Abstract:
A system and method for a shielded coaxial cable including a collar including a cylindrical housing having a cylindrical inner bore, the inner bore having top and bottom openings the top opening having a diameter about equal to an outer diameter of an outer insulating layer of the cable and the bottom opening having a diameter about equal to an outer diameter of a shield layer of the cable with a terminating portion of the shield layer exposed and returned over an exterior portion of said collar near the bottom opening with the terminating portion overlapping said exterior portion; and a termination ferrule joined to the terminating portion that overlaps the exterior portion to simultaneously provide an electrical communication between the shield layer and the collar and provide a strain relief for the shielded cable disposed within the inner bore.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates generally to shielded cable termination, and more specifically, but not exclusively, to a single connector providing environmental protection, strain relief, and cable shield termination to a high voltage shielded coaxial cable. 
         [0002]    In the assembly of many types of electrical equipment, it is common to use shielded cables. In general, these are electrical cables having one or more insulated conductors sheathed in a common conductive layer referred to as the shield. This shield is typically composed of braided strands of metal (e.g., copper or aluminum). These shielded cables are used with termination systems designed to provide both electrical and mechanical interface functions. 
         [0003]    Conventional systems are built using detachable connectors or bolted connections that may include a gland-type enclosure seal, often with the electrical interface and the mechanical interface provided as discrete elements. Providing conventional-style environmental protection, strain relief, and cable shield termination with the termination system often uses many parts joined with multiple crimping operations. As the number of parts and the number of crimping operations for terminating a shielded cable decreases, reliability improves and costs decrease. 
         [0004]    What is needed is a system and method that improves reliability and cost-effectiveness of shielded cable termination systems. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    Disclosed is a system and method that improves reliability and cost-effectiveness of shielded cable termination systems. Strategic orientation of elements of a termination collar allows many advantages including an arrangement where a single joining action (e.g., crimping and the like) that provides electrical termination of the shield portion of a shielded cable also physically engages the cable to provide strain relief. Other features of the collar provide any additional needed or desired electro-mechanical interface functions. 
         [0006]    The following summary of the invention is provided to facilitate an understanding of some of technical features related to shielded cable termination systems, and is not intended to be a full description of the present invention. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole. The present invention is applicable to other termination systems besides those used for shielded cable termination in an electric vehicle. 
         [0007]    A termination system for a shielded cable including a main conductor, an inner insulating layer, a shield layer and an outer insulating layer, including a collar including a generally cylindrical housing provided with a generally cylindrical inner bore, the inner bore having a top opening and a bottom opening, the top opening having a diameter about equal to an outer diameter of the outer insulating layer and the bottom opening having a diameter about equal to an outer diameter of the shield layer wherein the shielded cable including the outer insulating layer enters into the top opening and wherein the shielded cable excluding the outer layer exits the bottom opening with a terminating portion of the shield layer exposed and returned over an exterior portion of the collar proximate the bottom opening with the terminating portion overlapping the exterior portion; and a termination ferrule joined to the terminating portion that overlaps the exterior portion and simultaneously provides an electrical communication between the shield layer and the collar and provides a strain relief for the shielded cable disposed within the inner bore. 
         [0008]    A method for terminating a shielded cable including a main conductor, an inner insulating layer, a shield layer and an outer insulating layer, the method including a) removing an end portion of the outer insulating layer from the shielded cable which exposes a terminating portion of the shield layer; b) inserting the end portion through a generally cylindrical inner bore of a generally cylindrical metal collar, the inner bore having a top opening and a bottom opening, the top opening having a diameter about equal to an outer diameter of the outer insulating layer and the bottom opening having a diameter about equal to an outer diameter of the shield layer; c) folding the terminating portion back over an exterior portion of the collar proximate the bottom opening where the terminating portion exits, with the terminating portion overlapping the exterior portion; d) placing a terminating ferrule over the terminating portion that overlaps the exterior portion; and thereafter; e) joining the terminating ferrule to the terminating portion in such a way as to simultaneously provide an electrical communication between the shield layer and the collar and a strain relief for the shielded cable disposed within the inner bore. 
