US2715462A

US2715462A - Hydraulic classifier

Info

Publication number: US2715462A
Application number: US397205A
Authority: US
Inventors: Harold B Coulter
Original assignee: Dorr Co
Current assignee: Dorr Co
Priority date: 1953-12-09
Filing date: 1953-12-09
Publication date: 1955-08-16
Anticipated expiration: 1972-08-16

Description

l0 Sheets-Sheet l Filed Dec. 9, 1955 .vNm OF? ONm Nm .v.m N m Aug. 16, 1955 H. B. COULTER 2,715,462

HYDRAULIC CLASSIFIER Filed Dec. 9, 1953 lO Sheets-Sheet 2 T S n o, N G v O l I l I (1 1| I I Q l F ln\\ 1 l l l Ill| I D C! u .c N w Q a er Il ||li l nl j! l l 5\\ I n fn |ll /N N :IH I D u; k n l N N I l l n Ll.

INI'ENTOR.

E Harold B. Coulter Ll.

A TTOR NE Y Aug. 16, 1955 H. B. coULTER HYDRAULIC CLASSIFIER 10 Sheets-Sheet 3 Filed Dec. 9, 1953 /NvE/vof? Harold B. Coulter Arm/mfr Aug. 16, 1955 H. B. COULTER HYDRAULIC CLASSIFIER 10 Sheets-Sheet 4 Filed Dec. 9, 1953 /NVEN TOI? A TTOR/VEY Aug. 16, 1955 H. B. COULTER HYDRAULIC CLASSIFIER 10 Sheets-Sheet 5 Filed Dec. 9, 1953 Sono .mE Ecm zoro SE? E20 IN1/NMR Harold B. Coulter ATTORNEY Aug. 16, 1955 H. B. COULTER 2,715,462

HYDRAULIC CLASSIFIER Filed Dec. 9, 195s 1o sheets-sheet 6 I /NvEA/roH Harold B. Coulter l Fines D2 [06. [46 Dlscharge l i 0T A TTOHIVEY Aug. 16, 1955 H. B. COULTER HYDRAULIC CLASSIFIER l0 Sheets-Shee t 'T F'iled Dec. 9, 1953 Clear Water Overflow Fig. 8.

INVENTOR.

Harold B. Coulter BY Maul. 611/ ATTORNEY;

Aug. 16, 1955 H.. B. COULTER 2,715,462

HYDRAULIC CLASSIFIER Filed Dec` 9, 1953 10 Sheets-Sheet 8 o Clearwater o Overflow Fig.

INI/ENTOR.

Harold B. Coulter Feed /1 TTORNE Y ug- 16, 1955 H. B. COULTER 2,715,462

HYDRAULIC CLASSIFIER Aug. 16, 1955 H. B. COULTER HYDRAULIC CLASSIFIER 10 Sheets-Sheet lO Filed Dec. 9, 1953 TTORNE Y United States Patent informatie cLAssrrInR Harold B. Coulter, Larehmont, N. Y., assigner to The Dorr Company, Stamford, Conn., a corporation of Delaware Application December 9, 1953, Serial No. 397,295

12 Claims. (Cl. 209-159) This invention relates to the Wet or hydraulic classification treatment of pulp containing a range of particle sizes from fine to coarse, as exemplified by metallurgical pulps or puips of wet-ground ore, to effect the separation of the mixture of particles into a coarse and a fine fraction of sizes, these fractions herein to be simply termed the coarse fraction and the fines fraction, or else the oversize and the undersize. The coarse fraction then contains substantially all sizes above an intermediate size while the fines fraction contains substantially all those that are smaller than the intermediate Size.

Hydraulic separation such as herein contemplated takes place in a classication pool into which the pulp is fed, while the coarse fraction is withdrawn from the bottom of the pool and the fines fraction overows from the pool across a Weir. in order to aid and control the separation, the mixture of particle sizes while in transit through this pool may be kept mobilized by being subjected to the edect of controlled mechanical agitation, or subjected to the effect of a stream of auxiliary so-called hydraulic operating water up-dowing through the pool at a controlled velocity; however, as contemplated by this invention, the mixture in the pool is subjected to the joint elfects of both mechanical and hydraulic action, with the result that a desired coarse fraction above a certain mesh size will collect at the bottom of the pool to be withdrawn therefrom, while a corresponding fraction of line sizes with its carrier water overflows from the pool, this to afford superior means of separation control presently to be set forth.

It is among the basic problems in such wet classification or separation treatment that there be effected as sharp a separation as possible between the oversize and the undersize or else between the underflow sizes and the overflow sizes; thus the aim is to conduct the classification treatment in such a manner or with such type of apparatus that each of the two fractions be obtained as free as possible from stray sizes of the other fraction.

Another basic problem in such wet classification treatment or apparatus is that of providing control means whereby the point of separation or fractionation or cut between the two groups of sizes, the oversize and the undersize can be readily established and accurately adjusted. For example, if the feed be of a run containing particle sizes ranging, say, from 28 to 200 mesh, then it should be possible, for example, to make a clean split at say, 100 mesh, yet it should be possible to readily shift the cut to, say, 48 mesh. This calls for providing simple and effective means for so adjusting or shifting the cut" While deriving the respective size fractions clean, that is with a minimum of stray sizes admixed thereto. For example, the import ance of producing a clean coarse fraction is apparent where the classification apparatus operates in closed circuit with a wet grinding mill, the mill to receive coarse fraction particles for regrinding, and where the admixture of an appreciable amount of undersize or stray sizes would burden the circulating load through the mill and would accordingly reduce its efficiency as well as that of the circuit as a whole.

Cit

Moreover, there is the general problem that such an apparatus should be capable of handling eiectively a feed slurry containing a relatively wide range of particles of extreme sizes, that is, from relatively very fine to relatively very coarse.

Also there is to be considered in the operation of such classication treatment and apparatus the degree of dilution of the feed pulp, since it is desirable to produce a separation which remains substantially stable in spite of possible variations in the degree of feed dilution; another aspect lies in the fact that it may be desirable to derive the overow of fines at the highest possible density, there being the difficulty that a high rate of hydraulic water required might run counter to the goal of attaining the desired degree of overflow density.

