Abstract:
A foam generating device includes a source of compressed gas and a source of liquid adapted to produce a foam. A gas operated pump such as a diaphragm pump is provides which has a gas inlet communicating with the compressed gas source to drive the pump, a gas exhaust, a liquid inlet and liquid discharge to discharge said liquid from the pump. An injector disposed at the discharge side of the pump and is in communication with the gas outlet of the pump to inject exhaust gas into the liquid discharged by the pump to aerate the liquid and produce a foam. The device may be portable, vehicle mounted or stationary. The liquid may be water with an injector to inject a foaming agent into the water.

Description:
FIELD OF THE INVENTION 
     The present invention relates to devices for generating a foam product such as for fire suppression and retardation, dust control or the like. 
     BACKGROUND 
     Various fire-fighting agents have been used to fight fires. One of the more effective types of fire-fighting agents is water-based foam. This foam is composed of water and a surfactant (comprising a foam solution) and air or gas to expand the volume of the foam solution, converting the liquid solution into various consistencies of foam. Various means are utilized to aerate the foam solution. Ambient air may be aspirated into the solution at the nozzle end of a hose by an air-aspirating nozzle. This results in expansion ratios of approximately 3:1 to 5:1 over the original volume of the un-aspirated foam solution. A superior method of expanding the volume of the foam solution is to introduce compressed air into the solution prior to the solution reaching the nozzle at the end of the hose. This method usually results in expansion ratios of 10:1 to 100:1 or greater. Different expansion ratios result in different consistencies of foam, each of which is best suited to different fire-fighting environments. In addition, foam generated by compressed air foam systems is higher quality foam, with bubbles of a more uniform size, that allows the foam to last much longer. This is a substantial advantage in certain applications. For these and other reasons, foams with expansion ratios of 10:1 or greater are generally more efficient at smothering and controlling fires than foams with less than a 10:1 expansion ratio. 
     Heretofore, generation of compressed air foam has generally been dependent upon large, heavy, highly complicated systems composed of a water pump, an air compressor, a foam concentrate proportioner and a plethora of pipes, hoses, valves and regulatory devices. The expense of these systems has generally limited their acceptance and use to only those fire departments with large budgets and many highly trained personnel. 
     A portable foam generation system is disclosed in U.S. Pat. No. 5,623,995 issued Apr. 29, 1997 to Smagac. According to this disclosure, the liquid foaming solution is pumped by a gas operated pump driven by gas from a compressed gas cylinder. Compressed gas, e.g. nitrogen, from the cylinder is also injected proximate a stata tube at the discharge of the pump. 
     A drawback of portable foam generating systems of the type described above is that the compressed gas used to drive the pump is simply exhausted from the pump exhaust. Thus the compressed gas supply must separately supply both the pump and be injected into the liquid. It would be desirable to provide a system which would be efficient in the use of the compressed gas so that more foam could be delivered from a given quantity of compressed gas. 
     Still further, the stata tube described in the above patent is of a complicated construction. It would be useful to provide a device which provides for agitation and is of a simpler construction. 
     It is one object of the present invention to substantially simplify the process of generating foam which results in a compressed air foam generating system that is lighter, smaller, more reliable, self contained, requires less maintenance, and is less expensive and easier to operate than those that are currently available. 
     It is another object of the present invention to provide a foam generating device which can be produced cost-effectively in sizes that are much smaller than those currently manufactured. For that reason the subject invention will more effectively address the fire-fighting needs of smaller volunteer fire departments, industrial applications, rural and urban homeowners, vehicle owners and operators and many other applications that have not been able to afford the cost of acquisition, maintenance, or specially trained personnel that current compressed air foam systems demand. 
     It is another object of the present invention to reliability produce foam or other aerated product for use in fire suppression or application of a foam flame retardant or for purposes such as dust control, toxic waste clean-up, or the like. 
     Another purpose is to enable such fire or non-fire-related systems to be scalable in size so that applications that require smaller systems can be addressed. An additional purpose is to enable the use of compressed gasses other than air for the purpose of expanding the volume of foam or other solutions. 
     SUMMARY OF THE INVENTION 
     There is, therefore, set forth according to the present invention a foam generating device which addresses the above objects, among others, and which overcomes the drawbacks of prior systems. 
     Toward this end, the device includes a source of compressed gas such as, for example, a cylinder containing compressed air. A source of liquid adapted to produce a foam is also provided. The source may be a tank of liquid, expandable, foam solution, water such as the water in a swimming pool, spa or portable tank. A gas operated pump has a gas inlet communicating with the compressed gas which expands to drive the pump, a gas exhaust for the expanded gas, a liquid inlet and a liquid discharge to discharge the liquid at a positive pressure from the pump. Where water is the pumped liquid, the device includes a foaming additive and mixer to introduce the foaming additive at the pump discharge. To aerate the pumped solution for the production of, or to assist the production of foam, an injector is disposed at the discharge side of the pump. The injector in communication with the gas outlet of the pump to inject the exhausted gas into the liquid discharged by the pump. The aerated foam is thereafter delivered by piping, hose, nozzles, sprayers or the like to the area to be foamed. 
