US1948080A

US1948080A - Magnetic ore separator for wet and other operations

Info

Publication number: US1948080A
Application number: US451341A
Authority: US
Inventors: Percy H Thomas
Original assignee: Individual
Current assignee: Individual
Priority date: 1930-05-10
Filing date: 1930-05-10
Publication date: 1934-02-20
Anticipated expiration: 1951-02-20

Description

Feb. 20, 1934. v P. H. THOMAS 1 memmc om: SEPARATOR FOR war AND OTHER OPERATIONS Filed May 10, 1950 3 Sheets-Sheet 1 INVENTOR Fig.7 W 4 Feb. 20, 1934. 1,948,089

MAGNETIC ORE SEPARATOR FOR WET AND OTHER OPERATIONS P. H; THOMAS Feb. 20, 1934. P. H. THoMAs 1,948,080

MAGNETIC ORE SEPAR ATOR FOR WET AND OTHER OPERATIONS Filed May 10, 1930 3 Sheets-Sheet 3 Patented Feb. 20, 1934 UNITED STATES PATENT OFFICE MAGNETIC ORE SEPARATOR FOR WET AND OTHER OPERATIONS My invention relates to the process in which a separation of a magnetizable or partially magnetizable material from a mixture containing unmagnetizable material is accomplished by the use of a magnetic field and embodies more particularly the use of electromagnets so arranged and manipulated with regard to the feed of the mixed material thatboth large quantities of material can be handled and at the same time a thorough exposure of all the feed to the extracting influence of the magnetism is secured with the result that large tonnage capacity is obtained with a. simultaneous satisfactory recovery of the magnetizable and/or slightly magnetizable material with a high degree of purity. My invention also contemplates in connection with the handling of wet material means for washing the magnetizable materialsuch as concentrate-while under the influence of the magnetic field to clean it and thereby increase its percentage of metal content and also the dewatering of the recovered material, where such a result is advantageous. In virtue of the long distance through which the pulp passes while under the magnetic influence, and the favorable magnetic design as well as the fact that the material is kept within the desired distance of the magnet pole pieces together with other favorable features hereinafter described it is possible by this invention to get very much larger tonnage capacities in a magnetic separator than heretofore and to retain weakly magnetizable particles and even to concentrate some ores not usually treated magnetically; provided such ores have some magnetizable quality. It is also possible to wash the concentrate much more thoroughly without losing values. My invention has other novel features which will appear hereinafter. I

I have shown in Figs. 1 to '7 a favorable embodiment of my invention, where magnetic ore requiring concentration is to be handled by the wet process. Fig. 1 is a vertical section of the complete apparatus on the line F, F, Fig. 2, certain parts being omitted, showing the means provided for separating the magnetizable material from the gangue; Fig. 2 is an enlarged cross section of a portion of the enclosed channel through which the pulverized ore or pulp is passed for the purpose of concentration; Fig. 3 is an enlarged detail of the seal used at the sides of the enclosed channel showing certain structural details. Fig. 4 shows the shape and construction of the magnetic pole pieces; Figs. 5 and 6 show certain details of construction used to adjust the dimensions and position of the enclosed channel and hold it securely in position; Fig. '7 is a section showing 'a detail of the lining of the channel. Fig. 8 is an alternative form of pole piece and Figs. 9 and 10 are a side view and section of an alternative form of magnet construction.

Referring more in detail to the construction shown in Figs. 1 to 7 it may be pointed out that in the process of concentration the pulp,a wet" mixture of ground material, such as the pulp prepared in extracting magnetite ore,-which car- 5 ries an excess of water is passed through an enclosed channel constructed to conform more or less to the arc of a circle, one face of this channel corresponding to the outer surface of a revolving wheel. partly covered by a series of iron pole pieces which produce a strong magnetic field in the enclosed channel and the pulp in passing through this field has its magnetizable material so strongly ate tracted that it will cling to the belt which forms 7"; one side of the channel and moves with the revolving wheel. As the pulp emerges from this channel which is made long enough to give time for the desired portion of the magnetizable material to become drawn to the belt, the non-magnetic part of the mixture is free to leave themagnetizable part, leaving the latter purified and concentrated. As shown in the drawings the pulp moves in a more or less downward direction as it leaves the enclosed channel and the force of gravity and. centrifugal force both tend to cause the nonmagnetic material or waste to leave thosurface of the wheel on which the concentrate has been accumulated.

