Improvements in Magnetic Separators.
Year: 1896

page_text: Date of Application, 3rd Mar., 1896-Accepted, 9th May, 1896
COMPLETE SPECIFICATION.
Improvements in Magnetic Separators.
I, 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 relates to certain new and useful improvements in magnetic
separators, adapted for the separation, from mixtures containing them, of para-
magnetic substances of very low magnetic permeability or susceptibility, such as
bematite, siderite, menaccanite, rutile, troostite, garnet, and the like.
In the accompanying drawings,
Figure 1 represents, partly in side elevation and partly in section, an apparatus
embodying my invention;
Figure 2 represents a plan view thereof, partly in section;
Figure 3 represents an end elevation ;
Figure 4 represents a vertical section through one of the electro-magnets, the
cross belt and conveyor belt, ou a plane indicated by the line 4-4 of Figure 2;
Figure 5 represents a cross section on the line 5-5 of Figure 4;
Figure 6 represents a side elevation of one of the electro-magnets and a portion
of the conveyor belt, the cross belt being shown in section;
Figure 7 represents a front elevation of one of the electro-magnets and a portion
of the cross belt, the conveyor belt being shown in section;
Figure 8 represents a top plan view of one of the electro-magnets and a portion
of the conveyor belt; and
Figure 9 represents a bottom plan view of one of the electro-magnets.
Similar letters of reference indicate similar parts throughout the several
views.
Referring to the drawings, A indicates a feed hopper for the reception of the
ore mixture to be separated, said ore mixture having first been crushed to a
degree sufficient to separate the different minerals, preferably through a sieve of
No. 10 mesh. Within the bottom of this hopper rotates a feed wheel B, adapted
to supply the ore to the chute C in such regulated quantity as to deliver upon the
endless conveyor belt D a layer of about one-eighth of an inch in thickness, said
layer being spread out equally upon the belt D and of a breadth preferably some-
what less than the breadth of the pole pieces of the electro-magnets. Thus, in
practice, with electro-magnets having cores six and three-fourth inches high by
two and one-half inches wide by eight inches broad, and with pole pieces equally
broad, I have obtained the best results by having the breadth of the ore layer
slightly less than that of the core and pole pieces. With an ore layer, say
seven inches broad, moving directly beneath the pole pieces, I make the con-
veyor belt of a width that will give a margin of about two and a half inches on
the delivery side of the separated ferruginous material, for a purpose hereinafter
described.
The endless belt D may conveniently be stretched upon the rollers E, E', either
of which may serve as a driving pulley, and at various points are located the
supporting idlers F. Beneath the roller E¹ is stationed a receptacle divided

page_text: into two compartments G, G', by a partition G', the smaller compartment being
for the reception of any ore that may be diverted from the original path to the
margin of the conveyor belt, and which is to be again passed through the
apparatus, and the larger being for the reception of the main portion of
the moving layer after it has passed the electro-magnets and been deprived of
the minerals of low magnetic susceptibility thereby.
The electro-magnets that I have employed in practice are clearly shown in
detail in Figures 4 to 9 inclusive. They consist of cores a, of the dimensions
hereinbefore specified, provided with corresponding pole pieces b, each core being
wrapped with a winding c consisting of 19 layers of No. 10 copper wire 21 layers
deep. The pole pieces are adjustable toward and froin each other by means of the
slots and screws d, and decrease in thickness, as shown, toward their polar
extremities so as to form a highly condensed or concentrated magnetic field. The
cores of each magnet are connected by a cross piece e, through which screw bolts
pass into screw threaded recesses in the cores; and the pole pieces bare encased
within a frame (said frame being of non-magnetic material) made up of the end
pieces g, having screw bolts g' adapted to enter screw-threaded openings in the
pole pieces, and the side pieces having through bolts gl passing through slots c' in
the frame. As an additional feature, I also prefer to interpose between the polo
pieces, a spacing bar of vulcanized fibre or the like.
From the cross piece e, extend hangers / adapted to pass through openings in
ore of the frame beams H of the apparatus. These hangers are screw-threaded
at their upper ends for the reception of nuts A, whereby the height of the electro-
magnets above the conveyor belt D may be accurately adjusted.
In close proximity to the under surface of the pole pieces, I arrange a conveyor,
moving transverse to the conveyor D, and interposed between the pole pieces and
the surface of the ore layer. This transverse conveyor may conveniently consist
of an endless belt 1, of thin cotton, muslin or the like, or of a rotating disc of
thin metallic substance. The cudless belt L is passed over the roller M, and
receives motion from one of said rollers. The electro-magnets attract the minerals
of low magnetic susceptibility, in such manner as to cause a narrow line of their
particles to rise from the ore current immediately adjacent to and between the
opposing edges of the tapering pole pieces and to assemble against the under side
of the cross belt L. The function of the cross belt or its equivalent, is to carry
the attracted particles transversely of the ore current, and along this line of
attraction, to one end of the pole pieces where they accumulate until sufficient
weight has been added to the mass to cause the surplus to drop off. As this
surplus is constantly supplied, it results that a continuous stream of the attracted
particles is caused io flow transverse to the ore on the main belt, and said stream is
directed into a suitable collecting receptacle N by a chute R.
In Figures 1 and 2 of the drawings, I have shown an apparatus wherein in
conjunction with the main conveyor belt D, four electro-magnets, having their
windings connected in series and with a corresponding number of cross belts, are
employed; but I do not limit myself to this or any other number of electro-
magnets. It is advisable, however, to employ a plurality of electro-magnets, so
that, if the capacity of the first of the series is overtaxed, the succeeding ones
supplement their action, and for the further reason that the pole pieces of the
several mungnets, beginning with the first, may be placed in gradually increasing
proximity to the ore current. Thus, the first of the electro-magnets will attract
a less number of particles than if located nearer the ore current and consequently
there will be a less number of unattracted particles disturbed and swept out of the
main current toward the margin of the belt D, while the last of the series,
located at the minimum distance from the ore current, can be relied on
to withdraw whatever of particles to be attracted have been left by its
predecessors.
This carrying of unattracted particles out of the main ore current takes place,
however, to some extent, and may be compensated by making the belt D about

