FR2681682A1 - PIEZOELECTRIC IGNITION DEVICE AND PYROTECHNIC DEVICE SUCH AS A PETARD OR A SIGNALING TORCH, A FUMIGENE DEVICE, A MINE OR A PYROTECHNIC PROJECTILE, USING THE SAME. - Google Patents

Abstract

The present invention relates to an electric ignition device, as well as pyrotechnic devices such as a firecracker or a signaling torch, a smoke device, a mine, a pyrotechnic projectile implementing such an ignition device. The electric ignition device (9) comprises a piezoelectric body (16) whose terminals (17, 18) are connected to electrodes (30, 36, 31) cooperating with a pyrotechnic charge (37) which can be ignited by sparking; upon the appearance of at least one determined condition, actuating means (pedal 44) detecting this appearance apply to the piezoelectric body (16) a compressive stress which causes a high voltage to appear between these terminals (17, 18) itself causing the appearance of a spark or an electric arc between the electrodes (30, 36, 31) and the ignition of the pyrotechnic charge (37).

Description

The present invention relates to an electrical ignition device of the

  a type comprising a flammable pyrotechnic pyrotechnic charge, two electrodes disposed respectively on either side of a given area of the charge and mutually spaced by a determined distance capable of allowing the creation of an electric spark between them, through said zone of the charge, for igniting the charge, and a controlled electric generator, electrically connected to the electrodes to cause the creation of said spark in a controlled manner when at least one predetermined condition occurs; it also relates to a pyrotechnic device comprising a

  payload and such an ignition device.

  An electric ignition device of the type indicated in the preamble is described in the form of a detonator in US Pat. No. 3,361,064, which recommends, as a controlled electric generator, the combination of a battery and a capacitor. a switch makes it possible to connect either to the battery to charge it, or to the electrodes to discharge it with formation of a spark between them; an electrical resistance connected in parallel with the air gap of the electrodes makes it possible to avoid an accumulation of static electricity which

  may accidentally cause sparking.

  This known electric ignition device has the inconvenience

  come to require a battery which, over time, can be discharged and therefore no longer be able to charge the capacitor when it is necessary to use the electric ignition device; the maintenance of this last loan for use therefore requires a periodic change of the battery, or a periodic recharging of

  this one, which constitutes a constraint.

  This disadvantage is all the more noticeable when it is desired to use such an electrical ignition device to cause by means of the flammable charge by flashing the ignition of a deflagrating, illuminating or fumigating charge in pyrotechnic signaling devices intended to be used in case of distress, such as firecrackers that are placed on the railroad tracks or torches that are lit at the edge of railway tracks to signal a danger imposing an emergency stop or the smoke devices designed to signal shipwrecked persons Such devices are usually packaged in waterproof cases in view of what they must be kept at

  in spite of sometimes precarious and long-term storage conditions.

  SOE; in such cases, the periodic control of the batteries and their periodic change require the opening of the case and its closure again, or the use of a new case, which is particularly tedious and expensive, on the one hand , and can only lead to penetrations of moisture inside the pyrotechnic device, at the risk of putting

this one out of order.

  Naturally, this disadvantage may also be encountered when attempting to use for other pyrotechnic devices, for example mines or pyrotechnic projectiles such as bombs, shells or rockets, the electric ignition device described in the description.

aforementioned US patent.

  The object of the present invention is to propose an electric ignition device which, while being of the type indicated in the preamble, overcomes the disadvantages of the electric ignition device of this type.

  as described in the aforementioned US patent.

  For this purpose, the electric ignition device according to the invention, of the type indicated in the preamble, is characterized in that the controlled electric generator comprises: a piezoelectric body having 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 given 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 condition and then apply to the piezoelectric body

said compressive stress.

  Inasmuch as the ordered electric generator thus designed, of piezoelectric type, does not comprise a battery, and more generally of a component that may lose its functionality over time, an electric ignition device according to the invention requires much less monitoring and maintenance operations than the electrical ignition device described in the aforementioned US patent, which is a general advantage and, more particularly, makes such an electric ignition device particularly suitable for a integration with pyrotechnic devices whose monitoring and maintenance are difficult for example because they must be packaged in perfectly sealed cases, as is the case, for example, with firecrackers or signaling torches or smoke devices, or because that they must remain perfectly watertight themselves, as is the case with mines or pyrotechnic projectiles, it being understood that an electric ignition device according to the invention may also know other applications. Without control and without maintenance, the electric generator of an electric ignition device according to the invention remains clean to fulfill its function even after a long storage time and, however,

  its design can be simple, including the means of

  In order to detect the appearance of the determined condition that is to cause the flashing, then the piezoelectric body is subjected to the compressive stress necessary to generate the high voltage which, transmitted to the electrodes by the electrical connection circuit, causes this sparking. These actuating means can be very diverse, depending on the determined condition whose appearance must cause the spark.

  This determined condition may be solicited voluntarily

  by a user, who then acts voluntarily on the actuating means to apply to the piezoelectric body the compressive stress causing the sparking It may also be external to any user's wishes, and for example consist of the arrival of a

  vehicle, in which case the actuating means are sensitive to the application of

  cation of a charge, as may be the case in an application to the realization of a signal firecracker or mine, or in an impact on an objective, as may be the case in an application to the realization a pyrotechnic projectile, or in the occurrence of another phenomenon such as exceeding a certain temperature or a determined pressure in a chamber in which are located the actuating means which, then, are designed to move or deform under the action of the occurrence of this excessive temperature or excessive pressure and then apply to the piezoelectric body, directly or indirectly, the compressive stress leading to the spark. However, to prevent the piezoelectric body from generating the high voltage causing the accidental sparking, under the action

  compression constraint that 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 path, under the effect of the appearance of said determined condition, a position resting it occupies outside said determined condition and wherein the thrust body is functionally disjointed from the piezoelectric body to an activation position that it occupies in said

  determined condition and in which the thrust body is function-

  seated on the piezoelectric body and said path has said determined direction, so that the thrust body

  applies said compressive stress to the piezoelectric body.

  It should be noted that the concept of functional thrust body

  disjointed part of the piezoelectric body in the rest position

  that of physical spacing between the thrust body and the piezo body

  electric but does not necessarily imply such spacing; it also includes the possibility of mutual contact in the resting position, but without the result of this mutual contact the application of the said

  compressive stress to the piezoelectric body.

  Naturally, the passage of the thrust body from its rest position to its activation position, when the determined condition occurs in which it is desired to cause the spark, is closely

  depending on the nature of this condition.

