ELECTRICAL CONNECTOR

Abstract: A connector for hearing prothesis comprising two portions (4), (9) which interfit resiliently. The outer surface of the first portion (4) carries electrical contacts (5) each of which includes a spring (6). This first portion fits into a second portion (9) which carries on its internal surface electrical contacts (16) which contact the electrical contacts (5).

Description: ELECTRICAL CONNECTOR This invention relates to improvements in i connectors and articles having connectors thereon and is specifically designed for electronic connectors and 5 articles including such connectors which are used in hostile environments; such as exist within the human body. The connectors are specifically designed for use in multiple electrode applications such as for 10 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 15 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 being capable of being sealed. Australian patent specification 40981/78 was 20 concerned with this problem. It sought 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 electrical contact 25 was maintained for all contacts, it needed to be main¬ tained under pressure. Patent applications 40981/78 sought to achieve this by providing an elastomeric connector. This elastomeric connector in its preferred 30 form, is a layered connector and in this the conductive and nonconductive zones are formed and located side by side with the conductive zones extending fully through the connector so that the connector can be cut to any required size, provided the cut is transverse to .the 35 zones whilst still having effective conducting zones. OMPI If the connector is used in an implanted prosthesis, the individual conductors of the outgoing electrode group are located in the patient's body, and where these are being 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 5 upper metal plate in position and replace the pros¬ thesis unit with a new unit using the same upper connector assembly. In this way, there is no need to disturb the location of the conductors. The drawbacks of this development are pri - 0 arily the size of the unit which is not inherently constructed 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 5 to loosen in some cases. While it is possible to design electronic modules with very high reliability for chronic implan¬ tation in vivo, some failures must still be expected. In the situation where such a module is providing 30 multipoint stimulation through an array of 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 allows modules to be replaced, should circuit improvements OMH make this desirable. Generally a connector should fulfill the Λ. following criteria: 1. It should connect typically 10-20 electrodes 5 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 10 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- 15 tacts mounted on the internal surface of ' a second unit, wherein said first unit is shaped to resiliently fit within said second unit so that electrical contact occurs between each contact of the first array and each contact of the second array. Preferably each electrical 20 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 25 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 30 electrodes and connector materials when implanted with¬ in a patient's body. In the prior art implantable devices metal connector bodies were used for housing the electronics module. This necessitated placing the coils used to 35 receive power and signals had outside of the elect¬ ronics module. The electric leads connecting these coils to the electronics module passed through the wall of the module but any penetration or presence of body fluids about 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 and signals 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 of . the patient while the second unit incorporates an electronics -module for receiving and generating signals. In this case the prosthesis is for use and the electronics module for receiving and transmitting auditory signals is incorporated within the connector body and can * be easily surgically removed. The connector system 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 retalliza- tion running down the side of the package 4: a small spring 6 is welded to each band 5. One spring is made ■TRΪO _O PI V/1FO larger 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. 5 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 inert materials could be used. - The connector body consists of a cylindrical 10 section 9 closed at one end • 10, with a groove 11 of 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- 15. fies the above leakage current requirements. A silicone rubber boot not shown is placed over the top of the connector to prevent the ingrowth of tissue into the '0' ring groove: this would complicate replacement. The plate 14 incorporates a keyed recess 19 to enable easy 0 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 5 in the body are terminated by being welded to the butt of the plates 16 which are exposed on the bottom surface 18 of the connector body 9: 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. Y OMPI

Claims: CLAIMS 1. A connector comprising a first array of discrete electrical contacts mounted on the external sur¬ face of a first unit, a second array of discrete elect¬ rical contacts mounted on the internal surface of a second unit, wherein said first unit is shaped to resil¬ iently fit within said second unit so that electrical contact occurs between each contact of the first array and each contact of the second array. 2. A connector as claimed in claim 1 in which each electrical contact of one of said arrays is resiliently mounted on its unit not only to ensure permanent elect¬ rical contact but also to retain the first unit within the second unit. 3. An electrical connector for use in hostile environments comprising a first connector portion adapted to fit within a second connector portion, 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 resil¬ iently 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. 4. An electrical connector as claimed in claim 3 wherein the connector is cylindrical and the first and second portions are held together by the resilient inter- fit provided by the electrical contacts.

Inventors: DALY CHRISTOPHER N, MONEY DAVID K, PATRICK JAMES F
Applicants: COMMW OF AUSTRALIA, DALY CHRISTOPHER N, MONEY DAVID K, PATRICK JAMES F, COMMW AUSTRALIA
Application year: 1981
Main classification: A61N1
IPC codes: A61B5, A61F2, A61F11, A61N1, H01R13, H04R25, H05K7