Abstract:
An apparatus is for use with a container of liquid that is suspended from an aircraft flying over a ground target area. The container has an outlet through which the liquid is dropped from the container. The apparatus includes a diffuser configured to diffuse the liquid exiting the container outlet horizontally outward beyond the container into the air above the ground target area, whereby the liquid is diffused over a correspondingly wide area. The liquid can be fire extinguishing liquid, and the ground target area can be a forest fire.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 60/223,754, filed Aug. 8, 2000, and incorporates the Provisional Application by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to airborne water sprinkling systems.  
         BACKGROUND  
         [0003]    An airborne water sprinkling system is used to transport water to fight fires favoring aerial discharge of water based fire fighting agents such as a forest fire and to discharge water based fire fighting agents such as the water over the fire to extinguish the fire. The water is held in a container that is transported by an aircraft.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention provides an apparatus for use with a container of liquid that is suspended from an aircraft flying over a ground target area. The container has an outlet through which the liquid is dropped from the container. The apparatus includes a diffuser configured to diffuse the liquid exiting the container outlet horizontally outward beyond the container into the air above the ground target area, whereby the liquid is diffused over a correspondingly wide area.  
           [0005]    In a preferred embodiment, the liquid is fire extinguishing liquid, and the ground target area is a forest fire. A diffuser inlet receives the liquid, and diffuser outlets discharge the liquid into the air. The diffuser outlets are spaced horizontally from each other. A manifold of the diffuser communicates the diffuser inlet with the diffuser outlets. The manifold has rigid hydraulic lines extending from the diffuser inlet. Flexible hydraulic lines of the manifold extend from the rigid lines to the diffuser outlets. Buoyant structures are configured to maintain the diffuser outlets above the container when the container is submerged in a body of liquid. The diffuser is configured to diffuse the liquid by allowing the liquid to fall from the diffuser solely through the force of gravity.  
           [0006]    The diffuser can further have a hydraulic line. A first end of the hydraulic line is configured to be connected to the container outlet. A second end of the hydraulic line is configured to be connected to a second aircraft. The diffuser outlets are spaced apart along the hydraulic line. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a perspective view of a sprinkling system comprising a first embodiment of the present invention, showing the sprinkling system in one mode of operation;  
         [0008]    [0008]FIG. 2 is a top view taken on line  2 - 2  shown in FIG. 1;  
         [0009]    [0009]FIG. 3 is an expanded top view of a part shown in FIG. 2,  
         [0010]    [0010]FIG. 4 is a sectional view taken on line  4 - 4  of FIG. 2, showing parts in one configuration;  
         [0011]    [0011]FIG. 5 is a view similar to FIG. 4, showing the parts in a second configuration;  
         [0012]    [0012]FIG. 6 is a view similar to FIG. 1, showing the sprinkling system in a second mode of operation;  
         [0013]    [0013]FIG. 7 is a view similar to FIG. 1, showing the sprinkling system in a third mode of operation;  
         [0014]    [0014]FIG. 8 is a top view taken on line  8 - 8  of FIG. 7;  
         [0015]    [0015]FIG. 9 is a perspective view of a sprinkling system comprising a second embodiment of the present invention, showing the sprinkling system in one mode of operation;  
         [0016]    [0016]FIG. 10 is a view similar to FIG. 9, showing the sprinkling system in a second mode of operation;  
         [0017]    [0017]FIG. 11 is a view similar to FIG. 9, showing the sprinkling system in a third mode of operation; and  
         [0018]    [0018]FIG. 12 is a top view taken on line  12 - 12  of FIG. 11. 
     
    
     DESCRIPTION  
       [0019]    An example of a preferred embodiment of the present invention is shown in FIGS. 1 and 2. The preferred embodiment is an airborne sprinkling system  10  that is used to transport water to a forest fire  14  and to discharge the water over the fire  14 . The water is initially held in a container  18  that is transported aloft by an aircraft, such as a helicopter  20 . A diffuser  24  at the bottom of the container  18  diffuses the water horizontally outward from the container  18  into the air, to drop the water onto the fire  14  to extinguish it.  
