FR2717569A1 - Device for igniting a propellant charge. - Google Patents

Abstract

The technical sector of the invention is that of devices for igniting a propellant charge. The device for igniting a propellant charge (5) contained in an envelope (2) according to the invention comprises a jacket (12) slidably mounted in a tubular guide skirt (9) integral with the envelope, a composition ignition pyrotechnic (25) arranged in an internal volume of the jacket and intended during its initiation to push a projectile (15) which pulls the jacket, it is characterized in that the jacket is tubular in shape and has at its end front, a closure means (24) made integral by an unlockable connection means (20). Application to the field of telescoped type ammunition.

Description

The technical field of the invention is that of ignition devices

of

  propellant charge of ammunition, especially of the telescoped type.

  The telescoped munitions are characterized in that the projectile is disposed inside the envelope containing the propellant charge. This arrangement allows shorter ammunition to be defined, which allows the design

  more compact weapons and / or higher firing rates.

  But the development of such munitions faces a number of problems. Thus the projectile is no longer in position in the tube of the weapon when the ammunition is disposed in the room. It is the pressure of the gases generated by the combustion of the propellant charge that will initially bring the projectile into position in the tube of the weapon, then in a second time push it inside the tube. It is therefore feared that the combustion gases of the propellant charge advance the projectile before it has sufficiently penetrated into the tube of the weapon to be able to ensure a seal. Such a phenomenon would lead to a decrease

  sensitive performance but also premature erosion of the barrel of the weapon.

  Various solutions have been envisaged to avoid such a disadvantage.

  The patent FR2647890 proposes in particular to have at the front of the ammunition a cap connecting the projectile to an annular ring integral with the envelope of the ammunition. This device avoids any passage of gas to the front of the projectile, the cap being

  thrust by the combustion gases at the same time as the projectile.

  This device gives complete satisfaction in many cases. However, it is unsuitable in the case of ammunition with a thin-walled and fragile projectile (such as an explosive / fragmentable projectile). Indeed during the firing, the pressure of the combustion gases of the propellant charge is applied to the fragile wall of the projectile

  which entails a risk of deterioration if not premature explosion of it.

  It is therefore necessary to be able to control the firing sequence of the propellant charge of certain telescoped munitions, so as to protect a wall

  fragile projectile (wall located in front of the belt).

  It is for example known to use a propulsion gas barrier which separates the propellant charge into two parts. The chemical composition of this barrier makes it possible to delay the initiation of the front part of the propellant charge where the fragile wall of the projectile is located. However, since the range of use of a munition is very wide, it is very difficult to control the operation of such a munition.

chemical composition.

  US 4335657 discloses a telescoped ammunition mechanically controlling the firing sequence of the propellant charge. For this, a piston is a barrier between the priming composition and the propellant charge. When firing the primer, the piston, which has an axial stroke limited by a stop, slides by advancing the projectile until it is set. And it is only from this moment that the combustion gases of the primer can initiate the propulsive charge through orifices released by the piston arrived at the end of the race. Such a concept is particularly interesting because it makes it possible to ensure the firing of a propellant charge of ammunition telescoped in two stages, by protecting the

fragile wall of the projectile.

  However, such a piston also has disadvantages.

  First, the transmission of the combustion gases of the composition ensuring the ignition of the propellant charge is carried out radially through orifices which are limited in number and in diameter. This results in a braking and / or a disturbance of the transmission of the ignition to the propellant charge which adversely affect the performance of the ammunition. Then, the piston being closed at its front part, this results in an increase in the inert mass of the munition and a decrease in the amount of ignition composition that can be loaded, which reduces the speed of setting the projectile. It is the object of the invention to provide a device for igniting a charge

  propellant of a telescoped ammunition that does not have such drawbacks.

  Thus the ignition device according to the invention provides a simple and effective way a two-stage ignition of the propellant charge, while not causing

  unnecessary increase in the mass of the munition.

  It also allows to obtain a rapid ignition of the propellant charge

  principal by the ignition composition.

  Thus, the subject of the invention is a device for igniting a propellant charge contained in a shell of a telescoped type munition, comprising a jacket slidably mounted in a tubular guide skirt integral with the envelope, a pyrotechnic composition of ignition disposed in an internal volume of the liner and intended during its initiation to push a projectile which pulls the liner, ignition device characterized in that the liner is tubular and has at its front end, a closure means made solidary

  by a releasable connection means.

  Advantageously, the means for closing the front end of the liner is formed by a rear part of the projectile, part penetrating into an internal clearance of the liner and the releasable connection means between the front end of the liner and the liner. rear part of the projectile is an elastic ring

  resistant to a determined effort.

