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

ROCKET FOR A PROJECTILE INTENDED TO BE FIRED BY A CANNON

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

[0002] Projectiles fired from 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-bound ammunition, in which the projectile is attached to a casing that contains the propellant charge and carries an igniter for that 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 mortar fire.

[0005] In all cases, the projectiles are equipped with a fuze that triggers the ignition of an explosive or pyrotechnic charge, either at a specific point along their trajectory or upon impact with a target. The fuze typically includes a safety and arming device to ensure safe firing.

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

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

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

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

[0010] Although firing acceleration detection can still be performed, the low level of rotation of these projectiles does not allow for reliable reliance on such an event.

[0011] Thus, US patent 6951161 proposes combining the detection of firing acceleration with the counting of a certain number of projectile rotations within a given time window. Such a solution requires the implementation of a rotation sensor, for example a magnetic one, which complicates the rocket design.

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

[0013] French patent FR2633385 describes a device in which gas pressure in the weapon's chamber is detected by pistons that perforate a wall of the projectile to release a safety mechanism. This device is also complex and can lead to leaks between the projectile and the weapon's chamber.

[0014] Also known from US patent 4015531 is an electric rocket with a capacitor connected by a wire to an igniter that ignites the propellant charge. This capacitor provides the energy source for firing an electric detonator housed in a rotor, which misaligns the pyrotechnic chain. Such a capacitor cannot constitute a reliable weapon safety because it also serves as the ignition energy source. Such a rocket does not conform to military standards (and in particular NATO standard STANAG No. 4187).

[0015] US patents 5097765 and 3814017 describe devices incorporating one or more capacitors that power the rocket's electronic circuits and provide the detonator's ignition energy. These capacitors, incorporated into the firing mechanism, cannot constitute firing safety features that would allow a rocket to meet military standards.

[0016] The aim of the invention is to provide a rocket that allows for the simple and inexpensive detection of an event associated with firing that is distinct from the sole axial acceleration due to firing.

[0017] Thus the rocket according to the invention is particularly well suited to the definition of rockets for projectiles and munitions that can be fired from 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 rocket for a projectile intended to be fired from a cannon by the ignition of a propellant charge by an electrical ignition means, such as an electric igniter, rocket capable of moving from a safety position to an armed position, following firing, by the lifting of at least two different safety devices, rocket characterized in that it comprises a capacitor which is intended to be connected to the electrical ignition means of the propellant charge and which charges when the latter is ignited, and also a computer which detects the charge of the capacitor to allow the arming of the rocket 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 during firing.

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

[0022] The rocket may include a voltage divider between the electrical ignition means and the capacitor.

[0023] Advantageously, the rocket's capacitor can be placed between the gate and source of a field-effect transistor, the drain of this capacitor being powered by the electrical generator and 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 a munition intended to be fired from a cannon and comprising a projectile and a propellant charge equipped with an electrical ignition means, such as an electric igniter, fixed to a base, the projectile carrying a fuze according to the preceding characteristics and a wired connection linking the fuze to the igniter.

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

[0026] The invention also relates to a method of arming a rocket equipping a projectile during a 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 allowing the rocket to be armed, a method characterized by the following steps: - a capacitor of the rocket is charged from a signal of ignition of a propellant charge, - the charging of the capacitor is used as a first event associated with the firing and allowing the arming of the rocket, a computer detecting the charging of the capacitor to allow the arming of the rocket when this charge is greater than or equal to a reference value.

[0027] Advantageously, the launch acceleration can be used as a second event associated with the launch, enabling the rocket to be armed.

[0028] Advantageously, this process uses an electric generator which is started by inertia during firing, the activation of the generator ensuring the electrical supply of the rocket.

[0029] The invention will be better understood upon reading the description provided with reference to the attached drawings, in which:

[0030] is a schematic partial longitudinal cross-sectional view of a munition according to the invention;

[0031] is a simplified representation of a rocket according to the invention;

[0032] shows an example of the realization of a rocket according to the invention.