The invention provides improvements over the wet classilication machine employing the joint or compound eect of mechanical and hydraulic classifying action shown in the patent to W. C. Weber, No. 2,302,588, which produces a sharp cut easily and accurately controllable, and which is operable with minimum of hydraulic operating water, capable of absorbing appreciable changes in the dilution of the feed pulp substantially without affecting the out itself, even though capable of producing the overflowing undersize fraction at relatively great density, and of handling a feed pulp containing a wide range of particle sizes from fine to coarse.

lt is among the objects of the present invention to produce a machine possessing at least the operational characteristics and capabilities of the machine in the aforementioned patent, yet to be simpler of construction, lighter in weight, cheaper to build, as well as simpler to maintain, simpler to overhaul and simpler to service, and last but not least, which is more compact and which lends itself to a variety of structural modifications whereby it is conveniently and compactly adaptable for structural integration in a treatment system such as closed-circuit grinding. The significance of these objects will appear more precisely from the following outline of the machine shown in that patent. in that machine, the pulp is fed to a significantly shallow pool the bottom of which is formed by a horizontal circular false bottom in the form of a perforated plate usually termed a constriction plate. A hydraulic supply chamber is associated with the under side of the constriction plate unitary therewith and has hydraulic operating water fed thereto continuously in order that such auxiliary water may continuously rise in the pool through and upwardly from the constriction plate at a controllable rate, thus helping to maintain the particles in the pool in a mobilized state. Moreover, this hydraulic chamber with its constriction plate is mounted for oscillatory movement about a vertical axis by means of a hollow vertical column rising from the center of the constriction plate and suspended from an overhead bearing structure which carries drive mechanism for imparting the oscillatory movement through the column to the constriction plate and its associated hydraulic supply chamber. The slurry or pulp is fed to a central annular feed well surrounding the column, and under normal operating conditions the pulp in the pool is subjected to the joint effect of the oscillatory motion of the constriction plate and of the hydraulic water rising therethrough. A uniform distribution of hydraulic water over the entire bottom of the pool is thus obtained not only by reason of the fact that the water is being int troduced by the great many holes in the constriction plate,

but also because these holes are constantly being oscillated incident to the oscillatory motion of the constriction plate.

The classifier pool is furthermore defined by a cylindrical stationary boundary wall the top edge of which constitutes an overflow Weir for discharging the undersize fraction of the pulp. This cylindrical boundary wall of the pool is concentric with the constriction plate although e constriction plate.

Y pressure effective at the sands discharge passage.

3 of a'somewhat smaller diameter so that it is spaced slightly inwardly from'the periphery .of the constriction plate, yet also spaced upwardly from the marginal portion of the constriction plate. Thus, the constriction plate may os- 'cillate beneath the stationary lboundary wall, with the vertical distance between this wall and the constriction plate constituting an annular sands passage or solids transfer passageway leading outwardly from the pool bottom to allow for the outward migration and removal of the oversize fraction of the pulp from theV pool. l Importantly, along the periphery itselfvof the constriction plate there is provided what is herein termed a submerged sands discharge weir overwhich spill the sands or coarse fraction particles down into a receiving chamber which in turn surrounds the The sands discharge weir rises to a level atvleastrsomewhat higher than the sands passage, so that thereby there is maintained an annular sealing column ofsands in transit between the passageway and the weir.

The annular space between the constriction plate and the surrounding receiving chamber is covered and closed by a top portion of the receiving chamber, which top portion in fact supports the cylindrical boundary wall of the pool by being rigidly connected therewith.

A body or column of clear water maintained in the sands receiving chamber defined by a clear water overflow Weir of adjustable height balances the column of pulp or mobilized particles in the pool, and this balance represents a hydraulic equilibrium condition in the machine, whereby the separation or cut is readily controllable, namely, as by adjustment of the height of the clear water overflow wexr.

The coarse fraction particles upon the oscillatory constriction plate will move or migrate outwardly, radially in all directions towards and through the sands discharge passage and over the submerged sands discharge weir which surrounds the passage, and into the surrounding sands receiving chamber whence they can be removed into emergence from a body of clear water as by any suitable conventional elevating means or-by controlled spigot Ysuch as above outlined, is simpler, lighter and cheaper of construction, with a substantial reduction Vof the oscilla- 1 tory, or moving, masses, which is more compact and which is more readily and more compactly adaptable to environmental structural conditions.

In order to attain these objects, this invention provides a classifying pool in which the feed pulp enters the pool at a point spaced from the point oftines overow discharge and lfrom the point of sands underow discharge. For example, the pulp may pass in a longitudinal direction from end to end through the pool undergoing classification, the underflow discharge being by way of a sands passage at the bottom of the pool and through a connecting sands column outside this passage. The desired kind Vof classitication of the pulp in the pool is effected by the conjoint action of hydraulic water being introduced in substantially uniform distribution at the bottom of the pool and of horizontal longitudinal back-and-forth or vibratory movement of the bottom face of the pool. This movement is such as to provide suiiicient acceleration and decelera- Vtion within its vibratory cycle, to continuously induce and maintain an intensified degree of relative movement between surface and the strata of oversize particles supported thereby. The cut between the two fractions is controllable by way of adjusting a static hydraulic counter- One mode of so controlling the hydraulic counter-pressure is by way of a water Vcolumn superimposed upon the sands column and defined by an adjustable clear water overflow .at thek super-elevation level. That is to say, the oversize particles from the sands column may be allowed to spill into a clear water chamber thence to be removed upwardly by the suitable elevating mechanism, or downwardly by a Y suitably controlled spigot discharge valve.

The machine according to this invention is organized in such a manner that the pool in effect is confined within a space defined by a horizontal bottom face, a pair of longitudinal side wall faces, and a vertical transverse face at each end, provision being made for the transverse end Y connected with the bottom portion imparts thereto repetitive baek-and-forth movements of a suitable frequency and suitable length of stroke.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustra tive and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall with- 1 Y in the metesk and bounds of the claims, or for formsY that are their functional as well as conjointly cooperative equivalents, are therefore intended to be embraced by those claims.

Figure 1 is a diagrammatic longitudinal sectional view of one embodiment of the machine, indicating the horizontal classification zoning of the solids in the pool, and

also indicating how the adjustment of the height of the clear water overflow column controls the separation.

Figure 2 is a diagrammatic longitudinal sectional view of .an embodiment similar to that of Figure 1, although with the sands discharge weir shown stationary.

Figure 3 shows a perspective view of the Figures 1 and 2 embodiment although more fully implemented with respect to the diaphragm connections, and provided with spigot discharge for the sands fraction.

Figure 4 is a side view of the preceding embodiment structurally more complete, and provided with endless elevating mechanism for sands discharge.

