Note: Descriptions are shown in the official language in which they were submitted.
iO~59;:5
1 Back round o the Invention
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In numerous localities, substantial quantities of
wood and wood scraps are available w~lich may provide an
inexpensive source of ~uel. A problem has always existed
concerning the burning of wood efficiently for heating
purposes, and particularly in burning green wood or wood
which has not properly dried or been seasoned.
One of the most importan~ problems in regard to
burning of wood for space heating purposes relates to the
fact that substantially all wood and especially green wood
contains a very substantial amount of creosote and moisture
along with some volatile gases such as methane. In the
burning of wood, the creosote and moisture is driven off
the wood by the heat, and in most wood burning devices,
oxygen and moisture cause the creosote to solidify on the
interior surfaces of the heat exchanger and stack or flue.
As time goes by, the quantity of solidified creosote builds
up on the interior of the heat exchanger or stack so that
less and less heat is transmitted to the space being heated,
and a greater and greater risk of chimney fires is created.
The woods which are readily available and inexpensive
for use in heating are those which are high in creosote
content, and such woods include poplar or aspen, willow,
pine, tamarack, cedar, balsam, hemlock and birch.
In some locations sawmill slabs or scrap is readily
available and inexpensively obtained, but such material is
primarily the outer parts of logs including bark, which is
the particular part where a substantial amount of creosotes
are found.
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l In -the past, there have been some furnaces or
burners which have attempted -to burn wood or alternately
burn oil in the same irebox or combustion chamber. However,
it does not produce eficient burning of the wood or green
wood by simply burning oil in the same combustion chamber.
Su~ o the Invention
The present invention produces efficient and
complete burning o the combustion gases and volatile -~
materials in the fire chamber of the burner or urnace
before such combustion gases are allowed to escape into
the heat exchanger and flue. This complete combustion is
obtained by injecting secondary combustion air, preerably
preheated, above the burning logs in the urnace and
causing and using such air to produce a cyclonic action
in the combustion chamber so that all o the methane gas ~ ;
and creosote is eficiently burned before the combustion
gases are allowed to escape. Such secondary combustion
air is injected in an array or curtain of jets directed ~ `
trans~ersely across the exit port for the combustion gases
20 prior to the entrance of such combustion gases into the ~;
heat exchanger and flue. An aspirator tube extends the
full length of the combustion chamber to create such jets
of air and the aspirator tube is supplied with heated fresh
air from a preheating chamber in the front wall o the
furnace which also keeps the front wall of the urnace at
an acceptably low temperature as to avoid any danger to
people in the vicinity of the furnace. The heating chamber
- in the front wall also substantially surrounds the access
door through which logs are supplied into the burner so
that the front door is also kept at an acceptably minimal
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1 temperature, -thus permitti~c~ it to be opened ~or feeding
the fire. ~dditional aspirator tubes adjacent the
longitudinal sidewalls o~ the combustion chamber direct
additional jets o heated secondary air above the log
fire on the grates to a~d to the cyclonic turbulence and
contribute to the complete combustion of gases and creosote
before the combustion gases are allowed to escape from the
combustion chamber.
The combustion chamber is provided with an elongate
shape to accommodate logs which are in fireplace lengths
rather than in stove wood lengths as has been commonly known.
In one particular embodiment, logs of 18 to 23 inches in
length are easily accommodated.
The flame from an oil burner is directed into the
combustion chamber through the sidewall at a location
approximately midway along the length of the sidewall.
As a result of this location of the port through which the
oil fired flame is injected into the fire chamber, the oil
or gas fueled flame is directed approximately midway along
the length of the logs lying in the combustion chamber.
The oil fired flame directed into the combustion chamber
creates a double cyclonic action in both ends of the
elongate combustion chamber so that substantially identical
combustion occurs throughout the entire combustion chamber, ~ `
thus causing the entire logs to be ignited and burned
simultaneously. ;
It should be recognized that, whereas it is not ;~-
essential that the oil or gas fueled flame be used to
supplement the heat provided frGm the wood fire in the
burner, at all times, it may be desirable to supplement
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1 the h~at provided Erom the wood fixe by the oil or gas
fueled fire when the demands for heat are more than can
be supplied from the wood fueled fire. When the wood
fueled fire is used in conjunction with the oil or gas
fueled flame, combustion of the wood ueled fire is
assisted, both as to intensity, and as to assuring that
maximum burning of the logs in the burner or furnace is
accomplished. In many instances, the heat provided from
the wood fueled ~ire will be adequate.
Description of the Drawings
Figure 1 is a perspective view of the furnace with `
portions of the paneling broken away for some clarity of
detail.
