Abstract:
Connector assemblies for use with implantable medical devices having easy to assemble contacts are disclosed. The connector assemblies are generally formed by coupling a plurality of ring contacts, sealing rings, and spring contact elements together with at least one holding ring to form a connector having a common bore for receiving a medical lead cable. Contact grooves or spring chambers for positioning the spring contact elements are formed in part by assembling multiple components together. A further aspect is a provision for encasing each connector assembly or stack inside a thermoset layer or a thermoplastic layer before over-molding the same to a sealed housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a regular U.S. application of provisional application No. 61/171,043, filed, Apr. 20, 2009, which incorporates by reference the description of application Ser. No. 12/421,874, filed Apr. 10, 2009, which is a regular utility application of Ser. No. 61/044,408, filed Apr. 11, 2008. The contents of the foregoing applications are expressly incorporated herein by reference for all purposes. 
    
    
     BACKGROUND 
     Implantable medical devices for providing electrical stimulation to body tissues, for monitoring physiologic conditions, and for providing alternative treatments to drugs are well known in the art. Exemplary implantable medical devices include implantable cardio defibrillators, pacemakers, and programmable neurostimulator pulse generators, which are collectively herein referred to as “implantable medical devices” or IMDs. These IMDs typically incorporate a hermetically sealed device enclosing a power source and electronic circuitry. Connected to the sealed housing, also known as a “can,” is a header assembly. The header assembly includes electrical contact elements that are electrically coupled to the electronic circuits or to the power source located inside the can via conductive terminals. The header assembly provides a means for electrically communicating, via an external medical lead cable, the electronic circuits or power source located inside the device with the actual stimulation point. 
     Industry wide standards have been adopted for, among other things, the dimensions, size, pin spacing, diameter, etc. for the receptacle and the medical lead cable. Furthermore, good electrical contact must be maintained during the life of the implantable medical device and the medical lead cable for use with the IMD must not disconnect from the receptacle located in the header, yet be detachable for implanting and programming purposes and for replacing the IMD when necessary. 
     Although prior art connector contacts provide viable options for medical device manufacturers, the IMD discussed herein and the various headers provide many benefits to manufacturers and practitioners. Furthermore, in-line connectors, while discussed with specific implantable applications, may be used in other industries and applications, including consumer electronics, electrical connectors, and industrial electronics, such as aviation, automotive, oil and gas, etc. 
     SUMMARY 
     Broadly speaking, in-line connector stacks are disclosed. Examples include in-line connector stacks placed inside an encapsulation layer so that the encapsulated stack may be tested for aligning and conductivity before it is installed or placed into a header of an IMD. Different in-line connector stacks comprising different seal and conductive elements may be used with the encapsulation layer concept of the present application. Furthermore, while the specification describes specific applications of the connector stacks in combination with a header of an IMD, the stacks may be used in other applications and industries requiring multiple conductive sources in an in-line configuration. 
     An exemplary method is directed to a method for manufacturing an in-line connector. In one specific example, the method comprising encapsulating an in-line connector stack comprising a common bore with an encapsulation layer to form an encapsulated stack comprising two end surfaces; wherein a plurality of seal elements and conductive contact elements are located between the two end surfaces; aligning a plurality of slots formed on the encapsulation layer with the plurality of conductive contact elements; placing two end caps at the two end surfaces of the encapsulation layer to retain the plurality of seal elements and conductive contact elements inside the encapsulation layer; and wherein the encapsulated stack comprises a common bore and two end openings. 
     An exemplary apparatus comprises a header assembly comprising a header comprising a bore, an in-line connector stack comprising a plurality alternating seal elements and conductive contact elements encapsulated by an encapsulation layer positioned inside the bore, and a snap fit end cap comprising a bore mechanically engaged to the header, which defines a seam therebetween, and wherein the header comprises a plurality of slots aligned with a plurality of slots formed on the encapsulation layer. 
     A further exemplary method is directed to a method for manufacturing an in-line connector. The method, for example, may comprise the steps of forming an encapsulated stack by placing a plurality of seal elements, springs, and conductive contact elements through an opening of a cylindrical housing comprising a bore and a plurality of slots formed laterally of the opening; engaging an end cap to the opening of the cylindrical housing; aligning the plurality of slots on the cylindrical housing with the plurality of conductive contact elements; and testing the encapsulated stack by applying an electrical signal across one of the conductive contact elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following drawings form part of the present specification and are included to further demonstrate certain aspects of the disclosed IMDs, connector stacks, and headers. The present embodiments may be better understood by one or more of these drawings in combination with the detailed description of examples presented herein. 
