US3781736A - Shield for permanent magnet structure - Google Patents

Shield for permanent magnet structure Download PDF

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Publication number
US3781736A
US3781736A US00301094A US3781736DA US3781736A US 3781736 A US3781736 A US 3781736A US 00301094 A US00301094 A US 00301094A US 3781736D A US3781736D A US 3781736DA US 3781736 A US3781736 A US 3781736A
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US
United States
Prior art keywords
permanent magnet
magnet
air gap
flux
shield
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
US00301094A
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English (en)
Inventor
R Parker
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General Electric Co
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General Electric Co
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Filing date
Publication date
Application filed by General Electric Co filed Critical General Electric Co
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Publication of US3781736A publication Critical patent/US3781736A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/02—Permanent magnets [PM]
    • H01F7/0205—Magnetic circuits with PM in general
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2321/00—Details of machines, plants or systems, using electric or magnetic effects
    • F25B2321/002—Details of machines, plants or systems, using electric or magnetic effects by using magneto-caloric effects
    • F25B2321/0023—Details of machines, plants or systems, using electric or magnetic effects by using magneto-caloric effects with modulation, influencing or enhancing an existing magnetic field

Definitions

  • a shield or guide to reduce leakage flux in the vicinity 2 1 301 094 of the air gap of a permanent magnet is provided by positioning magnetic sleeves or plates in engagement with surfaces of the permanent magnet adjacent the [52] US. Cl. 335/304, 335/306 air gap.
  • the Sleeves or plates are polarized at their [51] hit. Cl. H01 7/02 Surfaces which g g the permanent magnet.
  • Each [58] Field of Search 335/301, 304, 306 Sleeve or plate has its Surface which abuts the perma nent magnet of the same polarity as the portion of the [56] References C'ted permanent magnet which it engages.
  • the sleeves or UNITED STATES PAT plates may be flexible. Ferrites and cobalt-rare earths 2,936,408 5/1960 DeBennetot 335/306 are ory magnetic materials for the sleeves and 2,925,517 2/1960 Glass 335/306 X plates. 3,168,686 2/1965 King et a]. 335/306 0 3,205,415 9/1965 Seki et al 335 301 x 5 Clams, 3 Drawmg Flgures m m a ,ll 5 r '/v s il 1 1 PATENIEU [ll-I825 191s FlG-l w W 5 M J &
  • the present invention provides a shield or guide to reduce leakage flux in the vicinity of the air gap of a permanent magnet.
  • the permanent magnet is provided with sleeves or plates in engagement with its surfaces adjacent to the air gap.
  • the engaging surface of the sleeve or plate possess the same polarity as the surface of the permanent magnet with which it is in contact. This establishes a barrier to leakage flux which would otherwise emanate from the magnet.
  • the sleeves or plates may be formed of flexible material and may be in the form of ferrites or cobalt-rare earth materials.
  • the shield provided by the sleeves or plates should have a high coercive force and should have just sufficient magnetic potential to neutralize the magnetic potential producing the leakage flux.
  • a hollow cylindrical alnico magnet has its north pole indicated by the letter N and its south pole indicated by the letter S. Adjacent to the north pole is a sleeve 11' of magnetic material. Adjacent to the south pole is a sleeve 12 of magnetic material.
  • the sleeves 11 and 12 are magnetically oriented to provide an exterior surface of one polarity and an interior surface of the opposite polarity. The polarity of the interior surface of the sleeve magnets 11 and 12 is the same as the polarity of the magnet with which it is in contact. This has the effect of repelling what would otherwise be leakage flux emanating from the magnet 10.
  • the sleeves l1 and 12 serve as barriers to leakage flux from magnet 10.
  • the result is that the normal distribution of flux from the alnico sleeve is modified and a larger percentage of flux is returned through the inside of the alnico sleeve.
  • This arrangement is typical of the arrangement used to focus an election tube.
  • the weight of an alnico 8 sleeve to produce 1000 gauss in the center of sleeve (point H is 10 pounds with the conventional approach using no magnetic shielding.
  • a design to incorporate shielding has an alnico 8 weight of4 pounds and gives 700 gauss before application of shielding.
  • As a flexible ferrite shield is applied the flux density increases to l000 gauss. Three pounds of magnetic shielding is required. Consequently, there is an overall weight saving of three pounds or 30 percent and an economic advantage in that the cost of the flexible ferrite is less than one-third that of alnico.
  • the correct choice of thickness of magnetic sleeves l1 and 12 enables the flux density at the outer surface of the magnet 10 to be held at approximately zero. In this condition the magnetomotive force of the sleeves l1 and 12 exactly balances the magnetomotive force of the surface flux leakage of the magnet 10.
  • This flux cancellation system will work for any permanent magnet system but confers maximum advantage in permanent magnet circuits having long limbs supplying flux to very high permeance air gaps.
  • FIGS. 2 and 3 illustrate the invention applied to a magnetic structure having a rectangular configuration.
  • a pair of alnico magnets 13 and 14 have the polarity indicated by the letters N" and S, respectively.
  • a steel member 15 provides a magnetic flux path.
  • a plurality of magnetic plates 16, 17 and 18 engage the surface of the magnet 13.
  • a plurality of magnetic plates 21, 22 and 23 are in contact with the surface of the magnet 14 immediately adjacent the air gap between the magnets 13 and 14.
  • Each surface of the plate magnets 16-18 and 21-23 has the same polarity as the surface of the alnico magnet 13 and 14 with which it is in contact as indicated by the letters N" and 5".
  • the plate magnets 16-18 and 21-23 serve as guides and barriers for the magnetic flux emanating from the magnets 13 and 14.
  • the plates 16-18 and 21-23 are preferably composed of cobalt-rare earth magnetic materials prepared in accordance with U.S. Pat. Nos. 3,625,779, 3,639,181, and 3,652,343 which are incorporated herein by reference.
  • the use of cobalt-rare earth magnetic plates as flux leakage barriers adds very little to the weight of the permanent magnet and greatly increases the effective flux output.
  • a smaller and lighter magnet can produce the same effective flux output as a larger magnet which does not have the type of flux leakage barrier disclosed herein.
  • tests indicate that the useful gap density can be increased by 35 percent by using such a shielding approach.
  • a magnetically shielded permanent magnet structure comprising:
  • a structure as claimed in claim 1 wherein the shielding sleeve is composed of a cobalt-rare earth alloy.
  • a structure as claimed in claim 2 wherein the shielding sleeve is composed of a ferrite magnet material.
  • a magnetically shielded permanent magnet structure comprising:
  • each flat magnet shleld compnsmg flat magnets possesses the same polarity as the portion of the sitioned around, and in contact with, said elongated magnet structure adjacent said air gap, said flat magnets being magnetized in a direction 5 elongated magnet which it engages.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)
  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
  • Microwave Tubes (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
  • Hard Magnetic Materials (AREA)
US00301094A 1972-10-26 1972-10-26 Shield for permanent magnet structure Expired - Lifetime US3781736A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US30109472A 1972-10-26 1972-10-26

