Abstract:
A dual-clamp device attaches a pair of metal clad cables to a junction box. The clamp device is integrally formed defining a pair of side-by-side cable receiving members separated by a central web. Each cable receiving member is generally in the form of an elongate split cylinder permitting radial resilient movement. Forward fingers on each cable insertion end of the cable receiving member provides for engagement with the wall in the junction box upon insertion. The cable receiving member supports the wall of the junction box between the forward fingers and a spring tab on the central web.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a device used to secure metal clad (MC) armored cable to a box or a wall. More particularly, the present invention relates to a dual integrally formed clamp which facilitates easy installation of armored cable(s) to the box. 
       BACKGROUND OF THE INVENTION 
       [0002]    There are currently two methods for attaching MC armored cable into box openings. One employs existing internal/external clamps and added secondary connectors/fittings. The internal clamps usually are attached to the box by means of a threaded screw. This serves to keep the connector in place, and to compress the connector onto the cable once inserted. This is, however, a manual process, and can be difficult to thoroughly tighten down to the necessary torque. If the clamp is on the inside, knockout holes must be removed before cable insertion. Also, the protruding screw on the backside of the box might become a concern for the end user at times. 
         [0003]    A second method is to attach a connector to the existing box. This is typically done on the outside. In most cases, this involves removing existing box knockout holes, inserting the connector, and finally inserting the cable into the connector body. Usually the inside body of the connector has teeth or fingers to grab and hold the cable in place. Removal of these systems is very difficult, due in part to the nature of the design. Most of these systems have two separate functions, the front of the connector latches to the body of the box, and independently, the teeth on the rear (usually located inside the fitting) hold the cable in place. The front latching mechanisms are typical of multi-finger designs that make it difficult to remove the connector without destroying the fingers. 
         [0004]    For other designs, once the cable is inserted, an interference fit is created, by means of the teeth flexing towards the outer housing of the assembly. The walls of the connector wedge the outer walls of the box, internally by the cable, and externally by the box. These connectors can be removed by removing the interference, i.e., the cable body itself, from the connector. These connectors can be difficult to install while the cable is in the fitting, due to the fact that the fitting is already flared out and now must be compressed into place into the box. 
         [0005]    Other connectors for attaching cable to a box are known. U.S. Pat. No. 2,458,409 and U.S. Pat. No. 3,858,151 and U.S. Pat. No. 4,012,578 all disclose a single piece cable connector. However, each connector must be inserted from inside the box. 
         [0006]    U.S. Pat. No. 4,990,721 shows a one-piece connector that is inserted from outside the box. U.S. Pat. No. 6,194,661, U.S. Pat. No. 6,355,884 and U.S. Pat. No. 6,521,831 each show a duplex connector, i.e. two connectors alongside each other. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a dual-clamp device for attaching a pair of metal clad cables to a junction box. The junction box has a pair of side-by-side knockout openings in the wall thereof to permit access to the interior of the box. The clamp device includes an integrally formed clamp body defining a pair of side-by-side cable receiving members separated by a central web. Each cable receiving member is generally in the form of an elongate split cylinder permitting resilient radial movement. Each cable receiving member includes a cable insertion end insertable into the knockout opening of the box and a cable receiving end insertably accommodating the cable. Forward fingers adjacent each of the cable insertion ends provide for engagement with the wall of the box. The cable receiving members support the wall of the junction box between the forward fingers and the web. 
         [0008]    In a preferred embodiment, the forward fingers are struck outwardly from the clamping body. 
         [0009]    Each cable receiving member is radially compressible to allow insertion of the cable insertion end into the knockout opening. Each cable receiving member is also radially expandable to permit insertion of the cable into the cable receiving end. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a side perspective views of a preferred embodiment of a pair of the clamps of the present invention; 
           [0011]      FIG. 2  is a front perspective views of the preferred embodiment as shown in  FIG. 1 ; 
           [0012]      FIG. 3  is a top plan view of the preferred embodiment as shown in  FIG. 1 ; 
           [0013]      FIG. 4  is a front plan view of the preferred embodiment as shown in  FIG. 1 ; 
           [0014]      FIG. 5  is a side plan view of the preferred embodiment as shown in  FIG. 1  shown partially disposed inside a knockout hole of a junction box. 
