Abstract:
A method for mixing fire fighting gel in situ within a water tank of a fire fighting aircraft. A first step involves mounting a chemical tank to a fire fighting aircraft having a water tank. A second step involves injecting gel forming chemical from the chemical tank into a turbulent flow of water entering the water tank of the aircraft to achieve a required ratio of gel forming chemical and water, with the turbulent flow of water serving to mix the gel forming chemical with the water.

Description:
FIELD 
       [0001]    There is described a method for mixing fire fighting gel in situ within a water tank of a fire fighting aircraft and a fire fighting aircraft that has been modified in accordance with the teachings of the method. 
       BACKGROUND 
       [0002]    Specialized aircraft, both airplanes and helicopters, have been developed for use in fighting fires. Each airplane has a large water tank and is equipped with a water scoop which skims water from a surface of a lake, river or other body of water to fill the water tank. Each helicopter has a snorkle that can be dropped into a body of water and a pump to draw water up the snorkle into the water tank. These innovations enable the airplanes and helicopters to refill their water tanks without having to return to an airport. 
         [0003]    It has been determined that the use of a fire fighting gel is more effective in fighting fires than the use of water alone. At the present time, airplanes and helicopters must return to a gel mixing site to get their tanks refilled with fire fighting gel. With helicopters, the gel mixing site can be a large clearing. With airplanes, the gel mixing site must be at an airport. Valuable time is being lost in travelling to and from distant airports. Merely adding chemical to water in the water tank of a fire fighting airplane or helicopter is not an option, as mixing is required for chemical and water to form fire fighting gel. What is required is a manner of adding and mixing chemical in the tank of a fire fighting airplane or helicopter to form fire fighting gel. 
       SUMMARY 
       [0004]    According to one aspect, there is provided a method for mixing fire fighting gel in situ within a water tank of a fire fighting aircraft. A first step involves mounting a chemical tank to a fire fighting aircraft having a water tank. A second step involves injecting gel forming chemical from the chemical tank into a turbulent flow of water entering the water tank of the aircraft to achieve a required ratio of gel forming chemical and water, with the turbulent flow of water serving to mix the gel forming chemical with the water. 
         [0005]    The reason the above described method works is the turbulence caused during filling. With an aircraft, the water scoop fills the water tank in between five to twelve seconds. With a helicopter, water is pumped up the snorkle to fill the water tank at rates which vary between five seconds and one and one half minutes. It will be appreciated that the more rapid the filling action, the greater the associated turbulence, which can be used to mix gel forming chemicals with water to form fire fighting gel. 
         [0006]    According to another aspect, there is provided a combination of components for use in practising the method. The combination includes a fire fighting aircraft having a water tank, a chemical tank mounted to the aircraft and a chemical injection assembly for injecting chemical from the chemical tank into a conduit through which water passes when filling the water tank from a body of water. When the fire fighting aircraft is an airplane, water to fill the water tank is fed into the conduit from a water scoop which skims water from a surface of a body of water. When the fire fighting aircraft is a helicopter, the conduit is a snorkle tube with associated pump water that draws water from a body of water up the snorkle tube into the water tank. 
         [0007]    Once the critical issue of mixing was solved, a secondary problem that had to be addressed was how to inject sufficient chemical to form the gel in the short time span that it took for the water scoop to fill the water tank. Beneficial results were obtained through the use of a cylinder with a double acting piston. The double acting piston divides the cylinder into a first chamber and a second chamber. A first supply connection connects the first chamber with the chemical tank. A first injection connection connects the first chamber with an injector nozzle. A second supply connection connects the second chamber with the chemical tank. A second injection connection connects the second chamber with an injector nozzle. Check valves are provided which are activated by movement of the double acting piston. Movement of the double acting piston in a first direction results in chemicals in the first chamber being forced through the first injection connection to the injector nozzle and concurrently results in chemicals being drawn from the chemical tank through the second supply connection to fill the second chamber. Movement of the double acting piston in a second direction results in chemicals in the second chamber being forced through the second injection connection to the injector nozzle and concurrently results in chemicals being drawn from the chemical tank through the first supply connection to fill the first chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein: 
           [0009]      FIG. 1  is a schematic view of a chemical injector with no flow between the injector package and the water tank in a helicopter. 
