US3851118A - Electroacoustic transducer having a preformed non-magnetic gentering sleeve - Google Patents

Electroacoustic transducer having a preformed non-magnetic gentering sleeve Download PDF

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Publication number
US3851118A
US3851118A US00003424A US342470A US3851118A US 3851118 A US3851118 A US 3851118A US 00003424 A US00003424 A US 00003424A US 342470 A US342470 A US 342470A US 3851118 A US3851118 A US 3851118A
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United States
Prior art keywords
pole plate
diameter
duct
centering sleeve
retaining ring
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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
Application number
US00003424A
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English (en)
Inventor
D Kleis
A Hanneman
C Penning
G Schenkel
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US Philips Corp
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US Philips Corp
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Publication date
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    • 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

Definitions

  • MAGNETIC CENTERING SLEEVE Inventors: Derk Kleis; Adriaan l-llanneman;
  • This invention relates to a device for converting acoustic vibrations into electric oscillations and conversely.
  • the invention relates to an electro-acoustic transducer provided with a magnet system comprising an annular permanent magnet and pole plates arranged one on either side of the magnet, the first pole plate being rigidly secured to a soft-iron core which is arranged centrally relative to the two pole plates and together with the second pole plate defines an annular effective air gap, and a centering member made of a non-magnetic material centering the core relative to the second pole plate.
  • Such a device is known from German Patent Specification No. 953,41 1.
  • the device described in this patent is in the form of a microphone and has amagnet system in which an annular centering member is disposed between the core and the other pole plate.
  • This centering member has the function of centering the core with respect to the upper plate, i.e. of adjusting the effective annular air gap entirely within the permissible tolerances.
  • a magnet system as described in the said patent specification is widely used in microphone technology and is fixed in a known manner by gluing, soldering or clamping.
  • the invention is characterized in that the centering member forms part of a casing which encloses the magnet system as a centering sleeve on the inner surface of which are provided at least two abutment members which, viewed in the axial direction, are disposed on different levels and the disposition of which corresponds to that of the pole plates.
  • the centering sleeve is provided with an abutment member for the magnet ring which is located between the abutments for the pole plates.
  • the abutments may take the form of an assembly of at least three projections arranged in a circle of a fitting rim, the diameter of both forms corresponding with the diameter of the component of the magnet system to be .centered.
  • Stacking is made even easier by using conical abutments. This is also of advantage in manufacturing the centering sleeve from a synthetic material. Manufacture is effected by injection moulding, the conical design being highly desirable for release from the mould.
  • the pole plate having the larger diameter, which, however, is smaller than that of the magnet is provided with projections on a diameter corresponding to that of the member. If the abutment comprises a plurality of studs, the number and the positions of the projections correspond to those of the studs.
  • the core may simply be made in one piece with the adjacent pole plate.
  • a magnet system centered by stacking elements in the centering sleeve must be fixed.
  • the fixing may be effected not only by the aforementioned known methods, but also by means of the centering sleeve itself.
  • an axial abutment is provided at the side of the smaller pole plate, while at the side of the greater pole plate the centering sleeve is provided with a plurality of radially arranged inwardly bent lugs which press against the larger pole plate. In assembly, these lugs are thrust inwards by pressing and simultaneous heating.
  • the centering sleeve in order to fix the magnet system there is provided in the centering sleeve at the side of the smaller pole plate an axial abutment and at the side of the larger pole plate a retaining ring made of a non-magnetic material, the centering sleeve being further provided with a fitting rim which corresponds with the circumference of the retaining rim. j The retaining rim is secured tothe centering sleeve by means of an adhesive.
  • the magnet system is fixed between the axial abutment and the lugs or the retaining rim, respectively.
  • the core together with the adjacent pole plate is provided with a central continuous duct.
  • the pole plate, which together with the core forms the annular effective air-gap, carries a diaphragm.
  • this diaphragm substantially covers the entire pole plate.
  • the space immediately behind the diaphragm communicates with the space behind the magnet system. This influences the acoustic properties of the microphone and especially its directional characteristic.
