Improvements in Magnetic Separators.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
Improvements in Magnetic Separators.
I, WILLIAM CLARK, of the Firm of A. M. & Wm. Clark, of 53, Chancery Lane,
in the County of Middlesex, Fellow of The Chartered Institute of Patent Agents,
do hereby declare the nature of this invention (a communication to me by Charles
Frederick Courtney, of Sulphide Street, Broken Hill, in the Colony of New South
Wales, Mine Manager), to be as follows:-
This invention relates to magnetic separators especially designed for the
treatment of Broken Hill sulphide ores and tailings in the wet state.
The apparatus comprises a double series of pole pieces attached to a truncated
cone of non-magnetic material mounted upon a vertical rotary spindle constituted
by the magnet cores themselves; a hopper for the material to be treated provided
with a rotary feed roller and inclined shoot delivering the material to the
apparatus; a brush for detaching the separated magnetic portion of the material
which adheres to the pole pieces on the cone; and separate receiving hoppers into
which the magnetic and non-magnetic portions of the material are respectively
delivered.
In practice a pair of apparatus thus constituted would be housed in a single
casing to form practically one machine, the spindles being driven by gearing
(constructed of non-imagnetic material) adapted to rotate the cones in opposite
directions; but for convenience I will describe a single machine only.
The magnet cores which together form the vertical rotary spindle are attached
to the upper and lower ends respectively of the cone, and the pole pieces connected.
to the cores, are arranged upon the cone in alternate order, the north poles which
are connected to the core at the one end of the cone alternating with the south
poles which are connected to the core at the opposite end of the cone.
The pole
pieces form spirals about the cone at equal distances from one another and in
order to obtain a highly concentrated magnetic field upon the surface of the cone,
the pole pieces are of tapering form and are slightly raised above the surface
of the cone, their adjacent edges being parallel so that the most concentrated
magnetic current is between the outer edge of one pole and the outer edge of the
next pole of opposite sign.
The cone is made of brass or other non-magnetic material, whilst the pole
pieces are of soft iron let into or secured to the cone by screws or otherwise so
as to be readily renewable.
The bobbins carrying the exciting coils are made sufficiently loose upon the
spindle to allow the latter to rotate freely within them, the bobbins being
supported or suspended from the case in a fixed position, thus dispensing with
the use of contact brushes. The degree of concentration can be regulated as
required by varying the strength of the current supplied to the coils.
The outer ends of the spindles comprised in a pair of apparatus are connected
by stationary yokes of soft iron to facilitate the completion of the magnetic
circuit, the magnets in the two members of the pair being arranged with the
poles in alternate order, that is to say with a north and a south pole projecting

page_text: at the top of the casing and a south and a north pole at the bottom. The yoke
at the top is recessed and attached to the ends of the cores forming the upper
part of the two spindles, by a set screw which rotates with the core the latter
turning freely in the yoke, and the yoke at the bottom is also recessed and serves
as a footstep bearing for the two spindles.
At the top of the cone at one side is a hopper with a feed roller which delivers
the material to an inclined shoot whence the material falls on to the upper part
of the surface of the cone at that side. A brush of non-magnetic material is
caused to bear against the side of the cone and is supported in suitable guides
so as to be adjustable for wear. The space surrounding the cone is divided into
two compartments and beneath the lower edge of the cone are two aprons form-
ing receiving hoppers, the one to receive the magnetic portion of the material
swept off by the brush, whilst the other receives the non-magnetic or less
magnetic portion of the material which falls from the cone by gravity.
The apparatus when arranged for the treatment of wet material is enclosed
in a water-tight casing, the casing being filled with water so as to cover the
cone and poles. The lower part of the spindle passes out through a packed
gland of non-magnetic material in the bottom of the casing, the gland serving
as a bearing; the upper part of the spindle is supported in a bearing on a cross
beam.
