EP0463974A1 - Safety and arming-means in an ammunition - Google Patents

Abstract

The subject of the invention is a safety and arming device for ammunition, capable of ensuring the alignment of the pyrotechnic chain and of occupying two different positions, a first in which the detonation of the ammunition is prevented and a second in which detonation is transmitted. It consists of a chain of interruption means 3 having a passage 2a made along a diameter perpendicular to the directions of the stresses undergone by the ammunition during the operational phases and incorporating or not a relay composition 2 actuated along a helical path of an angle alpha in order to bring the passage 2a from the first position, called the safety position, in which it is arranged in a plane substantially orthogonal to the axis of alignment of the pyrotechnic chain, into the second position, called the arming position, in which it is aligned with the axis 6 of the chain. The helical movement is the combination of a translational movement and of a rotational movement alpha through approximately 90 DEG and is executed in three successive phases, a first phase A, during which, above all, a translational movement and a low rotation of between 0 and 15% of the angle alpha are obtained, then in a phase B of high rotation of between approximately 15 and 85% of the angle alpha , and finally in a phase C, above all a translational movement and a low rotation into the armed position. The invention is used for military charges. <IMAGE>

Description

The technical sector of the present invention is that of the safety and arming devices of a pyrotechnic chain placed between an initiation composition and a composition for initiating the explosive charge of a munition.

Many security devices have been proposed to perform this function. As a general rule, a pyrotechnic flap (disc for example) is used which by rotation passes from a safety position to an armed position. Various security systems ensure the release of the shutter under the intended firing or lighting conditions.

Thus, patent FR-A-2 463 386 describes a safety device timed by a spiral spring. However, this device is applied to a revolving projectile and the bolt describes an arc to go from the safety position to the armed position.

The patent FR-A-2 344 809 describes a rocket whose safety flap consists of a movable shaft first in rotation then in translation to pass from the safety position to the armed position, the display of the armed position being provided by an intermediate piece.

The significant mechanical stresses on weapons and ammunition, when firing propellants or when impacting on the sea for underwater weapons and ammunition dropped from aircraft, are likely to cause accidental operation and untimely weapon or ammunition.

The seat of the excitation (operation) comes essentially from the armament security device (DSA) which contains primary explosives.

In the case of an underwater ammunition dropped from aircraft, the mechanical stresses undergone by the ammunition or the weapon, at the impact of the sea, are significant. The characteristics of the stresses undergone depend on several factors: drop altitude, speed of impact on the sea, state of the sea, impact incidence, etc. By definition, the ammunition or underwater weapon is designed to operate at a specific immersion. Premature operation at impact shows a lack of reliability and an absence of system security and engages the safety of the launching aircraft at low drop altitudes, which is often the case.

The aim of the present invention is to reduce the harmful effects of these constraints and to improve the safety and reliability of operation of the DSA, by avoiding untimely operations due to accidental events, but also premature operation due to a transient alignment of the pyrotechnic chain during significant mechanical constraints, the impact on the sea of underwater weapons and ammunition dropped from an aircraft.

The invention therefore relates to a security and arming device for ammunition, capable of ensuring the alignment of the pyrotechnic chain and being able to occupy two different positions, a first in which the firing of the ammunition is prohibited and a second in which the ignition is transmitted, characterized in that it consists of a chain interrupting means comprising a passage made along a diameter perpendicular to the directions of the stresses undergone by the ammunition during the operational phases, integrating or not a relay composition, actuated along a helical trajectory of angle α to bring the passage from the first so-called safety position in which it is located in a plane substantially orthogonal to the axis of alignment of the pyrotechnic chain, in the second so-called arming position where it is aligned with the axis of the chain.

The helical movement can be the combination of a translational movement and a rotational movement α of approximately 90 °.

The helical movement of the means can be carried out in three successive phases, a first phase A during which a translation movement and a slight rotation of between 0 and 15% of the angle α are especially ensured, then in a phase B of significant rotation of between approximately 15 and 85% of the angle α, and finally in a phase C above all a translational movement and a slight rotation to the armed position.

The means may consist of a shaft placed perpendicular to the axis of the pyrotechnic chain, the helical movement being obtained using a pin assembly of helical guide / groove.

