EP0534840A1 - Crush sensitive pyrotechnical device such as a signal petard, a mine or similar - Google Patents

Abstract

The present invention relates to a crush-sensitive pyrotechnic device, such as a signal petard, a mine or similar. This device comprises, for igniting a working pyrotechnic charge (8), a piezoelectric body (16) whose terminals (17, 18) are connected to electrodes (30, 36, 31) interacting with a pyrotechnic ignition charge (37), which can be ignited by sparking; on appearance of at least one predetermined crushing condition, actuation means (pedal 44) detecting this appearance apply to the piezoelectric body (16) a compressive stress which causes a high voltage to appear between its terminals (17, 18), this high voltage itself causing the appearance of a spark or an electric arc between the electrodes (30, 36, 31), the ignition of the pyrotechnic ignition charge (37), and the ignition of the working charge (8). <IMAGE>

Description

The present invention relates to a pyrotechnic device sensitive to crushing such as a signaling firecracker, a mine or the like, comprising a useful pyrotechnic charge chosen from a group comprising explosion-proof charges and military charges with thermal effect, explosion-detonating, smoke or lighting device, and an ignition device comprising a pyrotechnic ignition charge in pyrotechnic connection with the payload and means for causing the ignition charge to ignite and, through the latter, l 'ignition of the payload in a controlled manner upon the appearance of at least one determined condition of crushing.

Such a pyrotechnic device is described for example in French patent application No. 89 12981 filed on October 4, 1989 by the Applicant, in the form of a signaling firecracker commonly known as a "lane firecracker", intended to be placed on a lane railroad to signal, by a deflagration emitted at the passage of a train, a danger imposing an emergency stop of this one.

To this end, this known device uses, as ignition charge, a pyrotechnic composition directly sensitive to the compression which it undergoes, between suitably shaped components of the device, when it is crushed by a wheel of the train. .

The use of a charge directly sensitive to compression, as an ignition charge, makes it necessary to reconcile an imperative of reliability of the device, leading to choosing an ignition charge particularly sensitive to compression in order to offer a certainty of ignition of this ignition charge and, through it, the ignition of the explosion-proof payload during the crushing of the device, and a requirement for safety in the manufacture, storage and handling of the device, leading to choosing an ignition charge as insensitive as possible to shocks, which also implies a low sensitivity to compression.

As a result, the firecracker provided with the known ignition device, described for example in the aforementioned French patent application, is not entirely satisfactory, insofar as it cannot present both absolute safety and reliability .

A similar problem arises in the case of mines, which must be particularly sensitive to crushing, under given conditions, but must not endanger manufacturing, storage and handling personnel; for this purpose, mines are generally provided with complex ignition devices, that is to say both expensive and delicate to produce, on the one hand, and prone to malfunction, on the other hand.

• deux électrodes disposées respectivement de part et d'autre d'une zone déterminée de la charge d'allumage et mutuellement espacées d'une distance déterminée propre à permettre la création d'une étincelle électrique entre elles, à travers ladite zone de la charge d'allumage, pour enflammer cette dernière, au moins dans ladite condition déterminée d'écrasement,
• un corps piezo-électrique comportant deux bornes et susceptible de générer une haute tension entre celles-ci lorsqu'il est soumis à une contrainte de compression d'une valeur dépassant une valeur déterminée, selon une direction déterminée,
• un circuit de raccordement électrique de chaque borne du corps piezo-électrique à une électrode respective,
• des moyens d'actionnement pour détecter l'apparition de ladite condition déterminée d'écrasement et appliquer alors au corps piezo-électrique ladite contrainte de compression.

The object of the present invention is to remedy these drawbacks and, to this end, a pyrotechnic device sensitive to crushing is proposed, of the type indicated in the preamble, characterized in that the ignition charge is flammable by sparking, and in that the means for causing the ignition charge to ignite comprise:

• two electrodes disposed respectively on either side of a determined zone of the ignition charge and mutually spaced by a determined distance suitable for allowing the creation of an electric spark between them, through said zone of the charge d 'ignition, to ignite the latter, at least in said determined condition of crushing,
• a piezoelectric body comprising two terminals and capable of generating a high voltage between them when it is subjected to a compressive stress of a value exceeding a determined value, in a determined direction,
• an electrical connection circuit of each terminal of the piezoelectric body to a respective electrode,
• actuating means for detecting the appearance of said determined crushing condition and then applying said compression stress to the piezoelectric body.

Since it is no longer necessary for the ignition charge to be sensitive to crushing, it can be given, as well as the payload, a composition making it insensitive to shocks and thus considerably increase safety manufacturing, storage and handling of the device, the sensitivity of which to the appearance of the determined crushing condition relates to an appropriate choice and calibration of the actuation means, and no longer directly of the nature of the ignition charge.

The manufacturing, storage and handling safety of the device and its reliability, in terms of operating certainty when the determined crushing condition occurs, can therefore be optimized independently of one another, without incompatibility .

One can advantageously choose actuation means of the mechanical type and it is noted that then, the device according to the invention does not comprise any component liable to lose its functionality over a long period of time, so that '' it does not require monitoring and maintenance. This advantage is particularly important if we take into account the difficulty of monitoring and maintenance presented by pyrotechnic devices of the type concerned by the present invention, that is to say that they must be packaged in perfectly sealed cases, such as This is the case with signaling firecrackers, either because they themselves must remain perfectly watertight, as is the case with mines.

Without control and without maintenance, a pyrotechnic device in accordance with the present invention can thus remain capable of fulfilling its function even after a long storage time and, however, its design can remain simple including as regards the actuation means intended to detect the appearance of the determined condition of crushing which should cause the ignition charge to ignite and, consequently, the ignition of the payload, and then apply to the piezoelectric body the compressive stress capable of generating the high voltage which, transmitted to the electrodes by the electrical connection circuit, causes this spark.

These actuation means can be very diverse, depending on the one hand on the choice of location of the piezoelectric body inside the device and on the other hand on the completed crushing condition whose appearance must cause sparking, namely generally the more or less brutal application, for example by a vehicle, of an orientation load at least approximately determined, most often approximately vertical, to the device itself occupying an approximately determined orientation, most often approximately horizontal, on a support such as a railway rail, in the case of a firecracker, or the ground, in the case of a mine.

However, to prevent the piezoelectric body from generating the high voltage causing sparking accidentally, under the action of a compressive stress which would not be at least approximately oriented in said determined direction, it is preferred that the actuating means comprise a thrust body movable relative to the piezoelectric body along a determined trajectory, under the effect of the appearance of said determined crushing condition, from a rest position which it occupies outside of said determined crushing condition and in which the thrust body is functionally disjoint from the piezoelectric body at an activation position which it occupies in said determined crushing condition and in which the thrust body is functionally in support on the piezoelectric body and said trajectory has said determined direction, so that the thrust body applies said compressive stress to the piezoelectric body.

It will be noted that the notion of thrust body functionally disjoint from the piezoelectric body in the rest position certainly includes that of physical spacing between the thrust body and the piezoelectric body but does not necessarily imply such spacing; it also includes the possibility of mutual contact in the rest position, however without this mutual contact resulting from the application of said compression stress to the piezoelectric body.

Naturally, the mode of passage of the thrust body from its rest position to its activation position, upon the appearance of the determined crushing condition in which it is desired to cause sparking, is closely a function of the nature of this condition.

By way of nonlimiting example, in a particularly simple and reliable manner and in a sufficiently small footprint to be compatible with the production of a firecracker like a mine, in the most frequent case where the device according to the invention is intended to react to the application of a crushing load in a determined orientation while it rests in a determined orientation on a support such as a railroad or the ground, the piezoelectric body is advantageously arranged, inside the device, so that said determined direction of compression to which it reacts coincides with said determined orientation of the load, in which case the thrust body can advantageously constitute a pedal for detecting the appearance of a crushing load in said determined direction, this pedal being sensitive to a thrust or to a shock applied in said determined condition crushing, in said determined direction, from the rest position to the activation position.

Preferably, the device according to the invention comprises safety means suitable for avoiding accidental sparking, that is to say occurring outside the appearance of said determined crushing condition, and these safety means may have various aspects, which can be combined at will in the same device.

Thus, the device according to the invention can advantageously include mechanical safety means against an accidental application of said compression stress, leading to sparking, to the piezoelectric body.

When, preferably, the actuating means comprise a thrust body as indicated above, in particular a thrust body forming a pedal, these mechanical safety means may advantageously include means for retaining the thrust body in position rest, capable of releasing the thrust body under the effect of the appearance of said determined crushing condition, and for example to automatically release the thrust body when the latter, in the rest position, receives a force exceeding a predetermined threshold, oriented towards its activation position. The retaining means can then be constituted, for example, in the form of bridges of material sensitive to shearing, retaining the thrust body in the rest position and shearing when the appearance of this force exceeds a determined threshold, or even under other forms. Naturally, it is also possible to provide means for retaining the thrust body in the rest position, which in turn are capable of being actuated at will when the device is put into service, in order to then release the thrust body for passage to its activation position on the appearance of said determined crushing condition, for example in the form of a detachable pin at will. The means for retaining the thrust body in the rest position, capable of automatically releasing it when said determined condition appears, may advantageously be associated, in certain applications, with means for elastic urging of the thrust body from the rest position towards its activation position, which cause an energetic passage of the thrust body from its rest position to its activation position as soon as it is released from the action of the retaining means, which results on arrival in the activation position by the application, to the piezoelectric body, of a shock itself causing sparking; the thrust body then behaves like an inertial mass when it is released with respect to the retaining means; it is thus possible to use a less sensitive piezoelectric body, that is to say itself offering increased security against accidental sparking.

The safety means can also be electrical safety means, capable of preventing accidental creation of said spark in the event of accidental application of said compression stress, normally capable of causing sparking, to the piezoelectric body.

When the actuation means comprise a thrust body as indicated above, in particular a thrust body forming a pedal, these electrical safety means can comprise, in the electrical connection circuit of each terminal of the piezoelectric body to a respective electrode, a switch mechanically coupled to the thrust body so as to be open when the thrust body is in the rest position and closed when the thrust body is in the activation position. Alternatively or cumulatively, the electrical safety means may also include an auxiliary circuit electrically connecting the terminals of the piezoelectric body and a switch interposed in this auxiliary circuit and mechanically coupled to the thrust body so as to be closed when the thrust body is in the rest position and open when the thrust body is in the activation position. Also as a variant or in addition, the electrical safety means may also include means for guiding one, at least, of the electrodes with respect to a movement of approaching or moving away from the other electrode, and coupling means between the thrust body and said guided electrode so that the electrodes are mutually spaced apart by a distance greater than said determined distance and too large to allow the creation of an electric spark between them, through said zone of the load, in the event of accidental application of said compression stress to the piezoelectric body, while the thrust body is in the rest position, and are spaced apart from said determined distance when the body thrust is in the activation position; thus, it is necessary that the thrust body has passed from its rest position to its activation position so that the electrodes are placed, relative to each other, at a distance suitable for allowing sparking between them; naturally, this latter embodiment of the electrical safety means assumes that the electrical ignition device forms a structural unit grouping together the piezoelectric body, the actuation means, the electrodes, the load and the connection circuit.

In general, the electric ignition device according to the invention can form such a structural unit, but it can also form two separate structural units, one of which groups together the piezoelectric body and the actuation means, including the 'other includes the electrodes, the ignition charge and the payload, and which are connected to each other by the electrical connection circuit, or more precisely by an electrical connection cable forming part of this circuit. Thus, in the case of a signaling firecracker, it is possible to dissociate the piezoelectric body and the actuating means, on the one hand, necessarily placed on the track, and the electrodes and the pyrotechnic charges respectively flammable by sparking and deflagrating, on the other hand, which it may be preferable to place next to the track, in order to make the deflagration more easily audible by the train engineer; in the case of a mine, the location of the unit containing in particular the payload can be offset relative to the unit comprising the actuation means, for example to take account of the movement of a vehicle to be destroyed between the moment when it applies a crushing load to the actuating means, causing the piezoelectric body to be stressed, and the moment when the payload acts.

Naturally, the installation of the various components of a device according to the invention can be freely chosen by a person skilled in the art, as a function of requirements, in particular of size.

In this regard, a particularly advantageous embodiment of the device according to the invention, when the latter forms a single unit, is characterized in that the ignition charge is aligned with the thrust body and one of the terminals of the piezoelectric body and interposed between them, in said determined direction, in that the thrust body defines one of the electrodes, on one side of the ignition charge, and in that the other electrode is interposed between the ignition charge and said terminal of the piezoelectric body, on the other side of the ignition charge, and in electrical conduction contact with said terminal at least when the thrust body is in the activation position.

