US1958521A - Magnetic separator - Google Patents

Description

May 15, 1934. c PAYNE 1,958,521

MAGNETIC SEPARATOR Filed Oct. 31, 1931 2 Sheets-Sheet l l/Vl/Z-WTOR 67a reme Q v y 1934- c. Q. PAYNE 1,958,521'

MAGNETIC SEPARATOR 7 Filed 001.. 31, 1931 2 Sheets-Sheet 2 Patented May 15, 1934 UNITED", STATES PATENT OFFICE 9 Claims.

This invention relates to improvements in magnetic separators, and particularly to the separation of minerals of low magnetic susceptibility which require a highly intense magnetic field in order to act upon them.

It is the object of the invention to provide a magnetic separator in which the particles to be separated, in passing over the rotor and between the pole pieces, are subjected to a continuous intense magnetic influence, but one which involves only a minimum movement of the attracted particles relative to the rotor surface.

Another object of the invention is to provide a magnetic separator of the type herein described,

in which point and edge convergences of magnetic flux-density are set up at spaced intervals both axially and circumferentially of the rotor whereby particles of low magnetic susceptibility are attracted and separated from non-magnetic particles more completely than in machines heretofore used in this field.

Another object of the invention is to provide a magnetic separator of the type described, in which wear upon the rotor due to abrasion by the particles undergoing separation will not materially alter the magnetic influence to which the particles are subjected.

Various other objects and advantages of the invention will appear as this description proceeds.

Referring now to the accompanying drawings which show a preferred form of embodiment of the invention from which however various modifications and changes may be made, without departing from the scope thereof:

Figure 1 is a cross-section on line 1--1 of Figure 2,

Figure 2 is a cross-section substantially on the line 2-2 of Figure 1, showing an embodiment of the invention which employs'two bipolar electromagnets, and two rotor-armatures placed between opposing polepieces,

Figure 3 is an enlarged cross-section of a rotor and its polepieces with diagrammatic view of the magnetic flux-circuit passing through them,

Figure 4 shows a segment of the interleaved discs of the rotor provided with blunt toothed edges. and

Figures 5 and 6 illustrate diagrammatically the concentration of the fiux density at the points and edges of the interleaved discs.

The separator consists essentially in improved means for attracting magnetizable particles in controlling their movements while they are with- 55 in the magnetic field and in removing them from the field. It also consists in means for adjusting the width of the field-gap in relation to the size of the mineral particles to be separated therein. It also consists in an effective combination of electromagnetic units whereby two magnetic fields are obtained on one magnetic flux circuit.

Magnetic separation is based on the movement of magnetizable particles in or near a magnetic field, and is caused by differences of magnetic density. Mineral particles differ widely in their relative attractability, e. g. magnetite having several hundred times that of garnet. In the case of the feebly magnetic minerals with which the present invention is chiefly concerned, I have found that a highly intense or highly convergent magnetic field such as that employed in the well known Wetherill type of separator is not well adapted to secure a clean separating action. The magnetic flux of such a field acts as a whole, and in the presentation of the ore mixture the attracted particles must be lifted against gravity a considerable distance relative to their size during a very short interval of time. I have found it far more effective to localize or subdivide the attracting power of the field by means of a large number of inductively magnetized discs which expose magnetized edges and points and which are interleaved with non-magnetic discs, of such thickness that a, magnetizable particle requires only a slight lateral movement to reach either of its bounding edges when placed between them. Such particles, moving with the rotation of the discs are more easily attracted and held while they are falling under the influence of gravity than when they are lifted against it. They can also thus be acted on during a more efiective interval of time.

In attaining the above purpose I employ a series of thin magnetic discs 10 and non-magnetic discs 11, which are mounted on a shaft 12 and form a rotor-armature 13, preferably between two opposing electromagnets 14 and 15. These laminated discs also tend to suppress Foucault, or eddy currents which would be generated if the armature were made of solid metal and revolved at high speed. These currents cause resistance to rotation and heating. The discs also form the separating drum on which the ore mixture is fed from the hopper 16 by means of the rotary feeder 1'7. The chutes 18 and 19 serve to separate and space the feed stream before it reaches the rotors 13--13. I also provide the edges of these discs 10 with a series of blunt longitudinal teeth 20 whose pitch is so great compared with their depth that the bounding edges both of the valleys and also of the tops of these teeth areable to attract and hold magnetic particles while passing through the magnetic field. The tops and valleys of these teeth form arcs or tangents of concentric circles whose diameters differ only slightly from each other. These teeth also perform another important function in the separating action. Their points, or corners S (Figure 5) afford a still greater attracting force than the edges since the magnetic flux is here super-saturated by reason of its convergence from three directions. Any circumferential movement of the particles held to the tops or valleys of the discs" edges is strongly resisted when they reach these point convergences of the flux density.

