US2696301A

US2696301A - Magnetic separating device

Info

Publication number: US2696301A
Application number: US130704A
Authority: US
Inventors: Wallace W Mojden; Emerson J Tenpas
Original assignee: Eriez Manufacturing Co
Current assignee: Eriez Manufacturing Co
Priority date: 1949-12-02
Filing date: 1949-12-02
Publication date: 1954-12-07
Anticipated expiration: 1971-12-07

Description

Dec. 7, 1954 w, w, MOJDEN ETAL 2,696,301

MAGNETIC SEPARATING DEVICE 2 Sheets-Shet 1 Filed Dec. 2, 1949 IN VEN TOR.

Ma 17mm: (1.1 b7 7 BY Me rsa/1 J. Ten ca;

Dec. 7, 1954 w, w, MQJDEN ET AL 2,696,301

MAGNETIC SEPARATING DEVICE Filed Dec. 2, 1949 2 Sheets-Sheet 2 IN VEN TOR.

MAGNETIC SEPARATING DEVICE Wallace W. Mojden and Emerson J. Tenpas, Erie County, Pa., assignors to Eriez Manufacturing Company, Erie, Pa., a corporation of Pennsylvania Application December 2, 1949, Serial No. 130,704

9 Claims. (Cl. 209-219) This invention relates generally to a magnetic separating device and more particularly to a method and apparatus for separating extremely fine magnetizable powdered material from extremely fine non-magnetizable powdered material.

The removal of fine iron from fine powders has been a challenge to the magnetic separation industry for some time. As powders become finer, the cohesive attraction of the particles for each other and most everything else increases. The powders tend to stick to the surface of a separator such as a belt or drum, and be carried around and discharged with any iron that may be attracted. In addition, the attraction of a magnet to a particle of iron is in proportion to the mass of the particle of iron until the iron particle approaches one micron in size, when its reluctance is increased many times. The separation difficulties can be appreciated when we realize that a magnet must attract a minute particle of iron from a cohesive mixture and must remain clean of the cohesive or sticky powder.

A major fault with all previous experimental devices has been the large amount of non-magnetic material removed with the iron. Unsuccessful experimental devices utilized either an induced grid type magnetic separator or large and expensive magnetic induced roll types to overcome the problem. The grid type was not selfvcleaning and was not commercially acceptable. The induced roll separator was not successful due to the tendency for the powder to adhere to the rolls and be carried around with the iron. The induced roll type separator is large, heavy, and expensive. Iron particles do not leave the rolls, but accumulate, making manual cleaning necessary.

No magnetic separating device has heretofore been devised to successfully separate extremely fine magnetizable material from extremely fine non-magnetizable material. Even when it has been possible to successfully attract the fine magnetizable particles, plugging up usually occurs, due to the reluctance of the nonmagnetizable particles to separate from the magnetizable particles. It has also been difiicult to attract extremely fine magnetizable particles inasmuch as the attraction of a magnetizable material to a magnet is in proportion to the mass of the magnetizable particle.

Because of the difliculty of attracting extremely fine magnetizable particles, it has been necessary to expose them to a very strong magnetic field which is best obtained at the edge of an air gap. The amount of iron contamination contained in most fine materials is usually so great that a self-cleaning unit becomes imperative. Where a rotating magnetic drum has heretofore been used for separation of fine particled material, it has been practically impossible to remove the magnetic material from the drum inasmuch as the non-magnetizable material sticks to the surface of the drum.

It is, accordingly, an object of our invention to overcome the above and other defects in present methods and apparatus for separating fine magnetizable particles from non-magnetizable particles and it is more particularly an object of our invention to provide apparatus for separating fine magnetizable particles from nonmagnetizable particles which is simple in construction,

economical in cost, economical in manufacture, and efficient in operation.

Another object of our invention is to provide novel magnetic means for separating extremely fine magnetizable material from non-magnetizable material.

United States Patent Another object of our invention is to provide a novel method of separating extremely fine magnetizable material from non-magnetizable material.

