Solid fuel burning furnace having a burn control stack

Abstract

A stack, having improved efficiency, for venting exhaust gases from a combustion chamber of a solid fuel burning apparatus, such as a boiler, to a flue. The stack, which can be retrofitted to certain wood burning furnaces or boilers includes an elongated tubular member having a first end, a second end and at least one inlet proximate the first end. The second end of the elongated tubular member defines an outlet which is adapted to register with a flue so as to vent combustion, or exhaust, gases from the combustion chamber to the atmosphere. Further, the stack includes at least one conduit member which is in fluid communication with the first tubular member. The conduit member includes an open end adapted to be in fluid communication with the combustion chamber and an oppositely disposed closed end which is proximate the inlet of the elongated tubular member and is in fluid communication with the inlet of the elongated member. The conduit member(s), defines a channel for communicating exhaust gases from the open end of the conduit member to the inlet of the elongated member creating a tortuous airflow path for combustion gases from the combustion chamber to the chimney via the open end of the conduit member through the outlet of the elongated tubular member to the flue.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention pertains to wood burning furnaces. More particularly, it relates to a more efficient stack for exhausting combustion gases from a wood burning furnace, particularly, a wood burning boiler.

2. Description of the Related Art

Wood burning furnaces are well known in the art of heating. In a typical wood burning furnace, a combustion chamber is provided for receiving and combusting wood, often in the form of split logs. Exhaust gases are vented through a flue to the chimney. Air flow into the combustion chamber is controlled so as to control the rate at which the wood fuel burns. It is known in the art, to use such a wood burning furnace as a boiler for the production of hot water and/or steam. And, it is known in the art to use exterior wood burning boilers as an auxiliary heating source. A state-of-the-art wood burning boiler includes a water jacket surrounding the combustion chamber. This water jacket may include water-filled conduits which are routed through the combustion chamber or a faceted interface between the water jacket and the combustion chamber for increasing the surface area of the interface, and, typically, a mechanism for controlling air flow into the combustion chamber responsive to water temperature.

It is known in the art to use baffles, as seen in FIG. 1 or as taught in U.S. Pat. No. 4,401,101, issued on Aug. 30, 1983, to Lunde, to control the flow of exhaust gases within the combustion chamber in order to increase the efficiency of the furnace. What is missing in the art is a high efficiency stack that can be readily retrofitted to certain existing wood burning boilers or which can be an integral part of a newly constructed wood burning boilers.

BRIEF SUMMARY OF THE INVENTION

According to one embodiment of the present invention, a stack for venting exhaust gases from the combustion chamber of a solid fuel burning apparatus, such as a boiler, to a flue is provided. The stack can be incorporated into a furnace at the time of manufacture or it can be retrofitted to certain wood burning furnaces or boilers includes an elongated tubular member having a first end, a second end and at least one inlet proximate the first end. It will be appreciated by those skilled in the art, that the elongated tubular member can have circular cross-section or a rectangular cross-section. As used herein, the term rectangular cross-section is used to denote a cross-section in which adjacent sides are of either equal or unequal length. The second end of the elongated tubular member defines an outlet which is adapted to register with a flue so as to vent combustion, or exhaust, gases from the combustion chamber to the atmosphere.

In order to create a tortuous airflow path from the combustion chamber into the stack, the stack includes at least one conduit member which is in fluid communication with the first tubular member. The conduit member includes an open end adapted to be in fluid communication with the combustion chamber for receiving combustion gases and an oppositely disposed closed end which is proximate the inlet of the elongated tubular member and is in fluid communication with the inlet of the elongated member in order to allow passage of the combustion gases through the inlet into the elongated tubular member. The conduit member thus defines a channel for communicating exhaust gases from the combustion chamber via the open end of the conduit member to the inlet of the elongated member thereby creating a tortuous airflow path from the open end of the conduit member to the outlet and the flue.

