Abstract:
A conductor protector for providing crush resistant support to the conductors in a cable and implementing a ground connection between the metallic shield of a cable and a common ground point employs an elongated, trough-like member composed of electrically conductive, structurally rigid material particularly adapted for use in conjunction with cable shield ground clamps. Conductive extensions project from one end of the conductor protector to provide a conductive path between the cable shield and a location exterior of the cable jacket, eliminating the need to remove the jacket prior to assembly into a ground clamp.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to devices for implementing a ground connection between a metallic shield of a cable and a common ground point. More particularly, the present invention relates to clamp devices which mount to service cables and connect via a flexible or rigid conductor with a common ground point. 
     Service cables, which may be buried underground or suspended above ground, are typically constructed in a tubular fashion with numerous thin metal conductors or pairs of conductors surrounded by a conductive ground shield. The shield is in turn surrounded by a protective jacket of tough, flexible plastic or rubber. The conductive shield of a service cable is intended to prevent electromagnetic fields and lightning from penetrating the cable and interfering with signals being transmitted on the conductors. To function properly and safely, cable shields must be grounded at spaced ground points established by regulations and/or operational specifications and practices. The invention generally relates to clamp assemblies adapted to create and maintain such ground connections. 
     In applications to which the present invention relates, the clamp assemblies are ordinarily positioned within a cabinet, housing or other enclosure (hereafter collectively termed “enclosure”) to provide a grounding connection between the metallic shield of the service cable/s and a common ground point. Such enclosures are frequently located outdoors and/or underground where the enclosures and their contents are subjected to intense environmental changes. For example, it is not uncommon for the enclosure to heave as a result of frost while the service cables are frozen in position in the ground. Moisture in the form of rain, ground water or condensation is also frequently present within the enclosure. 
     U.S. Pat. No. 5,429,532 discloses one type of cable shield ground clamp to which the present invention generally relates. The clamp is constructed of a generally U-shaped yoke. A keeper has a driver which threadably engages threaded surfaces on the inside of the yoke legs. The keeper has a clamp jaw which may be compressively engaged against a cable shield or shields received in an aperture defined by the yoke. The yoke then connects to a common ground point via a flexible ground wire connection. 
     As cables are tightened within such a clamp, damage can occur to the conductors within the cable or to the shield surrounding the conductors, or both. It is known in the art to install protective devices within such cable shield/ground clamp assemblies to prevent damage to the cable conductors. U.S. Pat. No. 5,722,840 discloses one type of conductor protector to which the present invention generally relates. The conductor protector takes the form of a protective shoe that may be inserted between the conductors and the cable clamp jaw to prevent crushing of the inner conductors. The protective shoe is an elongated semi-sleeve-like or trough-like member composed of electrically conductive material and having a longitudinally extending channel. The cable may be placed in the channel of the shoe or the shoe may be inserted within the shield. In either configuration, the shoe partially surrounds the inner conductors. The cables are then placed within the clamp and the jaw is tightened. As the jaw compresses the cables, the rigidity of the shoe provides crush resistance while allowing the clamp to be tightened to ensure a mechanical engagement of high integrity. 
     To install the protective shoe disclosed in U.S. Pat. No. 5,722,840, the protective jacket must be removed from the cable to ensure a proper electrical connection between the cable&#39;s conductive ground shield and the ground clamp. While introduction of the conductor protector disclosed in U.S. Pat. No. 5,722,840 presented a significant improvement over industry practice and provided crush resistance and strain relief not previously available, those skilled in the art will recognize that there are drawbacks to removal of the protective jacket. Removal of the protective jacket presents new avenues for moisture to penetrate the cable. Loss of the linear strength and abrasion resistance of the protective jacket weakens the cable and the resulting cable shield/ground clamp assembly. In addition, the process of jacket removal involves scoring around the cable with a sharp knife, often resulting in nicks or cuts in the underlying shield, thus weakening the shield. Such weakened shields are prone to failure and consequent loss of ground continuity. Furthermore, removal of the jacket adds a step to the labor required to install a cable shield/ground clamp assembly. 
     SUMMARY OF THE INVENTION 
     Briefly stated, the invention in a preferred form is a conductor protector for providing crush resistant support for conductors while maintaining cable ground shield continuity in service cable shield/ground clamp assemblies. The conductor protector is an elongated, trough-like member composed of electrically conductive, structurally rigid material. A longitudinally extending channel allows the conductor protector to surround and partially enclose the conductors. A first end of the conductor protector is tapered to facilitate inserting the conductor protector between the conductors and the shield or between the shield and the outer protective jacket. At least one extension of the trough-like member integrally projects from the opposed end and extends toward the first end to define a generally U-shaped structure adjacent to the exterior surface of the conductor protector. The extension provides a conductive path from the cable shield to a location exterior of the cable protective jacket, eliminating the need to remove the protective jacket prior to assembly into a ground clamp. The extension also aids in properly longitudinally positioning the conductor protector within the cable. 