In this construction I have shown a belt, which may well be of thin rubber running on the periphery of the wheel on top of the iron pole pieces and also over a smaller idler pulley on a separate shaft. This belt comes between the iron pole pieces and the pulp in the enclosed channel and it is upon this belt that the concentrate is held by the magnetic field. This belt emerges from the channel at a-point wherethe magnetizable material is still under the influence of the mag- 10o netic pole pieces and only at a later point leaves the surface of the wheel to pass over the idler at which point it carries theconcentrate out of the magnetic field.

In these Figs. 1 to 7 the revolving wheel is shown at 1, being carried by the shaft 2. The enclosed channel through which the pulp passes is shown at 3, this channel being formed by the cover back or shield 29, and the belt 5. The pulp to be treated is accumulated in the head tanlrfi, 11

This wheel surface is covered or 70 through the launder *1 and a constant head is maintained in the head tank 6 by the overflow 8 which should be made adjustable and of suffiart.

I have shown 3 nozzles 9a, 9b, 9c, feeding pulp to the channel 3, I will point out that the position of the nozzle 9n must not be located so far to the left that the material discharged will not enter the channel 3. If the wheel revolves in the direction of the solid arrow "the motion of the wheel and the spouting velocity of the pulp work together but when the rotation of the wheel is in the direction of the dotted arrow, the wheel velocity acts against the spouting velocity of the pulp. The location of the nozzle 9a toward the left increases the distance travelled by the pulp in the channel and the time required-which is usually favorable for the operation.

By the use of more than one nozzle I am able 2 to have the magnetic field operate upon a portion of the pulp first, whichis favorable in'some cases to a more perfect action. The pulp introduced at the other nozzles then finds the concentration process well advanced on the first portions of the pulp introduced. These nozzles are so shapedusually as long narrow slots,as to distribute the pulp across the entire width of the channel.

The channel 3 has its discharge opening near the point 10, there the tailings are free to fall into the launder or drain l1. The partition or baflle 11a serves to aid this action.

I use a jet of clear water from a nozzle 22 located beyond the bafiie 11a to wash the concentrate and to remove any remaining impurities, or gangue including the dirty water adhering to it. The concentrate being still under the re-.

straining influence of the magnetic field will not be easily washed ofi. The material caught in the launder 23 maybe discharged to waste or treated p further if desirable.

It will'be noted that the chutes leading to the nozzles 9a, 9b, 90, have one side vertical and one side steeply inclined. As a result the heavier particles which are usually the valuable material will tend to settle on the inclined side and'be fed at the bottom of the jet onto the belt. They will thus become fixed without being dragged through the liquid pulp and the chance of mechanically entraining gangue will be reduced. At a point near 12 the belt leaves the surface of, the pole pieces to pass over the idler pulley 13 and the concentrate is removed from the influence of the magnetic fieldand is free to drop off onto the hopper 14 or be washed off by the water from nozzles l5.15. In some. cases I use nozzles 16, 16 for this purpose operating on the belt afterit leaves the idler 13. .In some cases I use scrapers 1'7, 17a to remove the concentrate. I may use insteadof a scraper a revolving brush revolving against the direction of motion of the belt 17b. The scraper 17 operates on the belt after and the scraper 17a before it passes the idler 13. This latter permits the collecting of concentrate by the scraper 17c and the use of water later to wash off the residue in a separate launder. The use of this scraper 17a. enables the concentrate to be collected without excess water thus if advisable saving subsequent dewatering. The hopper 14 discharges into the launder 18 or onto a belt except when it is desired to keep the concentrate collected by 17a. separate, in which case two launders are used. I

When more water is desirable in the concentrating process, either to facilitate the washing of the concentrate or to cause increased'agitation or to speed up the rate of flow in the enclosed channel,-I introduce jets from nozzles 19, 20and 21 here shown dotted since they lie behind the plane of the section shown.

