Method of making a connector head of a multipolar lead of an active implantable medical device

Abstract

Forming a connector head for a generator of an active implantable medical device by providing a pin (20) having alternating smooth sections (21) for receiving an electrical contact (210) and a profiled section (22); disposing the electrical contacts on the smooth sections; injecting into a first mold a flexibly resilient material around the profiled sections of the pin to produce isolation elements between the electrical contacts; injecting in a second mold a rigid material around the pin to form the connector head with the electrical contacts and isolation elements embedded therein; and withdrawing the pin from the cavity of the connector head thus formed. The material provides precise axial and radial positioning of the different elements, and good electrical insulation.

Claims

1. A process for producing a connector head for a generator of an active implantable medical device, the connector head including a substantially cylindrical cavity for reception of a multipolar lead, said cavity comprising an alternation of annular electrical contact elements and annular isolation elements, said annular isolation elements having an inner sealing profile, comprising: providing a cylindrical pin having a diameter substantially equal to the diameter of the cavity, said pin having alternately smooth sections for receiving a plurality of annular electrical contact elements, and profiled sections having a profile that is a complement of said inner sealing profile; arranging said annular electrical contact elements on said smooth sections of the pin while axially leaving an interval between said annular electrical contact elements, said interval corresponding to said profiled sections, wherein the annular electrical contact elements have an inner portion and an outer portion, wherein the inner portion defines a inner diameter defining the cavity; injecting in a first mold containing said pin and arranged annular electrical contact elements a first material around the profiled sections so as to produce the annular isolation elements, said first material being a resiliently flexible material when solidified having a first hardness, wherein the annular isolation elements have an inner portion and an outer portion, wherein the inner portion extends into the inner diameter defining the cavity; dimensioning said first mold so that the outside diameter of the annular isolation elements is less than the outside diameter of the annular electrical contact elements, such that the outer portion of the annular electrical contact elements extends beyond the outer portion of the annular isolation elements creating an adhesive zone defined on either side by a side on the outer portion of adjacent annular electrical contacts and a top of the outer portion of a annular isolation element between the adjacent annular electrical contacts; injecting into a second mold containing said pin, said arranged annular electrical contact elements, and said annular isolation elements a second material around the pin so as to produce the connector head, said second material when solidified having a second hardness greater than said first hardness, said second material anchoring the annular electrical contact elements into a position and preventing movement of the annular electrical contact elements by the second material filling and extending beyond the adhesive zone; and axially releasing the pin from the cavity of the connector head thus obtained.

2. The method of claim 1 further comprising, prior to injecting the first material, bringing the annular electrical contact elements to respective determined axial positions on the smooth sections of the pin, and maintaining them in position by a positioning tool during the injection steps.

3. The method of claim 2, wherein the positioning tool comprises annular grooves formed on the outer diameter of the annular electrical contact elements and bodies for locking in position the annular electrical contact elements, cooperating with the annular grooves.

4. The method of claim 1, further comprising providing the first hardness with a hardness less than 80 Shore A.

5. The method of claim 1, further comprising providing the first material as one of an elastomer material and a thermoplastic polymer.

6. The method of claim 5, wherein the elastomer material further comprises a silicone compound.

7. The method of claim 5, wherein the thermoplastic polymer further comprises a thermoplastic polyurethane.

8. The method of claim 1, further comprising providing the second material with a hardness greater than or equal to 70 Shore D.

9. The method of claim 1, wherein the second material further comprises a thermoplastic polymer.

10. The method of claim 9, wherein the thermoplastic polymer further comprises a thermoplastic polyurethane.

11. The method of claim 1, further comprising forming an adhesion between the first material and the second material.

12. The method of claim 11, wherein the adhesion further comprises a chemical adhesion.

13. The method of claim 1, further comprising holding the annular electrical contact elements axially in place by injecting said first material and thereby forming said annular isolation elements therebetween.

Description

DRAWINGS

(1) Further features, characteristics and advantages of the present invention will become apparent to a person of ordinary skill in the art from the following detailed description of preferred embodiments of the present invention, made with reference to the drawings annexed, in which like reference characters refer to like elements and in which:

(2) FIG. 1 is a perspective view of a connector head manufactured according to the method of the present invention;

(3) FIG. 2a is a perspective view of a pin with four electrical contacts used in the method of the present invention;

(4) FIG. 2b is a side view of the pin of FIG. 2a;

(5) FIG. 3 is a sectional view illustrating the steps of molding in accordance with a first preferred embodiment of the present invention;

(6) FIG. 4a is a perspective sectional view illustrating the second molding step in accordance with a first preferred embodiment of the present invention;

(7) FIG. 4b is a perspective sectional view illustrating a second molding step in accordance with a second preferred embodiment of the present invention; and

(8) FIG. 5 is a cross-sectional view of a connector head resulting from the second molding step according to FIGS. 4a and 4b.

