US3593239A - Magnetic system - Google Patents

Magnetic system Download PDF

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Publication number
US3593239A
US3593239A US801375A US3593239DA US3593239A US 3593239 A US3593239 A US 3593239A US 801375 A US801375 A US 801375A US 3593239D A US3593239D A US 3593239DA US 3593239 A US3593239 A US 3593239A
Authority
US
United States
Prior art keywords
plate
magnet
auxiliary
main magnet
permanent
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
US801375A
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English (en)
Inventor
Wytze Hofman
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.)
US Philips Corp
Original Assignee
US Philips Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from NL6802907A external-priority patent/NL6802907A/xx
Priority claimed from NL6814825A external-priority patent/NL6814825A/xx
Application filed by US Philips Corp filed Critical US Philips Corp
Application granted granted Critical
Publication of US3593239A publication Critical patent/US3593239A/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
    • H01F7/00—Magnets
    • H01F7/02—Permanent magnets [PM]
    • H01F7/0205—Magnetic circuits with PM in general
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/02—Permanent magnets [PM]
    • H01F7/0273—Magnetic circuits with PM for magnetic field generation
    • H01F7/0289—Transducers, loudspeakers, moving coil arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type
    • H04R9/02—Details
    • H04R9/025—Magnetic circuit
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2209/00—Details of transducers of the moving-coil, moving-strip, or moving-wire type covered by H04R9/00 but not provided for in any of its subgroups
    • H04R2209/022—Aspects regarding the stray flux internal or external to the magnetic circuit, e.g. shielding, shape of magnetic circuit, flux compensation coils