  • a retaining ring When a retaining ring is used, it is suitably formed with a hole which corresponds to and is aligned with the channel.
  • the hole may be closed by an acoustic resistance in known manner.
  • spacers are interposed between the retaining ring and the adjacent pole plate.
  • the duct contains a partition which extends in the axial direction and divides the duct into two partial ducts, one of which opens into a closed space in the casing behind the retaining ring l and the other opening into the space between the retaining ring and the magnet system.
  • the rear surface of the diaphragm then communicates with two independent spaces.
  • the partition is tubular so as to form an annular second duct.
  • a communication path is established between the annular chamber (between the retaining ring, the centering sleeve, the pole plate and the tubular partition) and the ambient atmosphere.
  • the space behind the diaphragm communicates with the ambient atmosphere through the annular channel and, as the case may be, through the acoustic resistances so that the device (rod microphone) has a cardioid directional characteristic.
  • the device according to the invention may take the form of a box microphone.
  • the centering sleeve forms part of the top cover of a box-shaped case
  • a tube integral with the bottom cover of the microphone casing is concentrically arranged in the duct provided in the core so as to form an annular second duct.
  • the tube communicates with the ambient atmosphere and the annular channel communicates with the boxshaped space.
  • the said retaining ring, the tube and, as the case may be, the spacers to be made in one piece from a synthetic material.
  • the pole plate adjacent the effective airgap When a microphone'is to be mounted in a centering sleeve according to the stacking method, it has proved of advantage for the pole plate adjacent the effective airgap to be provided with a diaphragm beforehand.
  • the diaphragm is cemented to the pole plate.
  • the thickness of a diaphragm is negligible for all practical purposes so that the axial abutment need not be modified.
  • the axial abutment should be dimensioned to take this into account. It is possible not to cement the diaphragm having a reinforced edge to the associated pole plate, but to place it in a specially provided fitting edge in the centering sleeve.
  • the diaphragm is not only centered but also fixed in this fitting edge.
  • stacking of the device according to the invention may be started at either end.
  • the larger pole plate may be provided with a diaphragm and introduced as the last component into the centering sleeve, the assembly then being fixed in the manner described.
  • the centering sleeve may take the form of a casing of a microphone capsule adapted to be accommodated in the microphone casing.
  • the centering sleeve may alternatively be designed as an internally threaded ring which can be screwed onto a standardized handset.
  • the centering sleeve forms a part of the earpiece.
  • the device then is designed as a telephone receiver.
  • FIG. I is a cross-sectional view of a device in the form of a microphone provided with a retaining ring according to the invention
  • FIG. 2 shows a similar rod microphone having a cardioid directional characteristic
  • FIG. 3 is an exploded view of this microphone
  • FIG. 4 is a cross-sectional view of a modified embodiment of this microphone.
  • FIGS. 5 and 6 are cross-sectional views of boxshaped microphones employing different techniques for fixing the magnet system.
  • the magnet system of a microphone is accommodated in a casing I.
  • the casing is made of a synthetic material by means of injection moulding.
  • the casing is designed as a centering sleeve for centering and adjusting the component parts of the magnet system.
  • This magnet system comprises a magnet ring 2 made of an oxydic ceramic material, for example, Ferroxdure. The upper and lower surfaces of this ring have been ground flat to ensure good magnetic engagement with pole plates 3 and 4.
  • a core 5 is integral with the pole plate 4 and forms an annular effective air gap 6 together with the pole plate 3.
  • the pole plates 3 and 4 and the core 5 are made of soft iron.
  • a coil 7, secured to the diaphragm 8, is arranged in the air-gap 6.
  • the diaphragm 8 has a flat edge 9 and a diameter equal to that of the pole plate 3. The edge 9 is cemented to the pole plate 3.
  • Assembly is effected as follows.
  • the casing l is turned upside down.
  • the pole plate 3 provided with the diaphragm 8 is placed against an abutment 10 in a centering member 11.
  • This centering member may comprise either a circular fitting edge or at least three abutment studs arranged in a circle.
  • the magnet ring 2 is then placed in a fitting edge 12.
  • the pole plate 4 with the core 5 is placed in a centering member 13 which has a form similar to that of the centering member ll. However, the diameter of the member 13 is larger than that of the member II.
  • diameter of the fitting edge 12 is intermediate those of the centering members 111 and 13.
  • the air-gap 6 is automatically set to the desired size.
  • a concentric arrangement of the magnet ring 2 is not very critical since the desired magnetic fiux in the effective air-gap 6 is scarcely influenced thereby.
  • the fitting edge 12 is provided to prevent the inner surface of the magnet ring from extending so far towards the axis as to interfere with the axial movement of the coil 7.
