Rocket for a projectile intended to be fired by a cannon

Abstract

The aim of the invention is a rocket (11) for a projectile intended to be fired by a cannon by lighting a propelling charge using an electric ignitor (6). This rocket (11) can transition from a safety position to an armed position post-firing by removing at least two different safeties. This rocket (11) is characterised in that it comprises a capacitor (20) that is intended to be connected to the electric ignitor (6) and that charges when the propelling charge is ignited, and also a computer (18) that detects the charge of the capacitor (20) to allow the rocket (11) to be armed when this charge is above or equal to a reference value, with the charge of the capacitor (20) constituting a first firing safety.

Description

[0001] The technical field of the invention is that of rockets for projectiles intended to be fired by a cannon.

[0002] Projectiles fired by a cannon are associated with a propellant charge which, once ignited, generates propellant gases whose pressure allows the projectile to be fired.

[0003] These projectiles can be in the form of cartridge munitions, in which the projectile is attached to a case which contains the propellant charge and which carries an igniter for this charge.

[0004] These projectiles can also be independent of the propellant charge which is only associated with them at the time of firing, for example for a mortar shot.

[0005] In all cases, the projectiles are equipped with a fuse that triggers the firing of an explosive charge or a pyrotechnic charge, at a given moment on the trajectory, or upon impact with a target. The fuse typically includes a safety and arming device that guarantees the safety of the shot.

[0006] For many years, military standards (and in particular NATO standard Stanag No. 4187) have required that safety and arming devices can only be released following the detection of two different events associated with the shot.

[0007] Such a recommendation leads to a high level of safety since the release of a single safety is not enough to arm the rocket.

[0008] It is classic when defining projectiles fired by a rifled barrel gun to detect, on the one hand, the firing acceleration, and on the other hand, the rotation acceleration communicated by the gun.

[0009] Meeting these requirements is more difficult when the projectiles are fired from smoothbore guns, for example tank guns or smoothbore mortar tubes.

[0010] While the detection of shot acceleration can still be performed, the low level of rotation of these projectiles does not allow us to reliably rely on such an event.

[0011] Thus, patent US6951161 proposes to associate the detection of firing acceleration with the counting of a certain number of rotations of the projectile in a given time window. Such a solution requires the installation of a rotation sensor, for example magnetic, which complicates the definition of the fuse.

[0012] Patent application US2008 / 0210115 describes a safety device in which the second event associated with the shot is a measurement of the pressure or temperature at the projectile's warhead. Such a solution is also complex and expensive to implement.

[0013] Patent FR2633385 discloses a device in which the gas pressure in the weapon chamber is detected by pistons that pierce a wall of the projectile to release a safety device. This device is also complex and can lead to leaks between the projectile and the weapon chamber.

[0014] Also known from patent US4015531 is an electric rocket comprising a capacitor which is connected by a wire connection to an igniter ensuring the ignition of the propellant charge. This capacitor constitutes the energy source which ensures the ignition of an electric detonator housed in a rotor ensuring a misalignment of the pyrotechnic chain. Such a capacitor cannot constitute a reliable arming safety because it also constitutes the source of ignition energy. Such a rocket does not comply with military standards (and in particular NATO standard Stanag n°4187).

[0015] Patents US5097765 and US3814017 show devices incorporating one or more capacitors whose function is to power the electronic circuits of the rocket and provide the energy for firing the detonator. These capacitors incorporated in the firing chain cannot constitute firing safety devices that would make a rocket compliant with military standards.

[0016] The aim of the invention is to propose a rocket making it possible to detect in a simple and inexpensive manner an event associated with the shot which is distinct from the sole axial acceleration due to the shot.

[0017] Thus the rocket according to the invention is particularly well suited to the definition of rockets for projectiles and munitions which can be fired by smooth tubes.

[0018] The invention also relates to a munition equipped with such a rocket and a method of arming such a rocket.

[0019] Thus, the invention relates to a fuse for a projectile intended to be fired by a cannon by the ignition of a propellant charge by an electrical ignition means, such as an electrical igniter, a fuse capable of passing from a safety position to an armed position, following firing, by the lifting of at least two different safeties, such that the fuse comprises a capacitor which is intended to be connected to the electrical ignition means of the propellant charge and which charges when said propellant charge is ignited, said fuse also comprises a computer which detects the charge of the capacitor to allow the arming of the fuse when this charge is greater than or equal to a reference value, the charge of the capacitor constituting a first firing safety.

