Foam former and foam sprinkler

Abstract

The invention relates to an optimized foam former (1) for foaming a foam-water concentrate, which foam former consists of a curved grate having diamond-shaped openings (13) and sharp edges (12). The structure of the foam former increases the foam formation and ensures uniform distribution of the foam over a large area. Existing water sprinklers having a nozzle (3) and a spray disk (2) can be provided with the foam former (1) and thus converted into foam sprinklers in a simple manner. The foam former (1) is arranged in such a way that the foam former (1) protrudes beyond the spray disk (2) toward the nozzle (3).

Description

[0001] The present invention relates to a foam sprinkler according to patent claim 1. Foam sprinklers are mainly used in the field of firefighting, since certain fires, in particular liquid fires, cannot be effectively fought with water but only with extinguishing foam.

[0002] Firefighting foam consists primarily of filling gas (e.g., air), water, and a foaming agent. The water and foaming agent are usually in the form of a liquid foam concentrate, which is distributed in the fire area via several foam sprinklers during a fire. To foam the foam concentrate, the liquid is typically forced through a sieve. Similar to beating egg whites into ice with a whisk, beating with the sieve causes foam formation by mixing air into the foam concentrate. US 2015 / 0375271 A1 presents a spraying device in which the foam-forming sieve is tubular and consists of a rolled-up metal expanded metal mesh. GB 1356654 A presents a device for foaming a foam concentrate, with an outlet pipe having foam-forming projections on its inside.These projections can be provided by arranging an expanded metal mesh on the inside of the outlet pipe.

[0003] The ratio between the volume of the generated foam and the volume of the original foam water concentrate is called the "expansion factor." Depending on the application, different expansion factors are advantageous; these are classified as follows: Replacement page for page 2 of the description

[0004] Low expansion foam with an expansion ratio < 20 Medium expansion foam with an expansion ratio ≥ 20 to < 200 High expansion foam with an expansion ratio ≥ 200

[0005] To extinguish fires of fire class B (fires involving liquid or liquefiable substances), it is advantageous to use low expansion foam with an expansion factor between 2 and 20.

[0006] The state of the art presents various solutions for combining a sprinkler with a strainer to provide a foam sprinkler.

[0007] US 3,830,309 presents a device for foaming a foam water concentrate, in which the foam water concentrate is thrown through a foam-forming sieve consisting of a metallic expanded metal mesh.

[0008] EP 3266503 A1 discloses a foam sprinkler in which a sieve in the form of a cage is arranged laterally around the spray disc.

[0009] As patent application JP 2016182225 A discloses, a strainer can be placed between the outlet of a sprinkler supply line and the spray deflector. A disadvantage of this foam sprinkler is that the foam water concentrate is first foamed through the strainer, and the foam is then distributed over the spray deflector. Due to the low density of the foam, the distribution effect of the spray deflector is limited, and the foam is slowed down and even partially reliquefied. Conversely, according to JPS 53146298 U and JP 407299156 A, the spray deflector is placed between the outlet of the sprinkler supply line and the strainer. A disadvantage of the foam sprinklers according to JP 2016182225 A, JP 407299156 A, and JPS 53146298 U is that the strainer completely encloses the outlet of the supply line. Sprinklers are usually equipped with a shutter which is pushed out and ejected when triggered.In the presented arrangement, the closure gets stuck in the sieve and thus impairs the flow and the uniform distribution of the foam.

[0010] The patent JP H07 299156 A already describes a foam sprinkler according to the state of the art.