Then, the aforementioned switch, mechanically coupled to the thrust body so as to be open when the thrust body is in the rest position and closed when the thrust body is in the activation position, can advantageously be produced in the form of a discontinuity in said mutual electrical conduction contact when the thrust body is in the rest position; it is easily understood that this discontinuity disappears by re-establishing said mutual electrical conduction contact as soon as the thrust body reaches the activation position.

It will be noted that this results in a particularly simple and reliable embodiment of the device according to the invention.

When it is feared that, in certain circumstances, the inertia of the device according to the invention between the appearance of the determined crushing condition and the operation of the useful pyrotechnic charge is too great, taking into account for example the speed of the train whose driver is to be warned in the case of a track firecracker or the speed of a vehicle to be destroyed in the case of a mine, more particularly when the device is in the form of a single unit, provision can be made to improve this device so that the ignition charge is flammable not only by sparking, but also by percussion, or by constitution of this ignition charge in the form of two charges, of which l one is sensitive to sparking and the other to percussion, either by carrying out a single flammable charge both by sparking and by percussion; then, it is provided that the means for causing the ignition charge to ignite comprise means for striking the latter when said determined crushing condition occurs.

For this purpose, when the device is in the form of a single unit in which the ignition charge is aligned with the thrust body, defining one of the electrodes, and one of the terminals of the piezoelectric body and inserted between them, in said determined direction, and in which the other electrode and said terminal of the piezoelectric body are in mutual electrical conduction contact when the thrust body is in the activation position, with discontinuity in this mutual contact electric conduction when the thrust body is in the rest position, it is advantageous to provide that the ignition charge is integral with a first electrode and disjoined from the second electrode when the thrust body is in the rest position, and that the second electrode is shaped as a striker; thus, the appearance of the determined crushing condition simultaneously causes the closure of the electrical connection circuit of the terminals of the piezoelectric body to the electrodes, so as to cause sparking between them, within the ignition charge. , a percussion of the latter with the effect of ignition if this percussion is sufficiently energetic, due to a particularly brutal crushing of the device; for this purpose, for example, the first electrode may be constituted by the thrust body and the second electrode is integral with said terminal of the piezoelectric body.

• La figure 1 montre, en vue de dessus, un pétard de signalisation selon l'invention, d'un type défini de façon générale dans la norme française NF-F 54-0011 d'Octobre 1982, destiné à être fixé sur le champignon d'un rail de chemin de fer pour émettre une déflagration sous la charge d'une roue d'un convoi ferroviaire ; le pétard est supposé ainsi fixé sur le champignon d'un rail.
• La figure 2 montre une vue de ce pétard en coupe par un plan moyen de symétrie perpendiculaire au rail et repéré en II-II à la figure 1.
• Les figures 3 et 4 montrent un premier exemple de dispositif d'allumage piezo-électrique susceptible d'équiper le pétard illustré aux figures 1 et 2, en une vue analogue à celle de la figure 2 et à plus grande échelle, respectivement avant et après application de la charge provoquant la déflagration.
• Les figures 5 et 6 montrent, en des vues correspondant respectivement à celle de la figure 3 et à celle de la figure 4, un deuxième exemple de réalisation de dispositif d'allumage piezo-électrique susceptible d'équiper le pétard illustré aux figures 1 et 2.
• Les figures 7 et 8 montrent, en des vues correspondant respectivement à celle de la figure 3 et à celle de la figure 4, un troisième exemple de réalisation de dispositif d'allumage piezo-électrique susceptible d'équiper le pétard illustré aux figures 1 et 2.
• Les figures 9 et 10 montrent, en des vues correspondant respectivement à celle de la figure 3 et à celle de la figure 4, un quatrième exemple de réalisation de dispositif d'allumage piezo-électrique susceptible d'équiper le pétard illustré aux figures 1 et 2.
• La figure 11 illustre, en une vue analogue à celle des figures 3, 5, 7, 9, une variante de réalisation du pétard illustré aux figures 1 et 2, avec générateur piezo-électrique dissocié de la charge pyrotechnique inflammable par étincelage et de la charge pyrotechnique déflagrante.
• La figure 12 montre une autre variante de réalisation du pétard de voie illustré aux figures 1 et 2, supposé fixé sur le champignon d'un rail, en une vue en coupe par un plan moyen de symétrie coïncidant sensiblement avec un plan longitudinal médian du rail.
• Les figures 13 et 14 montrent un premier exemple de dispositif d'allumage piezo-électrique susceptible d'équiper le pétard illustré à la figure 12, en une vue analogue à celle de la figure 12 et à plus grande échelle, respectivement avant et après application de la charge provoquant la déflagration.
• Les figures 15 et 16 montrent un deuxième exemple de dispositif d'allumage piezo-électrique susceptible d'équiper le pétard illustré à la figure 12, en une vue analogue à celle de la figure 12 et à plus grande échelle, respectivement avant et après application de la charge provoquant la déflagration.

Other characteristics and advantages of the invention will emerge from the description below, relating to a few nonlimiting examples of implementation, as well as from the appended drawings which form an integral part of this description.

• Figure 1 shows, in top view, a signaling firecracker according to the invention, of a type defined generally in French standard NF-F 54-0011 of October 1982, intended to be fixed on the mushroom d 'a railroad for emitting a deflagration under the load of a wheel of a railway convoy; the firecracker is supposed to be thus fixed on the mushroom of a rail.
• FIG. 2 shows a view of this firecracker in section through a mean plane of symmetry perpendicular to the rail and identified in II-II in FIG. 1.
• Figures 3 and 4 show a first example of a piezoelectric ignition device capable of equipping the firecracker illustrated in Figures 1 and 2, in a view similar to that of Figure 2 and on a larger scale, respectively before and after application of the charge causing the explosion.
• Figures 5 and 6 show, in views corresponding respectively to that of Figure 3 and that of Figure 4, a second embodiment of a piezoelectric ignition device capable of equipping the firecracker illustrated in Figures 1 and 2.
• Figures 7 and 8 show, in views corresponding respectively to that of Figure 3 and that of Figure 4, a third embodiment of a piezoelectric ignition device capable of equipping the firecracker illustrated in Figures 1 and 2.
• Figures 9 and 10 show, in views corresponding respectively to that of Figure 3 and that of Figure 4, a fourth embodiment of a piezoelectric ignition device capable of equipping the firecracker illustrated in Figures 1 and 2.
• FIG. 11 illustrates, in a view similar to that of FIGS. 3, 5, 7, 9, an alternative embodiment of the firecracker illustrated in FIGS. 1 and 2, with a piezoelectric generator dissociated from the flammable pyrotechnic charge by sparking and from the explosion-proof pyrotechnic charge.
• FIG. 12 shows another alternative embodiment of the track firecracker illustrated in FIGS. 1 and 2, assumed to be fixed on the head of a rail, in a sectional view through a mean plane of symmetry substantially coinciding with a median longitudinal plane of the rail .
• Figures 13 and 14 show a first example of a piezoelectric ignition device capable of equipping the firecracker illustrated in Figure 12, in a view similar to that of Figure 12 and on a larger scale, respectively before and after application of the charge causing the explosion.
• Figures 15 and 16 show a second example of a piezoelectric ignition device capable of equipping the firecracker illustrated in Figure 12, in a view similar to that of Figure 12 and on a larger scale, respectively before and after application of the charge causing the explosion.

Reference will firstly be made to FIGS. 1 to 10 where a signaling firecracker commonly known as a "firecracker" of known general design has been illustrated, described for example in French patent application No. 89 12981 of October 4, 1989 of the Applicant, if we except the piezoelectric nature of the ignition device used, which is on the other hand characteristic of the present invention.

• une coupelle inférieure 5 métallique, approximativement horizontale, sous laquelle les griffes 3 sont fixées par exemple par rivetage, de façon non représentée,
• une pièce en matière plastique 6 positionnée sur la coupelle inférieure 5, cette pièce 6 servant de fond à un conteneur 7 à poudre déflagrante 8, de forme générale annulaire, approximativement de révolution autour de l'axe 4,
• un dispositif d'allumage 9 qui est porté par la pièce 6 suivant l'axe 4 et de ce fait entouré par le conteneur 7 à poudre déflagrante 8, et dont quatre exemples de réalisation seront décrits respectivement en référence aux figures 3 et 4, 5 et 6, 7 et 8, 9 et 10,
• une autre pièce en matière plastique 10 disposée autour du dispositif d'allumage 9 et formant avec la pièce 6 précitée le conteneur 7 à poudre déflagrante 8,
• une coupelle supérieure 11 métallique, enfermant avec la coupelle inférieure 5 sur laquelle elle est sertie périphériquement l'ensemble des composants précités du pétard, à savoir les pièces 6 et 10 délimitant le conteneur 7 à poudre déflagrante 8, c'est-à-dire ce conteneur 7 lui-même et la poudre déflagrante 8, ainsi que le dispositif d'allumage 9.

It will simply be recalled that this firecracker 1, intended to be temporarily fixed on the mushroom 2 of a rail, by means of claws 3, in a position in which it has an approximately vertical axis 4 and which will serve as a reference for the rest of the description, includes:

• an approximately horizontal metallic cup 5 under which the claws 3 are fixed, for example by riveting, in a manner not shown,
• a plastic part 6 positioned on the lower cup 5, this part 6 serving as a bottom for a container 7 with explosion-proof powder 8, of generally annular shape, approximately of revolution around the axis 4,
• an ignition device 9 which is carried by the part 6 along the axis 4 and therefore surrounded by the container 7 with explosion-proof powder 8, and four embodiments of which will be described respectively with reference to Figures 3 and 4, 5 and 6, 7 and 8, 9 and 10,
• another plastic part 10 disposed around the ignition device 9 and forming, together with the aforementioned part 6, the container 7 of explosion-proof powder 8,
• an upper metal cup 11, enclosing with the lower cup 5 on which it is crimped peripherally all of the aforementioned components of the firecracker, namely the parts 6 and 10 delimiting the container 7 with explosion-proof powder 8, that is to say this container 7 itself and the explosion-proof powder 8, as well as the ignition device 9.

To this end, while the lower cup 5 has a generally flat shape, perpendicular to the axis 4, the upper cup 11 is only flat and perpendicular to the axis 4 in a central area 12 covering the device from above. 9 and partially the container 7, and has around this central zone 12 a frustoconical peripheral zone 13 of revolution around the axis 4, diverging downward by enveloping the container 7 in the direction of a distance from to the axis 4 and thus connecting the central zone 12 of the upper cup 11 to the periphery of the lower cup 5, where crimping is carried out 14.

The lower 5 and upper 11 cups are for example made of aluminum or aluminum alloy in accordance with the teachings of the aforementioned French patent application, or else of brass. However, it is understood that only the design of the ignition device 9 is characteristic of the present invention and that such an ignition device could be integrated into track firecrackers of other design without being removed for as much of the scope of the present invention.

As shown in FIG. 1, the axis 4 is defined by the intersection of two planes linked to the firecracker 1, namely a plane 212 which merges at least approximately with a median longitudinal plane of the rail and a plane 213 perpendicular to the plane 212 and thus disposed approximately perpendicular to the longitudinal median plane of the rail, these two planes 212 and 213 constituting planes of symmetry for the claws 3, and the ignition device 9 is elongated along the plane 213, symmetrical with respect to the latter and located symmetrically with respect to plane 212; the plane 213 merges with the section plane II-II of FIGS. 3 to 10.

In each of its illustrated embodiments, the ignition device 9 comprises a rigid base, electrically insulating and for example made of plastic; this base 15, which constitutes a part lower part of the ignition device 9, is directly carried by the part 6 with which it is made integral by any appropriate means, and possibly by making a single piece with this part 6.

Along axis 4, the base 15 encloses a piezoelectric body 16 sensitive to a compression stress along this axis 4, that is to say capable of emitting a high voltage between two terminals 17, 18 respectively facing towards the down and up, when it is subjected along axis 4 to a compressive stress exceeding a determined value.

To receive the piezoelectric body 16, the base 15 has along the axis 4 a housing 19 having a shape suitable for retaining the piezoelectric body 16 against any radial movement with reference to the axis 4.

This housing 19 is however open upwards and downwards and the piezoelectric body 16 is retained there against sliding along the axis 4 by two metal blades 20, 21 perpendicular to the axis 4 and at plane 212 and mutually parallel to this level, the first of which is trapped in an integral manner between the base 15 and the part 6 and in electrical conduction contact with the terminal 17 of the piezoelectric body 16 and the second of which runs along the base 15 via the above it, on which it is retained by any appropriate means and is in electrical conduction contact with terminal 18 of the piezoelectric body 16.

The two blades 20 and 21 have the plane 213 as the respective plane of symmetry.