  According to other features of the invention, the guide skirt comprises at its front end an annular flange which ensures the centering of the rear part of the projectile and the jacket comprises at its end arm a shoulder which ensures its guidance inside. skirt, flange and shoulder that can cooperate after initiation of the pyrotechnic composition to achieve an axial stop. The jacket comprises at least one sealing means with the guide skirt, means comprising at least one seal disposed in a circular groove of the surface

outer shoulder.

  The rear part of the projectile comprises at least one seal, arranged in a circular groove arranged on the rear part and sealing with the jacket. According to another characteristic of the invention, the ignition device for a propellant charge contained in a casing closed at its front by a guide tube whose inner housing has a diameter smaller than the outer diameter of a projectile belt, is characterized in that after initiation of the pyrotechnic composition, the shoulder of the jacket abutting against the flange of the skirt and the releasable connection means between the projectile and the jacket being released, the initiation of the propellant charge by the pyrotechnic ignition composition is produced only when the projectile belt is engaged inside the inner housing of the guide tube in order to protect the pressure generated by the combustion gases from the propellant charge, a wall of

  projectile located in front of the belt.

  The invention will be better understood on reading the description which will follow, made

  with reference to the accompanying drawings in which: - Figure I shows in axial section a telescoped munition according to the invention. FIG. 2 represents in axial section a telescoped munition according to the invention

  after firing and rupture of the projectile / jacket connection.

  FIG. 3 shows in axial section a telescoped munition according to the invention

  at the moment of ignition of the propellant charge.

  Referring to FIG. 1, a telescoped munition 1 comprises a casing 2, preferably made of plastic or composite and closed at a rear end by a base 3, made of metallic material, which carries

a primer 4 of known type.

  The envelope which contains a propellant charge 5 is closed at its end

  before by a guide tube 6 also made of metal material.

  A front seal 7 ensures the pressure-tightness of the combustion gases of the propellant charge, between the casing 2 and the guide tube 6, while a seal

  rear 8 seals between the casing and the base 3.

  The base 3 receives integrally, for example by a threaded connection, a metal guide skirt 9. The latter, of tubular shape, has a bore 10 limited forwards by an annular flange 11 of internal diameter less than that of

the bore 10.

  A jacket 12, metallic and also of tubular shape, comprises on its external face a cylindrical bearing surface 13 and a shoulder 14 located at its end.

arrièere.

  The liner is slidably mounted inside the skirt 9. To do this, the shoulder 14 and the bore 10 on the one hand, and the cylindrical bearing surface 13 and the collar 11 on the other hand, have slippery adjustments. An O-ring 19 is placed in a circular groove of the shoulder 14 and provides a static and dynamic seal to gases generated by an ignition composition.

between the shirt 12 and the skirt 9.

  A projectile 15, which is here of the gyro-stabilized type, is held at its front part 17 by a cap 18 made of plastic material. The latter has a sliding fit with an inner housing 27 of the guide tube 6. Such a cap

  is described in the patent FR2647890.

  A rear portion 16 of the projectile 15 is secured to the liner 12, at an internal clearance 21 formed at the front end thereof and thus constitutes a means for closing the liner 12. This fastening is here ensured by an elastic ring 20 which is housed in corresponding grooves arranged on the projectile and the shirt. The ring constitutes a releasable connection means

  between the rear part of the projectile and the shirt.

  An O-ring 22 is disposed in a groove in the rear part of the projectile and rests on the internal clearance 21. It seals

  the gases between the projectile and the shirt 12.

  The volume delimited by an inside diameter 23 of the liner, the rear part 16 of the projectile and the primer is filled by the pyrotechnic ignition composition 25 intended to push the projectile forwards. The rear part 16 of the projectile thus constitutes a means of closing the jacket which delimits a maximum volume for the pyrotechnic composition without causing a penalizing increase in mass.

inert.

  The projectile 15 has on its outside diameter a belt 26 intended to

  take the stripes of the tube of a weapon not shown.

  The outer wall 28 of the projectile (here explosive / fragmentable type), which is in front of the belt, is thin and therefore fragile. It must not be subjected to the pressure generated by the combustion gases of the propellant charge 5 which

  could damage it and cause premature explosion.

  Figure 2 shows the telescoped munition 1 after firing. The primer 4, initiated by percussion or electrically ignites the pyrotechnic composition 25. The combustion of the latter generates a pressure on the rear portion 16 of the projectile 15 which pushes the projectile assembly 15 / folder 12 towards the front of the ammunition . When the shoulder 14 of the jacket abuts against the annular collar 11 of the skirt 9, the pressure of the combustion gases increases until the rupture or release of the unlockable connection means 20 between the projectile and the jacket. The groove of the projectile in which is mounted the elastic ring 20 has a depth substantially equal to the diameter of the ring, while the groove formed in the clearance 21 of the jacket has a depth slightly

  greater than the diameter of the ring.