           [0015]      FIGS. 6 and 7  shows side and front plan views respectively of a further preferred embodiment of the present invention. 
           [0016]      FIG. 8  is perspetive showing of a end cap employed in combination with the dual clamp devise of the present invention. 
           [0017]      FIGS. 9 and 10  show respectively a longitutal cross sectional view and end view of the dual clamp device of the present invention including the inserted end cap of  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0018]    An improved dual-clamp device  10  constructed in accordance with the present invention is illustrated in  FIGS. 1 and 2 . The dual-clamp device  10  can be inserted through a pair of side-by-side openings  52  in a wall  51  of a junction box  50  as illustrated in  FIG. 5 . Although this device can be snapped-in to a junction box to secure a pair of MC armored cables to the box (and thus be considered a clamp), it can also be a stand-alone fitting as well. 
         [0019]    As shown, clamp device  10  includes two clamps  12  and  13 , side-by-side that are connected by an intermediate web  14  optionally configured with a pre-load spring tab  19  shown in  FIGS. 6 and 7 . As shown in  FIG. 4 , neither clamp defines a full circle. Instead, there is a longitudinal cut or split  16 ,  18  along each clamp. As can be appreciated, the dual-clamp device can be made from a flat continuous sheet of metal or any other rigid material that is then stamped before it is rolled at both ends into either an “S” or a “3” shape configuration. This configuration enables the clamp device  10  to be radially resiliently movable as well as flexible so as to contract when inserted into a knock-out opening  52  in a junction box  50 . As shall be discussed in detail below, once snapped in, the spring tab  19  of the web  14  in connection with the teeth  30 ,  32  on the tubular body, firmly grasp the wall  51  of the junction box  50 . The spring tab  19  of the intermediate web  14  creates an interference when the dual-clamp device  10  is assembled with the box  50  so it can not be inserted all the way into the box. Thus, the spring tab  19  of the web  14  functions as a stop and prevents the dual-clamp device  10  from being inserted too far within the box  50 . It can be seen that the dual-clamp device  10  is utilized to connect a pair of electrical MC armored cables  60  each having a helical groove  61  formed in its outer covering with a junction box. 
         [0020]    As seen in  FIG. 2 , each clamp  12 ,  13  includes a generally cylindrical tubular body  12   a ,  13   a  which receives the MC armored cable  60  at its front end. In the front end, a set of arc-shaped flanges  15  extend radially inwardly toward the space for the MC armored cable  60 . In addition, the flanges  15  extend toward the center (see  FIG. 5 ) to catch the metal clad portion  61  of the MC armored cable  60 . An annular outer rim  17  of the flange has a curved surface which additionally prevents damage to the wires if they are pressed against the flange  15 . 
         [0021]    As particularly shown in  FIGS. 8 through 10  the present inversion may optionally employ an end cap  70  is formed of a plastic material which is flexible and resilient. The end cap  70  includes a generally cylindrical body  72  and an upstanding central portion  74  having a flat planar face  76 . The area between the cylindrical body  72  and the upstanding portion  74  forms generally a flexible spring which allows the end cap  70  to be inserted into the front portion of the clamps  12  and  13 . The cylindrical body  72  includes a rim  78  having cut out portion  79  therein. The cut out portions are aligned with the flanges  15  so as to permit insertion of the end cap into the clamp. A stop  77  holds the end cap  70  in place. The planar portion  76  of end cap  70  is rupturable by insertion of the conductors (not shown) of the armored cable  60  thereinto. In that regard, the planar portion  76  includes a generally star shaped opening  80  which facilitates entry of the conductors therethrough. Extending in radial fashion about the star shaped opening  80  are a plurality of partially formed slits  82  which facilitate rupturing of the planar member  76  upon insertion of the conductors of table  60  therethrough. The end cap may be used to seal the clamps  12  and  13 . Moreover, in situations where only one clamp is being used, the end cap  70  provides for closure of the unused clamp. 