On one side 22 of the plane 212, these two blades 20 and 21 form a normally closed switch and, for this purpose, they are in mutual electrical conduction contact in a state of rest illustrated in FIGS. 3, 5, 7, 9 so to then short-circuit the two terminals 17 and 18 of the piezoelectric body 16 in order to cancel any consequence of the accidental application, to the latter, of a compression stress along the axis 4, while they are mutually disjoint in an illustrated activation state in FIGS. 4, 6, 8, 10 so that, then, a compressive stress of sufficient value, that is to say exceeding said determined value, applied to the piezoelectric body 16 along the axis 4 results in l initiation of the explosion-proof powder 8 under conditions which will be explained later.

More specifically, from terminal 17, the blade 20 extends perpendicular to the plane 212, between the part 6 and a lower face 23, perpendicular to the axis 4, of the base 15, until the junction of this face lower 23 with a side face 24 of the base 15, in turn parallel to the plane 212 and turned in the direction of a distance from the axis 4; at this level, the blade 20 bends at a right angle upward, that is to say parallel to the axis 4, to follow this lateral face 24 until the junction of the latter with an upper face 25, perpendicular to the axis 4, of the base 15; at this junction, the blade 20 bends again at a right angle, this time towards the axis 4, to present a return 26 which, in the state of rest illustrated in FIGS. 3, 5, 7, 9, is oriented perpendicular to the axis 4 and to the plane 212, towards which the return 26 has a free end zone 27 cantilevered above a cavity 28 arranged in the upper face 25 of the base 15, on the side 22 of the plane 212, between the housing 19 for the piezoelectric body 16 and the side face 24; the blade 20 is rigid enough to remain perpendicular to the axis 4, at its return 26, in the rest position illustrated in FIGS. 3, 5, 7, 9, but it is nevertheless sufficiently flexible, elastically or plastically, to being able to gain a conformation illustrated in FIGS. 4, 6, 8, 10 in which it is curved downwards at its extreme zone 27 and penetrates through this zone into the cavity 28.

The blade 21, for its part, rests on the upper face 25 of the base 15, being perpendicular to the axis 4 and to the plane 212, from the terminal 18 to an end zone 29 also placed in cantilever above the cavity 28, so as to partially overlap the end region 27 of the return 26 of the blade 20 above this cavity 28 and to establish said mutual electrical conduction contact in the rest position illustrated in FIGS. 3, 5, 7, 9 while this contact ceases by bending the extreme zone 27 without deformation of the extreme zone 29 in the position illustrated in FIGS. 4, 6, 8 , 10.

In addition to their end zone 27, 29 respectively, located on the side 22 of the plane 212, the two blades 20 and 21 have an end zone 30, 31, respectively, on the other side 32 of this plane 212.

The conformation of these end zones 30, 31 and the corresponding conformation of the base 15 vary according to the exemplary embodiments of the ignition device 9 illustrated respectively in FIGS. 3 and 4, 5 and 6, 7 and 8, 9 and 10, of a way that we will describe now.

In the embodiment illustrated in FIGS. 3 and 4, the blade 20 remains perpendicular to the axis 4 and to the plane 212 as far as its end zone 30, located under a cavity 33 arranged in the lower face 23 of the base 15 of the side 32 of the plane 212, which cavity 33 also opens out in the direction of a distance from this plane, in a lateral face 34 of the base 15, which is parallel to the plane 212, turned in the direction of a distance from to it and occupies a position symmetrical to that of the lateral face 24 with respect to this plane 212; in practice, the cavity 33 thus opens facing a localized area 35 of the part 10.

Inside the cavity 33 is housed, integral with the base 15, a metal cup 36 resting down on the end zone 30 of the blade 20, with which this cup 36 is therefore in electrical conduction relation by a bottom zone 41.

The cup 36, open upwards inside the cavity 33, contains a charge 37 of a pyrotechnic explosion-proof composition that can be ignited by sparking and constitutes, by its bottom 41, an electrode connected to the terminal 17 of the piezoelectric body 16 with a view to creating a spark capable of causing the pyrotechnic composition to ignite 37.

The end zone 31 constitutes the other electrode, connected to the terminal 18 of the piezoelectric body 16 and, for this purpose, is oriented parallel to the axis 4 and to the plane 212, downwards, above the cup 36 , inside a passage 38 arranged for this purpose between the upper face 25 of the base 15 and the cavity 33 thereof.

The end zone 31 of the blade 21 is mounted to slide parallel to the axis 4 in the passage 38 and, in the rest position illustrated in FIG. 3, forms a projection above the upper face 25 of the base 15 of so as to be connected to the latter, between the passage 38 and the terminal 18, only by means of two elbows 39, 40; the elbow 39 is located in the rest position above the face 25, at a distance from the latter, and connects the end zone 31 of the blade 21 to a section 241 of the latter descending from the elbow 39 towards the elbow 40 , in the direction of approximation both vis-à-vis the face 25 of the base 15, at which this elbow 40 is located, and a approximation vis-à-vis the axis 4 and from plan 12.

When the blade 20 has its conformation illustrated in FIG. 3, corresponding to the state of rest, the end zone 31 is spaced from the bottom 41 of the bucket 36, parallel to the axis 4, by a distance D too great for , in the event of accidental appearance of a high voltage between the terminals 17 and 18 of the piezoelectric body 16 while the end zones 27 and 29 of the blades 20 and 21 are disjoined, thus allowing the appearance of a difference in potential between the two electrodes constituted respectively by the bottom 41 of the cup 36 and by the end zone 31 of the blade 21, a spark or an electric arc is formed between the latter, through the zone of the pyrotechnic charge 37 located between them .

On the other hand, thanks to the conformation which has just been described, the blade 21 can also deform plastically or elastically to take the conformation illustrated in FIG. 4, in which its section 241 is applied practically against the upper face 25 of the base 15 with virtually complete disappearance of the elbow 40, passage of the elbow 39 practically at the right angle and sliding of the end zone 31 downward in the passage 38, so that the end zone 31 comes close enough to the bottom 41 of the bucket 36, if necessary by penetrating inside the pyrotechnic charge 37 as illustrated in FIG. 4, so that the distance d, measured parallel to the axis 4, between the electrodes thus formed by the end zone 31 of the blade 21 and the bottom 41 of the bucket 36 allows the creation of a spark or an electric arc between them, to ignite the pyrotechnic charge 37, if the body piezoelectric 16 is subjected parallel to the axis 4 to a compressive stress causing the appearance of a high voltage between its terminals 17 and 18; then, as shown in FIG. 4, the pyrotechnic charge 37 ignites by causing the formation of hot gases which escape from the cavity 33 at the level of the face 34 of the base 14 and, by causing localized deformation of the part 10, ignite the charge of explosion-proof powder 8 itself causing the opening of the container 7 and of the upper cup 11 and the emission of the desired detonating signal.

In the example illustrated in FIGS. 5 and 6, the end zone 30 of the blade 20 is unchanged, with respect to what has been described with reference to FIGS. 3 and 4, as well as its mode of cooperation with the cup 36 housing the charge 37 of an explosive pyrotechnic composition, itself housed inside a cavity 33 similar to the cavity 33 previously described, except that it is moreover filled with a pyrotechnic charge 40 to thermal effect which, in particular, is thus placed in contact with the charge 37 of explosion-proof pyrotechnic composition and is flush with the face 34 of the base 15.

We also find in this example the passage 38 which, however, does not open towards the bucket 36 centrally relative to the latter, that is to say facing its bottom 41, but laterally relative to the bucket 36, opposite the rim 42 thereof.

In this example, the possible deformation capacities of the blade 21 are not used, and the blade 21 runs along the upper face 25 of the base 15, retaining its orientation perpendicular to the axis 4 and to the plane 212, of the terminal 18 from the piezoelectric body 16 to the passage 38, at the level of which it bends downwards at 90 °, in the form of an end zone 31 oriented as described with reference to FIGS. 3 and 4, c 'is to say parallel to the axis 4 and to the plane 12 and turned downwards; parallel to the axis 4, the end zone 31 of the blade 21, constituting a first electrode, is distant from the rim 42 of the cup 36, constituting the second electrode, by a distance δ such that, when a high voltage appears between the terminals 17 and 18 of the pyrotechnic body 16 placed under compressive stress parallel to the axis 4 while the end zones 27 and 29 of the two blades 20 and 21 are mutually disjoint, as illustrated in FIG. 6, it establish between the electrodes thus formed, through the pyrotechnic composition 40, a spark or an electric arc causing the ignition of this charge 40, itself causing the ignition of the charge 37 which in turn causes, after localized deformation of the part 10 opposite the cavity 33, the inflammation of the explosion-proof powder 8 and the phenomena which result therefrom, and which have been described previously with reference to FIGS. 3 and 4.

The geometry of the cavity 33 can be easily determined for a person skilled in the art so that the air gap between the electrodes constituted respectively by the end zone 31 of the blade 21 and by the rim 42 of the cup 36 communicates more widely with the inside of the latter, that is to say with the load 37, than with the outlet of the cavity 33 in the lateral face 34 of the base 15.

The exemplary embodiment illustrated in FIGS. 7 and 8 differs from the exemplary embodiment illustrated in FIGS. 5 and 6 in that the charge 37 of explosion-proof pyrotechnic composition is housed directly in the cavity 33, in the absence of the cup 36 previously described, and completely fills this cavity 33 until it is flush with the lateral face 34 of the base 15; in this case there is no charge 40 of composition with a thermal effect; moreover, in this example, the cavity 33 opens outwards from the base 15 only through the lateral face 34 of the latter.

The blade 21 retains the conformation described with reference to FIGS. 5 and 6, that is to say has as an electrode an end section 31 oriented parallel to the axis 4 and to the plane 212 and penetrating inside the cavity 33 by a passage 38 connecting, inside the base 15, the cavity 33 to the upper face 25 of this base 15.

To compensate for the absence of the bucket 36 as an electrode, the end zone 30 of the blade 20 is curved upwards 90 °, parallel to the axis 4 and to the plane 212, to penetrate into the cavity 33, through the base 15, via a passage 43 arranged in the latter, between its lower face 23 and the cavity 33, in alignment with the passage 38 parallel to the axis 4.

The end zones 30 and 31 of the blades 20 and 21 are thus placed directly opposite one another inside the load 37, and mutually spaced, parallel to the axis 4, by a distance 4 such that the appearance of a high voltage between terminals 17 and 18 of the piezoelectric body 16 while the end zones 27 and 29 of the blades 20 and 21 are mutually disjoint, as shown in Figure 8, causes a spark or a electric arc inside the pyrotechnic charge 37 and, thus, causes it to ignite itself causing localized deformation of the part 10 opposite the cavity 33 and the ignition of the explosion-proof powder 8, with the resulting effects which have been described above.

The example illustrated in FIGS. 9 and 10 presents great analogies with that illustrated in FIGS. 7 and 8 except that the cavity 33 housing the pyrotechnic charge 37 is placed inside the container 7 instead of be separated from it, in the idle state, by part 10.

To this end, in comparison with the examples described above, the base 15 is extended in the direction of a distance from the plane 212, on the side 32 thereof, until it penetrates inside the container 7, and the cavity 35 is arranged in the upper face 25 of the base 15.

Correlatively, the end zone 31 of the blade 21 is oriented perpendicular to the axis 4 and to the plane 12, and rotated in the direction of a distance with respect to the latter, to enter the cavity 35 through a passage 38 itself even perpendicular to the plane 212; the blade 20, meanwhile, curves 90 ° upwards to go along the side face 34 of the base 15 in the direction of a distance from the plane 12 on the side 32 thereof, then curves again at 90 ° to enter the cavity 33 through a passage 43 aligned with the passage 38 perpendicular to the plane 12; the extreme zone 30 of the blade 20 thus forms a return towards the axis 4 and the plane 212 through the passage 43, and thus penetrates into the cavity 33, as well as into the pyrotechnic charge 37, directly opposite the extreme zone 31 of the blade 21 and at a distance Δ from the latter defined as above.

Thus, when the piezoelectric body 16 is subjected to a compressive stress causing the appearance of a high voltage between its terminals 17 and 18 and assuming that the end zones 27 and 29 of the blades 20 and 21 are separated as the shows figure 10, between the extreme zones 30 and 31 of these blades 20 and 21 appears a spark or an electric arc which causes the ignition of the pyrotechnic charge 37 and, consequently, that of the explosive powder 8, with the phenomena which ensue and which have been described previously.

