US2543289A - Dual container wood burning stove - Google Patents

Description

1951 D. E. HOWES ET.AL 2,543,289

DUAL CONTAINER WOOD BURNING STOVE Filed OCL. l'7, 1946 2 Sheets-Sheet l Feb. 27, 1951 D. E. HOWES ET AL 2,543,289

DUAL CONTAINER woon BURNING STOVE Filed Oct. 17, 1946 2 Sheets-Sheet P BY cz x w ATTORNEYS Patented Feb. 27, 1951 DUAL CONTAINER WOOD BURNING STOVE Douglas E. Howes and Frank G. Smith, Northfield, Vt., assignors to Norwich University, Northfleld, Vt., a corporation of Vermont Application October 17, 1946, Serial No. 703,810

This invention relates to wood burning stoves. It provides a stove structure formed to use wood more efficiently than the wood burning stoves of the prior art. A useful reference stove for comparison is the one in Seeleys Patent No. 2,348,933 of 1944.

In prior art stoves of Seeleys type, the wood is put in a fuel magazine, a part burns to make heat. The burning wood also makes gases by distillation from the wood which is not burning. These gases are fed into the heat of the combustion zone to make more heat in burning, and finally the charcoal resulting fromdistilling gases from wood gets into the combustion zone toburn to make more heat. This mode, of operation broadly has been well known fora long time and Seeleys stove is only a late example of prior art efiorts to put this type of wood stove into more general use than it has had.

The prior art wood stove has two objectionable operations which cause a lot of trouble when used by the general public. The wood in the fuel magazine is liable to burn faster than desired when the temperature is high enough not only to distill gases but also to burn them. When this trouble is avoided by lowering the burning rate the combustion is liable to give a temperature to distill gases but not to fully burn them. The proportion of gases unburned will condense in the stove or the stove pipe and the heating apparatus will progressively gum up resulting in a very messy condition. This is highly objectionable from the users standpoint. The average user of the stove is extremely likely to meet one or the other of these objectionable conditions, either because he is ignorant of the stoves proper operation, or does not want to give it enough study and personal attention.

The stove of this invention is constructed to take care of itself and avoid both objections. It is also adapted to give other advantages as will be pointed out. The way to provide the improved stove will be explained from the example of the drawings.

In the drawings:

Fig. 1 is a front elevation of the stove;

Fig. 2 is a section on line 22 of Fig. 4;

Fig. 3 is a section on line 3-3 of Fig. 2; and

Fig. 4 is a section on line 44 of Fig. 3.

The stove indicated will first be considered in a form for use as a simple room heating stove particularly adapted for wood fuel.

The stove shell I with suitable insulatinglining 2 in the lower portion, Figs. 3 and 4, has ash pit doors 3 and. 4. with draft dampers 5 and i.

3 Claims. (Cl. 12673) The shell also has in the upper portion two pairs of doors I, 8 and 9, I0, each pair at different levels, Figs. 1 and 3. A smoke pipe II is connected to the upper portion of a back extension l2, Fig. 4, on shell I to be explained.

Inside the shell slightly above the bottom is a horizontal plate [3. It divides the shell horizontally and is in the nature of a grate to hold wood on top. Ash pit space is that in the shell below plate E3. The ash pit space is divided by vertical wall 14 so that there is one ash pit with door 3 and another with door 4. The dampers 5 and 6 in these doors each control an air inlet to the corresponding ash pit. The air inlet for one ash pit is not an air inlet for the other. The plate l3 has two slots I5 for one ash pit and two slots l6 for the other ash pit. These slots will pass air up and ash down through plate l3. This plate i3 is preferably an air tight cross partition except for slots I5 and I6 and is not a type of shaking grate.

The top side of plate [3 will support a mass of Wood fuel in the shell. This wood may be put through doors 9 and I0, to fill the shell from plate l3 up to these doors. are merely for convenience when one wants access at a lower level than the level of doors 9 and ID. The whole mass of wood in the shell is held by an inside partition wall ll of the shell in a vertically'divided condition of two columns of wood, one resting on plate l3 above one ash pit, the other column resting on plate 13 above the other ash pit.

