Improvements in Magnetic Separating Apparatus.
Year: 1898

page_text: Improvements in Magnetic Separating Apparatus.
I, ALEXANDER MELVILLE 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
Metallurgische Gesellschaft A.G. of 14, Junghofstrasse, Frankfort-on-the-Main,
Germany), to be as follows:
This new magnetic separating apparatus is suitable for the treatment of weak
magnetic materials in strong magnetic fields such as can be produced by means of
wedge-shaped magnets and to which the materials are supplied at the sharpened
edges of the pole pieces. This new apparatus is distinguished from known apparatus
of this class by the novel form of the magnetic field, by the fact that conveyor bands
are either wholly or partly dispensed with, and that, in some cases, only a portion of
the active iron masses is energized directly by the electric current. Heretofore the
strongest magnetic concentration of the lines of force have been produced by arranging
a south pole close to and opposite each sharpened north pole. This has been effected
either by means of the two poles of one and the same electro-magnet or by means
of alternating poles of a group of single electro-magnets which of course had to be
arranged in such a manner that the path of the magnetic lines of force takes its
course, as in a so-called closed or annular magnet, that is to say with the exception of
the interruptions where north and south poles face each other (i.e. the fields of
operation of the magnetic separator) there must be at all points of the path of the
lines of force sufficient iron masses to allow the lines of force which are produced in
the magnet by the electric coils to return back into themselves and to close the
magnetic circuit without any considerable loss by dispersion into the surrounding
medium.
The fields which are thus formed at the places of interruption had their greatest
density at the polar edges, and there was therefore nothing to prevent the magnetic
materials which were supplied to one pole edge from jumping over to the other pole
edge and becoming attached thereto, so that it was necessary to provide stripping
bands running round both pole edges for the purpose of removing the adhering
particles in order to keep the edges always clean for the continuance of the
operation.
An essential improvement in this respect is embodied in the new magnetic
separator of this invention in which there are arranged opposite to the magnetic edge
over which the material to be separated is supplied two separate wedge-shaped
magnets having polarities opposed thereto. Thus when the material is supplied for
instance, to one north pole, two south poles are arranged opposite to the said north
pole. The two south poles are preferably mounted so that one south pole
is higher than the north pole, whilst the other south pole is situated almost
vertically below the north pole, so that the said north pole will serve, in a well
known manner, at the same time as a partition, on one side of which the magnetic
material falls whilst the non-magnetic material falls on the other side.

page_text: ..
The result of such an arrangement of poles is that the sum of the lines of force
which issue from the north pole, divides or spreads itself into the two south poles,
so that the magnetic field thus produced, is most concentrated at the supply pole
and is considerably weaker at the two other poles, the result being that no
material can adhere to the latter, and the stripping belts can be dispensed with
entirely.
A further great advantage consists also in the influence which can be exerted upon
the form and position of the magnetic field. The amount of the force of magnetic
attraction depends not only on the number of the lines of force (intensity of the field)
but also on the position and direction of the lines of force relatively to one another.
A para-magnetic body is moved from a place of lower intensity to a place of higher
intensity, and the motive force is greater under.conditions otherwise equal, the greater
is the difference of intensities of the two places. Consequently there would be the
greatest force of attraction in the magnetic field in which, other circumstances being
equal, the lines of force have the greatest difference in direction one to the other.
In the separating machine of this invention this object is effectually attained by the
lines of force issuing from the point of one magnet being torn apart, so to speak, by
the points of the two other magnets, whereby the magnetic field receives an
advantageous-bunch-like shape..
Experiments made with a three-imagnet machine and with a two-magnet machine,"
which operated under otherwise completely identical conditions, have proved that the
three-magnet machine consumed only 40% of the electrical energy which was required
by the two-magnet machine to effect the separation of one and the same mixture of
A third advantage may be obtained with mixtures of minerals which are to be
separated and which are of that kind that are free from strong magnetic constituents
(iron, magnetic iron, magnetic pyrites, roasted spathose, iron stone, etc.,) namely
that also the last stripping band over the supply pole may be dispensed with.
ore.