Figure 2 is a transverse section view taken at 2-2
in Figure 1.
Figure 3 is a longitudinal section view taken
approximately at 3-3 in Figure 2.
Figure 4 is a horizontal view taken at 4-4 in
Figure 3.
~ Detailed Description of the Invention
One form of the invention is illustrated in the
drawings and is described therein. The combined wood and
oil hurning furnace is illustrated in Figure 1 and is
indicated in general by numeral 10.
The furnace includes an outer shell or shroud 11
I through which air is circulated to be heated and then
I directed back to the heating ducts of the building or space
to be heated. Furnace 10 also includes an inner housing 12
~ which defines the combustion chamber 3. The furnace also
; 30 includes a heat exchanger 14 which conducts the hot
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1 combustion ~ases from the housing 12 and through the
interior spaces of the outer shell 11 and to a manifold 15
which collects all the combustion gases and discharges such
gases to an outlet flue 16 for connection to a stack.
It will be recognized that the heat exchanger 14
comprises a plurality of rectangular metal ducts 14.1 which
are generally rectangular in configuration and are spaced
apart so -that air may circulate all around the ducts 14.1
for maximum heat exchange. The outer shell or shroud 11
has an interior divider wall 17 which divides the interior
of the outer shell 11 into an intake or preheating
compartment 11.1 and a second heating compartment 11.2
which completely surrounds the inner housing 12.
The shell or shroud 11 has an air intake opening
11.3, adapted for connection to the air return ducts of a
building heating system for delivering air to the furnace
to be heated. The air traverses a portion of the heat
exchanger 14 which is in the chamber 11.1, and proceeds
to a fan 18 which propels the air through the wall 17 and
into the heating chamber 11.2. The air in the heating
chamber 11.2 circulates around the outer periphery of the
inner housing 12 and also through the heat exchanger 14 in
the chamber 11.2 and thence is moved outwardly through the
air discharge opening 11.4 which is adapted for connection
to the hot air delivery ducts in the heating system of
a building.
The combustion chamber 13 of the inner housing 12
has a lower portion 13.1 defining a fire pit and an upper
portion 13.2 in which combustible gases and particles are
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1 substantially consumed beEore being allowed ko exit from
the combus-tion chamber.
The upper portion of the housing 12 has a large
discharge opening 19 through which combustion gases are
directed into a manifold or discharge plenum 20 which is
connected to the heat exchanger 14.
The lower portion 13.1 of the combustion chamber ~
is lined with fire brick 21 at tne two longitudinal sides -
and across the rear or back side. This lower portion or
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10 fire pit of the combustion chamber confines the logs L ~ ;
which are placed in tha fire chamber for burning. The
lower portion of the housing has horizontal grates 22
forming the bottom of the fire pit. The grates are laid
on shoulder portions of the housing structure and are
spaced apart to allow ashes to fall between the grates.
A removable ash drawer 23 is V-shaped and rests upon a
V-shaped panel 24 forming a part of the housing,
The drawer 23 has a front panel 23.1 with a handle
23~2 afixed thereon. The front panel of the drawer and
the handle lies substantially flush with the outer panel 25
of the hollow or chambered front wall 26 of the housing 12.
As appears in Figure 1, the front panel 25 lies substantially
flush with the adjacent portions of the outer shell 11 of
the furnace.
The hollow or chambered front wall 26 of the
housing 12 has a charging or access opening 27 formed
; therethrough and which is normally closed by an access
or fire door 28, which is mounted on hinges 29. An inner
panel 30 of the chambered wall 26 cooperates with the outer
panel 25 in defining a preheating chamber 26.1 which extends
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1 all across the width of the housing 12 above the access
opening 27, and extends downwardly along hoth sides of
the access opening 27 approximately to -the bottom of the
access opening 27 and door 28. The metal plate 30 transmits
heat from the combustion chamber 13 to the air in the
preheating chamber 26.1 so tllat the air therein is heated.
The front wall 26 also defines a passage 26.2 for
draft air which enters through a draft opening 25.1 in the
outer panel 25 and which may be controlled by a regulator
valve. The draft passage 26.2 is defined by a lower
portion 30.1 of the inner panel which defines a draft air
opening 30.2 through which the draft air is directed into
the fire pit adjacent the grates 22.
In the upper portion 13.2 of the combustion ;
chamber, the sidewalls 12.1 and back wall 12.2 are
protected from intense heat by auxiliary panels 12.3 which
are spaced inwardly.
