US2081445A - Magnetic separator - Google Patents

Description

May 25, 1937. L. v. ANDR EWS-ET AL MAGNETIC SEFARATOR Filed J une 28, 1934 3 SheetsrSheet L. VI ANDREWS' HAROLL E %LTON y` 1937. L. v. ANDREWS El' AL 2,08l,445

MAGNETIC SEPABATOR Filed June 28, 1934 3 Sheets-Sheet 2 Sme/VW L. V ANDREWS' HARQLD i: VWQLTON May 25, 1937. L. v. ANDRr-:ws El' AL 2,0s,445

MAGNETI C SEPARATOR Filed June 28, 1934 3 Sheets- Sheet 3 L. I HNDRE WG' 'QROLD E' mqLroN &7 .5

patente& May 25, 193 7 MAGNETEC SEPARATOR L. V. Andrews and Harold F. Walton, Worceste', Mass., assigncrs to Riley Stoker Corporation, Worcester, Mase., a corporation of Massachusetts Application June 28, 1934, Serial No. '732,910

small, compact and inexpensive, and which preferably comprises coils of a simple cylindrical shape.

With these and other objects in View, as will be apparent to those skilled in the art, the invention resides in the combination of. parts set orth in the specification and coVere-d by the claims appended hereto.

Referring to the drawings illustrating one embodiment of the invention, and in which like reference numerals indicate like parts.

Fig. 1 is a sectional elevation of a magnetic Separator, the section being taken on the line l--l of Fig. 3;

Fig. 2 is a perspective view of the coil supporting structure, with the coils and sleeves removed; Fig. 3 is a section on the line 3-3 of Fig. 1;

Fig. 4: is an elevation of the drum which surrounds the coils;

Fig. 5 is a section on the line 5-5 of Fig. l; and

Fig. 6 is a perspective view of the iron pole pieces for the drum before the drum is cast thereon.

'7 Claims.

This invention relates to magnetic separators, and more particularly to separators of the electromagnetic type having an iron core surrounded by a coil of insulated wire, these parts being arranged to set up a strong magnetic field and produ-ce a separation of particles of iron from non-magnetic material. In the specication and claims the word iron" is used in a broad sense to include all magnetic materials, whether the word is applied to the particles to be separated or to portions of the Separator itself.

Magnetic separators of this type are ordinarily energized by a direct current, and when the circuit is opened, either intentionally by means of a switch or accidentally'by reason of a broken wire, the powerful magnetic field will suddenly collapse. This will momentarily induce a very high Voltage in the coil, which may result in a breaking down of the insulation. In order to avoid this danger, it has been the practice to utilize special switches which connect a resistance across the coil just prior to the opening of the connection with the line. These switches are expensive, they cause a surge in the line when they are operated, and they provide no protection in case of an accidentally opened circuit.

It is accordingly one object of the invention to provide a magnetic Separator which is so constructed and arranged that no unduly high voltage will be induced in the coil when the circuit therethrough is opened.

It has previously been proposed to construct magnetic separators in the form of a rotating drum which surrounds a stationary electro-magnet. A stream of mixed iron and non-magnetic material is delivered to the outer surface of the drum, and the iron particles adhere to the drum and are carried out of the stream. In these prior constructions it has been found difiicult to obtain a 'suificiently strong magnetic field to hold large iron particles without using large and expensive coils, and if the field is made sufciently strong the smaller iron particleswill not be released from the drum. In some cases coils of *special and expensive distorted shapes have been utilized in an attempt to provide satisfactory operation. y

It is accordingly a further object of the invention to provide a magnetic separator of the type having a stationary electro-magnet surrounded by a rotatable drum, which will produce a very strong magnetic field at one side of the drum and practcally no field at another side.

-It is a further object of the invention to provide such a Separator which will be comparatively having two spaced Vertical side walls ll] connected by an end wall l I to provide a structure substantially U-shaped in cross-section, as shown particularly in Fig. 5. Each side wall ID is ormed with a circular opening IZ therein, these openings being coaxial. Cover plates M and l5 are mounted over the openings, and a cylindrical iron bar IE extends horizontally across the casing and is supported at its ends in the cover plates. The parts so far described are preferably made of iron.

A cylindrical drum l'l surrounds the bar [6 concentrically, and is arranged to be rotate-d by a suitable means. As illustrated the drum is supported on end plates l8 and [9 rotatably mounted on ball bearings 28 on the bar 16. The `plate i& is provided with an annular fiange El having a groove 22 therein to receive a driving belt 23. The drum l'l is arranged to provide moving pole pieces, and for this purpose the drum is formed of a main body of non-magnetic material, such as brass, having inserts 25 of iron in the form of rectangular bars extending parallel to the axs of the drum. These bars are arranged with their inner and outer'surfaces fiush with the corresponding surfaces of the non-magnetic portion of the drum. The bars 25 are preferably made alternately long and short, as shown particularly in Fig. 4, since this provides a more The embodiment illustrated comprises a casing a uniform distribution of the magnetic fiux longitudinally of the drum.

