US 3712962 A
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Description (OCR text may contain errors)
Jan. 23, 1973 J. M. EPLEY 3,712,962
IMPLANTABLE PIEZOELECTRIC HEARING AID Filed April 5, 1971 3 Sheets-Sheet 1 FIG I SKI N IMPLANTED EXTERNAL RECE'VER Jfif 'F MICROPHONE JOHN M. EPLEY INVENTOR BUCKHORN, BLORE, KLARQUIST & SPARKMAN ATTORNEYS Jan. 23, 1973 J. M. EPLEY IMPLANTABLE PIEZOELECTRIC HEARING AID 3 Sheets-Sheet 2 Filed April 5, 1971 OUTPUT JOHN M. EPLEY.
INVENTOR BY BUCKHORN, BLORE, KLARQUIST & SPARKMAN ATTORNEYS Jan. 23, 1973 J. M. EPLEY IMPLANTABLE PIEZOELECTRIC HEARING AID 3 Sheets-Sheet 3 Filed April 5, 1971 JOHN M. EPLEY INVENTOR BlKKHORN, BIO/(l, KIARQUISI & SIARKMAN ATTORNEYS United States Patent Ofice US. Cl. 179-107 R 17 Claims ABSTRACT OF THE DISCLOSURE An implantable hearing aid apparatus is described using a piezoelectric transducer device. One embodiment of the device is a bendable piezoelectric member which may be inserted between two bones in the ossicular chain of the middle ear for movement of such bones in accordance with an audio frequency electrical signal applied to such transducer. Another embodiment of the transducer member is a cylindrical piezoelectric member which elongates when a signal is applied thereto for movement of the ossicular bones. The transducer may also be used as a pickup device to sense the mechanical movement of the ossicular bones and produce a corresponding electrical output signal which may be applied to the nerves of the inner ear.
BACKGROUND OF THE INVENTION The subject matter of the present invention relates generally to implantable hearing aid apparatus using a piezoelectric transducer, and in particular to such an apparatus in which the piezoelectric transducer is used to move the bones of the ossicular chain in the middle ear when an electrical input signal is applied thereto, or to produce an electrical output signal in response to movement of such bones so that such output signal may be applied to the nerves of the inner ear.
The implantable hearing aid apparatus of the present invention is an improvement over conventional hearing aid apparatus in that it is completely hidden from view so that it does not have the unsightly appearance of conventional hearing aids. In addition, the present hearing aid employs a piezoelectric transducer which is very compact so that it can be positioned between two bones of the ossicular chain without any appreciable impairment of movement of such bones during the normal operation of the ear in response to sounds. Previous implantable hearing aids have employed piezoelectric transducers but they were not of the bending type and were not positioned between the bones of the ossicular chain. Thus, as shown on page 54 of the article by Jako and Jensen, in the publication American Academy of Opthalmology and Otolaryngology, Course 319, Conservative Tympanoplasty, published Oct. 1, 1966, one prior art device included a piezoelectric transducer used as a microphone pickup in the tympanic membrane of the middle ear to produce an output signal which is applied to a piezoelectric output transducer mounted in the oval window of the inner ear to move the fluid in the cochlea of the inner ear. The piezoelectric transducer device of the present invention is much more efficient and requires less power than the prior art apparatus. Another advantage is that there is less harmonic distortion in the hearing aid apparatus of the present invention.
It is therefore one object of the present invention to provide improved implantable hearing aid apparatus which may be completely hidden from view including a compact piezoelectric transducer device.
Another object of the present invention is to provide such a hearing aid apparatus in which the piezoelectric transducer is a bendable device with high efliciency and low power dissipation.
3,712,962 Patented Jan. 23, 1973 A further object of the invention is to provide such a hearing aid apparatus in which the piezoelectric transducer device is adapted to be inserted between two bones of the ossicular chain so that it does not interfere with the movement of the ossicular chain in response to sound vibrations during normal operation of the ear.
Still another object of the invention is to provide such a hearing aid apparatus of low harmonic signal distortion and of a relatively simple and inexpensive construction.