     To contribute to the production of foam and/or a consistent foam product, an agitator may be provided proximate the injector to further mix the aerated solution for the production of foam. The agitator may be embodied as a screen in the discharge line for the pump. 
     The device may be fixed, vehicle mounted or may be included as a backpack unit with the user carrying the compressed gas cylinder and a water bag or tank containing the foaming solution. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     These and other features and advantages will become better understood with reference to the description, claims and drawings wherein: 
     FIG. 1 illustrates one embodiment of the present invention at a fixed location; 
     FIG. 2 illustrates another embodiment of the present invention adapted to be disposed on a vehicle; 
     FIG. 3 illustrates and embodiment adapted to be carried as a backpack; 
     FIG. 4 is a side view of illustrates the mixer for mixing air and generating foam; 
     FIG. 5 is a front view of a screen for the mixer; and 
     FIG. 6 is a front view of a clamp for the mixer of FIG.  4 . 
    
    
     DESCRIPTION 
     Turning to the drawings, FIG. 1 shows one embodiment of the device  10  adapted for generating foam according to the present invention. The device  10  as illustrated is adapted for fixed applications such as out buildings, rural residences and the like. 
     The device  10  includes a source of compressed gas embodied as compressed air cylinders  12   a-d  each coupled to a gas header  14  through valves  16 . The header  14  conducts the compressed gas from the cylinders  12   a-d , or any one or several of them, to a gas operated pump  18 , which may be a diaphragm-type pump as is known in the art. The compressed gas operates one or more diaphragms within the pump  18  for pumping of liquid thereby. The compressed gas exhausted by the pump  18  is exhausted at an exhaust  20 . 
     The pump  18  has a suction  22  in communication with a liquid source which may be a body of water such as a swimming pool  24 , spa, pond, water tank or the like. Accordingly, as shown in FIG. 1, a suction pipe  26  extends from the pool  24  to the suction  22  of the pump  18 . While the suction pipe  26  is shown as a dip tube into the pool  24 , it is to be understood that the suction pipe  26  could be connected to the pool circulation system to reduce the negative head on the pump  18 . The pump  18  also includes a discharge  28  at which the liquid as pumped under pressure by the pump  18  is conducted for purposes of which will hereinafter become evident. Connected to the discharge  28 ) is a discharge line  30 . 
     To mix a foam generating substance such as a class A foam concentrate as is known in the art, the device  10  includes a proportioner  32  which is connected through a conduit  34  to a tank or bottle  36  containing the foam generating concentrate. The proportioner  32 , as is known in the art, includes pistons operated by the discharge pressure in the discharge line  30  to pump the foam generating concentrate from the bottle  36  and admit it into the discharge line  30  for mixing therewith. The proportioner  32  can be set and regulated to admit the desired concentration of the foam generating concentrate from the bottle  36 . 
     To mix the water from the pool  24  and a foam generating concentrate admitted at the proportioner  32 , the device  10  includes a mixer  38  disposed in the discharge line  30 . The mixer  38  is shown in FIGS. 4-6. The mixer  38  is adapted to agitate the liquid-foam mixer as well as to inject compressed air into the mixture for the generation of a consistent and well-defined foam product for firefighting, toxic cleanup, dust control and the like. For toxic cleanup, the foam concentrate can be a fluid of the type and quantity compatible with the desired use. 
     The mixer  38  has a tubular body  40  having at each end a flange  42  along the length of the body  40  a tubular T-connection  44  is provided through which air is admitted into the mixer  38  as hereinafter described. The liquid from the pump  18  is conducted through body  40  and along the discharge line  30 . Connected at each end of the body  42  is the discharge line  30  and accordingly, the discharge line includes flanges  46  which meet with and adapted to abut the flanges  42  of the body  40 . Disposed between the flanges  42 , 46  is an agitator  48  embodied as a screen mounted in a rubberized gasket  50 . The gasket  50  includes a circumferential lip  52  adapted to seal against the flanges  46 , 42 . While only one agitator  48  is shown in FIG. 4, it is to be understood that at the other end of the body  40  would be another agitator  48  of a like design. 
     To couple the body  40  of the mixer  38  into the discharge line  30 , flange clips  54  of the type shown in FIGS. 4 and 6 are provided. The flange clips  54  are of known design and each include semi-cylindrical halves  56   a,b  joined at a pivot  58  for opening and closing the halves  56   a,b  about an axis A to release the connection between the flanges  46 , 42 . Each of the clips  54  has a circumferential channel to retain the flanges  46 , 42  in an abutting and sealing relationship trapping the agitator  48  there between. Opposite the pivot  58 , each clip includes upstanding clasp portions  60 , one of which pivotally mounts a threaded fastener  62 . In operation, the agitator  48  is disposed between the flanges  42 , 46  and the clip  54  is placed thereabout retaining the flanges  42 , 46  in the channel therein. The fastener  62  is pivoted from its phantom position shown in FIG. 6 through a slot contained in the opposite clasp  60 . The fastener  62  is threaded along a threaded shank  64  to draw the clasps  60  together and thereby secure the body  40  to the discharge line  30 . 
