US3891809A - Magnet system for an acoustic transducer - Google Patents
Magnet system for an acoustic transducer Download PDFInfo
- Publication number
- US3891809A US3891809A US273299A US27329972A US3891809A US 3891809 A US3891809 A US 3891809A US 273299 A US273299 A US 273299A US 27329972 A US27329972 A US 27329972A US 3891809 A US3891809 A US 3891809A
- Authority
- US
- United States
- Prior art keywords
- upper plate
- core
- magnet system
- ferromagnetic
- magnet
- 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
Links
- 230000005294 ferromagnetic effect Effects 0.000 claims abstract description 22
- 239000000463 material Substances 0.000 claims abstract description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 11
- 230000005291 magnetic effect Effects 0.000 claims description 8
- 229910052742 iron Inorganic materials 0.000 claims description 6
- 230000002093 peripheral effect Effects 0.000 claims description 6
- 229920006395 saturated elastomer Polymers 0.000 claims description 6
- 239000003302 ferromagnetic material Substances 0.000 claims description 4
- 230000005520 electrodynamics Effects 0.000 abstract description 4
- 238000000465 moulding Methods 0.000 abstract description 4
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 229910001177 Ticonal Inorganic materials 0.000 description 1
- HPYIMVBXZPJVBV-UHFFFAOYSA-N barium(2+);iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[O-2].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Fe+3].[Ba+2] HPYIMVBXZPJVBV-UHFFFAOYSA-N 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 239000000696 magnetic material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Images
Classifications
-
- 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
- ABSTRACT Magnet system for an acoustic transducer, in particular an electrodynamic microphone, which system comprises a main magnet and a ferromagnetic circuit the upper plate of which together with a centrally arranged core defines an annular effective air-gap, the upper plate being provided with a centering member which preferably comprises at least 3 re-entrant projections and is integral with, and is made of the same material as, the upper plate.
- the re-entrant projections are moulded and calibrated in a single moulding operation during the manufacture of the upper plate.
- the re-entrant projections may be in the form of bridge pieces joined to a disk which is made of the same material.
- the invention relates to a magnet system for an acoustic transducer, in particular for an electrodynamic microphone, which system comprises a main magnet and a cooperating ferromagnetic circuit having a ferromagnetic upper plate which, together with a centrally arranged core, defines an annular effective airgap.
- the core is centered with respect to the upper plate by means of a centering member which is joined to the upper plate and the larger part of which is located at the lower end of the effective air-gap.
- This magnet system which is mounted in a microphone, comprises an annular main magnet provided with two pole pieces, a soft-iron upper plate and a soft-iron core rigidly secured to the lower plate. This core is centered by a separate centering ring made of a non-magnetic material which is glued to the lower surface of the upper plate.
- a system according to the invention is characterized in that the centering member is integral with, and is made of the same material as, the upper plate.
- the upper plate is provided with an inner edge formed with re-entrant projections during manufacture.
- the centering member comprises at least three re-entrant projections on the inner edge of the upper plate.
- the upper plate is stamped from a sheet in a single operation, the re-entrant projections being calibrated either in the same operation or in a subsequent operation.
- a further advantage in comparison with the known magnet system consists in that in the centering process only one tolerance is significant, whereas in the use of a separate centering ring, as is the case in the known magnet system, the tolerance of the mounting thereof is to be added to the said tolerance.
- a magnet system according to a further embodiment of the invention is characterized in that each re-entrant projection takes the form of a bridge piece which is joined to the ferromagnetic part of the core opposite the upper plate and is integral therewith.
- the magnet system comprises a magnet core on which a ferromagnetic disk is placed at the level of the upper plate. Both the upper plate and the disk are made in a single moulding operation, the disk and the upper plate being joined to one another by narrow bridge pieces.
- the crosssectional area of each of these elements is reduced so that the material is magnetically saturated at this point.
- the reluctance is considerably increased so that the magnetic leakage via the projections is greatly reduced.
- FIG. 1 is a cross-sectional view of an embodiment of a system according to the invention
- FIG. 2 is a plan view of the upper plate used in this system
- FIG. 3 is a cross-sectional view of the upper plate taken on the line [-1 in FIG. 2,
- FIG. 4 is a cross-sectional view of another embodiment according to the invention.
- FIG. 5 is a sectional view taken on the line V--V of FIG. 4.
- the magnet system shown in FIG. 1 is a system which is used in many types of electrodynamic microphones. It comprises an annular magnet I made of an oxidic ceramic substance, for example, ferroxdure.
- the magnet l is provided with an upper plate 2 and a lower plate 3 which is integral with a core 4.
- the inner edge 5 of the upper plate 2 together with the upper edge 6 of the core 4 defines an effective air-gap 7. This air-gap serves to receive a moving coil, not shown, which is secured to a diaphragm, not shown.
- the lower plate 3 and the core 4 are made of soft iron.
- the upper plate 2 (see FIGS. 2 and 3), which is made of sintered iron, is provided with 3 re-entrant projections 8, the end of each projection having a reduced cross-sectional area.
- the ends 8 are bent downward through a distance such as to allow sufficient space for the largest deflection which the moving coil may perform in operation.