Publications (1)

Publication Number Publication Date
US3781736A true US3781736A (en) 1973-12-25

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ID=23161919

Family Applications (1)

Application Number Title Priority Date Filing Date
US00301094A Expired - Lifetime US3781736A (en) 1972-10-26 1972-10-26 Shield for permanent magnet structure

Country Status (9)

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US (1) US3781736A (it)
JP (2) JPS49132595A (it)
DE (1) DE2347039A1 (it)
ES (1) ES419858A1 (it)
FR (1) FR2204854B1 (it)
GB (1) GB1454754A (it)
IT (1) IT995956B (it)
NL (1) NL7314663A (it)
SU (1) SU824901A3 (it)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4359706A (en) * 1979-12-18 1982-11-16 Arnold Flack Magnet pole pieces and pole piece extensions and shields
US4536230A (en) * 1979-03-13 1985-08-20 Stani Vyzkumny Ustav Materialu Anisotropic permanent magnets
US4549155A (en) * 1982-09-20 1985-10-22 The United States Of America As Represented By The United States Department Of Energy Permanent magnet multipole with adjustable strength
US6084491A (en) * 1995-08-24 2000-07-04 The United States Of America As Represented By The Secretary Of The Army Permanent magnetic reluctor structures and methods
US6573817B2 (en) 2001-03-30 2003-06-03 Sti Optronics, Inc. Variable-strength multipole beamline magnet
US20030151811A1 (en) * 2002-02-08 2003-08-14 Rene Helbing Optical signal control device and method for utilizing same
US20100230180A1 (en) * 2007-10-10 2010-09-16 Kazuto Yamauchi Capacitance change detection circuit, touch panel and determination method
US20120206001A1 (en) * 2011-02-16 2012-08-16 Toyota Motor Engineering & Manufacturing North America, Inc. Magnetic field focusing for actuator applications
US20130038147A1 (en) * 2011-08-10 2013-02-14 Toyota Motor Engineering & Manufacturing North America, Inc. Three Dimensional Magnetic Field Manipulation in Electromagnetic Devices
US8810345B1 (en) * 2013-08-23 2014-08-19 J. Thomas Goserud Device for retrieving and securing golf ball marks
EP3382678A1 (en) * 2017-03-27 2018-10-03 Ecole Polytechnique Federale de Lausanne (EPFL) An electromagnetic actuator
US10137582B2 (en) 2016-11-18 2018-11-27 Wahl Clipper Corporation Flux bridge for pivot motors

