US1425235A - Magnetic separator - Google Patents

Description

W. E. F. BRADLEY.

MAGNETIC SEPARATOR.

APPLICATION FILEDYSEPT. 21. 1918.

Patented Aug. 8, 1922.,

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MAGNETIC SEPARATOR. V I APPLICATION FILED SEPT. 21,1918. 7 1 425 235 Patented .8 1

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W. E. F. BRADLEY.

MAGNETIC SEPARATOR.

APPLICATION FILED SEPT. 21. 1918.

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PHASE RELATION OF CURRENT E. F. BRADLEY. MAGNETIC SEPARATOR.

APPLICATION FILED SEPT. 21, 1918.

- Patented Aug. 8 11922,

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W "LL v 723050 N P5016 STATES WALTER E. F. BRADLEY, 3F NEW YORK, N. Y.

MAGNETIC SEPARATOJRI.

Specification of Letters Patent.

Patented Aug. S, 1922.

Application filed September 21; 1918. Serial ltlo. 255,172.

To all whom it may concern."

Be it known that I. VALTER E. F. BRAD- LEY, a citizen of the United States, residing at New York. county of New Yo1'k.'State of New York. have invented certain new and useful Improvements in Magnetic Separators. of which the following is a specification.

The invention relates in general to the magnetic separation and classification of mixtures containing finely divided magnetic and nonmagnetic substances. Such operations are often performed for example on magnetic sands. mixtures of magnetic and non-magnetic metal filings and many other mixtures, for the purpose of classifying or concentrating one or more of the substances mixed. in order that the separation or classification may be most efliciently acconr plished. the component particles should have the greatest possible freedom or independence of motion within'the apparatus. whereby the separating force is enabled to exert its influence with the minimum obstruction to their movement away from each other. On the other hand. the proximity of the mixture to the source of magnetic influence is important to enable the separating force to act strongly and to minimize the loss of magnetic material with the non-magnetic constituent. The separating process is in most instances relative. that is to say, it is not perfect. and repeated treatment is resorted to for approaching more nearly to perfection. Hence the action is progressive in its nature and any imperfection involving loss of magnetic material become cumulative. wherefore the great importance of having the mixture at all times within close range of the source of magnetism and supported in such manner as to give the component particles great freedom of motion.

An important object of the present invention is to provide apparatus by which the advantageous conditions above noted can be maintained and taken advantage of. and to thereby obtain a high elliciency in the separating and classifying process. ()ther important objects and advantages will appear from a detailed description of an embodiment of the invention illustrated in the accompanying drawing. in said drawing:

Figure l is a side elevation of a separator housing and magnetic conveyor, constructed in accordance with the invention, with parts omitted or removed;

Figure :2 is a detail transverse section, on a larger scale. showing the location of a magnet coil with respect to the magnet core;

Figure 8 is a detail longitudinal section taken through several coils and showing a portion of the core in face View;

Figure 4 is a wiring diagram showing the windings and connections of the seve 'al coils where for example. three phase alternating current at 60 displacement is employed for energizing the magnets;

Figure 5 is a diagram showing the phase relation ot the current in the three phase system;

Figure (3 is a diagram showing a direct current wiring and control system for energizing the magnets;

Figure 7 shows diagrammatically a current relation which may be obtained in the direct current system from the control device shown in Figure 6.

An important feature of the separation or classification of mixtures of magnetic and non-magnetic materials, according to the present invention. resides in applying to the otherwise unsupported mixture, a magnetic sustaining or suspending force, opposed to gravity and progressively varied in such manner as to effect travel of the magnetically supported particles over a sufficiently extended path to secure separation or concentration of one or more constituents to the desired degree. During its entire course through the apparatus, the mixture is free from mechanical support so that free movement of a non-magnetic particle under the influence of gravity or a magnetic particle under the influence of the magnetic force is facilitated. At. the same time, the progres sive variations in the magnetic force repeatedly redispose the mixed particles to free them from each other and aid in their sepa ration. while the suspended material as it progresses toward the point of final discharge becomes more and more purely of magnetic content.

