EP1462756B1 - Method of defence of a vehicle or a structure against a threat such as a projectile and device to carry out said method - Google Patents

Abstract

The double acting pyrotechnic actuator (1) incorporates two pyrotechnic charges (8a,8b) each connected to distinct chambers (4a,4b) separated by a piston (5). The actuator positioning method consists of successively controlling the two charges in sequence so as to ensure, by the action of the second charge, a braking of the piston displacement which was controlled by the first charge. The time gap between the initiation of each charge is chosen to ensure the desired positioning of the piston. Independent claims are included for a pyrotechnic actuator and a vehicle defense device implementing the method.

Description

The technical field of the invention is that of methods and devices for defending a vehicle or structure against a threat such as a projectile (missile or rocket).

We know by FR2809172 a device for protecting a vehicle using a launching tube of a projectile. The tube can be oriented in at least one plane by a pyrotechnic jack with single or double effect.

This jack allows the device to have several possible launch directions. Each launch direction corresponds to a position of the piston of the cylinder. Thus a simple effect cylinder allows to give the tube two different positions: that corresponding to the cylinder in the state of rest and that corresponding to the actuator activated.

A double-acting cylinder makes it possible to give the tube three different positions: that corresponding to the jack in the idle state and the two extreme positions corresponding to the initiations of each of the two pyrotechnic charges.

The effectiveness of this device is limited because only three firing directions are possible. It is therefore necessary to provide several launching devices having different orientations with respect to the vehicle.

We also know by the FR2722873 a defense device in which a turret is oriented in site and in the field by electric motors. The motors are slaved and allow to obtain any desired orientation for the turret. It is then possible to launch a defense ammunition in the optimal direction to counter the threat.

This defense device is however heavy and bulky and the electric power it requires is also important.

It is the object of the invention to provide a defensive method of a vehicle or a structure that does not have such disadvantages.

Thus the method according to the invention makes it possible to launch a defense munition in the optimal direction while implementing at least one pyrotechnic actuator which provides speed and power for positioning.

• on détermine, à partir de la vitesse et de la direction de la menace, les angles de sites et de gisement à donner au tube de lancement de la munition de défense ainsi que l'instant auquel cette munition doit être éjectée hors du tube suivant cette direction,
• on déclenche en séquence les moyens de positionnement du tube puis le tir de la munition,
• on commande, avant ou après les moyens de positionnement, des moyens assurant le freinage et/ou l'arrêt des moyens de positionnement lorsqu'ils ont orienté le système de tir suivant les angles souhaités.

Thus, the subject of the invention is a method of defending a vehicle or a structure against a threat such as a projectile, a method employing means for positioning in situ and / or in a bearing of at least one launching tube. of a defense munition, means which comprise at least one pyrotechnic jack, a method in which the speed and the direction of the threat are determined by means of measuring and calculating means, characterized by the following steps:

• from the speed and direction of the threat, the site and bearing angles to be given to the launch tube of the defense ammunition and the time at which the ammunition is to be ejected from the tube following this direction,
• the positioning means of the tube are fired in sequence and then the firing of the ammunition,
• before or after the positioning means, means are provided for braking and / or stopping the positioning means when they have oriented the firing system according to the desired angles.

According to a particular embodiment, at least one positioning means is a double-acting pyrotechnic jack incorporating two pyrotechnic charges having an opposing effect each connected to a separate chamber, the two chambers being separated by a movable piston, the method is then characterized in that, in order to ensure the braking of at least one positioning means, the two pyrotechnic charges of the jack in question are successively ordered in sequence so as to ensure by the action of the second load a braking of the movement of the piston which has been controlled by the first load, the time interval between the initiation of each load being chosen so as to provide the desired positioning for the piston.

According to a variant of the process, it will be possible to measure the pressure in the first chamber in which the first charge is initiated, this pressure will be compared to a value Theoretical memory then corrected the time interval before initiation of the second charge and / or open a vent in at least one of the chambers so as to take into account the difference observed between the theoretical pressure and the measured pressure.

Thus, when the pressure measured in the first chamber is less than the stored theoretical pressure can delay the moment of initiation of the second load and / or can open a vent in the second chamber.

Conversely, when the pressure measured in the first chamber is greater than the stored theoretical pressure can be anticipated the moment of initiation of the second load and / or can open a vent in the first chamber.

It will also be possible to determine the actual position of the piston and use this measurement to correct the instant of initiation of the second charge and / or to open a vent in one or the other of the chambers.

The invention also relates to a defense device implementing such a method.

This device allows the defense of a vehicle or structure against a threat such as a projectile. It comprises means for positioning in situ and / or in the field of at least one launching tube of a defense munition, positioning means which comprise at least one pyrotechnic jack, the device also comprising means for detecting the approach projectile and calculating means for determining the location and bearing angles to be given to the launch tube of the defense munition and the time at which the ammunition is to be ejected from the tube in the firing direction, characterized in that it comprises electronic control means ensuring initiation in sequence of the pyrotechnic actuator (s) for positioning and firing of the ammunition, as well as means ensuring the braking and / or stopping of the positioning means when have oriented the firing system according to the desired angles.

According to a particular embodiment, the braking and / or stopping means of the positioning means are formed by deployable abutment surfaces integral with the body of the pyrotechnic jack or cylinders, the deployment of the abutment surfaces being controlled by the electronic control means.

Advantageously, the device is characterized in that the defense munition comprises a zone of spatial efficiency at a nominal distance of use, and in that two consecutive abutment surfaces carried by a cylinder body are separated by a distance which determines an angular positioning gap for the tube ensuring recovery of the areas of effectiveness of the defense munition for the two consecutive directions and at said nominal distance of use.

According to another embodiment, one of the positioning means in site and / or in the reservoir comprises at least one double-acting pyrotechnic jack incorporating two pyrotechnic charges having an opposing effect each connected to a separate chamber, the two chambers being separated by a mobile piston, and the electronic control means provide initiation in sequence of the two pyrotechnic charges of the jack concerned with a time interval chosen so as to ensure the braking of the piston and the desired positioning in the site and / or in the bearing.

According to an alternative embodiment the defense device may comprise means for measuring the pressure in the two chambers of one of the pyrotechnic cylinders, these means being connected to the electronic control means, the latter being able to compare the pressure measured in a first chamber with at least one theoretical value so as to correct the time interval before initiation of the second load of the jack concerned.

