Self-contained Foam Fire Extinguishing System

Abstract

A self-contained high expansion foam fire extinguishing system providing an independent source of pressurization to a container holding a mixture of water and foam concentrate for delivery to a foam generator having a plurality of nozzle members and a stratified screen to produce high expansion foam upon activation of the system by a fire detecting sensor.

Parent Case Text

This is a continuation-in-part of my co-pending application Ser. No. 782,343 filed Dec. 9, 1968 now U.S. Pat. No. 3,592,269.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a new type of foam fire extinguishing system of the type having a storage tank for foam producing matter. A foam generator for producing foam, said system especially adapted for installation in a store or other structures.

2. Prior Art

A self-contained efficient and highly reliable high expansion foam system for the extinguishing of a fire in a building has long been a desired goal. High expansion foam is a relatively new development for fighting fires, especially in buildings or other enclosed structures. The prior art discloses some high expansion foam fire fighting devices, both portable and fixed installations. For the purposes of this invention, the term "high expansion foam" will be understood to define a foam which expands a given volume of water together with a concentrated mix (in solution) from 300 to 1,500 times its original volume.

One of the devices disclosed by the prior art generates high expansion foam through the use of a source of foam concentrate, but requires that air be mixed therewith through an air stream created by rotation of an external fan. The foam is formed by the flowing of air through a screen after the stream has been wet with the spray of foam concentrate. This device specifically requires the use of a fan to inject the air required to form the foam.

The present invention solves the need for external air moving equipment and uses no force other than the partial vacuum created by the flow of foam concentrate to draw in ambient air. The ambient air is drawn in by the partial vacuum without the need of any fan or other air moving equipment.

Another device disclosed by the prior art requires a tubular casing enclosing two sets of nozzles, the first set being connected to a source of foam concentrate, the second set of nozzles being connected to a source of carbon dioxide. A foam forming net is disposed in front of the two sets of nozzles to produce foam from the mixture of carbon dioxide and foam concentrate. The device requires the combined action of carbon dioxide and the foam producing concentrate and as a result requires the inclusion of additional pressurizing equipment and nozzles for the disposition of carbon dioxide. The present invention requires no additional source of mixing agent and therefore obviates the problems raised by the described device. In the present invention, the air is drawn into the foam generator solely as a result of the partial vacuum created by the output of foam concentrate.

SUMMARY OF THE INVENTION

The basic problem to be solved by the present invention system is to provide a high expansion foam generating system to be used as a fire fighting system, and which is completely self-contained and therefore substantially independent of external conditions.

The high expansion foam fire extinguishing system utilizes a pre-mixed high expansion foam concentrate. When a sensor detects the presence of a fire, a valve is opened, placing the high expansion foam concentrate under pressure from an inert gas, typically gaseous nitrogen. Placing the high expansion foam concentrate under pressure forces the concentrated mixture into a manifold having a plurality of attached nozzles. When the concentrated mixture is forced through the nozzle, a cone of liquid concentrate is emitted.

The cone of liquid concentrate is emitted into a foam generator defined by an upper wall, a bottom wall, a pair of side walls, a rear wall and a screen. The structure of the foam generator insures that the stratified screen is substantially parallel with the floor or other surface of the enclosure within which the present invention is disposed. The top walls and bottom wall of the foam generator extend upwardly from the screen and at an angle therefrom. The bottom wall is terminated a suitable distance from the screen to permit insertion of the foam concentrate input and the foam emitting nozzles. The top wall is terminated by a rear wall of the foam generator, the foam generator being enclosed by appropriate side walls. As mentioned, the foam concentrate input is inserted through an opening of the foam generator formed by the bottom wall, rear wall and side walls of the foam generator. The manifold of foam emitting nozzles is disposed within the interior of the foam generator, the nozzles being directed toward the screen. The axis of the cone of foam concentrate is substantially parallel to the angle of the top and bottom walls of the foam generator.

