EP2192376A1 - Propulsion device with regulated engagement - Google Patents

Abstract

The cartridge has a rear chamber (1) including an ignition unit. A confining unit confines a propelling powder i.e. progressive combustion powder, in the rear chamber, while allowing passage of gases resulting from combustion of the powder via vents of the rear chamber. A low pressure chamber (3) forms a projectile propulsion chamber, and is communicated with an intermediate chamber (2) having constant volume by an opening (13) of a predetermined section. A wedging disk is made of polystyrene, felt or carton, and placed around an igniting tube.

Description

The present invention relates to a propellant cartridge of a large caliber projectile.

The invention aims as an application the propulsion of so-called ALR projectiles (A reduced lethality).

The reduced lethal projectiles have a reduced mass in order to limit the effects of shocks on the crowds. They are pulled at low speed and are also made with light materials, for example plastic.

Projectile propulsion devices of large caliber are known.

By big caliber, it means here a caliber greater than or equal to 90mm.

These known devices for large caliber projectile are however not adapted to the ALR application.

They are generally formed by an ignition system for igniting a propellant powder disposed in a combustion chamber, the pressure thus generated in the combustion chamber causing the propulsion of the projectile in the barrel of the weapon, then its ejection.

To ensure safe propulsion of the large caliber projectile, there is a large amount of propellant powder in the combustion chamber.

For this, it is understood that the amount of powder must be all the more important that the size is large.

It should also be noted that with these devices, the volume of the combustion chamber varies as the projectile progresses in the tube of the weapon, the base of the projectile forming a front wall of the combustion chamber.

However, the greater the volume of the chamber, the greater the risk of having unburnt powder in the room.

This amount of unburnt is not controlled.

As a result, the amount of powder initially introduced into the combustion chamber to ensure safe propulsion of the large caliber projectile may actually be insufficient to achieve the desired result.

This problem is all the more critical as the caliber is big.

The known devices for propelling a large caliber projectile thus tend to either add more powder to eject a projectile with a minimum speed, compatible with the safety requirements, or to intervene directly on the definition of the propellant powder ( geometry, thermodynamic characteristics) to increase the volume of gas generated.

The problem of the variation in the amount of unburnt, implying a variation of the exit velocity of the projectile, is thus bypassed.

On the other hand, such a workaround can not be considered for an ALR application.

Indeed, for an application ALR, the output speed of the projectile is low (of the order of a few hundred meters per second), which is incompatible with the use of an excess amount of propellant powder.

On the contrary, to achieve a relatively low projectile exit velocity, a reduced amount of propellant powder must be employed.

The design of an ALR munition for a large caliber weapon requires low speed performance. It therefore involves small amounts of propellant powder while the volume of the chamber of the weapon is important. This therefore entails the risk of obtaining unburned powder in the chamber of the weapon, because there is then a difficulty in achieving an optimal combustion rate of the powder because of insufficient containment for the latter.

In addition, for an ALR application, the output speed of the projectile of the propulsion device must be controlled, which is not possible with an existing large-caliber propulsion device. It does not control the amount of unburnt, because of the large volume of the combustion chamber.

In addition, this effect would be reinforced by the use of a small amount of powder in a known large-caliber propulsion device. This would only increase the uncertainty about the amount of unburnt, thereby increasing the uncertainty about the exit velocity of the projectile. For example, for a reduced lethal projectile of 90mm caliber (mass of the order of 2 to 3 kg), it is necessary to consider a quantity of powder 5 to 20 times less important than to propel a conventional projectile 90 mm.

Because of this uncertainty, it is therefore not excluded that the projectile, under the effect of insufficient thrust, strongly rubs or even hangs within the propulsion device or even progresses by sudden, blocking when the pressure is insufficient then progressing again when the pressure (which increases following the stopping of the projectile) reaches again a sufficient level.

For example, for a projectile of 90mm caliber, the length of the propulsion device on which the projectile is likely to move before being ejected, is of the order of 4 meters; and this length increases with increasing size.

