US2189419A

US2189419A - Material classifier

Info

Publication number: US2189419A
Application number: US193300A
Authority: US
Inventors: John H V Finney
Original assignee: Individual
Current assignee: Individual
Priority date: 1938-03-01
Filing date: 1938-03-01
Publication date: 1940-02-06
Anticipated expiration: 1957-02-06

Description

Feb. 6, 1940. y J. v. FINNEY 2,189,419

l l MATERIAL CLASSIFIER Filed March l, 1938 4 Sheets-Sheet 1 Feb. 6, 1940. J. H. v. FINNEY MATERIAL CLASSIFIER Filed March l, 1938 4 Sheets-Sheet 2 WWA/7;

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Gmunmjs Feb. 6, 1940. J. H. v. FINNEY 2,189,419

MATERIAL CLASSIFIER Filed March l, 1958 4 Sheets-Sheet 3 Feb. 6, 1940.

J. H: V. FINNEYv MATERIAL CLASSIFIEB Filed March l, v1938 4 Sheets-Sheet 4 Patented Feb, e, 1940 PATENT OFFICE MATERIAL CLASSIFIER John H; V. nney, Denver, Colo., assignor to Homer C. Hirsch, El Paso, Tex,

Application March 1, 1938, Serial No. 193,300 1s claims. (C1. 209-464) The present invention is concerned generally with material classiiiers of the kind chieiiy used in handling ores during metallurgical operations,

5 and especially with classiiiers wherein solid particles are suspended in abody of liquid, usually water, from which the particles-settle out accordingto size and density. The desired classiiication oi' the particles is obtained by settling out iiner particles in suspension. K

There are many uses to which classifiers may be put other than those involved in ore dressing or metallurgical operations, so that although I deu scribe my invention and the advantages thereof in connection with handling ore, it will be realized that I am not necessarily limited thereto. Also, features of the present invention may be used with many different constructions, but because of the particular adaptation of the present invention thereto, I show the invention in conjunction with my improved classiiier disclosed in my copending application Serial No. 169,586, iiled October 18, 1937. In that improved type of classifier I have overcome diiiiculties inherent in earlier classiiiers that produce a lack of flexibility and technical control ofthe product, and this has been done by providing separate and independent'means for controlling'the factors of agitation, size of particle separated, capacity measured by gross input, and density of overflow. By separating and independently operating the physical elements controlling these several factors, the classifier is made entirely iiexible and may be easily and quickly adjusted to meet any condition of ore, size or quantity of product, and rate of feed.

For example, the size of line particles left in suspension is made independent of pulp density in the overflow. Consequently, the point at which separation is eiected may be changed to increase or decrease the size of particles carried by the overiiow without altering the pulp density; and likewise, water may be added` to the feed to decrease the pulp densityand suitable adjustmentsv can be made in the particle 'size control apparatus to compensate for the added amount of liquid with the result that the size of particle discharged is unchanged. Because the coarse sands are washed by currents set up in the liquid from independently operated agitating means, the oversize discharge can be thorougly washed free of fines without adding wash water which necessarily decreases pulp density and without altering the speed of raking which controls the over-all capacity of the classifier. For a iurthe coarse or oversize fraction and leaving the ther discussion of these advantages and the re` sults thereof, reference should be had to my above-mentioned copending application.

lIt is common practice to connect the classifier in a closed circuit with a mill operating to crush or reduce ores, in such a way that the mill discharge iiows into the classiiier in which solid particles are divided into the coarse or over-size fraction which-is returned to the mill for regrinding, and a line fraction which is removed from the closed circuit for other metallurgical treatment. The oversize returned to the mill is termed the circulating load, and in order to keep the mill operating under conditions of high efciency, the circulating load is several times the weight of the iines, which represent the recovery from the mill. Typically, it has become common practice to have a circulating load of twelve to sixteen or even more times the amount ground and recovered as fines; that is, for every ton of fines removed from the classifier, there are twelve to sixteen or more tons of insumciently ground material flowing in the circuit back to the mill from the classifier for regrinding.

The combination of a relatively high circulat- 25 ing load and a high velocity ofiiow in the closed circuit imposes an extremely heavy load'on the classifier which is required to have a large capacity in order to function properly. In classiers using screw conveyors, an increase in capacity is obtained by increasing the diameter of the conveyor screw, with the result that the diameter reaches relatively large values, particularly when only a single conveyor is used in a classifier. It then becomes impractical to place the overilow launders above the conveyor as has been prior practice, because the minimum depth of tank required for this construction is equal to the diameter of the conveyor plus the space occupied by. the iaunder. The slope of the inclined tank 40 bed being fixed, the length of the tank is proportionately increased along with the increased total'depth. Such an enlarged tank is. wasteful because it holds a body of liquid much greater than is necessary to secure satisfactory separation of the suspended particles, and the increased cost of construction becomes so high that it is entirely out of proportion to the capacity of the tank. Moreover, the size of such la unit'is so large that floor space, which is generally at a premium, is often not available for an installation of this character.

From these considerations it will be apparent that increased capacity obtained by merely increasing the size of the parts of a classifier with- 55 out changing the construction from that previously used, produces an impractical and uneconomical device.

