Note: Descriptions are shown in the official language in which they were submitted.
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FIRE RESISTANT ELECTRICAL BOX
The present invention relates to electrical boxes such as junction boxes and
more
particularly, to a fire resistant electrical junction box.
BACKGROUND OF THE INVENTION
The use of fire resistant electrical boxes is known in the art. Such boxes are
used
to impede the passage of fire through a wall from one room to another. Thus,
while walls
may be made of a fire resistant material, the fire can sprf:ad through the
space between
walls and the fire will gain access to the space through electrical boxes.
A further requirement for fireproof electrical boxes is their use as junction
boxes
for containing electrical components which are needed for fighting a fire.
Thus, sprinkler
systems may be electrically actuated and/or power may lbe supplied to such
sprinklers
through suitable electrical wires. Naturally, such wires must be as resistant
as possible to
the heat of a fire.
In the prior art, various approaches have been utilized to provide electrical
boxes
which have fire resistance. Thus, as shown in U.S. Patent 3,720,783, a cover
member is
provided for a junction box which forms a tubular collar which can be broken
away along
a series of lines of weakness in order to form the front of the junction box
with the wall
surface. U.S. Patent 4,087,624 shows a collar attachment which is adjustable
in size.
It is also known to insulate the interior of the housings of the junction
boxes and
such structures are shown in U.S. Patents 3,646,244; 4,3~07,813 and 4,413,683.
An
electrical junction box which is formed of interior and exterior components is
shown in
U.S. Patent 4,667,840 wherein the junction box is manufactured of a fiberglass
material
and an interior space being filled with a material such as calcinated gypsum
which is
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allowed to harden. A hole is then drilled through the interior and exterior
boxes to permit
access to the interior of the box.
While such structures do provide a certain degree of fire resistance, the
steps of
drilling through an insulating material does provide for av path for the fire
to follow and as
well, results in a box which requires a number of steps to manufacture.
SLf~LMARY OF THE INVENTION
It is an object of the present invention to provide a fire resistant
electrical box
which is highly fire resistant while at the same time is relatively
inexpensive to produce
and is adaptable for a number of different wires.
According to one aspect of the present invention, there is provided a fire
resistant
electrical box comprising an inner box having a plurality of inner box walls
defining an
enclosure having an open side; an outer box having a plurality of outer box
walls, each of
the outer box walls being spaced from a corresponding inner box wall; an
insulating
member between each of the outer box walls and corresponding inner box walls;
the
insulating material being of a ceramic fiber blanket type; and at least one
set of aligned
apertures in one of the outer box walls and a corresponding inner box wall to
receive an
electrical wire.
According to a further aspect of the present invention, in a building having
electrical wires therein, there is provided the improvement comprising a fire
resistant
electrical junction box, the fire resistant electrical junction box comprising
an inner box
having a plurality of inner box walls defining an enclosL~re having an open
side; an outer
box having a plurality of outer box walls, each of the outer box walls being
spaced from a
corresponding inner box wall; a fire resistant insulating member between each
of the
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outer box walls and corresponding inner box walls; the fire resistant
insulating material
being of a ceramic fiber blanket type; at least one set of aligned apertures
in one of the
outer box walls and a corresponding inner box wall; a connecting member
mounted about
each one of the apertures on the outer box wall; a cover secured to the fire
resistant
electrical junction box surrounding the open side; and an electrical wire
extending
through the set of aligned apertures, the electrical wire being in intimate
juxtaposition
with the insulating material.
In greater detail, the electrical box of the present invention, as set forth
above, has
an inner box and an outer box. Both are preferably formed of a suitable fire
resistant
material and in a conventional form of manufacture, may be formed of a
suitable steel
material. Conventionally, many such boxes are of a rectangular configuration
although
other configurations such as an octagonal box may equally well be employed. A
preferred material would be a 14 gauge steel.
The inner box and outer box are each formed of a plurality of walls with the
walls
of the outer box being spaced from a corresponding wall of the inner box.
Preferably, all
walls are equidistantly spaced although other arrangements could be used if
desired.
The insulating material is one which permits the passage of a wire
therethrough
and which material will yield to the pressure of such a wire. Such materials
may be of the
ceramic fiber blanket type.
