US3409806A - Electromagnetic devices with great magnetomotive forces - Google Patents

Description

Nov. 5, 1968 ELECTROMAGNETIC DEVICES WITH GREAT MAGNETOMOTIVE FORCES Filed Oct. '14, 1965 6 Sheets-Sheet l 'Fig. 7

PRIOR ART Fig.2

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ELECTROMAGNETIC DEVICES WITH GREAT MAGNETOMOTIVE FORCES Filed Oct. 14, 1965 6 Sheets-Sheet 2 Fig. 4 34 W w 2 z: 3/ i I5 35 q :5

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M'ciaaf 7 0- M 6 Sheets-Sheet 4 L. FRITZ ELECTROMAGNETIC DEVICES WITH GREAT MAGNETOMOTIVE FORCES Nov. 5, 1968 Filed Oct. 14, 1965 INVENTOR LO/M-f Ff BY Mddd fiver AIR-7 Nov. 5, 1968 L. FRITZ 3,409,806

ELECTROMAGNETIC DEVICES WITH GREAT MAGNETOMOTIVE FORCES Filed Oct. 14, 1965 6 Sheets-Sheet 5 Fig. 72

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99 9a 99 95 X /'95 T "T E- X H I l I\ I I I PRIOR ART INVENTOR Lev/L0 F'Z'I'ZL BY ELECTROMAGNETIC DEVICES WITH GREAT MAGNETOMO'IIVE FORCES Filed Oct. 14, 1965 L. FRITZ Nov. 5, 1968 6 Sheets-Sheet 6 r R A R m R P R 01% mm W, mm 0 United States Patent 3,409,806 ELECTROMAGNETIC DEVICES WITH GREAT MAGNETOMOTIVE FORCES Lothar Fritz, Cologne-Braunsfeld, Germany, assignor to Steinert Elektromagnetbau, Cologne-Braun'sfeld, Germany Filed Oct. 14, 1965, Ser. No. 495,903 Claims priority, application Germany, Dec. 15, 1964, St 23,085 31 Claims. (Cl. 317-155.5)

ABSTRACT OF THE DISCLOSURE An electromagnet having main pole portions magnetically insulated from each other. The pole portions'are subdivided into a number of partial poles enclosing an auxiliary coil. The auxiliary coil and a principal coil generate the same polarity in each of these partial poles. The latter are connected by a bridge-member of low magnetic resistance, so that the pole face is enlarged. The resulting lines of magnetic force extend largely in a substantially perpendicular direction thereto. With the resulting enlargement of the pole face larger effective forces are realized for a given predetermined magnitude of current through the electromagnet.

The present invention relates to electromagnetic devices. More particularly, the invention relates to electromagnetic devices wherein a great portion of the total magnetic flux generated in the device is available for exerting a pulling or attracting effect upon a load to be lifted by such a magnetic device. The electromagnetic devices of the present invention include electromagnets of substantially cylindrical or a drum-like configuration having a circular cross-section of substantially constant diameter or different diameter circular cross-sections, an annular cross-section of substantially constant inner and outer diameters or different outer diameter annular crosssections. Also included are electromagnets of E-type configuration and various non-armature type electromagnets and electromagnets having various configurations and numbers of poles for various purposes such as, for example, magnetic separators, magnetic load lifters, protective magnets, overbar magnets and underbar magnets.

Generally, it is possible to increase the lifting power of an electromagnet by increasing the field strength or magnetomotive forces, that is the ampere turns, of the electromagnet. With a given pole system, increasing the field strength is possible only by increasing the flux produced by the excitation or magnetizing coils. To increase the flux produced by the magnetizing coils requires an increase in current supplied to such coils, so that current consumption increases. Increased current consumption increases the heat produced by the coils and leads to decreased current flow in said coils and a decrease in the magnetomotive force, field strength or magnetic potential. However, increasing the current requires additional energy, so that it would be more desirable to increase the lifting power of an electromagnet by increasing the effectiveness of the magnetic device, that is the ratio of the usefulfiux available for acting upon a load to be lifted to the total flux generated in the magnetic device.

In known electromagnetic devices, the pole portions are but a small part of the total magnetic surface, that is the entire area defined by the effective ferromagnetic pole faces and the areas located between these effective pole faces, due to the large area required for adequate windings for the magnetizing coils.

The principal object of the present invention is to provide new and improved electromagnetic devices.

3,409,806 Patented Nov. 5, 1968 Another important object of the present invention is to provide electromagnetic devices wherein a great proportion of the totally generated magnetic flux leaves or enters the effective faces of the pole portions in a direction normal to said effective pole faces.

.Another object of the present invention is to provide such electromagnetic devices which are inexpensive in operation.

Another object of the present invention is to provide such improved electromagnetic devices which are inexpensive in manufacture.

