Abstract:
A fitting that anchors electrical wiring to a junction box or electrical panel includes gripping members which can releasably hold electrical wiring, in or out of armored conduit, and interference members which allow the fitting to be inserted through knock out apertures and, when in place, extend to prevent withdrawal from the aperture. Optionally a rotatable collar actuates the mechanisms and abuts the wall of the box or panel, eliminating any lateral movement when the interference members are engaged.

Description:
This application claims the benefit of U.S. Provisional Patent Application No. 61/367,882, filed Jul. 27,2010 , the contents of which are incorporated in this disclosure by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to fittings for connecting electrical cables and flexible conduit to electrical panels and junction boxes. 
     The intention of the invention is to make an improved fitting that allows easier insertion of the electrical cables into the trailing end of the fitting and into the electrical panel or junction box at the same time. Historically, armored cable (AC) or metal-clad cable (MC) has been connected to a panel by a tubular fitting including a leading end having a threaded nose and a trailing end having a lateral screw mounted laterally through the fitting wall. Alternatively, a set of strap and screws were attached to the trailing end. The threaded nose was inserted into an aperture in the panel and a locknut tightened thereon secured the fitting to the panel. 
     AC or MC cable was then inserted into the trailing end and the lateral screw or the strap screws were tightened to secure the cable to the fitting. It is important to have secure grounding and since the fitting is made out of metallic material it creates a good electrical continuity (grounding) between the electrical panel and the cable. 
     Typically wiring a construction project electrically, whether it is a building or factory, requires electrical contractors to make hundreds to thousands of such individual connections. Moreover, such installation necessitates using tools to achieve a secure connection, including a wrench for the lock nut and a screw driver for the laterally mounted screw. Therefore, it should be appreciated that completing all of these connections can be very time consuming, since contractors usually use such tools on each connection. 
     Recently, several types of snap engagement fittings have been introduced as a means of connecting cables to electrical panels and junction boxes in order to reduce the time and effort required for installation of fittings in electrical wiring. Although using such snap engagement fittings eliminates the use of tools for installation, they typically require substantial effort to snap them on the junction box or panel. 
     Furthermore, if there is a need for a retrofit or disconnection of the fitting, the contractors have no choice but to use tools to remove the snap engagement fittings and that, in turn, also involves substantial effort and force. 
     Therefore, what is needed is a fitting for securing electrical cables to the panel or junction box of a type that does not require the use of any tools for installing or removal, of either the leading or trailing end, and that allows the leading end to connect quickly and securely to the electrical junction box and the cable to be securely fitted into the trailing end. Such a fitting would vastly reduce the time and effort involved in installing or removing electrical cables in a structure&#39;s wiring. The desired fittings must be designed to work with standard electrical panels, boxes, housings, and the like, while allowing quick and easy connection through standard size knock out apertures. 
     The present invention offers a quick connect fitting for an electrical panel or junction box that requires no tools for connecting or removal of the fitting. Moreover, it needs much less effort and force for installation or removal compared to the existing snapping fittings. Due to its unique design, there are large contact areas between the electrical panel or junction box, the fitting, and the cable jacket that in turn result in very good electrical continuity or grounding. 
     SUMMARY 
     In one version of the invention, the fitting has an arrangement on the leading and the trailing ends for attaching the electrical cables to the junction box. The fitting comprises a pair of co-axial hollow, tubular, electrically conductive electrical connectors with two different diameters. The hollow tubular connector with smaller diameter (hereinafter the inner cylinder) fits inside the other hollow tubular connector with a bigger diameter (hereinafter the outer cylinder) allowing a rotation about an axis with respect to one another (hereinafter the connector). The connector has a fastening arrangement on the leading end for connecting to a junction box and has a fastening arrangement on the trailing end for connecting to the electrical cable. 
     The leading end comprises a resilient, electrically conductive strip formed in cylindrical-shaped ring (hereinafter the leading spring) that is secured and positionally fixed to the nose of the inner cylinder by means of a partial or through constraining rib on the outer diameter of the inner cylinder nose that fits in the gap between the two ends of the ring and obstructs the leading spring axial rotation. 
