PYROTECHNIC CARTRIDGE FOR FLAMMABLE GAS PREMIX

Abstract

The present invention relates to a cartridge for a premix of flammable gas or inert gas with or without propellant powder, making it possible to propel a mobile at speeds of interest, and reusable. More particularly, a case (10) of the cartridge is designed with an optimized geometry integrating two chambers, an upstream chamber (11) and a downstream chamber (12) forming a longitudinal duct with variable section, and in which said duct has a convergent nozzle shape at an outlet of the upstream chamber (11) opening into the downstream chamber (12), and a flared shape at an inlet of the downstream chamber (12) and relative to the outlet of the upstream chamber, said flared shape being capable of generating a turbulent flow of a fluid propelled through the upstream chamber (11) and entering the downstream chamber (12). Advantageously, this geometry will make it possible to increase the combustion speed in the ballistic phase. Figure for the abstract: Fig. 1.

Description

Title of the invention: PYROTECHNICAL CARTRIDGE FOR FLAMMABLE GAS PREMIXTURE Field of invention

[0001] The present invention relates to the field of pyrotechnic cartridges, in particular for mixtures of flammable and / or inert gases under pressure, and possibly containing propellant powders. In particular, the invention provides a new cartridge with an ignitable charge which is ready to use, reusable and has a chamber geometry which optimizes its performance. State of the art

[0002] Different types of pyrotechnic cartridges are known from the state of the art, the design of which varies depending on the desired application.

[0003] In the ballistic sense, a "cartridge" secures a "projectile" (or "mobile" more generally), a "case" (or a "casing"), itself containing a "propellant" (reactive material releasing the propulsion energy), as well as a means of "igniting" or "priming" said propellant. In particular, on powder pyrotechnic cartridges, a "primer" which contains a small quantity of reactive material sensitive to shock allows, by its combustion, to ignite the main charge of propellant powder. The combustion of the powder causes the release of a large volume of very hot gas which, confined in the cartridge, causes a high overpressure. When the pressure increases sufficiently to overcome the force of forcing or retaining the projectile at the neck of the case, the projectile detaches from the case and, pushed by the high-pressure gases expanding behind it, accelerates inside the barrel and exits through the muzzle at a determined speed.Once the projectile has exited the "launch tube" or "gun", the driving gases are fully expanded to the external pressure and the projectile continues its flight freely until impact with a target.

[0004] Propellant powders are generally used in ballistics because they allow a mobile to be propelled at high speed. However, they are not without drawbacks. Propellant powders generate strong erosion of weapon barrels by the high temperatures reached on the surface of the metal, and by the high-speed powder grains abrading the wall. They also result in the production of a muzzle flash, due among other things to the solid residues of combustion of the powders and the post-combustion of the chemical species which can generate this reaction, which is handicapping in a military context (high visibility). In addition, pyrotechnic regulations are restrictive for the use, supply and storage of these propellant powders in a civilian context.

[0005] Gas cartridges represent an interesting alternative to propellant powder cartridges. However, the latter have mainly been used with inert gases (such as CO2 or N2O) for various civilian uses, and in vehicle airbag systems with a mixture of cold gas in the cartridge and pyrotechnic material in another compartment.

[0006] Indeed, applications in ballistics remain quite limited and often reserved for air guns or airsoft guns, where gas is used to propel the projectile. Inert gas cartridges (without combustion) do not allow military projectiles to be pushed at useful speeds in a reasonable space. These cartridges do not contain flammable premixes under pressure, nor propellant powder, and do not allow their contents to be primed, which results in insufficient power for most of the intended applications.

[0007] On the other hand, when comparing the thrust capacity per unit mass of propellant as well as the achievable speeds, it turns out that light gas charges are more advantageous than pyrotechnic powder charges. In addition, the use of gas as a propellant charge allows for cleaner combustion and is less polluting for the environment compared to the use of propellant powders. It is therefore interesting to have pyrotechnic cartridges suitable for containing premixtures of flammable gases or mixtures of propellant powder and inert gas under high pressure for the propulsion of projectiles. International patent application WO 2014 / 144104 gives an example of a gas rifle and its cartridge.

[0008] However, it is still necessary to optimize the performance of pyrotechnic cartridges with flammable gas charges to consider their use in ballistic applications. Statement of the invention

[0009] The present invention aims to improve the combustion performance of a pyrotechnic cartridge for a flammable gas charge.

[0010] In particular, the present invention relates to a pyrotechnic cartridge for an inflammable gas charge comprising a case having a proximal end provided with a base, and a distal end adapted to receive a mobile or a manometric enclosure head, (i.e. a closed manometric enclosure measuring tool).