Naturally, in accordance with the function with which a firecracker is intended, the deflagration of the powder 8 and the phenomena which cause this deflagration in both of the previously described exemplary embodiments must result from the crushing of the firecracker 1, and more precisely of the upper cup 11 thereof, by a wheel of a railway vehicle, that is to say of the application to the cup 11 of a load directed along the axis 4 as indicated in F or in a direction forming an angle of the order of a few degrees with respect to this axis as indicated in F₁; naturally, the upper cup 11 is designed to withstand without crushing loads thus applied remaining below a predetermined threshold, and to crash only for loads thus applied exceeding this predetermined threshold, which results in a rapprochement of its central zone 12 with respect to the lower cup 5 either with preservation of their mutual parallelism as illustrated in the left half of FIGS. 4, 6, 8, 10, or by taking an obliquity of the zone 12 relative to the lower cup 5, with mutual approximation in the direction of a distance from the plane 212, as illustrated in the right half of Figures 4, 6, 8, 10; naturally, these considerations relate only to an initial phase of the crash, which then leads to total destruction of the firecracker of track 1.

To detect the application of a load parallel to axis 4 or forming an angle of only a few degrees with respect to it and exceeding a predetermined threshold, that is to say to detect the consecutive approach of the area central 12 of the upper cup 11 relative to the lower cup 5, with or without skew, between this central zone 12 and the base 15 is interposed in each of the examples illustrated in Figures 3 to 10 a pedal 44 guided in sliding parallel to the axis 5 relative to the base 15, between a limit rest position illustrated in FIGS. 3, 5, 7, 9, which constitutes for this pedal 44 a high position, and a limit activation position illustrated in FIGS. 4 , 6, 8, 10, which constitutes for this pedal a low position in which the pedal 44 subjects the piezoelectric body 16 to a compressive stress along the axis 4 under conditions such that there is appearance between the terminals 17 and 18 of the piezoelectric body 16 of a high voltage causing sparking between the electrodes formed either by the cup 36 and the end zone 31 of the blade 21 (Figures 4 and 6), or by the end zones 30 and 31 of the blades 20 and 21 (Figures 8 and 10), after that the end zones 27 and 29 of the blades 20 and 21 have been mutually dissociated.

To this end, the pedal 44 is constituted, identically in the various examples illustrated, of two parts at the rate of a plate 45 electrically insulating and capable of breaking by shearing, and for example of plastic, and of a pushing body 46 advantageously metallic.

The plate 45 has a generally flat shape, perpendicular to the axis 2, between a curved upper face 47, placed in contact with the central zone 12 of the upper cup 11 at the level of the axis 4 and immediately around it , and a flat lower face 48 perpendicular to the axis 4 and placed opposite the upper face 25 of the base 15.

In the rest position, illustrated in FIGS. 3, 5, 7, 9, the pedal 44 rests locally by its face 48 on columns 49 forming an integral part of the base 15 relative to the upper face 25 of which these columns 49 form localized projections parallel to the axis 4, over the same height h measured from the blade 21 in the zones of the latter directly superimposed on the face 25.

Under the lower face 48 of the pedal 44 is provided by making in one piece a stud 50 forming under this face 48, parallel to the axis 4, a projection over a distance approximately identical to h so that, in the position rest illustrated in Figures 3, 5, 7, 9, this stud 50 is placed immediately above the end zone 27 of the blade 20 overhanging above the cavity 28 of the base 15 but so slightly offset, in the direction of a distance from the plane 212, relative to the end zone 29 of the blade 21. It is noted that the presence of this stud 50 does not cause dissociation of the end zones 27 and 29 of the blades 20 and 21 when the pedal 44 is in the rest position.

To allow the pedal 44 to gain its activation position when the central zone 12 of the cup 11 tends to collapse under the effect of a load exceeding a predetermined threshold, applied either parallel to the axis 4, or at an angle of the order of a few degrees relative to this axis, the plate 45 has, opposite each of the columns 49, in its face 44, a respective cutout 51 releasing opposite the associated column 49 a respective tongue 52 constituting the support means of the plate 45 on the corresponding column 49 respectively, this tongue 52 being placed in cantilever with respect to the rest of the plate 45 and connected to the latter by a bridge of material 53 having parallel to the axis 4 an even lesser thickness, calibrated so that this bridge of material 53 breaks by shearing when the plate 45 receives parallel to axis 4 or at an angle of a few degrees relative thereto a force exceeding said predetermined threshold.

Then, as shown in FIGS. 4, 6, 8, 10, the material bridges 53 break and the plate 45, disjointed from the tongues 52 which remain retained by the columns 49, can descend towards the base 15, over a stroke h , until its face 48 rests on this face 25 by means of the blade 21.

In each of the exemplary embodiments illustrated in FIGS. 3 to 10, this results in the insertion of the end region 27 of the blade 20 into the cavity 28 of the base 15 under the action of the stud 50, that is to say say by the opening of the short circuit created by the end zones 27 and 29 of the blades 20 and 21, between the terminals 17 and 18 of the piezoelectric body 16, in the rest position. In addition, in the case of the example illustrated in Figures 3 and 4, this results in a crushing of the blade 21 between the elbow 44 and the end section 31, and by the penetration of the latter into the bucket 36, up to the aforementioned distance d from the bottom 41 thereof as shown in FIG. 4.

In addition, this descent of the plate 45 under the effect of a suitably oriented load, exceeding said determined threshold, must be accompanied by the application, to the piezoelectric body 16, of an axial compression stress capable of causing the appearance of a spark or an electric arc between the electrodes formed as indicated above.

This compressive stress is applied by the thrust body 46, integral with the plate 45 and more precisely retained integrally inside a blind hole 151 drilled along the axis 4 in the lower face 48 of this plate 45.

More specifically, the blind hole 151 is delimited by an inner peripheral face 152 which is cylindrical of revolution around the axis 4, with a radius less than the distance separating therefrom the stud 50 from the face 48 in each of the examples illustrated in Figures 3 to 10, the passage 38 in the examples illustrated in Figures 3 to 8, the cavity 35 in the example illustrated in Figures 9 and 10, and the columns 49, in practice located in the immediate vicinity of the side faces 24 and 34 of the base 15 so as to make it possible to locate the tongues 52 at the periphery of the plate 45 in each of these examples. The blind hole 151 is further delimited by a concave bottom face 153, also of revolution around the axis 4.

The thrust body 46, meanwhile, has a head 54 for securing with the plate 45, which head 54 is defined respectively in the direction of a distance from the axis 4 and upwards by an outer peripheral face 55 cylindrical of revolution around the axis 4 with a radius identical to that of the inner peripheral face 152 of the blind hole 151 and by an upper face 56 convex, of revolution around the axis 4 and closely complementary to the bottom face 153 from blind hole 151.

Downwards, the head 54 is delimited by a flat lower face 57, annular of revolution around the axis 4, which face 57 is connects in the direction of a distance from the latter to the outer peripheral face 55 and is set back from the lower face 48 of the plate 45, parallel to the axis 4, a distance H greater than h .

In the direction of approximation with respect to the axis 4, the lower face 57 of the head 54 is connected to a hammer 58 produced in one piece with the head 54, and more precisely to a cylindrical outer peripheral face 59 of revolution around axis 4, of this hammer 58.

This outer peripheral face 59, with a radius less than that of the inner peripheral face 152 of the blind hole 51 and at most equal to the radius of the housing 19, assumed to be cylindrical of revolution around the axis 4, or to the radius of a geometric cylinder of revolution around this axis 4 and inscribed in this housing 19, extends downwards, from the lower face 57 of the head 54, over the aforementioned distance H, and is connected downwards to one face lower plane 60 of the hammer 58, which face is perpendicular to the axis 4 and thus coplanar with the lower face 48 of the plate 45.

The lower face 60 of the hammer 58 is thus placed opposite the piezoelectric body 16 along the axis 4, with the interposition of the blade 21, and is separated from the height h, with respect to this blade 21, in the rest position illustrated in FIGS. 3, 5, 7, 9. On the other hand, when the pedal 44, comprising the plate 45 and the thrust body 46 behaving as a whole, descends from the stroke h relative to the base 15 to gain the activation position illustrated in FIGS. 4, 6, 8, 10, the face 60 of the hammer 58 comes into contact with the blade 20 to apply to the piezoelectric body 16, by means of the latter, the compressive stress along the axis 4 capable of causing the appearance between the terminals 17 and 18 of the piezoelectric body 16 of a high voltage, itself resulting in sparking between the electrodes defined above, the extreme zones 27 and 29 of blades 20 and 21 being dissociated from each other.

During the descent of the pedal 44 towards the base 15, the outer peripheral face 59 of the hammer 58 and the inner peripheral face 152 of the blind hole 151 provide a function of guiding the plate 45 with respect to the base 15, such so that the plate 45 substantially retains its general orientation perpendicular to the axis 4.

To this end, around the housing 19 and more precisely respectively on either side of the blade 20, the base 15 has projecting on its upper face 25, advantageously by making in one piece, two partial crowns 61 mutually symmetrical by with respect to plane 13 and respectively symmetrical with respect to plane 12.

Delimited towards the plane 13 by plane faces 62 parallel to this plane 13, the partial rings 61 are delimited in the direction of approximation with respect to the axis 4 by an inner peripheral face 63 cylindrical of revolution around this axis 4 with a diameter substantially identical to that of the outer peripheral face 59 of the hammer 58 and in the direction of a distance with respect to the axis 4 by an outer peripheral face 64 also cylindrical of revolution around the axis 4 , with a diameter substantially identical to that of the inner peripheral face 152 of the blind hole 151. Upwards, each of the partial rings 61 is delimited by a flat upper face 65 perpendicular to the axis 4, and located at a level greater than that of the blade 21, in the zones thereof directly superimposed on the upper face 25 of the base 15, by a distance greater than h and at most equal to H, and for example equal to H in the example illustrated, if one refers to the state of rest illustrated in FIGS. 3, 5, 7, 9.

Thus a sliding sliding guide contact is established parallel to the axis 4 between the outer peripheral face 59 of the hammer 58 and the inner peripheral face 63 of the partial rings 61, on the one hand, and between the outer peripheral face 64 of these partial rings 61 and the inner peripheral face 152 of the blind hole 151, on the other hand, without hindrance in passing the plate 45 from the rest position illustrated in FIGS. 3, 5, 7, 9 to the activation position illustrated in FIGS. 4, 6, 8, 10.

A person skilled in the art will easily understand that the various embodiments of a lane firecracker according to the invention, as well as the various embodiments of the piezoelectric ignition device 9, which have just been described only constitute nonlimiting examples, with respect to which numerous variants may be provided without departing from the scope of the present invention.

A person skilled in the art will also easily transpose the arrangements which have just been described in the case of a firecracker to the production of a mine, characterized in particular by the replacement of the explosion-proof powder 8 by a military charge and by the presence of well-known safety features in the mining sector.

More particularly in the case of the track firecracker, a variant may consist in dissociation of the single unit integrally mounted on the head of a rail, constituted by the firecracker track 1 described with reference to FIGS. 1 to 10, in two units, one of which will be mounted on the head of a rail and the other juxtaposed to the rail and each of which will comprise a respective part 9a, 9b of the piezoelectric ignition device according to the invention, as will now be described in reference to FIG. 11 where these two units have been designated by 66 and 67 respectively.

• le conteneur 7 ne contient pas de poudre déflagrante 8, celle-ci pouvant être remplacée par un matériau de remplissage non représenté, propre à communiquer au conteneur 7 une certaine résistance à l'écrasement tout en étant propre à s'écraser lorsqu'une charge dépassant ledit seuil prédéterminé est appliquée à l'unité 66 suivant une direction parallèle à l'axe 4 ou formant un angle de quelques degrés par rapport à celui-ci ; à titre de matériau de remplissage, on peut utiliser par exemple une structure alvéolaire, comme on en connaît dans les domaines de l'armement et de l'aéronautique ;
• le socle 15 ne comporte pas de cavité 33 et ne contient pas de composition pyrotechnique 37, et les zones extrêmes 30 et 31 des lames 20 et 21 ne sont pas placées en regard l'une de l'autre pour constituer des électrodes, mais sont raccordées électriquement et mécaniquement, par tout moyen approprié tel que soudure, vissage ou enfichage, à des conducteurs électriques souples 68, 69 d'un câble de raccordement électrique 70 qui sort de l'unité 66, par exemple en traversant des trous respectifs non représentés de la pièce 10 et de la zone 13, également non représentée, de la coupelle supérieure 11, pour assurer un raccordement électrique mutuel des deux unités 66 et 67.

