Abstract:
An apparatus for producing a sustained flame, comprising: a first reservoir for containing a first flame-fueling liquid; a second reservoir for containing a second flame-fueling liquid; a first wick having a first end disposed within the first reservoir and a second, flame-bearing end generally located above the first end; a second wick disposed substantially adjacent to the first wick, having a first end disposed within the second reservoir and a second, flame-bearing end above the first end; and at least one air channel disposed to supply oxygen to each wick, where a first end of the at least one air channel is generally located near the flame-bearing end of each wick; whereby, when the first and second flame-fueling liquids are supplied to the first and second reservoirs, the first and second flame-fueling liquids are communicated up the first and second wicks to fuel flames emanating from the flame-bearing ends of the first and second wicks. 
     A method for controlling a flame comprising: controlling a first flow of air to a first flame; controlling a second flow of air to a second flame; wherein the first flame and the second flame are concentrically disposed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims priority to copending U.S. provisional application entitled, “Systems and Methods for Controlling Characteristics of a Flame,” having Ser. No. 60/379,031, filed May 8, 2002, which is entirely incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to apparatus and methods for controlling a flame. 
   BACKGROUND 
   Some fuels burned by oil lamps produce relatively large amounts of smoke, but are still in use because they have other beneficial properties. For example, citronella oil produces smoke but is useful for repelling insects, such as mosquitoes. Although a citronella lamp user can avoid the buildup of smoke by extinguishing the lamp and relighting it later, this is undesirable because it extinguishes the light source. Although the amount of light produced by citronella oil is less than other types of liquid fuels, it is nonetheless convenient to have this light source and many users find the pink colored flame to be attractive. 
   Air drafts around the flame tend to increase the amount of smoke produced, so some existing lamps provide a shield around the flame to protect from drafts. However, shielding the flame from drafts can result in an inadequate air supply to the flame. This inadequate air supply results in incomplete combustion, which also tends to increase the amount of smoke produced. 
   SUMMARY 
   The present invention is directed to unique methods and apparatus for controlling a flame. In one embodiment, independent control of the characteristics of an inner flame and an outer flame is provided by controlling the flow of fuel and air to the flames. The apparatus and method reduces smoke by providing a stable airflow to the flames, thus reducing the effect of air drifting over the flames. The outer flame also reduces smoke by burning soot particles produced by the inner flame, and by shielding the inner flame from outside air. These features are especially useful when the fuel is citronella oil, which produces a relatively smoky flame. However, these apparatuses and methods apply to various types of liquid fuel, and are not limited to any particular type of liquid fuel such as citronella. 
   The size of the inner and outer flames can be independently controlled by controlling the flow of air and fuel to the flames. In one embodiment, the inner flame can be extinguished by closing off the fuel supply, then can be reignited by reopening the fuel supply. Using different types of fuels for the two flames results in different colors for the inner and outer flames, which provides a visually appealing effect. For example, using citronella oil for the inner flame and liquid paraffin oil for the outer flame results in an inner flame which is of a generally pink color, and an outer flame which is of a generally yellow color. Color characteristics are further controlled by reducing the airflow between the inner and outer flames, which may provide a single flame with a blend of colors from the two fuels. 

   
     DESCRIPTION OF THE DRAWINGS 
     In the drawings, individual components of the apparatus are not necessarily drawn to scale, or with the same proportions. 
       FIG. 1  is a perspective view of an exemplary embodiment of an apparatus for controlling a flame. 
       FIG. 2  is a top sectional view of the apparatus of FIG.  1 . 
       FIG. 3  is a partial side cutaway view of the apparatus of FIG.  1 . 
       FIG. 4  is a partial front cutaway view of the apparatus of FIG.  1 . 
       FIG. 5  is a cutaway view of the fuel reservoir section of FIG.  1 . 
       FIG. 6  illustrates a wick holder which can be used in conjunction with an embodiment of an apparatus for controlling a flame. 
       FIG. 7  is a perspective view of another embodiment of an apparatus for controlling a flame. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a perspective view of an exemplary embodiment of an apparatus for controlling a flame. The apparatus includes: fuel reservoirs  102  and  103 ; caps  104  and  105 ; fuel valves  106  and  107 ; air containers  108  and  109 ; air valves  110  and  111 ; wicks  112  and  113 ; shield  114 ; and collar  115 . 
