Abstract:
Water is mixed with fire suppressant polymer in a mixer absent a power source. The mixer receives water through a water inlet with water exhibiting high velocity and associated hydrodynamic force. Such velocity is achieved by locating the water inlet connected to a float or other part of an aircraft so that when the aircraft flies over water with the float dipping into the water, water is driven through the opening and into the water inlet of the mixer. A polymer inlet passes into the mixer. A bend is located downstream of the water inlet and the polymer inlet. The bend exhibits sufficient resistance to fluid flow direction therethrough that the polymer is sheared and thoroughly mixed and activated with the water. A colorant inlet is optionally provided within the mixer and the water and polymer mixture is then discharged into a tank for later utilization at a firefighting location.

Description:
FIELD OF THE INVENTION 
     The following invention relates to mixers for polymer based wildland fire chemicals to cause the polymer to be adequately mixed and activated to maximize fire chemical effectiveness. More particularly, this invention relates to a water and polymer mixer which does not require a pump, but which is powered by hydrodynamic forces present within the water, such as when high velocity water flow through a fluid pathway is provided by directly accessing a body of water through a pickup on an airplane skimming over a surface of the body of water. 
     BACKGROUND OF THE INVENTION 
     When combatting wildfire from the air, various tools can be utilized. One common tool is to load an appropriately configured aircraft with wildland fire chemicals, fly the aircraft over the fire or an area adjacent the fire to be protected, and discharge the fire chemical from the aircraft. While such fire chemicals are quite effective in suppressing wildfire, the aircraft must travel to a reloading base and return to the location of the wildfire before additional loads can be dropped, decreasing the effectiveness of such aircraft proportional to the distance the reloading base is from the fire and the time such reloading takes. 
     In many instances bodies of water are available in the area where the wildfire is occurring. Helicopters can be utilized with buckets suspended therefrom which can be loaded with water and then flown to the site of the wildfire and released. Water is not as effective as fire retardants or suppressants in combatting wildfire. Also, helicopters have a lesser payload capacity than airplanes. 
     It is also known to utilize airplanes for dropping water onto wildfires. Such airplanes are configured to skim over a body of water to load tanks therein with water. Such airplanes then fly to the site of the fire where the water can be released. 
     Water&#39;s effectiveness as a fire suppressant can be significantly enhanced by adding a suppressant polymer to the water. One such polymer material is provided under the trademark FIREWALL II, provided by MGG, LLC of Carmichael, Calif. One unique characteristic of such polymer material is that merely adding the polymer material to water does not provide the full benefit of fire suppressant capacity to the water. Rather, the polymer must be thoroughly mixed with the water. Shearing forces associated with such thorough mixing cause the water to have the polymer fully activated and dispersed therein, so that the fire suppressant effect of the water can be maximized. A pump is typically used which provides the required shearing/mixing force to activate the polymer. 
     While it would be desirable to add polymer to water in a fire fighting aircraft, complexities associated with the required mixing to impart the highest fire suppressant effect on the water polymer mixture, requires appropriate polymer mixing equipment. Such equipment requires a relatively large amount of power and has significant weight. When a firefighting aircraft is being outfitted for firefighting, it is desirable that as much of the available payload capacity of the aircraft be utilized for carrying water and polymer, as possible. Known pumping equipment burdens the aircraft with extra weight thus minimizing effectiveness. Accordingly, a need exists for a method to mix polymer with water without requiring a powered mixer or pump. 
     SUMMARY OF THE INVENTION 
     With this invention a mixer is provided which does not require a separate power source or a pump, making such a mixer readily deployable on a firefighting aircraft. Such an aircraft would have tanks for temporary storage of water and polymer mixed therein as well as polymer supply tanks and preferably colorant supply tanks. A mixer according to this invention is provided downstream of a water inlet and a polymer inlet, with the mixer configured to mix the polymer and water before the mixed polymer and water enters the tank where it can later be dropped in firefighting. 