[0011] Patent DE 195 39 991 C1 presents a foam sprinkler with a sieve positioned behind the spray disc in the direction of flow of the foam concentrate. Foaming therefore occurs largely outdoors, after the foam concentrate has been distributed via the spray disc. However, the foam concentrate is already partially pre-foamed upon impact with the spray disc. This solution poses the risk of overloading or clogging the sieve because the foam concentrate and the foam generated are driven through the sieve solely by their own momentum and tend to stick to it. For this reason, a perforated sheet with large, round holes was used as the sieve, which is also positioned at a considerable distance from the spray disc. The spray disc is usually designed to distribute the liquid in all directions, including back up.When using such a conventional sprinkler, only about 60% of the foam concentrate distributed over the spray deflector passes through the screen, and the larger, round holes improve the flow of the foam concentrate. However, this results in a smaller amount of foam with a lower average expansion index.

[0012] Various solutions have been proposed in the patent literature to optimize foam formation in the sieve area. JP 2001046543 A, JP 2016182225 A, US 5,820,027, EP 2572795 A1, GB 724185 A, and US 5,404,957 present foam nozzles with two consecutively arranged sieves, whereby the foam can continue to develop through each additional sieve. JP 2001046543 A presents another solution in which the foam nozzle is equipped with a single sieve, through which the foam water concentrate is centrifuged twice. Other common solutions consist in designing the sieve in a conical shape (see e.g. FR 2575082 A1, US 2013 / 0037282 A1, WO 2008 / 050973) or providing it with folds (see DE 100 04 916 A1).All these existing solutions follow the same approach: to optimize foam formation, a larger sieve surface is used, either by increasing the area of a single sieve or by using multiple sieves.

[0013] However, this approach and the specific solutions presented are difficult to implement with foam sprinklers. One reason for this is that the foaming process takes place outdoors, not in a pipe. It's difficult to force the foam water concentrate through conical, folded, or even multiple screens arranged one behind the other and then still distribute it with sufficient force over a large area. Added to this is the overall length of the foam sprinkler, which ideally should be as short as possible, reducing the risk of the sprinkler being knocked off by a forklift or a lifted load, for example, in a warehouse.

[0014] The present invention aims to improve a foam generator and a foam sprinkler of the type mentioned above in such a way that optimal foam formation over a wide pressure range and even foam distribution over a large area are ensured. Furthermore, the foam generator should be lightweight, compact, retrofittable to existing water sprinklers, and cost-effective to manufacture.

[0015] This object is achieved by a foam former having the features of patent claim 1 and a foam sprinkler having the features of patent claim 7. Further features and embodiments emerge from the dependent claims and their advantages are explained in the following description.

[0016] In the figure shows: Figure 1a-bSchematic arrangements of the nozzle, spray deflector, and foam generator, in section Figure 2aFoam sprinkler in use with water and spray pattern Figure 2bFoam sprinkler in use with foam water concentrate and spray pattern Figure 3aBars with a smaller thickness in the direction of flow than the width perpendicular to the direction of flow Figure 3bBars with a greater thickness in the direction of flow than the width perpendicular to the direction of flow Figure 4aDetail of a diamond-shaped opening Figure 4bDesign variant of the foam generator, top view Figure 5a-dPossible fastenings of the foam generator to the sprinkler of the nozzle, in section Figure 6aDesign variant of the foam generator with threaded rod, in section Figure 6bDesign variant of the sprinkler with foam generator and threaded rod Figure 7aDesign variant of the foam generator with folding rosette, in section Figure 7aDesign variant of the sprinkler with foam generator and folding rosette, in section

[0017] The figures represent possible embodiments, which are explained in the following description.

[0018] Conventional water sprinklers consist of a nozzle 3 and a spray disc 2, which are connected by connecting parts 4. The spray disc 2 is positioned at a distance from the nozzle 3's orifice in a central position aligned with the longitudinal axis of the nozzle 3. This spray disc 2 serves to distribute a liquid flowing from the nozzle 3 so that this liquid is distributed as homogeneously as possible and over a large area in the area surrounding the foam sprinkler.