For a so-called ALR application, the use of current devices with a reduced amount of powder can therefore lead to a firing failure (the projectile remains blocked in the device), or even to a degradation of the propulsion device itself.

However, devices adapted to the ALR application have already been proposed.

These devices however only concern small calibres.

By small gauge, we generally mean calibres of 40 mm or less.

For example, documents may be cited US 2005/0268808 (D1) and US 2007/0151473 (D2).

In order to obtain a projectile ejection speed that is both low (between 50 and 300 m / s) and controlled, the documents D1 and D2 use a first chamber, of reduced volume, containing the propellant powder and in which the combustion takes place; a second chamber where the gases from the combustion can relax and a gas passage between the two chambers.

The first chamber is called the high pressure chamber, the second chamber is called a low pressure chamber.

The amount of powder introduced into the high pressure chamber is low to obtain an equally low ejection velocity of the combustion gases.

The reduced volume of the high pressure chamber can limit or even avoid the presence of unburnt. In addition, the choice of the section of the passage orifice between the two chambers makes it possible to control the flow rate of combustion gas passing through the low pressure chamber.

By this means, the devices presented in these documents limit the uncertainty on the speed of ejection of the projectile.

The devices presented in documents D1 or D2 are therefore interesting ways to develop a device for propelling a projectile for an ALR application.

However, they are limited to projectiles of small calibres, and are not transferable in the state to the propulsion devices of projectiles of large caliber.

Indeed, to propel a projectile of large caliber (high mass), it is necessary to use a quantity of powder more important than for a projectile of small caliber.

However, the use of a larger quantity of powder in a chamber of volume similar to the volume of the high pressure chamber presented in documents D1 or D2, would lead to a rupture of the walls thereof.

In addition, the propulsion devices of a large caliber projectile have a long weapon tube, in which the projectile is guided to the exit. For example, for a 90mm caliber, the barrel of the weapon can reach a length of 4 meters.

The tube of small arms systems is much shorter.

Also, to avoid blockage of the projectile in the barrel of the weapon, whose volume would form the low pressure chamber of the documents D1 or D2, it would be necessary to increase the amount of powder in the high pressure chamber to ensure that effective ejection of the projectile out of the device.

This is not possible because it would only aggravate the safety problem related to the rupture of the walls of the high pressure chamber.

In addition, the powders used in documents D1 or D2 are bright powders whose rapid combustion would not be suitable (with the two-chamber propulsion device structure described by D1 and D2) to a safe ejection of a large caliber, that is to say an ejection without blockage of the projectile in the tube of the weapon.

One could think of using a bright powder to solve the problem of unburnt. However, such a solution is unsatisfactory because it leads to significant pressure peaks which may stress the body of the ALR projectile excessively, particularly when an attempt is made to obtain an output speed of the order of 300 m / s.

Finally, it should also be noted that the use of a high pressure chamber of volume similar to the volume of the high pressure chamber presented in documents D1 or D2, would limit the size of the flue gas passage in the chamber low pressure. Assuming that the walls of the high pressure chamber do not yield, this would lead to an insufficient gas flow to propel the projectile without blockage in the barrel of the weapon.

The invention thus aims to provide a propellant cartridge of a large caliber projectile, able to propel projectiles for an application ALR safely.

Therefore, the invention aims to provide a propellant cartridge of a large caliber projectile to ensure effective output of the projectile of the barrel of the weapon, at a speed of output at a time low, it is ie not exceeding a few hundred meters per second, and mastered.

• une chambre arrière comportant :
  • des moyens d'allumage d'une poudre propulsive,
  • un moyen pour confiner la poudre dans la chambre arrière tout en laissant passer les gaz issus de la combustion de la poudre par des évents de la chambre arrière ;
• une chambre intermédiaire, de volume constant, communiquant avec la chambre arrière par les évents ;
• une chambre basse pression, formant chambre de propulsion du projectile, et communiquant avec la chambre intermédiaire par un orifice de section prédéterminée.