Whereas the stack of the present invention can be retrofitted to certain existing wood burning furnaces or wood burning boilers, the stack can also be a component of a newly constructed wood burning furnace or boiler. In one embodiment, the conduit member is secured to, and carried by, the elongated member. In an alternate embodiment, the conduit member is secured to the end wall of the wood burning furnace. In this embodiment, the first end of the elongated member is received in the space between the conduit member and the end wall of the wood burning furnace. In yet another embodiment, the elongated member and the conduit member are coaxial. Also, while the stack of the present invention is discussed in the context of a wood burning furnace, it will be appreciated by those skilled in the art that the stack of the present invention could be utilized in any solid fuel furnace where it is desirable to control the flow of air through the combustion chamber.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The above-mentioned features of the invention will become more clearly understood from the following detailed description of the invention read together with the drawings in which:

FIG. 1 is a cross-sectional view of a prior art wood burning boiler;

FIG. 2 is a perspective view of one embodiment of the stack of the present invention;

FIG. 3 is a front elevation view of the stack illustrated in FIG. 2;

FIG. 4 is a top plan view of the stack illustrated in FIG. 2;

FIG. 5 is a side elevation view of the stack illustrated in FIG. 2;

FIG. 6 is a partial front elevation view in cross-section showing the stack of the present invention as used in conjunction with a wood burning boiler;

FIG. 7 is a side elevation diagrammatic view, in partial cross-section, of a wood burning boiler incorporating the stack of the present invention;

FIG. 8 is a front elevation diagrammatic view, in partial cross-section taken along line 7-7 seen in FIG. 7 of a wood burning boiler incorporating the stack of the present invention;

FIGS. 9 a and 9b are top plan views, in cross-section, of alternate embodiment stacks; and

FIGS. 10 a and 10b are top plan views, in cross-section, of other alternate embodiment stacks in which the elongated tubular member and the conduit member are coaxial.

DETAILED DESCRIPTION OF THE INVENTION

Wood burning furnaces have long been used for the production of heat and in the form of a boiler for producing heated water or steam. The heated water or steam can then be used as an auxiliary heat source. A state-of-the-art wood burning boiler is designated as 10 in FIG. 1. The state-of-the-art wood burning boiler 10 includes a firebox 12′ that defines a combustion chamber 14′. A door 16 is provided in one end of the firebox 12 for providing access to the firebox 12′ and for loading wood into the combustion chamber 14′. The flow of air into the combustion chamber 14′ is controlled by a vent 18′, shown schematically in FIG. 1, which can include a mechanism for controlling the vent 18′ which is responsive to water temperature. The firebox 12′, which can either be rectangular or circular in cross-section, is surrounded by a fluid-filled jacket, which typically contains water, which acts as a heat exchanger. In this regard, the fire in the combustion chamber 14′ heats the water in the water jacket 20′ to the desired temperature and this heated water is circulated through a system (not shown) for providing auxiliary heat to a number of different types of applications. A flue 22′ is typically provided as a passageway for exhaust gases from the combustion chamber 14 to the chimney 24′. In this regard, the flue 22′ can be vertical, extend through the top of the firebox 12′ and be integral with the chimney or can be horizontal, extend through an end wall of the firebox 12′ and adjoin the chimney. In order to restrict the flow of exhaust gases through the flue 22′ and thereby allow for a slower burn and greater heat transfer from the fire and combustion gases to the water in the water jacket 20′, a baffle, such as baffle 26 is frequently placed in the combustion chamber 14′ for redirecting, or controlling, the flow path of the combustion gases.

According to one embodiment of the present invention, as best illustrated by FIGS. 2 and 6, a stack 100 is provided for venting exhaust gases from a combustion chamber 14 of a wood burning apparatus, such as a boiler 90, to a flue. While the present invention is discussed with regard to a wood burning furnace or boiler, it will be appreciated that the present invention could be utilized in conjunction with any solid fuel burning furnace. The stack 100, which can be retrofitted to certain wood burning furnaces or boilers, includes an elongated tubular member 105. It will be appreciated by those skilled in the art, that the elongated tubular member 105 can have circular cross-section or a rectangular cross-section. As stated above, the term rectangular cross-section is used to denote a cross-section in which adjacent sides are of either equal or unequal length. Tubular member 105 has a first end 110, a second end 115 and at least one inlet 112 proximate the first end 110. The second end 115 of the elongated tubular member 105 defines an outlet 116 which is adapted to register with a flue 22 so as to vent combustion, or exhaust, gases from the combustion chamber 14 to the atmosphere through the chimney 24. In order to allow residue to be more easily cleaned from the first end of the elongated tubular member, a closeable door 118 can be provided in the first end 110 of the elongated tubular member 105.