  • a retaining ring 15 is pressed against the lower surface of the pole plate 4.
  • this retaining ring which is made of a synthetic material, is arranged in a fitting edge 16 in the casing.
  • the ring 15 is secured in the casing 1 by means of an adhesive in known manner.
  • the core 5 is formed with a central duct l9 and the retaining ring I5 is formed with a corresponding aperture 20 in which an acoustic resistance is inserted.
  • FIG. 2 is a cross-sectional view of a rod microphone, the magnet system of which has been assembled in a manner similar to that used in the microphone'of FIG. 1.
  • the retaining ring has a different form. It is provided with a tube 21 arranged centrally in the core 5 so that a second annular duct 22 is produced.
  • the retaining ring 15 has a protruding rim 23 at its outer surface so that an annular chamber 24 is formed between the polate plate 4 and the retaining ring 15.
  • the protruding rim 23 is formed with apertures 25 which register with apertures 26 in the casing 1.
  • the upper apertures are closed in the usual manner by acoustic resistances.
  • the space 17 beneath the diaphragm communicates through the central duct 19 with the large-volume space 18 in the stem of the microphone.
  • the space 17 also communicates through the annular duct 22 with the annular space 24 which communicates with the ambient atmosphere through the apertures 25 and 26.
  • the casing is divided into two parts.
  • the lower part 27 forms'the stem of the microphone.
  • FIG. 3 is an exploded view of this microphone with the exception of the stem 27.
  • the pole plate 4 is provided with three projections 28 which lie on a circle corresponding to that of the centering member 13. As a result, the diameter proper of the pole plate 4 is reduced and it also is smaller than that of the magnet ring 2, which is magnetically desirable.
  • a microphone having a closed chamber 24 a pressure microphone is shown in FIG. 4, and this chamber communicates with the space 17 beneath the diaphragm 18 through an acoustic resistor 29.
  • FIGS. 5 and 6 show box-shaped microphones.
  • the component parts of the magnet system 30 are stacked in the samemanner as has been described hereinbefore. However, the stacking takes place in a central portion 31 of an upper cover 32, which portion acts as the centering sleeve.
  • the centrally arranged tube 21 is not connected to a retaining ring, but to a lower cover 35. p
  • the retaining ring is dispensed with. Fixing is effected by means of lugs 33 formed at the lower end of the centering sleeve 31. These lugs are bent inwards by heating same and exerting pressure thereon.
  • An electroacoustic transducer device comprising a magnet system that includes an annular permanent magnet ring and first and second pole plates arranged one on each side thereof, the first of said pole plates being rigidly secured to a soft-iron core which is centrally arranged with respect to the two pole plates and together with the second pole plate forms an annular effective air-gap, a preformed casing that includes a centering sleeve made of a non-magnetic material for centering the core relative to the second pole plate, said centering sleeve enclosing the magnet system and having an inner surface provided with at least two axially spaced abutment members which correspond respectively to the locations of the first and second pole plates.
  • centering sleeve further comprises an abutment member for the magnet ring interposed between the abutment members for the pole plates.
  • At least one abutment member comprises at least three abutment studs arranged in a circle having a diameter which corresponds to the diameter of the component part of the magnet system to be centered.
  • a device as claimed in claim 5, characterized in that the component part to be centered comprises a pole plate provided with projections the number and positions of which correspond to those of the abutment studs.
  • At least one abutment member takes'the form of a fitting edge in the centering sleeve with a diameter which corresponds to the diameter of the component part of the magnet system to be centered.
  • a device as claimed in claim 12 further comprising spacers interposed between the retaining ring and the adjacent pole plate.
  • a device as claimed in claim. 13 characterized in that the spacers form part of a ring engaging the centering sleeve.
  • said retaining ring includes an axial tube extending into said duct and wherein the retaining ring, the tube and the spacers form an integral unit.
  • a device as claimed in claim. 12 characterized in that a partition which extends in the axial direction is accommodated in the duct and divides the duct into two part-ducts, the first of which opens into a closed chamber in the casing beneath the retaining ring and the second of which opens into a space formed between the retaining ring and the magnet system.
  • said preformed casing comprises upper and lower mating covers that together form a box-shaped casing
  • said core comprises an axially extending tube with a duct therein and the centering sleeve forms part of the upper cover of the box-shaped casing
  • the lower cover of the casing including a second axial tube which is arranged concentrically in the core duct so as to form an annular second duct.
  • a device as claimed in claim 1 further comprising a diaphragm fixed to said second pole plate and form a second annular duct therewith

