US2393439A - Method of making laminated cores for transformers - Google Patents

Method of making laminated cores for transformers Download PDF

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US2393439A
US2393439A US485942A US48594243A US2393439A US 2393439 A US2393439 A US 2393439A US 485942 A US485942 A US 485942A US 48594243 A US48594243 A US 48594243A US 2393439 A US2393439 A US 2393439A
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core
convolutions
portions
weld
welds
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Herbert E White
William H Borst
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00Details of transformers or inductances, in general
    • H01F27/24Magnetic cores
    • H01F27/25Magnetic cores made from strips or ribbons
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0206Manufacturing of magnetic cores by mechanical means
    • H01F41/0233Manufacturing of magnetic circuits made from sheets
    • H01F41/024Manufacturing of magnetic circuits made from deformed sheets
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00Metal working
    • Y10T29/49Method of mechanical manufacture
    • Y10T29/49002Electrical device making
    • Y10T29/4902Electromagnet, transformer or inductor
    • Y10T29/49073Electromagnet, transformer or inductor by assembling coil and core
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00Metal working
    • Y10T29/49Method of mechanical manufacture
    • Y10T29/49002Electrical device making
    • Y10T29/4902Electromagnet, transformer or inductor
    • Y10T29/49075Electromagnet, transformer or inductor including permanent magnet or core
    • Y10T29/49078Laminated

Definitions

  • Patented 'Jan. 22, 1946 METHOD OF MAKING LAMINATED COBES FOR TRANSFORMERS Herbert E. White, Cleveland Heights, Ohio, and
  • Our invention relates to transformers and the method of making them, and more particularly to transformer cores and the method of making and assembling them with coils to form transformers.
  • An object of our invention is to provide a new method for making a core for a transformer.
  • Another object of our invention is to provide a new method of assembling a core to form a trans-' former
  • a further object of our invention is to provide a new and improved core for a transformer which facilitates assembly and makes possible rapid completion of winding the strip a plurality of times about the mandrel.
  • Figure 3 shows the third step of welding together the successive convolutions of the magnetic material.
  • Figure 4 shows the wound and welded core after it has been cut into two pieces.
  • Figure 5 shows the core after the coils have been put in place and the two pieces of core connected together.
  • Figure 6 is a side view of Figure 5.
  • FIG. 7 shows another form of our invention.
  • FIG 8 shows still another form of our invention.
  • Figure 1 we show a mandrel III which has a slot II extending along one side thereof. Positioned in the slot is one end 9 of a long strip of magnetic material I! which is suitable for making transformer cores. A convenient material thickness for some transformers is one the order of .020 inch thick.
  • the magnetic strip material may be oxidized, or it may have a layer of lacquer or other insulating material on it. After the end of I the strip I2 is placed in the slot, the material is bent and several complete turns of the material 12 about the mandrel are made. Tension is maintained on the strip material l2 in order to assure that the successive convolutions. will be tight against the previous ones.
  • the strip material l2 can be fed from a reel (not shown) and suitable tensioning means can be provided to assure a suitably compact core. Due to the oxide, lacquer, or other insulating material which is on the magnetic strip l2, there will be a thin layer of insulation between the successive convolutions.
  • Figure 2 illustrates the core after the desired thickness has been obtained by making numerous turns of the strip material I! about the mandrel it. While tension is maintained on the loose end of the strip material I 2, and before the mandrel is removed from the shaft II, the successive convolutions are fixed together to prevent them from slipping with respect to each other, particular care being exercised to connect the outermost convolution to the one which is underneath it.
  • the welds II and H are preferably adjacent the cut ends of the core portion 20 and prevent the convolutions from slipping with respect to each other.
  • the mandrel can be removed from inside the core portions and 2
  • other holding means which do not leave this bent end to be disposed of may be used. It is also possible to saw through the magnetic material at two places without cutting the mandrel III in two, thereby saving it for further use.
  • Previously formed primary and secondary coils 22 and 24 comprised of many turns of fine wire may then be slipped onto the legs of one of the core portions, for instance, portion 20.
  • Insulating means l4 may be placed between the core and the coils.
  • Figure 5 illustrates two such means.
