Stoves and furnaces – Fireplaces or accessories – Fluid fuel
Reexamination Certificate
2000-05-22
2001-11-06
Yeung, James C. (Department: 3743)
Stoves and furnaces
Fireplaces or accessories
Fluid fuel
C126S09100A, C126S400000
Reexamination Certificate
active
06311687
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a heating oven according to the with an air-tight combustion chamber including a fresh air inlet and an exhaust gas outlet. The heating oven also includes at least one first heat storage element, which is heated by the combustion chamber and at least for the most part spaced apart from the combustion chamber, such that an air channel or a first flow channel is defined by the spacing.
2. Description of the Related Art
In known wood-burning tile stoves, the heat from wood combustion is supplied to heat storage means. To obtain good heat exchange between the hot exhaust gases from combustion and the refractory bricks of the heat storage means, it is known to deflect the hot combustion gases through the heat storage means to, by passing the bricks in the stove several times before the gases; reach the chimney.
Wood-burning tile stoves are very popular because the heating effect is considered very pleasant. The air is not heated, rather the walls and all other solid objects in the room are heated by radiation. In addition, air circulation is largely avoided, which means that no additional dust fills the air. Moreover, the air humidity and the balance between positive and negative ions are maintained which leads to a healthy, natural climate.
Wood-buming tile stoves have the disadvantage that the amount of wood necessary for operation requires considerable storage space. Such space is often unavailable especially in town houses on small lots or in multiple family dwellings.
German patent application DE 26 50 053 A1 discloses an oven having a heat retaining material surrounding the combustion chamber, which is operated with liquid or gaseous fuels. The encasing of the combustion chamber with heat retaining materials, especially chamotte, has the purpose of retaining the heat from the combustion process and continuous radiation of the heat.
A considerable amount of moisture forms from the combustion of the heating gas, in particular from natural gas, city gas, liquid gas (propane, butane, etc.) or heating oil. Further, DE 26 50 053 A1 discloses that the heat retaining material is disposed in direct contact with the combustion chamber, such that the combustion heat is immediately transferred to the heat retaining material. Thus, the combustion chamber only slowly reaches its final temperature, which remains far below 100° C. A temperature of 100° C. or possibly higher should also be avoided so that the operator does not suffer burns from the heat retaining material. However, this results into moisture condensation from the combusted gases on the walls of the combustion chamber. The combustion chamber corrodes, is no longer air-tight, the heat retaining material becomes sooted and the oven releases moisture via the heat retaining material into the room to be heated.
The German patent application DE 35 00 186 A1 discloses a heat retaining system for wood-fired heating stoves. The reference discloses that conventional ceramic retaining materials, such as chamotte, have poor thermal conductivity properties. With increasing thickness of the brick walls, in order to increase the retaining capacity, the heat release is increasingly delayed. To achieve a more rapid and a correspondingly good heat exchange, even with higher retaining capacities, i.e. thicker walls of the retaining medium, it is suggested to embed metal heat conducting elements into the retaining material. Further, air channels are provided in the side of the heat retaining material facing the combustion chamber, through which hot exhaust gases are guided to the chamotte or fireclay bricks of the heat retaining material by means of convection from the combustion chamber. Thus, the heat supply from the combustion chamber to the material is improved.
Should such a wood-burning tile stove be operated with gas, the heat retaining would become sooted because the moisture from the combustion gas would reach the heat retaining. Thus, the wood-burning stove of DE 35 00 186 A1 would not be suited for heating with gas or oil.
The German patent application DE 36 00 982 A1 discloses a wood-burning tile stove suited for hot air heating. A heating assembly is provided with a back wall arranged directly on the wall of the room, so that the thermal energy of the heating assembly is passed directly to the (cold) wall. It is suggested to arrange retaining bricks directly on the wall of the heating assembly in order to obtain a fast response with high retaining capacity of this tile stove.
Similar to the statements on DE 26 50 053 A1, wherein-the heating assembly is arranged on the wall of the heated room alone has the consequence that the assembly does not reach a temperature of 100° C. This temperature reduction is enhanced by the retaining bricks arranged thereon. Should this known tile stove be operated with gas, moisture would condense on the heating assembly and on the retaining bricks. Consequently, water would flow out of the stove.
Finally, the Austrian patent AT 376 787 discloses a wood-burning tile stove, which is available in prefabricated form, the work-initensive setting of the tiles is to be avoided. This is achieved by providing a dual-casing arrangement. The space between the inner casing and the outer casing is filled with heat-storing material only in the region where the walls face the room to be heated. The remaining region has lower air intakes and upper air outlets for the heated air. A particular disadvantage of this wood-burning tile stove is that the lower inflowing and the upper out flowing air produces a very unfavourable air draft in the room to be heated. The concept of such wood-buming stoves however is precisely that the heat should only be radiated from the stove to the surroundings. In addition, the known convection tile stove has a reduced heat retaining capacity due to the smaller volume of the retaining material. This known stove is therefore not capable of delivering heat over a longer time after the wood fire has been extinguished. Moreover, this known stove is neither suited for nor intended to be operated with gas or oil.
The German patent application DE-A 1 33 41 481 discloses a wood-burning tile stove. To achieve a rapid heating up of the room containing the stove, the firing chamber is completely surrounded by convection channels so that the air flowing directly along the chamber walls is greatly heated and can be passed as an air flow to the room. Despite good heat discharge, the outer walls of the oven opposed to the firing chamber become only moderately warm due to the strong convection flow.
Even if one operated the convection wood-burning tile stove of DE-A 1 33 41 481 with gas or oil, although no suggestion of same is given, the water vapor resulting from the combustion of gas or oil would condense on the walls of the combustion chamber. This is because the air flowing by the chamber walls is strongly heated, which self-evidently leads to a cooling of the chamber and prevents its temperature from rising above 100° C.
A particular object of the present invention is to provide a functional heating oven for gaseous or liquid fuels, which has a large heat retaining capacity despite its compact form.
SUMMARY OF THE INVENTION
The heating oven according to the invention is provided with a combustion chamber which is substantially air-tight with respect to its surrounding heat-retaining elements, so that the exhaust gases and moisture resulting from the combustion of a heating gas or liquid fuel cannot reach the heat-storing elements or retaining bricks. The term heating gas will be understood to include in particular natural gas, city gas, liquid gas (propane and butane, etc.) and oil will be understood to include in particular heating oil, lower alcohols, in particular methanol and ethanol, and lower natural alcohols, in particular rape oil. These fuels as well as wood and coal are suited for use in the heating oven of the present invention.
Heat exchangers are provided to transfer the heat from the combustion chamber to the
Darby & Darby
Yeung James C.
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