Definitions

  • Trifari ABSTRACT A magnetic system comprising an annular, axially magnetized, permanent main magnet, engaging on either end a soft iron plate; at the center of the main magnet and between the plates a soft iron core is arranged so as to be surrounded, with an airgap formed by one plate and said core, while on at least one of the plates an auxiliary magnet is provided which is magnetized mainly in the opposite direction of stray external magnetic flux.
  • the invention is characterized in that the auxiliary magnet completely covers the plate and surrounds it, the direction of magnetization of the auxiliary magnet being adapted to the shape of the plate and being at right angles to the surface thereof.
  • Object of the invention is to provide an absolutely stray-free magnetic system without the need for arranging the system in a pot.
  • a magnetic system can therefore by manufactured in a very simple manner.
  • the auxiliary magnet is separately manufactured in the form of a hood, which is simply slipped onto the associated plate when mounted.
  • the auxiliary magnet suppresses not only the external stray field but it also enhances the useful flux in the airgap. If this is not desired, the annular main magnet may be smaller, which involves a considerable saving of costs, since the manufacturing costs, or example, of oxideceramic magnets increase more than proportionally to the average diameters of these magnets.
  • An embodiment of the invention is characterized in that the plate has a conical sectional area, while the auxiliary magnet formed like a hood matches the conical shape of the plate.
  • the conical plate may be punched very easily from sintered iron sheet.
  • cylindrical portion of the auxiliary magnet may be provided with one or more cavities or holes. In this way a fairly considerable economy of material is obtained.
  • FIG. I is a cross-sectional view of a magnetic system comprising a lower plate with an auxiliary magnet
  • FIG. 2 is a cross-sectional view of a magnetic system having an upper plate with an auxiliary magnet
  • FIGS. 3 and 4 are cross-sectional views of a magnetic system having an upper plate and a lower plate with an auxiliary magnet
  • FIG. 5 is a cross-sectional view of a magnetic system having a conical lower plate with an auxiliary magnet
  • FIG. 6 is a erspective view of separate components of the magnetic system of FIG. 5.
  • FIGS. 7, 8 and 9 are cross-sectional views of a magnet system comprising an auxiliary magnet in various embodiments.
  • the magnetic system shown in FIGS. 1 to 5 comprises an axially magnetized annular magnet I of oxide-ceramic material having an annular upper plate 2 and a disc-shaped lower plate 3 both of soft iron.
  • the lower plate 3 is provided with a soft iron core 4, which forms the useful airgap 5 with the upper plate 2.
  • the lower plate of FIG. I is provided with an elastic auxiliary magnet 6. whose edge 7 fits intimately around the lower plate 3. Thus the external magnetic field disappears with the exception of the close proximity of the useful airgap.
  • the upper plate 2 of FIG. 2 is provided with an annular auxiliary magnet B, which completely grips around the upper plate 2.
  • this auxiliary magnet the external magnetic field. especially in the neighborhood of the useful airgap is drastically reduced.
  • FIGS. 3 and 4 show a combination of the embodiments shown in FIGS. 1 and 2. Both systems have practically no extemal magnetic field.
  • the hood-shaped auxiliary magnet 6 of FIG. 3 is formed by an oxide-ceramic disc 9, magnetized axially in the opposite direction and by a ring 10 of elastic magnetic material clamping around the disc 9 and the lower plate 3.
  • the upper plate 8 of FIG. 4 is thickened on the inner side I I in order to reduce further the stray field.
  • the lower plate! of FIG. 5 is pressed in a conical shape from a sintered iron sheet.
  • the auxiliary magnet 6 consists of a flexible synthetic resin mixed with ceramic, magnetic powder. It is formed by a disc which is secured by an adhesive to the bottom side of the lower plate 3.
  • FIG. 6 The components of this magnetic system are shown In FIG. 6 ina perspective view.
  • the auxiliary magnet 6, particularly the cylindrical portion 9 covers partly the baseplate 3.
  • the auxiliary magnet 6 of FIG. 7 is annular and has a cylindrical hole 12.
  • the cylindrical portion 9 of FIG; 8 has a cavity 13 adjacent the base plate 3.
  • the cylindrical portion 9 of FIG. 9 has a plurality of holes 14.
  • a magnetic system comprising,
  • annular, axially magnetized, permanent main magnet having first and second ends
  • first plate of soft ferromagnetic material having an inner side disposed adjacent one end of the main magnet and an outer exposed side and edges, and a second similar plate disposed adjacent the opposite end of the permanent magnet;
  • a soft ferromagnetic core extending from the first plate through the bore of the main magnet toward the second plate with an airgap established between the core and the second plate;
  • first auxiliary permanent magnet means disposed adjacent at least one of said two plates and this auxiliary magnet generally surrounding and in intimate contact with and covering only said exposed side and edges of the first plate and disposed in at least a portion of the usual path of external stray magnetic flux, the direction of magnetization of the auxiliary magnet being generally opposite the direction of magnetization of said stray tlux of the main magnet where the auxiliary magnet contacts said plate;
  • a second auxiliary, permanent magnet generally similar to the first and disposed similarly adjacent the second plate.
  • a magnetic system comprising,
  • annular, axially magnetized, permanent main magnet formed as a circular cylinder having first and second ends;
  • first plate formed as a solid disc of sofl ferromagnetic material having an inner side disposed adjacent the first end of the main magnet and an outer exposed side and edges, and a second plate formed as a ring with an aperture defining an inner edge, disposed adjacent the second end of the permanent magnet;
  • a soft ferromagnetic core extending from the first plate through the bore of the main magnet toward the second plate with an airgap established between the core and said inner edge of the second plate;
  • first auxiliary permanent magnet means formed as a cylinder with a central aperture disposed adjacent said first plate and this auxiliary magnet generally surrounding and in intimate contact with only the peripheral portions of said exposed side and edges of the first plate, and terminating at the junction of the first end of said main magnet and the first plate, and disposed in at least a portion of the usual path of external stray magnetic flux, the direction of magnetization of the auxiliary magnet being generally opposite the direction of magnetization of said stray flux of the main magnet where the auxiliary magnet contacts said plate.
  • a magnetic system comprising,
  • first plate of soft ferromagnetic material having an inner side disposed adjacent one end of the main magnet and an outer exposed side and edges, and a second similar plate disposed adjacent the opposite end of the permanent magnet, one of said plates being generally conical in cross section;
  • first elastic auxiliary permanent magnet means disposed adjacent the conical plate and conforming to the shape thereof, and generally surrounding and in intimate contact with only said exposed side and edges of the plate, and terminating at the junction of said first end of the main magnet and said first plate, and disposed in at least a portion of the usual path of external stray magnetic flux, the direction of magnetization of the auxiliary magnet being generally opposite the direction of magnetization of said stray flux of the main magnet where the auxiliary magnet contacts said plate.
  • a magnetic system comprising an annular, axially magnetized. permanent main magnet engaging on either side a soft iron plate, at the center of the main magnet a soft iron core is arranged so as to be surrounded by the main magnet and one plate. the other plate forming together with the core the useful airgap, while at least one of the plates is provided with an auxiliary magnet formed as an axially magnetized cylinder with a radially magnetized disc closing one end, and thus magnetized substantially in the opposite direction as the adjacent main magnet, characterized in that the auxiliary magnet substantially completely covers one of said plates and generally surrounds the same, said auxiliary magnet being in intimate contact with an exposed side of said plate and having a flange portion in intimate contact with edges of said plate and terminating at the junction of said plate and main magnet, the direction of magnetization of the auxiliary magnet matching the shape of the plate and being at right angles to the surface thereof.
  • auxiliary magnet comprises an elastic synthetic resin including therein a permanent magnetic power and corresponds in shape to the adjacent plate.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Electromagnetism (AREA)
  • Power Engineering (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Hard Magnetic Materials (AREA)
  • Permanent Field Magnets Of Synchronous Machinery (AREA)
US801375A 1968-03-01 1969-02-24 Magnetic system Expired - Lifetime US3593239A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL6802907A NL6802907A (enrdf_load_stackoverflow) 1968-03-01 1968-03-01
NL6814825A NL6814825A (en) 1968-10-16 1968-10-16 Auxiliary magnet for permanent magnet loudspeaker

