Abstract:
An electrical connector for connecting flexible metal conduit, armored cable, or metal-clad cable to a panel or junction box. The connector includes a connector body having a tubular nose portion on the leading end and a clamping arrangement on the trailing end. The clamping arrangement includes a fixed clamp arm integral with the connector body and a movable clamp arm that is adjustable with respect to the fixed clamp arm. A tubular insert can be fitted into an inner bore on the tubular nose portion to provide the proper end stop for the cable and to properly insulate the inner bore from any electrical contact with the wire conductors of the electrical cable. The tubular nose portion is exteriorly threaded to accept a lock nut or resilient locking ring for securing the connector to a panel or junction box and for properly grounding the cable to the panel or box.

Description:
FIELD OF THE INVENTION 
   This invention relates to connectors for attaching electrical cables to a panel or an electrical box. 
   BACKGROUND OF THE INVENTION 
   Electrical connectors for attaching an electrical cable to a panel, junction box, and the like are well known in the art. One such electrical connector, described in U.S. Pat. No. 5,553,787, comprises a connector body having a rectangular or square box configuration. The connector body comprises a top portion having a first tab portion disposed about the front edge of the top portion for connecting the electrical connector to an outlet box; a first side wall connected to the top portion; a second side wall also connected to the top portion; a bottom portion having a second tab portion disposed about the front edge of the bottom portion for connecting the electrical connector to the outlet box; and a rear end having a through-hole therein is connected to both the top and bottom portions; and a saddle and screw for concurrently securing the cable disposed within the connector body and securing the connector body to the outlet box. 
   Although the electrical connector described in U.S. Pat. No. 5,553,787 is capable of connecting an electrical cable to a junction box, it would not meet most local electrical codes for connection of high voltage metal-jacketed cable. Connectors for metal-jacketed cable must include an end stop for limiting the distance the cable is inserted, as the metal jacket must not advance past the panel or junction box wall. Only the wire conductors can be advanced past the panel wall into the electrical enclosure. Additionally, the portion of the connector that is beyond the stop is potentially exposed to the wire conductors and, according to the electrical code, must be insulated to prevent electrical shorts in case of damage occurring to the insulating jackets surrounding the wire conductors. The electrical connector of U.S. Pat. No. 5,553,787 clearly lacks a means of limiting the forward advance of a conventional metal-jacketed cable and further lacks an insulating surface at the forward end of the connector. 
   Therefore, electrical connectors of the prior art have not been fully optimized for connecting high voltage metal-jacketed cables to electrical panels, junction boxes, electrical distribution centers, and the like. 
   SUMMARY OF THE INVENTION 
   The invention is an electrical connector that is capable of connecting several types of electrical cables to a panel or junction box, including flexible metal conduit, armored cable, or metal-clad cable. The electrical connector can be easily configured in the field to handle several different sized electrical cables. The connector includes a connector body having a tubular nose portion on the leading end and a clamping arrangement on the trailing end. The clamping arrangement includes a fixed clamp arm integral with the connector body. A movable clamp arm is adjustable with respect to the fixed clamp arm. A tubular insert can be fitted into the inner bore of the tubular nose portion to provide the proper end stop for a specific size range of cable and to properly insulate the inner bore from any electrical contact with the wire conductors of the electrical cable. The tubular nose portion is exteriorly threaded to accept a lock nut or resilient locking ring for securing the connector to a panel or junction box and for properly grounding the cable to the panel or box. 
   OBJECTS AND ADVANTAGES 
   Several advantages are achieved with the electrical fitting of the present invention, including:
         (1) The electrical connector of the present invention is of simple construction, including a die-cast connector body, a movable clamp arm, an insulating insert that is typically molded of plastic, and fasteners for adjusting the movable clamp arm with respect to the fixed claim arm of the connector body.   (2) The electrical connector of the present invention provides an end stop for positively preventing the electrical cable from advancing into the junction box or panel.   (3) The insert provided is of continuous ring construction. Thus, all portions of the inner bore in the leading end of the connector body are protected from accidental electrical shorts from the wire conductors of the electrical cable.   (4) The clamping arrangement includes four fasteners that provide even clamping pressure on the inserted electrical cable and superior strain relief.   (5) A lateral tab is provided on the inner surface of both the movable and fixed clamp arms to engage grooves in the outer jacket of the inserted electrical cable and thereby provide better gripping force.       

