Improvements in Method of and Apparatus for Magnetic Separation.
Year: 1896

page_text: Date of Application, 3rd Mar., 1898-Accepted, 11th Apr., 1896
COMPLETE SPECIFICATION.
Improvements in Method of and Apparatus for Magnetic Separation.
1, JOHN PRICE WETHERILL, of corner of Cherokee Street and Delaware
Avenue, South Bethlehem, County of Northampton, State of Pennsylvania,
United States of America, Mining and Metallurgical Engineer, do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
My invention contemplates the separation, on a commercial scale, of paramagnetic
material of very low magnetic susceptibility, from mixtures containing the same,
and, especially, the separation of ferruginous material wherein the iron is present
in such small proportion or in such chemical combination that said ferruginous
material has been considered incapable of separation and segregation by magnetic
separators of the kind heretofore employed in the ore-dressing art.
In the present state of the art, so far as I am aware, the only minerals that are
recognized as commercially separable by magnets from ore mixtures containing
them are magnetic oxide of iron (Fe,O) (natural or artificial), and pyrrhotite,
both of which have such a high degree of attractability as to adhere to the ordinary
seven inch hand magnet familiar to the mineralogist and to be readily removed by
familiar forms of separators. Aside from these two classes of ninerals, aud
possibly one or more others closely approximating them in attractability, the
knowledge that other ferruginous minerals are susceptible of magnetic attraction
has not passed the laboratory of lithologic-cabinet stage, and has never been the
subject of successful industrial working, despite the incentive offered by the
recognized high commercial value of the products that would result therefrom.
My present invention realizes broadly the industrial magnetic separation, on a
metallurgical scale, of substances of such low magnetic attractability that they are
either rated in the art as non-magnetic, or are not recognized as possessing any
magnetic attractability whatever. Examples of such substances are afforded by
the hematite or limonite present in admixture with sand in ore deposits (as, for
instance, the Clinton red fossil ore of Alabama); by the garnet, menaccanite and
rutile present in monazite sands; and, by spathic iron ore (siderite). These
substances, separated through the agency of the intense magneto-motive forces
incident to the practice of my invention, are typical of a considerable class, all
within a realm of feeble magnetic permeability, extraordinarily remote from that
of the so-called "maguetic" minerals, magnetite and pyrohotite, the abrupt gap
between the two classes of substances being unoccupied by substances of intermediate
and graduated magnetic susceptibility.
In the practice of my invention for the separation of these and like substances
from the non-magnetic gangue accompanying them, I first crush the composite ore
so that the particles to be separated break apart from each other, unless they are
already in that condition, and then pass it through a magnetic field of such extremely
high condensation or concentration that the hematite, or like substance of low
attractability to be separated, will be temporarily inductively magnetized, and
deflected into a line of imovement different from that of the gangue.
For the attainment of the best results, I feed the material to be separated
through the strongest lines of force of the highly concentrated or condensed
magnetic field, established across an interval (such as an air or water gap) in a
magnetic circuit; and, when the field is formed by the opposing poles of electro-
magnets I preferably feed the material into it in such manner that it will enter

page_text: from opposite sides of the field, and pass through the zones of greatest attraction
immediately adjacent to the pole piece edges, avoiding the central zone of sub-
stantially equal attraction midway of the poles; as a consequence whereof, the
particles to be attracted are arrested in the zones of greatest attraction and diverted
into receptacles provided for them, without coming into the neutral or weaker
zones at all. These features are of extraordinary importance for the successful
and commercial separation of the class of substances with which my invention
deals, as they render it possible to subject the entire mass of the attractable
particles to the maximum attractive influencing effect of the magnetic field, and
secure a corresponding economy in the expenditure of electrical energy for the
energizing coils of the electro-magnets, since the full effect of the energy employed
is that which is usefully exerted.
In the accompanying drawings, I have illustrated several forms of apparatus
suitable for the practice of my invention, although it will be apparent that its
broad features are capable of embodiment in other forms of construction based
upon the same general principles of operation.
