Abstract:
A spark arresting incinerator apparatus for burning combustible solid materials without the release of hot embers or ash capable of igniting materials outside the incinerator includes a firebox to contain the combustion, a grate disposed across the bottom of the firebox to support materials to be burned, an ash box disposed below the firebox and grate and connected to the firebox, the ash box having at least one screened and shielded combustion air inlet, a generally pyramidal cupola disposed above and connected to the firebox, and a chimney disposed above and connected to the cupola for the exit of combustion gases from the incinerator. The chimney includes a plurality of baffle plates each extending partially across the interior of the chimney, with the baffle plates disposed in staggered offset relation to each other, and also preferably includes a spark arrestor connected to the top of the chimney.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/809,091, filed May 30, 2006, by the same applicant. 
     
     FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to incinerators, and in its preferred embodiments more specifically relates to an incinerator structure that protects against the release of sparks or embers from the incinerator. 
       BACKGROUND OF THE INVENTION 
       [0003]    Residents of rural areas often do not have access to garbage and trash disposal services or to landfills for disposal of their household garbage and trash. It is very common, therefore, for such residents to burn their household trash. During periods of drought or other periods when the surrounding vegetation is dry, fugitive sparks and embers from the burning of trash can pose a heightened risk of igniting surrounding vegetation. It is common for governmental authorities to impose restrictions on burning during such periods as a safety measure. Although burning restrictions are effective in limiting fires, they do create hardships for rural residents because of the accumulation of trash. Accumulated trash is not only visually unsightly but can also create health hazards and attract pests that can, themselves, create health hazards. 
         [0004]    Conventional incinerators cannot be safely used to burn trash and the like during periods of high fire risk, because conventional incinerators are not sufficiently effective in preventing the release of embers and other solid combustion products that are the primary cause of accidental fires. The entrainment of embers and the like in the combustion gases that flow from a conventional incinerator through a chimney at relatively high velocity pose the primary risk, and conventional spark arrestors disposed at the chimney outlet are not sufficiently effective to eliminate that risk. 
         [0005]    The problems with accumulated trash can prompt some rural residents to dispose of trash improperly and illegally, such as by dumping trash and/or garbage along roadsides and/or on unoccupied land. Residents may also ignore an imposed burning ban and burn trash anyway, exacerbating the fire risk. 
         [0006]    There is a need for an efficient, effective, and affordable incinerator apparatus that can be utilized to incinerate household generated trash and garbage without allowing the escape of embers and ash capable of igniting combustible materials outside the incinerator. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides an incinerator apparatus designed for use at rural households and small business operations for the safe burning of trash and other combustible materials. It is an object of the invention to contain and control the combustion of such materials within the incinerator. It is also an object of the invention to prevent the emission of sparks or embers that could ignite vegetation or other combustible materials outside the incinerator. It is still further an object of the invention to provide an incinerator that is appropriately sized for use by a single household, and that may be effectively and safely operated by a single person. It is still another object of the invention to provide an incinerator that is relatively inexpensive and affordable to those who have a need for such an apparatus. 
         [0008]    The structure and features of the incinerator apparatus of the invention will be described below, with reference to the accompanying drawing figures. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a front elevation view of the preferred embodiment of the incinerator apparatus of the invention. 
           [0010]      FIG. 2  is a sectioned side elevation view of the chimney of a first embodiment of the incinerator apparatus, with the baffles in a first orientation. 
           [0011]      FIG. 3  is a sectioned side elevation view of the chimney of an embodiment of the incinerator apparatus, with the baffle plates in a second orientation. 
           [0012]      FIG. 4  is a top plan view of a square chimney embodiment, with baffle plates. 
           [0013]      FIG. 5  is a side elevation view of the preferred embodiment of the incinerator apparatus of the invention, with steps extending to the front of the apparatus. 
