Abstract:
An electrical fitting for snap engagement of electrical cables or conduit to an electrically conductive panel or junction box. The fitting features a flangeless tubular body having a snap ring surrounding its leading end. The tubular body and snap ring are electrically conductive. The snap ring includes one or more projections cantilevered from its outer circumference. The projections include insertion limiting or grounding tabs and wall engagement tangs. The insertion limiting tabs provide extensive surface contact between the fitting and the junction box, thereby improving continuity and lowering the millivolt drop. The wall engagement tangs lock the fitting within the panel or junction box and provide strain relief to prevent easy withdrawal of the fitting there from. The snap ring is secured to the leading end of the tubular body by one or more locking tangs extending inwardly from the inner periphery of the snap ring.

Description:
This application is a Continuation-In-Part of U.S. patent application Ser. No. 10/256,641 entitled “High Continuity Electrical Fitting”, filed Sep. 27, 2002 now U.S. Pat. No. 6,780,029, and still which is a Continuation-In-Part of U.S. application Ser. No. 10/053,076 filed Jan. 17, 2002, U.S. Pat. No. 6,709,280. 

   FIELD OF THE INVENTION 
   This invention relates to fittings for connecting electrical cables to a panel and specifically to an improved snap engagement electrical fitting that includes a flangeless tubular body that is mechanically simpler and easier to produce than previous flanged versions of the tubular body. 
   BACKGROUND OF THE INVENTION 
   Historically, the most common form of attaching cable and electrical metal tubing (EMT) to electrical junction boxes was by means of an interior-threaded lock nut, which is screwed onto the exterior-threaded electrical fitting that extends into the junction box. 
   Recently, snap fitting connectors have become popular as a means of connecting cables to electrical junction boxes. One such type of snap fitting is disclosed in U.S. Pat. No. 6,709,280 (hereinafter the &#39;280 patent), filed Jan. 17, 2002 and incorporated herein by reference. The snap fitting improved the functionality of the quick connect fitting by providing a snap ring with a grounding tang of a novel design that provided a tighter fit between the quick connect fitting and the junction box or panel that it connected to. The snap fitting of the &#39;280 patent therefore improved the electrical continuity and lowered the millivolt drop between the fitting, the cable, and the junction box. 
   An improved snap engagement fitting was disclosed in U.S. patent application Ser. No. 10/256,641 (hereinafter Ser. No. 10/256,641), filed Sep. 27, 2002 and incorporated herein by reference. The fitting of Ser. No. 10/256,641 improved the continuity of the snap engagement fitting by providing a snap ring including a locking tang lanced out of the grounding tang. By lancing the locking tang out of the grounding tang, a greater portion of the outer periphery of the snap ring is available for forming the grounding tang. The larger grounding tangs provide more contact between the junction box and the snap ring thereby providing improved electrical continuity and a lower millivolt drop between the fitting, the cable, and the junction box. 
   Although the snap engagement fittings of the &#39;280 patent and Ser. No. 10/256,641 vastly improved the electrical continuity of snap engagement fittings constructed of a tubular body and a snap ring, the disclosures required a flange on the tubular body which added to the weight and cost of production of the tubular body. Accordingly, the present invention provides a snap engagement electrical fitting with a flangeless tubular body, which reduces the complexity of the tubular body and makes it easier to produce and therefore lowers the cost of production of the fitting. 
   These and other advantages will become apparent by reading the attached specification and claims in conjunction with reference to the attached drawings. 
   SUMMARY OF THE INVENTION 
   The present invention is an electrical fitting for snap engagement of electrical cables or conduit to an electrically conductive panel or junction box. The fitting features a flangeless tubular body having a snap ring surrounding its leading end. The tubular body and snap ring are electrically conductive. The snap ring includes one or more projections cantilevered from its outer circumference. The projections include insertion limiting or grounding tabs and wall engagement tangs. The insertion limiting tabs provide extensive surface contact between the fitting and the junction box, thereby improving continuity and lowering the millivolt drop. The wall engagement tangs lock the fitting within the panel or junction box and provide strain relief to prevent easy withdrawal of the fitting there from. The snap ring is secured to the leading end of the tubular body by one or more locking tangs extending inwardly from the inner periphery of the snap ring. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a plan view of the preferred embodiment of a blank that has been stamped out and will be formed into the snap ring of the present invention. 
       FIG. 2  is a plan view of a snap ring after the blank of  FIG. 1  has been formed into a circular shape. 
       FIG. 3  is a side view of the snap ring of  FIG. 2 . 
       FIG. 4  is a side view of the preferred embodiment of a snap ring according to the present invention. 
       FIG. 5  is a side view of a preferred embodiment of a tubular body that will be used with the snap ring of  FIG. 4 . 
       FIG. 6  is a perspective view of the tubular body of  FIG. 5 . 
       FIG. 7  is a perspective view of the preferred embodiment of a snap engagement electrical fitting according to the present invention. 
       FIG. 8  is a perspective view of a second embodiment of the snap ring according to the present invention. 
       FIG. 9  is a perspective view of a second embodiment of a tubular body that will be used with the snap ring of  FIG. 8 . 
       FIG. 10  is a perspective view of a second embodiment of a snap engagement electrical fitting according to the present invention. 
       FIG. 11  is a side schematic showing the snap engagement fitting of  FIG. 7  inserted into an opening in a panel and with an electrical cable inserted into the trailing end of the fitting. 
   