The vertical partition wall ll runs from the top wall of the shell, Fig. 2, down to a level some distance above horizontal plate l3. Wall E1 in the shell I forms two vertical magazines A and B to hold the wood fed to the stove, part in one and part in the other magazine. These two magazines A and B are generally closed magazines from the top to the bottom but with both bottoms opening into a common space extending across the whole shell above plate l3. Fuel magazines A and B are thus positioned to feed the Wood by gravity to a common space below them, intended for the stove combustion zone or zones as will be explained. The wall I! extends close enough to plate [3 to avoid a bridging of the wood between the two columns to interfere with the independent gravity feed in each column to plate I3.

Extending across the rear wall of shell I is an air feeding pipe [8. It has an air damper 2| at one end and air damper 22 at the opposite end.

Pipe [8 has an inside cross wall 20. dividing it The doors I and 8 into two sections. When damper 2| is open, air outside the shell will feed in pipe i8 and into the combustion zone adjacent openings l9 from the pipe l8. When damper 22 is open, air will feed to the combustion zone adjacent openings 23 from the pipe l8. This is for feeding secondary air to these combustion zones and under damper control for each zone. This air feeding pipe l8, as seen in Fig. 3, is located adjacent the outlet from the combustion space above the grate plate 13 as such outlet feeds toward the smoke pipe.

The stove shell I has the box-like extension i 2, shown in horizontal cross section by Fig. 4, and in vertical section by Fig. 3. This extension is in the nature of a radiator as will be explained. It has two vertical passages R and R separated by a partition 24. They are respectively connected to the combustion space above plate It by horizontal openings and d, Fig. 4, and to a common smoke pipe II at the top of Fig. 3. The outline of this radiator extension from the front of the stove is indicated by dotted lines in Fig. 2. An ordinary damper e is indicated for opening (1 to shut off any draft up passage R. Passage R is not in use all of the time during stove operation while passage R is used the entire time.

The stove in its simple form is used as follows: fuel magazines A and B are filled with wood through doors 9 and H], which are then closed. The doors 9 and I 6 when closed become substantially air tight by use of suitable packing, not shown. Doors 1 and. 8 are used for convenience to start the fire and. are normally closed and air tight. The fire may be started with combustion of wood at the bottom of magazine A, or both magazines A and B, with both their corresponding ash pit doors open and air feeding pipe [8 with all its openings feeding air in. However, since the idea of operation, in part, is to burn the wood of magazine A for a continuously burning fire and burn the wood of magazine B intermittently, the drafts to magazine B are now closed. This is not the whole idea, however, and the remainder of the stoves mode of operation needs special explanation.

When the structure described is considered it will be seen that the following mode of operation is provided to use the wood fuel efiiciently. By opening damper in the ash pit, the wood from magazine A can be kept burning with air supplied through openings It. This burning can heat the whole stove. The products of combustion go out opening 0, Fig. 4, into radiator R to smoke pipe i I. Enough wood is kept burning con-- tinuously in this way to maintain a temperature of about 1109 F. in the hot zone of the combustion space. The quantity of the heat is enough for slow distillation of the wood in both magazines A and B and also for the stove to give off heat to a room for its primary heating use. The wood. in magazine B is kept from burning by keeping air away from it, by keeping ash pit door 3 and its air damper 5 closed, so no air passes up through openings l5, Fig. 4, and keeping damper 22 closed to shut off air supply to openings 23. And damper e is preferably closed. The wood in magazine B is separated from that in magazine A only by partition wall ll. The close adjacency causes passage of heat from magazine A to the wood of magazine B, which helps to distill combustible gases from the wood in magazine B and helps avoid overheating the wood in magazine A, which would tend to create a run away, or too rapid, burning of the wood supplying the fire.

The gases from distillation of wood in magazine 13 pass down into the combustion space. With damper e, Fig. 4, closed, the flow of these gases is over to and above the hot zone of the combustion space. They are burned to make more heat in that hot zone. As the products of combustion from this zone pass through opening 0, Fig, 4, they are supplied with secondary air through openings E9 of pipe I8 with damper 2i open for the purpose. This secondary air helps complete the combustion of the gases, which may finish burning in radiator R and give oil their heat and enter the smoke pipe i I with substantially no unburned wood gases left to condense anywhere, as in the smoke pipe I i.