   These and other objects and advantages of the present invention will be better understood by reading the following description along with reference to the drawings. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view of a first embodiment of an electrical connector and insert according to the present invention as viewed from the trailing end. 
       FIG. 2  is a perspective view of the electrical connector of  FIG. 1  as viewed from the leading end. 
       FIG. 3  is a front view of the electrical connector of  FIG. 2 . 
       FIG. 4  is a sectional view of the electrical connector taken along line  4 - 4  of  FIG. 3 . 
       FIG. 5  is a front perspective view of a tubular insert that forms a portion of the electrical connector of  FIG. 2 . 
       FIG. 6  is a sectional view of the tubular insert taken along line  6 - 6  of  FIG. 5 . 
       FIG. 7  is a sectional view similar to  FIG. 6  of an alternate embodiment of a tubular insert according to the present invention. 
       FIG. 8  is an exploded perspective view of the electrical connector of  FIG. 1  including three alternative embodiments of tubular insert. 
       FIG. 9  is an exploded perspective view of a second and preferred embodiment of an electrical connector and insert according to the present invention as viewed from the trailing end. 
       FIG. 10  is a sectional view of the electrical connector of  FIG. 1  including a lock nut at the leading end for securing to an electrical panel. 
       FIG. 11  is a sectional view of the electrical connector of  FIG. 1  including a snap ring at the leading end for securing the connector to an electrical panel. 
       FIG. 12  is an exploded perspective view of the electrical connector of  FIG. 9 . 
       FIG. 13  is a view of the trailing end of the electrical connector of  FIG. 9  depicting an electrical cable inserted and locked therein. 
   

   
     
       
             
           
             
             
           
         
             
                 
             
             
               INDEX TO REFERENCE NUMERALS IN DRAWINGS 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
                20 
               electrical connector, first embodiment 
             