   INDEX TO REFERENCE NUMERALS IN DRAWINGS 
   
       
       
         
             20  snap engagement electrical fitting 
             22  electrical cable 
             24  opening 
             26  wall 
             30  tubular body 
             32  tubular shaped snap ring 
             34  leading end of fitting 
             36  trailing end of fitting 
             37  blank 
             38  U-shaped cutout 
             40  wall engagement tang 
             42  slits 
             44  insertion limiting or grounding tab 
             46  locking tang 
             48  leading end of snap ring 
             50  trailing end of snap ring 
             52  end of wall engagement tang 
             54  central axis of snap ring 
             56  base portion of insertion limiting tab 
             58  end portion of insertion limiting tab 
             60  leading end of tubular body 
             62  trailing end of tubular body 
             64  depression in tubular body 
             70  second embodiment of snap engagement electrical fitting 
             72  tubular body of second embodiment 
             74  tubular snap ring of second embodiment 
             76  gap 
             78  distance 
             80  outer surface of wall engagement tang 
             82  central axis of fitting 
             84  inner periphery of snap ring 
         
       
     
  
   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention comprises an electrically conductive fitting for easy snap engagement of an electrical cable to an electrical panel or electrical junction box. Once connected into a knockout in the panel or junction box, electrical continuity or grounding is provided between the fitting, an inserted cable or conduit, and the panel or junction box. This invention relates to and incorporates herein by reference in its entirety pending U.S. application Ser. No. 10/256,641 filed Sep. 27, 2002 and U.S. Pat. No. 6,709,280 filed Jan. 17, 2002. 
   With reference to  FIG. 11 , the present invention is a snap engagement electrical fitting  20  for connection of an electrical cable  22  or electrical conduit into an opening  24  in the wall  26  of a panel or junction box (not shown). The snap engagement fitting  20  includes a tubular body  30  and a tubular shaped snap ring  32  surrounding the tubular body  30 . The fitting  20  includes a leading end  34  for insertion into the opening  24  in the wall  26  and a trailing end  36  that is capable of receiving an electrical cable  22  or conduit. 
   Referring to  FIG. 1 , the snap ring is typically constructed of spring steel and is typically stamped out of a flat sheet of spring steel. The stamped out snap ring is typically referred to as a blank  37  and includes U-shaped cutouts  38  that define wall engagement tangs  40 , slits  42  that define insertion limiting or grounding tabs  44 , and locking tangs  46  along one edge of the blank  37 . 
   The blank  37  depicted in  FIG. 1  is formed into the tubular shaped snap ring  32  as shown in  FIGS. 2–4 . As shown in  FIG. 3 , the tubular snap ring  32  includes a leading  48  and a trailing  50  end. The wall engagement tangs  40  extend outwardly from the snap ring  32  with their ends  52  oriented toward the trailing end  50  of the snap ring  32 . The locking tangs  46  extend inwardly from the snap ring  32  toward the central axis  54 . Extending outwardly from the snap ring  32  are the insertion limiting tabs  44 , which have a base portion  56  integral with and cantilevered from the snap ring  32  and an end portion  58  orthogonal to the central axis  54  of the snap ring  32 . 
   With reference to  FIGS. 5 and 6 , the tubular body  30  includes a leading end  60 , a trailing end  62 , and a depression  64  formed circumferentially around its outer surface. In the preferred embodiment depicted in  FIGS. 5 and 6 , the depression  64  is located near the leading end  60  of the tubular body  30 . 
