EP2239535A1 - Ignition device of a munition by percussion - Google Patents

Abstract

The device (4) has a firing pin intended to impact a pyrotechnic composition (8) to activate ignition, where the firing pin has a rod (15) that slides when ammunition is fired through effect of firing acceleration from a starting position to a deployed position. The rod is integrated with a percussion tip (12) occupying a fixed position in contact with the pyrotechnic composition. A hammer (21) strikes the rod during impact of the ammunition on a target to cause ignition of the composition.

Description

The technical field of the invention is that of ammunition firing devices using a mechanical striker impelling a pyrotechnic composition.

In a conventional manner the firing devices comprise a firing pin which is projected by inertia on the pyrotechnic composition after the lifting of a certain number of safety barriers. This striker is also often projected by a spring, so as to ensure a self-destruct function (when for example there is no impact on a target).

The patent FR-2689972 thus describes a firing device for a projectile medium caliber (caliber between 20 mm and 50 mm). This device comprises a striker which can be pushed to a primer by a spring.

In order to avoid any risk of inadvertent percussion during the storage or transport phases, the primer is secured to an arming rotor that keeps it away from the striker before firing.

Such an architecture is however complex and requires the realization of many mechanical parts with precise machining.

In a conventional manner, the self-destruct spring is maintained in the bandaged state during all the storage and transport phases. Even if this spring compresses slightly more during the firing to allow more often the withdrawal of the locks of the gate rotor, sufficient energy for self destruction requires storage of the spring in the bandaged state.

The purpose of the invention is to simplify such a device by proposing an architecture in which the percussive primer is always aligned with the striker, but the shocks undergone during the storage and transport phases can not, however, provoke percussion of the primer.

With the device according to the invention, only the constraints related to shooting can make the device bootable. The invention thus makes it possible to completely secure the percussion function during the storage and transport phases.

The invention also allows the implementation of a self-destruction mechanism in which the spring means do not have to be compressed during assembly.

There is therefore not, thanks to the invention, storage of springs in the banded state which ensures a maintenance of the performance of the device despite storage phases of long durations and with significant temperature intervals.

Also known by the patent FR-1300100 an ammunition firing device comprising a striker integral with a percussion body which is locked in the safety position by balls.

This device therefore comprises a firing pin which is permanently aligned with the primer but which is locked by security means which are erased during firing.

These safety means comprise two flyweights inertia, the first flyweight releasing the balls locking the striker.

This device is of complex structure. It is indeed necessary that the two weights slide in a well-defined order so that the firing pin is released. Indeed the balls are pushed by one of the weights against the second weight. It is therefore necessary for the latter to deviate rapidly during firing to avoid jamming the balls.

It is also necessary that the second weight remains locked (at least temporarily) to allow the ejection of the striker locking balls. This locking is provided by other balls housed in a groove of the second weight, groove whose bottom is tapered. These locking balls therefore deviate during firing by their axial inertia to engage against a ramp of the firing pin.

This particularly expensive solution from the point of view of machining and mounting eliminates the rotational speed of the projectile. However, it is unreliable, the balls remaining in the locking position only by the sole action of the return spring of the weight.

Specifically to the impact on the target is, in a conventional way, the only inertia of the striker (including that of the second weight) and acting against the effect of a spring, which will ensure the initiation of the primer.

As all the known solutions thus implementing the inertia of a striker, the energy available to the impact on a target is proportional to the mass of the firing pin and the distance traveled by the latter to initiate the primer. This energy E is equal to myD, where m is the mass of the striker, D is the distance traveled by the striker, and y is the deceleration experienced at impact on a target.

The conventional geometries in which the strikers are sliding rods not driven by springs, lead to relatively large strokes (of the order of tens of millimeters).

The object of the invention is to propose a device of simple design in which only the constraints linked to the firing can make the device startable, and in which the percussion function of the energy supply function for the percussion is completely dissociated.

This allows the definition of percussion firing devices more compact because it is no longer necessary to provide a significant stroke for the firing pin.

The invention is more particularly applicable in the field of rockets and firing devices comprising micro-machined or micro-engraved elements (MEMS technology such as Micro Electro Mechanical System).

For some years now it has been proposed to carry out all or part of the ammunition safety devices using chips incorporating electromechanical micro-machined or micro-etched elements either in an element deposited on a substrate or directly on the substrate itself. -even. This technology known as the MEMS (Micro Electro Mechanical System) makes it possible today to achieve micro-mechanisms by implementing a technique similar to that for the realization of electronic integrated circuits.

We know in particular by patents EP-1780495 and EP1780496 safety and arming devices implementing a micro-machined or micro-etched pyrotechnic chain interruption flap.

