The invention pertains to deformable hearing aids. More particularly, the invention pertains to such hearing aids that change shape in response to dynamic changes in the shape of a user""s ear canal.
It has been recognized that, in certain circumstances, hearing aids can significantly improve the quality of life of individuals that have a hearing deficiency. Contemporary hearing aids are often small enough to fit completely into a user""s ear canal. Their small size makes them much more acceptable than older more visible aids.
Despite improvements, there continue to be problems with known hearing aids. Two of these problems are comfort and performance. Contemporary in-the-ear hearing aids usually have an exterior housing molded in accordance with the shape of a user""s ear and ear canal. Such housings are often formed of rigid plastic such as an acrylic.
The rigidness often results in a less than comfortable fit when in place and can produce discomfort during the insertion and removal process. In extreme cases, usually resulting from ear surgery, the shape of the user""s ear or ear canal has been altered such that a conventional hearing aid could not be inserted.
Up to now, there was no economically feasible way to create a soft-shell that was accurately reproducing the ear impression outer features with a designed thickness. Unlike acrylic hard shells that are slushed to a desired thickness, soft elastomeric materials do not easily produce strong and accurate shells. Processes that could be used if they were efficient include Rotomolding, Dipping, and Injection Molding. Those methods are also cumbersome as to prevent high volume manufacture of soft hearing aids.
Performance is an issue with rigid shells in that the shape of the ear canal changes while talking or eating. This change in shape can compromise the seal formed between the shell and the ear canal. Integrity of this seal is important in minimizing external feedback around the shell. This in turn limits the user""s usable gain and reduces over-all performance of the aid. Maintaining the integrity of this seal makes it possible to operate the aid at higher gain levels, and better compensate for the user""s hearing deficiency providing a higher degree of user satisfaction.
Thus, there continues to be a need for hearing aids that are more comfortable to insert and wear than have heretofore been available. There also continues to be a need for improved performance and higher gain, where appropriate, but without performance degrading external feedback.
The invention relates to a process for manufacturing a compliant hearing aid starting with an impression of the ear and subsequent creation of a mold that produced a shell of designed shape and size accurately. The process accurately produces a shell that is attachable to a face plate with components creating a soft, ergonomic, compliant, comfortable hearing aid.
A multi-material housing for a hearing aid provides a compliant region which is a reproduction of an impression of a portion of a user""s ear canal. When inserted, the housing deforms in accordance with the shape of the ear canal so as to permit comfortable insertion. Once inserted, the reproduced region of the housing sealingly abuts the respective portion of the ear canal so as to provide a seal and prevent feedback. Additionally, the housing deforms in response to deformation of the ear canal as the user moves his or her jaw.
The deformability of the housing makes it possible to mold internal component receiving cavities therein with openings which are too small to permit insertion of the components when the housing is in its normal state. However, in response to a deformation force applied to the respective component, the housing deforms thereby enabling the respective component to slide past the obstruction region and into the premolded component receiving cavity. For example, a receiver could be inserted into a deformable shell at either the audio output end of the shell or at the exterior open end of the shell.
The housing has an external periphery defined by a layer of a first deformable material. The layer of the first deformable material bounds, at least in part, an interior region with an interior surface.
The exterior layer can be molded separately and then filled at least in part, with a compliant filling material. Alternately, an internal, male, mold can be formed which matches the interior surface of the exterior layer. The exterior layer can, in turn, be slid onto the male mold much like a sock can be slid onto the respective wearer""s foot.
A sheet member can be incorporated into the housing so as to minimize the possibility of internal feedback when the respective hearing aid is being used. This member can be positioned adjacent to the battery door to block any inflow of liquid interior filling material.
The exterior periphery layer and the interior filling material can be silicone, latex, polyurethane, polyvinyl or any other type of time, heat or U.V. curable elastomer. The preferred hardness of the selected elastomers falls in a range of less than 90 ShoreA.
In a first method of making the housing, a hard plastic shell corresponding to the shape of a user""s ear canal is formed by conventional methods. The shell is then attached to a keyed, rigid baseplate and installed in a molding fixture.
Material such as silicone or urethane is poured into the mold. This material will form a female mold which defines the outside surface of a compliant housing.
The mold and the hard shell can be detached from the keyed base and installed in a mold fixture to create a male mold which forms the interior surface of the soft shell. Elastomeric material is poured into the shell to form the male mold or shape. Removing the shell, or template, creates a space between the inner and the outer molds. This space defines the size and shape of the soft shell or outer layer to be formed.
An elastomer such as silicone, polyurethane, polyvinyl or a latex can be poured or injected into the mold space. Once cured the shell can be removed from the mold. An advantage of this process is that the same rigid shell is used to form the exterior, female, and interior, male counterpart molds. Removing the rigid shell produces a space which is an accurate copy of the shell. That space is then filled with the liquid, castable elastomer.
Often times components such as an output transducer, a receiver, are too large to be inserted in the deformable shell or layer without distortion. However, given the deformability of the shell, applying an insertion force to the respective component or components can cause the shell to temporarily change shape or expand thereby permitting the respective component to be slid through a constricted path so as to be appropriately located in an internal cavity of the shell. Remaining spaces in the shell can be filled with a backfilling material, preferably after providing a rigid plastic outer shell around the exterior deformable shell. For example, UV curable plastic can be applied to the deformable shell, and cured whereupon a rigid protective layer is formed around the exterior of the shell. It can then be backfilled with a filling material which is the same or different material without concern that the filling material will distort the desired shape of the shell.
In yet another form of processing, a hard shell, representing a casting of a portion of a user""s ear canal is used to create a deformable exterior shell as described above. This shell is then used to create a mold of an interior plug which houses the components.
When filled and cured, the exterior surface of a plug matches the interior surface of the soft shell. That soft shell can then be slid onto the plug. The exterior soft shell can then be attached at one or more regions by glue or the like to the plug. Since the same hard shell was used to create both the exterior deformable soft shell and the interior plug, the two parts match exactly.
In an alternate embodiment, the exterior soft shell or sock can be selectively bonded to the interior plug thereby creating a skin-feel to the surface of the shell. In this instance, the surface of the shell is slightly movable relative to the interior plug.
In yet another aspect, the deformability of the soft shell can be used to advantage during manufacture. When installing components, the components can be pushed through small channels in the shell, by distorting same temporarily. After insertion, the shell returns to its normal shape. This interior can then be filled, at least in part, with a curable deformable material. The material of the shell and the interior material can be the same or different depending on desired characteristics.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.