   As shown in  FIG. 7 , in the assembled fitting  20 , the locking tangs  46  of the snap ring  32  are received in the depression  64  of the tubular body  30 . The snap ring  32  is formed of spring steel and shaped on a mandrel into its circular shape. The circular snap ring  32  is formed into a discontinuous or split ring having a diameter less than the outer diameter of the tubular body  30 . Thus the split or snap ring  32 , being constructed of the resilient spring steel, can be spread slightly in diameter and pressed over the leading end  60  of the tubular body  30  until the inward-directed locking tangs  46  snap into the depression  64  in the tubular body  30 . The snap engagement electrical fitting  20  therefore consists of the tubular body  30  and tubular shaped snap ring  32  held thereon by the spring pressure of the snap ring  32 . 
   As shown in  FIGS. 4–7 , the preferred embodiment of the snap engagement electrical fitting  20  (see  FIG. 7 ) includes the depression  64  near the leading end  60  of the tubular body  30  (see  FIG. 5 ) and the locking tangs  46  on the leading end  48  of the snap ring  32  (see  FIG. 3 ). The first and preferred embodiment of the fitting  20  therefore has the locking tangs  46  compressed by spring pressure into a depression  64  near the leading end  60  of the tubular body  30 . 
   A second embodiment  70  of the snap engagement electrical fitting, depicted in  FIGS. 8–10 , has the depression  64  formed approximately midway longitudinally along the tubular body  72  (see  FIG. 9 ) and the locking tangs  46  formed on the trailing end  50  of the snap ring  74  (see  FIG. 8 ). The assembled electrical fitting  70 , shown in  FIG. 10 , includes the snap ring  74  secured near the leading end  60  of the tubular body  72  but with the depression  64  and inserted locking tangs  46  located proximate the middle of the tubular body  72 . Both embodiments of the snap engagement electrical fitting function in a similar manner, with the difference being that, once inserted in a panel, the locking tangs  46  and depression  64  are located inside the panel for the first embodiment  20  (see  FIG. 11 ) of the fitting and outside the panel for the second embodiment  70  of the fitting. 
   With reference to the side view of the snap ring  32  in  FIG. 3 , there is a gap  76  defined by the longitudinal distance  78  between the wall engagement tang  40  and the end portion  58  of the insertion limiting tab  44 . The distance  78  is critical in that it must be large enough to allow inward flexing of the wall engagement tangs  40  as they are pressed into the opening  24  in the wall  26  of a panel or junction box such as depicted in  FIG. 11 . The distance  78  must also be small enough such that, once the wall engagement tangs  40  have cleared the wall  26  and snap back to their unbiased positions, there is no excessive distance in the gap  76  to allow excessive longitudinal movement of the fitting  20  with respect to the wall  26 . Therefore, excessive longitudinal movement is prevented by sizing the gap  76  correctly. Preferably, the gap  76  is no more than 0.077 inch larger than the thickness of the wall  26 . 
   Reference is directed to  FIG. 11  for the operation of a snap engagement fitting according to the present invention. It should be noted that the snap engagement fitting  20  in  FIG. 11  is the preferred embodiment of the snap engagement fitting  20 , with the depression  64  proximate the leading end  60  of the tubular body  30  and the locking tangs  46  on the leading end  48  of the snap ring  32 . The snap ring  32  is secured to the tubular body  30  by spring pressure forcing the locking tangs  46  into the depression  64 . The insertion limiting or grounding tabs  44  are for limiting the insertion of the fitting  20  into the opening  24  and for providing electrical continuity or grounding of the fitting  20  to the wall  26  of the panel or electrical box (not shown). The snap ring  32  and tubular body  30  are both preferably constructed of electrically conductive metal, and with the snap ring  32  secured to the tubular body  30  by the strong spring pressure of the snap ring  32 , good electrical continuity is established between them. 
