Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to efficient fireplace units
and in particular to a unit which is adaptable for zero
clearance installation in a mobile home against any type
wallboard material. The device of this invention is designed
to efficiently consume fuel in a controlled fire with negli-
gible partially burned combustion productions being formed.
In addition the unit is designed to pressurize the room in
which it is mounted by using outside air only as the com-
bustion source of oxygen and by heating a portion of the
lQ outside air admitted to the unit for circulation into the
room. Cool room air from the floor is also circulated around
the unit.
In order to utilize a fireplace in a mobile home,
the unit must not utilize, as an oxygen source, air from
within the room to be heated. In addition, a damper or
other obstruction in the flue is not allowed. Accordingly,
a conventional fireplace would provide a safety hazard in
a mobile home.
As discussed, for example, in U. S. Patent
No. 4,059,090, owned by the assignee of this patent applica-
tion, the common domestic open fireplace heats a room pri-
marily with radiant energy from the fire, and as is well
known, the vast majority of the heat of combustion is lost
via the chimney. In addition, fuel is only incompletely
consumed creating visible smoke, sparks and the like which
exit the fireplace through a chimney.
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In addition, an open fireplace draws warm air
from within the house into an open flue with the combustion
gases. Therefore, the open fireplace not only depletes oxy-
gen within the room, but depressurizes the room so that cold
air will be drawn in through cracks and openings around doors
and windows. Accordingly, an open fireplace is a highly
inefficient heating device.
There have been past attempts to design efficient
fireplace type heating units. The above-noted patent is
one attempt whereby combustion air is drawn into the fire-
place through a controlled vent, and outside air is circu-
lated around the firebox and through the flue for heating
to be expelled into the room.
Another type unit is shown in U. S. Patent
No. 4,074,679. In this unit, however, the firebox is lined
with fir~brick to absorb heat so that the exterior of the
device will be su~ficiently cool to avoid a safety hazard.
This device, however, loses efficiency marketedly as an
air heater by utilizing firebrick between the fire, itself,
and the heat exchange surface which the air to be heated is
passed over.
It has been discovered, however, that a compact
and efficient fireplace unit can be constructed according to
this invention which will utilize outside air as a sole source
of combustion air with a controlled amount being admitted to
the firebox. Outside air also is circulated around the
firebox to be heated and expelled into the room whereby the
room is pressurized with heated air to minimize the flow of
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cold air into the structure through cracks around doors
and windows. The device of this invention then does not
depend upon oxygen within the room fGr combustion. In
addition, it has been discovered that by circulating the
combus*ion air around the firebox before admission to the
interior thereof, a much more efficient, controlled com-
bustion will take place within the unit whereby the smoke
rising from the chimney will consist almost entirely of
complete products of com~ustion and therefore will be
invisible. Furthermore, heated combustion air has been
found to facil~tate complete combustion of the fuel to a
powdery ash whereby cleaning the unit to remove the ashes
will be necessary only infrequently.
In addition, the efficient design of the device
lS of this invention permits the manufacture of a small compact
unit which may be mounted on any firm floor against any type
of wall construction material, whether plaster~oard, wood,
or the like. In extensive tests, the unit of this invention
has been found to comply with accepted standards for zero
clearance installation in mobile homes or other structures.
Accordingly, it is an object of this invention
to provide a fireplace heating unit which will utilize out-
side air exclusively as a source of combustion oxygen.
It is another object of this invention to provide
a fireplace heating unit which may be mounted directly against
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any wall material without providing a clearance or dead air
space for safety purposes.
It is yet another object to provide a fireplace space
heating unit which will efficiently heat outside air and room
air and expel the heated air into the room whereby the structure
will be pressurized against the admission of cold air from
around windows, doors, and the like.
It is still another object of this invention to provide
a metal zero clearance fireplace unit which will efficiently
preheat combustion air so that the fuel consumed in the unit
will be completely consumed and the pollutants expelled there-
from into the atmosphere will be negligible.
The present invention accordingly provides an isolated
fireplace, space heater for utilizing the heat of combustion of
fuel therein to heat the interior of a structure without with-
drawing air from the interior of said structure for combustion,
comprising: a firebox having a floor, back, and two sides adapted
to be disposed within a structure to be heated; hood means
mounted on the upper portion of said firebox for collecting
gaseous products of combustion from said box; flue means in
communication with said hood means for venting said products to
the atmosphere external to the structure; a first metal skin
surrounding the floor, sides, and back of said firebox, and said
hood means, said first skin being spaced therefrom to define
with said box and hood means a first air passage between the
outer surface thereof and the inner surface of said skin; means
carried by said device for admitting outside air to said air
space and for circulating said air therethrough; vent means
carried by said first skin for venting outside air from the
passage into the interior of the structure to be heated whereby
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when fuel is consumed in said firebox outside air will be
circulated therearound and vented into the structure; door means
coupled to the front of said device for enclosing said firebox
and said first skin to isolate the interior of said firebox
from the interior of the structure; control means disposed with-
in the air passage for diverting a portion of the air therein
into the firebox to supply combustion air when fuel is consumed
therein; insulating means surrounding the outer surface of said
first skin for minimizing heat loss therefrom when fuel is
consumed in said firebox; and a second skin surrounding the
sides, back, floor and upper portion of said first skin and
spaced therefrom to define a second air passage; flow means -
carried by said device for circulating air from within the
structure through said second passage.
These and other objects will become readily apparent
with reference to the drawlngs and following description wherein:
FIGURE 1 is a perspective view of a unit according to
this invention without the flue.
FIGURE 2 is a cross-sectional view of the device with
a portion of the insulating material removed and the inlet and
flue pipes broken away.
FIGURE 3 is a top view of the device of FIGURE 1 with
top portions reviewed to illustrate the interior structure.
FIGURE 4 is a cross-sectional view taken along line
4-4 of FIGURE 2.
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FIGURE 5 is a view similar to FIGURE 4 taken along
line 5-5 of FIGURE 2 and showing an optional damper in the
flu~.
FIGURE 6 is a fragmentary view of the optional
damper shown in FIGURE 5.
FIGURE 7A is a fragmentary view taken along line
7-7 of FIGURE 6 showing the damper stop with the damper in
the fully open position.
FIGUR~. 7B is a view similar to FIGURE 7A illus-
trating the damper stop with the damper in the fully closed
position.
With attention to the drawings and to FIGURES 1-3
in particular, the device o~ this invention includes a fire-
box 10 which mounts, preferably, a log retainer 12 on the
floor thereof. Firebox 10 consists of right and left sides
14 and 15, a floor 16, a back 17 and a hood 18. Hood 18
connects the upper portion of box 10 to a flue 20.
PrPferably fuel is placed between the retainer
12 and the back 17 o~ firebox 10. However, as wi~l be
obvious to those skilled in the art, andirons may be sub- -
- stituted for retainer 12, if desired. The products of
combustion then leave the firebox 10 through hood 18 and
enter the flue 20 and exit to the atmosphere.
Firebox 10 and hood 18 are surrounded by a first
metal skin 22 on both sides, the back, bottom, and top. The
outer surface of skin 22 mounts an insulat;on sheath 24.
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The sheath 24 is prefera~ly a silica-alumina felt such as
Fiberflax. Fiberflax 1/2 inch Duri-blanket felt has a
density of 6 pounds per cu~ic foot, and will withstand
2300~F on a continuous basis with a melting point above
3200F. Fiberflax is a trade~ark of The Carborundum
Company of ~iagara Falls, New York.
As shown in FIGURE 3, vertical channel spacer
mem~ers 26 separate the fire~ox back 17 and the first metal
- skin 22 to proviae a space for the circulation of air to be~armed. In addition, fire~ox 10 is mounted on feet 28.
A conduit 30 extends through an opening in the bottom of
skin 22 to provide outside air to be heated. The outside
air pre~erably is drawn into the device by a fan ~not
shown~- As will be o~Yious to those skilled in the art,
the ~Jent (,not shown) for conduit 30 should be controlled
so that it may ~e fully closed when the fireplace of this
invention is not in use. Air to be heated then enters the
device through conduit 30 and circulates in the space be-
tween the firebox and the inner surface of skin 22. A
portion of this air enters the firebox 10 through a plurality
of ports 32 mutually spaced along the front portion of sides
14 and 15.
With attention to FIGURES 2 and 4, a preferred
embodiment of this invention utilizes a com~ustion control
assembly 34 to control the combustion air admitted through
ports 32. The control assembly consists of a housing 36
which surrounds ports 32. ~ous m g 36 contains a baffle ¦
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plate 38. Combustion air enters assembly 34 through a
port 40. Port 40 is controlled, preferably, by a door 42
pivotally mounted on housing 36. An exterior handle 44 is
provided so that the door may be opened and closed.
S Combustion air then enters port 40 and circulates
around baffle plate 38 to be admitted to firebox 10 through
ports 32. As will be obvious to those skilled in the art,
port 40 may be located as shown in FIGURE 4, or it may be
located in the bottom portion of housing 36 with an internal -
circulation in the opposite direction and with baffle plate
38 disposed accordingly. The purpose of the control assembly
is to further preheat the combustion air, as will be sub-
sequently explained. Combustion air circulates around
firebox lO, enter~ port 40 and circulates around ~affle
plate 38 whereby it becomes heated before being admitted
to the interior of firebox lO through ports 32.