In accordance with the present invention, at least one pole portionis subdivided into a principal partial pole portion and at least one auxiliary partial pole portion associated therewith. The pole portions, subdivided or not, are spaced from each other, so that they are magnetically insulated from each other and that a magnetic potential difference may be established therebetween. Similarly, as a pole portion is subdivided into partial pole portions, the coil of excitation is likewise subdivided into a principal partial coil and an auxiliary partial coil. The principal coil with its cross-section is received between two neighboring pole portions, whereas the cross-section of the auxiliary coil is received between two neighboring partial poles. The auxiliary coil is wound and fed with current in such a manner, that both the principal and the associated auxiliary partial pole assume the same mag netic polarity. Furthermore, the end portions of said associated partial pole portions are connected by a suit? able bridge member of high magnetic conductivity having a surface extending in a common plane as determined by the effective pole faces of the bordering partial poles. Due to this, the effective magnetic pole face of the subdivided pole portion is largely increased. The identical polarity of both partial pole portions embracing the bridge member provides for the desired great proportion of flux components extending in a direction normal to the effective pole face of the subdivided pole portion.

In order that the invention may be readily carried into effect, it will now be described with reference to the accompanying drawings, wherein:

FIG. 1 is a schematic diagram of a two pole magnet of known type;

FIG. 2 is a schematic diagram, partly in section, of a three pole E-type electromagnet of known type; I

FIG. 3 is a schematic diagram, partly in section, ofan embodiment of a three pole E-type electromagnet of the present invention;

FIG. 4 is a view of the embodiment of FIG. 3 taken along the lines IVIV of FIG. 3; 7

FIG. 5 is a schematic diagram of an embodiment of a substantially cylindrical or drum-like electromagnet of the present invention;

FIG. 6 is a view of the embodiment of FIG. 5 taken along the lines VI--VI of FIG. 5;

FIG. 7 is a view of the embodiment of FIG. 5 taken along the lines VIIVII of FIG. 5;

FIG. 8 is a schematic diagram of a modification of the embodiment of FIG. 5;

FIG. 9 is a schematic diagram of another modification of the embodiment of FIG. 5;

FIG. 10 is a schematic diagram of still another modification of the embodiment of FIG. 5;

FIG. 11 is a schematic diagram, partly in section, of an embodiment of a combination substantially cylindrical and substantially annular electromagnet of the present invention;

FIG. 12 is a view of the embodiment of FIG. ll taken along the lines XII-XII of FIG. 11;

FIG. 13 is a sectional view of an electromagnet of known type of the type of FIGS. 11 and 12;

l4 is a view 13 taken along the lines XIV--XIV of FIG. 13;

FIG. 15 is a view of part of the core structure of the electromagnet of FIG. 13 and y I 7,

FIG. 16 is a view of part'ofthe core 'structure of 'an electromagnet of the type of FIG. 13 modified in accordance with the present invention' In the figures, the same components are identified bythe'sa'rne reference numerals; In each of the'electromagnets described hereinafter, the core structure compr'i'ses'pole portionsand an overbar, underbar or centerbar joining such pole portions, all preferably of ferromagnetic material. H y

'FIG'. 1 shows a two pole electromagnet of the prior art. As this is generally true with regard to anypairof pole portions, there is a critical area, in which the normal components of the magnetic induction are extremely weak. This area'corresponds to the hatched region as indicated above,vand at least one auxiliary excitation or magnetizing coil or winding is positioned in the subdivided pole portions. By means of such an auxiliary coil of excitation, pole portions are provided which produce controllable and variable .magnetomotive forces and, consequently,v acontrollable, distributionaof.magnetic ':potential along. the effective pole faces; the 'field distribution at the. effective faces of the pole portions being determined by the arrangement, positions and dimensions of the auxiliary coils. According tothe respective choice of auxiliary coils and according to the magnitude and direction of the current traveling through these auxiliary coils, the magneticforce 'lin'es entering and leaving the effective pole faces may becontrolled and varied in defined by the extensions of'the inner surfaces of the pole pieces 11, 12 '(which are connected through the underbar portion 13) and'by the common plane of the effective pole faces 14, 15 and there is a zone 16, indicated by broken lines, in this area in which the normal components of the lines of magnetic force approach and pass through zero. The defined area is thus the least effective one of the pole pair. There are n-l such areas for every n poles.

The pole portions 11 and 12 may be provided with pole shoes 17 and 18, respectively, indicated by broken lines. Although the pole shoes 17 and 18 serve to decrease the distance A between the opposing surfaces of the pole portions 11 and 12, they produce at the same time an additional stray flux between them which loads the magnetic circuit without providing a useful effect at the effective faces of the magnet. The pole shoes 17 and 18 thus lead to a greater loss of magnetic potential in the magnet itself. If a larger number of pole portions is utilized, to decrease the distance A, the pitch of the pole portions, that is the number of pole portions per length unit, is decreased, so that the resultant effect is only partially desirable. If the pole separation is too small, the resultant effect is quite undesirable.

FIG. 2 shows a three pole electromagnet, likewise of the prior art. The three pole electromagnet of FIG. 2 may be of substantially E-shaped configuration and comprises end pole portions 21 and 22 and a center pole portion 23 equidistantly spaced from each of the end pole portions. An underbar 24 joins the pole portions 21, 22 and 23. As may be seen, the pitch (corresponding to distance B) of this device is advantageous, but the distance A between adjacent pole portions is undesirably large, so that only a small proportion of the total magnetic pole area is constituted by the effective pole faces 26, 27, 28. An excitation or magnetizing coil 25 is positioned between the end pole portions 21 and 22 and around the center pole portion 23 and produces a magnetic force in the plane of the effective faces 26, 27 and 28, respectively, of the pole portions 21, 22 and 23. The magnetic potential prevailing along the magnetic pole face of the entire device has a distribution of substantially quadrilateral or trapezoidal configuration.

