Claims
- 1. A stove comprising:
- a firebox for initiating the combustion of fuel, said firebox including a fuel supporting lower portion with a draft inlet therein;
- a first conduit disposed under said firebox for conveying combustion air to said draft inlet and for insulating the underside of said lower portion;
- a second combustion chamber receiving hot gases of combustion from said firebox and continuing the combustion;
- a second conduit which receives combustion air from said first conduit adjacent said draft inlet and which conveys the combustion air which has not passed through said draft inlet along the periphery of said firebox and into said secondary combustion chamber, thereby increasing the flow of combustion air through said secondary combustion chamber during periods of low combustion and for continuing the insulation of said firebox, said first and second conduits cooperating to envelop
- 2. The stove of claim 1 wherein said second conduit includes a narrowed section adjacent said secondary combustion chamber which increases the velocity of combustion air flowing therethrough and baffle means for directing the combustion air into the flow of combustion gases passing from said firebox.
- 3. The stove of claim 1 wherein said firebox and said secondary combustion chamber are closed to the atmosphere except for said first conduit which introduces combustion air into the stove and said third conduit which conveys gases of combustion from said second combustion chamber.
- 4. The stove of claim 1 wherein said second conduit comprises at least one upwardly extending portion which is narrow and long in cross section and which has at least one long wall defined by an exterior wall of said firebox.
- 5. The stove of claim 4 wherein said one long wall is defined by a front wall of said firebox, and baffle means is provided adjacent the upper end of said second conduit portion, for injecting the combustion air passing therethrough substantially horizontally into the flow of combustion gases passing from said firebox.
- 6. The stove of claim 1 wherein said draft inlet includes obliquely disposed vane means for directing combustion air into said firebox at at least one oblique angle
- 7. The stove of claim 6 wherein said vane means comprises a plurality of radially extending, obliquely disposed vanes positioned proximate a plurality of draft inlet openings to swirl the combustion air entering said firebox
- 8. The stove of claim 4 wherein four narrow, long upwardly extending second conduit portions are included which cooperate to surround four sides of said firebox.
- 9. The stove of claim 8, further comprising a back baffle centrally disposed in the upper portion of said secondary combustion chamber spaced from back and top walls of said secondary combustion chamber, said back baffle having a width which is less than the width of said secondary combustion chamber, said back baffle deflecting the rising gases of combustion from the secondary combustion chamber to protect said back and top walls.
- 10. A free standing stove comprising:
- a firebox for initiating the combustion of fuel, said firebox including a bottom with a draft inlet therein, for admitting combustion air into said firebox and for permitting combustion by-products to drop downwardly therethrough and out of said firebox;
- a first conduit juxtaposed beneath said firebox for preheating combustion air, conveying such air to said draft inlet and collecting combustion by-products from said firebox;
- an open secondary combustion chamber juxtaposed above said firebox for continuing the combustion, said secondary combustion chamber receiving the gases of combustion from said firebox and further oxidizing the gases, said secondary combustion chamber including a lower portion;
- a second conduit in thermal contact with at least a portion of the periphery of said firebox for conveying air into said lower portion of said secondary combustion chamber, said second conduit receiving air from said first conduit; and
- a third conduit for conveying the gases of combustion from said secondary combustion chamber.
- 11. A stove comprising:
- a firebox for initiating the combustion of fuel, said firebox including a lower portion with draft inlet means therein and being defined by upwardly extending walls;
- a first conduit beneath said firebox for conveying combustion air to said draft inlet means;
- an open secondary combustion chamber above said firebox for receiving gases of combustion from said firebox and continuing the combustion;
- second conduit means surrounding said walls of said firebox for conveying combustion air to said secondary combustion chamber and for preheating the combustion air; and
- a third conduit for conveying the gases of combustion from said secondary combustion chamber.
- 12. The stove of claim 11 further comprising baffle means mounted adjacent the upper end of said second conduit means, for injecting the combustion air into said secondary combustion chamber at substantially right angles to the flow of combustion gases passing from said firebox.
BACKGROUND OF THE INVENTION
This is a continuation-in-part application of my earlier application bearing the same title, filed July 1, 1980, designated Ser. No. 165,046, now U.S. Pat. No. 4,359,040.
This invention relates to free standing stoves in which heat from the stove may be used to heat the air in a room and/or to cook food.
Free standing wood and coal burning stoves were used for many years prior to the advent of electricity and the widespread use of fuel oil and natural gas. The term "free standing" as used herein is intended to define the type of stove which is complete in and of itself. For example, it need not necessarily be positioned within or be used in combination with any other type of stove or fireplace. It may be advantageous in some instances, however, to utilize a fireplace flue stack in the event the stove is going to be positioned in the vicinity of a fireplace.
Stoves of this type are intended to burn the fuel as completely as possible and transmit the heat released thereby into the room or dwelling. Early stoves were often constructed of cast iron or other metals which were capable of absorbing and subsequently releasing large amounts of heat. Wood and coal burning stoves have thus historically relied primarily upon radiation of heat from the stove into the immediately surrounding air space. While such stoves were acceptble to the early pioneers who lived in small dwellings and had abundant, free fuel close at hand, shortcomings became apparent as civilization and technology progressed. Specifically, the inefficient design of early stoves resulted in most of the heat passing up out of the stove through the flue stack.