The foam is formed by a combination of air and high expansion foam concentrate striking the screen. Air is drawn through the orifice defined by the bottom, rear and side walls of the foam generator. A substantial portion of the air heated by the fire will only enter the foam generator at this formed orifice because the upper wall and rear wall fully covers the nozzle output.

The screen constitutes a multi-layer structure, the first layer being a metallic honeycombed sheet, the bottom layer of the screen being a metallic mesh structure The honeycombed screen and mesh structure provide a suitable ratio of hole area to surface area to utilize the available free energy in the vicinity of the screen openings. The nozzles are spaced along the manifold at a predetermined distance that is necessary to insure full coverage of the screen surface. Since the cones formed by emitted concentrate fully cover the screen, the system constitutes a linear generator in that an even distribution of foam is created along the entire length of the foam generator. The nozzles are disposed at an angle with respect to the floor of the enclosure to provide that the axis of the cone of emitted foam concentrate is substantially parallel to the top and bottom walls of foam generator and also to provide substantially uniform distribution across the screen.

The foam emitted from the screen is directed downward because of the orientation of the screen. The heated air is drawn through the foam cooling the air. The foam will continue to be generated cooling the entire area of the building. Since the foam has a high water content, the fire will be extinguished. The high expansion foam concentrate contains a detergent which acts to clean the inner areas of the buildings as well as extinguish the fire.

It is therefore an object of the invention to provide a fire extinguishing system which is independent of external water supplies, pressurization and electric power.

It is a further object of the invention to provide a self-contained fire extinguishing system which utilizes a high expansion foam concentrate.

It is still a further object of the invention to provide a foam generator without the use of motors, fans or other air moving devices.

A still further object of the invention is to provide a linear foam generator.

The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objectives and advantages thereof will be better understood from the following description considered in connection with the accompanying drawing in which a presently preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawing is for the purpose of illustration and description only, and is not intended as a definition of the limits of the invention.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1a is a partial sectional view showing the presently preferred embodiment of this invention installed within a building and the manner in which it is employed to extinguish a fire which may have occurred within the building.

FIG. 1b is an alternative embodiment of the pressure system for the fluid and compressed gas motive means shown in FIG. 1.

FIG. 2 is an enlarged cross-sectional view showing the foam generator portion of FIG. 1 enlarged in size.

FIG. 3 is an enlarged perspective view of the foam generator of FIG. 1.

FIG. 4 is a plan fragmentary view of the multilayer screen forming part of the generator of FIG. 3.

FIG. 5 is a partial cross-sectional view of the multilayer screen taken along lines 5--5 of FIG. 4.

FIG. 6 is an enlarged sectional view of an exemplary nozzle as may best be seen in FIG. 3 forming part of the generator.

FIG. 7 is a schematic view showing the discharge cone of the fluid solution as it exists from one of the nozzles forming part of the generator of the present invention system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is now made to FIG. 1a, wherein a presently preferred embodiment of this invention is shown installed within an appropriate enclosure generally designated by the reference numeral 10. The foam generator is generally designated by the numeral 20 as shown extended from the ceiling or roof 11 of enclosure 10 by cables or chain 12. The exterior wall of the storage building 10 is numbered 13 and the interior wall 14. The ground or the floor of the building is numbered 15. The present invention foam system is self-contained and requires no external source of electric power, hydraulic power or gas power. Included within the system, in order to generate foam upon the occurrence of a fire within a building 10 there is provided a source of inert gas such as nitrogen under pressure shown within a container 21. Container 21 is connected through an appropriate line 22 to a valve-pressure regulator 23 to a concentrate mix solution tank 24. A line 39 exits from tank 24 and connects to a manifold 25 through an opening 26 in the wall 14. Foam generator 20 is constructed of top wall 27, bottom wall 28, rear wall 29 and a pair of side walls enclosing a cavity between top wall 27, bottom wall 28 and rear wall 29. As shown in FIG. 1a and FIG. 2, top wall 27 is typically suspended from ceiling 11 by chain 12, top wall 27 and bottom wall 28 being substantially parallel. In addition, an additional bottom portion 30 depends from rear wall 29 co-planar with bottom wall 28, bottom walls 28 and 30 defining an orifice therebetween. Side walls not shown in FIG. 1a and FIG. 2 are coupled to the side surfaces of top wall 27, rear wall 29 and bottom walls 28 and 30 to fully define the orifice opening into the inner cavity of foam generator 20.