         [0009]    A termination system for a pair of shielded cables electrically coupled to a pair of contacts through an enclosure wall, each shielded cable including a main conductor, an inner insulating layer, a shield layer and an outer insulating layer, including a pair of collars, one for each shielded cable, each collar including a generally cylindrical housing provided with a generally cylindrical inner bore, the inner bore having a top opening and a bottom opening, the top opening having a diameter about equal to an outer diameter of the outer insulating layer and the bottom opening having a diameter about equal to an outer diameter of the shield layer wherein the shielded cable including the outer insulating layer enters into the top opening and wherein the shielded cable excluding the outer layer exits the bottom opening with a terminating portion of the shield layer exposed and returned over an exterior portion of the collar proximate the bottom opening with the terminating portion overlapping the exterior portion; and a pair of termination ferrules, one termination ferrule for an associated one of the pair of collars, each termination ferrule joined to the terminating portion that overlaps the exterior portion of the associated collar and simultaneously providing an electrical communication between the shield layer and the associated collar and providing a strain relief for the shielded cable disposed within the inner bore of the associated collar; wherein the enclosure wall includes a pair of cylindrical bores, each bore associated with one of the contacts; wherein each collar is seated at a seating reference in a different one cylindrical bore provided in the enclosure wall; wherein a first distance from the collar seating reference of a first cylindrical bore to the first contact is different from a second distance from the collar seating reference of a second cylindrical bore to the second contact; wherein a first shielded cable configured for connection to the first contact through the first cylindrical bore has a first length of the main conductor extending from the first collar associated with the first shielded cable sufficient to engage the first contact when the first collar is seated at the collar seating reference of the first cylindrical bore; wherein a second shielded cable configured for connection to the second contact through the second cylindrical bore has a second length of the main conductor extending from the second collar associated with the second shielded cable sufficient to engage the second contact when the second collar is seated at the collar seating reference of the second cylindrical bore; wherein the first length of the main conductor is unable to engage the second contact when the first collar is seated in the second cylindrical bore; and wherein the second length of the main conductor is unable to engage the first contact when the second collar is seated in the first cylindrical bore. 
         [0010]    Other features, benefits, and advantages of the present invention will be apparent upon a review of the present disclosure, including the specification, drawings, and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the present invention and, together with the detailed description of the invention, serve to explain the principles of the present invention. 
           [0012]      FIG. 1  illustrates a termination system used with a pair of high voltage shielded cables; 
           [0013]      FIG. 2  illustrates a sectional view of the termination system shown in  FIG. 1 ; 
           [0014]      FIG. 3  illustrates a detail view of a shield termination/strain relief portion of the termination system shown in  FIG. 2 ; 
           [0015]      FIG. 4  illustrates the terminated pair of high voltage shielded cables mounted within a housing; and 
           [0016]      FIG. 5  illustrates a sectional view of one of the mounted terminated high voltage shielded cables of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    Embodiments of the present invention provide a system and method that improves reliability and cost-effectiveness of shielded cable termination systems. The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. 
         [0018]    Various modifications to the preferred embodiment and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein. Reliable and cost-effective termination of shielded cable is important in many applications, but particularly so for termination of the high voltage cables used in electric vehicles (EVs). The following example describes the present invention in the context of EV cable termination to simplify the discussion as an aid in understanding. The present invention is not limited to such use. 
         [0019]      FIG. 1  illustrates a termination system  100  used with a pair of high voltage shielded cables  105 . Each high voltage shielded cable  105  includes a main conductor  110  attached to a terminal  115 . The specifics of terminal  115  and the method of attachment to main conductor  110  are generally not central to the present invention. High voltage shielded cable  105  further includes an inner insulating layer  120  surrounding main conductor  110  as it extends from a collar  125 . A position of each collar  125  is fixed physically on high voltage shielded cable  105 , this position determining a distance main conductor  110  extends from collar  125 . Fixing the position of each collar  125  on high voltage shielded cable  105  with differing specified distances for main conductor  110  aids in decreasing mis-assembly by helping to ensure that the correct cable is installed in the correct location (because terminal  115  will not align with a mating connection when installed at an incorrect location). 
