FR2691796A1 - Self-destruct system for sub-munition, esp. from carrier shell - has secondary percussion pin actuated by gas generator after appropriate delay - Google Patents

Abstract

The system, especially for a shell with a main charge and primary (2) and secondary (15) percussion pins, with the latter designed to operate after a specific delay, has the control for the secondary percussion pin made in the form of gas generator (111) inside a closed housing (13) which has the percussion pin (15) projecting from its front end (13a). The housing (13) can have an intermediate annular zone of reduced strength which is designed to rupture under the pressure of the gas produced by the generator. In a variant the housing can be in two sections with a sealed telescopic joint which also separates under the gas pressure. The gas generator can be pyrotechnic in form, with detonative and gas-producing compounds, or chemical, with a liquid such as an acid inside an ampoule, and a metal adjacent to it. The gas generator can be set off by an auxiliary spring-loaded or piston-operated percussion element (35) inside the housing. ADVANTAGE - Ensures safe and automatic detonation of sub-munition if it fails to reach target.

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 slide movable from a safety position to an arming position, the system being of the type comprising a secondary striker movable inside the slide from a safety position to a percussion position starting means, and control means for causing the displacement of the secondary striker after a predetermined delay.

 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 slider 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 this type of submunition, embedded in 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 calculated to be greater than the time required for the munition to reach 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.

 In document US-4 998 476, a self-destruction system is described 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 production cost.

 In document EP-0 205 956, a self-destruction system is described 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.

 Finally, 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, for actuating, at the end of the stroke, a means for initiating 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.

 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 control means of the secondary striker is constituted by a gas generator housed in a closed body comprising a front part extended by the secondary striker, and a rear part connected to the front part by means of controlled opening or rupture, sensitive to the gas pressure generated by the generator inside the body.

 According to a first embodiment of the invention, said body comprises an intermediate annular zone of lower mechanical resistance, constituting the aforementioned means with controlled rupture, intended to rupture by the pressure reached by the gas inside the body.

 According to a second embodiment of the invention, the front and rear parts of said body are partially fitted one inside the other and secured by crimping with low mechanical resistance constituting the above-mentioned means with controlled rupture, in order to be separable. one from the other by the pressure reached by the gas inside the body.

 According to another characteristic of the invention, the gas generator is for example of the pyrotechnic type and comprises a priming composition sensitive to percussion and a gas generating composition, which are contained in an envelope, or is for example of the type chemical and comprises at least two products which, brought into contact with each other, cause a chemical reaction which causes gas emission, one of the products being for example an acid, while the other product is a metal .

 According to yet another characteristic of the invention, the operation of the gas generator is controlled by a percussion device housed inside the body containing the generator and comprising an auxiliary striker secured to a movable piston armed by a spring and a releasable locking device which retains the auxiliary striker in the armed state.

 In the case of a pyrotechnic type generator, the auxiliary striker punctures the envelope which encloses the generator and strikes the priming composition to cause the initiation of the gas generating composition.

 In the case of a chemical type generator, the auxiliary striker punches an envelope containing the acid to bring it into contact with the metal located near the envelope and initiate the chemical reaction, the metal possibly being the material constituting the auxiliary striker.

 The invention applies in particular to a munition, in particular a submunition on board a cargo shell for example, in which the initialization of the aforementioned predetermined delay corresponds to the moment when the locking device of the generator control device gas, which retains the auxiliary striker, is released or withdrawn after the ejection of the submunition of the cargo shell, that is to say when the slide passes into the armed position.

 In this case, the operation of the self-destruction system is subject to the passage of the slide in the arming position, that is to say that the locking device of the gas generator control device is released by the passage of the slide in the cocking position. As a variant, a locking device can be defined which is released whatever the position of the slide. In the latter case and when the slide remains locked in the safety position, there is not strictly speaking self-destruction of the munit ion, but neutralization of the latter by destruction of the primer.

 According to an important advantage of the invention, each gas generator and its associated percussion device are arranged inside a body, which makes it possible to prefabricate them in series according to the delays that it is desired to obtain. This avoids piecemeal manufacturing for a munition of a given type, which facilitates assembly and maintenance operations.

