US2461068A

US2461068A - Downdraft stove

Info

Publication number: US2461068A
Authority: US
Priority date: 1942-08-29
Filing date: 1942-08-29
Publication date: 1949-02-08
Anticipated expiration: 1966-02-08

Description

L. LOCKWOOD DOWNDRAFT STOVE Feb. 8, 1949.

2 Sheets-Sheet. 1

Filed Aug. 29, 1942 i/zueruor v Ozi QMM L. LOCKWOOD VDOWNDRAFT STOVE Feb. 8, 1949.

2 Sheets-Sheet 2 Filed Aug. 29, 1942 I Patented Feb. 8, 1949 UNITED STATES PATENT OFFICE DOWNDRAFT STOVE Lee Lockwood, Des Moines, Iowa Application August 29, 1942, Serial No. 456,619

1 Claim. 1

In the art of furnaces, especially household heating coal-burning furnaces, it is highly desirable that provision be made for refueling only at long intervals, twelve or twenty-four hours, and also that provision be made for controlling the combustion from its maximum to an amount only sufficient to maintain combustion somewhat in the nature of a pilot light, without any such attention by an operator as is ordinarily required in using a poker to break up masses of caked coal in the coal magazine, and thereby feed it by gravity to the burning fuel on the grate.

The object of my invention is to provide a furnace of the magazine'down draft type which is relatively light in weight and inexpensive in construction.

A further object of my invention is to provide a, heater of the type employing a magazine to receive a charge of fuel of such an amount that it needs to be charged only once or twice a day, of such construction that a predetermined temperature level may be maintained for a number of hours, say siX or eight, without changing damper adjustments.

More specifically, it is my object to provide a furnace in which the thin sheet metal walls of the combustion chamber at the area where the maximum combustion occurs, is prevented from burning out or being destroyed by heat by the utilization of the incoming air which is necessary for combustion purposes, in forming a constantly flowing stream of cool air directly over the outer surface of the sheet metal forming the combustion chamber, to thereby perform the double function of maintaining the sheet metal at such temperature as to prevent the heat against the inner surface from burning out the sheet metal, and at the same time pre-heating the air just prior to its entrance into the combustion chamber to aid combustion, and whereby a substantial reduction in the weight of the furnace is effected by the elimination of the necessity for such linings.

Another object of my invention is 'to provide a furnace of standard construction which may be manufactured by so-called quantity production and which will operate successfully with all of the various classes or kinds of coal ordinarily used for furnaces and which may be fueled with a large enough amount of coal to burn for a long period of time, for instance twenty-four hours, and which will automatically prevent the coal from caking or sticking to the sides of the fuel magazine so that it feeds by gravity to the combustion area until the magazine is completely r I 2 emptied, withoutany attention on the part of an operator.

There are certain kinds of coal now being used in furnaces which are characterized as being relatively soft and, when heated to a certain degree, willmelt. and become plastic and will expand and generate a gas which condenses in the form of creosote, and when this kind of coal is used in .an ordinary magazine furnace, such expansion causesthe mass of coal in the-magazine to stick to the sides of the magazine and fail to feed by gravity to the combustion area-, hence, at frequent intervals of time it must be loosened by an operator. Furthermore, some of the gas generated within the magazine condenses-in the form of creosote upon the fuel door at'the top of the magazine, andunless the creosote is frequently removed-by an operatonit prevents the door from being tightly closed and permits the gas to escape into the household.

Another object of my invention is to provide a furnace in which any gases that may be accumulated-in the upper portion of the fuel magazine are drawn downwardly into the combustion area and consumed, thereby serving a, useful heating'function'and at the same time preventing the creation of creosote and thereby avoiding the injurious results produced by creosote in the upper portion of the fuel magazine and on the fuel door.

A further object is to provide a furnace of this class in which'air for combustion purposes is fed to the combustion area and the lower part of the fuel magazine 'in a downwardly moving path around the entire inner surface of the fuel magazine and the entire outer surface of the column of coal, whereby combustion takes place more rapidly and completely at this point, thereby forming a cylindricalicolumn of coked coal andashes aroundthe unburned column of coal, thereby preventing thecoal from sticking to the fuel magazine and permitting it to freely move by gravity to thecombustion area, and this ;regard1ess of whether the area under combustion at any given time iS at its maximum or itsminimum- A further object is to provide means for maintaining the upper portion of the fuel magazine in a relatively -cool condition to thereby prevent the generation of an excessive amount of gas within the fuel magazine without impairing .the heat radiatingcapacity of the furnace casing.

