Note: Descriptions are shown in the official language in which they were submitted.
~058465
CICGI~OI]ND OF 'I`~-~F~, ].~VI~'l'ION
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The invention re]ates generally to heating
app~ratus and ;n particular to a wood-burning heating
apparatus having a high heat conversion effi.ciency.
Wood-burning stoves have been available for
centuries. Perhaps the most well-known wood-burning
stove is the Franklin stove which, while being practical
or its tilne, burned wood i.nefficiently. That stove,
like most cast iron stoves available today, provides for
updraft combustion, such as is found in a fireplace and
in which the volatile gases (volatiles), which are driven
- off as the wood burns, are generally left unburned. The
unburned volatiles remain for two reasons, first because
the gases, by the time they have left the wood, are
generally too cool for secondary combustion and second,
because oxygen that is admitted to the stove or fireplace
is usually consumed by the coals at the base of the fire
mass, causing the gases to rise through an oxygen-deficient .
atmosphere. The loss of the hot, unburned volatile gases
is a serious problem, because they represent approximately
half of the total heat value of the wood. It is as though
one were to run an open li.ne of natural gas up a chimney
without bothering to igni~e it first. In addition, the
volatile gases given off from the wood without being ignited ..may condense on the cool sides of long metal flue pipes
and drip out as creosote whi.ch may sometimes be inadvertently
and dangerously burned, in their solid creosote form, as a
chimney fire.
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~ .t is t:herefore a principal object of thi.s
inverltion to provide a helting apparatus having improved
combustion efficiency. A further object of the invention
is to provi.de a wood-burning heating apparatus having
controlled combustion rates.
Yet further objects of the invention are to
provide a wood-burning apparatus which is reliable, which
is simple to operate, which is capable of long-term operation
with a single load of wood, which has a high heat output,
: 10 and which can be set for reduced heat output during pre-
selected times.
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~0584~i5
~ o~ r~ J (IL,-L)~lr~ d~ r(l~ t~, ~h~
invcntion fc~1~ure~ a hc~L1~-col1Elucting frcamc~ meJnl~e~~
enclosin(J a pr:ilmary cornbustiorl chamber, a secondary
eombustion chall1ber in (JaseOUS communi.catic)n Wi th the
primary eombustio1l ehamber, and a bafEle system in
gaseo~1s eommunicatio1-l w;th the seeondary eombustion
ehamber for providing a ]ong internal Elame path. A
vertically oriented downwardly directed baffle separates
the primary and seconclary eombustion ehan1bers. The
baffle in eombination wi-th the frame member provides an
opening eonneeting bottom portions oE the primary and
seeondary eombustion ehambers for providing gaseous
eommunieation therebetween. A first air supply path
provides preheated air for promoting eombus-tion in the
primary eombustion ehamber. A seeond air supply path
provides preheated air to the seeondary combustion ehamber.
A eombustion produets exit aperture at a top portion of
the frame and in gaseous communication with the haffle
system, provides an exit port for the eombustion produets.
In an embodiment of the invention there is
featured a pivoting side door ineluding a bafEling means
for providing a smokeless loacl:in~ ap~rture in the Erame
side wllen the door is pivoted -to al1 open eonditio1l.
In yet another aspeet oE the invention, a therrno-
statieally eontrolled inlet port may be provided in the
frame for supplying air to the fir.st supply path.
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105846S
liFS(`I~ `ON OF 'I`IIE llR,~ GS
Othe~r fcatures, objects, and advantages of
the invention ~ill appear from the following description
of a preferred embodimellt taken together with the drawings,
in which:
Figure 1 is a front perspective view of a
heating apparatus according to the invention, :
Figure 2 is a back perspective view of the ~- .
heating apparatus of Figure l;
Figure 3 is a cut-away front perspective view ~ .
of the heating apparatus according to the invention; :~
Figure 4 is a cross-sectional view taken along
lines 4-4 of Figure 3; and
Figure 5 is an enlarged view of the circled
area of Figure 4.