Other previous types of construction are objectionable in that no separate control of fluid velocity near the point of outlet is possible. The classification efficiency is greatly increased in accordance with the disclosure of my copending application by using independent means for determining this outflow velocity in order to control the size of particles separated from the liquid, but the full value of this means is not realized unless it is adjustable to obtain separation at any point desired and to permit compensation for changes in the other factors affecting operation. Size control means can be further improved in accuracy if there is suicient space around it to permit adjustments that produce a non-uniform liquid velocity in the outlet means to increase the sharpness of separation.

A common and well-known weakness in classifiers of conventional constructions has been the bearing rotatably supporting the lower end of the spiral conveyor. Because the conveyor must of necessity extend below the liquid surface substantially to the end of the tank, this lower bearing has been submerged in the tank liquid where it is in contact with the liquid and open to the abrasive particles suspended therein. These abrasive particles are small enough to enter the bearing and cause excessive wear, necessitating frequent removal and replacement of the worn bearing with obvious attendant expense and loss of time while the equipment is shut down. Many expedients have been resorted to in an attempt to prevent entry of the liquid and abrasive particles into the bearing, and these devices have included special types of bearings, packing rings and seals, and pressure lubrication designed to maintain a lubricant pressure inside the bearing equal to or greater than the liquid pressure outside the bearing. None of these devices can be regarded as more than moderately successful from a practical viewpoint since they have not succeeded in entirely eliminating the diiilculties inherentin a submerged bearing, and vunless very carefully attended to, these devices frequently fail mechanically and deprive the bearing of any protection they may afford. submerged bearings have often been considered the Weakest point in classiers using a screw conveyor, and have been particularly objectionable when it is desired to place the classifier in continuous operation twentyfour hours a day because they are frequent causes of shut-downs. e Y

In my above-mentioned copending application I disclosed the use of a horizontally extending paddle wheel mounted over the screw conveyors for independently agitating the liquid within the tank. That arrangement is subject to some of the same objections discussed above in connection with overflow launders arranged above the conveyors, and is impractical when a conveyor of relatively large diameter is used because it requires the liquid level to be higher than the top of the conveyor at its lower end.

It thus becomes a general object of this invention to provide an improved type of classifier in which a single, large diameter screw conveyor of large sand capacity operates in a shallow body of liquid of which the surface may be lower than Y the top of the conveyor.

Another general object of the invention is to provide liquid outlet means in a classifier of this .type that is adapted to control the size of particle discharged in the outgoing liquid and which is adjustable for selecting any desired size of particles.

It is also an object to provide an improved type of liquid outlet means which may be adjusted to actual operating conditions to secure greater sensitivity and sharpness of separation by obtaining a non-uniform liquid velocity through the means.

Another object of my invention is to provide a bearing structure for a classifier using a rotary conveyor in which the bearing, although located at a point lower than the liquid level, is completely free from any danger of entry of liquid and abrasive particles into the bearing.

A further object of my invention is to provide suitable independently operated agitating means for a classifier having a vlarge diameter screw conveyor. i

These objects of -my invention have been attained in a classifier having a tank with an inclined bed adapted to contain a body of liquid and the solid particles to be classified, liquid inlet means, and liquid outletmeans, by providing a large diameter screw conveyor comprising a central rotatable member and helical ribbon flights mounted on the shaft and rotated thereby, the helical ribbon being annularly spaced from the central member. The helical ribbon is supported on the central member only at points above the level of the tank liquid, but the conveyor itself extends down into the liquid substantially to the end `of the tank. Suitable bearing means is provided for rotatably supporting the lower end of this rotating central member and the bearing is supported in turn at a position beyond the lower I end of the ribbon. Means are provided to prevent entry of liquid into the bearing. While in a simplified form of my invention the means for preventing entry of liquid into the lower end of the bearing may be a simple closure wall sealing the end of the bearing sleeve, in a preferred form of my invention the overflow launder is located centrally and longitudinally of the tank and the conveyor bearing sleeve is located within this overflow launder where itis not in contact with liquid within the tank. In the annular space between the central conveyor member and the helical ribbon is located not only the overflow launder but also baffles forming a -sorting column or columns adjacent the overflow launder t control the size of particles separated from the liquid. Independent rotary agitating means is located on the side walls of the tank and to one side of the conveyor means to wash the sands near the upper end of the liquid body and thoroughly agitato the incoming feed.

How the above as well as other objects and advantages of my invention are secured will be more apparent by reference to the following description and the annexed drawings, in which:

Fig. 1 is aside view, partially in elevation and partially in vertical median section. of a preferred form of my invention;

Fig. 2 is a plan view of the classifier shown in Fig. 1;

Fig. 3 is an end elevation of the lower end of the tank;

Fig. 4 is a vertical cross-section at the end of the tank on line 4-4 of Fig. 1;

Fig. 5 is an enlarged cross-section similar to Fig. 4, showing a modified form of adjustable baffle construction;

Fig. 6 is a fragmentary vertical section through the end of a variational form of classifier; and

Fig. '7 is a plan view of another variational form of classifier, the lower end of which is constructed as shown in Fig. 6.

