US2437681A - Submerged-belt type magnetic separator - Google Patents

Description

arch 116, 1948. R. E. CROCKETT ETAL SUBMEHGED-BELT TYPE MAGNETIC SEPARATOR 3 Sheets-Sheetl Filed May 27, 1943 MDDL/NGS 7211A uvcs MDDL/NGS 711/L/NG5 INVENTORS Posse r-EI Cece/rm 3461-3 fi seLToN.

MM'tM A TTORNEYS.

arch 16, 1948.

Rose-RTE. PAGEJ R. E. CROCKETT ET AL .SUBMERGED-BELT TYPE MAGNETIC SEPARATOR Filed May 27, 1943 mm 5 S M 6 a m m N 7 m mk R 3 c w w m 2 a MR4 M m CH 5 M Patented Mar... 16, 1948 SUBMERGED -BELT TYPE MAGNETIC SEPARATOR Robert E. Crockett and Page S. Haselton,

Montclair, N. J.

Application May 27, 1943, Serial No. 488,668

21 Claims. 1

This invention relates to magnetic separators :oi the submerged belt type for separating finely divided magnetic particles from other material. It is particularly adapted among other possible uses, for the separation of magnetic ore particles, such as magnetite, from the gangue.

Heretoiore the most successful magnetic separators for such purposes have comprised a carrier belt running over a pair of pulleys and extending in a, generally horizontal or somewhat inclined position, with the lower belt stretch sa ging along a catenary curve and partially submerged in a settling basin, and with a series of magnet pole pieces extending with a corresponding curvature, along the upper surface of such belt stretch. The material to be treated is fed against the lower surface at one end of the lower belt stretch, whereby the magnetic particles are caused by the series of magnets to adhere to the belt and be carried along to a discharge point, while the non-magnetic particles are being washed from the belt and settle into tailings or middlings hoppers. In such machines it is important to have the belt stretches suspended in loose sagging position, or substantially in accordance with a catenary curve, and with the series of magnet pole pieces following a corresponding curvature. This is because if the belt were pulled tight to conform to a series of pole pieces arranged along a straight line, the conditions are such that among other dificulties, the belt will be quickly pulled apart. While this type of machine, if properly operated, is highly efiicient in the sense that the concentrates delivered therefrom will be substantially free of gangue, yet the tailings may embody a measurable amount of unrecovered magnetite, and there is a substantial percentage of the ore which is discharged as middlings and has to be reground and retreated.

According to the present invention, the necessity of using a belt stretch and series of pole pieces with a catenary curvature, is avoided and the percentage of the magnetic particles recovered may be increased. This is accomplished by so positioning the belt that its active stretches will hang substantially vertically, and thus along straight lines without any substantial tensioning. Consequently the series of magnet pole pieces may also extend along a straight line. With the preferred forms of the invention, the belt may be suspended from a single drive pulley located above the liquid level, whereby an elongated loop of the belt extends downwardly along one side of a series of magnets and thence upwardly along the other side of the same magnets. If desired,

the lower portion of the belt may run over an additional pulley.

With such vertical positioning of the active belt stretches, the ore may be fed against the belt at areas spaced considerably from the lower part of the belt, and whereby any particles which are not immediately attracted to the belt will have opportunity to fall for a considerable distance along the face of the belt and in the magnetic field, with the consequence that substantially all of the magnetic particles will be captured on the belt before they have opportunity to pass out of the magnetic field, and any magnetic particles which become dislodged from the upper areas of the belt stretches, will have opportunity to be gathered on to the belt again even after falling a considerable distance, and hence will not be lost in the tailings. In the former types of machines where the belt stretches run generally horizontally or in a somewhat inclined position, once any of the magnetic particles have settled or fallen from the belt to points below regions of a relatively strong magnetic field, they cannot be recovered and elevated again against the force' of gravity. However, with the vertical belt stretches of the present invention, the magnetic force at tracts the particles to the belt either in a horizontal direction or sidewise and downwardly, and hence not in opposition to the force of gravity. And also with the present invention such particles as may be dislodged from the belt during the washing steps have a much greater opportunity to be recaptured since they must fall through a vertically elongated field instead of merely through a generally horizontal shallow field.

The vertical arrangement of the belt stretches also makes it possible to construct a compactly arranged gang separator comprising several of the separating units arranged side-by-side in one housing or tank, and with the active belt stretches of one unit facing corresponding belt stretches of adjacent units. Thus all the space between such facing stretches may be subjected to an intense magnetic field from two units, with a number of consequent advantages hereinafter referred to. Also the vertical arrangement of the belt stretches makes it possible to so arrange the magnets that an active pole piece may .be provided at both ends of each magnet, viz., with one pole adjacent the downwardly running belt stretch and the other pole adjacent the upwardly running belt stretch. This makes it possible to greatly reduce, or diminish by half, the number of magnets required and at the same time utilizes about twice as large a proportion of the belt area, as compared with the prior practice above referred to.