     The water inlet is to be deployed from a float (or other part of the aircraft) of an aircraft. This opening is configured on the float such that when the aircraft is flying over water with the float touching the water, water is caused to be rapidly drawn into the opening at exceptionally high velocity. The mixer is configured so that this high velocity water follows an abruptly turning pathway downstream of the polymer inlet. This abruptly turning pathway causes the polymer to exhibit shear when in contact with the water which causes the polymer to be fully activated and dispersed within the water to maximize the fire suppressant effect of the water and polymer mixture. 
     In a preferred embodiment this bending fluid pathway is fitted with a pair of elbows downstream of the water inlet and the polymer inlet. These elbows are preferably 90° elbows oriented in distinct directions. Water passing through these elbows is thus caused to turn in a first direction and then turn in a second direction while being forced through the elbows at high velocity. The diameter of the fluid pathway, the sharpness of the curving of the elbows, the orientation of the elbows relative to each other and the velocity of the water are selected so that the polymer in the water exhibits sufficient shear to be effectively dispersed and activated within the water after passing through these elbows. The water and polymer mixture can then be passed into a tank for storage until ready to be dropped from doors in the bottom of the tank. 
     OBJECTS OF THE INVENTION 
     Accordingly, a primary object of the present invention is to provide an apparatus for mixing polymer fire chemicals with water through hydrodynamic forces alone, and without requiring a separate mixer or pump. 
     Another object of the present invention is to provide a method for mixing water and fire chemicals together without requiring the weight and energy demands of a pump or dynamic mixer machine. 
     Another object of the present invention is to provide a polymer based fire chemical and water mixer interposable along a fluid pathway between a water inlet and a tank for water mixture, the mixer powered solely by hydrodynamic forces within the water. 
     Another object of the present invention is to provide a fire fighting aircraft configured to carry fire chemicals and gather water directly from a body of water, and mixing stored chemicals with water taken up from the body of water before storing a mixture of water and chemicals within a tank of the aircraft which can later be dropped at a fire fighting location. 
     Other further objects of the present invention will become apparent from a careful reading of the included drawing figures, the claims and detailed description of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front elevation partial schematic view of a fire fighting aircraft with a chemical tank, colorant tank and chemical mixer configured to add and mix chemicals with water before the water enters a tank of the fire fighting aircraft, according to this invention. 
         FIG. 2  is a perspective view of a chemical and water mixer according to a preferred embodiment of this invention. 
         FIG. 3  is a side elevation view of that which is shown in  FIG. 2 . 
         FIG. 4  is a perspective view of an alternative single elbow mixer according to an alternative embodiment of this invention. 
         FIG. 5  is a side elevation view of that which is shown in  FIG. 4 . 
         FIG. 6  is a perspective view of a non-planar chemical and water mixer providing an alternative embodiment of that which is shown in  FIG. 2 . 
         FIG. 7  is a side elevation view of that which is shown in  FIG. 6 . 
         FIG. 8  is a perspective view of a concentric polymer and water mixer with portions of the mixer shown in broken lines and portions of the mixer shown in solid lines. 
         FIG. 9  is a top plan view of that which is shown in  FIG. 8  with interior portions thereof shown in broken lines and exterior portions thereof shown in solid lines. 
         FIG. 10  is a side full sectional view of that which is shown in  FIG. 9  revealing interior details of the concentric mixer of this alternative embodiment. 
         FIG. 11  is a perspective view similar to that which is shown in  FIG. 8  except that exterior structures are shown in solid lines and interior structures are shown in broken lines. 
         FIG. 12  is a perspective view of a tandem mixer according to a further alternative embodiment of this invention with interior structures shown in solid lines and exterior structures shown in broken lines. 
         FIG. 13  is a top plan view of that which is shown in  FIG. 12  and with interior structures shown in broken lines. 
