Electrical junction box for support of a hanging appliance

An electrical junction box for supporting a hanging load includes a base plate and a sidewall extending from it. The base plate has a pair of square bolts holes at opposite positions next to the sidewall. The sidewall has a pair of tabs bent inward, each tab having a bolt hole aligned with one of the square bolt holes. A square necked carriage bolt extends through each square bolt hole and its aligned tab bolt hole, with a lock nut on each of the bolts for supporting the hanging load. A spacer sleeve surrounds each of the bolts, between the base plate and the tabs, forming a rigid structure when the nuts are tightened. The sidewall further includes mounting holes for side mounting of the junction box for a supporting structure, permitting flush mounting of the box relative to a ceiling.

BACKGROUND OF THE INVENTION 
This invention relates to an electrical junction box providing mechanical 
support and electrical connection to a hanging appliance such as a ceiling 
fan or lighting fixture. 
Typically in the prior art, ceiling junction boxes are fastened to 
supporting structure by fasteners inserted vertically into the supporting 
structure, and a hanging appliance is suspended from the junction box by 
vertical screw fasteners threaded into tabs bent inwardly from the 
depending sidewalls of the box. Inherently in such an arrangement, the 
junction box is not flush with the supporting structure but hangs below 
it; and the threaded tabs, being typically about 1/16th inch thick, 
provide limited structural strength to the screw fastening of a hanging 
appliance. 
In 1987, the National Electrical Code was amended to prohibit the use of a 
standard electrical junction box as the sole support of a ceiling fan. 
Junction boxes must henceforward be specifically designed and approved for 
that purpose. 
It is an object of this invention, therefore, to provide an electrical 
ceiling junction box which is suitable both for flush mounting relative to 
a ceiling and for improved structural strength and integrity for mounting 
a hanging appliance. 
SUMMARY OF THE INVENTION 
Briefly, the invention may be summarized as: an electrical junction box for 
supporting a hanging load and including a base plate having adjacent 
opposite side edges thereof a pair of bolt holes, a sidewall integral with 
and projecting downwardly from the periphery of the base plate and 
containing holes for side mounting of the box on a supporting structure, a 
pair of opposed tabs projecting inwardly of said sidewall adjacent its 
lower edge, each tab having a tab bolt hole in alignment with one of the 
base plate bolt holes, a carriage bolt extending through each base plate 
bolt hole and its aligned tab bolt hole, and a lock nut on each bolt for 
securing a hanger bracket to the bottom of the box. A spacer sleeve may 
surround each bolt, between the base plate and tab, to form a rigid 
structure, and the carriage bolts may have square or ribbed necks seated 
in correspondingly shaped bolt holes in the base plate to prevent rotation 
of the bolts relative to the plate.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1, a ceiling joist 4 and ceiling 6 are shown 
representing the environment and mounting support for the electrical 
junction box of this invention, generally represented at 10. Junction box 
10 is formed of a single piece and includes a base plate 12 and a 
peripheral depending sidewall 14, the plate and sidewall together forming 
a box or space to make appropriate connections among incoming electrical 
wires. The base plate 12 includes a central aperture 16 for conduit or 
wiring, and the sidewall may include a plurality of conduit or wire 
apertures 18 appropriately spaced around its periphery. Where mention is 
made of conduit apertures or of other apertures in the junction box, it is 
to be understood to include those partially blanked apertures in which a 
blank disk remains to be knocked out to open an aperture for use. Such is 
the standard finished form of junction boxes as manufactured. The 
structure thus far described is well known and typical of the prior art. 
As shown in FIG. 2, the sidewall 14 includes, at opposite locations on its 
periphery, a pair of inwardly extending tabs 20. These tabs are part of 
the same sheet metal of which the junction box is formed, and are bent 
inwardly so as to be generally in parallel to the plane of the base plate 
12. Tabs 20 include elongate bolt holes or slots 22, which are aligned 
longitudinally with each other. 