The classifier illustrated in the drawings has a body or tank generally indicated at I which is adapted to contain a body of water or other liquid holding in suspension the solid particles that are to be classified. v'I'he side walls of the tank are vertical, and end wall II is generally so, while the bottom wall or bed I2 is inclinedlongitudinally of the tank. Bed I2 slopes uniformly throughout the length of the tank, the lower portion of the bed being submerged ybeneath the liquid as shown in Fig. 1, and the upper end of the bed extending above and beyond the liquid level to form a draining deck. As the coarse particles, termed sands, are moved over this deck, the excess liquid drained from them runs back into the tank.

A stream of liquid carrying suspended solid particles is conveyed into the classifier from a grinding` mill or other suitable source by inlet launder I5. Although this launder may continue straight on and empty directly into the main portion of the tank, it is preferred that launder I5 have a short transverse section I5a that dis- The coarse particles settle out' of the liquid in I. the tank onto inclined bed I2 and suitable rotary cated at 20 comprises a central rotating shaft 2| on which the two spiders 22 are mounted. The outwardly extending arms of spiders 22 are supports to which are secured longitudinally extending braces 23 at points intermediate the length of braces 23. As seen in Fig. 4, each spider 22 is providedl with four armsand consequently there are four braces 23, spaced 90c apart, around shaft 2|; but, of course, a larger or smaller number of arms and braces may be used if desired. 'I'he flights of helical ribbon 25 are secured to the braces and pass around'the outside faces, of members 23. The longitudinal braces are attached to the supporting arms of -the spiders at points removed from center shaft 2I so that an annular space is left between the shaft and rib,- bons 25.

Braces 23 and ribbon flights 25 form a rigid 4trussed structure mounted on shaft 2| to be rotated thereby. This trussed structurev has a cantilever end section at each end of the conveyor between spiders 22 and the ends of the shaft. In each of these centilever end sections,

braces 23 extend parallel to the center shaft and carry the helical ribbons to the end of the shaft, the trussed construction giving sufcient inherent strengthto allow the helical ribbon to overhang the end of the conveyor for a considerable distance beyond the last supporting spider 22.

Several advantages result from this trussed construction with the cantilever end sections, and among them is the ability to support the central rotating memberv2I at points inward of the end of conveyor 20. This type of arrangement is illustrated at the upper end of conveyor 20 where a -center shaft 2l is drivingly mounted inonehalf of a universal joint 21, and ribbons 25 extend upwardly around the universal joint sub stantially to the end of bed I2 and engage the sands on the bed almost up to the time that they drop over discharge lip I8. The other half of universal joint 21 is fastened to the end of a short shaft 28, rotatably mounted in

bearings

29 and 30, which are mounted in fixed positions relative to each other upon the Iframe-"work of tank I0. Bevelgear 32 is keyed to shaft 28 in'- termediate bearings 29 and'3Il and meshes with driving pinion 33 which is secured to drive shaft 34 rotatably mounted in

bearings

29 and 35, shaft 34 extending at right angles to shaft 28. Drive sprocket 36 is fastened to shaft 34 and is driven lby chain 31 frommotor 38 mounted upon platform 39 erected upon tank I0. Rotary conveyor 20 isvthus driven from motor 38 or other source of power, and suitable means may be added, either velectrical control means or a mechanical transmission, for varying the speed of rotation of the conveying means.

The advantage is also taken at the other end of the conveyor of the overhanging end section to support the center shaft in bearings above the end of the conveyor, but the construction and arrangement of parts will be more easily understood if there is first described the liquid outlet means for discharging liquid and suspended particles from the tank. As will be seen particularly from Fig. 3. end wall II of the tank is formed with a vertically extending slot 42 which is preferably reinforced around its margin by the channel and angle construction indicated at 43. In this vertical slot 42 is placed overflow launder 45. The two spaced vertical side walls 46 of launder 45 have the shape of a trapezium, as illustrated in Fig. 1. with the top edge of the side walls horizontal. The two side walls are joined along their bottom edges by a rectangular bottom wall which is preferably substantially parallel to tank bed I2, and are joined at their back edges by a rectangular back wall which extends upwardly between the side walls from the bottom wall to the top of the side walls. The lower end of launder 45 is open and discharges liquid and suspended fines from the'classier into any suitable launder. The entire overflow launder is supported from tank wall II by attaching it to the flange structure 43 about the margin Aof slot 42, and, of course, the width of slot 42 is determined by the necessary dimensions of launder 45, since the connection between the launder and the end wall of the tank must be fluid tight in order to prevent leakage of the liquid within the tank. The horizontal top edges of lopposed side walls 46 form a pair of spaced parallel weirs over which liquid inside the tank flows into launder 45 and the height of the liquid level Within the tank is determined by the location of these weirs.

Overflow launder 45 is elongated longitudinally of tank I0 as shown particularly in Fig. 2, and is located centrally of the tank in order to receive the lower portion of bearing sleeve 48 between the launder side walls as shown in Fig. 1. The wall means nforming the launder and overflow weirs defines a space beneath the liquid level from which liquid is excluded and in which the lower end of shaft 2l and bearing sleeve 48 is placed to prevent entry of liquid into the lower end of 4the shaft bearing. Sleeve 48 rotatably supports the lower end of the rotary conveyor shaft which extends downwardly to a point below the liquid level in the tank, and the sleeve has one or more internal liners 49 that provide journal bearings for shaft 2|. Sleeve 48 extends upwardly from the lower end of and around shaft 2I to a point where the upper end of the sleeve is above the liquid level in the tank and consequently, even though open, is'out of contact with the liquid so that particles cannot enter and bearings inside the sleeve are not subject to deterioration caused by abrasive particles. Lower spider 22 is sufciently spaced from the end of shaft 2I that bearing sleeve 48 is long enough for this purpose, and the cantilever section at the lower end of screw conveyor 20 overhangs the bearing sleeve and carries the ribbon ights 25 down substantially the length of the tank to end wall I I.