The helical groove can be made on the shaft according to the profile shown in FIG. 3.

The interruption means can be provided with means for displaying the two safety and arming positions.

The helical movement can be controlled by a motor system of the rack and pinion type actuating the interruption means.

The helical movement can be controlled by hydrostatic pressure acting on the interrupting means.

The helical movement can be controlled by borrowing gas taken from the propellant of the ammunition acting on the interrupting means.

An advantage of the present invention lies in the fact that the pinching, punching, rubbing phenomena of initiating explosives which are sensitive to them are eliminated, since the active materials are placed in a position of least stress.

Another advantage lies in the fact that the device provides a delay, or mechanical inertia, additional to the alignment of the priming chain which is not detrimental to the system, absorbs the stresses and mechanical stresses along a preferential axis (perpendicular to the direction of movement). ammunition).
This is then always in contact with any smooth walls, during the maximum stress phase.

Another advantage lies in the fact that the combined translation and especially rotation movement (1/4 turn), makes it possible to visualize in a precise and unambiguous way the armed position of the DSA from a reference mark engraved at the end of the means of interruption, either directly if the end of the axis is visible, or by returning the position of this reference using an optical fiber for example, and not on an additional separate part.

It should be noted that this control is easier and more precise on a pyrotechnic component of the "axis" type than on a pyrotechnic component of the "disc" type.

Knowledge of this information (armed or unarmed) is of paramount importance regardless of the configuration of the weapon or ammunition.

• la figure 1 est une coupe partielle de la chaîne pyrotechnique ,
• la figure 2 est une coupe AA de la figure 1 montrant deux types d'application,
• la figure 3 illustre la combinaison des mouvements de translation et de rotation selon l'invention,
• les figures 4 à 6 représentent trois exemples d'illustration de systèmes moteur de l'arbre.

Other advantages of the present invention will be better understood on reading the additional description which follows of an embodiment given by way of example in relation to a drawing in which:

• FIG. 1 is a partial section of the pyrotechnic chain,
• FIG. 2 is a section AA of FIG. 1 showing two types of application,
• FIG. 3 illustrates the combination of the translational and rotational movements according to the invention,
• Figures 4 to 6 show three examples of illustration of motor systems of the shaft.

The pyrotechnic chain partially represented in FIG. 1 comprises an electric or percussion initiator 1, a relay composition 2 carried by a shaft 3 in a passage 2a, and a main detonator relay 4 which is adjacent to a conventional explosive composition not shown. The assembly is integrated in an ammunition 5 partially shown and must be aligned in the armed position on the axis 6 of the pyrotechnic chain. The shaft 3 slides in a housing 7 of the ammunition according to a helical movement detailed in FIG. 3 as a result of a force applied according to arrow X on one of its ends. To this end, a guide pin 8 is fixed in the housing 7 and is engaged in a groove 9 formed on the shaft 3. A display means 3a for the position of the shaft 3 is provided at the end; this means can be a groove made at the end of the axis along a diameter. The meaning is chosen by convention.

The shaft 3 rotates around its axis of rotation 10 by an angle α, of the order of 90 °, and undergoes a translation (d) to bring the passage 2a or the composition 2 into alignment with the initiator 1 and relay 4. The shaft is locked in this position. However, after abnormal behavior in the flight or dropped phase of the ammunition, the tree can be returned to the safety position, either automatically or manually.

Figure 1, focusing in particular on the concept of the shutter axis type pyrotechnic device with a helical ramp and control of the flap position directly at the end of the axis, does not reveal the other characteristics of the DSA such as the devices for returning the pyrotechnic flap and blocking the flap in the safety position ( unarmed).

• ressorts à boudin, à lame, pour le dispositif de rappel, en se limitant aux dispositifs très simples,
• masselotte à inertie, butée effaçable, goupille et flamme de sécurité mobile, éventuellement goupille à cisailler dans certains cas pour le dispositif de blocage.

These devices, not shown, are simple in design and can be multiple:

• coil, leaf springs for the return device, being limited to very simple devices,
• inertia counterweight, erasable stop, movable safety pin and flame, possibly shear pin in certain cases for the locking device.

The positioning of these devices is indicated in the figures.

