Patent Abstract:
A coaxial connector for interconnection with a coaxial cable with a solid outer conductor by laser welding is provided with a monolithic connector body with a bore. A sidewall of the bore is provided with an inward annular projection angled toward a cable end of the bore. A sidewall of the inward annular projection and the sidewall of the bore form an annular laser groove open to a cable end of the bore. The annular laser groove is dimensioned with a taper at a connector end of the laser groove less than a thickness of a leading end of the outer conductor. The taper provides an annular material chamber between the leading end of the outer conductor, when seated in the laser groove, and the connector end of the laser groove.

Full Description:
BACKGROUND 
     1. Field of the Invention 
     This invention relates to electrical cable connectors. More particularly, the invention relates to a coaxial cable connector interconnectable via laser welding. 
     2. Description of Related Art 
     Coaxial cable connectors are used, for example, in communication systems requiring a high level of precision and reliability. 
     To create a secure mechanical and optimized electrical interconnection between the cable and the connector, it is desirable to have generally uniform, circumferential contact between a leading edge of the coaxial cable outer conductor and the connector body. A flared end of the outer conductor may be clamped against an annular wedge surface of the connector body via a coupling body. Representative of this technology is commonly owned U.S. Pat. No. 6,793,529 issued Sep. 21, 2004 to Buenz. Although this type of connector is typically removable/re-useable, manufacturing and installation is complicated by the multiple separate internal elements required, interconnecting threads and related environmental seals. 
     Connectors configured for permanent interconnection via solder and/or adhesive interconnection are also well known in the art. Representative of this technology is commonly owned U.S. Pat. No. 5,802,710 issued Sep. 8, 1998 to Bufanda et al. 
     However, solder and/or adhesive interconnections may be difficult to apply with high levels of quality control, resulting in interconnections that may be less than satisfactory, for example when exposed to vibration and/or corrosion over time. 
     Competition in the coaxial cable connector market has focused attention on improving electrical performance and long term reliability of the cable to connector interconnection. Further, reduction of overall costs, including materials, training and installation costs, is a significant factor for commercial success. 
     Therefore, it is an object of the invention to provide a coaxial connector and method of interconnection that overcomes deficiencies in the prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, where like reference numbers in the drawing figures refer to the same feature or element and may not be described in detail for every drawing figure in which they appear and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a schematic external isometric view of an exemplary embodiment of a coaxial connector installed upon a coaxial cable with a coupling nut spaced away from the connector along the cable for connector-to-cable interconnection. 
         FIG. 2  is a schematic isometric view of the coaxial connector of  FIG. 1  installed upon a coaxial cable, with the coupling nut seated upon the coaxial connector. 
         FIG. 3  is a schematic isometric view of the coaxial connector of  FIG. 1 . 
         FIG. 4  is a schematic cross section side view of  FIG. 2 . 
         FIG. 5  is an enlarged view of area A of  FIG. 4 . 
         FIG. 6  is a schematic exploded isometric partial cut-away view of the connector and cable of  FIG. 1 . 
         FIG. 7  is a schematic isometric partial cut-away view of the connector body of  FIG. 5 . 
         FIG. 8  is a schematic isometric view of an alternative connector body with notches on a flange of the connector body. 
         FIG. 9  is a schematic isometric view of an alternative connector body with longitudinal knurls on the connector body outer diameter. 
         FIG. 10  is a schematic isometric cut-away view of the overbody of  FIG. 5 . 
         FIG. 11  is an enlarged view of area B of  FIG. 4 . 
         FIG. 12  is a schematic cross section side view of an alternative overbody with corrugation on an inner diameter of the cable end. 
         FIG. 13  is a schematic cross section side view of an alternative overbody with a stepped surface on an inner diameter of the cable end. 
         FIG. 14  is a schematic cross section side view of a coaxial connector embodiment with an inner conductor end cap. 
         FIG. 15  is a schematic cross section side view of the coaxial connector of  FIG. 4  demonstrating a laser beam path during laser welding. 
         FIG. 16  is an enlarged view of area E of  FIG. 15 . 
         FIG. 17  is a schematic cross section side view of an alternative embodiment of a coaxial connector for laser welding interconnection. 
         FIG. 18  is an enlarged view of area C of  FIG. 17 . 
         FIG. 19  is a schematic cross section side view of the coaxial connector of  FIG. 17  demonstrating a laser beam path during laser welding. 
         FIG. 20  is an enlarged view of area D of  FIG. 19 . 
     
    
    
     DETAILED DESCRIPTION 
     Aluminum has been applied as a cost-effective alternative to copper for the conductors in coaxial cables. However, aluminum oxide surface coatings quickly form upon air-exposed aluminum surfaces. These aluminum oxide surface coatings may degrade traditional mechanical, solder and/or conductive adhesive interconnections. 
     The inventors have recognized that increasing acceptance of coaxial cable with solid outer conductors of aluminum and/or aluminum alloy enables connectors configured for interconnection via laser welding between the outer conductor and a connector body which may also be cost effectively provided, for example, formed from aluminum and/or aluminum alloy. 
     An exemplary embodiment of a laser weldable coaxial connector  2  is demonstrated in  FIGS. 1-4 . As best shown in  FIG. 4 , a unitary connector body  4  is provided with a bore  6  dimensioned to receive the leading edge of the outer conductor  8  of a coaxial cable  9  therethrough. Positioned for interconnection by laser welding, the leading edge of the outer conductor  8  extends through the bore  6  to a longitudinal position generally flush with the edge of a shoulder  10  of the connection interface  14  at the connector end  18 , presenting a common end face to the connector end  18 , as best shown in  FIG. 5 . The connection interface  14  may be any desired standard or proprietary connection interface  14  which includes access to a circumferential contact seam  16  between the bore  6  and the outer conductor  8 , the seam  16  generally parallel to a longitudinal axis of the coaxial connector  2 . 
     One skilled in the art will appreciate that connector end  18  and cable end  12  are applied herein as identifiers for respective ends of both the coaxial connector  2  and also of discrete elements of the coaxial connector  2  described herein, to identify the same and their respective interconnecting surfaces according to their alignment along a longitudinal axis of the coaxial connector  2  between a connector end  18  and a cable end  12 . 
     Where the diameter of the bore  6  is selected with respect to the diameter of the outer conductor  8  to be a close tolerance fit, laser welding interconnection of the outer conductor  8  and the connector body  2  may be performed without the addition of further material, such as welding rod or wire. The high level of localized heating from the laser, applied to the seam  16  between the outer conductor  8  and the connector body  2 , may be applied as a pulse directed to a target spot, with successive pulses applied to an overlapping spot portion to form a continuous weld between adjacent portions of the outer conductor  8  and the connector body  2 . 
     Prior to interconnection via laser welding, the end of the cable  9  may be prepared, as best shown in  FIG. 6 , by cutting the cable  9  so that the inner conductor  24  extends from the outer conductor  8 . Also, dielectric material  26  between the inner conductor  24  and outer conductor  8  may be stripped back and a length of the outer jacket  28  removed to expose desired lengths of each. A portion of the dielectric material  26  may be provided extending forward of the leading edge of the outer conductor  8 , for example as an interconnection impedance discontinuity reduction feature. 
     Where applicable, the cable end preparation may also include the step of straightening the cable end portion, for example to eliminate any bending in the cable resulting from bulk cable delivery of the cable wound in spools, so that when inserted into the bore  6 , the cable end is coaxial with the bore  6  along its length and the inner conductor  24  projects from the connector end  18  parallel to the longitudinal axis of the bore  6 . Thereby, the seam between the bore sidewall  20  and the outer diameter of the outer conductor  8  will be uniform around the circumference of the outer conductor  8 , increasing the uniformity of the resulting laser weld. 
     Because the localized heat of the laser welding process can disrupt aluminum oxide surface coatings in the immediate weld area, no additional care may be required with respect to removing or otherwise managing the presence of aluminum oxide on the interconnection surfaces. 
     An overbody  30 , as shown for example in  FIG. 10 , may be applied to the connector body  4  as an overmolding of polymeric material. The overbody  30  increases cable to connector torsion and pull resistance. The overbody  30  may also provide connection interface structure at the connector end  18  and further reinforcing support at the cable end  12 , enabling significant reductions in the size of the connector body  4 , thereby reducing overall material costs. 
     Depending upon the applied connection interface  14 , demonstrated in the exemplary embodiments herein as a standard 7/16 DIN interface, the overbody  30  may be provided with an overbody flange  32  and longitudinal support ridges  34  for a coupling nut  36 . The coupling nut  36  is retained upon the support ridges  34  at the connector end  18  by an overbody flange  32  and at the cable end  12  by a retention spur  38  provided on at least one of the support ridges  34 . The retention spur  38  may be angled toward the connector end  18 , allowing the coupling nut  36  to be placed over the cable  9  initially spaced away from the coaxial connector  2  during interconnection (see  FIG. 1 ), but then allowing the coupling nut  36  to be passed over the retention spur  38  and onto the support ridges  34  from the cable end  12 , to be thereafter retained upon the support ridges  34  by the retention spur(s)  38  (see  FIG. 2 ) in close proximity to the connector interface  14  for connector to connector mating. The support ridges  34  reduce polymeric material requirements of the overbody  30  while providing lateral strength to the connector/interconnection  2  as well as alignment and retention of the coupling nut  36 . 
     The overbody  30  may also extend from the connector end  18  of the connector body  4  to provide portions of the selected connection interface  14 , such as an alignment cylinder  39  of the 7/16 DIN interface, further reducing metal material requirements of the connector body  4 . 
     The overbody flange  32  may be securely keyed to a connector body flange  40  of the connector body  4  and thereby with the connector body  4  via one or more interlock apertures  42  such as holes, longitudinal knurls  43 , grooves, notches  45  or the like provided in the connector body flange  40  and/or outer diameter of the connector body  4 , as demonstrated in  FIGS. 7-9 . Thereby, as the polymeric material of the overbody  30  flows into the interlock apertures  42  during overmolding, upon curing the overbody  30 , for example as shown in  FIG. 10 , is permanently coupled to and rotationally interlocked with the connector body  4 . 
     As best shown in  FIG. 11 , the cable end  12  of the overbody  30  may be dimensioned with an inner diameter friction surface  44  proximate that of the coaxial cable outer jacket  28 , enabling polymeric friction welding between the overbody  30  and the outer jacket  28  prior to laser welding of the connector body  4  and outer conductor, thereby eliminating the need for environmental seals at the cable end  12  of the connector/cable interconnection. During friction welding, the coaxial connector  2  is rotated with respect to the cable  9 . Friction between the friction surface  44  and the outer diameter of the outer jacket  28  heats the respective surfaces to a point where they begin to soften and intermingle, sealing them against one another. To provide enhanced friction and allow voids for excess flow due to friction displacement and add key locking for additional strength, the outer jacket  28  and/or the inner diameter of the overbody  30  may be provided as a series of spaced apart annular peaks of a contour pattern such as a corrugation  46 , as shown for example in  FIG. 12 , or a stepped surface  48 , as shown for example in  FIG. 13 . Alternatively, the overbody  30  may be sealed against the outer jacket  28  with an adhesive/sealant or may be overmolded upon the connector body  4  after interconnection with the outer conductor  8 , the heat of the injected polymeric material bonding the overbody  30  with and/or sealing against the outer jacket  28 . 
     The inner conductor  24  extending from the prepared end of the coaxial cable  9  may be selected to pass through to the connector end  18  as a portion of the selected connection interface  14 , for example as shown in  FIG. 8 . If the selected coaxial cable  9  has an inner conductor  24  that has a larger diameter than the inner conductor portion of the selected connection interface  14 , the inner conductor  24  may be ground at the connector end  18  to the required diameter. 
     Although a direct pass through inner conductor  24  advantageously eliminates interconnections, for example with the spring basket of a traditional coaxial connector inner contact, such may introduce electrical performance degradation such as PIM. Where the inner conductor  24  is also aluminum material some applications may require a non-aluminum material connection point at the inner contact/inner conductor of the connection interface  14 . As shown for example in  FIG. 14 , a center cap  50 , for example formed from a metal such as brass or other desired metal, may be applied to the end of the inner conductor  24 , also by laser or friction welding. To apply the center cap  50 , the end of the inner conductor  24  is ground to provide a pin corresponding to the selected socket geometry of the center cap  50 . To allow material inter-flow during welding attachment, the socket geometry of the center cap  50  and or the end of the inner conductor  24  may be formed to provide annular material gaps  22 . 
     Laser welding apparatus may be provided with a fiber optic laser head extension which may be adjusted to aim the laser beam B at each target location along the seam  16 . Alternatively, the coaxial connector  2 , upon which the target location resides, may be maneuvered to align the target location with respect to the laser head  54 . A laser head  54  typically includes a collimator  56  and a focus lens  58  which focuses the laser beam B upon a focal point F at the target location. As shown in  FIG. 15 , the laser beam B extent has clearance requirements prior to reaching the focal point F which are satisfied by the connector end  18  facing orientation of the seam  16  in the exemplary embodiment. 
     Prior to and once beyond the focal point F, the laser beam B has an increasing diameter, progressively diminishing the effective power of the beam at longitudinal locations other than the focal point F. To maximize heat generation for welding, the laser head  54  may be positioned with respect to the seam  16 , such that the focal point F is below the seam  16  outer face, for example as shown in  FIG. 16 . Thereby, the highest power level is obtained as a molten area of the bore sidewall  20  and the outer diameter of the outer conductor  8  is formed within the seam  16 , rather than only along the outermost surface of the seam  16 , resulting in a weld with greater depth and strength. 
     In further embodiments, for example as shown in  FIGS. 17 and 18 , the bore  6  may be provided with an inward projecting stop shoulder  52  proximate the connector end  18  against which the outer conductor  8  abuts to form an inward facing circumferential seam  16  between the outer conductor  8  and the stop shoulder  52 . The seam  16  is provided generally normal to a longitudinal axis of the coaxial connector  2 . As shown in  FIGS. 19 and 20 , the ability of the laser beam B to reach the seam  16  without interference from the inner conductor  24  is a function of the coaxial cable dimensions and the distance from the connection interface  14  within the bore  6  at which the seam  16  is located. 
     In addition to increased adjustment requirements for the laser beam to follow the inner circumference of the seam  16 , the present embodiment also requires removal of additional dielectric material  26 , which may generate impedance discontinuity issues addressable by the addition of further impedance tuning features, such as dielectric spacers or the like. 
     One skilled in the art will appreciate that the connector and interconnection method disclosed has significant material cost efficiencies and provides a permanently sealed interconnection with reduced size and/or weight requirements. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 Table of Parts 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 2 
                 coaxial connector 
               
