US2818514A - Stressed ferrite cores - Google Patents

Stressed ferrite cores Download PDF

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Publication number
US2818514A
US2818514A US312746A US31274652A US2818514A US 2818514 A US2818514 A US 2818514A US 312746 A US312746 A US 312746A US 31274652 A US31274652 A US 31274652A US 2818514 A US2818514 A US 2818514A
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United States
Prior art keywords
core
ferrite
stress
magnetic
stressed
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US312746A
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English (en)
Inventor
Matilda F Goertz
Howell J Williams
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AT&T Corp
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Bell Telephone Laboratories Inc
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Filing date
Publication date
Priority to NL84264D priority Critical patent/NL84264C/xx
Priority to BE523180D priority patent/BE523180A/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US312746A priority patent/US2818514A/en
Priority to FR1080958D priority patent/FR1080958A/fr
Priority to CH324094D priority patent/CH324094A/fr
Priority to GB26718/53A priority patent/GB735989A/en
Application granted granted Critical
Publication of US2818514A publication Critical patent/US2818514A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus 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
    • H01F41/02—Apparatus 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
    • H01F41/0206—Manufacturing of magnetic cores by mechanical means
    • H01F41/0246—Manufacturing of magnetic circuits by moulding or by pressing powder
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/26—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on ferrites
    • C04B35/265—Compositions containing one or more ferrites of the group comprising manganese or zinc and one or more ferrites of the group comprising nickel, copper or cobalt
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
    • H01F1/34—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials non-metallic substances, e.g. ferrites
    • H01F1/342—Oxides
    • H01F1/344—Ferrites, e.g. having a cubic spinel structure (X2+O)(Y23+O3), e.g. magnetite Fe3O4
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F17/00—Fixed inductances of the signal type 
    • H01F17/04—Fixed inductances of the signal type  with magnetic core

