Abstract:
The invention is a stove system that is portable, has a double walled external structure for the passage of air used in combustion of the fuel, which air also maintains the external surface at a cool enough temperature that it can be touched, and which air flow prevents the waste of heat laterally to the ambient air from a hot outer surface. This increases cooking efficiency, because almost all heat that reaches the air flow between the two walls is drawn right into the combustion chamber in the form of preheated air by reason of the chimney effect. Thus almost no heat can escape the outside wall except by reaching the cooking pot bottom and pot sides after passing out the cover vents as exhaust. An internal heat concentrator ring improves the overall efficiency of the burner. The stove is preferably powered with coal, and uses about half as much coal as a conventional coal fired stove resulting from cooking efficiency. Provision is made for generation of electrical energy from the excess stove heat. Additionally, special thermally designed cook pots add to the stove system to decrease food cooking time while reducing the fuel required.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application continues in part from a patent application and claims the benefit thereof from U.S. patent application Ser. No. 12/005,212 filed Dec. 27, 2007, and claims the filing dates thereof as to the common subject matter therewith. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to the general field of heating apparatus, such as stoves for cooking. More specifically, it concerns a stove that combines cooking with a combustion source of heat such as coal and very high efficiency in doing so. In fact, the efficiency is so high that consumption of coal in the invention is a little more than half of that in prior art coal fired stoves. The invention is further distinguished from prior art coal fired stoves by being portable and cool enough to hold with bare hands. The efficiency and cool outer surface both result from a double walled exterior structure through which all combustion air is ingested. 
         [0004]    The present invention also solves the problem that is prevalent in many parts of the world that rely on solid fuel open flame cook stoves of not having any means of effectively generating electricity for use in lighting and battery charging of small devices such as radios. The incorporation of the thermo-electric generator module into the stove to generate electricity while cooking solves this problem. 
         [0005]    The goal of the present invention is to reduce the use of fuel used for cooking and thus aid in the reduction of emissions effecting both climate change and health. The design of a new more efficient cookware to be used with the stove adds to this goal of overall fuel economy. 
         [0006]    2. Description of the Prior Art 
         [0007]    The art and science of cooking goes back many thousands of years. Art work by cavemen shows knowledge of cooking with fire. When coal was discovered, a highly concentrated combustible fuel source that provided very high temperatures with slow fuel consumption became available. Over time, it was learned that using coal for cooking dictated construction of cooking apparatus from materials that could withstand high temperatures, such as iron and steel. 
         [0008]    But iron and steel have two significant drawbacks when viewed in the context of the present invention. First of all, they readily absorb radiated and conducted heat, and in turn radiate that heat to the ambient atmosphere. Second, they make the cooking apparatus very heavy. The result is significant wasteful loss of heat that is intended for cooking, and essentially no portability. 
         [0009]    It is well known that hot air is less dense than cold air. This causes hot air such as created by a combustion source to rise. In a closed structure containing a heat source and having openings at the bottom and at the top, a tower of rising air is created. This phenomenon is known as the chimney effect. 
         [0010]    Another well known physical principle is that the velocity of a gas such as air passing through a walled structure such as a cylinder increases as the cross section of the structure decreases. Thus if the structure is a cylinder, as its diameter decreases, the velocity of the air increases. The presence of a throat, or narrowed cross section, creates what is known as a venturi. 
         [0011]    It is known in the prior art to make heat containing structures with a double walled construction. Two examples of that are U.S. Pat. Nos. 6,761,160 and 5,203,316. The latter is a double walled oven. Once, the double walled construction was in part done to make the outer wall cooler to the touch, U.S. Pat. No. 5,921,229. But so far as is currently known to the present inventors, the combination of chimney effect, a venturi, and a double walled construction has never been employed in a stove to increase the efficiency of the heating or cooking. Efficiency is increased because the combustion chamber is surrounded by a double walled structure through which all the combustion air moves, preheating it, and preventing the loss of nearly all the heat from escaping laterally. Rather nearly all heat generated by combustion is radiated to the bottom of the cooking pot or exhausted along the pot&#39;s walls to heat it by conduction. 