  • a slight air gap 21 may result but this may be advantageous in some types of transformers, such as are welding transformers, and the size of the gap may be controlled by inserting a magnetic non-conductor of desired thickness between the ends of the core portions before they are connected together.
  • FIG. 7 illustrates another form of our invention in which the two spaced welds I! and It were replaced by a single weld ll, and the two spaced welds l1 and
  • the core was then cut into the two core portions 20, 2
  • the two resulting portions are shown moved apart. Due to the width of the welds 2
  • weld area The space between the left edge of weld ll (Fig. 3) and the right edge of weld It, and the area of the weld 30 (Fig. 7) may be termed the weld area" and the core should be cut in two through a weld area on each side of the core because each of the two horseshoe-shaped core portions remaining after the cut will then have a welded portion which keeps the laminations of the core portion together. While it is preferable that the weld area" not extend over a great length of the circumference of the core it is possible that the welds, such as welds II, I, be separated by considerable distance so long as the welds defining the spread apart "weld area" enclose only the straight legs of the core. Thus when the core is cut into two portions there is no tendency oropportunity for the laminations to spread apart.
  • Figure 7 further illustrates how the core portion 20 is wound with a coil, in case a. pre-formed coil is not used.
  • the core portion is mounted in two caps, 34, and II, which are designed to hold th two out ends of the core portion. From each cap 34, 35 there is a bent arm I, 31; the arm 21 terminating in a fixed bearing ll, and the arm I being mounted in a bearing 40 and being connected to a motor I! which is adapted to rotate the arm 36 thereby rotating the core 2
  • the arms 86, II are bent in a direction such, and are just long enough, that the axis of rotation of the system extending through the bearings 38, ill passes through substantially the center of the core portion 2
  • supplies wire 42 which is wound about the core portion 20 to form a coil 43.
  • FIG 8 illustrates another form of invention in which the convolutions are held together by bolts and nuts 33 instead of by welding.
  • the mandrel l0 about which the magnetic strip material is wound can be any shape, such as round, oval, square, oblong, etc.; and may be made of any material. We prefer to use wood as it is inexpensive and easy to saw through.
  • the method of making a transformer comprised of a core and coil means about said core comprises the steps of: spirally winding a length of flat magnetic material to establish a core having a plurality of convolutions and forming a closed magnetic path, welding said includes said straight side portions, and then connecting said two core portions together to reform substantially theoriginal core.
  • the method of making a transformer comprised of a core and coil means about said core which comprises the steps of providing a length of flat magnetic core material, spirally winding said flat core material to establish a core having a number of convolutions which define a closed magnetic path, applying a plurality of weld means across the convolutions on only one end face of the said core for connecting the said convolutions together, cutting through said core and through said weld means thereby severing said core into at least two portions each having weld means adjacent its severed ends, applying coil means eonvolutions together in a direction across said convolutions, cutting through said core and through said weld to establish two separate core portions, the width of said weld being sufficiently greater than the width of the cut that each core portion includes an end portion having a portion of the weld whereby the positions of the severed convolutions with respect to each other in each of said separate core portions is maintained. applying coil means about at least one of said two coreportions, and then connecting said two core portions together to reform substantially the
  • the method of making a transformer comprised of score and coil means about said core comprises the steps of: spirally winding a length of flat magnetic material to establish a closed magnetic path cor'e having a plurality of eonvolutions and having two rounded portions with straight side portions therebetween, welding said convolutions together in a direction across said convolutions and subaantially at one of the junctions between a curved portion and the straight side portions, cutting through said weld to establish twosellarate dis-similar core portions one of which includes substantially all of said straight side portions, the width of said 7 weld being suiiiciently greater thanthe width of said out that each of said core portions includes an end portion having a portion of the weld whereby the positions of the severed convolutions with respect to each other in each of said separate core portions is maintained, applyingcoilmeanstothesaidcoreportionwhich to at least one portion of said core means. vand connecting said at least two core portions together by welding over and along the said welds which are adjacent the said severed ends
  • a transformer comprised of a core and coil means about said core. which comprises the stepsof: spirally winding a length of flat magnetic material to establish a core having a plurality of convolutions and forming a clwed magnetic path, connecting each of the said convolutions to its next adjacent convolution by welding'across said convolutions at two pairs of places on one edge face only of said core, one pair of said welds being on one leg of said core and the other pair of said welds being on the other leg directly across the core therefrom, and said welds in each of said pair of welds being spaced apart a sumcient distance to just accommodate a cutting instrument be- .tween them without cutting either weld area to magnetic path.