Realization of the inefficiency of the early stoves led to the development of more advanced units which took advantage of natural convection of air and combustion gasses through the stove. An example of this type of stove is disclosed in U.S. Pat. No. 4,127,100 to Baker. This patent describes a stove having the conventional box-like shape, fabricated from iron or steel plate. The stove includes a single combustion chamber or firebox in which wood is placed for burning. Draft inlets are positioned in the front of the firebox while the flue or stack is at the rear. An air duct is located toward the back of the firebox. The lower end of this air duct receives ambient air and directs it upwardly and then across the top of the firebox in a plurality of tubes before discharging the air out the front of the stove. The gases of combustion thus contact these air tubes before they exit out the rear of the firebox. As the hot gases pass out of the combustion chamber they are directed downwardly by a baffle plate which causes the gases to contact the upwardly extending air duct, thus imparting heat to the air as it enters the air duct.
The Baker design is typical of second generation wood burning stoves in that it attempts to utilize the natural convection of air and gases through the stove. While Baker's stove is an improvement over first generation designs, it is lacking in several respects. First, in this stove the greatest amount of combustion chamber heat is applied to the air tubes at the rear of the firebox where the ambient air is relatively cool, rather than toward the front of the firebox where the ambient air has reached its highest temperature. A second disadvantage with this stove is that means are not provided for preheating ambient air which is induced into the firebox. Perhaps this is one reason why the draft inlets are positioned in the front rather than at the bottom of the stove, thereby ensuring that the warm, rather than cool, air will be induced into the stove. However, this removal of warm air from the space to be heated defeats the purpose of even having a stove. Moreover, induction from the front provides for poor combuston of the logs in the firebox.
Efficient combustion is not only important to economize on fuel, but also to reduce the existence of particulate and other emissions passing up the flue stack, which not only pollute the air but also result in soot and/or creosote buildup in the flue stack. One way to reduce these emissions while obtaining the greatest amount of energy from a given amount of fuel is to use a plurality of combustion chambers. However, the substantial initial expense of multiple-chambered stoves has often not been justified despite a resulting increase in combustion efficiency. U.S. Pat. Nos. 4,201,185 to Black and 4,184,473 to McIntire exemplify recent efforts with stoves having two combustion chambers. These stoves both have the drawback of injecting unheated ambient air into a secondary combustion chamber. This dramatically reduces the efficiency which is otherwise possible when a secondary burn is included.
Hence, it is a primary object of the invention to provide an improved free standing stove which effectively and reliably overcomes the aforementioned limitations and drawbacks of the prior art proposals. More specifically, the present invention has as its objects one or more of the following taken individually or in combination:
(1) The provision of a stove which has improved combustion efficiency, which thereby results in economical use of fuel and relatively complete combustion, thereby reducing stack emissions which cause pollution and are likely to cause dangerous creosote buildup in the stack;
(2) To develop a stove having a primary and secondary combustion chamber, in which the secondary combustion air is substantially heated before injection into the secondary combustion chamber;
(3) To provide a wood stove in which the primary combustion chamber or firebox is adequately insulated to maintain the combustion temperatures therein and to reduce the danger of extremely hot external stove surfaces;
(4) The provision of a free standing stove which is suitable for burning wood and other solid combustibles, such as coal and the like, which may be easily adapted to exhaust into a flue pipe extending either from the top or the back thereof;
(5) The development of a free standing stove having primary and secondary combustion chambers in which combustion air is swirled and otherwise directed to maximize combustion efficiency;
(6) To provide a stove with a secondary combustion chamber in which the secondary combustion air is injected inwardly from the sides thereof so that combustion therein is centered at a point spaced from the combustion chamber walls, to thereby maximize combustion efficiency and prolong the stove life; and
(7) The provision of a free standing stove which maximizes combustion efficiency, yet which is relatively simple in construction and therefore inexpensive to purchase and to maintain.
This invention responds to the problems presented in the prior art by providing a stove including the following features: (1) a firebox for initiating the combustion of fuel, the firebox including a lower portion with a draft inlet therein; (2) a first conduit disposed under the firebox for conveying combustion air to a draft inlet and for insulating the underside of the firebox; (3) a secondary combustion chamber for receiving hot gases of combustion from the firebox and continuing the combustion; (4) a second conduit which receives air from the first conduit adjacent the draft inlet and which conveys all the air which has not passed through the draft inlet along the periphery of the firebox and into the secondary combustion chamber, thereby increasing the flow of air through the secondary combustion chamber during periods of low combustion and for continuing the insulation of the firebox; and (5) a third conduit for conveying the gases of combustion from the secondary combustion chamber to a flue.
The second conduit normally has at least one upwardly extending portion which is narrow and long in cross section and which has one long wall defined by an exterior wall of a firebox, thereby cooling the firebox wall and substantially preheating the secondary combustion air. In one preferred embodiment, four such narrow, long, upwardly extending second conduit portions are provided, which combine to surround four sides of the firebox, thus insulating the firebox to permit higher firebox temperatures.
Another embodiment of the invention includes baffle means disposed adjacent the upper end of the second conduit which directs the secondary combustion air inwardly away from the outer wall or walls of the stove, thereby causing substantial agitation between the secondary combustion air and the gases of combustion rising from the firebox and tending to reduce the temperature of the secondary combustion chamber walls to prolong the life thereof.
In yet another embodiment of the invention, the draft inlet includes obliquely disposed vane means for directing combustion air into the firebox at one or more oblique angles.
US Referenced Citations (11)
Non-Patent Literature Citations (1)
| Entry |
| Masters Choice-Defiance Company Brochure, 1980. |
Continuation in Parts (1)
|
Number |
Date |
Country |
| Parent |
165046 |
Jul 1980 |
|
Patent Grant
4483312