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5158323U (it) * 1974-10-31 1976-05-08
DE3566185D1 (en) * 1984-04-11 1988-12-15 Sumitomo Spec Metals Magnetic field generating device for nmr-ct
GB2196855B (en) * 1986-09-12 1991-06-26 Marubeni Kk Magnetic therapeutic device
RU2011106381A (ru) * 2011-02-22 2012-08-27 Закрытое акционерное общество "Нанотех-Актив" (RU) Магнитный модуль

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2925517A (en) * 1957-05-23 1960-02-16 Bell Telephone Labor Inc Electron beam focusing magnetic circuit
US2936408A (en) * 1954-11-18 1960-05-10 Csf Permanent magnets
US3168686A (en) * 1958-12-24 1965-02-02 Philips Corp Permanent magnet
US3205415A (en) * 1961-12-27 1965-09-07 Hitachi Ltd Permanent magnet device

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB886916A (en) * 1958-10-28 1962-01-10 Roe A V & Co Ltd Improvements in or relating to magnetic circuits employing permanent magnets or electro magnets
DE1801974A1 (de) * 1968-10-09 1970-05-27 Deutsche Edelstahlwerke Ag Streuarmes Dauermagnetsystem fuer magnetdynamische Lautsprecher,Mikrophone u.dgl.
US3768054A (en) * 1972-04-03 1973-10-23 Gen Electric Low flux leakage magnet construction

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2936408A (en) * 1954-11-18 1960-05-10 Csf Permanent magnets
US2925517A (en) * 1957-05-23 1960-02-16 Bell Telephone Labor Inc Electron beam focusing magnetic circuit
US3168686A (en) * 1958-12-24 1965-02-02 Philips Corp Permanent magnet
US3205415A (en) * 1961-12-27 1965-09-07 Hitachi Ltd Permanent magnet device

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4536230A (en) * 1979-03-13 1985-08-20 Stani Vyzkumny Ustav Materialu Anisotropic permanent magnets
US4359706A (en) * 1979-12-18 1982-11-16 Arnold Flack Magnet pole pieces and pole piece extensions and shields
US4549155A (en) * 1982-09-20 1985-10-22 The United States Of America As Represented By The United States Department Of Energy Permanent magnet multipole with adjustable strength
US6084491A (en) * 1995-08-24 2000-07-04 The United States Of America As Represented By The Secretary Of The Army Permanent magnetic reluctor structures and methods
US6573817B2 (en) 2001-03-30 2003-06-03 Sti Optronics, Inc. Variable-strength multipole beamline magnet
US20030151811A1 (en) * 2002-02-08 2003-08-14 Rene Helbing Optical signal control device and method for utilizing same
US7079319B2 (en) * 2002-02-08 2006-07-18 Rene Helbing Optical signal control device and method for utilizing same
US20100230180A1 (en) * 2007-10-10 2010-09-16 Kazuto Yamauchi Capacitance change detection circuit, touch panel and determination method
US20120206001A1 (en) * 2011-02-16 2012-08-16 Toyota Motor Engineering & Manufacturing North America, Inc. Magnetic field focusing for actuator applications
US8736136B2 (en) * 2011-02-16 2014-05-27 Toyota Motor Engineering & Manufacturing North America, Inc. Magnetic field manipulation in switched reluctance motors and design method
US20130038147A1 (en) * 2011-08-10 2013-02-14 Toyota Motor Engineering & Manufacturing North America, Inc. Three Dimensional Magnetic Field Manipulation in Electromagnetic Devices
US8736128B2 (en) * 2011-08-10 2014-05-27 Toyota Motor Engineering & Manufacturing North America, Inc. Three dimensional magnetic field manipulation in electromagnetic devices
US8810345B1 (en) * 2013-08-23 2014-08-19 J. Thomas Goserud Device for retrieving and securing golf ball marks
US10137582B2 (en) 2016-11-18 2018-11-27 Wahl Clipper Corporation Flux bridge for pivot motors
EP3382678A1 (en) * 2017-03-27 2018-10-03 Ecole Polytechnique Federale de Lausanne (EPFL) An electromagnetic actuator
US10692637B2 (en) 2017-03-27 2020-06-23 Ecole Plytechnique Federale De Lausanne (Epfl) Electromagnetic actuator

Also Published As

Publication number Publication date
IT995956B (it) 1975-11-20
NL7314663A (it) 1974-05-01
JPS5596614U (it) 1980-07-04
FR2204854A1 (it) 1974-05-24
ES419858A1 (es) 1976-07-01
JPS5629930Y2 (it) 1981-07-16
GB1454754A (en) 1976-11-03
DE2347039A1 (de) 1974-05-09
FR2204854B1 (it) 1979-08-03
JPS49132595A (it) 1974-12-19
SU824901A3 (ru) 1981-04-23

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