  As a nonlimiting example, but suitable for applications in the production of a firecracker or a signaling torch, or a smoke device, or a mine, or a pyrotechnic projectile, the thrust body may be sensitive to a thrust or shock applied in said determined condition in said determined direction, from the rest position to the activation position It may be a push on which the user acts voluntarily , for example in the case of a signaling torch or a smoke device, or automatically, for example in the case of a signaling firecracker or

  of a mine, or that an impact on a lens operates automatically.

  for example in the case of a pyrotechnic projectile It may still be an inertial mass detecting the application, to a structural unit comprising the thrust body, an acceleration or a

  deceleration, whether intentional or accidental, following the said direction

  undermined; thus, in the case of an application to the realization of a signaling torch or a smoke device, it can provide an ignition of the torch or the smoke device, that is to say a spark within the the pyrotechnic charge of the electric ignition device, by application of an appropriately directed acceleration to the whole of the torch or the smoke device and, in the case of an application to a pyrotechnic projectile, it is possible to provide an ignition of a pyrotechnic pyrotechnic charge with thermal effect, explosion or detonation, or a pyrotechnic charge smoke or light, under the effect of a determined orientation deceleration, the projectile is subjected to an impact on an objective. Depending on the case, the thrust body may have a biasing zone from its rest position to its activation position, accessible from outside the electric ignition device in the rest position, and thus constitute for example a button. pusher, especially in the case of application to a signaling torch or a smoke device, or a pedal, especially in the case of an application to a track firecracker or a mine, or a pusher disposed in warhead in the case of application to a pyrotechnic projectile, but it can also be fully housed in the electric ignition device, which is generally the case when it has the form of an inertial mass. Preferably, the electrical ignition device comprises safety means adapted to avoid accidental sparking, that is to say occurring outside the appearance of said determined condition, and these security means may have various aspects, which can

  be accumulated at will in the same electrical ignition device.

  Thus, the electric ignition device according to the invention may advantageously comprise 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 previously indicated, these mechanical safety means may advantageously comprise means for retaining the thrust body in the rest position, suitable for releasing the body of thrust under the effect of the appearance of said determined condition, and for example to automatically release the thrust body when it, in the rest position, receives a force exceeding a predetermined threshold, oriented towards its activation position The retaining means may then be constituted, for example, in the form of bridges of shear-sensitive material, retaining the thrust body in the rest position and shearing during the appearance of this force exceeding a determined threshold, or else under Other forms The retaining means may also be able to be actuated at will, to release at will the thrust body in pos It can then consist for example of a detachable pin at will, or a detent or a push button holding the thrust body in the rest position when they are not in position. are not actuated and releasing it when they are actuated to the retaining means of the thrust body in the rest position may advantageously be associated, in certain applications, with means for elastically biasing the thrust body from the rest position to its position activation, which cause an energetic passage of the thrust body from its rest position to its activation position when it is released from the action of the retaining means, which results in the arrival in position d activation by the application, to the piezoelectric body, of a shock causing itself spark; the thrust body then behaves as an inertial mass when it is released vis-à-vis the retaining means; it is thus possible to use a less sensitive piezoelectric body, that is to say

  offering itself increased security against accidental sparking.

  The safety means may also be electrical safety means, able to prevent accidental creation of said spark in case of accidental application of said compressive stress, normally capable of causing sparking, to the piezoelectric body. When the actuating means comprise a thrust body as indicated above, these electrical safety means may comprise, in the electrical connection circuit of each terminal of the piezoelectric body to a respective electrode, a coupled switch mechanically 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 comprise an auxiliary circuit connecting electrically the terminals of the piezoelectric body and

  a switch interposed in this auxiliary circuit and mechanically coupled

  only 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 alternatively or in addition, the electrical safety means may also comprise means for guiding at least one of the electrodes with respect to a movement towards or away from the other electrode, and means for coupling between the thrust body and said electrode guided such that the electrodes are mutually spaced 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 case of accidental application of said compression stress to the piezoelectric body, while the thrust body is in the rest position, and are spaced from said determined distance when the body of pous 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 to allow a spark between they; naturally, this last embodiment of the electrical safety means assumes that the electrical ignition device forms a unit

  of structure comprising the piezoelectric body, the means of action-

  the electrodes, the load and the connection circuit.

  In general, the electric ignition device according to the invention can form such a unit of structure, for example in the case of an application to the production of a firecracker, a safety torch or a device in the case of an application to a mine or a pyrotechnic projectile, but it can also form two disjoint structural units, one of which groups together the piezoelectric body and the actuating means, the other grouping together the electrodes and the load, and which are mutually connected by the electrical connection circuit; thus, in the case of application to the realization of a signal firecracker, it is possible to separate the piezoelectric body and the actuation means, on the one hand, necessarily placed on the track, and the electrodes and the electrodes. pyrotechnic charges respectively flammable by spark and explosion, on the other hand, that it may be better to place next to the track, in order to make the explosion more easily audible by

the mechanic of a train.

  Naturally, the present invention is not limited to an electric ignition device alone, but also extends to a pyrotechnic device such as a firecracker or a signaling torch, or a smoke device, or a mine, or a projectile pyrotechnic device, comprising a useful pyrotechnic charge selected from a group consisting of detonating charges, explosion charges, smoke loads, military charges with thermal, explosive or detonating effects, and an ignition device; according to the present invention, such a pyrotechnic device is characterized in that the ignition device is an electrical ignition device according to the invention, the pyrotechnic charge of which is in pyrotechnic connection with the payload of which, if appropriate, the flammable pyrotechnic charge by flashing may constitute a part In the case of a signal firecracker or a mine, intended respectively to deflagrate or to explode at the appearance of a

  charge, the aforementioned thrust body, forming part of the means of

  Advantageously, it is a pedal for detecting the occurrence of such a charge. In the case of a signaling torch, intended to illuminate voluntarily controlled, or a smoke device, intended to emit a smoke also voluntarily controlled, the above-mentioned thrust body can advantageously constitute a manually actuable push-button, or constitute an inertial mass, in which case this mass is advantageously resiliently biased from the rest position to the activation position and a trigger is provided retaining this mass in the rest position and an expansion in functional connection with this trigger and manually operable to release at will said mass of said retainer In the case of a projectile, whose thermal effect payload, explosion or detonation, in addition to smoke or light effect must be initiated during an impact on a goal, the aforementioned thrust body may consist of a pusher disposed in the shape of a warhead for gaining its activation position by direct impact against the objective, or in an inertial mass gaining its activation position under the effect of a deceleration experienced by the projectile during its impact on the objective; more specifically, in the first case, the thrust body forms a pusher disposed ogival along the axis of the projectile, is disposed in front of the body and forms a projection forwardly with respect to the ogive with reference to a sense normal progress of the projectile, and in the second case, the thrust body constitutes an inertial mass placed

  behind the piezoelectric body.

  Of course, other embodiments of the invention may also be provided, particularly in the case of other applications.

  Other features and advantages of the invention are

  from the description below, relating to some examples not

  implementing rules, as well as the accompanying drawings which form part of the

integral part of this description.

