Patent Application
20050263297
This application is directed to a foam-generating assembly for generating a foam particularly useful in preventing or extinguishing fires, and to a foam generator which is employed therein. It is also directed to a new method for generating a nitrogen-containing foam.
It is well known to use foams, and in particular foams containing nitrogen gas, to prevent or extinguish fires—see, for example, U.S. Pat. No. 6,112,819. Various constructions of apparatus for generating such foams have been devised. However, these known constructions are complicated and expensive to produce. The present inventors have developed a foam-generating apparatus which is simple in construction and inexpensive to produce, which will rapidly produce a nitrogen-containing foam of a desired expansion ratio, and which in one embodiment is sufficiently compact that it can be installed in an enclosed space, such as in an engine compartment or passenger cabin of a vehicle, airplane, boat, etc., to rapidly emit a fire preventing or extinguishing foam in the event of an impending or actual accident.
The inventive foam-generating assembly includes a foam generator and tanks which respectively contain a foamable aqueous liquid and nitrogen gas and which are connected to deliver their contents to the foam generator. The foam generator includes a header that defines a swirl chamber formed by a outer cylindrical wall, an inner cylindrical wall and a floor, and a spray nozzle is located in the center of its floor to emit a conical spray of the foamable aqueous liquid into the swirl chamber. An orifice is provided in the inner cylindrical wall to tangentially discharge nitrogen gas into the swirl chamber and around the spray nozzle and the liquid spray emitted therefrom to create a vortex flow of mixed liquid spray and gas. First and second mesh screens are provided through which the vortex flow will pass, first to provide a coarse foam and then a fine foam having the desired expansion ratio.
In one embodiment an extender tube can be positioned against the upper cylindrical wall to extend beyond the header and the first mesh screen, which can be in the form of an inverted frustoconical element, can be positioned in the extender tube, whereas the second mesh screen can be positioned across the outlet end of the extender tube. The outer cylindrical wall can have a larger diameter than the inner cylindrical wall, providing an annular ledge on which the extender tube is seated. The tanks can be spaced apart from the header and connected thereto by suitable conduits. A pressure regulator can be inserted in the gas conduit to control the pressure of gas delivered to the header.
In another embodiment, which provides a compact arrangement that enables the assembly to be installed in a compact space such as an engine compartment, the header can provide docking stations for the tanks and include passageways to deliver foamable aqueous liquid to the spray nozzle and nitrogen gas to the orifice in the inner cylindrical wall of the swirl chamber. A pressure regular can be attached to the header to provide control of the nitrogen gas pressure delivered to the swirl chamber. An on-off control valve which can be electrically controlled can be included to allow gas to flow from the nitrogen tank to the header, e.g., when a signal is received from a sensor in the vehicle in which the foam-generating assembly is located that senses rapid deceleration of the vehicle (indicating impending crash). The tank containing the foamable aqueous liquid can include a flexible bag in which the liquid is contained, and a conduit from the nitrogen tank can be connected to the liquid tank to provide the pressure therein that causes the liquid to be delivered from the bag into the header.
The method of the invention involves tangentially flowing nitrogen gas around an expanding cone-shaped spray of foamable aqueous liquid in a cylindrical swirl chamber to provide a vortex and then passing the liquid spray and nitrogen gas through first and second spaced mesh foaming screens to provide a fine foam that can rapidly spread out from the swirl chamber and cover nearby areas to prevent or suppress fires.
The invention will now be better understood by reference to the attached drawings, taken in conjunction with the following discussion.
A first embodiment of the inventive foam-generating assembly 10 is shown in
The foam generator 20 includes a header 21 which is hollowed out from its top to provide an internal swirl chamber S defined by an outer cylindrical wall 22, an inner cylindrical wall 24, and a floor 25. The header 21 is preferably a block of metal such as aluminum. The outer cylindrical wall 22 has a greater diameter than the inner cylindrical wall 24 so as to provide an annular ledge 23 therebetween. In a preferred embodiment the outer cylindrical wall had a diameter of 64 mm and extended a depth of 38 mm into the header, and the inner cylindrical wall 24 had a diameter of 61 mm and extended a further depth of 13 mm into the header.
As best seen in
A second passageway 28 extends from an internally threaded inlet end 28a in the side surface of the header to an elongated outlet orifice 28b in the inner cylindrical wall 24. The outlet orifice 28b is tangentially oriented relative to the inner cylindrical wall. A connector 47 which is located at the end of a valved conduit 46 that communicates with the nitrogen supply tank 55, is threadingly engaged in the inlet end 28a. Nitrogen from tank 45, which is spaced from the foam generator 20, can flow through the conduit 46 and the passageway 28 to tangentially enter the swirl chamber S and flow around the spray nozzle 27 and the liquid spray emitted therefrom to provide a vortex flow and a mixture of droplets of foamable aqueous liquid and nitrogen gas beyond the spray nozzle 27.
