Abstract:
A flamer may be used to sterilize poultry litter, soil, concrete, etc. The stationary or mobile flamer disclosed comprises a hood to contain the heat, an external frame, and burners. A fuel tank may be carried on the flamer or on a tractor. An additional embodiment provides for mounting the flamer on wheels, permitting the unit to be towed by a truck, four-wheeler, tractor, etc. The burners are adjustable as to angle, and fueling rate. A pressure in the fuel system is controlled by selectively switching between the liquid and vaporous components of the fuel. By limiting how low the pressure may fall, the flow of fuel from the tank to the torches is more consistent.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation-in-part application of U.S. patent application Ser. No. 10/687,854, filed Oct. 17, 2003, entitled Mobile Flame Sterilizer, and is incorporated by reference herein in its entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable. 
       REFERENCE TO MICROFICHE APPENDIX 
       [0003]    Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    The present invention relates generally to a flamer. More particularly the present invention relates to a fuel supply pressure controller for a stationary or mobile flamer. 
         [0006]    2. Background Art 
         [0007]    Poultry litter may be sterilized by chemical means. As usual, the issue becomes that of chemical retention and the effect of the chemicals on the environment. Poultry litter may also be sterilized by flame heat, as disclosed by Mackenzie in U.S. Pat. No. 3,962,044. Because he discloses stationary equipment for litter sterilization, the method of Mackenzie &#39;044 requires a significant investment in machinery to handle the litter for sterilization. Space for the machinery and appropriate shelter is also necessary. 
         [0008]    A tractor drawn flamer was disclosed by Pivonka in U.S. Pat. No. 6,014,835 for the purpose of flame cultivation. Because of its open-flame design, the flamer of Pivonka &#39;835 is not suitable for sterilization purposes. Because the use of the Pivonka &#39;835 flamer for sterilization was not considered, there was no motivation to make the flamer enclosed for sterilization. 
         [0009]    Handheld torches and flamers are available, again especially for weed control and ice melting. These flamers are not suitable for the large task of sterilizing large amounts of poultry litter or soil, etc. due to their small coverage and the weight that must be supported or drawn by the user. 
         [0010]    Propane, commonly called Liquified Petrolium (LP), is usually the fuel used for flamers such as those used to sterilize poultry litter. The equilibrium pressure inside a propane tank containing a saturated mixture of liquid and vaporous propane is strictly a function of the temperature of these contents. However, during periods of heavy fuel usage, the pressure inside the tank may fluctuate due to finite times required for boiling off of the liquid into vapor and variations in temperature. 
         [0011]    The rate flow of the fuel for a flamer is a function of the tank pressure. When the tank pressure varies, the fuel flow rate varies as well. Flaming, then, regardless of the purpose, may suffer in quality as long as the tank pressure is permitted to vary. 
         [0012]    A tractor drawn flamer was disclosed by Pivonka in U.S. Pat. No. 6,014,835, which is hereby incorporated by reference. This tractor drawn flamer is used for flame cultivation. 
         [0013]    A tractor drawn or mounted flamer was disclosed by Pivonka in U.S. Patent Application 2005/0084409 (Ser. No. 10/687,854), which is hereby incorporated by reference. This tractor drawn flamer is used for flame sterilization of poultry litter. 
         [0014]    Neither of the above mobile flamers make use of a pressure control system. 
         [0015]    There is therefore a need for a fuel pressure control system to use in conjunction with stationary and mobile flamers. 
       BRIEF SUMMARY OF THE INVENTION 
       [0016]    An object of the present invention is to provide control of the fuel supply pressure for a flamer. Such stationary and mobile flamers may be used, for instance, to sterilize materials such as poultry litter, soil, and pavement; or for weed eradication, or softening asphalt. Tractors are ubiquitous in the agricultural industry. Because of tractors&#39; versatility, implements are often made to mount to a tractor or be drawn behind a tractor. Heat has long been used for sterilization. So is it possible to utilize a tractor for transporting a mobile flamer to provide heat for sterilization. Such a flamer is mounted on the tractor—preferably on a three-point hitch or quick coupler. An additional embodiment of the present invention is represented by a flamer on wheels or skids and drawn behind a vehicle as a trailer. 