However, a firing device for mechanical firing using MEMS technology is not known to date.

One of the reasons for this lack of solution is the impossibility of making MEMS springs in the bandaged state. It is then necessary to compress these springs in a storage position with all the difficulties of conducting such an operation with a device of very small dimensions (a MEMS chip generally has dimensions less than or equal to 10 mm).

The device according to the invention is easily transposable to the realization of a device of very small dimensions and in particular a device made according to MEMS technologies.

The invention therefore relates to an ammunition firing device, comprising a firing pin intended to impact a pyrotechnic composition to control the initiation of the latter, characterized in that the firing pin comprises a sliding rod during firing. the ammunition by the effect of the firing acceleration from a rest position to an extended position, and lockable in the deployed position, rod secured to a percussion tip occupying a fixed position in contact with the pyrotechnic composition, the rod being completely inside the tip in the rest position and being projecting relative to the tip in the deployed position, the device further comprising a hammer capable of striking the rod during the impact of the ammunition on a target for initiating the composition.

The sliding rod can be locked in the deployed position by at least one centrifugal latch.

The sliding rod is advantageously connected to the tip by a tension spring.

The percussion tip may be secured to a partition which will delimit a cavity receiving the pyrotechnic composition, embrittlement means being provided to separate the tip of the partition during the impact of the hammer.

According to one embodiment, the hammer can be projected against the extensible rod by a spring means.

The hammer can thus be in the rest position before firing in the vicinity of the undeployed rod, the spring means being in the uncompressed state and the firing acceleration will cause the movement of the hammer and the compression of the spring means.

The hammer may be kept away from the firing pin by holding means comprising at least one centrifugal flyweight cooperating with a fixed ramp.

According to a particular embodiment, the entire device may be made in the form of micromachined planar elements or micro etched on a wafer.

The device may include a riser for setting up the pyrotechnic composition above the tip.

• la figure 1 montre la configuration générale d'une munition incorporant un dispositif selon l'invention,
• les figures 2a, 2b et 2c sont des vues schématiques en coupe d'un premier mode de réalisation d'un dispositif selon l'invention, la figure 2a montrant le dispositif en position de stockage, la figure 2b en position armée à l'issue du tir et la figure 2c en position de percussion,
• la figure 2d est une vue de détail montrant l'immobilisation d'un verrou en position déployée,
• les figures 3a, 3b et 3c sont des vues schématiques en coupe d'un second mode de réalisation du dispositif selon l'invention, la figure 3a montrant le dispositif en position de stockage, la figure 3b en position armée à l'issue du tir et la figure 3c en position de percussion,
• les figures 4a et 4b sont des vues schématiques en coupe d'un troisième mode de réalisation du dispositif selon l'invention (réalisation sous forme de MEMS), la figure 4a montrant le dispositif en position de stockage et la figure 4b en position armée à l'issue du tir,
• la figure 5 est une vue de détail d'un verrou centrifuge, et
• la figure 6 est une vue en coupe partielle de la plaquette micro usinée.

The invention will be better understood on reading the following description of various embodiments, a description given with reference to the appended drawings and in which:

• the figure 1 shows the general configuration of a munition incorporating a device according to the invention,
• the Figures 2a, 2b and 2c are schematic sectional views of a first embodiment of a device according to the invention, the figure 2a showing the device in storage position, the figure 2b in armed position at the end of the shot and the Figure 2c in percussion position,
• the figure 2d is a detail view showing the immobilization of a lock in the deployed position,
• the Figures 3a, 3b and 3c are schematic sectional views of a second embodiment of the device according to the invention, the figure 3a showing the device in storage position, the figure 3b in armed position at the end of the shot and the figure 3c in percussion position,
• the Figures 4a and 4b are schematic sectional views of a third embodiment of the device according to the invention (embodiment in the form of MEMS), the figure 4a showing the device in storage position and the figure 4b in armed position at the end of the shot,
• the figure 5 is a detail view of a centrifugal latch, and
• the figure 6 is a partial sectional view of the micromachined plate.

The figure 1 schematically shows in section a body 2 of a munition 1 which contains an explosive charge 3. This explosive is initiated by a firing device 4 and a safety and arming device 5 is interposed between the firing device and the explosive charge 3.

The safety and arming device 5 is shown here very schematically. It essentially comprises a screen 6 which makes it possible to interrupt the transmission channel 9 between a pyrotechnic composition 8 (integral with the firing device 4) and the explosive charge 3.