It will be seen from the foregoing that the whole stove full of wood can be kept under constant distillation to get gases to burn and add their heat to the heat from a relatively small wood burning fire and that the small wood fire is guarded against growing up progressively and undesirably into a run away fire from the large wood supply in the stove.

The rate of firing, using the wood fed by gravity from magazine A, as before stated, is at a high enough rate to cause the action of wood distillation to make gases and charcoal. The charcoal soon after starting, is the fuel at the bottom of the magazine while wood is added intermittently at the top to keep the small fire going. Considering only the fire supplied by the wood from magazine A, it will be clear that its firing and thus the heating rate of the stove may be varied from that given by the distillation temperature to a progressively higher rate by progressively increasing the air supply or draft for that fire. Thus the stove heat given by that fire alone may be varied.

The wood fuel fed into magazine B is held by that magazine as a reserve supply to provide for a much higher firing rate for the stove when it is desired, as it is in severe weather. At any time desired the damper 5 may be opened, also damper 22, and also damper c, all relating to the fuel in magazine B. When any damper combination setting supplies air through openings :5, Fig. 4, a fire is started using the wood or charcoal of magazine B in addition to its gases. It joins the constant fire under magazine A and the two fires then become one fire on one grate. simply a much larger fire with its automatic ravity feed of fuel to the fire so that now the stove is operating substantially as the Seeley stove of the prior patent or stoves of the same type will operate. There is this difference, however, that the priorstoves will operate only as a single fire. As stated before they are not properly controlled. They work too fast or not fast enough, having neither control means to operate them at a minimum gas burning" temperature at all times nor means to vary their firing rate over the useful range of the new construction herein disclosed. In the new stove, when the large or double fire is no longer needed, shutting off the air to omit supply for combustion under magazine B will cause a quick decrease of the heating rate for the stove. The charcoal at the bottom of magazine B will be sensitive to any lack of air supply, so the combustion at the base of magazine B will die down rapidly as soon as its air supply is shut off by management of its dampers.

It should be noted that the new stove will take a large quantity of wood at one filling. In spring and fall weather this large filling will maintain a wood fire for a long time before more Wood needed. The magazine B is preferably made substantially larger than magazine A. The latter is made large enough to run its one fire a long time in mild weather to give all needed stove heat. The gases from wood in .magazine B will help the stove give enough heat at such time.

Assuming that the stove is dimensioned to give enough heat in mild weather from its operation as a base burner under magazine A alone, the air controls will then prevent a base burner operation under magazine B. The solid fuel in the latter will stand by ready for use when a higher rate of fuel firing is needed. When more heat is needed the air supply dampers will be opened to supply air for the large base burner fire under magazine B. Then the air for the large fire Will be shut off, the large fire will quickly go out, but the small base burner fire will continue. In this way the central heating plant is operated at two firing rates, having th call fire operating constantly under magazine A and the large fire operating intermittently under magazine B and a resulting economy and efficiency in the use of wood fuel. Of course in mild Weather it is desirable to control the firing rate of the small fire alone. It should be noted however that it is desirable to maintain the small fire at a high enough rate to maintain a hot combustion zone, hot enough at all times to burn the gases of Wood distillation to avoid condensation. These gases are made by heat distillation constantly working on the fuel of both magazines, that is, all the wood in the stove. It can easily b seen, that the dampers controlling air to magazine A may be adjusted to maintain a zone of combustion in the magazine A at a temperature of about 100, or high enough to burn the wood gases as fast as they are generated in the stove. This temperature is important to the operation in the stove combination of a constantly operated base burner with a second cas burner intermittently operated by the expedient of closing its air intake and opening its combustion chamber to the combustion chamber of the constantly operating burner during periods when the latter only is operating, and by opening the air inlet to the intermittently operating burner and connecting its combustion chamber to the chimney during the periods when both burners are to be in operation. The provision for maintaining a fire at all times hot enough for burning the gases will avoid their condensation and an accumulation of gum in the heating apparatus. The provision of this constant hot burning zone will prevent a run away fire while permitting a relatively large quantity of wood in the stove. In this way the new stove structure is adapted to burn all the wood, gases, and charcoal from a full stove filling, but with more extended firing rates controlled to make the fuel last longer and he used more efiiciently than prior art structures are adapted to do.

