USRE23125E - Bone conduction hearing aid - Google Patents

Description

June 21, 1949. f

H..KocH

` BONE CONDUCTIQN BBARIHGAID f' Re. 23,125-

ongxnal FundA Deo. 451,' 1941;

YIIII". 'A

IN VEN TOR.

Reissued June 21, 1949 BONE CONDUCTION HEARING AID Henry Koch, Huntingdon, Pag, assignor to Dictograph Products Company, Inc., NewYork, N. Y., a corporation of Delaware Original No. 2,405,433, dated` August 6, 1946, Serial No. 425,039, December 31, 1941. Application forV reissue June 28, 1947, Serial No, 757,799

Claims. l.

This inventicnrelates to' audiphones and has particular reference to audiphone lreceivers having a vibrating contacter adapted to be placed in operative connectionwith the bonestructure of the user for transmitting audible sounds picked up by a suitablel microphone to the inner ear through the bone structure.

Bone conduction receivers may be divided'into two general classes, direct actingeand reaction. In the former the bone contacter is directly connectedtoA the vibrating'element, such as a reed, of7 an electromagnetic system, the magnet structure of'whieh is held relatively stationary by a headband or the like, so that the contacter Vibrates relatively thereto. In the reaction type of receiver, theA bone engaging contacter connected to thefvibrating element, such as a reed, issupported-by-aheadband or the like, so that the electromagnetic system hangs free and, inasmuch as this system hasV substantial mass7 it remainsstationary While the contactor vibrates relatively thereto byf reaction.

Each class of bone conduction receiver has certain advantages over the other, as Well as certain disadvantages. Thus, inasmuch as the reaction type of receiver vibrates bodily as a unit, itz necessarily also vibrates thefconnectingv portion of the headband as well, which imposesvsomerestraint on, the vibration-requiring increased mass against which the reed may react, thus requiring considerable power for operation.

The direct acting bone receiver does not require vibration of the headband since only the reed.. and contacter Aare-fvibrated, but the necessary: pressure of. the contacter against the bone in orderf to-obtain good conduction is considerable, and that results in suppression of the reedk or.` diaphragm towhichy the contacter is connectedand variation of theair gap.l This objection Vto direct-action receiverslis-largely overcome in the improvement disclosed in my Patent No. 2,144,458, in Whichn the contacter, forming part of the casingwall engaging the` body, is carried byy the reed, Which.is=made sufficiently stiff tov the,` stili reed cannot. withstand this abnormaly pressure andf-isvlexed With consequent variance' of the air gap and ineicient and ineffective re production. In one formof the invention of my .sa-id patent, resilient' material', such as rubber or felt is interposed between the -contactor and' the casing carrying the magnetic structure so thatv even under abnormal pressures onthe contactor` the air gapis not varied sufficiently to impair operation of the device. However, even though this cushion is resilient, it aiects'normal electromagnetic vibration and is-not entirelyl satisfactory.

The-present invention is concerned with im provements on the' direct-acting bone receiver disclosed in mysaid'P'atent No. 2,144,458, in which the general characteristics of the receiver there disclosed are retainedan-dthe disadvantage ofv susceptibility tov abnormal pressures of the contactorf againstthe head is eliminated. Thisv is accomplished in a preferred embodiment" of the present inventionby resiliently mounting the entire magneticstructure in the casing by spring means-softer or less resistant to flexingy than the stiff reed', i; e., which will flex beforethe reed'flexes; under abnormal pressures, so thaty the entireelectromagnetic system floats Within the casing to be restored'to its normal position by the, spring means when the abnormal pressure is released,` Without impairment in its operation during the period of abnormal pressure;

The receiver of thisinvention is also preferably mounted directly on the headband which lies flatwise against the-head-so -that anyy pressure against the headband will not change thepositionof the electromagneticstructure resiliently supportedwithinthe casing inthe manner described.

Fora more-.complete understanding of the invention; reference mayv behad to the accompany'- ing drawing, in which:

Figurewl illustrates theY bone conduction receiver of this invention supported cna headband;

face plate for the receiver VAL as-I it-is held llatwisel against the head. Projecting-slightly beyond ,the surface'of theiace -plate Il is a bone-engaging contactor` or button' I2;- which is vibrated'by 'electrica-l means Withirrthecasing lll'so-as to transg mit its vibrations through the intervening bone to the inner ear of the user. The electrical means is energized by voice currents picked up by a suitable microphone I3 in circuit with a battery or other source of power I4 and preferably a vacuum tube or carbon booster amplifier, not shown, connected to the electrical means within the casing A by the fiexible electric cord IE having the separa-ble plug type connectors I6 plugged into the casing Ill.