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-destruction device according to the invention for illus
its operation according to a first mode of
embodiment, - Figures 2 to 4 are three schematic sectional views
of three examples of realization of the auto system
destruction, respectively, based on the first mode
of the invention, - Figure 5 is a schematic sectional view of a mu
nition equipped with a self-destruction system according to a
second embodiment of the invention, the grout
bucket in which the self-destruction system is housed
being shown in the safety position, - Figure 6 is a schematic sectional view of the mu
nition illustrated in figure 5, but with the slide
shown in the armed position, - and Figure 7 is a schematic sectional view along
line VII-VII in Figure 5.

 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 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 a cocking position where the primer 6 is aligned along the axis of the striker 2 (Figure 1). The priming device 3 therefore constitutes a switch for the pyrotechnic chain 1, the load 4 being initiated only if the slider 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 and whose function is to self-destroy the submunition in the event of a malfunction of pyrotechnic chain 1.

 The self-destruction system 10 comprises a gas generator 11 actuated by a control device 12, which are housed inside a hollow metal body 13 and of cylindrical shape, and a secondary striker 15 which projects outside the body 13.

 In general, the body 13 comprises a front part 13a extended by the secondary striker 15, and a rear part 13b connected to the front part by means of controlled opening or rupture, which are sensitive to the gas pressure generated by the generator 11 inside the body 13.

 In a first embodiment illustrated in FIGS. 1 to 4 and with particular reference to FIG. 2, the body 13 has an intermediate annular zone 18 of less mechanical resistance, which is produced by a groove machined at the external periphery of the body 13 , for example.

 In the example considered here, the striker 15 is fixed to the external face of a bottom wall 19 provided at the end of the front part 13a of the body 13. Towards its other end, the body 13 ends in a flange 20, and it is closed by a disc 21. Referring again to FIG. 1, the bucket grout 5 comprises two housings 22a and 22b separated from each other by an internal wall 23 pierced with an orifice passage 24. The housing 22a contains the detonator initiator 6 and opens to the outside by two diametrically opposite orifices 25 and 26. The housing 22b is cylindrical in shape, extends over a length greater than that of the body 13 and opens out onto the slide 5.

 The self-destruction system 10 is mounted inside the housing 22b of the slide 5. The flange 20 of the body 13 bears against a shoulder 28 provided in the internal wall of the housing 22b, and the body 13 is immobilized at by means of an elastic ring 29 for example mounted in a groove 29a of the slide 5 and which bears against the disc 21. The secondary striker 15 is then located at a distance from the internal wall 23 separating the housings 22a and 22b.

 In the embodiment illustrated in FIG. 2, the gas generator 11 is of the pyrotechnic type, and it is formed of an envelope 30 containing a priming composition 31 sensitive to percussion and a gas generating composition 32. This envelope, for example metallic, is located in the front part 13a of the body 13, being held in position by an elastic ring 34 for example, or by gluing. The control device 12 of the generator 11 comprises, housed in the rear part 13b of the body 13, an auxiliary striker 35 associated with an arming spring 36 and with a locking member 40 having the shape of a cylindrical pin for example, which enters the body 13 through a cylindrical opening with an axis perpendicular to the axis of the body 13.

 The auxiliary striker 35 is integral with an end face of a piston 41 slidably mounted inside the body 13. The piston 41 has two grooves 42 and 43 at its outer periphery. A seal 44 is housed in the groove 42, while the locking member 40 which passes through radial openings provided in the slide 5 and the body 13 protrudes into the groove 43, so as to axially immobilize the piston 41 and the auxiliary striker 35 at a distance from the casing 30 of the generator 11. The spring 36, which is in the banded state, bears against the rear face of the piston 41 on the one hand, and against the disc 21 for closing the body 13 on the other hand I1 should be noted that the turns of the spring 36 are contiguous to prevent the piston 41 from moving backwards beyond its immobilization 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 arming position to bring the detonator primer 6 substantially opposite the main striker 2. The locking device 40 is released from the body 13 and the piston 41 is pushed towards the generator 11 by the spring 36.

 The release of the locking device 40 engaged in the groove 43 of the piston 41 can be obtained by a tensile force exerted by an external device, or by centrifugal force by placing the locking device 40 in a radial direction relative to the axis of the submunition. A concrete example allows both to release the locking device will be given later with reference to Figures 5 to 7.

