US20140163309A1 - Implantable actuator for hearing aid application - Google Patents

Abstract

An electromechanical actuator for an implantable hearing aid device including a mechanical output structure that has a first portion and a second portion, wherein the first portion is a mechanical attachment structure to attach a stapes prosthesis, and wherein the second portion is a wire-like member coupling the mechanical attachment structure to a magnetically permeable armature shaft assembly.

Description

RELATED APPLICATIONS
• The present application is related to U.S. Provisional Patent Application No. 60/631,512 entitled “Implantable Fixation System for Anchorage of Medical Devices,” filed 30 Nov. 2004, which is hereby incorporated by reference herein in its entirety.
FIELD OF THE INVENTION
• The present invention relates to treatments for hearing loss. In a particular form, the present invention relates to an implantable actuator capable of direct stimulation of the middle and inner ear auditory systems.
BACKGROUND OF THE INVENTION
• Today state-of-the-art conventional hearing aids are able to treat hearing loss, in particular sensorineural hearing loss, very efficiently but still have some major disadvantages such as occlusion of the auditory canal, feedback at high amplification levels and stigmatization of the patients with hearing loss. Further they are rather ineffective in the treatment of conductive and mixed hearing loss. Whilst the present invention is described in relation to the treatment of hearing loss it will be appreciated that the invention will have other applications consistent with the principles described in the specification.
• It is an object of the present invention to provide a stimulation device capable of being included in an implantable hearing aid device that addresses one or more of the disadvantages of conventional hearing aid devices.
SUMMARY OF THE INVENTION
• In a first aspect the present invention accordingly provides an electromechanical actuator comprising:
• • first and second magnets arranged to provide a biasing field in a field region between two substantially opposed pole faces of said first and second magnets;
  • a magnetically permeable armature located in said biased field region between said opposed pole faces, the location of the magnetically permeable armature defining a first and second working gap between the magnetically permeable armature and respective opposed pole faces of the first and second magnets;
  • a magnetically permeable armature shaft assembly supporting said magnetically permeable armature, said magnetically permeable armature shaft assembly arranged to allow movement of said magnetically permeable armature between said opposed pole faces in a longitudinal direction defined by the movement of said armature shaft assembly;
  • biasing means for providing a biasing force to said magnetically permeable armature shaft assembly to bias said magnetically permeable armature to a predetermined location between said opposed pole faces; and
  • magnetic flux generating means responsive to an input signal to generate a signal flux to modulate said biasing field in said field region thereby providing an unbalanced force to said magnetically permeable armature causing actuation of said magnetically permeable armature shaft assembly.
• Preferably, said first and second magnets are supported by a magnet support assembly and wherein said magnet support assembly, said magnetically permeable armature and said first and second working gaps form a first magnetic circuit.
• Preferably, said magnetic flux generating means is supported by a flux generating means support assembly and wherein said flux generating means support assembly, said magnetically permeable armature, said magnetically permeable armature shaft assembly and one of said first and second working gaps forms a second magnetic circuit.
• Preferably, said magnetic flux generating means comprises an electrical coil.
• Preferably, said flux generating means support assembly comprises a magnetically permeable structure having a recess to receive a shaft of said magnetically permeable armature shaft assembly, thereby forming a transverse air gap between said shaft and the walls of said recess.
• Preferably, said recess is substantially cylindrical in shape.
• Preferably, said transverse air gap is minimized to reduce the reluctance of said second magnetic circuit.
• Preferably, said biasing means includes a first biasing member and a second biasing member.
• Preferably, said flux generating means support assembly comprises said first biasing member and wherein said first biasing member further comprises a magnetically permeable spring in mechanical contact with a shaft of said magnetically permeable armature shaft assembly.
• Preferably, said second biasing member comprises a diaphragm in mechanical contact with said shaft.
