Fire extinguisher

Abstract

A fire extinguisher includes a body defining a storage chamber containing an extinguishing agent, a gas generator configured to pressurize the extinguishing agent in order to dispense it outside the body through an exit opening. The exit opening is equipped with a misting nozzle, and the extinguishing agent has a solidification temperature less than −10° C., the saturating vapor concentration of the extinguishing agent taken at −10° C. and at 1 bar being less than the extinguishing concentration of the extinguishing agent determined according to the ISO 14520 standard for a heptane fire at 1 bar.

Claims

1. A method for extinguishing a fire in an environment with a temperature less than or equal to 10° C., comprising at least one step of dispensing an extinguishing agent by a fire extinguisher comprising: a body defining a storage chamber containing the extinguishing agent, a gas generator configured to pressurize the extinguishing agent in order to dispense it outside the body through an exit opening, the exit opening being equipped with a misting nozzle, and the extinguishing agent having a solidification temperature less than −10° C., a saturating vapor concentration of the extinguishing agent taken at −10° C. and 1 bar being less than an extinguishing concentration of the extinguishing agent determined according to the ISO 14520:2015, 3.sup.rd edition, standard for a heptane fire at 1 bar, and wherein the misting nozzle generates liquid droplets of extinguishing agent with a size less than or equal to 50 μm at −10° C., the extinguishing being ensured by a two-phase flow of the extinguishing agent prior to its contact with the fire zone.

2. The method according to claim 1, wherein the gas generator is configured to impose a maximum pressure on the extinguishing agent greater than or equal to 3 bar.

3. The method according to claim 2, wherein the gas generator is configured to impose a maximum pressure on the extinguishing agent greater than or equal to 7 bar.

4. The method according to claim 1, wherein the extinguishing agent is FK-5-1-12.

5. The method according to claim 1, wherein the gas generator comprises a pyrotechnic gas generator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the invention will be revealed by the following description, given without limitation, with reference to the appended drawings, in which:

(2) FIG. 1 shows schematically in longitudinal section and example of an extinguisher according to the invention,

(3) FIG. 2 is a perspective view of a portion of the extinguisher of FIG. 1, and

(4) FIGS. 3A and 3B show the displacement of the movable wall in the example of the extinguisher of FIG. 1 during the dispensing of the extinguishing agent.

DETAILED DESCRIPTION OF EMBODIMENTS

(5) Shown in FIG. 1 is an example of a fire extinguisher according to the invention.

(6) The device 1 includes a body 2 extending along a longitudinal axis X and defining a storage chamber 4 in which an extinguishing agent (not shown) is present. The extinguishing agent can be present in the liquid state. In the case where the extinguisher is used at high temperature, the extinguishing agent can be in the gaseous state. Prior to the beginning of dispensing, the storage chamber 4 can have a non-zero free volume (i.e. a non-zero volume not occupied by the liquid medium containing the extinguishing agent). As a variant, the entire volume of the storage chamber is occupied by the liquid medium containing the extinguishing agent prior to the beginning of dispensing.

(7) FK-5-1-12 or Novec™ 1230 (perfluoro-4-(trifluoromethyl)-3-pentanone) can be cited for example as examples of usable extinguishing agents.

(8) In one exemplary embodiment, the extinguishing agent can have a saturating vapor pressure less than or equal to 70 mbar at −10° C. FK-5-1-12 in particular verifies this condition.

(9) The extinguishing agent has a solidification temperature less than −10° C. It is thus in the liquid state when it is dispensed at −10° C. The solidification temperature of the extinguishing agent can in particular be less than or equal to −55° C. in certain extreme cases.

(10) The extinguishing agent can have a viscosity at −10° C. less than or equal to 2 centistokes.