The present invention thus proposes a propulsion cartridge for a projectile having a caliber of at least 90 mm, characterized in that it comprises:

• a rear bedroom with:
  • means for igniting a propellant powder,
  • means for confining the powder in the rear chamber while allowing the gases from the combustion of the powder to pass through vents in the rear chamber;
• an intermediate chamber of constant volume communicating with the rear chamber through the vents;
• a low pressure chamber, forming a projectile propulsion chamber, and communicating with the intermediate chamber through a predetermined section orifice.

• le moyen pour confiner la poudre dans la chambre arrière tout en laissant passer les gaz issus de la combustion de la poudre par les évents de la chambre arrière comprennent une grille dont la taille de maille est inférieure à la dimension, avant combustion, d'un grain de poudre ;
• la chambre arrière comporte des moyens pour confiner, dans une première phase de combustion, la poudre et les gaz de combustion issus de la combustion de la poudre dans la chambre arrière et pour, lesdits moyens étant susceptibles, dans une deuxième phase de combustion, de céder sous l'effet de la température et/ou de la pression ;
• le moyen de confinement de l'alinéa précédent est formé par une feuille mince en métal ou en alliage métallique, par exemple en étain ;
• les moyens d'allumage comprennent un tube d'allumage autour duquel la poudre est disposée et un système d'allumage, par exemple de type amorce à percussion ou amorce à initiation par décharge capacitive, disposé à la base du tube d'allumage ;
• la cartouche comprend un disque de calage, par exemple en polystyrène, feutre ou carton, disposé autour du tube d'allumage et contre une paroi de la chambre arrière pour caler la poudre propulsive dans la chambre arrière ;
• l'orifice de section prédéterminée est formé d'une tuyère ou d'un tube;
• la poudre propulsive est une poudre à combustion progressive.

Other technical features of the invention may be provided, taken alone or in combination:

• the means for confining the powder in the rear chamber while allowing the gases from the combustion of the powder to pass through the vents of the rear chamber comprise a grid whose mesh size is smaller than the size, before combustion, of a grain of powder;
• the rear chamber comprises means for confining, in a first combustion phase, the powder and the combustion gases resulting from the combustion of the powder in the rear chamber and for, said means being capable, in a second combustion phase, of yielding under the effect of temperature and / or pressure;
• the containment means of the preceding paragraph is formed by a thin sheet of metal or metal alloy, for example tin;
• the ignition means comprise an ignition tube around which the powder is disposed and an ignition system, for example of the percussion primer type or capacitive discharge initiation primer, arranged at the base of the ignition tube;
• the cartridge comprises a setting disk, for example polystyrene, felt or cardboard, arranged around the ignition tube and against a wall of the rear chamber to wedge the propellant powder in the rear chamber;
• the orifice of predetermined section is formed of a nozzle or a tube;
• the propellant powder is a progressive combustion powder.

• la figure 1 représente une vue en coupe d'un dispositif de propulsion régulée selon l'invention, comportant une cartouche de propulsion et un tube pour un projectile ;
• la figure 2 représente une vue agrandie de la partie inférieure de la cartouche de la figure 1.

Other features of the invention will be set forth in the following detailed description with reference to the figures which represent, respectively:

• the figure 1 is a sectional view of a controlled propulsion device according to the invention, comprising a propulsion cartridge and a tube for a projectile;
• the figure 2 represents an enlarged view of the lower part of the cartridge of the figure 1 .

The following description is based on the Figures 1 or 2 .

The firing device is constituted by a weapon comprising a tube 21 intended to fire a projectile 22, and a propellant cartridge 20 housed in a chamber 23 of the weapon connected to the tube 21. Such a weapon structure is classic and it is not necessary to describe it in more detail.

The propellant cartridge 20 comprises a rear chamber 1, an intermediate chamber 2, a low pressure chamber 3 within which the projectile 22 is disposed and an orifice 13 of predetermined section. for the passage of gases from the intermediate chamber 2 to the low pressure chamber 3.

The rear chamber 1 comprises an ignition tube 5 around which is disposed a propellant powder 6.

This propellant powder 6 may be formed of cylindrical grains. The outer diameter of these grains may for example be of the order of 5 mm.