By referring to Figure l of the drawings, this action will be more clearly understood. The separator housing or casing 10 has an inclined surface or wall 11 above which are disposed the electromagncts 12 with their pole faces directed against the wall 11 to maintaina magnetic flux through the latter, all of which will be more fully explained hereinafter. Suffice it to say, that the character of this magnetic flux is such as to sustain, against gravity, magnetic material which may come within its influence; and it is so varied as to cause the suspended substance to travel in a kind of-rolling or step by step manner toward the lower end of the wall 11. A feed hopper 13, for example, of some type which is adapted to be connected with a supply source while excluding atmospheric air, is mounted at the top of housing 10 for delivery of a finely divided mixture of magnetic and nonmagnetic materials to be separated. The upper end of inclined wall 11 is curved off below the hopper 13 so that material delivered by the hopper falls upon the exposed surface of wall 11 and thus comes within .the influence of the ma netic field. As the nature of this magnetic field has already been assumed to have such a character as to cause the material to 11, it will be obvious that the mixture delivered to it will pass along curved portion of Wall 11 and reach a point at which gravity is opposed solely by the magnetic force. The mixture being made up of magnetic particles and non-magnetic particles the force of gravity is opposed in its effect on the one and not opposed in its effect on the other. Separation thus tends to occur, at

first roughly due to. the inseparability of a certain proportion of the mixture, as where magnetic particles and non-magnetic particles are attached together and fall beyond the influence of the magnetic field. Further more, imperfections of operation cannot be entirely avoided and some magnetic particles fall at once or during the early stages of classifying operation Whereas some nonmagnetic particles become entrained or for other reasons fail to escape at once from the mixture and progress part way with the magnetic particles. The result, obviously,'is to provide a gradual increase in concentration of the magnetic component of the mixture as it progresses in its travel. Furthermore, the relative concentrations of the material which falls at different portions of the travel are so marked and regular that classifications of the discharge can be made according to the point at which it occurs. For this reason I prefer in most instances to collect the discharge at a plurality of points as at 14, 15 and 16. The discharged material in receiver 15 contains considerable magnetic material mixed with the non-magnetic material, for reasons above stated. and will usually pay to run through the apparatus again. The material collected in receiver let is practically a non-magnetic concentrate whereas that recovered in receiver 16 is a magnetic concentrate. Slidegates or valves 1T, 18,

19, and 20, 21, 22 may be mounted in the receivers 14, 15 and 16 to control the admission and withdrawal of material to and from the respective receivers while excluding atmospheric air.

By referring to Figures 2 and 3 of the drawing, further details of construction will be understood. The housing 10 is here shown as comprising side walls of, for example, sheet iron or steel, upon the upper edges of which are secured the longitudinal strips or plates 23. 24 of non-magnetic material such as brass. These plates of non-magnetic material may extend across the ends as shown at 25 (Figure 3) but the space between them in'nnediately beneath the magnetic poles is closed by a relatively thin sheet 26 of perineable soft iron and provides an unbroken continuous surface on the under surface of which the mixture is suspended by the magnetic field. Sight openings as shown at 27 may be provided where desired in the housing walls and covered with transparent material to exclude air. In some cases as where the material treated is liable to oxidize or otherwise subject to chemical action, any desired reducing gas or other at mosphere may be introduced through the inlet 28 as shown in the end of the housing wall in Figures 2 and 3. a

The magnets may be constructed in the manner shown by Figures 2 and 3, for example. In this embodiment they comprise laminated cores of comb-like form, the teeth 29 serving as pole pieces and the body portion 30 serving as a core about which the coils 31 are wound, as will be described more in detail in connection with other figures of the drawing. The teeth 29 space the lower portion of the coils, and to space the upper portions, I provide special spacing members 32, of U-shape in cross section, the bottom or base portion of the U being struck out to form ears 33 which are turned'down flat against the sides of the core pieces and bolted or otherwise secured thereto, as shown at 34. The leads to the magnet coils may pass through the perforations formed in the production of the cars 33. These spacing elements 32 are of 'nonmagnetic material. such as brass, and may be closed at their outer edges by plates or bars of similar material. These spacing elements 32, in addition to holding the coils 31 apart. perform the function of radiating heat from the ma nets.

he electrical connection of the several coils is subject to certain important considerations which must be observed. That is to say, there must be an alternating or pulsating mangetic effect of a very particular character, in order that the movement of the mixture may be effected. This may be obtained either from a direct current source or from a multiphase alternating current source as will be explained. Figures 4 and?) show diagrammatically the connections and the phase relations where for example, a three phase alternator, ofsuitable frequency. is employed. The three phases must be connected for obtaining a displacement of 60 rather than the ordinary 120 displacement. and hence each phase must have two slip rings and be in effect a separate independent circuit with no electrical connection or common point with either of the other phases. The phase relation thus obtained, as shown in Figure 5, is such that the algebraic sum of the currents in the different phases varies cyclically from positive to negative values and back to positive. In other words, there is an alternating group of currents, so disposed that the different currents of the group are passing through their respective cycles of positive and negative values in regular succession with their algebraic sum momentarily equal to zero only at two points during each cycle. The coils 31 are electrically divided into groups 31, 31", etc., corresponding with the number of phases, that is to say, a group of coils in the present instance comprises three, each of which is electrically connected with one of the phases, the first with cirsuit 1 (Figure 5), the second with circuit 2 and the third with circuit 3. Like numbered coils of the several groups are connected together in series but in alternate directions as shown in Figure 4, and each of these three circuits has its terminals connect d with one pair of slip rings on the alte nator.

