US2471911A - Magnetic separator - Google Patents

Description

y 1949- R. H. ST EARNS 2,471,911

MAGNETIC SEPARATOR Filed Aug. 30, 1944 4 Sheets-Sheet l INVENTOR. fax/via f/ yam/s y 1949- R. H. sngl xm s 2,471,911

MAGNETIC SEPARATOR Filed Aug. 50, 1944 V 4 Sheets-Sheet 2 May 31, 1949. R. H. STEARNS MAGNETIC SEPARATOR 4 Sheets-Sheet 3 Filed Aug. 30, 1944 .INVENTOR. flash/:11 6 Jmm/J Arron/5x y 31, 1949- R. H. STEARNS 2,471,911

MAGNETIC SEPARATOR Filed Aug. 30, 1944 4Sheets-Sheet4 INVENTOR. fins/m1 Jaw/m @221 mz-x m Patented May 31, 1949 MAGNETIC SEPARATOR Roswell H. Stearns, Wauwatosa, Wis., as slgnor to Stearns Magnetic Mtg. 00., Milwaukee, Wis., a

corporation of Wisconsin Application August/30, 1944, Serial No. 551,802

1 Claim. (01. 209-225 This invention relates which are primarily designed for the refining and recovery of low grade iron ores.

It is a well known fact that supplies of the rich ores in America of the hematite variety have been greatly depleted and are being rapidly further reduced to such an extent that it is now necessary to resort to the separation and concentration of the low grade magnetite ores and those commonly known as magnetic taconite.

' It'is also a well known fact that deposits of low grade ores, such as set forth above for instance, are large and abundant in this country and are conveniently located for handling and shipping, but heretofore great difliculty was encountered in efilciently and cheaply separating and concentrating such low grade ores. Most of these low grade ores contain clay matter and other impurities which must be eliminated by washing and scrubbing while under the influence of a magnetic field. v

Objects of this invention are to provide a magnetic separator which will eiliciently and cheaply separate and, concentrate low grade ores, and which is so constructed that it has means for thoroughly washing and scrubbing the ores while subjected to a blanket like magnetic field so as to quickly and effectively free the ore from the gangue to thus secure a rich, free, iron concentrate and obtain a very high recoverey of such ore with a minimum waste in the tailing product.

Further objects are to provide a simple and effective means of feeding the mixture in a thin and uniformly spread sheet into a primary maghaving an electromagnet structure of the alternate pole type in which there are alternate rows of magnet poles transversely of the belt with the poles provided with elongated fingers extending longitudinally of the belt and arranged in spaced intermeshed or staggered relation to thus spread the magnetic lines of force over a large area and thereby produce a blanket like magnetic field, thus maintaining the ore in a uniform thin sheet and creating a highly agitating effect,

to magnetic separators I rolling the ore completely over and over and causing a zig-zag movement crosswise of the moving belt, thus not only producing a beneficial scrubbing action which removes the silicious coating on the ore but also freeing the ore from other matter such as the entrained gangue matter and bonded inclusions ofiron and gangue as a middlings product.

Further objects are to provide a separator in which the ore is carried in suspension while fresh clean water is caused to wash and impinge against the suspended ore, the water travelling in a direction counter to that of the belt thus carrying any floating gangue matter away from I the, concentrate discharge end of the machine, the water becoming cleaner and cleaner as the concentrate discharge end of the machine is approached so that the final concentrates are washed in substantially clean water.

Further objects are to provide an electromagnetic separator in whichv means are provided for protecting the magnets and the windings thereof from the water used in the cleaning, washing and scrubbing of the ore, and to so construct the separator that only the belt and the projecting poles of.the electromagnets dip into the water.

In greater detail, further objects are to provide an electromagnetic separator in which the electromagnet windings are housed between an upper and a lower jacket with the poles extending below the lower jacket and with the upper jacket provided with downturned marginal flanges overhanging and spaced from upturned marginal flanges on the lower jacket, and to provide means for forcing-clean, fresh air around the magnet windings and discharging the air through the space between the marginal flanges of the upper and lower jackets to thus remove any moisture that may form due to condensation or sweating of the parts.

Further objects are to provide a magnetic separator provided with a plurality of rows of sprays which may be' independently adjusted for different zones in the separator, which will spread the water into a uniform sheet and project it against the travelling belt, in which the pressure or head of water is indicated for each row of sprays, in which a high pressure feed spray is employed to assist in the feeding of the material to the separator, and in which means are provided for spreading the material uniformly on the under side of the travelling belt. An embodiment of the invention is shown in the accompanying drawings, in which:

Figure 1 is a longitudinal sectional view through the separator with some of the parts broken away and some of the parts shown in full.

