Abstract:
An adjustable hanger bar assembly including an adjustable hanger bar having tubular inner and outer bar members, an electrical box having a top wall with a deep channel therein, and a mounting plate having one or more tensioner tangs. The inner bar member is adapted to slide within the outer bar member. The adjustable hanger bar assembly includes mounting fasteners and an interior channel in which the mounting plate is assembled. With the electrical box mounted to the hanger bar assembly by the mounting fasteners, the hanger bars are tightly held between the channel walls of the electrical box. The tensioner tangs create tension between the mounting bars, the mounting plate, and the electrical box, thereby forming a secure connection between the components that will withstand vibrational forces and prevent separation of the electrical box from the mounting bars.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to electrical boxes, and specifically to an adjustable bar hanger and electrical box for mounting an electrical fan or similar device to a ceiling. 
     BACKGROUND OF THE INVENTION 
     Although many mounting devices have been proposed for mounting a heavy device such as an electrical fan to a ceiling, most such devices are substantially complex, rendering them expensive to manufacture. Also, such proposed devices, although structurally sound enough to mount a heavy electrical fan, do not adequately protect against the excessive vibrational forces generated by the rotating fan and thus transmitted to the mounting device. Over a period of time, such vibrational forces tend to loosen the connections between the mounting device and the electrical box, thereby creating a dangerous condition in which the fan and fan box are susceptible to falling from the ceiling. 
     What is needed therefore is an improved mounting device that is substantially simple and inexpensive to produce and that also substantially reduces the possibility of vibrational forces causing the electrical box to become loosened from the mounting device. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is an adjustable hanger bar assembly for mounting an electrical fan or similar device to an overhead structure. The adjustable hanger bar assembly includes an adjustable hanger bar, an electrical box, and a mounting plate. The adjustable hanger bar includes an inner and outer bar member, with the inner bar member adapted to slide within the outer bar member to create an adjustable hanger bar assembly. Each of the mounting bars includes a substantially tubular elongated bar portion and an end plate. The adjustable hanger bar assembly includes an interior channel in which the mounting plate is assembled. The electrical box includes mounting holes therein. The adjustable hanger bar assembly may be adapted to fit between two rafters or similar supports and anchored to the supports by driving fasteners through the end plates of the mounting bars. The electrical box may be loosely assembled to the mounting plate by driving mounting fasteners between the electrical box and the mounting plate. The electrical box can then be slid to any desired position along the adjustable hanger bar assembly after which the mounting fasteners are tightened thereby securing the electrical box to the adjustable hanger bar assembly. The electrical box includes a top wall with a substantially deep channel and channel walls formed therein. With the electrical box mounted to the adjustable hanger bar assembly, the hanger bars are held substantially tightly between the channel walls. The mounting plate is substantially planar and formed of substantially thick metal and includes a plurality of tensioner tangs that are bent out of the plane of the mounting plate at its outer corners. When the mounting fasteners are tightened, the tensioner tangs act to create tension between the mounting bars, the mounting plate, and the electrical box, thereby creating a substantially tight connection between the components that will withstand vibrational forces and prevent separation of the electrical box from the mounting bars. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       Reference is made herein to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
         FIG. 1  is an exploded isometric view of an adjustable hanger bar assembly, in accordance with embodiments of the invention. 
         FIG. 2  is a side view of the electrical box portion of the adjustable hanger bar assembly of  FIG. 1 . 
         FIG. 3  is a top view of the electrical box. 
         FIG. 4  is a bottom view of the electrical box. 
         FIG. 5  is a sectional view of the electrical box taken along line  5 - 5  of  FIG. 4 . 
         FIG. 5   a  is a sectional view of the electrical box taken along line  5   a - 5   a  of  FIG. 4 . 
         FIG. 6  is a bottom isometric view of the electrical box. 
         FIG. 7  is a top isometric view of the electrical box. 
         FIG. 8  is an isometric bottom view of the mounting plate portion of the adjustable hanger bar assembly of  FIG. 1 . 
         FIG. 9  is a plan view of the mounting plate. 
         FIG. 10  is a side view of the mounting plate. 
         FIG. 10   a  is a detail view of the mounting plate showing the tensioner tang. 
         FIG. 11  is a bottom view of the adjustable hanger bar assembly of  FIG. 1 . 
         FIG. 12  is an end view of the adjustable hanger bar assembly. 
         FIG. 13  is a sectional view of the adjustable hanger bar assembly taken along line  13 - 13  of  FIG. 11 . 
         FIG. 14  is a top isometric view of the adjustable hanger bar assembly. 