  1 shows, in top view, a signal firecracker according to the invention, of a type defined generally in the French standard NF-F 54-0011 of October 1982, intended to be fixed on the mushroom. a railway rail to emit an explosion under the load of a wheel of a railway train; the firecracker is supposed so

fixed on the mushroom of a rail.

  FIG. 2 shows a view of this firecracker in section through an average plane of symmetry perpendicular to the rail and marked II-II at the

figure 1.

  FIGS. 3 and 4 show a first example of an electric ignition device according to the invention capable of equipping the firecracker illustrated in FIGS. 1 and 2, in a view similar to that of FIG. 2 and on a larger scale, respectively before and after applying the load

causing the blast.

  FIGS. 5 and 6 show, in views respectively corresponding to that of FIG. 3 and that of FIG. 4, a second embodiment of an electric ignition device according to the invention

  likely to equip the firecracker illustrated in Figures 1 and 2.

  FIGS. 7 and 8 show, in views respectively corresponding to that of FIG. 3 and to that of FIG. 4, a third embodiment of an electric ignition device according to the invention

  likely to equip the firecracker illustrated in Figures 1 and 2.

  FIGS. 9 and 10 show, in views respectively corresponding to that of FIG. 3 and that of FIG. 4, a fourth embodiment of an electric ignition device according to the invention

  likely to equip 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 pyrotechnic charge.

  flammable by spark and pyrotechnic charge explosion.

  FIGS. 12 and 13 show diagrammatic cross-sectional views of a smoke device and a lighting torch in accordance with the present invention, that is to say using an ignition device.

  electrical connector according to the present invention.

  FIGS. 1 to 10 show a signaling firecracker commonly known as a "highway firecracker" of known general design, described for example in the French patent application No. 8912981 of the 4th

  October 1989 of the Claimant, apart from the piezo

  the ignition device used, which, on the other hand, is

  characteristic of the present invention.

  It will be recalled simply that this firecracker 1, intended to be fixed temporarily 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:

  a lower metal cup, approximately horizontal

  tale, under which the claws 3 are fixed for example by riveting, not shown, a plastic part 6 positioned on the lower cup 5, this piece 6 serving as a base for a container 7 explosive powder 8, of general shape annular, approximately revolution about the axis 4, an ignition device 9 which is carried by the part 6 along the axis 4 and thus surrounded by the container 7 explosion powder 8, and four embodiments 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 with the aforementioned part 6 the container 7 powder 8, an upper cup It is metallic, 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 7 delimiting the container 7 explosion powder 8, that is to say, the container 7 itself

  and the explosive powder 8, as well as the ignition device 9.

  For this purpose, while the lower cup 5 has a generally flat shape, perpendicular to the axis 4, the upper cup 11 is flat and perpendicular to the axis 4 in a central zone 12 covering from above the device 9 and partially the container 7, and present around this central zone 12 a frustoconical peripheral zone 13 of revolution about the axis 4, diverging downwards 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 is made the

crimping 14.

  The lower and upper cups 5 are for example

  made of aluminum or aluminum alloy in accordance with

  French patent application cited above. However, it is well

  understood that only the design of the ignition device 9 is

  of the present invention and that such an ignition device could be integrated with other route design firecrackers without

  within the scope of the present invention.

  As shown in Figure 1, axis 4 is defined by

  section of two plans related to firecracker 1, namely a plane 212 which is at least approximately coincident with a median longitudinal plane of the rail and a plane 213 perpendicular to the plane 212 and thus disposed approximately perpendicular to the median longitudinal 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 the plane 212; the

  plane 213 merges with the sectional plane II-II of Figures 3 to 10.

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

  made in one piece with this piece 6. According to the axis 4, the base 15 encloses a sensitive piezoelectric body 16

  at a compressive stress along this axis 4, that is to say, able to emit a high voltage between two terminals 17, 18 turned respectively downwards and upwards, when subjected along the 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 adapted to retain the piezoelectric body 16 against any radial movement in

reference to axis 4.

  This housing 19 is, however, open upwards and downwards and the piezoelectric body 16 is retained against sliding along the axis 4 by two metal strips 20, 21 perpendicular to the axis 4 and in the plane 212 and mutually parallel at this level, the first of which is trapped integrally 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 by the above it, on which it is retained by any appropriate means and is in conductive contact

  with terminal 18 of the piezoelectric body 16.

  The two blades 20 and 21 have plane 213 as a plane

respective 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 contact with electrical conduction in a state of rest illustrated in FIGS. 3, 5, 7, 9 so that then short-circuit the two terminals 17 and 18 of the piezoelectric body 16 to cancel any consequence of the accidental application thereof to a compressive stress along the axis 4, while they are mutually disjointed in an activation state illustrated in Figures 4, 6, 8, 10 so that then a compression stress of sufficient value, that is to say beyond said determined value, applied to the piezoelectric body 16 along axis 4 translates into the initiation of the

  explosive powder 8 under conditions which will be explained later.

  More precisely, starting from the terminal 17, the blade 20 extends perpendicularly to the plane 212, between the component 6 and a lower face 23, perpendicular to the axis 4, of the base 15, up to the junction of this face lower 23 with a side face 24 of the base 15, meanwhile parallel to the plane 212 and rotated in the direction of a distance relative to the axis 4; at this point, the blade 20 bends at a right angle upwards, that is to say parallel to the axis 4, to follow this lateral face 24 to the junction thereof with an upper face 25, perpendicular to the axis 4, of the base 15; at this junction, the blade 20 bends again at right angles, 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 the plane 212, towards which the return 26 has a free end zone 27 cantilevered above a cavity 28 formed 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 sufficiently rigid 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, for to be able to gain a conformation illustrated in FIGS. 4, 6, 8, 10 in which it is curved downwards at its zone

  extreme 27 and enters through this zone into the cavity 28.

  The blade 21, in turn, rests on the upper face 25 of the base 15, being perpendicular to the axis 4 and the plane 212, of the terminal 18 to an extreme zone 29 also placed cantilevered above the cavity 28, so as to partially overlap the end zone 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 stops by bending the end zone 27 without deformation of the end zone 29 in the position

illustrated in Figures 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 embodiments of the ignition device 9 illustrated respectively in FIGS.

  and 4, 5 and 6, 7 and 8, 9 and 10, in a manner to be described now.

  In the embodiment illustrated in FIGS. 3 and 4, the blade 20 remains perpendicular to the axis 4 and to the plane 212 to its end zone 30, situated under a cavity 33 provided in the lower face 23 of the base 15 of the 32 of the plane 212, which cavity 33 also opens in the direction of a distance relative to this plane, in a side face 34 of the base 15, which is parallel to the plane 212, turned in the direction of a distance relative to to it and occupies a position symmetrical to that of the side face 24 with respect to this plane 212; in practice,

  cavity 33 thus opens facing a localized area 35 of the part 10.