         FIGS. 1A ,  2 A,  3 A,  4 A,  5 A,  6 A, and  7 A show an in-line connector stack of alternating conductive and non-conductive elements, an encapsulation layer for receiving the in-line connector stack, a header for receiving the encapsulated stack, and a sealed electronic case for mating with the header. 
         FIGS. 1B ,  2 B, and  3 B show a header comprising two in-line connector stacks, which are positioned in respective encapsulation layers. 
         FIGS. 4B ,  5 B, and  6 B show a header attached to an electronic case comprising an encapsulated in-line stack and an integrated snap fit end cap comprising a holding ring. 
         FIG. 8  is a cross-sectional side view of the header of  FIG. 4A . 
         FIG. 9  is a semi-schematic perspective view of the header of  FIG. 4B  attached to a sealed electronic housing. 
         FIG. 10  is a semi-schematic partial cross-sectional side view of the device of  FIG. 9 . 
         FIG. 11  is a semi-schematic cross-sectional side view of an alternative encapsulated stack. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description set forth below in connection with the appended drawings is intended as a description of the presently preferred embodiments of apparatus, system and method for making and using IMDs, in-line connector stacks, and headers and is not intended to represent the only forms in which they may be constructed or utilized. The description sets forth the features and the steps for constructing and using the IMDs, in-line connector stacks, and headers of the present examples in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and structures may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention. As denoted elsewhere herein, like element numbers are intended to indicate like or similar elements or features. 
       FIG. 1A  to  FIG. 7A  show a stackable connector in various stages of assembly and different views for clarity. The connector stack  10 , which comprises a plurality of seal elements  50 , conductive elements  52 , and spring contact elements  54 , are configured to fit inside an encapsulation layer  12  to form an encapsulated stack  14 . The encapsulated stack  14  is configured to fit inside a molded header  16 , which has slots  56  or openings for accessing to weld the leads  58  from the electronic case (See, e.g.,  FIGS. 7A and 5B ) with the conductive elements  54 . The openings  56  are then back filled with a curable implantable material, such as silicone and other medical grade elastomers or resins. Another opening  56 . 1  may be provided for inserting a holding ring  60  with a locking screw  60 . 1  for more permanently securing the lead cable  44  to the connector stack, as shown in  FIG. 6A . In one embodiment, end caps  15  are incorporated, either at only one end of the stack  10  or at both ends, as shown in  FIG. 1A  in exploded view. The end caps  15  are positioned adjacent an end seal element  50 . 1  and provide engagement with the encapsulation layer  12 . In one example, the end caps  15  provide added sealing by incorporating interior ribs or rings for sealing against the electrical lead cable  44 . The end caps  15  may have the same or higher durometer as the seal element but may be lower to facilitate insertion at the inlet. The end seal element  50 . 1  may be similar to the middle seal elements but also includes sealing means, such as ribs and projections, for sealing against the end cap. 
     As shown, the encapsulation layer  12  comprises a generally cylindrical tube comprising one or more slots  64 . In one example, the number of slots  64  corresponds to the number of conductive contact elements  52 , which can vary depending on the desired applications and electrical contacts. The encapsulation layer  12  comprises a lip  74  at each end for engaging the end cap  15 . As shown, the in-line stack  10  comprises three conductive elements. However, less than or more than three may be incorporated without deviating from the spirit and scope of the present invention. When installed into the header  16 , the slots  64  on the insulation layer  12  align with the slots  56  on the header  16  so that leads  58  from the can  22  may be accessed and attached to the conductive elements  52 . 
     Thus, a feature of the present assembly, method and device for making and using an IMD, in-line stack, and header is understood to include a plurality of alternating seal elements  50  and conductive elements  52  located inside an encapsulation layer  12  comprising a plurality of slots  64 , and wherein the plurality of slots align with a corresponding number of conductive elements  52 . In one specific example, a canted coil spring  54  is in electrical contact with each conductive element  52 . As shown in  FIG. 2A , the canted coil spring  54  is located within a groove  66  formed along the inside bore  68  of the in-line stack, which is common with the bore  62  of the header  16 . In a particular embodiment, the groove  66  is formed utilizing a back wall and a side wall of a conductive contact element  52  along with a side wall of an adjacent seal element  50 . However, the groove  66  may be formed using different features and walls utilizing different conductive rings and seals than as shown, such as that shown in  FIG. 11 , further discussed below. Signals or current passing from the leads  58  ( FIG. 3A ) of an electrical housing or case are configured to pass through corresponding conductive elements  52  which then pass through corresponding springs  54  and to corresponding electrode ring terminals  70  on the lead cable  44 , which then pass through corresponding electrode leads  72  ( FIG. 6A ). 