In FIG. 2A, a section has been shown showing a percussive primer 11 associated with a relay 12. FIG. 2B shows a relay tablet consisting of a capsule 13 containing a priming explosive 14. The initiator is stationary and is located designated by the reference 1 in Figure 1.

FIG. 3 shows an example of a groove for a projectile of the submarine munition type. According to the invention, this groove provides a combined translation-rotation movement while allowing progressive movement. FIG. 3 represents an example of a development of the helical ramp, that is the variation of the angle of rotation α as a function of x as a function of the displacement D. The respective extreme values are 90 ° and 15 mm, but they can be obviously modified by those skilled in the art. In the first half of the bench press, the curve has a first portion having a radius of curvature R₁ of the order of 10 mm, followed by a second portion having a radius of curvature R₂ of the order of 8 mm. Halfway through the shaft 3, the curve changes direction according to a radius R₃ of the order of 8 mm followed by a final portion of radius R₄ of about 10 mm. The movement of the shaft 3 is therefore done according to 3 phases of rotation A, B and C whose respective final values are 12, 78 and 90 ° and corresponding to the translations also respective of 5, 10 and 15 mm.

• une phase A où l'arbre présente en début de la phase d'alignement (sollicitations maximales), un mouvement de translation prédominant afin de placer l'explosif-relais suivant des axes de moindres contraintes mécaniques,
• une phase B où on assure un alignement en rotation prédominant, combiné à un alignement en translation à l'issue de l'impact sur la mer ou après, en phase immersion. L'angle d'alignement en rotation peut être tout autre; mais, il est voisin de 90° en général.
• une phase C où on obtient en fin de phase d'alignement un mouvement de translation prédominant afin de réduire l'inertie mécanique de l'équipage mobile (volet équipé de joints d'étanchéité, frottement du pion de guidage dans la rainure et ressort de rappel) et parfaire l'alignement de la chaîne pyrotechnique (pression d'alignement de faible niveau).
  L'angle d'alignement en rotation peut être tout autre; mais, il est voisin de 90° en général.

The displacement of the shaft 3 takes place in three phases:

• a phase A where the shaft exhibits, at the start of the alignment phase (maximum stresses), a predominant translational movement in order to place the relay explosive along axes of less mechanical stress,
• a phase B where a predominant alignment in rotation is ensured, combined with an alignment in translation at the end of the impact on the sea or after, in the immersion phase. The rotational alignment angle may be quite different; but, it is close to 90 ° in general.
• a phase C where a predominant translational movement is obtained at the end of the alignment phase in order to reduce the mechanical inertia of the moving assembly (shutter fitted with seals, friction of the guide pin in the groove and spring of reminder) and perfect the alignment of the pyrotechnic chain (low level alignment pressure).
  The rotational alignment angle may be quite different; but, it is close to 90 ° in general.

The movement of the pyrotechnic flap, shown according to the development of the helical ramp, must not have a radius of "slight curvature" in order to avoid any blockage of the pyrotechnic flap (movement of the guide pin in the groove), hence the interest of the helical ramp which meets all of these criteria.

One advantage of the helical ramp is that it makes it possible to bring almost into contact (a few 1/10 of a mm possible), without risk of mechanical stress, two pyrotechnic elements ensuring the correct operation of the pyrotechnic chain at the detonic level.

It is also possible to vary the pitch of the ramp and thus adapt the general shape of the kinematics of the mobile, to the specifications of the DSA and to the conditions of operational use. The requirements and criteria may be the same as those above for pyrotechnic shutters driven by an electric motor, moving by borrowing gas or by any other device. The advantages presented by the helical ramp are preserved. The pitch of the ramp is then adapted according to the specifications of the DSA and the level of the physical phenomenon allowing the alignment of the pyrotechnic chain.

In Figure 4, there is shown an example of drive means of the shaft 3 which consists of a rack 20 secured to said shaft and a pinion 21. The shaft is held in the safety position by the device 24 (locking pin for example). This pinion is rotated by the reduction motor 22 via the axis 23. Of course, this motor is conventionally controlled during the flight sequence.

Unpowered, the reduction motor is free. The DSA is in the safety position by the action of a return device (spring for example).

The electrical supply of the reduction motor, generated by the ammunition according to a determined sequential, conditions the pyrotechnic alignment, the blocking device being broken. The return device is then compressed by the pyrotechnic component.