In the exemplary embodiment illustrated in FIG. 11, the unit 66 intended to be fixed on the head of the rail is identical in its geometry and its composition to the firecracker illustrated in FIGS. 1 and 2, in the exemplary embodiment detailed in FIG. 9 and found in FIG. 11, to designate the components of the unit 66, the same references as in FIG. 9, except that:

• the container 7 does not contain any explosion-proof powder 8, which can be replaced by a filling material not shown, capable of imparting to the container 7 a certain resistance to crushing while being capable of crushing when a load exceeding said predetermined threshold is applied to the unit 66 in a direction parallel to the axis 4 or forming an angle of a few degrees from it; as filling material, it is possible to use, for example, a honeycomb structure, as is known in the fields of armaments and aeronautics;
• the base 15 does not have a cavity 33 and does not contain a pyrotechnic composition 37, and the end zones 30 and 31 of the blades 20 and 21 are not placed opposite one another to form electrodes, but are electrically and mechanically connected, by any suitable means such as welding, screwing or plugging, to flexible electrical conductors 68, 69 of an electrical connection cable 70 which leaves the unit 66, for example by crossing respective holes not shown of part 10 and of zone 13, also not shown, of upper cup 11, to ensure mutual electrical connection of the two units 66 and 67.

Naturally, the geometry and the composition of the unit 66 can also be different taking into account the absence of explosion-proof powder 8 and any other pyrotechnic composition; in particular, the content 7 and the aforementioned possible material for filling it can be eliminated, and the envelope formed by the cups 5 and 11 be modified accordingly in its geometry and its design, it being understood that it must remain suitable for being crushed by a wheel of a railway vehicle, with actuation of the pedal 44.

The unit 67 comprises, for its part, a metal casing 71 advantageously produced by mutual crimping 74 of a lower cup 72 and of an upper cup 73 having shapes analogous to those of the lower cup 5 and to that of the upper cup 11 firecracker lane 1, respectively.

Inside the metal casing 71 thus formed, a bottom piece 75 made of plastic material and lining the lower cup 72 and a piece 76 also made of plastic material and lining the upper cup 73 delimit a container 77 with explosion-proof powder 78.

In a central position inside this container 77, the part 75 delimits a cavity 79 containing a pyrotechnic charge 80 at any point similar to the pyrotechnic charge 37; the cavity 79 is open, so that this pyrotechnic charge 80 is placed in direct contact with the deflagrating powder 78, as in the example of embodiment of the firecracker 1 illustrated in FIGS. 9 and 10.

Two metal blades 81, 82 housed in a protuberance 83 of the part 75 and thus electrically isolated from each other have free end zones 84, 85 located inside the cavity 79, facing one another, and mutually spaced apart from the aforementioned distance 4, suitable for allowing the formation of a spark or an electric arc between them, through a zone of the load 80, when the blades 81 and 82 are supplied with high voltage, and free ends 86, 87 opening to the outside of the metal casing 71, in a connector 88 suitable for receiving the cable 70 while ensuring electrical continuity between the conductor 68 and the free end 86 of the blade 81, of a part, and between the conductor 69 and the free end 87 of the blade 82, on the other hand.

It is understood that insofar as the operation of the unit 67 is not dependent on it being crushed by a wheel of a railway vehicle, its geometry and its composition may also be different.

It is easily understood that when the unit 66 receives a load exceeding the aforementioned predetermined threshold, applied parallel to its axis 4 or at an angle of a few degrees relative to this axis, the pedal 44 leaves its rest position, illustrated in FIG. 11, to gain his position activation, analogous to the position of the pedal illustrated in FIG. 10, which separates the end zones 27 and 29 from the blades 20 and 21, on the one hand, and applies compression to the piezoelectric body 16 according to the axis 4, resulting in the appearance of a high voltage between its terminals 17 and 18. This high voltage is transmitted by conductors 68 and 69 to the electrodes formed by the end zones 84 and 85 of the blades 81 and 82, at the inside the unit 67, which causes the appearance of a spark or an electric arc between these electrodes and the ignition of the charge 80 which, itself, ignites the powder 78 and causes its deflagration, with opening of the metal casing 71.

Naturally, although a person skilled in the art readily understands that it is preferable, as a safety against accidental ignition of the explosion-proof powder 8 or 78, to provide at least one mechanical safety constituted in the various examples illustrated by the support of the pedal 44 via the tabs 52 on the columns 49 of the base 15, in the rest position, and at least one electrical safety device, constituted in these different examples by the short circuit established between the terminals 17 and 18 of the piezoelectric body 16 in the rest position and, in the example illustrated in FIGS. 3 and 4, by a distance D, between the electrodes, excessive to allow the formation of an electric arc or a spark between them under the effect of the high voltage possibly generated between the terminals 17 and 18 of the piezoelectric body 16, some of these safeties could be omitted.

In addition, for electrical safety, provision could be made for the circuit between the terminals 17 and 18, on the one hand, and the electrodes, on the other hand, to be open in the rest position, in particular at the level of the blade 21 then produced in two superimposable but mutually separate parts in the rest position, and closes by mutual junction of these two parts in the activation position; a person skilled in the art will easily realize such security from the arrangements described with regard to the free end zones 27 and 29 of the blades 20 and 21 and the automatic opening of the circuit between them when the pedal 44 descends towards the base 15.

Such a possibility of ensuring the electrical connection between the spark electrodes and the terminals of the piezoelectric body by a circuit open in the rest position and closing automatically in the activation position is illustrated in FIGS. 13 and 14, in the case of an embodiment of a variant, illustrated generally in FIG. 12, of an embodiment of the track firecracker described with reference to FIGS. 1 to 10.

• la coupelle inférieure 5, approximativement horizontale dans une position d'utilisation, illustrée à la figure 12, dans laquelle le pétard 89 repose par cette coupelle inférieure 5 sur le champignon 2 d'un rail sur lequel il est retenu provisoirement par des griffes 3 fixées sur la coupelle inférieure 5 par exemple au moyen d'un rivet 90 disposé suivant un axe 4, alors approximativement vertical, autour duquel le pétard 89 présente une forme générale de révolution ;
• la pièce 6 qui, à la différence de celle qui a été décrite en référence aux figures 1 à 10, définit non seulement le conteneur 7 à poudre déflagrante 8, présentant la forme générale annulaire précédemment décrite, mais également une paroi périphérique intérieure 91, tubulaire de révolution autour de l'axe 4 pour délimiter le conteneur 7 vers cet axe 4, en l'absence d'une pièce correspondant à la pièce 10 décrite en référence aux figures 1 à 10 ; la paroi 91 est munie de larges lumières 92 obturées par un paillet 93 empêchant la migration de la poudre 8 vers l'axe 4 sans constituer d'obstacle au passage de gaz chaud à l'actionnement du pétard 89 ; la paroi 91 présente en outre, axialement à l'opposé de son raccordement avec la zone de la pièce 6 formant le fond du conteneur 7, un rebord annulaire 94 tourné vers l'axe 4, s'éloignant de la coupelle inférieure 5 dans le sens d'un rapprochement vis-à-vis de cet axe 4 et délimitant autour de celui-ci une ouverture 95 ;
• un dispostif d'allumage 9 dont deux exemples de réalisation seront décrits respectivement en référence aux figures 13 et 14, 15 et 16 et qui est disposé suivant l'axe 4, à l'intérieur du volume délimité autour de celui-ci par la paroi 91, son rebord 94 et une zone de la coupelle inférieure 5 localisée entre la paroi 91 et l'axe 4 compte tenu de la conformation de la pièce 6 dans ce mode de réalisation, et porté par la coupelle inférieure 5 sur laquelle ce détonateur 9 est avantageusement fixé au moyen du rivet 90 précité ;
• la coupelle supérieure 11 enfermant avec la coupelle inférieure 5, sur laquelle elle est fixée par un sertissage périphérique 14, la pièce 6 sur laquelle elle s'appuie vers le bas à proximité immédiate du sertissage 14, d'une part, et au niveau du rebord annulaire 94, d'autre part, le conteneur 7 à poudre déflagrante 8, que la coupelle supérieure 11 délimite pour partie directement en l'absence de pièce 10, et le dispositif d'allumage 9.

If one refers to FIGS. 12, 13 and 14 as well as to FIGS. 15 and 16 which show another embodiment of this variant, it can be seen that the firecracker 89 illustrated in these figures has great analogies with that which has been described with reference to FIGS. 1 to 10, in the sense that there are found there, approximately identical unless otherwise stated:

• the lower cup 5, approximately horizontal in a position of use, illustrated in FIG. 12, in which the firecracker 89 rests by this lower cup 5 on the mushroom 2 of a rail on which it is temporarily retained by claws 3 fixed on the lower cup 5 for example by means of a rivet 90 disposed along an axis 4, then approximately vertical, around which the firecracker 89 has a general shape of revolution;
• the part 6 which, unlike that which has been described with reference to FIGS. 1 to 10, defines not only the container 7 with explosion-proof powder 8, having the general annular shape previously described, but also an inner peripheral wall 91, tubular of revolution around the axis 4 to delimit the container 7 towards this axis 4, in the absence of a part corresponding to the part 10 described with reference to Figures 1 to 10; the wall 91 is provided with large openings 92 closed by a flake 93 preventing the migration of the powder 8 towards the axis 4 without constituting an obstacle to the passage of hot gas when the firecracker 89 is actuated; the wall 91 also has, axially opposite its connection with the area of the part 6 forming the bottom of the container 7, an annular rim 94 facing the axis 4, moving away from the lower cup 5 in the sense of approximation with respect to this axis 4 and delimiting around it an opening 95;
• an ignition device 9, two embodiments of which will be described respectively with reference to FIGS. 13 and 14, 15 and 16 and which is arranged along the axis 4, inside the volume delimited around it by the wall 91, its rim 94 and an area of the lower cup 5 located between the wall 91 and the axis 4 taking into account the conformation of the part 6 in this embodiment, and carried by the lower cup 5 on which this detonator 9 is advantageously fixed by means of the aforesaid rivet 90;
• the upper cup 11 enclosing with the lower cup 5, on which it is fixed by a peripheral crimp 14, the part 6 on which it rests down in the immediate vicinity of the crimp 14, on the one hand, and at the level of the annular rim 94, on the other hand, the container 7 with explosion-proof powder 8, which the upper cup 11 partly delimits directly in the absence of part 10, and the ignition device 9.

The lower cup 5 retains the generally flat shape, perpendicular to the axis 4, previously described while, to maintain its ability to be crushed by a wheel 96 of a rail vehicle despite a greater height depending on the axis 4 due to a greater height of the ignition device 9 along this axis 4, in comparison with the embodiment of the firecracker described with reference to FIGS. 1 to 10, the upper cup 11 has between its central zone 12, flat, and its peripheral zone 13, frustoconical, by which the crimping takes place 14 on the lower cup 5, an intermediate zone also frustoconical of revolution around the axis 4, diverging from the central zone 12 towards the peripheral zone 13 with an angle at the top of the cone (not referenced) greater than that of the zone 13; this angle, which coincides with that of the rim 94 on which the upper cup 11 poses by this intermediate zone 97, is such that a wheel 96 with an average diameter, among the most usual diameters in the field of railways, approaching the firecracker 89 while rolling on the rail in any longitudinal direction 98, is applied tangentially to this intermediate zone 97, to then cause the firecracker 89 to be crushed, initially by plastic deformation of the upper cup 11.

The greater height of the ignition device 9 in the case of the embodiments illustrated in Figures 13 and 14 and in Figures 15 and 16 results from the fact that its components, essentially functionally similar to those of the ignition devices 9 described with reference to FIGS. 4, 5 and 6, 7 and 8, 9 and 10, in these two cases are essentially superimposed mutually along axis 4 instead of being at least partly mutually juxtaposed perpendicular to this axis 4, which simplifies the manufacture of the firecracker and makes it more economical without compromising the reliability of this firecracker, reducing the size of the ignition device 9 around the axis 4 and therefore d '' increase the volume of the container 7 of the load 8 for an identical diameter of the lower cup 5 and, in the case of the embodiment illustrated in Figures 15 to 16, to provide in a particularly simple way a possibility of function operation of the firecracker not only by crushing but also by percussion, to best respond to the different speed conditions under which it can be approached by a wheel 96.

As in the case of the embodiments illustrated in Figures 3 and 4, 5 and 6, 7 and 8, 9 and 10, the ignition devices 9 of the embodiments illustrated in Figures 13 and 14, 15 and 16 include a base rigid 15, electrically insulating, which constitutes a lower part thereof; taking into account the conformation of the part 6 in the embodiments illustrated in FIGS. 13 and 14, 15 and 16, this base 15 is no longer carried by this part 6 but by the lower cup 5, in an area thereof located between the axis 4 and the wall 91, and it is fixed to the lower cup 5 for example by means of the above-mentioned rivet 90 and a counter-riveting washer 99 ensuring the support of the rivet 90 on the lower cup 5.

Along axis 4, above the rivet 90 and the counter-riveting washer 99, the base 15 has a housing 19 in which is retained, against any radial movement with reference to axis 4, the piezoelectric body 16, however released from the base 15 downwards and upwards, along the axis 4. The piezoelectric body 19, designed and arranged so as to be sensitive to compression along the axis 4, has respectively downward and upward its terminals 17 and 18, between which a high voltage appears in the case of such compression along axis 4.

