Abstract:
A connector anchors as outer conductor onto a cable and connects the outer conductor to the cable&#39;s inner conductor without exposing the inner conductor to the ambient environment. The connector includes a longitudinally split cylinder having a thicker center wall and a pair of flanking walls that wrap around a notched section of the cable and contact the inner conductor. An inner ring with multiple recessed interior circumferential grooves wraps around and overlaps the split cylinder so that the grooves will emboss and grip the cable&#39;s jacket without piercing the jacket when swaged. The outer conductor is placed over the inner ring. An outer ring anchors the outer conductor to the inner ring when swaged.

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein may be manufactured and used by or for the Government of the United States of America for Governmental purposes without the payment of any royalties. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a swaged-on connector, and, in particular, to a conductive connector for electrically tapping an inner conductor of a mine sweeping cable to provide an electrical connection to an outer conductor, and simultaneously coaxially anchoring the outer conductor to the cable. 
     BACKGROUND OF THE INVENTION 
     Magnetic influence minesweeping cables create magnetic fields in the areas around the cables in order to cause magnetic influence mines deployed in a marine environment to explode prematurely, i.e., without damaging a ship. The magnetic field is typically created by a pair of exposed oppositely-charged conductors—a forward electrode and an aft electrode—that comprise parts of a cable being towed behind a minesweeping vessel. The cable typically also includes a continuous length inner conductor that is sealed from the corrosive saltwater environment, typically by a cable jacket wrapped around the cable. In one configuration, the insulated inner conductor provides electricity to the exposed aft electrode. Thus, a need has been recognized in the art to anchor an external conduct or to an environmentally-sealed, jacketed, coaxial cable without breaking the integrity of the jacket, while at the same time providing an electrical connection between an internal conductor in the cable and the external conductor. 
     SUMMARY OF THE INVENTION 
     The invention provides a compact, corrosion resistant, environmentally sealing, conductive connector for creating a water tight electrical connection between an inner conductor of a coaxial cable and an outer conductor, where the outer conductor is overlaying a peripheral section of the coaxial cable. The inner conductor and the outer conductor can be two dissimilar metals, each used for its unique properties while their negative properties are avoided. For example, aluminum is an excellent conductor and lightweight, but corrodes easily so it is kept sealed in the cable by the sealing action of the connector. Titanium has excellent resistance to corrosion, but it has low conductivity so it can only be used efficiently by keeping conductive lengths to a minimum. 
     The cable is insulated by a jacket, where the jacket can be composed of an insulating material such as polytetrafluoroethylene (PTFE) that is known to be very difficult to attach to, in part because it has a very low coefficient of friction. A common, well-known use of PTFE is in Teflon™, a DuPont product which is idiomatic as being a material to which nothing sticks. The invented connector enables conduction of a high electrical current between an inner conductor and an outer conductor of the cable, while maintaining a hermetic seal and structural integrity of the cable. 
     In an exemplary application, the connector is a fitting on a magnetic minesweeping cable developed by the United States Navy. The connector attaches the outer conductor to the cable, and provides an electrical path between the attached outer conductor and the electrically tapped inner conductor. The application requires a connector that provides a water tight seal, which is corrosion-resistant in a seawater or salt water environment, where the outer conductor comprises an electrode composed of a metallic material that is different than the inner conductor. 
     The connection mast remain water tight even if submerged in several hundred feet of seawater. In many applications, the cables will be stored on a winch, and the cable can be quite hot if wraps are left wound on the winch during a mine sweep. In the exemplary application, the cable can be stored outdoors before being deployed, and therefore the connector must perform under cold weather conditions as well as high temperature conditions. The cable fitted with the invented connector must also be able to handle large temperature variances such as when being shipped via air where temperatures can be below freezing, and in shipping containers in the sun that can reach in excess of 160° F. 
     In an exemplary embodiment of the invention, the connector includes a pair of intermediate halves of a longitudinally split open-ended cylinder, where the split open-ended cylinder has a split-cylinder length. Each intermediate half has a semi-cylindrical wall with a thicker center wall having a center length and a smaller center diameter. The thicker center wall has adjacent a pair of flanking walls, where the pair of flanking walls bookend the center wall, and each flanking wall has a flanking wall length and a flanking wall diameter. Each flanking wall diameter is greater than the diameter of the center wall, such that the flanking walls are thinner than the center wall. The pair of intermediate halves are assembled on a notched cable as the split open-ended cylinder, wherein the split open-ended cylinder is simultaneously electrically contacting two or more exposed layers of the inner conductor of the cable. 
