Launching structure for a pyrotechnic cartridge and pyrotechnic cartridge provided with such a launching structure

Abstract

- Launching structure for a pyrotechnic cartridge and pyrotechnic cartridge equipped with such a launching structure. - The launching structure (2) comprises a socket (3) and a pyrotechnic ejection system (4), the pyrotechnic ejection system (4) being activated by the application of an electric current and being mounted in a housing (9) provided at one end (3A) of the socket (3) and being accessible from the outside, the interface (10) between the pyrotechnic ejection system (4) and the socket (3) being provided with an insulator (11) which is configured to completely electrically isolate the pyrotechnic ejection system (4) from the socket (3) so that in the event of electromagnetic interference such as a lightning strike, which could generate an electric current which tends to propagate in the socket (3), the pyrotechnic ejection system (4) is not impacted by this electric current and is not at risk of being activated unintentionally.

Description

technical field

[0001] The present invention relates to a launching structure for a pyrotechnic cartridge and a pyrotechnic cartridge provided with such a launching structure. State of the art

[0002] Although not exclusively, the present invention can be applied for example to the protection of an aircraft such as an airplane or a helicopter.

[0003] It is known that, to counter the various threats it faces, an aircraft such as a fighter jet can be equipped with defensive decoy systems. Depending on the type of threat, the aircraft can carry different types of decoys, including infrared decoys. In the case of infrared decoys, which are specifically designed to protect the aircraft against infrared homing missiles, each decoy comprises at least one pyrotechnic charge housed in a launch structure equipped with a socket and a propellant. The pyrotechnic charge is ejected from the launch structure and detonated to emit an infrared decoy signal.

[0004] The pyrotechnic charge is ejected by applying an electrical pulse to the impeller. Because this type of triggering mechanism relies on an electrical current, it is necessary to implement measures to prevent the accidental firing of one or more decoys in the event of electrical or electromagnetic interference (electrostatic discharges, electromagnetic radiation, etc.) affecting the decoy system mounted on the aircraft.

[0005] In particular, simultaneous and untimely firing of several decoys, caused for example by a lightning strike, can lead to catastrophic effects, due in particular to the cumulative mechanical stresses generated during these firings.

[0006] The risk is increased when the decoys are installed in a container (or pod) mounted on the aircraft, for example, underneath the aircraft. This is because they are then close to the container's surface, which conducts the lightning current, resulting in stronger induced fields than on the aircraft's structure. The effects of the lightning strike are applied directly to the container, making the pyrotechnic decoys highly vulnerable.

[0007] This risk exists for other types of pyrotechnic cartridges besides pyrotechnic decoys.

[0008] Furthermore, we know: by document EP 0 375 922 B1, a system for launching explosive or smoke bodies, which includes a plastic casing and a pyrotechnic ejection system made in the form of a screw; and by document US 2006 / 096489 A1, a cartridge casing, which is either electrically insulated or made of a material that is not electrically conductive.

[0009] There is therefore a need to have a solution to prevent the untimely ejection of the pyrotechnic charge from a pyrotechnic cartridge, particularly during an electromagnetic attack such as a lightning strike, for example. Description of the invention

[0010] The present invention aims to provide such a solution. To this end, it relates to a launching structure for a pyrotechnic cartridge, for example an infrared decoy, said launching structure comprising at least one socket and a pyrotechnic ejection system, said pyrotechnic ejection system being activated by the application of an electric current and being mounted in a housing provided at one end of the socket and being accessible from outside the socket.

[0011] According to the invention, the interface between the pyrotechnic ejection system and the socket is provided with an insulator which is configured to completely electrically isolate the pyrotechnic ejection system from the socket.

[0012] Thus, thanks to this electrical insulator, in the event of an external disturbance such as a lightning strike, which could generate an electric current that tends to propagate through the cartridge case, the pyrotechnic ejection system, for example an impeller, is electrically isolated from the case and is therefore not affected by this electric current. Consequently, it is not at risk of being accidentally activated by such an electric current.

[0013] This protects a pyrotechnic cartridge containing this launch structure from accidental triggering during electrical or electromagnetic attacks such as electrostatic discharges or electromagnetic radiation.

[0014] Furthermore, in addition to being effective, this solution is simple to implement and inexpensive.

