FR2691795A1 - Self-destruction system, esp. for sub-munition delivered by carrier shell - has detonator with auxiliary primer in form of pyrotechnic or chemical heat generator - Google Patents

Abstract

The system, incorporating a main (2) and an auxiliary percussion pin (16) designed to operate after a given delay, has an auxiliary primer in the form of a heat generator (11), the thermal energy from which is transmitted to a heat-sensitive detonator (6). The heat generator can be pyrotechnic in form, comprising a container (13) with a percussion-sensitive priming compound (14) and a thermal energy generating compound, or it can be chemical, with two products which produce an exothermic chemical reaction when they come into contact, e.g. sulphuric acid and potassium chlorate. The second of the two products can be held in a metal container which the acid eats through in a given time. ADVANTAGE - Ensures safe destruction of sub-munition after given period of time.

Description

 The present invention relates to a system for self-destruction of ammunition, in particular of a submunition of cargo shells, the ammunition being provided with a military charge initiated by a pyrotechnic chain comprising a main striker and a means initiation carried by a movable slide from a safety position to an arming position, the system being of the type comprising an auxiliary means housed inside the slide and intended to initiate the initiation means after a delay determined.

 Generally, after the ejection of a submunition from a cargo shell, the slider which carries the means for initiating the load goes into the cocking position, and when the submunition comes into contact from the ground or a target, the main striker initiates the military charge by percussion of the priming means.

 However, the explosion of the military charge will not occur if the ram is not in the cocking position or if the main striker does not work. In both cases, the submunition, which rests on the ground, remains dangerous.

 It is known to equip such a munition, on board a cargo shell, with a self-destruction system which detonates the military charge or which destroys the means for initiating the charge, after a predetermined delay which is greater. at the time of flight in free fall of the ammunition before reaching the ground or a target moving on the ground.

 Document US Pat. No. 4,873,927 describes a self-destruction system comprising a pyrotechnic delay which is initiated at the time of the arming of the masterbeam slide. After a certain time of combustion of the pyrotechnic delay, the initiation of the military charge is initiated. However, such a system has the disadvantage of being very expensive.

 Document US-4 998 476 describes a self-destruction system comprising a hydraulic or pneumatic piston. This piston, pressing against an oil chamber, moves as soon as a reduction in the volume of this chamber occurs as a result of the opening of a calibrated orifice through which the oil can be evacuated. The piston is then driven in displacement and, at the end of the race, it releases a striker which initiates the initiation of the military charge. Such a system is in reality a micromechanism which requires very great precision in production, mounting and operation. It is therefore very sensitive to the external environment and of a high cost of production.

 Document EP-0 205 956 describes a self-destruction system having a piston fitted with a secondary striker retained by a pin. After ejection of the submunition, the pin flows gradually to break after a determined time under the action of a spring. Such a system has the disadvantage of not being precise, since the delay is determined by the creep time of the pin.

 Document FR-78 04497 describes a pyrotechnic delay comprising a piston movable in translation, under the effect of gases generated by the firing of a pyrotechnic initiator, to initiate at the end of the race a means of initiating the military charge . The function of such a delay is in fact to detonate the military charge after the munition has penetrated the target.

In other words, this delay is not linked to a self-destruction function.

 Finally, document EP-0 456 484 describes a self-destruction system sensitive to a rise in the outside temperature which causes the melting of a ring made of a eutectic alloy. A secondary striker applied under pressure against this ring allows the initiation of a detonator when the ring is melted.

Such a system makes it possible to neutralize the device for initiating the load to prevent it from exploding following an untimely rise in the outside temperature.

 The object of the invention is to design a system for self-destruction of ammunition which is simple, inexpensive and easy to install in the ammunition.

 To this end, the invention provides a self-destruction system of the aforementioned type and which is characterized in that the auxiliary means for initiating the priming means is a heat generator, the thermal energy produced by the generator being transmitted to the heat-sensitive initiating means to initiate it after said delay.

 According to a first embodiment of the invention, the heat generator is of the pyrotechnic type and comprises a priming composition sensitive to percussion and a composition generating thermal energy which are contained in an envelope.

 According to a second embodiment of the invention, the heat generator is of the chemical type and comprises at least two products which, in contact with each other, cause a chemical reaction of the exothermic type with release of heat.

