US2908773A - Electroacoustic transducer - Google Patents

Electroacoustic transducer Download PDF

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Publication number
US2908773A
US2908773A US630829A US63082956A US2908773A US 2908773 A US2908773 A US 2908773A US 630829 A US630829 A US 630829A US 63082956 A US63082956 A US 63082956A US 2908773 A US2908773 A US 2908773A
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United States
Prior art keywords
armature
ring
air
diaphragm
gap
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
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US630829A
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English (en)
Inventor
Rolla Adriano
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General Telephone Laboratories Inc
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General Telephone Laboratories Inc
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Publication date
Priority to BE562437D priority Critical patent/BE562437A/xx
Application filed by General Telephone Laboratories Inc filed Critical General Telephone Laboratories Inc
Priority to US630829A priority patent/US2908773A/en
Application granted granted Critical
Publication of US2908773A publication Critical patent/US2908773A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R11/00—Transducers of moving-armature or moving-core type

Definitions

  • This invention relates to elec-troacoustic transducers and more particularly, to such devices of the ring armature type.
  • vIn ring armature transducers such as disclosed in Patent 2,520,640, granted August 29, 1950 to Ralph R. Kreisel, a diaphragm Vis secured to a ring armature, the armature being supported at its outer edge.
  • An air-gap is provided at the inner edge of the ring armature, and the inner edge of the armature vibrates in saidV air-gap.
  • These transducers are generally provided with an .annular magnetic structure that is arranged so that a portion of the structure is located both above and below the ring armature. amount of space wherein the diaphragm can be secured to the ring, and very little flexibility is afforded as to the shape of the diaphragm.
  • Another disadvantage of the edge-supported ring armature is the fact that the airgap in the voice current ilux path changes when a signal is received at the transducer, with the result that the reluctance of this path also changes and introduces distortion.
  • Another object is to provide a ring armature transducer that will minimize the above mentioned distortion
  • a ring armature transducer wherein the ring is supported approximately midway between its inner and outer edges, with an airgap provided at each edge.
  • the armature rocks about said support, or fulcrum, in response to a voice signal, with the result that as one air-gap decreases the other air-gap increases, and the reluctance of the flux path is -thereby maintained at a relatively constant value.
  • the circular, dished diaphragm 4 which is preferably made of a non-magnetic material such as aluminum, is held in a xed position at its periphery by being clamped between items 1 and 3.
  • the ring armature 5 is made of a material with a high permeability and engages a shoulder of diaphragm 4 to which it is secured by a suitable cement or the equivalent, being held against lateral movement by the fixed position of the diaphragm.
  • the armature is also held in a fixed position relative to the magnetic structure by the magnetic forces acting therein, as will be described below.
  • the magnetic structure consists of an annular core 7 having a U shaped cross section.
  • This core is madeof a magnetic material having high permeability and a high specific resistivity (Allegheny metal or similar), which is arranged to lit snugly against the inner bottom and side walls of housing 1 as shown.
  • An annular fulcrum 6, or spacer ring,' is mounted on the top edge of magnet 9 Vas shown, so as to engage ring yarmature 5 near the center thereof.
  • Paths '15 and 16 indicate the flux set up by permanent magnet 9, which path 17 illustrates the path that is followed by ux set up by exciting coils 8 andV 10.
  • Path 15 can be traced out ofthe north pole of magnet 9, through air-gap 13, through the left side of rin-g armature 5, down through i air-gap 11, through the left vertical and bottom left secstructure of ring armature transducers, and the assembly thereof, and thereby to facilitate the fabrication and reduce the cost of manufacture.
  • a further object of the invention is to simplify the structure so as to minimize the number of rejects, and thereby to reduce the cost of manufacture.
  • Fig. l is a cross sectional view of the transducer.
  • Fig. -2 is an enlarged cross sectional view of the magnetic structure, showing the magnetic ux p paths.
  • Fig. 3 is an enlarged fragmentary section of the transducer illustrated in Figs. ⁇ l and 2, showing the ring armature in its operated positions.
  • Flux path 16 can be traced out of the north magnetic pole of magnet 9, through airgap 14, through the ⁇ right hand section of armature 5, down through air-gap 12, through the right vertical and bottom sections of core 7, and into the south magnetic pole of magnet 9.
  • magnet 9 vilows downward through both of the air-gaps, 11 and 12. Both edges of the ring armature are thereby attracted to the annular core, with the result that the armature is held in a fixed normal position by the magnetic forces acting thereon.
  • the components of the magnetic structure are arranged so as ,to maintain equal forces at both the inner and outer edges of the ring, so as to equalize f air-gaps 11 and 12, and thereby hold the ring in a fixed i Figs. 4 and 5'are cross sectional views of the transducer,
  • the transducer shown in Fig. l comprises a housing 1, a cover 3,"and a clamping ring 2, which are secured Atogether-as shown to provide this flux path, it is seen that when fiux is owing downward through air-gap 11 in response to the first half cycle of an incoming signal, an equal ⁇ amount of ux is ⁇ flowing upward through air-gap 12.
  • the voice signal flux is seen to aid the permanent magnet magnet flux in air-gap 11, :while opposing 'the permanent magnet flux in air-'gap "12.
  • armature 5 rocks over on fulcrum 6to the position shown as line 19 in Fig. 3.
  • the voice frequency fiux ' would be reversed in direction so as to ow upward through air-gap 11 and downward through air-gap 12, thereby opposing the permanent magnet flux at the left edge of armature while aiding the fiux at the right edge 'of the armature.
  • This reversal would therefore cause the armature to rock back through its normal position to a position along line 18 of Fig. 3, air-gap 11 being increased in length while air-gap 12 is decreased in length.
  • ring armature '5 is seen to rock back and forth on fulcrum 6 under the -infiuence of the magnetic forces acting thereon.
  • the air-gap in the alternating 'fiux path remains very nearly constant, since an increase in the length of air-gap 11 will cause a corresponding decrease in the length of air-gap 12, and vice versa.
  • the armature movement causes a corresponding movement of ⁇ diaphragm 4, which is secured to the inner edge of the armature, as shown in Fig. l.
  • the rocking action of the armature thereby causes the diaphragm to vibrate, and sound waves are thereupon transmitted from the device.
  • Diaphragm 20 in Fig. 4 is very similar to the diaphragms shown in previously potented ring armature transducers, such as the Kreisel patent previously referred to.
  • Diaphragm 20, preferably of aluminum, is mounted on the inner edge of the ring armature by cement or other suit-able means, as shown.
  • Other types of diapliragms can also be provided, one of these being item 21 in Fig. 5, wherein the diaphragm is secured to the outer edge o-f the ⁇ ring type armature.
  • Varisuc-h as acoustical damping, to improve the response characteristics of the transducer.
  • Various acoustical damping systems arewell-known in the art, and would be readily adaptable to applicants transducer.
  • An electroacoustic transducer comprising an annular permanent magnet, a fixed -annular core of magnetic material, a ring shaped magnetic armature, a diaphragm, and an exciting coil, said magnet and said exciting coil mounted within said core, means for positioning said armature adjacent to said core forming thereby two air-gaps separating said armature ⁇ from said core, said armature maintained in said position by the tractive infiu'ence of said permanent magnet, said armature Secured lto said diaphragm, excitation of said coil with voice current varying said tractive influence to cause both said air-gaps to alternately open and close, thereby imparting -a vibratory motion to said diaphragm causing sound waves to be emitted therefrom.
  • An acoustical device comprising an annular magnetic structure and a ring armature, a spacer ring in- ⁇ eluded within said structure having a diameter less than the outer diameter of said armature, said spacer ring located so as to support said armature in spaced relation to said structure 'and serve as a fulcrum for said armature, thereby delineating a pair of air-gaps between said armature and said structure, a diaphragm, said armature linked to said diaphragm, and means including said diaphragm for transmitting a sound wave from said device corresponding to an incoming electrical'signal, and for transmitting an electrical signal from said structure corresponding to ⁇ sound waves impinging upon said diaphragm.
  • An electroacoustic transducer comprising a ring armature, -an annular magnetic structure, and a spacer ring having a diameter less than the outer diameter of said armature, said ring mounted so as to support said armature in spaced relation to said structure with a first air-gap separating the inside edge of said armature from ,said structure and a second air-gap separating the outside edge of said armature from said structure, and means including said structure for causing magnetic flux to flow .over two paths through said armature, the first path including said first air-gap and the second path including said second air-gap.
  • An acoustic device comprising a non-magnetic dished lcircular diaphragm, a housing, anvannular magnetic core having two circular pole pieces, said core mountedwithin said housing and adjacent to the base thereof, a cylindrical permanent magnet, an exciting coil, said permanent magnet ⁇ and exciting coil mounted within said core, a magnetic ring armature, said armature secured to said diaphragm, a spacing ring mounted on said magnet, said spacing ring having a diameter less than the outer diameter of said armature, said armature supported by said spacing ring so as to maintain each edge of said armature in juxtaposition to each of said pole pieces with an air-gap separating each edge from its corresponding pole piece, said armature maintained -in said position by vthe magnetic forces acting thereon.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
US630829A 1956-12-27 1956-12-27 Electroacoustic transducer Expired - Lifetime US2908773A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
BE562437D BE562437A (fr) 1956-12-27
US630829A US2908773A (en) 1956-12-27 1956-12-27 Electroacoustic transducer