Advantageously, the device may comprise means for determining the actual position of the piston of the pyrotechnic cylinder or the positioning in site or in the bearing given by the cylinder, these means being connected to the electronic control means.

According to another variant of the invention, the device may comprise at least one vent for each chamber, vent whose opening can be controlled by the electronic control means and will put in communication said room with the outside.

• la figure 1 est un schéma en vue de dessus représentant l'engagement par un dispositif selon l'invention d'un projectile menaçant un véhicule,
• la figure 2 est un logigramme montrant la succession des étapes dans un premier mode de réalisation d'un dispositif de défense selon l'invention,
• la figure 3 est une vue en coupe d'un mode de réalisation d'un actionneur pyrotechnique mis en oeuvre dans un dispositif de défense selon l'invention,
• les figures 4a et 4b sont des coupes transversales de cet actionneur, coupes réalisées au niveau d'un moyen d'arrêt suivant le plan dont la trace AA est représentée à la figure 3, la figure 4a montre le moyen d'arrêt au repos et la figure 4b à l'état activé,
• la figure 5 est analogue à la figure 1 et montre le recouvrement des zones d'efficacité pour deux positions successives de l'actionneur en gisement.
• les figures 6a et 6b sont des vues en coupe d'un autre mode de réalisation d'un actionneur pyrotechnique mis en oeuvre dans un dispositif de défense selon l'invention, la figure 6a montrant un moyen d'arrêt au repos et la figure 6b un moyen d'arrêt activé.
• la figure 7 est une vue schématique en coupe d'un dispositif de défense selon l'invention,
• la figure 8 est une vue schématique en coupe d'un autre mode de réalisation d'un dispositif de défense selon l'invention,
• la figure 9 est une vue en coupe longitudinale d'un autre mode de réalisation d'un vérin pyrotechnique mis en oeuvre dans un dispositif de défense selon l'invention,
• la figure 10 est un exemple de courbes représentant l'évolution des pressions dans les chambres d'un tel vérin ainsi que la course de vérin obtenue,
• la figure 11 est un exemple de courbe montrant l'intervalle de temps entre l'initiation de deux générateurs pyrotechniques d'un vérin en fonction de la course souhaitée,
• la figure 12 est une vue en coupe d'un autre mode de réalisation d'un vérin mis en oeuvre dans un dispositif de défense selon l'invention,
• la figure 13 est un logigramme montrant la succession des étapes dans un dispositif de défense selon un deuxième mode de réalisation de l'invention.

The electronic control means may cause the firing of the ammunition at such an instant that it comes out of the tube substantially at the moment when the angles of elevation and location are obtained. 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 is a diagram in plan view showing the engagement by a device according to the invention of a projectile threatening a vehicle,
• the figure 2 is a logic diagram showing the succession of steps in a first embodiment of a defense device according to the invention,
• the figure 3 is a sectional view of an embodiment of a pyrotechnic actuator implemented in a defense device according to the invention,
• the Figures 4a and 4b are cross sections of this actuator, cuts made at a stop means along the plane whose track AA is represented at the figure 3 , the figure 4a shows the means of stopping at rest and the figure 4b in the activated state,
• the figure 5 is analogous to the figure 1 and shows the overlap of the efficiency zones for two successive positions of the reservoir actuator.
• the Figures 6a and 6b are sectional views of another embodiment of a pyrotechnic actuator implemented in a defensive device according to the invention, the figure 6a showing a means of stopping at rest and the figure 6b a stop means activated.
• the figure 7 is a schematic sectional view of a defensive device according to the invention,
• the figure 8 is a schematic sectional view of another embodiment of a defense device according to the invention,
• the figure 9 is a longitudinal sectional view of another embodiment of a pyrotechnic jack implemented in a defensive device according to the invention,
• the figure 10 is an example of curves representing the evolution of the pressures in the chambers of such a cylinder as well as the cylinder stroke obtained,
• the figure 11 is an example of a curve showing the time interval between the initiation of two pyrotechnic generators of a cylinder according to the desired stroke,
• the figure 12 is a sectional view of another embodiment of a jack implemented in a defense device according to the invention,
• the figure 13 is a logic diagram showing the succession of steps in a defense device according to a second embodiment of the invention.

The figure 1 shows in top view a vehicle 1 such a combat tank which carries at its glaze before a defense device 2 according to the invention. This device comprises a small turret 3 which carries a tube 4 for firing a defense munition 5.

This tube 4 is orientable in site and in deposit. The angle α represented in the figure between the direction δ of the axis of the tube 4 and a vertical plane P is the bearing angle. This angle is obtained by rotating the turret 3 relative to the vehicle 1.

The elevation angle is not shown here. This angle is that made by the direction δ of the tube 4 with a horizontal plane.

The positioning in site and in the field is obtained by pyrotechnic cylinders (not visible in this figure).

The device 2 makes it possible to defend the vehicle 1 against a threat that is a projectile 6 (missile or rocket). There are shown here two successive positions of the projectile 6a and 6b.

The vehicle comprises measurement and calculation means for determining the speed V and the direction Δ of the threat 6.

These means comprise a firing line 9 associated for example with a tracking radar 7 which is carried by the turret 8 of the vehicle 1.

In a conventional manner and taking into account the characteristics of the defense munition, the firing line determines in space the direction δ which is the optimal firing direction of this ammunition 5 so that it can counter the threat 6.

The ammunition 5 may be a munition generating a sheaf of splinters (focused along a sector or not) or a munition generating a blast effect.

This munition has a volume of efficiency E which is here represented with a substantially elliptical shape. This volume is the one within which the probability of destruction and / or destabilization of the threat 6 by the munition 5 is equal to 1.

The fire control also calculates the instant at which this munition must be ejected out of the tube 4 in this direction δ. This instant is calculated from the speed V of the projectile 6 detected and the speed v (known) of the defense munition 5. It is also calculated taking into account the volume of effectiveness and the fact that the interception must take place at the level of an interception sphere SI centered on the defense turret 3 and of radius R. This radius is fixed to the design of the system so as to minimize the effects on the vehicle 1 (this sphere has a radius of between 5 and 10 m).

The optimal direction δ is therefore that which makes it possible to encompass the projectile / threat 6 in the efficiency volume E of the defense munition 5 when this projectile arrives at the level of the interception sphere SI.

The firing line thus determines the site and bearing angles to be given to the launch tube 4 of the defense munition so that the axis of the latter is merged with the direction δ.