BRIEF DESCRIPTION OF DRAWINGS Other objects and advantages of the present invention will be apparent from the following detailed description of certain preferred embodiments thereof and from the attached drawings, of which:
FIG. 1 is a schematic diagram showing one embodiment of the implantable hearing aid apparatus of the pres ent invention including a bending type of piezoelectric transducer;
FIG. 2 is a perspective elevation view of the transducer device used in the hearing aid apparatus of FIG. 1;
FIG. 3 is a section view taken along the line 33 of FIG. 2;
FIG. 4 is an enlarged section view taken along the line 44 of FIG. 3;
FIG. 5 is a schematic diagram of another embodiment of the hearing aid apparatus of the present invention in which the piezoelectric transducer is used as a pickup device to produce an output signal in response to movement of the bones of the ossicular chain;
FIG. 6 is an elevation view of another embodiment of the piezoelectric transducer device used in the apparatus of FIGS. 1 and 5;
FIG. 7 is a horizontal section view taken along line 7-7 of FIG. 6;
FIG. 8 is an enlarged vertical section view line 8-8 of FIG. 7;
FIG. 9 is a perspective view of a further embodiment of a piezoelectric transducer which may be employed in the hearing apparatus of the present invention;
FIG. 10 is an enlarged section view taken along line 10-10 of FIG. 9;
FIG. 11 is a perspective view of still another embodiment of a piezoelectric transducer employed in the hearing aid apparatus of the present invention; and
FIG. 12 is an enlarged horizontal section view taken along line 1212 of FIG. 11.
DESCRIPTION OF PREFERRED EMBODIMENTS As shown in FIGS. 1 to 4, one embodiment of the implantable hearing aid apparatus of the present invention includes a piezoelectric transducer device 10 of the bendable type shown in US. Pat. 2,841,722 of Gravely granted July 1, 1958, which is connected through leads 11 and 13 to the audio frequency signal output of an implanted radio receiver circuit 12. The receiver circuit is coupled by an internal antenna 14 beneath an outer layer 16 of the skin on the head of the user to an external antenna 18 of a radio transmitter 20 positioned outside the body of such user. This external transmitter and associated amplifier is connected at its input to a microphone 22 and may be provided as a compact unit also containing the power supply batteries for such transmitter which may be completely hidden from view in the clothes or the eyeglasses of the user. Thus, the implantable hearing aid apparatus of the present invention avoids the unsightly appearance of conventional hearing aids.
The receiver 12 may be self-biased by charging power supply capacitors therein with the radio frequency signal transmitted from the transmitter 20' using a circuit similar taken along to that shown in US. Pat. 3,209,081 of Ducote et al., granted Sept. 28, 1965, which also shows a suitable transmitter. The receiver circuit may be made extremely small and with low power dissipation by using a semiconductor integrated circuit including field eflfect transistors. The implanted receiver 12 is encapsulated in a covering of suitable inert plastic material, such as epoxy resin or silicone rubber. Of course, the covering material must be waterproof and implantable into the tissue without causing infection or damage. It should be noted that it may be preferable to provide rechargeable batteries within the implanted receiver 12 in which case a charging coil and associated rectifiers are provided with such charging coil positioned adjacent the outer surface of the skin 12 so that such battery may be recharged through an inductance coil positioned adjacent to such charging coil from an external A.C. power supply.
As shown in FIG. 1, the transducer is mounted with its free ends 24 positioned between two bones of the ossicular chain in the middle ear, such as the stapes 26 and the incus 28. The transducer device 10 is not fixed to any bone or other element of the ear, and as a result, does not interfere with the normal operation of the ossicular chain in transmitting sound vibrations from the tympanic membrane 30 through the malleus 32, incus 28 and stapes 26 to the inner ear. This has the advantage that the user, who hears normally at some frequencies, or only has a partial deafness may still hear in a normal manner after the hearing aid is implanted.
As shown in FIGS. 2, 3 and 4, the piezoelectric transducer device 18 includes two pending piezoelectric members 34 and 36 sold under the trademark Bimorph by the Clevite Corporation, Piezoelectric Division, of Bedford, Ohio. Each of the piezoelectric members 34 and 3'6 is formed by a pair of piezoelectric ceramic plates 38 and 40 which are separated by an intermediate conducting layer 42 and are provided with outer conducting layers 44 and 46. As shown in FIG. 4, the piezoelectric ceramic plates 38 and 40 may be connected in parallel with the two outer conducting layers 44 and 46 being connected together at one terminal lead 48 of the receiver 12, while the intermediate conducting layer 42 is connected to the other lead 50 of the receiver. As a result of poling the piezoelectric ceramic material in the same direction, both of the ceramic plates 38 and 40 in each of the members 34 and 36 bend in the same direction when a signal voltage is applied to terminal leads 48 and 50. However, the two piezoelectric members 34 and 36 are oriented to bend in opposite directions for greater efiiciency. The crystalline piezoelectric ceramic plates 38 and 40 are poled in the same direction in a conventional manner by applying a DC. electrical field of the proper polarity during their formation. Of course, other piezoelectric materials can be employed, such as quartz and Rochelle salt, which do not require this poling.