The wheel 1 may be driven by a belt\ 24 running on the pulley 25 fast on the shaft 2 or by other means. It may be pointed out that the forces tending to pass the pulp. through the channel 3 are principally the spouting force of the pulp in the nozzles 9a, 9b, 9c, the force of gravity acting on the pulp as it passes from the nozzle 9a to the points 10 and 12 and the action of the outer surface of the wheel 1, when this revolves faster than the pulp. Also the jets from the nozzles 19 and 20. The forces opposing the passage of pulp 1 are friction and eddies and the movement of the wheel where this is slower than or opposed to that of the pulp, also the jet from the nozzle 21.

The cover member 4 is comprised of two supporting side pieces 26, Fig. 2 and Fig. 3, each carrying a non-magnetic stiffening plate 28 and a curved back 29 (Figs. 1 and 2) which serves to form the outer wall of the enclosed channel 3.

This curved cover back 29 is covered with a rub- 'ber lining 30 (Figs. 2 and 3 which takes wear and of the wheel including the magnet windings may,

be more clearly seen in Figs. 2 and 3. The wheel 1 includes side plates 31 each bolted to a hub 32 Fig. 1, secured on the shaft 2,

intermediate plates

33, 34 and spacing rings 35, 35, 35. The

intermediate plates

33, 34 are of steel and are annular in form, each being. clamped between two spacing rings 35, 35 by through-

bolts

36, 36. The

plates

31, 33, 34 and the rings 35 are all of magnetic material, the rings 35, preferably of cast iron and the plates of steel of good magnetic quality. I

Coils'of magnet wire

37, 38, 39 are placed in the open spaces between the

plates

31, 33, 34 and are wound onthe rings 35. They serve to produce the. magnetic flux required for the operation. Connections between the coils may be made at the points 40 on the outer surface so that the coils may be conveniently separated for disman- .tling purposes. In this case it is desirable/ to wind each coil in two halves with the connections between the halves at the bottom as shown at 41. The lead of coil 37 may be taken out through the plate 31 at 42 as shown. The leads may be taken to the shaft and connected to a supply in the well known manner through slip rings. I prefer to wind the

coils

37 and 38 in one direction and coil 39 in the opposite direction. Fig. 2 shows only one half of the construction, the center line 0, c, being the center plane of the wheel in the plane of rotation. The section of the wheel lying to the left of the center line (not shown in the figure) is a duplicate of that shown to the right, as will be clear to those skilled in the art. The inside coil in the left hand half (not shown) is wound in the same direction as the corresponding coil 39 and the two outside coils in the left hand, corresponding to 37 and 38, are wound in the same direction as the latter. The effect of this arrangement of windings is to cause

coils

37 and 38 to produce an independent magnetic circuit which includes the

adjacent plates

31 and 34, the spacing rings 35, 35 lying below these coils and the

pole pieces

43,44, 45, Fig. 4, lying outside the coils 3'7 and 38. Since the coils 3'7 and 38 are wound in the same direction the plate 33, Fig. 2, will carry little or no magnetism, as will be understood. Similarly the two corresponding coils in the left hand half of the wheel will produce asingle magnetic circuit of their own. The two center coils of which coil 39 is the right hand coil will produce a third magnetic circuit. the direction of the magnetism in the third being in the opposite direction to that in the other two. The plate 34 and the corresponding plate in the other half each acts as a part of both the two adjacent magnetic circuits and carries a double quantity of magnetism.

It should be explained that there is a nonmagnetic plate 47 the full width of the wheel (Fig. 3) placed over the coils to protect them. This plate 47 bears on the outside of all the

plates

31, 33, 34 and is screwed to them. To make a still better seal a rim piece 31a (Figs. 2 and 3) of non-magnetic material such as brass is screwed to the plate 31 and the plate 4''! screwed and brazed to it as shown in Fig. 3. The iron pole pieces 43 to 46 (Fig. 4) are shrunk on top of this plate and are secured to the edges of the

plates

31, 33, 34 by the same screws that hold the plate 47. By this construction is secured a very rigid wheel thoroughly protected windings, good magnetic conditions and easy assembling. The rim of the wheel as a whole just described is carried from the hubs 32 (Fig. 2) by the two side plates 31. For purposes of ventilation and general access,