[0019] To provide a foam sprinkler, existing water sprinklers can be provided with the foam former 1 according to the invention ( Figure 1a). The foam former 1 is arranged behind the spray disc 2 in the flow direction of the foam water concentrate, so that the foam water concentrate is first accelerated, pre-foamed and distributed over the spray disc 2, and then foamed by the foam former 1. It is particularly advantageous if the foam former 1 has a curved shape in the direction of the nozzle 3 and is arranged such that the foam former 1 protrudes beyond the spray disc 2 in the direction of the nozzle 3 and the spray disc 2 is thus located "inside the foam former" 1. Another possible embodiment, in which the foam former 1 has a depression in the middle, is shown in the Figure 1bshown. Since the entire foam water concentrate is propelled through the foam generator 1, regardless of the direction in which it is distributed by the spray disc 2, a maximum amount of foam is formed with the most uniform bubble size possible. This design with the spray disc 2 in the foam generator 1 also has the advantage of being significantly more compact than existing devices, since the overall length of the sprinkler is only slightly affected by the additional foam generator 1.

[0020] For applications where no sprinkler is required, for example, when the extinguishing system is triggered centrally via a fire alarm, the foam generator 1 can, of course, also be mounted directly in front of a nozzle 3. This nozzle 3 can also be additionally equipped with a spray disc 2 to adapt the spray pattern to the desired area of application.

[0021] When the sprinkler is triggered, the cap of nozzle 3 is typically tilted sideways by a spring and ejected. To prevent this cap from getting caught in the foam generator 1, a sufficient distance must be maintained between the edges of the foam generator 1 and the nozzle 3 opening. Catching the cap in the foam generator 1 must be avoided at all costs, as this would otherwise impair the flow and uniform distribution of the foam.

[0022] The foam imager 1 consists of a grid with bars 11 and openings 13 (see Figure 4b For use with a sprinkler, the grille is made of metal, such as stainless steel, brass, aluminum, or any other metal or metal alloy, as required. For other applications in lower temperature ranges, the grille may also be made of plastic or other sufficiently stable materials.

[0023] According to the invention, the foam generator 1 must meet two essential criteria. First, it should impede the flow of the foam water concentrate or foam as little as possible, so that the foam maintains a high velocity and the spray pattern is not affected. Second, the foam generator 1 should ensure the best possible and uniform foam formation, regardless of the operating pressure.

[0024] To achieve good flow, the openings 13 of the foam generator 1 must be sufficiently large. For the present invention, a minimum diameter of more than 1 mm, preferably more than 4 mm, is provided. Such sizes avoid any risk of overloading or clogging of the foam generator 1, even and especially at particularly high flow rates. Foam sprinklers with a K-factor between K20 and K160, and even K200, have been developed.

[0025] The foam sprinklers presented here can therefore achieve particularly high flow rates of extinguishing agent at the same pressure. Existing foam sprinklers currently available on the market have a maximum K-factor of 115. Thanks to the higher performance of the foam sprinklers according to the invention, a better and faster extinguishing effect can be achieved.

[0026] Since the presented foam generator 1 neither influences nor impairs the spray pattern of the sprinkler, the same sprinkler can be used to spray both foam water concentrate for producing foam 6 and pure water 5 ( Figures 2a-bThis has advantages, for example, for warehouses that are being converted or where different materials are stored alternately, so that the sprinkler system can sometimes be operated with extinguishing foam and sometimes with water, depending on the material stored. Since the spray pattern does not change when retrofitting with a foam generator according to the invention, this also has the advantage that all calculations that have already been made remain valid and applicable. This can be important if an existing sprinkler system, which was previously used with an extinguishing agent containing fluorine for better foam distribution, is now used with a foam generator so that a fluorine-free extinguishing agent can be used.

[0027] In order to achieve the best possible foam formation, the foam former 1 is preferably used with the following properties.

[0028] Foam formation occurs through the addition of air to the foam water concentrate. To promote this mixing, it is advantageous to create turbulence in the foam water concentrate in the area of the foam generator 1 and to increase the contact area between the foam water concentrate and the air.