[0011] The cartridge of the invention is particular in that: - the case has two chambers, an upstream chamber and a downstream chamber forming a longitudinal conduit with variable section, and in which - said conduit has a convergent nozzle shape at an outlet of the upstream chamber opening into the downstream chamber, and a sharply flared shape at an inlet of the downstream chamber and relative to said outlet of the upstream chamber, said flared shape being capable of generating a highly turbulent gas jet in the downstream chamber.

[0012] The invention thus proposes a cartridge comprising a geometry of internal chambers making it possible to generate by jet a high level of turbulence in the downstream chamber, and suddenly and significantly increasing the combustion speed once the flame enters it.

[0013] In one embodiment, the pyrotechnic cartridge is intended for ballistic applications and therefore receives a mobile at its distal end. The optimized geometry of the cartridge will therefore ensure a high combustion speed in the ballistic phase, when the gas is released and pushes the mobile.

[0014] In another embodiment, the pyrotechnic cartridge is intended for use as a pressure vessel, and therefore receives a pressure vessel head. The optimized geometry of the cartridge will therefore be used for measurement and research purposes on combustion with flammable gas charges.

[0015] Whatever the intended use of the pyrotechnic cartridge, the cartridge will be designed with an optimized internal chamber geometry to improve combustion. More particularly, the conduit formed by the upstream chamber and the downstream chamber has: - at the level of the upstream chamber, a first part of constant section of a first diameter followed by a second part of convergent section becoming a neck of narrowed section of a second diameter, said neck being located at the level of the outlet of said upstream chamber, and - at the level of the downstream chamber, an inlet portion of constant section with a third diameter greater than said second diameter.

[0016] The cartridge case may incorporate a dynamic seal between the outlet of said upstream chamber and the inlet of the downstream chamber, such as a sealing valve. It is thus possible to use the upstream chamber as a storage chamber dedicated to the gas.

[0017] In one embodiment of the pyrotechnic cartridge, the conduit also comprises a convergent nozzle shape at the outlet of said downstream chamber.

[0018] A second objective of the invention is to provide a pyrotechnic cartridge with optimized geometry that is suitable for reuse and easy to manufacture.

[0019] To this end, the invention proposes to produce the cartridge case in two parts, a first part integrating the upstream chamber, and a second part integrating the downstream chamber, as well as connecting the two parts together in a sealed and secure manner at an outlet of the upstream chamber. Preferably, in a connection between said two parts, a distal end of the first part is inserted into the second part, and incorporates attachment means, such as clip-on or screw-on attachment means, and a seal.

[0020] For its part, the base of the pyrotechnic cartridge comprises a gas filling and adjustment port, said port integrating a support plug followed at its bottom by a sealing valve and a return spring, as well as comprising a sealing system with said base. Similarly, the base integrates a pair of through-lugs having a coating of insulating material, and opening out as a pair of uncoated projections on an internal side of the base.

[0021] Furthermore, the charge of the cartridge is not limiting of the invention. The cartridge may comprise a charge chosen from a gas or mixture of flammable and / or inert gases, with or without propellant powder.

[0022] In the embodiment intended for ballistic applications, the cartridge comprises said mobile assembled in the downstream chamber by means of a sealing system and one or more fixing means capable of fracturing under the effect of pressure, and of releasing said mobile during a rise in pressure in said downstream chamber. For example, the mobile can be screwed into the downstream chamber and said fixing means or means correspond to threads.

[0023] Other characteristics and advantages of the invention will be apparent from reading the following description of a non-limiting example of embodiment of the invention with reference to the attached drawings. List of figures

[0024] [Fig.l] represents a longitudinal sectional view of a cartridge according to an embodiment of the invention;

[0025] [Fig.2] represents a longitudinal sectional view of a cartridge according to another embodiment of the invention;

[0026] [Fig.3] represents an enlarged view of a connection between the upstream chamber and the downstream chamber of the cartridge according to the embodiment illustrated in [Fig.l];

[0027] [Fig.4] represents an enlarged view of the attachment of the mobile in the downstream chamber of the cartridge according to the embodiment illustrated in [Fig.l];

[0028] [Fig.5] represents a front view of the inner side of the cartridge cap according to the embodiment illustrated in [Fig.l] and in section along the section lines AA and BB;

[0029] [Fig.6] shows different embodiments of a cartridge; and

[0030] [Fig.7] illustrates the effect of the internal geometry of the cartridge according to an embodiment of the invention on the optimization of combustion, in particular at the level of the rate of pressure rise following ignition of a flammable gas premix in a cartridge. Detailed description of the invention

[0031] The present invention relates to a novel pyrotechnic cartridge with an optimized design and geometry for containing an inflammable charge, in particular a mixture of flammable gas under pressure, possibly mixed with a propellant powder charge, or a propellant powder charge immersed in an inert gas. Advantageously, the cartridge of the invention is ready to use, reusable, and ensures safe, efficient and effective combustion.

