CA1076442A - Heating apparatus having improved combustion - Google Patents

Abstract

Abstract 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 or the flue gases to thereby increase the overall efficiency of the stove.

Description

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}lE~'l`lNG Al'PAR~'J.'US IIAV' C [MPI~OVJ.I) COMBUSTION

~ wood-burnin~ heatirlg apparatus, used as a parlor stove and providLng a signi~i.cant heat output, ..
is disclosed. 'llle stove has primary and secondary com~ustion chambers and a baffle system for directing ;~
flue gases along a circuitous path from the secondary combustion chamber to an eY~lt aperture whereby a significant proportion of the heat o:E said gases ls given up to the apparatus. A vertically oriented downwardly ~' direc~ed baffle separates the combustion chambers, First ~ :
and second air paths supply air to the primary and secondary ~'' ' ',, combustion chsmbers respectively. ~le 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 over211 efficiency of the stove.

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~ rile .invc~lt:ion rclat:es g~rlera]..ly ~o hcat:i.rlc apparatus ~.md in par-ticular to a wood-burlling heatinc apparatus havincJ a hi(Jh heat conv~rsion effi.ci.ency.
This is a div.ision of copend.ing Canadian Paterlt ~pplication Seri~l No. 29~,050, filed March 2, 1978.
Wood-burniny stoves have been available for centuries. Perhaps the most well-known wood-burning stove is the Frclnklin stove whi.ch, while being pract:ical for its t.ime, burned wood inefficiently. Th~t 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 general].y too cool for secondary co~bustion and second, because oxy~en `
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 t.he wood. It is as though one were to run an open line of natural gas up a chimney without .
bothering to ignite it first. In addition, the volatile ~`.-gases given off from the wood without bei.ng ignited may condense on the cool sides of long metal flue pipes and drip out as creosote which may sometimes be inadvertent].y and dangerously burned, in thei.r solid creosote form, as a chimney fire.
It is therefore a principal object of this invention to provide a heating apparatus having improved combustion efficiency.

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Ye~ fur~h~r objectc; o~ ~h~ :Lnvcntion are to provide a wood-burn;l-g appara~u5 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, and whicli can be set for reduced heat output during pre-selected times.
According to the present invention, there is provided a wood--burning heating apparatus includi.ng a heat conducting frame member enclosing a primary combustion ~ -chamber, a secondary combustion chamber in gaseous cornmuni-cation with the primary combus-tion chamber, and a baffle system in gaseous communication with the secondary ;
coMbustion chamber, for providing a long internal flame path. A vertically oriented, downwardly directed ba~fle is provided for separating the primary and secondary ~ ~
combustion cha~bers, the baffle in combination with the frame member providing an opening connecting the primary and secondary combustion chambers for the gaseous communi- ;cation therehetween. A primary air supply path provides air for promoting combustion in the primary combustion chamber, and a pivotable damper provides in one position ;-an updraft combustion apparatus and in a second position a horizontal combustion apparatus. Means interconnects the damper with a side fuel loading door for preventing the side door from fully opening when the damper is in the second position. A combustion products exit aperture is provided at the top portion of the frame and in gaseous communication with the baffle system for providing an exit port for comubstion products.

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_~_ _ _ OLher fecl~ures, objec~s, and advanta~es of the invention will appear from the followi.ng dcsc~.i.p~i.on of a prefexred embodiment talcen toge~her wi~h 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 hea~ing 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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Dl~SC~RIl'rX()I~ OI A PRl`L l`lcRI D l~MI~OI)IMI.NT

General D~sc~ iption . .
Reerring to ~igure 1, a wood-burning heating apparat~ts 8 has an exterior franne member 10 preferably comprised of a heavy-duty cast irori. ï~le sides 12a, 12b ~ront 12c with doors 12e, 12:E, baclc 12g, top :1 2h, and bottom 12i of the frame member are joined in a channeled construction to fonm an integral, air~tight unit l~e front pivoting doors 12e, 12f, allow the heating apparatus to be opened from the Eront Eor both loading o E wood and for viewing the fire when the heating apparatus is used as a fireplace. A pivoting side door 14 of the apparat:us, has hinges 15a, 15b which allow it to pivot about a vertical -rotation axis, ~hereby wood may be loaded into a primary , combustion chamber 16 (Figure 3) from the side o the apparatus. In its closed position, door 14 seals against a gasketing material such as a one-quarter inch diameter asbestos rope sealing member. Door 14 interlocks with a damper 18 (Figures 3 and 4) whose position is controlled by a handle 20 so that the door can be fully opened or;ly ;
when the apparatus is in an updra~ combustion configuration as described in more detail below. l:llus trated top member 12h supports a cast iron cooking surface 21.
Reerring to Figures 2 and 3, air is supplied to the primary combus tion chamber 16, througll a primary inlet port 22, by a primary air S-Tpply flow paLIl havi ng branches 24a, 24b (Figures 3 and 4~. Inlet port 22 is ;~
thennostatically controlled by a thermos l-at 26 which operate5 a pivoting damper 28, removably covering an aperture 30 in the bac1c frarne member 12g. lllcrlllostat: 26 ::

