Note: Descriptions are shown in the official language in which they were submitted.
1137373
WOODBURNING HEATING APPARAT~S
Bac~ground of the Invention
This invention relates generally to a woodburning
heating apparatus and in particular to an airtight woodburning
S heating apparatus employing horizontal combustion.
As the price of oil and gas fuels increases, more and
more households are turning to woodburning apparatus to provide
at least a portion and in some circumstances all of the heat for
a dwelling. In some instances fireplaces are used. However the
fireplace is an inefficient heater; and in response to the
increased demand or wood burning heating apparatus, a myriad of
woodburning stoves have been designed and manufactured.
One class of particularly efficient woodburning stoves
are those stoves which have controlled air inlets. These stovesr
often termed airtight, can have many different configurations.
Two of the airtight stoves which are particularly successful, are
capable of operating using horizontal combustion. ,hey are the
Vigilant and the Defiant, both manufactured by Vermont Castings,
Inc., Randolph, Vermont, the assignee of this appl-ication. The
Vigilant and the Defiant are both relatively large heating
apparatus having heat outputs, at maximum burning capacity, of
about 45,000 and 55,000 BT~'s respectively. This large heat out-
put, while desirable for heating lar~e volumes, clearly can over-
power the typical ~family room" or "den" in which the stoves are
often placed. As a result, it is desirable to produce a smaller
version of a horizontal combustion apparatus.
Most practically, one would simply reduce the dimen-
sions of either the Vigilant or the Defiant to produce a stove
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having a smaller wood capacity, smaller dimensions, and a lower
heat output. Unfortunately, however, as the size of the stove
is reduced, designs which are satisfactory in a large stove
present major problems, because, for example, parts are much
closer to one another and to the primary combustion chamber of
the apparatus. As a result, it is not acceptable to merely
reduce the dimensions of already existing stoves in order to
meet the need of a smaller, efficient, long lasting, and reliably
made stove.
An object of this invention is therefore a heating
apparatus having a reduced maximum heat output, and which is long
lasting, reliable, practical and efficient. Other objects of
the invention are a heating apparatus wherein the user can service
the apparatus, and which can be reliably manufactured with mini-
mum cost.
According to the present invention there is provided
a wood burning heating apparatus which includes a heating
conducting frame member having front, bac~, and side vertical
wall panels with a top panel and a bottom panel for enclosing a
defined volume. A fireback is provided and means is provided
for forming an air supply path and a combustion products exist
flame path for operating the wood burning apparatus in a
horizontal combustion mode. Baffle means is provided at the
beginning of the combustion products exist flame path including
a plurality of substantially vertically oriented spaced apart
baffle members for reducing the concentration of exiting
combustion gases impinging upon a portion of the frame member.
The flame path circuitously extends from the combustion products
exit path beginning to an exit aperture, and a moveable damper
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pivots about an axis for providing in a first position, an
updraft combustion apparatus and in a second position a horizontal
combustion apparatus.
More specifically, the invention features a plurality
of interconnecting removable wear plates, which define, in
combination with the wall panels and a removable fireback, a
primary air supply path and a long circuitous internal flame
path. The wear plates are supported by the bottom panel.
Turning now to other features of a specific embodiment
of the invention, the primary air supply path has a first
enclosed elongated path for supplying air at a first side of
the apparatus to a primary combustion chamber. The long flame
path circuitously extends from the second end side the apparatus
substantially between the fireback and at least one wear plate,
and the frame member, to the top back portion of the apparatus.
The frame member, and preferably the top panel and
a side wall panel at the back portion of the apparatus, may be
adapted to define a flue gas exit aperture for the flame path.
The exit aperture preferably enables a flue collar to be attached
in either a top exiting or a rear exiting configuration.
The movable damper is pivotal about a longitudinal axis
for providing in a first position an up draft combustion apparatus
and in a second position a horizontal combustion apparatus. A
mechanical linkage may be provided for moving the ~amper between
the first and second positions. The damper extends less than
the full width of the apparatus (looking from the front) and
preferably cooperates with the frame member for providing
sealing relationships as described below.