         [0020]    The container  18  is in the form of a bucket  26  surrounded by a wire net  28 , as shown in FIG. 1. The bucket  26  is suspended from the helicopter  20  by a suspension structure  30 . The suspension structure  30  includes three suspension wires  32 . An upper end of each suspension wire  32  is attached to the helicopter  20  by a hook  36  affixed to the helicopter  20 . A lower end of each suspension wire  32  is attached to the upper end of the bucket  26  and to the upper end of the net  28 .  
         [0021]    As shown in FIGS. 3 and 4, the bucket  26  has a cylindrical side wall  38 , a flat bottom wall  40  and an open top  42 . The side wall  38  has orifices  50  located at various heights from the bottom wall  40 . Some or all of the orifices  50  can be plugged to pre-select a water level within the container  18 , as explained below. The bottom wall  40  has two similar semicircular panel doors  56  that are shaped to fit closely within corresponding semicircular door openings  58  defined by apertures  59  in the bottom wall  40 . Each door  56  has an arcuate edge  60 , a straight edge  62 , and an orifice  64  serving as a container outlet. The straight edges  62  are hinged to a rectangular central strip  65  of the bottom wall  40 . The panel doors  56  can be pivoted about the central strip  65  between a closed position and an open position. In the closed position, shown in FIGS. 3 and 4, the doors  56  are received closely within the respective door openings  58 . In the open position, shown in FIG. 5, the doors  56  are tilted upward out of the door openings  58 .  
         [0022]    A motor  66 , shown schematically in FIG. 4, can be attached to the panel doors  56  to open and close the doors  56 . The motor  66  can be controlled through an electrical line  67  by a switch (not shown) within the cockpit of the helicopter  20  (FIG. 1).  
         [0023]    As shown in FIG. 4, the two container outlets  64  are connected to a 3-port connector  68  by two flexible hydraulic lines  70 . The connector  68  is retained in an opening  72  in the bottom of the net  28 . The connector  68  is connected to an inlet  78  of an electrically-controlled outlet valve  80 . The valve  80  is electrically connected by an electrical line  82  to another switch (not shown) within the cockpit. Using the switch, an operator can cause the valve  80  to adopt an open condition or a closed condition. An outlet  84  of the valve  80  is connected to an inlet  88  of the diffuser  24 .  
         [0024]    As shown in FIGS. 1 and 2, the diffuser  24  has a manifold  89  that includes four rigid hydraulic lines  90  that extend radially outward from the diffuser inlet  88  and, further, horizontally outward beyond the container  18 . The manifold  89  also includes four flexible hydraulic lines  92  that extend from radially-outer ends  94  of the four rigid lines  90  to four respective diffuser outlets  96 . The outlets  96  discharge water from the flexible lines  92  into the air. Four air-filled balloons  97  are attached to distal ends of the four flexible lines  92  near the diffuser outlets  96 .  
         [0025]    In operation, the container  18 , with the diffuser  24  attached, is carried aloft by the helicopter  20 . When carried aloft, the flexible lines  92  extend downward due to gravity. The container  18  is filled with water from an open water source, such as a lake  100 , as shown in FIG. 6. To fill the container  18 , the helicopter  20  gradually descends, thereby lowering the container  18  into the lake  100 . Water from the lake  100  forces the panel doors  56  (FIG. 5) open and enters the container  18 . Opening of the panel doors  56  can be assisted by the motor  66  (FIG. 4). The container  18  is gradually submerged in the lake  100  as it fills with the water. Although the rigid lines  90  are totally submerged, the diffuser outlets  96  remain near the surface of the lake  100  due to buoyancy of the balloons  97 .  