           [0010]      FIG. 2  is a schematic view of the chemical injector shown in  FIG. 1  with flow between the injector package and the water tank. 
           [0011]      FIG. 3  is a schematic view of the chemical injector shown in  FIG. 1  with flow between the injector package and the water tank. 
           [0012]      FIG. 4  is a side elevation view of a helicopter prior to mixing of fire fighting gel. 
           [0013]      FIG. 5  is a side elevation view of the helicopter shown in  FIG. 4  during mixing of fire fighting gel. 
           [0014]      FIG. 6  is a schematic view of an injector with no flow between the injection assembly and the water tank in an airplane. 
           [0015]      FIG. 7  is a schematic view of the chemical injector shown in  FIG. 6  with flow between the injector package and the water tank. 
           [0016]      FIG. 8  is a schematic view of the chemical injector shown in  FIG. 6  with flow between the injector package and the water tank. 
           [0017]      FIG. 9  is a schematic view of a chemical injector assembly with an alternative piston configuration. 
           [0018]      FIG. 10  is a schematic view of the piston configuration shown in  FIG. 6  with arrows showing liquid movement as the piston travels in a first direction. 
           [0019]      FIG. 11  is a schematic view of the piston configuration shown in  FIG. 6  with arrows showing liquid movement as the piston travels in a second direction. 
           [0020]      FIG. 12  is a perspective view of a portion of the chemical injector assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The method and fire fighting aircraft modified in accordance with the method will now be described. A fire fighting helicopter, generally identified by reference numeral  10 , will be described with reference to  FIG. 1 through 5 . A fire fighting airplane, generally identified by reference numeral  100 , will be described with reference to  FIG. 6 through 8 . 
       Structure and Relationship of Parts: 
       [0022]    Referring to  FIGS. 4 and 5 , a fire fighting aircraft such as a helicopter  10  has a water tank  12  that allows for ejection of water or other fluid from the helicopter  10 . Referring to  FIG. 1 , a conduit, such as a snorkle tube  14 , with an associated pump  16  draws water from a body of water  13  up the snorkle tube  14  into the water tank  12 . Referring to  FIG. 4 , a chemical tank  18  is mounted to the helicopter  10  with a chemical injection assembly  20  provided for injecting chemical from the chemical tank  18  into the snorkle tube  14  through which water passes when filling the water tank  12  from a body of water. 
         [0023]    Referring to  FIG. 1 , the chemical injection assembly  20  includes a cylinder  22  with a double acting piston  24  that divides the cylinder  22  into a first chamber  26  and a second chamber  28 . A first supply conduit  30  connects the first chamber  26  with the chemical tank  18  and a first injection conduit  32  connects the first chamber  26  with an injector nozzle  34 . A second supply conduit  36  connects the second chamber  28  with the chemical tank  18 . A second injection conduit  38  connects the second chamber  28  with the injector nozzle  34 . Check valves  40  are activated by movement of the double acting piston  24 . Referring to  FIG. 3 , movement of the double acting piston  24  in a first direction results in chemicals in the first chamber  26  being forced along the first injection conduit  32  to injector nozzle and concurrently results in the chemicals being drawn from the chemical tank  18  along the second supply conduit  36  to fill the second chamber  28 . Referring to  FIG. 2 , movement of the double acting piston  24  in a second direction results in chemicals in the second chamber  28  being forced along the second injection conduit  36  to the injector nozzle  34  and concurrently results in the chemicals being drawn from the chemical tank  18  along the first supply conduit  30  to fill the first chamber  26 . 
         [0024]    Referring to  FIG. 7 , a fire fighting airplane  100  may also be used. Airplane  100  has a water tank  102  that allows for ejection of water or other fluid from the airplane  100 . Water to fill water tank  102  is fed into a conduit, such as a water scoop  104 , by skimming water from a surface of a body of water  103 . A chemical tank  108  is mounted to the airplane  100  with a chemical injection assembly  20  provided for injecting chemical from the chemical tank  108  into the water scoop  104  through which water passes when filling the water tank  102  from a body of water  103 . 
