Note: Descriptions are shown in the official language in which they were submitted.
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2.
CONN~C~OR
This invention relates to improvements in
connectors and articles having connectors thereon and
is specifically designed for electronic connectors and
articles including such connectors which are used in
hostile environments; such as exist within the human
body.
The connectcrs are specifically designed for
use in multiple electrode applications such as for
hearing prostheses, visual prostheses and other in vivo
electronic systems, such as control of muscle funct-
ions. The invention is not, however, to be considered
restricted to such functions.
The object of the invention is to provide a
connector which can be used in multiple electrode
applications and which is physically small, but which
permits the formation of effective and durable elect-
rical connections whilst bein~ capable of being sealed.
Australian patent specification 40981/78 was
concerned with this problem. It sou~ht to achieve elect-
rical contact between a plurality of individual
contacts without emphasizing the need for absolute
electrical insulation between the individual contacts
of the array. However to ensure that e'lectrical contact
was maintained for all contacts,, it needed to be main-
t~ined under pressure. Patent applications 409~1/78
sought to achieve this by providing an elastomeric
connector.
This elastomeric connector in its preferrred
orm, is a layered connector and in this the conductive
and nonconductive zones are formed and located side by
side with the`conductive zones e~tending fully through
'the connector so that the connector can be cut to any
required size, provided the cut is transverse to the
zones whilst still havin~ effective conducting zones.
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3.
If the connector is used in an implanted
prosthesis, the individual conductors of the outgoing
electrode group are located in the pa~ient's body, and
where these are bein~ used to stimulate, say, the inner
ear, they are located to terminate adjacent the part-
icular areas to be stimulated.
After some time, there may well be a fibrous
growth around these conductor members and it would be
difficult to remove these and, certainly, it would be
difficult to remove them and replace them with another
group of electrodes. If the prosthesis unit ceases to
operate, it will be understood that it is only necess-
ary to open the patient's skin near the point of
location of this unit, undo the screws holding the
15 upper metal plate in position and replace the pros-
thesis ur.it with a new unit using the same upper
connector assembly. In this way, there is no need to
disturb the location o~ the conductors.
The drawbacks of this development are prim-
20 arily the size of the unit which is not inherentlyconstructed to facilitate miniturization; screws or
other fastening means are needed to hold the unit
together and to maintain electrical contact and do not
facilitate surgical simplicity, as well as being prone
25 to loosen in some cases.
While it is possible to design electronic
modules with very high reliability for chronic implan-
tation in vivog some failures must still be expected.
In the situation where such a module is providing
30 multipoint stimulation through an array o electrodes,
which once implanted in the stimulus site cannot necess-
arily be replaced, it is desirable that the module be
connected to the electrode array in such a way as to
allow disconnection of the faulty module and reconnect-
35 ion to an operational module~ This approach also allowsmodules to be replaced, should circuit improvements
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4.
make this desirable.
~ enerally a connector should fulfill the
following criteria:
1. It should connect typically 10-20 electrodes
to the electronics module.
2. It should be as small as possible.
3. While it is desirable that all connections be
isolated by a high impedance, some current shunting is
acceptable inside the connector~ provided that it does
not result in a significant change of stimulus current.
To this end the present invention provides a
connector comprising a first array of discrete elect-
rical contacts mounted on the external surface of a
first unit, a second array of discrete electrical con-
tacts mounted on the internal surface of a second unit,wherein said first unit is shaped to resiliently fit
w;thin sald second unit so that electrical contact
occurs between each contact of the first array and each
contact of the second array. Preferably each electrical
contact of one of said arrays is resiliently mounted on
its unit not only to ensure permanent electrical con-
tact but also to retain the first unit within the
second unit.
The two units are preferably cylindrical and
composed of ceramic material. This construction means
that the connection can be separated by simply pulling
the two units apart.
In another aspect it is an object of this
invention to avoid prior art problems of corrosion of
electrodes and connector materials when implanted with-
in a pa~ientls body.
In the prior art implantable devices metal
connector bodies were used for housing the electronies
module. This necessitated placing the coils used to
receive power and signals had outside of the elect-
ronics module. The electric leads connecting these
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5.
coils to the electronics module passed through the wall
of the module but any penet~ation or presence of body
fluids abo~t the module or connector body could easily
result in an undesired electrical activity between the
coil leads and the electrode connection to the nerve
endings. Such current leakage would also result in
undesirable corrosion occurring.
To overcome this problem it is proposed to
manufacture the electronics module in a material trans-
~ parent to the frequencies used to provide power andsignals for the prosthesis.
Once such a transparent material is used it
is of course possible to place the coils within the
electronics module. This construction means that no
electric leads from the coil to the electronics module
are exposed at all. This ensures that there is little
chance of corrosion occurring and enhances the life and
useability of the connector.
A preferred form of connector will now be
described. The connector is intended for use in implant-
able prostheses in which one unit is connected via
electrical leads to the nerve endings o the patient
while the second unit incorporates an elec~ronics
module for receiving and generating signals. In this
~5 case the prosthesis is for use and t~e elec~ronics
module ~or receiving and transmitting auditory signals
is incorporated within the COnneCtQr body and can be
easily surgicall~ removed.
The connector s~stem is shown in an exploded
view in Fig. 1. It consists of an electronics module
package 4 and a connector body 9. The design of the
packaging for the electronics module is integral with
the connector design: the package 4 is circular with
each pinout being in the form of a band 5 of metalliza-
tion running down the side o~ the package 4: a smallspring 6 is welded to each band 5. One spring i~ made
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6.
lar~er than the others, to act as a key for the
otherwise unkeyed system. It is of course possible to
arrange the spring electrical contacts on the connector
or body 9 as an alternative.
S While the package 4 shown is made of ceramic
material to allow the use of a high frequency link to a
coil unit inside the package, other înert materials
could be used.
The connector body consists of a cylindrical
section 9 closed at one end 1~, with a groove 11 o~
triangular cross section machined into the inside face.
A precision '0' ring 13 is held in compression
between this groove 11 and a corresponding groove 15 in
a circular plate 14 pressed inside it: this seal satis-
fies the above leakage current requirements. A siliconerubber boot not shown is placed over the top of the
connector to prevent the ingrowth of tissue into the
'0' ring groove: th;s woul~ complicate replacement. The
plate 14 incorporates a keyed recess 19 to enable easy
opening of the connector for removal of the module 4.
Connector plates 16 pass through silicone
rubber lined holes 17 in the base 18 of the connector
and lie in vertical grooves in the connector body 9.
The leads from the electrode array implanted
in the body are terminated by being welded to the butt
of the plates 16 which are exposed on the bottom
surface 1~ of the connector body ~: subsequently this
area is sealed with a coat of adhesive silicone rubber.
We have found that the connector of our
invention is extremely suitable for use where multiple
electrode connections are required and it is also of
value as it enables the prosthesis or transducer assemb-
ly to be removed without the necessity of permanently
displacing the electrodes or other connections. At the
same time, the size of the connector of the present
invention is very much smaller than has previously been
obtainable.
.
