US1870446A - Sound recording device - Google Patents

Sound recording device Download PDF

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US1870446A
US1870446A US732225A US73222524A US1870446A US 1870446 A US1870446 A US 1870446A US 732225 A US732225 A US 732225A US 73222524 A US73222524 A US 73222524A US 1870446 A US1870446 A US 1870446A
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armature
stylus
sound
coil
recording device
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US732225A
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Earl H Foley
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FILMTONE Corp
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FILMTONE CORP
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    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B3/00Recording by mechanical cutting, deforming or pressing, e.g. of grooves or pits; Reproducing by mechanical sensing; Record carriers therefor

Definitions

  • EARL H. F0115 V @41pm/waxy Figure 3 is a vertical section of my recordingrdevice per se, and
  • igure 4 is an enlarged detail of the stylus arm assembly.
  • FIG.-2 wherein is diagrammatically Illustrated my system of amplification it will be seen that I have elected to divide it into three units preferably of two stages of amplification each.
  • the first unit comprises in the present instance, a radio receiving assembly A and a microphone receiving assembly B, either of' which may be ⁇ cut in on the system by a switch device'C.
  • the second and third units of amplification are each connected in circuit with the recording device D, but the third unit may be cut out upon occasion by the switch device E.
  • the third unit is provided with kenetron or rectifying tubes through which the system is served from a lighting or other similar circuit through Wires F whereby the current is given a final and great increase.
  • FIG 2 my system is shown with the microphone assembly B including the primary amplifier in circuit through the switch device C with the second amplifier, where the original current affected by the action of sound waves upon the microphone is again stepped up. Assuming'now that the switch E is thrown to place the second and third units of kamplification in circuit; as the third unit is served from a lighting or other similar high powered circuit the desired increase of electrical energy is'attained and delivered to my unique recording device D without loss in accuracy or precision in the fluctuations of the currenty caused by the action of sound waves on the microphone.
  • My recording device per se comprises a permanent magnet (l), preferably of the horseshoe type, the res ective poles of which are designated N and d), mounted by means of screws (3) a sectional, hollow soft iron pole pieces (4).
  • the two sections X and Y (4) constitute the fields and are preferably identical in shape and size.
  • Each pole piece is formed with a body (5) and anges (6), on the ends of which are provided posts (7). When assembled, the pole pieces form a hollow compartment with the posts (7 opposed to each other and having their ends slightly spaced apart.
  • a coil (8) formed with a central longitudinal opening (9) communicating medially of its length with a vert-ical opening (10) also formed therein. Extending through theV longitudinal opening (9) in the coil is a soft iron armature (11) which is hingedly mounted by a non-magnetic fitting (12) to one of the posts (7 of the pole pieces (4),l
  • non-magnetic cover plates (l5) carrying suitable binding posts (16) for the wire terminals (17) of the coil and the wire terminals (18) of the amplification system, so that when the system is in circuit with my recording device, the coil (8) is ener 'zed with a resultant polarization of the so t iron armature.
  • the fiow of current in the coil is not constant due to fluctuations theren resultin from the action of sound waves er; the receiving device, thus the intensity of polarization of the armature (11) will mani- Jestly vary thereby causin it to be alternately attracted toward the fie ds X and Y.
  • armature (11) Carried adjacent to the free end of the armature (11) is a depending rod (19) which extends through an opening provided in the lowermost cover plate (15) and into engagement with the stylus arm (20) which is thus given a movement corresponding to that of the armature.
  • adjusting screws l(21) In order to regulate the movement of the armature (11) I have provided adjusting screws l(21) the same being carried by the and between these is N. -ad
  • the effect of screwing down on the upperl screw(21 in making the adjustment above described is to cause the upper pad 23 to be more compressed than the lower pad and the effect of the pads and the spring is to cause a dampening or cushioning action which compensates for the difference in force required to move the cutting point downwardly into the flhn and that required to raise it.
  • the stylus arm is formed with a head (20a) provided with an opening through which extends a screw for mounting the arm in a boxing (26) carried by the lowermost cover plate (l5).
  • the screw (25) is adjustable vertically through the medium of elongated slots (27) so that the angular relationship of stylus (28) may be regulated with respect to the record tape (29). It may be said here that the smoothness of the cut made by the stylus is dependant upon the angle at which the stylus is held against the record tape.