The operation is as follows:-The material to be treated is filled into the
hopper arranged at the top of the apparatus whence it is fed by the roller and
slide to the upper end of the cone and is by the rotation of the cone distributed
in a film over the surface of the latter. The more magnetic particles of the
material adhere to the poles and are carried round with the cone until they come
in contact with the brush which removes and delivers them to the appropriate
receiver, while the feebly magnetic or non-magnetic portions of the material
fall down over the face of the cone by gravity into the receiver provided for
them.
The invention is also applicable to the separation of para-magnetic substances
of different degrees of magnetic permeability, as, by regulating the electric
current whereby the magnets are excited, a substance having a higher magnetic
permeability may be separated from that one having a lower magnetic perme-
ability.
Dated this 24th day of Octaban 1900
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.
I, WILLIAM CLARK, of the Firm of A. M. & Wm. Clark, of 53, Chancery Lane,
in the County of Middlesex, Fellow of The Chartered Institute of Patent Agents,
do hereby declare the nature of this invention (a communication to me by Charles
Frederick Courtney, of Broken Hill, in the Colony of New South Wales), and
in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement:-
This invention relates to the magnetic separation of paramagnetic substances,
particularly those of low magnetic permeability, from ores and mixtures with
which they are associated, by passing said ores or mixtures in a comminuted
state through a condensed or concentrated magnetic field. The invention is
more especially designed for the treatment of Broken Hill sulphide ores and

page_text: and is particularly adapted for treating materials in water, the object
being to effect the separation in the most economical manner and without
employing expensive or delicate apparatus and especially without using belts
or bands for feeding the material to the machine; the objection to the employ-
ment of belts or bands being, as is well known, that these appliances, besides
requiring frequent renewal, do not readily lend themselves to operation with a
wet process.
According to this invention the comminuted ore or other mixture is subjected
in the form of a thin film to a highly concentrated magnetic field so as to avoid
risk of the paramagnetic particles becoming prematurely detached from the
magnetic poles and swept away by the passing stream of matter of lower magnetic
perineability with which they are associated. Further, the material under
treatment is prevented from falling freely under the influence of gravity at the
moment when the material enters the magnetic field; so that the paramagnetic
particles contained in the mixture, however low their magnetic permeability,
are not liable to become lost in consequence of their passing over or escaping
from the magnetic poles under the influence of momentum acquired previous to
their entrance into the magnetic field. From the moment of such entrance how-
ever, and so long as the material remains within the magnetic field, those
particles which are paramagnetic or possess a higher degree of magnetic perme-
ability are retained by magnetic attraction, whilst those particles which are
diamagnetic or possess a lower degree of magnetic permeability become free to
yield to the attraction of gravity and to fall out of the magnetic field, whereby
a practically thorough separation is effected between these constituents of the
ore or other mixture.
The apparatus of our invention comprises an electro-magnet having multiple
pole pieces of positive and negative polarity forming alternate helices around
the periphery of a supporting drum of truncated conical form composed of
non-magnetic material, the drum being mounted to revolve about a vertical axis
within a casing or water tank and carried by gudgeons which also constitute the
electro-magnetic cores, the pole pieces of one sign being in magnetic connection
with the core at one end of the drum and the pole pieces of the contrary sign
being connected to the core at the opposite end of the drum so that they present
a succession of magnetic fields in the direction of the circumference of the drum.
The apparatus further comprises means of feeding the material on to the upper
part of the drum; a brush for removing such portion of the material as adheres
to the drum; and bins for receiving the separated components of the mixture.
The apparatus so constituted may be combined together in pairs as hereafter
described, each pair being contained within a single casing so as to form a double
machine.
In the accompanying drawings forming part of this specification, Figure 1 is a
side elevation of a double machine, the casing and bins and a portion of one
drum being shewn in section. Figure 2 is a horizontal section on line a—b,
Figure 1, and Figure 3 is a vertical section on line c-d, Figure 1. Figure 4
is a cross section of two adjacent pole pieces, drawn to a larger scale, and
Figure 5 is a detail of a modification with parts in section.
