EP2077431B1 - Micro-machined or micro-engraved safing and arming device - Google Patents

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 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 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 US 6167809 describes a miniature device, according to the preamble of claim 1, also using MEMS technology but in which the second latch is actuated by the acceleration and not by the centrifugal force. A first lock is released by a flyweight which under the effect of the acceleration will move in the opposite direction against the action of a spring, will unlock the first lock and set in a stop means. The second latch is disengaged from a latch 59 and is set in motion by a not shown actuator, constituted by a pyrotechnic composition inserted in a channel. As stated in this patent, the second latch moves forward without any effect of the centrifugal force.

The patent US 6964231 describes such a micro-machined safety device comprising a flap carrying a pyrotechnic charge and sliding by the action of the centrifugal force. This shutter itself is immobilized by a lock that is erased by the acceleration of firing of the projectile.

Another tilting lock releases the shutter which is led to its armed position by the centrifugal force of inertia. The rocking latch is actuated by a pyrotechnic composition generating gas whose ignition is controlled by an electronic means.

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

However, it is of complex structure and in particular the second latch (rocking latch) requires the implementation of a pyrotechnic composition and means of initiation thereof. An electronics must therefore be provided to control the operation of this MEMS which is therefore unsuitable for use in ammunition of medium caliber (caliber less than 40 mm) for which the available volume is limited.

The object of the invention is to provide a micro-machined safety and arming device, of simple structure and satisfying the most demanding safety conditions, in particular requiring the presence of two independent environmental conditions for moving into an armed position.

The device according to the invention implements a 100% mechanical armament while ensuring a reliable pyrotechnic chain interruption.

Thus, the subject of the invention is a micro-machined or micro-engraved safety and arming device for a chain pyrotechnic projectile which is animated when firing an axial rotation movement, device comprising a substrate on which is disposed a pyrotechnic chain interruption flap which is movable in translation on the substrate, device in which the flap chain interruption is held immobilized by at least two latches, a first latch (or axial acceleration latch) which is released as a result of the application of the acceleration communicated to the projectile during firing and a second latch, characterized in that the second latch is a centrifugal latch which is released as a result of the rotation of the projectile, and in that the centrifugal latch comprises at least one interlocking locking finger of the substrate, which finger is held in an imprint of the flap when it occupies its locking position, the maintenance being provided by a micromachined centrifugal feeder which is itself slidably mounted in a the component.

The centrifugal weight will be slidably mounted against the action of a first spring means.

Braking means may be provided to slow the movement of the weight.

The flap itself can advantageously slide by the action of the centrifugal force and against the action of a second spring means.

The locking finger may be secured to the substrate by means of a flexible tongue.

According to a particular embodiment, the braking means may comprise lamellae secured to at least one of the flexible tongues, lamellae rubbing against a lateral surface of the weight.

The substrate will advantageously comprise an orifice on either side of the flap, the axis of these orifices, and therefore the direction of action of the pyrotechnic chain, being substantially parallel to the plane of the flap.

• 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 d'un mode de réalisation du dispositif de sécurité et d'armement selon l'invention dans sa position de sécurité,
• les figures 3a, 3b et 3c montrent ce même dispositif au cours des différentes étapes conduisant à son armement.

The invention will be better understood on reading the following description of a particular embodiment, description made with reference to the accompanying 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 view of an embodiment of the safety and arming device according to the invention in its safety position,
• the figures 3a , 3b and 3c show this same device during the different stages leading to its armament.

The figure 1 shows a projectile 1 of medium caliber (caliber less than 50 mm), which comprises a body 2 enclosing an explosive charge 3. The body 2 receives at its front part a rocket 4 which is screwed into a tapping of the body 2. The rocket 4 comprises a housing 8 which contains a firing charge 5. The firing load 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 initiate directly 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 terms of component 14.

Such an arrangement of a pyrotechnic warp shutter such 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 (hexanotrostilbene), 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 technologies. 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 2a which takes the scratches of the barrel of the weapon (not shown) and which communicates to the projectile 1 a rotational movement about its axis during firing.

The figure 2 shows in more detail the internal structure of the safety device 12 according to the invention.

The device therefore comprises a substrate 13 on which is disposed a pyrotechnic chain interruption flap 14 which is movable in translation on the substrate.

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.