     A plurality of locking prongs (hereinafter the locking prongs) are lanced radially and bent outward in a flat, concave, or convex shape at an angle with respect to the normal cross section plane of the connector. A pair of secondary plurality of tangs (hereinafter the centric tangs) is lanced outward radially next to the locking prongs and it constrains the connector lateral movement and provides further grounding. The outer cylinder has a plurality of openings on the protruded leading end (hereinafter the collar) out of which the locking prongs and centric tangs extend. 
     When the outer cylinder rotates radially in a disengaging direction on the inner cylinder, the openings are displaced and the respective edges of the openings force the locking prongs and centric tangs to retract in place in a circular pattern. The disengaging direction can be clockwise or counter clockwise depending on the direction of the locking prongs cut. 
     When the outer cylinder is released, it rotates in a direction opposite to the disengaging direction and the openings go back to their original location allowing the locking prongs and centric tangs to extend through the openings. The locking prongs edges dig into the interior surface of the electrical panel or junction box opening when released providing a secure attachment to the electrical panel while the centric tangs constrain the lateral movement of the fitting in the electrical panel. 
     The trailing end comprises a resilient, electrically conductive strip formed in a cylindrical-shaped ring (hereinafter the trailing spring) that is secured and positionally fixed into the interior surface of the outer cylinder on the trailing side by means of a partial or through constraining rib inside of the outer cylinder trailing end that fits in the gap between the two ends of the ring and obstruct the spring axial rotation. 
     A plurality of eccentric helical strips are lanced radially towards the central axis of the connector with flat ends having longitudinal protrusions that are bent inwardly to a smaller diameter than the outer diameter of the electrical cable in conjunction with which the fitting is used (hereinafter the trailing prongs). The leading ends of the trailing prongs are ragged to enable each prong to engage a trough in the armor surface of the electrical cable and thereby hold it fast to the trailing end of connector. 
     The tight engagement of the trailing prongs to the trough areas of the cable provides good surface contact between the trailing tangs and the cable, thus improving electrical continuity and grounding between the cable, the fitting, and the panel or junction box. 
     The inner cylinder has a plurality of openings matching the number of trailing prongs through which the trailing prongs pass to engage with the electrical cable. When the connector rotates to disengaging position, the longitudinal edges of the openings lift up the eccentric strips and consequently lift the trailing prongs to disengage them from the electrical cable while the leading end of the connector pushes the front spring prongs inside the collar. The described mechanism enables attaching the electrical cable to the fitting and inserting the fitting into the knock out hole on the electrical box at the same time. 
     Since the leading spring and the trailing spring are both in deflected state, after positioning the fitting into the knock out hole and the cable into the fitting, the entire assembly will lock automatically in place by releasing the fitting. Likewise if it is necessary to disconnect the cable from the electrical box, the contractor will rotate the connector to a disengaging position and the whole fixture unlocks, permitting removal of either the cable or the fitting or both. One or multiple sets of stops in the form of ribs or pins and channels can be incorporated into the fitting to guide and restrict the angular displacement range. In alternative embodiments of the invention, the leading and trailing springs may be comprised of two or more spring segments which are assembled to form a ring. 
     Therefore a secure and tool free method of installation or removal is made possible with minimal of effort and force applied, while maintaining a very good grounding on both ends of the connector. 
     The novel features which are characteristic of the invention, both as to structure and method of operation thereof, together with further objects and advantages thereof, will be understood from the following description, considered in connection with the accompanying drawings, in which the preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only, and they are not intended as a definition of the limits of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perpective view of a preferred embodiment of two spring lock electrical fittings according to the present invention attached to an electrical junction box. 
         FIG. 2  shows a perspective view of the spring lock electrical fittings of  FIG. 1  in alignment with an electrical junction box with the exploded fitting in disengaged and locked orientations. 
         FIG. 3  Including  FIGS. 3A-3D , shows an outer cylinder of the fitting in a side view, an end view a sectional view taken along line D-D in  FIG. 3A  in the direction of the appended arrows and a perspective view; 
         FIG. 4  including  FIGS. 4A-4D  shows an inner cylinder of the fitting in a side view, an end view a sectional view taken along line C-C of  FIG. 3B , in the direction of the appended arrows, and a perspective view. 