• In a second aspect the present invention accordingly provides an electromechanical actuator for an implantable hearing aid device comprising:
• • a hermetic housing of tubular shape closed on one side with a diaphragm and on the other side, with a hermetic feedthrough;
  • first and second magnets located in said hermetic housing arranged to provide a biasing field in a field region between two substantially opposed pole faces of said first and second magnets;
  • a magnetically permeable armature located in said biased field region between said opposed pole faces, the location of the magnetically permeable armature defining a first and second working gap between the magnetically permeable armature and respective opposed pole faces of the first and second magnets;
  • a magnetically permeable armature shaft assembly supporting said magnetically permeable armature, said magnetically permeable armature shaft assembly arranged to allow movement of said magnetically permeable armature between said opposed pole faces in a longitudinal direction defined by the movement of said magnetically permeable armature shaft assembly;
  • biasing means to provide a biasing force to said magnetically permeable armature shaft assembly to bias said magnetically permeable armature to a predetermined location between said opposed pole faces;
  • magnetic flux generating means including an electrical signal coil responsive to an input signal delivered by an electrical connection to said hermetic feedthrough to generate a signal flux to modulate the biasing field in said field region thereby providing an unbalanced force to said magnetically permeable armature causing actuation of said magnetically permeable armature shaft assembly;
  • a mechanical output structure including stimulation means to stimulate the inner ear auditory system responsive to actuation of said magnetically permeable armature shaft assembly; and
  • a lead electrically connected to outer pins of said hermetic feedthrough and mechanically attached to said titanium housing.
• In a third aspect the present invention accordingly provides an implantable stimulation device for stimulating an inner ear of a patient, said stimulation device including an electromechanical actuator responsive to an auditory signal for providing mechanical stimulation to said inner ear in response to said auditory signal.
• Preferably, said stimulation device further includes a middle ear prosthetic, said middle ear prosthetic reproducing in part or in full the function of the middle ear, wherein said electromechanical actuator includes actuation means to actuate said middle ear prosthetic thereby stimulating said inner ear in response to said auditory signal.
BRIEF DESCRIPTION OF THE DRAWINGS
• A preferred embodiment of the present invention will be discussed with reference to the accompanying drawings wherein:
• FIG. 1 is a perspective view of the interior components of an implantable hearing aid device incorporating an electromechanical actuator in accordance with a first embodiment of the present invention;
• FIG. 2 is a composite view of the implantable hearing aid device illustrated inFIG. 1;
• FIG. 3 is an elevation view in longitudinal diametric section of the electromechanical actuator illustrated inFIG. 1 having a low reluctance transverse gap;
• FIG. 4 is an elevation view in longitudinal diametric section of a second embodiment of an electromechanical actuator of the present invention having a flux conducting spring member;
• FIG. 5 is a lower elevation view in longitudinal diametric section of the electromechanical actuator illustrated inFIG. 1, showing the attachment of coil wires and lead;
• FIG. 6 is an elevation view in longitudinal diametric section of the electromechanical actuator illustrated inFIG. 1, showing the mechanical output structure;
• FIG. 7 is a side view of the mechanical output structure illustrated in the above figures, with an attached stapes prosthesis;
• FIG. 8 is a side view of the mechanical output structure illustrated in the above figures, having a ball joint between coupling rod and artificial incus;
• FIG. 9 is a side view of the mechanical output structure illustrated in the above figures, having a bendable coupling rod;
• FIG. 10 is a side view of the mechanical output structure illustrated in the above figures, having a partially bendable coupling rod;
• FIG. 11 is a side view of the mechanical output structure illustrated in the above figures, having a ball joint between artificial incus and stapes prosthesis; and
• FIG. 12 is a perspective view of a cochlear implant system showing one exemplary application of the electromechanical actuator of the present invention.
• In the following description, like reference characters designate like or corresponding parts throughout the several views of the drawings.
DESCRIPTION OF PREFERRED EMBODIMENT