 The auxiliary striker 35 secured to the piston 41 punctures the casing 30 of the generator 11 and initiates by percussion the priming composition 31, the combustion of which then causes that of the gas-generating composition 32. 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 gas pressure inside the body becomes such, after a predetermined delay, that the intermediate zone 18 of lower resistance of the body 13 will fail. The two front 13a and rear 13b parts of the body 13 separate from one another. The front part 13a, which supports the secondary striker 15 is therefore projected in the direction of the detonator initiator 6 under the action of the gas pressure. The front part 13a then abuts against the wall 23 which separates the two housings 22a and 22b from the body 13, and the secondary striker 15 initiates the detonator initiator 6 through the passage 24 of the partition wall 23, which causes the initiation of the charge 4, that is to say a self-destruction of the ammunition.

 In the exemplary embodiment illustrated in FIG. 3, the gas generator 11 is of the chemical type and comprises two products which, once brought into contact with one another, cause a chemical reaction which causes gas emission. One of the products is for example an acid 45, such as hydrochloric acid, stored in a glass ampoule 46 for example or in a capsule made of neutral material, such as that sold under the brand "TEFLON". The second product 47 is a metal, such as aluminum for example, in the form of a ring housed in a body 13 and substantially in contact with the glass bulb 46 while being retained by an elastic ring 48.

 The mixture of the two products is obtained by a control device 12 similar to that described in FIG. 2. The auxiliary striker 35 integral with the piston 41 is of cylindrical shape and extends over a length greater than that of the metal ring 47, to allow it to cross it and break the glass bulb 46.

 Alternatively, from this second embodiment, as illustrated in FIG. 4, the metal ring 47 is eliminated, and it is the auxiliary striker 35 which is formed of metal which can react directly with the acid stored in the ampoule 46. In this example, it will be possible to have, instead of the metal ring 47, a ring made of a material forming a catalyst to promote the chemical reaction at the extreme temperatures of use of the munition. This catalyst is for example aluminum chlorate, when hydrochloric acid and aluminum are used as basic products for the chemical reaction. The auxiliary striker 35 can advantageously be a hollow tubular element for increasing the contact surface between the metal and the acid in order to obtain a greater gas emission.

 It should be noted that the increase in the pressure of the gases inside the body 13, before the rupture of the intermediate zone 18 of less resistance of the body 13, causes a recoil movement of the piston 41 which has just perforated the envelope 30 (Figure 2) or the glass bulb 46 (Figures 3 and 4). 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 41 can come back from the opening of the slide 5 where the locking member 40 was engaged, in order to avoid any gas leakage from the body 13 to the outside, through the 'passage opening of the locking pin 40 which would prevent the pressure inside the body 13 to be sufficient to cause one self-destruction.

 Referring to Figures 5 to 7, the slide 5 in which is housed the self-destruction system 10 according to a second 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 5, 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 (Figure 7), the bucket grout 5 compresses springs 57 which are pressed 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 41 of the control device 12 of the gas generator 11 is retained by the locking pin 40 freely engaged in an opening 59 of the slide 5. The pin 40 bears, on one side, in the bottom of the groove 43 of the piston 41 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. In the example considered here, the groove 43 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 slide 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. 6.

 When the slider 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 (FIG. 7). 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 51 of the body 52 of the submunition 50. When the slide 5 passes into the arming position, the pin 40 is no longer immobilized in its opening 59 by the wall of the housing 51.

The spring 36 which pushes the piston 41 thus causes the ejection of the pin 40, due to the particular conical profile of the groove 43 and the activation of the gas generator which is here pyrotechnic. The auxiliary striker 35 breaks the ampoule 46 containing an acid and a delay is initialized until the separation of the two parts 13a and 13b of the body 13 in which the generator 11 is housed.

 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 moved by the deceleration movement caused by the impact of the submunition on contact with a target or the ground, the self-destruction system 10 although initialized then produces 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 the latter 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 40 following the ejection of the submunition 50 from the cargo shell, and not following the passage of the bucket grout 5 in the cocking position. I1 will suffice for this to have the locking pin 40 in a radial direction relative to the axis of the submunition 50 in a housing such that the pin 40 is ejected by the centrifugal force of inertia, whatever the slide position 5.

The advantage of such an arrangement and 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 armed position.