Publications (1)

Publication Number Publication Date
US3593239A true US3593239A (en) 1971-07-13

Family

ID=26644303

Family Applications (1)

Application Number Title Priority Date Filing Date
US801375A Expired - Lifetime US3593239A (en) 1968-03-01 1969-02-24 Magnetic system

Country Status (6)

Country Link
US (1) US3593239A (enrdf_load_stackoverflow)
BE (1) BE729073A (enrdf_load_stackoverflow)
CH (1) CH494459A (enrdf_load_stackoverflow)
DE (1) DE1907969A1 (enrdf_load_stackoverflow)
DK (1) DK118903B (enrdf_load_stackoverflow)
FR (1) FR2003076A1 (enrdf_load_stackoverflow)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3783311A (en) * 1970-12-19 1974-01-01 Coral Audio Corp Magnetic device for use in acoustic apparatus
US3953687A (en) * 1973-11-05 1976-04-27 Carbonneau Industries, Inc. Magnetic structure for moving voice coil loudspeaker
US4187444A (en) * 1978-01-19 1980-02-05 Varian Associates, Inc. Open-circuit magnet structure for cross-field tubes and the like
US4293741A (en) * 1979-06-21 1981-10-06 Digre Clifford B Magnet assembly
USD267644S (en) 1981-08-03 1983-01-18 James B. Lansing Sound, Inc. Loudspeaker magnet housing
US5075662A (en) * 1989-11-14 1991-12-24 The United States Of America As Represented By The Secretary Of The Army Enhanced magnetic field within enclosed annular cavity
US5729617A (en) * 1995-07-27 1998-03-17 Nokia Technology Gmbh Magnet system
US20070038165A1 (en) * 2005-03-07 2007-02-15 Juvent Inc. Vibrational therapy assembly for treating and preventing the onset of deep venous thrombosis
US20070213179A1 (en) * 2006-03-09 2007-09-13 Juvent, Inc. Mechanical loading apparatus having a signal modulating assembly
US20080139979A1 (en) * 2005-07-18 2008-06-12 Juvent, Inc. Vibrational therapy assembly adapted for removably mounting to a bed
US8795210B2 (en) * 2006-07-11 2014-08-05 American Medical Innovations, L.L.C. System and method for a low profile vibrating plate
US20150213932A1 (en) * 2014-01-29 2015-07-30 Merry Electronics (Suzhou) Co., Ltd. External-magnet-type magnetic circuit

