US3621420A - Magnet system for an electrodynamic transducer - Google Patents

Magnet system for an electrodynamic transducer Download PDF

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Publication number
US3621420A
US3621420A US2595A US3621420DA US3621420A US 3621420 A US3621420 A US 3621420A US 2595 A US2595 A US 2595A US 3621420D A US3621420D A US 3621420DA US 3621420 A US3621420 A US 3621420A
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US
United States
Prior art keywords
magnetic
cup
core
magnetic core
cover
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
US2595A
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English (en)
Inventor
Rudolf Gorike
Wilhelm Kollesberger
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.)
AKG Acoustics GmbH
Original Assignee
AKG Akustische und Kino Geraete GmbH
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
Application filed by AKG Akustische und Kino Geraete GmbH filed Critical AKG Akustische und Kino Geraete GmbH
Application granted granted Critical
Publication of US3621420A publication Critical patent/US3621420A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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

Definitions

  • a magnet system for an electrodynamic transducer includes a magnetic core with a cover of a thermoplastic material thereon which includes a plurality of radially extending longitudinal ribs on its side face and studs which project from its end face and which bear against an inturned end wall of a magnetic cup. The ribs in turn bear against the sidewall of the cup.
  • the cup is provided with an aperture to receive a pole plate which is attached to the magnetic core and which defines an airgap with the edge of the end wall of the cup which bounds the pole aperture in the cup.
  • a baseplate is disposed over the opposite end of the core to retain the magnetic core in position within the cup.
  • thermoplastic material is then applied over the magnetic cup and the baseplate leaving the pole aperture in the end wall of the magnetic cup free.
  • the cover is made of a plastic material which contracts to a greater degree than the metal. so that all of the metal parts are pressed firmly against each other by the external coating of plastic material.
  • thermoplastic material is applied so that the pole aperture is opened to permit the pole plate to be secured to the magnetic core and this is advantageously done for example, by means of an adhesive applied with the aid of a gap-forming tool SUMMARY OF THE INVENTION
  • This invention relates in general to the construction of a system having many parts and in particular to new and useful magnet system for an electrodynamic transducer such as a microphone, or headphone, and to a method of producing such a magnet system.
  • the invention relates in particular to a magnet system which includes a magnetic core which is arranged in a magnetic cup which has an aperture adjacent one end so that a pole plate may be attached to the magnetic core and define an airgap with the wall of the magnetic cup which bounds an aperture of the cup adjacent one end of the core.
  • Means such as a baseplate is provided to hold the core within the cup.
  • a magnet system of this type in such a way that the parts thereof are held together by injected thermoplastic material. For example, attempts have been made to secure a magnetic core which is provided with a central bore and a coating of a plastic material in a fixed position and at the same time to connect the core to a pole plate.
  • a magnet system having parts thereof which are reliably held together even when subjected to shock or jolts, for example when dropped.
  • a magnet system for an electrodynamic transducer which includes a magnetic core which is provided with a covering or sheath on its side face which includes longitudinal ribs arranged at spaced locations around its circumference which bear against the wall of a magnetic cup.
  • the sheets includes studs at the end which bear against an inturned flange which bounds an aperture, or opening in the cup, and which accommodates a pole plate.
  • Retaining means such as a baseplate, which is arranged at the other end of the cup, holds the core and its cover within the cup.
  • An external coating of a thermoplastic material is then applied over the magnetic cup and the baseplate leaving free the pole aperture in the end wall of the magnetic cup.
  • the magnetic system of the invention is advantageously provided with a magnetic core which is formed as a conical frusturri.
  • the two end faces of the core are advantageously face ground so as to promote efficient magnetic contact.
  • the covering or sheath for the core includes the radially projecting ribs which define circumferential spaces therebetween forming acoustic channels which connect the airgap defined around the pole plate within the aperture of the magnetic receiving cup.
  • the core with its plastic coating is positioned within the cup and held in place by retaining means and the magnetic cup and the baseplate are given an external coating of a thermoplastic material which is applied so as to leave the end aperture of the cup free of material to facilitate the attachment of the pole plate.
  • the pole plate is then secured to the magnetic core so as to lie in the aperture of the magnetic cup and this is accomplished by means of an adhesive applied, for example, with the aid of a gap-forming tool.
  • FIG. 1 is a transverse sectional view of a magnet system constructed in accordance with the invention.
  • FIG. 2 is a perspective view of a magnetic core provided with a plastic covering or sheath.
  • the invention embodied therein comprises a magnet system for an electrodynamic sound transducer generally designated 20 which includes a magnetic core I which is of frustoconical configuration.
  • the core is provided with a tubular sheath or cover 2 of a thermoplastic material which is applied in a separate injection operation and which tightly embraces the core as indicated in FIGS. 1 and 2.
  • the cover 2 is provided with a plurality of circumferentially spaced longitudinally extending ribs 8 which leave recesses therebetween when the core and the cover are assembled into a magnetic cup 3.