openings

71, 71 are provided in the plates 31 as shown in Figs. 1 and 5. The conditions in my apparatus are favorable for cooling the ma net coils for they are in close contact with large bodies of metal which are exposed to strong air currents on account of the rotation of the wheel. The plates 33 help materially in withdrawing heat from the windings. The shapes of the pole pieces are shown in Fig. 4, which is a view looking at the face of the wheel. The air gaps of the magnets extending around the wheel are shown at 48, 48. These air gaps are the locations at which the intense magnetic field relied upon to attract the magnetic material is largely concentrated. The special zigzag shape of the air gaps serves to give a better distribution of magnetic field and to increase its total quantity, on account of the greater total cross section of the air gap secured. It may be noted that there are two

air gaps

48, 48 in series for each magneticcircuit.

In certain cases where conditions are not so exacting the pole pieces may consist of straight strips fastened symmetrically on the

plates

31, 33 and 34 as shown in Fig. 8, the air gap 48a corresponding to the air gap 48 and the pole pieces 43a, 44a and 45a to the

pole pieces

43, 44, 45. Similarly with the other air gaps and pole pieces.

In Fig. 3 is shown in brass guard piece 49, with a groove to receive detail the seal at the outer edge of the channel 3. It consists of a a flange 50 on the belt 5 and. a recess to take the rim 51 of the rim piece 31a. The stifiening plate 28 extends inwardly to cover the end of the rim 51 as shown. As the belt 5' and the rim 51 are rotating pieces while the guard piece 49 andthe stiffening plate 28 are stationary, a sufficient clearance must be left between them at the seals at the sides of the enclosed channel as shown in Fig. 3.

The curved cover back 29 and the side pieces 26 being of wood I support the guard piece 49 from the metal stifiener plate 28 by screws or otherwise.

The corrugated lining 30 is shown in Fig. 7, the direction of flow of the pulp being that shown by the arrow. The shape of the corrugations shown is for the purpose of causing transverse eddies in the pulp stream within the enclosed channel 3 (Fig. 3) so that all magnetizable particles in the stream may be'brought repeatedly in close contact with the magnetic field giving an opportunity for them to become attracted to the belt. This is often important because the attractive force of the magnetic field will be much greater near the pole pieces than at a distance and small difierences of distance may be important. While the strongly magnetizable particles are easily attracted it is only by means of very strong magnetic fields that the weakly magnetizable particles may be held. For this purpose a magnetically favorable apparatus has been here devised and large magnetizing currents are provided. It is further best to use as thin a belt 5 as practicable as the nearer the pulp approaches the pole pieces the stronger will be the attraction.

A further advantage of the corrugations is the washing effect of the eddies-in the pulp stream. By a thorough agitation and washing the particles of gangue slime lodged upon and among the magnetizable particles are disposed of. In some cases, however, it is more favorable to omit the corrugations and suppress the eddies to prevent the washing away of too large a portion of the weakly magnetizable particles.

In Figs. 1, 5 and 6, I have shown certain details of the means used for the support and adjustment 'of the cover member 4. This member is made adjustable for the purpose of permitting the control of the dimensions ofthe enclosed channel. The position of this element 4 is fixed radially in relation to the shaft 2 by means of adjustable rods 52a, 52b, 520, secured at one end to the stiffener plates 28 (Fig. 3) by the members 53 and at the other end to a plate 55 centered on the bearing box 27, by the members 54, 54, 54.

In the construction shown the members 53 and 54 have Tight and'left handed internal screw threads and the rods 52a, 52b, 520 are provided with corresponding exterior threads. The

lock nuts

59, 59 serve to lock the rods in position. Since the rods'52a, 52b, 52care separately adjustable the channel 3 (Fig. 3) may be given a varying depth at difierent points. For example by changing the length of the rod 52a a relatively greater or less depth of slot may be obtained at the top. Similarly by changing the length of the rod 520, a relatively greater or less depth can be secured at the discharge point 10. By changing the length of the rod 52b a relatively greater or less depth is secured at the intermediate parts or the enclosed channel.