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2222167B2 (de) * 1971-05-07 1979-08-16 The Rank Organisation Ltd., London Elektroakustischer Wandler
US4063448A (en) * 1976-08-25 1977-12-20 Agar Instrumentation Inc. Density meter coil assembly
JPS59139794A (ja) * 1983-01-31 1984-08-10 Ibuki Kogyo Kk 漏洩磁場を打消したホ−ンスピ−カ−

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1076838B (de) * 1956-06-14 1960-03-03 Deutsche Edelstahlwerke Ag Dauermagnetsystem mit zentralem Eisenkern
US3067366A (en) * 1958-10-15 1962-12-04 Philips Corp Magnet system having little stray

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1076838B (de) * 1956-06-14 1960-03-03 Deutsche Edelstahlwerke Ag Dauermagnetsystem mit zentralem Eisenkern
US3067366A (en) * 1958-10-15 1962-12-04 Philips Corp Magnet system having little stray

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3783311A (en) * 1970-12-19 1974-01-01 Coral Audio Corp Magnetic device for use in acoustic apparatus
US3953687A (en) * 1973-11-05 1976-04-27 Carbonneau Industries, Inc. Magnetic structure for moving voice coil loudspeaker
US4187444A (en) * 1978-01-19 1980-02-05 Varian Associates, Inc. Open-circuit magnet structure for cross-field tubes and the like
US4293741A (en) * 1979-06-21 1981-10-06 Digre Clifford B Magnet assembly
USD267644S (en) 1981-08-03 1983-01-18 James B. Lansing Sound, Inc. Loudspeaker magnet housing
US5075662A (en) * 1989-11-14 1991-12-24 The United States Of America As Represented By The Secretary Of The Army Enhanced magnetic field within enclosed annular cavity
US5729617A (en) * 1995-07-27 1998-03-17 Nokia Technology Gmbh Magnet system
US20070038165A1 (en) * 2005-03-07 2007-02-15 Juvent Inc. Vibrational therapy assembly for treating and preventing the onset of deep venous thrombosis
US8603017B2 (en) 2005-03-07 2013-12-10 American Medical Innovations, L.L.C. Vibrational therapy assembly for treating and preventing the onset of deep venous thrombosis
US20080139979A1 (en) * 2005-07-18 2008-06-12 Juvent, Inc. Vibrational therapy assembly adapted for removably mounting to a bed
US20070213179A1 (en) * 2006-03-09 2007-09-13 Juvent, Inc. Mechanical loading apparatus having a signal modulating assembly
US8795210B2 (en) * 2006-07-11 2014-08-05 American Medical Innovations, L.L.C. System and method for a low profile vibrating plate
US20150213932A1 (en) * 2014-01-29 2015-07-30 Merry Electronics (Suzhou) Co., Ltd. External-magnet-type magnetic circuit
US9281110B2 (en) * 2014-01-29 2016-03-08 Merry Electronics (Suzhou) Co., Ltd. External-magnet-type magnetic circuit

Also Published As

Publication number Publication date
FR2003076A1 (enrdf_load_stackoverflow) 1969-11-07
DE1907969A1 (de) 1969-09-25
BE729073A (enrdf_load_stackoverflow) 1969-08-27
DK118903B (da) 1970-10-19
CH494459A (de) 1970-07-31

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