(11) The body 2 also defines, in the example illustrated, a pressurization chamber 5 comprising a gas generator 20. In the example of FIG. 1, the gas generator 20 is a pyrotechnic gas generator. In a variant, not illustrated, the gas generator can be a cartridge of pressurized gas. The gas generator comprises at least one recess in which a pyrotechnic charge is present. More precisely, in the example illustrated in FIG. 1, the gas generator 20 includes an initiator 26 allowing initiating the combustion of the booster 27 which will trigger the combustion of the pyrotechnic charge 23 in order to generate the pressurizing gas. The pyrotechnic charge 23 can be in the form of a monolithic block or a granular material. The pyrotechnic charge 23 can have the same composition as the pyrotechnic charges typically used in the gas generators for airbags. The pyrotechnical load 23 has, however, dimensions suited to the intended operating duration (i.e. greater than those for pyrotechnic loads used in gas generators for airbags). Pyrotechnic compositions likely to be used in the gas generator 20 have in particular been described in the following documents: U.S. Pat. Nos. 5,608,183, 6,143,102, FR 2 975 097, FR 2 964 656, FR 2 950 624, FR 2 915 746, FR 2 902 783, FR 2 899 227, FR 2 892 117, FR 2 891 822, FR 2 866 022, FR 2 772 370 and FR 2 714 374. The gas generator can include one or more pyrotechnic charges. The gas generator 20 can be triggered electrically by the application of an electrical current to the terminals of the initiator, or mechanically (triggering by percussion). In the case of mechanical triggering, a firing pin strikes the firing device. In any case, the initiation of the firing device leads to the combustion of the pyrotechnic load 23 and to the liberation of gases arising from combustion.

(12) During its actuation in a medium at a temperature less than or equal to −10° C., the gas generator can be configured to impose on the extinguishing agent a maximum pressure greater than or equal to 3 bar, to 7 bar for example. This maximum pressure can be comprised between 3 bar and 30 bar, for example between 7 bar and 30 bar. The general knowledge of a person skilled in the art is sufficient for designing a gas generator so as to allow the application of a desired maximum pressure value.

(13) The pressurization chamber 5 is separated from the storage chamber 4 by a movable wall 7 in the example illustrated. The body 2 has, in the example illustrated, an axially symmetric shape, cylindrical here. Of course, the invention is not limited to shapes of this type for the body 2. The body 2 includes a lateral wall 2a extending along the longitudinal axis X of the body 2 and surrounding the storage chamber 4. The lateral wall 2a of the body 2 also surrounds the pressurization chamber 5. The body 2 also includes a first bottom wall 2b as well as a second bottom wall 2c. the first and second bottom walls 2b and 2c delimit longitudinally the body 2. The first bottom wall 2b delimits the storage chamber 4. The first bottom wall 2b has at least one exit opening 10 configured to deliver the extinguishing agent outside the body 2 during actuation of the gas generator 20. The second bottom wall 2c delimits the pressurization chamber 5. The pressurization chamber 5 is located between the movable wall 7 and the second bottom wall 2c. The storage chamber, for its part, is located between the first bottom wall 2b and the movable wall 7, the latter delimiting the storage chamber 4.

(14) The movable wall 7 can be formed from a metallic material, aluminum for example. Advantageously, the movable wall 7 consists of a single material to further simplify the method of manufacture of the device 1. The movable wall 7 is configured to separate the storage chamber 4 from the pressurization chamber 5 in a sealed manner. The movable wall 7 is configured to communicate to the extinguishing agent present in the storage chamber 4 the pressure imposed by the gas generated in the pressurization chamber 5. The direction of application of the pressure by the movable wall 7 to the extinguishing agent to be dispensed is substantially parallel to the longitudinal axis X of the body 2. As illustrated, the movable wall 7 extends transversely, for example perpendicularly, relative to the longitudinal axis X of the body 2. The movable wall 7 extends over the entire internal diameter D.sub.s of the storage chamber 4. The movable wall 7 is configured to not be ruptured under the influence of the pressure imposed by the gas generated in the pressurization chamber 5.

(15) The device 1 can also comprise a diaphragm 15 blocking in a sealed manner the exit opening 10 and configured to allow the departure of the extinguishing agent outside the body 2 when the pressure in the storage chamber 4 exceeds a predefined value. In other words, the diaphragm 15 is configured to prevent, when it is in a first configuration, the departure of the extinguishing agent outside the body 2; the diaphragm 15 is also configured to pass, in a second configuration when the pressure in the storage chamber 4 exceeds a predefined value, this second configuration of the diaphragm 15 allowing the departure of the extinguishing agent outside the body 2. The diaphragm 15 can, for example, be in form of a membrane configured to give way when the pressure in the storage chamber 4 exceeds a predefined value. In this case, the diaphragm 15 can, for example, be a membrane made of aluminum or of an Inconel® type alloy.

(16) A misting nozzle 18 is attached to the device 1 at the exit opening 10 of said device.

(17) The misting nozzles constitute nozzles known per se. These are nozzles allowing the generation of small droplets, for example with a size less than or equal to 50 μm, or even to 10 μm.

(18) The misting nozzle 18 allows generating a fog comprising small liquid droplets of the extinguishing agent. One example of a usable misting nozzle is the nozzle sold under the reference “DFN Misting Nozzle” by the IC Spray company. This example of a nozzle allows generating liquid droplets of extinguishing agent of a size less than or equal to 50 μm at −10° C.

(19) The method of dispensing the extinguishing agent by the example of a device illustrated in FIGS. 1 and 2 will now be described in connection with FIGS. 3A and 3B.

(20) The gas generator 20 is actuated first of all in order to pressurize the chamber 5. This overpressure created in the chamber 5 is transmitted by the movable wall 7 to the extinguishing agent present in the storage chamber 4. Once a predefined value is attained for the pressure in the storage chamber 4, the diaphragm 15 passes into a second configuration allowing the departure of the extinguishing agent outside the body 2 through the exit opening 10.

(21) As illustrated in FIG. 3B, the movable wall 7 is set into motion toward the first bottom wall 2b in order to cause the dispensing of the extinguishing agent. The movable wall 7 is set into motion along the longitudinal axis X.

(22) The extinguishing agent is dispensed outside the extinguisher by the misting nozzle 18 in order to obtain a fog 19 of fine liquid droplets of the extinguishing agent.

(23) The fact of treating the fire by droplets in the liquid state allows better cooling of the fire by the vaporization of the droplets of the extinguishing agent (the liquid phase of the extinguishing agent has a high vaporization energy at low temperature). Better effectiveness of extinguishing at low temperature that at higher temperature is thereby obtained. Tests conducted on FK-5-1-12 have made it possible to demonstrate a significant reduction of the concentration necessary for extinguishing at low temperature, provided that a portion of the product is transported in liquid form into the fire zone.

(24) As was described above, the extinguisher according to the invention is especially suited for extinguishing a fire at low temperature. However, it operates perfectly when it is used at higher temperatures. Under these conditions, the agent can conventionally be transported in gaseous form and it also extinguishes the fire in its gaseous form.

(25) Moreover, it is possible to use the extinguisher in an environment at a pressure equal to 1 bar, or less than 1 bar.

(26) During the dispensing of the extinguishing agent, the volume of the pressurization chamber 5 increases and the volume of the storage chamber 4 is reduced in the example illustrated. The sum of the volume of the pressurization chamber 5 and the volume of the storage chamber 4 is constant during the dispensing of the extinguishing agent. The movable wall 7 is configured to be displaced without deforming during the dispensing of the extinguishing agent. The movable wall 7 has a piston effect. The face of the movable wall 7 located on the side of the pressurization chamber 5 is subject to the pressure of the generated gas, this pressure is communicated to the face of the movable wall 7 located on the side of the storage chamber 4 in order to allow the dispensing of the extinguishing agent outside the body 2. The movable wall 7 causes, during its displacement, the dispensing of the extinguishing agent outside the body 2 in the manner of a syringe in the example illustrated.

(27) An example where an extinguisher with a piston is used to allow dispensing the extinguishing agent has just been described; however, using another system without a piston, using for example a dip tube connecting the gas generator to the extinguishing agent, does not depart from the scope of the invention.

(28) In addition, as indicated above, the invention can also be implemented with a bottle of pressurized gas, although the employment of a pyrotechnic generator is preferred.

(29) The expression “comprised between . . . and . . . ” must be understood to include the limits.