EP2482029B1 - Device for timing a movement of a micro-machined balance weight and security and weaponry device including such a timer device - Google Patents

Description

The technical field of the invention is that of micro-machined or micro-etched devices and more particularly devices for delaying a movement of a feeder which is incorporated in such a micro-machined device.

In recent years it has been proposed to produce miniaturized mechanical devices comprising micro-machined or micro-etched electromechanical 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.

This technique produces many types of devices, for example sensors, accelerometers, inertial units.

It is sometimes necessary in such a micromechanical device to provide a delay or a braking of the movement of a mechanical member, for example a flyweight subjected to the action of an engine, a spring or even subjected to forces inertial.

It has been known in particular for a few years to make safety and arming devices for a pyrotechnic projectile chain that are made using this MEMS technology.

Some concepts of such safety devices include a pyrotechnic warp shutter whose plane is located perpendicular to the direction of action of this chain. Such a device is described for example by the patent EP1601926 . The disadvantage with such a device is that the thickness of a MEMS shutter is not sufficient to stop a pyrotechnic effect. This leads to the association of such a component with an electric projection layer detonator (better known under the name of "Slapper"), as described by the patent US6173650 . In this case the screen does not stop a pyrotechnic effect but the projection of the plate intended to ensure the initiation of a detonation relay.

Other devices are also known 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 in particular patents EP1559986 , EP1559987 .

Safety and arming devices are also known for which the flap itself carries a pyrotechnic composition and can introduce it into an initiation chain. Such devices are described for example by patents US6622629 , US7552681 , US7490552 .

Finally, devices are known in which the direction of action of the pyrotechnic chain is substantially parallel to the plane of the flap. These devices are described by patents EP1780496 and EP2077431 which forms the basis of the independent claim. The latter devices are particularly well suited to security devices for medium caliber projectiles as they can be associated with percussion detonators.

For all known MEMS safety and arming devices, there is generally the problem of delaying the movement of a slide, a flyweight or the shutter itself.

It has been proposed, in particular by patents US6568329 and US6064013 , to ensure this slowdown by providing a slight clearance between the flyweight and its housing and arranging reliefs or indentations at the side faces of the weight and its housing. Given the play, when a force appears (for example of axial or centrifugal acceleration inertia), the indentations cooperate with each other and lead to a "zigzag" displacement of the weight, so a slow motion or timed. This is particularly useful when it is desired to ensure a delay in arming the device during the first 10 to 15 meters of the trajectory of the projectile out of the barrel of the weapon, which is generally imposed by the projectile safety standards. .

This known solution, however, has disadvantages.

The zigzag movement of the flyweight is a mechanical movement that is difficult to control. This results in uncertain reliability and delay, the value of which can not be guaranteed.

The parameters to be modified to adjust this delay are limited. An increase in the number of indentations on the weight will thus force to increase the radial clearance which increases the risk of blocking the weight. It is also often necessary to add a spring to control the movement of the weight, which increases the complexity of the device.

The object of the invention is to propose a device for delaying a movement of a flyweight, a device in which this movement is delayed by a retarding means which is designed so as to be able to control the delay obtained.

This slowing means also allows the realization of timed weights which are not associated with a spring.

Thus, the subject of the invention is a device for delaying a movement of a micromachined or micro-etched weight with respect to a substrate, the weight comprising at least one face bearing at least one indentation intended to cooperate with at least one another indentation carried by a housing in which the weight is moving so as to slow down the movement of the weight, device characterized in that the indentation or indentations which are carried by the weight (respectively by the housing receiving said weight) are carried by at least one flexible tongue which is itself integral with the weight (respectively the housing), the tongues can be deformed by bending during movement of the weight.

The tongue may be integral with the weight (respectively the housing) by its two ends.

According to one embodiment, the weight is movable in translation in the housing and has two lateral faces carrying at least one indentation which cooperates with at least one complementary indentation carried by the walls of the housing, at least one flexible tongue being provided in the vicinity of each side face of the weight, tongue integral with the weight (or the housing wall).

The device may comprise at least two flexible tongues in the vicinity of each side face of the weight, tongues integral with the weight (or the housing wall).

According to another embodiment, the weight is pivotally movable in the housing and comprises a sector bearing at least one indentation which cooperates with one or more complementary indentations integral with a flexible tongue carried by a wall of the housing.

The subject of the invention is also a safety and arming device for a pyrotechnic chain of a projectile which is animated when firing a longitudinal acceleration movement and / or axial rotation. This safety and arming device incorporates at least one flyweight whose movement is timed by a timing device according to the invention.

Advantageously, the housing of the feeder will be arranged in a shutter of interruption of the pyrotechnic chain.