  Thus, under the pressure of the gases which tends to push the projectile towards the front of the ammunition, the elastic ring 20 which is mounted substantially at the bottom of the projectile groove, opens and is entirely housed in the groove of the clearance 21. shirt. The projectile, which is no longer restrained, then continues to advance while being always guided and centered by the clearance 21, which ensures a good positioning of the

projectile in the barrel of the weapon.

  Substantially at the time of rupture of the connecting means 20, the belt 26 of the projectile engages in the housing 27 of the guide tube. The fit of the belt 26 in the guide tube 6 is tight. Thus, the fragile wall of the projectile located in front of the belt is protected from the pressure of the combustion gases of the

  propelling charge 5 by the guide tube 6.

  From the beginning of the translation of the projectile, the cap 18 engages inside the tube of the weapon. The cap is broken at the exit of the tube under the effect of the forces

Aerodynamic.

  The dimensioning of the component parts of the device according to the invention will be carried out in such a way that the force required to break or release the projectile / lug unlockable connection means is greater than that due to the translation of the liner into the skirt, but less than the resistance of the axial stop between the

flange 11 and the shoulder 14.

  FIG. 3 represents the telescoped munition 1 at the moment of ignition of the propellant charge 5 by the pyrotechnic ignition composition 25, when the part

  rear 16 of the projectile constituting the closure means leaves the jacket 12.

  The ignition is thus effected by the front opening of the liner 12, which is disengaged by the separation of the rear portion 16 of the projectile. Such an arrangement allows rapid initiation in all directions by a space between the front end of the liner and the rear end of the projectile whose size increases as the projectile continues to advance. The ignition of the propellant charge, according to the invention, is therefore carried out in two stages and the second stage begins only when the belt 26 of the projectile has penetrated inside the guide tube 6, which makes it possible to ensure protection

  effective of the fragile wall of the projectile.

  The guide tube 6 will be dimensioned in such a way that under no circumstances, under the pressure rise of the combustion gases of the propellant charge, can it shrink on the wall 28 of the projectile whose diameter is smaller than that of the belt. Of course, without departing from the scope of the invention, the unlockable connection between the liner 12 and the rear portion 16 of the projectile can be provided by another

  means that an elastic ring, for example by shear pins.

Claims (6)

  1 - Device for igniting a propellant charge (5) contained in an envelope (2) of a telescopic type munition (1), comprising a jacket (12) slidably mounted in a tubular guide skirt (9) secured to of the envelope, a pyrotechnic ignition composition (25) disposed in an internal volume of the jacket and intended during its initiation to push a projectile (15) which pulls the jacket, ignition device characterized in that the shirt (12) is tubular in shape and has at its front end a closing means (24) made   secured by a releasable connection means (20).   2 - Ignition device according to claim 1, characterized in that the closure means of the front end of the liner is formed by a rear portion (16)   projectile, part penetrating into an internal clearance (21) of the shirt.   3 - Ignition device according to claim 2, characterized in that the releasable connection means between the front end of the liner and the rear portion (16)   projectile is an elastic ring (20) resistant to a determined effort.   4 - Ignition device according to any one of claims 2 or 3,   characterized in that the guide skirt has at its front end an annular flange (11) which centers the rear part of the projectile and in that the liner has at its rear end a shoulder (14) which ensures its guiding at the inside of the skirt, flange and shoulder that can cooperate after initiation of the   pyrotechnic composition to achieve an axial stop.   - Ignition device according to claim 4, characterized in that the liner comprises at least one sealing means with the guide skirt, means comprising at least one seal (19) disposed in a circular groove of the surface outer shoulder.   6 - Ignition device according to any one of claims 2 to 5,   characterized in that the rear part of the projectile comprises at least one seal (22), arranged in a circular groove arranged on the rear part and providing a tightness with the shirt.   7 - Ignition device according to any one of claims 4 to 6, for   a propellant charge (5) contained in an envelope (2) closed at its front by a guide tube (6) whose inner housing (27) has a diameter smaller than the outer diameter of a belt (26) of the projectile, characterized in that after initiation of the pyrotechnic composition (25), the shoulder (14) of the liner being abutted against the flange (11) of the skirt and the releasable connection means (20) between the projectile and the shirt being released, the initiation of the propellant charge by the pyrotechnic ignition composition is performed only when the projectile belt is engaged inside the inner housing of the guide tube to protect the pressure generated by the combustion gases of the propellant charge,   a wall (28) of the projectile located in front of the belt.