Referring again to FIG. 2, the base plate 12 includes a pair of square bolt 
holes 24 registering with bolt holes 22 in the tabs. Within each of the 
square holes 24 a square neck carriage bolt 26 has a head 25 press fit 
non-rotatably therein and has an externally threaded shank extending 
through spacer sleeve 30 and a bolt hole 22 in the registering tab 20. At 
its lower end each bolt 26 extends through a circular opening in one of a 
pair of opposed flanges 31 on a conventional mounting bracket 32 for a 
hanging appliance. A locking nut 28, such as for example an interference 
type nut, is threaded onto the lower end of each of the carriage bolts 26 
to secure bracket 32 snugly against the underside of the box 10. Each 
sleeve 30 surrounds one of the carriage bolts 26 and extends from the 
inner surface of base plate 12 to the inner surface of a tab 20, thereby 
forming a reinforcement spacer or cylinder. 
As shown in FIG. 1 and 2, the sidewall 14 of the junction box 10 further 
includes a pair of mounting holes 40 on one side. Wood screws 42 extend 
through mounting holes 40 and are screwed laterally into the joist 4 for 
mounting the junction box. With this mounting arrangement, the box may be 
mounted flush with the ceiling 6, as shown, or at any position relative to 
the ceiling, whether recessed or protruding, as desired. 
FIG. 3 shows a prior art junction box 50 and will be helpful as a point of 
reference from which to distinguish the junction box of this invention. 
Junction box 50, like junction box 10 is formed of a single piece and 
includes a base plate 52 and a peripheral depending sidewall 54. The base 
plate 12 includes a central aperture 56 for conduit or wiring, and the 
sidewall includes a plurality of conduit or wire apertures 58 around its 
periphery. The sidewall 54 includes a pair of inwardly extending tabs 60. 
The similarity of prior art junction box 50 with the junction box 10 of 
this invention ends at this point. Tabs 60, for example, include threaded 
bolt holes 62 into which bracket-mounting carriage bolts (not illustrated) 
are adapted to be threaded upwardly into the tabs 60 to support a bracket 
(e.g. bracket 32) directly from tabs 60. The junction box 50 further 
includes one or more mounting holes 70 in its base for accommodating 
vertically disposed screws (not illustrated) used to secure the top of box 
50 flush against the underside of a ceiling or ceiling joist. 
In the prior art arrangement of FIG. 3, whatever mechanical load is applied 
by carriage bolts to tabs 60 is borne only by the relatively insubstantial 
threaded connection of the carriage bolts in the thin tabs 60, and the 
portions of these tabs integral with the sidewall 54. The associated 
carriage bolts are not additionally supported by the base plate 52, and no 
other reinforcement is provided. In addition, with this mounting 
arrangement, the junction box necessarily hangs down from its mounting 
structure and is therefore not flush with the ceiling but protrudes from 
it. 
By comparison, in the present invention the load on the carriage bolts 26 
is supported by positive locking engagement of the carriage bolts and the 
base plate 12. The total tensile strength of the hanging system is 
dramatically increased because the forces are not concentrated on the tabs 
20 but are distributed over the base plate of the box in the general area 
of the carriage bolt heads. The bolt holes or slots 22 in the tabs 20 are 
not threaded, and tabs 20 therefore do not in any way support bracket 32, 
but instead merely serve as guides for the carriage bolts 26, and supports 
for spacers 30. The reinforcing spacer sleeves 30 prevent undue bending of 
the tabs 20 and also permit the nuts 28 on carriage bolts 26 to be 
tightened down on the mounting bracket 32, thus providing greater rigidity 
and strength to the system. Furthermore, the lateral mounting arrangement 
provided by lag bolts 42 permits the underside of box 10 to be mounted 
flush with the ceiling, or to be recessed relatiee to it, as desired. 
One of the advantages of using the spacer sleeves 30 is that, when used 
with bolts 26 that are threaded for substantial portions of their lengths, 
the sleeves 30 cover the threaded portions of the bolts within the box 10, 
thus preventing the bolt threads from damaging electrical wires in the 
box. In this connection, instead of using the spacers it would be possible 
to use bolts 26 which are threaded only adjacent their lower ends, and 
which present smooth peripheral surfaces within box 10. It is not 
necessary that these latter bolts have external shoulders which engage the 
upper surfaces of the tabs 20. It is necessary only that the associated 
nuts 28 hold the heads 25 of the bolts securely against the base plate 12, 
so that substantially the full weight of the appliance supported by 
bracket 32 will be transmitted to plate 12. 
While this invention has been illustrated and described in connection with 
only certain embodiments thereof, it will be apparent that this 
application is intended to cover any such further modifications as may 
fall within the scope of one skilled in the art or the appended claims.