           [0014]      FIG. 6  is a side elevation view of an embodiment of the incinerator apparatus of the invention, without access steps. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0015]    The incinerator apparatus of the invention, generally designated by reference number  10 , comprises as principal components or sections a firebox  11 , an ash box  12  disposed below the firebox, a loading cupola  13  disposed above the firebox, a chimney  14  above the cupola, and a support base  15 . 
         [0016]    In the preferred embodiment firebox  11  is configured as a hollow, generally cubical box with an open top and an open bottom, having a front wall  16 , a rear wall  17 , side walls  18  and  19 , an upper edge  20  and a lower edge  21 . It is preferred that the height of firebox  11 , between upper edge  20  and lower edge  21 , but approximately equal to or even greater than the width of the side and rear walls. A grate  22  is disposed across the bottom of the firebox at lower edge  21 , between the firebox and the ash box for supporting material loaded into the firebox for combustion and to allow ash to fall from the firebox into the ash box. In the preferred embodiment the upper portion of front wall  16  extends solidly across the upper portion of the firebox between side walls  18  and  19 , and the lower portion of the front wall  16  of the firebox is formed by doors  23  and  24 , each pivotally connected to one of side walls  18  and  19 , respectively. Doors  23  and  24  are releasably secured in a closed position by firebox latch  25 . Access to the interior of firebox  11  through doors  23  and  24  is provided for cleaning, and for pre-combustion loading of material to be incinerated into the firebox. When the incinerator apparatus is in operation doors  23  and  24  should remain closed, both for the safety of the operator and to prevent the escape of hot combustion products. 
         [0017]    Ash box  12  includes side walls  26  and  27 , a rear wall  28 , and a closed bottom  29 . Ash box  12  also has an upper edge  30  surrounding an open top. The majority of the front of the ash box is closed by doors  31  and  32 , each of which is pivotally connected to one of side walls  26  and  27 . Doors  31  and  32  are provided for the removal of ash from the ash box, and are releasably secured in a closed position by ash box latch  33 . The portion of the front of the ash box between the upper edge of doors  31  and  32  is open to provide a front combustion air inlet  34 , covered by screen  35  to provide an inlet for combustion air. Side walls  26  and  27  and rear wall  28  also preferably include combustion air inlets  34  adjacent to their upper edges, also covered by screens  35 . The depth of ash box  12  is sufficient to accommodate at least the quantity of ash that is reasonably anticipated to accumulate during incineration of a batch of material, without interfering with the flow of combustion air through the air inlets in the ash box. During operation of the incinerator a draft through the structure is created by the outflow of hot combustion product gases, sufficient to pull air into the structure through the combustion air inlets while preventing the outflow of combustion products from those air inlets. The combustion air inlets are disposed at the upper edge of the ash box so that any embers or other hot solids that fall through grate  22  fall past the air inlets, and screens  35  are provided to assure that no embers or other hot solid particles are allowed to escape through the air inlets. 
         [0018]    Ash box  12  and firebox  11  may be formed as an integral unit, with side walls  26  and  27  of the ash box formed as extensions of side walls  18  and  19  of the firebox, and with rear wall  28  of the ash box formed as an extension of rear wall  17  of the firebox. Alternatively, the firebox and the ash box may be separately formed and connected during construction of the incinerator apparatus. 
         [0019]    In the preferred embodiment, cupola  13  is configured as a truncated pyramid, with a front wall  36 , side walls  37  and  38 , and a rear wall  39 . The base, at the lower edge  40  of the cupola, and the top, at the upper edge  41  of the of the cupola, are open, to form open passageways from the firebox to the cupola and from the cupola to chimney  14 , respectively. It is preferred that the height of cupola  13 , between the base and the top, be generally equal to or greater than the width of the base along the lower edge of each of the walls. The lower edge of cupola  13  is configured to mate with the upper edge of firebox  11 , and the cross-sectional dimensions of the cupola narrow toward its top. A loading door  42  is provided in front wall  36  to close an opening  43  in the front wall for introduction of material to be burned either prior to initiation of combustion or during incineration if needed. Door  42  is preferably pivotally connected to front wall  36  at the upper edge of the door, so that door  42  can be lifted upward using handle  44  and will automatically close when released. In this embodiment a latch to secure door  42  in a closed position is not necessary, although a latch could readily be provided if desired. 