Various further and more specific objects, features and advantages will more clearly appear from the detailed description given below taken in connection with the accompanying drawings which form a part of this specification and illustrate merely by way of example, preferred forms of the invention. The invention consists in such novel features, arrangements and combinations of parts as may be shown and described in connection with the apparatus herein disclosed.

In the drawings:

Fig. 1 is a side elevational View partially in section, showing a gang separator, including several units constructed in accordance with a preferred example of the invention;

Fig. 2 is a horizontal enlarged sectional view of one of the units taken substantially along line 2-=-2 of Fig. 1;

Fig. 3 is a verticalenlarged sectional view of a portion of one of the units, taken along line 3= 3 of Fig. 1 and Figs. 4 and 5 are vertical sectional views of alternative forms of the invention.

In Fig. 1 a tank or housing is shown at lil within whicha series of separating units'as at H-l4 maybe mounted. Each of these units may comprise a belt as at I5 formed of suitable non-magnetic material in accordance with known'practice. Each of these belts may be suspended and driven by'pulleys as at It. Preferably the peri'ph'eral'surfaces of the pulleys are made with a notched formation as at I! to'insure against slippage. 'The pulleys may be mounted on and driven by shafts as at l3 connected to a suitable source of power (not shown). The shafts may be mounted in vertically adjustable bearing blocks as at l9 to provide for adjustment of the suspended loop portion of the belt to'the desired height.

The suspended loop portion of the belt may extend down around, and up again over the surface of a U-shaped member 20 formed of thin 'sheet'material such as stainless steel or other non-magnetic materiaLand serving to provide a magnet compartment. Such compartment has parallel sides "and a semi-cylindrical bottom merging tangentially with the sides, which are also preferably'in planes tangent to the drive pulley as shown. As-shown in Fig. 2,- the vertical edges of the member-2'0 may be sealed along the side walls -of the tank H3. The tank l0 may bekept filled with water 'up-to-a liquid level such 'at each end, and =slidable into or out of posi- 'tion,on rigid bars as at 2|, secured'to the inside surface'of U-shapedmember 29. The bars 2| may as-shown in Fig.2, extend from one'side wall of the tank ill to the other, and thereby serve -to strengthen the tank as well as the member '20.

Further strengthening and. supporting meain'sfor the tank maybe provided as-neces'sa'ry, but for'clearne'ss isomitted from the drawings.

The side walls of the tank 10 maybe cut away over an area shaped to correspond to the shape of themagnet compartment, whereby each magnet may be readilyinspected from outside the tank andslid into placeor removed on the-bars *2! when necessary for further inspection, repair or replacement. The openings in the twoside walls of the tank may if desired be covered by removable cover plates as at 22, 22, for covering each magnet. Suitable detachable electrical connections for the magnets may be provided, but same are omitted on the drawings, for clearness.

If the separating units are of small capacity such that relatively narrow belts may be used, each of the magnets may be formed with pole pieces extending from near one edge of the belt to a position near the other edge. Usually, however, the belts will be of such widths that a pair of magnets as shown at B, B, in Fig. 2 may more conveniently be provided at each elevation. In that case access may be had to one of the magnets of each pair as at B, from one side of the tank I0, while access to the other magnet as at .3, maybe had from the other side. That is, oneehalf the magnets may be slidably inserted and removed from each side of the tank upon removing cover plates '22 or 22'.

As shown in Fig. 1, the upper magnets as at A may be formed at one end with upwardly extending pole pieces or shoes as at 23 whereby the zone of the magnetic field will be extended to a desired height above the liquid level for reasons explained below. The magnets B, B of which six pairs are shown for each unit, may all be of a like construction. Magnets C, D and E as shown may be shaped with pole pieces conforming'to the lower semi-cylindrical end of of the magnet compartment and with windings as shown of convenient shapes to fit the space provided in this part of the compartment. In accordance with known practice succeeding magnet pole pieces of the series may have alternate polarities. -However, if desired, magnets C, D and E may be so wound that'their active outer pole pieces are of the same polarity, to avoid agitation of the particles on the'belt while passing around the semi-cylindrical lower end of the magnet compartment. For the same reason if desired, the magnets along the arcuate part of the belt may be similar'to those used in magnetic pulleys of cobber machines, except semi-circular instead of circular,i. e.,with a succession of semi-circular polepieces of alternate polarity across the belt, so that each particle adhering to the belt Will retain its same polarities throughout its travel on "the arcuate portion and thus be securely retained in place. In some cases the-magnets A and .B at least may bei-n the "form of strong permanent magnets'instea'd of electromagnets, thus reducing the manufacturingand operation costs.