   To install the snap engagement electrical fitting  20  in an opening  24  in a wall  26 , an installer simply orients the leading end  34  of the fitting  20  toward the opening  24  and presses the fitting  20  into the opening  24 . The outer diameter of the fitting  20  at the leading end  34  and at the snap ring  32  is less than the diameter of the opening  24 , therefore the leading end  34  of the fitting  20  and the leading end  48  of the snap ring  32  easily enter the opening  24 . As the fitting is advanced by the installer, the perimeter of the wall  26  surrounding the opening  24  contacts the wall engagement tangs  40 . Since the wall engagement tangs  40  have their ends  52  oriented toward the trailing end  50  of the snap ring  32 , the outer surface  80  of the wall engagement tangs  40  are compressed inwards by the perimeter of the wall  26  at the opening  24 . As the fitting  20  is further advanced into the opening  24 , the wall engagement tangs  40 , as a result of the gap  76  being sized slightly larger than the wall thickness, spring outwards to their unbiased positions as the wall engagement tangs  40  clear the wall  26 . At this point the fitting  20  is securely locked into the opening  24  and a strong strain relief is provided by the wall engagement tangs  40  thereby preventing the fitting  20  from being easily withdrawn from the wall  26 . Fittings are required by the electrical code to withstand a rearward strain so that wiring from the installed cable  22  is not pulled free from their connections inside the wall  26 . Additionally, forward travel of the fitting  20  into the wall is limited by the insertion limiting tabs  44 , the end portions  58  of which are orthogonal to the central axis  82  of the fitting  20  and therefore limit the insertion of the fitting  20  into the opening  24 . 
   As shown in  FIG. 3 , the base portion  56  of the insertion limiting tabs  44  in their unbiased state extend beyond the outer diameter of the snap ring  32 . Openings  24  or knockouts in electrical panels and junction boxes conform to standard sizes. For a given size of snap ring  32  such as shown in  FIG. 3 , the base portion  56  is formed to extend beyond the diameter of the standard size opening it will be used in. With the fitting  20  installed in the opening  24 , as shown in  FIG. 11 , the base portion  56  of the insertion limiting tab  44  is therefore compressed by the wall  26  perimeter at the opening  24  and thereby held in good surface contact with the wall  26 . As the snap ring  32  and tubular body  30  are already in close contact, by snapping the snap engagement electrical fitting  20  into the opening  24 , good electrical continuity is established between the fitting  20 , the panel or electrical box, and any inserted electrical cable  22  or conduit having a conductive surface. 
   With reference to  FIG. 1 , there is shown a plan view of the blank  37  used to form the snap ring  32 . The blank  37  is typically stamped from a thin piece of spring steel, such as 1050 spring steel or equivalent, preferably between 0.015 and 0.025 inch in thickness, and includes a zinc plating layer of no less than 0.00015 inch thick. 
   With reference to  FIGS. 5 and 6 , the tubular body  30  would typically be constructed of zinc, or a similar metal to enable the body  30  to establish good electrical continuity between a metallic cable or conduit (not shown) and the snap ring. The tubular body  30  is typically die cast from zinc or similar metals used in die castings, such as aluminum and magnesium. The most preferred material of construction of the tubular body  30  is zinc. 
   As shown in  FIG. 2 , the most preferred arrangement of the snap ring  32  includes three insertion limiting tabs  44 , three wall engagement tangs  40 , and a plurality of inward directed locking tangs  46 . The snap ring  32  includes an inner periphery  84  and preferably the locking tangs  46  extend around at least 50% of the inner periphery and more preferably at least 75% of the inner periphery. Although this is the preferred arrangement it should be obvious by the above discussion and descriptions herein that other arrangements are also possible, and the claimed invention should not limited by the examples shown and given herein. 
   As shown in  FIG. 11 , an electrical cable  22  or electrical conduit can be secured to the trailing end  36  of the fitting  20  by any of several means such as the threaded screw hole ( 68 ) and receiving screw disclosed in U.S. Pat. No. 6,596,939, the spring steel locking ring ( 20 ) disclosed in U.S. Pat. No. 6,080,933, or the cylindrical-shaped split ring ( 24 ) of U.S. Pat. No. 6,670,553, all of which are incorporated herein by reference. 
   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 presently preferred 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.