[0020] The rocket may include an electric generator which is initiated by inertia when fired.

[0021] The rocket may include an inertial sensor which is connected to the computer and which constitutes a second firing safety.

[0022] The rocket may have a divider bridge between the electric ignition means and the capacitor.

[0023] Advantageously, the rocket capacitor may be arranged between the gate and the source of a field effect transistor, the drain of this capacitor being powered by the electric generator and being connected to a logic module of the computer, the source also being connected to a ground of the rocket, the threshold voltage V GS of the transistor constituting the reference value.

[0024] The invention also relates to ammunition which is intended to be fired by a cannon and comprising a projectile and a propellant charge equipped with an electrical ignition means, such as an electrical igniter, fixed to a base, the projectile comprising a fuse according to the preceding characteristics and a wire connection connecting the fuse to the igniter.

[0025] Advantageously, the ammunition may include a divider bridge between the electrical ignition means and the capacitor, a divider bridge which is housed in the base.

[0026] The invention also relates to a method for arming a rocket equipping a projectile during firing by a cannon, a method in which the firing is recognized by the detection of at least two different events usually associated with a firing, the combination of the two events making it possible to arm the rocket, a method characterized by the following steps: a capacitor of the rocket is charged from a signal of firing a propellant charge, the charge of the capacitor is used as a first event associated with the firing and allowing the arming of the rocket, a computer detecting the charge of the capacitor to allow the arming of the rocket when this charge is greater than or equal to a reference value.

[0027] Advantageously, we can use the firing acceleration as a second event associated with the firing and allowing the rocket to be armed.

[0028] Advantageously, in this process an electric generator is used which is initiated by inertia during firing, the activation of the generator ensuring the electrical power supply to the rocket.

[0029] The invention will be better understood by reading the description given with reference to the attached drawings and in which: [ Fig.1 ] is a schematic view in partial longitudinal section of a munition according to the invention; [ Fig.2 ] is a simplified representation of a rocket according to the invention; [ Fig.3 ] shows an example of the embodiment of a rocket according to the invention.

[0030] Referring to the figure 1 , a munition 1 according to the invention is intended to be fired by a cannon (not shown), for example a cannon of caliber greater than or equal to 40mm, such as a 120mm tank cannon.

[0031] This ammunition 1 comprises a projectile 2 and a propellant charge 3, in the form of grains of powder, and which is housed in a case 4, for example combustible. In a conventional manner, the case 4 is closed at its rear part by a metal base 5 which carries an annular sealing gasket 5a. The base 5 comprises an axial bore which receives an electric ignition means 6 (such as an igniter), integral with an igniter tube 7.

[0032] Bases equipped with igniter tubes are well known to those skilled in the art. For example, reference may be made to patents EP2108916 and EP1258695 which describe obturator bases fixed to combustible sockets and to patent EP1106959 which describes an igniter tube.

[0033] The projectile 2 is fixed to the socket 4 at a front connecting piece 8 and it is equipped with a sealing belt 9. Patent EP307307 describes an example of a connecting piece between a projectile and a combustible socket.

[0034] The projectile 2 carries at its rear part a deployable tail 10, pivotally mounted on axes integral with a tail 11.

[0035] Projectile 2 is for example an explosive projectile whose metallic body contains an explosive material (not shown). The explosive material is capable of being initiated by a fuse 11 (shown in dotted lines) which is housed in a base 2a of projectile 2.

[0036] According to a characteristic of the invention, the rocket 11 is connected to the igniter 6 (or more precisely to the electrical contact supplying the igniter 6) by a wire connection 12. The wire connection 12 could for example be glued to the internal wall of the fuel socket 4.

[0037] The rocket 11 could also be a programmable rocket. It would therefore be possible to associate the wired connection 12 connected to the igniter 6 with another wired connection (not visible figure 1 ) which will be connected to a contact pad on the base allowing programming signals to be introduced from the rocket 11 before firing.

[0038] There figure 2 schematically shows the fuse 11 of the projectile 2.

[0039] The rocket 11 comprises a safety and arming device 13 which here carries a detonator 14 secured to a movable flap 15.

[0040] The detonator 14 is intended to initiate the explosive charge 16 which is housed in the body of the projectile 2.

