Power-boosted combustion ignition cord

Abstract

Ignition cord for combustion of a propellant charge contained in the case of a cartridge, said cord being constituted by a core comprising a pyrotechnic material and surrounded by a sheath, in which the sheath is constituted by two concentric cylindrical tubes between which is arranged an energetic material in loose powder, characterized in that one of the two tubes is based on an energetic material in propellant powder extruded in a block and that the other of the two tubes is based on an energetic material in propellant powder extruded in a block or made of an inert polymer material.

Description

[0001] The present invention relates to a combustion ignition cord with enhanced power.

[0002] The technical field of the invention is that of cartridges comprising a propellant charge housed in a case and devices for igniting such propellant charges.

[0003] It is known to produce cartridges in which the propellant charge ignition device comprises energetic ignition cords which extend between an initiation means secured to a rear part of the case and the projectile. For example, we can consider patents US5129324, US5179250 and EP1092940.

[0004] Ignition cords, in combustion and not in detonation, most often comprise a plastic tube containing a pyrotechnic composition such as black powder or a composition combining boron and potassium nitrate or even aluminum and potassium perchlorate. These cords are well known and described in particular by patent FR2441598. In this case the power and energy of the ignition are provided exclusively by the pyrotechnic composition present inside the tube.

[0005] Ignition cords are used to ignite the propellant charge in a cartridge whose projectile penetrates deep into the powder bed, particularly for an arrow-type projectile with a long rod. Conventional axial igniter tubes cannot be incorporated with such projectiles.

[0006] In known cord-ignition cartridges, the cords extend between an axial igniter tube connected to the base and the case or projectile. In particular, in patents US5129324 and US5179250 the cords are arranged along the inner wall of the case and are held in place by plastic stars.

[0007] Also of interest is US Patent 3320882 which describes an ignition cord consisting of a continuous column of a mixture of lead azide and a particulate metal confined in a metal sheath.

[0008] In order to improve the performance of arrow shells, it is necessary to implement new propellant powders.

[0009] Unlike older powders such as single base (B19T) or double base (GB19T), the new formulations have a much lower ignitability. Therefore, the energy and power of the ignition system must be significantly increased.

[0010] Energy is related to the amount of pyrotechnic material involved in ignition, while power is related to the time over which this energy is diffused into the bed of propellant powder. Thus, the problem with conventional ignition cords such as ITLX ® cords is that they have a limited maximum amount of energy compared to the energy required to ignite the new propellant powders.

[0011] Furthermore, increasing the amount of pyrotechnic composition in the cord generally leads to a decrease in the combustion rate and therefore a decrease in the cord speed. As a reminder, ignition cords have a combustion regime (~500 m / s) unlike detonating cords. This decrease in speed leads to a decrease in power where it is needed to increase it.

[0012] The present invention proposes to solve these problems by proposing a combustion ignition cord providing in particular 100 to 1000% compared to simple cords (for example ITLX ®< ) in terms of ignition power, then making it possible to ignite the new generations of propellant powders, which cannot be ignited by the cords of the prior state of the art.

[0013] The idea behind the present invention is to increase the amount of energy available while maintaining a similar operating time to the standard cord, thus increasing the power. This increase is achieved according to the invention by means of a relay loaded with propellant powder, of small or medium caliber for example. The standard cord can still be used because it allows the ignition propagation speed to be controlled. The relay is used to significantly increase the energy delivered.

[0014] In order to facilitate the implementation of this relay, it is envisaged according to the present invention to implement an over-sheath around the standard cord in order to be able to fill the interstices thus generated by the energetic material serving as a relay, for example medium-caliber powder. The connection between the over-sheath and the sheath of the standard cord can be made by means of one or more mechanical connections. The material of the sheath and the over-sheath are made of plastic, but it is also possible to provide them in energetic material in extruded propellant powder.