  Inside the cavity 33 is housed, integrally with the base 15, a metal cup 36 resting down on the end zone of the blade 20, with which this cup 36 is consequently in relation

  electric conduction by a bottom zone 41.

  The cup 36, open upwardly inside the cavity 33, contains a charge 37 of a flammable explosion-proof pyrotechnic composition and, by its bottom 41, constitutes an electrode connected to the terminal 17 of the piezoelectric body. 16 for the purpose of creating a spark capable of causing inflammation of the composition

pyrotechnic 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 the plane 212, downwards, above the bucket 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 on the slide

  parallel to the axis 4 in the passage 38 and, in the rest position shown in Figure 3, forms a projection above the upper face 25 of the base 15 so as to be connected to the latter, between the passage 38 and the terminal 18, only through two elbows 39,; 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 thereof descending from the elbow 39 to the elbow 40 , in the direction of approaching both the face 25 of the base 15, at which this elbow 40 is located, and of a relationship with respect to

axis 4 and plan 12.

  When the blade 20 has its conformation shown in Figure 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, a distance D too large for , in case of accidental occurrence 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 disjoint, thus allowing the appearance of a difference in potential between the two electrodes formed respectively by the bottom 41 of the bucket 36 and the end zone 31 of the blade 21, there is formed between them a spark or an electric arc, through the pyrotechnic charge zone 37 located

between them.

  By cons, thanks to the conformation just described, the blade 21 can also deform plastically or elastically to take the conformation shown in Figure 4, in which its section 241 applies substantially against the upper face 25 of the base 15 with virtually complete disappearance of the elbow 40, passage of the elbow 39 substantially at the right angle and sliding of the end zone 31 downwards in the passage 38, so that the end zone 31 is sufficiently close 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 constituted by the extreme 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 piezoelectric body 16 is subjected parallel to the axis 4 at a compression stress causing the appearance of a high voltage between its terminals 17 and 18; then, as shown in Figure 4, the pyrotechnic charge 37 ignites causing the formation of hot gases escaping from the cavity 33 at the face 34 of the base 14 and causing localized deformation of the piece 10, igniting the explosive powder charge 8 causing itself to open the container 7

  and the upper cup Il 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, compared with what has been described with reference to FIGS. 3 and 4, as well as its mode of cooperation with the bucket 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 also filled with a pyrotechnic charge 40 with a thermal effect which, in particular, is thus placed in contact with the charge 37 of pyrotechnic composition

  explosion and is flush with the face 34 of the base 15.

  There is also in this example the passage 38 which, however, does not open towards the bucket 36 centrally with respect thereto, that is to say facing its bottom 41, but laterally by

  relative to the bucket 36, opposite the flange 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, keeping its orientation perpendicular to the axis 4 and the plane 212, of the terminal 18 from the piezoelectric body 16 to the passage 38, at which point it bends downwards to 90, in the form of an end zone 31 oriented as described with reference to FIGS. 3 and 4; that is parallel to the axis 4 and 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 flange 42 of the bucket 36, constituting the second electrode, by a distance 6 such that, when a high voltage appears between the terminals 17 and 18 of the pyrotechnic body 16 placed in 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. between the electrodes thus constituted, 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, the piece 10 facing the cavity 33, the ignition of the explosive powder 8 and the resulting phenomena, 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 formed respectively by the end zone 31 of the blade 21 and the rim 42 of the cup 36 communicates more widely with the interior of the that is to say with the load 37, that with the outlet of the cavity 33

  in the lateral face 34 of the base 15.

  The embodiment illustrated in FIGS. 7 and 8 differs from the exemplary embodiment illustrated in FIGS. 5 and 6 by the fact that the charge 37 of the explosive pyrotechnic composition is housed directly in the cavity 33, in the absence of the bucket 36. previously described, and completely fills this cavity 33 to flush with the lateral face 34 of the base

  ; there is not in this case a load 40 of composition with thermal effect.

  than; in addition, in this example, the cavity 33 opens out of the base 15 only by the side face 34 thereof. The blade 21 retains the conformation described with reference to FIGS. 5 and 6, that is to say present as an electrode an end section 31 oriented parallel to the axis 4 and the plane 212 and penetrating inside the the cavity 33 by a passage 38 connecting, inside the base 15, the

  cavity 33 at the upper face 25 of this base 15.

  To overcome the absence of the bucket 36 as an electrode, the end zone 30 of the blade 20 is in turn curved upwardly 90, parallel to the axis 4 and the plane 212, to enter the cavity 33 , through the base 15, through 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 to such that the 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 mutually disjoint, as shown in Figure 8, causes a spark or a electric arc inside the pyrotechnic charge 37 and, thus, causes the ignition thereof causing itself the localized deformation of the piece 10 facing the cavity 33 and the ignition of the explosive powder 8, with the resulting effects

  and which have been previously described.

  The example illustrated in FIGS. 9 and 10 has great similarities with that illustrated in FIGS. 7 and 8 except that the cavity 33 housing the pyrotechnic charge 37 is disposed inside the

  container 7 instead of being separated, in the state of rest, by the part 10.

  For this purpose, in comparison with the examples previously described, 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. Correspondingly, the end zone 31 of the blade 21 is oriented perpendicular to the axis 4 and the plane 12, and turned in the direction of a distance relative to these, to enter the cavity 35 by a passage 38 itself perpendicular to the plane 212; the blade 20, in turn, is bent upwardly 90 to follow the lateral face 34 of the base 15 in the direction of a distance from the plane 12 of the side 32 of the latter, and then bends to again 90 to enter the cavity 33 by a passage 43 aligned with the passage 38 perpendicular to the plane 12; the end zone 30 of the blade 20 thus forms a return towards the axis 4 and the plane 212 through the passage 43, and thus enters the cavity 33, as well as in the pyrotechnic charge 37, directly opposite the extreme zone 31 of the blade 21 and at a distance A thereof 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 and 21 are disjointed as shown FIG. 10, between the end zones 30 and 31 of these blades 20 and 21, is 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

  follow and have been described previously.

  Naturally, in accordance with the function with which a track firecracker is intended, the deflagration of the powder 8 and the phenomena which lead to this deflagration in both of the previously described embodiments must result from the crushing of the firecracker 1, and more precisely the upper cup 11 thereof, by a wheel of a railway vehicle, that is to say 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 F 1; Naturally, the upper cup It is intended to withstand without crushing the applied loads remaining below a predetermined threshold, and to crash only for loads thus applied exceeding this predetermined threshold, which results in a reconciliation of its central zone 12 vis-à-vis the lower cup 5 is with preservation of their mutual parallelism as illustrated in the left half of Figures 4, 6, 8, 10 or by an obliquity of the zone 12 relative to the lower cup, 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 crushing, which then leads to the total destruction of the

track firecracker 1.