         [0012]    It is documented in the prior art that waste heat can be used to generate electricity, US Patent Application, Publication No. 20060016446, from a furnace and that the technology to do so has been shown in U.S. Pat. No. 5,892,656 for a thermoelectric module. 
       SUMMARY OF THE INVENTION 
       [0013]    Bearing in mind the foregoing, it is a principal object of the present invention to combine the principles of the chimney effect, a venturi, and a double walled construction to both increase the heating efficiency and maintain the outer wall of a stove cool enough to touch. 
         [0014]    It is a related object of the present invention to use the increased efficiency to economize on the consumption of fuel. Given that an efficient combustion cooking apparatus will necessarily be completely enclosed making it difficult or almost impossible to add fuel during the cooking of a meal, it is a further related object of the invention to employ the efficiency of the present invention to increase the cooking time available for a given amount of fuel. 
         [0015]    It is an object of the present invention to include a provision for adding fuel during a long cooking time period by the use of a pellet fuel addition chute which does not require the removal of any cooking pots. 
         [0016]    It is another object of the present invention to employ the efficiency and relatively cool outer wall of the present invention to make the apparatus portable, even movable when in use. 
         [0017]    An additional object of the present invention to make the apparatus easy to clean by providing an open bottom through which expended fuel can drop, and with a grate disposed at the bottom of a handle equipped removable bucket to readily dump out remaining expended and unexpended fuel. 
         [0018]    It is another object of this invention is the use of a chimney on the upper face of the fuel grate to further improve the combustion of the fuel and add to the efficiency of the stove. A further object of this invention is to have a heat concentrator ring disposed above the combustion area such that it focuses the heat to the bottom of the cook pot and improves the heat transfer to the thermo-electric heat collection pipe below it. 
         [0019]    Other objects and advantages of the present invention will apparent to those skilled in the art upon consideration of the following descriptions and the appended drawings. 
         [0020]    In accordance with a major aspect of the present invention, there is provided a cooking apparatus that is portable, has a double walled external structure for the passage of air used in combustion of the fuel, which air also maintains the external surface at a cool enough temperature that it can be touched, and which air flow prevents the waste of heat laterally to the ambient air from a hot outer surface thereby contributing significantly to cooking efficiency of the apparatus. Basically almost all heat that reaches the air flow between the two walls is drawn right into the combustion chamber in the form of preheated air by reason of the chimney effect. Thus almost no heat can escape the outside wall except by reaching the cooking pot bottom and pot sides after passing out the cover vents as exhaust as intended. The device also includes an externally adjustable air flow regulator disposed within the double wall structure. The stove is preferably powered with coal, and uses approximately half as much coal as a conventional coal fired stove because of its cooking efficiency. 
         [0021]    More specifically the structure of the invention is comprised of an outside cylindrical wall, an inside wall in the shape of a truncated cone, a bottom having a large opening in the center, and a vented removable cover. Combustion air is drawn in a multiplicity of rectangular ports from the chimney effect of the combustion further down line. The air passes between the outside wall and cone shaped inside wall after entering the ports. This preheats the air, but it still keeps the outside wall cool enough to handle with bare hands. 
         [0022]    The cover includes a multiplicity of vents, from which hot air is exhausted. The cover is an annular ring with a large open center is where the bottom of a pot containing food is exposed to the radiation of the fire and the hot air inside the stove. The hot air then exits the vents and heats the outside of the walls of the pot. The exhaust air flow can be regulated by the sliding dampers placed along the rim of the exhaust vent cover. Disposed within the cone is a removable bucket described next. 