     In one embodiment, a snap fit end cap  18  is incorporated for securing the encapsulated stack  14  inside the header bore  62  of the header  16 , as shown in  FIGS. 3A-5A . The snap fit end cap  18  has provisions for engaging the header  16  and for providing an axial force on the encapsulated stack  14  to at least slightly compress the stack inside the header. For example, the snap fit end cap  18  and the header  16  may incorporate interference detent arrangements that snap in place utilizing axial interference. A seam is defined between the end cap  18  and the header  16 , which is sealed by the force or pressure of the snap fit arrangement. In another example, curable implantable material is applied to further seal the seam. As shown, one or more raised bumps or ribs  36 . 1  are incorporated in the bore of the end cap  18  for sealing against the exterior surface of a lead cable. The one or more raised bumps or ribs  36 . 1  would provide additional sealing from potential leakage into the bore of the in-line stack in addition the seal elements. 
     By stacking the connector stack  10  into an encapsulation layer  12  and encapsulating it as a stack unit  14 , the stack is aligned and can optionally be tested before placing the stack  14  into the header. In other words, the encapsulated stack unit  14  may be viewed a free-standing axially compressed stack that is aligned and adapted to receive an electrical lead cable  44  (FIGS.  6 A and  7 A). Thus, a technician can better perform quality control on the stack  14  before placing it into a header  16  or into a connector housing and then molding it in place with resin. Previously, a technician can only test the stack after it has been assembled onto the electrical case  22  ( FIG. 7A ), which can only be done by installing the same into a header  16 . For example, a technician can test the stack unit  14  as shown in  FIG. 2A  by inserting a lead cable into the stack bore  68  and applying signals or current through the slots  64  to electrically communicate with the aligned conductive elements  52 . As such, the in-line connector stack  14  has utility independent of being placed into the header  16  and/or for use with an implantable device. 
     Refer again to  FIG. 1A , the encapsulation layer  12  may be made from thermoplastic or TPE material and preferably non-conductive. In one example, the encapsulation layer is made from a thermoset plastic and comprises a generally cylindrical shape structure comprising slots  64  and end lips  74  for retaining or engaging the end caps  15 . In an alternative embodiment, one or two end seals  50 . 1 , which are seal elements located at the two ends of the stack  10 , are configured to seal against the lead cable and also function to engage the encapsulation layer  12 . In this alternative embodiment, end caps  15  may be eliminated. 
     In an alternative embodiment, a locking ring with a locking screw is incorporated in the snap fit end cap  18  ( FIG. 4B ) for securing the lead cable. 
     In an alternative embodiment, the end cap  18  is integrally formed with the header  16  and a rear opening (not shown) is instead incorporated on the header, near element  20  of  FIG. 5A . In this alternative embodiment, the stack unit  14  would be installed through the rear opening, which is subsequently back filled with a curable resin. 
     In an alternative embodiment, the connector stack  10  is made from particular seal elements and ring contact elements as described in the &#39;874 application. In still other embodiments, the connector stack is made from particular seal elements and ring contact elements as described in provisional application Ser. No. 61/240,157, filed Sep. 4, 2009, the contents of which are expressly incorporated herein by reference. In still yet other embodiments, the connector stack  10  is made from particular seal elements and ring contact elements as described in co-pending application Ser. No. 12/062,895, filed Aug. 4, 2008, the contents of which are expressly incorporated herein by reference. 
     In an alternative embodiment, the encapsulated stack  14  is over molded with a polymeric header casting resin instead of being inserted into the pre-formed header  16  as shown. The over molded header in this alternative embodiment, not including the pre-formed header  16 , is then attached to an electronic case, i.e., sealed can, of an implantable medical device  22 . 
       FIGS. 1B to 3B  show yet another alternative header assembly  24  comprising a double bore arrangement  26   a ,  26   b . Each bore is configured to store an encapsulated stack  14 , similar to the embodiment of  FIGS. 1A to 7A , and has a snap fit end cap  18  for retaining the stack  14  inside the bore. In one embodiment, a center rib  28  incorporates two detents in superjacent format. The two detents in superjacent format are configured for snap fit engagement with the end caps  18 . 
     In an alternative embodiment, the header  24  is configured to receive the two connector stacks  14  in a side-by-side configuration instead of one on top of another as shown in  FIG. 2B . In other embodiments, more than two connector stacks  14  may be incorporated into the header  24  in a side-by-side configuration, one on top of another configuration, or a pyramid type configuration. 
