EP2482028B1 - Security and weaponry device with breakable bolt - Google Patents

Abstract

The device (12) has a substrate (13) onto which a shutter (14) is positioned to ensure blocking of a channel. The shutter is movable in translation on the substrate. The shutter is immovable in a safety position by an acceleration lock (17) that is released following to the application of axial acceleration imparted to a projectile during firing. The lock includes a breakable tongue connecting the shutter to the substrate. The tongue is oriented and dimensioned such that axial inertial stresses are developed during firing and exerted on the shutter to cause the tongue to break.

Description

The technical field of the invention is that of security and arming devices for a pyrotechnic chain of a projectile and in particular micro-machined security and arming devices.

Security and arming devices (or DSAs) are well known. They generally comprise a screen closing a transmission channel which connects a detonator and a pyrotechnic charge.

The screen is thus interposed on the transmission of the detonation wave between the detonator and the load and it prevents the operation of the latter.

One of the problems encountered with conventional devices is their size. The pieces are relatively massive to be able to ensure the interruption of the pyrotechnic chain. The motor means for moving the screen must be powerful. In most cases, springs are used which remain bandaged during the storage phases, which can lead to a degradation of their mechanical characteristics and to a loss of reliability of the armament.

In recent years it has been proposed to carry out all or part of the safety and arming 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. This technology known under the name of MEMS (Micro Electro Mechanical System) makes it possible today to achieve micro mechanisms by implementing a technique similar to that for producing electronic integrated circuits.

The patent EP2077431 thus describes a micro-machined safety and arming device in which the arming is completely mechanical while satisfying the most demanding safety conditions.

Thus a first lock or acceleration lock is released during the firing. This lock moves back against the action of a return spring and it emerges from a rod secured to the shutter. Once cleared from the shutter, the first lock immobilizes relative to the substrate by appropriate indentations.

A second latch or centrifugal latch is released by the displacement (under the effect of the rotation of the projectile) of a counterweight housed in the flap.

Such a safety and arming device thus makes it possible to use two independent environmental conditions for arming: the longitudinal firing acceleration and the centrifugal acceleration. This double security allows this device to comply with the highest standards of projectile arming safety (STANAG 4187).

This safety and arming device, however, has disadvantages.

The first lock in particular (acceleration lock) occupies a significant place in the device. It imposes an increase in the dimensions of the substrate of the component and also requires to provide on the movable flap a rod cooperating with the first lock. So that this rod does not remain protruding in the armed position in the pyrotechnic transmission channel, it is necessary to increase the stroke of the flap, which further penalizes the dimensions of the device.

The object of the invention is to propose a micro-machined safety and arming device that does not have such a disadvantage.

The device proposed by the invention incorporates a simplified structure acceleration lock which ensures both compactness and reliability for the device.

Thus, the subject of the invention is a micro-machined or micro-engraved security and arming device for a pyrotechnic chain of a projectile, the device comprising a substrate on which is disposed a shutter ensuring the closure of a channel, flap which is movable in translation on the substrate, wherein the flap is held immobilized in the safety position by at least one acceleration lock which is released as a result of the application of the axial acceleration communicated to the projectile during firing , characterized in that the acceleration lock is constituted by at least one breakable tab connecting the flap to the substrate, oriented tongue and dimensioned so that the axial inertia forces developed during the firing and exerted on the flap cause the breaking of said tongue.

At least one tongue may be oriented along the axis of the projectile so as to be stressed in tension or in compression.

At least one tongue may be oriented perpendicular to the axis of the projectile so as to be stressed in shear.

At least one tongue may be connected to the flap and / or the substrate by a support of increasing width between the tongue and the flap and / or the substrate.

• la figure 1 est une vue schématique en coupe d'un projectile de moyen calibre équipé d'une fusée incorporant un dispositif de sécurité et d'armement selon l'invention,
• la figure 2 est une vue simplifiée d'un mode de réalisation du dispositif de sécurité et d'armement selon l'invention dans sa position de sécurité,
• les figures 3a et 3b sont des vues agrandies de deux exemples de réalisation d'une languette d'un verrou d'accélération,
• les figures 4a et 4b sont des vues agrandies de deux autres exemples de réalisation d'une languette d'un verrou d'accélération,
• les figures 5a et 5b sont des vues agrandies de deux autres exemples de réalisation d'une languette d'un verrou d'accélération.

Other advantages will appear on reading the following description of particular embodiments, a description given with reference to the appended drawings and in which:

• the figure 1 is a schematic sectional view of a medium-caliber projectile equipped with a rocket incorporating a security and arming device according to the invention,
• the figure 2 is a simplified view of an embodiment of the safety and arming device according to the invention in its safety position,
• the Figures 3a and 3b are enlarged views of two embodiments of a tab of an acceleration lock,
• the Figures 4a and 4b are enlarged views of two other embodiments of a tab of an acceleration lock,
• the Figures 5a and 5b are enlarged views of two other embodiments of a tab of an acceleration lock.