  To detect the application of a load parallel to the axis 4 or forming an angle of only a few degrees with respect thereto and

  exceeding a predetermined threshold, that is to say to detect the reconciliation

  consecutive portion of the central zone 12 of the upper cup 11 relative to the lower cup 5, with or without obliquity, between this central zone 12 and the base 15 is interposed in each of the examples illustrated in FIGS. pedal 44 guided sliding parallel to the axis 5 relative to the base 15, between a rest position illustrated in FIGS 3, 5, 7, 9, which constitutes for this pedal 44 a high position, and a limit position of activation illustrated in Figures 4, 6, 8, 10, which is 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 a high voltage is produced between the terminals 17 and 18 of the piezoelectric body 16 causing the spark between the electrodes constituted by either the bucket 36 and the end zone 31 of the blade 21 (FIGS. 4 and 6), or by ex areas tremes 30 and 31 of the blades 20 and 21 (FIGS. 8 and 10), after the zones

  extremes 27 and 29 of the blades 20 and 21 have been mutually dissociated.

  For this purpose, the pedal 44 is constituted, identically in the various examples illustrated, two parts due to an electrically insulating plate and adapted to break by shear, for example plastic, and a body thrust 46 advantageously metallic.

  The plate 45 has a generally flat shape,

  dicular to the axis 2, between a convex upper face 47, placed in contact with the central zone 12 of the upper cup 11 at 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 Figures 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, on the same height h measured from the blade 21 in the zones thereof

  directly superimposed on face 25.

  Under the lower face 48 of the pedal 44 is provided by making in one piece a pin 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 3, 5, 7, 9, this stud 50 is placed immediately above the end zone 27 of the blade 20 cantilevered above the cavity 28 of the base 15 but slightly shifted, in the sense of a distance

  relative to the plane 212, with respect to the end zone 29 of the blade 21.

  It is noted that the presence of this stud 50 does not cause dissociation.

  end zones 27 and 29 of the blades 20 and 21 when the pedal 44

is in the rest position.

  To enable the pedal 44 to gain its activation position when the central zone 12 of the cup 11 tends to sag 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 with respect to this axis, the plate 45 has opposite each of the columns 49, in its face 44, a respective cutout 51 clearing the associated column 49 a respective tongue 52 constituting the

  means of support of the plate 45 on the column 49 respectively corres-

  this tongue 52 being placed cantilevered with respect to the remainder of the plate 45 and connected thereto by a bridge of material 53 having parallel to the axis 4 a still smaller thickness, calibrated so that this material bridge 53 breaks by shearing when the plate 45 receives parallel to the axis 4 or at an angle of some

  degrees therefrom a force exceeding said predetermined threshold.

  Then, as shown in Figures 4, 6, 8, 10, the material bridges 53 are broken and the plate 45, disjoint tabs 52 which remain retained by the columns 49, can descend to the base 15, on a stroke h , until its face 48 rests on this face 25 by

through the blade 21.

  In each of the exemplary embodiments illustrated in FIGS. 3 to 10, this translates into the depression of the end zone 27 of the blade in the cavity 28 of the base 15 under the action of the pin 50, that is to say by opening the short circuit created by the end zones 27 and 29 of the blades and 21, between the terminals 17 and 18 of the piezoelectric body 16, in the rest position. In the case of the illustrated example, in Figures 3 and 4, this results in a crushing of the blade 21 between the elbow 44 and the end portion 31, and by the penetration of the latter inside the bucket 36, to the aforementioned distance d of the bottom 41 of it as the

shows figure 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, an axial compressive stress capable of causing the appearance of a spark or an electric arc between the electrodes formed as

indicated it previously.

  This compression stress is applied by the thrust body 46, integral with the plate 45 and more precisely retained integrally inside a blind hole 151 pierced 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 cylindrical in revolution about the axis 4, with a radius less than the distance separating it from the stud 50 of the face 48 in each of the examples illustrated in FIGS. FIGS. 3 to 10, the passage 38 in the examples illustrated in FIGS. 3 to 8, the cavity 35 in the example illustrated in FIGS. 9 and 10, and the columns 49, in practice located in close proximity to the lateral faces 24 and 34 of the base 15 so as to locate the tabs 52 at the periphery of the plate 45 in each of these examples The blind hole 151 is further defined by a

  153 concave bottom face, also of revolution around the axis 4.

  The thrust body 46, in turn, has a head 54 of

  secured to the plate 45, which head 54 is delimited

  in the direction of a distance relative to the axis 4 and upwards by an outer circumferential face 55 cylindrical of revolution about the axis 4 with a radius identical to that of the inner peripheral face 152 of the blind hole 151 and by a convex upper face 56, of revolution about the axis 4 and closely complementary to the face of

bottom 153 of the blind hole 151.

  Downwards, the head 54 is delimited by a planar lower face 57, annular of revolution about the axis 4, which face 57 is connected in the direction of a distance relative thereto 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 approaching the axis 4, the lower face 57 of the head 54 is connected to a hammer 58 made in one piece with the head 54, and more precisely to an outer peripheral face 59,

  cylindrical of revolution about the axis 4, of this hammer 58.

  This outer peripheral face 59, of a radius smaller 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 about the axis 4, or to the radius of a geometric cylinder of revolution about 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 downwardly to one side 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

tray 45.

  The lower face 60 of the hammer 58 is thus placed facing the piezoelectric body 16 along the axis 4, with the interposition of the blade 21, and is spaced from the height h, with respect to this blade 21, in the rest position illustrated in Figures 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 the race h relative to the base 15 to gain the activation position illustrated in Figures 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, via 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 leading itself to the spark between the electrodes defined above, the extreme zones 27 and 29 of the blades 20 and 21 being

dissociated mutually.

  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 for guiding the plate 45 with respect to the base 15, such that so that the plate 45 retains substantially its general orientation perpendicular to the axis 4. For this purpose, around the housing 19 and more precisely respectively on either side of the blade 20, the base 15 has projecting on its face 25, advantageously by embodiment in one piece, two partial rings 61 mutually symmetrical by

  relative to the plane 13 and respectively symmetrical with respect to the plane 12.

  Delimited towards the plane 13 by flat faces 62 parallel to this plane 13, the partial crowns 61 are delimited in the direction of approach towards the axis 4 by an inner peripheral face 63

  cylindrical of revolution around this axis 4 with a substantial diameter-

  identical to that of the outer peripheral face 59 of the hammer 58 and in the direction of a distance relative to the axis 4 by an outer peripheral face 64 also cylindrical of revolution about the axis 4, with a substantially identical diameter 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 higher than that of the blade 21, in the areas thereof directly superimposed on the upper face of the base 15, a distance greater than h and at most equal to H, and for example equal to H in the illustrated example, if one refers to the 'state of

  rest illustrated in Figures 3, 5, 7, 9.

