Patent Publication Number: US-4318443-A

Title: Foam generating fire fighting device

Description:
This is a continuation of application Ser. No. 933,595, filed Aug. 14, 1978, now abandoned. 
    
    
     TECHNICAL FIELD 
     This invention relates to fire fighting equipment, and more particularly to a fire fighting foam generating device for introducing air into a foam generating solution. 
     BACKGROUND ART 
     In the past several years fire fighting techniques have included the use of applying a saponaceous or surfactant solution to burning material. These solutions are saturated with air to produce an abundance of bubbles turning the solution into a voluminous froth to smother the burning material and extinguish the fire. Typical foam generating devices are described and claimed in U.S. Pat. No. 1,753,429 issued to Rice on Apr. 8, 1930 and entitled &#34;Apparatus for Producing Foam&#34; and U.S. Pat. No. 2,908,334 issued to Duggan, et al on Oct. 13, 1959 and entitled &#34;Process and Apparatus for Generating and Discharging Foam&#34;. 
     Such prior art foam generating devices have used specially designed complex and expensive nozzles for the introduction of air into the foaming agent and for agitating the air-foaming agent mixture to produce foam at the nozzle head. This technique requires a large amount of pressure to pump the foaming agent through the nozzle in addition to specially designed nozzles. Additionally, prior art foam generating devices include complex mechanical systems making them difficult to maneuver when fighting a fire and which are difficult and costly to maintain. 
     A need has thus arisen for a foam generating device that is simple in operation and is operable with a minimum amount of pressure to pump the foaming agent. Additionally, a need has arisen for a foam generating device in which the aeration and agitation of the foam generating solution are accomplished without the need of specially designed nozzles. 
     DISCLOSURE OF THE INVENTION 
     In accordance with the present invention, a foam generating device for aerating and agitating a foam generating solution is provided. 
     In accordance with the present invention, a foam generating device is provided for generating and discharging foam. The device includes a container for receiving and storing a foam generating solution. A discharge tube is connected to the container, and an ejector tube is disposed within the container for discharging the foam generating solution to the discharge tube. Foam generating structure is disposed between the ejector tube and the discharge tube exterior of the container and includes a chamber communicating with the ejector tube for permitting the passage of the foam generating solution therethrough to the discharge tube. A pressure generator communicates with the container for forcing the foam generating solution through the ejector tube and the foam generating structure. The pressure generator further communicates with the chamber for aerating the foam generating solution. 
     In accordance with another aspect of the present invention, an apparatus for generating and discharging fire extinguishing foam includes a container for receiving and storing a foam generating solution. A discharge tube is connected to the container, and an ejector tube is disposed within the container for discharging the foam generating solution to the discharge tube. An aeration chamber is provided and includes a plurality of apertures. The aeration chamber is disposed between the ejector tube and the discharge tube exterior of the container and is operable to permit the passage of the foam generating solution therethrough. A source of propellant is provided for introducing a propellant into the container for forcing the foam generating solution through the ejector tube and the aeration chamber. The propellant communicates with the aeration chamber apertures for introducing air into the flow of the foam generating solution to generate foam within the discharge tube. 
     In accordance with yet another aspect of the present invention, a method for producing foam from a foam generating solution includes the step of storing a foam generating solution in a container. A propellant is passed through the container to force the foam generating solution into a foam generating chamber. The foam is generated by aerating the foam generating solution within the chamber by passing a propellant through the chamber. The aerated foam is agitated within a foam discharge tube. The propellant further discharges the agitated foam from the discharge tube. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     A more complete understanding of the invention and its advantages will be apparent from the following Detailed Description taken in conjunction with the accompanying Drawings in which: 
     FIG. 1 is a side elevational view, partially in section, of the foam generating fire fighting device of the present invention; and 
     FIG. 2 is a sectional view taken in the same plane of FIG. 1 of the foam generating structure of the present foam generating fire fighting device. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates the present foam generating fire fighting device and is generally identified by the numeral 10. Foam generating device 10 includes a tank 12 leak tightly sealed at either end to an upper header 14 and a lower header 16. Tank 12 and headers 14 and 16 are constructed of materials impervious to or protected from the foam generating solution stored therein. The lower end of tank 12 includes a base 18. Tank 12 includes a foam generating solution 24 filled to a level indicated at 26. Foam generating solution 24 for use in the present foam generating device 10, is selected depending upon the type of fire to be extinguished. 