[0041] This safety and arming device 13 is not shown in detail because such devices are well known. The movable flap 15 (in rotation or in translation) makes it possible to misalign the detonator 14 and the explosive charge 16 (or more precisely to misalign the detonator 14 and an orifice 17 allowing the passage of the detonation wave and which allows it to attack the explosive charge 16).

[0042] The safety and arming device 13 moves from a safe position (in which the detonator 14 cannot initiate the explosive charge 16) to an armed position in which the detonator 14 is effectively aligned with the orifice 17, and can therefore cause the detonation of the explosive charge 16.

[0043] This transition from the safety position to the armed position can only be done by lifting at least two different safeties, lifting which occurs following the firing of ammunition 1.

[0044] The rocket 11 thus comprises a computer 18 which is intended to control the passage of the safety and arming device 13 to its armed position. The computer 18 is produced for example in the form of a microprocessor which is supplied with energy by an electric generator 19.

[0045] It has also been represented on the figure 2 a wired connection 21 which connects the computer 18 to a programming contact secured to the base 5. This wired connection is intended to introduce a programming value into a memory of the computer 18, for example firing timing.

[0046] The electric generator 19 is advantageously a generator which is initiated by inertia when fired, for example a priming battery.

[0047] Such generators are well known (see for example patents US7504177, DE50115732 and US9647276). They comprise an electrolyte which is contained in a bulb broken by inertial forces during firing. The electrolyte is thus positioned between the electrodes of the battery which can then deliver a current.

[0048] It is also possible to advantageously use a thermal battery comprising a pyrotechnic composition which is initiated by a firing pin released by the acceleration of firing. Such thermal batteries are also well known, for example from the patents: EP2573850, WO2017069787, US5458995 and US10062910.

[0049] In accordance with the invention, the rocket comprises a capacitor 20 which is connected by the wire connection 12 to a means of electrical ignition of the propellant charge, here the igniter 6.

[0050] Concretely, the capacitor 20 is mounted in parallel with the igniter 6 and it is a part of the firing current of the initiator 6 which is thus diverted towards the capacitor 20 which is therefore only charged at the time of the actual firing of the projectile 2. To limit the intensity of the current carried by the wire connection 12, a voltage divider can be provided which will be housed in the vicinity of the initiator 6. This solution will be described later.

[0051] Of course the figure 2 is very schematic and one terminal of the capacitor 20 is connected to the power supply pole of the igniter 6 while the other terminal of the capacitor 20 is to the electrical ground of the weapon. This grounding is done by means of the obturator base 5 (as for the igniter) and the wire connection 12 is then a two-wire connection. The grounding can also be done by the body of the projectile 2 which is in contact with the barrel of the weapon (and the wire connection 12 can then be single-wire).

[0052] The capacitor 20 is connected to the computer 18 which can thus detect the charged or uncharged state of the capacitor 20.

[0053] The computer 18 is not supplied with energy before the shot since it is the activation of the electric generator 19 by the acceleration of the shot which provides it with current.

[0054] Once activated, the calculator 18 will measure the charge level of the capacitor 20, for example by comparison with a reference value stored in memory, or more simply by switching a static relay whose switching level (reference value) is set by an electronic circuit (incorporated into the fuse 11) to a level corresponding to the minimum discharge current of the capacitor 20 which is expected.

[0055] The method of arming a rocket according to the invention thus comprises the following two stages: a capacitor of the rocket is charged from a signal of firing a propellant charge, the charge of the capacitor is used as a first event associated with the firing and allowing the arming of the rocket.

[0056] It is therefore the sufficient charge level of capacitor 20 which constitutes the first safety feature for firing rocket 11. If this level is insufficient, this means that there has been no ignition of a propellant charge.

[0057] The computer 18 then does not control the arming of the safety and arming device 13 and the detonation of the explosive charge 16 cannot take place.

[0058] The second firing safety device is constituted by an inertial sensor (such as an accelerometer 22) which detects the firing acceleration. The accelerometer 22 is connected to the computer 18 which includes a logic module verifying the presence of the two events which releases the safety and arming device 13 of the rocket 11.

[0059] The safety and arming device 13 of the rocket 11 can therefore only move from a safety position to an armed position following the lifting of two different safeties: the detection of the ignition current of the propellant charge and the detection of the longitudinal firing acceleration.

