US2045098A - Apparatus for magnetic separation - Google Patents

Description

C. Q. PAYNE APPARATUS FOR MAGNETIC SEPARATION Filed Sept. 14, 1933: 2 Sheets-Sheet l INVENTOR.

June 23, 1936. I c Q PAYNE 2,045,698

APPARATUS FOR MAGNETIC SEPARATION Filed Sept. 14, 1955 2 Sheets-Sheet 2 INVENTOR. Clarence 0; Pay

Patented June 23, 1936 UNITED STATES PATENT OFFICE 2,045,098 APPARATUS FOR MAGNETIC SEPARATION Clarence Q. Payne, Stamford, Conn. Application September 14, 1933, Serial No. 689,373

6 Claims. (01. 209-219) This invention relates to improvements in magnetic separators, for increasing the efficiency and economy of separating both feebly and strongly magnetic from non-magnetic minerals.

concentrations of the tudinal and circumferential as well as point convergences thereof caused by the stub teeth on magnetic lines of force set I .up in the magnetic fields by reason of the longi- It is an object of the invention to provide a the disc edges. My present invention is a con- 3 magnetic separator in which the separating eletinuation of said application so far as the features ment, which revolves freely between opposing of the latter are common to both.

pole-faces, is enabled to exert the maximum at- I have found that while this type of rotor op.- tracting force by means of magnetic convergences crates successfully in the separation of feebly upon the feed stream, and at the same time to 'magnetic minerals when it is rotated at moderate 1 suppress mechanical disturbances or entanglespeeds, certain disadvantages develop when it is ment of the feed-stream while acting upon it at rotated at high speeds. The effect of high speed a high speed of rotation. is to cause the disc teeth to exert hammer blows Another object of the invention is to control upon the mineral particles as they are fed upon the direction of the feed-stream at its entrance the rotor and also as they descend through the 15 into the field-gap, and to facilitate the discharge field-gap while undergoing separation; This of the magnetic particles attached to the rotor at causes mechanical disturbances and scattering of the end of the field. the feed-stream, and a thorough separating Various other objects will appear from the folaction is thus made more diflicult. My present lowing description. invention overcomes these mechanical disturb- 20 In the accompanying drawings which show a ances or entanglements and permits the rotor to preferred embodiment of the invention: be revolved at quite high speeds in separating Figure 1 is a vertical cross section on line I--l feebly magnetic minerals and thus greatly inof Figure 2, creases the capacity of the separator. It has also ;5 Figure 2 is a horizontal cross-section about on the further advantage that by reducing the field line 2*2 of Figure 1, strength of the electromagnet it is possible to sep- -Figure 3 is an enlarged part section of a rotorarate strongly magnetic minerals as well, and to disc showing cylindrical edge with radial filled revolve the rotor at 'very high speeds without slots, causing its surface to suffer destructive Wear.

Figure 4 shows an enlarged perspective view of The structure of the separator will be quite 30 a segment of the rotor-armature of the construcclear from Figures 1 and 2. Here two separate tion shown in Figure 3 with interleaved magnetic electromagnets E R. F G and E2 R2 F2 G2 and non-magnetic discs and with longitudinal are supported one above the other upon channel slots filled with non-magnetic material, irons J J2 and J3 J 4, bolted to the vertical up- Figure 5 is a partial elevation with the shaft in right members of the separator frame. A regu- .35 cross-section of a rotor-disc whose cylindrical lated stream of ore is fed from the hopper I-I edge is provided with low stub teeth, by means of feed-rollers I into each of the Figure 6 is a perspective view of a segment of unipolar fields of the electromagnets shown in the rotor-armature shown in Figure 5, made up Figures 1 and 2, by means of suitable guide plates of magnetic and non-magnetic discs, K K2 K3 and K4 K5 K6. The field-gaps of 40 Figure 7 shows in perspective the segment of a each bipolar electromagnet are here referred to rotor-armature composed of magnetizable discs as unipolar fields. This is a convenient or conof alternately smaller diameter than their adjoinventional term to include those in which the ing discs, and whose outer circumferential edges lines of force all pass in the same direction and A5 are brought to the same cylindrical surface by do not reverse at any point. It distinguishes 4 means of longitudinal and circumferential filling them from the multipolar type of field in which strips of non-magnetic material, and, frequent reversals of the lines of force take place.