In a specific embodiment of the invention, the damper
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has a first panel member which pivots about a pivot axis between
a substantially vertical position and a substantially
horizontal position and first and second ear panel members which
are integrally connected to the first panel member in a spaced
apart configuration and in substantially vertical planes. These
ear members pivot about the longitudinal damper pivot axis and
substantially remain in their respective vertical planes. The
fireback has a cup-shaped forwardly or inwardly protruding
section which meets in a sealing engagement with protruding
members extending from the back wall. Gaseous flow is thus
directed from the flame path toward the exit aperture or opening.
The cup-shaped section, the protruding members, the frame member,
and the damper, form sealing relationships when the damper is
in either the first or the second position.
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Preferably, the protruding members each have cut-away
side portions for providing more complete gaseous removal from
upper back corners of the heating apparatus when the damper is in .
its first position. In any case, the damper is preferably remo-
vable from the apparatus as are the wear plates so that if they
wear out they can be easi!y and conveniently replaced by the
user. The damper is preferably moved between its first to second
positions by an articulated linkage which provides a mechanical
resistance against movement of the damper as a result of
impinging combusted gases in at least the second position of the
da~per.
Brief Description of the Drawings
Other objects, features, and advantages of the inven-
tion will be apparent from the following description of a pre-
ferred embodiment taken together with the drawings in which:
Fig. 1 is a front perspective view of a preferredembodiment of a heating apparatus according to the invention;
Fig. 2 is a rear perspective view of the preferred
embodiment of the heating apparatus according to the invention;
Fig. 3 is a partially cut away, somewhat schematic
perspe~tive view of the preferred embodiment of the heating
apparatus according to the invention;
Fig. 4 is a cross-sectional view through the center of
the apparatus along the lines 4-4 of Fig. 1;
~lg. 4(a) ~8 a croa~-~ectlonal view taken along llnes
4A-4A of Flgure 4;
F~g. 5 18 a cross-~ectional vlew along the llnes of
Flg. 4;
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Fig. 6 is a cross-sectional view along lines 6-6 of
Fig. 4~ , -
Fig. 7 is a perspective detaiI view of the damper
structure;
~ig. 8 is an end cross-sectional view of the damper-
frame structure; and
~ ig. 9 is a detailed perspective, partially schematic,
view of the damper-handle linkage according to the invention.
Description of a Preferred Embodiment
Referring to Figures 1 and 2, a wood-burning heating
apparatus 8 has an exterior ~rame member 10 preferably comprised
of a heavy-duty cast iron. The sides 12a, 12b, front 12c with
door 12e, back 12f, top 129, and bottom 12h of the frame member
are joined in a channeled construction to form an integral, air-
lS tight unit. ~he front pivoting door 12e, which pivots down on
hinges 14a, 14b, allows the heating apparatus to be opened from
the front for both loading wood into a primary combustion chamber
16 (Figure 3) and for viewing the fire when the heating apparatus
is used as a fireplace. In its closed position, door 12e seals
against a gasketing material such as an inert mineral fiber woven
rope sealing member. A damper 18 (Figures 3 and 4) whose posi-
tion is controlled by a handle 20 allows the heating apparatus to
be operated in an updraf~ combustion configuration ~like a
fireplace) or in a horizontal combustion configuration as
described in more detail below. Illustrated top member 12g sup-
ports a cast iron cooking surface 21.
~ eferring to Figures 2 and 3, air is supplied to the
primary combustion chamber 16, through an inlet port 22 as
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described in more detail below. Inlet port 22 is thermo- ~~
statically controlled by a thermostat 26 which operates a
pivoting draft shutter 28, removably covering an aperture in the
back frame member 12fo Thermostat 26 is for example a coil Of
bimetallic material connected to shutter 28 by a flexible chain
32. Heating apparatus 8 also has a control lever 34 for regu-
l~ting thermostat 2~. A manually controlled night air inlet port
35 in side member 12b provides the air inlet for air supplied to
the primary combustion chamber 16 especially for night or low
level operation.
