US2405433A

US2405433A - Bone conduction audiphone

Info

Publication number: US2405433A
Application number: US425039A
Authority: US
Inventors: Koch Henry
Original assignee: DICTOGRAPH PRODUCTS CO Inc
Current assignee: DICTOGRAPH PRODUCTS CO Inc; DICTOGRAPH PRODUCTS COMPANY Inc
Priority date: 1941-12-31
Filing date: 1941-12-31
Publication date: 1946-08-06
Anticipated expiration: 1963-08-06
Also published as: USRE23125E

Description

Ali@ 6 19416 H. KOCH BONE CONDUCTION AUDIPHONE Filed Dec. 5l, 1941 Il l .Il u n Lm. Mwr. h 2, .6 .A A \s 5 .1 .1 M 3 n 3 1 I' Plas,

, INVENTOR- f/f/VA'Y HOCH l I? Mm EY5 BYl Patented ug. 6, i946 BONE CONDUCTION AUDIPHONE Henry Koch, Jamaica, N. Y., ass'gnor to Dictograph Products Company, Inc., New York, N. Y., a corporation of Delaware 'in Application December 31, 1941, serial No. 425,03919/ 8 Claims. 1

This invention relates to audiphones and has particular reference to audiphone receivers having a vibrating contactor adapted to be placed in operative connection with the bone 'structure of the user for transmitting audible sounds picked up by a suitable microphone to the inner ear through the bone str'ucture.

Bone conduction receivers may be divided into two general classes, direct acting and reaction. In the former the bone contactor is directly connected to the vibrating element, such as a reed, of an electromagnetic system, the magnet structure of which is held `relatively stationary by a headband or the like, so that the contactor vibrates relatively thereto. In the reaction type of receiver, the bone engaging contactor connected to the vibrating element, such as a reed, is supported by a headband or the like, so that the electromagnetic system hangs free and, inasmuch as this system has substantial mass, it remains stationary while the contactor vibrates relatively thereto by reaction.

Each class of bone conduction receiver has certain advantages over the other, as well as certain disadvantages. action type of receiver vibrates bodily as a unit, it necessarily also vibrates the connecting portion of the headband as well, which imposes some restraint on the vibration requiring increased Thus, inasmuch as the remass against which the reed may react, thus ren quiring considerable power for operation.

The direct acting bone receiver does not re- Uluire vibration of the headband since only the reed and contactor are vibrated, but the necessary pressure of the contactor against the bone in order to obtain good conduction is considerable, and that results in suppression of the reed or diaphragm to which the contactor is connected and variation of the air gap. This objection to direct action receivers is largely overcome in the improvement disclosed in my Patent No. 2,144,458, in which the contactor, forming part of the casing wall engaging the body, is carried by the reed, which is made suiiciently stiff to resist deformation and consequent varying of the air gap under headband normal pressures.

Nevertheless, under abnormal conditions, a greater pressure is applied to the button, sometimes on the order of a pound or more, so that the stiff reed cannot withstand this abnormal pressure and is eXed with consequent variance of the air gap and ineicient and ineffective reproduction. In one form of the invention of my said patent, resilient material, such as rubber or felt is interposed between the contactor and the casing carrying the magnetic structure 'so that even under abnormal pressures on the contactor the air gap is not varied suliiciently to impair operation of the device. However, even though this cushion is resilient, it aiects normal electromagnetic vibration and is not entirely satisfactory.

The present invention is concerned With improvements on the direct-acting bone receiver disclosed in my said Patent No. 2,144,458, in which the general characteristics of the receiver there disclosed are retained and the disadvantage of susceptibility to abnormal pressures cf the contactor against the head is eliminated. This is accomplished in a preferred embodiment of the present invention by resiliently mounting the entire magnetic structure in the casing by spring means softer or less resistant to flexing than the stiff reed, i. e., which will ieX before the reed fleXes under abnormal pressures, so that the entire electromagnetic system ioats 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 this invention is also preferably mounted directly on the headband which lies iiatvvise against the head so that any pressure against vthe headband will not change the position of the electromagnetic structure resiliently supported within the casing in the manner described. y l

For a more complete understanding of the invention, reference may be had to the accompanying drawing, in which:

Figure 1 illustrates the bone conduction receiver of this invention supported cn a headband and connected in a microphone circuit;

Fig. 2 is a longitudinal section through the receiver illustrating the interior construction thereof; and

Fig. 3 is a longitudinal section through a modied form of the receiver of this invention.

Referring to Fig. l, the bone conduction receiver A includes a casing I0 ofv hard rubber, phenolic resin, or the like, mounted on a headband Il, which forms a closure for the corresponding open side of the casing I0 and also serves as a face plate for the receiver .A as it is held flatwise against the head. Projecting slightly beyond the surface of the face plate Il is a bone-engaging contactor or button l2, which is vbrated by electrical means within the casing lil so as to transmit its vibrations through the intervening bone to the inner ear of the user. The electrical means .3 is energized by voice currents picked up by a suitable microphone I3 ln 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 flexible electric cord I5 having the separable plug type connectors I6 plugged into the casing I0.

The aforemetioned electrical means within the casing Iil may be electromagnetic, a piezo-electric crystal, or any other means responsive to energization by voice currents to produce sufficiently 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 comiprises a bar magnet I'I resiliently supported within the casing IB 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 20 countersunk in the face plate I I YAlso secured to the same end of the bar magnet I'I is the reed 2 I, 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 I1 by screws 24 and carrying the voice coil 25. The reed 2l and the magnet I'I are free of and spaced from face plate I I' and casing I0, respectively.