         FIG. 14  is a side full sectional view of that which is shown in  FIG. 12 , taken along line  14 - 14  of  FIG. 13  and revealing interior details of this tandem mixer. 
         FIG. 15  is a perspective view of that which is shown in  FIG. 12  with exterior details shown in solid lines and interior details shown in broken lines. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, wherein like reference numerals represent like parts throughout the various drawing figures, reference numeral  10  ( FIGS. 1-3 ) is directed to a mixer for mixing fire chemical polymer P with water W. The mixer  10  does not require a power source, but rather is powered by hydrodynamic forces existing within the flow of water W through a water inlet  20  into the mixer  10 . These hydrodynamic forces are sufficient, when driving the water W through the mixer  10  as configured according to this invention, to thoroughly mix and activate the polymer P so that the water and polymer mixture M is ready for maximum effectiveness in use at a firefighting location. 
     The mixer  10  is configured to reside upon an aircraft A ( FIG. 1 ) with floats F configured to route water W directly from a body of water over which the aircraft A is skimming, through the water inlet  20  and into the mixer  10 . Thus, motion of the aircraft A over the body of water provides the source of hydrodynamic forces which powers the mixer  10 . The aircraft A also includes a tank T for storage of the water and polymer mixture M and doors D for dropping the water and polymer mixture M when the aircraft A has traveled to a firefighting location. Water W enters the float F along arrow B ( FIG. 1 ) and water and polymer mixture M is dropped from doors D along arrow E. 
     While a single mixer  10  is depicted with a single float F active in directing water into the mixer  10  and onto the tank T, the aircraft A typically has two floats F and each float F can be fitted with its own pickup to receive water W thereinto, coupled to separate mixers  10  (or a common mixer  10 ) and then directed to a common tank T (or potentially separate tanks). The mixer  10  is preferably located along a line for the water W between the pickup in the float F and the tank T. As an alternative, the mixer  10  can be located within the tank T itself as depicted in broken lines by mixer  10 ′ ( FIG. 1 ). 
     In essence, and with particular reference to  FIGS. 1-3 , basic details of the mixer  10  are described. The mixer  10  includes a water inlet  20  located downstream from a source of water fed by a pickup on a float F of the aircraft A. The mixer  10  also includes a polymer inlet  30  leading from a polymer tank  34  or other source of polymer P. The water inlet  20  and polymer inlet  30  are each located upstream of a bend  40 . This bend  40  includes at least one elbow and preferably includes a first elbow  42  and a second elbow  44 . The water W passes with sufficient hydrodynamic forces through the elbows  42 ,  44  that polymer P added to the water W upstream of the bend  40  is thoroughly mixed and activated by the shearing forces encountered as the water passes through the elbows  42 ,  44  of the bend  40 . A colorant inlet  50  is preferably provided downstream of the bend  40  which is fed by colorant C from a source of colorant, such as a colorant tank  54 . Finally, a mixture M of water W and polymer P is discharged from an outlet  60  of the mixer  10  which then leads to the tank T. 
     More specifically, and with continuing reference to  FIGS. 2 and 3 , specific details of the mixer  10  are described, according to a first embodiment. In this first embodiment the mixer  10  is in the form of a fluid pathway defined by circular cross-section tubular members. The water inlet  20  is preferably a section of straight cylindrical pipe. Similarly, the outlet  60  is preferably formed of a similarly sized and shaped circular cross-section pipe. The water inlet  20  feeds into the open end of this cylindrical pipe providing the water inlet  20 . The polymer inlet  30  is preferably located in the cylindrical side wall of this inlet pipe forming the water inlet  20 . Water W passes through the water inlet  20  and polymer P passes through the polymer inlet  30 . The polymer inlet  30  is preferably fitted with a line which leads to a polymer tank  34 . This polymer tank  34  is most preferably located within one of the floats F of the aircraft A ( FIG. 1 ) but could be located at other locations on the aircraft A. 