               
                 4 
                 connector body 
               
               
                 6 
                 bore 
               
               
                 8 
                 outer conductor 
               
               
                 9 
                 cable 
               
               
                 10 
                 shoulder 
               
               
                 12 
                 cable end 
               
               
                 14 
                 connection interface 
               
               
                 16 
                 seam 
               
               
                 18 
                 connector end 
               
               
                 20 
                 bore sidewall 
               
               
                 22 
                 material gap 
               
               
                 24 
                 inner conductor 
               
               
                 26 
                 dielectric material 
               
               
                 28 
                 outer jacket 
               
               
                 30 
                 overbody 
               
               
                 32 
                 overbody flange 
               
               
                 34 
                 support ridge 
               
               
                 36 
                 coupling nut 
               
               
                 38 
                 retention spur 
               
               
                 39 
                 alignment cylinder 
               
               
                 40 
                 connector body flange 
               
               
                 42 
                 interlock aperture 
               
               
                 43 
                 longitudinal knurl 
               
               
                 44 
                 friction surface 
               
               
                 45 
                 notch 
               
               
                 46 
                 corrugation 
               
               
                 48 
                 stepped surface 
               
               
                 50 
                 center cap 
               
               
                 52 
                 stop shoulder 
               
               
                 54 
                 laser head 
               
               
                 56 
                 collimator 
               
               
                 58 
                 focus lens 
               
               
                   
               
             
          
         
       
     
     Where in the foregoing description reference has been made to materials, ratios, integers or components having known equivalents then such equivalents are herein incorporated as if individually set forth. 
     While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus, methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of applicant&#39;s general inventive concept. Further, it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope or spirit of the present invention as defined by the following claims.

Technology Classification (CPC): 1