Self-cleaning, high heat exchange wood or coal stove

A self-cleaning, high heat transfer wood or coal stove includes an interior cylindrical squirrel-cage configured fuel grate comprised of parallel air-conducting pipes for heating forced cold air. This arrangement of pipes not only provides for a self-cleaning stove interior due to the cyclical condensation and combustion of deposited effluents produced by combustion, but also greatly enhances the heat transfer capability of the stove by increasing the surface area available for heat exchange. The cyclical condensation and combustion is effected by incrementally rotating the interior cylindrical fuel grate by turning, using a handle inserted into one of a plurality of rod sockets which reside on the front of the stove. The stove of this invention is constructed with separate doors for convenient fuel loading and ash removal, and the fuel loading door is disposed to engage the combustion chamber opening with an air-tight and secure fit. The compact and efficient construction further provides a versatile stove capable of heating a relatively large volume of living space in proportion to its relatively small size.

BACKGROUND OF THE INVENTION 
This invention relates to apparatus for heating such as coal and wood 
burning stoves. 
The formation of layers of creosote on the interior surfaces of stoves and 
chimney flues has long plagued users of wood and coal stoves. This oily, 
sticky, tar-like substance results from the burning of wood or coal and is 
deposited wherever such gaseous combustion effluents are exposed to 
surfaces cooler than the vaporization temperature of creosote. This highly 
flammable residue usually forms in passageways and on interior walls of 
flues above the area of combustion, since those areas are generally cool 
enough for upwardly moving, draft-borne creosote gases to condense upon 
them. Every year, a great number of individuals suffer losses due to fires 
caused by a dangerous build-up and ignition of creosote within such flues. 
Periodic cleaning of these creosote deposits to ensure against these fires 
is a costly, tedious, and messy task. In addition, wood and coal stoves 
which are currently commercially available, often require large combustion 
chambers and accordingly, large quantities of wood or coal in order to 
heat typical living quarters. This drawback is caused by the limited and 
inefficient exchange of heat energy from the burning fuel to the ambient 
air in the room. The housing of such a stove has limited surface area for 
delivery of heat to the surrounding air and therefore, must consume large 
quantities of fuel in order to be effective for space heating purposes. 
Accordingly, it is an object of the present invention to provide a wood or 
coal stove for which such troublesome cleaning chores are reduced, and the 
risk of such dangerous fires are greatly diminished by the incorporation 
of means for self-cleaning removal of undesirable creosote layers during 
the operation of the stove. 
It is a further object of the invention to provide a compact, efficient, 
and high heat exchange wood or coal stove which consumes relatively little 
fuel and occupies less space than conventional stoves in relation to the 
amount of heat which is supplied for space heating. 
SUMMARY OF THE INVENTION 
In accordance with these objects of the invention, a stove is provided 
which may use wood, coal, or other fuels and which is adapted to 
automatically self-clean away the deposits of creosote layers from 
interior surfaces of the stove in order to prevent dangerous fires. Also, 
the air-conducting (air-cooled) pipes or tubes which become positioned 
above the fire, serve to condense and collect creosote for preventing its 
later deposit in the flue or chimney. This creosote-condensing removal 
advantage is obtained by employing a barrel or squirrel-cage-like assembly 
of air-conducting pipes or tubes mounted between end plates which are 
revolvable. These pipes extend longitudinally within the stove housing and 
are disposed as a group to receive and support fuel for combustion, the 
fuel being introduced through the front end of the stove. This cylindrical 
squirrel-cage arrangement of tubes acts as a grate for holding burning 
fuel and for allowing ash material to fall between the tubes to an ash 
chamber below. When this squirrel-cage array of tubes is rotated about its 
longitudinal axis, hot tubes at the bottom of the combustion chamber 
directly beneath and adjacent to the burning fuel are thus revolved away 
from the hottest region in the chamber toward the top of the chamber. 
There the previously hot tubes become cooled by forced air flow through 
them, and rising, gaseous creosote condenses out upon their cooled 
surfaces. 
When the squirrel-cage assembly is rotated further, the respective 
positions of the hot and cooled tubes is reversed. Consequently the 
creosote which was deposited on the uppermost tubes is then volatilized by 
being adjacent to the combustion, and much of it becomes consumed by 
burning as it rises through the hot flames. 