Referring to Fig. 3, the illustrated heating apparatus
B has a removable, left wear plate 50, a removable fireback 52,
and a removable right wear plate 54. Wear plates 50 and 54 and
fireback 52 are supported by bottom panel 12h and are contoured
so that the wear plates and fireback 52 engage along seams 56, 57
in a substantially airtiqht fit. Wear plates 50, 54 thus prevent
lateral movement of the fireback away from its engaging contact
with back panel 12f as described in more detail below. The
longitudinal position of the wear plates with respect to the side
panels is fixed by screw connections 58, 59 (Fig. 4). A support
member 59a attached to wear plate 50 engages a boss 59b of side
wall 12b to prevent excessive tightening force at screw connec-
tions 58 from destructively damaging or distorting the wear
plate. A corresponding structure employing member 59c from
buffer plate 82a (Fig. 6~ and a protruding member 59d from wear
plate 54 prevent distortion of plate 54.
Wear plates 50 and 54 and f ireback 52 are removable
from the interior of the apparatus 8 through the front opening.
These elements are more subject to deterioration because of their
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close proximity to the intense heat in the primary combustion
chamber 16. They may therefore be replaeed by the user without
having to disassemble the entire stove frame member 10. In addi-
tion wear plates 50 snd 54 and fireback 52 help protect the out-
side frame walls of the heating apparatus from undue wearresulting from exposure to the primary combustion chamber heat.
Wear plates 50 and 54 and fireback 52, in combination
with side walls 12a and 12b and back wall 12f delimit the space
in which a primary air supply path 60, a primary/secondary air
supply path 61, a night air supply path 62, and a circuitous,
combusted products flame path 64 are defined. The primary air
supply path 60 and the primary/secondary air supply path 61 each
begin at the thermostatically controlled inlet port 22. Air
entering through port 22 thus divides at the enclosure side of
lS the port into the two paths 60 and 61. The primary air supply
path 60 passes, in the illustrated embodiment to a left side of
the heating apparatus B and enters the primary combustion chamber
16 through a tapered slot 74 in wear plate 50. The slot is
tapered to provide a desired air flow rate across the entire
length of the slot and has a wider opening toward the back of the
apparatus. The primary path through which these primary gases
are directed is defined by wear plate 50 and a portion of fire-
back 52, in combination with the outside wall panels of the
heating apparatus, and a horizontal baffle member 65 (described in
connection with Fig. 5). The primary/secondary air supply gases
from air inlet port 22 are directed toward the right hand portion
of the apparatus through a bottom elongated enclosure 77 (Fig. 5)
formed by fireback 52 in combination with the rear panel 12f and
the horizontal baffle member 65. This directed air path ~turns
30 the corner~ at the back, right hand portion 77a of the apparatus ,
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. and is directed beneath a multiple baffle plate 77b through a
.
slot 78 into the primary combustion chamber 16.
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The oxygen rich air directed from inlet-Z2 to --
primary/secondary path 61 serves two functions. A first portion~
of the air exits from path 61 through holes 7g in fireback 52.
These oxygen rich preheated gases (heated by contact with the
fireback) contribute to primary combustion in the primary com-
bustion chamber 16. The remaining preheated, oxygen rich gases,
which turn corner 77a, pass into the primary combustion chamber
where they substantially immediately combine and mix with com-
busted gases 80 which are exiting through wear p'ate exhaust slot
- 80a. Slots 78 and 80a are thus formed by dividing the aperture
in wear plate 54 by plate 87a. Thereby, a portion of the primary
conbustion chamber 16 adjacent the slot opening 78 in wear plate
54 becomes, in effect, a secondary combustion chamber. The com-
busted gases exiting through openings 80a are controlled in part
by baffles 88, 84, 85 of wear plate 54, three corresponding
baffles 83a, 84a, 85a integral with side 12a and baffles 86, 87
of baffle plate 77b ~as described below), and are guided along
the long circuitous internal flame path 64 to an eXit aperture 88
in the frame structure.