Figure 5 is a plan view of Figure 4.

Figure 6 is a cross-sectional view taken on line 6 6 of Figure 4. Y

Figure 7 is a cross-sectional view taken on line 7 7 of Figure 4.

Figure 8 is a cross-sectional view taken on line 8,-8 of Figure `4.

Figure 9 is a longitudinal sectional view, diagram-V matcally similar to that of Figure 2, of another embodiment of the apparatus.

. Figures 10, 1l, l2, 13 present a diagrammatic eX- ample of the hydraulic classifier as exemplified in a closed circuit grinding system, Figure 10 being a side view, Figure 11 being a top view, Figure l2 being an end view taken on line 12-12 of Figure 10, Figure 13 being an 'f end view taken on line 13-13 of Figure l0.

Figure 1 is a highly diagrammatic view of one embodiment of the classifying apparatus with legends and an example tabulation applied thereto for the sake of permitting ready understanding of the basic function of in a longitudinal horizontal direction may be imparted *A to the bottom as is indicated by arrows Ai. v The longitudinal Vside walls indicated at 15 may be considered as unitary with the bottom 12 and to vibrate bodily therewith, while the sealing connections V13 and 14 may be considered as being effective between the respective stationary walls and 11 and the respective adjoining ends of bottom 12 and of side walls 1S. Pulp fed to the classifying pool or bath is indicated at 16; a coarse fraction or sands discharge i7 is defined by a submerged discharge passage 1S, a submerged overow weir 18a, and also by an overlap 18h; an overiiow for the nes fraction is indicated at 19; a sands receiving chamber 2t) has a controlled spigot discharge valve 29a through which coarse fraction solids may be discharged at a controlled rate as these solids spill over the sands discharge weir 18a and into the receiving chamber 2t?. The receiving chamber 2) communicates with a clear water column 21 having a clear water overflow 22 of adjustable height. The introduction of auxiliary hydraulic water at the bottom of the classifying pool is indicated by a horizontal pipe 23 having a vertical supply pipe 24 provided with a control valve 25, the horizontal pipe 23 having orifices 23a for emitting jets of i. ater at a downward angle towards the bottom 12, so that the water may in effect rise in uniform distribution from the bottom for the purpose of sustaining the particular classification effects in this pool such as will herein be set forth in greater detail.

While a feed pulp of a given size analysis and comprising a mixture of solids ranging from fine to coarse, is fed at a more or less uniform rate to the classifying pool at one end thereof, with the auxiliary hydraulic water currently rising from the bottom at a suitable rate and the bottom itself being currently vibrated in the direction of arrows A1, then as a result of such conjoint hydraulic and mechanical action, the solids in the feed pulp mixture form themselves into a bottom zone or strata a containing substantially only the coarse fraction or sands which it is desired to have discharge through the passage 1S into the receiving chamber 2t), a top zone c containing the fraction of fines that are to leave the bed by way of an overflow 19, and an intermediate zone b herein termed the teeter zone inasmuch as it contains mixed sizes from which after a period of detention or teetering the respective over-andunder sizes eventually find their way out through the iines overow 19 and through the sands discharge t7 respectively. The separation or cut between the overowing fraction and the sands fraction is determined by the height of superelevation H of the clear water overflow 22 over the top level L1 of the pool.

A tabulation in Figure l presents as an example a series of separation cuts defined in terms of Tyler mesh size, indicating the relationship between respective super-v elevations in inches and corresponding values in cumulative weight, of solids content in the overowing fraction. For instance, if by adjustment of the superelevation H1 a cut be eected at 65 Tyler mesh, such an operating condition would produce a 5 superelevation a solids content of 21.2% in the overowing fraction at 6" superelevation a solids content of 25.2% in the overflowing fraction, at 7" superelevation solids content of 30.1%, and at 8 superelevation a solids content of 34.0% in the overflowing fraction. The term cumulative weight means that the value here given for any one Tyler mesh size for a chosen super-elevation represents the sum total of the weights of solids retained by that mesh size and by the respective preceding mesh sizes for that same superelevation.

Figure 2 is a diagrammatic view in longitudinal section of the apparatus in substance resembling that of Figure l although additionally showing a vibrating device for actuating the tank bottom, suspension means for the vibratable body portion of the classifier tank, and also indicating a structurai modification of the sands discharge weir in that the weir is here stationary with the end wall construction of the tank rather than unitary and bodily movable with the bottom.

Thus, Figure 2 shows the classifier tank itself comprising a stationary feed end 26, a stationary discharge end 27, a vibratory body portion 23 having a bottom 28a and side walls 28h, flexible sealing connections or diaphragms 29 and 3) being indicated between each stationary end portion of this tank structure and the respective adjoining end portions of the movable body portion 2S. The body portion 28 is here shown suspended as by means of hangers indicated at 31 and 32, so as to be free to be vibrated in the horizontal longitudinal direction indicated by arrows Az.

A vibrating device 33 is shown to comprise the vibrator 3d proper being rigidly connected to the vibratable bottorn a of the classifier tank, as indicated by brackets 35. The vibrator 34 is here diagrammatically shown to comprise a pair of

shafts

36 and 37 geared up with one another as by gears g1 and g2, the shafts carrying

eccentric weights

38 and 39 so disposed with respect to one another and with respect to bottom 23a that the desired horizontal vibratory movement is imparted thereto incident to the operation of the vibrating device. The vibrator 34 is actuated by a motor 40 having a drive connection with shaft 36 indicated by a drive belt 4i.

The stationary feed inlet end 26 is shown to be provided with an inclined feed trough 42, and spaced slightly inwardly from the inlet end there is shown to be provided a stationary transverse stilling baffle 43. The stationary discharge end 27 of the classifier tank comprises an overow receiving launder 44 into which discharges the fraction of fines deriving from the top zone c of Figure l. The stationary discharge end comprises a submerged discharge passage 45 associated with a sands discharge weir d6 whereby to deliver the coarse or sands fraction derived from the bottom zone a of Figure l. The stationary structure at the discharge end of the classifier tank here also comprises a sands receiving chamber 47 into which spill the sands from the discharge weir 46, from which receiving chamber the sands discharge at a controllable rate as by a spigot valve 4S.