• Referring now toFIGS. 1 and 2, there are shown perspective and composite views depicting the components of an implantablehearing aid device100 incorporating anelectromechanical actuator50 according to a first embodiment of the present invention.Hearing aid device100 includes ahousing1 formed from titanium tubing that is substantially cylindrical and of circular cross section.Hearing aid device100 further comprises atitanium diaphragm6, atitanium ring21 and amulti-pin feedthrough9 which are joined by hermetic laser welds.Coupling rod7, which is part of the moving mechanical output structure ofelectromechanical actuator50, is placed inring21 and is hermetically welded to it. This assembly provides a hermetically closedhousing1 that is suitable for implantation in the human body.
• Lead11 which provides the input signal toelectromechanical actuator50 is connected tofeedthrough9. To protect the connection site of thelead11,electromechanical actuator50 may be covered by a silicone filledtitanium cap10. In this embodiment directed to a hearing aid device, thetitanium cap10 provides multiple flat surface regions to allow secure manipulation of the device during implantation with surgical tweezers or little tongs. Thetitanium cap10 also has a conical shape that provides mechanical transition between the small diameter of thelead11 and larger diameter of thetitanium tube1.
• Referring now toFIG. 3, there is shown an elevation view in longitudinal diametric section of the first embodiment ofelectromechanical actuator50 of the present invention incorporating a low reluctance transverse gap.Armature2,shaft12 andcoupling rod7 form the moving part of theactuator50. Asarmature2 andshaft12 form part of the magnetic circuits which driveelectromechanical actuator50 they are made of soft magnetic alloys. However, as would be understood by those skilled in the art, other suitable materials having the desired magnetic permeability properties may also be used.
• Shaft12 is made of titanium to enable hermetic closing of the actuator by welding it to aring21. The resulting moving structure is elastically supported at one side by adiaphragm6, which performs the function of a restoring spring. As such,diaphragm6 prevents magnetic snap over. On the other side,shaft12 is supported in the longitudinal direction by aspring bearing5 having a spring constant sufficient to provoke, together withdiaphragm6, the demanded dynamic characteristic of this spring-mass structure.
• Thearmature2 is centred between twopermanent magnets3aand3bthereby forming two workinggaps17aand17b.Bothmagnets3aand3bare polarized in the same direction substantially in parallel to the actuator axis and the direction of movement ofshaft12, and provide polarizing flux in workinggaps17aand17bthat extends through thearmature2. This first magnetic circuit is closed through the magnet supports16aand16band theshort sleeve15 which are again fabricated from soft magnetic alloys.
• A second magnetic circuit comprisessignal coil4,coil core13,long sleeve14, themagnet support16b,thearmature2 and theshaft12.Signal coil4 includes twoinput coil wires23 which are connected to lead11 by virtue offeedthrough9. Preferably, all elements forming the second magnetic circuit other than thesignal coil4 are made of soft magnetic alloys to conduct the signal flux generated bycoil4. This magnetic signal circuit includes two air gaps: the workinggap17band atransverse gap18 formed between thecoil core13 and theshaft12. Thetransverse gap18 between thecoil core13 andshaft12 has been minimized in order to provide a low reluctance thereby minimize losses in the magnetic circuit.
• In operation, the signal flux passing through the workinggap17bhas the effect of modulating the polarizing flux generated by themagnets3aand3bin the process either increasing or decreasing the flux in the workinggap17bdepending on the direction of the current passing through thesignal coil4. This in turn increases or decreases the attractive force ingap17bcompared to the constant polarizing flux ingap17awhich results in a net force pulling the armature upwards or downwards. In this manner, small changes in the signal flux generated bycoil4 will result in corresponding actuation ofshaft12 thereby providing an electromechanical actuator of enhanced sensitivity.
• Referring now toFIG. 4, there is shown an elevation view in longitudinal diametric section of a second embodiment of anelectromechanical actuator55. The main structure of theelectromechanical actuator55 is the same as shown inFIG. 3, however, thespring bearing5 and thetransverse gap18 of theFIG. 3 embodiment are replaced by flux conductingspring members25 in this second embodiment. Flux conductingspring members25 are preferably made of soft magnetic alloys providing reduced reluctance to overcome the losses resulting from the increasedair gap18 when compared to the air gap between theshaft12 andcoil core13 in the first embodiment.