Another object of our invention is to provide a rotatable magnetic drum or cylinder with novel means for removing magnetizable material gathered on the face thereof.

Another object of our invention is to provide means for flowing fine powdered material onto the face of a revolving magnetic cylinder and a novel rotatable induction member associated therewith to remove the magnetizable particles in said powdered material from the face of said cylinder after the non-magnetizable material is removed therefrom by centrifugal force or grav- 1ty.

Another object of our invention is to provide a battle or baffles for re-enteriug the material to be separated onto the face of a rotating magnetic cylinder.

Another object of our invention is to provide means adjacent a magnetic drum for agitating the material and air adjacent to the face of the drum.

Another object of our invention is to provide a novel combination and arrangement of parts in a magnetic separating device to separate fine magnetizable material from fine non-magnetizable material.

A more particular object of our invention is to provide a magnetic separating device embodying the following principles of operation:

1. To momentarily overcome the cohesive attraction of a powder by violently and mechanically tearing the powder apart;

2. To momentarily speed up the movement of a powder to thin and stretch out the powder;

3. To have relative movement between a stretched gultd film of powder and a series of strong magnetic 4. To directly expose the pole pieces or gap edge (the point of maximum flux concentration) to the powder;

5. To magnetically attract and hold magnetic particles to the face of a rapidly revolving cylinder and by centrifugal force throw off the non-magnetic particles, keeping carry-over to a minimum;

6. To re-introduce the powder to a rapidly revolving cylinder by a series of baffies for repeated combingd by a series of strong exposed magnetic pole pieces; an

7. To automatically remove the iron from the surface of the cylinder continuously and without wear to the cylinder.

Other objects of our invention will become evident from the following detailed description, taken in conjunction with the accompanying drawings, in which Fig. l is a side elevational view partly in section and more or less in diagrammatic form of our novel magnetic1 separating device for extremely fine powdered materia Fig. 2 is an enlarged diagrammatic side elevational view of a magnetic cylinder and the re-entrant bafile and the cleaning drum associated therewith; and

Fig. 3 is a side elevational view of a modified form of re-entrant bafile for our novel magnetic separating device.

Referring now to the drawings, we show in Figs. 1 and 2 a rotatable cylinder 1 having banks of magnets 2, preferably U-shaped, spaced around the internal periphery thereof and secured to the outer shell of the cylinder 1 by screw bolts 3. The U-shaped magnets 2 pro- .vide a progressive series of magnetic fields running parallel to the axis of the cylinder 1. We show in Figs. 1 and 2 a cylinder 1 having four U-shaped banks of magnets 2 spaced around the inner periphery thereof thereby providing eight magnetic fields; however, any suitable number of magnets maybe used. The cylinder 1 is preferably revolved at a relatively high speed compared with present magnetic drums or pulleys. The powdered material to be separated is introduced to the surface of the cylinder 1 from a chute 6 which is designed to slowly feed material to the face of the cylinder 1 in a relatively fine even flow. The chute 6 may have a bracket 7 attached thereto to, which is attached an armature 8 disposed adjacent the outer face of the cylinder 1. Upon rotation of the cylinder 1, the changing magnetic fields of the magnets 2 cause inward and outward movement of the armature 8 thereby causing vibration of the chute 6. Our device will operate extremely well without the armature 8; however, in certain types of installations, it is desirable to have such a device for vibrating the chute 6. A conventional magnet (not shown) is preferably disposed in the feed line before the chute 6 to remove any tramp iron before entering the face of the cylinder 1 to prevent damage.

We provide an arcuate shaped re-entrant bafile 11 spaced from the outer face of the cylinder 1 with the distance between the baffle 11 and the face of the cylinder 1 gradually decreased from the entrance point of the material at the chute 6 to the lower end of the baffle 11. The bat-He'll has inwardly curved portions 12 spaced around the periphery thereof to progressively redirect the direction of flow of material thrown outwardly from the face of the cylinder 1 back into the face of the cylinder 1 several times as it passes around to the bottom side thereof.