The frequency of the alternations, within certain limits, has a direct influence upon the efiiciency of the separating action. I find that good results are. secured with all frequencies between five and seventy cycles per minute, the higher frequency offering better speed of operation. Also the angle, at which the separator is inclined, has an important bearing upon the result. Some travel is obtained with the separator set horizontal but I find that an angle of 45 is very satisfactory, gravity assisting the magnetic field to advance the material step by step with each alternation.

Figures 6 and 7 show an example of the energization of the magnets from a direct current source. Here again the coils are assumed to be electrically divided into groups of three (31% 31 etc.), the corresponding coils of successive groups being energized in the reverse sense. The line wires 6061 are each connected in parallel with a number of liquid terminals 62-63 arranged in pairs with one positive and one negative terminal for each end of each mag-= net circuit. There are six groups of magnets in the example selected, and three energizing circuits, each circuit including one coil of each group. Taking for example, the circuit which includes the first coil of each group, it will be seen that the circuit comprises the conductors 64 and 65. One of these conductors 64 'is electrically connected with the two contact members 66 and 67 operated by cams 68 and 69 to alternately make connections, each with its corresponding liquid terminal 62 or 63. The other conductor 65, is electrically connected with two contact members 70 and 71 which are operated by cams 72 and 73 to alternately make contact with another pair of liquid terminals in the reverse order. Circuit is thus closed through conductors st and 65 first in one direction and then in the other direction, the corresponding coil of each group being thereby energized. Conduc tors 7-1 and 75 are slmilarly connected and circuits are similarly closed through them to energize the second coil of each group, and so also with conductors 76 and 77 for the third coil of each group. The cams 68, 69, 7 2, 7 3, etc. are all conveniently mounted on the same or connected shafts to maintain a desired relation or timing of the several circuit connections. As shown in the diagram, Figure 7 the currents in these three circuits bear a similar relation to each other as those explained in connection with the diagram, Figure 5. That is to say, the algebraic sum of the group, alternates from a positive value to a negative value and back to positive in a cyclic manner, each phase of the group following another at 60 dis placement. The individual phase, however, in this instance, is interrupted between its positive and negative values, the current in another phase being effective during the period of such interruption.

lVith the principle involved in the excitation clearly pointed out, those skilled in the art will be able to devise numerous modifications or embodiments of the invention to perform the essential functions thereof, and the examples above given are merely explanatory or suggestive.

In general, it may be stated that the separator herein shown is well suited to form part of a connected or continuous metallurgical process for the reduction of ores such as magnetite, or where a magnetic oxide of iron, for example. is produced from a highei oxide-ore and is to be concentrated as a preliminary to further reduc: tion. The principles of construction herein shown enable such material to be treated under exclusion of air and without previous cooling. In the treatment of higher oxide ore to produce a magnetic oxide, a preliminary crushing and grinding, followed by screening, partial reduction and concentration may, for instance, be involved. In such a system, the discharge from an intermediate portion of the separator may advantageously be returned to the grinder and pass through the screening and partial reduction apparatus to be again subjected to concentration, the repeated treatment eflec tively recovering a large portion of the magnetic content which might otherwise be lost.

I claim i a 1. A magnetic separator comprising in combination a series of electro'magnets with their pole faces directed generally downward and disposed in sequence one after another. means for supplying material to the magnetic influence thereof. and means for energizing said magnets in groups of a plurality of relatively displaced cyclic current phases, the algebraic sum of the currents of a group alternating cyclically from a positive value to a negative value and back to positive.

2. A magnetic separator comprising in combination an inclined wall of magnetically permeable material. means forv supplying material to the under surface thereof. a series of electromagnets disposed above said inclined wall for directing a magnetic flux through the same. and means for energizing said magnets in groups of a plurality of current phases. each phase having a circuit independently of theothers and such circuit including a corresponding coil in each of the other groups. the corresponding coils of successive groups being energized in the reverse sense.

3. A magnetic separator comprising in combination a series of eleetro-magnets disposed in sequence one after another. the windings of said electrormagnets being connected in groups to form a plurality of electrically independent circuits, means for supplying to said circuits a relatively displaced. cyclically varying multi-phase current. in which the sum of the currents of the different phases varies cyclically from a positive value to a negative value and back to positive, and means for supplying material to the magnetic influence of the electro-magnets.

\VALTER E. F. BRADLEY.

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