         [0022]    As shown in  FIG. 1 , the rear portion of the clamps  12 ,  13  provides for cable receiving and includes a tapered lead in  20 . The lead-in  20  guides the cable to allow easier insertion of MC armored cables into the clamps and prevents contact of the MC armored cables with burrs or other sharp edges. 
         [0023]    The front portion of the dual-clamp device  10  has fingers or teeth  30 ,  32  to catch onto the inside wall of the box when assembled. The teeth  30 ,  32  are lanced outwardly from the body of the clamps  12 ,  13 . The teeth prevent the dual-clamp device  10  from being pulled out of the box  50  unless a sufficient force is applied such as when the user pries it out with a secondary tool such as a screwdriver or an equivalent. As seen, the teeth  30 ,  32  can be formed integrally from cutouts on the tubular bodies  12   a    13   a.    
         [0024]    As the dual-clamp device  10  is inserted into the pair of circular openings  52 , each tubular body radially contracts to allow entry. Further movement of the dual-clamp device  10  into the junction box moves the teeth  30  and  32  past the wall  51  and into engagement with inner surface thereon. The resilient radial movement of clamps  12 ,  13  is provided by the split cylindrical configuration of the tubular bodies  12   a ,  12   b.    
         [0025]    When the teeth  30  and  32  have been passed through the wall  51  of the junction box and engaged the inside thereof, the spring tab  19  of intermediate web  14  comes into contact with the outer surface of the wall  51 . This is shown in  FIG. 5 . The teeth  30 ,  32  and the spring tab  19  of intermediate web  14  provide a firm connection between the dual-clamp device and the junction box. 
         [0026]    Thus, the dual-clamp device  10  is held against movement relative to the wall  51  of the junction box  50  by the cooperation between a set of outwardly projecting teeth  30  and  32  and the spring tab  19  of intermediate web  14  which engage opposite sides of the wall  51 . To hold the dual-clamp device  10  in the junction box, the spring tab  19  of intermediate web  14  engages the outer surface of the junction box while teeth  30  and  32  engage the inner surface of the junction box. 
         [0027]    The rear section of each clamp is provided with inwardly projecting fingers or tabs  40  formed integrally with the clamps  12 ,  13 . The fingers are lanced towards the center of the body of clamps  12 ,  13  similar to the teeth  30 ,  32 . The tabs  40  project inwardly from the tubular wall of the dual-clamp device  10  to catch any MC armored cable received. Although three tabs  40  are included for each clamp in the embodiment shown, there may be other variations in numbers and placement. The tabs  40  are offset from each other to accommodate the pitch of the cable. 
         [0028]    The tubular bodies  12   a  and  12   b  of the dual-clamp device  10  is designed to radially expand. This is accomplished by the fact that each side of the clamp has the cut  16 ,  18  mentioned above, that is positioned down the entire length of the dual-clamp device  10  in a direction that is parallel to the inserting cable  60 . This allows for a flexing of the body radially outwardly to accommodate cable insertion. This movement may be limited towards the front of the dual-clamp cable  10  due to the fact that the wall of the body of the box  50  and the front of the cut section  16 ,  18  of the device are becoming an interference fit as the cable  60  is inserted. 
         [0029]    The distal ends of the tabs  40  provide a pre-load to the groove  61  as the MC armored cable  60  is pushed into the dual-clamp device  10 . For instance, when the MC armored cable is inserted into the clamp, the tabs  40  are disposed in a spatial arrangement such that at least one tab  40  may be in threaded engagement and may “dig” in between helical grooves  61  formed in a flexible electrical MC armored cable  60  to prevent the MC armored cable  60  from being pulled out of the dual-clamp device and to provide a solid connection between the dual-clamp device  10  and the MC armored cable. 
         [0030]    The tabs  40  can be formed with a particular length such that its inner end portions can be disposed correspondingly with the same pitch as the helix of the groove  61 . In addition, tabs  40  are cut with their inner-edge portions sloping at the same angle relative to a central axis of the dual-clamp device  10  as in which the turns of the helical groove  61  slope relative to the longitudinal axis of the MC armored cable  60 . Thus, the inner surfaces of the tabs  40  form a portion of a helix of substantially the same pitch and diameter as the pitch and diameter of the helical groove  61  in the exterior wall  62  of the MC armored cable  60 . 