   The fuel reservoirs  102 ,  103  contain liquid fuel, for example, liquid paraffin, mineral oil, citronella oil, or a variety of other suitable fuels. In one embodiment, the fuels contained in fuel reservoirs  102 ,  103  are different, so that the color characteristics of the flames may be different. Caps  104 ,  105  allow the fuel reservoirs  102 ,  103  to be filled, and also seal to prevent air from entering fuel reservoirs  102 ,  103  through the cap opening. In one embodiment, caps  104 ,  105  are safety caps to prevent buildup of excess vapor pressure. Each fuel valve  106 ,  107  is in fluid communication with one of the fuel reservoirs  102 ,  103 , so that when fuel valve  106 ,  107  is open, ambient air flows into fuel reservoir  102 ,  103 . 
   Each fuel reservoir  102 ,  103  is in liquid communication with one of the wicks  112 ,  113 . The wicks  112 ,  113  may be made of any suitable material, such as glass fiber or metal mesh, as long as the wick draws liquid fuel from the fuel reservoir. 
   Each air valve  110 ,  111  is in fluid communication with an air container  108 ,  109 , so that when air valve  110 ,  111  is open, atmospheric air flows into air container  108 ,  109 . 
   Air flows from air container  108 ,  109  to the flame-bearing end of a corresponding wick  112 ,  113 . Supplying air through a container provides a regulated and continuous flow of air to the flame, reducing the effect of any air currents or turbulence around the apparatus. 
   The exemplary embodiment may also include a shield  114  surrounding wicks  112 ,  113 , and a collar  115 , which fastens shield  114  to the fuel reservoirs  102 ,  103  and/or air containers  108 ,  109 . Shield  114  acts to prevent a user from coming into direct contact with the flame, and also to prevent air drafts from affecting the flame. Shield  114  has an aperture  116  to allow exhaust gases to escape from the apparatus. The aperture of a conventional lamp must be relatively large in order to provide an adequate air supply to the flame, but aperture  116  can be relatively small because the apparatus supplies air to the vicinity of the flame through an air channel (see FIG.  2 ). A small aperture may be desired because it prevents air drafts from extinguishing the flame. 
     FIG. 2  is a top sectional view of the apparatus of FIG.  1 . In one embodiment, fuel reservoirs  102  and  103  and air containers  108  and  109  are separate pie-shaped pieces arranged to form a substantially circular base  101 . In an alternative embodiment, fuel reservoirs  102  and  103  and air containers  108  and  109  are instead portions of substantially circular base  101 , formed by separation walls  201  and  202  inside one-piece base  101 . 
   In this exemplary embodiment, wicks  112 ,  113  (see  FIG. 2 ) are concentrically disposed atop the base  101  at wick receiving areas  203  and  204 , respectively. The wicks can be made of, for example, a tubular form of cotton/glass fiber. A portion of each wick  112 ,  113  is in fluid communication with fuel reservoirs  102 ,  103  through openings  205 ,  206  in fuel reservoirs  102 ,  103 . Wick  112  is supplied with air from air container  108 , through opening  207  in air container  108 , which opens into air channel  208  in the hollow center of the first wick  112 . Wick  113  is supplied with air from air container  109 , through opening  209  in air container  109 , which opens to air channel  210  in the space between the inner and outer wicks  112  and  113 . 
     FIG. 3  is a partial side cutaway view of the apparatus of FIG.  1 . In this view, air containers  108 ,  109  are visible, but fuel reservoirs  102 ,  103  are not. Air channel  208  ( FIG. 2 ) has a first end  301  located near the flame-bearing end  302  of wick  112 , and a second end  303  located in air container  108 . Air channel  210  ( FIG. 2 ) has a first end  304  located near the flame-bearing end  305  of wick  113 , and a second end  306  located in air container  109 . 
   When air is allowed to flow freely through air channels  208  and  210 , each of the wicks  112 ,  113  produces a distinct and separate flame at its flame-bearing ends  302 ,  305 . Flames with different characteristics can be produced by using different fuels in fuel reservoirs  102 ,  103 . One characteristic that varies with the type of fuel is the flame color: liquid paraffin produces a yellow flame; citronella oil produces pink; oil blended with copper salts produces green or blue; oil blended with lithium salts produces red. These flame colors can be manipulated by controlling the flow of air through air channels  208  and  210 . 