• The use ofmultiple spring members25 separated byflux conducting spacers26 increases the sectional area that can be passed by the magnetic flux to further reduce the overall reluctance of the magnetic circuit. Compared to one spring that is simply increased in thickness, the multiple springs provide higher compliance.
• Referring now toFIG. 5, there is shown an elevation view in longitudinal diametric section of the first embodiment of theelectromechanical actuator55 showing the attachment of thecoil wires23 and lead11.Coil wires23 are attached to feedthroughpins24 by, for example, brazing, welding or gluing with an electrically conductive glue. To preventcoil wires23 from coming into contact with movingshaft12 orspring bearing5, acover20 is placed between the coil wires and the shaft.
• Theterminals27 oflead11 are inserted in a crimpingtube31 that is welded to thefeedthrough pin24. Crimping thetube31 mechanically attacheslead terminal27 and establishes a low-impedance electrical connection. In this embodiment, acap10 protects the whole connection site. Thecavity32 formed by thecap10 is filled up with silicone to provide a firm mechanical attachment of thelead11. To enable proper sterilization of the silicone, thecap10 providesmultiple openings28.
• Referring now toFIG. 6, there is shown an elevation view in longitudinal diametric section of the movingmechanical output structure110 forming part of the implantablehearing aid device100 illustrated inFIGS. 1 and 2.Mechanical output structure110 comprises acoupling rod7 and anartificial incus8, both made of titanium and, in this embodiment, welded together. Asilicone coating38 coversartificial incus8. Theartificial incus8 closely emulates the long process of the incus of the human middle ear, and is placed next to it during implantation.
• The length of thecoupling rod7, measured from the outer surface of thediaphragm6 to the end of thecoupling rod7, is chosen in the range from approximately 3 mm to approximately 20 mm, and preferably in the range from approximately 5 mm to approximately 8 mm, to place theartificial incus8 in the intended location. The angle formed by the axis of thecoupling rod7 and the axis of theartificial incus8 is chosen in the range from 80° to 150°, preferably in the range from 115° to 125°, in order to correctly orientate theartificial incus8 according to the anatomical conditions in the human middle ear.
• The cross sectional profile of theartificial incus8 is elliptical with a numeric eccentricity in the range from 0 to 0.5 in order to provide reliable mechanical connection of the stapes prosthesis by crimping. Additionally, theartificial incus8 is covered with asilicone coating38 that has a thickness chosen in the range from 0.05 mm to 0.2 mm in order to allow proper stapes prosthesis attachment and crimping. It should be appreciated that the above dimensions and distances are approximate and that other dimensions may be established in alternative embodiments.
• Referring now toFIG. 7, there is shown a schematic diagram of one embodiment of the mechanical output structure ofFIG. 6 with an attachedstapes prosthesis33.
• Referring now toFIG. 8, there is shown another embodiment of the mechanical output structure having a ball joint35 betweencoupling rod39 andartificial incus40 to allow intra-operative adjustment of the angle between thecoupling rod39 and theartificial incus40.
• Referring now toFIG. 9, there is shown yet another embodiment of the mechanical output structure having abendable coupling rod41 to allow intra-operative adjustment of the orientation and the location of theartificial incus8.FIG. 10 shows yet another embodiment of the mechanical output structure having a two part coupling rod, astiff part42 next toactuator50,55 and abendable part36 next to theartificial incus8 to allow intra-operative adjustment of the orientation and the location of theartificial incus8.
• Referring now toFIG. 11, there is shown a further embodiment of the mechanical output structure having astapes prosthesis34 directly attached to theartificial incus43 via a ball joint37 to allow intra-operative adjustment of the insertion angle of thestapes prosthesis34.
• Referring now toFIG. 12, there is shown implantablehearing aid device1200 implementing anelectromechanical actuator1210 according to a preferred embodiment of the present invention. In this preferred embodiment, implantablehearing aid device1200 is a totally implantable Cochlear™ prosthesis (also referred to as a Cochlear™ implant system, Cochlear™ prosthetic device and the like) which functions as an implantable stimulation device for stimulating the inner ear by employing an electromechanical actuator responsive to an auditory signal. As would be apparent to those skilled in the art, the electromechanical actuator of the present invention can be utilized in current or future implantable medical devices. These implantable medical devices can be either partially or totally implanted in an individual, and such implantation may be temporary or permanent.