In accordance with the present invention, the effectiveness of an electromagnetic device is considerably increased by constructing the electromagnetic device with the greatest possible pole pitch B and the smallest possible distance A between opposing pole portion surfaces. The distance A between opposing pole portion surfaces approaches zero. The increase in magnetic force available at the effective pole faces as produced by the present invention is greater than about 40% relative to prior art devices.

Thus, in accordance with the present invention, at least one .pole portion of the electromagnet is enlarged to the maximum possible extent by subdividing the pole portion and providing it with a bridge member in the manner magnitude and direction. This possibility may be *expanded by associating a greater number of auxiliary: coils rather than one such coil with a subdivide pole portion.

In accordance with the present invention thedistance A between opposing pole portionsurfaces maytherefore be decreased, theoreticallythat is to the point where the effective faces .of the .pole portions are almost completely of ferromagnetic material, so that merely a minimum gap is left therebetween. In spite of such a small distance or gap, there would be no magnetic short-circuiting in the devices of the present invention, as would result in a magnet of the prior art of the type of FIG. 1 if the pole shoes 17 and 18 were to abuteach other, because in connection with this invention the lines of magnetic force are caused to extend in a direction substantially normal to the effective pole faces. a

It is thus seen that in the electromagnetic devices'of the present invention, the pole portions areenlarged neither at the expense of the space required for the coil of excitation nor does an additional loss of magnetic force or flux occur as in FIG. 1. If the coil space were decreased as -a result of the enlargement of the pole portions,- the' current supplied to the magnetizing coil would have to be increased in order to maintain the original magnetic force. An increase in energizing current would require not only additional energizing power, but moreover would raise the temperature of the device to a level at which the device would be deteriorated or even be destroyed.

In FIG. 3, the electromagnetic device is a three pole electromagnet of substantially E-type or 'E-shaped con" figuration, as is the electromagnet of FIG. 2. In accord ance with the present invention, however, the end pole portions 31 and 32 and the center pole portion 33 equidistantly spaced from each of the end pole portions each are subdivided into a principal partial pole portion 31a, 32a and an associated auxiliary partial pole portion 31b, 32b, 33b, 33c. Auxiliary excitation or magnetizing coils or windings 34 and 35 are received between adjacent partial pole portions 31a, b; 32a, b; 33a, b, c respectively, in accordance with the present invention. 1

The auxiliary winding 34 is positioned in the end pole portions 31 and 32 and the auxiliary winding 35 is positioned in the center pole portion 33. -An underbar 36 joins the pole portions 31, 32 and 33. The principal excitation or magnetizing coil 37 is positioned between the end pole portions 31 and 32 and around the center pole portion 33. The partial pole portions belonging to one common pole portion each are connected by a bridge member of high magnetic conductivity, which in case of the embodiment of FIG. 3 is formed as a flat plate 31', 32', 33', and 33". As a result, the effective ferromagnetic pole face of the individual subdivided pole portions is considerably increased. Neighboring cross-sections of the coils, as the cross-sections of the coils'34, 35, 37 in the left region of FIG. 3 on the one hand andin the right region of FIG. 3, on the other hand each apply the same magnetic polarity to partial pole portions belong-. ing to one common pole portion. If the current supplied to the individual coils 34, 35, or 37 is varied in magnitude and direction, the magnetic field strength present at the effective pole faces may be controlled correspondingly.

Due to the enlargement of the pole portions 31, 32 and 33 of the electromagnet of FIG. 3 by means of subdividing the pole portions and providing the magnetic bridge members 31', 32, 33" and due to the positioning of the auxiliary magnetizing coils 34 and 35 in the pole portions 31, 32 and 33 of said electromagnet, the distance A between opposing pole portion surfaces is decreased to a minimum without loss of energy, for example due to additional stray flux, whereas the .pole pitch B may be maintained at a maximum. The total magnetic force produced by the electromagnet of FIG. 3 is, of course, the sum of the magnetic forces produced by each of the principal magnetizing coil 37 and the auxiliary magnetizing coils 34 and 35.

The electromagnet of FIG. 3 utilizes about the same amount of material as the electromagnet of FIG. 2 and consumes about the same amount of power, but produces a considerably greater amount of field strength available at the effective faces of the pole pontions for attracting a load or the like. The effective ferromagnetic faces of the end pole portions 31 and 32 are 38 and 39, respectively, and the effective ferromagnetic face of the center pole portion 33 is 41.

In each of the devices of the present invention, the pole portions and connecting bars are all of any suitable material such as, for example, ferromagnetic material.

In the end areas of the pole portions 31, 32 of FIG. 3, the direction of the line of magnetic force is substantially the same as in the corresponding effective end faces 26, 27 of FIG. 2, indicated by arrows C and F. The same holds true for the central area of the center pole portion 33 of FIG. 3 and the center pole portion 23 of FIG. 2, as indicated by arrows G.