In the drawings,
1
Figure represents a vertical section of one form of the apparatus;
Figure 2 represents a horizontal section thereof;
Figure 3 represents a side elevation thereof;
Figures 4 and 5 represent, respectively, and on a somewhat larger scale, a plan
view and side elevation of a modified form of conveyor, which may in some
instances be substituted for the conveyor shown in the preceding views;
Figure 6 represents, in cross section, a modification in the relative aspect of the
pole pieces:
Figure 7 represents, in side elevation and partial section, a modified form of the
apparatus:
Figure 8 represents a horizontal section thereof;
Figures 9 and 10 represent sectional views of further modifications.
Similar letters of reference indicate similar parts throughout the several
viewe.
Referring to the drawings. A indicates a suitable frame or housing for the con-
venient mounting and support of the several parts making up the entirety of the
apparatus. In the upper part of the frame are supported the feed hoppers B, B,
for the reception of the material to be treated, which is crushed or comminuted to
a degree sufficient to break apart from each other the particles to be separated.
At the bottom of each hopper B is located a device for feeding the material in an
even layer of graduated thickness to a chute b, said device consisting preferably of
feed rollers occupying the bottom of the hopper and mounted in bearings d
vertically adjustable within brackets e by means of a set-screw, or the like, so as
to adjust the width of the feed-opening and consequently the thickness of the layer
of material fed therefrom, ns may be desired.
Each feed roller c receives a constant motion of rotation from a belt g driven
from a pulley upon a power shaft C actuated from any suitable source of power,
and upon the same power shaft C is mounted a pulley for driving the conveyor
belt as hereinafter described. Transverse to the frame is secured the electro-
magnetic element of the invention. In the form represented in the drawings, this
electro-magnetic element is supported from suitable brackets / bolted to the machine
frame and is made up of two cores m joined by a connecting yoke n, ench core
being provided with a bobbin having a wrapping of wire coils p, in series with
each other, the direction of winding of the two coils being such as to produce
opposite polarities in their respective pole ends. The pole pieces are adjustable
toward each other preferably through the intermedincy of the screw-bolts t passing
through elongated slots made through the body portion of the pole pieces. The
adjustment of the pole pieces is toward and from each other in a direction transverse
to the longitudinal axis of the cores and the pole pieces are made of sufficient
length that they will, when adjusted as closely together as is contemplated, still

page_text: entirely cover the proximate ends of the cores. The extreme ends of the pole
pieces are made removable and replaceable, when worn, by means of a dove-tail
joint, as indicated, and over and about these ends extend conveyors which feed the
material forward laterally into the magnetic field. These conveyors may consist
of endless belts s of thin linen or canvas passed over the actuating pulleys i, and
may bear upon their outer surface the conveying slats or transverse strips shown in
Figs. 1 and 3, should these be found desirable in case of excess of magnetic
attraction at the pole extremities for the particular material under treatment;
although, in many cases they may be entirely dispensed with.
There the material to be separated is of such a character that it is desirable to
dispense with any intervening substance between it and the pole piece over which it
is fed, I may feed the material directly upon the upper surface of the pole-piece
and move it along said upper surface and over the extremity of the pole-piece by
means of the conveyor shown in Figs. 4 and 5 of the drawings, said conveyor con-
sisting of sprocket chains e having cross slats moving in contact with the upper
surface of the pole piece so as to convey the material deposited thereon forward,
and passing over the sprocket pulleys ².
It will be noted that the cross-sectional area of the cores m and of the yoke n are
indicated in the drawing as substantially equal. They are therefore practically
the same magnetic carrying capacity, and the pole pieces are of corresponding
dimensions, not larger in cross-sectional area than that of the cores and yokes, so that
the magnetic lines of force may not be dispersed upon entering the pole-pieces. At
their ends, on the contrary, the pole pieces taper toward each other, thereby
decreasing in cross-sectional area and causing à corresponding condensation or
crowding together of the magnetic lines of force so as to form a concentrated magnetic
field of extraordinary attractive power.