Thus by reason of the spaced magnetic and nonmagnetic discs 10 and 11 an edge concentration of flux density is provided axially of the rotors at each side edge of both the teeth and valleys of the discs 10, as is indicated graphically at e in Figures 5 and 6, and by providing the tooth projections 20 a greater convergence of the flux density is secured at the points of the teeth S than at their edges whereby an intense magnetic attraction at spaced intervals both longitudinally and circumerentially of the rotor is brought about.

This greatly assists the removal of the attracted particles from the field without interference with the non-attracted particles when they have reached the end of the field. In the case of strongly magnetic particles, it is quite a difiicult matter to remove them from a highly intense magnetic field, especially, if they are attached to a smooth support. They then respond to the action of the magnetic field as a whole and a reverse movement is set up. This causes them to form columns by inductive action under the contending forces, and as the tops of the columns get knocked off by the rush of the non-magnetic part of the feed stream at the exit of the field, the separating action is interfered with. In the case of feebly magnetic particles a similar tendency "exists to a lesser degree.

the ore mixture while it is passing through the field. A wiper 32 preferably of a rubber blade variety removes any strongly magnetic particles from the rotors 1313' which may have become mixed with the feebly magnetic particles.

In my previous Patent No. 641,148, granted January 9, 1900, I have shown and claimed means for separating an ore mixture by means of pulsations or undulations of magnetic density. These means comprised wedge shaped, or pyramidal teeth upon the separating carrier. I found in practice however, that serious objections developed to this construction. The ratio of the pitch to the depth of these teeth being only about one to one, or one and one-half to one, the valleys between the teeth were not available for separation. This facilitates the escape of magnetic particles between the pulsations, i. e. between the tooth edges. Moreover, the edges and points of the teeth being exposed to the attrition of the feed stream would gradually wear and become rounded, thus losing a certain amount of their effective holding power. In my present invention a practically continuous separating action is obtained with only a minimum relative movement of the magnetic particles while they are being attached and held to the highly charged disc edges. For this purpose the teeth 20, (Figure 4) are made quite blunt and shallow, the

ratio of their pitch P to depth 0 being quitelarge, viz: about ten to one. In this way both the boundingedges e. of the valleys and of the tops of the teeth form arcs or tangents of concentric circles whose diameters difier only slightly and they are both made available for separation. Moreover, any wear of the tops of the blunt teeth by attrition from the feed stream does not reduce the sharpness of the points or of the bounding edges of the teeth, and they are thus continuously available for the purpose explained above.

It will be seen from Figure 3 that since the lines of force do not emerge from the disc edge at the neutral line lc-lc, of the rotor armature 13, and since they reverse their polarity on opposite sides of the neutral line, no feebly magnetic particles can be held to the disc edges beyondthis point.

My invention may be employed with various types or designs of electromagnets but I have preferred to illustrate it as shown in Figures 1 and 2 by means of two bipolar electromaguets which are opposed, and have their field coils so connected that when energized they form two magnetic fields on the same magnetic flux circuit as shown by the broken line and arrows in Figure 1. In this way, no interference is caused by the magnet units with the two feed streams as they pass through the separator fields, and the maximum capacity as well as the greatest structural economy is thus obtained.

The yokes A, B, of the electromagnets, Figures 1 and 2 may be supported in any convenient way as upon the angle irons C C attached to the frame D D D D of the machine. The yokes are enabled in this way to slide readily upon their supports in adjusting the widths of the field gaps. Each of the yokes A, B, has bolted to it the magnet cores A A B B and polepieces A A B B The field-coils A A B B which surround the cores enable the two electromagnets to be energized. The rotor armatures 13 and 13' revolve in the field gaps thus formed between the opposing polepieces A B and A B. These rotor armatures also form the drums on which the material to be separated is fed by means of suitable guide plates 18 and 19 as shown in Figure 2. The rotors and polepieces are so proportioned and assembled that by extending the magnetic field a suflicient arc below the horizontal diameter of the rotors, the attracted particles are enabled to be discharged at a considerable angle of divergence from a vertical line as the feed stream leaves the field. Aided by centrifugal fo rce a clean separating action is thus obtained. The division plate 21 is located at a suitable distance below the rotors for this purpose and deflects the non-magnetic particles into through them. They are bolted to the ends of the polepieces A B and A B and support the full thrust of the bi-polar fields when the latter are energized. Each bracket bearing 24 and 25 is provided with plates 26 carrying a threaded bolt 27 and by means of shims 28 at the rear of each one of the polepieces and by means of the thrust bolts 27, and locking bolts 29 shown in Figure 2, the polepiece faces A and B may be moved so that the width of the air gap on each side of the rotors can thus be varied to suit the grain size of the material undergoing separation. Nonmagnetic guide brackets 30 and 31 through which the rotor shaft passes without bearings for the shaft also support the inner ends of the polepieces as shown in Figure l, and assist to maintain the opposing electromagnets in horizontal alignment.

