EP2402706B1 - Safety and arming device with MEMS technology inertia lock - Google Patents

Description

The technical field of the invention is that of microelectromechanical projectile safety and arming devices.

It is known to make Mechanical Security and Armament Devices (or DSA) which are incorporated into rockets projectiles of any caliber. Today we seek to achieve these devices using MEMS technology (Micro Electro Mechanical Systems) which allows a strong miniaturization suitable for integration on medium caliber projectiles for example.

The purpose of the safety and arming devices is to isolate the detonator from the explosive charge of a projectile and to allow communication between these two components of the pyrotechnic chain only when (according to current standards such as STANAG No. 4157) at least two distinct shooting environment conditions are met. The insulation between detonator and loading is most often achieved by means of a plate also called screen or drawer obstructing a light communicating these two components.

The shooting environment conditions used to authorize the removal of the drawer are often as illustrated EP-2077431 on the one hand, the acceleration along the firing axis and, on the other hand, the acceleration of the projectile's rotation on its axis due to its gyrostabilization (shooting in a rifled barrel).

The patent EP-2077431 uses these two stresses to, initially, release an inertial lock with flyweight thanks to the acceleration along the axis of fire then, in a second time, to slide transversely the drawer in a position releasing the light thanks to the acceleration in rotation.

As presented in EP-2077431 , the device has two disadvantages.

First, the drawer is hooked only to the inertial lock. The transverse forces received by the drawer as a result of the shocks received by the device (for example during the logistic phases or of placing the projectile in the weapon), are therefore communicated by the drawer latch that may be deflected and blocked and not be able to be released during the shooting.

Secondly, the bolt weight is subjected after unlocking to the transverse forces due to the rotation of the projectile. These transverse forces cause the weight to the drawer and can lead to its unlocking and even its positioning in front of the light, thus disrupting the boot.

We also know by FR-2932561 a security and arming device comprising a mobile screen immobilized by an inertial lock. The arming of the screen is provided by a gas generator. Such a device is not implemented in a projectile subjected to an acceleration of rotation and the problem that seeks to solve the invention does not arise for this device. Note that the implementation of a gas generator to move the screen is a complex and expensive solution that is made necessary by the lack of sufficient centrifugal inertia.

The invention proposes to solve the problems encountered in a device as described by EP-2077431 , on the one hand by joining the lock with the body of the device and on the other hand by guiding the weight of the latch on its path.

The subject of the invention is thus a device for securing and cocking microelectromechanical technology for a projectile, a device incorporating a slideway that can be movable under the effect of the centrifugal acceleration relative to the body of the device and immobilized in a position by at least one inertial lock, lock comprising at least one means ensuring its locking in the unlocked position, characterized in that the inertial lock comprises a flyweight having at least one straight groove whose longitudinal axis is parallel to the direction of movement of the lock, groove in which is positioned a pin fixed guide secured to the safety and arming device, the groove having a length sufficient to allow movement of the weight relative to the pin, the slide being in its secured position secured to the body of the safety device and arming by means of a fastening means integral with the weight.

Advantageously, the hooking means comprises at least one first lug corresponding with at least one first integral hook shape of the drawer and at least one second lug corresponding with at least one second hook form integral with the safety device body and arming, the first and second lugs being oriented in the same direction, ends of the lugs oriented opposite the direction of movement of the release of the flyweight.

According to another characteristic of the invention the guide pin may comprise a rectangular section occupying substantially the entire width of the groove.

Advantageously, the weight is suspended between at least two springs whose main axis of deformation is parallel to the direction of movement of the lock.

• la figure 1 représente le dispositif de sécurité et d'armement en position de sécurité,
• la figure 2 représente le dispositif de sécurité et d'armement avec le verrou inertiel en cours de déverrouillage, et
• la figure 3 représente le dispositif de sécurité et d'armement en position armée.

The invention will be better understood on reading the additional description which follows with reference to the appended drawings in which:

• the figure 1 represents the safety and arming device in the safety position,
• the figure 2 represents the safety and arming device with the inertial lock being unlocked, and
• the figure 3 represents the security and arming device in the armed position.

According to figure 1 , a safety and arming device 1 is mounted on an explosive projectile and separates a detonator placed for example below the device (mark D) and an explosive charge placed above the device (mark E). Projectile, detonator and explosive charge are not shown.

The safety and arming device 1 is made, just like that described by the patent EP-2077431 , according to MEMS technology (micro-machined or microgravity device on a substrate).

It thus comprises a body 2 (or substrate) on which is mounted a sliding drawer 4 which ensures the interruption of the pyrotechnic chain.

The body 2 comprises two holes 3 arranged on either side of the spool 4. The axis 21 of these holes 3, and thus the direction of action of the pyrotechnic chain (DE), is thus substantially parallel to the plane of the spool 4 .

Such an arrangement of a pyrotechnic warp shutter so that the direction of the pyrotechnic chain is opposite the thickness of the slide 4 and not perpendicular to the plane of the slide (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 drawer associated therewith.

It is noted that the detonator D must have the minimum size to ensure operation and it will be coupled to an explosive charge or a pyrotechnic relay E appropriate. It has been verified that by using a detonator comprising a 10 milligram output stage of Hexogen coupled to a very insensitive relay, for example in HNS (hexanotrostilbene), it was possible to make holes 3 (or transmission channels) of less than 1 mm ² section (channel diameter of the order of mm) while ensuring the desired initiation transmission.

It is thus possible to ensure an interruption of the pyrotechnic effect with a silicon drawer 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 corresponds here to the dimension L of the spool 4 located on the figure 1 .

