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.