The aforementioned electrical means Within the casing i Il may be electromagnetic, a piezo-electric crystal, or any other means responsive to energization by voice currents to produce sufciently powerful vibrations for intelligible transmission through the bone to the inner ear. Electromagnetic means are shown in the drawings by way of illustration of the invention, and in Fig. 2 comprises a bar magnet Ii resiliently supported within the casing Ii] by means of a leaf spring I8 secured at one end thereto by screws I9 and at its other end to the face plate II, as by bolts countersunk in the face plate II.

Also secured to the same end of the bar magnet I'I is the reed 2|, having a generally L shape and forming at its free end a narrow air gap 22 with the opposed end of the pole shoe 23 secured to the other end of the bar magnet I by screws 26| and carrying the voice coil 25. The reed 2| and the magnet IT are free of and spaced from face plate II and casing I0, respectively.

- VoiceI coil 25 is connected to connector plugs it by filaments 26 soldered to studs 2'I on concluetor plates 2t insulated from headband I I and connected through springs 29 and friction buttons 3i? to the plugs I6.

i Secured to the free end of the reed 2| is a contactcr button I2 whose outer surface projects only slightly beyond the skin engaging surface of face plate I i'. For a small area contactor I2 as shown such slight projection is desired in order that the skin beneath it will be compressed slightly more than the surrounding skin beneath the face plate I I, so that the skin is firm and hence more conductive of the vibrations at the point of application thereof.

The average degree of skin compressibility, over the mastoid eminence, for example, is such that the projection of the contactor I2 beyond the face plate I I need not exceed from V64 to 1/aa of an inch, so that the button is substantially flush with the face plate'. The degree of projection of the contactor in the drawings is shown exaggerated in the interest of clarity. It will be understood that where the contactor constitutes a large part or all of the area of the face plate, as shown in my aforementioned patent, there will be less cr no projection of the contactor beyond the face plate, because the need for localized skin compression decreases as the area of the contactor increases.

The contactor I 2 extends through a hole in the face plate II', which is sufficiently oversize that there is no contact between the contactor I2 and the face plate I I. The consequent narrow annular slot around the contactor I2 is sealed by a ring of felt 3| against ingress of moisture, dirt and the like, this ring 3| being clamped between the contactor I2 and the reed 2|.

The air gap 22 has a width on the order of a few thousandths of an inch and the reed 2| is thick and consequently stiff, so that a force on the contactor I2 in excess of normal headband pressures, i. e., greater than about five ounces, is necessary in order to deflect the reed 2| suihciently to affect the air gap 22. Thus, if the stiffness selected for reed 2| is such that a force of eight ounces is necessary to deflect it at the air gap, the stiffness of spring I8 is made such that it flexes before the reed 2I is flexed, e. g., when a pressure in excess of six to seven ounces is applied to the contactor I2. These degrees of stiffness are predicated on normal headband pressures in the neighborhood of ve ounces, so that a pressure in excess thereof is abnormal. Obviously, if the normal headband pressure is greater or less than that in the given example, the reed 2| will be made stiffer or softer, as the case may be, and spring IB will always bemade to iiex under a contactor pressure somewhat less than that required to deiiect the reed 2|.

In operation of the bone conduction receiver illustrated in Figs. 1 and 2, the face plate I I' is held firmly against the head, such as on the mastoid eminence, by the headband II, with a normal pressure of five ounces. The contactor I2 does not move under this pressure because the stiffness of the reed 2| is such that a greater pressure is required on the contactor IZ before the reed is flexed. Consequently the contactor compresses the skin beneath it slightly more than does the surrounding skin-engaging portion of the face plate I I', so that a firm vibration conducting coupling between it and the bone is provided. Energization of the electromagnetic system results in vibration of the contactor I2 relatively to the headband Ii and casing I0 and transmission of its vibrations through the intervening bone to the inner ear.

n If the pressure on the contactor I2 is increased abnormally, as when the user presses on the casing III while it is on his head, or presses his linger on the contactor I2 while the receiver is not on his head, the spring I8 will flex, allowing the contactor I2 to recede into the casing, the entire magnet system moving therewith without any flexing of the reed 2|. Even when the device is in use and the casing is pressed against the head or a tight hat placed over the headband II producing a similar effect, the operation of the receiver is not impaired.