         FIG. 5  is a top view of a blank that can form the leading spring of the fitting. 
         FIG. 6  including  FIGS. 6A-6C  shows the leading spring of  FIG. 5  in its natural state in an end view, a side view and a perspective view. 
         FIG. 7  including  FIGS. 7A ,  7 B shows a spring lock electrical fitting of the present invention in locked configuration in an end view and a perspective view. 
         FIG. 8  shows a blank that forms the trailing spring of the fitting. 
         FIG. 9 , including  FIGS. 9A-9D  show the trailing spring of  FIG. 8  in a side view, an end view, a top view and a perspective view, respectively. 
         FIG. 10  including  FIGS. 10A ,  10 B shows a loaded leading spring in a top view and a perspective view. 
         FIG. 11  including  FIGS. 11A-11D  shows a trailing spring in its natural state in a side view, an end view, a top view and a perspective view. 
         FIG. 12  including  FIGS. 12A-12D , shows a trailing spring in its natural state in locking position engaged with an electrical cable in a side view, an end view, a top view and a perspective view. 
         FIG. 13  including  FIGS. 13A-13D , shows a loaded trailing spring in its deflected state disengaged from an electrical cable in a side view, an end view, a top view and a perspective view. 
         FIG. 14  including  FIGS. 14A-14D , shows a side view and three sectional views of a fitting attached to an electrical panel with the two springs, the sectional views being taken along lines p-p, r-r and u-u of  FIG. 14A  in the direction of the appended arrows. 
         FIG. 15  including  FIGS. 15A-15C , shows a spring lock electrical fitting in locked position attached to an electrical panel in a side view, in a section view taken along line N-N of  FIG. 15B  in the direction of the appended arrows and in a perspective view. 
         FIG. 16  including  FIGS. 16A-16C , shows a spring lock electrical fitting in compressed position attached to an electrical panel in a side view, a sectional view taken along line M-M of  FIG. 16A  in the direction of the appended arrows and in a perspective view. 
         FIG. 17  including  FIGS. 17A-17C , shows the cross section view U-U of  FIG. 14B  with two broken top views of  FIG. 4A  depicting two alternatives of the stopper mechanisms. 
         FIG. 18  including  FIGS. 18A-18D , shows an alternative design of the spring lock electrical fitting in locked position in a side view and attached to an electrical panel in a sectional view taken along the line B-B of  FIG. 18A  in the direction of the appended arrows, a perspective view and an end view. 
         FIG. 19  including  FIGS. 19A-19D , shows the alternative design of  FIG. 18  in the released or disengaged position in a side view and attached to an electrical panel in a sectional view taken along line A-A of  FIG. 19A  in the direction of the appended arrows, a perspective view and an end view. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning first to  FIGS. 1 and 2 , the present invention provides an electrical fitting  2  that secures a flexible electrical cable conduit  1  to an electrical panel or junction box  3  through the knock out hole  4  shown in  FIG. 1  and  FIG. 2 . In the present configuration, fitting  2  connects a flexible electrical conduit  1  which supports a plurality of electrical wires (not shown) to the electrical junction box  3  enabling a secure connection while it establishes a conductive path. Furthermore the fitting of the present invention enables spring lock engagement of the fitting  2  to the electrical junction box  3  on its leading end and spring lock engagement of the flexible electrical cable  1  to the fitting  2  on the trailing end of it. The flexible electrical cable conduit  1  generally consists of an outer metal sheath that has been formed from a strip of metal that has been helically wound and interlocked to produce a contour forming crowns  71  and troughs  72 . (depicted in  FIG. 14 .) 
       FIG. 2  shows two exploded views of a version of the present invention where each set of fittings  2  is aligned with an electrical junction box  3  and a flexible electrical cable  1 . The top figure is an exploded view of the fitting  2  that shows the fitting assembly  20   a in loaded state ready for insertion into the knock out hole  4  of the electrical junction box  3  along the axis  5 . The bottom figure is an exploded view of the fitting  2  shows the fitting assembly  20   b in the natural spring state of the components (hereinafter locked state). As shown in  FIG. 2  the fitting assembly consists of a plastic insulator  7 , a leading spring ring  10 , an outer tubular electrically conductive cylinder  200  that slides about the axis over an inner tubular electrically conductive cylinder  8 , and a trailing spring ring  9 . 