     The polymer  30  can be metered into the mixer  10  in a variety of different ways. In a simplest embodiment, an orifice is merely provided which allows the “Venturi Effect” to suck polymer into the mixer  10  to join with water W entering through the water inlet  20 . A check valve can also be provided which is normally closed but which readily opens when the low pressure associated with the high velocity water W passing through the water inlet  20  is experienced adjacent the polymer inlet  30 . Generally, the faster the flow rate of the water W the higher the rate at which polymer P is passed through the polymer inlet  30 , so that a desired ratio of polymer P to water W can be achieved by merely selecting orifice sizes at the polymer inlet  30 . 
     Alternatively, a dosing system can be provided which controls flow of polymer P through the polymer inlet  30 . Such a dosing system could be automated, such as with sensors to measure water W flow rates and control polymer P flow rates through the polymer inlet  30  to match. Alternatively, such a dosing system could be at least partially manual, such as with an operator utilizing a switch or other manually operable control element to cause polymer P to be injected when desired and at a desired flow rate. Such a switch could also alternatively be opened by some passive actuator, such as a switch on the float F which opens when the float F is impacting a body of water, and which is otherwise closed. Multiple valves can be provided of different types depending on the design particulars of the particular system being implemented. If desired, a plurality of polymer inlets  30  can be provided to strategically place the polymer P where desired within the flow path of the water W. 
     The bend  40  preferably includes the first elbow  42  and second elbow  44  having circular cross-sections and diameters similar to that of the pipe forming the water inlet  20  and water and polymer outlet  60 . These elbows  42 ,  44  are oriented in this embodiment within a common plane, but with orientations opposite each other so that the water W and polymer P must first turn in a first direction and then turn in a second direction opposite the first direction. For instance, if the first elbow  42  causes the fluid flow through the fluid pathway of the mixer  10  to turn upward from horizontal, the second elbow  44  causes the fluid flow to be diverted from upward back to horizontal. If the first elbow  42  causes the fluid flow to be diverted to the left, the second elbow  44  causes the fluid flow to be diverted to the right. 
     The elbows  42 ,  44  are preferably each 90° elbows. As an alternative, the elbows  42 ,  44  could have a lesser or greater degree of bend. The elbows  42 ,  44  are shown in this embodiment as directly adjacent each other. However, the elbows  42 ,  44  could be spaced by a straight cylindrical section therebetween having various different lengths. 
     The bend  40  benefits from maintaining a circular cross-section fluid pathway entirely therethrough. In this way, any debris which might be drawn through the water inlet  20  into the mixer  10  has a relatively high propensity to pass cleanly through the mixer  10 . If any such debris should become trapped within the bend  40 , such debris would relatively easily be removable, such as by disassembly of portions of the fluid pathway upstream of the water inlet  20 , grasping hold of any such debris and removing it in a direction opposite the direction with which the debris entered the bend  40  portion of the mixer  10 . 
     The colorant inlet  50  is preferably located in the cylindrical outlet  60  downstream of the bends  40 . Colorant C is entered into this colorant inlet  50 . The colorant C is routed to the colorant inlet  50  from a colorant tank  54 . As with the polymer inlet  30 , a simplest embodiment could merely have the colorant inlet  50  flow rate controlled by a Venturi orifice which is activated by the flow rate of fluids passing the colorant inlet  50 . A check valve can also be supplied to keep the colorant inlet  50  closed until such fluid motion through the fluid pathway and passed the colorant inlet  50  is experienced. As an alternative, some form of dosing system or other control could be provided for the colorant inlet  50  which could have any of a variety of configurations generally matching the various options available for the polymer inlet  30 , described in detail above. 
     The colorant tank  54  could be located anywhere upon the aircraft A, and is shown in an exemplary embodiment within a fuselage of the aircraft A ( FIG. 1 ). The colorant C does not affect the fire suppressant capability of the water and polymer mixture M, but does allow fire fighting personnel to more readily view which areas have already been treated with the water and polymer mixture M to most effectively distribute the water and polymer mixture M at a firefighting location. 
