Abstract:
An electrical conduit ground assembly is provided for electrically and environmentally shielding an electric cable that inserts into a junction box via a through-hole. The assembly includes an adapter flange, first and second annular gaskets, first and second annular washers, a slip-ring, a ground adapter, first and second lock-nuts and a gland nut. The adapter flange has an internally threaded proximate end, an externally threaded mezzanine, a hexagonal seat, and an externally threaded distal end insertable into the through-hole. The first annular gasket inserts into the proximate end. The first and second washers insert into the proximate end. The annular ground adapter electrically connects the cable and the annular conduit between the first and second washers. The second annular gasket has an annular shaft and a circular brim. The gland nut screws into the proximate end of the adapter flange.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The invention is a Continuation-in-Part, claims priority to and incorporates by reference in its entirety U.S. patent application Ser. No. 14/051,385 filed Oct. 10, 2013, released as Publication 2014/0041938 and assigned Navy Case 102763, which is a Continuation-in-Part of U.S. patent application Ser. No. 13/385,470 filed Jan. 26, 2012, issued as U.S. Pat. No. 8,562,361 and assigned Navy Case 101421, which claims the benefit of priority, pursuant to 35 U.S.C. §119, the benefit of priority from provisional application 61/628,298, with a filing date of Oct. 11, 2011. 
    
    
     STATEMENT OF GOVERNMENT INTEREST 
     The invention described was made in the performance of official duties by one or more employees of the Department of the Navy, and thus, the invention herein may be manufactured, used or licensed by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 
    
    
     BACKGROUND 
     The invention relates generally to fittings for electrical cable ground adapters, especially those used aboard marine vessels and platforms. In particular, the invention relates to embodiments for a flange connector to a junction box. 
     The United States Navy currently provides electromagnetic (EM) shielding from coupling to topside (i.e., above-deck) cables. Such cables can be inserted into a junction box for environmental protection and interconnection with electrical components. 
     SUMMARY 
     Conventional electrical ground adapters yield disadvantages addressed by various exemplary embodiments of the present invention. In particular, various exemplary embodiments provide an electrical grounding adapter within a conduit sealing assembly for electrically and environmentally shielding an electric cable. Various exemplary embodiments provide an electrical conduit ground assembly for electrically and environmentally shielding an electric cable that inserts into a junction box via a through-hole. The exemplary assembly includes an adapter flange, first and second annular gaskets, first and second annular washers, a slip-ring, a ground adapter, first and second lock-nuts and a gland nut. The adapter flange has an internally threaded proximate end, an externally threaded mezzanine, a hexagonal seat, and an externally threaded distal end insertable into the through-hole. 
     In various exemplary embodiments, the first annular gasket inserts into the proximate end and includes frustum and cylinder portions. The first annular washer inserts into the proximate end and disposal on the first gasket. The slip-ring inserts into the proximate end and disposal on the first washer. The second annular washer inserts into the proximate end and disposal on the slip-ring. The annular ground adapter electrically connects the cable and the annular conduit and inserts between the first and second washers and securable by the slip-ring with the cable installed in the junction box. The second annular gasket has an annular shaft and a circular brim that radially extends from a brim end that faces the second annular washer. 
     The gland nut screws into the proximate end of the adapter flange, the gland nut having a hexagonal proximate end and an externally threaded distal end. The annular shaft of the second annular gasket inserts into the gland nut from the threaded distal end. The first lock-nut screws onto the mezzanine and abut the landing, whereas the second lock-nut screws onto the distal end of the adapter flange. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and various other features and aspects of various exemplary embodiments will be readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, in which like or similar numbers are used throughout, and in which: 
         FIGS. 1A and 1B  are respectively exploded and assembly perspective views of a swage tube ground adapter assembly; 
         FIG. 2  is an exploded perspective view of junction box ground adapter components; 
         FIG. 3  is a cutaway elevation view of an exemplary junction box adapter assembly; 
         FIG. 4  is a perspective assembly view of a junction box adapter; and 
         FIG. 5  is a perspective cutaway view of the junction box adapter. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized, and logical, mechanical, and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. 