 To initiate the heat generator, the self-destruction system comprises a control device housed in the slide, this device consisting of an auxiliary striker secured to a piston movable in translation pushed by a spring, and a releasable locking device which retains the auxiliary striker at a distance from the heat generator.

 According to the first embodiment, when the locking device is released, the secondary striker punctures the envelope which encloses the heat generator and strikes the initiating composition which causes the initiation of the composition generating thermal energy.

 In this case and according to another characteristic of the invention, the thermal energy produced by the heat generator propagates in the mass of the bucket grout, made of a material which is a good thermal conductor, and the delay at the end of which the priming means is initiated is a function of the thermal inertia of this material.

 According to the second embodiment of the invention, the two products which constitute the heat generator comprise an acid stored in an envelope, such as a bulb, while the second product is stored in a second metal envelope located between the ampoule and the priming means, and when the locking device is released, the auxiliary striker breaks the envelope containing the acid.

 In this case and according to another characteristic of the invention, the delay at the end of which the initiating means is initiated corresponds to the time taken by the acid, such as sulfuric acid, to attack the metal shell, in aluminum for example, and come into contact with the second chemical, such as potassium chlorate to cause a chemical reaction with evolution of heat.

 The invention applies to a munition, in particular, a submunition on board a cargo shell for example, and the initialization of the aforementioned predetermined delay corresponding to the moment when the locking device of the control device of the generator of heat is released or removed after the ejection of the submunition of the cargo shell, that is to say when the passage of the slide in the armed position, for example.

 In this case, the operation of the self-destruction system is subject to the passage of the slide in the arming position.

 Alternatively, a locking device can be defined which is released whatever the position of the bucket grout. In the latter case and when the slide remains locked in the safety position, there is not strictly speaking a self-destruction of the ammunition, but a neutralization of the latter by destruction of one primer.

 According to an important advantage of the invention, the self-destruction system is of simple construction involving only a few elements, which facilitates assembly and maintenance operations, and is of reliable operation.

Other advantages, characteristics and details of the invention will emerge from the explanatory description which follows, given with reference to the attached drawings given solely by way of example and in which - Figure 1 is a schematic sectional view of a sys
self-destruct according to a first mode of
embodiment, - Figure 2 is an axial sectional view of a munition
equipped with a self-destruction system according to the pre
mier embodiment of the invention, the slide
in which the self-destruction system is housed
being shown in the safety position, - Figure 3 is an axial sectional view of the ammunition
similar to that illustrated in Figure 2, but with the
grout bucket shown in the armed position, - Figure 4 is a partial sectional view along the
line IV-IV of Figure 2, - and Figure 5 is a schematic sectional view of a
self-destruction system according to a second mode of reaction
reading of the invention.

 The principle of the invention is illustrated in Figure 1 with the schematic representation of a pyrotechnic chain 1 consisting of a main striker 2, a priming device 3 and an explosive charge 4 for example. The priming device 3 is constituted, in a manner known per se, by a slider 5 movable in translation which supports a detonator primer 6 intended to be struck by the main striker 2 to initiate the charge 4.

 The bucket grout 5 is movable between a safety position where it keeps the primer 6 away from the striker 2, and an arming position where the primer 6 is opposite the striker 2 (Figure 1). The priming device 3 therefore constitutes a switch for the pyrotechnic chain 1, the load 4 can only be initiated if the slide 5 has passed into the arming position.

 Such a pyrotechnic chain 1 is in particular incorporated in ammunition, in particular in a submunition of cargo shells, and for the reasons explained in the preamble, there is a self-destruct system 10 linked to the initiating device 3 of the pyrotechnic chain 1 which comprises an auxiliary means for initiating the primer 6 carried by the slide 5 and whose function is to self-destroy the submunition in the event of a malfunction of the pyrotechnic chain 1.

 The auxiliary initiation means for the primer 6 is constituted by a heat generator 11 initiated by a control device 12. In the first embodiment considered here, the generator 11 is of the pyrotechnic type and is formed of an envelope 13 containing a priming composition 14 sensitive to percussion and a composition 15 generating thermal energy. The control device 12 comprises an auxiliary striker 16 secured to a piston 17 movable in translation under the action of a cocking spring 18, and a locking member 20 which retains the piston 17, biased by the spring 18, remote from generator 11.