     In an exemplary variation illustrated herein, the cable&#39;s inner conductor has three conductive layers. The cable jacket and each of the inner conductive layers are coaxial. The cable is prepared to establish electrical contact at a specific location on the cable. The preparation includes removing a sectional length of the cable jacket, where the sectional length is about the length of the split-cylinder length, and its removal exposes an outermost layer of the inner conductor. In a subsequent step a shorter sectional length of a center portion of the outermost layer is removed, thereby exposing a middle layer of the inner conductor, and leaving a pair of flanking sectional lengths of the exposed outermost layer. The cable preparation steps of removing the sectional length of the jacket and the shorter sectional length of the center portion of the outermost layer, circumferentially notches the cable; therein providing an electrical contact point and a mechanical stronghold on the cable. 
     In another subsequent step, an electrical joint compound can be applied to the exposed layers of the inner conductor and the conductors after they are manually abraded with a wire brush. The electrical joint compound in combination with abrasion generally is selected to reduce electrical resistance as the abrasion and joint compound break up and dissolves any oxides formed on the inner conductor. It also provides protection for the connection against the harmful effects of the environment. 
     The pair of intermediate halves is assembled in the notch, such that the center wall contacts the middle layer, the flanking walls contact the flanking sectional lengths of the exposed outermost layer. The trimmed ends of the cable jacket are substantially flush with the ends of the assembled intermediate halves. The assembly produces an electrical contact and the intersecting intermediate halves are seated in the notch of the cable, and therefore the assembled split cylinder also provides mechanical resistance to translational movement at the mechanical position. Also, the harder material of the intermediate halves relative to the inner conductors and its ability to be plated, help create a better electrical connection during the swaging process. 
     The cable has a core strength member, and therefore the cable jacket and the inner conductor can be trimmed without substantially reducing the strength of the cable, as the strength member provides tensile strength to the cable. 
     The invented conductive connector also includes an inner ring with a larger inside diameter, and a longer length than the pair of intermediate halves. The inner ring functionally bridges the notch in the cable, and is swaged onto the cable and intermediate halves, thereby providing a mechanical attachment with the jacket and an electrical connection with the pair of intermediate halves. The inner ring is an open-ended cylinder with recessed inside circumferential grooves that are proximate to the open ends of the inner ring. The inner ring has an inside diameter that is sufficiently large to allow the inner ring to slide over the cable and the split open ended cylinder. The inner ring can be swaged onto the cable jacket without affecting the integrity of the jacket. The swaged on inner ring provides a corrosion resistant seal that is substantially anchored to the cable, restraining both translational movement and rotational movement. The swaging causes the recessed circumferential grooves to emboss the jacket. Swaging is complete when the inner ring reaches a roundness within tolerance limits that produce a water tight seal, where the seal is good even at several hundred feet. The embossed jacket substantially forms an interference fit with the recessed inside circumferential grooves. Preferably, the depths of the grooves are less than the thickness of the jacket so that the embossing does not pierce the jacket when swaged. The circumferential grooves can be selected to mechanically seal against various kinds of cable jacket materials other than PTFE. Other materials include PVC, FVDC, EPDN, Santoprene™—a product of Monsanto, Pylon™ and Neoprene™—both, products of DuPont, polyesters, acrylics, and other polymeric materials. The swaging also presses the pair of intermediate halves against the inner conductor, therein forming an excellent conductive contact and frictional resistance between the cable&#39;s inner conductors and the walls of the intermediate halves. The outermost layer of the inner conductor abuts the center wall. 