Figure 2 is a side elevation of the separator with parts broken away.

Figure 3 is a sectional view on of Figure 1.

Figure 4 is a sectional view on the line the line 3-3 of Figure 1.

Figure 5 is a fragmentary sectional view showing one of the overflow portions.

Figure 6 is a view looking upwardly towards. the pole pieces.

Figure '7 is a sectional view on the line 1-1 of Figure 6.

The separator comprises a plurality of electromagnets indicated generally by the reference character I and consisting of cores 2 surrounded by energizing windings 3 and attached at their upper ends to'longitudinally extending yoke or top members I and provided at their lower ends with pole pieces 5. The electromagnets are cated within a housing or casing 6 formed of nonmagnetic metal and terminating in an upper marginal edge I. The casing is completed by an upper portion 8 which is provided with a downwardly extending marginal edge portion 9 overhanging the edge portion I and spaced therefrom.

The construction of electromagnet is shown in greater detail in Figure '7. The yoke members 4 consist of magnetic rectangular bars which are secured to the cores 2 by means of bolts I0, see Figure 7. The pole pieces 5 are secured to the under side of the cores 2 by means of screws II. The pole pieces-are formed of magnetic material and are spaced a slight distance from the cores 2 by means of the non-magnetic casing B, the screws I I passing through the casing and clamping the casing tightly between the cores 2 and the neck portions I2 of the pole pieces 5. These neck portions are each provided with forwardly and rearwardly projecting portions constituting pole pieces. The pole pieces are arranged in transverserows and the pole pieces-of adjacent rows are arranged in staggered relation to each other, as shown in Figure 6. The pole pieces 5, as will be seen particularly from Figure 6, are elongated both towards the feed end and the delivery end 01 the machine and are approximately narrow, oval-shaped members formed integrally with the neck portions l2. The pole pieces of one row intermesh with the pole pieces of adjacent rows, as shown in Figure 6, so as to produce a multiplicity of strong magnetic fields.

A pair of wooden guide strips I3 are located on the under side of the casing 6 and on opposite sides of the pole pieces. These wooden marginal .strips form bearing rails for the side edges of a rubber or composition non-magnetic belt I4. The.

belt I4 is a continuous belt and passes below the pole pieces 5; and bears on their smooth under faces and also bears on the guide railsor marginal wooden strips I3. Preferably the lower portion of the magnetassembly is slightly'bowed downwardly to accommodate approximately the catenary shape that the belt assumes.

At the feed end of the machine a transverse guiding wooden member or bar I5 is provided and has a rounded bottom guiding surface for the-belt I4. A guide roller I6 is positioned immediately adjacent the guide member I5. At the delivery end of the belt the wooden guiding rails as'well as the magnet assembly are curved up- --wardly, as shown in Figure l. The belt passes over a driving pulley I'I adjacent the concentrate delivery end of the machine and over an adjustable idler roller I8 adjacent the iced or inlet portion of the separator. The driving roller II is driven in any suitable manner as from the motor I9.

It is to be noted that the upper portion 8 of the housing is so formed as to provide a series of transverse compartments 20, 2I and 22 each supplied with circulating air through the air manifold or supply pipe 23, such manifold or supply pipe being fed from a blower 24 driven by a motor '25, see Figure 3.

It will be seenthat air is blown into the space between the upper and lower portions 8 and 6 of the casing and serves to cool the coils of the electromagnet and also to prevent moisture from collecting on the electromagnets or other portions within the casings 6 and 8. The air is discharged between the marginal portions I and 9 of the lower and upper casings and thus-it will be seen that the electromagnet coils are kept thoroughly dried and well ventilated by the means 7 hereinabove described.

The separator is adapted to effect separation while the material is being passed through water and while it is being sprayed. For this purpose a tank or water containing trough like member 26,

see Figure 1, is provided and extends from the feed end of the machine to the concentrate de livery' end thereof. This trough like member is formed so as to provide a tailings hopper 21 and also a middlings hopper 28 adapted to respectively receive the tailings and middlings, as will be described hereinafter.

For convenience each of the hoppers may be formed in two portions,

as shown most clearly in Figure 3. Each of the a point beyond the dewatering section 30. 'A pair of box like overflow or discharge members indicated by the reference character 32 are provided adjacent the feed end of the machine, as shown in Figure 2. One of the overflow portions 32 is shown in section in Figure 5. The marginal edge I of the trough like member 26 is cut down at each.

of the discharge portions 32, as shown in Figure 5, to maintain the water level at the line indi-. cated by the reference character 33 in Figure 5.