By securing the casing ID to the headband Il, as shown, so that a large area of the latter engages the head, the effect of pressure on the headband, as by a tight hat, is minimized and usually precluded. This advantage is not possible with headbands of the pivoted fork type shown in my said patent, where the headband is spaced from the head and hence is more susceptible of movement and consequent suppression of the contactor under abnormal pressures. It will be understood that this arrangement of headband co-extensive with or continuous with the face plate may be employed with advantage on any type of bone receiver, such as those described in my said patent.

in the modified form of the invention shown in Y Fig. 3, the bar magnet I7 is suspended by a spring I8 from the inside vof the casing I to which spring I8 is secured by bolts 32 located opposite the center of the magnet Il'. Secured to opposite ends of magnet I'I by screws 33 is a U-shaped spring 34 carrying at its center the armature 35 screwed to contactor I2', which may be a hard rubber button or other non-metallic material. Pole shoes 23 also secured to the ends of the bar magnet I`| by the screws 33 form narrow air gaps with the armature 35 and carry the voice coils 25 connected in the :microphone` i circuit through 'filaments 26', bushings 3.6, 4and connectors i6'.

The contactor projects slightly beyond-thesurface of the face plate l-I", whichis coextensive lwith the headband Il, and a felt washer 3'l f lseals Vthe annular space rbetween the perimeter of the contactor l2 andthe hole thereforin the face plate H. As before, the spring 34, which 'corresponds tothe reed 2l of Fig. 1 as a spring, 'is sumciently stiff that it tdoes not flex -under pressures of button l2' on the ybone equal to normal -or 'slightly greater, depending upon requirements. However, spring 't8' is softer than "spring 34, so that itilexes under abnormal pressures on contacter l2', allowing the entire'velectromagnetic structure to move vinwardly until vvequilibrium is obtained. When the pressure is "released the system is restored by spring -|8-, without impairment of the operation of the receiver during this interval of abnormal pressure. 'The arrangement of Fig. 3 differs from that of Fig. 2 in that the -ux paths Yare shorter and `the movement under abnormal pressure is in the direction of the-pressure vinstead of aboutsprin'g I-B' as a form of pivot in Fig. 2. The operatic-n is the same in'each'case.

It will be seen that the present invention pro- `videsa simple and effective solution to the problem of operation of bone conduction receivers, while preserving the advantages thereof, and -while certain preferred embodiments of the invention have been illustrated and `described herein, it is to be understood that they are merely illustrative and do not llimit'thein'vention Within the 'scope of the claims.

I claim:

l. In an audiphone receiver, the combination of an electromagnetic means adaptedfto `respond to varying currents substantially throughout the audible frequency range, a casing having a face plate adapted Ato engagethe'body of the user, a contactor forming at least part of the bodyengaging surface of said face plate and vibrated by said electromagnetic means relatively to said casing, relatively stiff spring means connecting said contacter and electromagnetic means, and resilient means connecting said electromagnetic means directly connected to said casing and supporting said electromagnetic means, spring means and contactor for bodily movement of the same as a unit relatively to said face plate in response to excessive pressures applied to said contactor, said resilient means having a stiffness less than that of said spring means.

2. In an audiphone receiver, the combination of an electrical means adapted to respond to varying currents substantially throughout the audble frequency range, a casing having a face plate adapted to engage the body of the user, a contactor forming at least part of the body-engaging surface of said face plate and vibrated by said electrical means relatively to said casing, relatively stii spring means connecting said contactor and electrical means, means supporting said face plate and contacter in simultaneous connection with the bone structure of the user with a predetermined pressure less than that required to substantially flex said spring means, and resilient means directly connecting said electrical means to said casing and supporting said electrical means, spring means and contactor and said supporting means for bodily movement of the same as a unit relatively to said face plate under pressure on said contactar greater than said predetermined pressure.

3. 'In an audiphone receiver, ithe @combination 'of an electrical means adapted to respond to varying currents vsubstantially @throughout the vaudible frequency range, afcasng enclosing 'said electrical means, a headband secured 'to ysaid casing and forming -a wall thereo'fengaging the body of the user with a predetermined pressure,

vresilient means .directly connecting =said electrical 'means to said 'casing ifor bodily movement relat1vely thereto, said resilient means having `a stiffness precluding substantial yflexing under contactcr'to said electrical'means and Vhavinga.

stiffness greater thantliato'f said resilient means, kwhereby pressure r'on said contactor in excess o said predetermined 4pressure causes 'flexing 'of said resilient means and bodily movement "of said electrical means, spring means and contactor as a'unit relatively vtosaid casing.