The knowledge of the instant (T _R ) at which the defense munition 5 must be ejected from the tube 4 and that of the dynamic characteristics of the positioning means in the site and / or the deposit (inertia of the moving parts of the turret 3, accelerations communicated by the actuators, response time of the initiation means of the pyrotechnic actuators) make it possible to determine a first instant (T _G and / or T _S ) at which the one or more positioning means in situ (instant T _S ) or in the field (instant T _G ) must be ordered.

Moreover, the knowledge of the instant (T _R ) at which the defense munition 5 must be ejected from the tube 4 makes it possible to determine a second instant (T _T ) at which the propellant charge of the munition 5 must be fired. This data is specific to the developed defense device and it depends on the characteristics of the propulsive means (pressure and velocity communicated to the munition, response time of the ignition means of the propellant charge).

The logigram of the figure 2 shows the succession of the steps of the method according to a first embodiment of the invention.

Block C1 corresponds to the delivery by the firing line of the positioning instructions of the tube in site (S) and in the bearing (G) and the instant (T _R ) at which the munition must leave the launching tube to counter threat 6 at the SI interception sphere.

An electronic control means integrated in the defensive device (or the firing line) then calculates (block C2) the instant (T _T ) at which firing of the munition must be controlled so that its exit from the tube intervenes at the instant T _R. This instant corresponds to the moment of exit of the ammunition 5 (T _R ) minus the ignition step of the propellant charge of the latter and the internal ballistic stage of the ammunition in the tube 4.

The control means also calculates (block C3) the instant of initiation (T _S ) of the pyrotechnic load of the positioning cylinder in situ.

It also calculates (block C4) the initiation instant (T _G ) of the pyrotechnic charge of the positioning cylinder in the bearing. All calculations will be performed simultaneously.

The control means then sequentially causes the different initiations of the pyrotechnic charges of the cylinders as well as firing according to the time sequence thus calculated.

Block A1: triggering of the positioning in the field (T _G ), block A2 triggering of the positioning in the field (T _S ), block A3 triggering of the firing (T _T ). The relative order of the A1 and A2 triggers will depend on the setpoint angles given in the site and on the bearing.

On the figure 2 it is considered that the order relative to the positioning in deposit intervenes first. This is of course the longest rally that is triggered first. The objective being a rallying in site and simultaneous deposit at time T _R.

The line L shows the simultaneity at the planned instant T _R of positioning in the site, in the bearing and the exit of the munition out of the tube.

Thus the ammunition 5 leaves the launch tube 4 when the positioning means have oriented the firing system at the desired angles.

The method according to the invention thus provides a simple trigger sequence of the tube positioning means and the firing of the ammunition.

In addition, means will be provided for braking and / or stopping the positioning means when they have oriented the firing system according to the desired angles. Blocks A4 and A5 symbolize these commands F _G (braking / stopping of positioning in the bearing) and FS (braking / stopping of positioning in the field).

This minimizes the mechanical disturbances brought to the munition 5 by the movements of the launch tube 4.

The positioning means use one or more actuators or pyrotechnic cylinders. These actuators as described by FR2809172 comprise a piston which slides in a cylinder. The displacement of the piston is caused by the gases of a pyrotechnic composition, such as a propellant powder.

To control the braking of such a pyrotechnic actuator can for example cause a deformation localized cylinder, deformation preventing the piston from passing a certain point.

Depending on the structure of the braking / stopping means used, these means can be controlled at the same time as the positioning means or after.

The figures 3 , 4a, 4b show an exemplary embodiment of a linear pyrotechnic actuator 10 double effect (pyrotechnic jack) incorporating means for stopping the actuator, which means will be advantageously controlled before or at the same time as the positioning means.

This actuator comprises a cylindrical case 11 of axis 13 which is closed at each end by a cover 12a, 12b. This case contains five rings 14a, 14b, 14c, 14d and 14e which delimit an internal cylindrical housing 15 divided into two chambers 16a and 16b by a piston 17 integral with a rod 18.

The case 11 and the rings 14 form the body of the jack. The rings make it possible to position and wedge braking / stopping means 23a, 23b, 23c and 23d. The case 11 ensures the cohesion of the cylinder body.

The piston is represented here in the initial position of the jack, position in which the rod 18 is secured to the jack by a shearable radial pin 19 disposed between the rod 18 and the lid 12b.

Gas sealing means such as annular joints (not shown) are interposed between the piston 17 and the housing 15.

Each chamber 16a, 16b can be pressurized by a pyrotechnic charge generating gas 20a, 20b. These charges are arranged at the covers 12a, 12b which ensure the closure of the case 11, covers which are traversed by the rod 18. Gas seals are provided between the covers and the rod 18.

The pyrotechnic charges 20a, 20b consist for example of 2 to 3 grams of propellant single base powder. Each composition may be initiated by an igniter (not shown) which is connected by conductors 21a, 21b to electronic control means 22.

The initiation of the load 20a will cause the break of the pin 19 and the movement of the piston 17 in the direction D2 until it abuts against the cover 12b.

Alternatively, the initiation of the load 20b also causes the break of the pin 19 and the displacement of the piston 17 in the direction D1 until it abuts against the cover 12a.

According to the invention, this jack incorporates braking and / or stopping means of its piston which are formed by deployable abutment surfaces 23a, 23b, 23c and 23d integral with the body of the jack. These abutment surfaces are more particularly visible at the figure 4a . They comprise two portions of circular washers 24 and 25 which are housed in a cylindrical groove 26 arranged between two consecutive rings 14c and 14d.

These washer portions are fixed at their ends to two piezoelectric actuators 27, 28. The actuators 27, 28 of each abutment 23 are connected in pairs to the electronic control means 22. A housing (not shown) shared between each ring 14 makes it possible to receive each actuator 27 or 28. The actuators are chosen such that when they are supplied with electric current they shorten and thus bring the two washer portions 24,25 of the axis 13 of the cylinder body.

When the braking means is at rest ( figure 4a ) the washer portions 24 and 25 are completely inside the groove 26 and they do not interfere with the passage of the piston 17 in the housing 15.

When the braking means is activated ( figure 4b ) the washer portions 24 and 25 exit the housing 15 and project therein. They then form an abutment surface which stops the cylinder 17 at the groove 26 considered.

The washers have a thickness of the order of 3 mm and are dimensioned radially such that they are, in the activated position, in contact with the groove 26 with a contact surface sufficient to ensure the stopping of the piston.