Figure 8 illustrates diagrammatically the sub- The widths of the field gaps between the rotordivision of a crushed mineral aggregate composed armatures and their opposing pole-faces are '50 of magnetic and non-magnetic material into conregulated by means of compression brackets as '50 centrate, middling, and tailing particles. shown in'Figure 2 at Q Q2. These compression In my copending application for patent, Serial brackets are of non-magnetic material, such as No. 572,274, filed October 31st, 1931,1haveillusbronze, so as not to short circuit any of the trated and described a bipolar electromagnet prolines of force of the magnetic flux generated by 25 vided with rotors made up of interleaved magt e electromagnet T ey Contain bea fo netic and non-magnetic discs having low stub the ends of the rotor shaft, and are splined to teeth on their edges, and which rotate freely bethe ends of the stationary armature E- and of tween opposing pole-faces. This design of sepathe pole pieces P P2 as shown in Figure 2. These rator has distinct advantages in the separation of brackets are bolted to their supports with shims I feebly magnetic minerals owing to the powerful DI D2 D3 D4 comprising thin plates and by'regulating their number the widths of the air gaps on each side of the rotor-armatures can be accurately adjusted to provide ample field space for the passage of the mineral particles undergoing separation.

The upper armature-rotor R is made to revolve at a high speed viz: one at which, for most magnetic minerals the resulting centrifugal force will exceed the weight of the particles fed upon it by the guide plate K3. They will all tend to be thrown away from the rotor surface and will strike the bumping block T. The electric current from the generator W energizes the field coils F F2 and the magnetizing effect of the armature-rotor is regulated by the rheostat Y, so that when the feed stream descends into the field gap, the magnetic concentrate particles represented by I 0, Figure 8, will all be held to the rotor discs, and will be carried over the division plate K4, while the remaining particles represented by l I and I2, Figure 8, will not be held, but will pass out of the field and will be guided by the plates K5, K6 to the armature-rotor R3 of the lower bipolar electromagnet. The lower armature-rotors are made to revolve at a slower speed than those of the upper electro-magnet, and exert therefore less centrifugal force. At the same time their magnetizing effect, regulated by the rheostat Y2, is made so intense that all those remaining middling particles of the feed stream represented by H, Figure 8, will be attracted and carried beyond the division plate K1, thus separating them from the non-magnetic tailing particles l2, Figure 8. It will be understood that when the magnetic particles which are attracted and held to either rotor approach 'the position of the neutral lines X X2 and X3, X4 they are automatically discharged, since the lines of force which represent the magnetic fields and are shown diagrammatically by horizontal broken lines and arrowheads, do not emerge at the neutral lines.

Figures 3, 4, and 7 illustrate by sectional views the means employed to accomplish the improved result. Figures 3 and 4 show interleaved mag netic and non-magnetic discs M and N so assembled that their edges form a continuous cylindrical surface. Radial slots L are cut at spaced intervals along the circumference of the discs and these are filled with strips of non-magnetic material such as bronze, etc., whose edges form part of the cylindrical surface of the rotor.

When two of the rotors thus assembled are mounted on a single shaft as shown in Figure 2, and placed between opposing pole-faces of a bipolar electromagnet as shown in Figures 1 and 2 at E P they then form parts of the magnetic flux circuit generated by the electromagnet. Here the circumferential edges M2, and the longitudinal edges M3 of the magnet discs M form strong condensation or convergences of the lines of force within the field while their point intersections, as at M4, form still stronger convergences thereof. The magnetic particles of the feed-stream can thus be attracted and held to the disc edges of the rotor without the disturbing eifect of shocks and jars delivered to them by any projecting teeth as they are being attracted and held to the smooth-rotor surface while undergoing separation. This improves the efliciency as well as the capacity of the separating action and makes the erally applicable to strongly magnetic as well as to feebly magnetic minerals. It also enables the magnetic particles to be more easily removed from the field by overcoming any tendency to slide back into the field at the end thereof, when the disc edges are not provided with longitudinal slots, or with low stub-teeth.