In order to lubricate the belt as it passes over the-surfaces of the =member:2ll and to exclude ore particles, etc., irom entrance .betweensuch surfaces and the belt, lubricating .iluid, preferably water, is introduced at .rspaoed points through pipes as at '25, communicating-with a vertical header 26 connected at 2'l'to a suitable source of supply. As shown in'Fig. 2, pipes .25'may-be'sealed through the 'sheet:metali2!l. todischarge thelubricating fluid at points .along the .middle of the belt,'the pipes being conveniently arranged :between adjacent pairsof magnets. ,Thelubricatingfiuid as dischargedragainst'themiddle of the belt, spreads out over the underside of the :belt and should be cf-sufiicient volume and subjected to suficient pressuresothatit .will slightly-float the belt away-from the magnet surfaces, andflow outwardly from the edgesof the belt, as indicated -at 2"l, -F ig."2, and-into the body of water ;in:the tank lll. Thus outwardcurrentso'f the lubricating'fiuidat the edgesof the. belt'will prevent: ore

--and'gangueparticl'es from gettingunder the belt.

In order that the lubricating fluid will be free to flow outwardly at all points along the edges of the belt, the belt should be of a width as shown in Fig. 2, substantially less than the width of the tank. Thus there will be no danger of the belt edges contacting with the side walls of the tank and obstructing the outward flow of the lubricant. To also avoid danger of magnetic particles being drawn under the edges of the belt, the magnet pole pieces as shown in Fig. 2 should preferably terminate substantially inwardly of the edges of the belt as shown at 28. This will insure that the magnetic particles will be drawn on to the outer surface of the belt at points inwardly of the belt edges, rather than into the corner areas 21.

As shown in Fig. 1, the belts on alternate separating units are preferably driven in opposite directions. This enables ore to be fed in as by feed troughs or pipes 30, 30 located in alternate spaces between units, while enabling the concentrates to be taken out at each of the intervening spaces between adjacent units. A liquid mixture of the ore introduced through feed pipes 30, 30' may be directed as by plates 3|, 3| into proximity of the surfaces of the downwardly moving belt stretches. As the ore falls below the liquid level, most of the magnetic particles thereof will be promptly drawn against the belt together with such gangue as may be enmeshed by the magnetic particles. Such of the remaining gangue as contains no magnetic particles, after it falls below the plates 3| or 3|, will be quite free to fall through spaces 32, 32' down to tailings hoppers as shown at 33, 33', for withdrawal through suitable known types of clotures. Meanwhile, magnetized particles while being carried on the downward stretches of the belts, will have their polarities reversed as they pass each of the succeeding magnet pole pieces of alternate polarity. This will result in sufiicient agitation of the particles adhering to the belt to cause considerable gangue to be liberated, but at the same time some of the magnetic particles may also be dislodged. While the dislodged gangue will be free to fall to the tailings outlets, any of the dislodged magnetic particles will be attracted sideways and downwardly by the combined actions of the forces of the magnetic field and gravity, back on to the belt. Because the paths through which the particles can fall are elongated and subject throughout to strong magnetic fields, practically all of the magnetic particles will be firmly captured or recaptured on the downward stretches before the lower arcuately curved portions are reached.

Since such effective means is thus provided for recapturing dislodged magnetic particles, the magnetic masses on the down stretch of the belt may be subjected to intense cleaning action from forceful jets of water, applied to the belt for example from spray pipes as at 34. Thus the larger part of the gangue will be separated from the ore in the spaces 32, 32 and will settle into the tailings hoppers. The magnetic particles on the belt including some particles embodying nonmagnetic material, will then be carried around the arcuate lower portion of the magnetic field and upwardly on the upward stretch of the belt. At this region particles on the belt, while again passing pole pieces of alternate polarity, may be subjected to a still more intense washing action by water supplied through a series of spray pipes as at 35. This will serve to dislodge such of the particles as embody or comprise any substantial amounts of non-magnetic material. These will fall into middlings hoppers as at 35, 36. I! mag netic particles are dislodged along the upward stretches, they will have ample opportunity to be attracted sideways and downwardly for recapture on to the belt under the combined forces of gravity and the magnetic fields, as is the case at the downward stretches of the belt. Also if the recaptured particles embody any considerable amount of non-magnetic material, they may be again dislodged by jets from pipes 35 to finally fall into the middlings hopper. Thus by the time the particles arrive at the region of the water line on the upward stretches, they will be free of practically all gangue as well as middlings. Since the particles containing no magnetic material are practically all separated out at the downward stretches of the belt and fall into the tailings hoppers, the middlings particles which are finely separated from the upward stretches will substantially all embody some magnetic material. And since the material on the upward stretches is subjected to intensive and repeated washings with repeated opportunities for dislodged magnetic particles to be recaptured, the middlings will comprise only such particles as embody some non-magnetic material and a small proportion of magnetic material insufi'icient to classify the particles as concentrates. Thus the amount of middlings which have to be reground and retreated will be comparatively small.