     To admit air into the mixer  38 , the T-connection  44  may contain a like clip  54  (not shown) mounting a nipple (not shown) to the mixer  38 . 
     Returning to FIG. 1, air from the pump exhaust  20  is conducted by a conduit  65  to the mixer  38 . The fluid, pumped by the pump  18  through the proportioner  32  and mixer  38  is agitated by the agitators  48  and the air exhausted from the pump  18  is injected into the liquid to produce a foam in the discharge line  30 . 
     To direct the foam generated by the device  10 , the discharge line  30  is connected to a hose  68 , a length of which may be wrapped about a hose reel  70 . The hose  68  includes at one end a nozzle  72  and a manually operated on off valve  74  to turn the supply of foam to the nozzle  72  on and off. 
     In operation, the user would close the valve  74  and turn on the gas valve  16  at the cylinders  12   a-d . Compressed gas operates the pump  18  to pump water through the suction pipe  26  from the pool  24  into the discharge line  30 . When the valve  74  is opened and the nozzle  72  is directed to the desired area, the fluid passes through the proportioner  32  where a foam generating concentrate (or other desired chemical) is mixed into the water in the discharge line  30 . At the mixer  38  the liquid/concentrate mixture is agitated by the agitator  48  and the air from the pump exhaust  20  is injected to produce a foam in the discharge line and hose which is directed from the nozzle  72  onto the desired area. As can be appreciated, by using the exhaust air from the pump  18 , the compressed air of the cylinders  12   a-d  is efficiently used to first drive the pump  18  and thereafter to become injected into the liquid to produce a foam product. The injection of the air and the use of the agitators  48  has been found to produce a consistent, foam product usefully in fighting fires or applying fire retardants. 
     Turning to FIG. 2, an embodiment of the device  10  adapted to be mounted to a vehicle such as a pickup truck, utility truck, van or the like is shown. According to the embodiment, the device  10  includes a cylinder  12 ′ connected through a valve  16  and line  76  to the pump  18 . The pump  18  has its suction pipe  26  connected to a tank  78  containing a premixed liquid product for generating foam. The discharge  28  of the pump  18  passes through the mixer  38  where the liquid foam product is agitated and has air injected therein through a line  65 . The discharge line  30  is connected to a hose  68  having at one end a nozzle  72  and valve  74 . According to this embodiment of the device, the proportioner of the previous embodiment is not required in that the liquid is a premixed product adapted for generating foam. 
     Turning to FIG. 3, there is shown a further embodiment of the device  10  according the present invention adapted to be carried as a backpack adapted to be carried by an individual for fighting brush fires, applying toxic cleanup materials and the like. The device  10  of FIG. 3 includes a mounting platform  80  which would include shoulder straps (not shown) or the like for carrying by the firefighter. Mounted to the platform  80  is the cylinder  12 ′ containing compressed gas, pump  18  and the header  14  extending from valve  16  for operating the pump  18 . The discharge line  30  of the pump  18  passes through a mixer  38  and is connected to a hose  68  having at its end a nozzle  72  and valve  74 . Air discharged from the exhaust  20  of the pump  18  is directed to the mixer  38  by line  65  for injection into the premixed foam generating solution. To provide a supply of foam generating solution, the device  10  includes a refillable bag  82  having an outlet  84  adapted to be coupled to the suction pipe  26  for the pump  18 . Thus the firefighter would manually turn on the valve  16 , shown as an angle valve in FIG. 3, to operate the device  10 . The bag  82  would be filled with foam generating solution which would be pumped by the pump  18  agitated and mixed with air at the mixer  38  to produce foam to be sprayed through the nozzle  72 . When the bag  82  is empty, it would be refilled with foam generating concentrate. 
     In lieu of the bag  82 , a tank or bladder may be carried by the firefighter. 
     The device  10 , as described above, can be adjusted to produce different characteristics of foam based upon the concentrates used, the amount of air injected into the foam and the agitation provided by the agitators  48  such as by increasing or reducing the mesh of the screen. 
     The foam generating device  10  is adapted to produce a foam product which has greater firefighting and flame retardant properties than does water. Furthermore, the surfactants of the foam provides for wetting of a greater area with a smaller quantity of liquid pumped, and retains the surface of the material or area treated wet for a longer period of time. Further, by expanding the liquid product and generating foam, a smaller quantity of liquid can be used to generate a large quantity of foam for firefighting, toxic waste cleanup, dust control or the like. 
     While we have shown certain embodiments of the present invention, it is to be understood that it is subject to many modifications and changes without departing from the spirit and scope of the appended claims.