         [0026]    Next, the helicopter  20  ascends, raising the container  18  and the diffuser  24  out of the lake  100 . As shown in FIG. 4, the panel doors  56  of the container  18  automatically close under the force of gravity. Closing of the panel doors  56  can be assisted by the motor  66 . With the panel doors  56  closed and the valve  80  in a closed condition, the container  18  is substantially watertight. Water gradually spills out of any of the orifices  50  in the side wall  38  that are unplugged until the water level within the container  18  is lowered to the level of the lowest unplugged orifice  50 . Thus, the water level in the container  18  can be pre-selected by plugging only those orifices  50  that are below a desired water level.  
         [0027]    Subsequently, the helicopter  20  transports the container  18  and the diffuser  24  to the forest fire  14  to discharge the water over the fire  14 , as shown in FIG. 1. As shown in FIG. 7, while the helicopter  20  is traveling over or hovering over the forest fire  14 , the valve  80  is switched to the open condition. This enables the water to pass from the container  18  through the container outlets  64  into the diffuser  24 , driven only by the force of gravity. The water is forced out of the diffuser outlets  96  into the air by a hydraulic head pressure, corresponding to the height H of the container  18  relative to the diffuser outlets  96 .  
         [0028]    Each diffuser outlet  96  directs the water radially outward from the outlet  96  in all directions under the force of the hydraulic head. As water falls from each diffuser outlet  96 , it spreads over a circular area  102  of diameter D, as shown in FIG. 8. This yields a water distribution pattern defined by lower-density areas  104  and higher-density areas  106 . Each lower-density area  104  receives water from only one of the diffuser outlets  96 , whereas each higher-density area  106  receives water from two of the diffuser outlets  96 . The higher-density areas  106  thus receive about twice the water density as the lower-density areas  104 . The rate of water discharge from each diffuser outlet  96  and the diameter D are determined by the structural configuration of the diffuser outlets  96  and the dimensions of the flexible lines  92  (FIG. 7).  
         [0029]    In this sprinkling operation, the water is diffused in two manners. Specifically, the water is distributed by the manifold  89  to the outlets  96  that are located horizontally outward from the container  18  and from each other. Additionally, each outlet  96  individually diffuses the water by spraying the droplets radially outward.  
         [0030]    As explained above with reference to FIG. 4, the outlet valve  80  is controlled by a switch within the cockpit through the electrical line  82 . Alternative, the valve  80  can be controlled by a wireless remote control system, thereby obviating the electrical line  82 . In that case, the valve  80  would be powered by a battery affixed to the container  18 . The valve  80  would be electrically connected to a remote control receiver, and a corresponding transmitter would be located in the cockpit.  
         [0031]    An example of a second embodiment of the invention is shown in FIG. 9. A sprinkling system  110  of the second embodiment has features that are similar to those of the sprinkling system  10  of the first embodiment (FIG. 1). As in the first embodiment, water in the second embodiment is held in a container  114  that is suspended from a helicopter  118 . Also, as in the first embodiment, a diffuser  124  diffuses water horizontally outward from the container  114 , through diffuser outlets  126 , into the air. However, in contrast to the first embodiment, the diffuser outlets  126  are arranged as a string of diffusers extending horizontally in only a single direction. Also, in contrast to the first embodiment, the diffuser  124  has no outlet valve, and the weight of the diffuser  124  is borne jointly by two helicopters.  
         [0032]    The container  114  of the second embodiment has the same structure as described above with reference to the first embodiment (FIGS. 3 and 4). Specifically, the container  114  includes a bucket  128  within a net  130 , both suspended from the first helicopter  118  by a suspension structure  132 . Two container outlets  120  in a bottom wall  136  of the bucket  128  are connected by two flexible hydraulic lines  140  to a 3-port connector  138 . The connector  138 , in turn, is connected to the diffuser  124 . The diffuser  124  includes a suspension wire  142  having a first end  144  attached to the bottom of the net  130  and a second end  148  attached to a second helicopter  150 .  