The manner in which the pipe connections may be made for the spray pipes such as at 34 and 35, is shown at the righthand portion of Fig. 1. That is, pipes 35 for example may be brought to the outside of the tank l0 and connected to a vertical header as at 31, which in turnis connected to a suitable source of supply as at'38.

As the concentrates on the upward belt stretches approach the water line, provision is made for removing therefrom anyslime, scum or floating impurities and at the same time to give the concentrates as withdrawn a final thorough washing. This may be accomplished by mounting plates as at 4!] at spaced positions from the belt to extend from below the water line to a substantial distance above, and affording a trough space along the face of the belt. Water pipes as at 4| are provided along the top edges of plates 46. These spray pipes as indicated in Fig. 3 may extend inwardly from each side of the machine and be formed with outlets for projecting forceful sheet like jets of water, as at 42, downwardly.

The sheet jets 42 have the effect of causing any insecure protruding magnetized masses on the belt to be rolled downwardly and back into the water or back into more compact firmly secured positions on the belt areas. Any slimes which might otherwise be present on the concentrates are washed ofi. At the same time the water at '52 causes a downwardly flowing stream in the spaces between the plates 40 and the belt, so that the surface of the liquid is kept free of slimes at the points where the concentrates are carried up out of the water.

As the concentrates are carried on the belt upwardly past the pipes 4|, they continue to be held on the belt by the magnetic field of the extended pole pieces or shoes 23 on the upper magnets. As the particles are elevated out of this field, they fall into a take-oil trough 43. Any of the particles which do not fall from the belt of their own accord, may be washed off to also fall into the trough 43, as by sprays 44. As shown in Fig. 3, the trough 43 may be shaped with a downward inclination in both directions from the center Tlinev of. the" belt. :In :order .to discharge the concentrates 'from the trough, 1'9. :spray pipe r45 may be provided with outlets :as at 46, :11 rfor directing -sprays toward both ends ;respectively of the trough 143. The upperisidezedges m .lip portions of the'trough d3'mayzcompriserstripsrof rubber or other'fieXible material asz'at-"fl -which will yield to theextentn-ecessaryito :pern'iitrthe magnetized masses of; concentratestol= be carried up on the belt without' being dislodgeduntilithey are I above the trough level.

With the embodiment "of -thellnventionnshown in Fig. 1, it will be apparent that :any :desired number of separating units :may :be mounted :in closely spaced relationin raisingle :tank, :thus saving the expense o'fJseparate sideswallstfor tanks individual to'e'ach unit andatthersame time making economical use of all'ithespace'withintazsingle large tank. If desired, 'it' will Ialso 'be :apparent that single'separator unitsior pairszof unitsimay be constructed as shown in Fig.1. .tIn either icase substantially the entire ispacevwithintthe loop of each belt is occupied "by magnetsxandmy the drive pulley. Also substantially the whole length and width of each'belt except lion the areasion ithe pulleys and theirbearings :and :shaftlng in; submerged positions. .If submerged. pllleys are used, there may be a substantial tendency: for theiparticles to get under the belt on the pulleys'and into bearings, thus causing excessive wear, J in addition to the difficulties 'of 'maintaining lubrication'and preventing deterioration'of submerged operating parts.

In the prior magnetictseparatorsof the types above mentioned, it has beenffound desirable to have a series ofiabout 2lma'gnets-(or'pairs of magnets). With the arrangement or Fig. '1,'the number of magnetsper unit may bereduce'd by more than one-half, due to-t'he use of the pole pieces at both endsof eachmagnetand because the active field areas are elongated vertically in the normal direction not :fall .ofthe particles.

While the use of both poles of each magnet necessarily involves the presence. OftWO air gaps in the magnetic circuit of each magnet, viz., .at each end of the. magnet, 'with'amonsequent increase. in the reluctance of the circuit, yet such increased reluctance is minimized to. aconsiderable extent when the machine is in operation due to'the presence of magnetized tmassesof particles (on the belt, which substantiallyifllli'ln .the'ralr gapslin the magnetic circuits. This is especiallyttrue under'full load conditions when the presence of strong fields is most important. .sAlso sincetthe number of magnets used is much *smallerithan heretofore necessary, the amount.of:current.used in the windings ofeachmagnetmay'he greatlyincreased without using 'a greateri totaliamount :of current than heretofore necessary. .Hence it is possible to economically maintain the magnetic fall iWithOLlt dangernof flogging efiects when the machine is :run :at .heavy capacity, and yet .insuringzthat allzmagnetized particles .will be sub- 'ject to capture .and'recapture'by one: or" the other 'o'fzthetwo belts.