DETAILED DESCRIPTION

(9) With reference to the drawings FIGS. 1-6, preferred embodiments of the method forming a connector head in accordance with the present invention will now be described. It should be understood that the attached drawings are given as non-limiting examples.

(10) Referring to FIG. 1, a connector head 10 for a generator of an active implantable medical device is shown. The connector head 10 comprises a substantially cylindrical cavity 11 for receiving, in accordance with the IS-4/DF-4 standard (ISO 27186-2010), a connection plug of a multipolar lead (not shown) so as to couple electrical signals between the generator of the device and, e.g., the heart of a patient.

(11) EP 1641084 A1 and its counterpart U.S. Pat. No. 7,175,478 (Sorin CRM S.A.S.) describes an example of one such quadripolar connection plug, which description is incorporated herein by reference. Specifically, this connection plug is of the prior art and is an isodiameter one, having at one end thereof an axial electrical contact pin and, on the body of the plug, three annular electrical contact zones made by conductive cylindrical rings. The electrical contact zones are alternately separated by intercalary insulating cylindrical zones to electrically isolate the electrical contact areas from one another.

(12) One can thus, in a single motion insert the connection plug into cavity 11 of head 10, simultaneously to perform all the necessary electrical connections between the generator and the poles of the connection plug.

(13) For this purpose, cavity 11 must of course be provided with elements homologous to those present on the connection plug. These elements will now be described in detail in connection with the above referenced standard.

(14) As shown in FIG. 1, cavity 11 of head 10 comprises a threaded screw insert 100 that is used to hold the connection plug in cavity 11. In this regard, a screw 120 is inserted into screw insert 100 and tightened against the axial pin of the connection plug (not shown), after the axial pin has been fully inserted in a socket 1010. This obtains a secure electrical connection between the axial pin and the generator. Cavity 11 includes alternating electrical contact and isolation elements (collectively an alternation 200).

(15) More specifically, alternation 200 comprises three annular electrical contact elements 210, provided for making electrical contact with the corresponding conductive rings of the connection plug in order to transmit, with the axial pin, all high/or low voltage electrical signals from the electronics of the generator to the heart via implanted multipolar lead, and vice versa. Electrical contact elements (or electrical contacts) 210 should be able to receive the connection plugs of the leads and meet the insertion and extraction force, as well as the electrical performance requirements defined in the above referenced (or other applicable) standard.

(16) With reference still to FIG. 1, electrical contacts 210 are composed of two annular cylindrical sub-elements, namely a cage 211 made of a biocompatible material such as stainless steel, e.g., type MP35N, and a spring contact 212 received by cage 211 within a groove 2111 formed in its internal surface part, along the inside diameter. Spring contact 212 is preferably a cylindrical spring. More preferably, it is a single piece of implantable resilient metal and performs a function of making a resilient contact with the conductive rings of the connection plug of the lead, so as to obtain the best electrical contact with a low contact resistance.

(17) The outer diameter of cage 211 forms an electrical connection zone or pad for the wire connecting spring contacts 212 to the electronics of the generator. Such an electrical connection is generally made by laser or electrical welding.

(18) With reference to FIG. 1, electrical contacts 210 are alternately separated along the alternation 200 by annular isolation elements (or seals) 220 that are disposed to be opposite the insulating areas of the connection plug, so to create electrical isolation between the electrical contacts 210 and to carry out the electrical insulation and sealing of the cavity 11 vis--vis the external environment. Isolation elements 220 must also guarantee high-voltage insulation and remove the leakage paths at the inner diameter with the isolating zones of the connection plug as well as at their outside diameter, at the interface with the cavity 11.

(19) As shown in FIG. 1, seals 220 are formed of a seal body 221 made of an elastic biocompatible material, such as a silicone elastomer, of hardness less than 80 Shore A. The inner annular face of seal body 221 carries a sealing profile 222, in the preferred embodiment consisting of two rings that provide radial compression against an insulating region of the connection plug when the latter is inserted into connector head 10, thus ensuring sealing of cavity 11 and the insulation between two consecutive conductive rings of the connection plug and of corresponding spring contacts 212.

(20) All electrical contact and isolation elements described above are embedded together in head 10 of the connector itself, made of a material of greater hardness than the elastic material of seals 220, such as a thermoplastic polyurethane having hardness greater than or equal to 70 Shore D. To make head 10 of the connector of FIG. 1, the invention provides a method for implementing a molding of a pin 20, shown in FIGS. 2a and 2b.