  • a slot (30) through which a second adjusting screw passes to hold the stylus arm in place, and a spring (32) seated in aV recess (33) in the boxing functions to oppose any unsteadiness or dfsplacement of the head.
  • the record tape (29) is fed from a suitable spool (not shown) across a support (34) to a reel or spool (35) which is actuated through the medium of suitable gearing (36) operatively connected with a power element (not shown), and a standard (37) is provided for supporting the permanent magnet (l) in the proper relationship to direct the stylus against there-tape, the same is rendered detachable by means. of a screw (38). 4.
  • a sound recording device comprising an armature associated wit-h an electrical device sensitive to fluctuations in current induced by sound waves, a stylus arm formed with a,slot therein and arranged to be actuated by said armature, adjustable pivoting means for said stylus arm, inherently resilient means for resisting adjustment of said pivoting means in one direction, and adjusting means extending through the slot in the stylus for positively supporting said pivoting means and adapted to regulate the 'position of said pivoting means against the resistance of said inherently resilient means.
  • a sound recording device comprisingl an armature associated with an electrical device' sensitive to fluctuations in current inducedby sound waves, a stylus arm formed with a slot therein and arranged to be ac- A tuated by said armature, a boxing provided with slots, pivoting means for said stylus arm carried by the boxingand adjustably mounted in the slots therein, a spring in said boxing for resisting adjustment of said piv-I oting ⁇ means, and manually adjustable means extendingthrough the slot in the stylus for supporting said pivoting means and adapted to vregulate the position of said pivoting means against the resistance of said spring.
  • a device for recording the fluctuations in an electrical current comprising a permanent magnet, a core carried by the magnet, a coil within the core and connected with the electrical circuit for polarizing the core, said coil being provided with intercommunicating openings, an armature carried in one of said openings, and inherently resilient supporting means for the armature carried in the other of said openings and attached to the core.
  • a sound recording device comprising an armature and a coil in an electro-magnetic field in circuit with a source of electrical energy sensitive-to sound waves, said armature being pivoted at a point without a coil, Aand additional means extending through the coil for supporting the armature at a point intermediate its length for the purpose defined.
  • a sound recording device comprising an electro-magnetic field in circuit with a source of electrical energy sensitive to sound waves, an armature and a coil included in said field, and the armature being arranged to extend ⁇ through the coil, means for pivotally su porting the armature at a point without t e coil, means for supporting said armature at a point within the coil, and adjustable means adapted to engage said armature at a point removed from the pivoting means for regulating the vibrations of said armature for the purpose defined.
  • a device for recording the fluctuations in an electrical current comprising a permanent magnet, a sectional core carried by the magnet, a coil within the core and connected with the electrical circuit for polarizing the core, said coil being provided with vertical and longitudinal communicating openings therethrough, an armature carried in one of said o enings, and spring means carried in the otiier of said openings and attached to the core for supporting the armature.
  • a sound recording device comprising a coil connected with a source of electrical energy sensitive to sound waves, said coil being provided'with vertical and longitudinal communicating openings therethrough, a core surrounding the coil, a permanent magnet associated with the core, an armature carried in one of the openings in the core, spring means for supporting the armature extending through the other opening in the coil and attached to the core, and means for ad. j usting the armature for the purpose defined.
  • a sound recording device comprising a stylus arm, a stylus carried by the arm, said stylus arm, a stylus carried by the arm, sai-d ing an opening and a slot therein communicating with the opening, a housing for the head, adjustable means engaged With the head through the opening therein, said means being carried in a slot formed in the housing, adjustable means carried by the housing and extending within the slot in the head for raising and lowering the head, and a spring ldevice Within the housing and engaging the head and exerting its pressure in opposition to the aforementioned adjustable means for the purpose defined.
  • a device for recording electrical fluctuations comprising a permanent magnet, a sectional core carried by said magnet, a coil Within the core provided with a longitudinal opening, an armature ivotedin said opening and means for norma ly positioning said armature said means consisting of a reversely curved non-magnetic spring connected at its center to the armature and at its ends to the core.
  • a sound recorder adapted for cutting a hill and dale record in relatively hard material such as a. photographic film, the combination of a cutting sty us, means for creating a magnetic field, means for substantially varying said eld in accordance with sound to be recorded, an armature, means for biasing said armature to a position in said field and means for resisting the movement of said armature from said position, said means being more effective on displacement of said armature in one direction than on displacement of said armature in the opposite direction.