     Conduits for these cables can employ an exemplary cable shield ground adapter (CSGA) conduit to achieve grounding effectiveness exceeding 80 decibels (dB) while facilitating expedient replacement, in contrast to conventional shielding configurations. The background section of parent U.S. Pat. No. 8,562,361 includes further details about the conventional configurations. The exemplary CSGA can be used in a swage stuffing tube, or within an exemplary fitting that connects to a junction box. 
     Swage tubes, as military part M24235/17, have several standard sizes as listed at http://www.shipboardelectrical.com/swagetubes.html including a tube body, gland nut and gland ring. The tube body can be stainless steel or aluminum. For purposes of disclosure, sizes B, C, D and K are described herein, although the principles described herein can be extended to additional cable sizes. Respective cable bore diameters for sizes B, C, D and K are Ø0.515 inch (″), Ø0.640″, Ø0.750″ and Ø1.171 inches (″). MIL-S-24235/2C provides the military standard dimensions for electrical cable packaging, available at http://dornequipment.com/milspecs/pdf/24235-2C.pdf. 
       FIGS. 1A and 1B  respectively show perspective exploded and cutaway assembly views  100  and  105  of exemplary swage tube components. A gland boss or nut  110  presents an annular access and includes outer threads  115  for installation. The gland nut  110  is typically composed of brass or aluminum and includes a hexagonal proximate end and an externally threaded distal end. A stuffing upper gasket or seal  120  and an optional insert upper gasket  125  provide an environmental seal for the stuffing tube interior for the access at the gland nut  110 . 
     A gland ring  130  constitutes a shim or spacer between the upper gasket  120  and other components in the swage tube  180 . The views  100  and  105  show orientation from upstream at the left to downstream at the right in the direction for inserting a cable to be shielded and grounded. An upper pair of slip rings  140  and  145  provides axial restraint between a CSGA diaphragm  150 , and the gland ring  130 . A lower pair of slip rings  160  and  165  provides axial restraint between the CSGA diaphragm  150  and a lower gasket or seal  170 . Another optional insert upper gasket  125 , together with the lower gasket  170 , provide an environmental seal for the stuffing tube interior of a swage tube  180 , into which the components can be inserted. 
     The insert upper gaskets  125  enable a large size swage tube  180  to accept a thinner cable and maintain environmental integrity, thereby expanding installation flexibility. The upper gaskets  120  and  125  have a geometric configuration reminiscent of a top-hat or stove-hat. The lower gasket  170  has a geometric configuration approximating a frustum (e.g., truncated cone). The gaskets  120 ,  125  and  170  provide environmental seals for the CSGA in the swage tube and are composed of rubber, with various sizes disclosed in Publication 2014/0041938. 
     For purposes of grounding, a “stetson” or “porkpie” design for the CSGA diaphragm  150  is incorporated herein, which can be produced as a metal ribbon or strip with a repeating pattern, cut to length, the tabs bent inward or outward, and the ends joined together to wrap around an electrical cable to be grounded. Publication 2014/0041938 illustrates deployable and flat strip views respectively in  FIGS. 13 and 14  of the stetson configuration. The tube adapter assembly includes for the swage tube  180  the CSGA diaphragm  150  to protect a cable, but also the fittings, e.g., the gland nut  110 , spacer rings  140  and  160 , and gaskets  120  and  170  to provide environmental protection, especially salt-water spray contamination. An analogous adapter assembly for a junction box application similar to that provided for the swage tube is described herein. 
       FIG. 2  illustrates a perspective view  200  of a junction box adapter flange  210 . An upstream or proximate end  220  includes interior helical threads  225  at a mouth to receive the lower gasket  170 . A threaded mezzanine segment  230  enables an upstream nut to secure the flange  210 . A hexagonal landing  240  provides a mounting surface for the flange  210 . The mezzanine  230  and landing  240  constitute a midsection of the flange  210 . A downstream or distal end  250  includes external helical threads for a downstream nut. The flange  210  is typically composed of brass or aluminum. 