The lower end of sleeve 48 may be left open as shown in Fig. 1, but the walls of launders 45 prevent entry of liquid into the lower end of the bearing sleeve, because they exclude liquid within the tank from conta-ct with this lower end of this sleeve. Consequently, the bearing surfaces are completely protected from abrasive parties entering the bearing from the tank liquid. This particular construction has the ad,- vantage that even though the lower end of the conveyor shaft and its bearing is at a lower elevation than the liquid level as determined by the tops of launder walls 46, the end of the bearing is not submerged in the tank liquid. Sleeve 48 is continuous from its upper end to the end of launder 45 to shield the bearing from liquid that may splash on thevsleeve as it ows over into the launders, but this liquid will not work back into the bearings since there is no hydrostatic head forcing it into the bearing.

Bearing sleeve 48 is stationary with respect to the conveying means and is supported in bearing block 50 at a point beyond the lower end of ribbon 25. Bearing block 50 is guided vertically and held against transverse horizontal movement by the faces of launder walls 46 where they pass between flanges 43 around opening 42, and is hung by threaded bolt 5I from cross bar 52 resting on the side walls of tank I0. By turning adjustment nuts 53 on rod 5I, block 50 and the lower end of the conveying means may be raised or lowered, permitting vertical adjustment of the conveying means with respect to the inclined tank bed 12. Block 50 is preferably fastened to sleeve 48, and pairs of guides 54 on walls 46 hold the block and sleeve against longitudinal movement on shaft 2l. This adjustable support of the lower end of the conveyor is of particular advantage in starting the conveyor after the classier has been temporarily shut down. After a short shutdown, the sands have settled out of the liquid and are packed around the lower portions of the helical flights, and it is necessary to apply tremendous torque to the conveyor in order to start it rotating again. On the other hand, if the lower end of the conveyor can be raised but a few inches from rthe bottom of the tank, it is freed of a great deal of this load and starts much more easily, and when once started it can then be slowly lowered toward the bottom of tank I0, gradually removing the accumulated sands as it goes downwardly, until it is once more in its correct operating position with respect to bed I2. lhe articulate character of central member 2I imparted by universal joint 21 permits this angular movement of the conveyor without disturbing the alinement of driving gears 32 and 33.

Bearing sleeve 48, being non-rotatable, is a convenient support also for bafiles 55 placed one on either side of launder 45. Baliies 55 are mounted on the opposite ends of two lead screws 56 rotatably mounted in bosses on collars 51 attached to sleeve 48, Each collar 51 has two bosses and a. collar 58 is placed on the screw 55 between the two bosses to keep the screw from moving endwise. In order that bailles 55 may be simultaneously moved toward or away from the side walls of launder 45, the bales have attached to them threaded nuts engaging lead screws 56, each of which has both rightand.

left-hand threads. By this construction, rotation of screws 56 moves both bailles simultaneously an equal amount toward or away from side walls 46 of the overflow launder.

As shown in Fig. 4, side walls 46 of overflow launder 45 are preferably vertical, and baffles 55 are also vertical and parallel to the side walls. Each side wall 46 and its associated bailie 55 form vertically extending wall means which define between them a vertically extending space 50, which is termed a sorting column. While it may be suicient to have but one such sorting column, it is preferred to havetwo as shown.

AAt the top of each sorting column 60 is the overiiow Weir defined by the top edge of a launder wall 46. The velocity of the liquid flowingvertically through sorting columns 60 determines the size of particle carried in suspension by the liquid over the weirs and into the overflow launder. Bailles 55 extend from a point above the normalv liquid level to a point below that liquid level in order to prevent liquid from reaching and overowing the weirs except by passing through the sorting columns 60. The sorting columns are preferably of considerable vertical extent as shown, in order that relatively. stable conditions, free from eddy currents outside the sorting column, may be established and an accurate separation of the -particles accomplished. For a given rate of discharge into the overflow launder, the vertical velocity through the sorting column decreases as bailles 55 are moved away vfrom walls 46 and the cross-sectional area of the column is increased. Conversely, decrease in cross-sectional area increases the vertical liquid velocity. Obviously, the point of separation between particles settled out and the particles carried on over in suspension is determined by the liquid velocity.

,For a further discussion of the advantages and typical variations in the yconstruction of sorting columns, reference should be made to' my copending application mentioned above.

V'Iransverse'baille 62 is attached to bearing 44 and extends perpendicularly to the sleeve axis. Batlle 62 is positioned on sleeve 48 as close as practical to the top edge of the back wall of launder 45. In this position the baille prevents liquid in the tank from flowing over the rear wall of the launder, except for a negligible amount which may flow upwardly between the baille and the end vof the launder. Baffie 62 extends vertically the full height of bailles 55, and extends horizontally out to the extreme positions to 'be occupied by baflles 55. Batlles 55, as shown in Fig. 2, extend from end wall II` to baille 62, except for the necessary clearance. 'The ends of sorting columns 60 'are thus actually defined by tank wall II and baffle 62.