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is for e7~aml~1c an ~" coi.l o~ bilne~alli.c ma~er.ial connected to daln~er 2$ by a ~lexible cha:in 32. Ileating ~.
apparatus 8 also has a damper control lever 34 for ;.
re~u].ating thermostat 26. A manually controlled night/
secondary air inlet port 35 in side member 12a provic~es the air inlet or air supplied to a secondary combustion chamber 36 (Fi~ure 3) through a secondary air flow path 37. `~
Referring to Figure 3, primary 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 2~a, 24b. ~us, the primary . -. -air is preheated and therefore helps to keep a hotter .
~ire going with less air and wood being consumec~. The - -primary combustion chamber is bounded by the substantially vertically oriented downwardly extendin~ fireback baffle 38, side door 14 and side wall 12a of the rame 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 ori.ented 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 ~4 is defined ~y the pane]. 40 in combination with the rame mernbers, here the bottom and front frame members.
The secondary combustion chamber is bo~lnded by the vertically oricnted panel ~rO in colr~ atiol- with frame m~mbers 12b, 12c, . . . . . . .
12g, 12h, and 12i. As noted above, the se~colldctr~ combustio chamber rec~ives prelleated air ~rom the air inlet port 35 ,'~, :-"

~ 1076~42 t}lrough t:he sccoll(lary aL-r sur)ply ~:low path 37. llle flow path 37 compri~cs an i.mpel~oratc section l~ whicll ;
extends between the inlet port: 35 and panel ~0,. and a perforate section 49 extending ~rom panel 40 i.nto the ~. ~
secondary cornbustion chamber. - :
The Flame Path Behind the ireback ba~fle 38 are a plurality o connecting smolce passages 50, 52 which provide a ci.rcuitous .-~
path from the secondary combustion charnber to the flue ..
exit opening at fl.ue collar 58. ~lese passages direct the spent flue gases from the secondary combustion ~-chamber to the left end of the illustrated apparatus through pass~ge S0, then upward into the upper channel :
or passage 52 back toward the right-hand portion of the ~ ~.
stove, wlere they exit through the flue col~ar 58.
~ he secondary combustion chamber, taken l:o~ether .. with .the smoke passages, make up the flan,e path. Since the heat of the flue gases is considerabl.e, and is trans-erred to the surfaces of the stove as the flue gases traverse the passages, a significant amount of lleat is given off to the room, especially through the side -and bac~ frame members, rather than being lost up the chimney.
In addition, since the passages are adjacent to the primary ~ -combustion chamber, higher temperat~lres are maintained ~;
within the fire mass itsel, which aids in burning the volatile gaseous products escaping from the burning wood. : ~: -~le i].lustrated fl.ue collar 5~ is attached to the top panel 12h and provi.des a vertical or top exit for the spent flue gases. In othcr elnbodiments of t:he i.nvention, .
the flue collar can be attached, ~or example, to ~n upper :.'.:`, ~ .

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1~76~2 portion of back panel melnber ],~ to provi.de a rear '~ ~' exit or the flue gases. '~
he Prirnary ~i,r llow _ath . ..
As noted above, the thermostatically controlled inlet port 22 supplies air for the primary air 10w path.
Am~ient air enters the apparatus through aperture 30 in ' ' frame back wall 12g and almost imme~di.at:ely clivides between . ~' the side branch 2~a and the back branch 24b. l~a'~ portion - ' '' of the incoming air wllich passes into the back branch 24b is directed along the back of fireback bafle 38 and is '~.' constrained to follow a path adjacent to the fireback ;~ .
baffle by an enclosing member 64. Fireback baf'1.e 38 ',~
has a plurality o ho~es 66 extending therethrough for providing preheated primary air to the back of the primary ~ombustion chamber. Illustrated enclosing member 64 is a cast iron plate and branch 24b has a substanCially constant cross-sectional area along its leng~h. ,' That portion of the ambient air passing through ' aperture 30 which ollows sicle branch 2~a passes through the ba~1e 38 at a lower section of the ba1e (Figure 3) and is directed into the primary combustion chamber along a periodically slotted conduit 68 which extends from ba1e 38, along side wall 12a (below side door 1~) and or approximately one ifth the dis~ance along a bottom section ~ , of front wall 12c. The slotted conduit has a cross'-sectional ~ ~
ar.ea which is substantially constant and isparTtially open at i ': ', end 70, Primary air is tllus provided to promote a uniform ; ~;
flow of combl~stion supporting oxygen across the entire primary combustion chamber. ' : .
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The air provided by primary flow branches 24a and 24b thus enters -the primary combustion chamber along the bottom back and bottom left-hand boundary surfaces of the chamber (looking from the front), and provides combustion 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 sack 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 from the substantially triangular shaped, ;
vertical plate member 94 to the vertical panel 40. Ylate member 94 extends transversely between the fireback 38 and ~ ;
back wall 12g and vertically from a level nea~ 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.
The above-described heating apparatus having the baffle means for providing a smokeless loading is also described and is claimed in copending divisional application Serial No. 330,771, filed June 28, 1979.

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'll~e ~lpper ba~fle 92 e~:~ellds above baf~le 90 and consists o~ a c~st platc meillber ex~encli.rlg from ver~i.cal bafle ~0 t-o a posi~ion near side wall 12a. Ba~le 92 thereby creates an ~perturc 96 so that ~I-Ie fl~1e gases pass ~rom the lo~; ~
horizontally directed passage 50 through aperture 96 ~o ~ ;
the upper hori~ontally directed passage 52 from which they exit through flue colla~ 58.
The Damper ,~
The damper 18 of the heating apparatus enables the apparatus to 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 sho~n by the arrow 98 (Figure 3). When the damper is placed in . ~.~

2 substanti~lly horizontal pOSitiOII iridicated by dotted . - ~-lines 100 (~igure 4)~ the apparatus can be used as a fireplace with the flue gases e~iting from the primary combustion chamber along a patl generally indicated by ~ ~
arrow 102. r1~is 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 pos;tion) or othel~ise, smoke will pour out of door opening. An interlocking arrangement bett~een the door 14 and the.damper 18 ensures that the ~lue is closed before the side door 14 can be fully opened.' The illustrated arrangement consists of a h~ndle 20 on tlle damper wllicll is in the verti.cally downward positi.on and engages cloor 14 i the door is opened and the flue is not clos~d. Othcr arrangelnents can also be used, , .

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In an embodiment of the invention, the opening 44 may have a height of between 3 and 5 inches and is preferably 4 1/2 inches high. It has been found for the particular apparatus depicted in Figure 3, that the height of opening 44 is important and a height substantially greater than 4 1/2 inches increases the heat output of the apparatus and also its conversion efficiency.
To further 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 example an asbestos gasketing material, and the other joining member 133. This construction provides an airtight, ~ physically secure and rigid structure.
The above-described heating apparatus including the channeled construction is also described and is claimed in copending divisional application Serial No. 330,773, filed June 28, 1979. ;~
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The present invontion provides an effective ~ ~
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apparatus fox reducing the volatiles found in typical up- -draft combustion by pro~iding a horizontal combustion heating apparatus wherein the flames move horizontally in the primary combustion zone. This is radically different from typical updraft combustion and provides more effiaient 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 temper-atures to ignitie them. In addition, the manually con-trolled inlet port 35, which is segregated from the primary air source, , ........................................................... ..

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provi.(~cs ai.r whi.cll is ductccl down a pa~ ral wi.th the hca~(cl baclc wall and whi.ch is hea~ed by the 1-1e ~ases.
This challnel pre~lea~s the air to main~ain the air at tlle elevated ternperaturcs requir~d ~or sccondary col-nbustion.
Thus, oxygen from the secondary nigi~t iniet port 3S is directe into the secondary combustion chamber through numerous air ports to mix with the combustible gases and to provide secondary combustion. (During night operation ~hen the ~ .
thermostat is turned down and damper 18 is closed, the secondary/night inlet port provides sufficient air to maintain a self-regulating cyclic operation.) In addition, behind the ~ireback which is provided at the back of the primary combu~stion 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~ signi~icant heat tr~nsfer ... ..
occurs from the flue gases to the surfaces of the stove, which in.turn is givFn of into the room rather than being lost up the chimney. In addition, the circuitous path aids in maintaining a higher temperature in the combustion charnber which aids in burning the volatile gases driven of~ from the wood. Thus, a large heat output is available.
In addition, the fire is controlled by not only the structure of the apparatus but by the tllermostatically colltrolled input port 22 which supplies the prill7ary air.
There is thus provided a wood-burlling heati.ng ~ :
apparatus having an exceedingly high efici.ency due both to its secondary comb-lstion chamber and thc secondary air supply suppor~ing it, as well as to i~s long 1ue gas f1DW

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pa~h and hori~.orl~al colnl~-~st-i.orl.
Other embodi~.lell~s of the invention, including additions, s~tracti.ons, deletions, and other modifications of the preferred elnbodiment of the invention will be obvious to one skilled in the art and are within ~he scope of the followillg claims.

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Claims

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 communication with said primary combustion chamber, and a baffle 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 said frame member providing an opening connecting said primary and secondary combustion chambers for providing said gaseous communication therebetween, a primary air supply path for providing air for promoting combustion in said primary combustion chamber, a pivotable damper for providing in one position an updraft combustion apparatus and in a second position a horizontal combustion apparatus, 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, and a combustion products exist aperture at a top portion of said frame and in gaseous communication with said baffle system for providing an exit port for combustion products.