In order to utilize to the fullest extent the advantage of high rotor speed, I have found it desirable to reverse the direction of the feedstream as it enters the magnetic field as shown in the sectional view of the upper electromagnet of Figure 1. This is accomplished by means of a resilient bumping block, preferably of rubber as shown at T, against which the mineral particles of the feed-stream are charged as they are conveyed by the guide plate K3 upon the rotor, and then rebound and leave its surface while the centrifugal force of the rotor, is impressed upon them. Upon striking the bumping block T their impact is partly absorbed and they return to the rotor surface, enter the field above the horizontal diameter of the rotor and descend through it thus under better control.

The plan view of the upper electromagnet is shown in Figure 2. Here two laminated disc rotors of the construction shown in Figures 3, 4 or 7, are mounted on the same shaft and are made to revolve in the fields established between the opposing pole-faces of the stationary bar armature E and the pole pieces P and P2. The magnet cores of the field coils F and F2 and the yoke or back-piece G, ture E, form parts of the same magnetic flux circuit as shown by broken lines and arrowheads in Figure 2. The upper rotor R of Figure 1 is revolved at a higher speed than rotor R3 of the lower electromagnet by means of suit I1 able belts and pulleys from the shaft V supported by bearings bolted to the frame of the separator, and driven by a belt from an outside source of power or by other means.

Nearly all ores occur in association with rock minerals, and must first be crushed in order to unlock or free them mechanically from each other before they can be grouped together according to their composition. A true middling product however, or at least one to which the term is herein employed in magnetic separation, is one which comprises ore and gangue particles attached together and which require finer crushing in order to unlock them. This is illustrated diagrammatically in Figure 8 by groups of particles I 0, II and I2 which are shaded to represent concentrates, middlings and tailing products. It is obvious that a method which will achieve such a group separation has a great advantage in economy over one which will not since it is then only necessary to crush the middling product to a degree of fineness required to unlock the attached minerals and reseparate it instead of crushing all the concentrates and the tailings as well to the same degree of fineness.

The improved separation is therefore accomplished in accordance with my invention by subjecting the feed stream to a stronger centrifugal force in order to overcome mechanical entanglement of the diverse particles while passing it over the first rotor which revolves at a higher speed preferably with lower magnetizing effect than that of the second rotor thus removing a clean concentrate product. The remainder of the feed stream is then acted magnetizing force while passing over the second rotor than over the first rotor which may revolve it at a slower speed than the first, thus separating clean tailings from the middlings product.

and the stationary armaupon by a greater I am able in this way to employ strong oppos- 75 ing forces in effecting a separation between magnetic and non-magnetic materials. These forces may far exceed the Weight of the individual particles depending upon the nature of the material itself.

Since the second rotor may, in certain applica tions, be revolved at quite slow speeds, it is possible to employ in such cases either the rotor-ar- 1 mature construction shown in Figures 3 and 4, which has smooth cylindrical disc edges, or else that shown in Figures 5 and 6 which has low stub teeth on its disc edges. Where no mechanical disturbances of the feed-stream are occasioned by either construction the choice between the two types of rotor construction will depend upon the nature of the material to be separated.

Figure '7 shows a rotor-armature composed of laminated magnetizable discs M5 of alternately smaller diameter than their adjoining discs M, and whose outer circumferential edges are brought to the same cylindrical surface by means of longitudinal and circumferential filling strips of non-magnetic material L and 0.

It is thus possible by my invention to effect an economy in the cost of preparing magnetic ores and minerals for separation even when they are finely mineralized by beginning their separation at a coarser size than a complete unlocking of their constituents would otherwise require. It is also possible to greatly improve the efficiency of magnetic separation by independent control of the magnetizing and centrifugal forces exerted upon individual group particles by two successive armature-rotors revolving in unipolar magnetic fields.

