Patent Publication Number: US-2013247374-A1

Title: Method of forming a crimp-through crimp connector for connecting a conductor cable to an electrode

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a division of U.S. patent application Ser. No. 12/363,445, filed Jan. 30, 2009. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to methods of manufacturing a medical apparatus. More specifically, the present invention relates to methods of manufacturing an implantable cardiac electrotherapy lead. 
     BACKGROUND OF THE INVENTION 
     Current implantable cardiac electrotherapy leads (e.g., cardiac resynchronization therapy (“CRT”) leads, bradycardia leads, tachycardia leads) utilize crimp connectors to transition from conductor cables to welded joints at the electrodes or shock coils. Such transitions are excessively expensive to create for a number of reasons. First, each transition employs a relatively expensive crimp connector individually cut using a wire electrical discharge machining process. 
     Second, the process for creating the transition is labor intensive. To achieve adequate electrical contact between a crimp connector and the conductive core of a cable conductor, insulation must be removed from the cable conductor where the crimp connector will be crimped onto the cable conductor. 
     Third, difficulty associated with the process of creating the transition results in substantial scrap. Crimp connectors may be unidirectional and are often reversed when crimped onto the cable conductor, resulting in the scrapping of the crimp connector and the cable conductor. The configuration of the crimp connector requires relatively tight tolerances for fit and placement of the crimp connector relative to a shock coil when undergoing welding. Failure to satisfy the tight tolerances can result in a weak weld between the crimp connector and the shock coil, or welding can burn a hole through the connector again requiring the lead to be scrapped. 
     There is a need in the art for a crimp connector that reduces the costs associated with connecting a cable conductor to a lead shock coil. There is also a need in the art for a method of employing such a crimp connector in connecting a cable conductor to a lead shock coil. 
     SUMMARY 
     An implantable cardiac electrotherapy lead is disclosed herein. In one embodiment, the lead includes an electrode on a distal portion of the lead, a conductor extending proximally through the lead from the electrode, and a crimp connector coupling a distal end of the conductor to the electrode. The connector may include a body with an outer surface, an inner surface, proximal and distal ends, a cavity, and at least one splice opening. The inner surface defines the cavity, the proximal and distal ends respectively define proximal and distal openings leading to the cavity, and the at least one splice opening extends from the outer surface to the inner surface and is oriented generally transverse to an axis extending between the proximal and distal openings. 
     In another embodiment, an implantable cardiac electrotherapy lead includes a tubular body, an electrode on the tubular body with a termination ring, the termination ring having an arcuate inner surface and a proximal edge, a cable conductor including an end, the cable conductor having a conductive core and an insulation jacket, and a crimp connector with an inner surface defining a cavity and an arcuate outer surface, the crimp connector coupling the cable conductor to the termination ring. The arcuate outer surface of the crimp connector nests substantially continuously against the arcuate inner surface of the termination ring. The crimp connector may include a segment of pre-drawn tubing. In another embodiment, the crimp connector further includes at least one splice opening oriented substantially transverse to a longitudinal axis of the crimp connector. In another embodiment, the at least one splice opening is at least one laser cut splice opening having a sharp edge at its intersection with the inner surface of the crimp connector. In still another embodiment, in a post-crimped position, the sharp edge penetrates the insulation jacket on the cable connector providing for electrical communication between the crimp connector and the cable connector. In yet another embodiment, the outer surface of the crimp connector is fixedly attached to the proximal edge of the termination ring. 
     In another embodiment, a method of manufacturing an implantable cardiac electrotherapy lead includes providing an electrode on a tubular body of the lead, forming a crimp connector from a segment of a pre-drawn tubing, receiving an end of a cable conductor in a cavity of a crimp connector, and welding an outer surface of the crimp connector to an edge of the electrode. In another embodiment, the crimp connector includes at least one splice opening. In another embodiment, the at least one splice opening is a laser cut splice opening having a sharp edge at its intersection with an inner surface of the crimp connector. In still another embodiment, the method includes crimping the crimp connector causing the sharp edge of the splice opening on the crimp connector to penetrate an insulation layer of the cable conductor to place the crimp connector in electrical contact with a conductive core of the cable conductor. 