The materialis fed by any suitable means, not shown, into a feed hopper 34,'see Figure l, and passes down the feed chute 35 and is de livered through the upturned portion of the feed chute through a slot 36 extending transversely across the belt and beneath the belt. A spreading table or feed distributing member 31' is providedand a transverse blocking strip 38 is located rearwardly or towards the feed and of the machine and spaced slightly from the delivery slot 36, as shown in Figure 1, to prevent material from spreading rearwardly. The spreading table 31 constitutes a plateau for providing a very thin film of material uniformly spread whereby substantially only magnetic material is picked directly upwardly against the under side of the belt and entangling of nonmagnetic material is reduced to a minimum. The forward travel of the belt as indicated by the arrows in Figure 1 removes the material from the spreading plate or feed portion 31 so that the material is carried from the feed portion of the device in a uniform the 8mm! into the timid" Q from the bclt into the middlings hopper. concentrates stilljclingto the belteven though the d j :belt' passes through 'a less and lessintense mag- =netic zoneas it approaches the delivery end of so'that'the material finally de- I livered from the belt when it :passes beyond the iniiuenceotthe magnets is a high grade con spirit or invention;v

and evenly spread layer on the under side oi the belt.

in order to facilitate the feeding of the materiala iced spray pipe II extends transversely across the machine beneath the ieed chute I g and has a series of small army openings opening mean that the-best 6 I results are velocity oi the sprays being. less and less-as the teed end or the machine is approached. Any other relative pressures or heads could be maininto the feed chute II to assist in theieeding'oi the material-and also to assist in uniformly 'dissimportedjby means or adjustable tie bolts I";

iustment.

The tailings or non-magnetic V hopper '21. It is'preierable to have the electromagnetsiadiacent the feed end .oi the machine strongest and the electromagnetsfi oi. the machine weakeshthe" at thc-,-dcliver! ell! v magnets locatedadiacent the middle portionxot the separator, or? intermediate strength.

Means, notshown. are provided-for controlling a the amount of current supplied the electromag nets to' thcreby control their relative strengths. By having thestrongest magnetic eiiect over the tailings hopper, allot the magnetic material,- both y the strongly magneticyand the faintly magnetic. is held againstthe under sidejoi thebelt over the tailings hopper. However; over 'the middlings hopper the magneticeflect is less than the faintly tributing the material. The inner end of the feed chute .ll is v 7 10 These bolts may'be-adiustedto-vary 7 between the spreading table II and j v the belt "to thus vary, the The feed chute ll is sufliciently springy to accommodate the relatively slight movement occasioned by this admess fails tained on the sprays as desired.

It is to be noted also that the driit or travel voi the water adjacent the belt isin a direction opposite to that crime travel of the belt and floating particles are thus caused to travel tosuch'point the concentrates 'fall into the concentrate hopper or discharge hopper 3|, see Figure 1. The middlings, if they are of no particular'value, may be discarded or if the material is such that the middlings have a reasonable 7 amount of magnetic material therein, they may be reground andagain passed through the machine either alone or. mixed with fresh material.

It is to be noted particularly with reference to thearrangement of sprays in Figure 1 and the arrangement of magnet poles in Figurefi that while magneticmaterial or middlings therefore fall a the. separator.

centrate. It istobc distinctly understood, howthesameintensity or other arrangementsof relative intensity from may be obtained without departing from the The magnetic material sprayed by means of a plurality of tranversely extending spray pipes 38 provided with spray openings directed upwardly. and provided with angularly adiustablebaiile or guiding members ll' so as to spreadtheindividual streamsirom the'openingsxinto a thin, uniformsheet of water which is. projected'ag ainst the belt in a direction contrary to thatjoi the travel of the belt. The "bailles also act as guards to protect the openings in the pipes from falling material. Each of the groups of sprays is interposed between the. respective groups of sprays and the supply maniiold 42. Also the feed versely extending spray pipe 39 is connected to a that described hereinabove including the highly magnetic and the faintly magnetic material is "held against theunder side of the travelling belt and is carried through theliquid bath. The ma- "t'crial clingingto: the under side of the belt is The ' ever, that the magnets, if desired, may all-be oi the material is being sprayed it is bounding and zigzflsging and turning over and over as it passes from a row of magnetpoles of one polarity tothe next adjacent row oi poles 'ofthe opposite polarity. The material is caused to zigzag or shift laterally of the belt by means of the staggered intermeshing relation of the pole pieces, as shown in Figure 6, and it is obvious, that as the material passes irom a pole'piece of one polarity to a polepiece of another polarity that there is a tumbling or turning action in addition to the zigzag shifting action of the material. This rapid changing of position of the particles while in the magneticfield not only produces a beneficial scrubbing action which removes the silicious coating from the pm, but it also frees from entrainment other gangue matter and bonded inclusions 'of iron and gangue as a middlings product. The sprays are so arranged that they act on the material at the points of greatest agitation and thus additionally assist in the separating action.

