referring more specifically to the drawings , for illustrative purposes the present invention is embodied in the apparatus generally shown in fig1 through fig3 . it will be appreciated that the apparatus may vary as to configuration and as to details of the parts without departing from the basic concepts as disclosed herein . referring first to fig1 and fig2 the present invention a cold compressed air foam fire suppression apparatus 10 in accordance with the present invention is generally shown . as will be seen , the apparatus 10 comprises a foam expansion manifold 12 , an on / off charge valve 14 , a solution tank 16 , a pressure - regulated air supply system 18 , a pair of check valves 20a and 20b , associated tubing 22a and 22b , a discharge hose 24 and a frame assembly 26 . air supply system 18 provides a source of regulated compressed air preferably at a discharge pressure of approximately 155 psi to solution tank 16 and foam expansion manifold 12 . the regulated compressed air enters solution tank 16 , pressurizes a solution contained therein , and sends the solution to foam expansion manifold 12 . the regulated air also enters foam expansion manifold 12 where it mixes with the pressurized solution coming from solution tank 16 . check valves 20a and 20b within air supply system 18 prevent any solution from foam expansion manifold 12 from backing - up and entering air supply system 18 . this mixture of air and solution causes a desired foam to form and expand and accelerate out foam expansion manifold 12 . the foam exits the system 10 through foam expansion manifold 12 and is controlled by charge valve 14 located on discharge hose 24 . all the components of fire suppression system 10 are mounted on a metal frame assembly 26 . frame assembly 26 is preferably fabricated from rigid , lightweight 11 / 4 inch square metal tubing or the like . solution tank 16 is mounted between a pair of frame rails 28a and 28b , and air supply system 18 is affixed above solution tank 16 in a parallel orientation relative to solution tank 16 . a hitch 30 is mounted on the frame along with front castors 32a and 32b and rear castors 33a and 33b ( not shown ). all the plumbing components within the system are of hydraulic - quality parts or the like . solution tank 16 stores a mixture of chemical and water which , when combined with high pressure air , forms a fire suppressing foam . the chemical used can be aqueous film forming foam , clean agent foam , common dish soap or like environmentally safe chemical . on the top of solution tank 16 is a water / chemical fill port 34 that that has a hose adapter to allow filling solution tank 16 with water . water / chemical fill port 34 also allows chemicals to be added to solution tank 16 . the chemical is typically added to solution tank 16 first , followed by adding water to solution tank 16 . when water is added to solution tank 16 and begins mixing with the chemical , a solution is formed . this process of forming the solution is commonly referred to as batch mixing , and forming the solution in this manner eliminates the need for chemical proportioner , thus assuring that any imbalance caused by a malfunctioning proportioner unit will not have a derogatory effect on operation of the invention . a vent valve 36 is located on top of solution tank 16 to allow the release of air pressure prior to refilling solution tank 16 with the chemical and water . a pipe , hose or other like coupling 38 is located at the forward end of the solution tank 16 to provide a fluid coupling between foam expansion manifold 12 and solution tank 16 . air supply system 18 preferably comprises a pair of air tanks 40a , 40b , a pair of corresponding pressure regulators 42a , 42b located downstream of air tanks 40a , 40b , a pair of corresponding check valves 20a , 20b located downstream of pressure regulators 42a , 42b , and a junction connector 44 . air tanks 40a , 40b are standard underwater dive tanks and store cold compressed air ( ideally - 20 ° f . to - 30 ° f .) at approximately 3000 psi . air tanks 40a , 40b supply the pressurized air required for the system 10 to function ; however , preferably only one air tank operates at any given moment to supply pressurized air to the system 10 . this dual air tank configuration provides redundancy to the system in the event of air supply exhaustion or a malfunction of the other air tank . pressure regulators 42a , 42b are of the standard scuba diving type and regulate the compressed cold air supply down to a pressure of approximately 155 psi . the operator can switch air sources , for example , by shutting off the regulator 42a located downstream of air tank 40a and opening the regulator 42b downstream of air tank 40b . the air exiting either regulator 42a or 42b ( or both if desired ) is sent to a junction connector 44 which routes some of the air to the solution tank through the tubing 22a . check valves 20a , 20b located between regulators 42a , 42b and the solution tank 16 prevent the backflow of air or solution into air tanks 