GB1598794A

GB1598794A - Electrical sockets

Info

Publication number: GB1598794A
Application number: GB2629580A
Authority: GB
Original assignee: Needle Industries Ltd
Current assignee: Needle Industries Ltd
Priority date: 1977-03-10
Filing date: 1978-03-07
Publication date: 1981-09-23

Description

(54) IMPROVEMENTS IN OR RELATING TO ELECTRICAL SOCKETS (71) We, NEEDLE INDUSTRIES LI MITED, a British Company, of Arrow Works, Studley, Warwickshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an electrical socket and in particular, but not exclusively, to such a socket which is suitable for use with a plug member to provide a connector adapted for implantation in an animal body.

The electrical socket of this invention may be incorporated in a cardiac pacemaker for implantation in a human body, to allow the connection of a catheter (such as is described and claimed in our co-pending Application Serial No. 1598792 Application No. 8918/78]) to the pacemaker (such as one constructed as described and claimed in our co-pending Application Serial No. 1598793 [Application No. 8919/78]).

With an implanted cardiac pacemaker system, it is most important that the connec tlon between the proximal end of the electrode catheter (the distal end of which communicates with the heart for stimulation thereof) and the implanted cardiac pacemaker (which normally is located some considerable distance from the heart) is very reliable and able to withstand the implanted environment for a considerable number of years. Not only must the connection offer very low electrical resistance, it must furthermore be hermetically sealed against the environment and body fluids at the site of implant. Spring-loaded metal-to-metal connectors together with fluid-tight seals have been used previously, but these have proved in practice to offer an increasing electrical resistance with time, owing to corrosion, and this can in turn lead to premature failure to the overall pacemaker system even though the life of the pacemaker itself has not expired.

According to this invention, there is provided an electrical socket for receiving a plug member having an insulating body portion and a conducting spigot projecting from the body portion whereby an electrical connection is made to the conducting spigot, which electrical socket comprises an insulating body defining a bore for sealingly receiving the body portion of a plug member, a block of resilient conducting rubber material located within the bore and defining a first recess for receiving the spigot of a plug member and defining a further recess spaced from the first recess, and an electrical contact provided through a wall of the socket body portion defining the bore which contact makes an electrical connection with the block of conducting rubber material, the electrical socket being suitable for use with said plug member having a spigot a crosssectional dimension of which is greater than that of the first recess in the block of conducting rubber material whereby the block is deformed on insertion of the plug member spigot into the recess so as to make an electrical connection therebetween, the deformation of the block of rubber material caused by the insertion of the spigot into the first recess being accommodated at least in part by a reduction in volume of the further recess.

The further recess is preferably in the form of an annular channel disposed around the block of conducting rubber material, part-way between the ends thereof.

The bore defined by the electrical socket is preferably circular in cross-sectional shape, so as to be able to receive a plug member having a resilient body portion also of circular cross-section and of such dimensions that the body portion is a sealing fit within the bore. To assist the retention of such a plug member within the bore of the electrical socket, an inwardly-projecting annular rib may be provided within the bore of the socket body portion, for engagement with the body portion of the plug member.

The conducting rubber material is preferably a silicone rubber which has been loaded with carbon particles - or a similar conductor - and such rubber is known per se. It exhibits excellent properties when a conductor displaying resilience or flexibility is required, and thus is used for instance for making contact pads for electrodes which must be maintained in contact with the skin of an animal or human body. The resilient properties of the material in all directions have proved valuable in this invention, in making an excellent electrical connection with the spigot of the plug member.

To ensure the rubber material is deformed on insertion of the plug member spigot in the first recess therefor in the block of conducting rubber material, the recess should have a smaller cross-sectional dimension than the spigot of the plug member with which the socket is to be used. For instance, the first recess could be of square and the spigot of circular cross-sectional shape, the slde of the square being smaller than the diameter of the spigot. It is preferred however for the cross-sectionnl shape of the first recess to be circular, and for the spigot to have a larger diameter than that of the first recess. Then, as the spigot is driven into the recess, the rubber material will be deformed to fit closely around the spigot and to make a low-resistance electrical connection therewith, the deformation being accommodated at least in part by a reduction in the volume of the further recess.