[0032] In a non-limiting embodiment of the invention, the cartridge is intended for the propulsion of a mobile. [Fig.l] illustrates such an embodiment of the cartridge.

[0033] The cartridge 1 comprises a case 10 defining a cylindrical conduit with variable section provided with a base 2 on a proximal side and a mobile 3 on a distal side of the cartridge.

[0034] The cartridge case 10 is designed with two chambers, an upstream chamber 11, and a downstream chamber 12. The upstream chamber 11 is closed by the base 2 on a proximal side of the cartridge and is intended to contain the cartridge charge. The base 2 integrates the functions of filling, gas mixture adjustment, purging and ignition of the premix, as will be described later. According to another embodiment, the cartridge corresponds to a closed manometric enclosure ([Fig.2]).

[0035] Contrary to technical prejudice, it turns out that by optimizing the geometry of the chambers, and in particular of the longitudinal duct that they define, it is possible to increase the combustion speed while avoiding a combustion accident at the operating pressures necessary to have interesting performances.

[0036] According to this optimized geometry (see [Fig.l] and [Fig.2]), the upstream chamber 11 comprises a portion of convergent section 111 followed by a neck 120 defining a passage of reduced section opening into the downstream chamber 12. The downstream chamber 12 has for its part a sudden flare in its section at the level and relative to the outlet of the neck 120. A convergent nozzle (illustrated circled by dotted lines in [Fig.2]) is thus formed making it possible to maintain a laminar flow at the level of the upstream chamber, and to concentrate the flame in a jet which will become turbulent when passing into the downstream chamber 12, also called the “turbulent chamber”.

[0037] More particularly, the upstream chamber 11 comprises a first part of constant section having a first diameter D1, followed by said convergent nozzle shape. This latter shape is defined by a part with convergent section 111 gradually narrowing down to the neck 120 of narrowed section and having a second diameter D2. For its part, the downstream chamber 12 has an inlet portion of constant section of a third diameter D3, greatly increased compared to the diameter D2 of the neck, and similar or close to the first diameter D1. As illustrated in the figures, the parts of the upstream and downstream chambers follow one another along a longitudinal axis of the cartridge, and the section of said parts corresponds to their respective cross section.

[0038] This chamber geometry generates a high level of turbulence in the downstream chamber 12 by jet, suddenly and significantly increasing the combustion speed once the flame enters it. It is thus possible to ensure a high combustion speed in the ballistic phase, when the mobile 3 is released and enters a launch tube not shown, despite the high dilution of the mixtures.

[0039] As regards the geometry of the downstream chamber 12, the latter may have a constant section ([Fig.l]) or have the geometry of the upstream chamber, i.e. a first part of constant section, followed by a converging section and a neck of reduced section ([Fig.2]). The geometry of the downstream chamber is chosen as a function of a caliber of the mobile (or of the head) to be connected to the cartridge, a constant section being suitable when the caliber of the mobile is compatible with a diameter of said constant section. On the contrary, when the caliber of the mobile to be connected is less than said constant section, the downstream chamber is provided with a converging section and a neck of reduced section at its outlet, this geometry serving as a progressive hydrodynamic connection up to said mobile.

[0040] According to a preferred embodiment of the invention, and as illustrated in the figures, the case is made in two parts PI, P2, a part PI integrating the upstream chamber 11, and a part P2 integrating the downstream chamber 12. The two parts PI, P2 of the case are assembled together in a sealed manner at the neck 120 of the upstream chamber 11. According to a non-restrictive embodiment ([Fig.3]), one of the parts is inserted into the other at one of its ends, and the low-pressure seal is ensured by an O-ring 9 disposed between the two. The dynamic seal for its part is ensured by means of a dynamic seal 7 whose internal pressure deforms the wings of the seal, which generates a linear contact between the seal and the adjacent parts thus ensuring the seal of the assembly. This embodiment is very advantageous in that it allows said parts to be manufactured by traditional means of single-piece parts.