• la figure 1 montre de façon schématique un premier mode de réalisation d'un dispositif de temporisation selon l'invention incorporant une masselotte mobile en translation sur un substrat,
• la figure 2 montre de façon agrandie la coopération des indentations pour ce premier mode de réalisation,
• la figure 3 montre un deuxième mode de réalisation d'un dispositif de temporisation incorporant une masselotte mobile en translation sur un substrat,
• la figure 4 montre de façon agrandie la coopération des indentations pour ce deuxième mode de réalisation,
• la figure 5 est une vue schématique d'un exemple de dispositif de sécurité et d'armement qui incorpore un dispositif de temporisation dans lequel la masselotte coulisse par rapport à un volet d'interruption de chaîne pyrotechnique,
• les figures 6a et 6b montrent deux variantes de réalisation d'un dispositif de temporisation selon l'invention, et
• les figures 7a et 7b montrent un troisième mode de réalisation d'un dispositif de temporisation incorporant une masselotte mobile en rotation sur un substrat.

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 shows schematically a first embodiment of a delay device according to the invention incorporating a flyweight movable in translation on a substrate,
• the figure 2 shows in an enlarged way the cooperation of the indentations for this first embodiment,
• the figure 3 shows a second embodiment of a delay device incorporating a mobile flyweight in translation on a substrate,
• the figure 4 shows in an enlarged way the cooperation of the indentations for this second embodiment,
• the figure 5 is a schematic view of an exemplary safety and arming device which incorporates a delay device in which the weight slides relative to a pyrotechnic chain interruption flap,
• the Figures 6a and 6b show two alternative embodiments of a timing device according to the invention, and
• the Figures 7a and 7b show a third embodiment of a delay device incorporating a flyweight rotatable on a substrate.

The figure 1 shows in a very simplified way part of a timing device 1 micro-machined or micro-engraved according to MEMS realization techniques which are well known to those skilled in the art.

This device is incorporated in a micromechanism (not shown) which is more complex and is designed to perform certain functions (sensor, accelerometer, inertial unit, safety and arming device).

The other components of this micromechanism are not shown because they are not the subject of the present invention, the description of which will be limited to that of the operation of the single time delay device.

The micromechanism will comprise in particular a movable flyweight 3.

For the sake of clarity, we therefore limited ourselves to representing on the figure 1 a substrate 2 relative to which a flyweight 3 moves in a housing 4. The flyweight is movable relative to the substrate in direction A by the action of, for example, a motor or an actuator (such as a spring 13) or still by the effect of the acceleration forces undergone by the said weight (in particular when the device is a security and arming device incorporated in a projectile).

In the latter case, according to the orientation of the device 1, the acceleration of the flyweight may therefore be the longitudinal acceleration due to shooting or the acceleration of axial rotation of the projectile.

The weight 3 slides in a housing 4 which can be made in the substrate 2 itself (as figured here) but also in another element of the device, which would itself be mobile.

The weight 3 comprises two lateral faces 3a, 3b which carry reliefs or indentations 5 intended to cooperate with other reliefs or indentations 6 carried by the walls of the housing 4.

The cooperation of these indentations 5 and 6 makes it possible to slow down the movement of the weight. Here the profile of the indentations is triangular. It would of course be possible to implement profiles of different indentations: rounded, rectangular, trapezoidal ...

In the remainder of the description, the term indentation will be used in a nonlimiting manner as a generic term to designate these complementary teeth or reliefs and this, whatever the shape and the number of these indentations.

According to an essential feature of the invention, some of the adjacent indentations of each side face 3a, 3b of the weight are integral with a flexible tongue 7 which is itself secured to the element bearing these indentations. Here the integral indentations of a tongue 7 are carried by the flyweight 3 itself.

This flexible tongue 7 is delimited by the etching of an opening 8 in the flyweight 3. The tongue 7 is integral with the weight by its two ends. Such an arrangement makes it possible to stiffen the tongue. It also makes it possible to make the device reversible, braking can then be done in the two opposite directions of displacement of the weight relative to its housing. Such an arrangement may be useful in a configuration which will be described later with reference to the figure 5 .

As we see better on the figure 2 when the weight 3 moves (arrow D) as a result of the action of a motor or the inertial forces associated with acceleration, the indentations 6 of the substrate 2 push the indentations 5 of the weight 3. resulting friction cause a deflection of the tongue 7 which spreads, in a direction perpendicular to the direction D (arrow F), the indentations 5 of the weight 3 with those 6 of the substrate 2. The displacement of the flyweight is thus made possible thanks to the flexibility of the tabs 7 located on either side of the weight 3 while the clearance between the weight 3 and its housing 4 is however reduced.

The indentations 6 of the substrate are in fact substantially in contact with the sidewalls 3a, 3b of the weight. It will be noted that with such a reduced clearance, a "zigzag" displacement of the flyweight 3 (as in the known devices) would be impossible. Moreover, since the indentations carried by each lateral face 3a, 3b of the counterweight are symmetrical, the displacement of the counterweight 3 is rectilinear in the housing 4.