Further, the stack 100 includes at least one conduit member 120 which is in fluid communication with the first tubular member 105. In this regard, the conduit member(s) 120 includes an open end 122 adapted to be in fluid communication with the combustion chamber 14 for receiving combustion gases and an oppositely disposed closed end 126 which is proximate the inlet 112 of the elongated tubular member 105 and is in fluid communication with the inlet 112 of the elongated tubular member 105 in order to allow passage of the combustion gases through the inlet 112 into the elongated tubular member 105. The conduit member 120 thus defines a channel for communicating exhaust gases from the combustion chamber 14 via the open end 122 of the conduit member 120 to the inlet 112 of the elongated tubular member 105 thereby creating a tortuous airflow path, depicted by the arrows in FIG. 6, from the open end 122 of the conduit member 120 to the outlet 116 defined by the second end 115 of the elongated tubular member 105 and the flue 22. In the depicted embodiment, the interaction of the elongated tubular member 105 and the conduit member 120 causes the airflow path of the combustion gases to substantially reverse direction, thereby creating a tortuous airflow path as shown in FIG. 6.

Whereas the stack of the present invention can be retrofitted to certain existing wood burning furnaces or wood burning boilers, the stack can also be a component of a newly constructed wood burning furnace or boiler 90 having a firebox 12 having an opening such as a door 16 in at least one end for receiving a solid fuel, such as wood 28 and having a main body portion defining a combustion chamber 14 with a firebox end wall 30 opposite the open end. A vent member 32 is provided for allowing combustion air to flow into the combustion chamber 14. A control mechanism, illustrated schematically at 34, can be provided and in active engagement with the vent member 32 for selectively regulating the flow of combustion air into the combustion chamber 14. It will be recognized by those skilled in the art that while a vent member 32 is illustrated diagrammatically as being associated with the door 16, other ways of permitting or injecting combustion air into the combustion chamber 14 may be utilized as desired.

In the embodiment discussed above and illustrated in FIGS. 2-6, the conduit member 120 is secured to, and carried by, the elongated tubular member 105. In an alternate embodiment, illustrated in FIGS. 7-9, a stack 100′ is provided in which the conduit member 120′ is secured to the end wall of the wood burning furnace or boiler 90. In this embodiment, the first end 110′ of the elongated tubular member 105 is received in the space 128 between the conduit member 120′ and the end wall 30 of the wood burning furnace or boiler 90. The inlet described above is defined by the open first end 110′ of the elongated tubular member 105. As best illustrated in FIG. 8, this embodiment also provides for a tortuous airflow path, as seen by the arrows, for the exhaust gases from the combustion chamber 14 to the chimney 24. It will also be appreciated that in yet another embodiment, illustrated in FIGS. 10-11, a stack 100″ is provided in which the elongated tubular member 105 and the conduit member 120″ are coaxial. As alluded to above, and as illustrated in FIG. 11, elongated tubular member 105′ and conduit member 120′″ can have a circular cross-section. Also, while the stack 100 of the present invention is discussed in the context of a wood burning furnace, it will be appreciated by those skilled in the art that the stack of the present invention could be utilized in any solid fuel furnace where it is desirable to control the flow of air through the combustion chamber. While various spatial relationships between the elongated tubular member 105 and the conduit 120 have been discussed and illustrated, it will be appreciated by those skilled in the art that there may be other spatial arrangements that nevertheless create a tortuous airflow path as discussed above. It will also be appreciated by those skilled in the art, that where more than one conduit members 120 is provided, or where all or a portion of the conduit member 120 surrounds the first end 110 of the elongated tubular member 105 as illustrated in FIGS. 9 and 10, the channels between the sides of the elongated tubular member 105 and the conduit(s) should be symmetrical in order to allow for uniform burning of the wood 28 within the combustion chamber 14.

From the foregoing description, it will be recognized by those skilled in the art that a stack for a wood burning furnace or boiler, which can be retrofitted to certain existing furnaces, or can be a component of a newly constructed furnace, or boiler, has been provided. The elongated tubular member 105 and the conduit member 110 co-act to create a substantially vertical tortuous airflow path for the combustion, or exhaust, gases from the combustion chamber 14 to the chimney 24. By creating a tortuous airflow path for the combustion, or exhaust, gases to follow from the combustion chamber 14 to the chimney 24 greater efficiencies are realized in terms of increased burn times, more efficient heat transfer from the combustion chamber to the water jacket and more efficient burning of the fuel resulting in less particulate matter in the exhaust gases and less ash.

While the present invention has been illustrated by description of several embodiments and while the illustrative embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant's general inventive concept.

