Note: Descriptions are shown in the official language in which they were submitted.
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METHOD FOR PRODUCING IN-EAR HEARING
AIDS AND IN-EAR HEARING AID
The present invention relates to a method for producing in-the-ear hearing
devices.
In the production of shells for in-the-ear hearing
devices, the customary practice followed at present by
the audiologist is to make a mold in the shape of the
individual auditory canal, by taking an impression,
usually of silicone.
This mold is subsequently sent to the producer of the
hearing devices, where the hearing device shell is
molded from a plastic on the basis of this mold.
This procedure is problematical from various aspects:
= In the production method based on the aforementioned
impression of the outer ear, polymer materials which
lead to relatively hard, dimensionally stable shells
have to be used. This virtually always leads to the
shell having to be re-worked on account of remaining
pressure points when the finished in-the-ear hearing
device is fitted into the individual ear. Since the
trial fitting usually does not take place at the
premises of the producer, a laborious procedure of
sending the device back and forth is often required
before the shell individually fits.
= The aforementioned procedure no doubt makes it
possible for the resultant shell to correspond in its
outer shape to the impression, but not for complex
internal shapes to be formed, as would be desirable
for functional parts of the hearing device to be
received in an optimized way in terms of fitting. In
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this respect, we understand functional parts as
meaning all units which are responsible for picking
up, processing and reproducing the audio signals,
that is of microphones, digital processors,
loudspeakers and the associated auxiliary units, such
as for remote control of binaural signal
transmission, batteries etc. In this respect, it
must be pointed out that optimum packing of these
functional parts in a way which utilizes the space
available can only be carried out on an individual
basis, since the geometry of the. auditory canal may
vary greatly individually.
The procedure described is, on the one hand, highly
labor-intensive, and the resultant hearing device
usually remains less than optimum with respect to its
wearing comfort and space utilization. The materials
used in the case of said conventional production method
also require a relatively great wall thickness of the
shell of the in-the-ear hearing device, which reduces
the space available=for said functional parts move than
is the case anyway.
The present invention has the purpose of overcoming
these disadvantages mentioned.
According to the present invention, there is provided a method for
producing in-the-ear hearing devices, comprising steps of:
making a mold in the shape of an individual auditory canal,
producing a hearing device shell corresponding to the mold,
installing functional parts of the hearing device, and
digitizing the shape in 3D, the hearing device shell being thus
created by an additive construction method comprising a step of depositing
one sectional layer after the other, on top of one another, characterized in
that firstly sectional layers of a plurality of individual hearing device
shells
are respectively created virtually in parallel, before the following sectional
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layers of the individual hearing device shells are deposited on already
created layers in the additive construction method.
Preferably, for this purpose, it is distinguished by the fact that
the shape of the individual outer ear is digitized
three-dimensionally (3D) and the device shell is
created by an additive construction method. Additive
construction methods are also known from "rapid
prototyping".
Preferably, with respect to additive methods being used in rapid prototyping
or those still under development, reference is made, for example, to Wohlers
Report 2000, Rapid Prototyping & Tooling State of the Industry.
Preferably, of the additive processes known at present for rapid
prototyping, it is found that laser sintering, laser
lithography or stereolithography, or the thermojet
method are particularly well suited for achieving the
aforementioned object.
These and further additive construction methods from
"rapid prototyping" are known per se. Therefore,
specifications of the preferably used additive
construction methods are only briefly summarized:
~ Laser sintering:
Hot-melt powder is applied in a thin layer from a
powder bed, for example by means of a roller. The
powder layer is solidified by means of a laser beam,
said laser beam being guided according to a sectional
layer of the hearing device shell by means of 3D
shape information of the hearing device shell. A
solidified sectional layer of the shell is obtained
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in the otherwise loose powder. This layer is lowered
from the powder laying plane and a new layer of
powder is applied over it, and this layer of powder
is in turn solidified by laser according to a
sectional layer, etc.
= Laser lithography or stereolithography:
A first sectional contour according to a sectional
layer of a hearing' device shell is solidified by
means of UV laser on the surface of liquid
photopolymer. The solidified layer is lowered, is
again covered by liquid polymer and the second
sectional layer is solidified by means of UV laser.
= Thermojet method:
The contour formation in accordance with a sectional
layer is carried out in the same way as in an inkjet
printer by liquid application according to the
digitized 3D shape information. After that, the
deposited sectional "picture" is solidified.
Once again, according to the principle of the additive
construction methods, the device shell is built up by
depositing layer after layer.
As regards additive construction methods, and the
preferred ones mentioned above, reference may be made
to the following further publications:
= "Selective Laser Sintering (SLS) of Ceramics",
Muskesh Agarwala et al., presented at the Solid
Freeform Fabrication Symposium, Austin, TX, August
1999, and
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= Donald Klosterman et al., Direct Fabrication of
Polymer Composite Structures with Curved LOM", Solid
Freeform Fabrication Symposium, University of Texas
at Austin, August 1999.