 The bucket grout 5 is made of a material which is a good thermal conductor, such as steel or an aluminum or zinc alloy, and it comprises two housings 5a and 5b separated by an internal partition 22. The housing 5a contains the primer detonator 6 and opens to the outside through two diametrically opposite orifices 23 and 24 opposite the main striker 2 and the load 4, respectively, while the housing 5b is of cylindrical shape and opens to the outside of the slide 5.

 The thermal generator 11 is housed in the bottom of the housing 5b of the bucket grout 5 and it is immobilized by means of an elastic ring 25, for example, which bears against the casing 13 of the generator 11. The ring 25 is mounted in a groove 25a provided in the internal wall of the housing 5b.

 The piston 17, the front face of which is secured to the auxiliary striker 16 has two grooves 27 and 28 at its outer periphery. A seal 29 is housed in the groove 27, while the locking member 20, such as a pin for example, which passes through a radial opening provided in the slide 5, protrudes into the groove 28, so axially immobilizing the piston 17 and the auxiliary striker 16 at a distance from the generator 11. The spring 18 associated with the piston 17 is in the banded state, and it bears against the rear face of the piston 17 on the one hand, and against a disk 30 on the other hand. The disc 30 bears against a shoulder 31 provided towards the open end of the housing 5b, and it is immobilized by means of an elastic ring 32 mounted in a groove 32a provided in the internal wall of the housing 5b. It should be noted that the turns of the spring 18 are contiguous to prevent the piston 17 from moving back from its immobilized position for reasons which will be explained below.

 Assuming that such a self-destruct system 10 is mounted in a submunition on board a cargo shell, the operation is as follows.

 After firing the shell and once the munition has been ejected, the slider 5 passes into the cocking position to bring the detonator primer 6 substantially opposite the main striker 2. The locking device 20 is released from the slider 5, and the piston 17 is pushed towards the generator 11 by the spring 18.

 The release of the locking device 20 from the groove 28 of the piston 17 can be obtained by a tensile force exerted by an external device, or by centrifugal force by placing the locking device 20 in a radial direction relative to the axis of the submunition. A concrete example enabling the locking device to be released will be given later with reference to FIGS. 2 to 4.

 The auxiliary striker 16 integral with the piston 17 punctures the casing 13 of the generator 11 and initiates by percussion the initiating composition 14, the combustion of which then causes that of the composition 15 generating thermal energy. In normal operation, the ammunition is initiated either in contact with the ground, or in contact with a target as a result of the percussion of the primer 6 by the main striker 2. If for some reason or other, the ammunition is not not initiated, the thermal energy released by the generator 11 which has propagated in the mass of the slide 5 ends up causing a rise in temperature of the slide 5 which is such, in particular at the level of the internal partition 22 which separates the generator 11 of the primer 6, that this, sensitive to heat, is initiated after a certain delay, a function of the thermal inertia of the material constituting the bucket grout, and causes a self-destruction of the submunition if the slider 5 is in the arming position, or destruction of the primer 6 otherwise.

 It should be noted that the operation of the thermal generator 11 can cause an increase in the pressure inside the housing 5b of the slide 5 which can cause a recoil movement of the piston 17 which has just perforated the casing 13 of the generator 11. This backward movement is limited by the turns of the spring 36 which come into contact with each other to form a stop. This stop acts before the piston 17 can come back from the opening of the slide 5 where the locking member 20 was engaged in order to avoid any loss of pressure through this opening.

 Referring to Figures 2 to 4, the slide 5 in which is housed the self-destruction system 10 according to the first embodiment of the invention, is slidably mounted inside the housing 51 of the body 52 of a submunition 50, of the "bombette" type, as described in more detail in US Pat. No. 4,488,488.

 Referring to Figure 2, the slider 5 is held in the safety position by the main striker 2 which projects into a radial opening 54 of the slider 5. The main striker 2 is, in a manner known per se, screwed into a nut 55 integral in rotation with the body 52 of the submunition 50.