         [0023]    The removable bucket is comprised of a tapered portion at its top and a lower cylindrical portion. The cylindrical portion is perforated by a plurality of apertures. When the removable bucket is disposed in the stove, a part of the cylindrical portion projects beneath the bottom of the cone. The apertures are thus exposed to the air flow between the outside wall and the cone. At the intersection of the tapered portion and the cylindrical portion of the bucket is disposed a grate. The grate supports a combustible fuel such as coal in the air flow that passes through apertures. The grate represents the narrowest cross section of the entire route of air flow through the apparatus, and thus acts as a venturi, which increases the temperature at the point of combustion. 
         [0024]    The bucket additionally has riser tabs placed about its circumference to which a narrow support shelf is affixed. This support shelf is to provide a stable platform for the heat concentrator shield and to make a tight fitting closure between the fire box and the inner stove wall. Said shield is a concave dished metal plate with an opening in its center through which the combustion heat is concentrated. This shield also acts as a funnel in the re-fueling process by directing the fuel pellets to the fuel grate in an even manor. 
         [0025]    The stove is also optionally fitted with a thermo-electric generator (TEG) module which is capable of producing sufficient power to charge a battery which in turn can provide useful energy for lighting, cell phone recharging, radio operation and the like. 
         [0026]    The heat collection pipe of the TEG is inserted into an opening disposed in the side of the stove at a height above the rim of the fire box and below the underside of the heat concentrator ring. A fixture on one of the support tabs of the fire box is used to secure the heat transfer pipe of the TEG unit. A ceramic bushing is inserted in through the walls of the stove through which the TEG heat pipe is inserted and remains thermally insulated from the stove walls. The output of the TEG is plugged into its control box which is mounted on the stove platform base. 
         [0027]    The stove base provides a means to support the control box whose function is to regulate the battery charging and the power distribution as well as provide operational status indicators. Additionally the stove base provides a more stable base for the stove, if required, as well as adding a safety factor in the event that hot ash falls out the bottom. 
         [0028]    The stove system incorporates specially designed cookware which takes full advantage of the stove design. The pots have concentric metal rings protruding from their bottom such that the rings act as heat absorption and transmission devices. The pots have ears on the periphery of the pot to allow for the pot to nest inside the heat chamber of the stove to maximize the heat transfer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    Various other objects, advantages, and features of the invention will become apparent to those skilled in the art from the following discussion taken in conjunction with the appended drawings, in which: 
           [0030]      FIG. 1  is a perspective front view of the high efficiency combustion stove of the present invention. 
           [0031]      FIG. 2  is a broken cross sectional view of the present invention showing the perforated bottom, the air flow regulator, removable bucket, grate, double walled construction and vented cover. 
           [0032]      FIG. 3  is an exploded view showing the perforated bottom, outer wall, the plates of the air flow regulator, truncated cone that forms the inner wall of the double wall construction, removable bucket with handle, grate and vented cover. 
           [0033]      FIG. 4A  is a schematic view showing the air flow through the structure of the stove and the combustible fuel on the grate. 
           [0034]      FIG. 4B  is a top view of the stove. 
           [0035]      FIG. 5  shows an alternative embodiment of the inventive stove with filtration means in the exhaust vents of the cover, to remove carbon monoxide and other pollutant discharges from combustion. 
           [0036]      FIGS. 6A ,  6 B,  6 C,  6 D, shows the Thermo-electric generator and its control module. 
           [0037]      FIG. 7 . is the Control module flow diagram. 
           [0038]      FIGS. 8A ,  8 B is the cook pot showing its concentric rings. 
           [0039]      FIGS. 9A ,  9 B,  9 C,  9 D,  9 F shows the firebox  40 . 
           [0040]      FIGS. 10A ,  10 B,  10 C,  10 D,  10 E,  10 F shows the exhaust damper. 
           [0041]      FIGS. 11A ,  11 B shows opening  108  in side of Pot  10 . 
           [0042]      FIG. 12  shows a perspective view of the stove. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0043]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
         [0044]    Reference is now made to the drawings, wherein like characteristics and features of the present invention shown in the various figures are designated by the same reference numerals. 