  • the magnetic core 1 comprises a solid body in its unfinished rough-cast state.
  • the magnetic cup is provided with an end wall 5 having an opening 22 of a size to accommodate a pole plate 12 and still leave an airgap between the pole plate 12 and the edge bounding the aperture of the end wall 5.
  • the cover 2 is provided with a plurality of studs or projecting elements 4 which extend longitudinally and provide a resilient engagement of the cover with the end wall 5.
  • the ribs 8 may be dimensioned so that when the magnetic core 1 with its cover 2 is inserted into the magnetic cup 3 the ribs will be slightly deformed and the core 1 will be held securely within the cup 3.
  • the axially extending studs 4 limit the extent in which the core 1 can be inserted into the cup 3.
  • an external coating 7 of a plastic material is injected around the magnetic cup 3 after the magnetic core I has been inserted therein.
  • a baseplate or other holding means 6 of a magnetically conductive material is inserted into the injection mold so that it is pressed against the magnetic core 1. Because the plastic material of the coating 7 contracts to a greater extent than metal all of the metal parts are pressed firmly against each other by the external coating.
  • the external coating 7 adheres firmly to the magnetic cup 3 due to friction and it includes an inwardly extending portion 9 which extends over the baseplate 6 and an inwardly turned flange portion 7a which extends over the end wall 5 of the magnetic cup 3.
  • Openings l0 and I] are formed in alignment on the respective baseplate 6 and the portion 9 and may be employed for acoustic purposes in conjunction with the air channels fonned by the recesses 8a and defined between the cover and the interior wall of the magnetic cup 3.
  • the pole aperture 22 is left free and this permits the pole plate 12 to be fixed to the free end face of the magnetic core I so as to lie in the aperture and define a pole gap with the end wall bounding the aperture.
  • the attachment of the pole 12 to the magnetic core I is accomplished for example, by means of a contact adhesive.
  • the construction permits the attainment of a uniform airgap around the plate 12 with the aid of a gap-forming tool.
  • pole plate 12 In view of the low mass of pole plate 12 it is not likely to become detached or displaced as a result of inertia when the system receives a sharp knock.
  • the construction forms a compact magnetic system all parts of which are impact and shockresistant and are therefore substantially insensitive to rough treatment.
  • a magnetic system for an electrodynamic transducer comprising a magnetic core, a cover of thermoplastic material arranged around the side surface of said core and having a plurality of ribs on its side face and a plurality of projecting stud members on an end face, a magnetic cup in which the magnetic core is received and having an end wall with a pole aperture, said cover having a stud projecting from its end face bearing against an end wall of said magnetic cup, a pole plate attached to said magnetic core and disposed in the pole aperture of said end wall and defining an airgap between the periphery of said pole plate and the edge of said end wall bounding the pole aperture, a baseplate arranged adjacent the end of said magnetic cup which is opposite to said pole plate to retain the magnetic core, and an external covering of thermoplastic material extending over the magnetic cup and baseplate and leaving free the pole apertures in the end wall of said magnetic cup.
  • a magnetic system according to claim 1, wherein said magnetic core is in the form of a conical frustum.
  • a magnetic system according to claim I, wherein said magnetic core comprises a solid body in its unfinished roughcast state.
  • a magnetic system according to claim 1, wherein said baseplate includes an opening, said external thermoplastic coating having an opening aligned with said baseplate opening.
  • a magnetic system according to claim 1, wherein said ribs of said cover define air channels therebetwcen from the surface of said cover to said magnetic cup, said baseplate having an opening communicating with said air channels and being exposed by said external covering.
  • a magnetic system according to claim 1, wherein said core is a solid material of frustoconical configuration, said cover defining an annular end portion surrounding said core and forming a planar base with the end of said core for receiving said pole plate, said external covering including an intumed end portion extending around said magnetic cup adjacent each end thereof.
  • a method of producing a magnet system for an electrodynamic transducer which includes a magnetic core, a magnetic cup in which the magnetic core is received having an end wall with an aperture for a pole plate which is attached to the magnetic core so as to leave an airgap between the periphery of the pole plate and the edge of the pole aperture, and means such as a baseplate arranged at the other end of the magnetic cup to retain the magnetic core in the cup, comprising applying a cover of thermoplastic material which has an exterior plurality of projecting ribs on its side and at least one stud projecting from its end over the magnetic core, inserting the core with its cover into the magnetic cup to cause the studs to bear against an end wall of the magnetic cup, inserting the baseplate into the magnetic cup over the core at the other end thereof, applying an external coating of a thennoplastic material over the cup and baseplate leaving free the pole aperture in the end wall of the magnetic cup, and securing the pole plate to the magnetic core so that it lies in the pole aperture.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
  • Headphones And Earphones (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
  • Stringed Musical Instruments (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)
US2595A 1969-01-14 1970-01-12 Magnet system for an electrodynamic transducer Expired - Lifetime US3621420A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AT34269A AT289916B (de) 1969-01-14 1969-01-14 Verfahren zur Herstellung eines Magnetsystems für elektrodynamische Schallwandler