The contact of the socket making an electrical connection with the block of conducting rubber material preferably is in the form of a metal stud having a barb-like head projecting into the bore and fitting within a correspondingly-shaped, but smaller, recess in the block of conducting rubber material such that the material is deformed to fit thereover. Conveniently, the wall of the socket body portion defining the bore is made of a ceramic material and the metallic stud - preferably of platinum - is provided in the wall during manufacture of the socket member so that a hermetic seal is formed therearound. Conveniently, a platinum flange is provided around the socket adjacent the end of the bore through which the plug member is inserted, whereby the socket may be sealed to the body or case of a piece of electrical equipment - for instance a cardiac pacemaker casing. Such sealing may be effected to create a hermetic seal, for example by an electron beam welding technique, and electrolytic corrosion may be avoided in this way. Platinum is selected for the flange and for the contact when employing a ceramic for the part of the socket body portion defining the bore because of the relative ease of forming a hermetic seal between a ceramic material and platinum.

Reference is directed to our co-pending Application Serial No. 1598791 (Application No. 10280/77) wherein we have described and claimed an electrical connector comprising an electrical socket member as described and claimed herein in combination with a plug member therefor. Reference is also directed to our co-pending Applications Serial Nos. 1598792 and 1598793 (Applications Nos. 8918/78 and 8919/78) wherein we have described and claimed our electrode catheter and a cardiac pacemaker which may make use of the electrical connector described and claimed in our just-mentioned co-pending Application Serial No. 1598791 (Application No.

10280/77).

By way of example only, a specific embodiment of this invention will now be described in detail, reference being made to the accompanying drawings, in which: Figure I is a cross-sectional view through an electrical socket arranged in accordance with this invention; Figure 2 is a side view of an electrode catheter including a plug member suitable for use with the socket member of Figure 1 and Figure 3 is a cross-sectional view, but on an enlarged scale, through the plug member shown in Figure 2, as fitted to an electrode catheter.

Referring to the drawings, there is shown a plug and a socket connector intended for connecting an electrode catheter of a cardiac pacemaker system to a pacemaker casing. The connector comprises a plug member 10 and an electrical socket 11, the plug member 10 being moulded directly on the end of the electrode catheter 12 and the socket 11 being adapted for incorporation in the casing of the pacemaker itself.

The electrical socket 11 (Figure 1) comprises a main body 13 made from a ceramics material and defining a blind circular bore 14. An inwardly directed annular rib 15 is provided within the bore 14, spaced slightly from the open end thereof and upstanding from the wall defining the bore by about 0.1 mm. A circular metallic flange 16 (for instance of titanium) is provided on the ceramics body portion 13 around the open end of the bore 14 during the manufacture of the socket, so that the flange 16 is hermetically bonded to the main body 13.

Similarly a conducting contact 17 is provided through the blind end wall of the main body 13 so as to project into the bore 14.

The contact is conveniently of platinum, and is also hermetically sealed to the main body.

Within the bore 14, the contact 17 has an enlarged head 18, provided with barbs 19 directed towards the blind end of the bore.

Located within the bore 14 is a block 20 of relatively soft, resilient conducting silicone rubber material, loaded with carbon particles to render the block electrically conducting. The block 20 is of circular cross-section to fit closely within the bore 14, and has a circular recess 21 opening co-axially towards the open end of the bore 14. A second co-axial recess is provided for receiving the head 18 of the contact 17, the block 20 being deformed to fit over the head and engage with the barbs 19, thereby making a good electrical connection therebetween. An annular channel 22 is provided part-way between the ends of the block 20 of conducting silicone rubber material.

The conducting silicone rubber material is known per se and comprises relatively soft, resilient silicone rubber which has been loaded with carbon black. Such material displays reasonable electrical conductivity, though the resistance offered depends to some extent upon the degree of compression of the material. A typical material is that known as Dow-Corning Q4-1602 Silastic (Registered Trade Mark).

The plug member 10 (Figures 2 and 3) comprises a body portion 23 of circular cross-section and is provided with three annular ribs 24, each having the general cross-sectional shape of a barb directed generally away from the free end of the plug member 10. The body portion 23 its moulded from insulating silicone rubber, and is thus flexible, relatively soft and resilient. The material is similar to that of the block 20, except that it has not been loaded with carbon black; as such the material displays excellent insulating properties. A typical material for this purpose is that known as Dow-Corning MDX-4-4210 Clean-Grade Elastomer. The body portion 23 is moulded around a metal spigot 25, which projects from the free end of the body portion for connection with the socket member of Figure 1. The diameter of the spigot 25 should be slightly greater than that of the recess 21 when the block of silicone rubber is located in the bore 14 of the socket 11.