         [0033]    The diffuser also includes a flexible hydraulic line  152  having an inlet end  154  and an opposite closed end  156 . The inlet end  154  is connected to the connector  138 . The flexible line  152  is suspended along its length from the suspension wire  142  by a series of hooks  158  spaced apart along the length of the suspension wire  142 . The closed end  156  of the flexible line  152  is thus indirectly connected to the second helicopter  150  by means of the suspension wire  142 . The weight of the diffuser  124  is consequently borne by both helicopters  118  and  150 . The diffuser outlets  126  are spaced apart along the length of the flexible line  152 . These outlets  126  are similar to the diffuser outlets  96  of the first embodiment (FIG. 1).  
         [0034]    In operation, the container  114 , with the diffuser  124  attached, is carried aloft by the helicopters  118  and  150 , as shown in FIG. 9. The container  114  is filled with water from a lake  160 , as shown in FIG. 10. The helicopters  118  and  150  gradually descend, thereby lowering the container  114  into the lake  160 . The container  114  is gradually submerged in the lake  160  as it fills with the water. Next, the helicopters  118  and  150  ascend, raising the container  114  out of the lake  160 . Subsequently, as shown in FIG. 9, the helicopters  118  and  150  transport the container  114  and the diffuser  124  to a forest fire  162  to drop the water over the fire  162 . Throughout these steps of filling (FIG. 10) and transporting (FIG. 9) the container  114 , the altitude of the second helicopter  150  relative to the first helicopter  118  is maintained such that all of the diffuser outlets  126  are above the container  114 . This prevents the water from flowing out of the container  114  through the diffuser outlets  126  under the force of gravity.  
         [0035]    As shown in FIG. 11, while the helicopters  118  and  150  are traveling over or hovering over the forest fire  162 , the altitude of the second helicopter  150  relative to the first helicopter  118  is lowered so that the water flows from the container  114  through the diffuser  124  by the force of gravity. The water is forced out of each diffuser outlet  126  into the air by a hydraulic head pressure corresponding to the height H′ of the container  114  relative to the diffuser outlets  126 .  
         [0036]    The diffuser outlets  126  direct the water radially outward in all directions under the force of the hydraulic head. As the water falls from the diffuser outlets  126 , it spreads over circular areas  164  of diameter D′, as shown in FIG. 12. This yields a water distribution pattern defined by lower-density areas  166  and higher-density areas  168 . Each lower-density area  166  receives water from only one of the diffuser outlets  126 , whereas each higher-density area  168  receives water from two of the diffuser outlets  126 . The higher-density areas  168  thus receive about twice the water density as the lower-density areas.  
         [0037]    In the sprinkling operation described with reference to FIG. 11, the water is diffused in two different manners. First, the water is distributed to the outlets  126  that are located horizontally outward from the container  114  and from each other. Secondly, each outlet  126  diffuses the water by spraying the water radially outward.  
         [0038]    While discharging the water over the fire  162 , the helicopters  118  and  150  can move side-to-side to broaden the spread of the water over the fire  162 . In doing so, the second helicopter  150  optimally moves side-to-side more than the first helicopter  118 , because the second helicopter  150  carries a lighter load. This is because the first helicopter  118  bears the weight of the container  114  and the water within the container  114 , whereas the second helicopter  150  does not. Because the second helicopter  150  bears a lighter load, it can be rated for lower weight capacity than the first helicopter  118 .  
         [0039]    Calculations for operating the sprinkling system  10  (FIGS.  1 - 8 ) borne by one helicopter, described with reference to the first embodiment, are as follows. For this exemplary scenario, assume that the design discharge water density is 5 liters/m 2 /minute. Also assume that the effective water density is 3 liters/m 2 /minute, which is about the density of heavy rain, assumed to be the water density that can reach the fire (This assumption is subject to future test confirmation and adjustment.), allowing say, loss to air of 2 liters/m 2 /minute of water density.  
         [0040]    If each diffuser outlet delivers 60 liter per minute, vertically downwards, horizontal area covered by each sprinkler is 12 m 2 =(60 liters/minute)/(5 liters/m 2 /minute)=12 m 2  receiving 5 liters/m 2 /minute water density. Note that since 2 liters/m 2 /min. is assumed to be lost, 3 liters/m 2 /minute is the final water density falling on the burning objects and their vicinity. Since πD 2 /4=area of a circle. 12 m 2  is the area of a circle of diameter of 3.91 m; i.e. 12=πD 2 /4.  