However, a significant difference can be observed within the area extending between pole portions 21, 23, 22 of FIG. 2 and the area of FIG. 3 defined between pole portions 31, 33, or 32 respectively. In FIG. 2, as indicated by arrows D and E, in these particular areas A the lines of the magnetic field strength extend in a substantially tangential direction, so that in this area the field strength may not exert any pulling effect upon a load to be attracted.

In the embodiment of FIG. 3, the corresponding area A, in which the lines of force, as represented by arrows D and E, extend tangentially is considerably reduced. In the remaining area, by which the distance A of FIG. 3 is reduced in comparison with the distance A of FIG. 2, the force lines extend as shown by arrows H, I and I, K. i.e. substantially normal to the effective pole faces 38, 39, or 41, respectively. 7

Due to this arrangement according to the invention, with the field strength or flux in the electromagnet of FIG. 3 being only 86% of that usual in this type of device, the magnetic pulling force of an electromagnet in compliance with the invention, could be increased by 38%.

The electromagnet of FIG. 3 may be modified by providing a narrow gap, slit or recess in the bridge section of the effective face of each of the pole portions extending into the area housing the auxiliary coil positioned therein. Such gaps are shown in FIG. 5 and thereafter. In the electromagnet of FIG. 3, the gaps, indicated in broken lines, are substantially perpendicular to the plane through the effective faces of the pole portions. The gaps cause a step-like raise of the magnetic potential at the effective pole faces, so that the distribution of the potential is not of trapezoidal configuration but that of a number of superimposed trapezoids, the number of superimposed trapezoids corresponding to the number of gaps. If a gap is provided for each of the pole portions, the effectiveness of the electromagnet is increased still further.

FIGS. 5, 6 and 7 are views of another embodiment of the present invention. The embodiment of FIGS. 5, 6 and 7 is of substantially cylindrical or drum-like configuration, the cross-section of the electromagnet being of substantially circular configuration with a constant diameter for each of the pole portions and for the portion supporting the principal magnetizing coils. The portion supporting the principal magnetizing coil has a smaller diameter than the pole portions.

The electromagnet of FIGS. 5, 6 and 7 comprises end pole portions 51 and 52 and a center pole portion 53 equidistantly spaced from each of the end pole portions. A centerbar 54 (FIGS. '6 and 7) joins the pole portions 51, 52 and 53. A pair of principal excitation or magnetizing coils or windings 55 and 56 are coaxially positioned on the centerbar 54 between the center pole portion 53 and the end pole portion 51 and the end pole portion 52, respectively.

In accordance with the present invention, the end pole portions 51 and 52 and the center pole portion 53 are enlarged in a similar manner as the pole portion of FIG. 3. Likewise, an auxiliary excitation or magnetizing coil or winding 57 is positioned in the end pole portion 51 between principal partial pole portions 510 and associated auxiliary partial pole portion 51b, an auxiliary magnetizing coil 58 is positioned in the end pole portion 52 between principal partial pole portion 52a and associated auxiliary partial pole portion 52b, and auxiliary magnetizing coils 59, 61, 62 and 63 are positioned in spaced relation from each other in the center pole portion 53 between principal partial pole portion 53a and associated auxiliary partial pole portions 5312, c, d, e, respectively. Each of the auxiliary magnetizing windings is coaxially positioned on the centerbar 54. As the ends of the partial pole portion of the common pole portions of FIG. 3 are connected by the plate- like bridge members 31', 32, 33', 33", the ends of the disc-like or annular partial poles of FIG. 6 are connected by ring- like walls 51, 52', 53, 53", 53', and 53"", having the same function as the platelike bridge members 31', 32', 33', 33". The outer cylindrical surfaces of these walls again extend in the same planes as the effective pole faces of the auxiliary and principal partial pole portions and contribute to the effective ferromagnetic pole face, without causing any additional loss of flux, because the principal and the auxiliary coils associated with each other are again polarized in such a manner, that both pole portion ends connected by a wall are of the same magnetic polarity, thereby ensuring substantially normal direction of the lines of forces with regard to the effective pole faces defined by the end faces of the partial poles and the bridge member connected therebetween.

A plurality of narrow annular gaps, slits or recesses may be provided in the pole portions extending from the effective face of each of the pole portions into the area housing the auxiliary coil positioned therein. The gaps are in a plane substantially perpendicular to the axis of centerbar 54 which is the axis of the electromagnet. A gap 64 is provided in the end pole portion 51, a gap 65 is provided in the end pole portion 52 and gaps 66, 67, 68 and 69 are provided in spaced relation from each other in the center pole portion 53, each of said last mentioned gaps being associated with one of the auxiliary coils 59, 61, 62, 63.

The auxiliary magnetizing coils 59, 61, 62 and 63 are arranged, positioned and dimensioned to provide the same polarity to the entire effective face of the center pole portion 53. Such same polarity is provided regardless of the polarity of the magnetic circuit, and with the cooperation of the principal magnetizing coils 55 and 56 and the auxiliary magnetizing coils 57 and 58. The auxiliary coils 57 and 58 in the end pole portions 51 and 52, respectively, influence the magnetic force distribution or pattern at the effective face of the center pole portion 53 and the flux pattern in the interior of the magnet.