• Hearing aid device1200 comprisesexternal component assembly1242 which is directly or indirectly attached to the body of the recipient, and aninternal component assembly1244 which is temporarily or permanently implanted in the recipient.External assembly1242 typically comprisesaudio pickup devices1220 for detecting sound, aspeech processing unit1216, a power source (not shown), and anexternal transmitter unit1206 comprising anexternal coil1208.Speech processing unit1216 processes the output ofaudio pickup devices1220 that are positioned by theear1222 of the recipient.Speech processing unit1216 generates coded signals which are provided toexternal transmitter unit1206 viacable1218.
• Internal components1244 comprise aninternal receiver unit1212, astimulator unit1226, and a movingelectromechanical actuator1210 according to a preferred embodiment of the present invention.Internal receiver unit1212, which comprises an internaltranscutaneous transfer coil1224, andstimulator unit1226 are hermetically sealed within ahousing1228. Collectively,transmitter antenna coil1208 andreceiver antenna coil1224 form an inductively-coupled coil system used to transfer data and power via a radio frequency (RF) link114. Acable1230 extends fromstimulator unit1226 toactuator1210.
• Actuator1210 is coupled to the inner ear fluids viaartificial incus8 extending through a cochleostomy. Signals generated bystimulator unit1226 are applied bymechanical actuator1210 to inner ear fluids. It should be appreciated that the arrangement shown inFIG. 12 is a schematic representation only, and that embodiments of theelectromechanical actuator1210 of the present invention may be positioned in a variety of locations to provide the desired stimulative effect. For example, in the embodiment shown inFIG. 12,actuator1210 is coupled to the inner ear fluids viaartificial incus8. However, a variety of stapes prostheses may be attached toartificial incus8 in alternative embodiments, as described above.
• It should also be appreciated thatelectromechanical actuator1210 may be secured to the recipient utilizing a variety of techniques now or later developed. In one embodiment,electromechanical actuator1210 is configured to be implanted in a recipient utilizing an embodiment of a fixation system described in commonly owned U.S. Provisional Patent Application No. 60/631,512 entitled “Implantable Fixation System for Anchorage of Medical Devices,” filed 30 Nov. 2004, which is hereby incorporated by reference herein in its entirety.
• A brief consideration of the above described embodiments will indicate that the invention may be employed to remedy any source of conductive hearing loss. Additionally, these embodiments of the electromechanical actuator may be configured to provide sufficiently high output levels to treat severe sensorineural hearing loss while being sufficiently small to completely fit into a human mastoid.
• It should also be appreciated that Cochlear™ implant system1200 described above is just one exemplary system in which the electromechanical actuator of the present invention may be implemented. The electromechanical actuator of the present invention may be implemented in a myriad of embodiments of a cochlear implant system, hearing aid or other medical devices or systems now or later developed.
• Advantageously, the dimensions and shape of embodiments of the electromechanical actuator of the present invention may be selected to take into account the anatomy of the implantation site. For example, for an actuator that is to be placed in a hole drilled into the human mastoid, an elongated cylindrical shape such as that described above has been found to be advantageous. In addition, in the above or other application, embodiments of the actuator may have a diameter and a length which are sufficiently small to allow placement of the actuator in narrow anatomical locations as required. A further advantage of embodiments of the present invention directed to hearing aid devices is that they are able to deliver sufficiently high output levels to manage progressive hearing loss in order to prevent revision surgeries. A still further advantage is that certain embodiments of the actuator are highly energy efficient thereby minimizing power consumption and facilitating autonomy.
• Although a preferred embodiment of the method and system of the present invention has been described in the foregoing detailed description, it will be understood that the invention is not limited to the embodiment disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention as set forth and defined by the following claims.
• It will be understood that the term “comprise” and any of its derivatives (eg. comprises, comprising) as used in this specification is to be taken to be inclusive of features to which it refers, and is not meant to exclude the presence of any additional features unless otherwise stated or implied.