         [0020]    Chimney  14  preferably comprises a hollow body with a continuous side wall  45 , an open lower end  46  and an open upper end  47 . Chimney  14  is disposed over and extends upwardly from cupola  14 , and is connected at lower end  46  to the top  41  of the cupola so as to prevent the escape of combustion products through the connection between the chimney and the cupola. In the preferred embodiment the cross-sectional configuration of chimney  14  is square, partly to simplify the construction and installation of baffles, but the scope of the invention is not limited to any particular configuration, and other configurations, such as circular, could readily be used if desired. 
         [0021]    When combustible materials are burned, hot combustion products, primarily gases but with solids entrained in the gases as smoke, ash, and embers, rise from the combustion zone, and in most combustion apparatus the combustion products are routed through a chimney with a substantially reduced cross-sectional area in comparison to the area of the combustion zone. As a result of the reduction in area of the chimney, the velocity of the combustion products flowing upwardly through the chimney increases, which conventionally serves to assure the exhaust of combustion products from the combustion zone and to reduce the pressure within the combustion zone to assure the inflow of combustion air. 
         [0022]    The movement of combustion products through a chimney at a relatively high velocity has a tendency to entrain embers and other relatively large particles in the gas flow, which particles are frequently released from the chimney with the combustion gases. Embers drop out of the flow of combustion gases soon after they exit from the chimney, and such fugitive embers are the primary cause of accidental fires outside the combustion apparatus. 
         [0023]    In the preferred embodiment of the incinerator apparatus of the invention, the combined height of firebox  11  and cupola  13  above grate  22  is relatively high in proportion to the horizontal dimensions of those components, and chimney  14  is relatively short in comparison to the chimney of a conventional incinerator, fireplace, or other conventional combustion apparatus. Further, the cross-sectional area of firebox  11  at top  20  is essentially the same as the cross-sectional area at grate  22 , and the cross-sectional area of cupola  13  reduces gradually between the connection of cupola  13  to firebox  11  and the connection of chimney  14  to the cupola. As a result of this structure, combustion gases move upward through firebox  11  and cupola  13  a relatively low velocity and with an increased retention time, and move through chimney  14  at relatively low velocity. Because of the low velocity of the flow of combustion gases, embers and other solids are much more likely to drop out of the combustion gases within the firebox or cupola, before entering the chimney, and the entrainment of embers and other solids in the combustion gases that flow through the chimney is greatly reduced. 
         [0024]    In addition, as combustion gases move upward through the reducing cross-sectional area of cupola  13  toward the entry into chimney  14 , the flow of the combustion gases is not laminar, but becomes more turbulent, with the creation of swirls and eddies within the cupola. Generally, the flow pattern is such that the velocity of the flow at the cupola walls is lower than the velocity of the gas flow closer to the center of the cupola. Embers and other solids entrained in the combustion gases are forced toward the walls of the cupola, into the area of reduced velocity, where they are more likely to drop out of the gas flow and return to the firebox. 