[0033] Referring to Figure 1, a munition 1 according to the invention is intended to be fired from a cannon (not shown), for example a cannon of caliber greater than or equal to 40mm, such as a 120mm tank gun.

[0034] This ammunition 1 comprises a projectile 2 and a propellant charge 3, in the form of powder grains, housed in a casing 4, for example, combustible. Conventionally, the casing 4 is sealed at its rear by a metal base 5 which carries an annular sealing gasket 5a. The base 5 has an axial bore which receives an electrical ignition means 6 (such as an igniter), attached to a igniter tube 7.

[0035] Cartridge bases fitted with ignition tubes are well known to those skilled in the art. For example, one can refer to patents EP2108916 and EP1258695, which describe sealing bases fixed to combustible cartridge cases, and to patent EP1106959, which describes an ignition tube.

[0036] The projectile 2 is fixed to the socket 4 at the level of a front connecting piece 8 and is equipped with a sealing belt 9. Patent EP307307 describes an example of a connecting piece between a projectile and a combustible socket.

[0037] The projectile 2 carries at its rear part a deployable tail assembly 10, mounted pivotally on axes integral with a tail assembly tail 11.

[0038] Projectile 2, for example, is an explosive projectile whose metallic body contains an explosive material (not shown). The explosive material can be initiated by a fuse 11 (shown in dashed lines) which is lodged in a base 2a of projectile 2.

[0039] According to a feature 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 link 12. The wire link 12 may, for example, be glued to the inner wall of the combustible sleeve 4.

[0040] The rocket 11 can also be a programmable rocket. Therefore, the wired connection 12, linked to the igniter 6, can be combined with another wired connection (not visible in Figure 1) which will be connected to a contact pad on the base, allowing programming signals to be introduced to the rocket 11 before firing.

[0041] Figure 2 schematically shows the rocket 11 of projectile 2.

[0042] The rocket 11 includes a safety and armament device 13 which here carries a detonator 14 attached to a movable flap 15.

[0043] The detonator 14 is intended to initiate the explosive charge 16 which is housed in the body of the projectile 2.

[0044] This safety and arming device 13 is not shown in detail because such devices are well known. The movable flap 15 (rotating or translating) allows the detonator 14 and the explosive charge 16 to be misaligned (or more precisely, to misalign the detonator 14 and an orifice 17 allowing the passage of the detonation wave and enabling it to attack the explosive charge 16).

[0045] The safety and arming device 13 moves from a safety 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.

[0046] This transition from the safe position to the armed position can only be achieved by releasing at least two different safeties, a release which occurs following the firing of munition 1.

[0047] The rocket 11 thus includes a computer 18 which is designed to control the transition of the safety and arming device 13 to its armed position. The computer 18 is implemented, for example, in the form of a microprocessor which is powered by an electrical generator 19.

[0048] Figure 2 also shows a wired connection 21 which links the calculator 18 to a programming contact attached to the base 5. This wired connection is intended to introduce into a memory of the calculator 18 a programming value, for example of firing timing.

[0049] The electric generator 19 is advantageously a generator which is started by inertia when fired, for example a priming battery.

[0050] Such generators are well known (see, for example, patents US7504177, DE50115732, and US9647276). They consist of an electrolyte contained within a bulb that is broken by inertial forces during firing. The electrolyte is thus positioned between the electrodes of the battery, which can then deliver a current.

[0051] A thermal battery comprising a pyrotechnic composition, which is ignited by a striker released by the acceleration of the firing mechanism, can also be advantageously used. Such thermal batteries are also well known, for example from patents: EP2573850, WO2017069787, US5458995 and US10062910.

[0052] According to the invention, the rocket includes a capacitor 20 which is connected by the wire link 12 to an electrical ignition means for the propellant charge, here the igniter 6.

[0053] In practice, capacitor 20 is connected in parallel with igniter 6, and part of the ignition current of initiator 6 is thus diverted to capacitor 20, which therefore only charges when projectile 2 is actually fired. To limit the current carried by wire 12, a voltage divider can be provided, which will be located near initiator 6. This solution will be described later.