 In the safety position (Figures 2 and 4), the slider 5 is pushed by springs 57, which bear on one side against washers 58 crimped on the body 52 and the detonator primer 6 carried by the slider 5 is not axially aligned with the main striker 2.

 The piston 17 of the control device 12 of the heat generator 11 is retained by the locking pin 20 freely engaged in a radial opening 60 of the slide 5. The pin 20 is supported, on one side, in the bottom of the groove 28 piston 17 and, on the other side, on the wall of the housing 51 formed in the body 52 of the submunition 50 in which the slide 5 is slidably mounted. The groove 28 here has a profile formed by two conical surfaces.

 In a first ejection phase, following the firing of the cargo shell in which the submunition 50 is loaded, it is ejected from the cargo shell.

 In a second arming phase, a stabilizing tape for example (not shown) fixed to the main striker 2 is deployed when the munition 50 falls. The stabilizing tape, under the effect of its aerodynamic drag combined with a rotational movement of the submunition 50 causes partial unscrewing of the main striker 2 screwed into the nut 55.

 The main striker 2 then emerges from the opening 54 of the slider 5 which, by the relaxation of the arming springs 57 which are associated with it, is moved in translation towards its arming position illustrated in FIG. 3.

 When the bucket grout 5 is in the cocking position, it is in abutment by a shoulder 62, provided towards its end most engaged in the body 52 of the submunition 50 and against which the cocking springs 57 bear ( figure 4). The shoulder 62 is in abutment against an internal abutment surface 63 provided in the housing 51, and the detonator initiator 6 is then located opposite the striker 2. The slider 5 then partially projects outside the housing 5b of the slide 5 of the submunition 50. When the slide 5 goes into the cocking position, the pin 20 is no longer immobilized in its opening 60 by the wall of the housing 51. The spring 18 which pushes the piston 17 thus causes the ejection of the pin 20, in particular because of the particular conical profile of the groove 28, and the activation of the heat generator 11, as illustrated in FIG. 3.

 In a third phase which corresponds to the end of the fall to the ground of the submunition 50, the explosive charge 4 is initiated, in normal operation, following the percussion of the detonator initiator 6 by the main striker 2 which s 'is suddenly displaced by the deceleration movement caused by the impact of the submunition on contact with a target or the ground, and the self-destruction system 10 although initialized has no effect.

 On the other hand, in the event of malfunction of the main striker 2 for example, the submunition 50 is not initiated on impact, and it is the self-destruction system 10 which initiates the detonator primer 6 and causes firing the submunition 50 after a predetermined delay calculated to be greater than the time for the submunition 50 to fall to the ground. In this case, however, if the slider 5 has not passed into the arming position, the self-destruction system 10 is inoperative.

 Thus, as a variant, it is possible to provide for a release of the locking pin 20 following the ejection of the submunition 50 from the cargo shell for example, and not following the passage of the grout bucket 5 in the position of armament. It will suffice for this to have the locking pin 20 in a radial direction relative to the axis of the submunition 50 in a housing such that the pin 20 is ejected by the centrifugal force of inertia, whatever the position of the slide 5. The advantage of such an arrangement is that it allows the neutralization of the submunition 50 by destruction of the primer 6 after a certain delay, even if the slide 5 is not in an armed position.

As an example - the priming composition 14 sensitive to percussion
is a mixture in mass proportions of 53%
(+ 3%) potassium chlorate, 25% (+ 2%) thio
lead cyanate, 17% (+ 2%) of antimony sulfide and
5% (+ 2%) lead tricinate (common name for trinitro
lead resorcinate).

the composition generating thermal energy 15 is
a mixture in mass proportions of 30% (+ 5%)
tungsten, 10% (+ 2%) potassium perchlorate
and 60% (+ 5%) of barium chromate or a mixture of
80% (+ 2 * to - 12%) of titanium and 20% (+ 12% to - 2%) of
boron, - and the operating temperature of primer 6 is
about 250 to 300 C.

 In a second embodiment illustrated in FIG. 5, the heat generator 11 is of the chemical type and comprises two chemicals 70 and 71 which, in contact with each other, cause an exothermic reaction with release of heat, these two products being for example sulfuric acid 70 and potassium chlorate 71.

