Metal working – Piezoelectric device making
Reexamination Certificate
1998-06-10
2002-06-25
Vo, Peter (Department: 3729)
Metal working
Piezoelectric device making
C029S594000, C029S847000, C310S324000
Reexamination Certificate
active
06408496
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of implantable vibrational transducers, such as those used for correcting hearing impairment, and more particularly, to methods for fabricating such transducers using microfabrication processes and transducers produced by such processes.
The seemingly simple act of hearing is a thing that can easily be taken for granted. Although it seems to us as humans we exert no effort to hear the sounds around us, from a physiologic standpoint, hearing is an awesome undertaking. The hearing mechanism is a complex system of levers, membranes, fluid reservoirs, neurons and hair cells which must is all work together in order to deliver nervous stimuli to the brain where this information is compiled into the higher level perception we think of as sound.
As the human hearing system encompasses a complicated mix of acoustic, mechanical and neurological systems, there is ample opportunity for something to go wrong. Unfortunately this is often the case. It is estimated that one out of every ten people suffer some form of hearing loss. Surprisingly, many patients who suffer from hearing loss take no action in the form of treatment for the condition. In many ways hearing is becoming more important as the pace of life and decision making increases as we move toward an information based society. Unfortunately for the hearing impaired, success in many professional and social situations may be becoming more dependent on effective hearing.
A number of auditory system defects are known to impair or prevent hearing. To illustrate such defects, a schematic representation of part of the human auditory system is shown in FIG.
1
. The auditory system is generally comprised of an external ear AA, a middle ear JJ, and an internal ear FF. The external ear AA includes the ear canal BB and the tympanic membrane CC, and the internal ear FF includes an oval window EE and a vestibule GG which is a passageway to the cochlea (not shown). The middle ear JJ is positioned between the external ear and the middle ear, and includes an eustachian tube KK and three bones called ossicles DD. The three ossicles DD: the malleus LL, the incus MM, and the stapes HH, are positioned between and connected to the tympanic membrane CC and the oval window EE.
In a person with normal hearing, sound enters the external ear AA where it is slightly amplified by the resonant characteristics of the ear canal BB. The sound waves produce vibrations in the tympanic membrane CC, part of the external ear that is positioned at the distal end of the ear canal BB. The force of these vibrations is magnified by the ossicles DD.
Upon vibration of the ossicles DD, the oval window EE, which is part of the internal ear FF, conducts the vibrations to cochlear fluid (not shown) in the inner ear FF thereby stimulating receptor cells, or hairs, within the cochlea (not shown). Vibrations in the cochlear fluid also conduct vibrations to the round window (not shown). In response to the stimulation, the hairs generate an electrochemical signal which is delivered to the brain via one of the cranial nerves and which causes the brain to perceive sound.
The vibratory structures of the ear include the tympanic membrane, ossicles (malleus, incus, and stapes), oval window, round window, and cochlea. Each of the vibratory structures of the ear vibrates to some degree when a person with normal hearing hears sound waves. However, hearing loss in a person may be evidenced by one or more vibratory structures vibrating less than normal or not at all.
Some patients with hearing loss have ossicles that lack the resiliency necessary to increase the force of vibrations to a level that will adequately stimulate the receptor cells in the cochlea. Other patients have ossicles that are broken, and which therefore do not conduct sound vibrations to the oval window.
The hearing impaired patient today has a wide variety of hearing devices to choose from. Devices that have improved circuits, enhanced fitting parameters that allow the electronics to be customized to the patients individual hearing loss (i.e., similar to an eye glass prescription, one size does not fit all). New devices located completely in the patients ear canal are available that are cosmetically superior to the large bulky devices of years past and can be virtually invisible. Many manufacturers participate in the hearing marketplace which is a sizable 3 billion dollar worldwide market.
Prostheses for ossicular reconstruction are sometimes implanted in patients who have partially or completely broken ossicles. These prostheses are designed to fit snugly between the tympanic membrane CC and the oval window EE or stapes HH. The close fit holds the implants in place, although gelfoam is sometimes packed into the middle ear to guard against loosening. Two basic forms are available: total ossicular replacement prostheses which are connected between the tympanic membrane CC and the oval window EE; and partial ossicular replacement prostheses which are positioned between the tympanic membrane and the stapes HH. Although these prostheses provide a mechanism by which vibrations may be conducted through the middle ear to the oval window of the inner ear, additional devices are frequently necessary to ensure that vibrations are delivered to the inner ear with sufficient force to produce high quality sound perception.
Various types of hearing aids have been developed to restore or improve hearing for the hearing impaired. With conventional hearing aids, sound is detected by a microphone, amplified using amplification circuitry, and transmitted in the form of acoustical energy by a speaker or another type of transducer into the middle ear by way of the tympanic membrane. Often the acoustical energy delivered by the speaker is detected by the microphone, causing a high-pitched feedback whistle. Moreover, the amplified sound produced by conventional hearing aids normally includes a significant amount of distortion.
A recent breakthrough in the field of hearing impairment treatment is described in U.S. Pat. Nos. 5,554,096; 5,559,358; and 5,624,376, each of which is assigned to the assignee of the present application. These patents describe the use of floating mass transducers which may be implanted or mounted externally for producing vibrations in the vibratory structures of the ear. The floating mass transducers include a housing which may be vibrationally coupled to the vibratory structure within the ear, a mass mechanically coupled to the housing, and some means for vibrating the mass in response to an externally generated signal. Vibration of the mass, in turn, causes inertial vibration of the housing to produce the desired vibrations in the vibratory structure of the ear. The use of floating mass transducers for stimulating the vibratory structures of the ear has a number of advantages over other implantable devices. In particular, floating mass transducers can produce vibrations in the cochlea that have sufficient force to stimulate hearing perception with minimal distortion.
As described in these three patents, and in the co-pending applications which are listed below and also assigned to the assignee of the present application, the floating mass transducers are small devices composed of a number of discreet components which are attached to each other by conventional techniques, usually by hand construction. A first generation device being produced by the assignee of the present invention comprises a housing, and a magnet, a spring mechanism carrying the magnet, and a magnetic coil within the housing. Each of these components is placed in a metal housing, typically by hand, and the housing sealed and electrical leads brought out of the housing, also by hand. The method of fabrication is time-consuming, expensive, and presents a chance of human error in constructing the device. For these reasons, it would be desirable to provide improved fabrication methods for producing floating mass transducers for use in implantable devic
Maynard Ronald S.
Skjerven Morrill LLP
Tugbang A. Dexter
Vo Peter
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