CA1187559A

CA1187559A - Connectors

Info

Publication number: CA1187559A
Application number: CA000389876A
Authority: CA
Inventors: David K. Money; Christopher N. Daly; James F. Patrick
Original assignee: Commonwealth of Australia
Current assignee: Commonwealth of Australia
Priority date: 1980-11-13
Filing date: 1981-11-12
Publication date: 1985-05-21
Also published as: IT1139699B; IT8125025A0; WO1982001655A1; EP0064992A1

Abstract

Abstract A connector for a hearing prosthesis comprising two portions which interfit resiliently. The outer surface of the first portion carries electrical contacts each of which includes a spring. This first portion fits into a second portion which carries on its internal surface electrical contacts which contact the electrical contacts.

Description

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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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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 ~8755

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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 55~

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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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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.
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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An implantable prosthesis for use in hostile environments comprising a replaceable electronics module forming a first connector portion adapted to fit within a second connector portion which forms an implantable electrode and terminal having an array of electrodes for providing electrical stimulation to the body's nervous system, wherein said first connector portion carries on its external surface a first array of discrete electrical contacts and said second connector portion carries on its internal surface a second array of discrete electrical contacts, and said first connector portion with said first array is resiliently held within said second connector portion to ensure electrical contact between each contact of said first array and the complementary contact of said second array.

2. An electrical connector as claimed in claim 1 wherein the connector is cylindrical and the first and second portions are held together by the resilient interfit provided by the electrical contacts.