         [0045]    In summary, the invention is a cooking apparatus that is portable, has a double walled external structure for the passage of air used in combustion of the fuel, which air also maintains the external surface at a cool enough temperature that it can be touched, and which air flow prevents the waste of heat to the ambient air from a hot outer surface thereby contributing significantly to cooking efficiency of the apparatus. The device also includes an externally adjustable air flow regulator disposed within the double wall structure. The stove is preferably powered with coal, and uses approximately half as much coal as a conventional coal fired stove because of its cooking efficiency. The stove has an electrical generator module that converts the heat within the stove to electricity for charging a battery system to provide for useful work. Additionally the stove incorporates specifically designed cookware to take advantage of the stoves design and add to its overall fuel and cooking efficiency. 
         [0046]      FIG. 1  is a perspective front view of the high efficiency combustion stove  10  of the present invention. Seen is the outer wall  12 , rectangular ports  14  and removable cover  16 . The cover  16  includes a multiplicity of exhaust vents  18 , from which hot air is exhausted. The cover  16  is actually an annular ring. The large open center  24  is where the bottom of the pot (not shown until  FIG. 5 ) containing food is exposed to the radiation of the fire and the hot air inside the stove. The hot air then exits the vents  18  and heats the outside walls of the pot. 
         [0047]      FIG. 2  is a cross section view of  FIG. 4B  showing the assembled double walled stove  10 . It is comprised of an outside wall  12 , inside wall in the shape of a truncated cone  26 , a bottom  28  with a large central perforation  30 , and a removable cover  16  having exhaust vents  18 . When the stove  10  is in use, central perforation  30  in bottom  28  is substantially sealed off by the stove  10  being placed on a flat surface. Combustion air is drawn in a multiplicity of rectangular ports  14  as a result of the chimney effect of the combustion. The combustion air passes between outside wall  12  and cone  26  after entering ports  14 . This preheats the air, but it still keeps the outside wall  12  cool enough to touch with bare hands. It also prevents wasted heat loss to the ambient air around the stove. This objective is further aided by the presence of insulation  32  around the outside of the cone  26 . Disposed within the cone  26  is a removable bucket  36 . It is comprised of a handle  38 , tapered portion  40  and a lower cylindrical portion  42 . The cylindrical portion is perforated by a plurality of apertures  44 . When removable bucket  36  is assembled in the stove, a part of the cylindrical portion  42  projects beneath the bottom of cone  26 . The apertures are thus exposed to the air flow between outside wall  12  and cone  26 . At the intersection  46  of the tapered portion  40  and cylindrical portion  42  of bucket  36  is disposed a grate  48 . Grate  48  supports a combustible fuel such as coal (not shown until  FIG. 4 ) in the air flow that passes through apertures  44 . Chimney  80  is a cylindrical, perforated metal tube that is fastened to the center of the grate  48  such that it acts as a defined air path that improves the venturi flow and helps in the fuel pellet distribution. 
         [0048]      FIG. 3  is an exploded view showing the bottom  28  with central perforation  30 , above which is shown outer wall  12 . Further up is truncated cone  26  that forms the inner wall of the double wall construction, and removable bucket  36  with handle  38  upper tapered portion  40  lower cylindrical portion  42 , apertures  44 , and intersection  46 . Above that is grate  48  and removable cover  16  with exhaust vents  18 . It should be noted at this point that the diameter of grate  48  has the smallest diameter of any of the components through which combustion air passes, and this results in a venturi effect at the point of the grate, accelerating air flow. The effect is to supply more oxygen to the fuel that is supported on the grate, increasing the temperature of the combustion. Tabs  83  are placed so as to support a shelf  84  that itself supports the heat concentrator  82 . 