     The mixer  10  and polymer activation method of this invention are further exemplified by alternative embodiments disclosed herein, and particularly in  FIGS. 4-15 . With reference to  FIGS. 4 and 5 , details of a single elbow mixer  110  are described. The single elbow mixer  110  is similar to the mixer  10  of the preferred embodiment except that the bend  140  is fed by only a single elbow  142 . A water inlet  120  allows water W to be drawn into the mixer  110 . A polymer inlet  130  is provided to feed polymer P into the fluid pathway along with the water W. The single elbow  142  is then encountered along the fluid pathway downstream of the polymer inlet  130  and water inlet  120 . 
     A colorant inlet  150  is preferably provided downstream of the bend  140  through which colorant C can be introduced. A water and polymer mixture M then exits through an outlet  160 . The elbow  142  in this single elbow mixer  110  embodiment is shown as a 90° elbow. This elbow  142  could have other degrees of bend, such as greater or less than 90° if desired. 
     Mixers which exhibit a bend with at least two elbows are considered to more efficiently mix and activate the polymer P with the water W. However, when sufficiently high hydrodynamic forces are encountered, and with particular polymers P which may require less elevated shear forces for thorough mixing and activation with the water W, such a single elbow mixer  110  is considered as a potentially feasible alternative embodiment for the mixer  10  and polymer mixing method of this invention. 
     With particular reference to  FIGS. 6 and 7 , details of a non-planar mixer  210  are described. The non-planar mixer  210  is similar to the mixer  10  of the preferred embodiment except that the first elbow  242  and second elbow  244  are not entirely planar in the orientation of fluid flow therethrough, but rather cause fluid flow to occur along lines which are non-planar to each other. In particular, a water inlet  220  and polymer inlet  230  feed water W and polymer P into the mixer  210  in a manner similar to that of the mixer  10  described in detail above. The first elbow  242  of the bend  240  bends the fluid pathway in a first direction and within a first plane. The second elbow  244  is downstream of the first elbow  242  and also causes the flow through the fluid pathway to bend within a second plane. This direction of bending of the second elbow  244  is oriented to cause the fluid to be diverted out of the first plane in which the fluid had resided when passing through the water inlet  220 , past the polymer inlet  230 , and through the first elbow  242 . In one embodiment, where the first elbow  242  and second elbow  244  are each 90° elbows, the elbows  242  and  244  are oriented so that fluid flow downstream of the second elbow  244  is along a line and in the second plane oriented perpendicular to a line and first plane of the fluid flow before entering the bends  240 . 
     The water and polymer mixture M then continues out of the outlet  260  past a colorant inlet  250  for introduction of colorant C. It is not necessary that the planes in which the fluids enter and exit the non-planar mixer  210  be perpendicular to each other, but rather such planes can be skewed relative to each other in non-perpendicular and non-parallel relative orientations. While the elbows  242 ,  244  are shown directly adjacent each other, some cylindrical section could be interposed therebetween. 
     With particular reference to  FIGS. 8-11 , details of a concentric mixer  310  alternative embodiment are described. The concentric mixer  310  includes an inlet section  320  which includes an inner tube  322  inside of an outer tube  324 , with the inner tube  322  supported in its position within the outer tube  324  by standoffs  326 . Preferably these tubes  322 ,  324  are concentric such that an annular fluid flow path is provided within the outer tube  324  and outside of the inner tube  322 . A central circular cross-section flow pathway is also provided within the inner tube  322 . 
     A polymer inlet  330  is provided which passes through the wall of the outer tube  324  and wall of the inner tube  322 , so that polymer P is introduced into fluid flow within the inner tube  322 . A short tube  332  allows the polymer inlet  330  to so pass through the annular outer flow pathway of the inlet section  320 . Preferably, the standoffs  326  are provided as a set of three and work together along with the short tube  332  of the polymer inlet  330  to hold the inner tube  322  securely in place. 