[0015] In one particular embodiment, the pyrotechnic ejection system is provided with a threaded section configured to be screwed into a cooperating tapped section provided in the socket and forming said housing. In a first embodiment, the insulator is arranged on the inner face of the tapped section of the socket, intended to come into contact with the threaded section of the pyrotechnic ejection system, while, in a second embodiment, the insulator is arranged on the outer face of the threaded section of the pyrotechnic ejection system, intended to come into contact with the tapped section of the socket.

[0016] In the context of the present invention, the (electrical) insulator can be made of various common materials (specified below) exhibiting good electrical insulation properties. In a preferred embodiment, the insulator is made of parylene (or polyparaxylylene or poly(p-xylylene)). In addition to being a good electrical insulator, parylene offers numerous other advantages, including chemical inertness, good conformability, and easily controllable thickness.

[0017] In addition, in a preferred embodiment, the socket is connected to a mechanical mass (i.e., to a common reference potential, which is used as a voltage reference for different voltages existing in the application under consideration, and in particular that of the structure or fuselage of the craft, for example an aircraft, when the system (for example a decoy system) comprising the launch structure is mounted on such a craft).

[0018] Thus, in the event of an external attack such as a lightning strike, which generates an electric current propagating in the socket, this electric current is discharged to ground, which provides additional protection against a potential accidental triggering of the pyrotechnic ejection system.

[0019] The present invention also relates to a pyrotechnic cartridge, for example an infrared decoy, comprising at least a launching structure and a pyrotechnic charge.

[0020] According to the invention, said launching structure is a launching structure such as that described above.

[0021] The present invention further relates to a system, for example a decoy system, in particular for an aircraft and especially an airplane or a helicopter, said system comprising at least one charger and at least one pyrotechnic cartridge as described above. Brief description of the figures

[0022] Other advantages and features will become clearer from the following description of embodiments of the invention, given by way of non-limiting examples, with particular reference to the accompanying figures. In these figures, identical reference numerals designate similar elements. There figure 1 A longitudinal view, partially in cross-section, of a pyrotechnic cartridge comprising a launching structure according to a particular embodiment of the invention. figure 2 is a highly schematic view of one end of a launching structure, highlighting the arrangement of an insulator according to a preferred embodiment of the invention. figure 3 is a perspective view of part of a launch structure socket. figure 4is a perspective view of a pyrotechnic ejection system representing an impeller, which is intended to be screwed into the socket of the figure 3 . There figure 5 is a simplified view of a magazine for a firing system and pyrotechnic cartridges intended to be installed in that magazine. Detailed description

[0023] The following is described, with reference to figures 1 to 5 , an example (illustrative and non-limiting) of a launch structure for a pyrotechnic cartridge 1, including in particular a pyrotechnic ejection system.

[0024] In the following description, relating to a preferred but non-limiting embodiment, the pyrotechnic cartridge 1, as shown in the figure 1 , could correspond to a lure, particularly an infrared one,

[0025] Launch structure 2, partially and schematically represented on the figure 2and allowing the invention to be illustrated, is intended for a pyrotechnic cartridge 1 such as that of the figure 1 .

[0026] This launch structure 2 represents a structural part of the pyrotechnic cartridge 1, designed to receive a pyrotechnic charge 5 and to allow the launch (or ejection) of this pyrotechnic charge 5, as specified below. To this end, the launch structure 2 typically comprises, as shown in the figure 1 : a socket 3, preferably made of metal, with longitudinal axis XX; and a pyrotechnic ejection system 4 of the usual type, arranged in the socket 3 at one of the longitudinal ends 3A and 3B of the socket 3, in this case at the end 3A, being accessible from the outside at the level of this end 3A.

[0027] In the following description of a particular (and non-limiting) embodiment of the invention, the pyrotechnic ejection system 4 corresponds to an impeller.

[0028] The launch structure 2, comprising the socket 3 and the pyrotechnic ejection system 4, is designed to be made integral with a magazine forming part of a firing system, as specified below with reference to the figure 5 Launch structure 2 remains in the magazine after firing.

[0029] The pyrotechnic cartridge 1 also includes, in addition to the launching structure 2, an assembly 6 shown very schematically on the figure 1 , which is intended to be ejected from launch structure 2.

[0030] Set 6 includes: The pyrotechnic charge 5 is intended to generate a signal, for example an infrared decoy signal. This pyrotechnic charge 5 is installed inside the socket 3; a cap 7 closes the socket 3 at its end 3B opposite the end 3A which is equipped with the pyrotechnic ejection system 4; and an assembly 8 includes the usual safety and ignition means for igniting the pyrotechnic charge 5 at the appropriate time.