Extending upwardly from collars 51 are brackets 64 which support arcuate shield 65, shown in Fig. 4. Shield 65 extends completely over launder 45 and both sorting columns 60 to prevent any liquid or solid material from falling into these parts of the liquid outlet means from the rotary conveyor as it passes over the sorting columns and launder. Clearance between shield 65 and conveyor braces 23 is purposely reduced to a minimum so that any accumulation of sands deposited upon the upper face of the shield is removedv by braces 23 as they pass over the shield.

My improved construction permits the use of a rotary conveyor of relatively large diameter that extends substantially the full width of the tank and also extends down into the liquid substantially to end wall yet operation is satisfactory when the maximum liquid depth is less than the diameter of the conveyor and the body of liquid maintained within the tank is not excessively large. The helical flights 25 are mounted on the rotatable center shaft to leave an annular space between them and the shaft, and in this annular space is placed the liquid outlet means comprising the overflow launder 45, which discharges through an opening in end wail and bailles 55 that form the sorting columns.

Baiiles 55 and 62, as well as shield 65, are fastened to the lower bearing for the rotary conveyor and move with the conveyor when it is adjusted vertically by bolt 5| and nut 53 to avoid overloading from accumulated sands when operation is commenced.

Liquid agitating means is provided to obtain independent agitation of the 'liquid in addition to that secured by rotation of the conveying means. Without intending to limit the agitating means to the particular form shown, I have shown this means as `comprising paddle wheel 68` rotatably mounted on a side wall of tank l to turn about a horizontal axis.

smaller sprocket attached to shaft 34. This driving linkage is aconvenient one, but it will be understood that the paddle wheel 68 may be driven by another'prime mover instead of motor 38.

Agitator 68 is mounted at one side of conveyor 20 and is preferably located in bay I1 formed in the side wall of the tank as thisl construction permits a smaller clearance between the rotary conveyor and other portions of the tank side walls. Launder |50. is adjacent the periphery of wheel 68, and the incoming feed is preferably discharged directly into the path of the agitator blades to secure thorough agitation `of thesuspended particles near the point of inlet. Agitatlon at this point is designed primarily to break up agglomerated particles that are composed yof a number of smaller particles. In addition'to this function, agitator 68 sets up local currents through the tank liquid which vfollow the general path indicated by the arrows in Fig. 2. The relatively open construction of the rotary conveyor permits these currents inthe liquid to flow througl the conveyor away from the agitator near the vupper end of the liquid body and return through the conveyor to the agitator at the opposite side of agitator 68. These currents flow in a more or less horizontal plane and thoroughly wash the sands which have accumulated on the tank bottom in the space opposite agitator 63, which is the zone .of primary settling in which the largest particles settle out from the liquid. Finer particles, which settle out in deeper liquid, are moved by the conveyor Vupwardly along tank bed I2 and i are also subjected to washing action of the horizontal currents. 'I'his washing action removes from' the coarse sands anyne particles which 'may have been trapped therein or which still Sprocket 68, attached to the' paddle wheel shaft, is driven by chain 10 from a adhere to the larger particles and carries the ilnes back into suspension.

Fig. 5 discloses a variational manner of mounting bailies 55 to achieve greater flexibility in adjusting the size and shape of sorting columns 60. In this construction, bailles 55 are pivotally mounted at their upper ends to cross bars 12 fastened to collars 51. Hinges 13 forming this pivotal connection are adjustably fastened to cross bars 12 by one or more wing nuts and bolts as at .14. Each. bolt passes through an elongated slot in the cross bar, and when the wing nut is loosened, the baiiies may be moved toward or away from launder walls 46 throughout the range of movement permitted by the slot in the cross bar. By tightening the wing nuts, the bailles are held at the selected position, the adjustment be-` ing similar to that previously described. In addition, the pivotal mounting of each baille 55 by hinges 13 permits the baille to be adjusted angularly with respect to the other wall of the sorting column, so that the top end ofthe sorting column may be made either larger or smaller in cross-section than the bottom end. Each baille 55 is held in its angularly adjusted position by one or more braces 15 pivotally attached at the lower ends to the baffles and adjustably fastened at the upper ends to cross bar 12 by a wing nut and bolt as at 16, or other suitable adjustable fastening. The upper end of each brace 15 is slotted in order to obtain the necessary longitudinal movement of the braces with respect to cross bar 12. Thisadjustable construction permits the baflles to be swung betweenthe dash-dot positionsshown in Fig. 5 to produce a non-uniform liquid velocity that increases or decreases upwardly as desired. The result is betterA control of the conditions existing in the sorting columns, making them more sensitive and causing more accurate separation under certain conditions.