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US630829A US2908773A (en) 1956-12-27 1956-12-27 Electroacoustic transducer

Publications (1)

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US2908773A true US2908773A (en) 1959-10-13

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US630829A Expired - Lifetime US2908773A (en) 1956-12-27 1956-12-27 Electroacoustic transducer

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US (1) US2908773A (fr)
BE (1) BE562437A (fr)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1034200A (en) * 1910-10-24 1912-07-30 Louis W Carroll Telephone-receiver.
US1569411A (en) * 1922-04-18 1926-01-12 Westinghouse Electric & Mfg Co Dynamic transmitter
US2493734A (en) * 1945-05-23 1950-01-03 Sonotone Corp Magnetic insert earphone insertable in the ear of the user
US2567365A (en) * 1948-08-04 1951-09-11 Bell Telephone Labor Inc Polarized operator for telephone receivers
US2794862A (en) * 1952-07-03 1957-06-04 American Danish Oticon Corp Electro-acoustic apparatus
US2820107A (en) * 1954-12-22 1958-01-14 Sonotonc Corp Electro-mechanical signal transducers

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1034200A (en) * 1910-10-24 1912-07-30 Louis W Carroll Telephone-receiver.
US1569411A (en) * 1922-04-18 1926-01-12 Westinghouse Electric & Mfg Co Dynamic transmitter
US2493734A (en) * 1945-05-23 1950-01-03 Sonotone Corp Magnetic insert earphone insertable in the ear of the user
US2567365A (en) * 1948-08-04 1951-09-11 Bell Telephone Labor Inc Polarized operator for telephone receivers
US2794862A (en) * 1952-07-03 1957-06-04 American Danish Oticon Corp Electro-acoustic apparatus
US2820107A (en) * 1954-12-22 1958-01-14 Sonotonc Corp Electro-mechanical signal transducers

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Publication number Publication date
BE562437A (fr)

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