       FIG. 3  shows an exploded perspective view  300  of a through adapter for a junction box  310  having an outer surface  320  and an inner surface  330  that defines an interior region. The adapter flange  210  connects to the junction box  310  from the outer surface  320  via a circular through-hole or opening  340  into which the downstream end  250  inserts. The lower gasket  170  inserts into the upstream end  220 . The lower slip ring  160  provides axial restraint between the CSGA diaphragm  150  and the lower gasket  170 . 
     The upper slip rings  140  and  145  provide axial restraint between the CSGA diaphragm  150 , with the gland ring  130  separating these components from between the upper gasket  120 . The gland nut  110  includes external threads  115  to engage the interior threads  225  of the flange  210 . An upper lock nut  350  screws onto the mezzanine  230  to engage the landing  240 . A lower lock nut  360  screws onto the downstream end  250  to secure the landing  240  to the inner surface  330 . 
       FIG. 4  shows an installation assembly perspective view  400  of the junction box through adapter assembly  410 . The installation mounted to the junction box  310  features the landing  240  engaging the outer surface  320 . The upper nut  350  abuts the landing  240  at its upstream side. The gland nut  110  with the upper gasket  120  that protrudes therefrom inserts into the upstream end  220  of the flange  210 . 
       FIG. 5  shows a cutaway perspective view  500  of the junction box through adapter assembly  410 . The interior of the flange  210  at the landing  240  includes a tapering surface into which the lower gasket  170  inserts. The landing  240  includes an annular groove  510  facing the downstream end  250  for receiving an O-ring. The groove  510  is disposed on the surface of the flange  240  facing the outer surface  320  of the junction box  310 . The groove  510  extends radially outward from the opening  340  through which the downstream end  250  extends. The CSGA diaphragm  150  and accompanying rings  140  and  150  are disposed within the mezzanine  230  of the flange  210  longitudinally sandwiched between the upper and lower gaskets  120  and  170 . 
     The junction box through adapter assembly  410  described herein represents a modification of an analogous through adapter described in U.S. Pat. No. 8,562,361, particularly FIGS. 34-38. The modifications to the prior adapter enhance the utility of the adapter with respect to grounding cables and conduit installed in junction boxes composed of non-conductive composite or dielectric materials. The modified adapter retains the utility of the original design with respect to junction boxes made of metal, conductive materials or materials having a conductive coating. 
     The U.S. Navy is increasing the use of composite fixtures on combat vessels due to considerations of corrosion, weight and cost. While the composite materials have significant advantages in these three areas, the means of grounding the penetrations to these boxes is made more difficult. Metal fixtures can be grounded directly to a bulkhead or connected to the bulkhead via a conductive ground strap. Composite fixtures can conventionally ground a through connector in one of two ways: (1) via a ground strap attached to a grounding lug or bolt threaded into the body of the through adapter or (2) via an additional adapter component secured to the fixture into which the through adapter is inserted. 
     The additional component, i.e., the flange  210 , provides a threaded sleeve through which the CSGA  150  may be inserted and the ground strap is secured between the two adapter components. This corresponds to stacking two of the through adapters as previously described with the exception that only a single gland nut  110  would be required. Although the configuration would be effective, its excessive weight and unnecessary cost present disadvantages. 
     The modification to the exemplary through adapter assembly  410  from the parent invention includes the addition of machine threading to a portion of the flange  210  of the through adapter as well as a lock-nut  350  with matching interior threads. The unthreaded surface could be of a smooth finish or knurled to enhance frictional grip. The external portion of the flange  210 , which includes the upstream end  220 , mezzanine  230  and the landing  240 , is also referred to as the “upper portion” of the adapter assembly  410 . The downstream end  250  of the adapter that typically resides inside the junction box  310  is referred to as the “lower portion” of the adapter assembly  410 . 