         [0017]    The fuel supply pressure control system of the present invention provides a way to keep the fuel tank pressure near a predetermined value even during heavy fuel usage. To effect this control, fuel feed is selected from the vaporous and liquid components of the fuel. When vapor is being drawn from the tank, an equal amount of liquid must boil off to replace the vapor removed, plus a small volume equal to the volume of liquid converted to vapor. In contrast, when liquid is drawn off the fuel tank, the volume of liquid is much smaller than the volume of the same mass of liquid, i.e. the volume of the liquid is much smaller that the volume of the vapor. So the volume of vapor that must boil off in the tank to maintain the fuel tank pressure is greatly reduced. 
         [0018]    The fuel supply pressure control system of the present invention preferably makes use of a pressure switch, set to make or change contacts at a predetermined pressure. 
         [0019]    This is the pressure set point for the fuel supply. As long as the pressure is greater than the pressure set point, the flamer will utilize vaporous fuel. If the fuel supply pressure drops to or below the pressure set point, the contacts in the pressure switch will change, closing a vapor solenoid valve and opening a liquid solenoid valve, and liquid will be utilized by the flamer. The liquid fuel is vaporized after leaving the fuel supply tank. As the fuel travels toward the flamer torches, the pressure rises toward ambient. Boiling of the liquid fuel will result when it reaches the vaporizing portion of the torches, as the fuel attempts to reach an equilibrium state. Hence, at the torches, the fuel burned is vaporous, regardless of which solenoid valve is open at the time. 
         [0020]    Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0021]      FIG. 1  is a perspective view of the tractor-mounted flamer with a fuel tank mounted thereon; 
           [0022]      FIG. 2  is a side elevation view of the tractor-mounted flamer; 
           [0023]      FIG. 3  is a side elevation view of the tractor-mounted flamer; 
           [0024]      FIG. 4  is a rear elevation view of the tractor-drawn flamer; 
           [0025]      FIG. 5  is a perspective view of a wheel mounted flamer with the fuel tank mounted thereon; 
           [0026]      FIG. 6  is a perspective view of the underside of the tractor-mounted flamer; and 
           [0027]      FIG. 7  is a side elevation view of the tractor-mounted flamer being used to sterilize a surface; 
           [0028]      FIG. 8  is a first piping schematic for a flamer fuel supply pressure control system; 
           [0029]      FIG. 9  is a second piping schematic for a flamer fuel supply pressure control system; 
           [0030]      FIG. 10  is a first wiring detail for the flamer fuel supply pressure control system; 
           [0031]      FIG. 11  is a second wiring detail for the flamer fuel supply pressure control system; 
           [0032]      FIG. 12  is a flow diagram of the logic for the flamer fuel supply pressure control system; and 
           [0033]      FIG. 13  is a third piping schematic for a flamer fuel supply pressure control system; and 
           [0034]      FIG. 14  is a detail of a flamer fuel supply pressure controller. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0035]    A perspective view of one embodiment of the present invention is shown in  FIGS. 1 and 2 . A side view and a rear view are seen in  FIGS. 3 and 4 , respectively. A mobile flamer  100  is shown mounted on an implement hitch  105  of a tractor  110 . Fuel may, optionally, be carried on the flamer in a fuel tank  120 . In a second embodiment, the fuel may be separate from the flamer  100 , for instance, carried on the tractor in a tractor-mounted fuel tank  220 . 
         [0036]    A hood for the flamer  100  comprises an external frame  130  and skin  140 . Because the frame is external to the skin  140 , the frame is exposed to less radiant heat transfer, reducing the problems such as oxidation and fatigue caused by high temperatures and thermal cycling. In addition, the flamer  100  can be insulated while maintaining a reflective surface inside the flamer because frame  130  members are not in the way. 