         [0041]    For an arrangement of four sprinklers (FIGS. 1, 2,  7  and  8 ) fire area receiving 3 liters/m 2 /minute water density equals 4×a m 2 , and fire area receiving 6 liters/m 2 /minute water density equals 4×b m 2 . The duration of time that these areas can continuously receive water from an airborne water sprinkler system having a water container which can effectively discharge 480 liters through the 4 sprinklers equals 2 minutes, equivalent to 120 seconds, calculated as 480 liters/4 sprinklers/60 liters/minute.  
         [0042]    Now suppose the fire as sprinkled by water with the densities as described can be paralyzed (i.e. stopped from burning further to other unburnt objects) with 10 seconds of continuous sprinkling water falling on the same object region, then 480 liters water from the airborne water container can paralyze a fire of an area equaling 4(a+b)m 2 ×120 seconds/10 seconds=48(a+b)m 2  which is 12 times 4(a+b)m 2 .  
         [0043]    Suppose this area of 48(a+b) m 2  effectively covers a burning area of about 12×6.5 m×6.5 m (FIG. 8, by measurement in scale), then the area of fire front that can be paralyzed by one action of discharging 480 liters of water from the airborne water container equals 6.5 m×6.5 m×12=507 m 2 . If the fire front is less than 6.5 m, and this length of fire front is effectively fought by the water discharged, the length of fire front that can be paralyzed by one such action equals 507 m 2 /6.5 m=78 m.  
         [0044]    Suppose the fire front is 2 km (i.e. 2,000 m), it will then take 26 such operations to paralyze this fire front, because 2,000 m/78 m equals 25.6.  
         [0045]    If it takes two minutes for one helicopter to travel from the fire front to a water source to refill the airborne water container and then travels back to the fire front, then two helicopters each conducting 13 such operations in an overall time period of about 52 minutes (i.e. 52=26×2 minutes) can paralyze a fire front of 2,000 m long.  
         [0046]    Now suppose a larger airborne water container that can discharge water of 960 liters is used, then each helicopter operation will take about 6 minutes, (i.e. 6 minutes=2 minutes of traveling and filling water+4 minutes of discharging water) and paralyze 156 m fire front (156 m=2×78 m).  
         [0047]    In order to paralyze 2,000 m long fire front, it will take 13 helicopter operations (i.e. 2,000 m/156 m=12.8).  
         [0048]    If two helicopters operate alternatively on the fire front, it will take 52 minutes to discharge water to paralyze the fire front (i.e. 52=13×4 minutes). This is the same duration as before. But this will allow 4 minutes for traveling and water filling time for the helicopters. That is the water source can be further away.  
         [0049]    In the scenario above, water loss to air depends on the distribution of water drop sizes discharged, air down draft from helicopter, wind direction, fire gas upward movement. Therefore assumed loss of 2 liters/m 2 /minute may vary.  
         [0050]    The arrangement of four diffuser outlets is one way of arranging the diffuser outlets. There are other possible ways of diffuser outlet arrangement for varying the number of diffuser outlets, distance between diffuser outlets and their types, lengths of rigid tube and fixed tube.  
         [0051]    If there are additional helicopters fighting the fire from both ends of the length of burning objects, using the invented systems the same fire can be paralyzed in a shorter time.  
         [0052]    The above calculations relate to the sprinkling system  10  (FIGS.  1 - 8 ) borne by one helicopter. Calculations for operating the sprinkling system  110  (FIGS.  9 - 12 ) borne by two helicopters are as follows. For this exemplary scenario, assume that the design discharge water density is 5 liters/m 2 /minute. Also assume that the effective water density is 3 liters/m 2 /minute, which is about the density of heavy rain, assumed to be the water density that can reach the fire (This assumption is subject to future test confirmation and adjustment.), allowing say, loss to air of 2 liters/m 2 /minute of water density.  