In manufacture, the two electrical boxes are formed and then a piece of
insulating
material, cut to size, is placed on the rear wall of the outf;r box and the
inner box and
outer box partially assembled. Insulating pieces are then. placed in the side
walls to
substantially fill the space between the walls.
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BRIEF DESCRIPTION OF THE DR.t~WINGS
Having thus generally described the invention, reference will be made to the
accompanying drawings illustrating an embodiment thereof, in which:
Figure 1 is a perspective view of a closed electrical box according to an
embodiment of the present invention;
Figure 2 is a side sectional view taken along the Line 2 - 2 of Figure 1; and
Figure 3 is a perspective view of the electrical bo:~ of Figure 1 with the
cover off
and being shown partially in cutaway.
DESCRIPTION OF THE PREFERRED (EMBODIMENTS
Referring to the drawings in greater detail and by reference characters
thereto,
there is illustrated in Figure 1 an electrical box which is ;generally
designated by reference
numeral 10.
Electrical box 10 is comprised of a first inner box generally designated by
reference numeral 12 and a second outer box generally designated by numeral
24.
Inner box 12 is of a suitable metallic material, preferably a steel material,
and has
an inner box back wall 14, an inner box first side wall 16~, an inner box
second side
wall 18, an inner box top wall 20 and an inner box bottom wall 22.
Outer box 24 includes an outer box back wall 26, an outer box first side wall
28,
an outer box second side wall 30, an outer box top wall 3~2 and an outer box
bottom
wall 34. Each of the outer box walls is spaced substantially equidistantly
from a
respective inner box wall.
Provided in outer box top wall 32 are a plurality of threaded couplings 36, 38
and 40. Corresponding couplings are provided in outer box bottom wall 34, with
only
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one such coupling 38' being illustrated in Figure 2. Couplings 36, 38 and 40
may be
soldered/welded to outer box top wall 32 as indicated by reference numeral 42.
Mounted intermediate inner box top wall 20 and outer box top wall 32 is a
piece
of insulation 44. Similarly, insulation piece 46 is provided intermediate
inner box first
side wall 16 and outer box first side wall 28 and a similar piece of
insulation (not shown)
is mounted between inner box second side wall 18 and outer box second side
wall 30.
Insulation piece 50 is also provided intermediate inner box back wall 14 and
outer box
back wall 26 while a bottom insulation piece 52 is provided intermediate inner
box
bottom wall 22 and outer box bottom wall 34. Each insulation piece is
preferably of the
ceramic fiber blanket type which may be manufactured of an alumina-silica-
zirconia
material. Each piece is independent of the other and inserted between the
respective
inner and outer walls.
As may be seen in Figure 2, apertures 54 are provided in outer box top wall 32
and
outer box bottom wall 34 and which apertures are generally in alignment with
the
couplings 36, 38 and 40 provided in outer box top wall 32. Similarly,
apertures 56 in
inner box top and bottom walls 20 and 22 respectively are aligned with
apertures 54.
A cover member generally designated by reference numeral 58 includes an outer
wall 60 having flanges 63 extending inwardly at all peripheral edges thereof.
There is
also provided an inner wall 64 spaced from outer wall 60i and containing
insulation
therein.
Apertures 66 are provided at the corners of outer wall 60 of cover 58 to
receive
screws 70 which are designed to engage screw holes 71 in flanges 73 which
extend
inwardly from each of the respective outer walls.
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Electrical box 10 may be attached in a conventional manner to a supporting
member such as a stud. To this end, there are included brackets 72 which are
connected
to outer back wall 26.
Interiorly of the box, there may be provided an electrical mounting bar 76 and
which is secured to inner box back wall 14 in a known manner.
In use, electrical wire 80 which may be mounted in a suitable conduit 82 screw
threadably engaged with connectors 3 8, 3 8' is gently pushed through the
ceramic fiber
blanket type insulation such that the insulation is in intimate contact with
the wire. The
wire itself is preferably of a fire resistant type and then suitable
connections may be made
interiorly of the box. Cover 58 is then secured in place.
It will be understood that the above described emlbodiment is for purposes of
illustration only and that changes and modifications may be made thereto
without
departing from the spirit and scope of the invention.
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