A generally horizontal baffle plate 31 traverses ;~
a substantial portion of the upper interior of the combustion
chamber and i5 secured to one of the longitudinal sidewalls
12.1 adjacent the outlet opening 19. The baffle 31 is
also affixed to the rear wall 12.2 of the housing and to
the inner panel 30 of the chambered front wall 26. The
free edge 31.1 of the baf1e 31 is spaced from the adjacent
sidewall of the housing to define a combustion gases
discharye passage 32 through which all of the combustion
gases, moisture and air must pass as they travel from the
upper portion 13.2 of the combustion chamber to the
outlet 19.
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1 An array or curtain of adjacent jets or streams of
preheated secondary air are directed across the passage 32
from an aix supply or aspirator tube 33 which extends along
the free edge 31.1 of the bafle throughout substantially ~ .
the entire length oE the elongate fire chamber 11. ~he air : ;
tube 33 has its front end communicating with the preheating : .
air chamber 26.1 through an opening 33.1 in the inner
panel 30 of the chambered wall 26 to receive air under
pressure. The tube 33 has a plurality of discharge openings
or apertures 33.2 which direct streams or jets of the air
from the tube 33 transversely across the discharge passage 32
through which all of the combustion gases must flow.
The streams or jets of air are directed obli~uely downwardly ;
and toward the adjacent lon~itudinal sidewall of the inner
housing 12 so as to thoroughly expose all o the combustion
gases passing through the passage 32 to fresh heated air ~ :
for completing combustion and also ~or creating a cyclonic
turbulence.
Air is supplied into the preheating chamber 26.1
by a fan 34 mounted on the front panel 25 of the chambered
wall 26. Air from the an is moved through the preheating
chamber 26.1 and into the tube 33. .
A pair o additional air supply or aspirator tubes 35
and 36 are respectively located along the opposite ~:
longitudinal sidewalls of the combustion chamber and :~
immediately above the ire brick 21 which defines the
fire pit 13.1. The tubes 35 and 36 have discharge
apertures 35.1 and 36.1, respectively, which are oriented
to direct air horizontally outwardly away from the adjacent
sidewall and substantially horizontally into the central
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1 area of the combustion chamber. S~cond~ry air is thereby
provided which sweeps across ~he top of the fire pit and
of the logs and burning material ther~in. Air supply
tubes 35 and 36 are both connected to the air preheating
chamber 26.1 in the manner illustrated in relation to
tube 35 in Figure 3. The portions of the preheating
chamber 26.1 which extend downwardly along the side edges
of the access opening 27 have openings 26.2 through the
inner panel so as to direct air into the two tubes 35 and 36.
One of the longitudinal sidewalls 12.1 of the
combustion chamber has a large burner port 12.11 therein.
A fire brick liner 37 is provided for the port, and an .
auxiliary burner chamber 38 is mounted at an exterior
location with respect to the housing 12, but within the
shell 11 to surround the fire brick lined opening.
The auxiliary chamber 38 is lined with fire brick 37.1.
An oil burner 39 is mounted on a front panel 40 which lies
flush with the outer panel 25 of the chambered front wall 26
and flush with the remainder of the outer shell 11. The oil
burner 39 is connected into the auxiliary chamber 38 through
a duct 39.1. A guard bar 37.2 traverses the opening in the
housing sidewall to prevent aebris from being accidentally
inserted into the auxiliary chamber 38.
The usual type of thermostats are provided or
controlling the functions of the furnace 10. A thermostat
may be provided within the outer shell 11, and in the
vicinity of outlet 11.4 for assuring that when the ~:
temperature within the shell 11 drops to a irst level :
such as 180, the fan 34 will always be turned back on, .~ -:
30 and if the room thermostat is calling for heat, the oil `
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1 burner 39 will also be turned on; and such thermostat
being also for the purpose of turniny both the fan 34 .
and oil burner 39 ofE when temperatures in the shell 11
reach another temperature level, such as 200; and an
additional theremostat in the furnace will turn the
furnace fan 18 to full speed whenever the temperature
in the shell 11 rises to a third temperature level such~ ~
as 140; and as to reduce the speed of an 18 to half ~.
speed when the temperature in the shell reaches a fourth
lQ temperature level such as 100. These are conventional
and well known theremostatic controls and, except or
the control of the fan 34, comprise no portion of the
present invention.