             
                22 
               connector body 
             
             
                24 
               leading end of connector body 
             
             
                26 
               trailing end of connector body 
             
             
                28 
               flange 
             
             
                30 
               tubular nose portion 
             
             
                32 
               cable clamping arrangement 
             
             
                34 
               tubular insert 
             
             
                36 
               central axis of connector body 
             
             
                38 
               inner bore 
             
             
                40 
               outer surface of nose portion 
             
             
                42 
               threads 
             
             
                44 
               outer surface of insert 
             
             
                46 
               inner cylindrical surface of nose portion 
             
             
                48 
               leading end of insert 
             
             
                50 
               trailing end of insert 
             
             
                52 
               rim 
             
             
                54 
               orienting arrangement 
             
             
                56 
               longitudinal groove of insert 
             
             
                58 
               raised rib of connector body 
             
             
                60 
               directional arrow 
             
             
                62 
               front opening of insert 
             
             
                64 
               bottom of connector body 
             
             
                66 
               cylindrical wall of insert 
             
             
                68 
               outer tubular body portion of insert 
             
             
                70 
               inner tubular body portion of insert 
             
             
                72 
               brace 
             
             
                74 
               fixed clamp arm 
             
             
                76 
               movable clamp arm 
             
             
                78 
               aperture in movable clamp arm 
             
             
                80 
               threaded bore in fixed clamp arm 
             
             
                82 
               threaded fastener 
             
             
                84 
               arcuate center portion of clamp arm 
             
             
                86 
               flat wing 
             
             
                88 
               convex arcuate surface of fixed clamp arm 
             
             
                90 
               convex arcuate surface of movable clamp arm 
             
             
                92 
               lateral tab 
             
             
                94 
               common wall portion of insert 
             
             
                96 
               inner cylindrical surface of nose portion 
             
             
               100 
               electrical connector, second embodiment 
             
             
               102 
               connector body 
             
             
               104 
               fixed clamp arm 
             
             
               106 
               movable clamp arm 
             
             
               108 
               tubular insert 
             
             
               110 
               reinforcing wall 
             
             
               112 
               outer edge of flat wing 
             
             
               114 
               flat wing 
             
             
               116 
               tubular nose portion 
             
             
               118 
               lateral tab 
             
             
               120 
               indentation 
             
             
               122 
               planar edge 
             
             
               124 
               rim of insert 
             
             
               125 
               flange of connector body 
             
             
               126 
               electrical cable 
             
             
               128 
               groove 
             
             
               130 
               knockout 
             
             
               132 
               panel 
             
             
               133 
               first attachment arrangement 
             
             
               134 
               locknut 
             
             
               135 
               second attachment arrangement 
             
             
               136 
               snap ring 
             
             
               138 
               directional arrow 
             
             
               140 
               directional arrow 
             
             
               142 
               tang 
             
             
               144 
               end of electrical cable 
             
             
               146 
               electrical conductor 
             
             
               D1 
               distance rim extends from outer surface of insert 
             
             
               D2 
               diameter of inner tubular body portion of insert 
             
             
               D3 
               offset distance of the arcuate convex surface of the fixed clamp 
             
             
                 
               arm from the central axis of the connector body as compared to 
             
             
                 
               the inner cylindrical surface of the tubular nose portion 
             
             
                 
             
           
        
       
     
   
