Note: Descriptions are shown in the official language in which they were submitted.
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COMBINATION FIREPLACE AND COOKSTOVE
The present invention relates generally to fire-
place furnaces adapted for insertion within existing
conventional fireplaces and more particularly to a combina-
tion fireplace furnace and cookstove.
Conventional fireplaces are notoriously ineffi-
cient room heaters because they draw warm room air into
the fireplace and up the chimney when used. This problem
can be solved by use of doors on the fireplace, but their
use substantially reduces the radiation of heat from a
fire in the fireplace into the room.
To improve the efficiency of such fireplaces,
several approaches have been taken. Fireplace furnaces of
the "heatalator" type are well known, in which the fireplace
itself is built with special heat outlet openings in the
front wall of the fireplace above or alongside the fire-
place opening so that air can be circulated along side
.
and rear heat exchanging surfaces of the firebox and heated
for discharge into tha room through such openings. However,
these designs all require either rebuilding or modification
; 20 of an existing fireplace or installation of the furnace
during the original construction of the fireplace.
To provide a more efficient fireplace furnace,
I designed a self-contained prefabricated fireplace furnace
for insertion within a conventional fireplace, shown in
my U.S. Patent No. 4l015,581, issued April 5, 1977. The
heater unit includes a metal firebox within a surrounding
metal jacket. Room air i6 drawn into side inlet openings
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at the front of the jacket, warmed by the firebox walls
serving as heat exchange surfaces, and then expelled back
into the room through an upper portion of the jacket,
all by natural convection. Although this heater is satis-
factory to maintain warm temperatures in a room, it
requires a considerable length of time to heat a cold
room because of the low rate of air movement through the
heater.
Use of fans to provide forced air circulation
through fireplace heaters has been previously proposed in
; U.S. Patents Nos. 2,642,859 and 2,743,720. However, use
of such fans does not entirely solve the problem because
of their tendency to move air through the heater and back
into the room before the air could be adequately warmed
because of the limited heat exchange surface area in the
heater.
I therefore devised a further improved fireplace
furnace as disclosed in my Canadian patent application,
Serial No. 328,470, filed May 28, 1979. Such furnace has a
jacketed firebox with heat exchange tubes extending through
the firebox from the airspace at the rear of the firebox
to discharge openings at the front of the firebox. This
design enables efficient use of the heat produced by a fire
by circulating room air first through the side and rear air-
space and then through the heat exchange tubes, thereby
exposing such air to progressively hotter portions of the
firebox chamber.
Although my foregoing improved design provides
optimum efficiency in a fireplace furnace, it and all other
known fireplace furnaces have two disadvantages when com-
pared to conventional free-standing woodstoves, namely,
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(1) they cannot be used for cooking, and (2) they do not
radiate heat as effectively as a woodstove.
Therefore, a prlmary object of the present inven-
tion is to provide a fireplace furnace having all of the
advantages of my prior fireplace furnaces, and, in addition,
the advantages o a woodstove: namely, the ability to cook
and radiate heat effectively.
Another primary object of the present invention
is to provide a combination fireplace furnace and cookstove
adapted for insertion as a unit into the front opening of
an existing fireplace.
The present invention is an improvement of the
fireplace furnaces disclosed in my prior U.S. patent
No. 4,015,581 and my Canadian patent application, Serial
No. 32~,470, filed May 28, 1979. It employs a firebox
portion adapted for positioning within a fireplace, and an
integral cookstove portion which protrudes orwardly from
the front opening of a fireplace into a room when the fire-
box portion is positioned within the fireplace. The cook-
stove portion includes a cooking surface, and an access
~; opening with a door for enclosing the fire chamber. The
access opening and door can be positioned either at the
front wall or a side wall of the cookstove portion. The
access door to the cookstove portion is designed to be
interchangeable among a variety of doors.
A baffle means is provided within the chamber fordirecting products of combustion forwardly from the fire-
box chamber toward the cookstove chamber for heating the
cookstove portion, generally, and the cooking surface, in
particular, be~ore such gases escape up the chimney.
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The baffle means includes a s~ationary portion within the
firebox chamber and extending into the stove chamber and
a damper portion within the firebox chamber. The damper
is pivotable between open and closed positions for
selectably allowing products of combustion from a fire
in the firebox chamber either to rise directly to flue
means for exhaustion from the firebox thereby allowing the
-ookstove portion to remain relatively cool, or to be
directed forwardly into the stove chamber. The baffle
means can also include a second stationary portion spaced
below the first portion but above the access door, extend-
ing from the front wall into the cookstove chamber. The
invention also features an airspace between the firebox
walls and the walls of the fireplace having frontal openings
for allowing ambient room air to circulate into contact
; with the outer surfaces of the firebox walls for heating.