     As is generally shown in  FIGS. 2 and 3 , the tubular electrically conductive cylinder  200  is comprised of a tubular housing  11  with a smaller diameter collar  12  on the leading end that has a plurality of openings  13  which covers over leading spring ring  10 , a recessed area  14  where it accommodates the trailing spring ring  9 , a partial or through embossed rib  15  on the inner wall of the recessed area  14  that restrains rotary movement of the trailing spring ring  9  with respect to the housing  11 , and a plurality of ribs  16  (hereinafter outer stoppers) on the inner wall of the housing  11  to restrain axial rotation of the trailing spring ring  9 . 
     In the present illustration, one pair of outer stoppers is shown. Further it has a plurality of longitudinal strip bosses  17  around the peripheral of the tubular housing  11  for better grip. Additionally there is plurality of through openings  21  on the tubular housing  11  for the installers to visually check the location of the electrical cable (not shown) inside the fitting  2 . 
       FIG. 4  shows the next component of the fitting  2  which is an inner tubular electrically conductive cylinder  8  that has a secondary gripping area  26  with a plurality of gripping ribs  27  close to the trailing end  25 . The gripping area  26  further steps down to a cylindrical middle area  28  where it has a plurality of openings  29  and a plurality of ribs  30   a ,  30   b    30   c , and  30   d  (hereinafter inner stoppers) on the outer diameter that set the axial rotational range of the fitting assembly in cooperation with outer stoppers  16 . The middle area  28  further steps down in diameter to form the leading nose  31  of the inner cylinder where it defines the seat  32  for leading spring  10  (not shown) between the stepped down nose section  36  and the tip flange  33 . A partial or through embossed rib  34  runs longitudinally between step  36  and flange  33  to restrain rotary movement of the leading spring ring  10  with respect to the inner cylinder  8 . On the leading end,  24 , the cylinder is necked down to receive the plastic insulator  7  in the circular opening  35 . 
       FIG. 5  shows the leading spring ring  10  that is typically made of resilient material like spring steel alloys. Referring to  FIG. 5 , the leading spring ring  10  is formed out of a blank strip  48  that is formed to a circular shape making the cylindrical base  49  that further contains a plurality of tangs  37  and prongs  38  cut out from it. The tangs  37  and prongs  38  are bent outward, away from the ring axis  5 . They can be lanced in to concave, convex, or flat shapes. The two ends  45   a ,  45   b  of the strip blank  48  form the gap  85  (seen in  FIGS. 6A ,  6 C) when rolled into a circular ring. 
     Referring to  FIG. 6 , each prong  38  is bent in a convex form making a curled up, cantilever spring prong  38  with a parallelogram section having one end  39  integral with cylindrical base  49  and other free end  40 . The parallelogram cantilevered prongs lean towards the trailing edge  44  of the leading spring ring  10  enabling the tip of the prong edge  40  to dig in to the inner wall of the panel plate  6  of the electrical box  3  (see  FIG. 1 ). Each tang  37  is bent outward, making a cantilever spring with a rectangular section and one end  46  that is integral with the cylindrical base  49  adjacent to the prong end  39  with other end  47  free. Each flat tang  37  is paired with a curled up prong  38 . In locking position, the free end  47  of each tang  37  is in contact with the inside bore of the hole  4  on plate  6  (as seen in  FIG. 1 ). 
     The leading spring ring  10  has a smaller diameter than the  32  of the inner cylinder  8 . Therefore, when it seats on the seat  32 , the ring is completely fixed in place. The spring longitudinal movements are restrained by the step  36  and the flange  33  while its axial rotation is constrained by the rib  34 . The collar  12  of outer cylinder  200  slides over the seat  32  of the inner cylinder  8 , sandwiching the leading spring ring  10  in between. The openings  13  on the collar  12  that match in number of sets of prongs  38  and tangs  37  on the leading spring ring  10  govern the state of the leading spring ring  10  to the disengaged or locking state by rotating either the inner cylinder  8  or the outer  200  cylinder about the axis  5 . 