Again, the receiving chamber 47 provides a clear water column 49 having a clear water overiiow 59, the height of which is adjustable as is indicated by removable rings 51 providing an adjustable superelevation H2. A controllable supplementary water supply for the clear water column is indicated at 52, there being a valve 52S- for admitting such supplementary water if need be, to insure that the overow level Lz be maintained. The supply of hydraulic operating water to the classifying pool is indicated by a horizontal pipe 53 having suitably disposed orifices S4 for emitting water jets 55 towards the bottom 282, and by vertical supply pipes S6 and 57 shown to have control valves 56a and 57a respectively.

The perspective View of Figure 3 shows semi-diagrammatical a tank construction similar to that of Figure 2 although with the diaphragms connections more fully complemented and the discharge and the arrangement of pulp feed, the fines overtiow, and the sands discharge more clearly shown.

Thus the classier tank comprises a stationary feed end portion having a U-shaped flange 59 connected to corresponding U-shaped diaphragm 60 the connection being with the inner edge portion 61 of this diaphragm. The

outer end portion 62 of this diaphragm is connected to a correspondingly U-shaped vertical end flange 63 of a vibratory intermediate body portion 64 of the classier tank. The body portion 64 comprises a bottom 65, and a pair of side walls 66 and 67 unitary with the bottom 65. At the discharge end this body portion 64 of the tank is connected to a U-shaped diaphragm 6'7EL the connection being with the inner edge portion 67b of that diaphragm. The outer edge portion 67 of diaphragm 67 is connected to a stationary end portion 68 of the classifier structure, and portion 68 comprises an end wall 68a constituting the discharge end wall of the tank. The upper end portion of this end wall 68 is formed with an overow weir 69 whereby the nes fraction of the pulp bed B in the tank discharges into an overtiow discharge launder 70 having a Vweir portions 731 and 73C.

' chargeY from the` receiving chamber 74. Y chamber 74 is furthermore provided with a clear water kdischarge pipe The lower end portion of end wall 68a has extending therethrough by way of a corresponding y shaped opening V71 the coarse solids or sands discharge receiving chamber 74 is shownY to be formed by a hoppershaped portion 79 having at the inverted peak thereof a controllable lspigot valve for controlling the sands dis- The receiving column 81 having a clear water overflow pipe 82 the overflow level of which is variable and adjustable as to its effective height, as is indicated by removable rings 83. The term clear water overfiow is herein employed in the sense of providing a hydraulic column of a balancing liquid or relatively clear water significantly lighter by comparison ,than the pulpin thejcolumn represented by the classifier pool.

`VThe supply of auxiliary hydraulic operating water to the pulp bed B in the tank is indicated by a pair of

horizontal pipes

84 and 85 extending parallel to one another, as well Y as indicated by the direction of vibration imparted to the Vbody portion 64 of the tank, such being indicated by arrows A3; Each of the

horizontal pipes

84 and 85 emits downwardly at an angle towards the bottom jets of water indicated at 86,'such jets being emitted by way of a pair of rows of orifices, such rows being provided along each Side of the pipes '84Yand '85. Each of the horizontal

jet emitting pipes

84 and 85 are shown in turn to be supplied by'a pair of vertical supply pipes namely pipes $4a and 84h to Serve the horizontal pipe 84, and the vertical pipes 85a and 85b to serve the horizontal pipe 85. The showing of thevibrating device itself (such as is indicated at 33 in Figure 2), as well as the showing of suspension means Y forgthe vibratory portion of the tank (see suspension means V31Vand 32 in Figure 2) has been omitted from the Figure 3 perspective view. Y

The drawing Figures 4, 5, 6, 7, 8 show a practical implementation of a classifier unit which corresponds to the embodiment of diagrammatic Figures l, 2, 3. The unit Vcomprises a structural frame collectively indicated by the numeral 87, upon which is operatively mounted the structureV of the classifier proper. Y This classifier structure provides a classifier tank containing the pulp bath B,'and

comprises .a stationary feed end portion or section a for feeding pulp to the classifier bath, a stationary discharge end portion or section b for delivering the two pulp fractions, namely the fines and the sands, and Va vibratory intermediate tank portion or section c substantially defin-V ing the extent of the pulp bath B.

v The stationary sections s and b are operatively intercon- V nected with the vibratory tank portion c by means of U shaped diaphragm members D1 and D2.

Feed pulp is indicated at F to enter the feed end of the classifier unit, while the fines fractionV R is indicated to overow from the opposite or discharge end of the tank; the discharge of sands is indicated at S, the sands having Vbeen elevated from a sands receiving chamber to a point Vvibratory motion in a horizontal longitudinal direction and `of suitable characteristics is imparted tothe classifier tank section or structure c by means of a vibrating device V-i in the form of a channel ironY 95. From the middle por- Y L l operatively connected therewith, such vibrations being .indicated by arrows A3. Y Y The vibratory tank portion cis operatively suspended in Ythree-point fashion from the supporting frame 87 by means of a pair of hangers 88; and 89 at Ythe feed end thereof, and by a single hanger 90 at the discharge end thereof. The supporting frame 87 itself is inthe form of a steel structure comprising a set of four basic cornerV posts 91, 92, 93, 94. The posts `9,1 and 92 are interconnected at the top by a transverse member shown to be tion of this member 95 and laterally outwardly therefrom extends a bracketV 96 having a pair of rigid depending vertical members 98 and'99 for mounting and supporting a pulp feed trough 100 as part of the stationary section a.

" From each end portion of the transverse member 95 and laterally inwardly extend a pair of xedibrackets 96 and 97 respectively, which brackets serve as anchoring points for the hangers or

hanger rods

8,8 and 89.

The corner posts 93 and 94 are interconnected at the topY by a transverse structural member in the 4form of a channel iron 101. Both

transverse members

95 and 101 are interconnected at their middle portion by a longitudinal structural member or angle iron 102 which in turn also serves as ank anchoring for the single hanger or hanger rod 90.

The frame 87 furthermore is shown to have at each side thereof a pair of diagonal

intersecting bracing members

103 and 104, and at the freed end to have a pair of diagonal intersecting 'bracing members 103al and 104% The' aforementioned stationary pulp feed Ysection a comprises theV aforementioned feed trough 100 the Villner end of which is formed with a vertical U-shaped flange 105 'to which is fastened the innerv edge portion of the correspondingly U-shaped diaphragm D1.V The vibratory section c of the classifier tank unit comprises a bottom 1'06 and unitary therewith a pairV of

side walls

107, 108. Across the inlet end' of these side walls at the top thereof there is provided and fastened a transverse member 109 which serves for the attachment thereto of hangers S8 andV 89.V Similarly a transverse member 110 extends across the outlet end of the side walls, so as to serve for the attachment thereto of the hanger 90. The inlet end of the vibratoryl section c has a ver-` tical U-shaped ange 111 to which is fastened the outer edge portion of the diaphragm member-Di. At its discharge end the vibratory structure or section c is'formed with bottom extension 112 which in turn comprises a,

sands discharge Weir 113. VThis extension and sands discharge weir project into what is herein termed the sands discharge chamber 114 formed Vby the stationary discharge section b presently to be described in greater detail..