The screen 6 is movable in translation by the action of motor means which are represented here schematically by a spring 7. In a conventional manner, locking means (not shown) will release the flap 6 as a result of the detection of different events associated with ammunition firing (eg inertial locks).

This safety device does not form part of the present invention and it is therefore not necessary to describe it in detail. The safety and arming device 5, the firing device 4 and the body 2 of the ammunition are connected to each other by means not shown, for example by threaded rings.

The Figures 2a to 2c show a first embodiment of a firing device 4 according to the invention.

This device comprises a pyrotechnic composition 8 sensitive to percussion which is disposed in a cup 10 positioned in a cavity 31 of a front portion 11a of a body of the device 4. A percussion tip 12 is positioned in the bucket 10 and in contact with the pyrotechnic composition 8. This point is secured to a partition 13 which is interposed between the rear portion 11b and 11a before the body of the device. The partition 13 also makes it possible to close the cavity 31 and the bucket 10 enclosing the composition 8.

The front portions 11a and 11b of the rear body are connected to each other by means not shown, for example by a threaded ring. A washer 23 is interposed between these two parts.

The tip 12 is secured to the partition 13 by a shearable connection means 14, for example a thread.

The tip 12 has an internal housing inside which is slidably mounted a rod 15.

The rod 15 can slide between a folded position ( figure 2a ) and an extended position ( figure 2b ) by the effect of the acceleration force F related to the firing of the ammunition.

The rod 15 is lockable in the extended position by two centrifugal latches 16. These latches are cylindrical parts held in their folded position ( figure 2a ) by the internal cylindrical surface of the bore of the tip 12. They slide by the effect of the rotational acceleration developed during firing.

The figure 2d shows more precisely a latch 16 in the deployed position. It is seen that this lock is secured to the rod 15 by a tension spring 17. Two resilient tongues 18 are held folded in housings 19 when the latch 16 is in the folded position. These tabs 18 unfold when the latch 16 is deployed and they maintain the latch in its extended position. The spring 17 has the effect of maintaining the latch 16 in abutment against the tabs 18 and prevents inadvertent vibration or unlocking when the acceleration of rotation decreases.

It can be seen in the figures that a traction spring 20 is interposed between the point 12 and the rod 15. This spring ensures the maintenance of the rod in its deployed position ( figure 2b ) resting against the rear edge of the point 12. and also any movement of the rod 15 after deployment, even if the level of axial acceleration decreases.

The tip 12 and the rod 15 constitute a telescopic striker which is intended to initiate the pyrotechnic composition 8.

The device 4 further comprises a hammer 21 which is capable of striking the rod 15 during the impact of the munition on a target to cause the initiation of the composition 8.

According to the first embodiment which is described with reference to Figures 2a to 2c , the hammer 21 is constituted by a flyweight which is secured to the rear portion 11b of the body by a shearable ring 22.

The operation of the device is as follows.

The front (AV) and the rear (AR) of the ammunition have been marked by the letters AV and AR, respectively.

The device 4 is in the storage security state in the position shown in FIG. figure 2a . Note that in this position of the device, the rod 15 is completely inside the tip 12. No part of the tip 12 is also projecting relative to the partition 13 to the hammer 21.

Note that if a violent shock then caused the shearing of the ring 22, the hammer would be stopped by the washer 23. No shock would be received by the pyrotechnic composition 8. The safety of the device is therefore total.

Alternatively, it would be possible not to provide a washer 23 to ensure the hammer stop. In this case it is the partition 13 which will ensure the stop of the hammer. Security can be ensured by providing a partition 13 of sufficient thickness. There is no initiation of the composition because, in the state of rest, the rod 15 is not protruding with respect to the partition 13.

When the ammunition is fired by a weapon system, the device 4 ( figure 2b ) is subjected to axial acceleration forces F as well as a rotation Ω which generates a centrifugal force of inertia.

The rod 15 then slides and is locked in the deployed position ( figure 2b ) in centrifugal locks 16. In this armed configuration, the rod 15 is projecting relative to the partition 13 and the striker 12-15 is deployed.

At impact on a target ( Figure 2c ), the hammer 21 is subjected to a very large inertia force G which causes shearing of the retaining ring 22 (which is calibrated according to the forces involved).

The hammer 21 then violently impacts the rod 15 which pushes the tip 12 against the pyrotechnic composition 8 by shearing the threading 14.

Of course, it would be possible to provide another shearable means that the threading 14, for example a circular rupture leader carried by the partition 13.

The pyrotechnic composition 8 is initiated by the shock and the explosive charge 3 is detonated.

All the mechanical elements described here have a symmetry of revolution around the axis 38 of the device (except the locks 16 and their housings). It would of course be possible to make planar structure elements as will be described later.