         [0031]    The tubular wall of the dual-clamp device  10  can be constructed so that it has an outside diameter which is just slightly smaller than the inside diameter of the opening  52  in the wall  51 . Therefore, when the MC armored cable is inserted, it pushes out the teeth  30  and  32  to provide a tighter grip. On the other hand, if the MC armored cable is inserted first, before the device is inserted into the box, the outer diameter of the tubular wall  10  can be constructed so that it is slightly larger than the inside diameter of the opening  52 . In this case, the flexible tubular wall is resiliently flexed inwardly to press the tabs  40  against the bottom of the groove  62  as the dual-clamp device is shoved into the hole  52  in the wall  51 . The tabs  40  dig into the MC armored cable  60  to provide a firm electrical connection between the dual-clamp device and the MC armored cable when the cable is inserted. Since the tabs  40  are disposed in tight engagement with the groove  61  in the MC armored cable  60 , a relatively large force is required in order to pull the MC armored cable out of the dual-clamp device. 
         [0032]    The dual-clamp device  10  is designed to be easily snapped into the box  50 . This quick insert approach allows for easy installation as well as easier removal of the cable or the entire connector if desired and permit an installer to readily and quickly attach armored cable to the box. The purpose of this design is to allow the user, without the need for accessory tools, to assemble an MC armored cable into a metallic box (single/multi gang box) via the quick insert dual-clamp device  10 . This is achieved by pushing in the prepared cable into the desired opening of the box, where the cable will secure itself against the insert clamp during the insertion of the cable. This insertion dual-clamp device may be pre-attached to the outsides of the box, and will meet all listed safety electrical requirements. 
         [0033]    The present invention also contemplates the dual-clamp device  10  being pre-assembled with the box at the time of manufacturing. Preferably, the dual-clamp device  10  may be supplied already attached or assembled to the box, instead of being provided as a stand-alone component that will be added in the field. Usually, existing clamps are either added-on as a secondary step by the user, wherein a manual secondary step must be performed to fasten the cable securely to the box opening. The invention takes the approach of being an actual part of the box itself, instead of existing as a secondary operation or not requiring any other assembly step other than pushing the cable into the already assembled clamp. Thus, there is no need for the installer to carry separate components nor does the installer have to pry out knock-outs. It allows the user to simply insert the prepared cable into the desired location without any secondary operations. There is no need to tighten down any screws, or insert any connectors. 
         [0034]    Although the dual-clamp device  10  has been illustrated herein in association with MC armored cable  60  having only a single helical groove  61  in its outer surface, it is contemplated that a dual-clamp device constructed in accordance with the present invention could be utilized in association with a MC armored cable having a plurality of helical grooves formed in its outer surface. Of course, the inwardly projecting tabs  40  would be spaced so as to engage the helical grooves as the dual-clamp device was turned onto the end of the MC armored cable. It should also be noted that although the flange shields the wires from the end of the MC armored cable  60 , it is contemplated that under certain circumstances a plastic sleeve may be utilized in association with the end of the MC armored cable in a known manner to further shield the wires from the MC armored cable. In addition, it is contemplated that the dual-clamp device  10  could be used with MC armored cables other than MC armored cables for holding electrical wires. 
         [0035]    Further, a single clamp could also be used with an outer flange or a similar part instead of the intermediate web between the two clamps. Although the embodiment of dual-clamp device  10  advantageously formed from a single piece of metal is described such that the teeth  30  and  32 , intermediate web  14 , and tabs  40  are integrally formed, a single clamp construction facilitating connecting the device with the end of a single MC armored cable  60  is also envisioned by this invention. In addition, as can be seen in the drawings, when the dual-clamp device  10  is being formed, stress relief openings are advantageously formed at various parts such as on the intermediate web  14 . 
         [0036]    Various changes to the foregoing described and shown structures will now be evident to those skilled in the art. Accordingly, the particularly disclosed preferred embodiments are intended in an illustrative and not in a limiting sense. The scope of the invention is set forth in the following claims.