     While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. As will be realized, the invention is capable of modifications in various aspects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of a crimp connector in a pre-crimp position according to certain embodiments. 
         FIG. 2  is a side view of a crimp connector in a pre-crimp position according to certain embodiments. 
         FIG. 3  is a longitudinal cross-sectional view of a crimp connector in post-crimp position in place on a conductor according to certain embodiments. 
         FIG. 4  is a transverse cross-sectional view of a crimp connector in a post-crimp position in place on a conductor according to certain embodiments. 
         FIG. 5  is an isometric view of a lead with a connector/electrode connection according to certain embodiments. 
         FIG. 6  is an enlarged isometric view of the connector/electrode connection depicted in  FIG. 5 . 
         FIG. 7  is an enlarged top view of the connector/electrode connection depicted in  FIGS. 5 and 6 . 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description relates to the connection between cable conductors and an electrode on a medical lead. A medical lead may be used to monitor heart function and stimulate heart function. As such, a distal end of a lead may be placed within the heart and a proximal end may be connected to a controller such as a pacemaker, ICD or other type pulse generator via a lead connector end on the proximal lead end. The distal end of the lead may have a series of electrodes including a pacing electrode, a sensing electrode, and a shocking electrode or coil. Each of the electrodes may be connected via a cable/electrode connector to a respective cable conductor or respective series of cable conductors extending the length of the lead to the lead proximal end&#39;s lead connector end mechanically and electrically coupling the lead proximal end to the controller. The cable conductors may include a conductive core covered by an insulation layer or layers. As such, the connection between the connector and the cable conductor may require removing or penetrating the insulation to provide a positive electrical connection between the two. The present disclosure is directed at the cable/electrode connector used to connect cable conductors to electrodes. 
     In some embodiments, as disclosed below, the cable/electrode connector may be in the form of a crimp connector. The crimp connector allows for the cable conductors to pass into the connector such that the connector may then be squeezed, pressed, or otherwise caused to grasp the cable conductors, restraining them from slipping out of the crimp connector. Moreover, in order to effectively transmit electrical current, the crimp connector may either penetrate the cable conductor insulation or the insulation may be otherwise stripped prior to crimping to create a positive electrical connection. The crimp connector may in turn be welded or otherwise connected to the electrode to complete the electrical circuit. 
     For a discussion regarding a crimp connector  10 , according to certain embodiments, reference is made to  FIGS. 1 and 2 .  FIG. 1  is an isometric view and  FIG. 2  is a side view of a crimp connector  10  in a pre-crimp position according to certain embodiments. 
     As can be understood from  FIGS. 1 and 2 , in one embodiment, the crimp connector  10  may take the form of a body  12 . The body  12  may have an outer surface  14  and an inner surface  16  separated by a body wall  18  having a thickness  20  and the inner surface  16  may define a cavity  22 . The body  12  may have a proximal end  24  and a distal end  26  situated along a longitudinal axis  28  of the body  12 . The body  12  may also include splice openings  30  extending through the body wall  18 . 
     As shown in  FIGS. 1 and 2 , in one embodiment, the body  12  may have a pre-crimp shape of a tube, the inner surface defining a generally cylindrical cavity with a round, oval, or oblong shaped cross-section. Preferably, the cross-section is oval. In this embodiment, the tube may be a segment of pre-drawn tubing. The tube may have a length  32  and a width  34 , wherein the length  32  is longer than the width  34 . Alternatively, the width  34  may be wider than the length  32 . In the case of a cylindrical shape with a round cross-section, the width  34  may be equal to the diameter of the outer surface  14  of the tube. 