While the drum t'i may be manufactured in various ways, we prefer to first form by casting or otherwise a unitary iron structure as shown in Fig. 6, in which the bars 25 are held in their proper relative positions by means of a surrounding circular band This structure is placed in a suitable mold and the brass is cast about the bars. The casting is then taken from the mold, and the band removed by a suitable machining operation in a lathe or otherwise. The sicles of the bars which contact with the brass are made convex so that the bars are firmly held in place in the brass casting. The drum is preferably machined both inside and outside in order to provide smooth and accurate cylindrical surfaces, and it is shown slightly smaller in diameter than the openings 52 so that it may be readily removed or inserted therethrough.

In order to provide the necessary magnetic fiuX, we mount a stationary electro-magnet Within the drum This magnet comprises a central iron pole piece ?28 supported on the iron bar or core i@ half-way between the end plates ti) and !El and in line with the centers of the bars 25. The pole piece is shaped as a circular sector located in a plane perpendicular to the axis of the drum and through a large angle, in fact nearly 180 degrees. The pole piece 28 projects from the core !ti in a direction toward the casing wall i i, and the periphery of the pole piece is very close to the inner surface of the drum. At each side of the central pole piece is an ele-ctrical coil 3@ cylindrical in shape and having an outside diameter somewhat smaller than the inside diameter of the drum i?. The coils 33 are preierably identical they surround the core lt?, which is bored axiaily at si for suitable leads (not shown) through which electric current is conducted to the coils. Between each end plate and the adjacent coil we preferably provide a plate Sii, preferably of iron, which is similar in shape to the pole piece 28 but somewhat thinner and formed with a narrow radial arm 33 extending in the opposite direction from the main body of the plate. These arms 33 serve to support an arcuate iron plate 35 which extends substantially the entire length of the drum ll and close to the inner surface thereof.

In order to prevent possible damage to the insulation of the coils 3@ as a result of high voltage generated therein upon opening of the circuit and sudden Collapse of the magnetic field, we provide means forming a low resistance path for the flOW of induced current around the core 15. For this purpose we prefer to mount a sleeve 3? of Copper or other highly conductive non-magnetic material inside of each coil and surrounding the core. When the magnetic field collapses, a comparatively large induced current fiows momentarily in the low resistance path afforded by the sleeve and as a result there is no dangerously high voltage produced in the coil.

The material which is to be separated is delivered to the outer surface of the drum l'i by any suitable means. In the drawings we have shown for this purpose a chute or trough dil mounted above the drum and sloping downwardly toward the casing wall ll. On each side wall lil adjacent to the chute 4!) there is mounted a fianged guard member il, preferably of non-magnetic material, which overlies the adjacent end portion of the drum i? to prevent the stream of material from Contacting therewith. Beneath the drum l'l there is provided a partition 43 (Fig. 1) forming a division between the space 44 adjacent the casing wall ll and the space 45 in which the iron particles are to be deposited.

The operation of the invention will now be apparent from the above disclosure. A direct current is supplied to the coils 30, the connections being such that the magnetic flux produced by one coil opposes that produced by the other. This fiux passes outwardly from the core I 6 through the pole piece 23, which becomes strongly magnetized, and into such of the bars 25 as happen to be adjacent to the pole piece. If the direction of the current is such that the member 28 is a north pole, the bars 25 will also be north poles and in effect lateral extensions of the pole piece. From these bars a large part of the ux will travel in laterally diverging directions across to the casing end wall ll and side walls ID, the casing orming a magnetic south pole from which the flux returns to the ends of the core IE. The reluctance of this return path may be decreased by forming the cover plates M and I of iron. Some of the fiux will return to the core through the end plates !8 and ie, particularly if they are made of iron, and also through the plates 32. Non-magnetic material which is delivered by the chute il) will pass over the drum l'l and drop into the space M, while iron pieces which may have been mixed with said material will be strongly attracted by the magnetized iron bars As a result, rotation or the drum in an anticlockwise direction as Viewed in Fig. l will cause the iron pieces to be carried over the top of the partition :3 to a position above the space 45. When the bars 25 leave the pole piece 28 they will lose most of their magnetism and the iron pieces will fall therefrom. A slight residual magnetism may remain in the bars 25, however, and cause them to hold some of the smaller particles of iron until the bars reach a position close to the plate 35. Since this plate is connected to the ends of the core iG by means of the narrow iron arms 33, it will be given a comparatvely Weak magnetism which opposes and hence neutralizes the residual magnetism of the bars, allowing the small iron particles to fall.