The foam generator 20 also includes an extender tube 29 which sits on annular ledge 23 and extends beyond the upper end of the header 21. The extender tube can be sized to pressure fit against the upper cylindrical wall 22, or it can be connected to the header 21 by circumferentially spaced screws (not shown). A first foaming screen 30 is positioned within the extender tube to cause the vortex of gas and droplets of aqueous liquid contacting the screen and passing there-through to form a course nitrogen-containing foam (containing large bubbles). This first foaming screen is configured as an inverted frusto-conical element, and is preferably made of three layers 31 of metal mesh. The first foaming screen could alternatively be formed in the shape of a simple cone. Each mesh layer is preferably made of aluminum and has a 1.6×2.0 mm mesh size. The first foaming screen 30 is connected to the extender tube 28 by circumferentially spaced screws 32 or other suitable connectors.
A second foaming screen 33 extends across the outer end of the extended tube 28 and is connected at its periphery to the extender tube by suitable means such as circumferentially spaced screws (not shown). This foaming screen is preferably made of two layers of the same mesh as used in the layers of the first foaming screen. Coarse nitrogen-containing foam contacting and passing through the second foaming screen will be converted into a fine foam having an expansion ratio of, e.g., 160 to 250, and is very effective in spreading out from the foam generator to cover nearby areas and prevent or suppress fires. This foam-generating assembly is capable of producing 450 liters of foam in about 70 seconds from a 6.4 liter/second flow of nitrogen gas and a 0.029 liter/minute flow of foamable solution.
A second embodiment of a foam generating assembly 50 is shown in
The foam generator 60 includes a header 61 having a lateral docking extension 62, the header being hollowed out from its outer end to provide an internal swirl chamber C defined by an outer cylindrical wall 63, an inner cylindrical wall 65 and a floor 66. The header is preferably made of steel. The outer cylindrical wall 63 has a greater diameter than the inner cylindrical wall 65 so as to define an annular ledge 64 therebetween.
A first internally threaded blind bore 67 is formed in the bottom of header 61 beneath the swirl chamber to provide a first docking station, and a first passageway 68 extends from an internally threaded inlet end 68a in the bottom of the blind bore 67 to an internally threaded outlet end 68b at the center of the floor 66. A spray nozzle 69 is threadingly engaged in the outlet end 68b so as to spray an aqueous liquid passing therethrough into the center of the swirl chamber C. As indicated in
A second passageway 72 extends from an internally threaded inlet end 72a in the side of the header 61 to an outlet orifice 72b in the inner cylindrical wall 65 of the swirl chamber, the outlet orifice being tangentially oriented so as to emit gas therefrom in a tangential fashion around the spray nozzle 69.
A first foaming screen 73 (similar in construction to the foaming screen 29) is fixedly positioned on the annular ledge 64 and a second foaming screen (similar in construction to the foaming screen 33) is positioned across the outer end of the header 61. No extender tube is used.
A second internally threaded blind bore 75 is formed in the lateral docking extension 62 opposite a nipple 76. A third passageway 77 communicates with the base of the blind bore 75 and extends into the nipple 76. A valved pressure regulator 78 is attached to the nipple 76 and includes a control pin 79 that extends through the third passageway and into the blind bore 75. A conduit 80 connects with the inlet end 72a of the second passageway 72. A branch conduit 81 connects with an inlet end 82a of fourth passageway 82, and a pipe 83 connects with the outlet end 82b for connection to the bottom end of the tank 90.
The aqueous liquid supply tank 90 includes a threaded neck 91 that can sealingly engage in the blind bore 67 and a threaded inlet channel 92 in its bottom to which the pipe 83 can be connected. A flexible bag 93 is located in the tank and is sealingly connectable to the flow pipe 71 by clamp 94. This pouch can contain foamable aqueous liquid that can be discharged through the flow pipe 71 and first passageway 68 when pressurized by gas flowing into the tank via inlet channel 92. The bag 93 can be refilled with foamable aqueous liquid without removing the tank 90 from the first docking station by removing spray nozzle 69 and sealingly attaching a conduit to the outlet end 68b so as to supply foamable aqueous liquid under pressure to the first passageway 68 and back into the bag.
The nitrogen tank 100 includes a threaded neck 101 that can sealingly engage in the blind bore 75 and a spring-biased ball valve 102 is sealingly positioned in its neck. The ball valve can be opened by movement of the control pin 79 against the ball when the on-off valve of the pressure regulator 78 is opened. This can be done manually or electrically (note wires 78a which can be connected to a vehicle switch that activates one or more air bags in the event of rapid deceleration of the vehicle in which the foam-generating assembly is employed). Opening of the ball valve 102 will cause nitrogen from tank 100 to flow to and through passageway 72 to outlet orifice 72b, where it will tangentially enter the swirl chamber C, as well as to flow through pipe 83 to tank 90, where it will cause foamable aqueous liquid from bag 93 to flow through the spray nozzle 69 (after seal element 70 is ruptured) into the swirl chamber C. A gas-containing foam will be produced as explained previously relative to the first invention embodiment.
Although two specific embodiments of foam-generating assemblies and foam generators have been shown and described in detail, modifications therein can be made and still fall within the scope of the appended claims.
The present application claims the benefit of U.S. Provisional Application No. 60/566,327, filed Apr. 29, 2004, the contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60566327 | Apr 2004 | US |