Description

1946' H. E. WHITE ET AL 2,393,439
METHOD OF MAKING LAMINATED CORES FOR TRANSFORMERS Fil ed May 6, 1945 IN VEN TORS Her barf 5 Ma? BY WM/mwz /1. 5 /61 5&6 .ak z 3 ,06
Patented 'Jan. 22, 1946 METHOD OF MAKING LAMINATED COBES FOR TRANSFORMERS Herbert E. White, Cleveland Heights, Ohio, and
, William H. Borst, Hollis, N. Y.
' Application May 6, 1943, Serial No. 485,942
8 Claims.
Our invention relates to transformers and the method of making them, and more particularly to transformer cores and the method of making and assembling them with coils to form transformers.
Heretofore in the manufacture of transformers one practice has been to assemble a plurality of stamped laminations into a core having a closed magnetic path, and to wind coils around portions of this closed" path to make a transformer. This requires threading each of the numerous turns of the coils through the center opening in the core, and does not readily lend itself to rapid production of transformers. Another method has been to stamp the core laminations in variously shaped, sections, then to slip the legs through a preformed coil, and assemble the sections into substantially a continuous magnetic path. For best results with this .type of transformer the legs of the shaped sections should be interlaced. This method also does not lend itself to rapid produc-- tion. Many other methods have been tried but each has one or more time consuming operations which materially increases the cost of production.
It is an object of our invention to provide a means and method for rapid production of good transformers.
An object of our invention is to provide a new method for making a core for a transformer.
Another object of our invention is to provide a new method of assembling a core to form a trans-' former,
It is an object of our invention to provide a new method of assembling a transformer.
A further object of our invention is to provide a new and improved core for a transformer which facilitates assembly and makes possible rapid completion of winding the strip a plurality of times about the mandrel.
Figure 3 shows the third step of welding together the successive convolutions of the magnetic material.
Figure 4 shows the wound and welded core after it has been cut into two pieces.
Figure 5 shows the core after the coils have been put in place and the two pieces of core connected together.
Figure 6 is a side view of Figure 5.
Figure 7 shows another form of our invention, and
Figure 8 shows still another form of our invention.
Preferred forms of our invention are shown in the drawing, although it is to be understood that other forms, which will be easily obtained after reading a detailed description of the invention, are considered by us as coming within the scope of our invention.
In Figure 1 we show a mandrel III which has a slot II extending along one side thereof. Positioned in the slot is one end 9 of a long strip of magnetic material I! which is suitable for making transformer cores. A convenient material thickness for some transformers is one the order of .020 inch thick. The magnetic strip material may be oxidized, or it may have a layer of lacquer or other insulating material on it. After the end of I the strip I2 is placed in the slot, the material is bent and several complete turns of the material 12 about the mandrel are made. Tension is maintained on the strip material l2 in order to assure that the successive convolutions. will be tight against the previous ones.
We speak of taking turns of the strip material about the mandrel, but it is to be understood that this is only by way of example, and that on a mass production basis it probably will be much quicker and more satisfactory to mount the mandrel I 2 on a shaft I3, and to rotate the shaft. The strip material l2 can be fed from a reel (not shown) and suitable tensioning means can be provided to assure a suitably compact core. Due to the oxide, lacquer, or other insulating material which is on the magnetic strip l2, there will be a thin layer of insulation between the successive convolutions.
Figure 2 illustrates the core after the desired thickness has been obtained by making numerous turns of the strip material I! about the mandrel it. While tension is maintained on the loose end of the strip material I 2, and before the mandrel is removed from the shaft II, the successive convolutions are fixed together to prevent them from slipping with respect to each other, particular care being exercised to connect the outermost convolution to the one which is underneath it. We prefer to weld across the edges of the convolutions at four places I 5, I, I1, and ID, as is shown by securing each convolution to its next adjacent convolution, or convolutions, at four spaced points, we cut the core and the mandrel each into two pieces along a line extending between these welds, thereby establishing a first cor portion 20 and a second core portion 2|. The welds II and H are preferably adjacent the cut ends of the core portion 20 and prevent the convolutions from slipping with respect to each other. The welds It and it are adjacent the cut ends of the core portion 2| and prevent the convolutions from slipping with respect to each other. Each portion of the core thereby retains its shape. It is for this reason that we apply the four welds i5, IS, IT, and |8 to the uncut core, and space them in pairs with welds i5 and I6 and welds i1 and it being just far enough apart that a saw or other cutting device can pass between them.