The radial stroke of the washers is of the order of a millimeter and the response time of the known piezoelectric actuators ensures the deployment of the washers before the cylinder has traveled the path that separates it from the washer.

The example shown in figure 3 includes four braking means. The cylinder thus has (with the middle position and the two abutment positions against the covers) seven different positions for its rod and can therefore quickly and reliably position the tube in site or in the bearing according to seven different angles. It is of course possible to define a cylinder having a number of different braking means.

When the firing line has determined the site and bearing angles to be joined by the defensive device, it immediately controls the positioning of the braking means ensuring the desired angle (or the angle closest to the desired angle) .

Advantageously, the positioning cylinders will be defined so that two consecutive abutment surfaces carried by the cylinder body are separated by a distance which determines for the tube 4 an angular positioning gap ensuring recovery of the zones of effectiveness of the ammunition of the cylinder. defense 5.

As this is particularly visible in the figure 5 , the cylinder (not shown) providing the positioning of the tube in position 4 has two consecutive stop positions determining the directions δ1 and δ2 which respectively angles α1 and α2 with the plane P. These directions are sufficiently close to one of the other so that, at the level of the interception sphere SI, the zones of efficiency E1 and E2 overlap.

Thus, for any direction of approach of the threat bringing it between the directions δ1 and δ2, one is assured of an destruction or optimal disturbance of the threat.

The firing line may then choose for example the direction δ2 if the theoretical direction calculated for the pointing of the tube 4 is between δ1 and δ2.

The stop positions for the positioning cylinder in site are defined in a similar way.

In all cases it is thus ensured to obtain effective defense regardless of the angle of attack even if the number of possible pointing positions is limited.

The Figures 6a and 6b show another embodiment of a positioning jack according to the invention.

This mode differs from the previous one in that the jack 10 makes it possible to directly control a rotary movement.

For this purpose the piston 17 is in the form of a flap which is integral with an axis 29 capable of rotational movement relative to the body 30 of the jack. One end of the flap 17 which carries a seal 48 is in contact with an inner cylindrical wall 31 of the body 30 (see FIG. figure 6b ). A shear pin 32 is interposed between the shaft 29 and the body 30. It ensures the fastening of the flap 17 and the body 30 in the rest position of the cylinder.

The shaft 29 passes through the body 30 and is pivotally mounted relative to the body on bearings (not shown).

The body 30 delimits an internal housing which has the shape of a cylindrical sector of axis coincident with that of the rotating axis 29.

In its rest position, the flap 17 is in a median position which separates the housing from the body 30 into two chambers 16a, 16b of substantially equal volume and each having the shape of a cylindrical sector.

Furthermore the body carries two pyrotechnic charges 20a and 20b, each charge being connected to one of the chambers 16a, 16b.

Depending on the load 20a or 20b which is initiated by the electronic control means 22 the flap 17 moves in one or the other direction (R1 or R2). This embodiment therefore makes it possible to control a pivoting of the axis 29 which is between -90 ° and + 90 ° with respect to a median initial position of the flap.

It is of course possible to give the flap 17 an initial position which is not the median position. Such an arrangement will give the cylinder 10 an angular positioning capacity which will be greater in one direction of rotation than in the other.

The initial volumes of the two chambers 16a and 16b will then be different. It will therefore be possible in this case to provide different pyrotechnic charges for the one and the other chamber of the jack, for example masses of different pyrotechnic composition.

When a charge 20a or 20b is initiated, the pressure of the gases increases strongly in the volume 16a or 16b. The pin 32 is sheared and the flap moves in the direction R1 or R2.

The shutter drives the axis 29. The rotation can thus be between -90 ° and + 90 °.

This jack carries means for braking and / or stopping its flap 17 which are formed by deployable abutment surfaces 23a, 23b, 23c and 23d integral with the body 30 of the jack.

Each abutment surface comprises a wedge 33 pivotally mounted relative to an axis 34 integral with the body 30.

The corner extends over the entire height of the chamber 16a or 16b. It can pivot by the action of a piezoelectric actuator 35, incorporated in the wall 30 of the jack, and which is connected to the electronic control means 22 by a link 36.

The figure 6a shows all abutment surfaces in their rest position.

In this position they are not projecting with respect to the internal surface 31 of the body 30 and do not hinder the movement of the flap 17.

The figure 6b shows the corner 33 of the abutment 23a in the deployed position. Pushed by the piezoelectric actuator 35, the corner protrudes with respect to the internal surface 31 of the body and stops the shutter 17.

The contact surface of each stop will be chosen sufficient to ensure the stop of the shutter. It suffices to give the corner 33 a height of the order of 1 to 2 mm.

As in the previous embodiment can be provided a different number of abutment surfaces.

A number of abutment surfaces will preferably be adopted such that two consecutive abutment positions determine directions sufficiently close to one another so that, at the level of the interception sphere S1, the zones of effectiveness E1 and E2 of the defense munition overlap for two directions δ1, δ2 of the axis of the tube 4 (see figure 5 ).

The figure 7 shows a first example of a turret 3 for launching a defense munition 5. This turret comprises a turntable 37 which is integral with a vertical axis 29 and can therefore pivot relative to a fixed support 38 which is for example linked to a vehicle (not shown).

The pivoting of the pin 29 is done by bearings 41. This pivoting of the plate ensures the positioning of the tube 4 in the bearing.

The plate 37 carries the tube 4 which is secured to a base 40 that can pivot relative to the plate 37 about an axis 39.

The axis 29 is secured to a flap 17b of a pivoting jack 10b as described above with reference to the Figures 6a, 6b . The body 30 of the cylinder is also secured to the support 38 by a connecting means (not shown) such as screws or mounting tabs. The jack 10b ensures the positioning in position of the launcher tube 4 with respect to the support 38.

Moreover, the tube 4 can pivot relative to the plate 37 about the axis 39 which is perpendicular to the vertical axis 29.

A linear pyrotechnic jack 10a as described above with reference to figures 3 and 4 is hingedly mounted between the plate 37 and the base 40.

The body of the jack is articulated on a tab 42 secured to the plate 37. The end of the rod 18 of the jack is hinged to another tab 43, integral with the base 40.

The jack 10a makes it possible to control the positioning in situ of the tube 4 with respect to the plate 37 and to the support 38.