The portions of top wall 27 and bottom wall 28 nearest floor 15 are adapted to receive multilayer screen 31. Multilayer screen 31 is substantially parallel to floor 15. As can be seen in FIG. 2, multilayer screen 31 is comprised of a honeycombed layer 32 and an outer mesh layer 33. The details relating to honeycombed layer 32 and mesh layer 33 shall be explained in detail below.

Referring again to FIG. 1a, the foam system is activated when sensor 34 detects the presence of heat incident to a fire. Sensor 34 is a heat detector which initiates an alarm upon detecting an ambient temperature typically at a value of 135.degree.F. Sensor 34 is a conventional heat detector of the type manufactured by the Walter Kidde Corporation. The output of sensor 34 appears on line 35 and energizes a relay pack 36 which produces an electrical signal on signal lines 37 to the valve pressure regulator 23. Valve-pressure regulator 23 is an electrically activated device regulating the pressure to be imposed upon the concentrate mix solution tank 24. The valve-pressure regulator 23 can be set for outlet pressures typically in the range of 20-40 psi. One of the advantages of the present invention self-contained fire extinguishing system is to permit the generation of large quantities of foam while requiring only low pressure equipment for movement of the foam concentrate. Where the structure of the present invention utilizes a set of eleven foam emitting nozzles to be explained hereinbelow, 1,500 standard cubic feet per minute can be generated with a solution delivery rate of 19 gallons per minute at 35 psi. The ability to generate equivalent volumes of generated foam at lower pressures substantially reduces the cost of the equipment as well as making the system easier to fabricate. Valve-pressure regulator 23 is typically of a type manufactured by Accessory Products Corporation, Whittier, California, a division of Textron Industries and is designated as APCO No. 803501D-3. By opening valve-pressure regulator 23, the gaseous contents of container 21 is caused to flow through line 22, pressure regulator 23, line 38 and into the concentrate mix solution tank 24. Since the concentrate mix in container tank 24 is under pressure, the mixture is forced into line 39.

The high expansion foam concentrate is typically by weight composed to 3.0 to 4.5 percent Neodol 25, 30 to 35 percent Neodol 23-3A, 26 to 30 percent butyl ether dietheolene glycol and the balance of 30.5 to 41 percent of water. The concentrate is further diluted by volume to a concentration of 3 percent of the above foam concentrate and 97.0 percent water. Neodol 23-3A is defined in "Shell Chemical Bulletin, I.C.:6741" and is an aqueous solution of ammonium salt of a sulfated primary alcohol ethyoxylate containing on the average three ethylene oxide units. Neodol 23-3A can be characterized by a molecular weight of approximately 423, a concentrate of ethylene oxide by weight of 31.2 percent, a specific gravity at 25.degree.C of 1.01, and a pH of 7.3. It is a light colored viscous liquid containing about 60 percent by weight surfactant and ethanol is included as a solubilizor. Neodol 25 is commercially available from the Shell Chemical Company. Neodol 25 designates an alcohol blend characterized by the symbol R--OH where R is a blend of linear primary alcohols with 12, 13, 14 and 15 carbon atoms. The physical characteristics of Neodol 25 are a molecular weight of approximately 207, a specific gravity at 25.degree.C of 0.834, and a viscosity of 18.3 centipoise at 100.degree.F. A high expansion foam is distinguishable from low expansion foam concentrate by the expansion ratio which is defined by the volume of foam produced divided by the original volume of the concentrate. A high expansion concentrate has an expansion ratio of 300 to 1,500 while a low expansion concentrate has an expansion ratio of 10 to 20. The preferable ratio for use in buildings is 600 to 700. The expansion ratio can be changed by changing the pressure imposed on the concentrate. Referring to FIG. 1a, the valve-pressure regulator 23 can be set for a pressure of 25 - 40 psi. When the pressure is applied to the concentrate mix solution tank 24, the concentrate will have an expansion ratio substantially in the range of 500 - 700. The amount of concentrate available for fire fighting can be increased by putting a plurality of solution tanks 24 in series. Referring to FIG. 1b, in which an alternate form for the source of foam concentrate is shown, three solution tanks 24 are serially connected with the result approximately three times more foam can be produced. By putting a plurality of pressure sources and solution tanks 24 in parallel, the volume per unit of time of foam generated can be increased.