[0015] The compatibility in terms of ignitability between the internal pyrotechnic composition and the relay, which is made up of medium-calibre powder or other pyrotechnic composition such as black powder, must be sufficient for it to ignite quickly upon contact with the combustion products of the standard cord composition.

[0016] To this end, the present invention relates to a cord for igniting a propellant charge contained in the case of a cartridge, said cord being constituted by a core comprising a pyrotechnic material and surrounded by a sheath, in which the sheath is constituted by two concentric cylindrical tubes between which is arranged an energetic material in loose powder, characterized in that one of the two tubes is based on an energetic material in propellant powder extruded in a block and that the other of the two tubes is based on an energetic material in propellant powder extruded in a block or made of an inert polymer material.

[0017] In a first embodiment, the two tubes are based on an energetic material in propellant powder extruded in a block.

[0018] In a second embodiment, one of the tubes is based on a block extruded propellant powder energetic material and the other of the two tubes is made of an inert polymer material which is a low density polyethylene.

[0019] The tube(s) based on an energetic material in propellant powder extruded in block form may be solid or split tubes.

[0020] The energetic material can be chosen from single-base propellant powders, multi-base propellant powders, and pyrotechnic compositions.

[0021] Single-base propellant powders can be chosen from nitrocellulose powders, such as those marketed by Milan Blagogevic-Namenska under the references NC-16 and NC-161, B7T from Nammo Vihtavuori and PCL from PB Clermont.

[0022] Multi-base propellant powders can be chosen from Eurenco's NK1405 or PB Clermont's PBC2000 powders.

[0023] A pyrotechnic composition may be chosen from black powder (NP), benite, a boron / potassium nitrate (B / KNO 3 ) composition and their mixtures.

[0024] The core may be made of a thermite comprising at least one metal chosen in particular from Al, Mg and B, an oxidant chosen in particular from KNO 3 , KClO 4 and WO 3 , and a binder chosen from polymers and nitrocellulose.

[0025] A comparison of the ignition times between a conventional cord having a plastic sheath enclosing an ITLX ® core material and a cord according to the invention having a sheath formed of two concentric tubes based on extruded NC-16 propellant powder between which there is a double spherical base powder such as the PBC2000 powder from PB Clermont, with the same core, showed a division by 5 of the ignition time by the cord of the invention.

Claims

1. - Ignition cord for the combustion of a propellant charge contained in the case of a cartridge, said cord being constituted by a core comprising a pyrotechnic material and surrounded by a sheath, in which the sheath is constituted by two concentric cylindrical tubes between which is arranged an energetic material in free powder, characterized by the fact that one of the two tubes is based on an energetic material in propellant powder extruded in a block and the other of the two tubes is based on an energetic material in propellant powder extruded in a block or made of an inert polymer material.

2. - Ignition cord according to claim 1, characterized by the fact that Both tubes are made from an energetic material in propellant powder extruded in a block.

3. - Ignition cord according to claim 1, characterized by the fact that the inert material is low density polyethylene.

4. - Ignition cord according to one of claims 1 to 3, characterized by the fact thatthe tube(s) based on an energetic material in propellant powder extruded in a block are solid or split tubes.

5. - Cord according to one of claims 1 to 4, characterized by the fact that the energetic material is chosen from single-base propellant powders, multi-base propellant powders, and pyrotechnic compositions.

6. - Cord according to claim 5, characterized by the fact that single-base propellant powders are chosen from nitrocellulose powders.

7. - Ignition cord according to claim 5, characterized by the fact that a pyrotechnic composition is chosen from black powder (NP), benite, a boron / potassium nitrate (B / KNO3) composition and their mixtures.

8. - Ignition cord according to one of claims 1 to 7, characterized by the fact thatthe core is made of a thermite comprising at least one metal chosen in particular from Al, Mg and B, an oxidant chosen in particular from KNO3, KClO4 and WO3, and a binder chosen from polymers and nitrocellulose.

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