[0060] Even a violent shock which could be detected by the accelerometer 22, cannot arm the safety and arming device 13 since the ignition current of the propellant charge is absent.

[0061] Even a long fire when igniting the propellant charge cannot arm the safety and arming device 13 since the firing acceleration has not appeared.

[0062] An accidental ignition of the propellant charge, for example following a fire, cannot lift the arming safety device either, since the electric current intended for the igniter 6 is then absent and has not been able to charge the capacitor 20.

[0063] The invention therefore defines a rocket 11 which meets the highest safety requirements without it being necessary to equip the safety and arming device with an additional inertial lock.

[0064] As a variant, it is of course possible to associate the capacitor 20 with a mechanical inertial lock immobilizing the shutter 15 of the safety and arming device 13. This inertial lock will form the second safety device.

[0065] Of course, if the capacitor 20 is functionally attached to the fuse 11, it can structurally be arranged outside the fuse, for example in a specific housing of the projectile body 2.

[0066] Advantageously, the calculator 18 of the rocket 11 will itself constitute the safety and arming device, without it being necessary to provide a mobile flap 15.

[0067] To do this, simply use a 14 detonator of the projected element type (better known as a "Slapper"). These detonators are relatively insensitive and can only be activated by high voltage, and they also deliver enough energy to initiate a secondary explosive, which therefore also has reduced sensitivity. It is therefore possible (and authorized by the standards bodies) to use a slapper without a mechanical shutter ensuring misalignment of the pyrotechnic chain, but on the condition of having two independent firing safety devices controlling the operation of the fuse.

[0068] The firing safety is then ensured by the fuse 11 itself, which can only control the slapper after the two firing safeties have been lifted. In this case, the firing safeties will be logic locks independent of each other and which must be distinct from the firing chain itself.

[0069] There figure 3 shows an exemplary embodiment of a rocket 11 according to the invention and incorporating a detonator 14 with a projected layer.

[0070] As previously specified, the wired connection 12 is connected to the initiator 6 by a voltage divider bridge 23 which comprises two resistors R 1 and R 2 . Thus, in a conventional manner, the voltage u carried by the wired connection 12 is reduced compared to the ignition voltage U of the igniter 6. We have =UR 2 / (R 1 +R 2 ).

[0071] The divider bridge 23, even if it is functionally part of the fuse 11, is structurally arranged at the base 5. Thus the current passing in the wire connection 12 is reduced.

[0072] It would of course be possible to house the divider bridge 23 in the projectile, but this has no practical advantages because the current flowing in the wire connection 12 would be the same as that of the firing, which could pose problems of insulation and firing safety.

[0073] The capacitor 20 is powered through a load resistor R 3 , another resistor R 4 is connected in parallel between the terminals of the capacitor 20. The purpose of the resistor R 4 is to allow the discharge of the capacitor 20, after detection of its charged state by the computer 18, during the flight of the projectile. It thus allows the evacuation of parasitic charges which could disturb the operation of the rocket. R 3 and the capacitor 20 in fact form a low-pass filter making it possible to eliminate parasitic high frequencies

[0074] The firing of the igniter 6 ignites the propellant charge, therefore causes the capacitor 20 to charge.

[0075] We see that the rocket has a field effect transistor (MOS) 24 whose Drain (D) is supplied by the electric generator 19 (when it is switched on). The capacitor 20 is arranged between the gate (G) and the Source (S) of the transistor 24.

[0076] When the electric generator 19 is started, it supplies the computer 18 (link 25) but it also applies a voltage V DS, via link 26, to a logic module 27 of the computer 18.

[0077] When the capacitor 20 is charged to a voltage u which is higher than the threshold voltage V GS of the MOS transistor, (which therefore constitutes the reference value of the first firing safety of the rocket 11), the MOS transistor 24 closes and the current coming from the generator 19 is discharged to the ground 28 via the connection 29. This results in a voltage close to 0 volts applied to the logic module 27 of the computer via the connection 26. The load resistor R 5 makes it possible to avoid short-circuiting the generator 19.

[0078] Here this switching of MOS 24 is considered as a transition from 1 to 0. But this has no practical importance because inverting logic components can be implemented at the level of logic module 27 to detect the desired combination.

[0079] If capacitor 20 is not charged, it means that no ignition of the propellant charge has been detected. MOS transistor 24 then remains open and voltage V DS is equal to the voltage of electric generator 19, i.e. a logic level 1. This logic state 1 indicates to logic module 27 that the safety is not lifted, fuze 11 is not armed and initiation of Slapper detonator 14 is impossible.