  • a sound recorder adapt-ed for cutting a hill and dale record in relatively hard material such as a photographic film, the combination of a cutting stylus, means for creating a magnetic field, means for substantially varying said field in accordance with sound to be recorded, an armature, means for biasing said armature to a position in said .field and damping pads for resisting movements of said armature in opposite vdirections respectively, one of said pads offering greater resistance to movement of said armature than the other.
  • a sound recorder adapted for cutting a hill and dale record in relatively hard material such as a photogra hic film, the combination of a cutting sty us, means for creating a magnetic field, means for substantially varying said field in accordance with sound to be recorded, an armature, means for biasing said armature to a position in said field, means for applying greater force to said armature when said armature is displaced in one direction from said position than when displaced in the opposite direction from said position.
  • a device for recording sound, means creating a permanent magnetic field, opposed pole pieces, a pivotally mounted armature movable near one end between said pole pieces, a cutting stylus, a. pivotally mounted arm supportingsaid stylus, an operating connection between said armature and stylus connected to said armature adjacent said pole f pieces, the leverage between said armature and stylus being at least substantial unity, and damping pads engaging opposite sides of one end of said armature at a point distant from its pivotal support.

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  • Recording Or Reproducing By Magnetic Means (AREA)

Description

Aug. 9, 1932.
E. H. FOLEY SOUND RECORDING DEVICE Original Filed Aug. l5. 1924 2 Sheets-Sheet l Jay-Mvg ug- 9 1932- v E. H. FOLEY 1,870,446
SOUND RECORDING DEVICE Original vFiled ug. 15 1924 2 'Sheets-Sheet 2 @ww/:4m
EARL H. F0115 V @41pm/waxy Figure 3 is a vertical section of my recordingrdevice per se, and
igure 4 is an enlarged detail of the stylus arm assembly.
Like characters of reference are used to designate like or similar parts throughout the several views of the drawings.
Before introducing the elements of my system of amplification it is pointed out that in each instance a conventional amplifying unit of the audio-frequency tube type is utilized, and that where the system is served from a lighting or'other similar circuit the usual rectifying tubes are employed. Referring now particularly to Figure-2 wherein is diagrammatically Illustrated my system of amplification it will be seen that I have elected to divide it into three units preferably of two stages of amplification each. The first unit comprises in the present instance, a radio receiving assembly A and a microphone receiving assembly B, either of' which may be` cut in on the system by a switch device'C. The second and third units of amplification are each connected in circuit with the recording device D, but the third unit may be cut out upon occasion by the switch device E. The third unit is provided with kenetron or rectifying tubes through which the system is served from a lighting or other similar circuit through Wires F whereby the current is given a final and great increase. In Figure 2, my system is shown with the microphone assembly B including the primary amplifier in circuit through the switch device C with the second amplifier, where the original current affected by the action of sound waves upon the microphone is again stepped up. Assuming'now that the switch E is thrown to place the second and third units of kamplification in circuit; as the third unit is served from a lighting or other similar high powered circuit the desired increase of electrical energy is'attained and delivered to my unique recording device D without loss in accuracy or precision in the fluctuations of the currenty caused by the action of sound waves on the microphone. It will be manifest, therefore, that the principal advantage contemplated by this phase of my invention resides in the preservation of the relative values of thi minute fluctuations induced by the action of the sound waves on the original circuit of low amperage, and upon which the exact quantity and timbre of the sound are dependent, during the process of amplification to develop sufficient electrical energy to afford the rcquired power to record such fluctuations on ya permanent and durable record. It has been found impractical to record sound directly from a microphone for the reason that insufficient power is developed to cause the stylus to accurately record the overtones by which the quality and timbre ofv sound are characterized. With my apparatus however,
it has been found that sufficient energy can be developed to actuate my unique cutting loss of the necessary sensitiveness required to accurately translate the overtones.