   DETAILED DESCRIPTION OF THE INVENTION 
   With reference to  FIG. 1  there is shown a first embodiment of the present invention, an electrical connector  20  including a connector body  22  having a leading end  24  and a trailing end  26  separated by a flange  28 . A tubular nose portion  30  is provided on the leading end  24  and a cable clamping arrangement  32  on the trailing end  26 . A tubular insert  34  is shown in axial alignment with the connector body  22  to be inserted therein. 
   Referring to  FIG. 2 , the connector body  22  includes a central axis  36  and an inner bore  38  therein. The tubular nose portion  30  of the electrical connector  20  includes an outer surface  40  and threads  42  thereon on the outer surface. 
   As shown in  FIG. 3 , after being inserted in the inner bore  38  of the tubular nose portion  30 , the outer surface  44  of the tubular insert  34  substantially extends to the inner cylindrical surface  46  of the tubular nose portion  30 . 
   With reference to  FIGS. 5-7 , the tubular insert  34  includes a leading end  48 , a trailing end  50 , and an outward extending rim  52  at the trailing end  50 . As shown in  FIG. 6 , the rim  52  extends outward of the outer surface  44  by distance D 1 . 
   Referring to  FIG. 2 , the electrical connector  20  includes an orienting arrangement  54  for orienting the insert  34  with respect to the connector body  22 . The orienting arrangement  54  includes a longitudinal groove  56  in the outer surface  44  of the insert  34  extending from the rim  52  to the leading end  48  and a raised rib  58  extending longitudinally thereon along the inner cylindrical surface  46  of the tubular nose portion  30 . To join the insert  34  and connector body  22 , the insert  34  must be oriented with the longitudinal groove  56  of the insert  34  in alignment with the raised rib  58  of the connector body  22 . When the insert  34  is pressed into the connector body  22  in the direction of arrow  60 , the raised rib  58  of the connector body  22  engages the longitudinal groove  56  of the insert  34  thereby aligning the front opening  62  of the insert  34  toward the bottom  64  of the connector body  22 . 
   As shown in  FIG. 4 , the insert  34  is fully inserted in the tubular nose portion  30  of the connector body  22 , when the rim  52  seats against flange  28 . Preferably, the outer diameter of the insert  34  is very close to the inner diameter of the inner bore  38  of the nose portion  30  to cause a snug fit of the insert  34  within the nose portion  30 . Preferably the difference between the diameter of the inner bore  38  and the outer diameter of the insert  34  is between 0.004 and 0.012 inch. 
   As shown in  FIG. 6 , the tubular insert  34  may be formed in various configurations to provide an inner diameter D 2  to accommodate an electrical cable (not shown) of a specific size range. As shown in  FIG. 7 , the insert may include a solid cylindrical wall  66  or, as shown in  FIG. 5 , the tubular insert  34  may be constructed with an outer tubular body portion  68  and an inner tubular body portion  70 . A brace  72  extends between the inner tubular body portion  68  and the outer tubular body portion  68  to brace and support the two portions of the insert  34 . The inner tubular body portion  70  may be decreased in diameter to provide a smaller inner diameter to accommodate smaller diameter electrical cables. By providing inserts with various inner diameters, the electrical connector of the present invention has the advantage of accommodating a broad range of electrical cable sizes with a single size connector body. As shown in  FIG. 4 , the tubular insert  34  surrounds and covers the entire inner bore  38  of the nose portion  30  of the connector body  22 , thereby preventing any electrical shorts from occurring from wire conductors (not shown) extending through the nose portion  30 . 
   With reference to  FIG. 1  the electrical connector includes a fixed clamp arm  74  integral with the flange  28  and tubular nose portion  30  of the connector body  22 , a movable clamp arm  76  movable with respect to the fixed clamp arm  74 , and a cable clamping arrangement  32  for adjusting the position of the movable clamp arm  76  with respect to the fixed clamp arm  74 . The cable clamping arrangement  32  includes a plurality of apertures  78  in the movable clamp arm  76 , a plurality of threaded bores  80  in the fixed clamp arm  74 , and a plurality of threaded fasteners  82  for engagement through the apertures  78  of the movable clamp arm  76  into threaded engagement in the threaded bores  80  in the fixed clamp arm  74 . The fixed and movable clamp arms  74 ,  76  further include an arcuate center portion  84  that is coaxial with the inner bore  38  of the tubular nose portion  30 . Flat wings  86  extend laterally from the arcuate center portions  84  of the fixed and movable clamp arms  74 ,  76 . The flat wings  86  of the fixed clamp arm  74  include the threaded bores  80  and the flat wings  86  of the movable clamp arm  76  include the apertures  78 . 
   Referring to  FIG. 1 , the arcuate center portion  84  of the fixed clamp arm  74  includes a convex arcuate surface  88  and the arcuate center portion  84  of the movable clamp arm  76  includes a convex arcuate surface  90 . The convex arcuate surface  90  of the movable clamp arm  76  and the convex arcuate surface  88  of the fixed clamp arm  74  face the central axis  36  of the connector body  22 . As shown in  FIG. 4 , the convex arcuate surface  90  of the movable clamp arm  76  and the convex arcuate surface  88  of the fixed clamp arm  74  include a lateral tab  92  extending there from. 