As shown in FIGURES 1 and 5, the first metal skin
22 also mounts a vent opening or grille 46 along the upper
portion thereof directly in front of hood 18. Therefore,
2Q air circulating around the firebox lO will exit into the
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room to be heated through vent 46. Vent 46 may then be
closed or opened in the conventional fashlon to control the
flow of heated air from the device of this invention into
the room. Glass doors 48 are also provided to control access
to the interior of firebox lO. Doors 48 preferably have a
wire mesh 50 covering the inner surface thereof. Doors 48
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are intended to ins.ure that no room air enters the firebox
10 to exit the room through flue 20, except, of course,
when fuel is being placed into the firebox 10. In addition,
room air cannot be admitted into the space between the
walls o~ fire~ox 10 and the first skin 22. Therefore, the
fire~ox is totally isolated, and cannot deplete the oxygen
within th.e room to be heated. Furthermore, since outside
air is continuously circulated around the fire~ox and
expelled through vent 46 into the room, the room will be
pressurized by this flow of heated air.
The base 54 of the.first skin 22 is supported by
feet 56, which in turn rest on the floor. The ~uilding
codes require a hearth.extension in front of the fireplace.
~owever, the device of this invention could safely be placed
on a wooden ~loor.
~he device of this invention is further insulated
by a second skin 60 which surrounds the first skin on three
sides and on the front corners thereof. Skin 60 is separated
from skin 22 by a plurality of channel shaped, vertical
spacers 62, as shown in FIGURE 3. The top 64 of skin 60
forms a plurality of vents 66. As shown in FIGURE 2, room
air enters the space ~etween the insulated surface 24 of
.. s.kin 22 and the inner surface of skin 60 at the bottom
thereof and circulates upwardly around the first skin 22 to
exit at vents 66. A central opening 68 is provided for flue
20 and to permit the flow of heated room air upwardly around
the flue 20.
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As shown in FIGURES 5, 6, 7A and 7B, a damper may
be provided in flue 20 if desired. The damper consists of
a circular disc 70 mounted on a rod 72 and including a
damper stop 74. The damper stop 74 permits movement
from a fully open position as shown in FIGURE 7A to a
fully closed position as shown in FIGURE 7B. In mobile
home construction, however, safety requirements do not
permit the use of a damper. Therefore, if the device of
this invention is to be utilized with a mobile home, the
damper shown, for example, in FIGURES S and 6, would not
be included. The necessity for a damper is obviated by the
ability to close vent 36 and inlet 42 on control assembly 34.
In addition, a~ out~ide vent on conduit 30 could be pro-
vided to eliminate the flow of outside air to thé fire-
box 10.
The device of this invention then may be mounted -~
against any floor or wall material, and may be fully boxed
or enclosed within such materials. In addition, the device
of this invention could be externally mounted with a canti-
20 lever support in, for example, mobile homes. The need for
costly footings is eliminated, but if the fireplace of this
invention is installed in a mobile home, it should have leg
straps or similar bracing material secured to the foundation
of the mobile home so that the device will not be able to
move when the mobile home is being transported. The fire-
box 10 is preferably constructed of stainless steel with
the hearth and back of 14 gauge and the sides, front, and
hood of 16 gauge. The first skin 22 may be constructed of
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galvanized steel preferably of 26 gauge. The insulation 24
is preferably a 1/2 inch thick sheath of Fiber~lax insula-
tion, and the outer skin 60 is preferably also 26 gauge
galvanized steel. The space between the firebox 10 and
the first skin 22 is prefera~ly 4 inches.
In tests conducted with the device of this inven-
tion to determine compliance with UL 127 standard for
factory built fireplaces, it was found that the maximum
temperature rise at the zero clearance to the test unit
for a radiant fire was 58F above the ambient temperature.
The maximum temperature rise above ambient at the zero
clearance to the test structure for a brand fire was 89F.
The maximum temperature rise at the zero clearance to the
test unit ~or a flash fire was 106F above ambient. Accord-
ingly, the device of this invention was found to comply with
the above-identified standards.
In summary then, the device of this invention
comprises a compact zero clearance fireplace unit which is
fully isolated from the interior to be heated whereby out-
side air supplies combustion air and air to be heated and
- expelled into the room surrounding the fireplace. By pre-
heating the com~ustion air through the circulation of said
air around the firebox and preferably through a combustion
control assembly of this invention, a plasmatic effect is
produced. The combustion air may be preheated up to for
example 400F before it is admitted to the firebox. The
result is virtually complete combustion of the fuel at a
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rate controlled by the amount of combustion air admitted
to the firebox. The products of combustion expelled through
the flue have been observed to be virtually invisible as
compared to standard fireplaces which produce smoke, sparks,
and the like.
Accordingly, the device of this invention is a
highly efficient heating unit adapted for use in mobile
homes or other structures which is light in weight and
occupies a minimum of floor space. Because of the com~ined
insulating effects of the Fiberflax and the room air circu-
lating around the first skin, the device may be mounted ~.
against any wall paneling material without danger of fire,
or may be fully enclosed.
The invention may be embodied in other specific
foxms without departing from the spirit or essential
characteristics thereof. The present embodiment is there-
fore to be considered in all respects as illustrative and
not restrictive, the scope of the invention being indicated
by the appended claims rather than by the foregoing
description, and all changes which come within the meaning
and range of equivalency of the claims are therefore
intended to be embraced herein.
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