A barrier between the airspace and the fireplace chimney
prevents room air from escaping up the chimney. A jacket
surrounding and integral with said firebox portion, having
- ZO frontal openings, and spaced apart from the firebox walls
can also be employed to enclose the airspace.
The invention can further include multiple heat
exchange tubes which extend through the firebox chamber
from the airspace at the rear of the apparatus for improving
the heating eficiency of the apparatus. Such tubes can
include a row of upper tubes extending through an upper
portion of the firebox chamber to discharge he~ted air
above the cooking surface of the cookstove portion. Within
the firebox chamber such upper tubes are integrated with
the baffle means and damper so as to cooperate both in
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heating the air contained within such tubes and in direct-
ing products of combustion forwardly into the cookstove
chamber. Lower tubes can extend from the airspace through
both the firebox and cookstove chambers to discharge
openings on each side o~ the access opening at the front
of the cookstove portion. The lower tubes are positioned
to support combustible materials and to contact the hot
ashes and coals of a fire. ~hey are positioned at an
incline downward from the front access opening so that
combustible materials, such as logs, placed thereon are
easily moved to the firebox chamber.
Baffle means can be employed within the airspace
on the sides and rear of the fire~ox portion or directing
air flow along the sides and back of the firebox and to
particular heat exchange tu~es. In addition, a,r blowers
can be provided near the front openings of the air space
for forcing additional air through the airspace and tubes,
thereby augmenting the natural convection of such air.
The foregoing and other objects, advantages and
features of my invention will become more apparent fxom
the following description which proceeds with reference
to the accompanying drawings.
In the drawings:
Fig. 1 is a front elevational view of a combina-
tion fireplace furnace and cookstove according to my
invention shown pssitioned in the front opening of an
existing fireplace.
Fig. 2 is a vertical sectional view through a
typical fireplace taken along line 2 2 of Fig. 1, and
showing the apparatus of my invention installed in the
fireplace.
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Fig. 3 is a vertical sec~ional view of the fire-
place and apparatus of Fig. 1 taken along line 3-3.
Fig. 4 is a top plan view of the apparatus of
Figs. 1-3 with top portions of the jacket removed and part
of the firebox upper wall removed to expose the dampers,
inner baffles and heat exchange tubes.
Fig. 5 ls an enlarged partial front elevational
view of the apparatus of Fig. 1 showing a solid, adjustable-
draft door in lieu of the glass, edge-draft door of
Fig. 1.
Fig. 6 is a vextical section view of the structure
of Fig. 5 taken along line 6-6.
Referring to the drawings, Figs. 1-3 disclose a
combination fireplace furnace and cookstove apparatus 10
inserted somewhat like a drawer into the opening of a fire-
place 12. The apparatus 10 includes a firebox portion 14
positioned within fireplace 12 and a cookstove portion 15
protruding forwardly from he fireplace Both portions 14
and 15 are preferably made of heavy gauge steel. The
opposite sides, back and top walls of the firebox portion
14 surround a fire~ox chamber 17. Firebox portion 14 is,
in turn, surrounded by a sheet metal jacket 16. The walls
of the jacket are spaced from the walls of the firebox
portion to define an airspace 18 therebetween through
which room air is circulated.
The front of the jacket 16 is open and sub-
stantially flush with ~he front wall of the fireplace 12.
The open front of the jacket defines front room air
inlet openings 20, 21 at opposite sides of the cookstove
portion 15 into the airspace within the jacket. The open
front of the jacket above the upper wall portions of the
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firebox portion defines a warm air outlet opening 22 through
which warm air from the furnace is discharged back into
the room.
The front openings of the jacket are covered
with a grille front 24 including a rigid grille frame 25
and grille screen 26 supported by the frame. The grille
; front extends from a flange 27 defining an inner margin
surrounding the firebox portion to outer margins terminat- -
ing outwardly beyond the outer margins of the fireplace
front opening. Those portions of the grille front extend-
ing beyond the outer margins of the jacket 16 are backed
by sheets of air-impervious backing material 28, such as
asbestos or sheet metal, as shown in Figs. 3 and 4, to
prevent room air from entering the fireplace opening
around the furnace and flowing up the fireplace chimney.