A simplied construction is illustrated in Fig. 6, certain of these features being also shown in Fig. 7. In this form, conveyor 20 isconstructed as previously described, the chief changes being those brought about by differences in the means for preventing entrance of liquid into the lower end of the bearing sleeve and for supporting the bearing sleeve at a position beyond the end of ribbon 25, resulting from the use of a solid end wall ||a in the tank. The top edge of end wall Ila is the weir that determines the height of the liquid level within the tank, and liquid and suspended particles flow over the top edge of this wall into discharge launder 80. Bearing 48 is of suicient length that its upper end is above the level of the liquid, and its lower end is in actual contactl with and submerged in the liquid body. Instead of the lower end of bearing sleeve 48 being open, it is closed by transverse plate 8| attached to a flange around the lower end of sleeve 48. Plate 8| closes the lower end of the bearing and seals it against entry of liquid into the bearingsleeve at its lower end. The conveyor bearing is supported at its extreme lower end beyond the end of ribbon 25-by cable 82, or other similar means, attached to plate 8|. Cable 82 passes around rotatable drum 83 carried on cross member 84 of the tank frame. Rotation of drum 33, by suitable crank or lever means, raises or lowers the end of conveyor 2|) to eiect vertical adjustment of the conveyor with relation to tank bed I2 for the purposes previously described. This means for supporting the lower end of conveyor is preferred because it enables vertical adjustment of the conveyor, but if this feature is not desired it will be clear that a fixed supporting means of suitable character may be used. Plate 8l preferably extends entirely across the tank and engages the side walls to prevent horizontal -movement of the conveyor and hold sleeve 48 against rotation.

Fig. 7 illustrates a modified form of rotary conveyor means 20 especially designed for very heavy sand loads. In this form of conveyor, longitudinal braces 23a are attached intermediate their lengths to the outwardly extending arms of spider 22 at points spaced from the central shaft 2l, in the same manner as previously described, but there is this difference; that one end of all longitudinal braces is attached to shaft 2l by collar 81. Braces 23a thus have two distinct sections: one is the lower section in which Athe braces extend parallel, or substantially so,

t'o the central member of conveyor 20, andthe other is the upper section in which braces 23a are inclined with respect to the central member of the conveyor. tion of braces 23 is here shown as co-extensive with the lower cantilever end section of the conveyor which overhangs and surrounds bearing sleeve 48, the parallel extent of the'braces may be greater and in this case a'second spider 22 would be used farther up the shaft. Higher up on the conveyor than the point where the braces are inclined towards the center shaft, the helical ribbons 25 are supported either from the in' clined braces by short arms 88 or are supported directly from the center shaft by outwardly extending supports 89.

This modified form of conveyor is particularly adapted to heavy sand loads, because in that portion of the conveyor wherelthe sands have accumulated most, the longitudinal braces have been eliminated and are not dragged through the sands. This variational construction eliminates a considerable load on the conveyor that exists when sands have accumulated on bed I2 to a depth greater than the distance of braces 23 above the tank bed. Because the longitudinal braces are dragged broadside through the sands, they are subjected to a very considerable erosive action and as a result wear out rapidly. Hence the construction of Fig. 7 adds materially to the life of the conveyor unit as a whole, without loss of the advantages derived from a trussed conveyor construction with a cantilever end section.

Another variation illustrated in Fig. 7 adapted to heavy sand loads is the progressive change in radial width of ribbons 25. At the lower end of the tank where the sands are shallow, a relatively narrow ribbon 25 is sufcient. On the upper end of bed I2, particularly on the portion above the liquid level, a ribbon 25 of greater radial width may be convenient, as illustrated at the right-hand end of Fig. '7. Although the change in width from a narrow to a wide ribbon 25 may be made abruptly, a desirable `construction is to have a progressive change from the minimum to the maximum width of the ribbon, as in the central portion of Fig. 7. This progressive increase in ribbon width preferably takes place in the primary settling zone opposite agitator 68, as it is in this area that the accumulation of sands on bed I2 builds up. If desired, the ribbon width may change progressively for the entire length of the conveyor.

Having described a 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 Although the lower parallel sec` Athe invention and the appended claims, and not restrictive thereon, for various changes in arrangement and design of parts and combinations of the several features herein described may be made without departing from thelspirit and scope of my invention.

I claim:

1. In a classifier for selectively separating suspended solid particles from a liquid, the combination of a tank having an inclined bed and anend wall and adapted to contain a body of liquid and solid particles suspended therein to be classified; rotary conveying means for moving settled coarse particles along the inclined tank bed and out of the liquid to a place of discharge from the tank, said conveying means comprising a rotatable shaft with its lower end adjacentl the tank end wall, helical ribbon flights mounted on but spaced from the shaft and rotated thereby, and a bearing sleeve rotatably supporting the lower end of the shaft, the bearing sleeve extending from a point adjacent the tank end wall and lower than the liquid level in the tank upwardly through the space between the ribbon flights and the rotatable shaft to a point above the liquid level; and means preventing entrance of the liquid into the lower end of the bearing sleeve.

2. In a classifier for selectively separating suspended solid particles from a liquid, the oombination of a tank having an inclined bed and an end wall and adapted to contain a body of liquid and solid particles suspended therein to be'fclassified; rotary conveying means for moving settled coarse particles along the inclined tank bed and out of the liquid to a place of discharge from the tank, said conveying means comprising a rotatable shaft with its lower end adjacent the tank end wall, helical ribbon `flights mounted on but spaced from the shaft and rotated thereby, and a bearing sleeve rotatably supporting the lower end of the shaft, the bearing sleeve extending from a point adjacent the tank end wall and lower than the liquid level in the tank upwardly through the space between the ribbon ights and the rotatable shaft to a point above the liquid level; and a transverse sealing member closing the lower end of the sleeve to prevent entry of liquid into the bearing sleeve.