The figure 1 shows a projectile 1 of medium caliber (caliber less than 50 mm), which comprises a body 2 of axis 2a containing an explosive charge 3. The body 2 receives at its front part a rocket 4 which is screwed into a thread of 2. The fuse 4 comprises a housing 8 which contains a firing charge 5. The firing charge 5 is intended to be initiated by a pyrotechnic chain comprising a detonator 6 and a relay 7 (alternatively this relay 7 could be omitted and the detonator 6 would then directly initiate the priming charge 5). The detonator 6 is here a percussion detonator which is initiated by a striker 9 slidably mounted in a nose 10 secured to the casing 8 of the rocket 4. During the impact of the projectile 1 on a target, the striker 9 is projected onto the detonator 6. The striker is held in place during the storage and firing phases by a shear washer 11.

It is of course possible to implement the device according to the invention with an electric detonator 6 controlled for example by an electronic chronometry means or a proximity detector.

The rocket 4 also contains a security and arming device 12 which makes it possible to interrupt the pyrotechnic chain during the storage and firing phases of the projectile 1.

According to the invention, this safety and arming device is made in the form of a micro-machined or micro-engraved device (MEMS). It thus comprises a substrate 13 on which is mounted a sliding shutter 14 which ensures the interruption of the pyrotechnic chain.

The substrate 13 has two orifices 15a and 15b disposed on either side of the flap 14. The axis of these orifices 15a, 15b, therefore the direction of action of the pyrotechnic chain (6-7), is thus substantially parallel in the plane of the flap 14. This axis is also coincident with the axis 2a of the projectile.

Such an arrangement of a pyrotechnic chain interruption flap so that the direction of the pyrotechnic chain is opposite the thickness of the flap 14 and not perpendicular to the plane of the flap (as in the usual MEMS devices) is known in particular from the patent EP1780496 .

Those skilled in the art will refer to this patent which describes the general characteristics of such a type of priming chain and the shutter associated therewith.

It should be noted that the detonator 6 must have the minimum size to ensure operation and it will be coupled to a suitable pyrotechnic relay 7 (or 5). It has been verified that by using a detonator comprising an output stage of 10 milligrams of hexogen coupled to a very insensitive relay, for example in HNS (hexanitrostilbene), it was possible to make orifices 15a, 15b ( or transmission channels) of less than 1 mm ² section (channel diameter of the order of mm) while guaranteeing the desired initiation transmission.

It is thus possible to ensure an interruption of the pyrotechnic effect with a silicon flap having a length L of the order of 3 mm which is quite feasible with MEMS technology. This length of silicon of the order of 3 mm therefore corresponds here to the dimension L of the flap 14 identified on the figures 1 and 2 .

The projectile 1 is also provided with a belt 2b which takes the stripes of the barrel of the weapon (not shown) and which communicates to the projectile 1 a rotational movement about its axis 2a during firing.

The figure 2 shows in simplified manner the internal structure of a first embodiment of the safety and arming device 12 according to the invention.

The device comprises a substrate 13 on which is disposed a pyrotechnic chain interruption flap 14 which is movable in translation on the substrate in a cavity 31. figure 2 an arrow A which indicates the direction of movement of the flap 14 during arming. This direction is perpendicular to the axis 2a of the projectile (which coincides with the axis 16 of the orifices 15a and 15b).

The flap 14 is made by micro-machining or micro-etching according to MEMS production techniques which are well known to those skilled in the art.

We have shown on the figure 2 the orifices 15a and 15b which are arranged on either side of the flap 14 as well as the axis 16 of these orifices (thus the direction of action of the pyrotechnic chain). The dimension L of the flap 14 ensures the interruption of the pyrotechnic chain in the safety position of the device 12.

The chain interruption flap 14 is held immobilized by at least one acceleration lock 17.

The device will also preferably include another shutter latch which will be released by centrifugal force. This type of lock is not the subject of the present invention. He was not represented to simplify the description. For example, the solution described by the EP2077431 cited in the preamble of this application.

Note also that tabs 29 secured to the substrate 13 are engaged in notches 30 arranged on a side surface of the flap 14. These tabs do not prohibit the movement of the flap in the arming direction A. Tabs and notches constitute means for prohibiting the return of the flap in the safety position at the end of its arming movement.

The device here comprises an axial acceleration latch 17 consisting of two breakable tongues 18 which connect the flap 14 to the substrate 13. Each tab is integral with a lateral edge 14a or 14b of the flap 14. The figure 3a shows enlargedly an embodiment of such a tongue 18.

The tabs 18 ensuring the suspension of the shutter are oriented parallel to the axis of the projectile, so that the axial inertia forces F _γ , which are parallel to the axis 2a of the projectile, and which will be exerted on the flap 14 during firing will cause their break. We have shown on the figure 3a an arrow F _γ to show the orientation of these inertial forces.

