US1828284A - Vibratory system - Google Patents

Vibratory system Download PDF

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Publication number
US1828284A
US1828284A US231508A US23150927A US1828284A US 1828284 A US1828284 A US 1828284A US 231508 A US231508 A US 231508A US 23150927 A US23150927 A US 23150927A US 1828284 A US1828284 A US 1828284A
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US
United States
Prior art keywords
coil
ring
currents
damping
eddy
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
US231508A
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English (en)
Inventor
Clinton R Hanna
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.)
Westinghouse Electric Corp
Original Assignee
Westinghouse 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
Priority to NL24326D priority Critical patent/NL24326C/xx
Application filed by Westinghouse Electric Corp filed Critical Westinghouse Electric Corp
Priority to US231508A priority patent/US1828284A/en
Application granted granted Critical
Publication of US1828284A publication Critical patent/US1828284A/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; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R7/00—Diaphragms for electromechanical transducers; Cones
    • H04R7/02—Diaphragms for electromechanical transducers; Cones characterised by the construction
    • H04R7/12—Non-planar diaphragms or cones
    • H04R7/14—Non-planar diaphragms or cones corrugated, pleated or ribbed
    • 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
    • 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
    • H04R9/06—Loudspeakers
    • 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
    • H04R2209/021—Reduction of eddy currents in the magnetic circuit of electrodynamic loudspeaker transducer
    • 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