         [0020]    Each collar  125  is round, made of metal, and includes any necessary or desirable environmental protection and electrical termination features for high voltage shielded cable  105 . Collar  125  is designed to physically interface to a complementary mating structure (e.g., a housing, enclosure wall, or the like) that includes a simple round bore. Not only does the round geometry reduce manufacturing costs for collar  125  and the mating bore, it simplifies assembly and reduces assembly and installation costs for several reasons, one of which is that terminal  115  has no specific relative angular position requirement relative to high voltage shielded cable  105  and to collar  125 . 
         [0021]    Environmental protection includes one or more of a cable-collar seal  130  or an environmental-collar seal  135 . Cable-collar seal  130  provides an interior environmental control by radially sealing a portion of collar  125  to an insulating jacket layer of cable  105  to prevent/inhibit ingress of fluids (e.g., liquids and/or gases). Cable-collar seal  130  may be made of conventional materials and is retained within the top of collar  125  in a desired fashion to provide the desired level of environmental protection inside collar  125 . For example, cable-collar seal  130  may be retained using a separate clip or an integrated retention feature (e.g., a one-way snap or ramp provided in the top opening). In other cases, the retention feature may be formed after cable-collar seal  130  is installed, such as by compression or other mechanical process after cable-collar seal  130  is installed into collar  125 . 
         [0022]    Environmental-collar seal  135  provides an exterior environmental control by sealing a body portion of collar  125  to prevent/inhibit flow of fluids (e.g., liquids and/or gases) around an outside of collar  125  (e.g., between collar  125  and the complementary mating structure). Environmental-collar seal  135  may be made of conventional materials (e.g., an “O” ring or the like) and is retained within a collar channel provided in an exterior wall of the body portion to provide the desired level of environmental protection between collar  125  and the complementary mating structure. Note that environmental-collar seal  135  may be a serviceable “O” ring rather than a more expensive overmolded seal since termination system  100  is generally cylindrical. 
         [0023]    Collar  125  may provide any necessary/desired electrical interface (e.g., a shield termination) to the complementary mating structure by use of an exterior electrical contact  140  disposed within a collar groove in the exterior wall, the collar groove inboard (i.e., towards terminal  115 ) from the collar channel that locates environmental-collar seal  135 . Exterior electrical contact  140  provides an electrical contact between the body of collar  125  and the mating structure into which collar  125  is installed. Collar  125  slides axially with the complementary mating structure to provide assembly tolerance flexibility. Environmental-collar seal  135  mates to complementary sealing surface inside the circular bore that is part of the complementary mating structure. An outer diameter of exterior electrical contact  140  is less than an outer diameter of environmental-collar seal  135  which helps protect the complementary sealing surface from damage by exterior electrical contact  140  during installation. Exterior electrical contact  140  may be made of conventional materials (e.g., a metal coil spring or the like) and is retained within the collar groove on the body portion to provide the desired level of electrical coupling between collar  125  and the complementary mating structure. 
         [0024]    A termination ferrule  145  connects a shield of a shield layer of high voltage shielded cable  105  to collar  125 . In a preferred embodiment, termination ferrule  145  may be a simple extruded tube that is manufactured at very low cost. Termination ferrule is slid over an end of main conductor  110  and inner insulating layer  120  prior to fixing terminal  115 . Termination ferrule  145  is located properly along inner insulating layer  120  by use of an exterior stop  150  on the exterior wall of collar  125 . After termination ferrule  145  is located, it is crimped which simultaneously connects collar  125  to the shield and physically locks collar  125  in place on high voltage shielded cable  105 . Physical placement is achieved by deforming the body portion and compressing collar  125  against an insulating portion of high voltage shielded cable  105  that passes through a central bore of collar  125 . This deformation and compression provides strain relief for high voltage shielded cable  105 . In the context of collar  125 , the term strain relief refers to an ability to pull on the cable without compromising one or more features (e.g., seal integrity and/or mechanical/electrical interface quality) of termination system  100  beyond a predetermined threshold. 