The velocity of the pulp stream and its turbulence are affected by the relative depth of the channel 3. The width remains fixed in all positions. The lessening of the depth of the channel means a tendency for an increase of velocity and a change of turbulence. It further offers a control of the centrifugal force acting on the pulp stream which tends to separate the pulp stream from the belt 5. The effects produced by variations in the depth of channel may be very complex and different under one set of conditions and with one type of ore from other conditions and with other ores and I prefer to try out the best adjustments under working conditions with the means that I have described and it is possible readily thus to determine the best adjustment of the cover member 4.

The cover member 4 is kept accurately in a fixed position relatively to the plane of rotation of the wheel 1 by' the two guides and 61, moving in guide slots 62 and 63. These guides are mounted on plates 70, (Figs. 5 and 6) secured across the back of the cover member 4 as shown. These guide slots are formed in an A shaped vertical member 64. This member 64 is bolted to a foundation 65. It also carries a boss 66 which is connected by an adjustable hinged rod 67 to the guide ,61. This rod is adjustable by means of right and left hand threadsas is well known. Two lock nuts 69, are provided on the rod 67. The position of the cover member 4 circumferentially is determined by this rod 67. This-adjustment may be important andthe best position may be determined by trial. When a change in the position of the entrance to the channel is required due to a change in the position of the jet at 9a, or due to change in spouting velocity of the pulp stream or velocity of wheel 1, or otherwise, this adjustable rod 67 may be used.

In some cases I prefer to use a different construction of magnets as shown in Figs. 9 and 10. This construction has some elements very similar to that of the revolving field of an electric generator. The revolving element has a cast iron 'rim '73, carrying radially extending

magnetic cores

74, 74. Around these cores are magnetizing coils 75, '75 which may be connected in series as shown at 72. Over the pole pieces and the coils is placed a plate of non-magnetic material 76 secured at the sides of the rim to box plates 18, the coilsbeing thus tightly closed and protected. Pole pieces '7'? which are alternately north and south are placed above the cores outside the plate '76 and overhanging the cores as shown. This produces air gaps '79, 79. A belt 5a rides on these pole pieces corresponding to belt 5 of Figs. 1, 2, 3. This type ofconstruction produces lines of magnetism across the face at right angles to the plane of rotation, which sometimes has a favorable effect on the concentrating process. 1

The operation may be described as follows:

A supply of wet pulp containing ore or other material, a portion of which is magnetizable, preferably finely ground and carried in an excess of water is continuously supplied to the head tank at a sufiicient rate to cause an overflow at .8, Fig. 1, and a constant hydrostatic head in the tank. This will cause a flow of pulp out of the three nozzlesat a constant velocity. Assuming that the wheel 1 is revolving with the jets and ata higher velocity the wet mixture and the solid particles therein will be spread on the surface of the wheel within the channel and an opportunity given for the magnetizable particles to become fixed upon the belt. Since the belt is going faster than the pulp there will be a relative passing of the pulp over the belt and the solid particles will thus pass near the large number of strong spots and weak spots in the magnetic field produced by the iron pole pieces which lie under the belt. There will-be a tendency for the pulp to slow down somewhat on account of the friction and because the cover back is stationary. This tendency is resisted by the effect of gravity acting on the pulp as it goes lower on the wheel. If it is found advantageous the pulp may be made to slow down and it will then occupy a larger portion of the space in the channel and may even fill the channel entirely. If there is still greater slowing down the volume of pulp within the channel at any one point will tend to be greater and an internal pressure might develop. This would result in a tendency for a leakage of pulp on the sides through the seal partsiand-this would be objectionable, if in excess. The difficulty can be remedied by increasing the depth of the channel at this point either by the adjustments provided or by the original construction of the cover back 29. If the set up of the apparatus is such that the velocity of pulp increases at any point in the channel the channel may be made of less depth at that point and the pulp will be kept in closer relation to the belt.

When the pulp has reached the point of discharge of the waste material'practically every magnetizable particle will have had many chances to adhere to or become fixed upon the belt and most waste particles will have been'washed out from the adhering or fixed concentrate. At this point the ending of the cover back and the channel permits the waste to drop by gravity and through the action of centrifugal force from the belt and into the waste launder where it may be further treated if desired. After the discharge of the waste the concentrate under the influence of the magnetic field remains fixed on the belt and is carried past the partition 11. The concentrate may then be subjected to washing byclean water to remove the gangue adhering to it also muddy water that remains in it. As the attraction of the magnetic field is still effective there is little tendency to wash off any magnetizable particles and the metal content of the concentrate is improved.