   When airflow through air channel  208  to center of wick  112  is reduced, the color of the flame on wicks  112  and  113  is unaffected, but the size of the flame on wick  112  is decreased. When airflow through air channel  210  to the area between wicks  112  and  113  is reduced, the inner flame on wick  112  is unaffected, but the outer flame on wick  113  migrates from the outer edge of the wick and begins to merge with the inner flame on wick  112 . As airflow through air channel  210  decreases further, the flame-bearing end  305  of wick stops burning, though the area in between wicks  112  and  113  still contains hot gases which are a product of fuels from both fuel reservoirs  102 ,  103 . At this point, the inner flame on wick  112  is of a single color but the color of the merged flame in the area surrounding the inner flame is a blend of colors, a result of the mixture of fuels in this area. 
   In the embodiment illustrated in  FIG. 3 , the airflow through air channels  208  and  210  is reduced using air valves  110  and  111 . However, other mechanisms may be used to control airflow. 
     FIG. 4  is a partial front cutaway view, of the apparatus of FIG.  1 . In this view, fuel reservoirs  102 ,  103  are visible, but air containers  108 ,  109  are not. A portion of wick  112 , comprising a second end  401 , extends into fuel reservoir  102 . Similarly, a portion of wick  113 , comprising second end  402 , extends into fuel reservoir  103 . Fuel valves  106 ,  107  control the flow of air from the atmosphere into fuel reservoirs  102 ,  103 . 
   The fuel flows generally as follows: wicks  112 ,  113  utilize the surface tension of the liquid fuel to draw it up through the fibers of the wick by capillary action. When the wick  112 ,  113  burns fuel at its flame bearing end  302 ,  305 , an equal amount is drawn up the wick  112 ,  113  from fuel reservoir  102 ,  103  to replenish the burned fuel. In normal operation, fuel valves  106 ,  107  are open, so that air flows from the atmosphere into fuel reservoir  102 ,  103  to fill the void left by the burned fuel. 
   In another mode of operation, fuel valves  106 ,  107  are closed so that air is unable to flow into fuel reservoir  102 ,  103  to fill the void left by the burned fuel. In this mode, the internal pressure in fuel reservoir  102 ,  103  is reduced as the fuel burns. This reduced internal pressure resists the capillary action of the wick. When the reduced internal pressure is great enough to overcome the capillary action, liquid fuel is no longer drawn up the wick  112 ,  113  to replenish the burned fuel. At this point, the flame will diminish in size as the fuel already in the wick is burned, until that fuel runs out and the flame is finally extinguished. Thus, closing fuel valve  106  on fuel reservoir  102  will result in the flame of wick  112  being extinguished, while closing fuel valve  107  on fuel reservoir  103  will result in the flame of wick  113  being extinguished. If fuel valve  106  or  107  is reopened, then the corresponding wick will reignite after a period of time, unless both fuel valves  106  and  107  have been closed. 
   In the exemplary embodiment illustrated in  FIG. 4 , the apparatus also includes wick sleeves  403 ,  404  to carry wicks  112 ,  113 . In one embodiment, the wick sleeves  403 ,  404  are shaped to closely conform to the wicks  112 ,  113 . Wick sleeves  403 ,  404  prevent expansion of the flame to the lower part of the wicks  112 ,  113 , and increase the capillary pressure on wicks  112 ,  113 . Wick sleeves  403 ,  404  may be made of a heat-conductive material, for example, copper or glass, to lower the viscosity of the liquid fuel. In one embodiment, the wick sleeves  403 ,  404  are made of glass tubing and have an angled edge  405  at the end corresponding to the flame-bearing end  302 ,  305  of the wick. This angled edge  405  aids in the insertion and removal of the wick  112 ,  113 , and also reduces flow of liquid fuel down the side of wick sleeves  403 ,  404  and into air containers  108 ,  109 . 
     FIG. 5  is a cutaway view of the fuel reservoir section of FIG.  1 . The angle θ can be varied to produce reservoirs of various number and capacities. Wall  501  divides fuel reservoir  102  into a first portion  502  and a second portion  503 . The fuel reservoir  102  is fillable with liquid fuel through cap  104 , which is in fluid communication with first portion  502 . Fuel valve  106 , also in fluid communication with first portion  502 , controls the flow of air from the atmosphere into fuel reservoir  102 , as described with regard to FIG.  4 . At least one perforation  504   a-c  in wall  501  allows fuel to communicate between first portion  502  and second portion  503 . The fuel end  401  of the wick  112  is located in second portion  503 , such that it makes contact with liquid fuel flowing into second portion  503 . 