 The sulfuric acid is stored in an envelope 13 such as a glass bulb, and the potassium chlorate is stored in a second envelope 73 made of metal, such as aluminum for example, which is placed between the envelope 13 and the detonator primer 6. More specifically, the glass bulb 13 comes to bear, on one side, against an elastic ring 75 fixed in the wall of the slide 5 and, on the other side, against the second envelope 73 which is fixed for example by gluing inside the slide 5 to ensure sealing, while the second envelope 73 comes to bear against an annular stop 76 formed inside the housing 5b of the slide 5. The second envelope 73 is located near the primer 6 without the presence of a partition. Finally, the face of the second envelope 73 opposite the primer 6 comprises an opening closed by a thin spangle 77.

 The control device 12 of this chemical type heat generator 11 is the same as that described above and used to control the pyrotechnic type heat generator.

 In operation, when the latch 20 is released, the auxiliary striker 16 pushed by the spring 18 breaks the bulb 13, which has the effect of bringing sulfuric acid into contact with the second aluminum casing 73 which it chemically attacks . After a certain delay, the acid penetrates inside the second envelope 73 and comes into contact with potassium chlorate 71 to produce a heat emission which initiates the primer 6.

 Of course, the invention is in no way limited to the embodiments described above and given by way of example. In particular, to prevent the piston 17 from moving back beyond the opening for passage of the locking pin 20, the rear face of the piston 17 can be extended by a rod which abuts against the closing disc 30 of the housing 5b of slide 5.

Finally, the self-destruction system can be adapted to a priming device with circular displacement, such as a primer-carrying rotor.

Claims (9)

 1. Self-destruction system of an ammunition, in particular a submunition of cargo shells, the ammunition being provided with a military charge initiated by a pyrotechnic chain comprising a main striker and a means of initiation carried by a sliding slider from a safety position to an arming position, the system being of the type comprising an auxiliary means housed inside the slider and intended to initiate the priming means after a determined delay, characterized in that the auxiliary means consists of a heat generator (11), the thermal energy produced by the generator being transmitted to the priming means (6) sensitive to heat to initiate the latter after said delay.  2. Self-destruction system according to Claim 1, characterized in that the heat generator (11) is of the pyrotechnic type and comprises, in an envelope (13), a priming composition (14) sensitive to percussion , and a composition (15) generating thermal energy, the latter propagating in the mass of the slide (5), in a material which is a good thermal conductor, the predetermined delay at the end of which the initiating means (6) is initiated function of the thermal inertia of said material.  3. Self-destruction system according to Claim 2, characterized in that the slide (5) is made of a material such as steel, or an aluminum or zinc alloy, and in that the means of primer (6) is a detonator primer, known per se.  4. Self-destruction system according to Claim 1, characterized in that the heat generator (11) is of the chemical type with at least two products (70,71) which, in contact with one another, cause an exothermic chemical reaction with release of heat.  5. Self-destruction system according to Claim 4, characterized in that one of the chemicals is an acid (70), such as sulfuric acid, stored in an envelope (13), such as a bulb , and in that the other of the chemicals is potassium chlorate (71) stored in a second envelope (73) placed between the ampoule (13) of acid and the priming means (6).  6. Self-destruction system according to Claim 5, characterized in that the second envelope (73) is a metal envelope, such as aluminum, and in that the predetermined delay, at the end of which the means of priming (6) is initiated, corresponds to the time taken by the acid (70) to attack the second metal casing (73) and come into contact with potassium chlorate (71).  7. Self-destruction system according to any one of Claims 2 or 6, characterized in that the heat generator (11) is initiated by a percussion control device (12) housed in the slide (5) for puncture or break said envelope 113), said control device (12) comprising an auxiliary striker (16) secured to a piston (17) movable in translation under the action of an arming spring (18), and a locking member (20) which retains the piston (17), biased by the spring (18), away from the generator (11).  8. Self-destruction system according to Claim 7, characterized in that the piston (17) comprises a first peripheral groove (27) in which is housed a seal (29) and a second peripheral groove (28) in which protrudes the locking member (20), such as a pin for example, through a radial opening in the slide (5).  9. Self-destruction system according to Claim 7 or 8, characterized in that the locking member (20) is automatically released when the slide (5) is in the arming position.