The ignition tube 5 has orifices 51 disposed along its length and on its periphery which allow the ignition gases to pass in the direction of the propellant powder 6, originating from an ignition system 9 arranged at the base of the ignition tube 5.

The rear chamber 1 has means to ensure complete combustion of the propellant powder 6.

For this purpose, it comprises means for confining the propellant powder 6 in a reduced volume V ₁ , corresponding approximately to the difference between the volume of the rear chamber 1 and that of the ignition tube 5. In the example described here, reduced volume V ₁ is 0.4 liter for a caliber of 90mm (this volume could be different for a different projectile mass).

More specifically, the confinement means of the rear chamber 1 comprise a first confinement means 12 and a second confinement means 7.

The means 12 makes it possible to confine the powder 6 in the volume V ₁ of the rear chamber 1 while allowing the gases coming from the combustion of the powder 6 to pass through vents 8 of the rear chamber 1.

The means 12 may be a grid, for example metallic, having a mesh size smaller than the grain size of the propellant powder 6.

For example, if the grains of the propellant powder 6 are cylindrical and have, before any combustion, a dimension of the order 5mm, we can provide a grid 12 whose mesh size is of the order of 2mm.

Preferably a progressive combustion powder will be selected.

Such a powder is formed of cylindrical grains pierced with several holes, which leads to an increase in the combustion surface over time, and therefore to an increase in the volume of gas generated.

For example, a single base, 19-hole powder can be used, conventionally used in large caliber weapon systems.

Such a powder characteristic makes it possible to ensure a progressive increase in the pressure communicated to the projectile.

The confinement means 7, which surrounds the grid 12, participates in the confinement of the propellant powder 6 in the volume V ₁ of the rear chamber 1 on the one hand in the absence of combustion, and on the other hand during a first phase of combustion.

For this purpose, it can be achieved by a thin sheet of metal or a metal alloy, for example tin.

In the absence of combustion, for example when the cartridge is stored, the confinement means 7 makes it possible to have a solid, totally closed structure encompassing both the grid 12 and the propellant powder 6.

Then, once combustion has begun, the confinement means 7 make it possible to confine both the propellant powder 6 and the gases produced by the combustion of the powder 6 to a certain value of temperature and / or pressure within the rear chamber 1.

This is a first phase of combustion.

Beyond these temperature and / or pressure values, the confinement means 7 breaks and thus allows the combustion gases to pass through the gate 12 and the vents 8, towards the intermediate chamber 2.

This is a second combustion phase during which the grid 12 plays its full role.

The vents 8 are here arranged on the circumference of the rear chamber 1, and also at the end thereof. The vents 8 are sized to facilitate the evacuation of the combustion gases and thus prevent the destruction of the rear chamber 1.

The exact dimensioning of the vents will depend on the performance of the non-lethal system itself (projectile mass, projectile velocity) as well as the combustion characteristics of the propellant powder used. The skilled person will easily size these different parameters from the modeling tools available to him.

It will therefore be understood that once the confinement means 7 has yielded, the gate 12 allows the combustion gases to pass, but prevents the grains of propellant powder 6 whose dimensions exceed the mesh size of the grid 12, from passing to the intermediate chamber 2.

This makes it possible to ensure that the grains of propellant powder remain confined in their confinement volume V ₁ until they have reached an optimal combustion regime, for which it can be certain that they will not be extinguished. .

When the grains have reached a size smaller than that of the mesh of the grid 12, they then pass to the intermediate chamber 2, with the combustion gases.

The propellant powder 6 remains confined in a reduced volume, defined by the volume V ₁ , for a good part of its combustion.

With this arrangement, this considerably reduces the risk of unburnt, while avoiding a rupture of the walls of the rear chamber 1 comprising the propellant powder 6.

The containment means 7 is completed by a setting disc 10 disposed around the ignition tube 5 and against a wall 11 of the rear chamber 1. The setting disc 10 is not intended to break, and is intended to provide a background to the volume V ₁ in which the propellant powder 6 is arranged. This setting disc 10 may for example be made of polystyrene, felt or cardboard.