After the concentrate which is still fixed on the belt has passed the clean water nozzle 22 at 12, the belt leaves the wheel at a certain point carrying the concentrate outside the influence of the magnetic field, thus allowing it freedom to drop. On account of its wetness, however, there will be a tendency for-the concentrate to stick to the belt and it may be washed ofi by the jets 15, 15, 16, 16 or may be brushed ofi by the scraper 17 or 17a. In this case the concentrate would not be mixed with excess water which action would in some cases be favorable from the point of view of dewatering.

If the wheel 1 instead of revolving at a speed greater than the spouting velocity of the pulp, revolves at a less velocity, there will be a quieter action with less tendency for the washing oil from their position on the belt of the weakly magnetizable particles and generally a slower passage of pulp through the channel, giving more time for the magnetic field to act and other advantages. The minimum agitation will occur when .the velocity of the wheel and that of the pulp pulp is spread relatively thin over a. large belt area facilitating washing, but with a slower speed of wheel, the layer will be thicker, giving a rougher surface and in some ways favoring the effectiveness of the magnetic field on account of the strengthening effect of the magnetizable material lying on the belt in concentrating the field at the critical points.

This operation is very favorable from many points of view. The channel 3 where the concentration or magnetic attraction occurs is relatively very long giving ample opportunity for the complete selection of the magnetizable material. so that high velocities may be used. It is further a confined or closed space so that the pulp is under control and can be made to pass slowly or rapidly or to pass in a relatively quiet manner or very turbulently by the means already described. A critical factor is the conditions under which the waste is finally separated from the concentrate at the end of the channel. If the separation is made with the pulp emerging at slow velocity and low turbulence there will be little tendency for the washing away of the weakly magnetizable particles or particles ad-- hering to the belt at unfavorable points, and this while still permitting the effective washing at earlier parts of the path through the channel. These characteristics and the general construction shown are such that the passage of pulp at high velocities may be availed of and good sized channels used so that a large capacity output can be satisfactorily handled. Furthermore, the many adjustments including those in the control of the pulp feed to the wheel permit securing the best results with many different types of ore and processes of ore preparation.

The construction of the iron pole pieces is particularly favorable as they permit many variations in thedistribution of the magnetic field over the surface of the wheel and they may be readily interchanged and removed or repaired. The stray magnetism is greatly limited. Furthermore the magnetic field isapproximately uniformly distributed over the surface of the wheel on the average and once a magnetizable particle adheres to the belt its magnetic condition is not changed during its passage through the channel until the belt leaves the wheel at 12. Heretofore magnets fixed in position have often been used inside a moving non-magnetic shell and material held on the outer surface of the shell, but such particles as they pass by the magnet poles are subjected to a varying magnetic field and may pass through weak points in the field resulting in a tendency for the weakly adhering particles to be lost, this is a very important advantage of the invention described herein.

I may estimate that the advantages of my construction are such that in 24 hours in excess of a thousand tons of favorable crude ore can be concentrated in a single apparatus constructed approximately as that shown in which the wheel is only a few feet in diameter. On account of the very favorable magnetic conditions attainable in my apparatus, very fine material and materials having only slight magnetizability can be concentrated.

In certain of the figures such as Fig. 5, and others, certain parts are omitted for the purpose of showing other parts more clearly. This will carrying surface together with a continuous sheet but is useful wherever material, responding to the influence of a strong magnetic field, is to be separated from material not so subject or not so subject to the same degree. The invention shown as operating with wet pulp may be equally well used with dry mixtures and the magnetizable material will be segregated.

'I claim as my invention.

l. A magnetic separator, comprising a revolving magnetized wheel, having positive and negative pole pieces circumferentially disposed and substantially uniformly distributed over the outer circumference of said wheel, a non-magnetic belt running on said pole pieces, means for feeding a stream of liquid pulp onto said belt in a thin layer the pulp flowing on top of and in contact with the belt on whose surface the magnetic material is collected by the magnetic field through a predetermined operating range, and means for separately controlling the speeds of said pulp, and said belt to produce a relative velocity between them and thus causing the liquid pulp to continuously wash the layer of magnetizable material as it gathers on the belt under the magnetic influence.