         [0025]      FIG. 2  illustrates a sectional view of the termination system shown in  FIG. 1 . High voltage shielded cable  105   x  includes a shield  205  (e.g., a braided metal mesh of copper or aluminum or the like) that extends out of, and is folded/returned over, a bottom opening  210  of collar  125 . Termination ferrule  145  is installed over folded shield  205  and crimped, which forms the electric contact between shield  205  and collar  125 . Preferably folded back portion of exposed shield  205  extends a significant distance under crimped termination ferrule  145 . Exterior electrical contact  140 , when contacting the interior of the complementary mating structure, thus electrically communicates shield  205  to the complementary mating structure, providing an electrical termination/ground for shield  205 . As also shown in  FIG. 2 , a retaining clip  215  holds cable-collar seal  130  in place inside a top opening  220  of collar  125 , radially sealing an inside wall portion of collar  125  against an exterior insulating jacket layer  225  of high voltage shielded cable  105   x . 
         [0026]    The interior bore of collar  125  includes an interior stop  230  for mechanical interface to exterior insulating jacket layer  225 . High voltage electrical cable  105  is specified to have different lengths of the various layers pre-processed (e.g., cut), and when pre-processed correctly, collar  125  is easily and simply installed. The different layers of high voltage shielded cable  105   x  are serially exposed in a tiered progression from a proximal portion inside collar  125  towards a distal portion near terminal  115 . That is, high voltage shielded cable  105 , includes a first portion in which exterior insulating jacket layer  225  ends and shield  205  is exposed. There is a second portion having the exposed shield  205  of a sufficient length enabling it to a) extend out of bottom opening  210  and b) be folded back over a portion of collar  125  near bottom opening  210 . There is a third portion extending from the end of the exposed shield  205  to the distal end proximate terminal  115  which is covered with inner insulating layer  120 , and finally there is a fourth portion including the exposed main conductor  110  at the distal end. 
         [0027]    An important feature for the interior bore of collar  125  is that it includes a critical narrowing taper at interior stop  230 . This taper facilitates insertion of the exposed portion of shield  205  into collar  125  and out of bottom opening  210  without damage. An inner diameter of the interior bore of collar  125  at interior stop  230  where the narrowing taper begins must not be too great or it will not provide the stop when acting against a terminating edge of exterior insulating jacket layer  225 . Neither can the inner diameter be too small or it will contact the exposed portion of shield  205  causing it to bunch, tear, or gather inside collar  125 . An inner diameter of the interior bore of collar  125  at interior stop  230  where the narrowing taper ends is preferably as small as possible while permitting shield  205  to exit. A smaller diameter for the taper reduces an amount of distortion/compression required of collar  125  when crimping termination ferrule  145  to provide the desired cable strain relief.  FIG. 3  illustrates a detail view of a shield termination/strain relief portion  235  of the termination system shown in  FIG. 2 . 
         [0028]      FIG. 4  illustrates the terminated pair of high voltage shielded cables  105  of  FIG. 1  mounted in a housing  405 ; and  FIG. 5  illustrates a sectional view (D-D) of a portion  500  of one of the mounted terminated high voltage shielded cables  105   1  of  FIG. 4  installed within a bore  410   1  of housing  405 . Housing  405  includes a pair of bores  410 , each receiving and mating to an associated collar  125  of a respective one of the pair of high voltage shielded cables. In a preferred implementation, collar  125  does not include any independent mechanical interlock for retention within its associated bore  410 . Physical retention of high voltage shielded cable  105 , within housing  405  is provided by engaging terminal  115  with a fastener  415  to attach to a desired termination, for example a busbar  505 . As shown in  FIG. 4 , high voltage shielded cable  105   1  is coupled to a positive terminal of a battery (B+) and high voltage shielded cable  105   2  is coupled to a negative terminal of the battery (B−). The different lengths of main conductor  110  extending out of bottom opening  210  for the two terminated shielded cables  105  ensures that the high voltage cables cannot be attached to incorrect terminals. A distance between a reference point  510  on collar  125  and a reference point  515  on terminal  115  sets a poka-yoke length of main conductor  110 . 
         [0029]    Collectively with the poka-yoke lengths, all the cables of a collection cannot be mis-assembled. While a longer assembly may be mis-connected at a location designed for a shorter assembly, a remaining shorter assembly will be incapable of being connected at the remaining location designed for the longer assembly. The poka-yoke length differences are set large enough that assembly tolerance stack-up does not allow incorrect assembly. In the disclosed embodiments where the poka-yoke lengths are set by the crimping of termination ferrule  145 , the crimp is effective to maintain the positional differences of joinder of collar  125  to cable  105  among the collection. 
         [0030]    Collar  125  provides the environmental protection and electrical termination by appropriate interaction within its associated bore  410   x . Bore  410   1  includes an interior environmental seal portion  520  and an interior electrical interface portion  525 . Interior environmental seal portion  520  is sized and configured to engage environmental-collar seal  135  for desired weather seal properties (e.g., prevent water from entering into housing  405 ). Interior electrical interface portion  525  is sized and configured to engage exterior electrical contact  140  for desired electrical properties (e.g., electrical connection of shield  205  to housing  405 ). An inner diameter of interior environmental seal portion  520  is greater than an interior diameter of interior electrical interface portion  525  to help prevent exterior electrical contact  140  from damaging/degrading interior environmental seal portion  520  as collar  125  is installed into bore  410 . The greater a cycle life, the more that this concern is relevant. 
         [0031]    The systems and methods above has been described in general terms as an aid to understanding details of preferred embodiments of the present invention. In the description herein, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of embodiments of the present invention. Some features and benefits of the present invention are realized in such modes and are not required in every case. One skilled in the relevant art will recognize, however, that an embodiment of the invention can be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of embodiments of the present invention. 
         [0032]    Reference throughout this specification to “one embodiment”, “an embodiment”, or “a specific embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention and not necessarily in all embodiments. Thus, respective appearances of the phrases “in one embodiment”, “in an embodiment”, or “in a specific embodiment” in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics of any specific embodiment of the present invention may be combined in any suitable manner with one or more other embodiments. It is to be understood that other variations and modifications of the embodiments of the present invention described and illustrated herein are possible in light of the teachings herein and are to be considered as part of the spirit and scope of the present invention. 
         [0033]    It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application. 
         [0034]    Additionally, any signal arrows in the drawings/Figures should be considered only as exemplary, and not limiting, unless otherwise specifically noted. Furthermore, the term “or” as used herein is generally intended to mean “and/or” unless otherwise indicated. Combinations of components or steps will also be considered as being noted, where terminology is foreseen as rendering the ability to separate or combine is unclear. 
         [0035]    As used in the description herein and throughout the claims that follow, “a”, “an”, and “the” includes plural references unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. 
         [0036]    The foregoing description of illustrated embodiments of the present invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed herein. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the present invention, as those skilled in the relevant art will recognize and appreciate. As indicated, these modifications may be made to the present invention in light of the foregoing description of illustrated embodiments of the present invention and are to be included within the spirit and scope of the present invention. 
         [0037]    Thus, while the present invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of embodiments of the invention will be employed without a corresponding use of other features without departing from the scope and spirit of the invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the present invention. It is intended that the invention not be limited to the particular terms used in following claims and/or to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include any and all embodiments and equivalents falling within the scope of the appended claims. Thus, the scope of the invention is to be determined solely by the appended claims.