Claims

1. A stack for venting exhaust gases from a combustion chamber of a solid fuel burning apparatus to a flue, said stack comprising: an elongated tubular member having a first end, a second end and at least one inlet proximate said first end, wherein said second end defines an outlet, wherein said outlet is adapted to register with a flue; and at least one conduit member in fluid communication with said first tubular member, said conduit member having an open end adapted to be in fluid communication with a combustion chamber and an oppositely disposed closed end proximate to and in fluid communication with said inlet, wherein said at least one conduit member defines a channel for communicating exhaust gases from said open end of said at least one conduit member to said inlet whereby a tortuous airflow path is defined from said open end of said at least one conduit member to said outlet.

2. The stack for venting exhaust gases of claim 1 wherein two said conduit members are in fluid communication with said elongated tubular member in spaced relation.

3. The stack for venting exhaust gases of claim 1 wherein said at least one conduit member is carried by said elongated tubular member.

4. The stack for venting exhaust gases of claim 1 wherein said elongated tubular member and said at least one conduit member each have a rectangular cross-section.

5. The stack for venting exhaust gases of claim 1 wherein said elongated member and said at least one conduit member each have a circular cross-section.

6. The stack for venting exhaust gases of claim 5 wherein said elongated member is coaxial with said conduit member.

7. The stack for venting exhaust gases of claim 1 wherein said conduit member receives said first end of said elongated member within said channel.

8. The stack for venting exhaust gases of claim 1 wherein said stack for venting exhaust gases is a component of a solid fuel burning furnace.

9. The stack for venting exhaust gases of claim 8 wherein said solid fuel burning furnace is a boiler.

10. The stack for venting exhaust gases of claim 1 wherein said tortuous airflow path is a substantially vertical tortuous airflow path.

11. A solid fuel burning apparatus, said apparatus comprising: a firebox having an opening in at least one end for receiving the solid fuel and having a main body portion defining a combustion chamber with a firebox end wall portion opposite the open end; a vent member for allowing combustion air to flow into said firebox main body portion; a control mechanism in active engagement with said vent member for selectively regulating said flow of combustion air into said firebox main body portion; a stack member defined by an elongated tubular member having a first end, a second end and at least one inlet proximate said first end, wherein said second end defines an outlet, wherein said outlet is adapted to register with a flue for discharging gaseous combustion products from said combustion chamber; and at least one conduit member in fluid communication with said first tubular member, said conduit member having an open end adapted to be in fluid communication with a combustion chamber and an oppositely disposed closed end proximate to and in fluid communication with said inlet, wherein said at least one conduit member defines a channel for communicating exhaust gases from said open end of said at least one conduit member to said inlet whereby a tortuous airflow path is defined from said open end of said at least one conduit member to said outlet.

12. The stack for venting exhaust gases of claim 11 wherein two said conduit members are in fluid communication with said elongated tubular member in spaced relation.

13. The stack for venting exhaust gases of claim 11 wherein said at least one conduit member is carried by said elongated tubular member.

14. The solid fuel burning apparatus of Clam 11 wherein said apparatus further comprises a heating chamber surrounding at least a portion of said firebox, wherein said heating chamber is adapted for receiving a fluid to be heated by said solid fuel burning apparatus.

15. The solid fuel burning apparatus of claim 11 wherein said firebox main body portion has a substantially rectangular cross-section.

16. The solid fuel burning apparatus of claim 11 wherein said firebox main body portion has a substantially circular cross-section.

17. A solid fuel burning apparatus, said apparatus comprising: a firebox having an opening in at least one end for receiving the solid fuel and having a main body portion defining a combustion chamber with top, bottom and side firebox wall portions and a firebox end wall portion opposite the open end; a vent member for allowing combustion air to flow into said firebox main body portion; a control mechanism in active engagement with said vent member for selectively regulating said flow of combustion air into said firebox main body portion; a stack member defined by an elongated tubular member having a first end, a second end and at least one inlet proximate said first end, wherein said second end defines an outlet, wherein said outlet is adapted to register with a flue for discharging gaseous combustion products from said firebox; and at least one conduit member carried by said first tubular member, said conduit member having an open end adapted to be in fluid communication with a combustion chamber and an oppositely disposed closed end proximate to and in fluid communication with said inlet, wherein said at least one conduit member defines a channel for communicating exhaust gases from said open end of said at least one conduit member to said inlet whereby a tortuous airflow path is defined from said open end of said at least one conduit member to said outlet.

18. The solid fuel burning apparatus of Clam 17 wherein said apparatus further comprises a heating chamber surrounding at least a portion of said firebox, wherein said heating chamber is adapted for receiving a fluid to be heated by said solid fuel burning apparatus.