US3059156A - Means for controlling magnetic fields - Google Patents

Description

SABURO MlYATA MORIYA 3,059,156 MEANS FOR CONTROLLING MAGNETIC FIELDS Oct 16, 1962 Filed June 19, 1957 FIG. 3

FIG; 2

FIG. IO

F GL ll S.M.MORIYA United States Patent 3,059,156 MEANS FOR CONTROLLING MAGNETIC FIELDS Saburo Miyata Moriya, 58 Shimo Takanawa, Minato-ku, Tokyo, Japan Filed June 19, 1957, Ser. No. 666,703 2 Claims. (l. 317201) This invention relates to a means for controlling magnetic fields.

The invention relates to a method of controlling the flux of a permanent magnet to produce greater concentration of its magnetic force at a desired area.

It is an object of the present invention to provide a means and method of utilizing both poles of a permanent magnet in a more efficient manner and to materially reduce the amount of expensive permanent ma net alloy materials used.

Another object of this invention is to employ a plurality of magnets of small cross-sectional area so spaced and related that their combined effect is greater than that of a single magnet of the same total mass.

A further object of this invention is the provision of a means and method for shielding a permanent magnet from eddy currents that tend to reduce its magnetic characteristics.

Other objects and advantages will become apparent from the following detailed description taken with the accompanying drawings forming a part thereof.

In the drawings, wherein like characters of reference indicate like parts throughout;

FIG. 1 is a perspective view of a pair of magnets illustrating the principles of this invention;

FIGS. 1A and 1B are views in perspective further illustrating the principles of this invention;

FIG. 2 is an exploded perspective view of another illustration of the principles of this invention;

FIG. 3 is a perspective view of a further application of the principles of this invention;

FIG. 4 is a vertical sectional view of a magnet constructed according to this invention;

FIG. 5 -is a top plan view,'partly in section, showing a slightly modified magnet and shield arrangement;

FIG. 6 is a front elevation of a different form of the invention;

FIG. 7 is an elevational view of a modified form of the invention in FIG. 6;

FIG. 8 is a top plan view partly in section showing an arrangement involving the principles of the form shown in FIG. 7;

FIG. 9 is a perspective view showing the application of the principles of this invention to a horse shoe magnet;

FIG. 10 is a perspective view of a ring magnet embodying the principles of this invention, and

FIG. 11 is a perspective view of the invention of FIG. 10 having enlarged pole pieces.

In carrying out this invention, I employ as shielding means either air gaps or shields of non-permeable metal and as controlling means, low retentivity mild steel. I preferably use such steel for the pole pieces of my improved magnets.

Referring now to the drawings wherein FIG. 1 represents an example illustrating the principle of this invention; in this figure a pair of permanent magnets 1 having a diameter less than their length are each encased in a tube 2 of non-magnetic material. In FIG. 1A, the two magnets 3 are separated by an air gap 4, and kept in such spaced relation by wires or rods 5 of non-magnetic material. In FIG. 1B, the two bar magnets 6 are separated by means of a spacer or shim 7 of non-magnetic material. In FIG. 2, a plurality of magnets 8, are each enclosed in a tube or shield 9 of nonmagnetic material, with like poles adjacent each other,

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and the assembly is enclosed in a tube Ill of non-magnetic material. The assembly is provided with an N. pole piece 11 and a S. pole piece 12 each of suitable paramagnetic material, preferably low retentivity mild steel, to form a magnet assembly according to this invention.

In FIG. 3, I show a simple means of assembling and separating a plurality of magnets 13. A cylindrical member 14 preferably having an axial bore 15 is provided with a circular series of openings or bores 16 to accommodate the rod magnets 13.

A magnet constructed in accordance with the principles outlined above is shown in FIG. 4, wherein a plurality of magnets 17 are arranged in a circular order in suitable bores in a tubular member 18 of non-magnetic material, the whole being enclosed in a tubular shield 19 of non-magnetic material. The tube 19 is longer than the cylinder 18 and the pole pieces 20, 21 have hub portions 20, 21, respectively inserted in the tube 19 and in firm contact with the individual magnets 17.

In FIG. 5, there is shown a slightly modified arrangement of shielding for a magnet similar to that shown in FIG. 4. A plurality of magnets 22 each being enclosed ina tube 23 of non-magnetic material are assembled about a tube 24 of non-magnetic material and the assembly is enclosed in a tube 25 of non-magnetic material to form a magnet core. The magnet core thus formed is fixed between N. pole piece 26 and S. pole piece 27 of paramagnetic material, as mentioned above in the description of FIG. 2.

In FIG. 6 the two like magnet assemblies 28, 28' are arranged with like poles toward each other and as shown the magnet is provided with two N. pole pieces 29, 29 and a common S. pole piece 30. The structure thus assembled provides an elongated field without using long magnets. The magnet members 28, 28' may be formed like the assemblies of FIGS. 2 or 3, or even like the core portions of FIGS. 4 or 5.

The structure shown in FIG. 7 is a slight variation of that shown in FIG. 6. A plurality of like magnet assemblies 31, 31', 32, 32. are arranged with like poles facing each other in engagement with a common pole piece 34, and provided with like pole pieces 35, 35' at their outer ends. The elements 31, 31, 32, 32, may be as shown FIG. 8, or they may be formed in the manner of the core or magnet assemblies of FIGS. 3, 4 or 5.

In FIG. 8, the assembly represents one form of the magnet device of FIG. 7 and consists of a plurality of single magnets 36 each having a shield 37 and all acting on a common pole piece 34 with similar poles. A fragment of pole piece 35 also shows in this View.