An understanding of the generation of foam can be best gained by reference to FIG. 2. The concentrate is forced into line 39 and into manifold 25 with a resulting emission of concentrate at nozzle 60. The nozzle 60 can be attached to manifold 25 in any suitable manner but preferably by a threaded joint 62 as shown in FIG. 6. The nozzle 60 can have a spiral chamber 64 leading to an annular flanged output 66 which will produce an output emission forming a cone. The nozzle 60 separation along manifold 25 can be best seen in FIG. 3. The number of nozzles 60 coupled to manifold 25 can be any suitable number which will insure uniform distribution of solution upon multilayer screen 31, the preferred embodiment of the present invention utilizing a set of 11 nozzles 60 within each foam generator 20. The concentrate cone 68 emitted by a nozzle 60 is such that all parts of the multilayer screen 31 will be reached by the concentrate. If 11 nozzles 60 are spaced along manifold 25 of a generator 20, nitrogen pressure of 35 psi will produce 1,500 cubic feet of foam per minute. If the nozzle 60 separation is reduced or the nitrogen pressure increased, the foam generated per foot of generator will be substantially increased. The surface area created by the concentrate cone 68 (FIG. 7) is intersected by the foam generating screen 31. As shown in FIG. 2, multilayer screen 31 is attached to top wall 27 and bottom wall 28 in a manner which will insure that multilayer screen 31 is substantially parallel to floor 15. Although the angle of top wall 27 with respect to floor 15 can be any suitable angle, it is preferably disposed at approximately 45.degree. .+-. 15.degree. with respect to the surface of floor 15. Nozzles 60 are oriented with respect to the plane of top wall 27 and bottom wall 28 to insure that the cone of foam concentrate 68 is uniformly distributed across multilayer screen 31. This is accomplished by making the axis of the cone 68 substantially parallel to top wall 27 and bottom wall 28.

Although the preferred embodiment of the present invention is adapted to be used within fixed structures and secured as shown in FIG. 1a, it is within the scope of the present invention to provide for other means of supporting foam generator 20 and to use the system within any enclosed structure such as marine vessels and aircraft.

Referring now to FIG. 4 and FIG. 5, the structure of multilayer screen 31 can be best understood. In order to adapt multilayer screen 31 to produce the highest flow rate of foam, the surface area between the holes must be expanded to increase agitation. As set forth in Applicant's co-pending application, Ser. No. 782,343 filed Dec. 9, 1968, hammertone or crackle paint which increases the surface area is a solution to this problem. The present invention is substantially improved by utilizing multilayer screen 31. Honeycombed layer 32 substantially increases the surface area available for contact by the foam concentrate thereby providing a greater surface area for increasing agitation. In addition, honeycombed layer 32 substantially increases the hole area to allow a greater flow of generated foam. Honeycombed layer 32 constitutes a plurality of adjacent hexagonal orifices 70 bounded by the metallic honeycombed walls 71 forming honeycombed layer 32. Honeycombed layer 32 is selected to provide a proper balance between the surface area provided by metallic walls 71 and hexagonal orifices 70. Although it is within the scope of the invention to utilize any appropriate honeycombed layer 32, the preferred embodiment of the present invention utilizes honeycombed structure fabricated of raw or oxidized aluminum wherein the distance between opposed wall junctions of orifices 70 is approximately one-fourth inch. To provide adequate surface area, honeycombed layer 32 is approximately one-half inch thick.

