Abstract:
A duplex fitting including a radius cast on transition for effectively stopping advancement of the armor layer of one or more inserted cables while at the same time enabling easy passage of the conductors to the outbound end. Two inbound bores transition to a single outlet bore within the fitting. The duplex fitting includes a one-piece connector body having a leading end with a nose portion and a trailing end with two bores therein. Tubular cable retainers secured within the inbound bores snap-in connection of electrical cables to the trailing end. A fastening arrangement on the nose portion of the duplex fitting enables snap fit connection to a knockout hole in a panel or an electrical box.

Description:
This application is a Continuation in Part of U.S. patent application Ser. No. 12/384,467, filed Apr. 3, 2009 and still pending, which is a Continuation of U.S. patent application Ser. No. 12/080,482, filed Apr. 3, 2008 and now U.S. Pat. No. 7,882,886, which applications and patents are commonly owned by the assignee of the present invention, the entire contents of which are incorporated herein by reference herein. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to connectors for connecting electrical cables to a panel and specifically to a duplex electrical fitting with improved internal structure for enabling effortless pass-through of conductors through the internal bores. 
     BACKGROUND OF THE INVENTION 
     Duplex electrical fittings are used for wiring electricity in residential and commercial buildings. The duplex fitting enables connecting of one or two electrical cables through a single knockout aperture in an electrical box. In order to properly ground the outer layer of armored electrical cable, duplex fittings are typically constructed of conductive metal and include an inbound end to accept the insertion of electrical cables and an outbound end for connection to an electrical box. Duplex fittings typically include an internal bore that transitions from two bores at the inbound end of to one bore at the outbound end. There is typically scant space available surrounding an electrical box, thereby limiting the length of the duplex fitting as the fitting must fit within the cramped spaces between the electrical box, the walls, and the surround joists or similar structural members. 
     Although many prior art duplex fittings have been heretofore proposed, one shortcoming of the prior art cables is the difficulty in advancing the conductors thorough the internal structure of the fitting. Accordingly, what is needed is a duplex fitting that provides an easy pathway for advancing the electrical conductors of two inserted electrical cables to the outbound end of the fitting. 
     SUMMARY OF THE INVENTION 
     The invention is a duplex fitting having a one-piece connector body for securing electrical cables to a panel or junction box. The one-piece connector body includes a leading end with a nose portion having a bore therein and a trailing end with two bores therein. One or two tubular cable retainers secured in the trailing end enable snap in connection of electrical cables to the trailing end of the connector body. A fastening arrangement is included on the nose portion at the leading end of the connector body for securing the connector body to a knockout hole in a panel or an electrical box. The duplex fitting includes two inbound bores transitioning to a single outlet bore. An end stop at the transition area includes a radius surface thereon to enable the end stop to effectively stop advancement of the armor layer of the cable while at the same time enabling easy passage of the conductors there through to the outbound end. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a first embodiment of a duplex electrical connector according to the present invention. 
         FIG. 2  is a top view of a one-piece connector body that forms a portion of the duplex electrical connector shown in  FIG. 1 . 
         FIG. 3  is a side view of the connector body of  FIG. 2 . 
         FIG. 4  is a sectional view of the connector body taken along line  4 - 4  of  FIG. 3 . 
         FIG. 5  is a sectional view of the connector body taken along line  5 - 5  of  FIG. 2 . 
         FIG. 6  is a plan view of a blank used to form a cylindrical snap ring fastening arrangement for the leading end of the connector body in  FIG. 2 . 
         FIG. 7  is an end view of a cylindrical snap ring that has been formed from the blank of  FIG. 6 . 
         FIG. 8  is a side view of the cylindrical snap ring of  FIG. 7 . 
         FIG. 9  is a perspective view of a cable retainer that forms a portion of the duplex electrical connector of the present invention. 
         FIG. 10  is a plan view of a blank used to form the cable retainer of  FIG. 2 . 
         FIG. 11  is an end view of the cable retainer of  FIG. 9 . 
         FIG. 12  is a sectional view of the cable retainer taken along line  12 - 12  of  FIG. 11 . 
         FIG. 13  is a perspective view of the duplex electrical connector of the present invention from the leading end of the connector. 