[0031] Assembly 6 is known and is not described further. Similarly, the pyrotechnic ejection system 4 can be a conventional impeller.

[0032] The ignition of the pyrotechnic ejection system 4 causes the assembly 6 to be ejected from the socket 3 and the ignition means of the pyrotechnic charge 5 to be initiated. The pyrotechnic charge 5 then generates the signal (for example infrared) after its ejection from the socket 3.

[0033] As depicted on the figures 1 and 2The pyrotechnic ejection system 4 is mounted in a housing 9 located at end 3A of the socket 3, while remaining accessible from the outside (at this end 3A) so that it can be activated in the usual way by applying an electrical pulse. Activation of the pyrotechnic ejection system 4 is achieved by applying an electrical current pulse between two points of the pyrotechnic ejection system 4, illustrated respectively by two arrows F1 and F2 on the diagram. figure 2 .

[0034] According to the invention, the interface 10 between the pyrotechnic ejection system 4 and the socket 3 is provided with an insulator 11. This insulator 11 is formed and positioned to electrically isolate the pyrotechnic ejection system 4 from the socket 3.

[0035] In a preferred embodiment, the pyrotechnic ejection system 4 is provided with a threaded section 12, as shown in the figure 4It is configured so that it can be screwed, via this threaded section 12, into a cooperating tapped section 13 ( figure 3 ) which is provided in the socket 3 at the end 3A and which defines the housing 9.

[0036] In a first embodiment (represented on the figures 1 and 2 ), the insulator 11 is arranged on the inner face of the threaded section 13 (of the sleeve 3), intended to come into contact with the threaded section 12 of the pyrotechnic ejection system 4, when the latter is screwed into the sleeve 3.

[0037] Furthermore, in a second embodiment (not shown), the insulator 11 is arranged on the external face of the threaded section 12 of the pyrotechnic ejection system 4, intended to come into contact with the threaded section 13 of the socket 3 when the pyrotechnic ejection system 4 is screwed into the socket 3.

[0038] Within the scope of the present invention, arrangements of the pyrotechnic ejection system in the socket, other than the preferred one shown in the figures 1 to 4 are possible, provided that an insulator is put in place to electrically isolate the pyrotechnic ejection system from the socket.

[0039] Thanks to the insulator 11 (which is simple to install and inexpensive), in the event of an external disturbance such as a lightning strike, which could generate an electric current that might propagate through the socket 3, the pyrotechnic ejection system 4 is electrically isolated from the socket 3 and is therefore not affected by this electric current. Consequently, it is not at risk of being accidentally activated by such an electric current.

[0040] This provides optimal protection against electromagnetic interference in the pyrotechnical zone towards the 3A end of the socket 3, compared to electromagnetic fields generated by indirect lightning.

[0041] Therefore, the pyrotechnic cartridge 1 comprising this launch structure 2 is protected from accidental triggering during electrical or electromagnetic aggressions such as electrostatic discharges or electromagnetic radiation.

[0042] The addition of the insulator 11 around the pyrotechnic ejection system 4 (in the position shown on the figure 2 ) allows us to obtain a lure 1 that meets the most stringent design standards.

[0043] Within the scope of the present invention, the (electrical) insulator 11 can be made of various common, electrically insulating materials. For example: a PTFE-based Teflon material embedded in a matrix; a thermoplastic polymer of the polyamide type.

[0044] In a preferred embodiment, the insulation 11 is made of parylene (or polyparaxylylene or poly(p-xylylene)). In addition to being a good electrical insulator, parylene offers other advantages such as chemical inertness, good conformability, and easily controllable thickness.

[0045] In the (non-limiting) example shown on the figure 1 The socket 3 and the pyrotechnic charge 5 have circular cross-sections. In the context of the present invention, they may have cross-sections of other shapes, for example square or rectangular.

[0046] Furthermore, in a preferred embodiment, the socket 3 is connected to a mechanical mass, as schematically illustrated by dashes 14 on the figure 2, which respectively terminate in threaded holes 15 and 16 in the end 3A of the sleeve 3 for fixing screws (not shown). When the system including the pyrotechnic cartridge 1 is mounted on an aircraft, the mechanical mass generally corresponds to the mechanical structure of the aircraft or aircraft equipment.