It is important for the separation of weak magnetic materials that they should be
supplied in direct proximity to the pole edges and with the least possible velocity to
the
gap between the pole edges. This has heretofore been effected chiefly by means
of bands which passed around the pole edges but which were liable to very rapid
wear and which necessarily kept the material distant from the magnetic edge to the
extent of the thickness of the band. The conveyor bands can now be dispensed with,
as the mixture is supplied directly on to the surface of the magnet towards its edge
and is left free at the edge without being conveyed by artificial means around the
edge. For this purpose either the surface must have a suitable inclination in order
to allow the material to move by its own weight and overcome its own friction on
the said surface or artificial means of movement must be employed which remain
above and do not move round the edge of the magnet. The material is preferably
supplied close behind the magnet edge on to the surface of the magnet in regulated
quantity and in such manner as to meet the said surface with the least possible
velocity and then move along on the said surface.
For this purpose a feed hopper is preferably employed, the delivery aperture of
which is directly behind the maguet edge and whence the comminuted material falls
out in such manner that it strikes at a small distance above the surface of the
imagnet first upon a transverse lip and then passes from the latter on to the magnet.
This admits of the magnet edge being made as sharp as possible so as both to con-
'centrate the lines of force as much as possible and prevent the magnetic particles
from pernianently adhering, since the adhesion is greater to a broad than to a very
narrow edge. The operation of separation then takes place as follows:-the non-
magnetic particles flow at once over the pole edge and fall off, whilst the magnetic
particles have at first a tendency to adhere to the magnet edge but are pushed
onwards by the inaterial following and carried around the edge whence they drop off.
In machines for the separation of weak magnetic mixtures of ore, in which minerals
of comparatively great susceptibility (for example garnet, raw spathose, ironstone,
etc.) are to be extracted, the cost of manufacture of the apparatus may be reduced as
in this case only the magnet on to whose poles the material is supplied need be

page_text: provided with an electric coil, the two other cores then forming merely the iron
masses necessary for the return of the lines of force produced in the magnet. These
iron masses must be present in order that the lines of force shall not become dis-
persed into the air from the whole surface of the exciting magnet, but shall be
concentrated at and pass over thereto from the point of the magnet.
determining the direction of passing over, they fulfil the function of imparting the
bunch-like shape to the inagnetic field before referred to.
By thus
It is obvious that the shape of the magnetic field may be varied at will and that
by shifting the two magnets opposite to the supply pole, both the divergence of
the bunch of lines of force and the position of the apex or crown of the bunch on
the supply pole can be altered. It is to be noted that instead of two, three or
more magnets might be arranged opposite to the supply pole.
:
Dated this 10th day of October 1898.
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.
Improvements in Maguetic Separating Apparatus.
I, ALEXANDER MELVILLE 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
Metallurgische Gesellschaft A. G., of 14, Junghofstrasse, Frankfort-on-the-Main,
Germany,) and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:-
This new magnetic separating apparatus is suitable for the treatment of weak
magnetic materials in strong magnetic fields such as can be produced by means of
wedge-shaped magnets and to which the materials are supplied at the sharpened edges
of the pole pieces. This new apparatus is distinguished from known apparatus of this
class by the novel form of the magnetic field, by the fact that conveyor bands are
either wholly or partly dispensed with, and that, in some cases, only a portion of the
active iron masses is energized directly by the electric current. Heretofore the
strongest magnetic concentration of the lines of force has been produced by arranging
a south pole close to and opposite each sharpened north pole. This has been effected
either by means of the two poles of one and the same electro-magnet or by means of
alternating poles of a group of single electro-magnets which of course had to be
arranged in such a manner that the path of the magnetic lines of force takes its
course as in a so-called closed or annular magnet, that is to say with the exception of
the interruptions where north and south poles face each other (i.e. the fields of opera-
tion of the inagnetic separator) there must be at all points of the path of the lines of
force sufficient iron masses to allow the lines of force which are produced in the
magnet by the electric coils to return back into themselves and to close the magnetic
circuit without any considerable loss by dispersion into the surrounding medium.
The fields which are thus formed at the places of interruption had their greatest
density at the polar edges, and there was therefore nothing to prevent the magnetic
materials which were supplied to one pole edge from jumping over to the other pole
edge and becoming attached thereto, so that it was necessary to provide stripping
bands running round both pole edges for the purpose of removing the adhering
particles in order to keep the edges always clean for the continuance of the
operation.