         [0049]      FIG. 4A  is a schematic view showing the air flow through the structure of the stove and the combustible fuel on the grate. Combustion air is drawn into the stove  10  by the chimney effect of combustion through rectangular ports  14  in outer wall  12 . The combustion air then travels downwardly in passageway  60  between outer wall  12  and truncated cone inner wall  26 . Air flow then proceeds to enter apertures  44  in the lower cylindrical portion  42  of removable bucket  36 . Therein lies combustible fuel  66  which is on fire giving off heat shown at  68 . This causes the air to rise at  70  in what is commonly referred to as the chimney effect. This in turn caused more combustion air to be drawn in rectangular port  14 , travel down passageway  60 , and around to the fuel  66  for continued combustion. Tabs  83  support shelf  84  on which rests heat concentrator  82 . Damper  81  is used to control the exhaust stream and is placed over the exhaust ports as required to control the heat.  FIG. 4B  is a plan view of pot  10 . 
         [0050]    Turning to  FIG. 5 , it shows an alternative embodiment of the inventive stove with filtration means  72  in the exhaust vents  18  of removable cover  16 , to remove carbon monoxide and other pollutant discharges from combustion. It is within the contemplation of the inventors that the filtration means is not limited to a passive filter media, but can extend to a powered system such an electrostatic collector or other powered antipollution systems. Lastly, a cooking pot  74  with lid  76  and handle  78  is shown in phantom to illustrate how a cooking pot would be supported on the top of cover  16 . Ceramic bushing  109  is inserted through hole  108  going through both walls of the stove and is used to allow the TEG heat pipe  106  to enter the combustion area while being thermally insulated from the stove walls. 
         [0051]      FIG. 6A  (composite  6 A, 6 B, 6 C, and  6 D) shows the thermoelectric generator and its controller. TEG control box  91  contains the electronics for the charging and distribution of the generated power. The generator output plugs into socket  92  to supply the generated electricity to the electronics within the controller box. Socket  93  and USB outlet  94  are used to power the devices that are plugged into them. Jack  95  us the power outlet for the cooling fan on the stove mounted TEG unit. 
         [0052]      FIG. 6B  shows the controller  91  mounted on the stove base  99 . The stove attaches via the tabs  102  which screw into the stove legs. Controller support stand  100  slips into base socket  110  and allow the controller to be removed when not in use. Volt meter  96  is used to check the battery voltage and is activated by pressing momentary switch  97 . Switch  98  is the master on/off switch for the controller. 
         [0053]      FIG. 6C  is a top view of the TEG module showing the shroud cover  105  which is used to protect the TEG module from any spills that may occur during cooking and it also acts as a means to increase the efficiency of the cooling fan. The heat pipe  106  is inserted through the stove walls at opening  108 , into the combustion chamber to absorb the heat energy and transmit it to the TEG generator module. Power cord  107  is connected to the controller  91  to convey the generated power to the controller for battery charging and distribution. 
         [0054]      FIG. 6D  is a rear view of the TEG module showing the fan  104  which provides the cooling air that the TEG module requires in order to maintain the temperature differential across the generator module. 
         [0055]      FIG. 7  is the block diagram for the functionality of the controller  91 . 
         [0056]      FIG. 8A  (composite  8 A and  8 B) is the cookware pot  74  (bottom view) showing the design of the support tabs  88  which are used to maintain the pot at the proper height above the combustion chamber. The heat rings  89  are fused to the pot bottom to allow for maximum heat conduction to the pot bottom and are spaced such that the openings  90  are offset from each other. This positioning allows for the maximum heat absorption while maintain a good heat circulation beneath the pot improving the evenness of the cooking while increasing the speed of same. 
         [0057]      FIG. 9A  is a top view of fire box  49  showing the support tabs  83  the pot  36  and the pot handle  38 . 