Adjacent the lower terminus of the baffle 11, we provide a member 13 secured by a bracket 14 with the upper end thereof adjacent the cylinder 1. This causes the air adjacent the face of the cylinder 1 to become turbulent and the non-magnetizable material which adheres to the cylinder 1 is agitated and thrown from the cylinder 1 and it is caught by the curved baffle 15 and passed to a chute 15a extending to a point remote from the cylinder 1.

At a point more than three quarters of a turn from the chute 6 beyond the baffle 15, we dispose a rapidly revolving cleaning drum 16 with longitudinally extending, spaced, channel shaped members 17 secured by screw bolts 18 on the periphery thereof. The drum 16 is mounted on a shaft 16a parallel to the shaft 80 upon which the cylinder 1 is mounted. The drum 16 may comprise a plurality of side by side relatively thin disks (not shown) with transversely bent, radially extending arms or any other suitable magnetizable construction may be used to remove the magnetizable material from the face of the cylinder 1. The material used in constructing the drum 16 is preferably non-magnetizable material in order that the comparatively thin channel shaped members 17 adjacent the outer side or face of the cylinder 1 in the magnetic fields produced by the magnets 2 will be magnetically induced as they approach the face of the cylinder 1 thereby causing all or a major portion of the magnetizable material on the face of the cylinder 1 to be attracted thereto and gathered thereon.

The thin section of the channel members 17 provides increased flux concentration. As the drum 16 revolves due to induced magnetism from the changing rotating magnetic fields produced by the magnets 2, the magnetizable particles gathered on the channel shaped members 17 are carried away from the face of the cylinder 1 and out of the magnetic fields produced by the magnets 2 at which point the induced magnetism in the members 17 will be greatly decreased, thereby lessening the attraction of the fine magnetic powdered material to the drum 16 and it will be thrown into a chute 19 by centrifugal force or it will fall therein by gravity.

The cylinder 1 is rotated through a belt 21 and

pulleys

22 and 23 on the shaft 80 of the cylinder 1 and shaft 24 of an electric motor 25, respectively.

In the operation of our novel separating device, the air gaps and therefore the magnetic fields produced by the circumferentially spaced banks of magnets 2 run parallel to the axis of the cylinder 1. The cylinder 1 is preferably revolved at a high comparative speed. The fine material to be separated is introduced to the upper surface of the cylinder 1 from the chute 6, preferably in a fine layer of uniform depth. As the fine material strikes the outer face of the rapidly revolving cylinder 1, it will be immediately stretched out and thinned out and torn apart because the centrifugal force throws the material from the cylinder 1. This action exposes the magnetic particles in the material to be separated to the outer face of the cylinder 1. There is a slipping action or relative movement between the rapidly revolving cylinder 1 and the material passing thereon from the chute 6. The material never quite reaches the speed of the cylinder 1 so that we have continuous relative movement between the cylinder 1 and the material, causing the material to be combed by the series of magnetic fields.

The slipping magnetizable particles in the powdered material to be separated pass directly over the strongest portion of the magnetic fields produced by the banks of magnets 2 which is at the edge of the air gaps therebetween. The material thrown outwardly by centrifugal force from the cylinder 1 strikes the inner face of the re-entrant baffie 11 and the arcuate shaped curved surfaces 12 of the batlle 11 cause the particles to progressively change their direction of flow and pass several times into the face of the cylinder 1 as the material passes around the face of the cylinder 1 through approximately one-half a turn thereof. The material is repeatedly combed by the magnetic fields of the magnets 2 as it moves around the cylinder 1.