- the inner edges 10 of the ends 9 are calibrated.
- the upper plate 2 is centered with respect to the core 4 by the three projections 8.
- FIGS. 4 and 5 show another magnet system which comprises a centrally arranged permanent magnet 11 made of Ticonal. This magnet is provided with an upper plate 12 which through three re-entrant projections 18 is joined to a disk 14 which forms a pole piece for the magnet 11 on the upper surface thereof.
- the projections 18 are in the form of bridge pieces which have parts of reduced cross-sectional area.
- the ends 9 and the bridge pieces 19, respectively have portions the cross-sectional areas of which are reduced so that the centered material is saturated at these points, with a consequent very high reluctance.
- the upper plate 2, and the upper plate 12 together with the disk 14, respectively, are moulded in one operation in which the inner edge 10 and 15, 16 respectively, are calibrated to have the required dimensions.
- a magnet system for an acoustic transducer comprising, a main magnet and a ferromagnetic circuit which cooperates with the main magnet, said ferromagnetic circuit including a centrally arranged ferromagnetic core and a ferromagnetic upper plate having an opening therein which; together with the centrally arranged core, defines an annular effective air gap, said upper plate including a centering member integral therewith and made of the same ferromagnetic mate rial as the upper plate and comprising at least three circumferentially arranged reentrant projections on the inner edge of the upper plate with a part of each projection being dimensioned so that in operation said projection part is magnetically saturated, said core being centered wtih respect to the upper plate by means of the centering member the larger part of which is located at the lower end of the effective air gap.
- a magnet system for an acoustic transducer comprising, a main magnet and a ferromagnetic circuit which cooperates with the main magnet, said ferromagnetic circuit including a centrally arranged ferromagnetic core and a ferromagnetic upper plate having an inner portion approximately coaxial with the core and adjacent to one end of said centrally arranged core and a peripheral portion with an opening that defines an annular effective air gap separating the inner and peripheral portions of the upper plate, said upper plate including a centering member for centering the core with respect to the upper plate and comprising at least three circumferentially spaced bridge members integral with the inner and peripheral portions so that the parts of the upper plate form a unitary piece and with all parts thereof made of the same ferromagnetic material.
- a magnet system as claimed in claim 4 wherein a part of each bridge member is dimensioned so that in operation said part is magnetically saturated.
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Signal Processing (AREA)
- Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
- Hard Magnetic Materials (AREA)
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7110445A NL7110445A (enExample) | 1971-07-29 | 1971-07-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3891809A true US3891809A (en) | 1975-06-24 |
Family
ID=19813706
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US273299A Expired - Lifetime US3891809A (en) | 1971-07-29 | 1972-07-19 | Magnet system for an acoustic transducer |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US3891809A (enExample) |
| AT (1) | AT316668B (enExample) |
| DE (1) | DE2233656C3 (enExample) |
| FR (1) | FR2147288B1 (enExample) |
| GB (1) | GB1386358A (enExample) |
| IT (1) | IT963399B (enExample) |
| NL (1) | NL7110445A (enExample) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1957765A (en) * | 1934-05-08 | Magnetomotive force circuits | ||
| US2048222A (en) * | 1931-10-08 | 1936-07-21 | Deutsche Edelstahlwerke Ag | Improvements, in or relating to magnets |
| US2216961A (en) * | 1937-09-30 | 1940-10-08 | Rca Corp | Sound translating apparatus |
| US3462559A (en) * | 1964-08-03 | 1969-08-19 | Dallas Richard Wilder | Two-piece loudspeaker |
-
1971
- 1971-07-29 NL NL7110445A patent/NL7110445A/xx unknown
-
1972
- 1972-07-08 DE DE2233656A patent/DE2233656C3/de not_active Expired
- 1972-07-19 US US273299A patent/US3891809A/en not_active Expired - Lifetime
- 1972-07-26 IT IT27463/72A patent/IT963399B/it active
- 1972-07-26 GB GB3494072A patent/GB1386358A/en not_active Expired
- 1972-07-27 AT AT647972A patent/AT316668B/de not_active IP Right Cessation
- 1972-07-28 FR FR7227229A patent/FR2147288B1/fr not_active Expired
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1957765A (en) * | 1934-05-08 | Magnetomotive force circuits | ||
| US2048222A (en) * | 1931-10-08 | 1936-07-21 | Deutsche Edelstahlwerke Ag | Improvements, in or relating to magnets |
| US2216961A (en) * | 1937-09-30 | 1940-10-08 | Rca Corp | Sound translating apparatus |
| US3462559A (en) * | 1964-08-03 | 1969-08-19 | Dallas Richard Wilder | Two-piece loudspeaker |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2233656C3 (de) | 1979-12-06 |
| IT963399B (it) | 1974-01-10 |
| GB1386358A (en) | 1975-03-05 |
| FR2147288A1 (enExample) | 1973-03-09 |
| DE2233656B2 (de) | 1979-04-05 |
| NL7110445A (enExample) | 1973-01-31 |
| FR2147288B1 (enExample) | 1980-03-14 |
| AT316668B (de) | 1974-07-25 |
| DE2233656A1 (de) | 1973-02-08 |
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