     The upstream end  220  of the flange  210  is unthreaded to enhance component handling and installation by ship personnel. Threading of the full length can lead to unexpected hand injury during twisting. A threaded surface would also be problematic to grasping tools such as band wrenches, pipe wrenches and large pliers by likely damaging the threads and thereby compromising ability to either install or remove the lock-nut  350 . The upstream end  220  of the flange  210  is also of smaller outside diameter than the threaded mezzanine  230  enabling easier application of the upper lock-nut  350 . Preferably, this incorporates a National Pipe Straight (NPS) or National Pipe Taper (NPT) thread for the exterior threading on the external adapter portion as well as the exterior threading on the lower portion. 
     The associated upper and lower lock-nuts  350  and  360  employ the same NPS or NPT threading. The adoption of NPS or NPT thread facilitates broader use of the less expensive commercially available lock-nuts. The interior would retain a Unified Screw (UN) or Unified Screw Fine (UNF) threading in order to maintain compatibility with standard stuffing tube gland nuts. Designation of this preferred threading does not preclude the use of other types of threading. 
     The purpose of the modification is to simplify the means of attaching a grounding strap or plate to the adapter while minimizing the need for additional components. The lower portion of the adapter assembly  410  is inserted into the junction box  310  or fixture with the adapter seat landing  240  flush against the fixture. After insertion into the through-hole  340 , the lock-nut  350  is threaded onto the downstream end  250  to secure the through connector to the fixture wall. A flexible O-ring seal within the annular groove  510  can be provided between the landing  240  and the outer wall  320 . 
     A grounding strap or plate with a grounding lug of sufficient radius is disposed over the upper portion of the adapter flange  210  and fits over the threading until being flush with the exposed portion of the landing  240 . The lock-nut  350  is threaded onto the upper portion of the adapter to secure the grounding strap or plate to the adapter assembly  410 . The other end of the grounding strap or plate is secured to a ship&#39;s bulkhead. 
     The commercial potential for the ground shield adapter described within broad and global in nature. The designs can be used for commercial as well as naval ship construction. Due to the inherent design tolerance for either SAE or metric dimensions for swage tubes  180 , the exemplary design can be employed for both domestic and foreign ship construction. Although designed with maritime applications in consideration, the exemplary configurations described herein can also be extended for general construction practices where junction boxes, swage tubes or other breach type fittings might be required for facility cable penetrations that require EM grounding, stabilization, or weather sealing. 
     The U.S. Navy utilizes hundreds of topside components that require electrical power or signal connections to systems internal to the surface ship via cable. Because of the complex and system hostile electromagnetic (EM) environment the connecting cables must be protected from unwanted EM coupling to the signal or power cable. Thus, the cables can be protected from the EM environment by a conductive cable shield grounded via the CSGA assembly  410  to the ship&#39;s bulkhead. 
     Current CSGA technologies utilized by the Navy are difficult to manufacture due to machining, difficult to install, repair and replace due to design characteristics, have relatively short service life due to poor environmental design, and are very expensive (approximately $300 per unit in quantity). The Navy also currently purchases CSGAs assemblies in multiple sizes due to inability of conventional CSGA to adapt to multiple swage tube sizes or cable diameters, thereby significantly increasing acquisition, logistics and design costs. The strategic goal of the proposed design is to provide the Navy a cost efficient technology that can significantly reduce total ownership costs via acquisition maintenance and logistics across the fleet. 
     The exemplary embodiments incorporate relatively few parts. Common components include environmental seals that also perform as stabilizing structural components for cable centering and conductive spacers that perform diaphragm deformation control functions. The CSGA diaphragm  150  can employ a cut-stamped component of conductive sheeting to wrap around a cable. The exemplary adapter designs for the junction box  310  also utilize all components of the stuffing tube assembly, including the brass gland nut  110  conventionally unutilized for shielded cable applications. 
     While certain features of the embodiments of the invention have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments.