CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority from Italian patent application no. 102019000023679 filed on 11/12/2019, the entire disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention concerns a fire extinguishing system for a firefighting vehicle or device, in particular a compressed air foam system (CAFS) provided with an improved air management system.

BACKGROUND OF THE INVENTION

Firefighting systems, e.g. firefighting vehicles or devices, are provided with fire extinguishing systems configured to supply a fire extinguishing compound to be directed towards a fire in order to lead to its suppression.

In particular, compressed air foam systems (CAFS) are widely known in the art and are directed to the use a mixture of a preset percentage of compressed air and a water/foam agent solution. In greater detail, the water/foam agent solution comprises a foam agent additive dissolved into a great quantity of water, i.e. from 0,5 to 3% or to 8% in volume of additive. The compressed air is mixed to such solution into a mixing chamber module.

Such air-solution mixture is at higher pressure with respect to atmospheric pressure and is ejected by an outlet of a pipe directed to the fire, it expands forming a foam which has the properties to extinguish the fire. In particular, the air quantity of the foam can be regulated to assume a value comprised between 3 to 20 volume parts of air with respect to liquid solution. As defined in standard DIN

EN 16327, such an air/solution ratio comprised between 3 and

10 is defined a "wet foam", while an air/solution ratio comprised between 11 and 20 is defined a "dry foam".

According to the above, the main issue related to a CAPS system is to continuously measure the air flow and the water flow to be mixed together to provide a desired air/solution ratio. Therefore the measure of the two above flows is crucial.

While the measure of the water flow is substantially simple, the measure of air flow which can space between 3000 and 60001/min is not so direct.

A first way to measure the air flow is to use conventional air flow meters; however, these latter are very sensitive to condensation in the air because deposit of water or other particles carried by the air flow may deposit on the sensor and interfere with the current measurement signal, thereby modifying, slightly or even totally, the measured air flow.

A solution to the above problem has been found in air dryers that can be placed fluidically upstream with respect to the compressor voted to provide the compressed air flow in order to condensate the water present in the air sucked by the compressor. However, for the above mentioned air flow values involved, such air driers would have such a dimension that cannot be used on firefighting movables devices/vehicles .

Another known solution to measure the air flow rate is to use mass air flow sensors, as known in the fields of engine. Indeed, the air flow speed is so low with respect to their usual operative field that air cannot condensate at the sensor because the pressure drop is small.

However, the air flow may vary continuously because the flow or air/solution mixture can be continuously changed by the operator according to the condition of the fire. Such oscillations in the value of air flow lead to make oscillate mass air flow sensor, thereby providing vibration and noises in the system.

Another alternative solution could be to provide valves configured to have a working range from 40 to 4800 1/min. however, such valves are extremely expensive to be manufactured and not usual on the market.

According to the above, it's still a problem to measure and guarantee a correct pressurized air flow for CAFS system.

Therefore, the need is felt to provide CAFS system that can provide a quick and precise regulation of the air- solution mixture according to user's necessities.

An aim of the present invention is to satisfy the above mentioned needs in a cost-effective and optimized way.

SUMMARY OF THE INVENTION

The aforementioned aim is reached by a compressed air foam systems as claimed in the appended set of claims.

BRIEF DESCRIPTION OF DRAWINGS

For a better understanding of the present invention, a preferred embodiment is described in the following, by way of a non-limiting example, with reference to the attached drawings wherein:

• Figure 1 is a schematic representation of an innovative portion of the compressed air foam system according to the present invention;

• Figure 2 is a schematic representation of possible combination for providing an element of the compressed air foam system according to the present invention, and • Figure 3 is a schematic representation of the compressed air foam system according to the present invention

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 discloses a compressed air foam system, CAFS, 1 essentially comprising compressor means 2, an air regulation system 3 and a mixing chamber module 4. In particular, the compressor means 2 are fluidly connected in series to the air regulation system 3 which is fluidly connected in series to the mixing chamber module 4.

In greater particular, the compressor means 2 are configured to increase the pressure of air taken by an appropriate source 5, e.g. the atmospheres thanks to an air filter, between an inlet 2a and an outlet 2b of the compressor means 2. As known, the compressor means 2 may be of any typology according to the power request of the CAFS

1.

From the opposite side of the air regulation system 3, the mixing chamber module 4 comprises, schematically and essentially, a first inlet 4a fluidly connected to air regulation system 3, a second inlet 4b fluidly connected to a source 6 of foam solution, of known typology and an output

4c fluidly connected to an extinguishing equipment 7 configured to allow the ejection of the foam mixed in the mixing chamber module 4. It's clear that such extinguishing equipment 7 may be of any typology, e.g. a pipe comprising a dedicated nozzle at its termination.

The CAFS 1 advantageously comprises safety means 8 fluidly interposed between compressor means 2 and air regulation system 3 configured to allow the discharge of the compressed air pumped by compressor means 2 into air regulation system 3 if the pressure of such compressed air reaches a predefined value.

Preferably, such safety means 8 may comprise a pressure relief valve 9 fluidly connected downstream to output 2b and upstream to air regulation system 3 and configured to open and allow discharge of air regulation system 3 if its pressure reaches a threshold value, e.g. about 11 or 12 bar, being usually 10 bar the pressure of compressed air.

Safety means moreover allows to maintain stable the value of the pressure provided from compressor means 2 to air regulation system 3, avoiding pressure peaks.

Air regulation system 3 comprise according to the invention, a plurality of dosing modules 10 fluidly interposed in parallel between output 2b of compression means

2 and mixing chamber module 4, each dosing module being configured to be controlled to allow the passage of air from compression means 2 to mixing chamber module 4 and being configured to allow the passage of a predefined flow, which is different with respect to at least another of the dosing modules 10. In the exemplarily embodiment, seven different dosing modules 10 are fluidly interposed in parallel between compression means 2 and mixing chamber module 4.

Each dosing module 10 may comprise valve means 11 and a nozzle 12 fluidically in series one with respect to the other wherein the valve means 11 are upstream to the respective nozzle 12 and allows or deny the passage of air from compressor means 2 to nozzle 12. Each nozzle 12 is then fluidically directly connected to mixing chamber module 4.

According to a further aspect of the invention, a first dosing module 10 has a first base flow value and the other dosing modules have different flow values that are at least

N-times, wherein N is preferably an integer, of the first base flow value. Preferably, the other dosing modules have each a flow value which is the double of the preceding one.

Accordingly, in the disclosed embodiment the seven dosing modules 10 allows a modulation of the flow rate according to 2 ⁷ , i.e. 128, possible values for managing the flow rate in input to mixing chamber module 4.

Preferably, the first dosing module may be sized to allow a 50 1/m flow rate and as said above, the second 100

1/min, the third 2001/min, the fourth 4001/min, the fifth

800 1/min, the sixth 16001/min and the seventh 32001/min.

Furthermore, according to DIN EN 16327 the solution flow should be comprised between 200 to 16001/min, the air flow rate should be at least 3 times higher, i.e. 600 to

4800. According to the proposed embodiment, the theoretical maximum value is 63501/min, therefore the 600-48001/min of air range can be easily provided.

Since the pressure is maintained constant at the output of compressor means 2, thanks also to pressure relief valve

9, the flow of each dosing module 10 sum up to the mixing chamber module 10, thereby providing a desired air flow rate with a precision set by the minimum flow rate dosing module.

Indeed, by opening more valve means 11 at the same time, the flows passing through different nozzles 12 merge.

According to the above listed values, flows from 50, 100,

150 [...] up to [...] 6250, 6300, 6350 can be provided to air mixing chamber module, by modulating the opening of valve means 11.

According to a further aspect of the invention, each nozzle 12 can be realized by coupling together a specific number of smaller flow nozzle. Indeed, as shown in figure 2 which describes a possible set of nozzles bores, a 1001/min nozzle may be composed by two 501/min bores and a 32001/min nozzle may be composed by eight 4001/min bores. Therefore, as shown graphically, thanks to only two bores, all the possible ranges of flow rate may be achieved easily.