         FIG. 15  is a bottom isometric view of the adjustable hanger bar assembly. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , there is shown a preferred embodiment of an adjustable hanger bar assembly  20  according to the present invention. The adjustable hanger bar assembly  20  includes an adjustable hanger bar  22  that includes an inner bar member  24  and an outer bar member  26 . The inner bar member  24  is slideable within the outer bar member  26  of the adjustable hanger bar  22 , thereby creating an interior channel  28  within the adjustable hanger bar  22 . 
     The adjustable hanger bar assembly  20  includes a substantially planar mounting plate  30  including a bore  32  therein, the mounting plate  30  being slideable within the interior channel  28 . The adjustable hanger bar assembly  20  further includes an electrical box  34  that may be mounted to the adjustable hanger bar  22  with a single mounting screw  36  that is driven into mounting bore  32  of mounting plate  30  as shown in  FIG. 1  to secure the electrical box  34  to the mounting plate  30  and the adjustable hanger bar  22 . The electrical box  34  includes a top wall  38  and sidewall  40  that define an electrical box enclosure  42  therein. A channel  44  extends across the top wall  38  of the electrical box  34 . The mounting plate  30  includes one or more tensioner tangs  46  thereon. 
     With reference to  FIGS. 2-5 , the channel  44  of the electrical box  34 , which extends completely across the entire length of the top wall  38 , includes a channel bottom  48  and channel walls  50 . The top wall  38  of the electrical box  34  includes a through-hole  52  therein for enabling passage of a fastener for securing the electrical box  34  to the adjustable hanger bar assembly  20 . 
     As shown in  FIGS. 2 and 3 , the channel bottom  48  includes a bench  54  extending longitudinally along the channel bottom and a knock out wall portion  56  in the bench. The bench  54  includes two ends  57  and provides a resting surface for the mounting plate  30  when the electrical box  34  is assembled directly to the mounting plate  30 , such as for packaging of the adjustable hanger bar assembly. With the electrical box  34  and mounting plate  30  assembled together, the bench  54  enables the planar portion of the mounting plate to rest thereon on the bench  54 , and tensioner tangs  46  to extend free of the bench  54  and into the channel portions  58  between the bench and the channel walls  50 . Electrical box  34  further includes two screw receptacles  60  extending from the top wall  38  a knockout wall portion  62  in the top wall  38  between the screw receptacles  60 . 
     With reference to  FIGS. 4 and 5 , the screw receptacles  60  include bores  64  therein, which bores are in open communication with the electrical box enclosure  42 . A captive screw  66  (see  FIG. 5 ) is held therein in each of the bores  64 , one of which is visible in  FIG. 5 . Within the enclosure  42 , the electrical box further includes a raised surface  68  extending across the top wall  38 . The raised surface  68  includes two ends  70  and a boss  72  extending from each end  70 . The bosses  72  are integral with the sidewall  40  of the electrical box and include a through-hole  74  therein. Through-hole  52  extends through the raised surface  68  of the electrical box and a peripheral wall  76  extends from raised surface  68  and surrounds the through-hole  74 . 
     Referring to the isometric views of the electrical box  34  in  FIGS. 6 and 7 , the bottom view in  FIG. 6  depicts the electrical box enclosure  42 , the raised surface  68 , and the bosses  72  extending from each end  70  of the raised surface. The peripheral wall  76  surrounds the through-hole  74  that extends through the raised surface  68 . The top wall  38 , visible on either side of the raised surface  68 , includes one or more knockouts  62  therein. 
     The top view of the electrical box in  FIG. 6  depicts the channel  44  extending across the entire length of the top wall  38 , including the channel bottom  48  and channel walls  50 , the bench  54  with through-hole  52 , the screw receptacles  60 , and a knockout  62  in the top wall  38 . A second knockout has been removed and that side is depicted with an electrical fitting  78  seated in the knockout aperture. 
     With reference to  FIGS. 8-10   a , the mounting plate  30  is substantially planar and includes bore  32  substantially centered therein. The mounting plate  30  includes an upper surface  80 , a lower surface  82 , and two ends  84 . End bores  86  and a grounding aperture  88  are also provided in the mounting plate  30 , with the grounding aperture  88  adapted to accept a grounding screw (not shown) therein. The mounting plate is further provided with one or more tensioner tangs  46  as shown. The tensioner tangs  46  are each defined by a longitudinal slit  90  in the mounting plate  30  and each tensioner tang  46  is bent toward the lower surface  82  and out of the plane of the mounting plate. Preferably, the mounting plate is constructed of metal and is at least 0.1 inches thick, as denoted by dimension D1 in  FIG. 10   a.    
     When the electrical box is secured to the adjustable hanger bar as shown in  FIG. 11 , the grounding aperture  88  of mounting plate  30  is in alignment with the knock out wall portion  56  in the raised surface  68  of the electrical box  34 . Thus electrical box  34  may be grounded by affixing a grounding lug from the electrical box  34  to a grounding screw (not shown) that is thence driven into the grounding aperture  88 . Electrical box  34  can thus be constructed of metal or plastic as the box will be grounded through the mounting plate  30  and the adjustable hanger bars  22 . 