Given the presence of the rivet 90 and the counter-riveting washer 99, the cavity 19 opens downwards, not directly into a lower face 23, flat and perpendicular to the axis 4, by which the base 15 is supported. on the lower cup 5, but in a cavity 100 arranged in an area of the face 23 located around the axis 4 to receive the rivet 90 and the washer 99 of counter-riveting inside the base 15.

Between terminal 17 of the piezoelectric body 16 and the rivet 90 is trapped in an integral manner, inside the base 15, a metal strip 20 thus placed in electrical conduction contact with terminal 17 of the piezoelectric body 16.

The blade 20 is in all respects comparable to the blade 20 of the embodiments described with reference to FIGS. 3 and 4, 5 and 6, 7 and 8, 9 and 10 except for the fact that it is partially located at inside the cavity 100. In particular, it is flat, perpendicular to the axis 4 and to a plane passing through this axis 4 and corresponding for example, as illustrated, to the plane 213 while it is symmetrical with respect to another plane also passing through the axis 4 but perpendicular to the aforementioned plane, and then corresponding to the plane 212. Like the blades 20 previously described, it has on one side of the axis 4 an extreme zone 30 which is however housed inside the cavity 100; on the other side of axis 4, it extends until it leaves base 15 by a passage 101 arranged in it, radially with reference to axis 4, between cavity 100 and a lateral face 24 or outer peripheral face, cylindrical of revolution around the axis 4, delimiting the base 15 in the direction of a distance with respect to the axis 4 and thus facing the inner peripheral wall 91 of the part 6; at the level of this lateral face 24, the blade 20 bends upwards, at a right angle, that is to say so as to be locally oriented parallel to the axis 4, to go along this lateral face 24 then at again at a right angle, this time towards the axis 4, to penetrate again inside the base 15 in the form of a return 26 perpendicular to the axis 4, by another passage 102 arranged in the base 15, radially with reference to axis 4, and joining the lateral face 24 to a cavity 103, annular of revolution around the axis 4, that the base 15 has around the housing 19 of the piezoelectric body 16. In fact, in the case of the embodiments illustrated in FIGS. 13 and 14, 15 and 16, the lateral face 24 of the base 15 extends upwards to a level higher than that of the upper terminal 18 of the piezoelectric body 16 although lower than that of the annular rim 94 of the wall 91 of the part 6 so that the base 15 does not constitute ue not an obstacle to the actuation of the firecracker 89 by crushing the upper cup 11, and is connected upwards to an upper face 25 which is certainly plane and perpendicular to the axis 4 as previously described, but has an annular shape of revolution around the axis 4; this upper face 25 thus connects the lateral face 24 to an inner peripheral face 104 also cylindrical of revolution around the axis 4 but turned towards the latter, so as to delimit the cavity 103 in the direction of a distance from this axis 4.

Downward, this face 104 in which the passage 102 opens towards the axis 4, as well as other passages 105 arranged in the base 15 in a regularly distributed angular fashion around the axis 4 and also opening into the face lateral 24 of the base 15, is connected to an annular shoulder, plane 205, of revolution around the axis 4 and turned upwards, having, facing the passage 102, a localized notch, not referenced, for receiving the return 26, which is flush this shoulder 205 upwards.

Towards axis 4, the shoulder 205 is connected to a cylindrical face 106 of revolution around the axis 4, turned towards the latter and into which the passages 105 also open out. Downwards, this face 106 is connected to a annular, flat face 107, of revolution about the axis 4 to which it is perpendicular, which face 107 defines the bottom of the cavity 103. Towards axis 4, this bottom face 107 is connected to a cylindrical face 108 of revolution around the axis 4 and turned in the direction of a distance from the latter, towards which this face delimits the cavity 103, around the housing 19 of the piezoelectric body 16. This face 108 connects the face 107, upwards, to an upper face 109, annular, planar, of revolution about the axis 4, which face 109 is turned upwards like the upper face 25 but placed at a level below that thereof, and surrounds the housing 19 of the piezoelectric body 16 either directly (Figures 13 and 14), or by means of a recess 114, annular of revolution around the axis 4 (Figures 15 and 16).

Towards this axis 4, the return 26 of the blade 20 extends approximately until the connection of the shoulder 205 with the face 106 and is connected to a free end zone 27 turned at right angles, upwards, so as to form a hook with the return 26 immediately above the face 106.

By the free end zone 27 forming a hook, the blade 20 is in permanent engagement with a metal washer 110 having a general shape of revolution around the axis 4 and comprising in particular a radially external zone 111, with reference to the axis 4, by which it rests flat on the shoulder 205 and, locally, on the return 26 so as to be thus placed in electrical conduction contact with this return 26, which places it in permanent relation of electrical conduction with the terminal 17 of the piezoelectric body 16.

The radially outer zone 111 of the washer 110 is continuous, flat, perpendicular to the axis 4 and extends towards the latter from the face 104 to the level of the face 106, to which it is connected to a zone 112 radially inner with reference to axis 4, which zone 112 is in the form of teeth 113 oriented approximately radially with reference to axis 4 and regularly distributed angularly around it, defining between them notches not referenced in one of which is engaged the free end zone 27.

The teeth 113 are thus placed cantilevered towards the axis 4 relative to the face 106, inside the cavity 103, and extend towards the axis 4 as close to the face 108 without however coming into contact with it. They can flex plastically or, preferably, elastically, in particular downwards, and are calibrated so as to be able to flex when a wheel 98 imposes on the upper cup 11 a load F or F₁, as defined above, exceeding a threshold predetermined chosen as the load limit value capable of causing actuation of the firecracker 39 by crushing; on the other hand, they cannot bend under the sole weight of a pedal 44 which, in the embodiments of FIGS. 13 and 14, 15 and 16 as in the case of the embodiments of FIGS. 3 and 4, 5 and 6, 7 and 8, 9 and 10, serves as a transmission intermediary to the piezoelectric body 16, in the form of a compressive stress applied along the axis 4, of the crushing of the upper cup 11 by a wheel 96, y included in the assumption that the firecracker 89 is accidentally subjected to shocks, and even if these shocks are oriented along the axis 4.

The pedal 44 produced differently depending on whether reference is made to the embodiment of FIGS. 13 and 14 or to the embodiment of FIGS. 15 and 16.

We will first refer to Figures 13 and 14, observing that in this case, the terminal 18 of the piezoelectric body 16 is flush with the upper face 109 with respect to which it can also form a slight upward projection, with reference to the axis 4, with a view to direct cooperation with the pedal 44 when a wheel 96 applies a downward push to the latter, by crushing the upper cup 11.

In this case, the pedal 44 consists of the integral assembly, by any appropriate means, of four parts 115, 116, 117, 118 which will now be described with reference to FIGS. 13 and 14.

• une face périphérique intérieure 119, cylindrique de révolution autour de l'axe 4 avec un diamètre qui coïncide sensiblement avec celui de la face 108 que cette face périphérique intérieure 119 épouse entre la face 109 et le niveau des dents 113 si l'on se réfère à la position de repos illustrée à la figure 13, et de la face 109 jusqu'à proximité immédiate de la face 107 dans la position d'activation illustrée à la figure 14, de façon à définir une relation de guidage au coulissement relatif suivant l'axe 4 entre l'une et l'autre de ces positions limites illustrées respectivement aux figures 13 et 14 ;
• une face de fond 120, plane, perpendiculaire à l'axe 4 et tournée vers le bas, laquelle face de fond 120 se limite à une bande annulaire localisée à proximité immédiate de la face 119, autour de la pièce 116 qui sera décrite plus loin, et se trouve placée en regard de la face 109 dont elle est sensiblement espacée dans la position de repos illustrée à la figure 13 alors qu'elle est placée à proximité immédiate de celle-ci dans la position illustrée à la figure 14 ;
• une face annulaire, plane 121, de révolution autour de l'axe 4 auquel elle est perpendiculaire, cette face 121 que la face 119 raccorde à la face 120 étant tournée vers le bas, en regard de la face de fond 107 de la cavité 103, et reposant vers le bas sur les dents 113 de la rondelle 110 lorsque celles-ci ne sont pas déformées ou subissent une simple précontrainte de flexion vers le bas parallèlement à l'axe 4 comme le montre la figure 13, alors que cette face 121 est placée à proximité immédiate de la face de fond 107 de la cavité 103 sans toutefois entrer en contact avec cette face de fond 107 dans la position d'activation illustrée à la figure 14 ;
• une face périphérique extérieure 122, pour l'essentiel cylindrique de révolution autour de l'axe 4 et tournée dans le sens d'un éloignement par rapport à celui-ci, laquelle face 122 relie la face 121, vers le haut, à une face supérieure 123 annulaire, plane, de révolution autour de l'axe 4 auquel elle est perpendiculaire.

The part 115, made of electrically insulating material and for example plastic, ensures the mounting of the pedal 44 to slide along the axis 4 on the face 108 of the base 15 as well as, in part, the retention of the pedal 44 in the rest position illustrated in FIG. 13, by pressing on the teeth 113 of the zone 112 of the washer 110, not deformed or, if it has a certain elasticity, placed in slight pre-stress in bending of these teeth 113 downwards. For this purpose, the part 115 has the general shape of an inverted pot, of revolution around the axis 4, defined by:

• an inner peripheral face 119, cylindrical of revolution around the axis 4 with a diameter which substantially coincides with that of the face 108 which this inner peripheral face 119 matches between the face 109 and the level of the teeth 113 if we refer in the rest position illustrated in FIG. 13, and from the face 109 to the immediate proximity of the face 107 in the activation position illustrated in FIG. 14, so as to define a guide relation to relative sliding according to the axis 4 between one and the other of these limit positions illustrated respectively in FIGS. 13 and 14;
• a bottom face 120, flat, perpendicular to the axis 4 and facing downwards, which bottom face 120 is limited to an annular strip located in the immediate vicinity of the face 119, around the part 116 which will be described later , and is placed facing the face 109 from which it is substantially spaced in the rest position illustrated in FIG. 13 while it is placed in the immediate vicinity thereof in the position illustrated in FIG. 14;
• an annular, flat face 121, of revolution about the axis 4 to which it is perpendicular, this face 121 which the face 119 connects to the face 120 being turned downward, facing the bottom face 107 of the cavity 103 , and resting down on the teeth 113 of the washer 110 when these are not deformed or undergo a simple downward bending preload parallel to the axis 4 as shown in Figure 13, while this face 121 is placed in the immediate vicinity of the bottom face 107 of the cavity 103 without however coming into contact with this bottom face 107 in the activation position illustrated in FIG. 14;
• an outer peripheral face 122, essentially cylindrical of revolution around the axis 4 and turned in the direction of a distance from it, which face 122 connects the face 121, upwards, to a face upper 123 annular, flat, of revolution about the axis 4 to which it is perpendicular.

Rectilinear grooves 124, parallel to the axis 4 and regularly distributed angularly around it, are arranged in the outer peripheral face 122 of the part 115, from the upper face 123 thereof to its lower annular face 121, for a purpose which will emerge from the following description.

• une face inférieure 224 plane, perpendiculaire à l'axe 4 et placée en regard de la borne 18 du corps piezo-électrique 16, dont elle est espacée suivant l'axe 4 dans la position de repos illustrée à la figure 13 alors qu'elle est en appui vers le bas sur cette borne 18, dans des conditions propres à appliquer au corps piezo-électrique 16, par ailleurs en appui par sa borne 17 sur la lame 20 et, par l'intermédiaire de celle-ci, sur le rivet 90, une compression elle-même propre à provoquer l'apparition d'une haute tension entre ces bornes 17 et 18, dans l'état d'activation illustré à la figure 14 ;
• vers le haut, la forme d'un pic 125 par exemple tronconique de révolution autour de l'axe 4 de façon à se rétrécir vers le haut, lequel pic 125 émerge suivant l'axe 4, vers le haut, de la face supérieure 125 de la pièce 115 pour constituer une électrode qui, dans l'état de repos illustré à la figure 13, baigne dans une charge pyrotechnique 37 inflammable par étincelage, c'est-à-dire du type précédemment décrit en référence aux figures 3 et 4, 5 et 6, 7 et 8, 9 et 10.

The part 116, secured to the part 115 for example by overmolding or by force insertion, along the axis 4, in a housing suitably hollowed out in the face 120 of the part 115, has an indifferent shape if not that it is preferably of revolution around the axis 4 and comprises:

• a flat lower face 224, perpendicular to the axis 4 and placed opposite the terminal 18 of the piezoelectric body 16, of which it is spaced along the axis 4 in the rest position illustrated in Figure 13 while it is supported downward on this terminal 18, under conditions suitable for applying to the piezoelectric body 16, furthermore supported by its terminal 17 on the blade 20 and, by means of the latter, on the rivet 90, a compression itself capable of causing the appearance of a high voltage between these terminals 17 and 18, in the activation state illustrated in FIG. 14;
• upwards, the shape of a peak 125 for example frustoconical of revolution around the axis 4 so as to narrow upwards, which peak 125 emerges along the axis 4, upwards, from the upper face 125 of the part 115 to constitute an electrode which, in the state of rest illustrated in FIG. 13, is immersed in a pyrotechnic charge 37 which is flammable by sparking, that is to say of the type previously described with reference to FIGS. 3 and 4 , 5 and 6, 7 and 8, 9 and 10.