lIt isalsovevident-that the vertical belt construction'withzthe shortened seriesof magnets as 'ofI-Figlmakes possible a'largelsavingin floor and housingtspace required'for the units, .as compared with'tha generally horizontally extending belt arrangements :of the separators previously available.

flnthewemxbodiment of 'Figntapair of units 50, .5I is-.mounted in=a tank 552. 'Theupper pulley arrangements 'for the belts 'may as 'shown'be like .those of Fig. 1. With this embodiment, however,

only;the'llpwardrstlfetches .of-the belts are utilized. That is,:two seriesnofmagnets'lin:housings as at 55356 respectively aremounted along the rear -surfaces 0f :the upward ;belt :stretches, the magnet :ba'nks being fof 'the general "type and :numberhereto-fore used, except that they are arranged with their 'p'ole :pieces 1along straight vertical lines instead of along a catenary curve. The undersurfacesofLthebelts may be lubricated as2in1the1case of Fig. liby 'waterrsupplied through pipes;:as .atf5'l,*'5S,--59. At the l'owerends of the magnets :some of the lubricating water may be discharged :as: through nozzles 60 for preventing particles z'from'ibeing drawn .up between the belt 'andithemagnet assemblies. Deflector 'plates as at 361 may: also be :provided 'so that water from themozzle 99 will :pass downwar'dly'between the platesifil 'an'dthe' belt; asindicatedzby the arrows, and-thus further prevent particles .from entering underi thetbelt.

In :Fig. .4' the ore to be .treatedmay be .introduced :as through a feed .pipe '62 located-in the space between the upward. stretches, at arregion spaced: from the lower ends of the magnet banks. The :ore:particles:from thelfeed pipe 62 will tend 'toffall down through'the space-63 "toward a tailings shopperfi l. :In. so doing,.= the magnetic par- -ficles 'andtmasses will bercaptured :and carried up 'on thebelt 'while thegangue will be free to ffall into :the tailings'hopper. At points-above :the feed pipe -62, the "particles on the belts may bersubj'ecteds'tofintense washing action by jets :from spray pipes; as"at E5. :Here the action will be similar :to that between the 'upward belt -stretchesof Fig. 1. The "concentrates imay be removed byrthessame type :of -means provided in :Fig. 1 1, corresponding Lparts for that purpose in rFiguA beingzidentified by the same -reference characters as ;in ':Fig. 1, :accompanied :by prime 'm'aiiks. In: Fig. ":4- the .liquid: level is indicated at 965. .As 1 the :concentrates .pass above this level, "they may berrsubj ected to further "washing: from .--spraystas'atr61. z'Ihermaterial' which is dislodged ':by the sprays 61 may ".be :rdefiected back toward the :belts at thewaterline astbyacurveddeflector.;plate';68.

Thel lower end: of the: belt loops in Fig.4 may pass :over arcuately curved surfaces, these as --sh=own*;being in the. form of pulleys 10.

It -=-wil1 .be apparent that the embodiment .of Fig. :4 providesa convenient Tarrangcment for .zpairsof separatingunits. This'form'also'is .par- ,ticularly:applicablertocsituations where: it is defields at proper strength. Also-inxgang separa- .70 d' oceparatet theiore: into twoipart namely tors as of Fig. 1, the'magneticifields may :be more efficiently used, since the spaces between .adjacent units are subjected to the fields of two-"sets of magnets. This makes possible-.fairly -wide' spaces 1 tailings. andic'oncentrates, without; middlings.

"I'herconstruction shown .in Fig."5-maybe the same as that .of Fig. :-.4,except' that" Fig. .5 illusitratesvariousinovel:possibilitiesyas to the relawithin which tailingsand :middlings are free-to 3:5 tive arrangementsm thenorth-andtsouth'poles of the magnets. For example, it is possible to so arrange the magnets that the pole pieces which face each other will be of the same polarity, viz., so as to maintain opposing fields respec tively at each side of the space between each pair of units. This is shown at the lower portions of the banks of magnets in Fig. 5. In some cases, however, it may be found desirable to mount the magnets as shown in the mid portion of Fig. 5 Where the magnets for one unit are Staggered in position with respect to those of the other unit. This will create a field which under some conditions may tend to cause falling magnetic particles to assume a somewhat zigzag path, thus more effectively freeing the particles of gangue. As shown at the upper part of Fig. 5, the opposing pole pieces if desired may be of opposite polarity, thus giving the fields therebetween further different characteristics. The particular arrangement or combination of arrangements of pole pieces found preferable, may depend upon the nature of the ore being treated. One or another of the arrangements may be found most effective with ore particles of certain sizes, or where the gangue has peculiar characteristics.

It will be apparent that the various diiferent arrangements of the polarities of the magnets as shown in Fig. 5 may also be used with the separator units of either Fig. 1 or Fig.- l, either for the entire magnet banks or portions thereof.

While the invention in its various presently preferred forms is particularly adapted to separators of the submerged-belt type, it will be apparent that some of the features of the invention as defined in the appended claims are not limited to machines of that type.

Certain improved embodiments of the invention are disclosed and claimed in applicants oopending application Serial No. 793,714, filed December 24, 1947.

While the invention has been described in detail with respect to particular preferred examples, it will be understood by those skilled in the art after understanding the invention that various changes and modifications may be made without departin from the spirit and scope of the invention, and it is intended therefore in the appended claims to cover all such changes and modifications.

What is claimed as new and desired to be secured by Letters Patent is:

1. A magnetic separator comprising a tank for receiving a liquid mixture of magnetic particles and other material to be separated therefrom, a belt extending in the tank, means for supporting and driving said belt with a stretch thereof running upward substantially vertically from out of the liquid, and whereby an extended portion of such stretch is suspended in a position below the liquid level without substantial sagging or deviation from a vertical plane, means for feeding the mixture into the tank at a position spaced substantially from the region where said stretch portion passes up out of the liquid, and a plurality of magnets with pole pieces in alignment along one surface of said upwardly running stretch of the belt, whereby magnetic particles are caused to adhere to the opposite surface of said upwardly running stretch and be carried up out of the liquid.

2. A magnetic separator comprising a tank for receiving a liquid mixture of magnetic particles and other material to be separated therefrom, a belt extending in the tank, means for supporting and driving said belt with a stretch thereof running upward substantially vertically, whereby at least a portion of such stretch is suspended in a position below the liquid level without substantial sagging or deviation from a vertical plane, a plurality of magnets with pole pieces in alignment along one surface of said portion of the belt, whereby magnetic particles are caused to adhere to the opposite surface of said portion and be carried up out of the liquid, means for feeding the mixture into the tank at a submerged position on said opposite surface intermediate the ends of said alignment of pole pieces, whereby portions of the mixture may settle through the field of the lower pole pieces countercurrent to the travel of the magnetic particles carried up on the belt, and means above the liquid level for carrying the magnetic particles from the belt.

3. A magnetic separator comprising a tank for receiving a liquid mixture of magnetic particles and other material to be separated therefrom, a belt extending in the tank, means for supporting and driving said belt with a stretch thereof running upward substantially vertically from out of the liquid, and whereby an extended portion of such stretch is suspended in a position below the liquid level without substantial sagging or deviation from a vertical plane, means for feeding the mixture into the tank at a position spaced substantially from the region where said stretch portion passes up out of the liquid, a plurality of magnets with pole pieces in alignment along one surface of said portion of the belt, whereby magnetic particles are caused to adhere to the opposite surface of said portion and be carried up out of the liquid, and means both below and above the liquid level for forcefully applying water jets to the magnetic particles on the belt for dislodging and removing non-magnetic materialtherefrom. i

4. A magnetic separator comprising a pair of belts, a tank for receiving a liquid mixture of the material to be separated, means for suspending and driving said belts respectively with upwardly running stretches in said tank, said stretches including portions which run for a substantial distance in generally parallel relation and with opposed faces spaced apart by a submerged separating zone, and two series of magnets arranged along the back surfaces of said stretches respectively and subjecting said zone to a magnetic field for causing magnetic material to be attracted to said stretches and carried up out of said zone.

5. A magnetic separator comprising a pair of belts, a tank for receiving a liquid mixture to be separated, means for suspending and driving said belts respectively with upwardly running stretches in said tank and with opposed faces spaced apart by a submerged separating zone, and two series of magnets arranged along the back surfaces of said stretches respectively and subjecting said zone to a magnetic field for causiing magnetic material to be attracted to said stretches and carried up out of said zone, alternate magnets in each of said series having their pole pieces adjacent the belt stretch, of opposite polarity, and the pole pieces of one series being of opposite polarity with respect to the nearest pole pieces respectively of the other series.

6. A magnetic separator comprising a pair of belts, a tank for receiving a liquid mixture to be separated, means for suspending and driving said belts respectively with upwardly running stretches in said tank and with opposed faces spaced apart by a submerged separating zone, and two series of magnets arranged along the back surfaces of said stretches respectively and sub- 'je'cting said zone to a magnetic field for causing magnetic material to be attracted to said stretches and carried up out of said zone, alternate magnets in eac'hof said series having their pole pieces adjacent the'belt stretch, of opposite polarity, and the pole pieces of one series being of the same polarity as "the nearest pole pieces respectively of the other series.