The operation of the invention is as follows: The material to be separated is fed
from the hoppers B B and chutes to the conveying device, in a layer of the
appropriate thickness and is advanced by the conveyor laterally into the condensed
magnetic field. As it enters the magnetic field it passes through the zone of
greatest attraction thereof immediately adjacent to the pole extremities, whereupon
the particles to be attracted are arrested and detained momentarily in contact with
the surface of the conveyor as it passes from the polar extremity, whilst the tailings
are carried onward slightly so as to fall into the central space between the pole
extremities and into a receptacle D provided for their reception. The continued
movement of the conveyor carries the particles arrested by the attraction of the
polar extremities out of the range of such attraction, whereupon they fall from
the surface of the couveyor and are deflected by the hinged leaves into
receptacle E. Where the attracted particles have a very low capacity for
attractability, they fall from the polar extremities almost immediately after having
rounded them, and for this reason the hinged deflecting plates are carried well up
to the pass or interval between the poles, so that the possibility of subsequent
commingling of the separated products may be avoided. The degree of separation
of the hinged leaves is also capable of accurate adjustment by means of a set-screw
and slotted links as shown.
It will be observed that the material to be separated is thus fed laterally into
the magnetic field entirely avoiding the central zone where the attraction is weaker.
and where, as a consequence, any material, though otherwise capable of attraction,
would, be practically uninfluenced by either pole and would fall freely into the
receptacle below without being separated. By avoiding the central feed, my invention
is entirely devoid of this disadvantage, and, inasmuch as the particles to be attracted
enter initially the strongest zone of attraction, they are at once subjected to the
full separating power of the magnets, this separating power being brought to the
maximum required for the separation of materials of extremely low magnetic
capacity, by reason of the condensation of the magnetic circuit at the tapering pole
end, and with an extremely small expenditure of electrical energy.
It will, of course, be understood that I do not restrict the employment of my

page_text: invention to any particular use, but, as an example of the conditions under which it
may be successfully employed for the magnetic separation of hematite ore from
sand or other non-ferruginous material with which it is associated, I may state that
a mixture of such hematite ore and sand, comminuted to a degree sufficient to mas
through a sieve of No. 8 mesh and spread out in a moving layer of of an inch in
thickness, has been successfully separated by an apparatus of the kind just
described, and wherein the cores were each wrapped with 1050 windings of No. 10
copper wire, energized by an electric current of 84 amperes al 55 volts, the cross-
sectional area of the cores and yokes being about 26-87 square inches, and the pole
pieces (of the relative size indicated in the drawing) being separated from each
other at a distance of 3 of an inch. In this practice with hematite ore under the
conditions named, the speed of travel of the conveyors was shout 55 feet per
minute.
The feature of adjustability of the pole pieces toward each other is a great
desideratum to the successful use of the apparatus, for the reason that the strength of
the effective field can be delicately graduated thereby to correspond exactly to the
requirements of the particular substance treated, and without it being necessary to
alter the amperage of the electric current, for small variations. It is also important
that the material to be separated is fed past the magnet poles without initial
velocity due to gravitation, and at a moderate speed, so that the magnetic attraction
may not be neutralized by a preponderating force.
In some cases, it will be desirable to pass the tailings from a primary separation,
a second and even a third time through the apparatus, or (which is equivalent
thereto) through a number of them, where the magnetic susceptibility is
exceptionally low and a particularly complete separation is desired. Where the
material treated contains a plurality of magnetically separable constituents of
different susceptibilities, (as, for instance, the menaccanite and garnet present in
monezite sands) I find it convenient to primarily remove as beads the menaceanite
and garnet by an appropriate condensation of the field, and, afterward, to pass the
heads again through the apparatus (or through an adjacent like apparatus) wherein
the field is weakened sufficiently to leave the garnet but is still sufficiently strong
to remove the menacennite. The difference in the condensation of the fields can be
obtained either by decreasing slightly the amperage of the current or by increasing
the width of the working interval between the pole pieces, or by a combination
of the two expediente. I have found, in practice, that a difference of one ampere in
the strength of the current is sufficient for such separation of menaceanite and
garnet.
It will be observed that the efficiency of the separation hereinbefore described
depends upon obtaining a loral condensation of the magnetic circuit of such an
extraordinary character as to inductively magnetize and remove these minerals of
low magnetic attractability, and that fields of such high condensation are
remarkably susceptible to varying conditions and are capable of delicate adjustment.
Where a still stronger condensation is desired, I leave one of the pole pieces
untapered, as indicated in Fig. 6. In such case, I still employ the two belts, as
before, but use, as an ore conveyor, the only belt that passes around the tapered
pole, the increase in the attractive power of the field being obtained at the expense
of entting down the feeding capacity of the machine.