   Referring to  FIG. 5 , the inner tubular body portion  70  of the insert  34  is offset axially from the outer tubular body portion  68 . The inner tubular body portion  70  and the outer tubular body portion  68  share a common wall portion  94 . As shown in  FIG. 2 , the orienting arrangement  54  orients the common wall portion  94  so that, after being inserted into the connector body  22 , it will be adjacent the fixed clamp arm  74  or toward the bottom  64  of the connector body  22 . 
   Referring to  FIG. 4 , the arcuate convex surface  88  of the fixed clamp arm  74  is offset farther from the central axis  36  of the connector body  22  as shown by distance D 3 , than is the inner cylindrical surface  96  of the tubular nose portion  30 . This distance D 3  is preferably no less than the width D 1  of the rim  52  (see  FIG. 6 ), which is equivalent to the distance the rim  52  extends from outer surface  44  of insert  34 . The offset distance D 3  provides clearance at the lower end of the flange  28  of the connector body  22  for the rim  52  of the tubular insert  34  to seat against flange  28  and around the entire periphery of the flange  28 . 
   Referring to  FIG. 9  there is shown a second and preferred embodiment of an electrical connector  100  according to the present invention. The preferred embodiment of the electrical connector  100  includes a connector body  102 , fixed clamp arm  104 , movable clamp arm  106 , and tubular insert  108  similar to the first embodiment. The connector body  102  includes a reinforcing wall  110  along the outer edges  112  of the flat wings  114 . The reinforcing wall  110  stiffens the fixed clamp arm  104  and increases the strength and integrity of the tubular nose portion  116  and fixed clamp arm  104 . The movable clamp arm  106  includes a lateral tab  118  (see  FIG. 10 ) as in the first embodiment but the lateral tab  118  is formed by stamping it into the movable clamp arm  106  which, as shown in  FIG. 9 , forms the indentation  120  in the outer surface of the movable clamp arm  106 . In the second embodiment shown in  FIG. 9 , the orienting arrangement of the first embodiment  20  including a longitudinal groove  56  in the tubular insert  34  and the raised rib  58  of the connector body  22  (see  FIG. 2 ) have been replaced by planar edges  122  on the rim  124  of the tubular insert  108 . As shown in  FIG. 9 , the planar edges  122  of the tubular insert  108  engage the flat wings  114  of the connector body  102  and guide the tubular insert  108  into the connector body  102  until the tubular insert  108  seats against the flange  125  of the connector body  102 . 
   With reference to  FIG. 10 , the electrical connector of the present invention  20  is operated by inserting an electrical cable  126  into the inner bore  38  on the trailing end  26  of the connector body  22 . Lateral tabs  92  on the fixed clamp arm  74  and movable clamp arm  76  engage a groove  128  in the electrical cable  126 . The tubular nose portion  30  is then inserted through a knockout  130  in a panel  132  as shown. 
     FIGS. 10 and 11  illustrate two attachment arrangements for locking the electrical connector  20  to a panel  132 . In  FIG. 10 , a first attachment arrangement  133  includes a locknut  134  that is screwed onto the threads  42  of the nose portion  30  until the locknut  134  tightens the connector body  22  to the panel  132 . In  FIG. 11 , a second attachment arrangement  135  includes a resilient annular-shaped snap ring  136  that is first screwed onto the threads  42  on the nose portion  30  in the direction of arrows  138  until the snap ring  136  is tight against the flange  28 . A suitable snap ring for use with the electrical connector of the present invention is shown and described in U.S. Pat. No. 6,538,201, which is incorporated herein in its entirety by reference thereto, and which snap ring is available from Arlington Industries, Inc., of Scranton, Pa. The cable connector  20  and snap ring  136  assembly is then pushed in the direction of arrow  140  through the knockout  130  until the tangs  142  lock against the panel  132  and snap outward to hold the electrical connector  20  securely within the panel. 
   As shown in both  FIGS. 10 and 11 , the electrical cable  126  is inserted into the electrical connector  20  until its end  144  contacts the trailing end  50  of tubular insert  34 . The tubular insert  34  protects any electrical conductors  146  that are fed through the nose portion  30  of the electrical connector  20 . 
   With reference to  FIG. 12  there is shown the second embodiment of the electrical connector  100  with the tubular insert  108 , movable clamp arm  106 , and fasteners  82  exploded away from the connector body  102 . The planar edges  122  on the tubular insert  108  engage the flat wings  114  on either side of the fixed clamp arm  104  and will guide the tubular insert  108  into the connector body  102  until it enters inner bore  38  and seats against flange  125 . 
   With reference to  FIG. 13  there is shown a view from the trailing end of an electrical connector  100  according to the present invention after an electrical cable  126  has been inserted therein. The electrical cable  126  is held securely within the electrical connector  100  by the cable clamping arrangement  32  including the movable clamp arm  106  that has been tightened against fixed clamp arm  104  by threaded fasteners  82 . 
   With reference to  FIG. 8 , the connector body  22  and the movable clamp arm  76  of the present invention are preferably constructed of metal. The connector body  22  is preferably die cast of metal and the preferred material of construction is zinc alloy such as ZAMAK™, available from New Jersey Zinc Company of Newark, N.J. The movable clamp arm  76  of the present invention is preferably stamped and formed from metal and the preferred material of construction is galvanized low carbon steel. The tubular insert  34  is preferably molded of plastic. Preferable molding plastics for constructing the tubular insert  34  include polypropylene and nylon. 
   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.