The timing of displacement of the flyweight here results from the braking due to the friction indentations 5 and 6 on each other. The rectilinear movement is well controlled and the delay will depend on the flexibility of the tabs 7 and the number of indentations 5,6 in contact with each other, that is to say the intensity of the friction forces. These parameters are easy to master. This results in reliability and reproducibility of the delay which are excellent.

The figure 3 shows another embodiment of the invention wherein the indentations 5 carried by the two side walls 3a, 3b of the weight 3 are fixed.

They cooperate with indentations 6 which are integral with a flexible tongue 7 carried by the walls of the housing 4.

The figure 4 is an enlarged detail view of the cooperation between the indentations for this embodiment.

The operation is analogous to that described above with reference to Figures 1 and 2 .

When the weight 3 moves (arrow D) the indentations 5 of the weight 3 push those 6 of the substrate 2. The resulting frictional forces cause a deflection of the tongue 7 which spreads in a direction perpendicular to the direction D ( arrow F), the indentations 6 of the substrate 2 with those of the flyweight 3. The displacement of the weight is again made possible thanks to the flexibility of the tongues 7 located on either side of the weight 3, on the walls of the dwelling 4.

The figure 5 shows an example of application in which the delay device 1 is incorporated in a micro-machined or micro-engraved safety and arming device 100.

This device 100 comprises a shutter 9 of pyrotechnic chain interruption. This shutter 9 is itself movable in translation on the substrate 2 in a cavity 10. It is shown on the figure 5 an arrow B which indicates the direction of movement of the flap 9 during arming.

We also represented on this figure 5 orifices 11a and 11b which are disposed on either side of the flap 9 and the axis 12 of these orifices (thus the direction of action of the pyrotechnic chain). This direction 12 is perpendicular to the direction of movement B of the flap 9, and here it is merged with the axis of a projectile (not shown) within which the device is disposed.

There is shown here by way of illustration and not limitation a device in which the direction of action 12 of the pyrotechnic chain is substantially parallel to the plane of the flap. These devices are described by patents EP1780496 and EP2077431 .

The dimension L of the shutter 9 thus ensures here the interruption of the pyrotechnic chain in the safety position of the device 100.

This safety and arming device 100 naturally includes other elements, such as one or more locks for the shutter 9 which are released by the longitudinal acceleration and possibly by the rotation of the projectile. These elements are not part of the invention and it is not necessary to describe them in detail. Reference may be made to the patents described in the preamble to this application (and in particular to EP1780496 or EP2077431 ) to obtain structural details of different examples of safety and arming devices in which the invention may find application.

According to the embodiment shown in figure 5 , the flap 9 comprises a housing 4 inside which slides the flyweight 3. This flyweight 3 which is slidably mounted in the same direction B as the arming direction of the flap 9 will therefore be subjected to centrifugal forces of inertia for this device which is intended to be incorporated in a gyro-stabilized projectile.

The weight 3 is intended to ensure the lifting of a centrifugal latch of the flap 9. This lock is not shown because it is not the subject of the present invention. For example, one could consider the patent EP2077431 which describes an example of a centrifugal latch for a similar security and arming device configuration.

We notice on the figure 5 that the weight 3 incorporates indentations 5 which are integral with a flexible blade 7. These indentations cooperate with indentations 6 carried by the inner wall of the housing 4 of the weight. The configuration adopted here for the braking means of the weight is therefore identical to that described above with reference to the Figures 1 and 2 .

It would of course be possible to implement between the flap 9 and the weight 3 a configuration of the timing device 1 similar to that described with reference to Figures 3 and 4 .

Note that in the embodiment according to the figure 5 , and for which the flap 9 and the weight 3 have the same direction of displacement B, the means of braking the displacement of the weight 3 by the indentations of the flap 9 plays in a symmetrical way the role of braking means of the displacement of the part 9 by the indentations of the weight. This displacement is made possible because the tongue 7 is integral with the weight 3 at both ends. This arrangement which makes the movements of the device reversible has been detailed previously.

Such a provision is particularly interesting because it reduces the impacts on the shutter during arming and the risks of rebound of the shutter 9.

We have shown figure 1 a spring 13 which is interposed between the substrate 2 and the weight 3.

We notice that this spring is omitted on the figures 3 and 5 . With the invention, it is indeed not essential to use a spring to maintain the alignment of the weight and control the problems due to relative clearance between the weight and its housing. It is sufficient that the stiffness of the tongue 7 is sufficient so that it does not sag during shocks encountered during the transport and postage stages of a projectile.

Tab 7 will be sized to flex when the friction forces are caused by the intense acceleration associated with a shot. In a certain way, with the invention, the co-operation of the indentations 5, 6 between the flyweight 3 and the walls of its housing 4 can therefore act as a lock for the flyweight 3, which further simplifies the design of a device security and weapons. This depends, of course, on the acceleration conditions that the device must resist during the logistic phases and during the firing phases.