     Referring now to  FIGS. 4B to 6B , a set screw block  30  having a set screw  32  is incorporated in the snap fit end cap  34 . An opening  34 . 3  is thus provided on a side of the frustoconical cone section of the end cap  34  to provide access to the set screw  32 . The opening  34 . 3  may be back-filled with an implantable material or resin after the set screw  32  is turned to tighten against the lead cable  44  ( FIG. 5B ). The sect screw block  30  may be made from a plastic material and co-molded with the snap fit end cap  34 . In one embodiment, seal elements  36  having annular seal ribs are co-molded or over-molded with the end cap  34  for sealing against a lead cable. The seal elements  36  may be made from the same material as the seal elements  50 , which may be an elastomer or a thermoplastic elastomer (TPE), and inserted into the end cap  34 . 
     In an alternative embodiment, the end cap  34  is integrally molded with the header  24  and the header is provided with a rear opening, near element  20  ( FIG. 5B ). The encapsulated stack  14  may be placed into the bore of the header through the rear opening. The opening may then be back filled with an implantable material. A snap fit cap or flange (not shown) may also be used to close the rear opening instead of simply back filling the rear opening with a resin. The snap fit cap or flange may be use by itself to seal the rear opening or in combination with curable resin. 
     Also shown in the perspective transparent view  FIG. 4B  are three windows or slots  56  for accessing the leads  58  from the electrical case (not shown), such as a sealed can of an IMD. The windows are understood to be backfilled with an implantable material or resin after the leads are secured to the conductive ring contact elements. 
     Also shown in the perspective view of  FIG. 4B  is a set screw opening on the snap fit end cap  34 . As such, an opening on the header for a separate holding ring with set screw may be eliminated. 
     Also shown in the cut-away perspective view of  FIG. 5B  is an assembled implantable medical device  22  with a lead cable  44  inserted into the common bore of the encapsulated stack  14 . The implantable medical device  80  may be any number of devices, such as an implantable cardio defibrillator, pacemaker, and programmable neuro-stimulator pulse generator, to name a few. 
     Also shown in the cut-away perspective view of  FIG. 6B  are a set screw block  30  and two seal inserts  36 . In one example, the snap fit end cap  34  is made from a plastic material and is molded with at least one groove  82  for receiving the relatively softer sealing ring  36  comprising raised bumps or ribs  36 . 1 , such as made from silicone or a TPE material, which is separately formed and installed into the groove  82 . In another embodiment, the components are co-molded. 
       FIG. 8  is an enlarged cross-sectional side view of an exemplary header assembly, which is similar to that shown in  FIGS. 1A and 2B . The snap fit end cap  18  is provided with an annular lip seal  40  near the mating end and near the inlet or entrance to the bore of the end cap. 
       FIG. 9  is a perspective semi-transparent view of the assembly of  FIG. 4B  attached to an electronic case  80 . 
       FIG. 10  is a cross-sectional side view of the assembly of  FIG. 9 . 
       FIG. 11  is a cross-sectional side view of an encapsulated stack  90  provided in accordance with alternative embodiments, which comprises an in-line stack  92  positioned inside an encapsulation layer  94 . Also shown are conductive energizers  96 , which separately sit in grooves  98  formed by a conductive element  100  and two adjacent seal elements  102 . Note that the conductive elements  100  do not include side walls. As such, the grooves  98  are each formed by a conductive element  100  and two adjacent seal elements  102 . The seal elements are each shown with a single projection or lip  104  for sealing against a lead cable. In other embodiments, two or more lips  104  may be incorporated. In the various examples disclosed herein, an encapsulated stack comprising an in-line stack positioned in side an encapsulation layer is provided, which have slots or openings formed on the side thereof for aligning with respective conductive elements. The encapsulated stack, which may be sized to fit any number of contacts as required for a particular application, is configured to facilitate assembly and testing before the encapsulated stack is completed inside a header, connector, or other in-line assembly. 
     Although limited preferred embodiments and methods for making and using connector assemblies provided in accordance with aspects of the present invention have been specifically described and illustrated, many modifications and variations will be apparent to those skilled in the art. For example, various material changes may be used, incorporating different mechanical engagement means to attach the various components to one another, making use of two or more different materials or composites, making a sealing ring from multiple pieces rather than a singularly molded piece, etc. Still alternatively, the connector assembly may be used for any device that requires an in-line connection in which multiple conductive sources are to be relayed between a source generator and a source receiver, whether that device is configured for implanting or otherwise. Still furthermore, although thermoset and thermoplastic polymers are described for encapsulating a stack, other means may be used, such as a mechanical clamp. Also, aspects and features discussed for one embodiment may be used with other embodiments provided the combined embodiment is compatible. Accordingly, it is to be understood that the connector assemblies constructed according to principles of this invention may be embodied in other than as specifically described herein. The invention is also defined in the following claims.