In the separation of certain materials, magnetic and non-magnetic material may be cohesively held together on the face of the cylinder 1 after leaving the baffle 11. To overcome this, we have provided a member 13 with the upper end thereof adjacent the cylinder 1 to cause turbulence of the boundary layer of air adjacent the face of the rotating cylinder 1 whereby the material on the cylinder 1 is agitated and the non-magnetizable particles leave the cylinder 1 and pass to the chute 15a by gravity or centrifugal force or both. The magnetizable particles remain on the surface of the cylinder 1 attracted by the banks of magnets 2 until they reach the vicinity of the drum 16 which is magnetized by induction from the banks of magnets 2 and which is rotated by induced magnetism from the rotating magnetic fields of the banks of magnets 2 in the cylinder 1. The magnetic material remaining on the face of the cylinder 1 will be attracted to the magnetized channel shaped members 17 of the drum 16 and they will be pulled away from the face of the cylinder 1. As the drum 16 revolves, the channel shaped members 17 holding the magnetizable material gathered thereon will move out of the magnetic fields of the magnets 2 and the induced magnetism in the channel members 17 will be decreased thereby lessening the attraction of the fine magnetic particles to the channel shaped members 17 to which they are attached, and the magnetizable particles will be thrown from the members 17 by centrifugal force or they will fall therefrom by gravity into the chute 19. The side of the drum 16 remote from the cylinder 1 is normally out of the magnetic fields of the banks of magnets 2, or at least the stronger portions thereof. Also, the magnetic fields tend to shunt through the channel members 17 and the magnetic material attracted thereto adjacent to the cylinder 1 thereby lessening the induced magnetism at other points on the drum 16 more remote from the face of the cylinder 1. The comparatively thin iron channels 17 are normally magnetically induced to saturation. A major part of the iron being held to the face of the cylinder 1 transfers to the high intensity edges of the channels 17. As the cylinder 1 revolves, the induced channels 17 revolve With it. As the channels 17 on the induced drum 16 move away from the cylinder 1, they move out of the magnetic fields thereof, lose their induction, and the i1r9on is dropped or thrown into a flanged discharge chute The drum 16 may take many different forms such as a series of side by side disks with transversely offset arms on the outer side thereof, a unitary finned unit, or any other suitable magnetizable construction.

In Fig. 3, we show a modified form of the re-entrant baffle 11 shown in Figs. 1 and 2. Re-entrant baffle 50 in Fig. 3 has arcuate shaped portions 51 progressively decreasing in length in the direction of the rotation of the cylinder 52 and consequently the direction of the material on the face of the cylinder 52.

It will be evident from the foregoing description that we have provided a novel magnetic separating device for separating extremely fine magnetizable material from extremely fine non-magnetizable material wherein the magnetizable material is exposed directly to the strongest portion of the magnetic field of a rotating magnetic cylinder, wherein novel means are provided for separating the non-magnetic material from the magnetic material, wherein means are provided for progressively redirecting the flow of material back to the face of the cylinder, wherein means are provided for agitating the particles and air adjacent the cylinder, and wherein an induction cleaning unit is provided for removing the magnetizable material from the face of the cylinder rotated by induced magnetism from the magnets of the magnetic cylinder.

Various changes may be made in the specific embodi ment of our invention without departing from the spirit thereof or from the scope of the appended claims.

What we claim is: v

1. A magnetic separating device comprising a rotatable magnetic cylinder having spaced magnets around the periphery thereof, means for feeding material to be separated into the face of said cylinder, and a magnetizable member disposed adjacent said cylinder at a point remote from the point wherein the material is fed onto said cylinder said magnetizable member being forced to rotate by the magnetism induced therein by the rotating magnetic field of said cylinder whereby said magnetizable member is magnetically coupled to said cylinder to remove magnetic material from the face of said cylinder, the portion of said magnetizable member remote from said cylinder being outside of the active magnetic fields of said cylinder.