An essential improvement in this respect is embodied in the new magnetic

page_text: separator of this invention in which there are arranged opposite to the magnetic
edge over which the material to be separated is supplied two separate wedge-shaped
magnets having polarities opposed thereto. Thus when the material is supplied for
instance, to one north pole, two south poles are arranged opposite to the said north
pole. The two south poles are preferably mounted so that one south pole is higher
than the north pole, whilst the other south pole is situated almost vertically below
the north pole, so that the said north pole will serve, in a well known manner, at
the same time as a partition, on one side of which the magnetic material falls
whilst the non-magnetic material falls on the other side.
The result of such an arrangement of poles is that the sum of the lines of force:
which issue from the north pole, divides or spreads itself into the two south poles, so
that the magnetic field thus produced is most concentrated at the supply pole and is
considerably weaker at the two other poles, the result being that no material can
adhere to the latter, and the stripping belts can be dispensed with entirely.
A further great advantage consists also in the influence which can be exerted upon
the form and position of the magnetic field. The amount of the force of magnetic
attraction depends not only on the number of the lines of force (intensity of the field)
but also on the position and direction of the lines of force relatively to one another.
A para-magnetic body is removed from a place of lower intensity to a place of higher
intensity, and the motive force is greater under conditions otherwise equal, the greater
is the difference of intensities of the two places. Consequently there would be the
greatest force of attraction in the magnetic field in which, other circumstances being
equal, the lines of force have the greatest difference in direction one to the other.
In the separating machine of this invention this object is effectually attained by the
lines of force issuing from the point of one magnet being torn apart, so to speak, by
the points of the two other magnets, whereby the magnetic field receives an
advantageous bunch-like shape.
Experiments made with a three-magnet machine and with a two-magnet machine,
which operated under otherwise completely identical conditions, have proved that the
three-magnet machine consumed only 40% of the electrical energy which was required
by the two-magnet machine to effect the separation of one and the same mixture of
A third advantage may be obtained with mixtures of minerals which are to be
separated and which are of that kind that are free from strong magnetic constituents
(iron, magnetic iron, magnetic pyrites, roasted spathose, iron stone, etc.,) namely,
that also the last stripping band over the supply pole may be dispensed with.
ore.
It is important for the separation of weak magnetic materials that they should be
supplied in direct proximity to the pole edges and with the least possible velocity to
the gap between the pole edges. This has heretofore been effected chiefly by means
of bands which passed around the pole edges but which were liable to very rapid wear
and which necessarily kept the material distant from the magnetic edge to the
extent of the thickness of the band. The conveyor bands can now be dispensed with,
as the mixture is supplied directly on to the surface of the magnet towards its edge
and is left free at the edge without being conveyed by artificial means around the
edge. For this purpose either the surface must have a suitable inclination in order
to allow the material to move by its own weight and overcome its own friction on the
said surface or artificial means of movement must be employed which remain above
and do not move round the edge of the magnet. The material is preferably supplied
close behind the magnet edge on to the surface of the magnet in regulated quantity
and in such manner as to meet the said surface with the least possible velocity and
then move along on the said surface.
For this purpose a feed hopper is preferably employed, the delivery aperture of
which is directly behind the magnet edge and whence the comminuted material falls
out in such manner that it strikes at a small distance above the surface of the magnet
first upon a transverse lip and then passes from the latter on to the magnet. This
admits of the magnet edge being made as sharp as possible so as both to concentrate
the lines of force as much as possible and prevent the magnetic particles from perma-
nently adhering, since the adhesion is greater to a broad than to a very narrow edge.

page_text: The operation of separation then takes place as follows:-The non-magnetic particles
flow at once over the pole edge and fall off, whilst the magnetic particles have at first
a tendency to adhere to the magnet edge but are pushed onwards by the material
following and carried around the edge whence they drop off.