(21) With reference to FIGS. 2a and 2b, pin 20 is preferably constructed with a generally cylindrical shape having a diameter substantially equal to that of the cavity 11, and is segmented into a plurality of sections associated with different functional elements of cavity 11. The proximal end 23 of pin 20 corresponds to the input end of cavity 11, while distal end 24 is equipped with the components necessary for molding of the screw insert 100. The portion of pin 20 between its proximal end 23 and its distal end 24 is divided into an alternation of smooth sections 21 and profiled sections 22. Smooth sections 21 correspond to electrical contacts 210 described above which will be disposed thereon. With reference to FIG. 1, profiled sections 22 preferably have a profile 222 that is complementary to the sealing profile of seals 220.

(22) Pin 20 thus formed is placed on a plate 30 for injection molding (see e.g., FIGS. 4a and 4b). This placement involves using a positioning tool having members for wedging in position electrical contacts 210, to match with annular grooves 2112 formed on the outer diameter of electrical contacts 210. These positioning tool wedging members thus axially position electrical contacts 210 along the pin 20. In FIG. 4a, for example, the wedging members are constituted by vertical rods 310 fixed to plate 30 being inserted into the grooves 2112; FIG. 4b shows an alternative embodiment in which wedging members 310 are horizontal lugs also matching with peripheral grooves 2112 of electrical contacts 210. Pin 20 as thus fitted with wedging members is locked into a first mold 301 that can be seen in FIG. 3.

(23) With reference to FIG. 3, the axial positioning tools are not shown. This first molding step is intended to form seals 220 by an injection of a resiliently flexible material around the profile sections 22 of pin 20, through a nozzle 311. The resiliently flexible material may, for example, be a biomedical polymer as a Elast-Eon or ECSiI (trademarks) of AorTech Biomaterials, of hardness less than 80 Shore A. This provides pin 20 with seals 220 as shown in FIG. 4a.

(24) It should be understood that at this stage of the process, the coaxial alignment of electrical contacts 210 with seals 220 is guaranteed from the fact that these elements are carried by the same molding pin 20. The correct axial positioning of the seals 220 along pin 20 is assured by the position defined by the profiled sections on pin 20. Similarly, the axial positioning of the electrical contacts 210 is perfectly controlled by using the positioning tools and pin 20 described above.

(25) Also it should be understood that with each seal/electrical contact interface, the polymerization of the flexible resilient material creates in a radial plane a tight connection between the seal 220 and the corresponding lateral side of electrical contact 210. This later prevents, when over-molding of the assembly by a rigid material, any penetration of the material between the electrical contact 210 and the seal 220, which otherwise could create a leakage and electrical breakdown path between adjacent electrical contacts.

(26) With reference to FIG. 3, mold 301 for injection of the first resiliently flexible material is then replaced by a mold 302 into which the second rigid material to form cavity 11 and head 10 of connector is injected through nozzle 312. This rigid material may, for example, be an Elast-Eon or ECSil, of hardness greater than or equal to 70 Shore D.

(27) FIGS. 4a and 4b show in greater detail the installation of pin 20 into mold 302. A rod 320 is screwed on the components of the insert molding components 100 and intended to create a protected zone for the subsequent introduction of tightening screw 120.

(28) After removal of mold 302 and rods 320, connector head 10 is as obtained as shown in FIG. 5 (pin 20 is still present). One can see from this figure that the axial positioning of seals 220 is permanently fixed, to the extent they are embedded (i.e., anchored) in the rigid material of head 10.

(29) Similarly, electrical contacts 210, are maintained in axial position due to the fact that each electrical contact is clamped between two walls of rigid material. To obtain this result, the first mold 301 is dimensioned so that the outside diameter of the seals 220 is smaller than the outside diameter of the electrical contacts 210. Pin 20 can be released from cavity 11 by an elastic deformation of sealing rings 222.

(30) Note that wedging elements 310, 310 of electrical contacts 210 remain in place during the second molding step providing the rigid material. They are then laterally removed, which leaves windows that, in the case illustrated in FIG. 4b, are filled by silicone injection. In the alternative case illustrated in FIG. 4a, rods 310 are used to produce the electrical contact made with the conductive rings of the connection pin.

(31) Finally, one can observe in FIG. 5 the formation of adhesion zones 400, preferably a chemical adhesion at the interface between the resiliently elastic and rigid materials injected: These zones 400 ensure isolationa sealing from the external environment and between electrical contacts and the environment by providing an insulation barrier to leakage current.

(32) One skilled in the art will appreciate that the present invention may be implemented by embodiments other than those described above, which are provided for purposes of explanation and illustration, and not of limitation.