   In the exemplary embodiment, first portion  502  is hollow, and second portion  503  is solid, except for at least one first channel  505   a-c  and a second channel  506  connecting to first channels  505   a-c . Use of a solid central portion strengthens the base  101  (see FIG. 2 ). The open end  507  of second channel  506  lines up with opening  205  (see  FIG. 2 ) in the base  101 . 
   First channels  505   a-c  are aligned with perforations  504   a-c  so that liquid fuel contained in first portion  502  flows through perforations  504   a-c  into first channels  505   a-c , and from there flows into second channel  506 . Perforations  504   a-c  provide an air-tight seal around first channels  505   a-c . The fuel end  401  of the wick  112  is located in second channel  506  such that it makes contact with liquid fuel flowing into second channel  506 . In this embodiment, first channels  505   a-c  are substantially aligned along a horizontal axis and second channel  506  is substantially aligned along a vertical axis, but embodiments can include any alignment that allows the liquid fuel to flow from first portion  502  into second channel  506 . 
     FIG. 6  illustrates a wick holder  601  which can be used in conjunction with the fuel reservoir illustrated in FIG.  5 . In this embodiment, wick holder  601  fits into second channel  506  (see FIG.  5 ). Wick holder  601  is tubular, with an open end  602  which aligns with hole  205  (see  FIG. 2 ) when placed in second channel  506  (see  FIG. 5 ) and a closed end  603 . At least one slit  604  in wick holder  601  allows liquid fuel to flow from vertical channel  506  (see  FIG. 5 ) into fuel end  401  (see  FIG. 4 ) of wick  112  (see FIG.  4 ), and from there liquid fuel travels to flame bearing end  302  (see  FIG. 4 ) via capillary action. Wick holder  601  can be made of any suitable material such as metal or glass. 
     FIG. 7  is a perspective view of another embodiment of an apparatus for controlling a flame. Inner wick  112  and outer wick  113  are concentrically arranged, with an air channel  210  disposed between them. An additional air channel  208  is disposed in the approximate center of the inner wick  112 . An inner wick sleeve  403  surrounds one surface of inner wick  112 . An outer wick sleeve  404  surrounds one surface of outer wick  113 . Fuel reservoirs  102 ,  103  are in fluid communication wicks  112  and  113 . 
   In the example embodiment, the apparatus consists of several nested pieces. Wick sleeves  403  and  404  are substantially tubular in shape, and wicks  112  and  113  are shaped like hollow cylinders. Another tubular piece, air container  108 , is disposed between outer wick  112  and inner wick  113 , forming air channel  210  between the wall of air container  108  and the outer surface of inner wick  112 . 
   In the example embodiment, wick sleeves  403 ,  404  and air container  108  are each of different lengths. The length of air container  108  is such that when air container is placed inside outer wick sleeve  404  and their tops are substantially aligned, a portion  701  of air container  108  extends through opening  702  in outer wick sleeve  404 . Similarly, the length of inner wick sleeve  403  is such that when inner wick sleeve  403  is placed inside air container  108  and their tops are substantially aligned, a portion  703  of inner wick sleeve  403  extends through opening  704  in air container  108 . 
   Fuel reservoirs  102 ,  103  are in fluid communication with wick sleeves  403 ,  404 . In the exemplary embodiment, fuel reservoirs  102 ,  103  are an integrated part of wick sleeves  403 ,  404 , but in another embodiment fuel reservoirs  102  and  103  are separate pieces connected to wick sleeves  403 ,  404 . Caps  104 ,  105  allow fuel reservoirs  102 ,  103  to be filled. 
   In addition, threads  705  on the exemplary embodiment allow caps  104 ,  105  to regulate the flow of air into fuel reservoirs  102 ,  103 . When cap  104 ,  105  is in a tightly closed position, the pressure inside fuel reservoir  102 ,  103  is reduced as fuel is burned, and this reduced pressure resists the capillary action of wick  112 ,  113 , so that finally the wick stops drawing fuel and the flame is extinguished. When cap  104 ,  105  is not tightly closed, air flows into fuel reservoir  102 ,  103  as fuel is burned so that pressure is not reduced and the capillary action of wick  112 ,  113  continues. While threads  705  in cap  104 ,  105  are used in the exemplary embodiment, any mechanism which regulates the flow of air into fuel reservoirs  102 ,  103  could be used instead. 
   The foregoing description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments discussed, however, were chosen and described to illustrate the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variation are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly and legally entitled.