     As indicated in  FIGS. 1 and 2 , in one embodiment, the cavity  22  may be adapted to receive cable conductors  36 . The proximal end  24  and distal end  26  of the body  12  may define a proximal opening  38  and a distal opening  40  respectively leading to the cavity  22  and through which the cable conductors  36  may enter the cavity  22 . The cavity  22  may have a width  42  equal to the width  34  of the body  12  less the wall thickness  20  on each side of the cavity  22  and the width  42  may be sufficient to receive one, two, or any number of cable conductors  36 . The height  44  of the cavity  22  may be sufficient to receive at least one cable conductor  36 . It is noted here that the height  44  may be measured in a direction generally normal to the surface of the body  12  with splice openings  30 . This is because, in use, the splice openings  30  may preferably be in contact with each of the cable conductors  36  and thus side by side placement is preferable over stacking placement of cable conductors  36 . As such, the height  44  may preferably be limited to that required to receive one cable conductor  36 . However, those of skill in the art will understand and appreciate that multiple surfaces of the crimp connector  10  may include splice openings  30  so as to accommodate multiple cable conductor orientations where each cable conductor  36  is in contact with a splice opening  30 . As such, the height  44  is not limited to accommodating a single cable conductor  36 . 
     In one embodiment, the crimp connector  10  may include a splice opening  30  or a series of splice openings  30 . The splice openings  30  may extend through the wall  18  of the body  12  leading to the cavity  22 . As such, the splice openings  30  may create a splice opening face  46  with a height  48  equal to the thickness  20  of the body wall  18 , the splice opening face  46  defining the perimeter of the splice opening  30 . The splice openings  30  may be situated in line with each other and may be equally spaced. The splice openings  30  may extend through the body wall  18  substantially perpendicular to the outer and inner surface  14 ,  16 . Alternatively, they may extend through the wall  18  at an angle. In still another embodiment, the splice openings  30  may increase or decrease in size as they pass through the body wall  18 . In one embodiment, each splice opening  30  is formed by laser cutting, resulting in a relatively sharp edge at the inner termination of the splice opening  30  where the inner surface  16  of the body  12  intersects with the splice opening face  46 . 
     The splice openings  30  may be any shape. As shown in  FIGS. 1 and 2 , the splice openings  30  may be in the shape of a slot with a length and a width and may be oriented transverse to the longitudinal axis  28  of the body  12 . In the case of a slot type splice opening, the slot may extend across the body  12  and have a length substantially equal to the width  42  of the cavity  22 . 
     In one embodiment, the crimp connector  10  is a segment of pre-drawn tubing. In one embodiment, the body  12  is formed of a metal or alloy material (e.g., platinum-iridium, MP35N, or stainless steel) and has a wall thickness  18  of between approximately 0.004 inch and approximately 0.01 inch. In other embodiments, the crimp connector  10  is formed via other manufacturing processes such as metal injection molding etc. 
     Referring now to  FIGS. 3 and 4 , the crimp connector  10  may be squeezed, pressed or otherwise caused to crimp the ends of cable conductors  36 . This may occur in a crimping anvil and die shaped to achieve a desired resulting crimped shape. Preferably, the squeezing or pressing is directed normal to the surface of the body  12  containing splice openings  30 . It is noted that an oblong or oval shaped cross-section may be preferable so as to allow the crimp connector  10  to self-align in the crimping die.  FIG. 3  is a longitudinal cross-sectional view of a crimp connector  10  in a post-crimp position in place on a cable conductor  36 . The Figure shows the connector body  12 , the inner cavity  22 , the splice openings  30 , and a cable conductor  36 . The cable conductor  36  includes a conductive core  52  and an outer insulation jacket  54 . As shown, the conductive core  52  may be made up of several strands  56  of smaller wire. The intermittent portions of the wire strands  56  shown are due to the twisted nature of the strands  56  repeatedly crossing the plane of the cross section. The cable conductor  36  may enter the cavity  22  through a proximal end  24  and may extend beyond the distal end  26  as shown. Those skilled in the art will understand and appreciate that the further the cable conductor  36  extends into the cavity  22 , the better the connection strength and the electrical conductivity will be. 
     As shown, the connector  10  has been crimped onto the cable conductor  36  by squeezing or pressing the opposing walls of the connector  10  toward one another in a crimping die, preferably, one of the walls being a wall with splice openings  30 . As shown, the insulation  54  of the cable conductor  36  has been pressed into the splice openings  30  due to the forces compressing the cable conductor  36 . The sharp edge  50  formed between the splice opening face  46  and the inner surface  16  of the body  12  causes the insulation  54  to be severed and allows for electrical contact between the body  12  and the conductive core  52  of the cable conductor. In the present embodiment, this occurs at each of three splice openings  30  in the connector  10 . Moreover, the crimping process has caused the cable conductor  36  to be secured within the connector  10  due to frictional resistance between the cable conductor  36  and the inner surface  16  of the body  12 , but also due to bearing type resistance between the bulging portions of the cable conductor  36  and the splice opening face  46  surrounding the splice opening  30 . 