  Thus, a relative 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 crowns 61, on the one hand, and between the outer peripheral face 64 of these partial crowns 61 and the inner peripheral face 152 of the blind hole 151, on the other hand, without hindrance to the passage of the plate 45 from the rest position illustrated in FIGS. 3, 5, 7, 9 to the activation position illustrated in FIGS.

Figures 4, 6, 8, 10.

  A person skilled in the art will readily understand that the various examples of embodiment of a track firecracker according to the invention, as well as the various embodiments of the piezoelectric ignition device 9, which have just been described constitute only non-conventional examples. limiting, to which we can expect many variants

  without departing from the scope of the present invention.

  A person skilled in the art will also easily transpose the provisions that have just been described in the case of a track firecracker to the production of a mine, characterized in particular by the replacement of the explosive powder 8 by a military load and by the presence of

  security well known in the field of mining.

  In the case of track firecracker, a variant may consist of a dissociation of the single unit integrally mounted on the mushroom of a rail constituted by the firecracker of lane 1 described with reference to FIGS. 1 to 10, in two units of which one will be mounted on the mushroom of one rail and the other juxtaposed to the rail and each of which

  comprise a respective portion 9a, 9b of the piezo ignition device

  according to the invention, as will now be described with reference to FIG. 1 where these two units have been designated respectively by 66 and 67. In the exemplary embodiment illustrated in FIG. 66 intended to be fixed on the rail head is identical in its geometry and composition to the firecracker shown in Figures 1 and 2, in the embodiment shown in Figure 9 and can be found in Figure 11, for designating the components of the unit 66, the same references as in FIG. 9, except that: the container 7 does not contain any explosive powder 8, which can be replaced by a non-filler material represent,

  able to communicate to the container 7 a certain resistance to crush-

  while being fit to crash 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 with respect thereto; as filling material, it is possible to use, for example, a cellular structure, as is known in the fields of armament and aeronautics; the base 15 has no cavity 33 and does not contain pyrotechnic composition 37, and the end zones 30 and 31 of the blades 20 and 21 are not placed facing each other to form electrodes, but are electrically and mechanically connected, by any appropriate 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 passing through respective unrepresented holes of the part 10 and the zone 13, also not shown, of the upper cup 11, to ensure a mutual electrical connection

two units 66 and 67.

  Naturally, the geometry and composition of the unit 66 may also be different in view of the absence of explosive powder 8 and any other pyrotechnic composition; in particular, the container 7 and any abovementioned filling material thereof may be omitted, and the envelope formed by the cups 5 and 11 accordingly be modified in its geometry and design, it being understood that it must stay fit for a crash by a wheel of a

  railway vehicle with pedal actuation 44.

  The unit 67 has a metallic envelope 71

  advantageously achieved by crimping a lower cup 74

  72 and an upper cup 73 having shapes similar to those of the lower cup 5 and that of the upper cup Il

  of Firecracker 1, respectively.

  Inside the metal casing 71 thus formed, a base piece 75 made of plastic and doubling the lower cup 72 and a part 76 also made of plastic and doubling the upper cup 73 delimit a container 77 explosion powder 78. In a central position inside this container 77, the part 75 delimits a cavity 79 containing a pyrotechnic charge 80 completely similar to the pyrotechnic charge 37; the cavity 79 is open, so that this pyrotechnic charge 80 is placed in direct contact with the explosive powder 78, as in the embodiment of the firecracker

  lane 1 illustrated in FIGS. 9 and 10.

  Two metal strips 81, 82 housed in a protuberance 83 of the part 75 and thus electrically mutually insulated have free end zones 84, 85 located inside the cavity 79, facing one another, and spaced apart by the aforesaid distance A, capable of allowing the formation of a spark or an electric arc therebetween, through an area of the load 80, when the blades 81 and 82 are supplied with high voltage, and free ends 86, 87 opening outside the metal casing 71, in a connector 88 adapted to receive the cable 70 ensuring electrical continuity between the conductor 68 and the free end 86 of the blade 81, 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 a crushing of the latter by a wheel of a railway vehicle, its geometry and composition can

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 with respect to this axis, the pedal 44 leaves its rest position, illustrated in FIG. 11, to gain its activation position, similar to the position of the pedal shown in Figure 10, which disjoins the end zones 27 and 29 of the blades 20 and 21, on the one hand, and applies to the piezoelectric body 16 compression along the axis 4,

* translated by the appearance of a high voltage between its terminals 17 and 18.

  This high voltage is transmitted by the conductors 68 and 69 to the electrodes formed by the end zones 84 and 85 of the blades 81 and 82, 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 it to explode, with

  opening of the metal casing 71.

  Naturally, although a person skilled in the art easily understands that it is preferable, as a safety measure against accidental ignition of the explosive powder 8 or 78, to provide at least one mechanical safety device constituted in the various examples. illustrated by the support of the pedal 44 by means of the tabs 52 on the columns 49 of the base 15, in the rest position, and at least one electrical safety, constituted in these various 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, which is excessive to allow the formation of an electric arc or a spark between them under the effect of the high voltage possibly generated between terminals 17 and 18 of the body

  piezoelectric 16, some of these securities could be omitted.

  In addition, as electrical safety, it could be provided that the circuit between the terminals 17 and 18, on the one hand, and the electrodes, on the other hand, is open in the rest position, in particular at the blade 21 then made in two superposable but mutually disjoint 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 achieve such security from the provisions described about 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 down to the base 15. A man of the trade will also easily understand that a firecracker and, as an alternative to such a firecracker, a mine are not the only possibilities of application of an electric ignition device according to the invention, and the illustrated in Figures 12 and

  Two other non-limiting examples of application of such a device.

  FIG. 12 shows a smoke device 89 comprising a tubular casing 90 having a determined axis 91, containing a charge 92 of a fumigated pyrotechnic composition and connected at one of its axial ends to a coaxial cap 93 ,

  containing an electric ignition device 94 according to the invention.

  This device 94 comprises a piezoelectric body 95 of axis 91, having two terminals 96, 97 between which appears a high voltage when the piezoelectric body 95 is subjected to compression

along the axis 91.

  To receive the piezoelectric body 95, inside the base 93 is inserted a piece 98 of insulating plastic material, which is pierced with a blind hole 99 opening into an end face 100 of the base

93, opposite the envelope 90.

  In a zone that is comparatively closer to the envelope 90, this blind hole 99 constitutes a housing 101 for the piezoelectric body, immobilized by any appropriate means inside this housing and bearing in an axial direction 203 from the base 93 to the envelope 90 on a

  bottom face 102 of this blind hole 99.