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
US00003424A 1969-01-17 1970-01-16 Electroacoustic transducer having a preformed non-magnetic gentering sleeve Expired - Lifetime US3851118A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL6900876.A NL164451C (nl) 1969-01-17 1969-01-17 Inrichting voor het omzetten van akoestische in elektrische trillingen en andersom, voorzien van een magneetsysteem en een niet-magnetisch centreerorgaan.

Publications (1)

Publication Number Publication Date
US3851118A true US3851118A (en) 1974-11-26

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ID=19805905

Family Applications (1)

Application Number Title Priority Date Filing Date
US00003424A Expired - Lifetime US3851118A (en) 1969-01-17 1970-01-16 Electroacoustic transducer having a preformed non-magnetic gentering sleeve

Country Status (9)

Country Link
US (1) US3851118A (de)
AT (1) AT310271B (de)
BE (1) BE744569A (de)
BR (1) BR7016138D0 (de)
CH (1) CH512168A (de)
ES (1) ES375506A1 (de)
FR (1) FR2028536B1 (de)
GB (1) GB1299124A (de)
NL (1) NL164451C (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4205205A (en) * 1978-06-12 1980-05-27 Babbco, Ltd. Dynamic loudspeaker having magnetic assembly adhesively bonded within a surrounding basket
US4507800A (en) * 1982-01-06 1985-03-26 Analog & Digital Systems, Inc. Enclosed magnet loudspeaker
US6289106B1 (en) * 1997-08-08 2001-09-11 Hong Long Industrial Co., Ltd. Cap and center pole apparatus and method of coupling

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2083672B1 (de) * 1970-03-31 1973-10-19 Senzaki Seisakusho Kk

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH265675A (de) * 1946-10-21 1949-12-15 Ericsson Telefon Ab L M Elektrodynamische Anordnung zur Umwandlung von Schallschwingungen in elektrische Schwingungen oder umgekehrt.
DE1183134B (de) * 1961-12-08 1964-12-10 Heinrich Peiker Mikrophon
CH407233A (de) * 1963-12-14 1966-02-15 Peiker Heinrich Elektroakustischer Wandler
US3354541A (en) * 1965-06-04 1967-11-28 Gen Motors Corp Loudspeaker magnet structure and method of assembling same
US3453400A (en) * 1965-12-08 1969-07-01 Aldo L Coen Field structure for magnetic loudspeaker and methods of manufacture
US3524027A (en) * 1967-05-04 1970-08-11 Rolen Diversified Investors In Sound transducer with wall mounted diaphragm

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR872894A (fr) * 1940-06-07 1942-06-22 Henry Heinrich & Co Appareil électroacoustique pour l'enregistrement ou pour la reproduction des vibrations sonores
DE856614C (de) * 1940-12-31 1952-11-24 Guenther Wurdel Elektrodynamische Hoererkapsel
AT274916B (de) * 1966-02-14 1969-10-10 Elektroakusztikai Gyar Dynamisches Mikrophon
FR1541496A (fr) * 1966-10-22 1968-10-04 Philips Nv Microphone électrodynamique présentant une caractéristique directionnelle en forme de cardioïde
AT294211B (de) * 1967-06-10 1971-11-10 Elektroakusztikai Gyar Dynamischer Schwingspulenwandler, insbesondere Mikrophon oder Höher

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH265675A (de) * 1946-10-21 1949-12-15 Ericsson Telefon Ab L M Elektrodynamische Anordnung zur Umwandlung von Schallschwingungen in elektrische Schwingungen oder umgekehrt.
DE1183134B (de) * 1961-12-08 1964-12-10 Heinrich Peiker Mikrophon
CH407233A (de) * 1963-12-14 1966-02-15 Peiker Heinrich Elektroakustischer Wandler
US3354541A (en) * 1965-06-04 1967-11-28 Gen Motors Corp Loudspeaker magnet structure and method of assembling same
US3453400A (en) * 1965-12-08 1969-07-01 Aldo L Coen Field structure for magnetic loudspeaker and methods of manufacture
US3524027A (en) * 1967-05-04 1970-08-11 Rolen Diversified Investors In Sound transducer with wall mounted diaphragm

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4205205A (en) * 1978-06-12 1980-05-27 Babbco, Ltd. Dynamic loudspeaker having magnetic assembly adhesively bonded within a surrounding basket
US4507800A (en) * 1982-01-06 1985-03-26 Analog & Digital Systems, Inc. Enclosed magnet loudspeaker
US6289106B1 (en) * 1997-08-08 2001-09-11 Hong Long Industrial Co., Ltd. Cap and center pole apparatus and method of coupling
US6473515B2 (en) 1997-08-08 2002-10-29 Ching Tong Wong Cap and center pole apparatus and method of coupling

Also Published As

Publication number Publication date
ES375506A1 (es) 1972-05-16
BR7016138D0 (pt) 1973-02-27
FR2028536A1 (de) 1970-10-09
NL6900876A (de) 1970-07-21
AT310271B (de) 1973-09-25
NL164451B (nl) 1980-07-15
GB1299124A (en) 1972-12-06
DE2001852B2 (de) 1976-07-29
BE744569A (fr) 1970-07-16
NL164451C (nl) 1980-12-15
DE2001852A1 (de) 1970-07-30
CH512168A (de) 1971-08-31
FR2028536B1 (de) 1974-09-20

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