In. principle, in additive construction methods a thin
layer of material is in each case deposited on a
surface, either over the whole surface as in laser
sintering or stereolithography or, as in the thermojet
method, already in the contour of a section of the
shell under construction. The desired sectional shape
is then stabilized and solidified.
Once a layer has been solidified, a new layer is
deposited over this, as has been described, and this
new layer is in turn solidified and connected to the
already solidified layer lying below it. The hearing
device shell is thus constructed layer by layer by
additive layer-by-layer application.
For industrial production, it is preferable not just
for the sectional layer of one hearing device shell to
be deposited and solidified in each case, but for a
plurality to be deposited and solidified
simultaneously. In laser sintering, the laser,
normally under mirror control, successively solidifies
the sectional layers of a plurality of hearing device
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shells, before all the solidified sectional layers are
lowered in unison. Then, after a new layer of powder
has been deposited over all the already solidified and
lowered sectional layers, the plurality of further
sectional layers are formed in turn.
In order to solidify the sectional layers of the
hearing device shells, either a single laser beam
continues to be used, or several beams are operated in
parallel.
In an alternative to this procedure, a sectional layer
is in each case solidified with one laser, while at the
same time the layer of powder is being deposited for
the formation of a further hearing device shell.
Thereafter, the prepared layer of powder is solidified
according to the sectional layer for the next hearing
device shell by the same laser, while the previously
solidified layer is lowered and a new layer of powder
is deposited there. The laser then operates
intermittently between two or more hearing device
shells under construction, and so the idle time of the
laser occasioned by the deposition of powder for the
formation of one of the shells is exploited for
solidification of a sectional layer of another shell
under construction.
In an analogous way, the productivity when using
stereolithography is increased. When the thermojet
method is used and an analogous increase in
productivity is to be obtained, sectional layers of
more than one hearing device shell are deposited at the
same time.
It is thus possible by the method according to the
invention to create extremely complex shapes on the
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shell produced according to the invention, to be
precise both with respect to its outer shaping and with
respect to its inner shaping. Overhangs, inward
projections and outward projections can be readily
created.
Furthermore, there are known materials for additive
construction methods which lead to an elastomeric and
nevertheless dimensionally stable shell, which if
desired can be created differently locally, to the
extent of producing an extremely thin wall which is
nevertheless tear-resistant.
In an embodiment preferred at present, the mold in the
shape of the individual auditory canal is made in the
course of the production method according to the
invention by taking an impression, for example of
silicone, while not ruling out the possibility that in
the near future the shape of the individual auditory
canal will be scanned directly.
In a preferred embodiment of the production method
according to the invention, furthermore, said
digitization of the auditory canal is performed,
whether by taking an impression or by directly scanning
decentralized front centers, such as for example by the
audiologist. The shape recorded there, as represented
by digital 3D information, is transmitted to a
production center, whether by sending a data carrier or
by an Internet link etc. At the production center, the
hearing device shell is individually shaped, in
particular using the aforementioned methods. Final
assembly of the hearing device with the functional
modules is preferably also performed there.
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On account of the fact that, as mentioned, the
thermoplastic materials used generally lead to a
relatively elastic, compliant shell, the shaping is far
less critical in terms of pressure points than has
previously been the case. In a way similar to an
elastomeric plug, the shell of the finished in-the-ear
hearing device will adapt itself optimally to the outer
ear. The inclusion of one or more venting channels in
the hearing device shell is readily possible and
desired in this case, in order with the resultant
relatively tight fit of the hearing device in the
auditory canal to permit unimpaired ventilation of the
ear drum. At the same time, with the individual 3D
shape data, the interior space of the shell can also be
optimally and individually shaped for optimum reception
of the functional parts respectively to be provided in
an individual case.
Furthermore, the central production of the shells also
allows central storage and administration of the
individual hearing - device data to be performed,
including the data which define the shape of the
hearing device shells. If, for whatever reasons, a
shell has to be replaced, it can consequently be
readily reproduced by calling up the corresponding
individual data records and renewed production.
On account of the fact that the methods used according
to the invention for the production of hearing device
shells are extremely widespread, albeit from
prototyping, and described in the literature, there is
no need at this point to reproduce all the technical
details relating to these methods.
In any event, the adoption of this technology that is
already known from prototyping for the industrial and
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commercially acceptable production of in-the-ear
hearing device shells surprisingly gives rise to quite
significant advantages, and does so for reasons which
are not in fact important in prototyping, such as for
example elasticity of the thermoplastic materials that
can be used, the possibility of individual construction
with extremely thin walls etc.