40a , 40b and regulators 42a , 42b . junction connector 44 routes the remaining air through the tubing 22b to the foam expansion manifold 12 . referring also to fig3 foam expansion manifold 12 , which is fabricated from an aluminum or high strength polymer block or the like , includes a mixing chamber 46 having an inlet port 48 , an outlet port 50 and an air injection port 52 . mixing chamber 46 essentially comprises a longitudinal bore 54 with internal threads 56a , 56b at the input and output ends , respectively . inlet port 48 receives solution from the solution tank 16 and directs the solution into the mixing chamber 46 . air injection port 52 receives compressed air from air supply 18 and injects the air into the mixing chamber 46 at an optimum 68 ° relative to the path in which the solution enters mixing chamber 46 , or 22 ° relative to a line perpendicular to the longitudinal axis of mixing chamber 46 . the mixture of air and solution in the mixing chamber 46 causes a &# 34 ; supercharging &# 34 ; effect that accelerates the flow and causes the solution to expand to form a fire suppressing foam . up to a 40 : 1 solution - to - foam expansion occurs in the mixing chamber 46 , although the invention is conservatively rated for a 20 : 1 expansion . the foam accelerates out of foam expansion manifold 12 through outlet port 50 . note that air injection port 52 includes internal threads 58 . internal threads 56a on inlet port 48 and internal threads 56b on outlet port 50 allow connection to tubing 22a , 22b , respectively , and internal threads 58 on air injection port 52 allow connection to coupling 38 between air injection port 52 and solution tank 16 . in the preferred embodiment of the invention , air injection port 52 has an optimum inside diameter of 3 / 8 inch . varying the inside diameter of air injection port 52 varies the density of the foam produced in mixing chamber 46 . if the inside diameter of the air injection port 52 is increased above 3 / 8 inch , the volume of air increases but the pressure drops . this results in a drier foam that does not shoot as far . if the inside diameter of the air injection port 52 is decreased below 3 / 8 inch , the pressure increases but the volume of air decreases . this results in a wetter foam which shoots further that with a larger diameter . also , longitudinal bore 54 in mixing chamber 46 has an optimum inside diameter of 1 inch . varying the inside diameter of the longitudinal bore 54 of mixing chamber 46 also varies the density of the foam produced . if a larger inside diameter is used , the volume increases , but less air mixes to dry the foam . this results in a wetter foam that will shoot further but which empties solution tank 16 sooner . if a smaller inside diameter is used , the volume decreases and more air is used to dry the foam . the result is a drier foam which will not shoot as far due to the lower water weight as water is required to carry the foam , however the solution tank 16 depletes at a slower rate . charge valve 14 is located on discharge hose 24 opposite the end that is connected to outlet port 50 of foam expansion manifold 12 . charge valve 14 controls the delivery of the foam exiting the apparatus 10 . charge valve 14 is preferably a 3 / 4 inch ball valve or the like equipped with a handle 60 . charge valve 14 allows varying the moisture content of the foam produced by the foam expansion manifold 12 . the best foam is produced when charge valve 14 is wide open . in this condition , and with the pressures and other parameters of foam expansion manifold 12 described above , approximately 13 / 4 minutes of cold foam ( approximately 600 gallons ) can be produced from a 30 gallon solution tank . the moisture content ( wetness ) of the foam can be controlled by charge valve 14 . if charge valve 14 is partially closed , the bubbles break up , decreasing the volume of foam and making the foam wetter . wetter foams are best for deep seated fires in upholstery , etc . where it is desirable for the foam to penetrate the surface . drier foams are used for fires where it is desirable to make a foam blanket to insulate , isolate and seal off vapors . this takes air away from the fire and will quickly cause the fire to extinguish . although the description above contains many specificities , these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention . thus the scope of this invention should be determined by the appended claims and their legal equivalents .
a portable fire suppression system which uses cold compressed air foam to extinguish fires . a solution suitable for generating foam is mixed with air in an expansion manifold where the foam is supercharged and expands up to 40 times original volume . the foam is discharged out a nozzle controlled by a charge valve which controls flow rate and moisture content of the foam . the fire suppression system is mounted on a compact sturdy frame capable of withstanding parachute drops to remote sites , and includes a frame with a hitch and wheels for ground mobility .