This jack is double acting. It comprises two pyrotechnic charges 20a and 20b, connected to the electronic control means 22, and which control the output of the rod 18 or its entry into the cylinder body. Pointing can be achieved with positive or negative elevation angles.

The ammunition 5 is expelled from the tube 4 by a propellant charge 44 which is ignited by an igniter 45. The latter is initiated by a contact 46 which is connected by a wired connection, not shown, to the electronic control means 22 which are housed therein. the support 38.

The tube 4 is here represented as a tube closed at its rear part and the load 44 expels the ammunition out of the barrel tube. It is of course possible to provide a propellant charge in the form of a propellant integral with the munition. In this case the tube 4 will be open at its rear part which will reduce the decline suffered by the support 38.

The electronic control means 22 ensure the firing of the defense munition and the initiation of the different pyrotechnic charges of the cylinders 10a and 10b. They also ensure the deployment of braking means and / or stopping the piston of each cylinder.

According to the embodiments described above, the braking means will preferably be deployed as soon as the desired angles of elevation and location are determined.

Initiation of the pyrotechnic charges of the various cylinders will however be initiated according to an operating sequence such that the site and bearing positions occur substantially at the same time.

This operation has been described above with reference to the figure 2 .

The figure 8 differs from the figure 7 in that the linear jack 10a is replaced by a second pivoting jack 10c. The body 30c of this cylinder is secured to a yoke 47 secured to the end of the vertical axis 29 while the flap 17c of this cylinder is integral with the axis 39. This axis is integral with the base 40 carrying the tube 4. Thus the second cylinder 10c ensures positioning in the tube 4 site.

This embodiment makes it possible with two cylinders of identical and compact structure to provide pivoting in site and bearing of the system according to large deflection angles (greater than 90 °). The response time is very low (of the order of a hundred milliseconds) and the energy developed by the pyrotechnic compositions is sufficient to drive the moving and heavy parts in the desired time (mass of the order of 100 milliseconds). 50 kg).

As a variant, it will be possible to define linear or rotary jacks and in which the braking or locking means will be deployed after initiation of the pyrotechnic load of the jack.

It will thus be possible to design a jack in which the braking means will be integrated in the body of the piston or the movable flap. This braking means may for example be constituted by a pad between piston and cylinder body, which pad will be deployable by a piezoelectric actuator or by a pyrotechnic initiator.

It will also be possible to ensure the braking of the jack by delayed initiation of the second pyrotechnic load of the jack concerned. The counterpressure generated by this second load will ensure braking of the cylinder piston. The time interval between the initiation of the first and the second load of a given jack will modify the maximum stroke obtained with this jack.

We can then advantageously provide means for controlling the actual position of the piston.

These means will include, for example, means for measuring the actual position of the piston and / or means for measuring the actual pressure of the gases in the chambers. Ways Control electronics will then incorporate a rustic servo using this piston position information and / or pressure in the chambers to correct piston positioning.

To correct (to a certain extent) the real position of the piston it is possible to modify the time interval between the initiation of the two charges. The pressures in the chambers can also be changed by opening or closing vents communicating each piston chamber with the outside.

This second embodiment of the device and the method according to the invention will be described with reference to Figures 9 to 13 .

The figure 9 thus shows an exemplary embodiment of a pyrotechnic actuator or jack 10 incorporating such a pyrotechnic braking means.

This cylinder makes it possible to directly control a rotary movement. For this purpose it comprises a piston which has the form of a flap 17 integral with an axis 29 capable of a rotational movement with respect to a body 30.

One end of the flap 17 which carries a seal 48 is in contact with an internal cylindrical wall 31 of the body 30. A shearable pin 32 is interposed between the axis 29 and the body 30. It ensures the fastening of the flap 17 and of the body 30 in the rest position of the jack.

The shaft 29 passes through the body 30 and is pivotally mounted relative to the body on bearings (not shown).

The body 30 delimits an internal housing which has the shape of a cylindrical sector of axis coincident with that of the rotating axis 29.

In its rest position, the flap 17 is in a median position which separates the housing from the body 30 into two chambers 16a, 16b of substantially equal volume and each having the shape of a cylindrical sector.

Furthermore the body carries two pyrotechnic charges 20a and 20b, each load is connected to one of the chambers 16a, 16b and allows to pressurize it.

The pyrotechnic charges 20a, 20b are constituted for example by a gas-generating composition, such as 2 to 3 grams of a single propellant base powder. Each composition may be initiated by an igniter (not shown) which is connected by conductors 21a, 21b to electronic control means 22.

Depending on the load 20a or 20b which is initiated by an electronic ignition device, incorporated in the electronic control means 22, the flap 17 moves in one or the other direction (R1 or R2). This actuator thus makes it possible to control a pivoting of the axis 29 which is between -90 ° and + 90 ° with respect to a median initial position of the shutter.

The initiation of the load 20a causes the break of the pin 32 and the rotation of the flap 17 in the direction R2 until it abuts against the body 30.

Alternatively, the initiation of the load 20b also causes the break of the pin 32 and the rotation of the flap 17 in the direction R1 until it abuts against the body 30.

According to the invention, the electronic control means 22 incorporate a computer 120 as well as at least one memory or register 130.

This memory contains in numerical form characteristic curves giving the theoretical pressure in each chamber as a function of time.

The computer 120 is programmed so as to initiate in sequence the two pyrotechnic charges 20a and 20b.

When thus initiating a second charge (for example 20b) after the initiation of a first charge (20a), a counter pressure appears in the second chamber 16b after the appearance of the pressure in the first chamber 16a.

This against pressure causes a braking movement of the flap 17.

In the simple case described here where the pyrotechnic charges 20a, 20b used are identical for each chamber and where the initial volumes of the chambers 16a, 16b are also equal, the flap 17 will be positioned after a certain time at its initial median position. Indeed this position corresponds to the balance between the pressures in the two chambers.

Before reaching this equilibrium position, the speed of rotation of the flap will decrease and then change direction. There is therefore a flap position for which the speed of this one vanishes. This position will depend on the time interval between the initiation of the two pyrotechnic charges 20a and 20b.

If this time interval is short, the flap stroke will be reduced.

If this time interval is important the flap stroke will approach the maximum possible stroke.

It is therefore possible by playing on the time interval between the initiations of the two charges to give the flap 17 a race or a well-defined pivoting angle.