The auxiliary magnetizing coils of the end pole portions are arranged, positioned and dimensioned to provide to the entire effective face of each of the end pole portions 51 and 52 the opposite polarity from that of the effective face of the center pole portion 53 and influence the mag- 7 n'etic force distribution or pattern at said end pole porisn f e j.)

' The gaps 64, 65, 66, 67, 68'and 69 infliience th'e distribution of the magnetic potential at'the o uter surface of the device in a similar manner as described'in connection with the gaps in the elfectivepolefaces 38 39, 41 of FIG. 3. They maybe closed byfdiainagnetic aterial. Although each gap may be positioned 'anywher ebetween the axialends of the auxiliary magnetizing coil with which it is associated, it is preferable t o position the auxiliary coils and their corresponding gaps symmetrically a boufa plane perpendicular'to theaxis of 'ithe unit at 'the center oflsaid,axisequidistarit from the axial ends ofthe unit (1 16.10); The gaps may "be of any desired, suitable configuration, such as, for examplefs'traigflit;curved or ofzig-zag configuration. i W

, The excitation current preferably supplied to the principal magnetizing coils andthe auxiliary magnetizing coil s byany suitable known slip ring a range eager the like? as indic ated for example in FIG. 8, may be varied during the operation of the electromagnetic device. The excitation current maybe varied by lnyfsuitable means such as, for example, a variable resistor connected between the source of electrical power and the slip rings. (FIG. 8.)

FIGS. 8, 9 and are modifications of the embodiment of FIGS. 5, 6 and 7. FIGS. 8 and 9 illustrate that any desired suitable number n of auxiliary magnetizing coils may be positioned in the pole portions and are arranged, positioned and dimensioned in a manner whereb they cooperate with the principal magnetizing coils to provide the same polarity to the entire effective face of a pole portion and in a manner whereby they influence the distribution of the magnetic potential at the effective face of each pole portion and the fiux pattern'in the interior of the magnet.

The end pole portions may be neutral and thus devoid of auxiliary magnetizing coils or windings, as shown in FIGS. 8, 9 and 10, or any desired suitable number of auxiliary coils may be positioned in the end pole portions and arranged, positioned and dimensioned so that the resultant of their magnetomotive force is zero. A different structure from that utilizing a center pole portion and two end pole portions may be utilized. Any desired suitable number of principal magnetizing coils may be utilized and the current supplied to each may be varied in magnitude. Any desired suitable number of auxiliary magnetizing coils may be positioned in a pole piece.

FIG. 11 is a schematic diagram, partly in section, of an embodiment of a combination substantiallycylindrical and substantially annular electromagnet of the present inventionThe embodiment of FIG. ll utilizes an overbar 71. The cross-section of the electromagnet of,FIG. 11 is of substantial circular configuration surrounded by substantially annular configuration with an annular space between such configurations. The three pole electromagnet of FIG. 11 comprises any suitable material such. as, for example, ferromagnetic material as do the other embodiments of the present invention. The center poleportion has a substantially circular cross-sectionand the end pole portions have a substantially annular. cross-section.

The electromagnet of FIGS. 11 and 12 comprises an annular end pole portion 72, 73 and a center pole portion 74 equiradially spaced from the end pole portion. The overbar 71 joins the pole portions 72, 73 and 74. The unit is symmetrical about its axis 75. A principal excitation or magnetizing coil or winding 76 is coaxiallypositioned between the center pole portion 74 and the end pole portion 72, 73. In accordance with the present invention, the end pole portion 72, 73 and the center pole portion 74 again are subdivided into principal and associated auxiliary partial pole portions. End pole portion 72, 73 is subdivided into the outer principal partial pole portion 72a, 73a and the inner auxiliary partial pole portion 72b, 73b. Center pole portion 74 is subdivided int the princ ipal partial pole port'ion and the annnlar an liary partial'pole portion Q7411, c concentrically sur rounding the'central principal"partia1 pole portion 744. An annular auxiliary magnetizing coil 77 is positioned in th e endpoleportion'72, 73 and auxiliary magnetizing coils are positioned spaced relation from each other iii the g'enter pole portion 74' and concentrically therewith. The ends of associated partial pole portions againare joined bylb'ridge fnernbers 72', 73 74',74',' of high mag-. netic condrictivity and, in this embodiment; of annular configuration. By em of these interconnected rings, the effective pole faces of pole portions 72', 73, 74, respectively, again are largely in cgeasedwithout causing any additional loss of magneticfiux, since thelinels, of force extendin a, Substantialy normal direction witli re g ard to the'eifective pole faces, due to the equal rnagnetic polarity ofthepartial p'ole portions of one common ormain pole r rti -fl plurality of annular gaps similar to those of the other embodiments of the present invention are provided. A gap 81 is provided in the bridge member 72', 73 of the end pole portion 72', 73 and annular gaps 82 and 83 are provided in 'spacedrelation from each other in each of the annular bridge members 74', 74" of the center pole portiori 74.

Electromagnets of various configurations and for various purposes such as, for example, magnetic separators, magnetic load lifters, protective magnets, non-armature magnets other than those indicated, overbar magnets, underbar magnets, centerbar magnets and others may be constructed inaccordancewith the present invention to considerably increase the proportion of the. effective flux in the total fiux produced. The auxiliary excitation or magnetizingcoils maybe coaxially, axially, radially or otherwise positioned in the electromagnet unit.

FIG. 13 shows an electromagnet of known type of the type of FIG. '11 or of the type of FIG. 3. Theelectromagnet is designed to lift a load 91 which maycomprise, for example, asteel plate, which may function as an armature of the electromagnet. An overbar 98 joins the, pole portions and 96. An excitation or magnetizing winding or coil 99. is, positioned between the. center poleportion 96 andth e end pole, portion 95, coaxially with said pole portions. The center pole portion 96 is ,equiradially spaced from the end poleportion 95. i i v I n'the areas beneath the, effective, faces 93 and 94 of the'. pole portions, the normal component lines of the magnetic field are relatively large in magnitude and number whereas inthe areas b etween the center pole portion '96 andtheendpoleoportion,95, the lines of the magnetic. field are. relatively small in magnitude and number. As shown in FIG. 15, the field lines reverse themselves indirection about a broken line 101, so that theproportion of nor'inal components of the flux amounts toabout z ero., The. only exception are the corners of the substantially annular effective face because the edges of the pole portions exert a considerable influence at such corners. .7 I I In a load-lifting magnet of the type of FIG. 13, the ratio of-the effective faces'of the pole portions to the total surfaces ofsthe pole portions is usually about 0.35 or less. The substantially annular effective face 93' of the end'pole portion 95 which comprises approximately 65% the effective faces of the pole'portion contributes a niaximum of only about 10% to'the total pulling force of lifting power of the electromagnet;

"As lfereiribefore'd'escribed 'with reference'to the other embodiments of the presentinventiorij the magnetic force of the magnet is considerably increased by v the enlargement ofthe pole portions in the manner explained and the'positioningbfauxiliarymagnetizing coils therein in such positions, arrangements and of 'suchdiniension's that they'ip'rovide' the same polarity as"theprincipal'magnetip ing co'il although there is a difference in magnetic poten ,9 tial between the principal and the auxiliary partial pole portions.

FIG. 16 shows a part of the core structure of an electromagnet of the type of FIG. 13, modified in accordance with the present invention to include an auxiliary partial pole portion associated with principal pole portion 96'a and .an auxiliary magnetizing coil in the center pole portion 96. The auxiliary magnetizing coil is not shown in FIG. 16 in order to preserve the clarity of illustration of the magnetic field lines. In compliance with the principle of this invention, the ends of partial pole portions 96'a, b, which are remote from an overbar 98' joining these portions, are connected through a bridge member 96" which here is of annular configuration. As a result, a recess or housing 102 is formed, which is of substantially annular cross section. A gap 103, of the type described with reference to the hereinbefore described embodiments of the present invention, may be provided in the bridge member 96" extending from the housing 102 to, and opening from, the effective face 94' of said center pole portion.

The corner pattern or distribution of the magnetic field lines is not changed in the embodiment of FIG. 16 in comparison with FIG. 15. However, in FIG. 15, the field lines leaving the overbar 98 overcome the diamagnetic area between said overbar and the load 91 and close through the remaining ferromagnetic circuit. The field lines reverse themselves in direction about the line 101 in FIG. 15. In FIG. 16, the provision of the auxiliary partial pole portion 96a reduces the magnetic resistance of the magnetic circuit, so that the magnetic field strength at the effective face 94' may be considerably increased, whereas by provision of bridge member 96" the effective pole face itself is increased. The auxiliary coil (not shown), the cross section of which is received in housing 102, and the principal coil (not shown) arranged in the space between pole portions 95' and 96' are associated with each other in such a manner, that the ends of auxiliary and principal partial pole portions 9'6a and 96b both have the same magnetic potential, thereby again causing the lines of force to extend in a direction substantially normal with respect to the effective pole face 94'. In the embodiment of FIG. 16, the ratio of the effective faces93', 94 of the pole portions to the total pole surface of the magnetic device may be made about 0.6 5 rather than 0.35 as explained in conjunction with regard to FIG. 15.

While the invention has been described by means of specific examples and in specific embodiments, I do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from the spirit and scope of the invention.

What I claim is: 1. An electromagnetic device, comprising a first pole portion having an effective face; a second pole portion having an effective face spaced from said other face; a core structure joining said first and second pole portions; a principal magnetizing coil positioned on said core structure between said first and second pole portions; one of said first and second pole portions having a recess formed therein; an auxiliary magnetizing coil positioned in the recess formed in' said one of said first and second pole portions; and a gap formed in said one of said first and second pole portions extending from the recess to the effective face of the said one of said first and second pole portions forincreasing the magnetic force at said effective face. 2. An electromagnetic device, comprising ,a first pole portion having an effective face;

a second pole portion having an effective face spaced from said other face;

a core structure joining said first and second pole portions;

a principal magnetizing coil positioned on said core structure between said first and second pole portions;

each of said first and second pole portions having a recess formed therein;

an auxiliary magnetizing coil positioned in the recess formed in each of said first and second pole portions; and

a gap formed in each of said first and second pole portions extending from the recess thereof to the effective face thereof for increasing the magnetic force at the effective face thereof.