The outer layer of multilayer screen 31 is mesh layer 33. Mesh layer 33 is a metallic wire mesh preferably having a mesh substantially in the form of a diamond honeycomb. Mesh layer 33 is an appropriate metal preferably adapted to be plated with metals having high oxidation potentials. A metal is typically described as an active metal where it has a high oxidation potential, i.e., higher than 0.4, as shown in the Table of Potentials of Electrochemical Reactions in the Handbook of Chemistry and Physics, D86 (49th ed., 1968). A typical set of active metals meeting the above requirements are cadmium, zinc, chromium and platinum. Mesh layer 33 is preferably fabricated of carbon steel plated with cadmium or zinc. The combination of honeycomb layer 32 and mesh layer 33 substantially increases the agitation of the foam concentrate producing a greater flow rate at lower pressure. In addition, the foam produced is substantially more homogenious permitting greater penetration of the area to be filled by the foam.

The operation of the present invention fire extinguishing system can be best seen by reference to FIG. 1a and FIG. 2 wherein foam generators are shown emitting foam within the enclosed structure. As can be seen in FIG. 2, foam generator 20 is constructed to insure that the multilayer screen 31 is substantially horizontal and therefore parallel to the floor 15 of structure 10. Top wall 27 and bottom walls 28 and 30 are substantially parallel, top wall 27 and bottom wall 30 being joined by rear wall 29. Top wall 27 is joined to bottom wall 28 at the lower edges thereof by multilayer screen 31. The lateral edges of walls 28 - 30 are joined by side walls not shown. The fabricated walls of foam generator 20 provide for an orifice between bottom walls 28 and 30 through which air can be drawn for mixing with the cone 68 of foam concentrate to produce the generated foam.

Pressurized foam concentrate held in container 24 is forced through manifold 25 and from nozzles 60 producing cone 68 of foam concentrate to contact multilayer screen 31. As stated, the flow axis of cone 68 of foam concentrate is substantially parallel to top wall 27 and bottom wall 28 to provide for substantially uniform distribution of the foam concentrate on honeycombed layer 32 of multilayer screen 31. The conic stream 68 of foam concentrate creates a partial vacuum drawing the heated air 74 into orifice 73 defined by bottom wall 28, bottom wall 30 and the side walls joining walls 28 - 30. The mixture of air and the foam concentrate produces foam pile 75 through which heated air 74 is drawn. As stated, orifice 73 through which the partial vacuum draws heated air 74 is defined by an opening in bottom walls 28 and 30 laterally bounded by the side walls of foam generator 20. The drawing of heated air 74 through foam pile 75 substantially cools heated air 74 thereby accelerating the fire extinguishing process. Drawing heated air 74 through foam pile 75 is assured since top wall 27 and rear wall 29 substantially shroud nozzles 60 thereby leaving the only point of entry at orifice 73. Heated air 74 will carry particles emanating from burning article 76 and this in turn, will particularly contaminate cone 68 of foam concentrate as can be seen in FIG. 7. The outer surface or skin of the cone 68 of concentrate will be impregnated with the contaminating particles but so long as the velocity of the concentrate is sufficient to prevent total impregnation of the cone 68, foam generation at multilayer screen 31 will be effective.

The present invention fire extinguishing system produces a device which substantially solves problems existing in those devices disclosed by the prior art. The present invention system is totally self-contained requiring no external means for drawing air or other catalysts into foam generator 20 to combine with the foam concentrate for the generation of foam. Air is drawn through orifice 73 without the need of any fans or other air moving equipment. The combined mixture of foam concentrate and air strikes multilayer screen 31 thereby producing sufficient agitation to produce a stream of foam. Multilayer screen 31 comprising honeycombed layer 32 and mesh layer 33 produces substantially equivalent flow rates of foam at substantially lower pressures. The effect of these results permits the fabrication of a self-contained fire extinguishing system at substantially lower costs and without the problems inherent in those devices described by the prior art

Claims

I claim:

1. An improved fire extinguishing system of the type employing high expansion foam, the improvement comprising:

a. a reservoir containing a pre-mixed, high expansion foam producing fluid;

b. a foam generator comprising:

1. a plurality of nozzle members coupled to said reservoir;

2. a multilayer screen horizontally disposed and opposite said nozzles, said foam generator having top, bottom, rear and side enclosures, said bottom enclosure extending from said multilayer screen to a distance substantially in the vicinity of said nozzles and said top enclosure extending from said multilayer screen substantially beyond said nozzles, said rear enclosure depending downwardly from said top enclosure defining an orifice whereby air is drawn into said foam generator through said orifice defined by said enclosures when fluid is caused to be discharged through said nozzles for projection upon said multilayer screen where said high expansion foam is generated.

