US3721400A - Magnetic core assemblies - Google Patents

Magnetic core assemblies Download PDF

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Publication number
US3721400A
US3721400A US00655124A US3721400DA US3721400A US 3721400 A US3721400 A US 3721400A US 00655124 A US00655124 A US 00655124A US 3721400D A US3721400D A US 3721400DA US 3721400 A US3721400 A US 3721400A
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US
United States
Prior art keywords
bobbin
annular step
oriented annular
internal
external
Prior art date
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
Application number
US00655124A
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English (en)
Inventor
H Weissman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Honeywell Inc
Original Assignee
Honeywell Inc
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Filing date
Publication date
Application filed by Honeywell Inc filed Critical Honeywell Inc
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Publication of US3721400A publication Critical patent/US3721400A/en
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    • 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
    • H01F1/14—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 metals or alloys
    • 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
    • H01F41/0213—Manufacturing of magnetic circuits made from strip(s) or ribbon(s)

Definitions

  • This invention pertains to the manufacture of ferromagnetic core assemblies.
  • Ferromagnetic cores are well known in the art and have numerous applications.
  • the use of ferromagnetic material wound on a bobbin for a magnetometer sensor core has been known in the prior art.
  • the sensitivity of a magnetometer makes it very susceptible to changes in the magnetic characteristics of the sensor. After exposure of magnetometer sensors to temperature extremes, permanent changes in the magnetic characteristics of the sensor often result.
  • These changes in sensor characteristics are introduced by stresses applied to the ferromagnetic core when the bobbin tends to contract less with a decrease in temperature than does the tightly wound ferromagnetic ribbon.
  • the resulting stress in the ferromagnetic material causes permanent and not entirely predictable shifts in the characteristics of the ferromagnetic material.
  • the present invention provides a solution to the problem introduced by the difference between the thermal expansion of coefficients of a ferromagnetic ribbon and the bobbin about which it is wound.
  • the core assembly is constructed so that at extreme temperature the differing thermal expansion coefficients of the ferromagnetic windings and the bobbin material will not apply stress to the ferromagnetic ribbon. If the thermal coefficients of expansion of the bobbin and the ferromagnetic ribbon are exactly equal, no mechanical stresses will be introduced at temperature extremes. Since it is improbable that a practical magnetically inactive material can be found with a coefficient of expansion exactly equal to that of a ferromagnetic ribbon, addition steps must be taken to compensate for the differences in thermal coefficients of the two materials.
  • the bobbin is produced in two telescoping sections and one or several thin strips of Teflon or like material are inserted before winding the ferromagnetic ribbon around the internal portion of the bobbin. After the winding has been completed, the Teflon may easily be withdrawn before the two halves of the bobbin are assembled. Removal of the spacer strips at completion of the winding leaves a small space between the bobbin and the winding which allows for the unequal expansion and contraction of the ferromagnetic winding and the bobbin when temperature extremes are encountered.
  • FIG. 1 is a top view of the assembled core assembly.
  • FIG. 2 is a cross-sectional view of the assembled core assembly taken along section lines 2-2 of FIG. 1.
  • FIG. 3 is a pictorial view of the internal bobbin portion illustrating the use of a Teflon lamina during the winding of a ferromagnetic material to provide a space between the winding and bobbin after removal of the Teflon.
  • FIG. 1 an internal bobbin portion 11 and an exter nal bobbin portion 22 are shown in their assembled positions.
  • the bobbin portions are formed from Supra-Mica 555. Because it has a temperature coefficient similar to that of the ferromagnetic material.
  • the internal portion 11 has an outline when viewed in elevation which is defined by two inwardly facing half circles 13 which are connected by parallel lines 14 whose length is much greater than the radius of half circle 13 and which are tangent thereto.
  • the parallel lines 15 are connected to the second set of parallel lines 16 by arcuate segments 17 which have a radius considerably smaller than the radius defined by the half circles 13.
  • the external bobbin portion 22 as shown in FIG. 1 has an outer perimeter defined roughly by a rectangle with corners defined by arcuate segments 18.
  • the outer perimeter 14 of the internal bobbin portion 11 is enclosed within the inner perimeter of the external bobbin portion 22 leaving a very small space between the internal bobbin portion 1 1 and the external bobbin portion 22. The space is exaggerated for the purposes of clarity of the drawing.
  • FIG. 2 the internal bobbin portion 11 is shown inserted into the external bobbin portion 22.
  • External bobbin portion 22 is formed with a curved outer surface 23 to facilitate the winding of coils about the core assembly to form a magnetometer sensor.
  • An inner surface 25 of the external bobbin portion 22 is distinguished by an inwardly oriented annular step 24 which is located near a top surface 19 of the bobbin assembly.
  • An inner wall 25'of the external bobbin portion 22 has approximately a one degree slope opening toward a bottom surface 29 of the core assembly.
  • the internal bobbin portion 11 is constructed with a first outwardly oriented annular step 20 constructed so as to interface with the inwardly oriented annular step 24 of the external bobbin portion 22.
  • a second outwardly oriented annular step 21 is constructed such that when the'intemal bobbin portion 11 and the external bobbin portion 22 are interfaced, a residuum of space is left between the inner surface 25 of the external bobbin portion 22 and an outer surface 26 of the internal bobbin portion 11. This space is bounded by the first outwardly oriented annular step 20 and the second outwardly oriented annular step 21 and walls 25 and 26.
  • the aperture 12 of the internal bobbin portion 11 appears in cross section as a combination of three isosceles trapezoids.
  • the first isosceles trapezoid 27 is located with its longer parallel side parallel with the top surface 19 of the bobbin assembly and its non-parallel sides intersect the longer parallel side at approximately a 45 angle.
  • the second isosceles trapezoid 28 has its longer parallel side parallel to the bottom surface 29 of the bobbin assembly and its non-parallel sides intersect the longer parallel side at approximately a 45 angle.
  • the third isosceles trapezoid 30 shares its parallel sides with the shorter parallel sides of the first isosceles trapezoid 27 and the second isosceles trapezoid 28.
  • the non-parallel sides of the third isosceles trapezoid 20 are constructed to form a gentle linear taper outward from the bottom of the core assembly with a taper angle of about 1 to allow for mold release.
  • a lamina 31 is shown in its preferred position against the internal bobbin portion 11 with one end resting on the second outwardly oriented annular step 21 and with the surface of the lamina engaging the outer surface 26 of the internal bobbin portion 11.
  • the preferred embodiment uses a Teflon lamina because of its desirable low friction characteristics.
  • Ferromagnetic material 32 is wrapped several times around the internal bobbin portion 11 in the area between the first outwardly oriented annular step 20 and the second outwardly oriented annular step 21 and covering the surface 26 of internal bobbin portion 11 as well as the lamina 31.
  • the Teflon lamina 31 is removed to leave a small residuum of space to provide for the difference between the coefficient of expansion of the internal bobbin portion 11 and the ferromagnetic material 32.
  • the internal bobbin portion 11 with the ferromagnetic material wound loosely thereon is then inserted into the external bobbin portion 22.
  • the assembled bobbin then has an appearance as in FIGS. 1 and 2 except that the ferromagnetic material 31 loosely occupics the space between surfaces 25 and 26 in FIG. 2.
  • a toroid of electrically conducting material is wound about the assembled bobbin to enclose the flux path formed by the ferromagnetic material 31.
  • this core assembly has been shown to be an elongated annulus, the words core assembly as used here apply not only to toroidally shaped annular core assemblies but to a core assembly of any shape which provides a closed ferromagnetic path with an aperture through the area enclosed by the path so that windings can encircle the ferromagnetic flux path.
  • the preferred embodiment of the bobbin is constructed from Supra-Mica 555 because of its desirable temperature coefficient it is obvious that any ceramic material which is magnetically inactive may be substituted.
  • the lamina is formed from Teflon so that it may easily withdraw but it may be replaced with lamina of other materials.
  • a bobbin comprising an elongated rigid hollow annulus of magnetically inactive material, including internal and external interfitting portions;
  • said internal portion having a first outwardly oriented annular step which lies within the aperture of said external portion when the portions are assembled, the inwardly oriented annular step and the first outwardly oriented annular step cooperat- 3.
  • said internal portion has a second outwardly oriented annular step, said second step contacting the inwardly oriented annular step of said external portion when the portions are assembled.
  • FIG. 3 please delete reference numeral 27 and insert in its place reference numeral 21;
  • FIG 3 please delete reference numeral 27 and insert in its place reference numeral 21;