[0041] As illustrated in [Fig.3], the first part PI of the case is configured at its distal end with a reduced external section, so as to define a tenon 130 sliding inside the second part P2. The O-ring 8 is arranged in a groove of said tenon 130 and the dynamic seal 7 is arranged at an interface between the upstream chamber 11 and the downstream chamber 12. A connection between the two parts PI, P2 also includes attachment means, such as clip-on or screw-on means. According to another embodiment, not shown, the case is designed as a single block.

[0042] [Fig.4] illustrates the distal side of the cartridge incorporating the mobile 3, the latter being inserted into a distal end of the case and serving as a shutter for the latter. A pair of seals 6a, 6b ensure sealing, in particular a first internal toric seal 6a for static sealing between the mobile and the case, and a second external seal 6b for sealing between the case and the launch tube (not shown).

[0043] In a non-limiting embodiment of the invention, the mobile 3 is provided with one or more threads 31 making it possible to screw said mobile 3 into the downstream chamber 12 provided with a thread. The threads 31 are designed to fracture when a certain breaking pressure is reached, and to release the mobile by the shearing of these threads. In order to control the desired breaking pressure, the threads 31 have a truncated profile and / or their number is adjusted. In another embodiment, this rupture at the desired pressure can be envisaged by other fixing means 31 which can be fractured under the effect of pressure.

[0044] As already mentioned, at its proximal side, the cartridge integrates the base 2 ensuring the functions of filling, adjusting the gas mixture, purging and ignition of the premix under pressure. [Fig. 5] illustrates the design details of the base 2 according to different views and sections. Generally, the base 2 has a body defining a head 21 provided with a shutter body 22 which is inserted into the upstream chamber. The base 2 comprises a port 23 for filling and adjusting the gas integrating a support plug 24 followed at its bottom by a sealing valve 5, the latter being positioned in a cavity 25 in the head 21 of the base opening into a gas injection channel 26 passing through the shutter body 22, and also comprising a return spring 27 (see [Fig. 5], section AA).It should be noted that the cartridge has only one filling port, and is therefore designed to be charged with a gas premix, that is, a mixture of gases previously combined outside the cartridge.

[0045] The sealing at the filling port 23 is ensured by a series of seals 4a, 4b, 4c, 4d, also called a sealing system. A first seal 4a is arranged at an inlet of the injection port 23 on an external surface of the support plug 24. A second seal 4b is arranged at the interface between the side walls of the support plug 24 and the cavity 25. A third seal 4c is arranged at the interface between the sealing valve 5 and a bottom of the support plug 23. During the injection or adjustment of the gas, the sealing valve 5 can be actuated by an injector located on a system intended to receive the cartridge or on dedicated tooling on the external side. In addition, the base comprises a fourth sealing seal 4d at an external groove of the shutter body of the shutter body 22 to ensure sealing with the upstream chamber 11.

[0046] The base 2 also incorporates two terminals 28 mounted across the partition, electrically insulated by the interposition of an insulator 29, typically made of plastic or ceramic material (see section BB, [Fig.5]). Due to their shape, the terminals and the insulating parts are sealed against internal pressure. The cartridge can be primed with a conventional ignition system.

[0047] More particularly, the cartridges of the invention use a premixture of flammable, inert gas, with or without propellant powder or any combination of the preceding elements. The combustible fraction of the mixture may consist, in a non-limiting manner, of all types of usual reducing gases such as dihydrogen H2 or light alkanes such as methane CH4, propane C3H8, etc. Similarly, the oxidizing fraction may consist, in a non-limiting manner, of all types of oxidizing gases such as dioxygen O2.

[0048] [Fig.6] shows different embodiments of the cartridge. From top to bottom, this figure illustrates a longitudinal section and an external view of a .308 caliber cartridge and its dedicated mobile, a 25 mm cartridge and its dedicated mobile as well as a manometric enclosure and its dynamic pressure measuring equipment, also called 3bis head of the cartridge. In the illustrated embodiment, the manometric enclosure has a downstream chamber geometry making it possible to reproduce the combustion of a small caliber cartridge, and therefore has a convergent section and a reduced neck at the outlet of the downstream chamber. The invention is scalable up to large calibers (typically 155 mm, or even more).

[0049] Whatever the embodiment of the invention, the cartridge will be designed with a geometry defining two internal chambers connected to each other by a converging nozzle making it possible to generate a high level of turbulence by jet in the downstream chamber, and as has already been described.

[0050] [Fig.7] illustrates the evolution of the pressure when firing a cartridge having the geometry proposed by the invention and without said geometry. On the 2 shots, the effect is observed at the level of the speed at the exit of the barrel (muzzle velocity) rising to 740 m / s with the geometry optimization instead of 675 m / s without the optimization, all other things being equal, to the extent of the experimental variabilities; that is to say 10% more speed, representing 20% additional useful kinetic energy.