A is a tank wherein are mounted to revolve two vertical drums B B* each
having the form of a truncated cone; the two drums being similar in con-
struction, only one of them will be described. Each drum comprises oppositely
magnetized heads CD of soft iron and an intermediate peripheral portion or
body B of non-magnetizable material such as gun-metal fixed to the heads by
screws F and forming a support for multiple pole pieces CD. The pole
pieces CD are of soft iron and are fixed to the periphery of the heads C D and
to the support B by screws E, the pole pieces C₁ being connected to the head C
and the pole pieces D₁ to the head D, the pole pieces of the two sets extending
helically around the drum from opposite ends, and those of the one set or polarity
alternating with those of the other set or polarity around the periphery of the

page_text: drum.
The supporting peripheral portion B' of the drum is grooved to receive
the pole pieces which are embedded in the grooves for the greater part of their
depth so that the pole pieces are firmly supported in position and the intervening
gaps are closed by the non-magnetic material B¹.
The pole pieces CD are not embedded in the non-magnetic material B₁ for
their whole thickness but project slightly as shewn in Figure 4 so as to form
between adjacent pole pieces a shallow groove in which the particles of material
lie whilst within the magnetic field and leave exposed the salient acute edges c d
of the pole pieces where the strength of the magnetic field is greatest. With
the object of concentrating the magnetic force at their edges ed the pole pieces
are tapered towards their salient edges, the sides being bevelled so as to make
these edges acute.
In order to equalize the intensity of the magnetic field longitudinally of the
drum, the pole pieces are also tapered in the direction of their length, both as
regards width and thickness, the narrower and thinner free end of each pole piece
lying between the broader and thicker fixed ends of the adjacent pole pieces,
so that the gap intervening between each pair of adjacent pole pieces is of equal
width throughout its entire length.
The heads CD of each drum. are formed in one with gudgeons CD journalled
in bearings whereof the upper one V is carried by a bar Z extending across the
casing of the machine whilst the lower bearing is formed by a stuffing box O
through which the corresponding gudgeon passes out through the bottom of the
casing. The gudgeons at both ends of the drum are of sufficient length to pass
through and form the cores of electro-magnets C3 D of which the coils are
stationary, whilst the gudgeons CD2 which also form the cores of the electro-
magnets, rotate freely within them. The lower ends of the cores C2 D2 are
stepped in recesses formed in a yoke-bar G₁ of soft iron, their upper ends g
supporting a similar bar G, and the electro-magnet coils C3 D3 are suitably
supported as shewn.
The two drums B and B* and their electro-magnetic appurtenances are similar
in construction, and the gudgeon or core D2 at the one end of drum B is
magnetically connected to the core C2 at the same end of drum B* by the yoke
bar of soft iron in which the outer ends of the said two cores D2 C2 rotate as above
described and by which they are magnetically connected, whilst the corre-
sponding coils 1 Care similarly wound and have their windings connected so
that the core D2 and coil D3 at the one end of the drum B and the core C³ and
coil C³ at the same end of the other drum B* form the oppositely polarized limbs
of the same horse-shoe electro-magnet. The arrangement is the same at the
other side of the machine, the polarity being of course reversed relatively to the
drums so that the two cores C² 12 of each drum will be of opposite polarities.
The two cores CD2 at the bottom of the machine are geared together by
spur wheels J of non-magnetic material so that the drums B B* will be rotated
in opposite directions, when driven through a pulley N fast on one of the cores.
Pis a feed hopper whence the material is delivered on to the drum B through
the medium of a distributing roller Q and chute S, the roller Q being driven by
geared wheels (not shewn) from one of the gudgeons of the drum.
T is a brush of non-magnetic material supported so as to be adjustable for
wear, and bearing against the periphery of the drum B from top to bottom
thereof, the brush being so placed that any point on the periphery of the drum,
after passing beneath the chute S, will perform almost a complete revolution
about the axis of the drum before encountering the brush.