CAFS 1 further comprises a control unit 13 connected to mixing chamber module extinguishing equipment 7, to water flow rate sensors and to each valve means 11. Such control unit 13 is configured to control the opening or closure of each valve means 11 according to a signal coming from extinguishing equipment 7 and/or mixing chamber module 4.

Advantageously, such control unit 13 is an electronic control unit and therefore valve means 11 are electrically actuated valves and the aforementioned signals are signals provided by sensors configured to provide an estimation of related quantities from mixing chamber module 4 (i.e. mixing chamber module the water/solution flow provided at the mixing chamber module 4) and the extinguishing equipment 7, e.g. the flow rate of air-foam solution selected by the operator.

Indeed, the operator may select a desired air-foam solution, e.g. by pushing a button or by selecting on a specific display, and the control unit 13 is configured to elaborate the valve means 11 combination which has to maintained opened or closed to achieve such value. Therefore, it's necessary that the control unit 13 has memorized or has access to a memory where the value of the flow rate of each specific dosing module of the air regulation system 3 is stored, in order to select the correct opening/closure combination of valve means 11. Preferably, each value of desired air flow rate at the mixing chamber module 4 can be memorized with the associated opening/closure combination of the related valve means 11. Figure 3 discloses a more complete arrangement of a possible embodiment of all the elements of a CAFS 1.

In particular, compressor means 2 can be provided, in parallel, with further compressor means 2' configured to supply a further flow of compressed air, e.g. if such e compressor means 2, 2' are of low dimensions. Clearly, each compressor means 2, 2' can be provided with respective check valves 20, 20'.

The air regulation system 3 comprises, in the depicted case, eight dosing modules 10, each comprising valves 11 and nozzles 12 as detailed described above. As said, the air regulation system is configured to provide a 50 to 3000 (and optionally to 6000 or more) air flow rate.

The air regulation system 3 is then fluidly connected to mixing chamber module 4 and provided with a related check valve 21 and it's connected to safety means 8, as described above, and that may furthermore comprise pressure sensor means 26.

In detail, water supply to mixing chamber module 4 is spilled from a vehicle water supply line 22 which is fed by a related pump 23 configured to increase the pressure of water taken from a source, e.g. a tank carried by the vehicle. On the conduit fluidly connecting the water supply line 22 and the mixing chamber module 4, CAFS 1 may further comprise an optional reduction stage 24, per se known and therefore not described into detail, configured to reduce water supply to the mixing chamber module 4 if such water is needed for other priority operational uses by the vehicle.

Furthermore, always on the conduit fluidly connecting the water supply line 22 and the mixing chamber module 4

CAFS 1 comprises water flow meter means 25 configured to measure the flow rate of the water coming to mixing chamber module 4. In particular, water flow meter means 25 can measure a water flow rate, e.g. between 0 to 30001/min.

Optionally, upstream and downstream to reduction stage

3, CAFS 1 may also be provided with pressure sensor means 26 configured to detect the water pressure coming to mixing chamber module 24.

CAFS 1 is further provided with an additive dosing module 27 configured to provide a measure additive quantity to mixing chamber module 4. In particular and exemplarily additive dosing module 27 comprises an additive reservoir 28 from which, thanks to a pump 29, additive is pumped to mixing chamber module 4. On the conduit fluidly connecting the pump

29 to mixing chamber module 4 the additive dosing module 27 comprises safety means 8, preferably provided with a relief valve 9, to maintain the pressure below a preset threshold, e.g. 16 bar.

Additive dosing module 27 is furthermore provided on the conduit fluidly connecting the pump 29 and the mixing chamber module 4 CAFS 1 comprises additive flow meter means

30 configured to measure the flow rate of the additive coming to mixing chamber module 4. In particular, additive flow meter means 25 can measure a water flow rate between 0 to 30-60 1/min.