         FIG. 14  is a perspective view of the duplex electrical connector of the present invention from the trailing end of the connector. 
         FIG. 15  is a side view of the duplex electrical connector of the present invention with cables inserted in the trailing end and with the leading end in alignment with a knockout aperture in a panel. 
         FIG. 16  is a side view of an alternate embodiment of the duplex electrical connector of the present invention with cables inserted in the trailing end and with the leading end in alignment with a knockout aperture in a panel. 
         FIG. 17  is an exploded perspective view of a second and preferred embodiment duplex fitting according to the present invention. 
         FIG. 18  is a top view of a second and preferred embodiment of a one-piece connector body according to the present invention. 
         FIG. 19  is a side view of the connector body of  FIG. 17 . 
         FIG. 20  is an end view of the connector body as viewed from the top of  FIG. 17 . 
         FIG. 21  is a sectional view of the connector body taken along line  21 - 21  of  FIG. 18 . 
         FIG. 22  is an isometric view of the connector body of  FIG. 17  as viewed from the leading end. 
         FIG. 23  is an isometric view of the connector body of  FIG. 17  as viewed from the trailing end. 
         FIG. 24  is an isometric view of the interior half of the connector body taken along line  20 - 20  of  FIG. 18 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIG. 1  there is shown a first embodiment of the present invention, a duplex electrical connector  20  with a one-piece die cast connector body  22  having a leading end  24 , a trailing end  26 , a nose portion  28  with a cylindrical seat  30  on the leading end  24 , and two bores  32  in the trailing end  26 . A fastening arrangement  33  for fastening the electrical connector  20  to an electrical panel or junction box (not shown) includes a snap ring  34  that is shown exploded away from the leading end  24  and in alignment with the nose portion  28  and the cylindrical seat  30 . A cable retaining arrangement  36  includes two cable retaining split rings  38  that are shown exploded away from the trailing end  26  of the connector body  22  with a cable retaining ring  38  in alignment with each of the bores  32  in the trailing end  26 . 
     Referring to  FIGS. 2-5 , the one-piece die cast connector body  22  is die cast in one piece of metal. The connector body  22  includes an end flange  40  on the leading end  24  and an intermediate flange  42  at the end of the nose portion  28 . The cylindrical seat  30  extends between the end flange  40  and the intermediate flange  42 . The trailing end  26  of the connector body  22  includes a pair of substantially cylindrical wall portions  44  that define the bores  32 . As shown in  FIG. 4 , the connector body  22  is substantially hollow with bores  32  in open communication with leading bore  46  in the leading end  24  of the connector body. Openings  48  are provided in the cylindrical wall portions  44  surrounding each bore  32 . Curved shoulders  50  are provided at the transition of the trailing bores  32  to the leading bore  46 . Viewports  52  are provided in the shoulder area as shown in  FIG. 2 . 
     Referring to  FIGS. 6-8 , the cylindrical snap ring  34  is a split ring formed from a blank  54  having a leading edge  56  and a trailing edge  58 , as shown in  FIG. 6 , into a substantially cylindrical shape as shown in  FIGS. 7 and 8 . U-shaped cutouts  60  are punched out of the blank  54  to form locking tangs  62  on the interior of the blank  54 . Grounding tangs  64  are defined by slits  66  along the trailing edge  58  of the blank  54 . On the cylindrical snap ring  34 , as shown in  FIGS. 7 and 8 , the locking tangs  62  and grounding tangs  64  are bent outwards of the ring  34 . 
     With reference to  FIGS. 9 and 11-12 , there is shown a cable retaining ring  38  that forms a portion of the duplex connector of the present invention. As shown in  FIG. 10 , the cable retaining ring is formed from a blank  68  having a leading edge  70  and a trailing edge  72 . Slots  74  define cable retaining tangs in the blank  68  including a center cable retaining tang  76  and outer cable retaining tangs  78 . Center cable retaining tang  76  includes an edge  80  that is parallel with the leading and trailing edges  70  and  72  and outer cable retaining tangs  78  include edges  82  that are sloped in opposite directions at angle θ 1  away from leading edge  70 . U-shaped slots  84  define outward extending tangs  86 . For locking the blank  68  in place in order to form it into the cylindrical shaped cable retaining ring, an aperture  88  is provided in the blank  68 . A tab  90  is provided on one end of the blank  68  which will align with a groove  92  on the opposite end of the blank  68  when the blank is formed into the cylindrical cable retaining ring  38 . The outer tangs  78  include bend lines  94 . 