My recording device per se comprises a permanent magnet (l), preferably of the horseshoe type, the res ective poles of which are designated N and d), mounted by means of screws (3) a sectional, hollow soft iron pole pieces (4). The two sections X and Y (4) constitute the fields and are preferably identical in shape and size. Each pole piece is formed with a body (5) and anges (6), on the ends of which are provided posts (7). When assembled, the pole pieces form a hollow compartment with the posts (7 opposed to each other and having their ends slightly spaced apart. Retained within the hollow portion of the pole pieces is a coil (8) formed with a central longitudinal opening (9) communicating medially of its length with a vert-ical opening (10) also formed therein. Extending through theV longitudinal opening (9) in the coil is a soft iron armature (11) which is hingedly mounted by a non-magnetic fitting (12) to one of the posts (7 of the pole pieces (4),l
with its free end extending some distance outwardly from the coil and between adjacent.
posts (7 There is sufficient cleara e between the armature (11) and the walls of the opening (9) and ends of the posts (7) to permit limited movement of the armature, and the armature is normally held in a neutral intermediate position by non-magnetic S- shaped springs (13a) extending Vthrough the vertical opening (10) in the coil and mounted with their ends secured to the flanges (6) of the sections of the core. Also mounted on j the permanent magnet (1) by means of screws (14) are non-magnetic cover plates (l5) carrying suitable binding posts (16) for the wire terminals (17) of the coil and the wire terminals (18) of the amplification system, so that when the system is in circuit with my recording device, the coil (8) is ener 'zed with a resultant polarization of the so t iron armature. However, the fiow of current in the coil is not constant due to fluctuations theren resultin from the action of sound waves er; the receiving device, thus the intensity of polarization of the armature (11) will mani- Jestly vary thereby causin it to be alternately attracted toward the fie ds X and Y. Carried adjacent to the free end of the armature (11) is a depending rod (19) which extends through an opening provided in the lowermost cover plate (15) and into engagement with the stylus arm (20) which is thus given a movement corresponding to that of the armature. In order to regulate the movement of the armature (11) I have provided adjusting screws l(21) the same being carried by the and between these is N. -ad
respective cover plates (15), and each of these is formed with ahead (22)` carrying a felt pad (23) against the resistance of which the armature operates with a resulting limitation in the stroke thereof dependant upon the pressure exerted. Furthermore, it is manifest that more force is required to move the armature to affect cutting action upon a sound record than is required to relieve the cutting pressure, consequently to assure they application of greater power when working against the resistance of record material suitable adjustment may be made byscrews (2l) to move the armature nearer to the field Y and under a stronger magnetic influence. .T he screws are locked in position by screws (24). The effect of screwing down on the upperl screw(21 in making the adjustment above described is to cause the upper pad 23 to be more compressed than the lower pad and the effect of the pads and the spring is to cause a dampening or cushioning action which compensates for the difference in force required to move the cutting point downwardly into the flhn and that required to raise it.
By the combined effects of these instrumentalities it is possible to cut a symmetrical hill and dale sound groove in the film and thus avoid distortion of the record.
The stylus arm is formed with a head (20a) provided with an opening through which extends a screw for mounting the arm in a boxing (26) carried by the lowermost cover plate (l5). The screw (25) is adjustable vertically through the medium of elongated slots (27) so that the angular relationship of stylus (28) may be regulated with respect to the record tape (29). It may be said here that the smoothness of the cut made by the stylus is dependant upon the angle at which the stylus is held against the record tape. further provided with a slot (30) through which a second adjusting screw passes to hold the stylus arm in place, and a spring (32) seated in aV recess (33) in the boxing functions to oppose any unsteadiness or dfsplacement of the head.
The record tape (29) is fed from a suitable spool (not shown) across a support (34) to a reel or spool (35) which is actuated through the medium of suitable gearing (36) operatively connected with a power element (not shown), and a standard (37) is provided for supporting the permanent magnet (l) in the proper relationship to direct the stylus against there-tape, the same is rendered detachable by means. of a screw (38). 4.
It will be yapparent from the foregoing that when my system is placed in circuit with my recording device, that the armature (11) will be controlled. in its movement by the fluctuations in the current affected by soundl waves acting either upon the microphone or radio recelving set, and that such movements The stylus head (20a) is.
will be duly transmitted to the stylus (28) through the stylus arm (20) and rod (19), and that an accurate and precise record will be made upon the tape (29), it being assumed that the tape is actuated to move across the standard (34). Howeven it is also desired to emphasize the fact that by re-arrangement of the armature with respect to the coil, field and permanent magnet, that the fluctuations in current caused by sound waves may be recorded by furrows on the record possessing either vertical or horizontal irregularities.
While in the foregoing there has been illustrated and described such combination and arrangement of elements as constitute the preferred embodiment of my invention, it is nevertheless desired to emphasize the fact thatL interpretation of the invention should only be conclusive when made in the light of the Ysubjoined claims.
Having described my invention and its objects with such attention to detail as will thoroughly acquaint one skilled in the art with its construction and advantages, I claim c j l. A sound recording device comprising an armature associated wit-h an electrical device sensitive to fluctuations in current induced by sound waves, a stylus arm formed with a,slot therein and arranged to be actuated by said armature, adjustable pivoting means for said stylus arm, inherently resilient means for resisting adjustment of said pivoting means in one direction, and adjusting means extending through the slot in the stylus for positively supporting said pivoting means and adapted to regulate the 'position of said pivoting means against the resistance of said inherently resilient means.
2. A sound recording device comprisingl an armature associated with an electrical device' sensitive to fluctuations in current inducedby sound waves, a stylus arm formed with a slot therein and arranged to be ac- A tuated by said armature, a boxing provided with slots, pivoting means for said stylus arm carried by the boxingand adjustably mounted in the slots therein, a spring in said boxing for resisting adjustment of said piv-I oting` means, and manually adjustable means extendingthrough the slot in the stylus for supporting said pivoting means and adapted to vregulate the position of said pivoting means against the resistance of said spring.
3. A device for recording the fluctuations in an electrical current comprising a permanent magnet, a core carried by the magnet, a coil within the core and connected with the electrical circuit for polarizing the core, said coil being provided with intercommunicating openings, an armature carried in one of said openings, and inherently resilient supporting means for the armature carried in the other of said openings and attached to the core.
4. A sound recording device comprising an armature and a coil in an electro-magnetic field in circuit with a source of electrical energy sensitive-to sound waves, said armature being pivoted at a point without a coil, Aand additional means extending through the coil for supporting the armature at a point intermediate its length for the purpose defined.
5. A sound recording device comprising an electro-magnetic field in circuit with a source of electrical energy sensitive to sound waves, an armature and a coil included in said field, and the armature being arranged to extend `through the coil, means for pivotally su porting the armature at a point without t e coil, means for supporting said armature at a point within the coil, and adjustable means adapted to engage said armature at a point removed from the pivoting means for regulating the vibrations of said armature for the purpose defined.
6. A device for recording the fluctuations in an electrical current comprising a permanent magnet, a sectional core carried by the magnet, a coil within the core and connected with the electrical circuit for polarizing the core, said coil being provided with vertical and longitudinal communicating openings therethrough, an armature carried in one of said o enings, and spring means carried in the otiier of said openings and attached to the core for supporting the armature.
7.d A sound recording device comprising a coil connected with a source of electrical energy sensitive to sound waves, said coil being provided'with vertical and longitudinal communicating openings therethrough, a core surrounding the coil, a permanent magnet associated with the core, an armature carried in one of the openings in the core, spring means for supporting the armature extending through the other opening in the coil and attached to the core, and means for ad. j usting the armature for the purpose defined.
8. A sound recording device comprising a stylus arm, a stylus carried by the arm, said stylus arm, a stylus carried by the arm, sai-d ing an opening and a slot therein communicating with the opening, a housing for the head, adjustable means engaged With the head through the opening therein, said means being carried in a slot formed in the housing, adjustable means carried by the housing and extending within the slot in the head for raising and lowering the head, and a spring ldevice Within the housing and engaging the head and exerting its pressure in opposition to the aforementioned adjustable means for the purpose defined.
9. In a device for generating speech current from a sound record, the combination of means for creating a steady magnetic field,
opposing pole pieces in the magnetic circuit and spaced apart to form an airgap, an armature in the airgap, a support for said arma.- ture, resilient stops between the armature and pole pieces for controlling the movement of said armature, and means for operatively cordinecting said armature with a sound recor 10. In a device of the character described, means creating a steady magnetic field, opposing pole pieces in the magnetic circuit and spaced apart to form an air gap, an armature in the air gap and arranged to move toward and `from the pole pieces, damping means directly engaging and controlling the movement of said armature throughout its entire range of movement, and means for operatively connecting said armature with a member capable of carrying a sound record.
11. A device for recording electrical fluctuations comprising a permanent magnet, a sectional core carried by said magnet, a coil Within the core provided with a longitudinal opening, an armature ivotedin said opening and means for norma ly positioning said armature said means consisting of a reversely curved non-magnetic spring connected at its center to the armature and at its ends to the core. j
l2. A sound recorder adapted for cutting a hill and dale record in relatively hard material such as a. photographic film, the combination of a cutting sty us, means for creating a magnetic field, means for substantially varying said eld in accordance with sound to be recorded, an armature, means for biasing said armature to a position in said field and means for resisting the movement of said armature from said position, said means being more effective on displacement of said armature in one direction than on displacement of said armature in the opposite direction.