Yet another advantageous feature of this novel stove is achieved through 
the improved heat exchange capability made possible by the conductance of 
forced, cold air from outside the stove through these tubes. As the forced 
air travels through the conduction passages within the tubes, the ambient 
air becomes heated to a greater extent than would be possible by radiation 
from the exterior surface of the stove housing alone. For example, the 
illustrative embodiment of the invention disclosed has at least twice the 
heat exchange surface area as compared with a stove having just an outer 
housing. This increased surface area available for the transmission of 
heat greatly improves the fuel efficiency of the stove The tight seal 
formed between the fuel loading door and the combustion chamber prevents 
undesired leakage of combustion air through the chamber area, thereby 
enabling the rate of combusion to be controlled by an adjustable 
combustion air inlet.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a front view of the stove 10 having a substantially 
cylindrical housing 12 with a flue outlet 13 at the top and a front 
annular air tube support header 14 mounted within the housing. This 
annular header 14 holds the front ends of a plurality of uniformly spaced, 
cylindrically arranged parallel air tubes 16. These air tubes 16 extend 
longitudinally from the front toward the back of the stove 10 through a 
combustion chamber 17 and are held in place at the rear of the stove by 
rear hollow disk-like air-tube support header 15, supported by a rear 
bearing 18 as best seen in FIG. 2. The air conducting pipes or tubes 16 
are welded or swaged at 19 into holes in the respective hollow annular 
header 14 and hollow disk-like header 15, thereby forming a rigid 
squirrel-cage structure 21. 
The annular header 14 of this cage assembly of air tubes 16 is borne by two 
rollers 20, one of which is seen in detail in FIG. 4. These two rollers 20 
are rotatably mounted on the front of the stove ahead of the combustion 
chamber 17 and behind and below a fuel-load door 26. 
This fuel-load door 26 is supported on a hinged clamp 28 including a pair 
of parallel horizontal bars 27 joined by vertical angle irons 29 which 
extend between and are welded to the bars 27. 
At the left of the door 26 as seen in FIG. 1, the support clamp 28 is 
hinged to the front face 31 of the cylindrical housing 12. There are a 
pair of vertically spaced forwardly extending brackets 33 welded onto the 
housing front face 31. A hinge tube 35 is attached to the left end of the 
door clamp 28, and a hinge pin 37 extends through these brackets 33 and 
through the tube 35 for allowing the door clamp 28 and door 26 to swing 
forward away from a cylindrical fuel-loading entry 24 which extends 
forward a short distance ahead of housing front face 31. This round 
cylindrical fuel-loading entry 24 is welded to a rear ring portion 41 
(FIG. 2) of the annular header 14, and thus the entry 24 is rotatable 
integral with the squirrel-cage assembly 21. It is this round entry 24 
which has an encircling ring rail 25 secured thereto which rolls on the 
two support rollers 20. 
A center pin 44 hinges the door 26 to its support clamp 28 . The entire 
door 26 swings open on its hinge 35, 37, and the door is clamped shut by a 
dog 48 hinged at 49 to the front face 31 on the side opposite the hinge 
35, 37. This dog 48 has a rotatable screw-down handle 51, and the 
articulated door assembly 26, 28 with its center hinge pin 44 enables an 
effectively air-tight seal to be made by ring gasket 43 (FIG. 2) at the 
junction of the door 26 and the rotatable entry 24. This air-tight seal 
gasket 43 is made of heat resistant and wear resistant material, for 
example of ceramic or metal fibers and prevents an uncontrolled flow of 
air to the combustion chamber 17, thereby enabling the user to effectively 
and efficiently control the amount of air flowing into the combustion 
chamber as will be explained. 
As discussed above, the assembled array of air tubes 16 form a 
squirrel-cage grate 21 which is adapted to hold wood or coal fuel loaded 
through the entry 24 behind the door 26. As the fuel burns within this 
cylindrical combustion chamber 17 enclosed by the cage 21 of air tubes 16, 
cold air from outside of the stove 10 is drawn into a cold air intake 39 
of a blower 38 driven by an electric motor 40. This blower 38 has a 
discharge duct 45 connected by studs and nuts 53 to the rear face 47 of 
the housing 12. The rear bearing 18 is seated in a connection assembly 55, 
where the duct 45 is connected to the rear face 47 of the housing 12. The 
rotatable disk-like header 15 at the rear of the grate cage 21 has an 
axial duct 57 welded thereto and extending rearwardly, being journaled for 
rotation within the rear bearing 18. This axial duct 57 includes a 
plurality of radial ports 58 opening out into the hollow interior 60 of 
the header 15. 
Consequently, the blower 38 forces room air 59 through its discharge duct 
45 into the axial duct 57 and thence out through the ports 58 into the 
hollow interior 60 of the rotatable header 15. This cool room air 59 
enters the rear of the air tubes 16 and flows forwardly through them 
producing heated air 61 which enters the annular header 14. This heated 
air 61 blows radially inwardly through axial ports 62 (FIG. 4) in a 
cylindrical collar 64 encircling the entry 24 and radially spaced 
outwardly from this entry for forming an exit channel 22 for the heated 
air 61. The ring rail 25 includes multiple orifices 23 for directing the 
heated air 61 forwardly as shown by arrows 66 (FIG. 2) from channel 22 
into the room. In this way, space heating is accomplished with the present 
stove by both radiation of heat from the exterior housing 12 and by 
donduction and convection of forced hot air 61, 66. The air heating tubes 
16 effectively at least double the surface area available for heat 
exchange and thereby considerably enhance the efficiency of this stove. 