The intermediate chamber 2 has a predetermined constant volume V ₂ . In the example shown here, the volume V ₂ is 0.9 liter (90mm gauge).

The fact that the volume V ₂ of the intermediate chamber 2 is constant, and low in comparison with the volume V ₃ of the low pressure chamber 3, allows a rapid rise in pressure in this intermediate chamber 2 at a pressure level contributing to the good combustion of the powder grains present in the rear chamber 1.

By this means, it is ensured that there will be no unburned propellant powder 6 in the rear chamber 1 and the intermediate chamber 2.

As a result, there is no hazard on the exit velocity of the projectile 22 out of the weapon tube 21.

The low pressure chamber 3 has a variable volume V ₃ . Indeed, the base of the projectile 22 intended to move towards the outlet of the tube 21 itself defines a wall of this chamber 3.

Still in the context of the example shown here, the initial volume of the low pressure chamber is 3 liters (90mm gauge). This volume increases as the projectile 22 progresses in the tube of the weapon 21.

The orifice 13 may be formed by a tube or a nozzle. It makes it possible to regulate the flow of combustion gas passing from the intermediate chamber 2 to the low pressure chamber 3. The flow of gas introduced into the low pressure chamber 3 is thus perfectly regulated by the size of the orifice 13.

The rise in pressure is thus relatively progressive until it reaches a level sufficient to move the projectile within the tube 21 of the device. When the projectile 22 is in motion, the pressure level in the low pressure chamber 3 decreases in a slow manner and remains regulated by the flow of combustion gas entering the chamber 3, so that the thrust of the projectile is progressive.

It is for these reasons that we speak of cartridge with regulated progressivity.

Preferably, the orifice 13 may in particular be dimensioned so as to provide a flow of gas at least partially offsetting the pressure drop associated with the increase in the volume of the low pressure chamber 3. In such a case, this means that after the pressure increase phase, the pressure at the base of the projectile 22 remains sufficiently high during most of the course of the projectile 22 in the tube 21 of the weapon.

It will thus seek to limit the decrease of this pressure along the path of the projectile 22 in the tube 21 of the weapon.

For example, for a projectile 22 of 3kg propelled at a speed of the order of 250 m / s with a device without an intermediate chamber (thus without vents), the pressure drop is approximately 47% at the end. a meter of travel of the projectile 22 in the tube 21 of the weapon (passage of the pressure of 8.5 MPa to 4.5 MPa) and it is more than 76% at the exit of the tube 21 (after a 4m course of the projectile in the tube of the weapon).

By comparison, with the device according to the invention, the pressure drop is only 25% after one meter of travel of the projectile 22 in the tube 21 of the weapon (pressure change from 8MPa to 6MPa ) and it is 65% at the exit of the tube 21 of the weapon.

The decrease in the pressure pushing the projectile along the tube is therefore much more progressive with the device according to the invention.

Note also that with a device without an intermediate chamber and without vents it is not guaranteed to obtain a good powder combustion regime as permitted by the invention.

This progressivity is adjustable by adjusting the diameter of the orifice 13. The entire device will be dimensioned so that the powder is completely burned when the projectile leaves the tube.

This prevents any blockage of the projectile 22 in the tube 21 of the weapon or any movement alternating in advance and stopping the projectile 22 along the tube 21.

If, in the context of the same example, it sought to obtain the same exit velocity of the tube but with a combustion powder (to avoid unburnt), the peak pressure obtained would be of the order of 12 MPa while it is only 8 MPa with the device according to the invention.

In addition to the progressivity of the pressure decrease, the invention thus also makes it possible to reduce the shocks received by the projectile, which makes it possible to fire ALR projectiles made of materials with reduced mechanical characteristics, such as plastics.

With the means used by the invention, it is then possible to avoid a projectile blocking problem in the propulsion device. It is also able to control the ejection speed of the projectile.

The operation of the device can be presented as follows.