The skilled person will easily establish the charts which, for a given cylinder configuration (composition and mass of the pyrotechnic charges, inertia of the flap as well as the mechanism driven by it ...), will define the race obtained as a function of the time interval between each initiation.

These charts will be entered in the memory 130 or in a register of the computer 120. The latter will then order the appropriate initiation sequence in response to a set of instructions provided by a user or by a control system or automaton (for example through a control system). a control interface 140 or a fire control for a vehicle defense application).

• P1 qui donne l'évolution de la pression en fonction du temps dans la première chambre où la charge pyrotechnique est initiée (pression en Méga Pascals),
• P2 qui donne l'évolution de la pression en fonction du temps dans la deuxième chambre où la charge pyrotechnique est initiée (pression en Méga Pascals),
• C qui donne le débattement angulaire du volet 17 en fonction du temps (angle en degrés).

By way of example, for a rotary jack having a total chamber volume of 450 cm 3, and allowing a +/- 90 ° pivot relative to the initial position, each pyrotechnic charge consisting of 3 grams of single base powder, the figure 10 shows the curves:

• P1 which gives the evolution of the pressure as a function of time in the first chamber where the pyrotechnic charge is initiated (pressure in Mega Pascals),
• P2 which gives the evolution of the pressure as a function of time in the second chamber where the pyrotechnic charge is initiated (pressure in Mega Pascals),
• C which gives the angular movement of the shutter 17 as a function of time (angle in degrees).

The pyrotechnic charge of the second chamber is here initiated 20 milliseconds after the first charge. This results in a maximum travel of 90 ° which occurs after the time t = 40 milliseconds.

The figure 11 is an abacus which gives for this cylinder the value of the interval to be programmed between each initiation according to the maximum desired angular displacement.

It is of course possible to initiate only one charge. The maximum possible deflection (flap abutting against the body 30) is then conventionally obtained.

It is of course possible to give the flap 17 an initial position which is not the median position. Such an arrangement will give the cylinder 10 an angular positioning capacity which will be greater in one direction of rotation than in the other.

The initial volumes of the two chambers 16a and 16b will then be different. It will therefore be possible in this case to provide different pyrotechnic charges for the one and the other chamber of the jack, for example masses of different pyrotechnic composition.

The figure 12 shows another embodiment of a pyrotechnic actuator 10 with pyrotechnic braking. This actuator is produced here in the form of a linear double-acting cylinder comprising a cylindrical body 30 of axis 13 delimiting a cylindrical inner housing divided into two chambers 16a, 16b by a piston 17 integral with a rod 18.

The piston is represented here in the initial position of the jack, position in which the piston is secured to the body 30 by a shearable radial pin 19 interposed between the rod 18 and an end cover 12a. Gas sealing means such as annular joints not shown are provided between the piston and the body.

Each chamber 16a, 16b can be pressurized by a pyrotechnic charge generating gas 20a, 20b. These charges are arranged at the covers 12a, 12b ensuring the closure of the body 30, covers which are traversed by the rod 18. Gas seals are provided between the covers and the rod 18.

The initiation of the load 20a causes the break of the pin 19 and the movement of the piston 17 in the direction D2 until it abuts against the cover 12b.

Alternatively, the initiation of the load 20b also causes the break of the pin 19 and the displacement of the piston 17 in the direction D1 until it abuts against the cover 12a.

Again and in accordance with the invention the electronic control means 22 incorporate a computer 120 and at least one memory or register 130, and the computer 120 is programmed so as to initiate in sequence the two pyrotechnic charges 20a and 20b .

This initiation in sequence makes it possible to slow down the movement of the piston 17.

This one will be positioned after a certain time at its initial median position which corresponds in the example described here to the equilibrium between the pressures in the two chambers.

Before reaching this equilibrium position the piston speed will decrease and then change direction. There is therefore a position of the piston for which the speed of this one vanishes. This position will depend on the time interval between the initiation of the two pyrotechnic charges 20a and 20b.

If this time interval is short, the piston stroke will be reduced.

If this time interval is important the piston stroke will approach the maximum possible stroke.

It is therefore possible by playing on the time interval between the initiations of the two charges to give the piston 5 a defined maximum stroke.

Here again it will be sufficient for the skilled person to establish the abacuses which, for a given cylinder configuration (composition and mass of the pyrotechnic charges, inertia of the piston, the rod and the mechanism driven by the rod ...) , will define the race obtained according to the time interval between each initiation.

The actuators represented in figures 9 and 12 also comprise means for measuring the pressure in the two chambers 16a and 16b. These means consist of pressure probes 150a, 150b.

The probes 150a, 150b are connected to the control electronics 22 via links 160a, 160b.

In the embodiment of the figure 9 the probes are shown radially fixed in the cylindrical wall of the body 30. They could of course be carried by a bottom wall of the body or by a top wall (not shown). In the embodiment of the figure 12 the probes are attached to the covers 12a and 12b.

Thus the control electronics 22 can control the actual pressure in each of the chambers 16a, 16b and can compare this pressure to a theoretical value that is in memory.

It is then possible to correct the time interval before the initiation of the second load so as to take into account the pressure difference thus measured.

Indeed dispersions can occur at the level of real pressures, dispersions related for example to the variation of the characteristics of the different pyrotechnic charges of a production batch, or related to the operating conditions (temperature, atmospheric pressure).

If these dispersions were not taken into account, there would be a discrepancy between the position of positioning of the cylinder rod and the position actually observed.

Those skilled in the art will easily establish correction abacuses allowing, for a given cylinder geometry and as a function of a pressure difference measured in the first chamber, to determine the advance or the delay to be made at the instant of initiation of the second charge.

When the pressure measured in the first chamber is less than the stored theoretical pressure, the start time of the second load is delayed.

Conversely, when the pressure measured in the first chamber is greater than the stored theoretical pressure, the moment of initiation of the second charge is anticipated.

This provides a rustic control providing a single correction but is sufficient if the values of the dispersions remain low.

In some cases and especially if the dispersions are too large (greater than 5% in absolute value) it will be necessary to provide other means for regulating the pressure level in the chambers 16a and 16b.

We will be able to figures 9 and 12 show also provide at least one vent 170a, 170b in each chamber. These vents allow to place the chamber (16a or 16b) in communication with the outside of the cylinder body.

The vents represented at figure 9 carried by the bottom wall of the body 30. The vents shown in figure 12 are fixed radially to the cylindrical body 30.