     As shown in  FIGS. 11 and 12 , the level edge  80  on center cable retaining tang  76  and the sloped edges  82  on the outer cable retaining tangs  78  will act to force an inserted electrical cable (not shown) toward a point  96  on the inside of the cable retaining ring  38  that is opposite the center cable retaining tang  76 . As shown in  FIG. 12 , the cable retaining tangs  76  and  78  include end portions  98  that are bent away at angle θ 2  from the base portion  99  of the center cable retaining tang  76 . Preferably, end portions  98  of both center cable retaining tang  76  and end portions  98  of outer cable retaining tangs  78  are each bent at an angle θ 2  of between 20 and 30 degrees from the base portion  99  of the respective tang. Cable retaining tangs  76  and  78  are preferably each bent at an angle θ 3  of between 35 and 45 degrees from the sidewall  100  of the cable retaining ring  38 . 
     Preferably the connector body  22  of the present invention is die cast of metal in one piece and most preferably constructed of ZAMAK™, a casting alloy comprised mainly of zinc alloyed with aluminum, magnesium, and copper and available from Eastern Alloys, Maybrook, N.Y. By constructing the tubular body of ZAMAK™ or other appropriate metals, the connector body  22  will be electrically conductive and provide good continuity throughout the fitting. The snap ring  34  and cable retaining ring  38  are preferably constructed of spring steel to impart toughness and flexibility to the various tangs located thereon. The electrical connector  20  is used to secure electrical cables such as metal clad (MC), metal clad all purpose (MCAP), flex cable, or continuous corrugated MC cables to a panel. 
     With reference to  FIGS. 13 and 14 , the assembled duplex electrical connector  20  with one-piece connector body  22  in a perspective view from the leading end  24  ( FIG. 13 ) and a perspective view from the trailing end  26  (see  FIG. 14 ). Snap ring  34 , being constructed of flexible spring steel, is expanded from its unbiased condition and slipped over end flange  40  after which it contracts to its unbiased condition and seats on the leading end  24  of the one-piece connector body  22 . The cable retaining rings  38  in an unbiased condition are of a slightly larger diameter than the trailing bores  32  in the trailing end  26  of the connector body  22 . To assemble the duplex connector  20 , the cable retaining rings  38  are aligned such that the outward extending tangs  86  on the cable retaining rings  38  are in alignment with the openings  48  in the cylindrical walls  44  of the connector body  22 . The cable retaining rings  38  are then compressed slightly and slipped into the respective bores  32  in the connector body  22 . The assembled duplex electrical connector  20  thus includes the one-piece die cast connector body  22  with a snap ring  34  securely seated on the leading end  24  and two cable retaining rings  38  securely seated within the bores  32  on the trailing end  26  of the connector body  22 . 
     Operation of the duplex electrical connector  20  of the present invention is very simple. As a result of the snap ring  34  on the leading end  24  of the connector body  22  and the cable retaining rings  38  in the trailing end  26  of the connector body  22 , an installer simply pushes an electrical cable (not shown) into each of the bores  32  of the trailing end  26  of the duplex connector  20 . The cable retaining tangs  76  and  78  in each bore  32  engage the electrical cable and hold the cable securely within the connector body  22 . After the electrical cables are inserted, the leading end  24  of the duplex connector  20  is inserted within a knockout hole in a panel or junction box (not shown) and simply pushed until locking tangs  62  clear the wall of the panel or junction box and snap outward to their unbiased position. With locking tangs  62  sprung outward, the leading end  24  of the duplex connector  20  is held securely to the panel or junction box. As the connector body  22  is die cast in one piece and the snap ring  34  and cable retaining rings  38  are all constructed of metal, the duplex electrical connector  20  of the present invention establishes excellent electrical continuity between the electrical cables and the panel or junction box that it is secured to. 