3. An electromagnetic device as claimed in claim 2, wherein each of said gaps is of substantially narrow slitlike configuration.

4. An electromagnetic device as claimed in claim 2, further comprising means comprising diamagnetic material closing each of said gaps.

5. An electromagnetic device comprising a center pole portion having a substantially cylindrical effective face, said center pole portion having a plurality of annular recesses formed therein; a pair of end pole portions coaxially positioned with said center pole portion and equidistantly spaced from said center pole portion, each of said end pole portions having a substantially cylindrical effective face; a core structure joining said center and end pole portions; a pair of principal magnetizing coils each coaxially positioned between said center pole portions and a corresponding one of said end pole portions; and an auxiliary magnetizing coil positioned in each recess formed in said center pole portion.

6. An electromagnetic device, comprising a center pole portion having a substantially cylindrical effective face, said center pole portion having a plurality of coaxial substantially annular recesses formed therein; a pair of end pole portions coaxially positioned with said center pole portion and equidistantly spaced from said center pole portion, each of said end pole portions having a coaxial substantially annular recess formed therein and each having a substantially cylindrical effective face; a core structure joining said center and said pole portions; a pair of principal magnetizing coils each coaxially positioned between said center pole portions and a corresponding one of said end pole portions; and an auxiliary magnetizing coil positioned in each recess formed in said pole portions.

7. An electromagnetic device, comprising a center pole portion having a substantially cylindrical effective face, said center pole portion having a plurality of coaxial substantially annular recesses formed therein; a pair of end pole portions coaxially positioned with said center pole portion and equidistantly spaced from said center pole portion, each of said end pole portions having a coaxial substantially annular recess forrned therein and each having a substantially cylindrical effective face; a core structure joining said center and end pole portions; a pair of principal magnetizing coils each coaxially positioned between said center pole portions and a corresponding one of said end pole portions; an auxiliary magnetizing coil positioned in each recess formed in said center pole portion; and a gap formed in each of said pole portions extending from the recess thereof to the effective face thereof for increasing the magnetomotive force at the effective face thereof.

8. An electromagnetic device, comprising a center pole portion having a substantially cylindrical effective face, said center pole portion having a plurality of coaxial substantially annular recesses formed therein; a pair of end pole portions coaxially positioned with said center pole portion and equidistantly spaced from said center pole portion, each of said end pole portions having a coaxial substantially annular recess formed therein and each having a substantially cylindrical effective face; a core structure joining said center and end pole portions; a pair of principal magnetizing coils each coaxially positioned between said center pole portions and a corresponding one of said end pole portions; an auxiliary magnetizing coil positioned in each recess formed in said center pole portion; a gap formed in each of said pole portions extending from the recess thereof to the effective face thereof for increasing the magnetomotive force atthe effective face thereof; electrical power supply means for supplying current to said principal and auxiliary magnetizing coils; and means connected between said power supply means and said magnetizing coils for varying the magnitude current supplied to said coils. I

9. An electromagnetic device, comprising a center pole portion having a substantially cylindrical effective face, said center pole portion having a plurality of coaxial substantially annular recesses formed therein; a pair of end' pole portions coaxially positioned with said center pole portion and equidistantly spaced from said center pole portion, each of said end pole portions having a coaxial substantially annular recess formed therein and each having a substantially cylindrical effective face; a core structure joining said center and end pole portions; a pair of principal magnetizing coils each coaxially positioned between said center pole portions and a corresponding one of said end pole portions; an auxiliary magnetizing coil positioned in each recess formed in said center pole portion; and a gap formed in each of said pole portions extending from the recess thereof to the effective face thereof for increasing the magnetomotive force at the effective face thereof, each of said center and end pole portions having the same polarity over its entire effective face.

10. An electromagnetic device of substantially Etype configuration, comprising a center pole portion having a recess formed therein;

a pair of end pole portions equidistantly spaced from said center pole portion;

a core structure joining said center and end pole portions;

a principal magnetizing coil positioned around said center pole portion between said center pole portion and said end pole portions; and

an auxiliary magnetizing coil positioned in the recess formed in said center pole portion and assisting said principal magnetizing coil in providing a corresponding polarity for each of said pole portions.

11. An electromagnetic device as claimed in claim 10, wherein each of said end pole portions has a recess formed therein and further comprising an auxiliary magnetizing coil positioned in said recess and assisting said principal magnetizing coil in providing a correspondng polarity for each of said pole portions.

12. An electromagnetic device, comprising a substantially cylindrical center pole portion having a substantially annular recess formed therein;

a substantially annular end pole portion coaxially positioned around and spaced from said center pole portion;

a core structure joining said center and end pole portions;

a principal magnetizing coil coaxially positioned around said center pole portion between said center pole portion and said end pole portions; and

an auxiliary magnetizing coil positioned in the recess formed in said center pole portion and assisting said principal magnetizing coil in providing a corresponding polarity for each of said pole portions;

13. An electromagnetic device as claimed in claim 12, wherein said end pole portion has a substantially annular recess formed therein and further comprising an auxiliary magnetizing coil positioned in said recess and assisting said principal magnetizing coil in providing a corresponding polarity for each of said pole portions.