The opening of the vents 170a, 170b is caused by the electronic control means 22 to which they are connected by links 180a, 180b.

The vents will be made for example in the form of small valves normally closed, having a rod which closes the valve and which is integral with an electromagnet.

When the pressure measured in the first chamber is greater than the stored theoretical pressure can then be controlled opening the vent connected to the first chamber. This will reduce the value of the pressure in the first chamber to bring it substantially to the theoretical value. The vent can then be closed.

Conversely, when the pressure measured in the first chamber is lower than the stored theoretical pressure, it will be possible to control the opening of the vent connected to the second chamber.

This variant of the invention makes it possible to successively make several corrections to the pressures in the different chambers.

It will of course be possible to combine a correction at the initiation interval between the charges and a pressure regulation via the vent or vents.

This embodiment thus makes it possible to ensure servocontrol which makes it possible to overcome all the dispersions of the device (dispersion on the pressures in the two chambers but also on the delays between the initiations).

To perfect this servocontrol, it will also be possible to provide means for determining the position of the piston or flap. Such means are well known. They can be integrated in the jack or carried by the structure actuated by the jack. For example, an optical encoder carried by the rotary axis 29 may be used for a rotary jack as shown in FIG. figure 9 . We can for a linear cylinder as represented in figure 12 use an optical position sensor identifying the end of the cylinder rod.

The electronic control means will use the information relating to the actual position of the jack to control for example the vents and / or change the initiation interval between the loads.

Alternatively, the locking pin 19 of the piston or the flap may be replaced by a reversible device, for example a latch pushed by a spring and bearing on a flat surface. Such a solution makes it possible to produce a pyrotechnic jack that can be reused several times. It will be sufficient, for a new use, to reposition the flap or the piston to its locked initial position and to replace the pyrotechnic charge or gas generators that have been used.

Different variants are possible without departing from the scope of the invention. One could thus define a linear cylinder whose piston would not be at rest in the middle position but would be positioned more or less close to one of the end covers. The initial volumes of the two chambers would then be different.

One could also define a jack in which the pyrotechnic charges would be different for each room.

In all cases, the skilled person will establish during the design of the cylinder the abacuses necessary to allow the control of the desired positioning.

The actuators according to the invention can be used in different applications for which it is necessary to give a given amplitude movement very quickly.

The actuator according to the invention does not by itself to ensure the maintenance of an organ in a given position. This maintenance can, however, be provided by conventional means not shown and integral with the member controlled by the cylinder (for example a locking pawl).

According to the invention this actuator is particularly well suited to the implementation of a device for defending a vehicle or a structure against a threat such as a projectile.

Indeed, it is necessary for such an application to ensure the positioning in the site and / or in the field of at least one launching tube of a munition in a very short time interval (of the order of a few tens of milliseconds ).

The pyrotechnic energy used in the jacks is sufficient to ensure the displacement of the mechanical inertia of such defenses. Pyrotechnic cylinders also provide the required positioning speed.

The method according to this second embodiment of the invention also makes it possible to ensure the accuracy of the positioning in site and deposit despite the absence of mechanical stop corresponding to the desired positioning.

This stop is not necessary because it is sufficient to ensure the expulsion of the ammunition out of the tube when the latter is oriented in the desired direction. Indeed, the desired position is that at which the speed of the cylinder is virtually zero.

The electronic control device 22 can be programmed to trigger this shot a few moments before the arrival of the tube angular positioning in the site and in the correct bearing. The trigger is caused before the arrival at the position because the pressurization of the propellant charge of the defense munition and its course in the tube last for a certain time (of the order of 30 milliseconds). It is therefore necessary to anticipate to ensure the output of the ammunition out of the tube in the right direction and with the least possible lateral disturbances (positioning speed of the cylinders substantially zero).

As is visible for example on the figure 10 , this speed evolves very weakly over a range of about 8 milliseconds around the desired positioning value. When the ammunition comes out of the tube in this position it is hardly disturbed by the movements of the tube.

The pyrotechnic braking actuators can be implemented in turrets similar to those described above with reference to the Figures 7 and 8 .

As described above, these turrets are intended to defend a vehicle or structure against an attack by a missile or a rocket. It is essential that such a turret can ensure a quick and reliable positioning of the tube 4 in a determined direction during the detection of the threat by a firing line.

The positioning time is generally of the order of one hundred milliseconds.

With the pyrotechnic braking cylinders, the two pyrotechnic charges of each cylinder will be initiated in sequence as a result of the pointing instructions in site and in the bearing provided by the firing line (not shown) which is connected to the control means 22 which it controls the operation. Of course the firing line and the electronic control means 22 may form a single set.

Thus the control means will ensure the braking of the piston cylinders so that the speed of these pistons is substantially zero for the desired pointing values and communicated by the fire control.

Moreover, the electronic control means 22 will initiate the sequence of operation of one jack with respect to the other so that the positioning in the site and in the reservoir occur substantially at the same time.

The logigram of the figure 13 is similar to that described above with reference to the figure 2 . It makes it possible to highlight the different steps of the method and of the device according to the second embodiment of the invention (mode incorporating pyrotechnic braking for the actuator (s)).

This logic diagram thus shows the succession of orders generated by the electronic control means 22. The time differences between each initiation will depend on the structural characteristics of the turret, the cylinders and the launch tubes. The skilled person will determine them easily.

Block C1 also corresponds to the delivery by the firing line positioning instructions of the tube in site (S) and in the bearing (G) and the moment (T _R ) at which the defense munition must leave the tube launch.

The control means then calculate (block C2) the instant (T _T ) at which firing of the munition must be controlled so that its exit from the tube occurs at time T _R. This moment corresponds to the moment of exit from the ammunition (T _R ) decreased by the step of lighting the charge 44 and the internal ballistic stage of the ammunition in the tube 4.

The control means also calculate (block C30) the instants of initiation (Sa and Sb) of the two pyrotechnic charges of the positioning cylinder in situ to ensure a zero speed in site at the exit time (T _R ).

The control means 22 also calculate (block C40) the initiation instants (Ga and Gb) of the two pyrotechnic charges of the positioning cylinder in position to ensure zero velocity in the bearing at the exit instant (T _R ). All calculations will be performed simultaneously.

The control means then sequentially provoke the different initiations of the pyrotechnic charges of the cylinders as well as the firing according to the temporal sequence thus calculated.