-7. In a magnetic separator, the combination "of an upwardly running *carrier area, magnets alongone surface of said carrier area forcausing magnetic material to'be attracted to the opposite surface and carried upwardly, a trough extending generally transversely of the direction of movement of an upper portion of said carrier area, a flexible lip along the edge of said trough close 'to said-opposite surface and permitting the magnetic material on the carrier'to be carried up past the'trough, and means above the trough for dislodging the magnetic material from the carrier, to fall into said trough.

8. A magnetic separator comprising a=generally U-shaped surface. a belt, means for supporting and driving said belt with a lower loop having a stretch passing generally vertically downwardly overone side-of said surf-ace and thence around toprovide another stretch running generally verticallyupwardly-over the other side of said surface. magnetic means within said U-shapedsurface for causingmagnetic material tobe attracted -to the outside surfaces of both of said stretches and to the outside surface of the belt as it passes around the curved base portion of the U-shaped surface connecting said stretches, means to feed material to be separated against said downward stretch. and means for carrying separated magnetic particles from the belt after being carried up along a substantial portion of said upward stretch.

9. A magnetic separator comprising means forming a generally U-shaped surface, a 'belt, means for supporting and driving said belt with alower loop having a stretch passing downwardly over one side of said surface and thence around to provide another stretch running upwardly-overthe other side of said surface, a series ofsuperposed magnets within said -U-shaped surface for causing magnetic material to be attracted to the outside surfaces of both of said stretches,"saidmagnets being each arranged with one pole maintaining a field at said downward stretch and its other pole maintaining a field at said upward stretch, means to feed material to 'be separated against said downward stretch, and means for carrying separated magnetic particles from the belt after being carried up along a substantial portion of said upward stretch.

10. A magnetic separator comprising means forming a generally U-shaped surface, a belt, means for supporting and driving said belt with a "lower loop having a stretch passing downwardly over one side of said surface and thence around to provide another stretch running upwardly over the other side of said surfacamasnetic means within said U-shaped surface for causing magnetic material .to be attracted to the outside surfacesof .both of .said stretches, means to .feed material to be separated against said downward stretch, means .for carrying separated magnetic particlesfrom the belt after beingcarried up along a substantial portion of said upward stretch, and tank means within whichsaid loop is suspended, including a tailings hopper be- 12 low saiddownward stretch and a middlings hopper below said upward stretch.

'Il. .Amagnetic separator comprising a plurality of generally U-shaped surfaces arranged side-by-side in spaced relation to provide a separating zone between each pair, a corresponding plurality of belts, means for supporting and driving said belts, each with a lower loop having 'a stretch passing downwardly over one side of one of said U-shaped surfaces and thence around to provide another stretch running upwardly over the other side of the same U-shaped surface, and with upward stretches of one belt facing-an upward stretch of another belt, and magnetic means within said U-shaped surfaces for causing magnetic material to be attracted to the outside surfaces of both the downward and upward stretches.

12. A magnetic separator comprising a plurality of generally U-shaped surfaces arranged side-by-s'ide in spaced relation to provide a separating zone between each pair, a corresponding plurality of belts, means for supporting and driving said belts, each with a lower loop having a stretch passing downwardly over one side of one of said U-shaped surfaces and thence around to provide another stretch running upwardly over the other side of the same U-shaped surface, and with upward stretches of one belt facing an upward stretch of another belt, ma netic means within said U-shaped surfaces for causing magnetic material to be attracted to the outside surfaces of both the downward and upward stretches, and tailings and middlings hoppers respectively below downward and. upward stretches.

'13. A magnetic separator comprising a plurality of generally U-s'haped surfaces arranged side-by-side in spaced relation to provide a separating zone between each pair, a corresponding plurality of belts, means for supporting and driving said belts, each with a lower loop having a stretch passing downwardly over one side of one of said U-shaped surfaces and thence around to provide another stretch running upwardly over the other side of the same U-shaped surface, and with upward stretches of one belt facing an upward stretch of another belt, and magnetic means within said U-shaped surfaces for causing magnetic material to be attracted to the outside surfaces of both the downward and upward stretches, said magnetic means including magnets each with cores having one pole maintaining a field active for separation purposes at a downward stretch and another pole maintaining a field active for separation purposes at an upward stretch.

14. In a magnetic separator, a belt, means for supporting and-driving said belt in a position to have a vertically elongated suspended loop including :a generally vertical downward active :stretch and a generally vertical upward active stretch, means .for applying mixture to be separated to the @belt at a region near the upper end of such downward stretch, means for removing separated magnetic material from the belt at a region near the upper portion of said upward stretch, and ;a series of stationary magnet pole pieces within said loop, said series extending along said downward stretch thence around within the bottom of the loop and then up along said upward stretch.