[0054] Of course, Figure 2 is very schematic, and one terminal of capacitor 20 is connected to the power supply terminal of the igniter 6, while the other terminal of capacitor 20 is connected to the weapon's ground. This grounding is achieved via the obturator base 5 (as with the igniter), and the wire connection 12 is then a two-wire connection. Grounding can also be achieved through the body of the projectile 2, which is in contact with the weapon's barrel (and the wire connection 12 can then be a single wire).

[0055] Capacitor 20 is connected to calculator 18, which can thus detect whether capacitor 20 is charged or not.

[0056] Furthermore, the computer 18 is not supplied with energy before firing, since it is the activation of the electric generator 19 by the acceleration of the firing that provides it with current.

[0057] 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 rocket 11) to a level corresponding to the minimum discharge current of the capacitor 20 which is expected.

[0058] The method of arming a rocket according to the invention thus comprises the following two steps:

[0059] - A capacitor in the rocket is charged using a signal to ignite a propellant charge,

[0060] - the charging of the capacitor is used as a first event associated with the firing and allowing the arming of the rocket.

[0061] Therefore, the sufficient charge level of capacitor 20 constitutes the first safety measure for firing rocket 11. If this level is insufficient, it means that there has been no ignition of a propellant charge.

[0062] The computer 18 does not then command the arming of the safety and arming device 13 and the detonation of the explosive charge 16 cannot take place.

[0063] The second firing safety mechanism consists of an inertial sensor (such as an accelerometer 22) that detects the firing acceleration. The accelerometer 22 is connected to the computer 18, which includes a logic module that verifies the presence of both events, thereby releasing the safety and arming device 13 from the rocket 11.

[0064] The safety and armament device 13 of the rocket 11 can therefore only move from a safety position to an armed position following the lifting of two different safety measures: the detection of the ignition current of the propellant charge and the detection of the longitudinal firing acceleration.

[0065] 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.

[0066] Even a long fire during ignition of the propellant charge cannot arm the safety and arming device 13 since the firing acceleration has not appeared.

[0067] An accidental ignition of the propellant charge, for example following a fire, cannot also lift the arming safety since the electrical current intended for the igniter 6 is then absent and has not been able to charge the capacitor 20.

[0068] The invention therefore defines a rocket 11 that meets the highest safety requirements without the need to equip the safety and armament device with an additional inertial lock.

[0069] As an alternative, it is of course possible to associate the capacitor 20 with a mechanical inertial lock immobilizing the flap 15 of the safety and arming device 13. This inertial lock will form the second safety.

[0070] Of course, if the capacitor 20 is functionally attached to the rocket 11, it can structurally be located outside the rocket, for example in a specific housing in the projectile body 2.

[0071] Advantageously the computer 18 of the rocket 11 will itself constitute the safety and armament device, without the need to provide a movable flap 15.

[0072] This simply requires the use of a 14-element projectile detonator (more commonly known as a "slapper"). These detonators are relatively insensitive and can only be activated by high voltage; moreover, they deliver sufficient energy to initiate a secondary explosive, which is also less sensitive. It is therefore possible (and permitted by standards bodies) to use a slapper without a mechanical flap to prevent misalignment of the pyrotechnic chain, provided that two independent firing safety mechanisms are in place to control the operation of the rocket.

[0073] The firing safety is then ensured by the rocket 11 itself, which can only activate the slapper after both firing safety mechanisms have been disengaged. In this case, the firing safety mechanisms will be independent logic locks, separate from the firing chain itself.

[0074] Figure 3 shows an example of an embodiment of a rocket 11 according to the invention and incorporating a projected layer detonator 14.

[0075] As previously stated, the wire 12 is connected to the initiator 6 by a voltage divider 23 which includes two resistors R1 and R2. Thus, in a conventional manner, the voltage u carried by the wire 12 is reduced compared to the ignition voltage U of the igniter 6. We have =U R2 / (R1+R2).

