Ignition cord with enhanced combustion power

Abstract

Enhanced combustion ignition cord: An ignition cord for the combustion of a propellant charge contained within a cartridge case, said cord consisting of a core comprising a pyrotechnical material and surrounded by a sheath, characterized in that the sheath consists of two concentric cylindrical tubes between which is arranged a free-flowing powdered energy material. The two tubes are made of an inert polymer material or are based on an extruded powdered energy material, or alternatively, one of the tubes may be made of an inert polymer material and the other of an extruded powdered energy material.

Description

Title of the invention: Enhanced power combustion ignition cord

[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 ignition devices for such propellant charges.

[0003] It is known to produce cartridges in which the ignition device for the propellant charge comprises energetic ignition cords extending between an initiation means attached to a rear portion of the case and the projectile. For example, see patents US5129324, US5179250 and EP1092940.

[0004] Ignition cords, which are ignited by combustion rather than detonation, most often comprise a plastic tube containing a pyrotechnic composition such as black powder, a composition combining boron and potassium nitrate, or 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 supplied exclusively by the pyrotechnic composition inside the tube.

[0005] Ignition cords ensure ignition of the propellant charge in a cartridge where the projectile penetrates deeply into the powder bed, particularly for an arrow-type projectile with a long barrel. Conventional axial ignition tubes cannot be used with such projectiles.

[0006] In known igniter-cord cartridges, the cords extend between an axial igniter tube attached to the base and the case or projectile. In particular, in US patents 5129324 and 5179250, the cords are arranged along the inner wall of the case and are held in place by plastic star-shaped clips.

[0007] We can also mention US patent 3320882 which describes an ignition cord consisting of a continuous column of a mixture of lead azide and particulate metal confined in a metallic sheath.

[0008] As part of increasing the performance of fin-stabilized projectiles, it is necessary to implement new propellant powders.

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

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

[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's speed. As a reminder, ignition cords have a combustion rate of -500 m / s, unlike detonating cords. This decrease in speed results in a reduction of power precisely 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, thus making it possible to ignite the new generations of propellant powders, which are not ignitable by the cords of the prior art.

[0013] The idea behind the present invention is to increase the amount of available energy while maintaining a similar operating time to the standard fuse, 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 fuse can still be used because it allows control over the ignition propagation speed. The relay is used to significantly increase the energy delivered.

[0014] To facilitate the use of this relay, the present invention proposes implementing an over-sheath around the standard cord to fill the gaps created by the energetic material used as a relay, for example, medium-caliber powder. The connection between the over-sheath and the standard cord's sheath can be made via one or more mechanical links. The sheath and over-sheath are made of plastic, but they can also be made of extruded propellant powder.

[0015] The compatibility in terms of ignition between the internal pyrotechnic composition and the relay, which consists of medium caliber powder or other pyrotechnic composition such as black powder, must be sufficient for the latter to initiate rapidly on contact with the combustion products of the composition of the standard cord.

[0016] To this end, the present invention relates to an energetic ignition cord for a propellant charge contained in the case of a cartridge, said cord being consisting of a core comprising a pyrotechnic material and surrounded by a sheath, characterized by the fact that the sheath is made up of two concentric cylindrical tubes between which is arranged a free powdered energetic material.

[0017] In a first embodiment, the two tubes are made of an inert polymer material, said tubes being able to be connected to each other for example by radial fins, the whole being obtained by extrusion of the polymer material.

[0018] In a second embodiment, the two tubes are based on an energetic material in propellant powder extruded in one block.

[0019] In a third embodiment, one of the tubes is made of an inert polymer material and the other is based on an energetic material in extruded propellant powder forming in a block.

[0020] The inert material can be low-density polyethylene.

[0021] Tubes based on an energetic material in extruded block propellant powder can be solid or slotted tubes.

[0022] The energetic material can be chosen from single-base propellant powders, multi-base propellant powders, and pyrotechnic compositions.

[0023] Single-base propellant powders can be chosen from nitrocellulose powders, such as those marketed by the Milan Blagogevic-Namenska Company under references NC-16 and NC-161, the B7T from Nammo Vihtavuori and the PCL from PB Clermont.

[0024] The multi-base propellant powders can be chosen from Eurenco's NK1405 or PB Clermont's PBC2000 powders.

[0025] A pyrotechnic composition may be chosen from black powder (PN), holy water, a boron / potassium nitrate (B / KNO3) composition and mixtures thereof.

[0026] The core can be made of a thermite comprising at least one metal chosen in particular from Al, Mg and B, an oxidant chosen in particular from KNO3, KC1O4 and WO3, and a binder chosen from polymers and nitrocellulose.

[0027] A comparison of 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 is double spherical base powder such as PB Clermont's PBC2000 powder, with the same core, showed a division by 5 of the ignition time by the cord of the invention.

Claims

Demands

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

2. - Ignition cord according to claim 1, characterized in that the two tubes are based on an energetic material in propellant powder extruded in block.

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

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

5. - Cord according to any one of claims there 4, characterized in that the energetic material is selected from single-base propellant powders, multi-base propellant powders, and pyrotechnic compositions.

6. - Cord according to claim 5, characterized in that the single-base propellant powders are selected from nitrocellulose powders.

7. - Ignition cord according to claim 5, characterized in that a pyrotechnic composition is selected from black powder (PN), holy water, a boron / potassium nitrate (B / KNO3) composition and mixtures thereof.

8. - Ignition cord according to any one of claims 1 to 7, characterized in that the core is made of a thermite comprising at least one metal selected in particular from Al, Mg and B, an oxidant selected in particular from KNO3, KC104 and WO3, and a binder selected from polymers and nitrocellulose.