'It should be noted that while FIG. 4 shows a parallel connection of the two piezoelectric ceramic plates 38 and 40, it is also possible to connect them in series in which case the lower conductive layer 46 is connected to terminal 50 and the upper layer 44 remains connected to terminal 48 while intermediate layer 42 is disconnected. In this series connection, the piezoelectric ceramic material 38 and 40 is poled in opposite directions in order to produce the required bending.
As shown in FIG. 3, the free ends 24 of each of the piezoelectric members 34 and 36 are provided with a relatively thick metal plate 52 attached to the inner conductive coating 46 by epoxy resin or other suitable means. A housing or guide member 54 of suitable plastic material, such as Teflon, is attached to the outer surface of that portion of each metal plate 52 extending beyond the ends of the piezoelectric members 34 and 36. The guide member 54 is provided with a central aperture 56 for receiving the adjacent ends of the bones 26 and 28 of the ossicular chain between which the transducer is inserted. The guide members 54 are made of soft plastic so that they may be trimmed to the proper size during the implant operation.
A resilient spacer member 58 in the form of a cylindrical wedge of triangular cross section is provided between the two metal plates 52 to hold such plates in engagement with bones 26 and 28. The spacer member 58 may be made of a silicone rubber material or other resilient material so that the spacer acts as a damper and connterpoise spring. A fixed rigid spacer 60 of metal is attached between the other end of the piezoelectric members 34 and 36 by epoxy resin. The terminal lead wires 48 and 50 are attached to the same end of such piezoelectric members by a small quantity or bead 62 of epoxy resin which acts as insulating material. The wires 48 and 50 are connected to the conductive layers 42, 44 and 46 by soldering or a conductive epoxy resin underlayer containing a filling of silver particles or other suitable conductive material.
As shown in FIG. 5 in another embodiment of the invention, the piezoelectric transducer device 10' is employed as a pickup device having a pair of output conductors '64 and 66 which transmit the electrical output signal produced by such transducer when the ossicules 26, 28 move the piezoelectric members 34' and 36'. The audio-frequency output signal produced by the transducer 10' is transmitted through an amplifier 68 to a pair of output terminals 70 and 72 which may be connected directly to nerves in the inner ear or to a piezoelectric piston device mounted on the oval window of the inner ear for moving the fluid within the inner ear. Any suitable, implantable amplifier circuit may be employed for amplifier 68 so long as it is capable of low power dissipation to enable long battery life.
As shown in FIGS. 6, 7 and 8, the piezoelectric transducer device 10' of FIG. 5 may be similar to that of FIGS. 2, 3 and 4 except that each piezoelectric member 34 and 36' is formed with a single piezoelectric ceramic plate 74 which is provided with a conductive coating 76 of silver or the like on one side and is bonded to a metal plate 78 of stainless steel on its other side by epoxy resin or other suitable material. This bendable, piezoelectric member 74 is also sold by Clevite Corporation under their trademark Unimorph. Bending of the piezoelectric members 34 and 36' occurs because the metal plate 78 is of fixed length and is attached along the entire length of the piezoelectric ceramic member 74. It should be noted that the metal plate 78 extends beyond the end of the ceramic member 74 and also serves as the metal plates on which the guide members 54 of plastic material are attached. Of course, the modified piezoelectric transducer device 10 of FIGS. 6-8 can also be employed in the hearing aid apparatus of FIG. 1 and, similarly, the piezoelectric transducer device 10 of FIGS. 2 through 4 can be employed in the hearing aid apparatus of FIG. 5.
-A third embodiment of the piezoelectric transducer device 10" is shown in FIG. 9 and consists of a single piezoelectric member which may have two piezoelectric ceramic layers 38 and 40 like member 34 of FIGS. 3 and 4. Alternatively, transducer device 10" may be like piezoelectric member 34 of FIGS. 7 and 8. In this embodiment, the transducer device 10" has a fixed end at epoxy resin bond 62 which is attached to a bone 80 or other fixed anchor point within the ear. The free end of such transducer is provided with a metal plate 82 having a threaded hole through which a metal screw guide member 84 extends. The guide member 84 is hollow to provide a housing, such as a conical cavity, into which the stapes bone 26 fits. The guide member 84 is adjusted by a threaded shank portion 86 extending through such threaded hole to enable adjustment of the guide member relative to the stapes bone 26. Thus, vibration of the piezoelectric transducer device 10" due to the application of an input signal through Wires 48 and 50 causes a corresponding vibration of the stapes bone 26 even when the incus bone has been removed by surgery.