Figure 3 shows an enlarged section through one of the rotors and its opposing polepieces, with diagrammatic views of the magnetic flux through the rotor and polepieces in order to illustrate more clearly the control of the fiux density which is obtained in the field gaps by means of the thin interleaved magnetic and non-magnetic discs, and the teeth on their edges. Figure 4 shows a few of the disc edges in perspective view on a still larger scale. I have found that by making the teeth of the disc edges quite shallow so that the ratio of their pitch P to their depth 0 is about ten to one, I obtain a strong attracting force by convergence of the magnetic flux along the bounding edges of the discs both at the valleys 10 as well as along the tops 20 of the teeth. In this way the separating action is practically a continuous one, and the distance through which the magnetic particles require to be moved while they are in the field and before they are attached and held to the discs is extremely small. This greatly improves the separating action. Moreover, as already pointed out the comers or points of the teeth cause'a still greater intensity of magnetic attraction upon the feebly magnetic particles and any tendency'to slide backwards as they are moved out of the field, is thus resisted and overcome.

The operation of the separator will be quite clear from Figures 1, 2 and 3. Here when the field coils A A B B have been energized by means of an electric current, preferably from a dynamo-electric machine, the rotor armatures 13 and 13' are caused to revolve in their fields in the direction shown by the arrows by any convenient means such as a pulley 12a and belt driven from an outside source of power. The material to be separated is fed from a hopper 16, placed over each of the rotor-armatures, and the products of the separation are collected in bins or discharged by chutes 22-23 below the machine. A regulated feed-stream of the granular material is conveyed by means of the guide plates 18 and 19 upon the rotor armatures 13, 13'. The width of the field gap through which the feed-stream passes is regulated by means of the adjusting bolts and shims of the bearing brackets 24-25, which support the full thrust of the bi-polar magnetic fields. In this way suflicient clearance for free movement of the particles is provided allowing them to move beyond the influence of the edges of the interleaved magnetic and non-magnetic discs of which the former are highly magnetized by induction. The speed of the rotor is so regulated that the 'magnetic particles are aiIorded several opportunities of being brought into contact with the disc edges before they reach the discharge end of the field which is located below the horizontal diameter of the rotor so that the magnetic particles may be carried away from the non-magnetic particles at a divergent angle-and over the division plate 21 asshown in Figure 2, thus effecting a separation. In accomplishing this result the thickness of the rotor discs, the blunt teeth of large pitch-depth ratio on their edges, and the regulation of the width of the field-gap to suit the grain size of the feed-stream are the important features of my invention which secure a more perfect result in the separation of the feebly magnetic minerals.

While I have shown a preferred form of embodiment .of my invention, I am aware that modiflcations may be made thereto and I therefore desire protection on the scope and spirit thereof as described herein and claimed hereinafter.

I claim:

1. A magnetic separator comprising two opposing bipolar electromagnets, two rotor armatures composed of interleaved magnetic and non-magnetic discs and opposing polepieces between which said rotor armatures revolve and form parts of a single magnetic circuit generated by said electromagnets; in combination with means for varying the width of the field gaps between said rotor armatures and said polepieces and means for controlling the flux density of the magnetic fields, along the disc edges of said rotors by adjusted variations thereof, comprising blunt longitudinal teeth upon said rotor surfaces,

whose ratio of pitch to depth enables the bounding edges both of the valleys and of the tops of said magnetic disc teeth to attract and hold magnetic particles fed upon said rotors while passing through said fields, such ratio being at least ten to one.