In addition, the tongues 18 will be dimensioned such that this rupture only occurs for the inertia forces associated with the firing and not during the shocks received by the device during the handling phases or during the logistics operations.

The width e of the tongue 18 will thus be calibrated to break during an acceleration of the order of 50000 m / s ² , which is the order of magnitude of the accelerations experienced by the projectiles of medium caliber (lower caliber or equal to 40mm).

We notice on the figure 3a that the tongue 18 is connected to the flap 14 on the one hand and to the substrate 13 on the other hand by supports 20a and 20b whose width is increasing between the tongue 18 and the flap 14 on the one hand and the substrate 13 of somewhere else. These supports 20a, 20b are here triangular. Such an arrangement makes it possible to better control the location of the break on the tongue 18. By giving different dimensions to the widened supports 20a, 20b, it will be possible in particular to bring the rupture zone constituted by the tongue 18 closer to the flap or the substrate.

Depending on the architecture of the device 12, the axial acceleration lock 17 may be produced in the form of tongues that are stressed in tension, in compression, or in tongues stressed in shear, or in a combination of several types of tongues.

As an example, we have shown figure 3b an example of a device in which the tongue 18 is oriented perpendicular to the axis of the projectile (therefore perpendicular to the direction of F _γ ) so as to be stressed in shear.

Making the first lock in the form of breakable tabs makes the device more compact. It is no longer necessary to define a specific locking mechanism associating locks and return springs. The simplification of the mechanism also makes the device more reliable.

This solution is particularly well suited to the field of medium caliber projectiles for which the reversibility of the operation of the device (return to safety position) does not arise.

The figure 2 shows tabs of the acceleration lock disposed between flap 14 and substrate 13 at longitudinal edges 14a and 14b which are parallel to Armament Directorate A of Part 14. On this figure 2 one of the tongues (the tongue of the upper edge 14a) is therefore biased in tension and the other tongue (that of the lower edge 14b) is biased in compression.

Alternatively it is possible to have a tongue of a latch 17 according to the invention at the side edge 14c. This lock may comprise a tongue 18 working in shear as shown in FIG. figure 4a or a pulling tongue as shown in FIG. figure 4b .

One could also in some cases, and depending on integration constraints, achieve simple tabs in the form of rectangular bars.

The Figures 5a and 5b show such embodiments of tabs 18 in the form of bars. The figure 5a shows a bar 18 oriented relative to the inertia forces F _γ so as to be broken by traction. The figure 5b shows a bar 18 oriented relative to the inertia forces F _γ so as to be broken by shearing.

The acceleration latch according to the invention has been described here by way of non-limiting example in its application to a safety and arming device in which the direction of action of the pyrotechnic chain is substantially parallel to the plane of the flap. .

It is clear to those skilled in the art that it is possible to implement the invention for any other type of security device and armament with movable flap.

One could for example consider such an acceleration lock for safety devices and weapons in which the direction of action of the pyrotechnic chain is perpendicular to the flap. Such devices are described for example by EP1601926 .

This lock could also be envisaged for devices in which the shutter does not ensure the interruption of a pyrotechnic chain but the interruption of an optical control signal (for example for an initiation of an explosive by a laser beam ). Such devices are known especially from EP1559986 , EP1559987 .

It would also be possible to use a latch according to the invention for safety and arming devices in which the shutter interrupts a passage channel of a wafer projected by a detonator (of the "slapper" type), this device is described for example by US6173650 .

Finally, it will be possible to implement the invention in safety and arming devices for which the flap itself carries a pyrotechnic composition for introducing it into an initiation chain, devices as described, for example, by patents. US6622629 , US7552681 and US7490552 .

Claims (4)

1. A micro-machined or micro-engraved safety and arming device (12) for a projectile pyrotechnic train, device comprising a substrate (13) onto which a shutter (14) is positioned to ensure the blocking of a channel, such shutter being mobile in translation on the substrate (13), device in which the shutter (14) is held immobile in the safety position by at least one acceleration lock that is released further to the application of the axial acceleration imparted to the projectile during firing, device wherein the acceleration lock (17) is constituted by at least one breakable tongue (18) linking the shutter (18) to the substrate, tongue (18) oriented and dimensioned such that the axial inertial stresses developed during firing and exerted on the shutter (14) cause the said tongue (18) to break.
2. A safety and arming device according to Claim 1, wherein at least one tongue (18) is oriented along the axis (2a) of the projectile so as to be stressed in traction or in compression.
3. A safety and arming device according to Claim 2, wherein at least one tongue (18) is oriented perpendicularly to the projectile axis (2a) so as to be shear stressed.
4. A safety and arming device according to one of Claims 2 or 3, wherein at least one tongue (18) is linked to the shutter (14) and/or to the substrate (13) by a support (20a, 20b) of increasing width between the tongue (18) and the shutter (14) and/or the substrate (13).

Images