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~58465
Dl~':;CK:lI"I~lON 01 1~ LP~RI U ~M1301)IMI~NI
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~eneral nescr; ~,ion
Re:~el-ring to Ii;.gure 1, a wood-burning heating
apparatus 8 has an exterior frame member 10 preferably
comprised of a heavy~duty cast iron. The sides 12a, 12b,
front 12c with doors 12e, 12f, back 12g, top 12h, and
bottom 12i of the frame member are jo.;ned in a channeled
construction to form an integral, air-tight unit l~e
front pivoting doors 12e, 12f, allow the heating apparatus
to be o?ened ~rom the front for both loading o:f wood and
for viewing the fire when the heating apparatus is used
as a fireplace. A pivoting side door 14 o~F the apparatus,
has hinges 15a, 15b which allow it to pivot about a vertical
rotation axis, whereby wood may be l.oaded into a primary ~.
combustion chamber 16 (Figure 3) from the side of the .
. apparatus. In its closed position, door 14 seals againsta gasketing mater;.al such as a one-quarter lnch diameter
asbestos rope sealing member. Door 14 interlocks wi.th a
damper 18 (Figures 3 and 4) whose posi.tion is controlled
by a handle 20 so that the door can hc fu:l.ly opcnc-~d only
Whetl the appt'lratUS iS '; n an Updr.l.l~t C`Olnb-1StiOI'I COrl:Ei.gUratiOn
as described in mor~ c]ct:ail below. lllustrated top member
12h support:s a cast iron cooking surface 2:L.
l~eferr;ng to Figules 2 and 3, air i.s supplied
to the prilnary combust:ion challlber 16, through a pri.mary
inlet port 22, by a primary air supply flo~ pat:h having
branches 24a, 24b (Iigures 3 and 4). Inlet port 22 is
thermostati.ca].ly controlled by a thermostat 26 ~hich
operates a pivoting damper 28, removably covering an
aperture 30 in the back fraMe member 12g. Thermostat 26
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is for e~.am~ 11 x~ coil of l);metal]ic mal:erial
connected ~o dam~er 28 by a ~lexibl~ chain 32. ~eating
appara~us 8 also h~s a d~m~er control lever 34 for
regulating ther!llosta~ 26. A manually controlled night/
secondary air in]et port 35 in side member 12a provides
the air inlet for air supplied to a secondary combustion
chamber 36 (Figure 3) through a secondary air flow path 37.
Referrin~ to Figure 3, pri]-llary air entering
through aperture 30 travels through primary air supply
paths 24a, 24b and is heated by contact with the hot walls
which define the supply paths 24a, 24b. Thus, the primary
air is preheated and therefore helps to keep a hotter
fire going with less air and wood being consumed. The -
primary combustion chamber is bounded by the substantially
vertically oriented downwardly extending fireback baffle 38,
side door 1~ and side wàll 12a of the frame member, the
front doors 12e, 12f and front wall 12c of the frame member,
the top 12h and bottom 12i frame member panels, and a
vertically oriented interior panel 40 which separates the
primary combustion chamber from the secondary combustion
chamber 36.
The secondary combustion chamber is connected to
and is in gaseous communication with the primary combustion
chamber through an opening 44 in panel 40. Illustrated
opening 44 is defined by the panel 40 in combination with
the frame members, here the bottom and front frame members.
The secondary combustion chamber is bounded by the vertically
oriented panel 40 in combination with frame members 12b, 12c,
12g, 12h, and 12i. As noted above, the secondary combustion
~ 30 chamber receives preheated air from the air inlet port 35
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tllrou~h l)e se~ondary air supply ~ow path 37. Ille
f-low path 37 C0111p3^iSeS an imperforate section 48 which
extends bet~ween the inlet port 35 and panel 40, and a
perforate section 49 e~tending from panel 40 into ~lle
secondary combustion chamber.
Th_ Flame Path
Behind the fireback baffle 38 are a plurality of
connecting smoke passages 50, 52 which provide a circuitous
path from the secondary combustion chamber to the flue
exit opening at flue collar 58. These passages direct
the spent flue gases from the secondary combustion
chamber to the left end of the illustrated apparatus
through passage 50, then upward into the upper channel
or passage 52 back toward the right-hand portion of the
stove, where they exit through the flue collar 58.