2. A magnetic separating device comprising a rotatable cylinder, magnets disposed around the inner periphery of said cylinder, a chute for feeding material to be separated into the face of said cylinder, a bafile extending from said chute to the underside of said cylinder and spaced from said cylinder having portions shaped to redirect the flow of material thrown from said cylinder back to the face thereof, and a magnetizable rotatable member having the outer side thereof adjacent the periphery of said cylinder at a point remote from the point wherein material is fed onto said cylinder for removing magnetic particles from the face of said cylinder, the portion of said magnetizable rotatable member remote from said cylinder being outside of the active magnetic fields of said magnets carried by said cylinder whereby magnetizable material will drop by gravity therefrom at a point remote from said cylinder.

3. A magnetic separating device as set forth in claim 2 wherein the distance between said baffie and said cylinder gecreases from the upper to the lower side of said cylin- 4. A magnetic separating device as set forth in claim 2 wherein the length of said shaped portions decreases in the direction of rotation of said cylinder.

5. A magnetic separating device comprising a rotating magnetic cylinder having spaced magnetic fields around the periphery thereof, means for feeding material to be separated into the face of said cylinder, a baffie spaced from said cylinder leading from the point where said material is fed onto the face of said cylinder a substantial distance around said cylinder, and a magnetizable rotatable member disposed adjacent said cylinder at a point remote from the point on said cylinder where material is fed thereon and beyond the end of said baffie to remove magnetizable material from the face of said cylinder, the outer portion of said magnetizable rotatable member remote from said cylinder being without the active field of said magnetic cylinder said magnetizable member being rotatably actuated by the magnetic field of said cylinder whereby the peripheral speed of said magnetizable member is substantially equal to the peripheral speed of said cylinder.

6. A magnetic separating device comprising a rotatable magnetic cylinder having means to form spaced magnetic fields around the periphery thereof, means for feeding material to be separated onto the face of said cylinder substantially normal thereto, an arcuate shaped baffie spaced from the outer side of said cylinder having arcuate shaped portions for re-entering the material passing from said cylinder into the face of said cylinder, a radially extending member disposed adjacent the periphery of said cylinder at the end of said baffle to agitate the material and air on the periphery of said cylinder, and means for separately removing the magnetizable and non-magnetizable material from said cylinder and means for receiving the non-magnetizable material, said means termi- Eating in a baifie spaced from said radially extending mem- 7. A magnetic separating device as set forth in claim 6 wherein a rotatable magnetizable member is disposed adjacent said cylinder at a point remote from the point where said material is fed thereon to remove magnetizable particles from the face of said cylinder, the portion of said rotatable magnetizable member remote from said cylinder being disposed outside of the active magnetic fields of said cylinder.

8. A magnetic separating device comprising a rotatable cylinder, magnets disposed around the inner periphery of said cylinder, a chute for feeding material to be separated substantially normally into the face of said cylinder, a rotatable magnetizable member adjacent said cylinder having the outer side thereof adjacent the periphery of said cylinder at a point remote from the point where material is fed onto said cylinder for removing magnetic particles from the face of said cylinder, a portion of the outer side of said rotatable magnetizable member being outside of the active magnetic field of the magnets rotatable in said cylinder, a bafiie leading from the point where material is fed onto said cylinder around a substantial portion of said cylinder and opposite to said magnetizable member, and means on the inner side of said baffle for re-entering material to said cylinder being thrown therefrom by centrifugal force.

9. A magnetic separating device as set forth in claim 8 wherein said chute has an armature secured thereto disposed in the magnetic fields of said magnet whereby said chute is vibrated upon rotation of said magnets.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 148,517 Smith Mar. 10, 1874 336,402 Fisher Feb. 16, 1886 455,808 Wenstrom July 14, 1891 456,507 Fiske July 21, 1891 468,540 Cane Feb. 9, 1892 478,551 Ball July 12, 1892 487,073 Lovett Nov. 29, 1892 832,823 Wait Oct. 9, 1906 939,523 Ludwick Nov. 9, 1909 1,141,833 Salwen June 1, 1915 1,233,804 Pike July 17, 1917 2,326,575 Stearns Aug. 10, 1943 2,410,601 Crockett Nov. 5, 1946 FOREIGN PATENTS Number Country Date 38,367 Sweden Jan. 28, 1913