The ignition system 9 is initiated by an appropriate means integral with the weapon (according to the structure of the ignition system 9, a percussion means or electrical contact means will be used), the ignition gases are then directed by the ignition tube 5 to the propellant powder 6 via the orifices 51 of the ignition tube 5.

The propellant powder 6 is then initiated, and the confinement obtained by the confinement means 7, 10, 12 ensures a good combustion of the propellant powder 6.

The confinement means 7 then gives under the effect of the temperature and / or the pressure of the gases resulting from the combustion of the propellant powder 6, passing them to the intermediate chamber 2 through the vents 8 of the chamber back 1.

The grains of powder which have a size smaller than the mesh size of the grid 12 remain confined in the rear chamber 1.

Then, as and when the propellant powder 6 is burned, some grains may reach a size smaller than the mesh size of the grid 12 and pass into the intermediate chamber 2 to complete their combustion. This is not disadvantageous, the confinement having been maintained by the grid 12 in the rear chamber 1 for a sufficient time so that the grains do not go out thereafter.

At the same time, the combustion gases are directed to the low pressure chamber 3 via the orifice 13, at a rate regulated by the section of this orifice.

The pressure in the low pressure chamber 3 increases until it is sufficient to move the projectile 22.

The projectile 22 then begins to move in the tube 21, and its displacement is progressive under the effect of the gases which continue to enter at a regulated flow rate into the low pressure chamber 3 until the ejection of the projectile 22 is effective.

It is understood that the example described here and in particular the numerical values cited, are given for information only.

It would be possible to implement other types and geometries of propellant powders depending on the desired performance (exit velocity of the projectile of the tube of the weapon desired for a given mass of projectile).

It would also be possible to give other dimensional characteristics to the different chambers depending on the mass of the projectile and this desired output speed.

Claims (8)

Cartridge for propelling a projectile (22) having a caliber of at least 90 mm, characterized in that it comprises: A rear chamber (1) comprising: - ignition means (5, 9) of a propellant powder (6), - means (12) for confining the powder (6) in the rear chamber (1) while allowing the gases from the combustion of the powder (6) to pass through vents (8) of the rear chamber (1); • an intermediate chamber (2) of constant volume communicating with the rear chamber (1) by the vents (8); A low-pressure chamber (3) forming a projectile propulsion chamber (22) and communicating with the intermediate chamber (2) via an orifice (13) of predetermined section. A projectile propellant cartridge (22) having a size of at least 90 mm according to claim 1, wherein the means (12) for confining the powder (6) in the rear chamber (1) while allowing the gases to pass through from the combustion of the powder (6) by the vents (8) of the rear chamber (1) comprise a grid (12) whose mesh size is smaller than the size, before combustion, of a grain of powder ( 6). Cartridge for propelling a projectile (22) of at least 90 mm according to one of the preceding claims, in which the rear chamber (1) comprises means (7) for confining, in a first combustion phase, the powder (6) and the combustion gases from the combustion of the powder (6) in the rear chamber (1), said means (7) being able, in a second combustion phase, to yield under the effect of the temperature and / or pressure. Cartridge for propelling a projectile with a caliber of at least 90 mm according to the preceding claim, wherein the means (7) is formed by a thin sheet of metal or metal alloy, for example tin. Cartridge for propelling a projectile of at least 90 mm caliber according to one of the preceding claims, in which the ignition means (5, 9) comprise an ignition tube (5) around which the powder (6) is disposed and an ignition system (9), for example percussion primer type or capacitive discharge initiation primer, disposed at the base of the ignition tube (5). Cartridge for propelling a projectile with a caliber of at least 90 mm according to the preceding claim, in which there is provided a setting disk (10), for example made of polystyrene, felt or cardboard, arranged around the ignition tube (5). ) and against a wall (11) of the rear chamber (1) to wedge the propellant powder (6) in the rear chamber (1) Cartridge for propelling a projectile with a caliber of at least 90 mm according to one of the preceding claims, wherein the orifice (13) of predetermined section is formed by a nozzle or a tube. Cartridge for propelling a projectile with a caliber of at least 90 mm according to one of the preceding claims, in which the propellant powder (6) is a progressive combustion powder.

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