Block A10: activation of the positioning in the field (Ga), block A20 triggering of the positioning in site (Sa), block A3 firing (T _T ). The relative order of the triggers A10 and A20 will depend on the setpoint angles given in the site and in the field. In the figure, it is considered that the order relative to the positioning in the field occurs first. This is of course the longest rally that is triggered first. The objective being a rallying in site and simultaneous deposit at time T _R.

The control means of course ensure control from the firing of the pressures actually obtained in the cylinders and they correct if necessary (block A40 correction in the bearing Cor G, block A50 correction site Cor S) instants triggering pyrotechnic braking loads ( block A60 trigger braking on the bearing Gb, block A70 tripping the braking on site Sb) or control the openings of the vents (E _G , or E _S ).

The line L shows the simultaneity at the planned instant T _R of positioning in the site, in the bearing and the exit of the munition out of the tube.

Claims (14)

1. Process to defend a vehicle (1) or a structure against a threat such as a projectile (6), such process implementing elevation and/or traverse positioning means for at least one launching tube (4) for defence ammunition, means which comprise at least one pyrotechnical jack, process in which the velocity (V) and direction (Δ) of the threat are determined using measurement and calculation means, such process involving the following steps:

   - the elevation and traverse angles (α) to be given to the defence ammunition launcher tube are determined based on the velocity and direction of the threat as is the instant at which the ammunition must be ejected from the tube in this direction,

   - the positioning means for the tube (4) are triggered sequentially and the ammunition (5) is fired, and characterised by the following step,

   - means are activated, before or after the positioning means, ensuring the braking and/or stoppage of the positioning means when the latter have oriented the firing system at the required angles.
2. Defence process according to Claim 1, in which at least one positioning means is formed by a dual-effect pyrotechnical jack (10) incorporating two pyrotechnic charges (20a, 20b) which have an antagonistic effect each linked to a separate chamber (16a, 16b), the two chambers being separated by a mobile piston (17), such process characterised by the fact that, to ensure the braking of at least one positioning means, the two pyrotechnic charges (20a, 20b) of the jack in question are successively and sequentially activated so as to ensure by the action of the second charge a braking of the displacement of the piston (17) which has been activated by the first charge, the lapse of time between the ignition of each charge being selected so as to ensure the required positioning for the piston.
3. Defence process according to Claim 2, wherein the pressure is measured in the first chamber (16a, 16b) in which the first charge (20a, 20b) is ignited, this pressure is then compared to a memorised theoretical value and the lapse of time is corrected before the ignition of the second charge and/or the opening of a vent (170a, 170b) in at least one of the two chambers so as to take into account the deviation between the theoretical pressure and the measured pressure.
4. Defence process according to Claim 3, wherein, when the pressure measured in the fist chamber (16a, 16b) is less than the memorised theoretical pressure, the ignition time for the second charge and/or the opening of a vent (170a, 170b) in the second chamber is deferred.
5. Defence process according to one of Claims 3 or 4, wherein, when the pressure measured in the first chamber is greater than the memorised theoretical pressure, the ignition time of the second charge and/or the opening of a vent (170a, 170b) in the first chamber is advanced.
6. Defence process according to one of Claims 2 to 5, wherein the actual position of the piston (17) is determined and this measurement is used to correct the ignition time of the second charge and/or the opening of a vent (170a, 170b) in one or other of the chambers.
7. Device enabling a vehicle or structure to be defended against a threat such as a projectile, such device implementing the process according to one of the above Claims and comprising elevation and/or traverse positioning means for at least one defence ammunition launcher tube, such positioning means comprising at least one pyrotechnic jack (10a, 10b), such device also comprising means to detect the approach of a projectile and calculation means enabling the determination of the elevation and traverse angles to be given to the defence ammunition (5) launcher tube (4) as well as that of the instant at which the ammunition must be ejected from the tube in the firing direction, and comprising electronic control means (22) ensuring the sequential ignition of the pyrotechnic position jack or jacks (10a, 10b) then of the firing of the ammunition (5), wherein it comprises means (23a, 23b, 23c, 23d), to ensure the braking and/or stoppage of the positioning means when the latter have oriented the firing system in the required direction.
8. Defence device according to Claim 7, wherein the braking and/or stoppage means (23a, 23b, 23c, 23d) for the positioning means are formed by deployable abutment surfaces integral with the body of the pyrotechnic jack or jacks (10a, 10b), the deployment of the abutment surfaces being activated by the electronic control means (22).
9. Defence device according to Claim 8, wherein the defence ammunition (5) incorporates a spatial effectiveness zone (E1, E2) at a nominal distance of use (SI) and wherein two consecutive abutment surfaces carried on a jack body (10a, 10b) are separated by a distance which determine an angular positioning deviation for the tube (4) thus ensuring an overlap of the zones of effectiveness of the defence ammunition for the two consecutive directions and at said nominal distance of use.
10. Defence device according to Claim 7, wherein the elevation and/or traverse positioning means comprise at least one dual-effect pyrotechnic jack (10a, 10b) incorporating two pyrotechnic charges (20a, 20b) having an antagonistic effect each linked to a separate chamber, the two chambers being separated by a mobile piston (17), the electronic control means (22) ensuring a sequential ignition of the two pyrotechnic charges of the jack in question with a lapse of time selected so as to ensure the braking of the piston (17) and the required positioning in elevation and/or in traverse.
11. Defence device according to Claim 10, wherein it incorporates means (150a, 150b) enabling the pressure to be measured in the two chambers of one of the pyrotechnic jacks (10a, 10b), these means being linked to the electronic control means (22), the latter being able to compare the pressure measured in a first chamber to at least one theoretical value so as to correct the time lapse before ignition of the second charge of the jack (10a, 10b) in question.
12. Defence device according to one of Claims 10 or 11, wherein it incorporates means enabling the actual position of the piston of the pyrotechnic jack (10a, 10b) to be determined or else the position in elevation or in traverse given by this jack, these means being linked to the electronic control means (22).
13. Defence device according to one of Claims 11 or 12, wherein at least one pyrotechnic jack (10a, 10b) incorporates at least one vent (170a, 170b) for each chamber, such vent whose opening can be activated by the electronic control means (22) enabling said chamber to be made to communicate with the exterior.
14. Defence device according to one of Claims 10 to 13, wherein the electronic control means (22) cause the ammunition (5) to be fired at a time such that it exits the tube (4) substantially at the instant the elevation and traverse angles are obtained.

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