         [0037]    The skin  140  substantially contains the high temperature gases, protecting the surroundings and concentrating the heat to the material to be sterilized. 
         [0038]    Adjustable skids  150  are used to maintain an appropriate height above the litter or other material  700  (see  FIG. 7 ) to be sterilized. The weight of the flamer  100  may be shifted between the tractor hitch  105  and the skids  150 , as needed. The flamer  100  is picked up with the tractor hitch  105  and carried off the surface for transport, cooling, etc. 
         [0039]    An additional embodiment is shown in  FIG. 5  wherein the flamer  100  is carried on wheels  510  and drawn behind the tractor  110  by its tongue  520 . The wheels may be drawn up, allowing the flamer  100  to rest on its skids  150  when in use. One advantage to this embodiment is that the flamer  100  may be towed behind any of a multitude of vehicles such as a truck, four-wheeler, or tractor. 
         [0040]    The underside of the tractor-mounted flamer  100  is shown in  FIG. 6 . A plurality of burners  610  are arrayed across the front of the flamer  100 , the angles of which are adjustable, as shown by the dashed lines. A barrier  620  may optionally be provided to assist in concentrating the heat, containing the gases, and protecting the surroundings. An additional option is shown as a set of rake teeth  630  to loosen and stir the material  700  being sterilized. 
         [0041]    The mobile flamer  100  of the present invention is shown in operation in  FIG. 7 . The surface material  700  being sterilized may be poultry litter, other livestock manure, soil, concrete, etc. 
         [0042]    A schematic of the piping and instrumentation of the flamer fuel supply pressure control system is shown in  FIG. 8 . Propane is stored in the fuel supply tank  120 . A vapor fuel line  805  and a liquid fuel line  810  are plumbed into the fuel supply tank  120 . Note that this schematic is valid for mobile and stationary flamers. 
         [0043]    Various pressure gages  815  are provided to give insight into the current operation of the fuel system. The pressure gages  815  may be electronic and the readings displayed at a central location. The pressure gage readings may also be incorporated into a sophisticated control system. 
         [0044]    Pressure relief valves  820  are provided at various locations throughout the fuel system. The pressure relief valves  820  shown in  FIG. 8  expel overpressured fuel into the atmosphere. Another configuration would have the overpressured fuel piped to torches  825 . 
         [0045]    The fuel supply control system  800  is shown inside the dashed lines in  FIG. 8 . The fuel supply control system  800  comprises a vapor line solenoid valve  830  and a liquid line solenoid valve  835 . These valves are controlled by a pressure switch  840 . 
         [0046]    A second example of a flamer fuel system is shown in  FIG. 9 . In this example, a shutoff valve  910  is used to positively shut the flamer  100  down so no fuel flows. 
         [0047]    Examples of the electrical relationships between the pressure switch  840  and the solenoid valves  830 ,  835  are illustrated in  FIGS. 10 and 11 . In both these circuits, a battery  1010  is connected to the pressure switch  840  via an on/off switch  1020  which provides a shutdown of the flamer  100 . 
         [0048]    The system shown in  FIG. 10  is especially suited for the piping shown in  FIG. 8 . In  FIG. 10 , the pressure switch  840  comprises a single pole double throw pressure switch. The solenoid valves  830 ,  835  are normally closed valves, requiring electrical excitation to open. When the fuel source pressure decreases to the preset pressure set point, the pressure switch  840  is actuated, thereby changing the pole to which the battery  1010  is connected. At high pressures, the vapor solenoid valve  830  is open while the liquid solenoid valve  835  is closed. When the pressure drops to the pressure set point and the pressure switch  840  is actuated, the liquid solenoid valve  835  opens and the vapor solenoid valve  830  closes. 