The magazine A is shown smaller than magazine B, which is a useful provision in most cases, particularly in getting a low firing rate limit relative to a stove large enough to get a relatively high firing rate. In case of wanting only the advantage of a long heating operation of about the same firing rate, the magazines A and B may be of about the same size. In some cases it would be useful to provide more than two magazines. Each added one would then have the same operating arrangement with magazine A as that described for B. Then when the fuel in magazine B is exhausted another one would be switched in for intermittent use in the same manner.

6. Fuel in magazine A would need to be replenished, but that can be done with a small amount, while the heavy work of replenishing fuel could be delayed for a relatively longer time.

It will be clear that the control of the stove may be all, or part, or not at all under automatic control with respect to the broadest aspect of the invention. The simplest case to consider is that of a hand controlled stove embodying the structure adapted to carry out the wood burning operation. Suppose the simple stove is used to heat a one room log cabin in the woods. It will be very useful to the user in that it will save him much labor in the getting and feeding of his wood fuel supply. It will heat for many hours without requiring mor attention than to open or close the drafts which control the intermittently operated base burner fire. The invention is adapted not only for that simple use but likewise for a central house heating plant. The stov is clearly one of economical construction with no parts for movable operation except doors and dampers. It is a very low cost construction adapted for a much improved mode of operation in the use of wood fuel. The latter is made feasible for use in many situations where before this invention, the more expensive coal or oil fuels would be used instead of wood. Thus the invention helps close the competitive advantage of coal and oil fuel over woc-d fuel for house heating.

Having disclosed the new stove structure we claim as the invention:

1. A wood burning stove comprising a casing having a vertical heat conducting partition dividing the upper part of the chamber into two substantially air tight wood-receiving containers extending Vertically adjacent each other in heat exchanging relation, a Wood-supporting grate within the casing and below the partition to form adjacent and connected combustion spaces, an individual chimney connection into each combustion space, at least one separately controllable air inlet into each combustion space, and means for closing the chimney connection of one of the combustion spaces, whereby with the chimney connection and air inlet of one of the combustion spaces closed the heat developed in the second combustion space will cause distillation of wood in the first combustion space and its associated container resulting in distillation products which pass through and are consumed in the second combustion space.

2. A wood burning stove comprising a casing having a vertical heat conducting partition dividing the upper part of the easing into substantially airtight main and pilot wood-receiving containers extending vertically adjacent each other in heat exchanging relation, the partition being located nearer one side of the casing than the other whereby the main container is of substantially greater cross-sectional area than the pilot container, a wood-supporting grate within the casing and below the partition to form adjacent and connected main and pilot combustion spaces, an individual chimney connection into each combustion space, at least one separately controllable air inlet into each combustion space, and means for closing the chimney connection into the main combustion space, whereby with the main combustion space chimney connection and air inlet closed and those of the pilot space open the heat developed in the pilot combustion space will cause distillation of wood in the main container and combustion space resulting in distillation products which pass through and are consumed in the pilot combustion space, and with both main and pilot combustion spaces connected to the chimney and air inlet the heat produced by the stove will be increased.

3. A wood burning stove comprising a casing having a vertical heat conducting partition dividing the upper part of the casing into substantially air tight main and pilot wood-receiving containers extending vertically adjacent each other in heat exchanging relation, the partition being located nearer one side of the casing than the other whereby the main container is of substantially greater cross-sectional area than the pilot container, 2. wood-supporting grate within the casing and below the partition to form adjacent and connected main and pilot combustion spaces, an individual chimney connection into each combustion space, a separately controllable air inlet below the grate of each combustion space, a second separately controllable air connection into each combustion space adjacent its chimney connection, and means for closing the chimney connection into the main combustion space, whereby with the main combustion space chimney connection and air inlet closed and those of the pilot space open the heat developed in the pilot combustion space will cause distillation of wood in the main container and combustion space resulting in distillation products which pass through and are consumed in the pilot combustion space, and with both main and pilot combustion spaces connected to the chimmay and air inlet the heat produced by the stove will be increased.

DOUGLAS E. HOWES.

FRANK G. SMITH.

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

UNITED STATES PATENTS

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