US3859478A - Carbon microphone - Google Patents

Carbon microphone Download PDF

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Publication number
US3859478A
US3859478A US399598A US39959873A US3859478A US 3859478 A US3859478 A US 3859478A US 399598 A US399598 A US 399598A US 39959873 A US39959873 A US 39959873A US 3859478 A US3859478 A US 3859478A
Authority
US
United States
Prior art keywords
carbon
mixture
granules
dry powder
powder lubricant
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
US399598A
Other languages
English (en)
Inventor
William Donald Cragg
Anthony Newton Lawson
Henley Frank Sterling
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.)
STC PLC
Original Assignee
International Standard Electric 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
Application filed by International Standard Electric Corp filed Critical International Standard Electric Corp
Application granted granted Critical
Publication of US3859478A publication Critical patent/US3859478A/en
Assigned to STC PLC reassignment STC PLC ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: INTERNATIONAL STANDARD ELECTRIC CORPORATION, A DE CORP.
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
    • H04R21/00—Variable-resistance transducers
    • H04R21/02—Microphones
    • H04R21/021—Microphones with granular resistance material

Definitions

  • Carbon granules tend to pack into semi-solid blocks, giving reduced sensitivity.
  • a feature of the present invention is the provision of a carbon microphone comprising: a mixture of carbon granules and aggregated particles of a dry powder lubricant; the aggregated particles forming individual masses of between one and microns in size and not exceeding 2 percent by weight of the mixture.
  • the dry powder lubricant is a silica material.
  • the carbon granules 10 are irregular particles with hard surfaces.
  • the granules are generally of the order of 100 microns in size, while the surface irregularities are in the micron range.
  • the addition of a dry powder lubricant having particles 1 l of between one and 10 microns in size reduces friction between granules 10.
  • the dry powder lubricant particles 11 are attracted to the granules 10 by electrostatic forces and. once they are evenly distributed, act like ball hearings to reduce friction.
  • the lubricant particles can be mixed with the granules by tumbling. Once lubricant particles 11 are attached to granules 10 lubricant particles 11 will adhere quite firmly and are not displaced or broken down by large amplitude vibrations at frequencies of 20 kHz (kilohertz).
  • the drawing shows the distribution density and relative sizes of aggregated silica particles 11 among the carbon granules 10. Part of the sensitivity of a carbon microphone depends on varying the number of contacts between the microscopically rough surfaces of the carbon granules.
  • the aggregated silica particles are accumulations of a multitude of basic silica particles held together by electrostatic forces and appear to form branched fibrous structures between one and 10 microns in size and which are highly compliant. When distributed evenly throughout the carbon granules as shown in the drawing they reduce the tendency of the carbon granules to settle into a solid packed mass and increase the overall average compliance.
  • a carbon microphone comprising:
  • said aggregated particles forming individual masses of between one and 10 microns in size and not exceeding 2 percent of weight of the mixture.
  • a microphone according to claim 2, wherein said silica material is substantially 1 percent by weight of the mixture.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Lubricants (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
  • Carbon And Carbon Compounds (AREA)
  • Telephone Set Structure (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)
US399598A 1972-11-24 1973-09-21 Carbon microphone Expired - Lifetime US3859478A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB5431472A GB1360559A (en) 1972-11-24 1972-11-24 Carbon microphone

Publications (1)

Publication Number Publication Date
US3859478A true US3859478A (en) 1975-01-07

Family

ID=10470609

Family Applications (1)

Application Number Title Priority Date Filing Date
US399598A Expired - Lifetime US3859478A (en) 1972-11-24 1973-09-21 Carbon microphone

Country Status (15)

Country Link
US (1) US3859478A (enrdf_load_stackoverflow)
JP (1) JPS4984430A (enrdf_load_stackoverflow)
AR (1) AR199010A1 (enrdf_load_stackoverflow)
AT (1) ATA982873A (enrdf_load_stackoverflow)
AU (1) AU6192973A (enrdf_load_stackoverflow)
BE (1) BE807626A (enrdf_load_stackoverflow)
BR (1) BR7308746D0 (enrdf_load_stackoverflow)
CA (1) CA995349A (enrdf_load_stackoverflow)
CH (1) CH558626A (enrdf_load_stackoverflow)
DE (1) DE2358243A1 (enrdf_load_stackoverflow)
ES (1) ES420820A1 (enrdf_load_stackoverflow)
FR (1) FR2208266B3 (enrdf_load_stackoverflow)
GB (1) GB1360559A (enrdf_load_stackoverflow)
IT (1) IT1001915B (enrdf_load_stackoverflow)
NL (1) NL7315631A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996018197A1 (en) * 1994-12-09 1996-06-13 Breed Automotive Technology, Inc. Force sensing ink, method of making same and improved force sensor

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US486244A (en) * 1892-11-15 Charles clamond
US919908A (en) * 1908-07-13 1909-04-27 Harold Sheen Martin Electrical-resistance device.
US1086726A (en) * 1909-03-11 1914-02-10 Johan Burchardt Opsahl Resistance unit.

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US486244A (en) * 1892-11-15 Charles clamond
US919908A (en) * 1908-07-13 1909-04-27 Harold Sheen Martin Electrical-resistance device.
US1086726A (en) * 1909-03-11 1914-02-10 Johan Burchardt Opsahl Resistance unit.

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996018197A1 (en) * 1994-12-09 1996-06-13 Breed Automotive Technology, Inc. Force sensing ink, method of making same and improved force sensor
US5541570A (en) * 1994-12-09 1996-07-30 Force Imaging Technologies, Inc. Force sensing ink, method of making same and improved force sensor

Also Published As

Publication number Publication date
AR199010A1 (es) 1974-07-31
GB1360559A (en) 1974-07-17
ES420820A1 (es) 1976-04-01
IT1001915B (it) 1976-04-30
ATA982873A (de) 1976-05-15
FR2208266B3 (enrdf_load_stackoverflow) 1976-10-08
NL7315631A (enrdf_load_stackoverflow) 1974-05-28
BR7308746D0 (pt) 1974-08-22
CA995349A (en) 1976-08-17
AU6192973A (en) 1975-05-01
FR2208266A1 (enrdf_load_stackoverflow) 1974-06-21
CH558626A (de) 1975-01-31
BE807626A (nl) 1974-05-22
JPS4984430A (enrdf_load_stackoverflow) 1974-08-14
DE2358243A1 (de) 1974-05-30

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Legal Events

Date Code Title Description
AS Assignment

Owner name: STC PLC, 10 MALTRAVERS STREET, LONDON, WC2R 3HA, E

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:INTERNATIONAL STANDARD ELECTRIC CORPORATION, A DE CORP.;REEL/FRAME:004761/0721

Effective date: 19870423

Owner name: STC PLC,ENGLAND

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:INTERNATIONAL STANDARD ELECTRIC CORPORATION, A DE CORP.;REEL/FRAME:004761/0721

Effective date: 19870423