  In a portion that is more distant from the envelope 90, the blind hole 99 defines, by an inner peripheral face 103 that is cylindrical in revolution about the axis 91, an axially sliding guide slide for a thrust body 104. delimited by an outer circumferential face 105 cylindrical of revolution about the axis 91 with a substantially identical diameter to that of the face 103 to provide the aforementioned guidance axial sliding, and two end faces 106, 107 planes, perpendicular to the axis 91, the first of which rests against the piezoelectric body 95, without applying axial compressive stress to the latter, in the idle state, inside the blind hole 99 and the second of which forms a axial projection relative to the face 100 so as to be able to receive, when a user desires, a thrust in the direction 203 in order to put the piezoelectric body 95 in constraint of co axial expression and to bring up a high voltage

between its 96 and 97 terminals.

  To prevent such a compressive stress from accidentally being applied to the piezoelectric body 95, the thrust body 104, forming in this example a push button, is protected in its area protruding from the face 100 by a dome 108 peripherally secured to the base 93 at the face 100 thereof, this dome 108 being advantageously made of a rigid material capable of breaking when it is applied in the direction 203 a force or shock exceeding a predetermined threshold , which constitutes a mechanical safety against the application to the thrust body 104 of a thrust specific to

  put the body 95 in axial compressive stress.

  Between the plastic part 98 and the envelope 90, the base 93 delimits a cavity 109 communicating with the inside of the envelope 90, that is to say with the charge 92 of smoke composition, and containing a charge 110 of a pyrotechnic composition peculiar to

  ignite under the action of a spark or an electric arc.

  In the cavity 109 are also housed end zones 111, 112 of two mutually electrically insulated metal plates 113, 114, each of which furthermore has an end zone 115, 116 in electrical conduction contact with a respective one of the terminals 96 and 97 of the piezoelectric body 95; the end zone 115 of the blade 113 is thus interposed between the terminal 96 and the bottom face 101 while the end zone 116 of the blade 114 is interposed between the face 106 of the thrust body 104 and the terminal 97, without oppose that a thrust applied to the thrust body 104 in the direction 203 results in the application to the piezoelectric body 95 of a compressive stress along the axis 91,

  capable of causing the appearance of high voltage between its terminals 96 and 97.

  This high voltage also appears between the extreme zones 111 and 112 of the blades 113 and 114, which extreme zones

  mutually spaced electrodes of a distance

  as long as such a high voltage results in the appearance, between them, of a spark or an electric arc across the corresponding zone of

the load 110.

  When this charge 110 is ignited, it itself causes the ignition of the smoke charge 92, which can present

any known design.

  Such a smoke device 89 can be commissioned voluntarily by the user, by application of a thrust in the direction 203 to the dome 108 and, after breaking thereof, to the thrust body 104 which then transmits this thrust, in the form of a constraint

  of compression, to the piezoelectric body 95.

  The mechanical strength of the dome 108 may be calibrated to allow initiation by applying a thrust or shock, either by hand or by striking against or by means of any object,

  the envelope 90 being naturally made so that the inflamma-

  load 92, preceded by a voluntary opening of the envelope 90 followed by an automatic opening thereof, does not cause danger

for the user.

  FIG. 13 illustrates, for its part, a signaling torch 117 which, like the smoke device 89, comprises a tubular envelope 118 having an axis 119 and containing a charge 120 of a

  illuminating pyrotechnic composition.

  This envelope 118, closed at one end by a lid 121 easily detachable, is closed at its other end by a fixed base 122 having the shape of a handle holding a portion 123 of a piezo ignition device according to the invention

  whose other part 123b is placed between the load 120 and the shutter 121.

  More specifically, inside the base 122 is housed in a fixed manner a piezoelectric body 124 of axis 125 parallel to the axis 119, the piezoelectric body 124 having two terminals 126 and 127 between which it emits a high tension when subjected to compression stress

along the axis 125.

  The two terminals 126 are connected by respective flexible electrical conductors 128, 129, passing through the load 120 from side to side parallel to the axis 119 under suitable electrical insulation, to electrodes 130, 131 arranged between the load 120 and the shutter 121 inside the casing 118, and more specifically within a load 132 of a flammable pyrotechnic pyrotechnic composition directly superimposed on the load 120, between the latter and the shutter 130; the two electrodes 130 and 131 are mutually spaced, inside the charge 132, with an air gap such that there appears between them a spark or an electric arc when a high voltage occurs between the terminals 126 and 127 of the pyrotechnic body 124,

  consecutive to the application to the latter of a compression constraint

along axis 125.

  Such a compression stress can be applied at will to the piezoelectric body 124 by means of a thrust body 133 which, in this example, has the shape of an inertial mass guided to sliding inside the base 122, along the axis 125, for example in the same way as the thrust body 104 described with reference to Figure 12, that is to say in a hole 134 formed in the base 122 along the axis 125

  and opening opposite the terminal 127 of the piezoelectric body 124.

  However, this section 34 does not open outside the base 122 opposite the piezoelectric body 124, and instead has the opposite of the body 124 a bottom 135 on which rests a coil spring 136 housed in the hole 134 in axial compression preload so as to permanently apply to the thrust body 133 a thrust towards the piezoelectric body 124, under conditions suitable to allow the thrust body 133, under the effect of the spring 136, to apply to the body 124 the compressive stress capable of causing the appearance of a

  high voltage between these terminals 126 and 127.

  However, in a rest position illustrated in FIG. 13, the thrust body 133 is held away from the body 124, along the axis 125, by mutual engagement of a peripheral, annular groove 137 of the body 133 and a trigger 138 articulated inside the base 122 about an axis 139

  perpendicular to a non-referenced plane defined by the axes 119 and 125.

  To allow to release at will the trigger 138 of the groove 137, that is to say to release at will the thrust body 133 so that it, pushed by the spring 136, comes to apply to the body 124 the compression stress causing the appearance of a high voltage between its terminals 126 and 127, the trigger 138 is integrally connected, on the other side of the axis 139, to a trigger key 140, forming a projection out the base 122 opposite the axis 125 relative to the axis 119 so that it can be applied at will a pressure in the direction of penetration inside the base 122 and that this pressure results in a pivoting of the trigger 138 in the direction of a

  clearance vis-à-vis the annular groove 137 of the thrust body 133.

  A spring 141 maintained in compressive prestressing, inside the base 122, along an axis 142 perpendicular to the axes 119 and, between the key 140 and a counterpart 142, resiliently urges the key 140 towards its projecting position out of the base 122, in which the trigger 138 engages in the annular groove 137 of the thrust body 133

  to hold it in the rest position.

  In order to prevent an accidental release of the thrust body 133, the key 140 is advantageously retained in its position projecting from the cap 122 by mechanical safety means allowing only a voluntary release of the key 140 with respect to A non-limiting example of such means, there is illustrated a pin 143 disposed along an axis 144 parallel to the axis 139 and passing through this axis 144 on the one hand an area of the key 140 and secondly an area of the base 122, outside which it has an accessible area to allow its extraction at will,

  that is, the release of the key 140.

