Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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~he present invention relates to magnetic separators
and more specifically, to the magnetic separation of solid
waste materials.
Magnetic separation of solid waste materials is most
commonly performed by devices of the type having a continuous
belt moving past a magnetic assembly which generates a magnetic
field through which the belt moves. In these separators, mag-
netic material is attracted to the belt by the magnetic assembly
and drawn along by the belt to a collection area whereat further
separating or processing may be performed. Prior to separation,
the waste is shredded to insure that particle size does not
exceed manageable levels. Unfortunately, this process produces
sharp or razor-edged metal particles which puncture or gouge the
belt when attracted thereto. Further, the tendency of the
attracted particles to remain in a fixed position relative to
the magnetic assembly results in a sliding contact between the
particles and the moving belt which causes cutting, scoring and
abrading of the belt.
In addition, a certain amount of relatively light
non-magnetic waste, such as rags and paper, tangled with, or
draped over the magnetic particles, is carried along therewith,
thus rendering the separation process incomplete. Attempts to
solve this problem of entrained non-magnetic materials by
agitating the attracted magnetic particles with alternating
magnetic polarities have proved only partly successful.
A recent attempt to solve both of these problems
simultaneously involves the use of special cleats which protect
the belt surface and agitate the attracted magnetic materials
(see copending Canadian application No. 251,229, filed April 27,
1976, for a Cleated Conveyor Belt). Although this solution ~-~
is a significant improvement over
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the prior art, the need still exists to periodically replace worn
belts.
It is therefore a primary object of the present inYen-
tion to provide a magnetlc separator which not only eliminates
the probIem of belt wear but also strategicallr locates the
magnetic field to obtain eficient separation.
This is accompllshed ~y replacing t~e belt with a
more durable, rotating metal drum wherein the magnetic scrap
is attracted to the outer surface of the drum and carried
along by the rotation thereof to a scrap collection area or
conveying means.
It is a further object to provide a magnetic separator
which is highly efficient in separating light non-magnetic
materials from the separated magnetic scrap.
This is accomplished by magnetically suspending the
separated scrap from the underside of the rotating drum in
combination with a novel arrangement of the delivery and
discharge conveyors allowing effIcient extraction of selected
materials from the burden being delivered to the drum by the
delivery conveyors and release of the non-magnetic'materials
to fall a~ay prior to the rele,ase of the magnetic scrap at
the collection point or conveying means. -
With'the above and other objects in view t~at will
here~nafter appear, the nature of the invention will be more
readily understood by reference to the following description,
the'appended claims and the several views illustrated in the
accompanying d~awings.
~igure 1 is a perspective vie~ of the magnetic
separator of the pre~ent in~ention.
~igure 2 i,s- a diagramatic v~ew of the separator. '
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As illustrated in ~igure 1, the present invention
comprises a supply conveyor 1 and a magnetic materials -
collection chute 2, with a non-magnetic materials collection
area 3 therebetween. A magnetic wheel drum 5 havîng an
internal magnetic assembly 6, is located above the collection
area 3.
The drum is a rigid right-cylindrical member having
a curved outer surface 5a. The drum 5 is preferably composed
of a durable non-magnetic metal such as manganese, having a
number of transverse sweep bars 5b mounted thereon. A frame 7
supports the drum 5 for rotation about its longitudinal axis.
The magnetic assembly 6, including electro-magnet 8
and permanent magnet 9, is fixedly attached to the frame 7,
provision being made, however, for minor alignment adjustments.
The electro-magnet 8, which may be of conventional
design and construction, is symmetric about a line radial to
the drum 5 and forming a perpendicular bisector to the
longitudinal axis of the head pulley or roller 10 of the
supply conveyor 1. This has the effect of "aiming" the field
produced by the electromagnet 8 at the point lOa where the
incoming wastes would otherwise fall from the conveyor 1
into the collection area 3. At this point, the stream of
waste materials 11 "spreads", forming a more dispersed
stream which facilitates the removal of the magnetic materials
lla.
The permanent magnet 9 is formed of a number of
rectilinear segments arranged in a substantially arcuate
configuration along the periphery of the curved surface 5a
of the drum 5 with one end thereof immediately adjacent the
electro-magnet 8 on the side thereof near the chute 2.
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The axis of the electro-magnet is inclined toward
the conveyor 1 at an angle ~ of approxi~ately 55~ from the
vertical, while the angle ~ included between the vertical
and the distal end 9b of the permanent magnet 9 is approxi-
mately 40~.
It is to be understood, however, that the conveyor
angle 0 may vary from about 30 to more than 90 depending
upon several variables, not all of which are known or fully
understood, but includ;ng space limitations and compatibility
with existing structures and equipment. The permanent magnet
angle ~ is likewise dependent upon several variables, among
which is the value of the angle 0 in the particular installation.
A reverse roller 12 is mounted at the end of the
collection chute 2 spaced apar~ from the surface 5a of the
drum 5 and having its axis parallel to the axis of the drum 5
and intersecting the line defined by the distal end 9b of the
permanent magnet 9. The roller 12 is driven to rotate about
its axis in a direction opposite the direction of rotation of
the drum 5. -
In operation, the supply conveyor 1 carries shredded
waste materials 11, composed of magnetic and non-magnetic
materials lla and llb respectively, toward the drum 5. As
the waste 11 approaches the point lOa, the magnetic materials
lla are drawn toward the center of the electro-magnet 8 by
the magnetic field generated thereby and are thus held against
the curved surface 5a of the drum 5, while the non-magnetic
materials llb fall into the collection area 3.
The drum 5 rotates in the direction urging the
magnetic materials lla toward the collection chute 2. As
the drum 5 rotates, the magnetic "hold" on the materials lla
being held thereagainst, and pushed along by the sweep~bars
5b, is assumed by the permanent magnet 9. ~hen the materials
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pass the end 9b of the permanent magnet 9, they leave the
magnetic field and the "hold" is broken. At this point,
they assume a parabolic trajectory as shown in Figure 2
and eventually fall onto the collection chute 2. Any non-
magnetic materials llb caught on magnetic particles lla and
carried along therewit~ come into contact with the reverse
roller 12 which strips off the dangling materials and throws
them back into the non-magnetic materials collection area 3,
thereby preventing such materials from collecting on the lip
of the chute 2 and eventually clogging the system. If a
conveyor is used in place of the chute 2, the roller 12 may
be dispensed with, as the movement of the conveyor would
serve to prevent a buildup of non-magnetic materials llb
at the conveyor end.
It is to be noted that the magnetic materials lla
are "carried" through an arc of approximately 95 from the
point of first contact to the point of releas-e. The length
of this journey insures that there is sufficient opportunity
for light non-magnetic materials, which are caught on sharp
protrusions of magnetic particles or otherwise carried along
therewith, to fall away into the collection area 3.
Preliminary test results indicate that a drum
constructed of 3/8 inch manganese sheet has an expected useful
life of 5 years or more, as opposed to a six month lie span
for the improved 1exible belt previously disclosed. These
tests were conducted on a 72 lnch diameter drum separating
wastes wherein the average diameter of the metall;c particles
was about 3 inches. The space between the supply conveyor
and the drum sur$ace waS approximately 17 ~nches and ~he
center o the reverse roller 12 was 11 inches- from the
surface of the drum. The electro-magnet produced a field
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intensity of 500 gauss at the surface of the roller 10.