While I have described certain specific embodiments of my invention and the manner of its use it will be understood that various modifications and changes may be made therein without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. In a magnetic separator of the type de scribed the combination with an opposed pole electro-magnet of a rotor armature mounted between the pole faces of said electro-magnet, said armature comprising a series of interleaved alternating larger and smaller magnetic disks, the edges of said large-r disks having a continuous series of spaced transverse recesses, the recesses in the larger disks and the spaces between the larger disks and circumferential to the smaller disks being filled with non-magnetic material forming with the projecting portions of the larger disks an even, continuous, substantially smooth armature surface with fiat topped rectangular magnetic areas and the circumferential and transverse edges of the said projecting portions forming zones of concentration of flux density along circumferential and longitudinal lines and zones of still greater concentration at their meeting points.

2. In a magnetic separator of the type described the combination with an opposed pole electro-magnet of a rotor armature mounted between the pole faces of said electro-magnet, said armature comprising a series of interleaved alternating magnetic and non-magnetic disks, transverse filling strips of non-magnetic material, the non-magnetic disks and non-magnetic transverse filling strips forming an even, continuous, substantially smooth armature surface with fiat top rectangular magnetic areas, the circumferential and transverse edges of the said rectangular areas forming zones of concentration of flux density along circumferential and longitudinal lines and zones of still greater concentration at their meeting points.

3. A magnetic separator of the type described in combination with an opposed pole electromagnet, a rotor armature having a smooth continuous surface, said surface including a plurality of exposed areas of magnetizable material and of substantially rectangular shape, said areas having edges circumferential and longitudinal to said armature which are concentrated zones of flux density, said surface including a plurality of exposed areas of non-magnetizable material substantially equalnin width to the magnetizable areas, and means in said armature to intercept magnetic lines of force from said electro-magnet.

4. Apparatus for magnetically separating a mineral aggregate into concentrate, middling and tailing products comprising, in combination, an upper electro-magnet having opposed poles, a rotor-armature mounted between the opposed poles, said armature comprising a series of magnetic disks formed to provide circumferential teeth and non-magnetic material filling the circumferential and longitudinal spaces between said teeth, the outer surfaces of the teeth and of the non-magnetic material forming a substantially smooth, even, continuous surface with the teeth presenting numerous relatively small areas of magnetic material spaced circumferentially and longitudinally from each other, a second lower electro-magnet having opposed poles, an armature mounted between said poles, said armature having a series of interleaved disks, the edges of said disks having a series of blunt toothed magnetic projections with non-magnetic material therebetween, means for varying the field strength and inversely varying the speed of rotation of the two rotor armatures.

5. A magnetic separator for initial and final classification of magnetic material which comprises two pairs of opposing electro-magnet pole faces, separate rotor armatures mounted between the pole faces, said armatures being arranged for sequential contact with the material to be separated, means to rotate the first armature at a relatively high speed and. means to rotate the second armature at a relatively low speed, said first armature having a plurality of interleaved disks of different diameter forming circumferential slots and non-magnetic filling for said slots and forming a substantially continuous cylindrical surface, said second armature having a plurality of interleaved disks, said disks having blunt longitudinal teeth on the outer surface, whose ratio of pitch to depth enables the bounding edges both of the valleys and of the tops of said magnetic teeth to attract and hold magnetic particles fed upon the rotors while passing through the field, and means to separately energize the respective electro-magnets.

6. A magnetic separator of the type described in combination with an opposed pole electromagnet, a rotor armature having a smooth continuous surface, said surface including a plurality of exposed areas of magnetizable material and of substantially rectangular shape, spacing means between said magnetizable areas to space said areas one from the other, said spacing means being of substantial size whereby the longitudinal and circumferential edges of said areas act as concentrated zones of fiux density, and means in the armature to intercept magnetic lines of force from said electromagnet.

CLARENCE Q. PAYNE.

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