In Figs. 7 and 8, I have illustrated a modified form of apparatus embodying my
invention, the main distinguishing feature consisting in doubling the capacity of
the machine shown in Figs. 1 to 3, so as to enable it to treat simultaneously two
different bodies of material subjected to its action. Moreover, the magnetic fields.
instead of being formed between two poles of the same magnet are forined between
poles of separate magnets, with the result that the fields are more rigorously uniform
across their entire eflective zones of greatest attraction.
In this modified form of the apparatus, receiving bins for the separated products
are provided, as befure, and the feeding devices are of the same general character
as in the construction shown in Figs. I to 3, save that the conveyor belts s may be

page_text: inclined toward the pole ends, as shown. In this connection, it is to be observed
that this inclination should not exceed the angle of rest for the material treated,
and should usually be less than 30 degrees; so that the material may not slide on
the bolt, and thereby have imparted to it an inertia that would carry it rapidly
past the magnet poles, but so that it may be fed gradually, at the predetermined
moderate speed required, thereby having opportunity to be fully subjected to
the influence of the condensed field before being subjected to the force of
gravitation.
The electro-magnets, two in number, are secured to a portion A' of the frame of
the apparatus, by means of adjusting stems, connected to the magnet yokes y',
whereby the magnets as a whole can be moved from and toward each other, s. as
to vary the interval between the opposing pole ends, as required in practice.
Each magnet will be providel with two cores ', surroun led each with a bobbin i
upon which is wound the appropriate number of convolutions of copper wire.
The convolutions upon all four cores of the two magnets are conveniently
connected in series, and energized by a current from the same generator, the
direction of winding being such that the poles of each magnet shall be of opposite
sign, and that the minus pole of one magnet shall be opposite the plus pole of the
other, thereby constituting two independent magnetic fields. Care should be
taken to separate the cores and pole pieces of each magnet from each other
sufficiently far to prevent leakage across from one pole to the other of the same
magnet, as such leakage would have a tendency not only to weaken both magnetic
fields, but also to disturb the uniform distribution of the magnetic lines in each,
and thereby cause them to act unequally upon the material treated.
The pole pieces (and by this expression, I mean the continuation of the cores
beyond the energizing coils) are tapered at their ends, in the direction of their
thickness, and also preferably in the direction of their width, as shown.
In the construction shown in Fig. 9, the pole pieces are of like character to
those of the apparatus illustrated in Figs. 1 to 3 and are similarly adjustable.
The capacity of the apparatus is, however, also doubled, as will be apparent,
there being double sets of feed belts. In Fig. 10, I have illustrated the
employment of one of the electro-magnets shown in Fig. 9, placed opposite an
inducing body of soft iron, which arrangement I also find acceptable in practice
when the cores and pole pieces are energized to develop at the tapered pole ends,
the highly condensed or concentrated magnetic fields essential to the practice of
the invention.
Having now particularly described and ascertained the nature of my said inveu-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. The herein described method of separating ferruginous materials of inferior
magnetic susceptibility or permeability from non-ferruginous materials consisting
in bringing the mingled materials into a condensed or concentrated magnetic field
and deflecting the ferruginous material while under the influence of said
condensed field into a path of movement different from that of the non-ferruginous
material.
2. The method of magnetically separating substances of relatively very low
magnetic susceptibility from a mixture containing them, which consists in
establishing a magnetic circuit, concentrating said magnetic circuit across a
working area and developing therefrom intense magueto-motive forces sufficient
to inductively magnetize particles of such very low magnetic susceptibility,.
subjecting the mixture to the action of said intense magneto-motive forces and
thereby attracting and withdrawing from the mixture the particles to be removed,
and progressively removing the withdrawn particles from the field of action of
said intense magneto-motive forces.
3. The method of magnetically separating, from a mixture, substances of such
low magnetic attractability as siderite, hematite, garnet, or the like, which consists

page_text: in establishing a magnetic circuit, passing the mixture through
a part of the
circuit condensed to form a concentrated field sufficient to inductively magnetize and
withdraw the siderite, hematite, garnet, or the like, from the mixture, and
progressively removing the withdrawn minerals from the condensed portion of the
magnetic cirenit.