As shown in FIGS. 11 and 12, still another embodiment of the piezoelectric transducer device 10" may be in the form of a hollow, cylindrical tube 8 8 of piezoelectric ceramic material having a pair of electrodes 90 and 92 coated on its inner and outer surfaces which are connected, respectively, to the lead wires 48 and 50. In this embodiment of the invention, the piezoelectric transducer device 10" is positioned between the incus bone 28 and the footplate portion 94 of the stapes bone 26 when the arch portion of such stapes bone has been removed by surgery, such are portion being shown in phantom lines in FIG. 11. The tubular ceramic member 88 expands and contracts longitudinally in response to an electrical signal applied thereto by lead wires 48 and 50 and thereby oscillates the bones of the ossicular chain in the same manner as the embodiment of FIGS. 1 to 4. It will be obvious to those having ordinary skill in the art that many changes may be made in the details of the preferred embodiments of the present invention without departing from the spirit of the invention. Therefore, the scope of the present invention should only be determined by the following claims.
I claim: 1. An implantable hearing aid apparatus in which the improvement comprises:
transducer means including a piezoelectric transducer device adapted to be implanted in an ear; and
mounting means for mounting the transducer device between two movable bones in the ossicular chain of the ear to cause movement of said bones and said device together when an electrical signal is applied to said device, said piezoelectric device being free of any fixed connection which would prevent normal movement of said bones in response to sound.
2. Apparatus in accordance with claim 1 including input signal means for applying an audio frequency electrical signal to the transducer device to cause said device to move said bones in response to the audio signal.
3. Apparatus in accordance with claim 1 including output signal means for transmitting an audio frequency electrical signal from the transducer device when said device is moved by said bones.
4. Apparatus in accordance with claim 1 in which the transducer device is a piezoelectric cylinder member which is provided with axial movement when the audio signal is applied thereto.
5. Apparatus in accordance with claim 1 in which the transducer device includes at least one bendable piezoelectric bar member.
6. Apparatus in accordance with claim in which the transducer device includes a pair of bar members of piezoelectric material which bend in opposite directions when said audio signal is applied thereto, said bar members having interconnected ends attached together and free ends which are free to move relative to each other.
.7. .An implantable hearing aid apparatus in which the improvement comprises:
a piezoelectric transducer device adapted to be implanted in an ear including a pair of bar members; and
mounting means including a pair of. connectors on the free ends of said bar members which are adapted to be inserted between the two bones in the ossicular chain to provide the sole support for the transducer device.
8. Apparatus in accordance with claim 7 in which the connectors are metal plates attached to the bar members with end portions extending from the free ends of said bar members.
9. Apparatus in accordance with claim 8 in which the end portions of the metal plates are each attached at its outer surface to a housing member provided with a central opening for receiving one of said bones.
10. Apparatus in accordance with claim 9 in which the housing member is of plastic material.
11. Apparatus in accordance with claim 8 in which each of the metal plates is fixedly attached along the entire length of one side of the bar member, a conductive coating is provided on the opposite side of said bar member, and said bar member is made of a single layer of piezoelectric ceramic material.
12. Apparatus in accordance with claim -8 in which each of the metal plates is fixedly attached along only a short portion of one side of the bar member, a pair of conductive coatings are provided on the opposite sides of said each bar member, and said bar member includes a plurality of layers of piezoelectric ceramic material separated by an intermediate conductive layer.
13. Apparatus in accordance with claim 7 in which the pair of bar members have their interconnected ends separated by a rigid spacer member and have their free ends separated by a resilient spacer member.
14. Apparatus in accordance with claim 13 in which the resilient spacer member is made of silicone plastic material.
15. Apparatus in accordance with claim 2 in which the input signal means includes an implantable receiver circuit which produces said audio signal at its output.
16. Apparatus in accordance with claim 15 which also includes a remote non-implantable transmitter circuit for transmitting signals to said receiver circuit.
17. Apparatus in accordance with claim 3 in which the output signal means includes an implantable amplifier circuit.
References Cited UNITED STATES PATENTS 3,594,514 7/197'1 Wingrove l79107 R 2,928,069 3/1960 Petermann 310--8.3 X 3,181,016 4/1965 Rosenman 3l08.3 3,093,710 6/1963 Ten Eyck 179-110 A THOMAS W. BROWN, Primary Examiner US. Cl. X.R. 310-83