Definitions

  • one object of the invention is ⁇ to limprove the magnetic characteristics of high frequency ferrite cores.
  • Fig. l illustrates a ferrite core embedded in a constric- ,tive type plastic
  • 5 Fig..2 is a cross-.sectional View of the device illustrated in Fig. l taken in a plane through 2-2 of that ligure;
  • Fig. 3 shows an alternative stressed core structure Vusing a constrictiveplastic matrix
  • Fig.. 4 represents a structure in which a ferrite'core -is stressed by hydraulic pressure
  • Fig.,5 is a VView showing a cross-section of Fig. 4;
  • Fig. 6 is a schematic circuit diagram illustrating the use of stressed ferrite cores;
  • Figs. 71, 8 and 9 are plots oi the magnetic properties of materials under stress.
  • Ferrite Initial permeability FeFeqOl (normal) Approximately 10.
  • FeFe204 stresstreeL Approximately 70.
  • CuEegOl (qu nched) Do.
  • MnFenO Maximum approximately 250 (but inconsistent) k line specimens, however, of a formula such as (XY) Fe204,
  • the magnetostriction of the polycrystalline constructure can be reduced to almost zero, and the resultant core is substantially stress-free.
  • the preferred embodiment of the' invention which is an annular ring of a particu'larpolycrystalline ferrite embedded in a non-conducting constri'ctive plastic, is an exceedingly simple and inexpensive stressed core, having excellent magnetic properties, and little or no eddy current losses at high frequencies.
  • Fig. 1 illustratesv a stressed ferrite core assembly in which the annular ferrite core 11 has one or more copper windings l2 inductively linked therewith, and the core and Windings are embedded in an insulating constrictive plastic body 13.
  • the core may be made from a negative magnetostrictive nickel-zinc ferrite, the windings from insulated fine copperV wire, and the plastic of a materialv known commercially as Solectron 5003, which is a rigid styrenepolyester casting resin which shrinks approximately nine percent duringl curing. While the foregoing materials have proved satisfactory, other suitable negative magnetostrictive ferrites and constrictive insulating materials may also be employed.
  • shrinking insulating materials which have shrinkage factors of the same order of magnitude as the nine percent mentioned above could be used advantageously. From one or two percent shrinkage factor, which would be required to set up a useful stress in the core, up to about twenty percent, at which point the internal stresses make the body of the plastic break open as it cures, would be included in this range.
  • the approximate dimensions of the stressed core assembly shown in Fig. 1 are 2% inches diameter by 3715 inch thickness, with the ferrite core having a diameter of approximately 3/1 inch and a crosssection approximately l; inch square.
  • the coil or coils are normally of a relatively few number of turns or are moderately loosely wound in order to minimize interference with the constrictive effect of the plastic.
  • Fig. 2 is a cross-sectional view of Fig. 1 which shows the relative thinness of the core assembly, and the substantial radial and small axial extent of the enclosing plastic matrix.
  • the purpose of this dimensioning is to insure the application of sufficient radial stress on the ferrite core, and to prevent axial shrinkage from interfering with this radial stress.
  • the uniform inward force on the annular core creates a strong internal compression of the core along its circular extent, coincident with its closed magnetic circuit. This compression establishes a direction of easy magnetization parallel thereto, and the annular core tends to assume the magnetic characteristics of a single crystal, having one axis of easy magnetization.
  • a suitable polymerizing catalyst is added to the casting resin.
  • the ferrite core is then submerged in the liquid as by pouring the liquid over the core, and it is subjected to moderately increased temperature for several hours to accelerate the curing process.
  • a peroxide polymerizing catalyst and a cobalt promoter are added to the casting resin.
  • the coils on the magnetostrictive core may be electrically energized in the proper direction to reduce the diameter of the core as the plastic cures, and
  • the electrical current would be maintained until the plastic solidified, and, upon its release, the relaxation of the magnetostrictive deformation would tend to place the core under stress even without shrinkage of the plastic.
  • the core assembly of Fig. 3 includes the ferrite core 16 embedded in constrictive plastic matrix 17 with the core and plastic body being of approximately the thicknesses shown for the comparable elements of Fig. 2.
  • This type of core is suitable for magnetic coupling to one or more straight conductors or a single-turn coils such as may be used in static storage arrays for digital computors and the like.
  • Figs. 4 and 5 illustrate an alternative arrangement for compressing the core which was used in testing a number of annular core specimens.
  • a ferrite core specimen 21 is lirst inserted into the recessed annular brass casing 22, and the threaded brass retaining plug 23 is screwed into place. Hydraulic pressure is then applied to the oil 24 within the rubber tube 25 which encircles the core Z1.
  • the nut 26 holds the oil inlet copper tube 2'7 securely in place.
  • various pressures may be applied to the ferrite core through a suitable gauged hydraulic pressure system, and the magnetic properties of the ferrite core tested by means of a coil threaded through the open center of the unit.
  • Fig. 6 illustrates a schematic circuit diagram including a high frequency source 31, a stressed ferrite core 32 embedded in a lossless insulating matrix 33, and several coils 34, 35 and 36 linking the core with the high frequency source and other electrical apparatus (not shown).