In FIG. 9, I show a means of economizing on expensive alloy magnetic material in a horse-shoe magnet. A plurality of magnet elements 39 are assembled on a spacer 40 and are provided with pole pieces 41, 41 of paramagnetic material according to the principles of this invention, as pointed out hereinafter.

In FIG. 10, I economize on expensive magnet material by forming a ring magnet assembly 42 and providing annular pole pieces 43 and 44. The ring magnet 42 may be formed using the principle of my invention as illustrated in FIGS. 3, 4 and 5. This form is used whlen the magnetic force is to be concentrated at the po es.

In FIG. 11, I show a ring magnet member 45 having enlarged annular pole pieces 46 and 47. The ring magnet 45 may be made according to the principles of my invention as shown in FIGS. 3, 4 and 5. This form is used when the magnetic force is to be concentrated between the poles.

The employment of alloys such as those used in mag nets under the trade names of Alnico, MK. and others has caused a great reduction in magnet size or mass in relation to the strength or magnetic flux produced. These alloys are expensive and it is one of the purposes of this invention to materially reduce the mass and the cost of magnetic material used in producing a desired result by using a plurality of magnets having a combined mass of a single magnet having the power to accomplish the same result. This feature is of particular advantage where large evenly distributed magnetic fields are necessary, as for example in connection with 'belt or vibrating separators for particulate material containing ferro-magnetic particles; and in the use of magnetic filters for fluids containing ferro-magnetic particles. The last mentioned application is of particular value in filtering engine oils, machine tool coolants, and like fluids contaminated With paramagnetic particles.

The greatest pull of a magnet is at its poles, and this effect is used in loud speaker magnetos, mete-rs, etc., in which the force utilized is concentrated in a small air gap between the pole faces. Increasing the air gap, or the distance between the poles reduces the magnetic pull or attraction, but the pull at the poles themselves becomes greater. I find, however, that a considerable mass of relatively expensive magnetic alloy material is used unnecessarily, from the standpoint of economics.

The improvements disclosed herein overcome this economic loss. A plurality of small magnets having dimensions for operating at their peak efiiciency are arranged with their like poles in firm contact with common pole pieces of low retentivity mild steel, as illustrated in FIGS. 4 to 11 inclusive. The width length ratios of the individual magnets, such as the magnets 17, of FIG. 4, are preferably from 1 to 6 to 1 to 10, depending somewhat on the composition of the alloy of which they are composed. In the assembly, the pole pieces are magnetized with all the energy possessed by the individual magnets. Each pole piece acts as one end of a magnet with the combined flux of all the individual magnets and the assemblies are produced at much less cost than a single magnet having sufiicient attraction to replace them. It is important that all like poles firmly contact the pole pieces avoiding any air gap.

As magnets lose some of their individual efliciency when contacting one anothenespecially when like poles are brought together, therefore, the magnets of this invention are shielded by having means such as air gaps or non-magnetic material separating them, usually completely surrounding each individual magnet. The shielding must be the exact length of or very slightly shorter than the magnet to insure the firm contact of the magnets with the pole pieces. The shielding also helps to prevent demagnetizing of the magnets in the presence of strong fields or in contact with high retentivity steel.

When like poles of magnets are brought into contact with a common pole piece, the magnets lose their individual repelling characteristics, and all work together to form a large common pole. As the repelling action of groups of individual magnets is quite positive until A contact is made with the pole pieces, the magnets of this invention are usually assembled with their pole pieces and shields before magnetization of the alloy cores or individual magnets of high permeable paramagnetic material. After assembly, the entire unit is magnetized.

As an example illustrative of the saving enabled by applying the principles of my invention, I give the following example:

A magnet having a diameter of 10 mm. and a length mm. contacting pole pieces having a diameter of 80 mm. will have a more concentrated and evenly distributed flux than a magnet of twice the diameter and the same length, because the eificiency of the latter magnet should be that of 20 mm. X mm. But a single rod magnet of 20 mm. diameter and 160 mm. length contains 4 times the material of the 10 mm. x 80 mm. magnet. Two lengths of 10 mm. x 80 mm. magnets achieve the desired result with only one-fourth the magnet material of a 20 mm. x 160 mm. magnet. I find also that a very efiicient magnet assembly can be produced using individual magnets having diameters of 6 mm. and lengths of 48 mm.

What I claim is:

1. A magnet structure comprising a plurality of spaced apart elongated permanent magnets of like dimensions arranged symmetrically about an axis, each having a North pole and a South pole, like poles being aligned in the same axial direction to provide a common flux flow direction, each magnet comprising a rod and each being individually enclosed in a tube of non-ferrous, non-magnetic metal but being unshielded at the pole, a disc of paramagnetic material engaging each of the North poles and a disc of paramagnetic material engaging each of the South poles, a tube of non-ferrous, non-magnetic metal surrounding the series of magnets and a portion of each disc.

2. The structure as defined in claim 1, wherein the discs are larger than the tube which encloses the plurality of magnets each having an axial portion engaged by the tube surrounding the magnets.

References Cited in the file of this patent UNITED STATES PATENTS 318,058 Waite May 19, 1885 2,432,819 Schumacker Dec. 16, 1947 2,524,297 Quam Oct. 3, 1950 2,551,947 Hofl? May 8, 1951 2,587,299 Edgar Feb. 26, 1952 2,697,804 Phelon Dec. 21, 1954 2,749,486 Gould June 5, 1956 2,797,360 Rogers et al. June 25, 1957 2,822,528 Janssen et al. Feb. 4, 1958 FOREIGN PATENTS 299,264 Great Britain Oct. 25, 1928 386,732 Great Britain Jan. 26, 1933 287,480 Switzerland Apr, 1, 1953

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