     Prior to the present invention, conventional duplex connector bodies (not shown) with dual bores on the trailing end for accepting cable retaining rings were formed in two pieces as a method was not available for die casting the connector body in one piece. As shown in  FIGS. 1 and 4 , connector body  22  is die cast in one piece, including dividing wall portion  102  which is a portion of cylindrical wall portions  44  that form the bores  32  in the trailing end  26  of the connector body  22 . The one piece die cast connector body  22  leads to the myriad advantages as described hereinabove in this specification including 50% savings in raw material cost per connector body, elimination of several expensive secondary manufacturing steps, elimination of flash on the interior of the connector body, improvement of electrical continuity, and a reduction in the amount of tooling to produce the duplex connector body. 
     With reference to  FIG. 15  there is shown a side view of the duplex electrical connector  20  of the present invention with electrical cables  104 , one of which is in view, inserted in the trailing end  26  and with the leading end  24  in alignment with a knockout aperture  106  in an electrical panel  108 . After electrical cables  104  are inserted into the trailing end  26  of the duplex connector  20 , the leading end  24  is inserted through the knockout aperture  106  and advanced until locking tangs  62  clear the panel  108  and snap outward, thereby locking and securing the duplex connector  20  tightly and with excellent electrical continuity to the panel  108 . 
     Referring to  FIG. 16  there is shown a side view of an alternate embodiment of the duplex electrical connector  110  of the present invention. The alternate embodiment of the duplex connector  110  includes a one-piece connector body  112  having threads  114  on the leading end  24 . The duplex connector  110  is depicted with electrical cables  104  inserted in the trailing end  26  and with the leading end  24  in alignment with a knockout aperture  106  in a panel  108 . Duplex electrical connector  110  is simply inserted through the knockout aperture  106  and a locknut  116  is threaded on the threads  114  at the leading end  24  of the connector to secure the connector  110  to the panel  108 . The trailing end  26  of duplex electrical connector  110  is identical to the trailing end of the first embodiment and accepts electrical cables  104  in the same manner as the first embodiment. 
     With reference to  FIG. 17  there is shown a second and preferred embodiment of a duplex fitting  200  according to the present invention. The duplex fitting  200  includes a connector body  202  having an inbound end  204 , an outbound end  206 , and a nose portion  208  with a reduced diameter seat  210 . Connector body  202  includes two inbound bores  211  defined by tubular inbound walls  212  and dividing wall  214 . A reinforcing rib  216  extends longitudinally along the tubular inbound walls  212 . Reinforcing ribs  216  are aligned with the plane  218  dissecting the side-by-side inbound bores  210 . The connector body  22  includes a mid-body flange  220  and an inbound end flange  222 . Each reinforcing rib  216  extends from the mid-body flange  220  to the inbound end flange  222 . A fastening arrangement  33  for fastening the duplex fitting  200  to an electrical panel or junction box include snap ring  34 , that is shown in alignment for insertion on reduced diameter seat  210  of nose portion  208 . A cable retaining arrangement  36  includes a cable retaining ring  38  for insertion in each inbound bore  211 . 
     Unfortunately, as a result of the compact length, the transition from two bores to one bore within the short length of duplex fittings, and the need to stop the forward advance of the cable&#39;s armor at the transition, the conductors of electrical cables tend to hang up in prior art duplex fittings. As shown in  FIGS. 20, 21, and 24 , a critical feature has been provided to enable the conductors pass through the transition from inbound bore  211  to outbound bore  224 . To provide easier pass through of conductors, a radius or arcuate edge  226  has been provided on the end stop  228  at the outbound end  229  of dividing wall  214 . The arcuate edge  226 , as shown in  FIG. 24 , has provided unexpected results in that conductors pass much more easily through the transition area  230 . Thus conductors are much less likely to hang up in the interior of the connector body  202  at the transition from the inbound double bores  211  to the outbound single bore  224 . Connector body  202  further includes a chamfer  234  extending around the inner periphery  236  of the inbound bores  211  to facilitate insertion of cable retaining rings  38  during assembly of the duplex fitting. 
     Although the description above contains many specific descriptions, materials, and dimensions, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the embodiments of this invention. Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.