     The invention also includes an outer ring, which is an open-ended cylinder with a length that is similar to the split cylinder length of the pair of intermediate halves. The outer ring has an inside diameter chat is large enough to slide over the inner ring and outer conductor. The outer conductor is distributed around the inner ring, substantially overlaying most of the inner ring. The outer ring is slid over the outer conductor and substantially centered on the inner ring. The outer ring is then swaged-on locking the outer conductor between the inside of the outer ring and the outside of the inner ring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing invention will become readily apparent by referring to the following detailed description and the appended drawings in which: 
         FIG. 1  is a perspective view of an inner ring of a swaged-on, corrosion resistant, sealing, tension carrying connector; 
         FIG. 2  is a perspective view of a corrosion resistant outer ring that is to be swaged onto the inner ring, securing the underlying outer conductor to the inner ring; 
         FIG. 3  is a perspective view of a conducting pair of intermediate halves that are to be assembled into a notch cut into the cable, wherein the cylinder formed by the intermediate halves has a thicker center wall and the cylinder is in electrical contact with exposed stepped layers of the inner conductor; 
         FIG. 4  is a substantially longitudinal cross-sectional partial view of a minesweeping cable fitted with the illustrated connector; 
         FIG. 5  is a perspective view of the connector installed on a minesweeping cable; and 
         FIG. 6  is a perspective partial view of a cable prepared to receive the connector, where the cable is notched, exposing layers of the inner conductor. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The illustrated invention is a conductive connector  400 . As shown in  FIG. 3 , the conductive connector  400  includes a pair of intermediate halves  410  of a longitudinally split open-ended cylinder having a split-cylinder length  410 L, and a split-cylinder outside diameter  410 OD. Each intermediate half has a semi-cylindrical wall with a thicker center wall  412  having a center wall thickness  414 , a center smaller inside diameter  410 ID, and a center wall length  411 . The center wall  412  has a pair of flanking walls  420   a , 420   b  where the pair of flanking walls  420   a , 420   b  bookend the center wall  412 . Each flanking wall has a length  423   a , 423   b  and a thickness  422   a , 422   b ; where the flanking wall thicknesses  422   a , 422   b  are thinner than the thickness  414  of the center wall  412 , such that the flanking walls  420   a , 420   b  are thinner than the center wall  412 . The pair of intermediate halves is designed to simultaneously electrically tap two or more of the exposed layers of the inner conductor of the cable. Exposed layers  16   o , 16   o ′, 16   m  are illustrated in  FIG. 6 . 
     The intermediate halves are composed of a conductive metallic material. A suitable metal is a bard aluminum, and to reduce galvanic corrosion the intermediate halves are plated in tin. 
     The conductive connector  400  also includes an inner ring  460  as illustrated in  FIG. 1 , The inner ring  460  is substantially a cylinder with a pair of open ends  464   a , 464   b  (see  FIG. 4  to see both open ends  464   a , 464   b ). Each open end has a plurality of recessed inside circumferential grooves  466   a , 466   b  (see  FIG. 4  to see both grooves  466   a , 466   b ) that are proximate to the open ends of the inner ring  460 . The inner ring has an inside diameter  4601 D that is larger than the outside diameter  410 OD of the intermediate halves. The inner ring has a length  460 L that is longer than the intermediate halves length  410 L, such that the plurality of recessed inside circumferential grooves  466   a , 466   b  will extend beyond the intermediate halves  410  and overlay the cable jacket  18  when the inner ring is placed over the intermediate halves as shown in  FIG. 4 . The inner ring  460  is composed of a corrosion resistant metallic material. Preferably, the inner ring  460  is substantially composed of titanium plated with platinum. 
     The inner ring  460  is swaged on after being centered on the intermediate halves  460 , which are first placed over the exposed layers  16   o , 16   o ′ of the inner conductor  16 . The swaging embosses the grooves into the jacket  18 , providing a watertight, corrosion resistant seal with good resistance to rotational movement and excellent resistance to translational movement. Note that the depths of the grooves  466   a ,  466   b  are selected so that the jacket  18  isn&#39;t pierced during or after the swaging process. Typically, this means that the depths of the grooves are less than the thickness of the jacket. Before swaging, an electrical joint compound  498  (see  FIG. 6 ) can be applied to the inner conductors layers  16   o , 16   o ′, 16   m , and the inner conductor layers can be abraded as well. The abrasion and electrical joint compound facilitates electrical conduction between the inner conductor&#39;s exposed conductive layers  16   o ,  16   o ′, 16   m  and the walls  420   a , 420   b , 412  of the pair of intermediate halves  410 . 
     As illustrated in  FIG. 2 , the conductive connector  400  also includes an outer ring  490 , which is an open-ended cylinder with a length  490 L. The outer ring length  490 L is similar to the split-cylinder length  410 L of the pair of intermediate halves  410 . The outer ring  490  has an inside diameter  490 ID that is large enough to slide over the cable, the inner ring  460 , and the outer conductor  20  (as shown in  FIG. 4  and  FIG. 5 ). The outer conductor  20  is distributed around the inner ring  460 , substantially overlaying most of the inner ring. 
     The outer ring  490  is substantially composed of a corrosion resistant metallic material, wherein a suitable material is substantially titanium. 
