Patent Publication Number: US-9853370-B2

Title: Single fastener electrical connector

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 14/691,764, filed Apr. 21, 2015, which is a continuation of U.S. application Ser. No. 13/775,419, filed Feb. 25, 2013, now U.S. Pat. No. 9,065,191, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to connectors for creating an electrical bond between metallic conductors that are to be mechanically fastened together, such as for grounding a metallic structure through a grounding conductor. 
     BACKGROUND OF THE INVENTION 
     Safety dictates electrical grounding of exposed metallic parts of equipment housings or frames if there is a possibility that such parts could carry a current. For example, photovoltaic arrays need to be grounded because they produce electricity and are installed outdoors, exposed to the elements. Such arrays typically comprise a number of photovoltaic modules that are assembled onto a larger mounting structure and must be bonded to each other as well as to the grounded mounting structure. Bonded is used here in the technical sense to mean permanently joined to form an electrically conductive path that ensures electrical continuity and has the capacity to safely conduct any current likely to be imposed. The frames of the individual modules and the structural members on which the modules are mounted usually are made of aluminum. The aluminum is anodized to resist corrosion but the anodic coating insulates these pieces so that simple piece-to-piece contact does not electrically bond them together. 
     A common practice is to install a separate metallic grounding lug on each anodized piece. The grounding lug is mounted to the metal frame of a module by a thread-forming stainless steel screw with a star washer sandwiched between them. The grounding lug accepts a copper wire, which is forced into contact with the grounding lug by a stainless steel set screw. Thus, aside from the mounting screw, there are three parts involved in making such a bonded connection: a lug, a star washer and a set screw. U.S. Pat. No. 8,092,129 to Wiley, et al., which is incorporated by reference herein in its entirety, discloses various types of “bonding washers” that are positioned between the metallic pieces of photovoltaic modules and module supporting structures and pierce the anodic coating to create an electrical bond when the pieces are clamped together.  FIGS. 33 and 34  show a grounding lug assembly for use when only one of the metallic pieces has an anodic coating, such as for bonding a ground wire to that piece. That assembly, too, has at least three parts besides the mounting screw. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a metallic, one-piece electrical connector configured to receive a fastener and having features that grip and electrically bond two conductors as they are clamped together when the fastener is tightened. For example, the fastener may be threaded, one of the conductors may be a solar panel rack member and the other conductor may be a ground wire. 
     An electrical connector according to the invention comprises a one-piece, generally U-shaped metal body having a first leg, a second leg and a bight portion joining the legs. Each leg has an inner face, an outer face and a distal portion remote from the bight portion. The inner faces oppose one another and the distal portions are spaced to receive a first conductor between them. A first opening in the first leg and a second opening in the second leg are aligned to permit a fastener to extend through both openings. At least one outer projection is formed on the second leg and extends outward from the second leg&#39;s outer face for engaging a second conductor. A recess on the inner face of the distal portion of the first leg cradles the first conductor. At least one inner projection is formed on the distal portion of the second leg and extends inward from its inner face for engaging the first conductor. Thus, when a fastener is placed through the openings and is tightened with the second conductor abutting the outer face of the second leg and the first conductor in the recess, the outer projection(s) on the second leg is/are forcibly pressed against the second conductor and the first conductor is clamped between the legs to forcibly press the inner projection(s) against the first conductor. 
     The inner and outer projections preferably comprise a plurality of teeth adapted to embed themselves in the respective conductors when the fastener is tightened. The distal edges of the teeth preferably are substantially circular. The distal portion of the first leg preferably is outwardly convex, and the recess comprises the concave inside of the distal portion. 
     In one exemplary embodiment, the recess, the inner teeth and at least one of the outer teeth are substantially coplanar, and at least one of the outer teeth is formed on a (preferably outwardly) folded terminal portion of the second leg disposed substantially parallel to the distal portion of the second leg. Preferably, the inner teeth are respectively aligned with the outer teeth to form sets of oppositely directed teeth. 
     In another exemplary embodiment, the outer teeth are offset from the plane containing the recess and the inner teeth, preferably lying in a plane substantially normal to the plane containing the recess and the inner teeth. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Preferred embodiments of the disclosed invention are described in detail below purely as examples, with reference to the accompanying drawing, in which: 
         FIG. 1  is a perspective view of a first embodiment of the electrical connector of the invention shown assembled on a portion of a flat conductor and almost fully clamping a round conductor to the flat conductor; 
         FIG. 2  is a side elevational view of the assembly of  FIG. 1 ; 
         FIG. 3  is a side elevational view of the first embodiment of  FIG. 1  per se; 
         FIG. 4  is a bottom plan view of the first embodiment of  FIG. 3 ; 
         FIG. 5  is a perspective view of a second embodiment of the electrical connector of the invention shown assembled on a portion of a flat conductor and almost fully clamping a round conductor to the flat conductor; 
         FIG. 6  is a side elevational view of the assembly of  FIG. 5 ; 
         FIG. 7  is a side elevational view of the second embodiment of  FIG. 4  per se; 
         FIG. 8  is a bottom plan view of the second embodiment of  FIG. 7 ; and 
         FIG. 9  is a detail plan view of an optional knurled clamping surface suitable for inclusion in any embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1-4 , a first embodiment of the electrical connector of the invention comprises a one-piece, generally U-shaped body  2  preferably made of stainless steel. Body  2  has a first leg  4 , a second leg  6  and a bight portion  8  joining the legs. First leg  4  has an inner face  10 , an outer face  12  and a distal portion  14  remote from bight portion  8 . Second leg  6  has an inner face  16 , an outer face  18  and a distal portion  20  remote from bight portion  8 . Inner faces  10 ,  16  oppose one another and distal portions  14 ,  20  are spaced or can be urged apart to receive a first conductor C 1  between them. Legs  4 ,  6  have respective holes  22 ,  24  that are aligned to accommodate a fastener F, such as a threaded bolt, for securing the body to a second conductor C 2  with conductor Ci clamped between the legs. 