The discharge section or structure b comprises astationary tank structure 115 into which spill the sands from the discharge weir 113. The elevating Vmechanism M operates in this tank to effect the lifting of the sands from the tank bottom to a point of emergence where the sands are discharged from the classifier unit. The basic or body portion of the stationary tank structure 115 comprises an inner end wall 116 forming an overflow Weir W1 for discharging the fines fraction from the classifier bath lB, this inner end wall further having a specially Vshaped opening 117 `through which protrudes the bottom extension and sands discharge end of the vibratory tank structure c; an -outer VendA wall 1118 the top end of which provides the sands Vdischarge 119 prop er; a bottom 120 comprising a curved portion 121 Vand a straight although inclined portion 122;,and a pair of

side walls

123 and 124 of irregular outline the contours ofV which (see Figure 4) are in effect defined by the inner and the outer end walls 116 and 11'8 and by the bottom 120 of the stationary tank Vstructure 115. The basic or body portion of the stationary tank structure just defined has a vertical transverse partial partition wall the lower end of which terminates a perpendicular distance p from the tank bottom 120 to provide a passage 126 for the sands spilling from the discharge weir 113 to the bottom and to be picked up by the elevating mechanism M. Between the inner end wall 116 and the partial partition wall 125 there extends a horizontal wall portion 127 having a slight slope indicated by the angle g in Figure 8, this scope being in a direction laterally of the main longitudinal axis x-x of the classifier unit. Thus, there is formed a transversely extending discharge trough 128 terminating in a laterally overhanging trough portion 129 defined by a horizontal bottom portion 129@L and a vertical end portion 1295, the bottom portion 129a having a downwardly directed discharge pipe 129c for the disposal of the fines fraction overflowing from the weir W. The side wall 123 of the body portion of this tank structure has a passage 139 providing communication between this body portion of the tank or else between the sands receiving chamber therein and a clear water column provided at the outer side and adjoining the side wall 123. The clear water column is contained in and defined by a laterally overhanging structure comprising an outer vertical end wall 131, a pair of

vertical side walls

132 and 133, and a sloping bottom 134. Through this sloping bottom 134 extends a vertical clea1 water overflow pipe 135 the upper end of which defines variable and adjustable as to its height by reason of removable rings 136 constituting the upper end portion of the pipe.

The stationary tank structure 115 just described has its inner end or end wall 116 supported upon and by the corner posts 94 and 95 and by the transverse member 101 respectively, whereas the outer end or end wall 118 of that tank structure is supported by a pair of

auxiliary posts

137 and 138 which in turn have at the top thereof a pair of horizontally and longitudinally extending bracing

members

139 and 140 interconnecting the

auxiliary posts

137 and 138 with the basic corner posts 94 and 95 respectively. These horizontal bracing

members

139 and 146 in turn serve as supports or mountings for the sands elevating mechanism M in that they carry a pair of

horizontal bearings

141 and 142 of a horizontal transverse shaft 143 which in turn constitutes part of the elevating mechanism M. This shaft being driven by suitable power means (not shown) has fixed thereon a driving drum 144 which in turn carries an endless belt 145 provided with buckets or functionally equivalent elements for lifting the sands from the tank bottom to emergence and to the discharge 119. The lower end portion of this elevating mechanism or endless element are shown to depend freely into the tank, that is to say without the use of submerged bearings or the like, and in a manner to be allowed to seek its own operating position in the tank with respect to the sands lifting operation.

The discharge end of the vibratory tank structure c is operatively connected to the stationary tank strncture 121) by way of the U-shaped diaphragm member D2 in that the inner end portion 146 of the diaphragm member is fastened to the bottom and side Walls of the vibratory tank structure, whereas the outer edge portion 147 of the diaphragm member is fastened to the inner end wall 116 of the stationary tank structure 115.

For supply of the hydraulic water to the pulp bath B there are shown to be provided a pair of horizontal

feed emitting pipes

159 and 151 extending parallel to one another and in the direction of the longitudinal axis x-x of the classifier unit. The horizontal pipes 148 and 149 are spaced a distance d1 from each other, each pipe in turn being spaced an equal distance d2 from the

respective side Walls

107 and 108, and each pipe also being spaced a corresponding distance da from the bottom 106. Each of the horizontal

feed emitting pipes

150 and 151 has a pair of

vertical supply pipes

152, 153 and 154, 155 respectively. Each pair of these vertical supply pipes has a set of interconnecting pipe or

tube fittings

156 and 157 respectively, which fittings in turn are interconnected by a central pipe fitting 158 having a control valve 159 for regulating the supply of the hydraulic operating water to the

feed emitting pipes

150 and 151.

Another embodiment of a machine to provide the kind of classification operation herein set forth is shown in a diagrammatic longitudinal sectional view thereof in Figure 9. This embodiment is structurally so organized as to provide an example of how the desired vibratory movement of the tank bottom can be attained without requiring the use of such diaphragm members as are shown at D1 and D2 in Fig. 4.

This embodiment therefore provides a solid tank structure to hold the pulp bath, comprising a bottom, a pair of side walls, and a pair of end walls, namely, a pulp feed end wall and a fines overliow and sands discharge end wall. Vibratory movement is imparted to this tank structure while auxiliary operating water is introduced at the bottom. In addition, however, and importantly there are provided within this tank structure a stationary transverse wall plate at the feed end, and another similar stationary transverse wall plate at the opposite or discharge end of the tank structure. The effective volume of the pulp bath proper in this structure thus occupies the space defined by the bottom, the sides, and the two stationary wall plates at the ends. The space between the stationary wall plates and the end walls of the vibratory tank structure may be lled with a resilient compressible material, for example sponge rubber, which will have the effect of preventing these spaces from getting filled with water or pulp while being subjected to any, even though localized, pumping action due to the vibratory motion of the tank structure.