Thus, when the furnace is installed in a fireplace, room
air is forced to enter either the apparatus itself as
draft air for the fire, or the jacket for heating and re-
circulation into the room.
The firebox portion has vertical opposite side-
walls 44 (Fig. 4) meeting a vertical backwall A6. The
upper wall of the firebox portion includes a rear upper wall
portion 48 pitched downwardly and rearwardly from a top ex-
haust opening or flue 50 and a front upper wall portion 52
pitches downwardly and forwardly from exhaust opening 50.
Exhaust opening 50 extends through a top wall 54 of jacket
16 to allow for khe escape of hot gases and smoke from the
apparatus into the fireplace chimney. Exhaust opening 50
extends substantially the full width of the firebox por-
tion as shown in Fig. 4. A damper plate 56 mounted on a
shaft 57 within exhaust opening 50 is operated by a lever
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an~ rod type actuating linkage means 58 shown in
Fig. 2. The linkage terminates at a knob 60 at the
grille front 24 for adjusting the degree of closure
of exhaust opening 50.
The bottom of the firebox portion is open
thereby enabling the use of the fireplace floor on
which to build a fire or to collect ashes. This
feature also prevents the possibility of burning out
a bottom wall of the firebox portion.
Jacket 16 includes the slightly rearwardly
and downwardly sloping forward top wall portion 54
and a more steeply pitched rear top wall portion 62.
A generally vertical rear wall 64 joins the rear top
; wall portion and generally vertical opposite sidewalls
65. The jacket sidewalls slope rearwardly and
inwardly to conform to the usual shape of the sidewalls
of a fireplace. Although the bottom of the firebox
is open as previously mentioned, the bottom of the
jacket is closed by a bottom wall 66, which connects
the firebox to the jacket so that they are unitary.
The firebox and jacket are also interconnected at
flanged portions 68 surrounding the firebox exhaust
opening 50.
The cookstove portion 15 has vertical opposite
sidewalls 45 which are a forward continuation of firebox
sidewalls 44. Sidewalls 45 meet a front wall 47, a top-
wall 49 providing a cooking surface or cooktop, and botto~
wall portions 51 and 53 to enclose a stove chamber 55
which is a forward continuation of firebox chamber 17.
Cooktop 49 is a heavy horizontal rectangular plate which
meets th~ front upper wall 52 rearwardly of the grille
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front. Cooktop 49 overlaps sidewalls 45 and front wall 47.
Bottom wall 53 is a generally vertical wall connected
to flange 27 at each end. The bottom edge of wall 53 is
adapted for sealing against the fireplace floor and the
top edge of wall 53 is connected to wall 51. Wall 51 is
inclined upwardly and forwardly at about 60 from vertical
and connects to the bottom edge of front wall 47. The
ends of wall 51 are connected to lower edges of sidewalls
45.
Front wall 47 is inclined upwardly and forwardly
at about 30 from vertical and is connected on opposite
edges to the forward edges of sidewalls 45.
A rectangular front access opening 30 is provided
through front wall 47 for permitting access to the chambers
17 and 55, for example, for adding fuel to the fire.
Around the perimeter of opening 30 is a frame 32 for mount-
ing access door 34. Referring to Fig. 6, the frame comprises
a first flange portion 32a extending normally outward from
wall 47, and a second flange portion 32b extending from
the first portion 32a inwardly toward opening 30 parallel
to front wall 47. Two hinge mounts 36 are provided in the
lower horizontal member of frame 32 for mounting access
door 34. Mounts 36 are hollow cylinders for receiving
hinge pins 37 at the bottom of door 34 so that the door can
be opened downward (Fig. 5).
The opening frame is designed so that a variety of
doors can be used interchangeably on the apparatus. One
such door 34a is shown in Fig. 1. It has a rectangular
transparent tempered glass plate 38 moun-ted in the door
frame by a flange 39 which overlaps the edge o.f the glass.
Door 34a includes a flange 40 which partially overlaps
frame 32 and is spaced therefrom when the door is mounted
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so that room air can enter the firebox through the
resulting gap about the periphery of the door, as shown
by arrows 33 in Fig. 3. This design simultaneously
provides draft air to the fire chamber and an air barrier
over the inside of the glass to protect it from heat
and smoke, A simple rotating latch 41 latches the door
by rotating a radial member beneath a flange 32b of the
access opening frame.