In normal operation o the furnace 10, the furnace
: may he operated almost entirely on wood fuel, or may be
operated only minimally on wood fuel, according to the
desires and plans of the person utilizing the furnace. :~
Green or seasoned logs L will be placed in the fire
pit on the grates for ~urning and as to increase the heating . ~:
effect of the furnace. In practically all circumstances,
when a wood fire is burning in the fire pit, the fan 34
will be turned on, and preheated air from chamber 26.1 is
being blown through tubes 33, 35 and 36. In the combustion
of logs L in the fire pit, a substantial quantity of
comhustion gases including methane gas, moisture in the
orm o vapor, and creosote in small particles or vapor
form are driven of the logs by the heat of the fire and .-
exist in the upper portion of the combustion chamber.
: The preheated secondary air ~hich.is directed out of the
; 30 tuhes 33, 35 and 36 produces a substantial cyclonic -~
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1 turbulence in the upper portion of the combustion chamber
and over the logs L in the fire pit so that air and oxygen
is adequate to promptly burn all of the volatiles and
combustibles which are carried in the combustion gases. .
Air is supplied under the logs to prov.ide primary combustion
air, but the swirling turbulence in the upper portion of the : :
combustion chamber produces the thorough burning of the
various combustibles, both in gaseour form and in
particlized form. When the combustibles are ultimately
driven toward the outlet 19 and the heat exchanger 14,
the combustion gases must pass through the rather elongate
and narrow passage 32, and at this time the combustion
gases are subjected to the array or curtain of incoming
heated secondary combustion air so that an adequate supply
of oxygen is provided for completing the final combustion
of any gases that move upwardly toward the outlet 19.
This array of air streams or jets in a curtainlike :
arrangement is directed obliquely downwardly so that the
entire ~uantity of combustion gases in the upper portion
13.2 of the combustion chamber revolves downwardly and
then upwardly across the port 12.11. As a result of the ::
substantially complete combustion of all the combustibles
from the log fueled :Eire, there will be no discernible `.
collection of creosote or other solid materials in the . ~.
ducts of the heat exchanger or in the flue or stack. `
It may be desirable when burning green waod or
wood that is freshly cut and is likely to contain a ~:
substantial amount of creosote and moisture, to add
supplementary heat from the oil burner 39. When the oil
burner is turned on or energized, the burning fluid
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1 particles ar~ injected into the combustion chamber ~rom
the auxiliary chamber 38 at a location approximately
midway along the length of the combustion chamber and
midway along the length of the logs lying in the fire pit.
This injection oE the burning fluid Eueled fire in-to the
combustion chamber produces a double cyclonic action
throughout the entire combustion chamber so that the heat
of combustion from the fluid fueled fire is applied to :
substantially all portions of the length o~ the logs L
contained in the fire pit. As a result, the entire logs L
will be burning subs-tantially simultaneously. As the
stream o fluid fueled fire is injected from the auxiliary
chamber 38 and through the port 12.11 in the sidewall, the
streams or jets..of air from the air or aspirator tube 33
cause the stream of fluid fueled fire from the oil burner ~:
to be tipped or inclined downwardly so that this stream of
fire is directed downwardly into the Eire pit. This downward
inclination by reason of the air jets or streams from the
tube 33 contributes materially to the turbulence of the
combustion gases in the ire pit and contributes materially
to the complete combustion of all o the combustible gases
in the chamber 13.
It will be recognized that when the combustion gases
pass through the heat exchanger 14, the air in the furnace
is circulated from the intake opening 11.3 downwardly
through the cooler portion of the heat exchanger 14 and
thence through fan 18 and chamber 11.2 to and through the .. ~-
portion of heat exchanger which is closest to the inner .
housing 12, and therefore the hottest portion. From ~here
the circulating air is discharged from the opening 11.4
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1 for circulation back to the space -that is beiny hea-ted.
It will be seen that I have provided a new and improved
wood and oil burning furnace providing for efEicient
combustion of all of -the combustibles in the wood
fueled fire.
Preheated secondary air is injected into the upper
portion of the combustion chamber in an array of jets or
air streams in a curtainlike arrangement across the outlet
passage so that all of the combustion gases are subjected
to sufficient oxygen to complete their combustion. Three
separate air tubes in the combustion chamber produce a
swirling and turbulence in a cyclonic action with all of
the combustible gases so that such combustibles are entirely
consumed in the furnace. An auxiliary oil burner supplies
additional fluid fueled fire into the combustion chamber
at a location midway along the longitudinal sides of the
combustion chamber so that heat of combustion is directed,
in a cyclonic turbulence, to all portions of the logs ~-~
lying in the fire pik and particularly to the opposite
20 ends wherein oppositely directed cyclonic turbulence is~ `
produced. It should be understood that the fluid ~ueled
fire is produced in this illustrated form by an oil burner,
but the auxiliary heat could as well be supplied by other
fluid fuels such as natural gas, bottle gas, or the like.
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