After the core and the mandrel have been severed, each into two pieces, the mandrel can be removed from inside the core portions and 2|, and the end 9 of the strip material which was inserted into the slot H can be straightened out or broken oil. We prefer to break it of! as it is not necessary to the operation of our device, and this operation is faster than trying to straighten it. Obviously, other holding means which do not leave this bent end to be disposed of may be used. It is also possible to saw through the magnetic material at two places without cutting the mandrel III in two, thereby saving it for further use.
It is also possible to slide it sideways out of the core after the core convolutions have been connected together and prior to cutting the magnetic material.
Previously formed primary and secondary coils 22 and 24 comprised of many turns of fine wire may then be slipped onto the legs of one of the core portions, for instance, portion 20. Insulating means l4 may be placed between the core and the coils. We prefer to cut the core near one of the ends as shown, thereby making one end portion 2|! substantially larger than the other end portion 2|; then the coils 23, 24 are positioned on the larger end portion. After the coils have been slipped into position the cut ends are brought together and held under a slight amount of compression, such as in a vice, and means are provided for connecting the two end portions 20 and 2| together.
Figure 5 illustrates two such means. We prefer to weld the two portions together, such as is shown at points 25. It is also possible to have the welds 25 extend the full height of the core. It is also possible to weld the two portions together by a weld extending between welds I1 and II. It is also possible to bolt the two portions together, such as is shown at 26. A slight air gap 21 may result but this may be advantageous in some types of transformers, such as are welding transformers, and the size of the gap may be controlled by inserting a magnetic non-conductor of desired thickness between the ends of the core portions before they are connected together. If the two core end portions 20, 2| do not align exactly, due to the removal of portion 9 of the magnetic material, slight pressure may be applied laterally to force them into alignment. However, due to the thinness of the strip magnetic material l2, this mis-alignment is not serious, and may be overlooked entirely.
We have shown welds IS, l6, l1, [8 only on the top surface of the convolutions of core material because if there were a weld across the bottom edges of the convolutions as well as across the top edges there would be established an undesirable magnetic short circuit around the laminations.
Figure 7 illustrates another form of our invention in which the two spaced welds I! and It were replaced by a single weld ll, and the two spaced welds l1 and |l were replaced by a single weld 2|. The core was then cut into the two core portions 20, 2| by sawing along a line 32 extending through the welds 10, 3|. In Figure 7 the two resulting portions are shown moved apart. Due to the width of the welds 2|, 8| being greater than the width of the saw cut, each cut end of each core portion 2|, 2| will have a welded portion which will prevent the convolutions from slipping. Either before or after cutting, the mandrel can be removed. This method may be preferable to the previously described method as it pr bably will take less time to make one fairly wide weld than it will take to make two spaced welds.
The space between the left edge of weld ll (Fig. 3) and the right edge of weld It, and the area of the weld 30 (Fig. 7) may be termed the weld area" and the core should be cut in two through a weld area on each side of the core because each of the two horseshoe-shaped core portions remaining after the cut will then have a welded portion which keeps the laminations of the core portion together. While it is preferable that the weld area" not extend over a great length of the circumference of the core it is possible that the welds, such as welds II, I, be separated by considerable distance so long as the welds defining the spread apart "weld area" enclose only the straight legs of the core. Thus when the core is cut into two portions there is no tendency oropportunity for the laminations to spread apart.