[0080] Furthermore, the logic module 27 detects the firing acceleration seen by the accelerometer 22.

[0081] The components and logic wiring are chosen so that only the conjunction of the presence of a firing acceleration and a charge of the capacitor 20 makes it possible to activate the operation of the fuse 18, and in particular of a module 30 for managing the firing of the slapper detonator 14.

[0082] The rocket 11, and more particularly the firing management module 30, also receives, as described previously, the wired connection 21 allowing the programming of the desired operating mode for the rocket.

[0083] It can therefore be seen that the first firing safety device according to the invention uses electrical information which is stored in the fuse 11 before the latter can operate, the electrical generator 19 not yet being operational. The timing of a firing is however sufficiently rapid so that the information thus stored can be read by the fuse when it can operate. The discharge of the capacitor 20 only occurs gradually, through the resistor R4, after the safety device has been lifted. The capacitor 20 is not involved in the firing of the Slapper detonator 14. The energy for this firing comes from the electrical generator 19.

[0084] The invention is more particularly suited to ammunition fired from a smooth-bore weapon tube. It is clear, however, that it can also be implemented with ammunition fired from a rifled tube. The firing event associated with the ignition of the propellant charge can then be combined with either axial acceleration of the projectile or rotational acceleration.

Claims

1. - A fuze (11) for a projectile intended to be fired by a cannon by ignition of a propellant charge (3) using an electric ignition means (6), such as an electric igniter (6), wherein the fuze (11) is allowed to pass from a safety position to an armed position, following the fire, by releasing at least two different safeties, such that the fuze comprises a capacitor (20) which is intended to be connected to the electric ignition means (6) for igniting the propellant charge (3), characterised in that said capacitor (20) charges during the ignition of the propellant charge (3), the fuze also comprises a computer (18) which detects the charge of the capacitor (20) in order to allow the arming of the fuze (11) when this charge is greater than or equal to a reference value, the charge of the capacitor (20) constituting a first fire safety.

2. - The fuze according to claim 1, characterised in that it comprises an electrical generator (19) which is inertially primed during the fire.

3. - The fuze according to claim 1, characterised in that it comprises an inertial sensor (22) which is connected to the computer (18) and which constitutes a second fire safety.

4. - The fuze according to any one of claims 1 to 3, characterised in that it comprises a divider bridge (23) between the electric ignition means (6) and the capacitor (20).

5. - The fuze according to claims 2 and 4, characterised in that the capacitor (20) is arranged between the gate G and the source D of a field-effect transistor (24), the drain D of this capacitor being powered by the electrical generator (19) and being connected to a logic module (27) of the computer (18), the source S also being connected to a ground of the fuze, the threshold voltage VGS of the transistor (24) constituting the reference value.

6. - A piece of ammunition (1) intended to be fired by a cannon and comprising a projectile (2) and a propellant charge (3) equipped with an electric ignition means (6), such as an electric igniter (6), secured to a base (5), the projectile (1) comprising a fuze (11) according to one of claims 1 to 5, wherein a wire connection (12) connects the fuze (11) to the igniter (6).

7. - The piece of ammunition according to claim 6, characterised in that it comprises a divider bridge (23) between the electric ignition means (6) and the capacitor (20), wherein the divider bridge (23) is housed in the base (5).

8. - A method of arming a fuze (11) fitted to a projectile (1) when fired by a cannon, in which method the fire is recognized by the detection of at least two different events usually associated with a fire, the combination of the two events making it possible to arm the fuze (11), the method being characterised by the following steps: - a capacitor (20) of the fuze (11) charges from a signal for firing a propellant charge (3), - the charge of the capacitor (20) is used as a first event associated with the fire and allowing the arming of the fuze (11), a computer (18) detecting the charge of the capacitor (20) in order to allow the arming of the fuze (11) when this charge is greater than or equal to a reference value.

9. - The method of arming a fuze according to claim 8, in which method the fire acceleration is used as a second event associated with the fire and allowing the arming of the fuze (11).

10. - The method of arming a fuze according to one of claims 8 or 9, in which method an electrical generator (19) that is inertially primed during the fire, is used, the activation of the generator (19) ensuring powering of the fuze (11).

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