13. A sound recorder adapt-ed for cutting a hill and dale record in relatively hard material such as a photographic film, the combination of a cutting stylus, means for creating a magnetic field, means for substantially varying said field in accordance with sound to be recorded, an armature, means for biasing said armature to a position in said .field and damping pads for resisting movements of said armature in opposite vdirections respectively, one of said pads offering greater resistance to movement of said armature than the other.
14. A sound recorder adapted for cutting a hill and dale record in relatively hard material such as a photogra hic film, the combination of a cutting sty us, means for creating a magnetic field, means for substantially varying said field in accordance with sound to be recorded, an armature, means for biasing said armature to a position in said field, means for applying greater force to said armature when said armature is displaced in one direction from said position than when displaced in the opposite direction from said position.
15. The method of cutting4 a hill and dale sound groove in relatively hard material such as the usual motion picture film by means. of a cutting stylus operatively connected to an armature which operates between the poles of an electrical magnet and is connected to the armature by linkage having a leverage of at least substantial unity, which method consists in normally biasing said armature to position closer to one pole than to another, energizing said magnet by current which varies in accordance with the sound to be recorded, whereby said stylus is operated more strongly for displacement into the iilm than for displacement in the opposite direction, damping the movement of said stylus in both directions and drawing the lm against said stylus.
16. The method of cutting a hill and dale sound groove in relatively hard material such as the usual motion picture filmby means of a cutting stylus operativelfconnected to an armature which operates between the poles of an electro-magnet and is connected to the armature by means having a leverage of at least substantial unity, which method consists in normally biasing said armature to position closer to one pole than to another and energizing said magnet by current which is subject to relatively large variations in acf cordance with sound to be recorded, whereby said stylus is operated more strongly for displacement into the film than for displacement in the opposite direction, damping the movenient of said stylus in both directions and drawing the film against said stylus.
, 17. The method of cutting a hill and dale sound groove in relatively hard material such as the usual motion picture film by means of a cutting stylus operatively connected to an armature which operates between the poles of an electro-magnet and is connected to the armature by linkage having a leverage of at least substantial unit, which method consists in normally biasing said armature to position closer to one pole than to another, energizing said magnet by 'current which varies in accordance with the sound to be recorded, whereby said stylus is operated the coil and between the other pair of poles, an operating connection between the armature and sound record, cover means at opposite sides of said magnet closing the o iiing between the legs of the ma et an extending beyond the magnet van means for biasing said armature to a position between the oles and for damping the motion thereof sai last named means being partly supported by said pole pieces and partly by said cover means.
19. In a device 'for recording sound, means creating a permanent magnetic field, opposed pole pieces, a pivotally mounted armature movable near one end between said pole pieces, a cutting stylus, a. pivotally mounted arm supportingsaid stylus, an operating connection between said armature and stylus connected to said armature adjacent said pole f pieces, the leverage between said armature and stylus being at least substantial unity, and damping pads engaging opposite sides of one end of said armature at a point distant from its pivotal support.
In testimony whereof I aiiix my signature hereunto.
EARL H. FOLEY.
US732225A 1924-08-15 1924-08-15 Sound recording device Expired - Lifetime US1870446A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2432424A (en) * 1944-08-21 1947-12-09 Control Instr Co Inc Electromagnetic sound translating device
US2476684A (en) * 1945-10-12 1949-07-19 William K Rieber Phonographic transducer
US2514379A (en) * 1947-08-25 1950-07-11 Jr Charles R Douglass Electrodynamic recording head
US2563860A (en) * 1946-10-11 1951-08-14 Gray Mfg Co Sound recording and reproducing head

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2432424A (en) * 1944-08-21 1947-12-09 Control Instr Co Inc Electromagnetic sound translating device
US2476684A (en) * 1945-10-12 1949-07-19 William K Rieber Phonographic transducer
US2563860A (en) * 1946-10-11 1951-08-14 Gray Mfg Co Sound recording and reproducing head
US2514379A (en) * 1947-08-25 1950-07-11 Jr Charles R Douglass Electrodynamic recording head

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