Figure 7 further illustrates how the core portion 20 is wound with a coil, in case a. pre-formed coil is not used. The core portion is mounted in two caps, 34, and II, which are designed to hold th two out ends of the core portion. From each cap 34, 35 there is a bent arm I, 31; the arm 21 terminating in a fixed bearing ll, and the arm I being mounted in a bearing 40 and being connected to a motor I! which is adapted to rotate the arm 36 thereby rotating the core 2| and the arm II. The arms 86, II are bent in a direction such, and are just long enough, that the axis of rotation of the system extending through the bearings 38, ill passes through substantially the center of the core portion 2|. A reel 4| supplies wire 42 which is wound about the core portion 20 to form a coil 43.
Figure 8 illustrates another form of invention in which the convolutions are held together by bolts and nuts 33 instead of by welding.
The mandrel l0 about which the magnetic strip material is wound can be any shape, such as round, oval, square, oblong, etc.; and may be made of any material. We prefer to use wood as it is inexpensive and easy to saw through.
Although we have described our invention with a certain degree of particularity, it is to be understood that it is only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of theinvention as hereinafter claimed.
'of said convolutions to its next adjacent convolution to establish a plurality of welded areas across one edge face only of said core, cutting said core at a plurality of places each of which is between the outer ends of one of said welded areas to establish core portions, applying coil means to at least one of the core portions, and connecting the" cut ends of said core portions together to re-form substantially a closed mag--' netic path.
2. The method of making a transformer comprised of a core and coil means about said core, which comprises the steps of: spirally winding a length of flat magnetic material to establish a core having a plurality of convolutions and forming a closed magnetic path, welding said includes said straight side portions, and then connecting said two core portions together to reform substantially theoriginal core.
4. The method of making a transformer comprised of a core and coil means about said core, which comprises the steps of providing a length of flat magnetic core material, spirally winding said flat core material to establish a core having a number of convolutions which define a closed magnetic path, applying a plurality of weld means across the convolutions on only one end face of the said core for connecting the said convolutions together, cutting through said core and through said weld means thereby severing said core into at least two portions each having weld means adjacent its severed ends, applying coil means eonvolutions together in a direction across said convolutions, cutting through said core and through said weld to establish two separate core portions, the width of said weld being sufficiently greater than the width of the cut that each core portion includes an end portion having a portion of the weld whereby the positions of the severed convolutions with respect to each other in each of said separate core portions is maintained. applying coil means about at least one of said two coreportions, and then connecting said two core portions together to reform substantially the original core.
3. The method of making a transformer comprised of score and coil means about said core, which comprises the steps of: spirally winding a length of flat magnetic material to establish a closed magnetic path cor'e having a plurality of eonvolutions and having two rounded portions with straight side portions therebetween, welding said convolutions together in a direction across said convolutions and subaantially at one of the junctions between a curved portion and the straight side portions, cutting through said weld to establish twosellarate dis-similar core portions one of which includes substantially all of said straight side portions, the width of said 7 weld being suiiiciently greater thanthe width of said out that each of said core portions includes an end portion having a portion of the weld whereby the positions of the severed convolutions with respect to each other in each of said separate core portions is maintained, applyingcoilmeanstothesaidcoreportionwhich to at least one portion of said core means. vand connecting said at least two core portions together by welding over and along the said welds which are adjacent the said severed ends.
5. The method as set forth in claim 1 further characterized in this: that said out ends of the core portions are connected together by welding to reform substantially a closed magnetic path.
6'. The method as set forth in claim 2 further characterized in this: that said two core portions are connected together by welding to reform substantially the original core.
7. The method as set forth in claim 3 further characterized in this: that said two core portions are connected together by welding to reform substantially the original core.
8. In the method of making a transformer comprised of a core and coil means about said core. which comprises the stepsof: spirally winding a length of flat magnetic material to establish a core having a plurality of convolutions and forming a clwed magnetic path, connecting each of the said convolutions to its next adjacent convolution by welding'across said convolutions at two pairs of places on one edge face only of said core, one pair of said welds being on one leg of said core and the other pair of said welds being on the other leg directly across the core therefrom, and said welds in each of said pair of welds being spaced apart a sumcient distance to just accommodate a cutting instrument be- .tween them without cutting either weld area to magnetic path.
'1 E. WHITE. WILLIAM H. BURST.