Referring to Figs. 5 and 6 a second steel door 34b
is interchangeable wi~h glass door 34a. Door 34b fits tightly
against frame 32 when mounted on hinges 36, 37 to provide
airtight closure of the access opening. Two,simple rotating
latches ~2 latch door 34b by rotating radial members beneath
flanges 32b of the access opening frame. A manually adjust-
able draft mechanism 43, or a thermostatically controlled
draft mechansim (not shown) is positioned below the center
of door 34b to admit air into the stove chamber through
circular apertures 43a in the door. Mechanism 43 includes
a circular pIate, sized to overlap apertures 43a, mounted
at its center on a threaded shaft. The threaded end of the
shaft is received by a threaded bolt-like hole in the door
and the opposite end of the shaft has a T-shaped handle for
turning the mechanism. The draft of air through the apertures
is adjusted by screwing the mechanism outward from the door
to admit more air or inward for less air.
A row of upper heat exchange tubes 70 extend through
an upper portion of the firebox chamber. Each tube 70 has
an air intake opening 7'1 communicating with the airspace
within the back of jacket 16 and a fron~ discharge op~ning
72 opening into a jacket airspace 22 above the rear edge
of cooktop 49.
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The upper heat exchange tubes 70 pass through the
firebo~ chamber at an inclination from back to front thereof
and are of rectangular cross section with a flat bottom
surface facing downwardly toward the fire F within the fire-
box. Thus hot smoke and gases from ~ire F heat the tubes 70
and flow upwardly and forwardly along such tubes, as shown
by arrows 73 in Fig. 3, before passing about such tubes
and out through exhaust opening 50 into the fireplace flue,
as shown by arrows 74. In the embodiment shown, there are
four upper tubes spaced apart horizontally across the upper
portion of the firebox chamber through substantially its
entire width, although any number of such tubes could be
provided, including, if desired, other rows of tubes above
or below the row of tubes 70. Tubes 70, heated directly by
hot gases and smoke from fire F, heat air entering into
inlets 71 from the airspace at the back of the firebox.
The heated air passes from the tube outlets 72 into jacket
air outlet 22, through grille screen 26 and returns to the
room in which the fireplace is situated.
A second, lower pair of heat exchange tubes 76
extends through the bottom of the firebox and stove chambers
at an inclination upwardly from back to front. Such lower
tubes include intake openings 77 in communication with the
airspace behind backwall 46 and discharge openings 78
(Fig. 1) passing through the front wall 47 of the cookstove
portion, one opening on each side of the access opening 30.
The pair of lower tubes 76 are of rectangular cross section,
are sufficiently close together to support logs L, and
generally di~erge from rear to front (Fig. 4).
A ba~fle 80 extends between opposite sidewalls 44,
45 across an upper part of the firebox and stove chambers
17, 55 for directing rising hot smoke and gases from fire F
forward toward the front of the cookstove portion. Baffle
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80 includes a horizontal forward portion 82, inclined
intermediate portions 84 and a pivoted damper portion 86.
Horizontal portion 82 is spaced below the cooktop
49, and has a front edge spaced from front wall 47 to provide,
together with the cooktop, a pathway 83 for smoke and gases
which pass in contact with the cooktop, front wall and upper
portions of sidewalls 45.
Intermediate baffle portions 84 are gently inclined
continuations of forward portion 82 which extend between tubes
70 and sidewalls 44 to seal off these areas from the upward
passage of smoke and combustion gases.
Damper portion 86 is positioned above tubes 70 and
rearwardly of intermediate baffle portions 84, and extends
horizontally between sidewalls 44. It comprises a plate
affixed to a shaft 88. The shaft is loosely fitted into
holes in sidewalls 44 so that the damper can be pivoted between
an open position (Fig. 3) and a closed position (shown in
phantom lines in Fig. 2). The plate is sized so thati when
closed, its front edge meets the rear edges of baffles 84
and adjacent surfaces of tubes 70, while the rear edge of the
plate contacts rear upper wall 48. Thus, the damper forms a
complete barrier to rising smoke and hot gases when closed.
Closure of damper 86 is effected by lever and rod
type actuating linkage means 90 shown in Figs. 3 and 4. The
linkage terminates at a knob 61 at the grille front 24 for
manually adjusting the degree of closure of damper 86.