Accordingly, in the proposed embodiment, the mixing chamber module 4 is configured to mix together both the water, the additive and the air flow to provide the air/solution mixture to the extinguisher device 7.

Therefore, mixing chamber module 4 comprises a first mixer 31 configured to mix together the flow of water and the flow of additive and a second mixer 32, downstream to the first mixer 31, configured to mix together the water- additive solution with the air flow, thereby generating the solution-air mixture to be ejected by the extinguisher device

7. The water flowmeter 25, the additive flowmeter 25 and, where present, the pressure sensors 26 are all electrically connected to the electronic control unit to allow the elaboration of the correct air flow to be provided at the mixing chamber 4.

The operation of a CAFS 1 according to the present invention and as described above is the following.

The operator of the extinguishing device 7 selects a specific value of air-foam flow rate.Accordingly, a specific signal (calculated, as stated before, by electronic control unit) is provided to the control unit 13 which elaborates/elect the correct opening/closure combination of valve means 11.

For sake of the example, based on the above exemplarily values, if the operator needs a 1350 air flow to mixing chamber module, then the valve means of the first, second, fourth and fifth dosing modules 10 will allow the passage of fluid, thereby providing the correct air flow value.

The control of water and additive flow is per se known and therefore will be not described in detail. Again, the electronic control unit 13, knowing the needed air-solution mixture flow at the operator and the characteristic of the latter, will control consequently the water and solution flow to mixing chamber module 4.

According to the above, the present inventions is furthermore directed to a method for providing a predefined air flow rate to a mixing chamber module 4 of CAFS system comprising the steps of:

• Acquiring data related to the air flow rate needed at the mixing chamber module 4 of the CAFS 1;

• Selecting a specific combination of valve means 11 opening of at least one dosing module 10 which would comply with the needed air flow rate at the mixing chamber module 4;

• Actuating valve means 11 of the respective at least one dosing module 10 selected at the preceding point.

The aforementioned method can be advantageously memorized and carried out by elaboration means of an electronic control unit 13 as described above.

In view of the foregoing, the advantages of a compressed air foam system, CAFS, 1 according to the invention are apparent.

The proposed control is stable, robust and precise and can be realized in an economic way. Indeed, since pressure difference is maintained constant at openings of nozzles 12, their flow rate can be easily determined and it is insensible to dirty particles and to water condensation. Furthermore, nozzles have not the vibration/noise problems of the prior art systems and can be compacted in a very small space. For sake of example, a 4001/min nozzle has a diameter of only

2-3 mm.

Furthermore, the wear of such nozzles can be checked with cost-effective means such as feeler gauges and therefore the accuracy can be tested within time. Furthermore, since simple and mechanical elements are used, the CAFS 1 is particularly robust and can be used in different atmospheric conditions.

The use of the system is so simple, i.e. there is no need of complicated electronic controls, that also untrained personnel may use an extinguishing equipment base of the proposed CAFS 1.

In particular, the use of a twice-by-twice nozzle system provided a substantially binary system that can be controlled thanks to very simple software, e.g. thanks to memorized tables which defines a binary sum between nozzles.

Furthermore, the delays of slow-controlled systems (to avoid vibrations) are overcome, since the proposed CAFS 1 has immediate response.

The pressure relief valve 9 provides the defined inlet pressure upstream of the nozzle 11 in a simple and robust way.

It is clear that modifications can be made to the described compressed air foam system, CAFS, 1 which do not extend beyond the scope of protection defined by the claims.

First, the above described possible dosing module 10 combination is particularly advantageous because of its economies in manufacturing, however it's clear that different possible number of dosing modules 10 may be provided, comprising different values of minimum flow rate and different distribution of flow rate among them. Indeed, such characteristic may be customized according to the specific use of the extinguishing equipment 7.

As already said, valve means 11, compressor means 2 and extinguishing equipment 7 may be varied according to the typology of firefighting device/vehicle. Furthermore, it's also possible, even if not economic, to provide a hydraulic or pneumatic control of valve means

11 according to the claimed method.