  • the low loss non-conducting ferrite core assemblies may be used at much higher pulse repetition rates than the metallic ferro-magnetic storage elements which have been widely used heretofore.
  • the upper frequency limit of other devices such as magnetic ampliers may be extended by the use of these stressed ferrite cores.
  • remanence may be noted in almost every instance where the specimens are placed under compressive stress.
  • the manganese zinc specimen which has a positive magnetostriction as contrasted with the negative magnetostriction of the other specimens, exhibits a decrease in remanence with compression, and would require tension to increase its remanence.
  • the stress applied to the ferrite cores should be substantial, and increasing stress is found to improve the above-noted magnetic properties up to the Verge of mechanical breakdown of the ferrite samples. One-half or even a lesser fraction of this force is, however, suilicient to produce a marked improvement in the magnetic properties involved.
  • a pressure of 300 pounds per square inch was found to nearly double the remanence of specimen #5, using the hydraulic device of Fig. 5.
  • the characteristic curves ofthe stressed ferrite core specimen #1 which has the above-noted desirable ychemical composition, are shown inigs. 'f7 ⁇ and The ⁇ remanence'increases fromv 320 to I1460 gauss with compression and the maximum permeability increases from 12,600 to 36,800.
  • the hysteresis loop of specimen 2 which has a chemical composition that deviates somewhat from exact stoichiometric balance, is shown in Fig. 9. In this case the remanence increases from 900 to 1630 gauss with applied stress, and the maximum permeability increases from 7,900 to 12,300.
  • An annular ferrite core having substantial negative magnetostriction, a plurality of conductive paths inductively coupled to said core, and a rigid styrene-polyester resin encasing said core and applying stress to said core having a maximum compressive component in a circumferential direction in said core.
  • a high frequency source a ferrite core coupled to said source, and means for imparting a stress to said core producing a substantial compressive component in the direction of the principal magnetic eld in said core which is greater in magnitude than any compressive component in a direction perpendicular to said direction of principal magnetic field.
  • a high frequency source a ferrite core coupled to said source, and means including a plastic coating on said core for imparting a stress to said core producing a substantial compressive component in the direction of the principal magnetic field in said core which is greater in magnitude than any compressive component in a direction perpendicular to said direction of principal magnetic field.
  • the method of improving the magnetic characteristics of a high frequency ferrite core which comprises preparing an insulating constrictive plastic in liquid form, submerging said core in the constrictive liquid in such a manner that the annular distribution of said liquid adjacent the outer periphery of said core substantially exceeds the radial dimension of said core and the annular distribution of said liquid adjacent the inner periphery of said core, solidifying the liquid, during the soliditication of said liquid energizing an electrical circuit magnetically linked with said core in a direction to reduce the circumference of said core and deenergizing said circuit on solidication of said liquid, thus placing the annular core under an active stress having a maximum compressive component in a circumferential direction in said core.
  • An annular ferrite core having an approximate chemical formula of NioZna-,FezOg a plurality of conducting paths inductively coupled to said core, and means for applying a continuous stress to said core which has a maximum compressive component in a circumferential direction in said core.
  • a source of pulses of high repetition rate and a ferrite core coupled to said source, said core having substantial negative magnetostriction, and said core embedded in a constrictive plastic formed to impose on said core a maximum compressive stress in the direction of the magnetic field in said core.
  • a stressed magnetic core having an approximate composition as given by the chemical formula means for applying a magnetic iield to said core, and means including a rigid body of insulating material permanently associated with said core for maintaining said core under stress having a major uniform component in the direction of said magnetic field.
  • An annular ferrite core having substantial negative magnetostriction, a coil coupled to said ferrite core, and an insulating constrictive matrix of a plastic material encasing said core and coil and formed so as to impose on said core a stress having a maximum compressive component in a circumferential direction.
  • a polycrystalline ferrite core means for applying a magnetic iield to said core, and hydraulic means for applying stress thereto having a maximum compressive component in the direction of the magnetic field in said core.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Ceramic Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Dispersion Chemistry (AREA)
  • Soft Magnetic Materials (AREA)
  • Coils Or Transformers For Communication (AREA)
US312746A 1952-10-02 1952-10-02 Stressed ferrite cores Expired - Lifetime US2818514A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
NL84264D NL84264C (da) 1952-10-02
BE523180D BE523180A (da) 1952-10-02
US312746A US2818514A (en) 1952-10-02 1952-10-02 Stressed ferrite cores
FR1080958D FR1080958A (fr) 1952-10-02 1953-06-23 Noyaux de ferrite contraints
CH324094D CH324094A (fr) 1952-10-02 1953-09-03 Dispositif translateur de signaux à haute frèquence à noyau magnétique en ferrite et procédé pour sa fabrication
GB26718/53A GB735989A (en) 1952-10-02 1953-09-29 Improvements in or relating to high frequency magnetic cores