In the accompanying drawings V Figure 1 shows a'vertical central sectional view of my improved furnace showing the same loaded 7 is desired, then the damper 36 is also opened. When this has been done the combustion area extends up into the column of coal a substantial distance and a quantity of coal not previously in the combustion area is ignited and burned, in a manner somewhat similar to the placing of a fresh quantity of fuel upon an ordinary fire. This flow of the heated products of combustion into the furnace dome will heat the lid 19 for purposes hereinafter made clear.

Due to the tendency of the heated gases within the combustion area to rise within the fuel magazine, there will be some gas at the top of the fuel magazine which will tend to condense and form creosote. This, however, is prevented in two ways, first, the current of air admitted by the upper damper 28 will enter the top of the fuel magazine all around its circumference and carry the gases down to the combustion area all around the column of coal, and these gases will ignite and thereby increase the heating capacity. Furthermore, the lid 19 being heated prevents the gases from condensing upon the lid, hence, it is not necessary to remove creosote therefrom to keep the lid sealed in substantially gas-tight condition.

Due to the fact that gases are burning sub stantially all around the exterior of the column of coal and up into the fuel magazine, an outer layer of the column of coal is consumed and turned into ashes so that the expansion of the column of coal will not cause it to stick to the walls of the fuel magazine. In practice I have obtained coal having a maximum of such expansion tendency and a maximum of creosote forming quality, and I have successfully repeatedly burned an entire fuel magazine full without breaking the fuel loose from the fuel magazine with a poker, or otherwise, and without forming any perceptible amount of creosote on the furnace lid.

The furnace will work at maximum efficiency when hard coal is used, hence, it is adapted for use in every locality regardless of the kind of coal used for fuel.

By arranging the fuel door for the furnace dome at one side thereof and the flue l4 at the diametrically opposite side, then when the fuel door is opened and the lid to the fuel magazine is also open, any gases that may arise from the fuel magazine will be carried by the air currents entering through the fuel door opening to the dome into the flue and will not enter the room where the furnace is located.

I claim as my invention:

In a fuel burning heater of downdraft type having a housing, a grate extended across said housing adjacent the lower end thereof, an upright vertically elongated casing carried in a spaced relation within said housing having its lower end open and above said grate, with the upper portion of said casing defining a fuel magazine and the lower portion thereof a combustion chamber, partition means having side walls supported in a spaced relation between said casing and said housing such that the space between said partition means and said housing is open to the space above said grate to constitute a passage for flue gases, and the space between the side walls of said partition means and said casing defines an annular air chamber whereby said air chamber is in a heat exchange relation with the casing and said partition means to provide for a heating of the air therein, a top wall for said partition means positioned horizontally above said casing and formed with a fuel inlet which is open to the upper end of said casing, a cover for said fuel inlet, with said cover and top wall of the partition means constituting a closure for the upper end of said air chamber, said partition means having the lower end thereof terminating substantially at the lower end of said casing, a perforated bottom wall connected between the lower ends of said casing and said partition means, with said casing having its upper end open to said air chamber and being formed with peripheral air openings therein at a first position adjacent its lower end and at a second position spaced from said lower end whereby a first portion of air from said air chamber is admitted into said casing through the upper end thereof, a second portion of air through said air openings, and a third portion of air through the perforations in said bottom wall into the space above said grate, an air inlet means for said air chamber, and means for directing the air flowing through said air inlet means into said air chamber such that said first portion of air enters the air chamber at a, position spaced below the upper end of said casing and above the air openings in said second position prior to the admission thereof into the upper end of said casing, with said first and second portions of air, on admis- LEE LOCKWOOD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 38,673 Goewey May 26, 1863 132,211 La Rue Oct. 15, 1872 247,633 Gould Sept. 27, 1881 327,650 Boyd Oct. 6, 1885 604,991 Litchfield et a1. May 31, 1898 843,106 Roell Feb. 5, 1907 919,553 Dillon Apr. 2'7, 1909 953,465 Howard Mar. 29, 1910 1,322,425 Garey Nov. 18, 1919 1,441,531 Croslen Jan. 9, 1923 1,707,623 Box Apr. 2, 1929 1,717,657 Box June 18, 1929 1,939,832 Schott Dec. 19, 1933 954,929 Eichhorn Apr. 17, 1934 2,160,481 Lockwood May 30, 1939 2,225,527 Locke Sept. 9, 1941