     The outer ring is slid over the outer conductor  20  and centered over the previously swaged inner ring  460 . The outer ring is then swaged on, anchoring the outer conductor  20  between the outer ring  490  and the inner ring  460 . 
     In  FIG. 4 , the conductive connector  400  is attached to an S-cable  12  of a magnetic influence minesweeping system. S-cable  12  has a strength member  14 , and a jacket labeled  18  and  18 ′, to indicate that the jacket has had a sectional length removed. The jacket is typically composed of PTFE. The inner conductor  16  has three layers of aluminum wire, the innermost layer  16   i , the middle layer  16   m , and the outermost layer  16   o , Note that the use of three layers in the illustrated example is exemplary only, and that other cables can have more than three layers of aluminum wire without departing from the scope the invention. Only the outermost layer  16   o  is circumferentially notched, thereby exposing the underlying middle layer  16   m  and leaving a pair of flanking sectional lengths of the exposed outermost layer  16   o , 16   o ′,  FIG. 6  shows the cable prepared to be fitted with the pair of intermediate halves  410 . 
     The removal of sectional lengths of the cable jacket and the outermost layer of the inner conductor to establish electrical contact at a specific location on the cable does not prevent conduction along the outermost layer of the inner conductor. The intermediate halves, which are composed of a conductive metallic material, connect outermost layer  16   o  to outermost layer  16   o ′ when the connector  400  is installed. Similarly, the section of cable jacket between  18  and  18 ′ is bridged by the inner ring. 
     As mentioned previously, an electrical joint compound  498  can be applied to the exposed layers of the inner conductor, and the exposed layer can be abraded as required. The electrical joint compound  498 , as shown diagrammatically in  FIG. 6 , reduces electrical resistance as it dissolves the oxide on connectors. The nature of the oxide removal is not harmful. The compound creates a light surface etch with no deep, localized attack. It only attacks the oxide. It also provides protection for the connection against the harmful effects of the environment. 
     The pair of intermediate halves  410  is assembled in the notch of the S-cable  12 , such that the center wall  412  contacts the middle layer  16   m , the flanking walls  420   a , 420   b  contact the exposed uppermost layer  16   o ,  16   o ′, and the trimmed ends of the cable jacket  18 , 18 ′ are substantially flush with the ends  424   a , 424   b  of the assembled intermediate halves. 
     The completed assembly of the pair of intermediate halves  410  provides electrical contact between the intermediate halves and the inner conductor  16 . The ends of the flanging walls  420   a ,  420   b  are pressed in the notch by the swaging until the assembly abuts the elements defined by the notch  405  (see  FIG. 6 ) in the S-cable  12 . The notch therefore also provides an interference fit which holds the connector in place on the cable. 
     The cable has a core strength member  14 , so the cable jacket  18  and the inner conductor  16  can be trimmed without substantially reducing the strength of the cable, as the strength member  14  is not touched, and the strength member provides most of the tensile strength to the cable  12 . 
     The swaged on inner ring  460  is illustrated in  FIG. 4 . It is physically bridging the notch in the cable, where the notch is filled by the intermediate halves  410 . The swaging provides mechanical attachment of the inner ring  460  with the jacket  18  and an electrical connection to the pair of intermediate halves  410 . In this view the reader can see that the jacket  18  is embossed, and substantially forms an interference fit with the recessed inside circumferential grooves  466   a ,  466   b.    
     The outer ring  490  is also swaged on. The outer conductor  20 , which in the exemplary application is an external electrode of a minesweeping cable, is composed of a layer of a titanium clad copper conductor wire. The outer conductor  20  is distributed around the inner ring  460 , substantially overlaying most of the inner ring. The outer ring  490  is slid over outer conductor  20  and aligned with the intermediate halves  410 . The outer ring  490  is swaged on, thereby locking the outer conductor  20  between the inside of the outer ring  490  and the outside of the swaged inner ring  460 . Swaging is complete when the outer ring reaches a roundness within the tolerance limits. Typically, the outer conductor  20  is trimmed, removing any exposed short ends of the layer of the titanium clad copper conductor that extend out from under the outer ring  490 . The cable with the connector  400  installed is shown in  FIG. 5 . 
     It is to be understood that the foregoing description and specific embodiments are merely illustrative of the best mode of the invention and the principles thereof, and that various modifications and additions may be made to the invention by those skilled in the art, without departing from the spirit and scope of this invention, which is therefore understood to be limited only by the scope of the appended claims.