15. In a magnetic separator, a liquid basin, a series of drive pulleys on substantially parallel horizontal axes side-by-side above the liquid level, a series of belts, each suspended by one of said pulleys and each having an elongated loop extending down below the liquid level, a series of magnet pole pieces arranged along the inside of the submerged portions of each loop, said loops being spaced apart by separating zones, and means for driving alternate pulleys in opposite directions, whereby at alternate separating zones, the facing belt stretches both move downwardly and at intervening zones the facing belt stretches both move upwardly.

16. In a magnetic separator, a liquid basin, a series of drive pulleys on substantially parallel horizontal axes side-by-side above the liquid level, a series of belts, each suspended by one of said pulleys and each having an elongated loop exto be separated into the zones at downwardly traveling stretches, and means for removing recovered magnetic material from the upwardly traveling stretches.

17. A magnetic separator comprising a pair of generally U-shaped surfaces arranged side-byside in spaced relation to provide a separating zone therebetween, said surfaces including stationary portions forming the base portions of the U shapes, a pair of belts, means for supporting and driving said belts each with a lower loop having a stretch passing downwardly over one side of one of said U-shaped surfaces and thence around to provide another stretch running upwardly over the other side of the same U-shaped surface, and with the upward stretch of one belt facing the upward stretch of the other belt, and magnetic means within said U-shaped surfaces for causing magnetic material to be attracted to the outside surfaces of said belts as the stretches thereof pass downwardly around and upwardly.

18. A magnetic separator comprising a pair of generally U-shaped surfaces arranged side-byside in spaced relation to provide a separating zone therebetween, said surfaces including stationary portions forming the base portions of the U shapes, a pair of belts, means for supporting and driving said belts each with a lower loop having a stretch passing downwardly over one side of one of said U-shaped surfaces and thence around to provide another stretch running upwardly over the other side of the same U-shaped surface, a liquid basin within which said U- shaped surfaces and the belt loops thereon may be submerged, means for supplying material to be separated on to the downward belt stretches, means for removing tailings from beneath said downward stretches, means for removing middlings from beneath said upward stretches, and means for establishing magnetic fields tending to attract magnetic particles onto said stretches.

19. In a magnetic separator, a tank adapted to contain a body of liquid, a stationary U-shaped compartment therein containing an assembly of magnets, a travelling belt having a loop suspended in the tank with the inside surfaceof the loop contacting with the exterior surface of said compartment within the tank, and means for applying a mixture of magnetic and non-magnetic material to be separated onto said belt at one point and for separately removing the magnetic and non-magnetic material at other points, at least one side of said U-shaped compartment being constructed and arranged to open directly to the exterior of the tank to afford ready access to said magnet assembly without disturbance of the liquid in the tank or the belt suspended therein.

20. In a magnetic separator, a tank adapted to contain a body of liquid, a plurality of spaced compartments therein each containing an assembly of magnets, at least one side of each of said compartments opening to the exterior of the tank to afford ready access to said magnet assemblies, a plurality of belts each having a loop suspended in the tank to extend respectively about said compartments, and means above the.

liquid line for so suspending and driving said belts that facing generally vertical stretches'of successive belts will travel in the same direction. 21. In a magnetic separator, a tank adapted to contain a body of liquid, a plurality of spaced compartments therein each containing an assembly of magnets, at least one side of each of said compartments opening to the exterior of the tank to afford ready access to said magnet assemblies, a plurality of belts each having a loop suspended in the tank to extend respectively about said compartments, and means above the liquid line for so suspending and driving said belts that facing generally vertical stretches of successive belts will travel in the same direction, means for feeding material to be treated onto the downwardly running belt stretches, tailings hoppers being provided at the bottom of the tank beneath the downwardly running facing stretches, and middlings hoppers alternating in position with said tailings hoppers and located beneath the upwardly running facing stretches.

ROBERT E. CROCKETT. PAGE S. HASELTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 422,732 Conkling Mar. 4, 1890 971,163 Wood Sept. 27, 1910 438,897 Richards Oct. 21,1890 709,982 Heberle Sept. 30, 1902 2,003,430 Crockett June 4, 1935 945,408 Norton Jan. 4, 1910 1,146,140 Dutton July 13, 1915 2,160,628 Stefiensen May 30, 1939 800,370 Green Sept. 26, 1905 463,305 Hoffman Nov. 17, 1891 2,090,112 Crockett Aug. 17, 1937 .8 Bryan Nov, 12, 1918 FOREIGN PATENTS Number Country Date 4,690 Great Britain 1890 624,224 Germany Jan. 16, 1936

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