         [0025]    Referring to  FIG. 6 , the chemical injection assembly  120  includes a cylinder  122  with a double acting piston  124  that divides cylinder  122  into a first chamber  126  and a second chamber  128 . A first supply conduit  130  connects the first chamber  126  with the chemical tank  108  and a first injection conduit  132  connects the first chamber  126  with an injector nozzle  134 . A second supply conduit  136  connects the second chamber  128  with the chemical tank  108 . A second injection conduit  138  connects the second chamber  128  with the injector nozzle  134 . Check valves  140  are activated by movement of the double acting piston  124 . Referring to  FIG. 8 , movement of the double acting piston  124  in a first direction results in chemicals in the first chamber  126  being forced along the first injection conduit  132  to the injector nozzle and concurrently results in the chemicals being drawn from the chemical tank  108  along the second supply conduit  136  to fill the second chamber  128 . Referring to  FIG. 7 , movement of the double acting piston  124  in a second direction results in chemicals in the second chamber  128  being forced along the second injection conduit  136  to the injector nozzle  134  and concurrently results in the chemicals being drawn from the chemical tank  108  along the first supply conduit  130  to fill the first chamber  126 . 
       Operation: 
       [0026]    Referring to  FIG. 5 , in a helicopter  10 , fire fighting gel is mixed in situ within the water tank  12 . Referring to  FIG. 1 , the chemical injection assembly  20  is in fluid communication with the water tank  12  of the helicopter  10 . Referring to  FIG. 5 , water from a water source  13 , such as a lake, passes through the snorkle tube  14  into the water tank  12  of the fire fighting helicopter  10 . Referring to  FIG. 1 , the pump  16  helps uptake of water through the snorkle tube  14 . While water is entering the water tank  12 , the chemical injection system  20  injects chemicals into the snorkle tube  14  which causes a mixture of water and chemical to enter the water tank  12  which causes formation of a fire fighting gel. The injection time required to obtain an appropriate mix ratio of chemical to water varies depending on the mix ratio and the time of aircraft and conduit used. Referring to  FIG. 5 , for example, the use of a helicopter  10  with a snorkle tube  14  with a pump  16  creating a mix ratio of 0.5% to 3% may take from 5 seconds to upwards of 90 seconds. 
         [0027]    Referring to  FIG. 1 , the chemical injection system  20  works by movement of the double acting piston  24 . Check valves  40  are activated by movement of the double acting piston  24  and allow for movement of chemicals from the chemical injection system  20  to the water tank  12 . Referring to  FIG. 3 , movement of the double acting piston  24  in a first direction results in chemicals in the first chamber  26  being forced along the first injection conduit  32  to the injector nozzle and draws chemicals from the chemical tank  18  along the second supply conduit  36  to fill the second chamber  28 . Referring to  FIG. 2 , movement of the double acting piston  24  in a second direction results in chemicals in the second chamber  28  being forced along the second injection conduit  36  to the injector nozzle  34  and draw chemicals from the chemical tank  18  along the first supply conduit  30  to fill the first chamber  26 . Referring to  FIGS. 2 and 3 , injection of the chemical during water uptake is preferably done just prior to pump  16  to allow the pump  16  to mix the chemical with the water; however, it will be understood that the chemical can be injected into the water at any point along the snorkle tube  14 . 
         [0028]    Referring to  FIG. 6 , in an airplane  100 , fire fighting gel is mixed in situ within the water tank  102 . A chemical injection assembly  120  is in fluid communication with the water tank  102  of the airplane  100 . Water from a water source  103 , such as a lake, passes through the water scoop  104  into the water tank  102  of fire fighting aircraft. While water is entering the water tank  102 , the chemical injection system  120  injects chemicals into the water scoop  104  which causes a mixture of water and chemical to enter the water tank  102  which causes formation of a fire fighting gel. The injection time required to obtain an appropriate mix ratio of chemical to water varies depending on the mix ratio and conduit used. For example, the use of an airplane  100  using a water scoop  104  creating a mix ratio of 0.5% to 3% may take from 5-12 seconds. 