     When the fitting  2  is in locking position, the prongs  38  dig in to the inner wall of the electrical junction box and constrain the fitting  2  from axial movements along axis  5 . At the same time, the tangs  37  push against the knock out hole  4  inner bore constraining radial movements. Hence, the fitting locks in place tightly while providing a secure electrical continuity through prongs  38  and tangs  37 . 
       FIG. 7  shows the axial rotational directions of the fitting in order to lock it or disengage it. When the fitting is in locking state, the openings  13  are over the prongs  38  and tangs  37  allowing them to stick out through the openings  13 . To disengage, the outer cylinder rotates about the axis in disengage direction with respect to the inner cylinder shown in  FIG. 7 . 
     As the cylinders rotate, the longitudinal edges  20  of the openings  13  ( FIG. 3B ) which are adjacent to the integral ends  39  and  46  ( FIG. 6 ) of the respective prongs  38  and tangs  37  roll over the prongs  38  and tangs  37  forcing them downward radially towards axis  5 . The prongs  38  and tangs  37  disengage from the hole  4  inner bore to a diameter smaller than the knock out hole  4  and the collar  12  allowing the fitting to be easily removed. 
     Referring to  FIGS. 8-13 , the trailing spring ring  9  is formed out of a blank strip  61  into a circular shape making a cylinder consisting of two half cylinders  70   a  and  70   b . The two half cylinders form a disjointed ring on the trailing side  68  of the spring that sits into the circular recessed section  14  of the outer cylinder  200  with a typically larger diameter than the circular recessed section  14  ensuring a fixed position inside the bore of the outer cylinder. The axial movement of the ring is constrained by the recessed section  14  and the radial rotation is constrained by the rib  15  of the cylinder  200 . 
     Further, two helix extensions  55  and  56  wind inward towards axis  5  connecting the two flat plates  52  and  53  to the cylinder. The extensions are integral with the spring ring cylinder from the ends  62  and  63  sequentially and spiraling inwardly towards the axis  5  and ending in flattened ends at a certain angle (typically between 10 to 60 degrees) with respect to the tangent plane at intersection of the flat plate  52  with curve  55  and the flat plate  53  with curve  56 . A protruded tab  57  is angled down at bent line  54   a  toward axis  5  from flat plate  52  and subsequently a shorter tab  58  is bent down at line  54   b  staggered with the former tab towards axis  5  to form a circle with smaller diameter around axis  5 . 
     Further a circular opening with a smaller diameter than the diameter of the flexible electrical cable  1  is formed by means of two curvature cuts  59  and  60  through the free ends of angled tabs  57  and  58  subsequently to create the special formed tongues  64   a  and  64   b  of the tab  57  and tongues  65   a  and  65   b  on the free end of the tab  58 . The free ends of tongue  64   b  and  65   b  are bent down even further along the two bent lines  50  and  51  to follow the helix shape of the flexible electrical cable armor. 
     The configuration of the mentioned tongues  64 ,  65 , combined with the sum of angled features and staggered positions of the tabs enables the resilient tips of the tabs  57  and  58  to adapt to the contour boundary of the helix armor of a typical flexible electrical cable. The two ends  66   a  and  66   b  of the strip blank  61  form the gap  69  when rolled in to a circular ring. 
       FIG. 9  shows the trailing spring ring  9  that is typically made of resilient material like spring steel alloys. 
       FIG. 10  shows the leading spring ring  10  loaded in a deflected form when the fitting is in disengaged state. 
       FIG. 11  shows the trailing spring ring  9  in its circular shape where the gap  69  can be plainly seen. 
       FIGS. 12 and 13 , respectively, show the metal cable in the engaged and released states.  FIG. 12  shows only the trailing spring locking on the flexible electrical cable.  FIG. 13  shows the released state with the cable unrestrained. 
       FIGS. 14 and 15  show the fitting  2  in locked position out of and in a junction box  3 , respectively. When the fitting  2  is in locked position, the leading spring tangs  37  engage the walls of the aperture. The trailing spring ring is in free form state and is fully engaged on the outer surface of the flexible electrical cable armor and the tip of the tabs  57  and  58  fall in to the trough  72  of flexible electrical cable  1  (not shown). If a force beyond the spring resistance force is applied to pull the flexible electrical cable out, the reciprocal planes  52  and  53  stop the outward movement of the spring prongs when they come in contact with the inner wall sections  73   a  and  73   b  and as a result, securing the connection tightly. 