[0029] To generate a turbulent flow of the foam water concentrate, the webs 11 of the grid have an elongated cross-section, the longitudinal direction B of which is approximately perpendicular to the flow direction A ( Figure 3a ). It is particularly advantageous if the ratio b / d width / thickness of the webs 11 is greater than 1, preferably greater than 1.4 ( Figure 3a). This prevents the formation of a laminar flow in the area of the openings 13 and enables the formation of turbulence behind the webs 11 between two adjacent openings 13. If the webs 11 are wider than 1 mm, preferably wider than 1.5 mm, there is air in the area 7 behind the webs 11, which is mixed with the foam water concentrate by the effect of the turbulence and promotes foaming. Webs 11 that have a large thickness d in the flow direction A and a small width b perpendicular to the flow direction B are unfavorable for the formation of turbulence, since there is only little air in the area 7 behind the webs 11 and the flows behind the openings 13 can converge without significant turbulence ( Figure 3b). To further promote the generation of turbulence, the webs 11 according to the invention preferably have sharp, angular edges 12. Sharp, angular edges 12 cause a strong deflection of the liquid from the webs 11 and promote the generation of turbulence and thus the formation of foam.

[0030] As it flows through the foam former 1, the foam water concentrate stream is divided into many smaller, separate streams by the webs 11. The contact area between the foam water concentrate and the air can therefore be influenced by the number of webs 11 on the grid. To increase the number of webs 11 on the grid, the shape of the openings 13 was optimized such that the grid has a longer total edge length for the same total area. According to the invention, the grid has diamond-shaped openings 13 with diagonals x and y ( Figures 4a-b). Simple calculations show that with diamond-shaped openings 13, the circumference / area ratio of the opening 13 is significantly larger than with round, square, or rectangular openings. The decisive factor for the optimal effect of the foam former 1 is the ratio of the length of the diagonals x / y of the diamond-shaped openings 13. If the ratio is too small, for example, with x / y = 1, the openings 13 are square, which reduces the edge length. If the ratio is too large, for example, with x / y > 5, the diagonal b is too short and the opening 13 too narrow, which impairs the flow of the foam water concentrate or the foam. Tests have shown that optimal x / y ratios are between 1.5 and 4, particularly advantageously between 2 and 3. In this case, the term "diamond-shaped" also refers to the shape of a parallelogram, i.e., a quadrilateral that does not necessarily have four sides of equal length.

[0031] A possible, particularly effective design variant of the foam former has a grid with the following dimensions: width b of the webs 11 approx. 1.0-1.5 mm, thickness d of the webs 11 approx. 0.5-1.0 mm, length x of the openings 13 approx. 1.0-1.5 cm and width y of the openings 13 approx. 3.0-7.0 mm, with b / d ≅ 1.5 and x / y ≅ 2.4.

[0032] Such a grid can be manufactured by various methods, for example by punching and subsequent curving of a metal sheet, by sintering, or any other conventional manufacturing method. The use of a commercially available expanded metal mesh or expanded metal sheet has proven particularly efficient. With expanded metal mesh, the openings 13 are produced without material loss, and sharp edges 12 are also created. In addition, expanded metal mesh is commercially available in many dimensions and materials and is therefore inexpensive. When curving a flat expanded metal mesh or a metal sheet to form the foam former 1 as shown in Figures 1a-f and4b As shown, the shape and dimensions of some openings 13 may deviate slightly from the ideal value, particularly around the edges of the foam screen 1, where the curvature is most pronounced. However, it has been shown that this does not affect the effectiveness of the foam screen 1.