As the combusted gases 80 exit through slot 80a, thei-r
natural tendency is 'o bunch together and impinge directly upon
side wall 12a. This effectively concentrates the heat of the
combusted gases on side wall 12a and, at the area of impingement,
can turn the wall a cherry rçd color. Possible deterioration and
breakage of wall 12a can follow. This is due to the close proxi-
mity of wall 12a and wear plate 54. To better channel the gases
across the entire length of the slot 80a, to provide more uniform
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heating throughout the volume between wear plate 54 and side wall
12a, and to avoid overheating, the baffle system comprising
baffles 83, 84, 85, 86, 87 and the three baffles integral with
side wall 12a, is provided. The height of these baffles above
plate 87a, is proportional to the expected exhaust flow around
the baffle. In addition, outward projections ~7b, 87c, 87d (Fig.
4A) provide voids on pockets 87e, 87f, 879 of stagnant air whicb
effectively provide a boundary air layer which insulates the
hotest portion of the exhaust gases from impinging directly upon
side wall 12a. This structure effectively eliminates the con-
centration of gases against and hence possible overheating of
side wall 12a.
The long internal flame path which begins s~bstantially
at slot 80a of wear plate 54 directs the combusted gases exiting
chamber 16 back around the corner 77a, along a first left hand
directed lower path 90, to a second right hand directed upper
path 92, and then upward behind a cup shaped member portion 94,
of fireback 50, past damper 18 and through the flue collar 96 to
an exhaust pipe not shown. The flue collar connection enables
the collar 96 to provide either a rear exiting or a top exiting
configuration. The elements which define upper and lower paths
90, 92 are baffle members 100, 101, and 102 (Fig. 5) formed Dy
mating elements from the rear panel 12f and fireback 52. ~hese
elements provide the substantially sealing relationship to guide
the gaseous products of combustion along the flame pa~h to the
cup shaped member 94. The cooperating structure of the damper
18, cup shaped member 94, and the exit opening 88 is described in
detail further below.
The night air supply path 62 extends from inlet port 35
in side 12b, across the back of the stove, and around corner 77a
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.
to slot 78. This path is directed to a portion of slot 78 below
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plate 87a and terminates after about one inch of travel (in the
illustrated embodiment) along the lower side of baffle plate 87a. `
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The night supply path, defined substantially by baffle elements
65, 102 and upwardly turned member 104 (Figs. 4, 5, and 6),
enables a low level of operation to take place, for example, when
damper 28 is closed.
The heating apparatus thus far has been described and
depicted operating in the horizontal combustion mode wherein com-
busted gases exit through the long internal flame path past a
vertically positioned damper 18 to an exit aperture 88. The
apparatus 8, according to the invention, however, is designed to
be both a horizontal combustion apparatus wherein the damper 18
is in a substantially vertical position as shown in Fig. 3, and
also an updraft combustion apparatus (i.e. a fireplace) in which
damper 18 is pivoted about a longitudinal pivot axis 114 ~Figs.
4, 5, and 6) so that the main plate element 116 pivots downward
to a substantially horizontal position as shown in dotted outline
in ~igs. 7 and 8. This capability of operating in either an
updraft or a horizontal combustion mode requires that the appara-
tus be structured to provide a sealing relationship between the
damper and the flame path in the horizontal combustion mode of
operation so that gases from the primary combustion chamber are
blocked from exiting the apparatus directly through exit aperture
88; that is they must exit through the circuitous flame path.
Similarly, in the updraft combustion mode of operat1on, the
apparatus structure provides a substantially sealing relationship
with a now horizontally directed damper to prevent gases from the
circuitous flame path from exiting through exit aperture 88.
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Referring now to Figure 7, 8, and 9, the damper 18 is
designed to be removable from the apparatus without dismantling
the frame. Thus the damper does not extend the full width of the
apparatus. Damper 18 has the main pivotin~ panel member 116 and
ear panel members 120, 122. The damper 18 and top and back frame
panels are thus designed so that in its extreme positions, the
damper engages other elements of the apparatus to provide the
desired sealing relationships when the damper is vertical or
horizontal ~as described in more detail below).