       FIG. 15  and  FIG. 16  show the fitting  2  in disengaged position.  FIG. 16B  shows that the trailing spring is deflected and pushed outward releasing the flexible electrical cable  1 . To connect or disconnect the fitting, the outer cylinder rotates about the axis in disengage direction with respect to the inner cylinder shown in  FIG. 14 . 
     As the cylinders rotate, the longitudinal edges  22   a  and  22   b  of the two openings  29  and further the two stoppers  30   a  and  30   c  act as radial levers and lift up the spiral arms  55  and  56  of the trailing spring ring  9  and as a result, lifting the plates  52  and  53 . Therefore the locking prongs  38  that are attached to the said plates will lift up releasing the flexible electrical cable while the outer cylinder collar deflects the leading spring inside it. 
     At this point the fitting  2  is in disengaging state for installation, the flexible electrical cable  1  is inserted into the fitting  2  and the fitting  2  goes through the knock out hole  4  of the electrical panel  6 . If the fitting  2  is already installed and the contractor intends to remove it, the trailing spring ring  9  is in deflected state releasing the flexible electrical cable  1  and accordingly the leading spring ring  10  unlocks the fitting from the electrical panel  6  as described allowing removal of either the cable  1  or the fitting  2  or both. 
       FIG. 17  shows the stoppers that define the rotational range of the fitting and an alternative guiding channel to the described mechanism. The broken view on top right ( FIG. 17B ) shows the locations  16   a  and  16   b  of outer stopper  16  (of the outer cylinder) when it rests against inner stopper ribs  30   c  and  30   b  respectively. 
     The second broken view on the right ( FIG. 17C ) shows the alternative guiding channel with outer stopper  16  locations at  16   a  (locked position) and  16   c  (disengaged position) where the outer stopper  16  can be locked in the recessed niche to hold the springs deflected and the fitting in disengaged position. 
       FIGS. 18  A, B, C, and D show an alternative design of the present invention at an engaged position. The fitting  2  comprises two cylinders and two springs. The outer cylinder  80  slides over the inner one  81  with a trailing spring  83  fit to the trailing end  84  of the outer cylinder  80 . The trailing spring  83  secures the armored cable  1  in the fitting. At the same time, the leading spring  110  that is attached to the tip (nose)  86  of the inner cylinder  81  is compressed by the tailing spring force exerted on the inner cylinder pushing it back in lock direction and consequently tightening the leading spring star prongs  87  against the inner wall  88  of the junction box  3 . The trailing spring  83  is stronger than the leading spring  110  and has a plurality of prongs  89  that secures the armored cable  1  while holding the mechanism in locked position. 
       FIGS. 19  A, B, C, and D show the assembly in released position. To insert or release the fitting into or out of the knock out hole  4 , the trailing end  90  of the inner cylinder  81  that has a bigger diameter is pushed along the release direction filling the gap  91  between the stepped down portion  93  of the inner cylinder  81  and the trailing end  94  of the outer cylinder  80 . 
     As the inner cylinder  81  is pushed towards the junction box  3 , its slanted edge  95  lifts up the trailing spring prongs  89  and retracts them while providing a space  96  for the leading spring  110  to collapse back to its natural relaxed position ( FIG. 19B ). While holding the two cylinders close to one another, the whole assembly can be inserted in or taken out of the knock out hole  4 . As soon as the hold is released, the trailing spring force prevails and pushes the mechanism in to the lock position. 
     Use of the present invention saves a lot of time over traditional fittings and has more advantages over the current snapping fittings such as elimination of the need for manual use of tools to connect or disconnect as well as less effort to do it. 
     Armored electrical cables are supplied in different nominal sizes in accordance with the National Electrical Code. The spring lock electrical fitting of the present invention can therefore be produced in matching sizes to accommodate the various nominal sizes with the same concept and mechanism scaled to the pertinent sizes.