     Referring now to  FIG. 4 , a transverse cross-sectional view of a crimp connector  10  is shown, wherein the connector  10  is in a post-crimp position and in place on a cable conductor  36 .  FIG. 4  shows the connector body  12 , the inner cavity  22 , and two cable conductors  36 . The cable conductors  36  shown include a conductive core  52  and an outer insulation jacket  54 . As with  FIG. 3 , the conductive cores  52  may be made up of several strands  56  of smaller wire. As shown, the compressive force of the crimping connector  10  in conjunction with the sharp edge  50  at the splice openings  30  has severed the insulation  54  on the cable conductors  36  allowing electrical contact between the body  12  and at least one strand  56  of each of the conductive cores  52 . 
     For a discussion of the crimp connector  10  being employed to connect the cable conductors  36  to an electrode  58 , reference is made to  FIGS. 5-7 .  FIG. 5  is an isometric view of a lead  60  with a connector  10 /electrode  58  connection according to certain embodiments,  FIG. 6  is an enlarged isometric view of the connector  10 /electrode  58  connection depicted in  FIG. 5 , and  FIG. 7  is an enlarged top view of the connector  10 /electrode  58  connection depicted in  FIGS. 5 and 6   
     As indicated in  FIGS. 5-7 , in one embodiment, the electrode  58  or electrode assembly  58  extends about the tubular body  62  of the lead  60  and includes a termination ring  64  at a proximal end  66  of the electrode  58 . The proximal edge  68  of the termination ring  64  forms a welding face  70  of the electrode assembly  58 . A distal portion  72  of the crimp connector  10  may extend underneath the termination ring  64  leaving a proximal portion  74  of the crimp connector  10  extending out of the termination ring  64 . As such, the outer surface  14  of the crimp connector  10  may be substantially adjacent to and perpendicular to the welding face  70  of the termination ring  64  allowing for a weld between these two surfaces. It is noted that in this embodiment, the splice openings  30  (not shown) of the crimp connector  10  may be positioned opposite the welded connection to the termination ring  64  to assure a proper welding surface on the body  12  of the crimp connector  10 . 
     As best understood from  FIG. 6 , the outer surface  14  of the body  12  of the crimp connector  10  may be arcuate allowing it to generally mate with the arcuate shape of the inner surface  76  of the termination ring  64 . This may minimize gaps between the outer surface  14  of the crimp connector  10  and the welding face  70  providing for a better welded connection and minimizing weld burn through. 
     As can further be understood from  FIG. 6 , in one embodiment, the contour of the immediately adjacent, transversely extending faces  14  and  70  generally match and may be welded together via laser welding in the area  78 . In other embodiments, other forms of welding are utilized to join the faces  14 ,  70 , including resistance welding etc. In one embodiment, a series of spot welds (e.g., four spot welds) joins the faces  14 ,  70  in area  78 . In another embodiment, the weld formed in area  78  is generally continuous. Regardless of whether the faces  14 ,  70  are joined via a series of spot welds or a continuous weld, the welded area  78  defining an edge-to-surface weld is strong due to the relatively extensive length of the welded area  78  made possible by the length over which the faces  14 ,  70  extend adjacent to each other. 
     As illustrated in  FIGS. 5-7 , the cable conductors  36  (shown in phantom) extend through the tubular body  62  of the lead  60  and into the cavity  22  via the proximal opening  38  (see  FIGS. 1 and 2 ) defined by the proximal end  24 . Having crimped the cable conductors  36  in the crimp connector  10  and welded or otherwise connected the crimp connector  10  to the electrode  58 , the cable conductors  36  may extend through the length of the lead  60  to a controlling device at the other end thus completing the electrical circuit. 