     Referring to  FIGS. 11-15 , each of the bar members  24  and  26  include a tubular bar portion  90  and an end plate  92 . The tubular bar portion  90  includes a top wall  94 , side walls  96 , lips  98  extending inward of the side walls  96 , and a slot  101  between the lips  98 . The end plates  92  extend from the top wall  94  of the tubular bar portion  90  and include a plurality of nailing apertures  103  therein. As shown in  FIG. 12 , the end plate  92  includes a bottom edge  105  and a tab  107  extending outward orthogonally from the bottom edge  105 . The end plate  92  further includes a slot  109  therein and a nailing flange  111  adjacent the slot. An aperture  113  is provided in one of the side walls  96  of the bar members  24  and  26  and a bar mounting screw  115  is held captive in the aperture  113 . The bar mounting screws  115  are threaded into the aperture  113  and are adapted to be removed from the apertures  113  in the side walls  96  and inserted through the end plates  92  for securing the hanger bars  24  and  26  of the adjustable hanger bars  22  to a support structure (not shown). 
     As further shown in  FIG. 12 , the end plates  92  include one or more nailing apertures  103  for acceptance of fasteners such as nails or screws for securing the adjustable hanger bars  24  and  26  to a support. End plates  92  further include three rows of slots including a lower row  119 , middle row  121 , and upper row  123 . Each successive row of slots defines a line at which the end plate can be bent along a bend line horizontal to bottom edge  105  in order to increase the distance between the mounted end plate and the bottom edge  125  of the electrical box  34 . The bar members  24  and  26  can be mounted with tab  107  flush against the bottom of a support to accommodate ⅝-inch thick wallboard. Alternatively, the end plates  92  can be bent outward at slot rows  119 ,  121 , and  123  to accommodate respectively ¾-inch, 1-inch, and 1¼-inch wallboards. 
     With reference to  FIG. 1 , the adjustable hanger bar assembly  20  is used to secure an electrical device, such as a ceiling fan (not shown), to an overhead support. The electrical box  34  is first loosely assembled to the mounting bar  30  with mounting screw  36  to form an electrical box and mounting bar assembly. The mounting bar portion  30  of the electrical box and mounting bar assembly is then slid into interior channel  28  of adjustable hanger bar  22 . The end plates  92  can be bent at any of successive rows of slots  119 ,  121 , and  123  to accommodate the appropriate thickness of wallboard. The length of the adjustable hanger bar  22  is then adjusted to the proper length to span between two overhead supports (not shown), such as ceiling rafters. Fasteners (not shown) are then driven through nailing apertures  103  to secure the mounting bars  24  and  26  and the adjustable hanger bar assembly  20  to the overhead support. The electrical box  34  and mounting bar  30  assembly is then slid to the desired location for mounting the ceiling fan or similar electrical device. Mounting screw  36  is then tightened to secure the electrical box  34  and mounting plate  30  to the adjustable hanger bar assembly. An electrical device (not shown) is then secured to the assembly  20  by removing captive screws  66  from the bores  64  in screw receptacles  60  (see  FIG. 5 ) and placing the screws  66  through through-holes  74  xx in electrical box  34  and driving them into end bores  86  of mounting plate  30 . After the assembly is tightened, tensioner tangs  46  apply pressure between the mounting plate  30  and hanger bars  24  and  26 , thereby keeping the adjustable hanger bar assembly  20  tightly secured together during vibration of the electrical device. 
     As shown in  FIG. 13 , which depicts the adjustable hanger bar assembly in its fully assembled state, the distance between the channel walls  50 , as denoted by dimension D2, is no more than 0.05 inch greater than the dimension across the side walls  96  of the outer member  26 , as denoted by dimension D3. Thus the hanger bars  24  and  26  are held in a tight fit between the channel walls  50  in addition to being tightly clamped to the channel bottom  48  by mounting screw  36  and mounting plate  30 . This tight fit of the mounting bars within the channel  44  (see  FIG. 7 ) further stabilizes the adjustable hanger bar assembly  20  and prevents loosening of the assembly during vibration of a connected electrical device. 
     As shown in  FIG. 5 , the peripheral wall  76  surrounding the through-hole  52  helps prevent accidental grounding through the mounting screw  36  (see  FIG. 13 ) when the electrical box  34  is secured to the adjustable hanger bar  22  to form the adjustable hanger bar assembly  20 . The mounting bars  24  and  26  of the present invention are preferably constructed of metal. The electrical box  34  is preferably constructed of metal or plastic. 
     Having thus described the invention with reference to a preferred embodiment, it is to be understood that the invention is not so limited by the description herein but is defined as follows by the appended claims. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiments herein were chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention.