Title of Invention

MAGNETIC SEPARATOR WITH FERRITE AND RARE EARTH PERMANENT MAGNETS

Abstract MAGNETIC SEPARATOR WITH FERRITE AND RARE EARTH PERMANENT MAGNETS (57) Abstract: A magnetic separator with permanent magnets includes a ferromagnetic member (2) for the circuit connection be- tween at least two magnetic poles (3C) made up of ferrite magnets (12) in the bottom portion in contact with said ferromagnetic member (2) for the circuit connection, and of rare earth magnets (13) in the top portion that represents the entrance/exit surface (14) of the magnetic flux lines (15, 16). The ratio between the effective magnetic length of the ferrite magnets (12) and of the rare earth magnets (13) is preferably 2:1, and the preferred materials are strontium ferrite for the former and iron-boron-neodymium for the latter. In this way it is possible to combine the magnetic characteristics of the two types of permanent magnets so as to make them complementary and thus enhance the attractive effectiveness of the separator both for ferromagnetic materials with high or low shape factor, and for materials with high or low and sometimes very low permeability.
Full Text "MAGNETIC SEPARATOR WITH FERRITE AND RARE EARTH
PERMANENT MAGNETS"
The present invention relates to magnetic separators with permanent
magnets, and in particular to a separator provided with permanent magnets made
of ferrite and rare earth elements, capable of enhancing and optimizing the
attraction effect of variably ferromagnetic materials. The present application
specifically refers to a pulley separator, but it is clear that what is said also applies
to other types of magnetic separators (drums, plates, belts, etc.) which can be
provided with the permanent magnets described herein.
It is known that magnetic separators are used in all those applications where
it is necessary to attract and separate ferromagnetic materials of any shape and size
from mixed material. The attractive capacity of the separator depends both on the
magnetic field that it can generate (strength and gradient), and on the intrinsic
induction of the object to be separated as it results from its shape factor (e.g. the
sphere has the worst shape factor) and from its degree of permeability.
Attractive circuits (i.e. permanent magnets) made of ceramic materials such
as barium ferrite, and even better strontium ferrite, are known since more than
forty years. These magnets have a medium intrinsic and residual magnetic energy,
and are capable of attracting within a certain distance ferromagnetic materials with
high shape factor and/or medium-high permeability.
Other attractive circuits made of sintered materials with high intrinsic
residual magnetic energy, known as rare earth elements (samarium-cobalt, iron-
boron-neodymium), have been in use more recendy, in the last 15-20 years. These
magnets can attract within a relatively short distance, yet with great effectiveness,
even materials with low shape factor and/or medium-low and very low
permeability. Their effectiveness is however concentrated within few tens of
millimeters.
Therefore the object of the present invention is to provide a magnetic
separator which overcomes the limitations of known separators. This object is
achieved by means of a separator in which each magnetic pole is made up of
ferrite magnets in the bottom portion in contact with the ferromagnetic member for
the circuit connection between the poles, and of rare earth magnets in the top
portion that represents the entrance/exit surface of the magnetic flux lines.
The main advantage is that of combining the magnetic characteristics of the
two types of permanent magnets described above (ferrite and rare earth) so as to
make them complementary and thus enhance the attractive effectiveness both for
ferromagnetic materials with high or low shape factor, and for materials with high
or low and sometimes very low permeability.
In this way the attractive range of these magnets is greatly amplified and the
separator can operate with a productivity almost twice as much as a similar
separator with rare earth magnets, and with a quality of separation very high with
respect to a medium-low effectiveness of a similar separator with ferrite magnets.
Another significant advantage comes from the very simple structure of said
attractive circuits, which result easy to manufacture and to apply to any kind of
separator.
Further advantages and characteristics of the separator according to the
present invention will be clear to those skilled in the art from the following
detailed description of an embodiment thereof, with reference to the
accompanying drawings wherein:
Fig.l is a cross-sectional view of a prior art pulley separator with ferrite
magnets;
Fig.2 is a cross-sectional view of a prior art pulley separator with rare earth
magnets;
Fig.3 is a cross-sectional view of a prior art pulley separator with ferrite and
rare earth magnets according to the present invention;
Fig.4 is an enlarged diagrammatic view showing in detail the structure of an
attractive circuit according to the present invention;
Fig.5 is a partial plan view of a first possible arrangement of the polarities
for the separator of fig.3; and
Fig.6 is a partial plan view of a second possible arrangement of the polarities
for the separator of fig.3.
With reference to fig.l, mere is seen that a permanent magnet pulley 1
essentially consists of a ferromagnetic cylinder 2 around which there are applied
ferrite magnetic masses 3A, said cylinder 2 being enclosed by a protective casing 4
of non-magnetic material (e.g. stainless steel) that is preferably filled with a
blocking resin 5. This assembly is secured through end flanges onto a driving or
idle shaft, so that it can be preferably used as driving roller for a conveyor 6
provided with slats 7 on which the material 8 to be treated is drawn.
The dimension H1 indicates the effective working height with respect to the
layer of material 8 to be treated, and an indicative value for a pulley of 400 mm in
diameter is H1 = 80-90 mm for ferromagnetic parts with medium-high shape
factor and good permeability.
In fig.2 there is illustrated a pulley similar in shape and size to the one
above, with magnetic masses 3B of rare earth elements, in which the working
height H2 is 40-50 mm for ferromagnetic parts with medium-low shape factor and
low permeability, and within 30 mm of distance from the active surface for parts
with very low permeability.
In fig.3 there is illustrated a pulley similar in shape and size to the ones
above, with mixed magnetic masses 3C according to the present invention, where
for merely exemplificative purposes there are used in particular in each pole two
ferrite blocks 12 about 25 mm high located in contact with the ferromagnetic
cylinder 2 and one rare earth block 13 also about 25 mm high placed on top of and
in contact with the ferrite blocks 12 and close to the non-magnetic casing 4.
In the detail of fig.4 there is illustrated a permanent magnet circuit according
to the present invention including at least two poles 3C North-South each of which
is made up in the bottom portion, in contact with the ferromagnetic cylinder 2 for
the circuit connection between the poles, of ferrite magnets 12 (preferably
strontium ferrite) and in the top portion that represents the exit surface 14 of the
magnetic flux lines 15 when North pole, or entrance surface 16 when South pole,
of rare earth magnets 13 (preferably iron-boron-neodymium) capable of increasing
the values of the magnetic field and in particular of the magnetic field gradient.
In figs.5 and 6 there are illustrated for exemplificative purposes two possible
polarities arrangements in the longitudinal direction for magnetic pulleys; in
particular, fig.5 shows a chequered arrangement of the various North-South
magnetic poles whereas fig.6 shows the arrangement with longitudinal alternate
rows of North-South polarities.
For a comparison between the indicative field and field gradient values that
can be obtained in the three separators above, reference is made to the following
table. In this table, D is the distance at which the magnetic field is measured, while
G is the field gradient measured over the specified distance interval.

