventional type.

From the foregoing description of the arrangement and construction of the various parts of the classifier, it will be understood that in operation the various functions of the parts are entirely separate and independent of each other and consequently may be varied without in any way affecting a change in the functions of other If the total quantity of feed through launder I 6 is increased or if the proportion of oversize entering through launder l6 at a constant rate of feed is increased, a greater capacity for handling the oversize particles is arrived at by increasing the speed of revolution of screw conveyors 20 so that they more rapidly move the separated coarse particles along inclined bed I2 and discharge them from the machine. By increasing this rate of oversize particles, the pulp level in the tank may be reduced or kept at any desired point and the change in discharge rate does not bring about an undesirable increase in the amount of agitation in the liquid body.

Agitation of the liquid is effected independently by paddle wheeel 32 and the rate or amount of agitation may be increased independently of any other factor by driving sprocket 36 from a source independent of shaft 25. Since the washing action desired to clean the coarse of any adhering fine particles should increase in intensity approximately according to an increase in the rate of feed of coarse particles and subsequent discharge along bed l2, it is satisfactory under normal circumstances to drive shaft 33 from drive shaft 25.

The vertical velocity through sorting column or columns 58 is the controlling velocity in determining the size of particles carried by the overflow liquid. A sharp separation of fine and column, fall to the bottom of the tank and are moved along bed I2 by the raking means, while particles which settle more slowly are carried up- 'ardiy by the liquid stream and over the weirs into the discharge launders. The maximum particle size of the fines, that is, the size of particles at which separation. takes place, is consequently determined by the vertical velocity in the sorting columns, and this in turn depends upon the crosssectional area of the sorting columns. It will be clear that by moving plate 5| toward or away from end plate I I, the area of the column is varied accordingly. At any constant rate of liquid inflow through launder IS, the sorting column velocity will be increased by bringing plate 5| closer to the end plate and this will increase the size of the fine particles carried out. A wider separation between the plates will increase the area of the sorting column, lower the liquid velocity, and decrease the size of the separated fines. It will also be understood that variations in the rate of feed through launder 15 may be compensated for by changing the cross-sectional area of sorting column 58 so that a substantially constant velocity 'through the column and separation size is obtained. In this way the size of separation is entirely independent of the rate of feed to the classifier or the velocity of flow through other parts of the classifier.

Agitating means 32 is preferably placed intermediate inlet means I5 and the fluid outlet means so that all of the suspended solids are carried past the agitator and subjected to the washing action of the agitation currents. The agitating means is also placed at some point between the liquid outlet means at the deep end of the tank and the coarse particle discharge at the .upperend of the inclined bed so that the fine particles washed free from the coarser ones can be carried into suspension and into the stream of fluid moving toward and out the outlet means.

Having described the preferred form of my invention, with certain modifications thereof, it will be understood that the foregoing description is to be broadly construed as illustrative of the invention and the appended claims, and not restrictive thereon, for various changes in the arrangement and design of parts may be made without departing from the spirit and scope of my invention.

I claim:

1. Inaclassifier. for selectively separatingrzsuspended solid particles from a liquid, the combination of a tank having an inclined bed and adapted to contain a body of liquid and solid-particles suspended therein to be classified, inlet means admitting to the tank liquid carrying suspended solid particles, conveying means for moving settled coarse particles along the inclined bed and out of the liquid to a place of discharge from the tank, liquid agitating means located above the conveying means adapted to agitate a portion of the body of liquid to facilitate classification of particles, a baffle plate interposed between the agitating means and the conveying means to direct currents around and-along the conveying means in the direction of conveying movement,

and outlet means for discharging liquid and unseparated fine particles from the tank.

2. In a classifier for selectively separating suspended solid particles from a liquid, the combination of a tank having an inclined-bed and adapted to contain a body of liquid and solid particles suspended therein to be classified, inlet means admitting to the tank liquid carrying suspended solid particles, a rotatable helical conveyor for moving settled coarse particles along the inclined bed and out of the liquid to discharge them from the tank, a rotatable paddle wheel above the conveyor adapted to agitate a portion of the liquid body, a baiile plate interposed between the conto contain a body of liquid and solid particles suspended therein to be classified, inlet means admitting to the tank liquid carrying suspended solid particles, a. rotatable helical conveyor for moving settled coarse particles along the inclined bed and out of the liquid to discharge them from the tank, agitating means above the conveyor adapted to agitate a portion of the liquid body, a bafiie plate interposed between the conveyor and agitating means to direct currents around and along the conveyor in the direction of conveying movement, and outlet means for discharging liquid and unseparated particles from the tank, said outlet means comprising a pair of overflow launders, opposed walls of which form between the launders a sorting column through which the liquid fiows vertically to determine the size of fine particles carried with the discharged liquid, one of said launders separating the zone of agitation around the agitating means from the sorting column.

4. In a classifier for selectively separating solid particles from a liquid, the combination of a tank adapted to contain a body of liquid and solid particles suspended therein to be classified and having a longitudinally inclined bed which extends at one end of the tank upwardly beyond the liquid level, inlet means admitting to the tank liquid carrying suspended solid particles, a rotatable helical conveyor for moving settled particles longitudinally along the inclined bed and out of the liquid to discharge them at one end of the tank, outlet means for discharging liquid and unseparated fine particles from the other end of the tank, liquid agitating means located above the conveyor and between the-liquid inlet and the liquid outlet means, and a member extending transversely acrossthe tankbetween the agitating means and the outlet means to separate the zone of agitation around the agitating means from the outlet means.

5.' In a classifier for selectively separating solid particles from a liquid, the combination of a tank the end of the tank at the lower end of the bed for discharging liquid and unseparated fine particles, liquid agitating means located above the conveyor and between the upper end of the bed and the liquid outlet means, and a member extending transversely across the tank between the agitating means and the outlet means to separate the zone of agitation around the agitating means from the outlet means.

6. In a classifier for selectively separating solid particles from a liquid, the combination of a tank adapted to contain a body of liquid and solid particles suspended therein to be classified and having a longitudinally inclined bed which extends at one end of the tank upwardly beyond the liquid level, inlet means admitting to the tank liquid carrying suspended solid particles, a rotatable helical conveyor for moving settled particles longitudinally along the inclined bed and out of the liquid to discharge them from the tank at the upper end of the bed, liquid agitating means located above the conveyor and adapted to agitate a portion of the body of liquid, baflie means interposed between the conveyor and agitating means to direct currents around and along the conveyor in the direction of conveying movement, and outlet means near the end of the tank at the lower end of the bed for discharging liquid and unseparated fine particles, said outlet means comprising spaced vertically extending wall means forming a sorting column through which liquid flows vertically and an overflow weir at the top of the sorting column, said ,wall means including a member interposed between the agitation zone around the agitating means and the sorting column and extending both above and below the liquid level to prevent flow of liquid to said weir except through said sorting column, the agitating means being between the liquid outlet and the upper end of the bed;

JOHN H. V. FINNEY.

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