         [0053]    If each diffuser outlet delivers 60 liters per minute, vertically downwards, horizontal area covered by each diffuser outlet is 12 m 2 , calculated as (60 liters/minute)/(5 liters/m 2 /minute)=12 m 2  receiving 5 liters/m 2 /min. water density. Note that since 2 liters/m 2 /min. is assumed to be lost, 3 liters/m 2 /minute is the final water density falling on the burning objects and their vicinity. Since πD 2 /4 area of a circle, 12 m 2  is the area of a circle of diameter of 3.91 m (i.e. 12=πD 2 /4).  
         [0054]    There are various possible arrangement of flexible tubes and diffuser outlets. For an arrangement of eight sprinklers (FIGS.  9 - 11 ), the fire area receiving 3 liters/m 2 /minute water density equals 8a+2b m 2 , and fire area receiving 6 liters/m 2 /minute water density equals 7b m 2 . The time that these areas can continuously receive water from an airborne water container which can effectively discharge 480 liters through the eight sprinklers is 1 minute, equivalent to 60 seconds, calculated as 480 liters/8 sprinklers/60 liters/minute.  
         [0055]    Now suppose the fire as sprinkled by water with the densities as described can be paralyzed (i.e. stopped from burning further) with 10 seconds of continuous sprinkling water falling on the same object region, then 480 liters water from the airborne water container can paralyze a fire of an area, calculated as (8a+2b+7b)m 2 ×60 seconds/10 seconds=6(8a+9b)m 2 .  
         [0056]    Suppose the water sprinkled area is 3 times (8a+9b)m 2  for paralyzing a length of burning objects of 20 m (i.e. 20 m=0.833 assumed multiplier×8 diffuser outlets×3 m separation between each diffuser outlet), then the length of fire front that can be paralyzed by one action of discharging 480 liters of water from the airborne water container via the invented system is 20 m×2=40 m, within a time span of 1 minute. Note that 2=6(8a+9b)/3(8a+9b).  
         [0057]    Suppose the fire front is 2 km (i.e. 2,000 m), it will then take 50 such operations to paralyze this fire front, because 2,000 m/40 m=50.  
         [0058]    If it takes 2 minutes for the two helicopters to travel from the fire front to a water source to refill the airborne water container with effective water capacity of 480 liters and then travels back to the fire front, then the two helicopters will have to conduct 50 such operations in an overall time period of about 150 minutes (i.e. 150 minutes=50×(2+1) minutes) for paralyzing a fire front of 2,000 m long.  
         [0059]    Now suppose a larger airborne water container that can discharge water of 960 liters is used, then each helicopter operation will take about 4 minutes (i.e. 4 minutes=2 minutes of traveling and filling water+2 minutes of discharging water) and paralyze 80 m long fire front. In order to paralyze 2,000 m long fire front, it will take 25 helicopter operations (i.e. 2,000 m/80 m=25). Then it will take 100 minutes (i.e. 100 minutes=4 minutes per operation×25 operations) to paralyze a fire front of 2000 m long.  
         [0060]    Thus such airborne water sprinkler systems operated by two helicopters can be more time effective in fighting forest fires by using larger water containers and related helicopters of larger capacity.  
         [0061]    In the scenario above, water loss to air depends on the distribution of water drop sizes discharged, air down draft from helicopter, wind direction, fire gas upward movement. Therefore assumed loss of 2 liters/m 2 /minute may vary.  
         [0062]    The arrangement of eight diffuser outlets is one way of arranging the diffuser outlets. There are other possible ways of diffuser outlet arrangement for varying the number of diffuser outlets, distance between diffuser outlets and their lengths, and lengths of flexible tubes.  
         [0063]    If there are additional helicopters fighting the fire from both ends of the length of burning objects, using the invented systems the same fire can be paralyzed in a shorter time.  
         [0064]    The invention has been described with reference to preferred embodiments. Those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications are intended to be within the scope of the claims.