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Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2481393A (en) * 1945-05-30 1949-09-06 Armour Res Found Magnetic recording head
US2516164A (en) * 1947-01-18 1950-07-25 Gen Electric Three-phase magnetic core
US2542806A (en) * 1946-05-10 1951-02-20 Westinghouse Electric Corp Method of manufacturing wound core structures
US2572457A (en) * 1947-02-24 1951-10-23 Louis R Duman Transformer clamp
US2588173A (en) * 1948-08-24 1952-03-04 Gen Electric Method of making magnetic cores
US2652219A (en) * 1948-09-18 1953-09-15 Tri State Engineering Company Portable platform
US2655717A (en) * 1947-03-24 1953-10-20 Ulysses S Dunn Method of forming wound magnetic cores
US2700207A (en) * 1952-08-02 1955-01-25 Mcgraw Electric Co Method of making magnetic cores for transformers or the like
US2762988A (en) * 1951-05-25 1956-09-11 Harnischfeger Corp Magnetic core assembly
US2797395A (en) * 1952-01-22 1957-06-25 Westinghouse Electric Corp Cores
US2830277A (en) * 1953-06-16 1958-04-08 Gen Electric Welding of hinged butt joint magnetic cores
US2937352A (en) * 1953-04-23 1960-05-17 Gen Electric Magnetic core structure
US2937322A (en) * 1952-07-14 1960-05-17 Stone J & Co Ltd Magnet systems of electromagnetic regulators, relays or the like
US2958060A (en) * 1956-08-06 1960-10-25 American Mach & Foundry Inductor devices
US3142786A (en) * 1960-12-09 1964-07-28 Tsukamoto Kenkichi Miniaturized aluminum movable coil
DE1270195B (en) * 1963-08-03 1968-06-12 Vakuumschmelze Ges Mit Beschra Ferromagnetic cut ribbon core
EP0256347A1 (en) * 1986-08-15 1988-02-24 Asea Brown Boveri Inc. Method of making a magnetic core
USD771728S1 (en) * 2014-08-18 2016-11-15 Tokuden Co., Ltd. Three-leg iron core
USD800061S1 (en) 2014-08-26 2017-10-17 Tokuden Co., Ltd. Transformer

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2481393A (en) * 1945-05-30 1949-09-06 Armour Res Found Magnetic recording head
US2542806A (en) * 1946-05-10 1951-02-20 Westinghouse Electric Corp Method of manufacturing wound core structures
US2516164A (en) * 1947-01-18 1950-07-25 Gen Electric Three-phase magnetic core
US2572457A (en) * 1947-02-24 1951-10-23 Louis R Duman Transformer clamp
US2655717A (en) * 1947-03-24 1953-10-20 Ulysses S Dunn Method of forming wound magnetic cores
US2588173A (en) * 1948-08-24 1952-03-04 Gen Electric Method of making magnetic cores
US2652219A (en) * 1948-09-18 1953-09-15 Tri State Engineering Company Portable platform
US2762988A (en) * 1951-05-25 1956-09-11 Harnischfeger Corp Magnetic core assembly
US2797395A (en) * 1952-01-22 1957-06-25 Westinghouse Electric Corp Cores
US2937322A (en) * 1952-07-14 1960-05-17 Stone J & Co Ltd Magnet systems of electromagnetic regulators, relays or the like
US2700207A (en) * 1952-08-02 1955-01-25 Mcgraw Electric Co Method of making magnetic cores for transformers or the like
US2937352A (en) * 1953-04-23 1960-05-17 Gen Electric Magnetic core structure
US2830277A (en) * 1953-06-16 1958-04-08 Gen Electric Welding of hinged butt joint magnetic cores
US2958060A (en) * 1956-08-06 1960-10-25 American Mach & Foundry Inductor devices
US3142786A (en) * 1960-12-09 1964-07-28 Tsukamoto Kenkichi Miniaturized aluminum movable coil
DE1270195B (en) * 1963-08-03 1968-06-12 Vakuumschmelze Ges Mit Beschra Ferromagnetic cut ribbon core
EP0256347A1 (en) * 1986-08-15 1988-02-24 Asea Brown Boveri Inc. Method of making a magnetic core
USD771728S1 (en) * 2014-08-18 2016-11-15 Tokuden Co., Ltd. Three-leg iron core
USD800061S1 (en) 2014-08-26 2017-10-17 Tokuden Co., Ltd. Transformer

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