14. An electromagnetic device having a ferromagnetic housing including main pole portions with ferromagnetic effective pole faces magnetically insulated from each other, said device comprising at least one principal partial pole portion having an effective pole face and at least one auxiliary partial pole portion having an effective pole face and associated with said principal partial pole portion in spaced apart relationship, said principal partial pole portion and said auxiliary partial pole portion constituting togetherone of said main pole portions; at least one principal coil of excitation the cross section of which is received between two adjacent main pole portions; at least one auxiliary coil of excitation the cross section of which is received between said associated principal and auxiliary partial pole portions; means of unlimitedly low magnetic resistance interconnected between and in the common plane of the equally polarized pole faces of said principal and saidauxiliary partial pole portions for enlarging'the total ferromagnetic effective pole surface of said main pole portion composed of said partial poles; said principal and said auxiliary coils being associated with each other in such amanner, that the effective pole faces of both said principal and said associated auxiliary partial pole portion are of' the same magnetic polarity, so as to cause thelines of magnetic force to extend ina direction substantially normal with respect to said en-' larged effective pole faces.

15. An electromagnetic device according to claim 14, wherein said ferromagnetic housing is E-shaped and said means of low magnetic resistance is a pole plate (31; 32'; 33', 33"; 96") having a width corresponding to the distance between associated adjacent partial poles.

16. An electromagnetic device according to claim 15, wherein said pole plate (31'; 32; 33', 33"; 96") is provided with a gap.

17. An electromagnetic device according to claim 16, wherein said gap is of narrow, substantially slit-like configuration.

18. An electromagnetic device according to claim 16, wherein said gap is filled with a diamagnetic material.

19. An electromagnetic device according to claim 14, wherein said auxiliary coils are of different cross sections.

20. An electromagnetic device according to claim 14, wherein means are provided for controlling the current through said principal coil and through said at least one auxiliary coil independentlyof each other.

21. An electromagnetic device according to claim -14, having more than one auxiliary coil, comprising further means for varying the currents through each of said auxiliary coils independently of each other in magnitude and/ or direction.

22. An electromagnetic device according to claim 14, wherein said device is of substantially cylindrical configuration with said pole portions forming cylindrical rings, said means of low magnetic resistance being annular walls (51', 52', 53', 53*") made of ferromagnetic material and interconnected between the end portions of partial pole portions (51a, 51b; 52a, 52b; 53ae) forming one main pole portion (51, 52, 53) and said principal (55, 56) and said auxiliary (57, 58, 59, 61, 62, 63-) coils interposed between adjacent main pole portions (51, 52, 53) and adjacent partial pole portions (51a, b; 53c, 11, a, d, e; 52b, a), respectively, in coaxial relationship with said cylindrical pole portions.

23. An electromagnetic device as set forth in claim 22, wherein auxiliary coils associated with end pole portions (51, 52) of said device are of such polarity and size, that the sum of the ampere turns effective at said end pole portions substantially equals zero.

24. An electromagnetic device as claimed in claim 22, wherein at least one of said annular walls is provided with a circumferential gap (64-69).

25. An electromagnetic device according to claim 24, wherein said gaps (64-69) are filled with a diamagnetic material.

26. An electromagnetic device according toclaim 22, comprising slip rings and means for slidingly contracting said slip rings during rotation of said cylindrical electro- 13 magnetic device for electrically connecting at least one of said coils to suitable electrical power supply means.

27. An electromagnetic device as claimed in claim 26, comprising means for varying the magnitude and/ or directicn of the current supplied to said coils.

28. An electromagnetic device according to claim 22, comprising further auxiliary coils (61, 62) positioned between auxiliary coils (59, 63) associated with neighboring rprincipal coils (55, 56) and substantially coaxially therewith.

29. An electromagnetic device according to claim 14, wherein said electromagnetic device is of pot-like shape, said principal coil having an annular configuration and being positioned between an inner central cylindrical main pole portion (74) and an outer annular main pole portion (72, 73) concentrical with said inner main pole portion, said auxiliary coils Ibeing positioned at opposite sides of said principal coil (76) and substantially concentrical therewith between associated partial pole portions.

30. An electromagnetic device according to claim 29, wherein said inner rmain pole portion (74) is constituted by an inner cylindrical principal partial pole portion (74a) and at least one outer annular auxiliary partial pole portion (74b, 74c) concentrical with and spaced apart from said inner partial pole portion (74a), said outer main pole portion being constituted by an outer annular principal partial pole portion (72a, 73a) and an inner annular auxiliary partial pole portion (72b, 73b) concentrical with and spaced apart from said outer partial pole portion (72a, 73a), said means of low magnetic resistance being formed by annular plates (72', 73, 74', 74-") extending and interconnected between associated partial pole portions (72a, 72b; 73a, 73b; 74a, 74b, 74c), respectively.

31. An electromagnetic device according to claim 30, wherein annular gaps (81, 82) are provided in said annular plates (72, 73', 74', 74").

References Cited UNITED STATES PATENTS 1,199,921 10/1916 Poth 335--291 X 1,199,947 10/1916 Walker et a1. 335289 X 1,647,951 11/1927 Bing 335289 GEORGE HARRIS, Primary Examiner.

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