The secondary combustion chamber, taken together
with the smoke passages, make up the flame path. Since
the heat of the flue gases is considerable, and is trans-
ferred to the suraces of the stove as the flue gases
traverse the passages, a significant amount of heat
is given off to the room, especially througll the side
and back frame members, rather than being lost up the chimney.
In addition, since the passages are adjacent to the primary
combustion chamber, higher temperatures are maintained
within the fire mass itself, which aids in burning the
volatile gaseous products escaping from the burning wood.
The illustrated flue collar 58 is attached to the
top panel 12h and provides a vertical or top exit for the
spent flue gases In other embodiments of the invention,
the flue collar can be attached, for example, to an upper
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portion Or back pane] member 12g to provide a rear
e~it for the flue gases.
The Primary A;r ~low P~th
As noted above, tlle thermos~atically controlled
inlet port 22 suppl;es air for the primary air flow path.
Ambient air enters the apparatus through aperture 30 in
- frame back wall 12g and almost im~ediately divides between
the side branch ~4a and the back branch 24b. That portion
of the incoming air which passes into the back branch 24b
is directed along the back of fireback baffle 38 and is
constrained to follow a path adjacent to the fireback
baffle by an enclosing member 64. Fireback baffle 38
has a plurality of ho~es 66 extending therethrough for
providing preheated primary air to the back of the primary
- combustion chamber. Illustrated enclosing member 64 is a `
cast iron plate and branch 24b has a substantially constant
cross-sectional area along its length.
That portion of the ambient air passing through
aperture 30 which follows side branch 24a passes through
the baffle 38 at a lower section of the baffle (Figure 3)
and is directed into the primary combustion chamber along
a periodically slotted conduit 68 which extends from baffle
38, along side wall 12a (below side door 14) and for
approximately one-fifth the distance along a bottom section
of front wall 12c. The slotted conduit has a cross-sectional
area which is substantially constant and ispartially open at it
end 70. Primary air is thus provided to promote a unifor~
flow of combl~stion supporting oxygen across the entire
primary combustion chamber.
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lOS8465
Ihe a;l- provided by ~rimary ~low branches ?4a
and 24b thus enters the primary comb-lstion chamber along
~l~e bottom back ~nd bottom left-hand boundary surfaces
- of ~he cha,nber (looking from the front), and provides
combusticn along the entire bottom of the wood supply.
Upon reaching the right-hand portion of the primary
combustion chamber, the air flow (now containing volatiles)
continues through opening 44 into the secondary combustion
chamber and exits through the circuitous flow path provided
by the back baffle system arrangement extending between
baffle 38 and rear wall 12g.
Details of the Back Baffle System
Referring to Figures 3 and 4, the back baffle
system for directing the flue gases along the circuitous
- path through the space between baffle 38 and back wall 12g
consists of a lower baffle 90, an upper baffle 92, and a
vertical plate member 94. Illustrated lower baffle 90
consists of a cast plate member which extends in a
transverse direction between the fireback 38 and the
back wall of the frame. Illustrated baffle 90 extends
lengthwise rom the substantially triangular shaped,
vertical plate member 94 to the vertical panel 40. Plate
member 94 extends trarlsversely between the fireback 38 and
back wall 12g and vertically from a level near the botto~
of door 14 (preferably from lower baffle 90) to a
position above the top of door 14 (and preferably to the
upper baffle 92). Triangular plate 94 provides a barrier
to prevent flue gases in the space behind the fireback from
escaping through an opened side door.
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'llle llpp~r ~)a~le 92 e,;~ellds above baLfle 90
and CO~lSiS~S of a cast pl,-lte me~llber ex~ending from vertical
-~ baffle 40 ~o a position near side wall 12a. Baffle 92 tllereby
creates an ap~rtur~ 96 so lhat the flue gases pass from thelo~
horizontal]y directed passage 50 through aperture 96 to
the upper horizontal]y directed passage 52 from which
they exit through flue collar 58.