     Connected to header 14 is a fitting 30 for receiving and interconnecting an ejector tube 32 and foam generating assembly, generally identified by the numeral 34, to tank 12. Ejector tube 32 includes a weight 36 for maintaining ejector tube 32 centrally disposed within tank 12. Upper header 14 also includes a port 28 for filling and draining foam generating solution 24 from tank 12. 
     Foam generating assembly 34 includes a T-connector 38 interconnected to fitting 30. T-connector 38 receives fittings 40, 42 and 44. Fitting 40 is interconnected to hose 50. As shown in FIG. 1, hose 50 is interconnected to a pressure tank 52 through a regulator 54 and a valve assembly 56 to pressurize tank 12. Pressure tank 52 may contain, for example, nitrogen, carbon dioxide, halogen, freon, compressed air or mixtures thereof for maintaining foam generating solution 24 under constant pressure within tank 12. Alternatively, conventional water pump lines such as supplied from fire fighting tank trucks can be interconnected to hose 50 for pressurizing tank 12. 
     Fitting 42 of T-connector 38 is interconnected to a pressure release valve 60. Fitting 44 is interconnected to an elbow section 62 that receives a fitting 64. Fitting 64 is interconnected to a discharge hose 66. Foam is discharged from discharge hose 66 to a control valve 68 and a nozzle 70. Control valve 68 and nozzle 70 are conventional devices well-known to those skilled in the art. 
     Referring simultaneously to FIGS. 1 and 2 wherein like numerals are utilized for like and corresponding elements, it can be seen that T-connector 38 joins fittings 30, 40, 42 and 44 and defines a cavity 72. Disposed within cavity 72 and interconnecting fittings 30 and 44 is an aeration chamber, generally identified by the numeral 74. Aeration chamber 74 includes a stem portion 78 for insertion through fitting 30 for frictionally receiving ejector tube 32. Aeration chamber 74 further includes a threaded portion 80 for interconnecting aeration chamber 74 to fitting 44. An important aspect of the present invention are apertures 82 disposed circumferentially and centrally around aeration chamber 74. Apertures 82 function to introduce propellant or air into the flow of foam generating solution 24 between tank 12 and discharge hose 66 to aerate foam generating solution 24 to thereby produce foam. 
     In operation of the present foam generating fire fighting device 10, propellant in the form of compressed air or compressed gas enters cavity 72 from a pressure source indicated by flow directional arrow 90. The propellant then flows through passage ways 92 defined between fitting 30 and stem portion 78 of aeration chamber 74. The flow of propellant in tank 12 is indicated by flow directional arrows 94. As a result of propellant entering tank 12, an increase in pressure is experienced by the foam generating solution 24 within tank 12 such that the foam generating solution 24 is forced into ejector tube 32 as indicated by flow directional arrow 96. Foam generating solution 24 therefore flows through ejector tube 32, through stem portion 78 and threaded portion 80 of aeration chamber 74, through fitting 44 to discharge tube 66. 
     Propellant from pressure tank 52 also flows through apertures 82 of aeration chamber 74 indicated by directional arrow 98. Propellant, introduced through apertures 82 into the flow stream of foam generating solution 24 passing from tank 12 to discharge tube 66, generates a foam-air or gas slurry 100 present in elbow 62 and indicated by flow directional arrow 102. The foam-air slurry 100 then passes through fitting 64 into discharge tube 66. The foam-air slurry 100 is then highly agitated by the turbulence and back pressure created within discharge tube 66 to form foam 104 for discharge through nozzle 70 (FIG. 1). The size of discharge tube 66 can be selected to obtain foam of desired volume and fluidity. 
     It therefore can be seen that a single source of propellant is utilized for forcing foam generating solution 24 from tank 12 and also for aerating foam generating solution 24 to produce foam 104. Foam generating solution 24 passing through aeration chamber 74 is thoroughly aerated due to the apertures 82 that permit communication between a propellant and foam generating solution 24. The number and size of apertures 82 is dependent upon the expansion factor desired for the generated foam as determined by the particular foam application. 
     While the present foam generating fire fighting device has been illustrated and described as being portable, additionally, the device can be permanently affixed to mobile vehicles, such as fire fighting trucks. Foam generating assembly 34 can be interconnected for in-line operation using a conventional fire hose supplied by a fire fighting truck pumping system including a foam solution. Fittings 30 and 44 would be interconnected directly into the fire hose and fitting 42 would be closed for in-line operation. The system can also be utilized in a fixed system to protect buildings and stationary equipment. 
     While only one embodiment of the present invention has been described in detail herein and shown in the accompanying drawings, it will be evident that various further modifications are possible without departing from the scope of the invention.