  • My invention relates to vibratory systems, and it has particular relation to systems of the type known as microphones, wherein air-pressure fluctuations are translated intovelocity of the diaphragm or principal moving part thereof is independent of frequency and is faithfully proportional to the applied sound pressure.
  • Another object of my invention is to pro.- vide a microphone having incorporated in a movable portion thereof means for electromagnetically damping its motion.
  • Another object of my invention is to provide, in a device of the type designated, means whereby damping currents are prevented from causing distorted electrical pulsationsnot truly representative of impinging sounds.
  • a microphone of the moving-coil type with a supplementary closed coil, also soundactuated, in which eddy currents are generated by reason of its motion in a magnetic field.
  • the reaction of the eddy currents withthe magnetic field provides the necessary damping and, in order that these currents shall not influence the output from the micro: phone, shielding means are interposed in such Certain frequencies 7 on the coil generating the desired output voltages is minimized.
  • the shielding means may either be a closed multi-turn coil, or it may comprise merely a single closed turn having low resistance and placed co-axially 5 with the coils in which the damping-currents and the currents representative of sounds are generated by the motion thereof in the magnetic field.
  • a single winding, short-circuited through a resistor constitutes both the eddy-current and sound-current generator, and only a small portion of the generated voltage which appears at the resistor is utilized to energize a thermionic amplifier.
  • Fig. 1 is a View, in cross-section, of a microphone comprising a preferred embodiment of my invention, the relative proportions thereof being greatly exaggerated.
  • FIGs. 2 and 3 are fragmentary CIOSS-SBC- tional views of modified forms of my invention.
  • Fig. 4 is a diagram illustrating the improved response obtained from a microphone constructed and arranged. according to a modified form of my invention.
  • Fig. 5 is a diagrammatic view illustrating the mode of construction and manner of operation of the modification at my invention shownin Fig. 3. f
  • the device shown in Fig. 1 comprises a cup-shaped member 1 of magnetic material, in which a central pole piece 2 is axially relation to the closed coil that its influence positioned and is held firmly in-place by a 99 screw 3 or an analogous device.
  • An annular pole-piece 4 is mounted in the open end of the member 1, the central opening thereof cooperating with the pole-piece 2 to define a circular air-gap.
  • a corrugated or otherwise stiffened diaphragm 5 is mounted on a flexible annulus 6 of rubber or analogous material, the periphery of the annulus being clamped to the circular pole-piece 4 by a ring 7 held in position by a plurality of screws 8.
  • the exact manner in which the diaphragm 5 is resiliently suspended constitutes no part of the present invention, many other ways of mounting it being equally as effective as the way shown.
  • An aluminum ring 10 is attached to the under portion of the diaphragm by a plurality of screws 11, or by other appropriate means, and a coil 12 is ailixed to a supporting tube 13 carried by the under edge of the aluminum ring.
  • the support 13 for the coil may be a thin skirt made integral with the ring 10, in which event, the support is provided with a plurality of axial saw-cuts to prevent the circulation of eddy-currents therein.
  • Both the ring 10 and the coil 12 are positioned in the circular air-gap, for a purpose that will later be explained in detail.
  • a copper flange 14 of L.-shape in cross section is mounted on the lower face of the circular pole-piece and is held in place either by friction or by a plurality of screws 15, as illustrated.
  • the central pole-piece is surrounded by a magnetizing coil 16, through which direct current may be passed to give the desired flux-density in the air gap.
  • the coil comprises 1900 turns of N o. 18 wire, having a resistance of 8 ohms, and the magnetizing current was 1 ampere. This gave a fluxdensity of 12,000 gausses, which was entirely satisfactor
  • a ring 1% of packing material, such as felt, wool, or the like, may advantageously be disposed between the energizing coil and the under portion of the annular pole-piece, to prevent resonance effects from the chamber in which the coil is mounted.
  • the diaphragm 5 When the diaphragm 5 is exposed to soundwaves, it is set into vibratory motion, and voltages are induced in the ring 10 and the coil 12 which are proportional to the velocity of vibration.
  • the coil 12 is preferably connected in series with the primary of a stepup transformer (not shown), the secondary of which is comprised in the input circuit of a thermionic device.
  • the voltages induced in the ring cause eddy-currents to flow therein, the magnitude of these currents being proportional to the velocity of vibration of the ring in the airgap. he eddy-currents react with the magnetic field to oppose the motion of the ring therein, the amount of reaction being proportional to the current and, consequently, proportional to the velocity of vibration.
  • the eddy-ourrents flowing in the ring 10 induce Voltages in the coil 12 which are out of phase with the voltages induced therein by reason of its movement in the magnetic field, and give rise to a distorted output.
  • the copper flange 14 has the very important function of electrically shielding the coil from the effects of the eddy-currents in the ring.
  • the flange is directly in the path of the flux emanating from the ring, and prevents the energy from being transferred to the coil therefrom.
  • the copper flange 14 is replaced by a stationary coil 20 having substantially the same number of turns as the movable coil 12 carried by the diaphragm, the two coils being connected in series. Both coils are mutually coupled to the damper-ring 10, and the voltages induced therein by the eddy-currents flowing in the ring are substantially equal. By properly connecting the two coils together, these volt ages may be caused to so cancel that the only voltage appearing at the terminals of the movable coil is that voltage caused by its motion in the magnetic field.
  • the damper-ring 10 does not necessarily have to be made from a single short-circuited turn; it may consist of a plurality of turns, if desirable, closed through a low-resistance element If the total volume of wire is the same, the damping will be independent of wire size, thus permitting a fairly wide leeway in the choice of the wire to be used.
  • I which is a curve representing the relation between the voltage appearin at the terminals of the movable coil to t e sound frequency, over a wide range of sound frequencies.
  • the full line AB represents the response of a vibratory system in which the damper ring is a single closed turn, or a plurality of turns closed through a low-resist ance element. It will be noted that, at low frequencies, represented by the arrow G, the
  • avsingle coil 21 which is supported on an insulating form 22 carried by the diaphragm 5, serves both as a generator and a damping device.
  • the coil is connected in series with a resistor 23, as shown in Fig. 5, the resistance thereof being small in comparison with that of the coil. If the coil has ten times the resistance of the resistor, the voltage drop across the latter will be only one tenth of the drop within the coil, provided the frequencies are not so high that the inductance of the coil must be conphragm.
  • the voltage across the resistor 23 is also proportional to the velocity of motion,
  • the primer impedance of the transformer 24-25 is igh compared to the resistor.
  • the amount of the resistor included in shunt to the primary '24:, the potential across the primary 24; may be adjusted to the best value, thus enabling the output volume of the amplifier associated with-the secondary 25 to be controlled with out interfering with the damping of th microphone diaphragm.
  • a microphone constructed and arranged according to my invention gives an output that is substantially free from distortion over the entire range of sound-frequencies necessary for natural reproduction. It is extremely simple in construction and relatively inex nsive to manufacture.
  • a vibratory system a magnetic field, a vibratory member, means for vibrating said member in said field to produce an electromotive force, an additional member arranged to be vibrated in said field by said means to produce a damping force proportional to the velocity of said vibrations, and means whereby the currents induced in said second member are prevented from adversely influencing the electromotive forces generated in said first named member.
  • a yibratory member means for vibrating said member in said field to produce an electromotive force, an additional member arranged to be vibrated in said field by said means to produce a damping force proportional to the velocity of said vibrations, and means inductively associated with both of said members for preventing electrical interaction therebetween.
  • a vibratory system In a vibratory system, a magnetic field, a plurality of vibrating members, means for vibrating said members in said field to produce electromotive forces, and means for rendering the velocity of said members truly proportional to the force acting on said first named means and independent of the frequency thereof over a wide range.
  • a vibrator system a magnetic field, a vibratory memlzer, means for vibrating said member in said field to produce an electromotive force, means arranged to be vibrated in said field to produce a damping force proportional to the Velocity of vibration, and additional means for decreasing said damping force at high frequencies.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Apparatuses For Generation Of Mechanical Vibrations (AREA)
US231508A 1927-11-07 1927-11-07 Vibratory system Expired - Lifetime US1828284A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
NL24326D NL24326C (en)) 1927-11-07
US231508A US1828284A (en) 1927-11-07 1927-11-07 Vibratory system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US231508A US1828284A (en) 1927-11-07 1927-11-07 Vibratory system

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US1828284A true US1828284A (en) 1931-10-20

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NL (1) NL24326C (en))

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2556816A (en) * 1946-12-04 1951-06-12 Technicon Cardiograph Corp Polarized electromagnetic operator with damped coil armature
US2631202A (en) * 1947-12-30 1953-03-10 Rca Corp Dynastat volume control
US4764968A (en) * 1985-03-03 1988-08-16 Standard Elektrik Lorenz Aktiengesellschaft Disk diaphragm for a loudspeaker
US10872591B2 (en) 2016-07-13 2020-12-22 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. Compensation means for a loudspeaker system and loudspeaker system

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2556816A (en) * 1946-12-04 1951-06-12 Technicon Cardiograph Corp Polarized electromagnetic operator with damped coil armature
US2631202A (en) * 1947-12-30 1953-03-10 Rca Corp Dynastat volume control
US4764968A (en) * 1985-03-03 1988-08-16 Standard Elektrik Lorenz Aktiengesellschaft Disk diaphragm for a loudspeaker
US10872591B2 (en) 2016-07-13 2020-12-22 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V. Compensation means for a loudspeaker system and loudspeaker system

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Publication number Publication date
NL24326C (en))

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