         [0025]    As further protection against the escape of embers from the chimney, chimney  14  preferably includes a plurality of baffle plates  48  disposed in the interior of the chimney, in the flow path of the combustion gases and any remaining solids through the chimney. Baffle plates  48  preferably comprise thin flat plates, each connected at one end to the interior of sidewall  45  of the chimney and extending across the interior of the chimney through more than half the interior of the chimney. The baffles are disposed and connected in a staggered, alternating relationship to create a sinuous path through the interior of the chimney. Combustion gases and any entrained ash or embers entering the chimney come into contact with the first baffle encountered in the flow path, forcing the gases, etc., to move laterally past the free end of the baffle to continue moving up the chimney to the next baffle, and so on through the chimney. Pieces of ash and/or embers with sufficient mass to retain enough heat to pose an ignition threat outside the chimney will not remain entrained in the smoke flow through the chimney around the baffles to its upper end  47 , but will drop out of the smoke flow before exiting the chimney. Although, as noted above, chimney  14  may be formed with any desired cross-sectional configuration, a square configuration is preferred not only to facilitate the fabrication and installation of baffle plates  48 , but also because a square configuration increases the turbulence of the flow of combustion gases through the chimney. Embers and other solids are less likely to remain entrained in a turbulent flow, partly because of increased retention time within the chimney, and less likely to escape from the incinerator apparatus to pose a fire risk. 
         [0026]    The scope of the invention encompasses a number of variations in the construction and placement of baffle plates  48 . As one example, the baffles may be disposed with the plane of each baffle perpendicular to the longitudinal axis of the chimney, or may be inclined downward at an angle to the chimney axis. An upward incline could be used but is Pot preferred because of increased risk of passage of embers past the baffles. In the preferred embodiment baffle plates  48  are formed as solid plates, but in an alternative embodiment the baffles may be formed of a screen or mesh material in a supporting frame, to allow smoke and other gaseous combustion products to pass directly through the baffles while preventing the passage of ash or embers that would pose an ignition risk. 
         [0027]    In the preferred embodiment of the incinerator apparatus a screened spark arrester  49  is disposed at the upper end  47  of chimney  14 , to further assure that no hot ash or embers posing an ignition risk escape the chimney. Spark arrester  49  may be of any conventional design. Although not contemplated to be necessary, a spark arresting screen or grate may also be disposed at lower end  46  of chimney  14 , to trap any large particles remaining in the flow of combustion gases at that point and prevent their entry into the chimney. 
         [0028]    As further protection against the escape of ash or embers from ash box  12  carried by cross winds blowing through the combustion air inlets, wind shields  50  may be connected to the ash box above each air inlet to extend outwardly and downwardly at an angle, as shown in  FIG. 4 , to shield against cross winds without interfering with the entry of combustion air below the shields. Shields  50  are formed as flat rectangular plates of sufficient length to span across the associated combustion air inlet, connected at one edge to the ash box between the air inlet and the upper edge of the ash box, and extending outwardly and downwardly at a preferred angle of about forty-five degrees, with the opposite edge of the shield disposed below the lower edge of the associated combustion air inlet. Each shield occludes the associated combustion air inlet so as to prevent laterally blowing wind from bypassing the shield and blowing into the ash box through the combustion air inlet, without preventing air from being drawn through the air inlet around the shield. 
         [0029]    Support base  15  includes legs  51  extending downwardly from a frame  52  that is disposed at the lower edge of ash box  12  to support the incinerator structure above the ground or other surface upon which it is placed an operated. A set of preferably folding, drop-down steps  53  is also provided below ash box  12 , pivotally connected to frame  52 , to facilitate access to cupola door  42 . Steps  53  may also be provided as a permanently deployed non-folding structure that remains in place, or the steps may be omitted from smaller models of the incinerator, if not needed for access to the cupola door. 
         [0030]    In the preferred embodiment described above the cross-sectional configuration of the principal components of the incinerator apparatus is generally rectangular. However, a rectangular configuration is not essential, and it is to be understood that the scope of the invention encompasses other configurations as alternative embodiments. As a non-limiting example, ash box  12 , firebox  11 , and cupola  13  may be formed with a cylindrical configuration. In such an alternative embodiment the cross-sectional configuration of chimney  14  may be cylindrical, or the rectangular configuration of the preferred embodiment may be retained to, as noted above, facilitate the connection of baffle plates  48 . 
         [0031]    The foregoing description of the apparatus of the invention is intended to be illustrative and not limiting. In addition to the embodiments and variations described above, the apparatus is susceptible to further variations, all within the scope of the invention, in accordance with the following claims.