2. The fire extinguishing system as defined in claim 1 wherein said multilayer screen comprises a first honeycombed layer having a plurality of hexagonal cells disposed therethrough and a second mesh layer in intimate contact with said first honeycombed layer.

3. A fire extinguishing system as defined in claim 2 wherein said second mesh layer is plated with an active metal selected from a group consisting of cadmium, zinc, chromium and platinum.

4. A fire extinguishing system as defined in claim 1 including a pressurized source of inert gas, said pressurized source being coupled to said reservoir whereby said foam producing fluid is forced out of said nozzles.

5. A fire extinguishing system as defined in claim 4 wherein said pressurized source is pressurized in the range of 25 to 40 psi.

6. A fire extinguishing system as defined in claim 4 wherein said inert gas is nitrogen.

7. A fire extinguishing system of the type using high expansion foam comprising:

a. self-contained source means for containing pressurized gas;

b. reservoir means coupled to said self-contained source means for containing a pre-mixed high expansion foam producing concentrate;

c. foam generating means for drawing air into same and generating foam coupled to said reservoir means, said foam generating means comprising:

1. a manifold having spaced openings therein coupled to said reservoir means;

2. a plurality of nozzles coupled to said spaced openings in said manifold, said nozzles adapted to output said foam producing concentrate;

3. a multilayer screen horizontally disposed and being opposite said nozzles, said multilayer screen comprising a first honeycombed layer having a plurality of hexagonal cells disposed therethrough and a second mesh layer in intimate contact with said first honeycombed layer; and

4. an enclosure having top, bottom, rear and side walls, a portion of said top wall and said bottom wall being coupled to said multilayer screen, said enclosure defining an orifice through said bottom wall whereby the output of foam producing concentrate from said nozzles causes ambient air to be drawn through said orifice.

8. A fire extinguishing system as defined in claim 7 wherein said second mesh layer is plated with an active metal selected from a group consisting of cadmium, zinc, chromium and platinum.

9. A fire extinguishing system as defined in claim 7 wherein said pressurized gas is an inert gas.

10. A fire extinguishing system as defined in claim 9 wherein said inert gas is nitrogen.

11. A fire extinguishing system as defined in claim 7 wherein said self-contained source means is pressurized in the range of 25 - 40 psi.

12. A self-contained fire extinguishing system of the type using high expansion foam comprising:

a. a source of pressurized, inert gas;

b. at least one reservoir adapted to contain high expansion foam producing fluid, said reservoir coupled to said source of pressurized, inert gas; and

c. a foam generator having an enclosure of top, bottom, rear and side walls defining an orifice through said bottom wall, a multilayer screen including a first honey-combed layer and a second plated mesh layer, said multilayer screen being horizontally disposed and secured to portions of said top and bottom walls, a manifold having a plurality of spaced openings therein being disposed within said enclosure and coupled to said reservoir, and a plurality of nozzles each being coupled to one of said spaced openings and being opposite said multilayer screen and adapted to output said foam producing fluid uniformly upon said multilayer screen whereby the output of said foam producing fluid from said plurality of nozzles causes ambient air to be drawn through said orifice.

13. A fire extinguishing system as defined in claim 12 wherein said mesh layer is plated with an active metal selected from a group consisting of cadmium, zinc, chromium and platinum.

14. A fire extinguishing system as defined in claim 12 wherein said inert gas is nitrogen.

15. A fire extinguishing system as defined in claim 12 wherein said inert gas is pressurized in the range of 25 - 40 psi.