4. The method of separating from a mixture, substances usually regarded as
non-magnetic, which consists in establishing a magnetic circuit having an interval
across which the magnetic lines of force extend forming a magnetic field
substantially uniform along its length, condensing the magnetic lines at said
interval, conveying the substances to be separated into the longitudinal edge
portions of said condensed magnetic field, and causing said condensed magnetic
field to attract and deflect the attractable particles subjected to its action.
5. The method of separating from a mixture substances usually regarded as
non-magnetic, which consists in establishing a magnetic circuit having an interval
across which the magnetic lines of force extend forming a magnetic field
substantially uniform along its length, condensing the magnetic lines at said
interval, conveying the substances to be separated into the longitudinal edge
portions of said condensed magnetic field, and causing said condensed magnetic
field to attract and deflect the attractable particles subjected to its action, and
continuously removing the particles thus deflected.
6. The method of separating from a mixture substances usually regarded as
non-magnetic, which consists in establishing a magnetic circuit having an interval
across which the magnetic lines of force extend forming a magnetic field
substantially uniform along its length, condensing the magnetic lines at said
interval, conveying the substances to be separated to the strongest part of said
condensed magnetic field transversely to the length of the field and without initial
velocity due to gravitation and causing said condensed magnetic field to attract
and deflect the attractable particles subjected to its action.
7. The method of magnetically separating from a mixture substances usually
regarded as non-magnetic, which consists in establishing a magnetic cirenit having
an interval neross which the magnetic lines of force extend forming a magnetic
field, condensing the magnetic lines at said interval, and feeding the misture at
opposite sides of the neutral zone of attraction between the pule pieces, so that
the particles to be attracted will pass through the magnetic field through the zones
of greatest attraction and avoiding the central neutral zone: whereby the so-
attracted material is deflected into a dillerent path of movement.
8. The method of separating paramagnetic materials of different permeability.
from mixtures containing them, which consists in subjecting the mixture to the
action of a magnetic field sufficiently concentrated to remove said paramagnetic
material and then separating the removed paramagnetic material into its
components by subjecting it to the action of a magnetic field reduced in intensity
sufficiently to leave the less permeable component, but sufficient to remove the
component of higher permeability.
9. In a magnetic separator, an electro-magnet having a pole piece inpering
toward its free end, said free end being of less sectional area than the magnet core
so as to highly condense the lines of magnetic force, and a conveyor for with-
drawing the attracted material from the magnetic field.
10. In a magnetic separator, an electro-magnet. having a pole piece tapering
toward its free end, said free end being of less sectional area than the magnet core
so as to highly condense the lines of magnetic force, and a conveyor for with-
drawing the attracted material from the magnetic field, the tapering and of the
pole piece being arranged transversely to the direction of travel of the conveyor.
11. In a magnetic separator, an electro-magnet having a pole piece tapering
toward its free end and having a core substantially equal in breadth to the breadth
of the pole piece, and a conveyor passing around the pole piece for introducing
the ore into the magnetic field and withdrawing the attracted material from said
field.

page_text: magnetized particles, the entrance to said central receptacle being separated from
the outer receptacles by adjustable wings or shutters.
23. A magnetic separator, provided with opposing pole pieces having tapering
ends and separated by an interval forming a magnetic field, said tapering ends
being adjustable toward and from each other, and a conveyor for withdrawing the
attracted particles from the magnetic field.
24. A magnetic separator, provided with opposing pole pieces having tapering
ends and with their upper surfaces in substantially the same plane, endless
conveyors passing over and around said tapering ends, and means for supplying to
ench conveyor a layer of material to be separated of substantially the width of the
tapering ends.
25. A magnetic separator, provided with opposing pole pieces, movable toward
each other and having tapering ends and conveyors passing over the tapering euds
and feeding the material to be separated laterally toward the interval between the
pole pieces.
26. A magnetic separator, comprising a frame, an elect-magnet mounted
therein and having tapering pole pieces adjustable toward and from each other,
endless conveyors passing over and around the tapering ends of the pile pieces,
hoppers having feed rollers in their outlets for feeding in a layer the material to
be separated, and chutes for delivering the material to the conveyors.