[0051] The downstream chamber, also called turbulent, allows a rise in pressure by accelerating combustion at the moment when this is most effective, at the start of the ballistics of the mobile. The invention makes it possible to completely or partially replace the use of powders as propellants, and therefore it makes it possible to limit the effects of erosion in the weapon tubes, as well as to reduce the temperature in the combustion chamber. and therefore limit surface melting phenomena. In addition, the flammable gas premix cartridges according to the invention make it possible to obtain muzzle velocities higher than those obtained with the powder alone, greater ranges, to increase the permitted firing rates thanks to the lower temperatures of the gases generated, and to reduce or eliminate the muzzle flash caused by the powder for a lower visual signature.

[0052] The cartridge of the invention is also designed to ensure a reliable and secure seal, whether at the static pressure of the gas mixture or at the dynamic pressure generated during the combustion of the gas premix, with or without powder.

[0053] Advantageously, the cartridge of the invention is reusable, in particular the base and the case. Furthermore, apart from the mobile, the cartridge uses consumables from standard articles that are easy to supply and store, such as the various static and dynamic sealing joints. The use of the cartridge presents no difficulty and can be implemented by standard personnel as well as with launch tubes existing on the market. Maintenance and repair operations are also simple and easy, and large-scale production is possible.

Claims

Claims

1. Pyrotechnic cartridge (1) for flammable gas charge comprising a case (10) having a proximal end provided with a base (2) and a distal end adapted to receive a mobile (3) or a manometric enclosure head, characterized in that: - the case (10) comprises two chambers, an upstream chamber (11) and a downstream chamber (12) forming a longitudinal conduit with variable section, and in which - said conduit has a convergent nozzle shape at an outlet of the upstream chamber (11) opening into the downstream chamber (12), and a flared shape at an inlet of the downstream chamber (12) and relative to the outlet of the upstream chamber, said flared shape being capable of generating a jet of gas in the downstream chamber (12).

2. Cartridge (1) according to claim 1, in which the case (10) comprises a dynamic seal (7) between the outlet of said upstream chamber (11) and the inlet of the downstream chamber (12), such as a sealing valve.

3. Cartridge (1) according to one of the preceding claims, in which the conduit formed by the upstream chamber and the downstream chamber has: - at the level of the upstream chamber (11), a first part of constant section of a first diameter (D1) followed by a second part of convergent section becoming a neck (120) of narrowed section of a second diameter (D2), said neck (120) being located at the level of the outlet of said upstream chamber (11), and - at the level of the downstream chamber (12), an inlet portion of constant section of a third diameter (D3) greater than said second diameter (D2).

4. Cartridge according to one of the preceding claims, in which the conduit also comprises a convergent nozzle shape at the outlet of said downstream chamber (12).

5. Cartridge according to one of the preceding claims, in which the case is made in two parts (PI, P2), a first part (PI) integrating the upstream chamber (11), and a second part (P2) integrating the downstream chamber (12), and in which the two parts are connected to each other in a sealed and secure manner at an outlet of the upstream chamber (11).

6. Cartridge (1) according to claim 5, wherein in a connection between said two parts (P1, P2), a distal end of the first part is inserted into the second part (P2), and incorporates attachment means, such as clip-on or screw-on attachment means, and a seal (9).

7. Cartridge (1) according to one of the preceding claims, in which the base (2) comprises a gas filling and adjustment port (23), said port (23) incorporating a support plug (24) followed at its bottom by a sealing valve (5) and a return spring (27), as well as comprising a sealing system with said base (2).

8. Cartridge (1) according to one of the preceding claims, in which the base (2) incorporates a pair of through-lugs (28) having a coating (29) of insulating material, and opening out as a pair of uncoated projections on an internal side of the base (2).

9. Cartridge (1) according to one of the preceding claims, comprising an inflammable charge chosen from: - a gas or a mixture of inert and / or flammable gases, with or without propellant powder.

10. Cartridge (1) according to one of the preceding claims, comprising said mobile (3) assembled in the downstream chamber (12) by means of a sealing system and one or more fixing means (31) capable of fracturing under the effect of pressure, and of releasing said mobile (3) during a rise in pressure in said downstream chamber (12).

11. Cartridge (1) according to claim 10, wherein said mobile (3) is screwed into the downstream chamber (12) and said fixing means(s) correspond to threads (31).

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