Indeed, in the case of this embodiment, the pyrotechnic charge 37 intended to ignite by sparking to ignite the charge of explosion-proof powder 8 is integrated into the pedal 44, the part of which 117 which will now be described plays at both the role of bucket and the role of electrode, as well as the role of pushing part via parts 115 and 116 and, to a certain extent, of the pyrotechnic charge 37; in this context, the grooves 124 of the part 115, the cavity 103 and the passages 102 and 105 of the base 15, and the slots 92 of the wall 91 serve as a passage of fire between the ignition charge 37 and the powder charge explosion 8, the hot gases generated by the combustion of the charge 37 causing the destruction of the straw 93.

• une face de fond 126 plane, perpendiculaire à l'axe 4, tournée vers le bas de façon à être placée en regard de la face supérieure 123 de la pièce 115 et du pic 125 de la pièce 116, en étant espacée de ce pic 125, suivant l'axe 4, de la distance d définie en relation avec la figure 4 ;
• une face périphérique intérieure 127 cylindrique de révolution avec un diamètre sensiblement identique à celui de la face périphérique extérieure 122 de la pièce 115, de façon à épouser cette face périphérique inférieure 122, dans une relation d'emmanchement mutuel à force, de la face 123 de la pièce 115 jusqu'à proximité de la face 121 de celle-ci, toutefois à un niveau supérieur à celui de cette face 121 de façon à éviter tout contact de conduction électrique entre la pièce 117 et les dents 113 de la rondelle 110 dans la position de repose illustrée à la figure 13 ; la face périphérique intérieure 127 définit par ailleurs avec la face de fond 126 de la pièce 117 et avec la face supérieure 123 de la pièce 115 la cavité 128 qui, à l'intérieur de la pédale 44, loge la charge pyrotechnique 37 qui remplit intégralement cette cavité 128 ;
• une face inférieure 129 annulaire, plane, de révolution autour de l'axe 4 auquel elle est perpendiculaire, laquelle face 129 est placée en regard des dents 113, au-dessus de celles-ci sans contact avec celles-ci dans la position de repos illustrée à la figure 13 ;
• une face périphérique extérieure 130 cylindrique de révolution autour de l'axe 4 et tournée dans le sens d'un éloignement par rapport à celui-ci, cette face périphérique extérieure 130 présentant un diamètre inférieur à celui de la face 106 de la cavité 103 et plus précisément tel que ne puisse s'établir de contact de conduction électrique entre elle et la zone d'extrémité libre 27 de la lame 20 ;
• une face supérieure 131 plane, perpendiculaire à l'axe 4 et tournée vers le haut, à laquelle la face périphérique extérieure 130 relie vers le haut la face inférieure 129.

To thus play the role of electrode, the part 117 is metallic, like the part 116, and for example made of brass, so as to be electrically conductive. To play the role of bucket, it is delimited by:

• a flat bottom face 126, perpendicular to the axis 4, turned downward so as to be placed opposite the upper face 123 of the part 115 and the peak 125 of the part 116, being spaced from this peak 125 , along axis 4, of the distance d defined in relation to FIG. 4;
• an inner peripheral face 127 of cylindrical revolution with a diameter substantially identical to that of the outer peripheral face 122 of the part 115, so as to match this peripheral face lower 122, in a mutual press fit relationship, from the face 123 of the part 115 to near the face 121 of the latter, however at a level higher than that of this face 121 so as to avoid any electrical conduction contact between the part 117 and the teeth 113 of the washer 110 in the rest position illustrated in FIG. 13; the inner peripheral face 127 furthermore defines with the bottom face 126 of the part 117 and with the upper face 123 of the part 115 the cavity 128 which, inside the pedal 44, houses the pyrotechnic charge 37 which completely fills this cavity 128;
• an annular, planar lower face 129 of revolution about the axis 4 to which it is perpendicular, which face 129 is placed opposite the teeth 113, above them without contact with them in the rest position illustrated in Figure 13;
• an outer peripheral face 130 cylindrical of revolution about the axis 4 and turned in the direction of a distance from it, this outer peripheral face 130 having a diameter less than that of the face 106 of the cavity 103 and more precisely such that electrical conduction contact cannot be established between it and the free end region 27 of the blade 20;
• a planar upper face 131, perpendicular to the axis 4 and facing upwards, to which the outer peripheral face 130 connects upwards the lower face 129.

It will be observed that, along axis 4, the level of the lower face 129 of the part 117 relative to that of the lower face 121 and the respective radial dimensions of the outer peripheral face 122 of the part 115 and of the teeth 113, with reference to axis 4, are such that in the activation position illustrated in FIG. 14, the teeth 113 bent downward under the thrust of the face 121 of the part 115 and then placed opposite the peripheral face 122 of this part 115 are placed in electrical conduction contact with the mutual junction of the faces 129 and 130 of the part 117, which is then thus placed in electrical connection, via the washer 110 and the blade 20, with terminal 17 of the piezoelectric body 17; because the other terminal 18 thereof is placed in electrical conduction contact with the part 116, the compression stress then applied to the piezoelectric body 16 along the axis 4, resulting in the appearance of a high voltage between the terminals 17 and 18 of this piezoelectric body 16, causes sparking inside the pyrotechnic charge 37 between the electrodes constituted respectively by the peak 125 of the part 116 and the bottom face 126 of the part 117, the inner peripheral face 127 of which is comparatively further from the peak 125. On the other hand, in the rest position illustrated in FIG. 13, this electrical circuit is open on the one hand between the teeth 113 of the washer 110 and the lower face 129 of the part 117 and on the other hand between the terminal 18 and the part 116, which constitutes an electrical safety against an untimely sparking inside the pyrotechnic charge 37.

The part 118 can advantageously be used to further introduce mechanical safety against an untimely descent of the pedal 44 towards the piezoelectric body 16, from the rest position illustrated in FIG. 13, at the same As the tray 45 of the embodiments described with reference to Figures 3 and 4, 5 and 6, 7 and 8, 9 and 10.

To this end, the part 118 is made, like the plate 45, of a material capable of breaking by shearing; this material is also chosen electrically insulating for safety reasons, like the plate 45; the part 118 is thus advantageously made of plastic, for example.

• une face de fond 132 plane, perpendiculaire à l'axe 4 et tournée vers le bas, épousant la face supérieure 131 de la pièce 117 ;
• une face périphérique intérieure 133 cylindrique de révolution autour de l'axe 4 et tournée vers ce dernier, avec un diamètre identique à celui de la face périphérique extérieure 130 de la pièce 117 dont cette face 133 épouse la face 130 du raccordement de cette dernière avec la face 131 jusqu'à un niveau qui, dans la position de repos illustrée à la figure 13, se situe en dessous de la face supérieure 25 du socle 15 bien qu'au-dessus de celui de la face inférieure 129 de la pièce 117 ;
• une face inférieure 134 annulaire, plane, de révolution autour de l'axe 4 auquel elle est perpendiculaire, cette face 134 étant tournée vers le bas et délimitant ainsi la face 133 à l'opposé du raccordement de cette dernière avec la face 132 ;
• une face périphérique extérieure 135 cylindrique de révolution autour de l'axe 4 et tournée dans le sens d'un éloignement par rapport à celui-ci, cette face périphérique extérieure 135 présentant un diamètre inférieur à celui de la face périphérique intérieure 104 du socle 15, ainsi qu'au diamètre minimal du rebord 94 de la paroi 91 ;
• une face supérieure 136 plane, perpendiculaire à l'axe 4 et tournée vers le haut, à laquelle la face 135 se raccorde vers le haut et qui est placée directement en regard de la zone centrale 12 de la coupelle supérieure 11 qui, dans la position de repos illustrée à la figure 13, s'appuie sur cette face supérieure 136 par l'intermédiaire d'un tampon 137 d'un matériau élastiquement ou plastiquement compressible tel qu'une mousse synthétique, traversant l'ouverture 95 et assurant entre la zone centrale 12 de la coupelle supérieure 11 et la pédale 44, dans la position de repos, un entretoisement maintenant l'appui de la pédale 44 sur les dents 113 de la rondelle 110 par l'intermédiaire de la pièce 115.

This part 118 does not, however, in this case have the shape of a plate, but that of a cap which is force-fitted or molded onto the part 117 and having:

• a flat bottom face 132, perpendicular to the axis 4 and turned downward, matching the upper face 131 of the part 117;
• an inner peripheral face 133 cylindrical of revolution about the axis 4 and turned towards the latter, with a diameter identical to that of the outer peripheral face 130 of the part 117 of which this face 133 matches the face 130 of the connection of the latter with the face 131 to a level which, in the rest position illustrated in FIG. 13, is located below the upper face 25 of the base 15 although above that of the lower face 129 of the part 117 ;
• an annular, planar lower face 134 of revolution about the axis 4 to which it is perpendicular, this face 134 being turned downwards and thus delimiting the face 133 opposite the connection of the latter with the face 132;
• an outer peripheral face 135 cylindrical of revolution around the axis 4 and turned in the direction of a distance from it, this outer peripheral face 135 having a diameter less than that of the inner peripheral face 104 of the base 15 , as well as the minimum diameter of the rim 94 of the wall 91;
• a planar upper face 136, perpendicular to the axis 4 and facing upwards, to which the face 135 is connected upwards and which is placed directly opposite the central zone 12 of the upper cup 11 which, in the position rest illustrated in FIG. 13, rests on this upper face 136 by means of a pad 137 of an elastically or plastically compressible material such as a synthetic foam, passing through the opening 95 and ensuring between the zone central 12 of the upper cup 11 and the pedal 44, in the rest position, a bracing maintaining the support of the pedal 44 on the teeth 113 of the washer 110 by means of the part 115.

On its face 135, the part 118 carries radially projecting with reference to the axis 4, integrally for example by molding in one piece, a plurality of fins 138, preferably at least minus three, each of which has, in the direction of a distance from the axis 4, a straight edge 139, parallel to the axis 4; the different edges 139 are arranged in a geometric cylinder, of revolution around the axis 4, of a diameter substantially identical to that of the inner peripheral face 104 of the base 15 and are placed in sliding guide contact parallel to the axis 4 with this face 104 in the rest position illustrated in FIG. 13 as in the activation position illustrated in FIG. 14 and in the intermediate positions between these two limit positions, so as to complete the guidance of the pedal 44 to the translation along the axis 4 relative to the base 15, also provided by the cooperation of the inner peripheral face 119 of the part 115 with the outer peripheral face 108 of the base 15; a risk of jamming of the pedal 44 is thus avoided when, as is generally the case, the crushing force does not apply along the axis 4 as shown diagrammatically at F in FIG. 14, but so both inclined and off-center with respect to this axis, in practice by the intermediate zone 9 7 of the upper cup 111, as shown schematically in F₁ in FIG. 14.

To ensure the above-mentioned mechanical safety effect, each fin 138 has, projecting from its edge 139 in the direction of a distance from the axis 4, a tongue 140 capable of detaching, by shearing, from the rest of the fin 138 if it is subjected to a shearing force exceeding a determined threshold, in an ascending direction parallel to the axis 4. The tongues 140 are arranged, as shown in FIG. 13, so as to lean towards the low on the upper face 5 of the base 15 in the rest position; as soon as the pedal 44 is biased downward, relative to the base 15, with a force exceeding a predetermined threshold, they break by shearing, and no longer constitute an obstacle to the passage to the activation position, illustrated in Figure 14.

The operation of this embodiment of the firecracker 89 can be easily deduced from that of the firecrackers previously described.

If this firecracker, the components of which initially occupy the relative positions described with reference to FIG. 13, is subjected parallel to the axis 4 or obliquely with respect to the latter to a force F or F₁ exceeding a predetermined threshold, the cup 11 s 'crushing by causing the crushing of the buffer 137 between its central zone 12 and the pedal 44 which, then, initiates a descent which, if this effort is maintained with a sufficient value, causes the shearing of the tongues 140; this descent then causes the face 224 of the part 116 to come into electrical conduction contact with the terminal 18 of the piezoelectric body 16 and then the application to the latter, by this same part 116, of a compressive stress according to axis 4, which causes, if it is sufficient, the appearance of a high voltage between terminals 17 and 18; the descent of the pedal 44 being accompanied by the establishment of an electrical conduction contact between the part 117 and the teeth 113 of the washer 110, this tension also appears between the peak 125 of the part 116 and the face of bottom 126 of the part 117, which causes a spark between them, through the pyrotechnic charge 37, and consequently the ignition thereof; the hot gases resulting from the combustion of the charge 37 are transmitted by the grooves 124, the passages 102 and 105 and the slots 92, to the flakes 93 which they pass through to reach the charge of explosion-proof powder 8 which, when ignited, makes deflagration, with the ensuing phenomena which have been described with reference to Figures 1 to 11.