         [0049]    The circuit shown in  FIG. 11  is suited for use with the plumbing illustrated in  FIG. 9 . In  FIG. 11 , the pressure switch  840  comprises a single pole single throw pressure switch. The vapor solenoid valve  830  is a normally open valve, while the liquid solenoid valve  835  is a normally closed valve, requiring excitation to close. When the fuel source pressure decreases to the preset pressure set point, the pressure switch  840  is actuated, thereby energizing both solenoid valves  830 ,  835 . At high pressures, when neither valve is energized, the vapor solenoid valve  830  is open while the liquid solenoid valve  835  is closed. When the pressure drops to the pressure set point and the pressure switch  840  is actuated, providing connection to the solenoid valves  830 ,  835 , the liquid solenoid valve  835  opens and the vapor solenoid valve  830  closes. 
         [0050]    Because the vapor solenoid valve  830  is a normally open valve and thus, fuel may flow at any time, the additional, shutoff solenoid valve  910  is needed to provide secure shutoff of the fuel. This shutoff solenoid valve  910  is a normally closed valve, hence is closes when no power is provided to it. Note that the secure shutoff solenoid valve  910  may be used with the normally closed solenoid valves  830 ,  835  illustrated in  FIGS. 8 and 10  as well, providing redundant shutoff and the associated safety. 
         [0051]    Other wiring configurations are possible, and the present invention is not limited to those shown in  FIGS. 10 and 11 . 
         [0052]    Regardless of whether the fuel is from the liquid or vapor fractions of the tank  120 , the fuel pressure is dropped through a pressure regulator  845 . A shutoff solenoid valve  850  is used to turn the flamer  100  off except for a small flame, the fuel for which is provided through a needle valve  855 , bypassing the shutoff solenoid valve  850 . The small flame permits the torches  825  to be refired at any time. 
         [0053]    In  FIG. 12 , a logic diagram is shown for the flamer fuel supply pressure control system  800 . The fuel supply pressure  1210  is compared to a predetermined pressure set point in a comparator block  1220 . This comparison is preferably carried out mechanically in the pressure switch  840 . If the fuel supply pressure  1210  is greater than or equal to the pressure set point, p sp , the vapor solenoid valve  830  is open and vaporous fuel is used  1230  by the flamer  100 . If the fuel supply pressure  1210  is less than the pressure set point, p sp , the liquid solenoid valve  835  is open and liquid fuel is used  1240  by the flamer  100 . 
         [0054]    Note that appropriate hysteresis is required in the pressure switch  840  to avoid rapid switching between liquid and vaporous fuel. 
         [0055]    A second embodiment of the present invention includes the flamer fuel pressure control system  1300  depicted in  FIGS. 13 and 14 . In this embodiment, an electronic controller  1310 , either analog or digital, accepts a flow signal from a flow transmitter  1320  and a pressure signal from a pressure transmitter  1340 . Measurement and/or calculation of these values are well known to those of ordinary skill in the art. The electronic controller  1310  uses these signals to calculate an output for each of two control valves  1330 ,  1335 . The flow of vapor is continuously controlled by the vapor control valve  1330 , while the flow of liquid is continuously controlled by the liquid control valve  1335 . 
         [0056]    The electronic controller  1310  is detailed in  FIG. 14 . The flow and pressure signals, from the associated transmitters  1320 ,  1340  are shown input into the electronic controller  1310 . A flow set point  1410  is also available to the electronic controller  1310 , adjustable by an operator. The pressure set point  1420  may be predetermined by an operator, or it may be calculated as a function of a tank temperature signal from a temperature sensor  1350 , also shown in  FIG. 13 . In the usual fashion, as understood by those of ordinary skill in the art, errors, ε f , and ε p  for each of the controlled variables, f and p, are calculated in the respective calculation blocks  1430 ,  1440 . These are utilized in a control algorithm or algorithms  1450  such as a pair of Proportional Integral Differential (PID) loops with decoupling between the loops, or a multivariable algorithm such as a matrix control algorithm. These algorithms, as well as others, are well known in the art. The present invention is not limited to a particular automatic control algorithm  1450 . 
         [0057]    Outputs of the control algorithm  1450  include valve position set points  1460 ,  1470  for each of the two control valves  1330 ,  1335 . 
         [0058]    The above embodiments are the preferred embodiments, but this invention is not limited thereto. It is, therefore, apparent that many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.