In machines for the separation of weak magnetic mixtures of ore, in which
minerals of comparatively great susceptibility (for example garnet, raw spathose,
ironstone, etc.,) are to be extracted, the cost of manufacture of the apparatus may
be reduced, as in this case only the magnet on to whose poles the material is supplied
need be provided with an electric coil, the two other cores then forming merely the
iron masses necessary for the return of the lines of force produced in the magnet.
These iron masses must be present in order that the lines of force shall not become
dispersed into the air from the whole surface of the exciting magnet, but shall be con-
centrated at and pass over thereto from the point of the magnet. By thus determining
the direction of passing over, they fulfil the function of imparting the bunch-like shape
to the magnetic field before referred to.
It is obvious that the shape of the magnetic field may be varied at will and that
by shifting the two magnets opposite to the supply pole, both the divergence of the
bunch of lines of force and the position of the apex or crown of the bunch on the
supply pole can be altered. It is to be noted that instead of two, three or more
magnets might be arranged opposite to the supply pole.
The accompanying drawings illustrate a mode of carrying out the invention which
combines all the improvements.
Figure 1 is a front elevation of the apparatus,
Figure 2 is a section on the line 2-2 of Figure 1,
Figure 3 is a separate view of the poles on a larger scale.
The upper-shaped magnet B is mounted in an inclined position in the wooden
framing A. It is provided with the charging hoppers or trunks C C and is energized
by means of the coil D. The mixture charged into either hopper impinges upon,
and is arrested by, a horizontal lip a whence it falls between the front edge c of this
lip and the gauge bar E on to the magnet B down which it slides towards the edge b,
the gauge E being adjustable by means of screws e to regulate the amount of the
material supplied. It is important that this pole edge b be as sharp as possible in
order to prevent a long heard of magnetic particles from adhering thereto. This
pole edge is brightly polished or covered with a brightly polished steel plate, in order
that the particles slipping over it shall be hindered as little as possible by friction.
In many cases this covering may be made of non-magnetic material in order to
prevent the undermost particles in the stream of material being permanently retained
by the magnet. Vertically below the pole edges are the pole edges ff of the
magnet which are covered by caps H of non-magnetic material, adjustable by
means of set screws h to suit the various materials. In consequence of this arrange-
ment the non-magnetic particles fall over the cap H into a receiver whilst the
magnetic particles are drawn through the gap or interval. Opposite to, but slightly
higher than, the pole edges bb are the pole edges gg of the magnet G. The coils M. N
of magnets and G may be dispensed with in the case of materials of magnetic
properties such as those of garnet and spathose ironstone.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare what I
claim is:
1. An electro-magnetic separating machine characterized by the arrangement of
three (or more) magnet poles in such a manner that opposite one pole, namely, the
so-called supply pole, there are arranged two (or more) poles which are of different
polarity to the first mentioned pole.
2. An apparatus for the electro-magnetic separation of magnetic, preferably weak
magnetic, bodies characterized by the fact that the mixture to be separated is charged
on to the surface of a magnet and slides along said surface towards the edge of the

page_text: magnet by reason of its own weight alone, or with the aid of auxiliary means which
do not pass round the edge.
3. The process of magnetic separation according to which the material to be
separated is charged on to the magnet directly behind the magnet edge.
4. The process of magnetic separation in which the magnetic parts remain adhering
to the pole edge and are forced away (and fall down) by the further particles that
push on from behind.
5. An apparatus for carrying out the process specified in Claim 3, characterized by
a charging hopper mounted on the magnet, and on the lower side of which hopper
the outflow of the material to be separated is regulated by means of a slide and,
being delayed in its movement by transverse bars, falls on to the magnet.
6. The arrangement of an electro-magnet for magnetic separation in bi-polar fields,
characterized by the fact that it consists of several magnetic elements separated from
each other by the gap or interval intended for the separation and of which only one,
or a portion, is energized by the electric current.
7. The combination with the polar edge of the lower magnet of a cap of non-
magnetic material covering the said lower magnet edge.
8. A special form of construction of the machine specified in Claim 1, characterized
by the fact that opposite the so-called supply or exciting electro-magnet there are
arranged two iron cores in such a manner that the lines of force issuing from the edge
of the supply magnet are taken up by the edges of the two iron cores, and return into
themselves through the iron masses of said cores.
T
T
3000
CRADLY CELO
Cona
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.