 In the embodiment given in FIGS. 5 to 7, the self-destruction system 10 can be either of the pyrotechnic type (FIG. 2) or of the chemical type (FIGS. 3 and 4), the one represented corresponding to that of the figure. 3.

 However, in a self-destruction system 10 incorporated in the submunition 50 illustrated in FIGS. 5 to 7, the means with controlled opening which allow the body 13 of the generator 11 to be separated into two parts 13a and 13b are designed according to a second embodiment described below.

 The body 13 is formed of two front 13a and rear 13b parts partially fitted one inside the other and secured by a crimp 60 with low mechanical resistance, so as to be separable from each other when the gas pressure inside the body 13 reaches a certain value after a predetermined delay. The operation of the generator 11 remains unchanged regardless of the pyrotechnic (Figure 2) or chemical (Figures 3 and 4) type.

 In general, the body 13 and the quantity of the products which form the gas generator 11 are sized, so that the two parts of the body 13 separate from each other for a gas pressure which may be of 1 'order of a few tens of bars after a certain delay necessary for the submunition to reach the ground.

 By way of example, the initiation composition 31 sensitive to percussion is for example a mixture of potassium chlorate, lead thiocyanate, antimony sulfide and lead tricinate (common name of lead trinitroresorcinate), and the gas-generating composition 32 is based on azide (for example sodium) or based on perchlorate.

 Of course, the invention is in no way limited to the embodiments described above and given only by way of example. In particular, the means with controlled rupture which ensure the separation of the body 13 into two parts 13a and 13b can be produced in another form than a groove or a crimping. Finally, to prevent the piston 41 from moving back beyond the opening for passage of the locking pin 40, the rear face of the piston 41 can be extended by a rod which abuts against the closing disc 21 of the body 13.

Claims (10)

 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 slider movable from a safety position to an arming position, the system being of the type comprising a secondary striker movable inside the slider from a safety position to a percussion position of the means of priming, and a control means for causing the displacement of the secondary striker after a predetermined delay, characterized in that the control means of the secondary striker (15) consists of a gas generator (11) housed in a body (13 ) closed comprising a front part (13a) extended outside by the secondary striker (15), and a rear part (13b) connected to the front part (13a) by means (18; 60) with opening or r u uction controlled, sensitive to the gas pressure generated by the generator (11) inside the body (13).  2. Self-destruction system according to Claim 1, characterized in that said body (13) comprises an intermediate annular zone (18) of less mechanical resistance, constituting the aforementioned means with controlled rupture, intended to rupture under pressure gases inside the body (13).  3. Self-destruction system according to Claim 1, characterized in that the front (13a) and rear (13b) parts of said body (13) are partially fitted one inside the other and secured by crimping (60 ) with low mechanical resistance constituting the above-mentioned means with controlled rupture, in order to be separable from one another by the pressure of the gases inside the body (13).  4. Self-destruction system according to any one of Claims 1 to 3, characterized in that the gas generator (11) is of the pyrotechnic type, and comprises a priming composition (31) sensitive to percussion and a gas generating composition (32), which are housed in an envelope (30) mounted inside the body (13).  5. Self-destruction system according to any one of Claims 1 to 3, characterized in that the gas generator (11) is of the chemical type with at least two products (45,47) which, in contact with it one another, cause a chemical reaction that results in gas emission.  6. Self-destruction system according to Claim 5, characterized in that one of the chemicals is a liquid product, such as an acid, stored in an ampoule (46), and in that the other of the chemicals is a metal located near the bulb (46).  7. Self-destruction system according to any one of the preceding claims, characterized in that the gas generator (11) is initiated by a percussion control device (12) housed inside the body (13) .  8. Self-destruction system according to Claim 7, characterized in that the control device (12) comprises an auxiliary striker (35) armed by a spring (36), and a locking device (40) which retains the striker (35) in the armed position remote from the gas generator (11).  9. Self-destruction system according to Claim 8, characterized in that the auxiliary striker (35) is integral with a piston (41) slidably mounted inside the body (13), the piston (41) comprising a first peripheral groove (42) in which is housed a seal (43) and a second peripheral groove (44) in which protrudes the locking device (40) such as a pin for example which crosses radially the body (13).  10. Self-destruction system according to any one of the preceding claims, characterized in that the locking member (40) is released automatically during the passage of the slide (5) in the arming position.