         [0029]    Referring to  FIG. 6 , the chemical injection system  120  works by movement of the double acting piston  124 . Check valves  140  are activated by movement of the double acting piston  124  and allow for movement of chemicals from the chemical injection system  120  to the water tank  102 . Referring to  FIG. 8 , movement of the double acting piston  124  in a first direction results in chemicals in the first chamber  126  being forced along the first injection conduit  132  to the injector nozzle and draws chemicals from the chemical tank  108  along the second supply conduit  136  to fill the second chamber  128 . Referring to  FIG. 7 , movement of the double acting piston  124  in a second direction results in chemicals in the second chamber  128  being forced along the second injection conduit  136  to the injector nozzle  134  and chemicals from the chemical tank  108  being drawn along the first supply conduit  130  to fill the first chamber  126 . 
         [0030]    Referring to  FIGS. 9 through 12 , there is illustrated an alternative chemical injection assembly  220  that uses an alternative piston configuration. This alternative chemical injection assembly  220  was developed with three objectives in mind. The first objective was to reduce the amount of weight. The second objective was to reduce the complexity of the piping and valving. The third objective was to make installation and maintenance easier. For operation in alternative chemical injection assembly  220 , the chemicals from which foam is produced were intentionally made more concentrated and less viscose having a mix ratio of 0.1% to 3%. The alternative chemical injection assembly  220  includes a cylinder  222  having a first end  224  and a second end  226 . A working example of a cylinder  222  is shown in  FIG. 12 . Referring again to  FIGS. 9 through 12 , a pair of supply connection lines  228  and  230  at the first end  224  connects the cylinder  222  with a chemical tank  232 . A pair of injection connection lines  234  and  236  at the second end  226  connects the cylinder  222  with an injector nozzle (not shown in this view). A piston  240  divides the cylinder  222  into a first chamber  242  and a second chamber  244 . The relative size of the first chamber  242  and the second chamber  244  is altered as the piston  240  moves in a first direction toward the first end  224  (as shown by arrows  246  in  FIG. 11 ) or a second direction toward the second end  226  (as shown by arrows  248  in  FIG. 10 ). Referring to  FIG. 10 , as the piston  240  moves in the first direction  246 , the first chamber  242  contracts and the second chamber  244  expands. Referring to  FIG. 10 , as the piston  240  moves in the second direction  248 , the first chamber  242  expands and the second chamber  244  contracts. Referring to  FIG. 10 , a pair of unidirectional check valves  250  is positioned in the piston  240  that is open to permit flow through the piston  240  as the piston  240  moves in the first direction  246 . Referring to  FIG. 11 , check valves  250  close to block flow through piston  240  as piston  240  moves in second direction  248 . A pair of unidirectional check valves  252  are positioned in supply connection lines  228  and  230 . Referring to  FIG. 10 , check valves  252  are closed to block flow through supply connection lines  228  and  230  when piston  240  moves in first direction  246 . Referring to  FIG. 11 , checks valves  252  are open to permit flow through supply connection lines  228  and  230  into cylinder  222  when piston  240  moves in second direction  248 . Referring to  FIG. 10 , a pair of unidirectional check valves  254  are positioned in the injection connection lines  234  and  236  that close to block flow through the injection connection lines  234  and  236  when the piston  240  moves in the first direction  246 . Referring to  FIG. 11 , the check valves  254  open to permit flow through the injection connection lines  234  and  236  when the piston moves  240  in the second direction  248 . It will be appreciated that the opening and closing of the above-described check valves is activated by movement of the piston  240 . The piston  240  is moved by a rotating screw  256 . Referring to  FIG. 10 , gel forming chemical is transferred from the first chamber  242  to the second chamber  244  as the piston  240  moves in the first direction  246 . Referring to  FIG. 11 , the gel forming chemical is drawn along the supply connection lines  228  and  230  from the chemical tank  232  into the first chamber  242  and from the second chamber  244  into the injection connection lines  234  and  236  as the piston  240  moves in the second direction  248 . As previously described with respect to the chemical injection assembly  120 , while water is entering the water tank  102 , the alternative chemical injection system  220  injects chemicals into the water. The chemicals mix with the water forming a fire fighting gel. 
         [0031]    In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. 
         [0032]    The following claims are to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, and what can be obviously substituted. Those skilled in the art will appreciate that various adaptations and modifications of the described embodiments can be configured without departing from the scope of the claims. The illustrated embodiments have been set forth only as examples and should not be taken as limiting the invention. It is to be understood that, within the scope of the following claims, the invention may be practiced other than as specifically illustrated and described.