As the fuel supported by the air tubes 16 burns, ashes fall down through 
the spaces between them into an ash chamber 30 which is located at the 
bottom of the stove 10. The stove as a whole is supported by legs 32 (FIG. 
1). A generally rectangular longitudinally extending lower housing portion 
68 defines the ash chamber 30. As seen in FIG. 1, the round cylindrical 
top portion of the housing 12 plus this lower portion 68, gives an overall 
keyhole shape to the stove 10 as seen in front elevation. The ash chamber 
housing 68 is lined with fire brick 67 on the bottom and sides to retain 
interior heat and protect the metal housing 68. 
Access to the ash chamber 30 is provided through an ash chamber door 34 
which carries a hemispherical cap 36 associated with air intake ports 69 
for controlling the combustion draft to be established into combustion 
chamber 17, with the combustion gases going up through chimney flue 42. 
These ports 69 are adjusted by rotating the hemispherical body of the cap 
36 about its central threaded stud which projects forward from the ash 
chamber door 34. Similar to the larger fuel-load door 26 provided above, 
the ash chamber door 34 engages a substantially air-tight gasket 70 and is 
mounted on the front of the stove by a hinge pin mounting 50 at the left 
and is closed tight by a locking dog 52 at the right. This door 34 when 
opened gives access to an ash pit doorway 72 which is provided in the 
front of the lower housing portion 68. There is a front "porch" or ledge 
74 extending forward below the ash pit doorway 72 for facilitating 
handling of ashes. 
FIG. 3 illustrates the means of operation of the stove. Once fuel within 
the grate of air tubes 16 has burned for some time, a hollow rod-like 
handle 56 (FIGS. 3 and 4) is manually placed onto any one of the 
conveniently disposed rotation lugs 54 on the front of the ring rail 25 
(see FIG. 2) whose longitudinal axes are parallel to that of the stove. 
After the handle 56 is engaged on a lug 54, the user employs this handle 
for rotating the entire cage-like assembly 21, which includesthe ring rail 
or ring track 25, entry 24, front annular header 14, air tubes 16, rear 
disk header 15 and rear axial duct 57. This entire squirrel-cage assembly 
rotates as a unit on the rear bearing 18 and on the two front rollers 20. 
The ring rail 25 includes a rearwardly projecting annular lip (FIG. 4) 
which is in sliding sealing engagement against a wear-resistant gasket 73 
mounted in a groove in the front face plate 31 of the housing 12. 
The user turns the tube cage assembly 21 by means of the handle 56 when the 
fuel-loading door 26 is open at the time of inserting additional fuel. 
Thus, the door gasket 43 is away from the fuel-loading entry 24 at the 
time of rotating the tube assembly 21. This rotation causes hot air tubes 
which were beneath the burning fuel at the bottom of the combustion 
chamber 17 to be moved by an eighth to a quarter turn, progressing 
eventually around toward the top of the cylindrical cage 21. These newly 
uppermost hot air tubes become cooled by air flow 59, 61 and now serve as 
cooled condensation surfaces for creosote vapors which rise from the 
flames up toward the flue or chimney 42. 
At the time of the next re-filling with fuel, the user again turns the tube 
case assembly 21 by an incremental amount, for example an eighth to a 
quarter turn. The most convenient operation is to turn by the distance 
from one lug 54 to the next. In this embodiment there are eight lugs for 
providing a one-eighth increment of turning from one lug to the next one. 
Thus, the individual tubes which were farthest from the burning fuel on 
which creosote was deposited eventually become returned to the lower 
region in the combustion chamber 17 beneath the hot coals of fuel. Being 
closest to the hottest region in the chamber, the creosote is then burned 
off from these tubes. Thus, advantageously much of the heat energy of the 
creosote is usefully obtained, rather than going up into the flue 42. Some 
portion of this creosote will be volatilized and will recondense on other 
cool air tubes to be burned later. Most of the unwanted formation of 
dangerous creosote however, will be burned off from the air tubes by 
revolving them into position near the hot coals of the fire. The cool air 
tubes further act as condensing shields for the upper area of the inside 
of the housing and for the flue and chimney. They screen these regions 
from creosote condensation therein. By continuing to periodically rotate 
the cage assembly 21, the user provides an automatically self-cleaning 
action in this wood or coal stove which has improved, efficient heat 
exchange capability. 
In order to provide access to the tube cage assembly 21 for cleaning or 
scraping the air-conducting grate tubes 16, there is a removable access 
door 76 sealed to the housing 12 by a gasket 78, as shown in FIG. 1. 
Although the invention has been described with reference to a particular 
embodiment, it is to be understood that various changes and modifications 
may be made in the stove without departing from the spirit and scope of 
this invention as defined in the following claims and reasonable 
equivalents of the claimed elements.