The Figure 9 embodiment as herein exemplified is represented largely by a solid tank structure 160 suspended for longitudinal horizontal vibratory motion as by

hangers

161 and 162 similar to those shown in the embodiment of Figures 2 and 4, this tank structure 160 being vibrated by a vibrating device 163 of the kind also shown in Figure 2. The vibratory part of the tank structure 160 comprises a bottom 164, a pair of side walls 165 and 166, an end wall 167 at the pulp feed end having a pulp feed trough 168, and further comprises an end wall 169 at the discharge end. A stationary portion of the classifier tank structure endwise defining the classifier pool in this embodiment comprises a stationary transverse wall plate 189 spaced a small distance ti inwardly from the end wall 167 and a transverse wall plate 190 spaced a small distance t2 inwardly from the end wall 169, the spaces t1 and t2 being shown as filled with resiliently compressible sponge rubber R1 and R2 respectively. The end wall 169 has at the bottom end thereof a sands passage 172 and a submerged sands discharge weir 173 both in effect similar to a corresponding passage and weir in Figure 2. Surrounding the sands discharge is a sands receiving chamber 174 constituted by a. receiving tank structure 175 shown to be unitary with the classifier tank 160 proper and thus vibratable therewith. The receiving tank structure 17S substantially comprises an inner wall 176, an outer wall 177, a horizontal top wall plate 178 extending between the inner wall 176 and the end wall 169, and a bottom 179 having a curved portion 179a and a substantially inclined portion 1791, and furthermore comprises a pair of side walls 180 and 181 the outline or contours of which are defined substantially by the

wall portions

176, 178, 179 just enumerated. Moreover, this receiving tank structure has a transverse partition wall 182 the lower end of which terminates a perpendicular distance t3 from the inclined bottom portion 179b providing a sands discharge passage 183 through which the sands discharging over the weir 173 may gravitate to the lowest part of the receiving chamber 174 and thus into the reach of an endless bucket-belt type sands elevating mechanism 184. That is to say, the partition wall 182 thus defines a tank section 185 in which operates the elevating mechanism 184, and a clear water section or column 186 having a cleariwater ,overow pipe 187 defining Vav superelevation H45V of the clearrwater column overthe top face level of therpulp bath B1 contained in the tank structure 160.

overow Weir 188 at the top of end wall 169 provides for'the dischargeof the .fines fraction-delivered from the classifying pool ortbath B1 by this machine.

A iet-emitting pipe system for supplying the hydraulic operating water is indicated at( 188.

It willbe seen .that they transverse wall plates or end plates 189V and 190 of the .classifier are stationary, as isY the. jet-emitting pipe system 188, Stationary

overhead structure

191 and 192 is indicated to provide mountings for the stationary end walls 189 and 170 of the classifier.'

Whereas there has been shown in the foregoing ,eme bod'iment of this inventionY a classifier tank of rectangular o1' longitudinal shape with the feed entering at one end and the separated fractions leaving at the opposite end, with the horizontal vibration of the'bottom portion being Vin the longitudinal direction of the tank and also codirectional with the horizontal jet-emitting pipes, it is to be understoodthat the construction is not necessariIy to be thus limited. For example, the vibration applied to the tankbottom may be in a direction transversely of the i, be more than one point of discharge for each fraction of solids, inV that, for example, a fines overflow may be provided at each side of the tank, and similarly a sands discharge be provided correspondingly at each side.

The hydraulic classifier such as herein shown kand described, may be embodied in a closed-circuit grinding i operation as is illustrated diagrammatically in Figures l0,

12 vating mechanism M.Y The high end of the elevating mechanism M delivers the coarse fraction material into a receiving tank'198 where it is picked up by the usual rotary scoops 199 which are part of the feed end of the Y ball mill 193. Feed pulp -P enters the system at the feed Y end of the mill 193, while finished product slurry S con# taining the fines fraction leaves the system by overow from the classier 194, while overow water discharges at C'. Y ,Y While there has been shown and described a manner of controlling the density of the classifier pool .bytway of establishing the superelevation (as defined by the over- Y iow level in the sands receiving chamber), -such control 1l, 12, 13'in which instance the classifier will lend itself to a highly compact and convenient structural combina` tion' with a grinding mill, as of the ball mill type, with elevatingV apparatus provided for returning the coarse fraction discharge of the classifier to the feed end of the grinding mill. t Y

YThat is to say, feed pulp enters the ball mill at its outer end even as a coarse fraction material is beingY delivered Yto the kfeed end of the mill by the elevating mechanism;

The ground pulp discharging from the inner end of the mill enters the feed end of the classifier while the result,- ing lines fraction and the coarse fraction discharge from the opposite end, the coarse fraction in turn thus discharging into the feed end of the elevating mechanism for return thereby to the feed end of the mill. t

Referring to Figures l0, 11,12, 13, the system conn prises the ball mill 193 occupying the length l1, the classi# yfier 194 proper occupying the length ,12, and the elevating mechanism M'having a reciprocating'rake structure similar toV that employed in the well'known rake classitiers, which elevating mechanism M is here shown in plan view to occupy the lenghth I3. i Such elevating mechanism has a tank TV with a sloping bottom or deck 195 and a rake structure 196. This rake structure is mounted and driven in a manner to perform a repetitive cyclic Vmovement whichV comprises an upward sediment raking may be effected in other suitable ways, for example by f way vof measuring or obtaining indications of the'density of the classifier pool, and employing them as criteria for adjusting and controlling the rate of discharge of coarse fraction material from Ythe receiving chamber. Such manner of control requires eliminating the overflow means from the receiving chamber and Yit operates to throttle down the coarse fraction discharge means to a suitable extent when the density decreases to below a desired value t and to unthrottle the coarse fraction discharge means to a suitable extent when the density increases to above the desired value. Y

Automatic means may be provided for effecting such control by applying fluctuations' or changes in the density of the pool through suitable relay action in a manner to cont-rol the rate of discharge of coarse fraction material from the receiving chamber maintaining the desired i density in the pool. Such control is to function in the sense that an increase of density in the pool automatically effectsV a suitable increase in the rate of coarse fraction discharge, whereas a decrease of density automatically effects a suitable decrease in therrate yof coarse fraction discharge.Y That is to say, density variations in the pool manifest themselves by the fluctuations of ahydraulic column communicating with the pool, which fluctuations are relayed through suitable instrumentation to actuate the coarse fraction discharge means through which the coarse fraction discharges from the receiving chamberfthus to control the rate of coarse fraction discharge in a manner whereby the density in the pool is kept substantially constant at a desired value for which the automatic control device can be setto function.