     A bend  340  is provided downstream of the inner tube  322 . This bend  340  in this embodiment is shown with a first elbow  342  followed by a second elbow  344 , followed by a third elbow  346  followed by a fourth elbow  348 . The first and fourth elbows  342 ,  348  are preferably 45° bend elbows. The second and third elbows  344 ,  346  are preferably 90° bend elbows. Each elbow  342 ,  344 ,  346 ,  348  is preferably oriented with alternating orientations so that fluid flow through the bend  340  is serpentine in nature. 
     The bend  340  resides within a mixing section  352  defined by an outer cylindrical wall  354  with an annular region  356  surrounding the bend  340 . Flat end walls  355  define ends of this mixing section  352 . A colorant inlet  350  is preferably oriented in a downstream one of these flat end walls  355 . Some of the water W remains in the annular flow pathway and avoids the bend  340 , passing instead directly into the mixing section  352  and taking up the colorant C therein before joining with the polymer and water mixture M which has been mixed within the bend  340 . This embodiment is particularly advantageous where it is desirable for the colorant C to mix with the water W before the water W has encountered the polymer P. An outlet section  360  joins the two flow sections together before exiting of the water and polymer mixer M out of the outlet section  360 . 
     With particular reference to  FIGS. 12-15  details of a tandem mixer  410  are described according to an alternative embodiment. With the tandem mixer  410 , an inlet section  420  is provided similar to the water inlet  20  section of the mixer  10  of the preferred embodiment described above. This inlet section  420  leads to a manifold  432 . The manifold has the polymer inlet  430  passing thereinto. The manifold  432  feeds a left inlet  434  and a right inlet  436  which are oriented adjacent to each other. The left inlet  434  leads to a left bend  440 . The right inlet  436  leads to a right bend  445 . The left bend  440  includes a first elbow  442  and a second elbow  444 . The right bend  445  includes a first elbow  446  and a second elbow  448 . 
     These bends  440 ,  445  are preferably similar in size and shape and oriented directly adjacent each other. The polymer inlet  430  is preferably oriented precisely between the two bends  440 ,  445  so that some of the polymer P is routed with the water W into each of the bends  440 ,  445 . These elbows  442 ,  444 ,  446 ,  448  of the bends  440 ,  445  are preferably oriented similarly to the elbows  42 ,  44  of the bend  40  in the mixer  10  of the preferred embodiment described above. 
     These bends  440 ,  445  are preferably located within a mixing section  452  into which the colorant inlet  450  is directed, such as on an outer flat wall  455  of the mixing section  452 . An outlet section  460  is located downstream of this mixing section  452  for discharge of the mixture M of water and polymer along with colorant C out of the mixer  410 . The outlet section  460  is preferably out of line with the second elbow  444  of the left bend  440  and the second elbow  448  of the right bend  445 , so that further diversion of the fluid pathway occurs for further mixing of the polymer P with the water W and mixing with the colorant C before discharge of the mixture M out of the outlet section  460 . 
     This disclosure is provided to reveal a preferred embodiment of the invention and a best mode for practicing the invention. Having thus described the invention in this way, it should be apparent that various different modifications can be made to the preferred embodiment without departing from the scope and spirit of this invention disclosure. For instance, various different sections of the mixer  10 , while shown with a circular cross-section, could have other cross-sectional geometries. The various elements could be directly adjacent each other or spaced apart by intermediate structures and could be fastened together by adhesive bonding, welding, use of mechanical fasteners, or through other fastening methodologies. When structures are identified as a means to perform a function, the identification is intended to include all structures which can perform the function specified. When structures of this invention are identified as being coupled together, such language should be interpreted broadly to include the structures being coupled directly together or coupled together through intervening structures. Such coupling could be permanent or temporary and either in a rigid fashion or in a fashion which allows pivoting, sliding or other relative motion while still providing some form of attachment, unless specifically restricted.