The space within the casing A surrounding the drum B is divided by partitions.r
and y into two portions X and Y, which serve as bins to receive the separated
constituents of the material treated, the bottoms of these bins being respectively
formed by inclined aprons al y' which slope downwards from the lower edge of
the drum to their corresponding outlets and y². The partitions and y are
so situated that the bin Y receives all the particles which fall from the surface

page_text: of the drum B by gravitation alone, whilst those particles which adhere to the
drum by magnetic attraction are precipitated, aiter their removal from the
drum by the brush T, into the bin X.
The machine is adapted for treating the material either dry or in water. We
prefer to treat the material in water, and the apparatus illustrated in the
drawings is specially designed for the wet system of treatment. To this end
the casing A is made watertight and is filled with water to such a level as to
cover the drums and pole pieces, the stuffing boxes O affording freedom of
rotation to the gudgeons C2 D2 whilst preventing the escape of water.
In operation, the electro-magnet coils CD are supplied with current of a
strength proportioned to the degree of concentration required in the product,
and the drum being rotated at a suitable speed, the pulverized ore or other
mixture is fed into the hopper P, whence it is received by the roller Q which
distributes it evenly upon the inclined chute S whereby the material is gently
delivered in a thin uniform film upon the upper part of the drum. By the
revolution of the drum in the direction indicated by the arrow b, the particles
composing the film of material are at once subjected to the influence of gravity
acting in opposition to that of the magnetic attraction, and are eventually
carried round to a point where those particles which are non-magnetic, or
possess a lower degree of magnetic permeability, fall off the drum by their own
weight and are received in the bin Y whose edge is so situated that no such
particles as fall from the drum by gravitation alone shall find their way into
the bin reserved for the more magnetic particles. Those particles which adhere
to the drum by magnetic attraction are carried (by the continued rotation of the
drum) beyond the range of the bin Y and are arrested and removed from the
drum by the brush T which deposits them in the bin X.
If it be desired to effect further concentration by a repetition of the above
described process, the contents of either or of both bins may be conveyed to a
second apparatus in order to again undergo similar treatment.
The herein described apparatus, besides being adapted to the separation of
paramagnetic from diamagnetic substances, may also be used for the separation
of paramagnetic substances possessing different degrees of magnetic perme-
ability, by suitably regulating the speed of rotation of the drum and the strength
of the electric current whereby the magnets are excited.
The pole pieces D¹ C¹ may be projected from rings D4 C+ so forming crowns as
represented in Figure 5 and which will be shrunk on to the cores.
Reverting to the pole pieces C¹ D¹ we would have it understood that they may
be run in with white metal or other non-magnetic material in lieu of recessing
them as shown in Figure 4, and also that a greater or lesser number of such
pole pieces may be employed than is shown on Figures 1 and 2.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is:
1. A magnetic separator comprising an electro-magnet having a multiple
series of positive and negative pole pieces of helical form attached in alternate
crder around the periphery of a non-magnetic rotary drum of truncated conical
form mounted to rotate upon vertical gudgeons which themselves constitute the
cores of the electro-magnet and revolve within their exciting coils, the said pole
pieces tapering both as regards width and thickness in the direction of their
length and being bevelled and partially embedded in the non-magnetic drum
so as to have acute salient edges, the opposed edges of adjacent pole pieces
being equidistant, so as to produce an intense magnetic field having uniform
intensity longitudinally of the drum and adapted to continuously receive and
act upon a stream of material supplied to it, substantially as specified.
2. A duplex magnetic separator comprising two rotary drums of truncated
conical form composed of non-magnetic material, each drum being mounted to

page_text: rotate about a vertical axis and having helically arranged peripheral pole pieces
fixed in alternate order to magnetizable heads in one with the gudgeons of the
drum, which gudgeons also form rotary cores of stationary electro-magnetic coils,
the windings of the coils at the corresponding ends of the two drums being
connected, and their cores being magnetically coupled by a yoke bar in which
the cores rofate, so that the coils and cores at the upper side of the machine
constitute the two limbs of a single electro-magnet, the construction being
similar at the lower side of the machine, but with the relative polarity reversed
so that the two heads of each drum will be of opposite polarities, substantially
as specified.
Dated this 24th day of July 1900.
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.