The automatic control system just outlined to compensate for density fluctuations in the pool, may be ern-` ployed to operate without necessarily providing and having a submerged sands discharge weir associated with the bottom discharge passage of the pool, since the rate of transit of the material from the bottom zone of the pool through the passage may be controlled more directly by having the system control the rate of withdrawal of material accumulating in the Vreceiving chamber or pocket; so the control system will function to compensate t for density uctuations in the pool by varying the accu- Vabout 4 long,V about l wide, and about ,9 deep, with the sands discharge passage at the bottom 'being about 1/2" high and the sands dischargeV Weir about SAK high, the pool area being 4 square feet.

As for the vibrating motionV imparted to the bottom of the classifier pool, a practical or suitable operating range v Y for the vibrating stroke under conditions in this example lies in a ran-ge of about 1A; to about 1A", while the stroke frequency covers a practical range of 600 to 1.000 reciprocations per minute. Y AThis operating example provides for a stroke length about 3/16" at a stroke frequency on the order of 700 reciprocations per minute. in this example the hydraulic water is supplied by a pair of longitudinally extending horizontal pipes having a clearance from the bottom of the pool of about 1/2", with center to center spacing bet'ween the pipes of about 6, and the center of each pipe in turn spaced a distance of about 3 from the respective side walls of the pool.

In this example two jet-emitting pipes are provided parallel to one another each 4 feet long of 1/2 standard pipe, having .622 inside diameters and .840 outside diameters, with a spacing between the jet holes of 1.5/16 center to center, the jet holes themselves being drill holes produced with No. 37 drill, and having an area each of .00849 square inch, the nominal diameter of the drill hole being .1040 inch, and the total open area of the holes being 1.22 square inches for a total number of 144 holes. In this example the hydraulic water is emitted from the pipes by jets provided by a double row of jet orifices in each pipe so disposed that a row of jet openings at each side of each pipe would emit jets at an angle of about 20 below the horizontal. Head loss through the holes was 1 foot water column for a flow rate of lo gallons per minute. The jet emitting pipes extend in the direction of vibration or reciprocation imparted to the bottom of the classication pool.

With a feed to the classiier pool consisting of a deslimed sands mixture having a range of sizes of -20 to 200 Tyler mesh and feeding 79.5 tons per day (dry weight) there was obtained 59.0 tons per day (dry weight) in the underow and 20.5 tons per day (dry weight) in the overflow; the separation in terms of the size of the cut was 250 microns with a superelevation being maintained at 3%, and a supply of hydraulic operating water at the rate of 18 gallons per minute.

lt was observed that these operating data and operating results do not change appreciably if the above specific load of 79.5 tons feed pulp (dry weight) handled by the machine is increased to about double that quantity and even beyond that. Although the feed pulp in this instance contains 45.2% solids, it was observed that variations in the feed dilution did not materially affect or vary the above operating results, nor do they materially aiect the hydraulic water rate required for a certain separation. While the above data apply to a daily throughput of 79.5 tons, the machine is nevertheless rated for a full capacity of 150 tons per day (dry weight) without requiring any material change in the above operating conditions.

Screen analysis of the feed, of the underflow and of the overow were as follows:

UND E R- OVE R- FEED- FLOW FLOW- Percent of Percent of Percent oi Tyler Mesh total solids total solids total solids held by held by held by screen feed screen screen underflow overow 14 ned by a horizontal bottom face, a pair of side wall faces, and a transverse face at each end endwise defining the classifier pool, there being a horizontal bottom which presents said bottom face to the pool supporting structure for providing horizontal back-and-forth movement of said bottom, a pair of side wall portion unitary with said bottom to provide said side wall faces, a stationary wall portion at each end to provide said end faces of the classifying pool, and sealing means effective with respect to each end wall portion and the associated ends of the bottom and side wall portions for conlining the pulp undergoing classification between said stationary end wall portions, actuating means for imparting horizontal motion to said bottom structure such as will produce relative motion between said bottom and oversize particles thereon, controllable water supply conduit and distributing means for emitting hydraulic auxiliary water at a controlleed rate distributively in a manner whereby the water in effect rises in substantially uniform distribution from the bottom, and whereby in turn there are formed and maintained in said pool horizontal classication zones comprising substantially a sands zone of oversize particles at the bottom, a fines zone of undersize particles at the top, and an intermediate zone containing a mixture of undersize and oversize particles in teeter condition, there being provided an overow Weir for overflow discharge of undersize particles from said top zone of the pool, and an underflow discharge passage at the bottom, and adjustable means for controlling the rate of underflow discharge and thus for controlling the cut between the undersize and the oversize, so that by the concurrent action of the horizontal motion of the bottom face and of the rising iiow of the hydraulic water there are producible overflow and underow size fractions each substantially free from stray particle sizes of the other.

2. Apparatus according to claim 1 in which said sealing means comprise elements of exibly deformable material.

3. Apparatus according to claim 1 in which at least one of said sealing means comprises a closure wall portion edgewise rigidly connected to corresponding edge portions of said bottom and side wall portions to move unitary therewith.

4. Apparatus according to claim 1 in which at least one of said sealing means comprises a closure wall portion edgewise rigidly connected to corresponding edge portions of said bottom and said side wall portions to move unitary therewith, with the addition of resiliently compressible ller material interposed between said transverse wall portion and said closure wall portion.

5. Apparatus according to claim 1, in which said adjustable control means for sands discharge comprises conning means providing a sands column extending outside said passage for sand-sealing the same, a clear water column of adjustable height superimposed upon said sands column, and in which there is furthermore provided a receiving chamber communicating with said clear water column to receive sands spilling over from said sands column incident to the operation of the machine.

6. Apparatus according to claim 1 in which said adjustable control means for sands discharge comprises conning means providing a sands column extending outside said passage for sand-sealing the same, a clear water column of adjustable height superimposed upon said sands column; and in which there is furthermore provided a receiving chamber communicating with said clear water column to receive sands spilling over from said sands column incident to the operation of the machine; with the addition of sands removal means comprising a spigot valve provided at the bottom of said receiving chamber.

7. Apparatus according to claim 1 in which said adjustable control means for sands discharge comprises confining means providing a sands column extending outside said passage for sand-sealing the same, a clear water colv 15 umn of adjustable height superimposed upon said sands column; inY which thereis furthermore provided a receiving chamber communicating with said clear Water column' to receive sands spilling over from said sands column incidentV to the operation of the machine; with the further addition of sands Vdischarge means comprising a sands elevating device adapted toraise sands from the receiving chamber to a point above the clear water level.