[0047] Thus, we obtain, in particular, the following advantages: a pyrotechnic ejection system 4 (for example an impeller) which is protected against electromagnetic interference; circuits (for the application of the electrical current for activating the pyrotechnic ejection system 4) which are geometrically symmetrical, which allows for a strong limitation of electromagnetic couplings; the suppression of antenna effects existing in the prior art; and the reduction of the loop area between the zones for the application of the electrical current for activating the pyrotechnic ejection system 4.

[0048] The launch structure 2 and the pyrotechnic cartridge 1, as described above, can be used in various common types of system which are preferably, but not exclusively, intended to be mounted on an aircraft (such as an airplane and for example a fighter jet) or a helicopter.

[0049] As an example of the application of the pyrotechnic cartridge 1 and the launching structure 2, the following has been shown on the figure 5 A magazine 17 of a firing system 18 (in particular a decoy system or decoy launcher). The firing system 18 is mounted on an aircraft (not shown), for example a fighter jet, and is intended to protect the aircraft, particularly against infrared homing missiles, when it represents an infrared decoy system.

[0050] In the example of the figure 5 The magazine 17 is designed to hold a plurality of pyrotechnic cartridges. This magazine 17 typically includes: a guidance device 19 comprising housings 20, of shapes cooperating with those of the sockets 3 of the pyrotechnic cartridges 1, which are intended to receive the pyrotechnic cartridges 1; and a base 21 provided with the usual means for fixing the charger 17 on a structure of the aircraft and for controlling it.

[0051] Charger 17 has, among other functions: to ensure the retention of the casings 3 of the pyrotechnic cartridges 1 (via tubes and recesses) as well as the fixing elements of the magazine 17; to guarantee contact between the pyrotechnic ejection systems 4 of the pyrotechnic cartridges 1 and the electrical interfaces of the decoy system 18, via an electrical circuit; and to dissipate the recoil forces, generated by the launching structures 2 of the decoys 1, via a breech of the magazine 17

[0052] For each of the pyrotechnic cartridges 1, the launch structure 2 (including the socket 3 and the pyrotechnic ejection system 4) is made integral with the magazine 17, and it remains in the magazine 17 after firing (i.e. after the ejection of the assembly 6 of the pyrotechnic cartridge 1).

[0053] Thanks to the aforementioned characteristics of the launch structure 2, pyrotechnic cartridges 1 comprising such a launch structure 2, as well as the firing system 18 equipped with such pyrotechnic cartridges 1, are further protected against electrostatic discharges and effects induced by electromagnetic radiation, such as: lightning; fields emitted by various radiating sources (e.g., radar); disturbances induced by onboard equipment and components (power supply, oscillator, etc.).

Claims

1. Launching structure for a pyrotechnic cartridge, said launching structure (2) comprising at least one socket (3) and a pyrotechnic ejection system (4), said pyrotechnic ejection system (4) being activated by the application of an electric current and being mounted in a housing (9) provided at one end (3A) of the socket (3) and accessible from the outside, characterized in that the socket (3) is made of metal and in that the interface (10) between the pyrotechnic ejection system (4) and the socket (3) is provided with an insulator (11) which is configured to completely electrically isolate the pyrotechnic ejection system (4) from the socket (3).

2. Launching structure according to claim 1, characterized in that the pyrotechnic ejection system (4) is provided with a threaded section (12) configured to be screwed into a cooperating threaded section (13) provided in the socket (3) and forming said housing (9), and in thatthe insulator (11) is arranged on the inner face of the threaded section (13) of the socket (3), intended to come into contact with the threaded section (12) of the pyrotechnic ejection system (4).

3. Launching structure according to claim 1, characterized in that the pyrotechnic ejection system (4) is provided with a threaded section (12) configured to be screwed into a cooperating threaded section (13) provided in the socket (3) and forming said housing (9), and in that the insulator (11) is arranged on the external face of the threaded section (12) of the pyrotechnic ejection system (4), intended to come into contact with the threaded section (13) of the socket (3).

4. Launching structure according to any one of claims 1 to 3, characterized in that the insulation (11) is made of parylene.

5. Launching structure according to any one of claims 1 to 4, characterized in that the socket (3) is connected to a mechanical mass.

6. Pyrotechnic cartridge comprising at least one launching structure and one pyrotechnic charge, characterized in that said launch structure (2) is a launch structure according to any one of claims 1 to 5.

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