[0076] The voltage divider 23, although functionally part of the rocket 11, is structurally located at the base 5. Thus the current passing through the wire link 12 is reduced.

[0077] 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 link 12 would be the same as that of the firing, which can cause problems of insulation and firing safety.

[0078] Capacitor 20 is powered through a load resistor R3, and another resistor R4 is connected in parallel across the terminals of capacitor 20. Resistor R4 allows capacitor 20 to discharge after its charged state is detected by the computer 18 during the projectile's flight. This allows the removal of parasitic charges that could disrupt the rocket's operation. R3 and capacitor 20 effectively form a low-pass filter that eliminates high-frequency interference.

[0079] The ignition of the igniter 6, which ignites the propellant charge, therefore causes the capacitor 20 to charge.

[0080] We can see that the rocket includes a field-effect transistor (MOS) 24 whose drain (D) is powered by the electrical generator 19 (when it is triggered). The capacitor 20 is located between the gate (G) and the source (S) of the transistor 24.

[0081] When the electric generator 19 is started, it powers the computer 18 (connection 25) but it also applies a voltage V DS , via link 26, to a logic module 27 of the computer 18.

[0082] When capacitor 20 is charged to a voltage u that is greater than the threshold voltage V GSof the MOS transistor (which therefore constitutes the reference value of the first safety firing of rocket 11), the MOS transistor 24 closes and the current from the generator 19 is discharged to ground 28 via connection 29. This results in a voltage close to 0 volts applied to the logic module 27 of the computer via connection 26. The load resistor R5 prevents a short circuit of the generator 19.

[0083] 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 the logic module 27 to detect the desired combination.

[0084] If capacitor 20 is not charged, it means that no ignition of the propellant charge has been detected. MOSFET 24 then remains open and the voltage V DSis equal to the voltage of the electric generator 19, i.e. a logic level 1. This logic state 1 indicates to the logic module 27 that the safety is not lifted, the rocket 11 is not armed and the initiation of the Slapper detonator 14 is impossible.

[0085] Furthermore, the logic module 27 detects the firing acceleration seen by the accelerometer 22.

[0086] The components and logic wiring are chosen in such a way that only the conjunction of the presence of a firing acceleration and a charge of the capacitor 20 allows the operation of the rocket 18 to be activated, and in particular of a module 30 for managing the firing of the slapper detonator 14.

[0087] The rocket 11, and more specifically the firing management module 30, also receives, as described previously, the wired link 21 allowing the programming of the desired operating mode for the rocket.

[0088] It can be seen, therefore, that the first firing safety mechanism according to the invention uses electrical information stored in the rocket 11 before it can be activated, as the electric generator 19 is not yet operational. The timing of a firing is, however, sufficiently rapid for the stored information to be read by the rocket when it is ready to fire. The discharge of capacitor 20 occurs only gradually, through resistor R4, after the safety mechanism is released. Capacitor 20 does not play a role in the ignition of the Slapper detonator 14. The energy for this ignition comes from the electric generator 19.

[0089] The invention is particularly suited to ammunition fired from a smoothbore barrel. However, it is clear that it can also be implemented with ammunition fired from a rifled barrel. The firing event associated with the ignition of the propellant charge can then be combined with either axial or rotational acceleration of the projectile.

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), 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, the fuze being characterized in that it comprises a capacitor (20) which is intended to be connected to the electric ignition means (6) for igniting the propellant charge (3) and which charges during the ignition of the latter, and also 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, characterized in that it comprises an electrical generator (19) which is inertially primed during the fire.  3. The fuze according to claim 1, characterized 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 claim 1, characterized in that it comprises a divider bridge (23) between the electric ignition means (6) and the capacitor (20). 5. The fuze according to claim 2, characterized in that the capacitor (20) is arranged between the gate G and the source S 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) secured to a base (5), the projectile (1) carrying 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, characterized 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. 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 characterized 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 claim 8 or claim 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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