8. Apparatus according to claim 1 in which said sup- Y porting structure comprises a stationary framework surrounding the machine and having suspension means for operatively supporting said bottom from said framework.V

9. Apparatus according to claim l, in which said adjustable control means for sands discharge'comprises conlining means unitary with said bottom, providing a sands column extending outside said passage for sandsealingythe same, a clear water column of adjustable height superimposed upon said sands column; and in which there is furthermore provided a receiving chamber Ycommunicating with said clear water column, to receive VViromanother portion thereof,Y said pool'being conned within a tank structure comprising a horizontal bottom element vadapted to be moved in the horizontal plane, with driving means provided and operatively associated with said bottom element for continuously reversing the direction of movement in that plane, and controllable water supply conduit and distributing means extending from above into said pool and having water emitting lower terminalportions in the bottom zone of said poolA Y and'in spaced relationship with said bottom, for distributively emitting hydraulic auxiliary water at a controlled `rate towards said bottom, said lower terminal portionsbeing provided with orices for emitting water jets in a downwardly sloping direction towards said bottom and in a manner whereby the water in effect rises in ,substantially uniform distribution from the bottom and whereby there are adaptedrto be formed and maintained in said pool horizontal classification zones comprising substantially a coarse sands zone of oversize par- Vticles at the bottom, a tines zone Vof undersize particles at Ythe top, and an intermediate zone containing a mixture of undersize and oversize particles in teeter condition, there being provided an overow weir for overow discharge of undersize particles from said top zone of the pooLand an underfiow sands discharge passage at the bottom, and means for controlling the-rate of sands discharge from the poolv and thus controllinglthe' -cut between the undersize and the oversize; said bottomfelement being so constructed and mounted as to perform substantialiy rectilinear reciprocating motion.

ll. Apparatus according to claim 1, in which the means for controlling the rate of sands discharge from the pool comprise a sands discharge weir associated with the sands discharge passage across which weir sands may spill, a receiving pocket Vassociated with the weir for receiving the sands from said weir, and clear water overow means of adjustable height communicating with said receiving pocket for controlling the separation of the size fractions. i

12. Apparatus according to claim 1, in which said sealing means comprise a diaphragmrsealingly connecting the margin ofV one of said stationary end walls with the adiacent edge portions of saidV bottom and of said side wall portions.

References Cited in the tile Vof this patent UNITED STATES PATENTS

Claims

1. APPARATUS FOR THE HYDRAULIC CLASSIFICATION TREATMENT OF A PULP CONTAINING A MIXTURE OF PARTICLE SIZES RANGING FROM FINE TO COARSE, TO EFFECT THE SEPARATION OF THE MIXTURE INTO A FRACTION OF FINES AND A FRACTION OF SANDS, DEFINED AS UNDERSIZE AND OVERSIZE PARTICLES RESPECTIVELY, WHICH APPARATUS COMPRISES A LONGITUDINAL CLASSIFYING POOL HAVING SAID MIXTURE SUPPLIED THERETO IN A PORTION THEREOF AND SAID FRACTION DISCHARGED FROM ANOTHER PORTION THEREOF, SAID POOL PROPER BEING CONFINED WITHIN A SPACE DEFINED BY A HORIZONTAL BOTTOM FACE A PAIR OF WIDE WALL FACES, AND A TRANSVERSE FACE AT EACH END ENDWISE DEFINING THE CLSSIFIER POOL, THERE BEING A HORIZONTAL BOTTOM WHICH PRESENTS SAID BOTTOM FACE TO THE POOL SUPPORTING STRUCTURE FOR PROVIDING HORIZONTAL BACK-AND-FORTH MOVEMENT OF SAID BOTTOM, A PAIR OF SIDE WALL PORTION UNITARY WITH SAID BOTTOM TO PROVIDE SAID SIDE WALL FACES, A STATIONARY WALL PORTION AT EACH END TO PROVIDE SAID END FACES OF THE CLASSIFYING POOL, AND SEALING MEANS EFFECTIVE WITH RESPECT TO EACH END WALL PORTION AND THE ASSOCIATED ENDS OF THE BOTTOM AND SIDE WALL PORTIONS FOR CONFINING THE PULP UNDERGOING CLASSIFICATION BETWEEN SAID STATIONARY END WALL PORTIONS, ACTUATING MEANS FOR IMPARTING HORIZONTAL MOTION TO SAID BOTTOM STRUCTURE SUCH AS WILL PRODUCE RELATIVE MOTION BETWEEN SAID BOTTOM AND OVERSIZE PARTICLES THEREON, CONTROLLABLE WATER SUPPLY CONDUIT AND DISTRIBUTING MEANS FOR EMITTING HYDRAULIC AUXILIARY WATER AT A CONTROLLED RATE DISTRIBUTIVELY IN A MANNER WHEREBY THE WATER IN EFFECT RISES IN SUBSTANTIALLY UNIFORM DISTRIBUTION FROM THE BOTTOM, AND WHEREBY IN TURN THERE ARE FORMED AND MAINTAINED IN SAID POOL HORIZONTAL CLASSIFICATION ZONES COMPRISING SUBSTANTIALLY A SANDS ZONE OF OVERSIZE PARTICLES AT THE BOTTOM, A FINES ZONE OF UNDERSIZE PARTICLE AT THE TOP, AND AN INTERMEDIATE ZONE CONTAINING A MIXTURE OF UNDERSIZE AND OVERSIZE PARTICLES IN TEETER CONDITION, THERE BEING PROVIDED AN OVERLOW WEIR FOR OVERFLOW DISCHARGE OF UNDERSIZE PARTICLES FROM SAID TOP ZONE OF THE POOL, AND AN UNDERFLOW DISCHARGE PASSAGE AT THE BOTTOM, AND ADJUSTABLE MEANS FOR CONTROLLING THE RATE OF UNDERFLOW DISCHARGE AND THUS FOR CONTROLLING THE CUT BETWEEN THE UNDERSIZE AND OVERSIZE, SO THAT BY THE CONCURRENT ACTION OF THE HORIZONTAL MOTION OF THE BOTTOM FACE AND OF THE RINSING FLOW OF THE HYDRAULIC WATER THERE ARE PRODUCIBLE OVERFLOW AND UNDERFLOW SIZE FRACTIONS EACH SUBSTANTIALLY FREE FROM STRAY PARTICLE SIZES OF THE OTHER.