3. In a classifier for selectively separating suspended solid particles from a liquid, the combination of a tank having an inclined bed and an end wall and adapted to contain a bodyA of liquid and solid particles suspended therein to be classified; rotary conveying means for moving settled coarse particls along the inclined tank bed and out of the liquid to a place of discharge from the tank. said conveying means comprising a rotatable shaft with its lower end adjacent the tank end wall, helical ribbon flights mounted on but spaced from the shaft and rotated thereby, and a bearing sleeve rotatably supporting the lower end of the shaft, the bearing sleeve extending from a point adjacent the tank end wall and lower than the liquid level in the tank upwardly through the space between the ribbon ights and the rotatable shaft to a point above the liquid level; and wall means spaced from and surrounding the lower end of pended 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; rotary conveying means for moving settled coarse particles along the inclined tank bed and out of the liquid to a place of discharge from the tank, said conveying means comprising a rotatable shaft, helical ribbon flights mounted on the shaft and rotated thereby, and a bea-ring sleeve rotatably supporting the lower end of the shaft, the bearing sleeve extending from a point lower than the liquid level in the tank to a point above the liquid level; and a longitudinally extending liquid outlet launder centrally disposed ofjthe tank to receive the lower end of the bearing sleeve and exclude liquid in the tank from contact with the portion of thesleeve in the launder, said launder discharging liquid and unseparated ne particles from the tank.

5. In a classifier for selectively separating suspended solid particles fromfa liquid, the combination of a tank having an inclined bed 'and adapted to contain abody of liquid and solid particles suspendedtherein'to be classified; rotaryconveying means for moving settled coarse particles along the inclined tank bed and out of the liquid to a place of discharge from the tank, said conveying means comprising a' -rotatable shaft, helical ribbon flights mounted on the shaft and rotated thereby, and a bearing sleeve rotatably supporting the lower. end of the shaft, the bearing sleeve extending from a point lower thanthe vliquid level in the tank to a point above the pended 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; rotary conveying means for moving settled coarse Y particles along the inclined tank bed and out of and rotated' thereby, and a bearing sleeve rotatably supporting the lower end of the shaft, the bearing sleeve extending from a point lower than the liquid level in the tank to a point above the liquid level; and U-shapedweir-forming means forming a weir with spaced opposed walls over which the liquid and unseparated fine particles are discharged from the tank, said weir means being placedat the lower end of the tank in alinement with the conveying means with the lower end ofthe conveyor shaft and bearing sleeve extending between the opposed Weir walls.

7. 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; rotary conveying means for moving settled coarse particles along the inclined tank bed and out of the liquid f nularly spaced from the central member; and

liquid outlet means projectinginwardly from the tank. walls discharging liquid andunseparatedalong the inclined tank bed and out of the liquid veying means comprising a central rotatable member, and a helical ribbon. secured. to and annularly spaced from the central member; liquid outlet-means projecting inwardly from the tank wallsv discharging liquidand unseparated fine particles from the tank, said outlet means being located in the annular `space-between the central member and the helicalrbbon of the conveying means; and a stationary shield over theliquid outlet to divert back into the' tank ma terial falling from the helical ribbon.

9. 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; rotary conveying means for moving settled coarse particles along the inclined tank bed and out of the liquid to a place of discharge Vfrom the tank,

said conveying means comprising a rotatable shaft, and helicalribbon flights mounted on the shaft and annularly spaced therefrom; and liquid outlet means within the annular space between the shaft and the helical ribbon o'f the conveyingmeans for discharging liquid and unseparated fine particles from the tank, 'said outlet means comprising a pair of spaced, vertically extending walls of which one is supported from the tank walls and forms an overow Weir, and the other is supported from the conveying means, the two spaced walls forming a sorting column through which liquid discharged from the tank flows vertically to determine the size of fine particles carried by the discharged liquid.

10. In a classifier forl selectively separating sus-r y.to a place of discharge from the tank, said conpended 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; rotary conveying means for moving settled coarse particles along vthe inclined tank bed and out of the liquid to a place of dischargefrom the tank, said conveying means including a rotatable shaft extending longitudinallyof the tank, anda stationary bearing sleeve rotatably supporting the lower end of the shaft and liquid outlet means discharging liquid and unseparated fine particles from the tank comprising an overflow launder having overflow weir means at opposite side walls thereof and supported from the tank walls, a pair of Avertically extendingplates one at either side of the launder, and screw-threaded supporting means adjustably mounting the plates on the shaft-bearing sleeve, the plates being simultaneously movable toward or away.l from the launder by rotation of the threaded supporting means and forming with 'the launder side walls a pair of sorting columns through which liquid discharged from the tank 'flows todetermine the size of fine particles carried'by the discharged liquid. l

11. In a classifier for selectively separating suspended solid particles from a liquid, the comtary conveying means for moving settled coarse particles along the inclined tank bed and out of the liquid to a place of discharge from the tank; and liquid outlet means discharging liquid and unseparated particles from the tank, said outlet means comprising a fixed wall member forming an overflow Weir at its top edge, a movable wall member spaced from the fixed wall and pivotally mounted at its upper edge for angular adjustment with respect to the fixed wall, and lock means securing the movable wall in selected positions, the two Walls forming between them a generally vertically extending sorting column through which liquid discharged from the tank fiows to determine the size of fine particles carried by the discharged liquid.