     An object of the invention is to provide a new and improved conductor protector for use in a service cable ground connection. 
     Another object of the invention is to provide a conductor protector which ensures the integrity of the ground shield and conductors while implementing a high strength connection. 
     A further object of the invention is to provide a conductor protector having an efficient construction which may be installed in an efficient and low cost manner. 
     A yet further object of the invention is to provide a conductor protector that defines a conductive path from the conductive shield of a cable to a location exterior of the cable jacket without necessitating removal of the jacket. 
     Other objects and advantages of the invention will become apparent from the specification and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a conductor protector in accordance with the present invention; 
     FIG. 2 is a bottom view of the conductor protector of FIG. 1; 
     FIG. 3 is an end view of the conductor protector of FIG. 2 viewed from the right; 
     FIG. 4 is an end view of the conductor protector of FIG. 2 viewed from the left; 
     FIG. 5 is a top view of a second embodiment of a conductor protector in accordance with the present invention; 
     FIG. 6 is a bottom view of the conductor protector of FIG. 5; 
     FIG. 7 is a side view of the conductor protector of FIG. 6; 
     FIG. 8 is an end view of the conductor protector of FIG. 7 viewed from the left; 
     FIG. 9 is a perspective view of a ground clamp for which the conductor protectors of FIGS. 1-8 have particular applicability; 
     FIG. 10 is a perspective view of the conductor protector of FIG. 1 installed in a service cable (partially illustrated) in accordance with the present invention; 
     FIG. 11 is a perspective view of the conductor protector/service cable assembly of FIG. 10 rotated 180° and installed in a ground clamp in accordance with the present invention (service cables and ground wire partially illustrated); 
     FIG. 12 is a perspective view of the conductor protector of FIG. 5 installed in a service cable (partially illustrated) in accordance with the present invention; and 
     FIG. 13 is a perspective view of multiple conductor protector/service cable assemblies, as illustrated in FIG. 12, assembled in a ground clamp in accordance with the present invention (service cables and ground wire partially illustrated). 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the drawings wherein like numerals represent like parts throughout the figures, conductor protectors in accordance with the present invention are generally designated by the numerals  10  and  10 ′. Conductor protectors  10 ,  10 ′ in accordance with the invention are adapted to be inserted into a service cable  26 , having at least one conductor  30 , a conductive shield  32  and a protective jacket  28 . The conductor protectors are used in cable shield/ground clamp assemblies (FIGS. 11 and 13) which are ordinarily positioned within enclosures (not illustrated). Multiple service cables  26  typically enter an enclosure where their conductive shields  32  must be electrically connected to a common ground point. Conductor protectors  10 ,  10 ′ of the present invention are adapted to partially surround and protect the portion of the conductors  30  of service cables  26  which are tightened within a cable shield/ground clamp assembly, while providing strain relief and shield to ground continuity. 
     The conductor protector  10 ,  10 ′ is an elongated, trough-like member composed of electrically conductive, structurally rigid material. A first end  12  of the conductor protector  10 ,  10 ′ is tapered to facilitate its insertion into the cable  26 . Each conductor protector  10  has a longitudinal channel  24  adapted for partially surrounding the conductor pairs  30 . Conductor protectors are provided with at least one extension  16 ,  16 ′ projecting integrally from a second end  14 . Upon insertion into a cable  26 , as shown in FIGS. 10 and 12, the extensions  16  and  16 ′ provide a conductive path from the cable shield  32  to a location external of the cable protective jacket  28 . 
     With reference to FIGS. 1-4, a conductor protector  10  has a single extension  16  projecting integrally from the second end  14 . The extension  16  projects toward the first end  12 , defining a generally U-shaped structure adjacent to the outer arcuate surface  20  of the conductor protector  10 . A conductor protector  10 ′ having two extensions  16 ′ projecting integrally from the second end is shown in FIGS. 5-8. The extensions  16 ,  16 ′ project toward the first end defining generally U-shaped structures adjacent to the outer arcuate surface  20  of the conductor protector  10 ′. 
     In a preferred configuration, extensions  16 ,  16 ′ are thin paddle-shaped structures, having narrow first  18  and laterally expanded second  34  portions. As shown in FIGS. 2,  3 ,  4 ,  7  and  8 , the narrow first portion  18  is integrally connected to the second end  14 , and the second portion  34  projects toward the first end  12  of the conductor protector  10 ,  10 ′. The extensions  16 ,  16 ′ preferably project a distance greater than half but less than the entire length of the member. The second portion  34  of the extensions  16 ,  16 ′ has a longitudinally arcuate surface with a curvature similar to the curvature of the outer arcuate surface. This feature is best seen in FIGS. 3,  4  and  8 . The increased width of the second portion  34  presents an increased surface area for electrical connection to the ground clamp  40  or adjacent extensions  16 ′ in multiple cable assemblies. The curved profile of the expanded second portion  34  of the extensions  16 ,  16 ′ allows the second portion  34  to conform to the shape of the exterior of the cable  26  and the interior of the yoke  42  and keeper  56  of the ground clamp  40 , enhancing ease of assembly. 