This novel type of attractive circuit applied, for a comparative example, to
the above-mentioned pulley thus surprisingly allows to enhance the characteristics
of the two types of magnets at the distances where they are less effective, yet
retaining their advantageous characteristics in the zones where diey better work
individually.
This results clearly from the possibility of having a better performance in the
zone beyond 50 nun of distance from the active surface, thanks to the higher
gradient, with respect to the ferrite magnet pulley that has trouble with poorly
magnetizable materials; and similarly this results from the possibility of having a
significantly improved average performance in the zone within 50 mm, thanks to
the stronger field, with respect to the similar rare earth magnet pulley.
It is clear that the above-described and illustrated embodiment of the
magnetic separator according to the invention is just an example susceptible of
various modifications. In particular, the ratio between the effective magnetic
lengm of ferrite and rare earth elements in each pole may be different from the
above-illustrated 2:1 ratio, indicatively between 1:1 and 3:1, and obviously the
number, shape and arrangement of the magnetic poles can be freely changed
according to the needs.
WE CLAIM:
1. Magnetic separator with permanent magnets having a ferromagnetic
member for the circuit connection between at least two magnetic poles (3C),
characterized in that each magnetic pole (3C) is made up of ferrite magnets (12) in
the bottom portion in contact with said ferromagnetic member for the circuit
connection, and of rare earth magnets (13) in the top portion that represents the
entrance/exit surface (14) of the magnetic flux lines (IS, 16).
2. Magnetic separator as claimed in claim 1, wherein in each magnetic
pole (3C) the ratio between me effective magnetic length of the ferrite magnets
(12) and of the rare earth magnets (13) is between 1:1 and 3:1, being preferably
2:1.
3. Magnetic separator as claimed in claim 1 or 2, wherein it consists of a
ferromagnetic cylinder (2) around which mere are applied the magnetic poles (3C),
said cylinder (2) is enclosed by a protective casing (4) of non-magnetic material
filled with a blocking resin (5), this assembly is secured onto a shaft so that it can
be used for a conveyor (6) on which the material (8) to be treated is drawn.
4. Magnetic separator as claimed in one or more of the preceding claims,
wherein the ferrite magnets (12) are made of barium ferrite or strontium ferrite.
5. Magnetic separator as claimed in one or more of the preceding claims,
wherein the rare earth magnets (13) are made of samarium-cobalt or iron-boron-
neodymium.