page_text: two and one-half inches wider than the ore current, and having the magnet pole
pieces project about one inch beyond said current. The attracted particles of low
magnetic susceptibility which it is desired to separate, under these conditions, will,
for the most part, be swept clear of the belt D, by the cross belts L; but those
which are not, together with those portions of the unattracted particles brushed
out of the main ore current by the transverse movement of the attracted particles
depending from the cross belts, will constitute a middle product, which will be
carried along by the outer margin of the belt D and will be separated by the slat
or partition G and received into the receptacle G whence they are returned to
the feed hopper and returned with the crude ore so as to pass again through the
apparatus.
With an electro-magnet of the size and relative dimensions specified, and with.
the pole pieces spaced at about three-fourths of an inch apart, I have found that a
current of 5 amperes and 50 volts passed through the magnet windings from a
continuous current dyuamo will suffice to magnetize the pole pieces sufficiently to
attract the mineral Franklinite, garnet and Troostite from crushed Franklinite-
ore under the conditions specified and to effect their separation to the degree
required to render the remaining Willemite or zincite present in such ore suitable
for the Belgian furnace, after subsequent jigging out of the calcite present, and
the sifting out of such fines as will pass through a sieve of No. 60 mesh. Thus
with three of such electro-magnets acting upon a moving layer of comminuted
garnet, Franklinite, Troostite and Willemite, one-eighth of an inch in thickness,
the first of said magnets being located at a height of one-half an inch above the
ore, the second magnet three-eighths of an inch, and the third, one-fourth of an
inch, I have successfully removed the Franklinite, Troostite and garnet from the
Willemite. The speed of travel of the belts for this practice is about fifty-five-
feet per minute.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
1. 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, an ore conveyor below and in
close proximity to said tapering end and conveying the ore through a portion of
the highly concentrated field, the tapering end of the pole piece being arranged
transversely to the direction of travel of the conveyor, and a second conveyor for
withdrawing the attracted particles.
2. The combination with an ore conveyor, of electro-magnetic pole pieces located:
above and in near proximity to its conveying surface, said pole pieces having
tapering ends transverse to the direction of movement of the ore and adjustable
toward and from each other, and having a substantially uniform field of force
across the conveying surface, and a second conveyor for withdrawing the attracted
particles from the magnetic field.
3. The combination with an ore conveyor, of an electro-magnet located above
and in near proximity to its conveying surface, said magnet having tapering
pole pieces transverse to the direction of movement of the ore, and an enclosing
frame of non-magnetic material for the pole-pieces, the pole pieces being adjustable
within the frame.
4. The combination with an ore conveyor, of an electro-magnet located above
and in near proximity to its conveying surface, said magnet having tapering pole
pieces transverse to the direction of movement of the ore and adjustable toward
and from each other, au enclosing frame for the pole pieces and a spacing piece-
between the pole pieces.
5. The combination with an ore conveyor, of an electro-maguet above and in
near proximity to its conveying surface, said magnet having its pole pieces trans-
verse to the direction of movement of the ore, said pole pieces decreasing in

page_text: thickness from the cores outwardly toward each other, and a second conveyor for
withdrawing the attracted material from the magnetic field.
Dated this 3rd day of March 1896.
IIASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.