[0033] Thanks to the optimized shape of the openings 13 and the specific diameter of the webs 11 in the grid, a foam former 1 is provided that ensures strong foam formation despite the large openings 13. Tests have shown that with such a foam former 1, expansion ratios between 4 and 20 can be achieved. With the large openings 13, the flow of the foam water concentrate is neither influenced nor impaired, so that the foam is evenly distributed in the surrounding area and the foam former 1 is not overloaded, even at high flow rates. It has also been shown that foam formation with the presented foam former 1 works very well over a wide range of pressures and flow rates. Pressure ranges from 0.5 to 15 bar and flow rates between 10 and 1,000 liters per minute were tested. Flow rates of up to 10,000 liters per minute are also possible.This is particularly advantageous for foam sprinklers used to fight fires: When a fire breaks out, only those foam sprinklers located closest to the fire are activated, depending on the fire's requirements. The pressure in the sprinkler system's pipes is therefore very high, as is the flow rate of the affected foam sprinklers. As the fire spreads, more and more foam sprinklers are activated, so that the pressure in the pipes and the flow rate per foam sprinkler decrease. With the foam pattern 1 according to the invention, the spray pattern is kept constant even with large fluctuations in these values, thus achieving optimal extinguishing effectiveness.

[0034] The foam generator 1 according to the invention is also very suitable for retrofitting an existing sprinkler. Figures 5a to 5cshow how the foam generator 1 can be connected to the sprinkler using adapters 14. The adapter 14 is used for the correct positioning and attachment of the foam generator 1 to the sprinkler with very little time expenditure. It is important with the geometry of the adapter 14 that the spray pattern is not affected when retrofitting the foam generator 1 to an existing sprinkler, i.e., the connections between the foam generator and the sprinkler should, if possible, be positioned where a spray shadow already exists. If the foam generator 1 has a depression in the middle, the depth of this depression can be adjusted so that the foam generator 1 can be attached directly to the spray disc 2 without the adapter 14 ( Figure 5d ).

[0035] In the preferred embodiment, the adapter 14 consists of an elongated threaded rod 141, which is arranged in the center of the foam former 1 ( Figure 6a). For example, the threaded rod 14 protrudes from the inside through the central opening of the grille and has a nut with which the foam generator is attached from the outside. The spray disc 2 of the sprinkler is equipped with a thread in the middle, onto which the threaded rod 141 can be screwed. In the assembled state, the threaded rod 141 is arranged behind the spray disc 2 in the direction of flow ( Figure 5a ). The Figure 6b shows an embodiment of the invention in the assembled state.

[0036] In another possible embodiment, the adapter 14 has a folding rosette 142 ( Figure 7a ), which is attached to the recess below the nut with which the sprinkler was screwed to the pipe ( Figure 7b This folding rosette allows the foam imager to be positioned correctly, securely fastened, and retrofitted with very little time.

[0037] Another possible variant is to attach the foam generator to the connectors with which the spray plate is attached to the sprinkler ( Figure 5c ). This could be achieved, for example, by clamps or other suitable means.

Claims

1. A foam sprinkler comprising a nozzle (3), a spray plate (2), and a foam generator (1) for foaming a foam water concentrate, wherein the foam generator (1) consists of a curved grid with webs (11) and openings (13), the foam generator (1) is designed symmetrically to the center of the curvature, the openings (13) are rhombic, and the edges (12) of the webs (11) are sharp and angular, the foam generator (1): - either has a depression (1) in its center, which is directly attached to the spray plate (2), wherein the foam generator (1) is symmetrically attached to the spray plate, - or has an adapter (14) with which it is connected to the spray plate (2) or to the nozzle (3), wherein the foam generator (1) is symmetrically attached to the nozzle (3), wherein the spray plate (2) is located between the nozzle (3) and the foam generator (1) so that during operation of the foam sprinkler, the foam water concentrate is first accelerated, pre-foamed, and distributed over the spray plate (2), and then foamed by the foam generator (1), the foam generator (1) extends beyond the spray plate (2) in the direction of the nozzle (3) so that the spray plate is located within the foam generator, the nozzle (3) has a closure that is ejected sideways when the foam sprinkler is activated, and the curvature of the foam generator ends in a wide, open rim, and there is an opening between this rim and the other elements of the foam sprinkler, allowing the closure to be ejected sideways when the sprinkler is activated without getting caught in the foam generator (1).

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