The position of damper 18 is controlled by an articu-
lated linkage 124 (Fig. 9) which provides, in combination with
damper 18, a resistance against movement of the damper in the
horizontal combustion mode (damper verticai). Referring to
Figure 9, the linkage has two elements, the handle member 20 and
lS a link member 126 connected between end portion 128 of handle 20
and damper 1~. The connection of the link member provide freely
pivoting motion between the link and both the handle and the
damper.
A pivotal connection 129 is provided at the damper by
a retaining nut 129a threaded onto a right angle bent portion of
link 126. The bent portion passes through damper ear member 120
along a pivot aYis parallel to the damper pivot axis 114. The
connection at end portion 128 is made, in the illustrated embodi-
ment, by passing a U-shaped end of handle 20 through an eye 129b
of link 126. Other connecting structures could be employed.
Handle 20 is structured to pass through an opening 129c in rear
panel 12f (sealed by protruding member 132) and is supported by
the rear panel by capture hardware 129d. Illustrated portion
129e of handle 20 thus rotates on an axis parallel to the damper
pivot axis 114.
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Damper 18 is limited in its downward movement (to the ~-
horizontal operating positïon) by a protruding member 130 (Fig.
8) and in the horizontal position the damper panel 116 rests on
and is supported by member 130. ~pward movement of damper 18 (to
the vertical position) is limited by engaging contact of damFer
flanges 130a, 130b (Fig. 9) with corresponding inwardly directed
plate protrusions 132, 134. ~n reaching the vertical position,
link 126 and handle end portion 128 pass an aligned position,
wherein they are substantially parallel, so that thereafter,
movement urged by damper 18, from the vertical position is
resisted by engagement of end portion 128 with the protruding
member 135. -~
The unique damper construction advantageously uses the
minimal volume available in a stove wherein a vertical or a hori-
lS zontal flue gas exit can be employed and wherein the damper inintended to be removable. A full width damper construction which
might typically hinge or penetrate in the main frame members un-
desirably wastes available space in the primary combustion
chamber and further does not provide a damper element which is
easily removable without dismantling the frame. By providing a
reduced width damper, however, in a stove which provides both a
rear exiting as well as a top exiting flue gas exit capability,
the damper panel 116 must be moved inward, from an otherwise nor-
mal position (wherein, in the horizontal position, it bloc~s the
flame path and in the vertical position it seats adjacent
protruding section 131a of back panel 12f) toward the front of
the stove. This movement provides clearance for the flue collar
in its top exiting state. However, in this configuration,
inwardly directed plate protrusions 132, 134 must be provided, ~-
but these protrusions preferably do not extend inwardly for the
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full height of panel 116; protrusions 132, 134 are cut away from
panel 116 as shown, so that in the updraft mode of combustion
~damper in the horizontal position), combusted gas does not
stagnate in the rear upper corners of the stove. When portions
of protrusions 132, 134 are removed, however, the ears 120, 122
must be added to panel element 116 to maintain a sealing rela-
tionship when the damper is in a vertical position. Furthermore,
the curvature at the top ear members 120, 122, required to pivot
the damper, necessitates downward protrusions (only one downward
protrusion 136 is shown) from top panel 12g. Thus, the combined
requirements of updraft and horizontal combustion with a rear or
top exiting flue collar and a removable damper, in the
illustrated heating apparatus of restricted size, require a
unique design concept for the cast iron damper.
lS The protrusions 132, 134, in combination with cup-
shaped member 94, according to the preferred embodiment of the
invention, capture the damper in a pivoting position. Damper pin
protrusions (only pin 140 can be seen in Figs. 7 and 8) extending
from ear members 120, 122 are captured at the upper surface of
cup-shaped portion 94 of fireback 52. The pins thus define the
longitudinal axis 114 about which the damper rotates.
~ ther embodiments of the invention, including addi-
tions, subtractions, delections, and other modifications of the
preferred disclosed embodiment, will be obvious to those prac-
ticed in the art and are within the scope of the followingclaims.
What is claimed is: `
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