When an iron body is in contact with one of the bars 25 adjacent to the pole piece 28, the path from the core !8 to the iron body is completely iron except for the air gap between the pole piece and the bar, and this air gap can be made very small. As a result the iron body will be held firmly against the bar. The coils 38 are of a simple cylindrical shape and hence are comparatively inexpensive. They may be connected in parallel for one voltage, say 110, and in series for a higher voltage such as 220.

If the circuit through one of the coils is opened, either accidentally or intentionally, the sudden Collapse of the magnetic field will simply produce a momentary induced current in the low resistance path aforded by the copper sleeve 37. As a result, the production of dangerously high induced voltages in the coil is avoided. No special and expensive switches are required, and no line disturbances are created.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

l. A magnetic Separator comp'ising an iron core, an electrical coil surrounding the core and arranged to set up a magnetic field, means to direct a stream of mixed magnetic and non-magnetic material into the field and thus effeot a separation of the magnetic and non-magnetic material, and means forming a low resistance path through which induced current may flow around the core upon collapse of the field, whereby the coil is protected from high induced Voltages.

2. A magnetic Separator comprising an iron core, a sleeve surrounding the core and formed of non-magnetic material having a high electrical conductivity, an electrical coil surrounding the sleeve and arranged to set up a magnetic field, and means to direct a stream of mixed magnetic and non-magnetic material into the field and thus effect a separation of the magnetic and nonmagnetc material, the sleeve forming a low resistance path through which induced current may flow around the core upon collapse of the field, whereby the coil is protected from high induced voltages.

3. A magnetic Separator comprising an iron core, a copper sleeve surrounding the core, an electrical coil of insulated wire surrounding the sleeve and arranged to set up a magnetic field, and means to direct a stream of mixed magnetic and non-magnetic material into the field and thus effect a separation of the magnetic and non-magnetic material, the sleeve forming a low resistance path through which induced current may flow around the core upon Collapse of the field, whereby the coil is proctected from high induced voltages.

4. A magnetic Separator comprising a substantially horizontal iron core, two electrical coils surrounding the core and spaced apart axially, an iron pole piece extending radially from the core and located between the coils, the pole piece being shaped as a circular sector, a rotatable cylindrical drum surrounding the coils, the drum having a main body of non-magnetic material and a series of iron bars supported therein and parallel to the axis of the drum, the bars being alternately long and short, and means to deliver a stream of mixed magnetic and non-magnetic material to the outer surface of the drum.

5. A magnetic Separator comprising a substantially horizontal iron core, two electrical coils surrounding the core and spaced apart axially, an iron pole piece extending radially from the core and located between the coils, iron arms extending from the end portions of the core in the opposite direction from the pole piece, an iron member extending parallel to the core and connecting the outer ends of the arms, a rotatable cylindrical drum surrounding the coils and arranged to provide iron pole pieces which revolve close to the first mentioned pole piece and the iron member, and means to deliver a stream of mixed magnetic and non-magentic material to the outer surface of the drum at a region near the first mentioned pole piece.

6. A magnetic Separator comprising a substantially horizontal iron core, two electrical coils surrounding the core and spaced apart axially, an iron pole piece extending radially from the core and located between the coils, the pole piece being shaped as a circular sector, iron arms extending from the end portions of the core in the opposite direction from the pole piece, an arcuate iron member extending parallel to the core and connecting the outer ends of the arms, a rotatable cylindrical drum surrounding the coils, the drum having a main body of non-magnetic material and a series of iron bars supported therein and parallel to the axis of the drum, the bars being arranged to revolve close to the pole piece and said iron member, and means to deliv er a stream of mixed magnetic and non-magnetic material to the outer surface of the drum at a region near the pole piece.

7. A magnetic Separator comprising a substantially horizontal iron core, two electrical coils surrounding the core and spaced apart axially, an iron pole piece extending radially from the core and located between the coils, the pole piece being shaped as a circular sector, iron plates extending from the end portions of the core in the same direction as the pole piece, each plate being shaped as a circular sector, an iron arm extending in the opposite direction from each plate, an arcuate iron member extending parallel to the core and connecting the outer ends of the arms, a rotatable cylindrical drum surrounding the coils, the drum having a main body of non-magnetic material and a series of iron bars supported therein and parallel to the axis of the drum, the bars being arranged to revolve close to the pole piece and the iron member, and means to deliver a stream of mixed magnetic and non-magnetic material to the outer surface of the drum at a region near the pole piece.

I-IAROLD F. WALTON. L. V. ANDREWS.

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