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Manufacturing Cores, Coils, And Magnets (AREA)
  • Coils Or Transformers For Communication (AREA)
  • Magnetic Heads (AREA)
US00655124A 1967-07-21 1967-07-21 Magnetic core assemblies Expired - Lifetime US3721400A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US65512467A 1967-07-21 1967-07-21

Publications (1)

Publication Number Publication Date
US3721400A true US3721400A (en) 1973-03-20

Family

ID=24627631

Family Applications (1)

Application Number Title Priority Date Filing Date
US00655124A Expired - Lifetime US3721400A (en) 1967-07-21 1967-07-21 Magnetic core assemblies

Country Status (6)

Country Link
US (1) US3721400A (xx)
JP (1) JPS4530794B1 (xx)
DE (1) DE1764516A1 (xx)
FR (1) FR1581084A (xx)
GB (1) GB1175349A (xx)
NL (1) NL6810038A (xx)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4694868A (en) * 1984-12-10 1987-09-22 Siemens Aktiengesellschaft Apparatus for manufacturing a disc-shaped curved magnet coil
WO1988005545A1 (en) * 1987-01-27 1988-07-28 Sundstrand Data Control, Inc. Bobbin for a magnetic sensor
US5604971A (en) * 1993-09-30 1997-02-25 Steiner; Robert E. manufacturing method for variable laminations used in electro-magnetic induction devices
US5640752A (en) * 1993-09-30 1997-06-24 Steiner; Robert E. Controlled adjustable manufacturing method for variable laminations used in electro-magnetic induction devices

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4694868A (en) * 1984-12-10 1987-09-22 Siemens Aktiengesellschaft Apparatus for manufacturing a disc-shaped curved magnet coil
WO1988005545A1 (en) * 1987-01-27 1988-07-28 Sundstrand Data Control, Inc. Bobbin for a magnetic sensor
US4825166A (en) * 1987-01-27 1989-04-25 Sundstrand Data Control, Inc. Bobbin for a magnetic sensor
US5604971A (en) * 1993-09-30 1997-02-25 Steiner; Robert E. manufacturing method for variable laminations used in electro-magnetic induction devices
US5640752A (en) * 1993-09-30 1997-06-24 Steiner; Robert E. Controlled adjustable manufacturing method for variable laminations used in electro-magnetic induction devices

Also Published As

Publication number Publication date
JPS4530794B1 (xx) 1970-10-05
FR1581084A (xx) 1969-09-12
DE1764516A1 (de) 1971-08-05
GB1175349A (en) 1969-12-23
NL6810038A (xx) 1969-01-23

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