         [0058]      FIG. 9B  (composite  9 A,  9 B,  9 C,  9 D) is an isometric view of the fire box  49  showing the shelf support tabs  83  and the support shelf  84  which is used to support the heat concentrator ring  82 . Inverted V clip  85  is used to support and hold the terminal end of the TEG heat pipe and aligns it at the proper height from the combustion grate. Tabs  103  are used to support the burner grate and openings  44  are where the combustion air enters the lower part of the combustion chamber. This  FIG. 9B  is a view of the fire box  40  showing the air entry openings  44  and the bottom  42  along with the lifting handle  38 . Tab  103  is a shelf support tab and shelf  84  is used to support the heat concentrator ring. Inverted V clip  85  is used to support and hold the terminal end of the TEG heat pipe  106  and aligns it at the proper height from the combustion grate. Bent tab  103  is used to support the combustion grate. 
         [0059]    FIG.  9 C—The combustion grate  48  is a concave perforated metal with a chimney like cylinder  80  device placed in the center of the grate which aids in the even distribution of the fuel pellets and acts as a true chimney to improve the air flow through the fuel and direct the heat in a more concentrated column.  FIG. 9D  is a cross section of  FIG. 9C . 
         [0060]      FIG. 9E  is the heat concentrator ring  82  is shown with its handle  111  and the handle attachment ears  112 . The ring  82  is placed on the support shelf  84  of the fire box  40  and acts as a heat concentrator and heat buffer due to it mass. The ring is concave in design to facilitate the addition of fuel.  FIG. 9F  is a cross section of  FIG. 9E . 
         [0061]      FIG. 10A  (composite  10 A, 10 B, 10 C) Exhaust damper  81  fits over the exhaust vents in the stove cover and is held in place with clips  87  so as to permit the damper to slide around the perimeter of the cover to control the exhaust flow and thus the temperature as required. 
         [0062]      FIG. 10B  is an upright view of damper  81  showing the clips  87 .  FIG. 10C  is a view of damper  81  on cover  16 . 
         [0063]      FIG. 10D  shows the pellet chute  86  showing the chute stop  114  projecting from the sides to prevent the chute from sliding into the stove when inserted into the stove vent opening during use. Deflector  115  aims the pellet to the center of the heat concentrator ring as they slide down the chute. The deflector also prevents pellet breakage by slowing them down as the exit the chute. The break in the chute  113  is to allow the chute to be adjusted to a convenient angle for pellet addition by bending the chute at this location.  FIG. 10E  is a cross-section taken from  FIG. 10D .  FIG. 10F  shows the relationship of the chute  86  to the heat concentrator  82  and the top  16 . 
         [0064]      FIG. 11A  composite  11 A,  11 B) this view of the stove shows the ceramic bushing  109  placed in the TEG insertion hole  108  in the side of the stove  10  penetrating through wall  12  into the combustion chamber. This allows the TEG heat probe to enter into the stove combustion chamber without contacting the stove walls directly. This prevents any heat transfer loss to from the heat probe to the stove wall which will reduce the TEG efficiency. Insulation  32  is visible through the intake air holes  14  as it sits between the inner and outer stove walls. 
         [0065]      FIG. 11B  is a bottom perspective view of the stove showing the bushing  109  penetrating the inner stove wall. The inner truncated cone  26  of the inside wall along with the stove bottom  28  and the bottom opening  30  and the legs  101  are also clearly visible in this view. 
         [0066]      FIG. 12  this view is of the complete stove system showing the major components which are: The stove  10  the TEG module  116  (with shroud removed) the TEG controller  91  with its stand  100 . The intake holes  14  with the insulation  32  to separate the inner and outer walls of the stove and to provide additional heat shielding to the outer wall. The exhaust cover  16  with the exhaust vents  18  and the pellet chute  86  inserted into the stove through one of the vents. The cook pot is visible sitting on top of the stove and held in proper position by the tabs  88 . The entire stove system assembly sits on the base  99  and is attached through the legs  101  to provide a secure and stable platform for the cooking tasks. 
         [0067]    While the invention has been described, disclosed, illustrated and shown in various terms or certain embodiments or modifications which it has assumed in practice, the scope of the invention is not intended to be, nor should it be deemed to be, limited thereby Such other modifications or embodiments as may be suggested by the teachings herein are particularly reserved, especially as they fall within the breadth and scope of the claims here appended.