As a variant it is of course possible to provide more than one tongue in the vicinity of each side face of the weight.

For example, figure 6a thus shows a delay device 1 in which a weight 3 comprises two flexible tongues 7 at each wall 3a, 3b of the weight 3 and the figure 6b shows a weight 3 which moves in a housing whose walls, adjacent the side walls 3a, 3b of the weight, each carry two flexible tongues 7 carrying indentations 6.

The timing device according to the invention can also be implemented to delay or slow down a pivoting movement of a flyweight.

The Figures 7a and 7b show schematically a micro-machined or micro-etched delay device 1 in which the counterweight 3 is pivotally mounted in a housing 4 relative to the substrate 2 and at a pivot 14. The counterweight 3 here has the form of a sector with an external rim carries indentations 5. Such a weight may for example be a lock of a micro-machined device. In this case it will co-operate at the end of the race with other organs or mechanisms which are not represented here because they do not form part of the present invention.

The indentations 5 cooperate with a single indentation 6 which is integral with a flexible tongue 7, itself secured to the substrate 2 and defined by an opening 8.

We notice on the figure 7a that the pivot 14 is locked relative to the substrate 2 by a breakable blade 15. A pivoting torque exerted on the flap 3 to rotate it along the arrow R (for example as a result of an inertial force) will cause breakage of the coverslip 15.

The pivoting in the direction indicated by the arrow R will be slowed by the indentation 6 secured to the substrate 2. The frictional forces between the indentations 5 and 6 will bend the tongue 7 whose flexibility will allow the pivoting of the weight 3 The arrow F represents on the figure 7a the bending force exerted on the tongue 7.

The braking of the flyweight 3 therefore results from the friction of the indentations 5,6 on each other. The delay therefore depends on the flexibility of the tongue 7 and the number of indentations in contact with each other (here only one). These parameters are easy to master, it results reliability and reproducibility of the delay which are excellent. The figure 7b shows the position of the weight 3 at the end of its pivoting. It will be noted that the indentation 6 maintains the position of the flyweight 3 at the end of this pivoting movement. This is true if the accelerations undergone thereafter have a level lower than that which was necessary to bend the tongue. In the opposite case it will be necessary to provide a locking means (not shown).

It is understood that the embodiments of timing devices described above can be used in all types of micromechanical devices MEMS technology in which it is necessary to slow down or delay a displacement in rotation or in translation of a feeder. The field of application of the invention is therefore not limited to that of the safety and arming devices of the pyrotechnic projectile chains.

Claims (7)

1. A time control device (1) for the movement of a micromachined or micro-engraved counterweight (3) with respect to a substrate (2), the counterweight (3) incorporating at least one face having at least one indentation (5) intended to cooperate with at least one other indentation (6) on a housing (4) in which the counterweight (3) moves so as to ensure the delaying of such movement of the counterweight, device characterised in that the indentation(s) (5, 6) on the counterweight (3) (respectively on the housing (4) receiving said counterweight) is (are) made on at least one flexible tongue (7) itself integral with the counterweight (3) (respectively the housing(4)), the flexible tongue (7) being able to be deformed by bending during the displacement of the counterweight (3).
2. A time control device according to Claim 1, characterised in that the flexible tongue (7) is integral with the counterweight (3) (respectively the housing (4)) by its two ends.
3. A time control device according to one of Claims 1 or 2, characterised in that the counterweight (3) is mobile in translation in a housing (4) and incorporates two lateral faces (3a, 3b) having at least one indentation (5) and cooperating with at least one matching indentation (6) on the walls of the housing (4), at least one flexible tongue (7) being provided near to each lateral face (3a, 3b) of the counterweight, tongue (7) integral with the counterweight (3) or with the housing wall (4).
4. A time control device according to one of Claims 1 to 3, characterised in that it incorporates at least two flexible tongues (7) near each lateral face (3a, 3b) of the counterweight (3), tongues integral with the counterweight (3) (or with the housing wall (4)).
5. A time control device according to one of Claims 1 or 2, characterised in that the counterweight (3) is able to pivot in the housing (4) and incorporates a sector with at least one indentation (5) cooperating with one or several matching indentations (6) integral with a flexible tongue (7) integral with the housing wall (4).
6. A safety and arming device (100) for a pyrotechnic train of a projectile to which a longitudinal acceleration movement and/or an axial spin is imparted upon firing, device characterised in that it incorporates at least one counterweight (3) whose movement is delayed by a time control device (1) according to one of Claims 1 to 5.
7. A safety and arming device according to Claim 6, characterised in that the counterweight housing (4) is arranged in a shutter (9) intended to break the pyrotechnic train.

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