Publications (1)

Publication Number Publication Date
US3621420A true US3621420A (en) 1971-11-16

Family

ID=3488045

Family Applications (1)

Application Number Title Priority Date Filing Date
US2595A Expired - Lifetime US3621420A (en) 1969-01-14 1970-01-12 Magnet system for an electrodynamic transducer

Country Status (9)

Country Link
US (1) US3621420A (enrdf_load_stackoverflow)
JP (1) JPS4931645B1 (enrdf_load_stackoverflow)
AT (1) AT289916B (enrdf_load_stackoverflow)
BE (1) BE744441A (enrdf_load_stackoverflow)
DE (1) DE2001223C3 (enrdf_load_stackoverflow)
ES (1) ES375355A1 (enrdf_load_stackoverflow)
FR (1) FR2028288A1 (enrdf_load_stackoverflow)
GB (1) GB1263442A (enrdf_load_stackoverflow)
NL (1) NL7000139A (enrdf_load_stackoverflow)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2083672B1 (enrdf_load_stackoverflow) * 1970-03-31 1973-10-19 Senzaki Seisakusho Kk
US7270778B2 (en) * 2004-03-18 2007-09-18 General Electric Company Method for attachment of a plastic probe tip to a metal component

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2537253A (en) * 1946-08-20 1951-01-09 Chris S Andersen Electrodynamic telephone receiver
US3258543A (en) * 1962-10-01 1966-06-28 Electro Voice Dynamic microphone

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2537253A (en) * 1946-08-20 1951-01-09 Chris S Andersen Electrodynamic telephone receiver
US3258543A (en) * 1962-10-01 1966-06-28 Electro Voice Dynamic microphone

Also Published As

Publication number Publication date
JPS4931645B1 (enrdf_load_stackoverflow) 1974-08-23
AT289916B (de) 1971-05-10
GB1263442A (en) 1972-02-09
ES375355A1 (es) 1972-04-16
BE744441A (fr) 1970-06-15
NL7000139A (enrdf_load_stackoverflow) 1970-07-16
DE2001223C3 (de) 1978-12-14
DE2001223A1 (de) 1970-07-23
DE2001223B2 (de) 1978-04-27
FR2028288A1 (enrdf_load_stackoverflow) 1970-10-09

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