4. In an audiphone =receive1, lthe combination of an electrical means adapted to respond to Varying currents substantially throughout the audible frequency range, a 'headband having a relatively iiat portion adaptedtofengage'the head of the user, a casing I'-for --saidfelectrical means having a wall coextens'ive with said headbani portion, and a contactor `vibrated `vby said electrical means and .adapted to engage the Ihead of the user simultaneously --W'ith said headband portion.

5. In an audipho'ne rleceiver, the combination of an electrical means `adapted to respond -to varying currents substantially throughout the audible frequency range, `a "headband -having 'a relatively iiatV portion adapted toengage thehead of the user, a contactor vibrated bylsaid electrical means and substantially 1flush with said headh band portion for transmitting its vibrations through the bone to the inner ear, and a casing for said electrical means mounted on said headband.

6. In an audiphone receiver, the combination of electro-magnetic means adapted to respond to varying currents substantially throughout the audible frequency range, said electromagnetic means comprising a unit including a magnet structure, voice coil, vibratory armature, a relatively stiff spring connecting said armature and magnet structure and a contacter connected to said armature for Vibration therewith, a casing for said electromagnetic means, said contacter forming at least part of a wall of said casing, resilient means directly connecting said magnet structure to said casing and having less stiifness than said spring, whereby excessive pressure on said contacter-causes said resilient means to ex to permit bodily movement of said electromagnetic means as a unit relatively to said caslng.

'7. In an audiphone receiver, the combination of electromagnetic means adapted to respond to Varying currents substantially throughout the audible frequency range, said electromagnetic means comprising a unit including a magnet structure, voice coil, vibratory armature, a relatively stiff spring connecting said armature and magnet structure and a contacter connected to said armature for vibration therewith, a headband having an aperture for said contactor, a casing for said electromagnetic means mounted kon said headband, said headband forming a wall ,of the casing, and resilient means directly connecting said magnet structure to said casing and having a stiffness less than said spring, whereby said electromagnetic means moves bodily as a unit in said casing in response to excessive pressures on said contactor.

8. In an audiphone receiver, the combination `of electromagnetic means adapted to respond to varying currents substantially throughout the `audible frequency range, said electromagnetic `means comprising a unit including a magnet structure, voice coil, vibratory armature, a relatively stiiT spring connecting said armature and 4magnet structure and a contactor connected to said armature for vibration therewith, a headband having an aperture for said contactor, a casing for said electromagnetic means mounted on said headband, said headband forming a wall of the casing, and a second spring directly connecting said magnet structure to said headband and affording bodily movement of said electromagnetic means as a unit relatively to said casing yin a direction opposite to that of application of the contactor to the body of the user, said second spring having less stiiness than said iirst spring.

9. In an audiphone receiver, the combination of a vibrating mechanism comprising two members, relatively stil spring means connecting said members and permitting relative movement between at least portionsy of both members, electrical means adapted to respond to varying currents within the audible frequency range secured to said portion of one of said members and operatively opposed to said portion of the other member for relatively vibrating the latter, a contactor .connected to the said portion of said other member for vibration therewith, a resilient headband for holding said contactor rin engagement with the body of the user with a predetermined preslsure, and a leaf spring having less stiffness than member to and supporting the same on said headband, whereby the said portion of said member and the contactor are free to vibrate relatively to said other member and the headband and said leaf spring iiexes to permit bodily movement of said vibrating mechanism and contactor relatively to said headband in response to excessive pressure on said contactor without suppressing the vibration of said portion of said one member and contactor.

10. In an audiphone receiver, the combination of a vibrating mechanism comprising two members, relatively stiff spring means connecting said members and permitting relative movement between at least portions of both members, electrical means adapted to respond to varying currents within the audible frequency range secured to said portion of one of said members and operatively opposed to said portion of the other member for relatively vibrating the latter, a contactor connected to the said portion of said other member for vibration therewith, a resilient headband connected to the said portion of said one member and having a normal stiffness less than the stiffness of said spring means for holding said contactor in engagement with the body of the user with a predetermined maximum pressure, and a spring directly interposed in said connection between said headband and the said portion of said one member and having greater stiness than said normal stiffness of said headband but less stiffness than said spring means, whereby pressure of said contactor in excess of said predetermined maximum pressure causes said spring to iiex and permit bodily movement of said vibrating mechanism and relatively to said headband without affecting said spring means.

HENRY KOCH.

No references cited.

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