There is shown in the figures the orifices 15a and 15b which are disposed on either side of the flap 14 and the axis 16 of these orifices (thus the direction of action of the pyrotechnic chain). The dimension L of the shutter 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 two bolts.

A first latch 17 (or axial acceleration latch) and a second latch which is a centrifugal latch released as a result of the rotation of the projectile 1.

Thus, unlike the known device of US6964231 which requires a rocking latch actuated by a specific pyrotechnic composition, the device according to the invention directly uses the centrifugal inertia to unlock the flap 14 while maintaining the safety of the beginning of trajectory (no arming before a certain distance traveled out of the tube).

The first latch 17 cooperates with a notch 18a carried by a rod 18 secured to the flap 14.

This latch 17 is held engaged in the rod 18 by a spring means 19 interposed between the latch 17 and the substrate 13.

The latch 17 also carries a bar 20 carrying at least one indentation. This bar 20 is intended to cooperate with a complementary cavity 21 carried by the substrate to ensure immobilization of the first latch 17 in its unlocked position.

The spring means 19 is of course also made according to micro-machining or micro-etching technologies (MEMS technologies). The mechanical characteristics of the spring means 19 are chosen so that the latch 17 is released only as a result of the forces related to the firing acceleration of the projectile 1. This latch will however remain in its locking position when it is subjected to the efforts related to the handling or falling of the projectile.

The centrifugal latch comprises at least one locking pin 22 which is integral with the substrate 13.

The device here comprises two fingers 22 made in the form of cylindrical micro-machined or micro-etched discs and made integral with the substrate 13 via flexible tongues 23, also micro-machined or micro-engraved.

Each finger 22 is housed in a recess 24 of complementary shape and which is arranged in a housing 25 of the flap 14.

In the locking position shown in figure 2 the fingers 22 are held in the cavities 24 by a micromachined or micro-engraved centrifugal feeder 26 which is itself slidably mounted with respect to the substrate 13 and in the housing 25 of the shutter 14.

The weight 26 is held in its locking position ( figure 2 ) by a first spring means 27 (also micro-machined or micro-engraved). Of course the mechanical characteristics of the first spring means 27 are chosen so that the weight 26 moves only as a result of the forces related to the centrifugal acceleration resulting from the rotation of the projectile 1 during firing. The counterweight must however remain in its locking position when it will be subjected to efforts related to handling or falling of the projectile.

The substrate 13 carries a bar 28 carrying at least one indentation. This bar 28 is intended to cooperate with a complementary cavity 29 carried by the weight 26 to ensure immobilization of the weight 26 in its unlocked position.

The shutter 14 itself is slidably mounted in a housing 30 of the substrate 13. Once the latches 17, 22 are removed, the shutter 14 can slide in this housing 30 by the action of the centrifugal force and against the action of a second spring means 31 (here formed by two parallel springs).

Finally braking means are provided to slow the movement of the weight 26.

These means comprise lamellae 32 which are integral with the flexible tongues 23 and which rub against the lateral surfaces 33 of the weight 26 (surfaces which could possibly carry roughness or roughness). The braking means can slow down the movement 26 of the weight, so to slow the erasure of the centrifugal locks 22. This ensures a mouth security during firing. The arming device 12 will intervene after the course of a certain distance after the exit of the tube of the weapon.

The operation of this device will now be described with reference to Figures 3a to 3c .

The figure 3a shows the device in the position it adopts inside the barrel of the weapon when firing.

The firing acceleration causes the appearance of an axial inertia force Fy on the first latch 17. This latch thus releases the flap 14. The latch 17 remains immobilized in its unlocked position by the engagement of the bar 20 in the cavity 21.

The flap 14 is, however, still maintained in the safety position by the centrifugal latch 26/22.

Indeed the speed of rotation is not yet sufficient to cause the separation of the feeder 26. The interruption of the pyrotechnic chain by the flap 14 is always ensured.

The figure 3b shows the device in the position that it adopts after its exit from the tube of the weapon and at a distance of the order of about fifty meters.

The centrifugal acceleration has caused the appearance of a radial inertia force F ₁ ω which is exerted on the flyweight 26. The flyweight has gradually moved away against the action of the second spring means 27 and being slowed down by the friction of the lamellae 32 on the lateral surfaces 33 of the weight 26.

