CA1058465A - Heating apparatus having improved combustion - Google Patents

Abstract

HEATING APPARATUS HAVING IMPROVED COMBUSTION

A wood-burning heating apparatus, used as a parlor stove and providing a significant heat output, is disclosed. The stove has primary and secondary combustion chambers and a baffle system for directing flue gases along a circuitous path from the secondary combustion chamber to an exit aperture whereby a significant proportion of the heat of said gases is given up to the apparatus. A vertically oriented downwardly directed baffle separates the combustion chambers. First and second air paths supply air to the primary and secondary combustion chambers respectively. The air provided by the supply conduits to the respective combustion chambers is preheated and the air provided through the second path promotes secondary combustion of the flue gases to thereby increase the overall efficiency of the stove.

Description

~058465 CICGI~OI]ND OF 'I`~-~F~, ].~VI~'l'ION
_ _ _ ._ __ _ _ __ _ 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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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.

kh/~-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
_ _, _ . . _ . _ . ~ . . ~ _ ~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 - ~ ,., i , ~

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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 lQ58465 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 ~05~3465 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.

. . -- 9 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.

'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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~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 `- lOS8465 ~).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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Claims (14)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A wood-burning heating apparatus comprising:
a heat conducting frame member enclosing a primary combustion chamber, a secondary combustion chamber in gaseous com-munication with said primary combustion chamber, and a baffling system in gaseous communication with said secondary combustion chamber, for providing a long internal flame path, a vertically oriented, downwardly directed baffle for separating said primary and secondary combustion chambers, said baffle in combination with the frame member, providing an opening connecting bottom portions of said primary and secondary combustion chambers for said gaseous communication therebetween, a first air supply path for providing preheated air for promoting combustion in said primary combustion chamber, a second air supply path for providing preheated air to said secondary combustion chamber, and a combustion products exit aperture at a top portion of said frame and in gaseous communication with said baffling system for providing an exit port for combustion products.

2. The apparatus of claim 1 further including a thermostatically controlled inlet port in said frame for supplying air to said first supply path.

3. The apparatus of claim 1 further including a pivoting side door and including baffle means for providing a smokeless loading aperture in said side when said door is pivoted to an open condition.

4. The apparatus of claim 3 further including an asbestos sealing member between the side door and the frame member when the side door is in a closed position.

5. The apparatus of claim 1 wherein a branch of said first air path in said primary combustion chamber is a conduit having a plurality of slotted apertures.

6. The apparatus of claim 1 wherein said second air supply path comprises an air supply conduit connected at one end to a supply port and having its other end positioned in said secondary combustion chamber for supplying preheated air to promote secondary combustion in said secondary chamber.

7. The apparatus of claim 6 wherein a section of said supply conduit has, for one side thereof, a portion of said downwardly directed baffle.

8. The apparatus of claim 1 wherein said opening has a vertical height of between 3 and 5 inches.

9. The apparatus of claim 8 wherein said opening has a height of approximately 4 1/2 inches.

10. The apparatus of claim 1 further comprising a manually controlled inlet port for providing air to said second supply path.

11. The apparatus of claim 3 wherein said baffle means comprises a vertical panel extending parallel to a side of said frame member between said primary chamber and a back wall of said frame member, and positioned adjacent said side having the door.

12. The wood-burning heating apparatus of claim 1 further comprising:
a pivotable damper for providing in one position an updraft combustion apparatus and in a second position a horizontal combustion apparatus, and means for interconnecting said damper with a side, fuel loading door for preventing said side door from fully opening when the damper is in said second position.

13. The wood-burning heating apparatus of claim 1 wherein, said frame member has a plurality of exterior panels assembled to enclose said primary combustion chamber, said secondary combustion chamber, and said baffle system, and wherein, said panels are interconnected along their edges with a channeled construction.

14. The apparatus of claim 1 further including a east iron cooking element, gravity positioned in a top frame section of said frame member, and having a smooth upper cooking surface.