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US312746A US2818514A (en) 1952-10-02 1952-10-02 Stressed ferrite cores

Publications (1)

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US2818514A true US2818514A (en) 1957-12-31

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US (1) US2818514A (da)
BE (1) BE523180A (da)
CH (1) CH324094A (da)
FR (1) FR1080958A (da)
GB (1) GB735989A (da)
NL (1) NL84264C (da)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2947890A (en) * 1957-03-25 1960-08-02 Harris Transducer Corp Transducer
US2955217A (en) * 1957-03-06 1960-10-04 Harris Transducer Corp Transducer element
US2996695A (en) * 1955-12-06 1961-08-15 Cgs Lab Inc Controllable inductor
US3027526A (en) * 1957-12-23 1962-03-27 Burroughs Corp Magnetic core assembly
US3079470A (en) * 1959-12-21 1963-02-26 Armour Res Found Magnetic transducer head
US3351832A (en) * 1967-02-01 1967-11-07 Aerojet General Co Article of manufacture and apparatus for producing ultrasonic power
US3483497A (en) * 1968-01-15 1969-12-09 Ibm Pulse transformer
US3484630A (en) * 1967-12-11 1969-12-16 Doall Co Ultrasonic magnetostrictive transducer element
US3486149A (en) * 1968-01-15 1969-12-23 Ibm Variable ratio die cast pulse transformer
US20080266036A1 (en) * 2006-10-09 2008-10-30 Mccoy Bryan Wayne Magnetostriction aided switching

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2997443A (en) * 1955-03-03 1961-08-22 Plessey Co Ltd Modified nickel ferrite
BE562891A (da) * 1956-12-14

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1326366A (en) * 1913-02-07 1919-12-30 Motor Ignition & Devices Company Method of making electric coils.
US1876745A (en) * 1927-08-26 1932-09-13 Gen Cable Corp Method of applying heat to the coverings of electrically conductive cores
US2317166A (en) * 1939-08-15 1943-04-20 Victor R Abrams Pumping device
US2414525A (en) * 1944-02-25 1947-01-21 Westinghouse Electric Corp Process of applying insulation
US2452530A (en) * 1943-05-15 1948-10-26 Hartford Nat Bank & Trust Co Magnetic core
US2519277A (en) * 1947-01-15 1950-08-15 Bell Telephone Labor Inc Magnetostrictive device and alloy and method of producing them
US2526688A (en) * 1946-12-28 1950-10-24 Sprague Electric Co Process of producing electrical condensers
US2638567A (en) * 1950-05-05 1953-05-12 Eugene J Cronin Magnetostriction apparatus

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1326366A (en) * 1913-02-07 1919-12-30 Motor Ignition & Devices Company Method of making electric coils.
US1876745A (en) * 1927-08-26 1932-09-13 Gen Cable Corp Method of applying heat to the coverings of electrically conductive cores
US2317166A (en) * 1939-08-15 1943-04-20 Victor R Abrams Pumping device
US2452530A (en) * 1943-05-15 1948-10-26 Hartford Nat Bank & Trust Co Magnetic core
US2414525A (en) * 1944-02-25 1947-01-21 Westinghouse Electric Corp Process of applying insulation
US2526688A (en) * 1946-12-28 1950-10-24 Sprague Electric Co Process of producing electrical condensers
US2519277A (en) * 1947-01-15 1950-08-15 Bell Telephone Labor Inc Magnetostrictive device and alloy and method of producing them
US2638567A (en) * 1950-05-05 1953-05-12 Eugene J Cronin Magnetostriction apparatus

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2996695A (en) * 1955-12-06 1961-08-15 Cgs Lab Inc Controllable inductor
US2955217A (en) * 1957-03-06 1960-10-04 Harris Transducer Corp Transducer element
US2947890A (en) * 1957-03-25 1960-08-02 Harris Transducer Corp Transducer
US3027526A (en) * 1957-12-23 1962-03-27 Burroughs Corp Magnetic core assembly
US3079470A (en) * 1959-12-21 1963-02-26 Armour Res Found Magnetic transducer head
US3351832A (en) * 1967-02-01 1967-11-07 Aerojet General Co Article of manufacture and apparatus for producing ultrasonic power
US3484630A (en) * 1967-12-11 1969-12-16 Doall Co Ultrasonic magnetostrictive transducer element
US3483497A (en) * 1968-01-15 1969-12-09 Ibm Pulse transformer
US3486149A (en) * 1968-01-15 1969-12-23 Ibm Variable ratio die cast pulse transformer
US20080266036A1 (en) * 2006-10-09 2008-10-30 Mccoy Bryan Wayne Magnetostriction aided switching
US7880573B2 (en) * 2006-10-09 2011-02-01 Igo, Inc. Magnetostriction aided switching

Also Published As

Publication number Publication date
BE523180A (da)
GB735989A (en) 1955-08-31
NL84264C (da)
FR1080958A (fr) 1954-12-15
CH324094A (fr) 1957-08-31

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