A second horizontal baffle 91 extends between opposite
sidewalls 45 in stove chamber 55. It is positioned below
baffle 80 but above access opening 30. Baffle 91 thereby
serves to def~ect draft air, which enters around the edge o
glass door 34a, downward and separate it from the flow of
smoke indicated by arrow 83 in Fig. 3.
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A pair of electric motor operated air blowers 92,
93 are mounted in front openings of airspace 18, one on
each side of the firebox. They are operated by a control
knob 96 to blow ambient room air rearwardly into the air-
space.
A system of baffles within the airspace directs
incoming air to selected heat exchange surfaces and tubes.
Several variations may be employed within the spirit
of the present invention. For example, simplifi~d versions
of the above-described apparatus can be used which omit the
upper or lower tubes, or all of them. Similarly, jacket 16
could be omitted so that the side and rear walls of the
fireplace form the outer boundary of airspace 18. If this
arrangement is employed, a barrier must be provided for
preventing air within the airspace from escaping up the
chimney. This approach is particularly useful if the
existing fireplace is too small to accommodate the additional
space requirements of a jacket.
Cooktop 49 is described above as overlapping side
and front walls 45, 47. ~owever, if less cooking surface is
needed, or if safety reasons require it, the overlapping
portions of the cooktop may be eliminated. Similarly,
additional cooking surfaces can be provided in the cookstove
portion.
Among other variations, the blowers can be omitted
without impairing the ability of my appæatus to heat a room
by radiation for the cookstove portion and convection of
air through the tubes. The access opening can also be
positioned on a sidewall 45, rather than on the front wall,
so that longer logs can be inserted more easily into the
firebox chamber.
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The operation of the present invention will be readily
apparent from the foregoing description. ~lowever, summarizing
such operation, a fire is built within firebox chamber with
logs L or other material supported on or between the lower
heat exchange tubes 76, and door 34 is closed and latched.
Damper control handle 60 is adjusted to maintain damper plate
56 in a desired open position so that exhaust gases and smoke
can escape upwardly into the fireplace chimney. If steel
door 34b is employed, draft mechanism 43 is manually adjusted
to control the rate~ of burning of the fire.
With the fire burning satisfactoril~, blowers 92
93 are turned on using control knob 96. The blowers and
natural convection cause room air to enter the air space 18
along opposite sides of the firebox portion and circulate
through the airspace and tubes. The air is progressively
heated by contact with, and radiation from, the heat exchanging
surfaces of the firebox walls and tubes before such air is
forced out of front tube outlets 78 back into the room.
Initially, damper portion 86 is set in an open position
so that smoke and gases flow generally upward around tubes 70
to flue 50. Once the fire is burning satisfactorily and
access door 34 is closed, damper control handle 61 is operated
to close damper 86 at least partially~ This action diverts
the flow of smoke and gases toward the cookstove chamber.
Consequently, combustion products rise from fire F, and
portions of such products move forwardly along the lower
- suraces of tubes 70, while the remainder flow around the
tubes before moving forwardIy in the manner shown by phantom
arrow 85 in Fig. 3, Thereupon such products flow as shown by
arrow 83 beneath forward baffle portion 82, rise through the
opening between the front edge of baffle portion 82 and front
wall 47 and then flow backward beneath cooktop 49, causing the
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cooktop to be heated sufficiently for cooking purposes. The
smoke and gases then flow around the discharge ends of upper
tubes 70 and out through flue 50.
When it is desired to add additional fuel to the fire,
it is preerable to open damper 86 before opening the access
door. After doing so the door may be opened without smoke
and hot gases escaping into the room. Fuel, such as logs L,
can then be placed on the forward upper surfaces of inclined
lower tubes 76 and allowed to roll backward into the firebox
chamber. Then, after closing the access door, damper 86 is
again closed as described above.
The position of damper 86 can be adjusted selectively
to any position between its open and closed positions to
control the temperature o caoktop 49. Thus, the damper can
be opened so that the cookstove portion, including the cooktop,
remains relatively cool (for example, to avoid in~uries to
small unattended children) although hot air is being discharged
from the tubes 70, 76 to heat the room. Then, for cooking,
or to increase heat radiation into the room, the damper can
be partially or completely closed.
Having illustrated and described the principles of
my invention from what is presently a preferred embodiment,
it should be apparent to those skilled in tha art that other
modifications can be made without departing from such prin-
ciples. I claim as my invention all such modifications as
come within the true spirit and scope o the following claims~
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