Voice coil 425 is connected to connector plugs IB by filaments 26 soldered to studs 2l on conductor plates 28 insulated from headband I I and connected through springs 29 and friction buttons 30 to the plugs I6.

Secured to the free end of the reed 2I is a contactor 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 II need not exceed from l@ to 1&2 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 vpart or all of the area of the face plate, as shown in my aforementioned patent, there will be less or no projection of the contactor beyond the faceplate, because the need for localized skin compression decreases as the area of the contactor increases.

The contactor I2 extends through a hole in the face plate II', which is suiciently 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 3I being clamped between the contactor I2 and the reed 2 I The air gap 22 has a width on the order of a few thousandths of an inch and the reed 2I '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| suficiently to aifect the air gap 22. Thus, if the stiffness selected for reed 2l is such that a force of eight ounces is lnecessary 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 I8 will always be made to flex under a contactor pressure somewhat less than that required to deflect the reed 2 I.

In operation of the bone conduction receiver il iustrated 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 2I is such that a greater'pressure is required on the contactor I2 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 rm 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 I and transmission of its vibrations through the intervening bone to the inner ear.

If the pressure on the contactor I2 is increased abnormally, as when the user presses on the casing I0 while it is on his head, or presses his finger on the contactor I2 while the receiver is not on his head, the spring I8 will ex, allowing the contactor I2 to recede into the casing, the entire magnet system moving therewith without any flexing of the reed 2l. 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 lcasing Ill to the headband II, 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 fromthe 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 modied form of the invention shown in Fig. 3, the bar magnet II' is suspended by a spring i8' from the inside of the casing I0 to which spring I8 is secured by bolts 32 located opposite the center of the magnet II. 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'I by the screws 33 form narrow air gaps with the armature 35 and carry the voice coils 25' connected in the microphone circuit through filaments 26', bushings 36, and connectors I6'.

The contactor projects slightly beyond the surface of the face plate II, which is coextensive face plate l l.

with vthe 'headband Il, and a felt washer 3| seals the annular space between the perimeter ofthe contactor l2 and the hole therefor in the As before, th'e spring 34, which corresponds tothe reed 2l of Fig. '1 as a spring, is suicientlystilf that it does not lleX under pressures of button i2 on the bone equal to normal or slightly greater, depending upon requirements. However, spring I8 is softer than spring 34, so that it ilexes under abnormal pressures on contactor I2', allowing the entire electromagnetic structure to move inwardly until equilibrium is obtained. When the pressure is released the system is restored by spring I8', without impairment of the operation of the re-v ceiver during this interval of abnormal pressure. The arrangement of Fig. 3 differs from that of Fig. 2 in that the ux paths are shorter and the movement under abnormal pressure is in the direction of the pressure instead of about spring i8 as a form of pivot in Fig. 2. The operation is the same in each case.

It will be seen that the present invention provides a simple and effective solution to the problem of operation of bone conduction receivers, while preserving th'e 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 limit the invention within the scope of the claims.

I claim:

l. In an audiphone receiver, the combination of an electromagnetic means adapted to respond to varying currents substantially throughout the audible frequency range, a casing having a face plate adapted to engage the 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 stif spring means connectingr said contactor 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 audible 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 stiff spring means connecting said contactor and electrical means, means supporting said face plate and contactor 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 contactor greater than said predetermined pressure.

3. In an audiphone receiver, the combination of an electrical means adapted to respond to varying currents substantially throughout the audible frequency range, a casing enclosing said electrical means, a headband secured to said casing and forming ak wall thereof vengaging the body of the user with a predetermined pressure, resilient means directly connecting said electrical means to said casing for bodily movement re1- atively thereto, said resilient means having a stiffness .precluding substantial flexing under pressures approximately equal to said predetermined pressure, a contactor vibrated by said electrical means and extending through said wall for engaging the body of the user simultaneously with said wall, and spring means connecting said contactor to said electrical means and having a stiffness greater than that of said resilient means, whereby pressure on said contactor in excess of said predetermined pressure causes flexing of said resilient means and bodily movement of said electrical means, spring means and oontactor as a unit relatively to said casing.

4. In an audiphone receiver, the combination of an electrical means adapted to respond to varying currents substantially throughout the audible frequency range, a headband having a relatively flat portion adapted to engage the head of the user, a casing for said electrical means having a wall coextensive with said headband portion, and a contactor vibrated by said electrical means and adapted to engage the head of the user simultaneously with said headband portion.

5. In an audiphone receiver, the combination of an electrical means adapted to respond to varying currents substantially throughout the audible frequency range, a headband having a relatively flat portion adapted to engage the head of the user, a contactor vibrated by said electrical means and substantially flush with said headband 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 stilf spring connecting said armature and magnet structure and a contactor connected to said armature for vibration therewith, a casing for said electromagnetic means, said contactor forming at least part of a wall of said casing, resilient means directly connecting said magnet structure to said casing and having less stiffness than said spring, whereby excessive pressure on said contactor causes said resilient means to flex to permit bodily movement of said electromagnetic means as a unit relatively to said casing.

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 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 resilient means directly connecting said magnet structure to said Casing and having a stilfness less than said spring, whereby band having an aperture for said contacter, a casing for said electromagnetic means mounted von 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 in a direction opposite to that of application of the contacter to the body of the user, said second atively sti spring connecting said armature and 1o spring having less stiffness than Said first Spring.

magnet structure and a contacter connected to said armature for vibration therewith, a head- HENRY KOCH.