As shown in Figure 3, the body portion 23 is moulded directly on to the electrode catheter 12, shown in Figure 2. One end of the catheter terminates with the plug member 10, whereas the other end terminates with an electrode 34 having a conducting tip 35 and an insulating flange 36. The catheter 12 includes an outer insulating silicone rubber protective sleeve 26, conductors 27 and a plastics core 28. The spigot 25 is shaped to receive in a first counterbore 29 the conductors 27, to make electrical connection therewith, and in a second, smaller counterbore 30 the plastics core 28. The body portion 23 bonds during the moulding operation to the sleeve 26, and if required the spigot 25 can lightly be crimped on the conductors 27 to ensure a reliable electrical connection thereto.

In use, when the plug member 10 is fitted into the electrical socket 11, the spigot 25 enters the recess 21 in the block 20 of conducting silicone rubber located within the bore 14 and makes an electrical connection therewith. By arranging the diameter of the recess 21 to be of slightly smaller size than that of the spigot 25, the rubber is compressed and resiliently urged into engagement with the spigot, as the spigot enters the recess 21 and a good electrical connection is thereby achieved. The annular channel 22 allows the rubber to distort and deform as required to allow accommodation of the spigot 25 in the recess 21. The annular ribs 24, shaped as barbs, allow the body portion 23 of the plug member easily to enter bore 14 of the ceramic body 16 but restrain withdrawal of the plug member owing to their barb-like shape. The rib 24 nearest the catheter 12 rides over and engages behind rib 15 of the socket 11, and further assists in the retention of the plug member within the socket. Moreover, the ribs 24 of the plug member 10 effect a hermetic seal between the body portion 23 of the plug member and the main body 13 of the electrical socket, whereby the electrical connection between the spigot 25 and the block 20 of conducting silicone rubber material is isolated from the surrounding environment.

WHAT WE CLAIM IS: 1. An electrical socket for receiving a plug member having an insulating body portion and a conducting spigot projecting from the body portion whereby an electrical connection is made to the conducting spigot, which electrical socket comprises an insulating body defining a bore for sealingly receiving the body portion of a plug member, a block of resilient conducting rubber material located within the bore and defining a first recess for receiving the spigot of a plug member and defining a further recess spaced from the first recess, and an electrical contact provided through a wall of the socket body portion defining the bore which contact makes an electrical connection with the block of conducting rubber material, the electrical socket being suitable for use with a said plug member having a spigot a crosssectional dimension of which is greater than that of the first recess in the block of conducting rubber material, whereby the block is deformed on insertion of the plug member spigot into the recess so as to make an electrical connection therebetween, the deformation of the block of rubber material caused by the insertion of the spigot into the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. enlarged head 18, provided with barbs 19 directed towards the blind end of the bore. Located within the bore 14 is a block 20 of relatively soft, resilient conducting silicone rubber material, loaded with carbon particles to render the block electrically conducting. The block 20 is of circular cross-section to fit closely within the bore 14, and has a circular recess 21 opening co-axially towards the open end of the bore 14. A second co-axial recess is provided for receiving the head 18 of the contact 17, the block 20 being deformed to fit over the head and engage with the barbs 19, thereby making a good electrical connection therebetween. An annular channel 22 is provided part-way between the ends of the block 20 of conducting silicone rubber material. The conducting silicone rubber material is known per se and comprises relatively soft, resilient silicone rubber which has been loaded with carbon black. Such material displays reasonable electrical conductivity, though the resistance offered depends to some extent upon the degree of compression of the material. A typical material is that known as Dow-Corning Q4-1602 Silastic (Registered Trade Mark). The plug member 10 (Figures 2 and 3) comprises a body portion 23 of circular cross-section and is provided with three annular ribs 24, each having the general cross-sectional shape of a barb directed generally away from the free end of the plug member 10. The body portion 23 its moulded from insulating silicone rubber, and is thus flexible, relatively soft and resilient. The material is similar to that of the block 20, except that it has not been loaded with carbon black; as such the material displays excellent insulating properties. A typical material for this purpose is that known as Dow-Corning MDX-4-4210 Clean-Grade Elastomer. The body portion 23 is moulded around a metal spigot 25, which projects from the free end of the body portion for connection with the socket member of Figure 1. The diameter of the spigot 25 should be slightly greater than that of the recess 21 when the block of silicone rubber is located in the bore 14 of the socket 11. As shown in Figure 3, the body portion 23 is moulded directly on to the electrode catheter 12, shown in Figure 2. One end of the catheter terminates with the plug member 10, whereas the other end terminates with an electrode 34 having a conducting tip 35 and an insulating flange 36. The catheter 12 includes an outer insulating silicone rubber protective sleeve 26, conductors 27 and a plastics core 28. The spigot 25 is shaped to receive in a first counterbore 29 the conductors 27, to make electrical connection therewith, and in a second, smaller counterbore 30 the plastics core 28. The body portion 23 bonds during the moulding operation to the sleeve 26, and if required the spigot 25 can lightly be crimped on the conductors 27 to ensure a reliable electrical connection thereto. In use, when the plug member 10 is fitted into the electrical socket 11, the spigot 25 enters the recess 21 in the block 20 of conducting silicone rubber located within the bore 14 and makes an electrical connection therewith. By arranging the diameter of the recess 21 to be of slightly smaller size than that of the spigot 25, the rubber is compressed and resiliently urged into engagement with the spigot, as the spigot enters the recess 21 and a good electrical connection is thereby achieved. The annular channel 22 allows the rubber to distort and deform as required to allow accommodation of the spigot 25 in the recess 21. The annular ribs 24, shaped as barbs, allow the body portion 23 of the plug member easily to enter bore 14 of the ceramic body 16 but restrain withdrawal of the plug member owing to their barb-like shape. The rib 24 nearest the catheter 12 rides over and engages behind rib 15 of the socket 11, and further assists in the retention of the plug member within the socket. Moreover, the ribs 24 of the plug member 10 effect a hermetic seal between the body portion 23 of the plug member and the main body 13 of the electrical socket, whereby the electrical connection between the spigot 25 and the block 20 of conducting silicone rubber material is isolated from the surrounding environment. WHAT WE CLAIM IS:

1. An electrical socket for receiving a plug member having an insulating body portion and a conducting spigot projecting from the body portion whereby an electrical connection is made to the conducting spigot, which electrical socket comprises an insulating body defining a bore for sealingly receiving the body portion of a plug member, a block of resilient conducting rubber material located within the bore and defining a first recess for receiving the spigot of a plug member and defining a further recess spaced from the first recess, and an electrical contact provided through a wall of the socket body portion defining the bore which contact makes an electrical connection with the block of conducting rubber material, the electrical socket being suitable for use with a said plug member having a spigot a crosssectional dimension of which is greater than that of the first recess in the block of conducting rubber material, whereby the block is deformed on insertion of the plug member spigot into the recess so as to make an electrical connection therebetween, the deformation of the block of rubber material caused by the insertion of the spigot into the

first recess being accommodated at least in part by a reduction in volume of the further recess.

2. An electrical socket as claimed in claim 1, wherein the further recess is in the form of an annular channel disPosed around the block of conducting rubber material, part-way between the ends thereof.

3. An electrical socket as claimed in either of the preceding claims, wherein the conducting rubber material comprises a silicone rubber loaded with conducting particles.

4. An electrical socket as claimed in claim 3, wherein the conducting particles loaded in the silicone rubber are particles of carbon.

5. An electrical socket as claimed in any of the preceding claims, wherein the bore defined by the socket body portion is of circular cross-sectional shape to receive a correspondingly-shaped plug member body portion.

6. An electrical socket as claimed in any of the preceding claims, wherein an inwardly-projecting annular rib is provided within the bore of the socket body portion, for engagement with the body prtion of an inserted plug member.

7. An electrical socket as claimed in any of the preceding claims, wherein the crosssectional shape of the first recess is circular, to receive a plug member spigot of circular shape but of a larger diameter.

8. An electrical socket as claimed in any of the preceding claims, wherein the contact making an electrical connection with one block of conducting rubber material is in the form of a metal stud, a barb-like head being provided on the end of the stud projecting into the bore, and the block of conducting rubber material has a third recess the shape of which corresponds to that of the barb-like head but of a smaller size such that accommodation of the barb-like head in the third recess deforms the rubber material to make an electrical connection with the contact.

9. An electrical socket as claimed in any of the preceding claims, wherein the socket body comprises walls formed of a ceramic material to define the bore, a platinum stud extending through the walls to connect to the block of conducting rubber material and a metallic mounting flange is bonded to the walls around the opening to said bore.

10. An electrical socket substantially as hereinbefore described with reference to and as illustrated in Figure 1 of the accompanying drawings.