     Those skilled in the art will understand and appreciate that various modifications may be made to the present disclosure and still be within the scope of the present invention. For example, the body  12  may not be in the shape of a tube, but rather may have a top portion comprising a generally planar or arcuate surface with edges that wrap and hook below the planar surface creating a cavity between each of the wrapped/hooked portions and the bottom surface of the top portion, the wrapped/hooked portions separated by a gap. The cable conductors  36  may be received by the cavities defined by the hooked portion and crimping may cause the wrapped/hooked portions to grasp the cable conductors  36  against the bottom of the top portion. In similar fashion to the tube type body discussed above, this embodiment may have splice openings or slots in the top portion or in the hooked/wrapped portion for severing the insulation and creating electrical conductivity in addition to furthering the connector&#39;s ability to grasp the cable conductors  36 . 
     It is noted that the pre-crimp shape of the crimp connector  10  may take on many shapes ranging from completely flat to shapes with pre-formed cavities. In cases where a pre-formed cavity is provided, the crimping process may involve pressing or squeezing the crimp connector  10  to secure the connection to the cable conductor  36 . In other cases, the crimping process may actually involve further manipulation of the substrate shape prior to crimping the body to the cable conductor  36 . That is, in the case of a flat pre-crimp shape, an edge or edges of the flat body may be folded or rolled around the cable conductor  36  prior to pressing, squeezing, or otherwise crimping the connector  10  onto the cable conductor  36 . 
     In another embodiment, the splice openings  30  may not take the form of the slots discussed above, but may be circular, square, triangular, or any other shape. In some embodiments, the splice openings  30  may not be in line with one another but may be staggered from side to side or more randomly placed. In another embodiment, the splice openings  30  may be in the form of slots, but may extend the full width of the body  12  rather than only the width  42  of the inner cavity  22 . Alternatively, the splice openings  30  may stop well short of the width  42  of the inner cavity  22 . 
     In another embodiment, the splice openings  30  may not actually extend all the way through the wall  18  of the body  12 . In this embodiment, the splice opening  30  may comprise a recess on the inner surface  16  of the body allowing for the same severing and connection capabilities of the device discussed above, without fully penetrating the body wall  18 . In this embodiment, the crimping connector  10  does not need to be oriented so as to have the splice openings  30  directed away from the contact surface of the termination ring  64  of the lead  60  because welding may take place on either surface due the absence of splice openings  30  on the outer surface  14  of the connector  10 . Moreover, where the splice openings  30  are located in various positions within the connector  10  (e.g. not all on one side, but on multiple or all sides) the orientation of the connector  10  relative to the crimping die may be more flexible. That is, the crimp connector  10  would not have to be positioned for the crimping die to press on any specific side of the connector  10 . 
     The crimp connector  10  disclosed herein is advantageous for several reasons. First, the crimp connector  10  is bi-directional both with respect to its attachment to the electrode  58  and with respect to its attachment to the cable conductor  36 . That is, its symmetry allows for the connector  10  to be rotated so as to exchange positions between its distal end  26  and its proximal end  24 . This makes manufacturing easier and also minimizes waste for situations where the connector  10  is inadvertently reversed. Second, the crimp connector  10  does not require removal (e.g., ablation) of cable conductor insulation  54  prior to connecting the crimp connector  10  to the cable conductor  36 . This minimizes manufacturing steps for the medical lead  60 , reducing costs of production. Third, the crimp connector  10  may be formed from pre-drawn tube subjected to a relatively inexpensive laser cutting process, further reducing costs of production. Fourth, the crimp connector  10  offers improved welding strength and reduced welding difficulty. Accordingly, the crimp connector  10  substantially reduces manufacturing cost associated with connecting cable conductors  36  to the electrodes  58  of implantable cardiac electrotherapy leads  60 . 
     Additionally, the transverse orientation of the splice openings  30  may be advantageous due to the flexibility it provides regarding placement of the cable conductors  36 . That is, the cable conductors  36  entering the connector  10  may not need to be placed with any specificity relative to the lateral direction of the connector  10 . This is because the breadth of the splice opening  30  may allow for them to be placed anywhere across the width of the cavity  22  and still be in contact with a splice opening  30 . Thus, more assurance may be provided that electrical communication will occur between the conductive core  52  of the cable conductor  36  and the sharp edge  50 . 
     Although the present invention has been described with reference to preferred embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.