It can be seen that, thanks to the invention, the percussion function (which is ensured by the percussion tip 12, directly in contact with the pyrotechnic composition 8 and comprising a sliding rod 15) is completely dissociated from the energy supply function. for this percussion (which is ensured by the weight 21), flyweight which is then completely distinct from the tip 12 and its rod 5.

The masses of the tip 12 and its rod 5 then have no importance and can be greatly reduced. The percussion energy will be given by the weight 21 which may have any shape and be particularly adapted to the housing available in the ammunition.

The percussion energy being proportional to the mass of the weight 21 and the distance traveled by the latter to impact the rod 5, we see that if the mass of the weight is large enough, it becomes possible to reduce the distance to be traveled by the latter quite The percussion device according to the invention can therefore be very compact (it is thus possible to easily reduce by one third the axial size of the device).

The Figures 3a, 3b and 3c describe a second embodiment which differs from the preceding only in the structure of the hammer 21 which is implemented.

According to this mode the hammer 21 comprises radial bores 24 in which are positioned balls 25. The hammer 21 is guided in its housing 26 by a front seat 21a. Guiding is completed by the sliding of a rear extension 21b of smaller diameter in a hole 27 of the rear portion 11b of the body of the device.

A compression spring 28 is mounted around the rear extension 21b. This spring is interposed between the bottom of the housing 26 and the hammer 21.

It can also be seen from the figures that the rear portion of the housing 26 has a conical profile 26a whose conicity is oriented with the apex of the cone towards the front AV of the munition. The axial acceleration F of the projectile during firing causes the recoil of the hammer 21 and the compression of the spring 28. The balls 25 are spaced radially by the action of the centrifugal force of inertia. These balls then cooperate with the conical profile 26a which ensures a locking of the hammer 21 in the armed position shown in FIG. figure 3b .

Indeed, in a conventional manner and implemented in projectile rockets, the axial acceleration F decreases after the exit of the projectile from the tube of the weapon while the rotation is maintained. The balls 25 applied on the conical profile 26a provide a locking hammer 21 in the armed position with the spring 28 compressed.

Such an embodiment makes it possible to ensure a self-destruction function of the munition. Indeed during the impact on a target the shock is sufficient to cause the projection of the hammer 21 on the rod 15 ( figure 3c ). When the ammunition does not impact a target but is stopped (fall on the ground for example), stopping the rotation puts an end to the centrifugal force which applied the balls 25 to the profile 26a. The spring 28 then relaxes by projecting the hammer 21 on the rod 15 which ensures the initiation of the composition 8.

Various variants are possible without departing from the scope of the invention. It is in particular possible to define centrifugal latches of a different structure from that of the balls 25.

The invention may advantageously be implemented to produce a miniaturized firing device in the form of micro-machined or micro-plane planar elements on a substrate.

The Figures 4a, 4b and 5 show such an embodiment in which the body is made in the form of a micro-machined or micro-etched plate 30 disposed on a substrate 29. In a conventional manner, MEMS technology makes it possible to produce mobile mechanical elements having very large dimensions. reduced. For example, the substrate 29 shown here has a rectangular shape having dimensions of the order of 8 mm for the length and 4 mm for the width.

The machining carried out on the wafer 30 made it possible to produce a rectangular cavity 31 intended to receive the pyrotechnic composition (not shown).

The cavity 31 is delimited on one side by the partition 13 which is made in one piece with the wafer 30 and the tip 12. The partition 13 will have a sufficiently small thickness for the bulkhead connection 13 / tip 12 can break at the impact by the hammer 21. It will be possible to develop during the etching of the rupture primers between the tip 12 and the partition 13.

The hammer 21 is also obtained by etching. It carries two centrifugal weights 32 which are connected to the hammer 21 by flexible lamellae 33. The hammer is guided in its housing by its front reach 21a and its rear reach 21b which is in the form of a sliding tongue in the hole 27.

Each weight 32 comprises a semicircular profile which is intended to cooperate with a ramp 34 integral with the plate 30. The ramps 34 are oriented to be geometrically intersecting towards the front AV of the munition.

It can be seen that two compression springs 28 are fixed between the hammer 21 and the wafer 30. The MEMS technology does not make it possible to produce springs maintained in the bandaged state. The architecture of the device according to the invention makes it possible to implement a spring 28 which is in the idle state in the engraved configuration shown in FIG. figure 4a (and that is also the storage configuration).

It is only during firing that the springs 28 will be compressed by the axial acceleration forces (the axis 35 represents the firing direction of the ammunition and the letters AV and AR symbolize the front and the rear respectively. rear of the ammunition.