Note that the crushing of the upper cup 11 is accompanied by a deformation, in a barrel, of the wall 91 of the part 6, as shown in FIG. 14, which wall contributes to the mechanical safety of the firecracker by preventing its accidental crushing, under the force of a force having a value below the predetermined threshold from which it is considered that the crushing of the upper cup 11 is characteristic of the passage of a train.

The embodiment of the ignition device 9 illustrated in FIGS. 15 and 16 presents great analogies, including with regard to the production of the pedal 44, with that which has just been described with reference to FIGS. 13 and 14 so that we will limit ourselves to describing the differences between these two embodiments.

Structurally, an essential difference lies in the removal of the part 115 and in the mounting of the part 116, which is found identically, inside the recess 114 of the base 15, in a position in which it takes support, in an electrical conduction relationship, on terminal 18 of the piezoelectric body 16. To facilitate, during the crushing of the firecracker, the application, to the piezoelectric body 16, of compression, along the axis 4, capable of causing the appearance of a high voltage between the terminals 17 and 18 of the piezoelectric body 16, the part 116 is retained by friction inside the recess 114, so as to be able to slide down at the interior thereof when the firecracker 89 undergoes the above-mentioned crushing load F or F₁, and the piezoelectric body 16 forms a slight upward projection inside the recess 114, without however reaching the face upper 109 above which the peak 125, also forming in this case an electrode, on the other hand forms a projection along the axis 4.

In the absence of the part 115, the part 117 is mounted directly to slide along the axis 4 on the outer peripheral face 108 of the base 115, by its inner peripheral face 127, the two faces 108 and 127 being suitably shaped to this effect; the grooves 124 for the passage of fire, arranged in the room 115 if we refer to the embodiment described with reference to FIGS. 13 and 14, are arranged in the outer peripheral face 108 of the base 15, of the upper face 109 of this one, at the bottom face 107 of the cavity 103.

The pyrotechnic charge 37 for ignition, housed as in the case of the embodiment described with reference to FIGS. 13 and 14 inside the part 117, of which it marries, in the form of a compact mass, the bottom face 126 and an area of the inner peripheral face 127 adjacent to this bottom face 126, presents downwards, and towards the peak 125, a planar face 141 perpendicular to the axis 4 and covered by a spangle 142 if we refer to the rest state illustrated in FIG. 15. In this state, the peak 125, which defines one of the spark electrodes, is released from the pyrotechnic charge 37 and spaced from the bottom face 126 of the part 117, defining the other spark electrode, by a distance D, measured along the axis 4, defined as seen with reference to FIG. 3, it is that is to say unsuitable for allowing sparking even if a high voltage appears between the terminals 17 and 18 of the piezoelectric body 16; in the rest position, the peak 125 is also spaced from any other zone of the part 117, by a distance thus unsuitable for allowing sparking. Indeed, in the case of this embodiment, the part 117 is permanently electrically connected to the terminal 17 of the piezoelectric body 16 insofar as, in the absence of part 115, it bears directly on the teeth 113 of the washer 110; it is understood, however, that a person skilled in the art can easily modify the arrangements illustrated in FIGS. 15 and 16 so that the part 117 does not come into contact with the teeth 113 in the rest position illustrated in FIG. 15 , and does not come into contact with them, in an electrical conduction relationship, only when passing to the activation position illustrated in FIG. 16.

A person skilled in the art will readily understand that the transition to this position results, as the pedal 44 descends, by a progressive penetration of the peak 125 into the load 37, after perforation of the spangle 142, until that the peak 125 is no longer distant from the bottom face 127 of the part 117, along the axis 4, only by a distance d as defined with reference to FIG. 4, that is to say allowing the sparking through the load 37. It will be noted that the latter itself contributes, in this embodiment, to causing this sparking by serving as an intermediary for pressing the pedal 44 on the part 116 itself in support on terminal 18 of the piezoelectric body 16; the phenomena following sparking are identical to those which have been described previously.

Such an effect can be obtained whatever the speed at which the pedal 44 descends towards the base 15.

Note, however, that if this speed is high, the peak 125 of the part 116 can also behave like a striker with respect to the load 37 at which it is advantageous, therefore, to give a composition such that it can ignite not only by sparking, but also by percussion; the choice of such a composition falls within the normal aptitudes of a person skilled in the art.

Thus, if the descent of the pedal 44 is particularly rapid, due to the sudden application of the load F or F₁, it is by percussion and not by sparking, that is to say with less inertia, that the charge 37 ignites and causes the explosion powder 8 to ignite.

A person skilled in the art will readily understand that the various embodiments of a lane firecracker according to the invention which have just been described constitute only non-limiting examples, with respect to which many variants can be provided without going out of the scope of the present invention.

Similarly, it will appear to a person skilled in the art that the provisions which have been described in relation to a firecracker can be easily transposed in the case of other pyrotechnic devices capable of being actuated by crushing, and in particular in the case of mines. , directly conceivable from the arrangements which have been described by removing the claws 3 and, optionally, replacing these by means of support suitable for the support on which one wishes to lay the mine, and substitution for the explosion-proof powder 8 d '' A military payload with thermal, explosion, detonating, smoke or lighting effect.

Claims (17)

Pyrotechnic device sensitive to crushing such as a signaling firecracker (1, 89), a mine or the like, comprising a useful pyrotechnic charge (8, 78) chosen from a group comprising the explosive charges (8, 78) and the military charges with thermal, explosion, detonating, smoke or lighting effect, and an ignition device (9, 9a, 9b) comprising a pyrotechnic ignition charge (37, 80) in pyrotechnic connection with the payload (8, 78 ) and means for causing the ignition charge (37, 80) to ignite and, through it, igniting the payload (8, 78) in a controlled manner during appearance of at least one specific crushing condition, characterized in that the ignition charge (37, 80) is flammable by sparking, and in that the means for causing ignition of the ignition charge (37 , 80) include: - two electrodes (30, 31, 36, 84, 85, 117, 125) disposed respectively on either side of a determined zone of the ignition charge (37, 80) and mutually spaced by a determined distance (d,,) adapted to allow the creation of an electric spark between them, through said zone of the ignition charge (37, 80, 110, 132), to ignite the latter, at least in said determined condition d 'crushing, - a piezoelectric body (16) comprising two terminals (17, 18) and capable of generating a high voltage between them when it is subjected to a compression stress of a value exceeding a determined value, in a direction determined (4), - a circuit (20, 21, 68, 69, 81, 82, 110, 116) for electrical connection of each terminal (17, 18) of the piezoelectric body (16) to a respective electrode (30, 31, 36, 84, 85, 117, 125), - actuation means (44) for detecting the appearance of said determined crushing condition and then applying said compression stress to the piezoelectric body (16). Device according to claim 1, characterized in that the actuating means (44) comprise a thrust body (46, 117) movable relative to the piezoelectric body (16) along a determined trajectory (4) under the effect of the appearance of said determined crushing condition, of a rest position which it occupies outside of said determined crushing condition and in which the thrust body (46, 117) is functionally disjoint from the piezo- body electric (16) to an activation position which it occupies in said determined crushing condition and in which the thrust body (46, 117) is functionally supported on the piezoelectric body (16) and said trajectory has said direction determined (4), so that the thrust body (46, 117) applies said compressive stress to the piezoelectric body (16). Device according to claim 2, characterized in that the thrust body (46, 117) constitutes a pedal (44) for detecting the appearance of a crushing load in said determined direction (4), said pedal (44 ) being sensitive to a thrust or to an applied shock, in said determined condition of crushing, in said determined direction (4, 91), from the rest position to the activation position. Device according to any one of claims 1 to 3, characterized in that it comprises means (49, 52, 103, 140) of mechanical security against an application of said compressive stress to the piezo body electric (16). Device according to claim 4 in combination with at least claim 2, characterized in that the means (49, 52, 91, 113, 140) of mechanical safety comprise means (49, 52, 91, 113, 140) for retaining the thrust body (46, 117) in the rest position, capable of releasing the thrust body (46, 117) under the effect of the appearance of said determined crushing condition. Device according to claim 5, characterized in that the retaining means (49, 52, 91, 113, 140) are capable of automatically releasing the thrust body (46, 117) when the latter in the rest position receives a force exceeding a predetermined threshold, oriented towards its activation position. Device according to any one of Claims 1 to 6, characterized in that it comprises means (27, 29, 38, 39, 40, 41, 50, 112, 115, 117) of electrical safety to prevent accidental creation of said spark in the event of accidental application of said compression stress to the piezoelectric body (16). Device according to claim 7, in combination with at least claim 2, characterized in that the electrical safety means (27, 29, 39, 40, 41, 50, 113, 115, 117) comprise in said electrical connection circuit (20, 21, 68, 69, 81, 82, 110, 116) a switch (113, 115, 117) mechanically coupled to the thrust body (117) so as to be open when the thrust body (117) is in rest position and closed when the thrust body (117) is in the activation position. Device according to claim 7, in combination with at least claim 2, or according to claim 8, characterized in that the electrical safety means (27, 29, 38, 39, 40, 41, 50, 113, 115, 117 ) comprise an auxiliary circuit (26, 27, 29) electrically connecting said terminals (17, 18) of the piezoelectric body (16) and a switch (27, 29, 50) interposed in said auxiliary circuit (26, 27, 29 ) and mechanically coupled to the thrust body (46) so as to be closed when the thrust body (46) is in the rest position and open when the thrust body (46) is in the activation position. Device according to claim 7, in combination with at least claim 2, or according to any one of claims 8 and 9, characterized in that the electrical safety means (27, 29, 38, 39, 40, 41, 50 , 113, 115, 117) comprise means (38) for guiding one (31, 117) at least, of the electrodes with respect to a movement of approach or distance towards from the other electrode (30, 36, 125), and means (39, 48) for coupling between the thrust body (46, 117) and said guided electrode (31, 117) so that the electrodes ( 30, 31, 36, 117, 125) are mutually spaced by a distance (D) greater than said determined distance (d) and too great to allow the creation of an electric spark between them, through said zone of the charge (37), in the event of accidental application of said compression stress to the piezoelectric body (16), while the thrust body (46, 117) is in the repo position s, and are spaced apart from said determined distance (d) when the thrust body (46, 117) is in the activation position. Device according to at least claim 2, characterized in that the ignition charge (37) is aligned with the thrust body (117) and one (18) of the terminals (17, 18) of the piezoelectric body ( 16) and interposed between them in said determined direction (4), in that the thrust body (117) defines one (117) of the electrodes (117, 125), on one side of the ignition charge ( 37), and in that the other electrode (125) is interposed between the ignition charge (37) and said terminal (18) of the piezoelectric body (16), on the other side of the charge ignition (37), and in electrical conduction contact with said terminal (18) at least when the thrust body (117) is in the activation position. Device according to claim 11, in combination with at least claim 8, characterized in that said switch (113, 115, 17) has a discontinuity in said mutual electrical conductive contact when the thrust body (117) is in the position of rest. Device according to any one of Claims 1 to 12, characterized in that the ignition charge (37) is also flammable by percussion and in that the means for causing the ignition charge to ignite (37, 80 ) include means (125) for percussing it upon the appearance of said determined crushing condition. Device according to claim 13 in combination with at least claims 11 and 10, characterized in that the ignition charge (37) is integral with a first electrode (117) and disjoined from the second electrode (125) when the body thrust (117) is in the rest position, and in that the second electrode (125) is shaped as a striker. Device according to claim 14, characterized in that the first electrode (117) is formed by the thrust body (117) and in that the second electrode (125) is integral with said terminal (18) of the piezoelectric body ( 16). Device according to any one of Claims 1 to 15, characterized in that it forms a structural unit grouping together the payload (8), the ignition charge (37), the piezoelectric body (16), the actuating means (44), the electrodes (30, 31, 117, 125) and the electrical connection circuit (20, 21, 110, 116). Device according to any one of Claims 1 to 9, 13, characterized in that it forms two disjoint structural units (66, 67), one of which (66) groups together the piezoelectric body (16) and the actuating means (44), the other (67) of which includes the electrodes (84, 85), the ignition charge (80) and the payload (78), and which are connected to each other by a connection cable part of the electrical connection circuit (68, 69).

Images