The_Damper
The damper 18 of the heating apparatus enables
the apyaratus ~o be used both as a parlor stove and as a
fireplace. When the damper is in the substantially vertical
position shown in Figure 4, the heating apparatus operates
as a stove and the flue gases exit substantially as shown
; by the arrow 98 (Figure 3). When the damper is placed in
a substanti~lly horizontal position indicated by dotted
lines 100 (Figure 4), the apparatus can be used as a
fireplace with the flue gases exiting from the primary
combustion chamber along a path generally indicated by
arrow 102. This provides updraft combustion.
When fuel is loaded into the apparatus through
side door 14, the flue must be in the closed position
(the damper in a horizontal position) or otherwise,
smoke will pour out of door opening. An interlocking
arrangement between the door 14 and the damper 18
ensures that the flue is c]osed before the side door 14
can be fully opened.~ The illustrated arrangement consists
of a handle 20 on the damper which is in the vertically
downward position and engages door 14 if the door is opened
and the flue is not closed. Other arrangements can also be
used.
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o~ L ~ ~; 0 r t~ f~rlA~d ~rl,T)~ r.l~3s
In the l~re~erl-eQ embodiTilent of thc invention,
tlle openill~ 44 has a height of between 3 and 5 inches
and is preferably 4 1/2 inches high. It has been ound
for the particular apparatus depicted in Figure 3, that
the l-leight of opening 44 is important and a height sub-
stantially greater ~han 4 1/2 inches increases the heat
output of the apparatus and also its conversion efficiency.
To ~urther control combustion within the heating
apparatus, the illustrated frame members are interconnected
along their edges in a channeled construction (Figure 5).
The channeled construction consists of a cast groove 130,
at the edge 131 of one of the joining members, which receives
a layer 132 of plastic sealing material, for e~ample an
asbestos gasketing material, and the other joining member 133.
This construction provides an airtight, physically secure
and rigid structure.
Summary of the Advantages of the Invention
Thus the present invention provides an effective
apparatus for reducing the volatiles found in typical
updraft combustion by providing a horizontal combustion
heating apparatus wherein the flames move horizontally
in the primary combustion zone. ~lis is radically di~ferent
from typical updraft combustion and provides more efficient
operation of the stove. The apparatus thus aids the burning
of the volatile gases in several ways. First, by using
horizontal combustion, the gases are forced to pass close
to the hot coals which maintain sufficiently high temperatures
to ignite them. In addition, the manually controlled inlet
port 35, which is segregated from the primary air source,
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58465
~rovi(~ ir ~ is d~!ct-ed (~o~rin a p~i~h integrc~l with
the heated 1~ack wal] al~-. wh;ch is l~eated by tlle fllle g-3ses~
Ihis chanl1el preheaLs ~1e air ~o maintain the air at tle
elevated te111peratures required for secvndary com~ustion.
~1US, oxygen from the secondary night inlet port 35 is directed
into the secondary combustion chamber through nun-lerous
air ports to mix with the combustible gases and to provide
secondary combustion. (During night operation when the
thermostat is turned down and damper 18 is closed, the
secondary/night inlet port provides sufficient air to
maintain a self-regulating cycli~ operation.)
In addition, behind the fireback which is provided
at the back of the primary combustion chamber, the circuitous
path consisting of passages 50, 52 conducts the smoke back
and forth along the back of the apparatus and upwardly
toward the exit at the flue collar 58. Since the heat of
the flue gases is considerable, significant heat trans~er
occurs from the flue gases to the surfaces of the stove,
which in turn is given off into the room rather than being
; 20 lost up the chimney. In addition, the circuitous path aids
in maintaining a higher temperature in the combustion
chamber which aids in burning the volatile gases driven
off from the wood. ~us, a large heat output is available.
In addition, the fire is controlled by not only the structure
of the apparatus but by the thermostatically controlled
input port 22 which supplies the primary air.
There is thus provided a wood-burning heating
apparatus having an exceedingly high efficiency due both
to its secondary combustion chamber and the secondary air
supply supporting it, as well as to its long flue gas flow
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~).3til ~-3nd llori~ont ai. c`.oll31~usti.on.
Othe~r embof;~ ents of the ;nvention, includi.ng
~dditions, subtractions, deletions, and other modifications
of the preferred embodiment of the invention will ~e obvious-
to one skilled in the ar~ and are within the scope of the
following claims.
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