The rod 15, which is connected to the tip 12 by a spring 20 also obtained by etching, has also been etched. The figure 5 shows this set more precisely. The rod 15 carries two centrifugal latches 16 which are connected to it by engraved springs 17.

The etching technology makes it possible to produce the springs 17 integral with the rod 15 as well as the bolts 16, their flanges 36a cooperating with the abutments 36b and locking tabs 18 (locking means similar to that described with reference to FIG. figure 2d ).

The springs 17 are obtained in the state of rest. They are stretched during the deployment of the latches 16 by the action of centrifugal forces. The spring 20 is secured to the rod 15 and the tip 12. This spring is in the state of rest. It is stretched during firing by the action of axial acceleration efforts.

Of course, all the mobile elements (hammer 21, flyweights 32, springs 28, 20, 17, rod 15) have been made in such a way that they are not adherent on the substrate 29. The same is true for the tip 12 which must be able to be pushed by the rod 15. The wafer 30 therefore adheres to the substrate 29 only by its rectangular periphery and possibly by a part of the partition 13.

We have shown on the figure 6 a partial section of the device at the level of the cavity 31. It is seen that it has been disposed above it a riser 37 which allows the establishment of a mass of pyrotechnic composition 8 greater than what could be put in the single cavity 31.

The composition is placed in the form of, for example, a drop of pyrotechnic composition containing a primary explosive associated with a polymerizable binder and it covers the tip 12. A method of setting up such a composition is described for example by the patent EP1101076 .

The friction caused by the displacement of the tip 12 is sufficient to cause the initiation of the entire composition 8. A flap 39 ensures the closure of the riser 37. Another flap 40 closes an orifice 41 connecting the composition 8 to the pyrotechnic chain of the munition (not shown).

The operation of this embodiment is identical to that described above with reference to Figures 3a to 3c .

The firing acceleration causes both the recoil of the hammer 21 and the exit of the rod 15 from its housing in the tip 12. These movements have the effect of compressing the springs 28 and stretching the spring 20. The force Centrifugal also has the effect of removing the locks 16 of their housing which blocks the rod 15 in the deployed position.

This centrifugal force also removes the weights 32 which apply to the ramps 34 which ensures the maintenance of the hammer 21 in the armed position against the action of the springs 28.

At impact on a target the hammer 21 will be projected against the rod 15 which will push the tip 12 on the pyrotechnic composition. In case of stopping of the rotation it is the springs 28 which will push the hammer 21 thus causing the self-destruction.

Claims (9)

Device (4) for firing ammunition, comprising a striker (12, 15) intended to impact a pyrotechnic composition (8) to control the initiation thereof, characterized in that the firing pin comprises a rod (15) ) sliding when firing the munition by the effect of the firing acceleration from a rest position to an extended position, and lockable in the deployed position, rod (15) integral with a point (12) occupying percussion a fixed position in contact with the pyrotechnic composition (8), the rod (15) being completely inside the tip (12) in the rest position and projecting from the tip (12) in position deployed, the device further comprising a hammer (21) capable of striking the rod (15) during the impact of the munition on a target to cause the initiation of the composition (8). Ammunition firing device according to claim 1, characterized in that the sliding rod (15) is locked in the deployed position by at least one centrifugal latch (16). Ammunition firing device according to one of claims 1 or 2, characterized in that the sliding rod (15) is connected to the tip (12) by a tension spring (20). Ammunition firing device according to one of claims 1 to 3, characterized in that the percussion tip (12) is integral with a partition (13) defining a cavity (31) receiving the pyrotechnic composition (8), embrittlement means (14) being provided for separating the tip (12) from the partition (13) during the impact of the hammer (21). Ammunition firing device according to one of claims 1 to 4, characterized in that the hammer (21) can be thrown against the extendable rod (15) by spring means (28). Ammunition firing device according to Claim 5, characterized in that the hammer (21) is is in the position of rest before firing in the vicinity of the undeployed rod (15), the spring means (28) being in the uncompressed state and in that the firing acceleration causes the movement of the hammer (21) and the compression of the spring means (28). Ammunition firing device according to claim 6, characterized in that the hammer (21) is kept away from the firing pin by holding means comprising at least one centrifugal flyweight (25,32) cooperating with a fixed ramp (26a, 34). Ammunition firing device according to one of Claims 1 to 7, characterized in that the entire device is designed as micromachined or micro-planar planar elements on a wafer (30). Ammunition firing device according to claim 8, characterized in that it comprises a riser (37) allowing the setting up of the pyrotechnic composition (8) above the tip (12).

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