The body 2 has a substantially parallelepiped shape. The body 2 is pierced on either side of the drawer 4 by the aligned holes 3 and which materialize a light through the body 2 which constitutes the direction of action 21 of the pyrotechnic chain. The interior of the body 2 comprises the drawer 4 which is disposed substantially in the center of the device 1 and an inertial lock 20 disposed on one side of the body. The drawer 4 has a hook 5 on its rear side facing the latch 20 and two notches 6 on two other sides opposite the flanges of the body 2 carrying the holes 3.

The inside of the body 2 also comprises two micro-machined elastic strips 7 with the body 2, lamellae which are inclined in the direction of movement of the slide and facing each other. These strips 7 have substantially the orientation of the notches 6 of the drawer 4. They will be deformed by the passage of the drawer 4 and will then be housed in the notches 6.

In the safety position represented in figure 1 , the hook 5 is engaged in a first lug 8 integral with a flyweight 9 of the inertial lock 20. The flyweight 9 carries a second lug 10, symmetrically disposed at the first lug 8 relative to a direction 22 of displacement of the flyweight 9. This second lug 10 is engaged in a second corresponding hook 11 secured to the body 2. The set of these hooks and lugs is named attachment means 12.

The weight 9 is placed laterally to the drawer and to move in the same plane as that of the drawer 4 but in a direction perpendicular to the movement of the drawer 4. Thus the assembly remains compact, the thickness of the device is not increased by the race of the weight 9.

The flyweight 9 is retained at each of its ends and along the same longitudinal axis 22 by two springs 15 and 16. The weight 9 comprises a groove 13 oriented along the longitudinal axis 22. This groove 13 transversely traverses the flyweight 9 from side to side. go. Inside the groove 13 is positioned a fixed guide pin 14 which is integral with the body 2 at a bottom wall 23 on which is positioned the body 2 and the various moving parts (slide 4, weight 9 ...).

The lower part of the weight 9 comprises a pair of tongues 17. On either side of the lower spring 16 are two walls of the body which have notches 18 for receiving the tongues 17. The assembly formed by the tongues 17 and the notches 18 is a locking means of the inertial lock 20 in its unlocked position.

Still according to the figure 1 , the device being in the safety position, it is understood that the drawer 4 is secured to the body 2 of the device by the attachment means 12. In this manner the inertial lock 20 and in particular the weight 9 is not removed by the spool 4 of its position aligned along the axis 22 as a result of the shocks that can receive the device 1 during the logistic and postage phases of the projectile in a weapon.

The figure 2 shows the device when firing the projectile. The acceleration due to the firing generates an effort P This displacement of the flyweight causes the lugs 8 and 10 of the hooking means 12 to disengage from the hooks 5 and 11. It will be noted that for this purpose the lugs 8 and 10 and the hooks 5 and 11 are placed so that the recess (or ends) of the hooks is oriented downwards and that of the lugs upwards.

The upper spring is then extended while the lower spring 16 is in compression. Such mounting of the weight 9 between two springs 15 and 16 mounted in opposition allows to limit the buckling of the compression spring, to improve the guiding accuracy and especially to control the stiffness desired for the inertial lock.

During its translation, the weight 9 is guided by the pin 14 which is positioned in the groove 13, aligned with the axis 22 which is also that of the springs and the inertia force P. At the end of its stroke as on the figure 2 , the inertial lock 20 is locked by the engagement of the tongues 17 in the notches 18.

Then the spool 4 is free in translation and under the effect of the centrifugal acceleration R due to the rotation of the projectile it will be able to slide to the end of the body 2 of the device placed opposite the inertial lock 20 .

As a safety measure, the safety and arming device 1 should not be in an armed position before the projectile has left the barrel of the weapon. For this a braking means not shown but described in the patent EP 2077431 will slow the travel of the drawer 4 so that it reaches its end position in contact with a stop 25 once the projectile out of the tube.

The figure 3 shows the device 1 in the armed position. The drawer 4 is then abutted 25 in the body 2.

The slats 7 are engaged in the notches 6 and lock the drawer 4 in the armed position. The holes 3 are then released and the initiation of the detonator D will be able to cause the detonation of the explosive charge E.

Claims (4)

1. A safety and arming device (1) for projectiles and using micro-electromagnetic technology, such device (1) incorporating a slider (4) made mobile by the effect of the centrifugal acceleration with respect to the body (2) of the device (1) and immobilized in a safety position by at least one inertial lock (20), such lock (20) incorporating at least one means (17 and 18) to ensure its blocking in the unlocked position, device characterised in that the inertial lock (20) incorporates a counterweight (9) having at least one straight groove (13) whose longitudinal axis is parallel to the direction of movement of the lock, groove (13) in which a fixed guiding pin (14) integral with the safety and arming device (1) is positioned, since the groove (13) is of sufficient length to allow the displacement of the counterweight (9) with respect to the pin (14), the slider (4) in its safety position being made integral with the body (2) of the safety and arming device (1) by means of hooking means (12) integral with the counterweight.
2. A safety and arming device (1) according to Claim 1, characterised in that the hooking means (12) incorporate at least one spigot (8) corresponding with at least a first hook shape (5) integral with the slider (4) and at least a second spigot (10) corresponding with at least a second hook shape (11) integral with the body (2) of the safety and arming device (1), the first and second spigots (8 and 10) being oriented in the same direction, the ends of the spigots (8 and 10) being oriented in the opposite direction to the direction of movement that unlocks the counterweight.
3. A safety and arming device (1) according to one of Claims 1 or 2, characterised in that the guiding pin (14) incorporates a rectangular section substantially occupying the full width of the groove (13).
4. A safety and arming device (1) according to one of Claims 1 to 3, characterised in that the counterweight (4) is suspended between at least two springs (15, 16) whose principal strain axis (22) is parallel to the direction of movement of the lock.

Images