27. A magnetic separator, comprising a frame, an electro-magnet mounted
therein and having tapering pole pieces adjustable toward and froin each other,
-endless conveyors passing over and around the tapering ends of the pole pieces,
hoppers having feed rollers in their outlets for feeding in a layer the material to
be separated, chutes for delivering the material to the conveyors, and separate
receptacles for the tailings and separated magnetic particles, the upper portion of
the tailings receptacle being provided with adjustable wings or leaves serving to
deflect the separated magnetic particles into their receptacles.
28. A magnetic separator having the electro-magnets presenting two pairs of
tapering poles of unlike sign opposite to each other, and conveyors for feeding
the material to be separated laterally into the magnetic field from opposite sides
of the interval separating them and for withdrawing the attracted particles from
the magnetic field.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.

page_text: 12. In a magnetic separator, an electro-magnet having a polo piece tapering
toward its free end, said free end heing of less sectional area than the magnet cor
so as to highly condense the lines of magnetic force, an inducing body located
opposite the tapering pole end, and a conveyor for withdrawing the attracte!
material from the magnetic field.
13. In a magnetic separator, an electro-magnet having a pole piece tapering
toward its free end, so as to highly condense the lines of magnetic force, an
inducing body located opposite the tapering pole end, sail inducing body being
itself the pole end of an electro-magret, and a conveyor for withdrawing the
attracted material from the magnetic field.
14. In a magnetic separator, an electro-magnet having a pole piece tapering
toward its free end so as to highly condense the lines of magnetic force, an
inducing body located opposite the tapering pole end, and means for increasing or
decreasing the interval between the pole end and the inducing body, and a conveyor
for withdrawing the attracted material from the magnetic field.
15. In a magnetic separator, an electro-magnet having a pole piece tapering
Loward its free end in width and thickness, said free end being of less sectional
area than the magnet core so as to highly condense the lines of magnetic force, and
a conveyor for withdrawing the attracted material from the magnetic field.
16. A magnetic separator, provided with opposing pole pieces of opposite sign,
said pole pieces having tapered ends of less sectional area than their cores and
separated from each other by an interval forming a magnetic field, and a lateral
conveyor for each pole piece, said conveyor feeding material to be treated laterally
into the magnetic field and directly over the surface of the pole pieces so that the
particles to be magnetized will approach and enter the magnetic field through the
zone of greatest attraction immediately adjacent to each pole piece and will avoid.
the weaker zone midway of the pole pieces.
17. A. magnetic separator, provided with opposing pole pieces of opposite sign,
separated from each other by an interval forming a magnetic field, suid pole pieces
tapering at their ends, so as to have a sectional area less than that of their cores,
and conveyors for the material to be treated, said conveyors passing around the
tapering portions of the pole-pieces and in close proximity thereto.
18. A magnetic separator, provided with opposing pole pieces of opposite sign,
separated by an interval forming a magnetic field, said pole pieces tapering as
their ends toward each other, the form of such taper being in longitudinal section
substantially that of a right-angled triangle, and conveyors for the material to be
treated, said conveyors passing over the surfaces of the pole pieces and in close
proximity thereto.
19. A magnetic separator, provided with opposing pole pieces of opposite sign,
separated by an interval forming a magnetic field, said pole pieces tapering at
their ends toward each other and having their upper surfaces in substantially the
same plane, and conveyors for the material to be treated said conveyors passing
around the pole pieces and in close proximity thereto.
20. In a magnetic separator, an electro-muguet having two cores and a connecting
yoke, said cores being provided with wire wrappings and projecting pole pieces
having tapering ends, the sectional area of the pole pieces being substantially equal
to that of the cures and yoke except at the tapering ends of the pole pieces, and
conveyors passing around said tapering ends.
21. A magnetic separator, provided with opposing pole pieces having tapering
ends of less sectional area than the cores and separated by an interval forming
a magnetic field, conveyors passing over and around said tapering ends, a central
receptacle to receive inilings and outer receptacles to receive the withdrawn
magnetized particles.
22. A magnetic separator, provided with opposing pole pieces having tapering
ends of less sectional area than the cores and separated by an interval forming
a magnetic field, conveyors passing over and around said tapering ends, a central
receptacle to receive tailings and outer receptacles to receive the withdrawn