MAGNETIC SEPARATOR WITH FERRITE AND RARE EARTH PERMANENT MAGNETS

(57) Abstract: A magnetic separator with permanent magnets includes a ferromagnetic member (2) for the circuit connection be-
tween at least two magnetic poles (3C) made up of ferrite magnets (12) in the bottom portion in contact with said ferromagnetic
member (2) for the circuit connection, and of rare earth magnets (13) in the top portion that represents the entrance/exit surface (14)
of the magnetic flux lines (15, 16). The ratio between the effective magnetic length of the ferrite magnets (12) and of the rare earth
magnets (13) is preferably 2:1, and the preferred materials are strontium ferrite for the former and iron-boron-neodymium for the
latter. In this way it is possible to combine the magnetic characteristics of the two types of permanent magnets so as to make them
complementary and thus enhance the attractive effectiveness of the separator both for ferromagnetic materials with high or low shape
factor, and for materials with high or low and sometimes very low permeability.

Documents:

01092-kolnp-2006 abstract.pdf

01092-kolnp-2006 claims.pdf

01092-kolnp-2006 correspondence others.pdf

01092-kolnp-2006 description (complete).pdf

01092-kolnp-2006 drawings.pdf

01092-kolnp-2006 form-1.pdf

01092-kolnp-2006 form-3.pdf

01092-kolnp-2006 form-5.pdf

01092-kolnp-2006 international publication.pdf

01092-kolnp-2006 international search report.pdf

01092-kolnp-2006 pct form.pdf

01092-kolnp-2006-assignment.pdf

01092-kolnp-2006-correspondence others-1.1.pdf

01092-kolnp-2006-form-3-1.1.pdf

1092-KOLNP-2006-ABSTRACT 1.1.pdf

1092-kolnp-2006-assignment.pdf

1092-KOLNP-2006-CLAIMS 1.1.pdf

1092-KOLNP-2006-CORRESPONDENCE 1.1.pdf

1092-kolnp-2006-correspondence 1.2.pdf

1092-KOLNP-2006-CORRESPONDENCE.pdf

1092-kolnp-2006-correspondence1.2.pdf

1092-KOLNP-2006-DESCRIPTION (COMPLETE) 1.1.pdf

1092-KOLNP-2006-DRAWINGS 1.1.pdf

1092-kolnp-2006-form 18.pdf

1092-KOLNP-2006-FORM 2.pdf

1092-kolnp-2006-form 3.2.pdf

1092-kolnp-2006-form 5.pdf

1092-KOLNP-2006-FORM-27.pdf

1092-kolnp-2006-gpa.pdf

1092-kolnp-2006-granted-abstract.pdf

1092-kolnp-2006-granted-claims.pdf

1092-kolnp-2006-granted-description (complete).pdf

1092-kolnp-2006-granted-drawings.pdf

1092-kolnp-2006-granted-form 1.pdf

1092-kolnp-2006-granted-form 2.pdf

1092-kolnp-2006-granted-specification.pdf

1092-KOLNP-2006-OTHERS.pdf

1092-KOLNP-2006-PETITION UNDER RULE 137.pdf

abstract-01092-kolnp-2006.jpg


Patent Number 246181
Indian Patent Application Number 1092/KOLNP/2006
PG Journal Number 08/2011
Publication Date 25-Feb-2011
Grant Date 18-Feb-2011
Date of Filing 26-Apr-2006
Name of Patentee SGM GANTRY S.P.A.
Applicant Address VIA LENO, 2/D, I-25025 MANERBIO BS
Inventors:
# Inventor's Name Inventor's Address
1 MOLTENI DANILO VIA GIOVANNI, XXIII, 49, I-25025 MANERBIO BS
PCT International Classification Number B03C 1/18
PCT International Application Number PCT/IT2003/000726
PCT International Filing date 2003-11-07
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 PCT/IT2003/000726 2003-11-07 Italy