Ammunition and explosives – Igniting devices and systems – Electrical primer or ignitor
Reexamination Certificate
1998-09-14
2001-05-29
Carone, Michael J. (Department: 3643)
Ammunition and explosives
Igniting devices and systems
Electrical primer or ignitor
C102S202000, C102S202800
Reexamination Certificate
active
06237494
ABSTRACT:
BACKGROUND OF THE INVENTION
The technical scope of the invention is that of components allowing the ignition of a pyrotechnic composition or else of the propellant charge of a piece of ammunition.
Known igniters comprise a pyrotechnic composition able to generate a flame whose temperature is high enough to ignite a propellant charge or else a working pyrotechnic composition (smoke, flare or gas-generating composition for example).
The ignition composition is itself initiated by an electric means which can be a hot wire, an exploding wire or else a semi-conductor bridge.
These components suffer from drawbacks.
Thus, they all implement a pyrotechnic ignition composition, which has a certain sensitivity, notably to overheating or to electrostatic discharges.
The handling and manufacture of these components therefore presents certain risks and the ammunition or devices implementing such components also run the risk of inadvertent ignition.
Furthermore, known components only operate once and they therefore deliver all their energy further to the passage of a current through the electric ignition means. Such a mode of operation is abrupt and can cause ignition heterogeneities in the composition that are likely to disturb the future combustion rate and cause pressure waves.
It is therefore impossible using known components to spread the distribution of energy over time in order to control the ignition rate of the pyrotechnic composition or of the propellant charge.
It is known elsewhere, in the field of artillery, to use a plasma torch to generate pressure allowing a projectile to be fired.
These plasma torches can be used alone (see for example patent U.S. Pat. No. 2,899,864) or can be combined with a conventional solid or liquid propellant charge (see for example patent U.S. Pat. No. 5,231,242) in a gun commonly named the “Electro-Thermal-Chemical Gun”.
Known plasma torches are of considerable size (around 200 to 300 mm long) and consume a lot of energy (around one Megajoule) released in a manner that is difficult to control.
When they are used alone, they are designed so as to supply pressure allowing the projectile to be fired.
When they are combined with a propellant charge, the pressure moving the projectile results both from the combustion of the propellant charge and the plasma pressure generated by the torch, plasma that also modifies the combustion rate of the propellant charge.
In any event, the pressure supplied by the torch is substantial enough to allow an increase in the velocity of the projectile whilst keeping up the level of pressure applied to it.
Using such torches to ignite a pyrotechnic composition is totally out of the question, the energy developed and the pressure generated risk disorganising or destroying the pyrotechnic composition.
SUMMARY OF THE INVENTION
The aim of the invention is to propose an ignition component for a pyrotechnic composition or a propellant charge that does not suffer from the drawbacks of known ignition components.
Thus, the ignition component according to the invention ensures the reliable and reproducible ignition of pyrotechnic compositions and propellant charges.
It is inert, thereby substantially improving manufacturing safety and implementation and allowing ammunition to be developed that has greater resistance to environmental stresses (overheating, electrostatic discharges, shocks).
It is simply designed and is easy and inexpensive to manufacture.
A further aim of the invention is also to propose an ignition component allowing the ignition phenomenon of the composition or propellant charge to be controlled.
Used to ignite a propellant charge, the component proposed by the invention also allows extra energy to be supplied enabling greater velocities to be obtained for the projectile.
Yet another aim of the invention is to propose an ignition device which enables the ignition of a propellant charge to be controlled.
The subject of the invention is thus an ignition component for a pyrotechnic composition or a propellant charge, wherein it comprises at least two electrodes separated by a cylindrical insulating envelope marking out an inner volume, electrodes connected by a conductive ignition fuse arranged in the inner volume, the component thus forming a plasma torch whose size is such that it generates a plasma when it receives an ignition voltage less than or equal to 600 volts and is supplied with electric energy less than or equal to 5000 joules.
The ignition component according to the invention thus forms a plasma torch, but a torch of a very reduced size. In fact, in practical terms, such energy supply conditions cause a torch to be designed in which the distance separated the uninsulated parts of the electrodes through the free space (distance over which the electric arc is produced) is less than or equal to 10 mm (and is preferably around 5 mm).
The skill of the inventors lies in their considering that it was nevertheless possible to obtain a plasma using such a small structure, and in that the plasma obtained was enough to allow the ignition of a pyrotechnic composition or propellant charge.
In their development of the invention, they therefore deliberately set aside conventional wisdom in the field of pyrotechnic ignition components.
Thus, it could seem surprising that an ignition component intended to produce a flame could be designed that includes no flame-generating composition.
Neither could plasma torches lead them to a design for an ignition component. In fact, these torches are usually designed to deliver substantial energy levels required to set off a projectile. Such an area of use leads to the design of torches of a relatively substantial size in which the distance between electrodes is far enough for the strength of the electric arc discharge between electrodes to be high.
According to a variant embodiment, the ignition fuse can be formed of a fibrous conductive structure substantially filling all the inner volume marked out by the electrodes and the insulating envelope.
The fibrous structure will advantageously be formed by carbon filaments, or of one or several copper or magnesium wires. According to another characteristic of the invention, the component incorporates a cap blocking an exit boring for the gases generated and ensuring the confinement of the inner volume.
A further subject of the invention is an ignition device for a propellant charge using such an ignition component.
According to one variant, such an ignition device can incorporate at least three ignition components according to the invention integral with a support tube.
At least two ignition components can have their axes oriented in different directions.
According to another variant, the ignition device according to the invention can incorporate at least three ignition components evenly spaced on the external surface of the support tube and whose axes are substantially perpendicular to the axis of the support tube.
According to another embodiment of the invention, the ignition device can be such that the support tube also carries at least one pyrotechnic igniter.
The invention lastly concerns a propellant charge for a piece of ammunition incorporating a combustible envelope containing a propellant charge; charge characterised in that it incorporates an ignition device according to the invention.
Although low, the level of plasma energy generated by the component enables the pressure developed in the chamber of a small or medium calibre weapon to be increased and enables this pressure to be maintained for longer to the rear of the projectile.
It thus becomes possible using such a component to design small calibre (less than 14 mm) or medium calibre (less than 50 mm) Electro-Thermal-Chemical weapons and ammunition, which was impossible using known plasma torches whose range of use is limited to large calibres.
Moreover, the ignition component proposed by the invention, despite its small size, is able to deliver (using an appropriate electronic control device) several consecutive plasma jets separated by a few milliseconds.
By acting on the
Brunet Luc
Caillau Frantz
Espagnacq Andre
Guerenne Patrick
Carone Michael J.
Giat Industries
Oliff & Berridg,e PLC
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