     Conductor protectors  10 ,  10 ′ of the present invention are adapted for use with numerous ground clamps and ground connectors and particularly with ground clamps  40  of a type illustrated by FIG.  9 . The ground clamp  40  comprises a generally U-shaped yoke  42 , having generally parallel legs  44 ,  46 . The legs  44 ,  46  of the yoke  42  have opposed inwardly disposed thread surfaces  48 ,  50 . A receiving aperture  52  is generally formed at the upper inward portion of the yoke  42  for receiving one or more service wire ground shields  32 . A set screw  64  which may be any of numerous conventional forms is threaded at the upper cap of the yoke for anchoring the flexible ground wire  58  or other suitable grounding connector. Ground wire  58  is typically six inch No. 6 or No. 10 AWG lead wire and the wire terminal  60  is connected to a ground stud (not illustrated). The ground shields  32  are compressively secured to the ground clamp  40  by means of a keeper  56 , which is slidably displaceable and selectably fixedly positionable along the legs  44 ,  46  of the yoke  42 . 
     The conductor protector  10  of FIGS. 1-4 is intended for use in cable shield/ground clamp assemblies containing a single service cable. As illustrated in FIG. 10, a conductor protector  10  having a single extension  16  will create contact with the metal surface of the yoke  42  or keeper  56  of the ground clamp  40 . In cable shield/ground clamp assemblies having more than one service cable, the preferred embodiment  10 ′, illustrated in FIGS. 5-8 can be used. As illustrated in FIG. 13, the dual extensions  16 ′ of this embodiment provide electrically conductive paths from cable  26  to adjacent cable  26  as well as conductive paths between the shields  32  of the cables  26  and the ground clamp  40 . Multiple cables  26  may be installed in the same ground clamp  40  where extensions  16 ′ abut each other and the clamp surfaces thereby creating a conductive path traversing the cable shields  32  and the cable shield ground clamp  40 . The extensions  16 ′ engage in surface-to-surface relationship along a substantial interface to ensure and maintain a continuous and reliable ground path. 
     Service cables having thin metal conductors or fiber optic conductors can be problematic to ground without damaging the fragile conductors. The inner conductors are susceptible to crushing when the clamping mechanism is tightened. If the clamping mechanism is left loose to avoid crushing the conductors, loss of ground continuity or failure of the assembly may result. A conductor protector  10 ,  10 ′ in accordance with the invention may be installed either between the conductor pairs  30  and the conductive shield  32  thereby engaging the interior surface of the conductive shield  32  with the outer arcuate surface  20  the conductor protector  10 ,  10 ′ or the conductor protector  10 ,  10 ′ can be installed between the conductive shield  32  and the protective jacket  28  thereby engaging the exterior surface of the cable shield with the inner arcuate surface of the conductor protector  10 ,  10 ′. 
     In either of these arrangements, a ground path from the ground shield  32  traverses through the extensions  16 ,  16 ′ disposed exteriorly of the protective jacket  28 . In either configuration, the rigidity of the conductor protectors  10 ,  10 ′ and their location between the conductors  30  and the ground clamp  40  allow the conductor protectors to protect the conductors  30  even when the ground clamp  40  is securely tightened. 
     Either embodiment of the present invention can be used without removal of the protective jacket  28  of a service cable  26 . As shown in FIGS. 10 and 12, a lengthwise slit  66  is made in the protective jacket  28  to accommodate insertion of the conductor protector  10 ,  10 ′. According to a preferred embodiment of the invention, the jacket  28  remains intact and continues to protect the conductive shield  32  and to provide strain relief and moisture resistance to the cable  26 . The invention allows the protective jacket  28  to remain intact while providing a conductive path from the conductive shield  32  to a point exterior of the protective jacket  28 . 
     A conductor protector according to the invention allows the creation of a ground connection implemented by a cable shield/ground clamp assembly of high clamping integrity without compromising shield to ground continuity while also ensuring the integrity of the shield and the conductors. The conductor protectors are also easy to install and reduce installation costs by eliminating conventional steps in the grounding process. 
     While a preferred embodiment of the foregoing invention has been set forth for purposes of illustration, the foregoing description should not be deemed a limitation of the invention herein. Accordingly, various modifications, adaptations and alternatives may occur to one skilled in the art without departing from the spirit and the scope of the present invention.