12. In a classifier for selectively separating suspended solid particles from a liquid, the combination of a tank having an inclined bed and an end wall and adapted to contain a body of liquid and solid particles suspended therein to be classified; rotary conveying means for moving settled coarse particles along the inclined tank bed and out of the liquid to a place of discharge from the tank, said conveying means comprising a rotatable articulated shaft with its lower end adjacent the tank end wall, helical ribbon flights mounted on but spaced from the shaft and rotated thereby, a bearing sleeve rotatably supporting the lower end of the shaft, the bearing sleeve extending from a point adjacent the tank end wall and lower than the liquid level in the tank upwardly through the space between the ribbon flights and the rotatable shafts to a point above the liquid level; and adjustable means supporting the bearing sleeve from the tank wall at a point on the sleeve beyond the end of the helical ribbon for vertical adjustment of the conveyor relative to the tank bed:

13. In a classier for selectively separating suspended solid particles from a liquid, the combination of a tank having an inclined bed and an end wall and adapted to contain a body of liquid and solid particles suspended therein to be classiiied; rotary conveying means for moving settled coarse particles along the inclined tank bed and out of the liquid to a place of discharge froml the tank, said conveying means comprising a rotatable articulated shaft with its lower end adjacent the tank end wall, helical ribbon flights mounted on but spaced from the shaft and rotated' thereby, and a bearing sleeve rotatably supporting the lower end of the shaft, the bearing sleeve extending from a point adjacent the tank end wall and lower than the liquid level in the tank upwardly through the space between the ribbon flights and the rotatable shaft to a point above the liquid level; wall means surrounding the lower end of the bearing to exclude liquid in the tank from contact with the lower end of and entry into the bearing sleeve;

and adjustable means supporting the bearing sleeve at a point on the sleeve beyond the end of the helical ribbon for vertical adjustment of the conveying means relative to the tank bed, said adjustable support. being confined and vertically guided by said wall means.

1,4. In a classier 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 classiiied; rotary conveying means for moving settled coarse particles along the inclined tank bed and out of the liquid to a place of discharge from the tank, said conveying means comprising a central inclined rotatable member, outwardly extending supporting means attached to the rotating member, longitudinal braces attached to the supporting means at points radially spaced from the central member, and a helical ribbon secured to the braces and annularly spaced from the central member; a relatively stationary bearing assembly rotatably supporting one end of said central member, said bearing assembly comprising a tubular sleeve and a pair of spaced journal bearings Within the sleeve in which the shaft is journaled to support the shaft at at least one point inwardly of theend of the helical ribbon, the lower end of the sleeve being below the level of the tank liquid and the upper end of the sleeve being open and above the liquid level; means associated with the sleeve for excluding liquid from the lower end of the tubular sleeve; and the conveying means having a cantilever end section in which the helical ribbon overhangs the stationary bearing assembly.

15. In a classiiier for selectively separating suspended solid particles from a liquid, having a tank with an inclined bed and adapted to contain a body of liquid and solid particles suspended therein to be classified, the combination of rotary conveying means for moving settled coarse particles along the inclined tank bed and out of the liquid to a place of discharge from the tank, said conveying means comprising a central shaft and a helical ribbon mounted on the shaft and annularly spaced therefrom; and rotary agitating means at one side of the conveying means and adjacent one side wall of the tank at a point near the shallow end of the liquid body within the tank, said agitating means creating in the liquid body currents that flow transversely across the tank and through the conveying means to wash the coarse particles free of attached nes.

16. In a classifier for selectively separating suspended solid particles from a liquid, having a tank with an inclined bed and adapted to contain a body of liquid and solid particles suspended therein to be classified, the combination of rotary conveying means for moving settled coarse particles along the inclined tank bed and out of the liquid to a place of discharge from the tank, said conveying means comprising a central shaft and a helical ribbon mounted on the shaft and annularly spaced therefrom; rotary agitating means at one side of the conveying means and adjacent one side wall of the ltank at a point near the shallow end of the liquid body within the tank, said agitating means creating in the liquid body currents that flow transversely across the tank and through the conveying means to Wash the coarse particles free of attached ilnes;

,and liquid inlet means near the periphery of the agitating means discharging liquid and suspended particles into the tank in the path of the agitating means to wash the incoming feed and break up agglomerations.

JOHN H. V. FINNEY.

CERTIFICATE OF CORRECTION. Patent No. 2,189,l|19. 1 February 6,*191Lo. i JOHN H. v. FINNEY.

It is hereby certified that error appears in the above numbered patent requiring correction as follows: In the grant, line 2, residence of assignee, for "El -Pasco, Texas" read El Paso, Texas; page 8, first column, line 57, claim 12,' for the word "shafts" read shaft; and that the said Letters Patent should be read with this correction therein that the same may conformto the record 'of the case in the Patent Office.

Signed and sealed this 2nd day of April, A. D. l9hO.

y Henry Van Arsdale, (Seal) Acting Commissioner of Patents.