2. A magnetic separator comprising a magnetized wheel having positive and negative pole areas distributed over the surface, 'a non-magnetic belt running on the surface of said wheel covering said pole areas, means for feeding a liquid mixture of magnetizable and non-magnetizable material onto said belt and for maintaining said mixture in contact with said belt through the operating range of said pole areas, said feed ing operation being spread along over a portion of said operating range, said belt cooperating with the influence of said pole areas to accumulate a thin layer of magnetic particles from said mixture and means for maintaining a relative velocity between said belt with its thin layer of captured particles and the liquid, thus securing a continuous washing of the magnetizable par- 4 ticles as deposited and preventing the overlaying of nonmagnetizable particles temporarily carried with the magnetizable particles by later captured magnetizable particles.

3. A magnetic wheel for concentrating magnetic ore or similar mixtures, comprising a shaft, a plurality of steel discs, arranged around and supported from said shaft, -a plurality of circular magnetizing coils distributed between said steel discs, magnetizable filler rings placed inside said coils and between said discs and contacting with said discs, means for clamping together said discs and filler'pieces, a water tight covering secured on the outside of said discs and coils and circumferential magnetic pole pieces secured outside and upon said water tight covering and serving as a belt carrying surface.

4. A magnetic wheel for concentrating magnetic ores and similar mixtures, comprising. a shaft, a plurality of annular steel discs arranged around and supported from said shaft, a plurality of circular magnetizing coils distributed between said discs, magnetizable filler rings located inside said coils and between said discs and contacting with said discs, means for clamping together said discs and filler pieces, and circumferential ma netic pole pieces secured to the outside edges of but spaced fromsaid discs and serving as a belt of non-magnetic material inserted between said pole pieces and the edges of said discs.

5. A magnetic wheel for concentrating magnetic ores or similar mixtures, comprising a shaft, a

plurality of annular steel discs, arranged around and supported from said shaft, a plurality of circular magnetizing coils distributed between said discs, said coils being in pairs and those of a. pair being separated by an additional disc, magnetizable filler rings located inside said coils and between said discs and contacting with said discs, means for clamping together said discs and filler pieces and circumferential pole pieces secured to the outside edges of said discs and serving as a belt carrying surface, the magnetic flux in adjacent first named discs being in opposite directions.

6. A magnetic wheel for concentrating magnetic ores and similar mixtures, comprising a shaft, a plurality of annular ste el discs, arranged around and supported from said shaft,- a plurality of circular magnetizing coils distributed between said discs, magnetizable filler rings located inside said coils and between said discs and contacting with said discs, means for clamping together said discs and filler pieces, and circumferential magnetic pole pieces secured to the outside edges of said discs and servingas a belt carrying surface, together with unmagnetized intermediate discs located midway between said annular discs and dividing said coils and said filler pieces and carrying auxiliary pole pieces secured to the outer edge of said intermediate discs, each lying between and cooperating with two'of the first named pole pieces.

7. A magnetic separator, comprising a magnetic wheel having positive and negative magnetic pole areas distributed over the surface, a non-magnetic belt running on the surface of said wheel covering said pole areas, means for feeding a liquid mixture of magnetizable and non-magnetizable material onto said belt and for maintaining said mixture in contact with said belt through the operating range of said pole areas, said feeding operation being distributed along over a portion of said operating range, said belt cooperating with the influence of the magnetic pole areas to accumulate a thin layer of magnetizable particles from said mixture and means for maintaining a relative velocity between said belt with its thin layer of captured particles and the liquid, while in contact therewith, thus securing a continuous washing of the captured magnetic particles as deposited and preventing the admixture of nonable particles by later captured magnetizable particles.

8. A magnetic concentrator, comprising a revolving magnetic wheel, a non-magnetic belt riding thereon through a working range of magnetic action and means for feeding a liquid mixture of magnetizable and non-magnetizable particles onto and against said belt, for washing concentrate on the surface of said belt and for distributing said feed through a portion of the working magnetizable particles carried with the magnetizrange, whereby opportunity is offered for the PERCY H. THOMAS.