Claims (9)

1.-33. (canceled)

34. An electromechanical actuator for an implantable hearing aid device comprising:

a hermetic housing of tubular shape closed on one side with a diaphragm and on the other side, with a hermetic feedthrough;

first and second magnets located in said hermetic housing arranged to provide a biasing field in a field region between two substantially opposed pole faces of said first and second magnets;

a magnetically permeable armature located in said biased field region between said opposed pole faces, the location of the magnetically permeable armature defining a first and second working gap between the magnetically permeable armature and respective opposed pole faces of the first and second magnets;

a magnetically permeable armature shaft assembly supporting said magnetically permeable armature, said magnetically permeable armature shaft assembly arranged to allow movement of said magnetically permeable armature between said opposed pole faces in a longitudinal direction defined by the movement of said magnetically permeable armature shaft assembly;

biasing means to provide a biasing force to said magnetically permeable armature shaft assembly to bias said magnetically permeable armature to a predetermined location between said opposed pole faces;

magnetic flux generating means including an electrical signal coil responsive to an input signal delivered by an electrical connection to said hermetic feedthrough to generate a signal flux to modulate the biasing field in said field region thereby providing an unbalanced force to said magnetically permeable armature causing actuation of said magnetically permeable armature shaft assembly;

a mechanical output structure including stimulation means to stimulate the inner ear auditory system responsive to actuation of said magnetically permeable armature shaft assembly; and

a lead electrically connected to outer pins of said hermetic feedthrough and mechanically attached to said titanium housing,

wherein said mechanical output structure has a first portion and a second portion, and wherein the first portion is a mechanical attachment structure to attach a stapes prosthesis, and wherein said second portion is a wire-like member coupling said mechanical attachment structure to said magnetically permeable armature shaft assembly.

35. An electromechanical actuator for an implantable hearing aid device as claimed inclaim 34, wherein said mechanical attachment structure is of substantially cylindrical shape with an elliptical cross section having a numeric eccentricity ranging from approximately0 to approximately 0.5.

36. An electromechanical actuator for an implantable hearing aid device as claimed inclaim 34, wherein said mechanical attachment structure is covered with a silicone layer having a thickness of approximately 0.05 mm to approximately 0.2 mm

37. An electromechanical actuator for an implantable hearing aid device as claimed inclaim 34, wherein said wire-like member is a straight rod, and further wherein an angle between said mechanical attachment structure and said straight rod is chosen in the range of approximately 80° to approximately 150°.

38. An electromechanical actuator for an implantable hearing aid device as claimed inclaim 37, wherein said angle between said mechanical attachment structure and said straight rod is in the range from approximately 115° to approximately 125°.

39. An electromechanical actuator for an implantable hearing aid device as claimed inclaim 37, wherein ball joint means is disposed between said mechanical attachment structure and said straight rod to allow reorientation of said mechanical attachment structure with respect to said straight rod.

40. An electromechanical actuator for an implantable hearing aid device as claimed inclaim 34, wherein said wire-like member is at least partially bendable during implantation of said implantable hearing aid device.

41. An electromechanical actuator for an implantable hearing aid device as claimed inclaim 34, wherein said mechanical attachment structure includes further ball joint means to engage with a stapes prosthesis provided with a ball-shaped head.

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