In a degraded situation, a power cut or end of autonomy of the energy source (the motor then being free) causes the passage from the "armed" position to the "unarmed" position of the shutter by action of the device reminder.

FIG. 5 shows another example of drive means operating by the action of hydrostatic pressure. For this, the shaft 3 is provided at one end with a piston 25 provided with a seal 26 and sliding in a chamber 27. The latter communicates with the outside through the holes 28 made in the cover 29 secured to the body of the ammunition.

On impact on water, the tree (or the pyrotechnic flap) remains in its "safety" position thanks to a not shown return device (spring for example). The increasing hydrostatic pressure, exerted on the piston 25 of the shutter, conditions the alignment of the pyrotechnic shutter.

The return device makes it possible to control the instant of alignment of the shaft as a function of the desired depth.

For this device, a safety pin, housed in the hole 30 provided with a flame, can be placed on the shutter for the storage, transport and implementation configurations, until the ammunition is released.

In Figure 6, there is shown an example of means drive shaft 3 applicable to aerial and possibly submarine munitions. One end of the shaft 3 is provided with a piston 31 fitted with a seal 32 sliding in a chamber 33. The chamber is closed by a cover 34 which leaves the piston facing a circuit for taking samples of combustion gases.

In the safety position, the pyrotechnic flap is held in the "unarmed" position by the locking device 36 not shown.

The pressure of the gases taken from the propellant or from any other sub-assembly of the ammunition, for example gas generator or pressurized tank, etc., is brought by the conduit 35 into the chamber 33, the borrowing of gas taking place according to a determined sequence.

The gas pressure exerted on the piston 31 of the pyrotechnic shutter allows the alignment of the pyrotechnic chain, the locking device 36 of the shutter then being lifted, erased or sheared according to the blocking principle used.

The return device allows the flap to return to the safety position in the event of degraded situations in flight.

The concept developed according to a groove (ramp) of helical shape (combined and progressive movement of translation - rotation) is particularly suitable for this type of ammunition and alone makes it possible to reduce, even eliminate, the harmful effects of these constraints. This concept is applicable to electrical versions of the DSA, the electrical circuit not being modified.

Claims (9)

1 - Safety and arming device for ammunition, capable of ensuring the alignment of the pyrotechnic chain and being able to occupy two different positions, a first in which the firing of the ammunition is prohibited and a second in which the firing fire is transmitted, characterized in that it consists of a chain interrupting means (3) comprising a passage (2a) formed along a diameter perpendicular to the directions of the stresses undergone by the munition during the operational phases, integrating or not a relay composition (2), actuated along a helical trajectory of angle α to bring the passage (2a) from the first so-called safety position in which it is located in a plane substantially orthogonal to the alignment axis (6 ) of the pyrotechnic chain, in the second so-called arming position where it is aligned with the axis of the chain (6). 2 - Device according to claim 1, characterized in that the helical movement is the combination of a translational movement and a rotational movement α of approximately 90 °. 3 - Device according to claim 2, characterized in that the helical movement of the means is carried out in three successive phases, a first phase A during which we mainly ensure a translational movement and a low rotation of between about 0 and 15% of the angle α, then in a phase B of significant rotation between about 15 and 85% of the angle α, and finally in a phase C especially a translational movement and a slight rotation to the armed position. 4 - Device according to claim 3, characterized in that the means consists of a shaft (3) placed perpendicular to the axis (6) of the pyrotechnic chain, the helical movement being obtained using a pin assembly guide / helical groove (8,9). 5 - Device according to claim 4, characterized in that the helical groove (9) is formed on the shaft (3) according to the profile shown in Figure 3. 6 - Device according to any one of claims 1 to 5, characterized in that the interruption means is provided with means for displaying the two positions of security and arming. 7 - Device according to any one of claims 1 to 6, characterized in that the helical movement is controlled by a motor system of the rack and pinion type (21,20) actuating the interruption means (3). 8 - Device according to any one of claims 1 to 6, characterized in that the helical movement is controlled by hydrostatic pressure acting on the interrupting means (3). 9 - Device according to any one of claims 1 to 6, characterized in that the helical movement is controlled by borrowing gas taken from the propellant of the ammunition acting on the interruption means (3).

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