     The distal portion  14  of first leg  4  preferably is curved outward as shown to provide an arcuate recess  26  on its inner face that cradles round conductor C 1 . Distal portion  14  may be configured to provide a cradling recess of a different shape, for example, a V-shaped recess (not shown). Knurls  27  (see  FIG. 9 ) optionally may be formed on the inner surface of recess  26  to enhance the grip on and bond with conductor C 1 . Bonding with conductor Ci primarily occurs at the distal portion  20  of second leg  6  by means of two inner teeth  28  that project from the leg&#39;s inner face  16 . One tooth would suffice if it makes a good electrical bond; however, at least two teeth are preferred and all teeth directly oppose the longitudinal center of recess  26 , i.e., the centers of teeth  28  and the center of recess  26  lie in a common plane P 1  (see  FIGS. 2-4 ). 
     Bonding with conductor C 2  occurs at the distal portion  20  of second leg  6  by means of two outer teeth  30  that project from the leg&#39;s outer face  18 . Teeth  30  are formed on a terminal portion  32  of leg  6  that is folded outward 180° substantially flat against the remainder of distal portion  20 . Here, too, one tooth  30  would suffice if it makes a good electrical bond; however, at least two teeth  30  are preferred, the number being equal to the number of inner teeth  28 . Each outer tooth  30  preferably is aligned with a respective inner tooth  28  so as to form sets of aligned, oppositely directed teeth, all of which lie in common plane P 1 . Thus, when fastener F is installed and tightened, the clamping force exerted by the connector on conductors C 1  and C 2  acts directly along common plane P 1 , maximizing the penetrating effect of the teeth on their respective conductors. 
     Referring to  FIG. 2 , the outwardly folded terminal portion  32  of second leg  6  results in a thicker distal portion  20  and thus causes second leg  6  to be slightly inclined relative to conductor C 2 . As shown, this geometry initially focuses the clamping force of teeth  30  through a smaller area, resulting in an enhanced ability to break anodic coatings. When the fastener is tightened further for full clamping effect (not shown) the sharp distal edge of terminal portion  32  may also penetrate the coating. The damping force is optimized by keeping the distance from common plane P 1  to bight portion  8  as short as practicable and locating holes  22 ,  24  (and hence fastener F) fairly dose to common plane P 1 , preferably not more than about half the distance from common plane P 1  to bight portion  8 . 
     Teeth  28  and  30  may be any of the types of teeth disclosed in the aforesaid U.S. Pat. No. 8,092,129 to Wiley, et al., such as those shown in  FIGS. 3-8  and described at col.  7 , lines  14 - 31  thereof. The preferred tooth form is circular and the connector may have a thin coating of a material such as chromium or titanium nitride in order to achieve the desired tooth hardness so that the teeth can penetrate anodic coatings and become embedded in the underlying metal. 
     Referring to  FIGS. 5-8 , a second embodiment of the electrical connector of the invention similarly comprises a one-piece, generally U-shaped body  42 , preferably made of stainless steel, having a first leg  44 , a second leg  46  and a bight portion  48  joining the legs. First leg  44  has an inner face  50 , an outer face  52  and a distal portion  54  remote from bight portion  48 . Second leg  46  has an inner face  56 , an outer face  58  and a distal portion  60  remote from bight portion  48 . Inner faces  50 ,  56  oppose one another and distal portions  54 ,  60  are spaced or can be urged apart to receive a first conductor C 1  between them. Legs  44 ,  46  have respective holes  62 ,  64  that are aligned and located to accommodate a fastener F as described above in connection with the first embodiment. The distal portion  54  of first leg  44  similarly is preferably curved outward as shown to provide an arcuate recess  66  on its inner face that cradles round conductor C 1 . Knurls  27  (see  FIG. 9 ) and other recess shapes may be used as described above. 
     Bonding with conductor C 1  in this embodiment is similarly accomplished by means of two inner teeth  68  at the distal portion  60  of second leg  46  that project from the leg&#39;s inner face  56 . Here, too, one tooth would suffice if it makes a good electrical bond; how, at least two teeth  68  are preferred and all teeth directly oppose the longitudinal center of recess  66 , i.e., the centers of teeth  68  and the center of recess  66  lie in a common plane P 2  (see  FIGS. 6-8 ). Bonding with conductor C 2  also occurs at the distal portion  60  of second leg  46  by means of two outer teeth  70  that project from the leg&#39;s outer face  58 . In contrast to the first embodiment, however, the distal portion of second leg  46  is not folded; and outer teeth  70  are offset from plane P 2  and are centered along a plane PJ that is perpendicular to plane P 2  (see  FIG. 6 ). Tooth design options are preferably the same as those described in connection with the first embodiment. 
     The one-piece construction and configuration of the above embodiments make installation of these electrical connectors fast and easy: (1) a bolt is placed through the holes in the legs, (2) the legs are spread slightly to embrace conductor C 1 , and (3) the bolt is inserted in a predrilled hole in conductor C 2  and driven home to clamp the parts together. Some installers may find it more convenient to reverse steps 1 and 2. Either way, the result is a quick and effective electrical bond. 
     While preferred embodiments have been chosen to illustrate the electrical connector of the invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined by the appended claims.