2. In a magnetic separator of the type described including an opposed pole electromagnet and a rotor-armature mounted between the polefaces of said electromagnet, a series of interleaved alternating magnetic and nonmagnetic disks constituting said armature, the edges of said disks having a continuous series of shallow blunt toothed projections, in combination with means for energizing said electromagnet and producing in the field gaps along the bounding edges of the tops, slopes and valleys of the magnetic disks of said armature convergences of flux density of substantially the same intensity while the corners of said teeth, forming point intersections, produce convergences of greater magnetic density.

3. A magnetic separator comprising an electromagnet, a rotor-armature composed of interleaved magnetic and nonmagnetic disks, and opposing pole pieces between which said rotorarmature revolves, in combination with means for varying the width of the field gap between said rotor-armature and said pole pieces, and means for concentrating the flux density of the magnetic field along the circumferential disk edges of said rotor comprising blunt longitudinal teeth upon said rotor surface whose ratio of pitch to depth permits the magnetic disk teeth to continuously attract and hold magnetic particles fed upon said rotor on both the ridges and said rotor armature and said disks forming parts of a single magnetic circuit generated by said electromagnet; in combination with means for concentrating the flux density of the magnetic field along the disk edges of said rotor comprising blunt longitudinal teeth upon said rotor surface whose ratio of pitch to depth enables the bounding edges both of the valleys and of the tops of said magnetic disk teeth to attract and hold magnetic particles fed upon said rotors while passing through said fields, such ratio being at least ten to one.

5. A magnetic separator comprising an opposed pole electromagnet, a frame, supporting the magnetic poles, a. rotor armature mounted for rotation between said pole faces said poles being movably mounted on said frame, in combination with adjustable bearings for said armature shaft, comprising non-magnetic compression brackets adjustably spacing said pole pieces and supporting said armature in balanced relation therebetween, independent of'said frame against the tractive force of said electromagnet and'means connected with said brackets to adjust the field gaps between the armature and said pole faces, together with means for feeding material to be separated between the armature and a pole face.

6. A magnetic separator of. the class described having a bi-polar magnet and two magnetic fields adjacent the pole faces of said magnets, a frame supporting said magnet, and permitting movement of the magnet on the frame, said. magnetic fields being in a single magnetic circuit, an armature rotatable between each pair of said pole facesand composed of magnetic and non-magnetic disks, means to produce line and point convergences of the magnetic flux density in each field, and means to support the armatures in balanced relation between said pole faces and independentrof said frame comprising non-magnetic compression brackets supporting the full thrust of said electromagnet and providing bearings for the armature shaft, said pole faces being relatively movable with respect to said armature to adjust the field gaps.

, placed between said pole faces composed of a series of alternating magnetic and non-magnetic disks, each of said disks being provided with a series of shallow teeth whose tops form parts of the cylindrical surface of saidarmature and whose outer corners form points of flux convergence of relatively great density, the valleys of the teeth of the magnetic disks also forming lines of fiux convergence of lesser density,'and means to support said armatures in balanced relation between said pole faces comprising non-magnetic compression brackets supporting the full thrust of said fields and providing bearings for the shaft of said armature, and means connected with said brackets to adjust the field gaps between said armatures and pole faces.

. 8. An armature for a magnetic separator of the class described and adapted for mounting between the pole faces of an electrorhagnet, said armature comprising a plurality of substantially cylindrical disks of a magnetic material and a plurality of similar shaped disks of a non-magnetic material, said magnetic disks and nonmagnetic disks being interleaved, each of said magnetic disks having shallow teeth and valleys, the comers of the teeth forming a plurality of longitudinal lines of relatively great flux convergence, and the tops and valleys of the teeth forming a plurality of circumferential lines of flux convergence of lesser density, said lines of lesser flux density being substantially continuous in reaction on magnetic particles passing between the armature and a pole face, said transverse lines ofgreater flux density being non-continuous in effect on magnetic particles passing between the armature and a pole face.

9. A magnetic separator comprising a pair of oppositely positioned bi-polar electro-magnets with the N pole of each opposite the S pole of 119 the other to form pairs of opposing pole faces between which two magnetic fields are formed upon the same magnetic circuit, rotor armatures placed between opposing @pole faces but each spaced from one pole face to provide a relatively large field gap, and a frame to support said electro-magnets separably and movably thereon in adjustably spaced relation and said armatures in balanced relation between said pole faces comprising non-magnetic compression brackets sup- 129 porting the full thrust of said fields and providing bearings for said armatures, andmeans connected with said brackets to adjust the field gaps between said armatures and pole faces together with means for feeding material to be separated to said relatively large field gaps.

' CLARENCE Q. PAYNE.

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