' It has been found that the separator provides a high value concentrate and that thetailings are substantially free from any magnetic particles. It has also beeniound that the machine will separate at one passage of the material therethrough the tailings,the middlings and the concentrates.

iii)

individually a adjusted by means ofinlet valves H which are gauge 44, as shown in Figure 2, which gauge consists of an open-ended glass or other transparent tube so as to indicate .the'head or pressure at which the sprays are supplied. It has been found that by having the group of sprays close to the feed end of-the machlne'ot greatest. velocity the magnets adjacent such end of greatest and 76 It will be seen also that the material isspread *over the under surface ofthebelt at the feed end by means or the spreading table or small platform 31 and by means of the, feed spray 38 in a thin and uniform layer completely across the belt. Also it is to be noted that the magneticfield is of considerable width and extends from adjacent one side of the belt to adjacent the other side thereof and throughout the active length of the belt.

By-having the wooden guide rails l3, see Figure 3, and the transverse wooden guide member I! and by havinga relatively extensively exposed flat iace provided by the faces of the pole pieces 5, see

Figure 6, the belt is not subjected to much wear obtained. the

- 7 Also with a rubber belt or a compositionbelt it has been found that water acts as an excellent lubricant for the belt and thus as the belt is wet while the machine is in operation there is very little friction between the belt and the portions against which it bears during its travel.

It is to be noted also that by means of the construction hereinabove set forth and illustrated in the drawings there is no chance of the material getting in between the belt and the pole pieces and thus scoring of the pole pieces and cutting of the belt is avoided.

The water gauges for each of the sets oi sprays allows the operator to ascertain at a glance the exact head or pressure of water supplied the different groups of sprays so that he may set the sprays individually to the exact requirements for the particular material being treated by the separator. Also it is to be noted that there is a general drift of water towards the feed end of' the machine and thus the muddy or dirtiest water is driven towards the feed end of the machine and discharged through the discharge-means, the mud or other tailings collecting in the tailing compartment. By this means final washing of the ma terial takes place in clean water.

It is to be noted also that not only is the materia1 passed through a water bath during separation but the material is also highly agitated during its passage through the water bath. and in addition is subjected to the action of individually controlled sprays at the zones where the material is most highly agitated. Thus the nonmagnetic material held by the clinging magnetic material is freely shaken and washed from the magnetic material and a very high degree of separation is thus secured. If desired, spray means, not shown, may be provided to assist in removing the concentrates from the belt.

It is to be noted that the electromagnets are protected from the water and that moisture is prevented from forming on the electromagnets due to the air stream that is forced through the electromagnet assembly, such air stream also cooling the electromagnets.

Another feature that is to be noted particularly is that the material is fed directly against the lower side of the belt at the feed end of the machine and directly beneath powerful electromagnets and the material, therefore, is not allowed to drop away from the belt while it is being fed to the belt but is spread thereon in a uniform and thin layer by the spreading platform. This causes all of the material to be subjected to an intense magnetic field at the beginning of the separating process so that all magnetic material 8 will be held securely against the under side of the belt at the beginning of its travel through the separator and thus there will be practically no loss of magnetic material with the tailings.

Although this invention has been described in considerable detail, it is to be understood that such description is intended as illustrative rather than limiting, as the inventonmay be variously embodied and is to be interpreted as claimed.

I claim:

A magnetic separator comprising a liquid containing tank, an, endless belt having a lower stretch passing through the liquid in said tank, means for driving said belt, feed means at one end of said separator for feeding material to the under side of said belt, a plurality of magnets having rows of pole pieces extending transversely across said belt, said rows of pole pieces being spaced lengthwise of said belt and being of opposite polarity and having portions intermeshing with and spaced from portions of adjacent rows to provide a zone of changing polarity to produce zones of greatest agitation for magnetic material clinging to the under side of said belt, spray means directed towards said belt to produce circulation of the liquid adjacent the zones of greatest agitation, said spray means including pipes extending transversely across said tank and having upwardly directed spaced spray openings and slanting baiiies overhanging said spray openings and protecting said spray openings from falling material and serving to spread and direct a thin, substantially uniform sheet of water against the under side of said belt, said belt having a discharge portion at a point beyond said pole pieces, and means for receiving concentrates from the discharge portion of said belt.

ROSWELL H. STEARNS.

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

UNITED STATES PATENTS

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