The stiffness of the spring means 27, and the braking means 32,33 are defined so as to delay the passage of the weight 26 to its unlocked position, so that the configuration according to the figure 3b only intervenes about fifty meters from the barrel of the weapon. The security is then optimal for the servants of the weapon.

Once the weight 26 locked in this position by the engagement of the bar 28 in the complementary cavity 29, the centrifugal locks 22 are no longer maintained by the weight 26 (which also comprises profiles before 34 bevel that facilitate the release of the locks 22).

The flap 14 is then no longer immobilized by the locks 22 and can therefore adopt its unlocked position ( figure 3c ).

It is also displaced by the effect of a centrifugal inertia force F ₂ ω and against the action of the second spring means 31.

The movement of the flap causes the tongues 23 bearing the latches 22 to deflect. The housing 25 is defined with a depth sufficient to allow the bolts 22 to pass between the flyweight 26 and the flap 14.

The flap 14 no longer closes the orifices 15a, 15b. The direction of action 16 of the pyrotechnic chain is released and the device is in the armed position. An impact on a target will initiate the explosive charge of the projectile.

Note that the flap 14 is locked in its armed position by tabs 36 secured to the substrate 13 and which engage in notches 37 arranged on a side surface of the flap 14 so as to prohibit the return of the latter to its seat. security position.

We see that the device according to the invention is extremely simple and compact. It has a totally mechanical structure and can be incorporated into a medium caliber projectile at a lower cost.

The axis 35 along which moves the weight 26 and the flap 14 is perpendicular to the axis 16 of the direction of pyrotechnic action. When the device is placed in a projectile, the axis 35 therefore corresponds to a radial direction of the projectile and centrifugal inertia can be exerted on the flyweight 26 and the flap 14. The integration of the device in a projectile is therefore extremely simple despite the reduced dimensions for this device 12. Indeed the pyrotechnic alignment of the axis 16 necessarily leads to a correct orientation of the device relative to the projectile.

Various variants are possible without departing from the scope of the invention.

It is possible in particular to adopt different technical solutions for the means 20/21, 28/29 ensuring the immobilization of the locks. The forms of the spring means may be different. They will be defined according to the shooting constraints that the projectile must undergo.

It is also possible to associate the safety and arming device according to the invention with an electric initiation detonator 6 coupled for example to an electronic means of chronometry or proximity detection.

Claims (7)

1. A micro-machined or micro-engraved safety and arming device (12) for a pyrotechnic train of a projectile (1) to which axial spin is imparted after firing, such device comprising a substrate (13) onto which a shutter (14) to break the pyrotechnic train is positioned, such shutter being mobile in translation on the substrate (13), device in which the train-breaking shutter (14) is held immobile by at least two locks (17, 22), a first lock or axial acceleration lock (17) which is released further to the application of the acceleration communicated to the projectile (1) during firing, and a second lock (22), device characterized in that the second lock (22) is a centrifugal lock that is released further to the projectile (1) being made to spin, and in that the centrifugal lock comprises at least one locking finger (22) integral with the substrate (13), such finger being held in an indentation (24) in the shutter (14) when it is in its locking position, it being held in place by a micro-machined centrifugal counterweight (26) which is itself mounted able to slide in a housing (25) in the shutter (14).
2. A safety and arming device according to Claim 1, characterized in that the centrifugal counterweight (26) is mounted able to slide against the action of first spring means (27).
3. A safety and arming device according to Claim 2, characterized in that braking means (32) are provided to slow down the movement of the counterweight (26).
4. A safety and arming device according to one of Claims 1 to 3, characterized in that the shutter (14) itself slides through the action of the centrifugal force and against the action of second spring means (31).
5. A safety and arming device according to one of Claims 1 to 4, characterized in that the locking finger (22) is made integral with the substrate (13) by means of a flexible tab (23).
6. A safety and arming device according to Claims 3 and 5, characterized in that the braking means comprise lugs (32) integral with at least one of the flexible tabs (23), such lugs coming to rub against a lateral surface of the counterweight (26).
7. A safety and arming device according to one of Claims 1 to 6, characterized in that the substrate (13) incorporates an orifice (15a, 15b) on either side of the shutter (14), the axis of these orifices, and thus the direction of action of the pyrotechnic train, being substantially parallel to the plane of the shutter (14).

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