  Naturally, numerous variants can be made to the smoke device 89 and to the signaling torch 117 which have just been described without thereby departing from the scope of the present invention.

  this invention, this smoke device 89 and this signaling torch

  117 having been described, schematically, only in order to demonstrate the many possibilities of adaptation of an electric detonator according to the invention In particular, it is understood that one could use a piezo ignition device electrical 94 of the type described with reference to the smoke device on a signaling torch 117 and a piezoelectric ignition device 123a, 123b of the type described with reference to the signaling torch 117 on a smoke device 89 Similarly, a thrust body forming an inertial mass in the manner of the thrust body 133 could move from its rest position to its activation position, that is to say application to the piezoelectric body of a stress of compression resulting in the appearance of a high voltage at the terminals thereof, not under the action of an elastic bias but under the action of a violent acceleration communicated to all the t signaling or smoke device in the direction of relative displacement of the thrust body and the piezoelectric body, after voluntary or automatic elimination of a mechanical restraint of the body of

pushing in the rest position.

  A person skilled in the art will also easily deduce modes of application, described above, of a piezoelectric ignition device according to the invention to the smoke device 89 and to the signaling torch 117 two modes of application of the invention. such an ignition device to a pyrotechnic projectile comprising a payload with a thermal effect, explosion or detonation, or with smoke or light effect, intended to be initiated

  during an impact of the projectile on a target.

  A first embodiment of such a projectile can derive directly from the structure described with reference to FIG. 12, the load 92 constituting the suitable payload and the ignition device 94 according to the invention being arranged in a pointed configuration, according to FIG. axis 91 then constituting the axis of the projectile, so that the thrust body 104, placed in front of the piezoelectric body 95, forms a pusher protruding forwardly with respect to the ogive along the axis 91, reference being made in the normal direction of progression of the projectile; it will be noted that a dome-like protection dome 108 may be preserved in such an application, it being understood that it may be supplemented or replaced in its mechanical safety role by other known mechanical safety devices, in particular for immobilizing strikers in projectiles, provided in this case to temporarily lock the thrust body 104 in the rest position and release it either by manual action before firing, or automatically after firing, vis-à-vis a passage to his position

activation.

  A second embodiment of such a projectile can derive directly from the structure described with reference to FIG. 13 in the sense that a thrust body similar to the thrust body 133, and in particular constituting an inertial mass capable of sliding parallel to the axis 119 constituting the axis of the projectile or along this axis and arranged behind a piezoelectric body similar to the piezoelectric body 124, can gain an activation position of the latter under the effect of an acceleration that it undergoes forward, relative to the projectile, due to a deceleration experienced by the latter during its impact on an objective; these notions of front and rear are understood by reference to the normal direction of progression of the projectile; naturally, no similar spring or spring 136 is provided in this case but safety means holding the thrust body 133 in the rest position,

  replacement of the trigger 138 trigger 140, are advantageous

  These safety means may be selected from among the known mechanical safety devices that make it possible to release the thrust body 133 in a deliberately controlled manner.

  prior to firing the shot, automatically after firing.

  In general, the present invention is capable of

  many variants without so far from its scope.

Claims (19)

  1 Electric ignition device of the type comprising a pyrotechnic charge (37, 40, 80, 110, 132) flammable by spark, two electrodes (30, 31, 36, 84, 85, 111, 112, 130, 131) arranged respectively on either side of a given area of the charge (37,, 80, 110, 132) and mutually spaced by a determined distance (d, 6, A) to allow the creation of an electric spark between they, through said zone of the charge (37, 40, 80, 110, 132), to ignite the latter, and a controlled electric generator, electrically connected to the electrodes (30, 31, 36, 84, 111, 112, 130 , 131) to cause the creation of said spark in a controlled manner during the occurrence of at least one predetermined condition, characterized in that the controlled electric generator comprises: a piezoelectric body (16, 95, 124) having two terminals (17, 18, 96, 97, 126, 127) and capable of generating a high voltage between when it is subjected to a compressive stress of a value exceeding a determined value, in a determined direction (4, 91,), a circuit (20, 21, 68, 69, 81, 82, 113, 114, 128, 129) for electrically connecting each terminal (17, 18, 96, 97, 126, 127) of the piezoelectric body (16, 95, 124) to a respective electrode (30, 31, 36, 84, 85 111, 112, 130, 131),   actuating means (44, 104, 108, 133, 136, 138, 140) for detecting the occurrence of said determined condition and then applying to the   piezoelectric body (16, 95, 124) said compressive stress.   2 Device according to claim 1, characterized in that the actuating means (44, 104, 108, 133, 136, 138, 140) comprise a thrust body (46, 104, 133) movable relative to the body piezo electrical (16, 95, 124) following a determined trajectory (4, 91, 125) under the effect of the appearance of said determined condition, a rest position that it occupies outside said determined condition and in which the thrust body (46, 104, 133) is functionally disjoint from the piezoelectric body (16, 95, 124) to an activation position which it occupies in said determined condition and in which the thrust body (46, 104 133) is functionally resting on the piezoelectric body (16, 95, 124) and said path has said determined direction (4, 91, 125), so that the thrust body (46, 104, 133) applies said   compressive stress to the piezoelectric body (16, 95, 124).   3 Device according to claim 2, characterized in that the thrust body (46, 104) is sensitive to a thrust or shock applied in said determined condition along said determined direction (4,   91), from the rest position to the activation position.   4 Device according to any one of claims 2 and 3,   characterized in that the thrust body has a zone (45, 107) for biasing its rest position towards its accessible activation position   from the outside of the detonator (9, 9a, 9b, 94) in the rest position.   Device according to any one of claims 2 and 3,   characterized in that the thrust body (133) is integrally housed in the detonator (123 a, 123 b).   Device according to any one of claims 1 to 5,   characterized in that it comprises means (49, 52, 108, 139, 140, 143) for mechanical safety against inadvertent application of said accidental compression stress to the piezoelectric body (16, 95, 124). Device according to claim 6 in combination with   any of claims 2 to 5, characterized in that the means   (49, 52, 108, 139, 140, 143) comprise means (49, 52, 108, 139, 140, 143) for retaining the thrust body (46, 133) in the rest position, suitable for releasing the thrust body (46, 133) under   the effect of the appearance of said determined condition.   8 Device according to claim 7, characterized in that the retaining means (49, 52) are adapted to automatically release the thrust body (46) when it in the rest position receives a force   exceeding a predetermined threshold, oriented towards its activation position.   9 Device according to claim 7, characterized in that the retaining means (108, 131, 140, 143) are adapted to be actuated at will, to release at will the thrust body (133) in the position of   rest for a passage to its activation position.   Device according to any one of claims 7 to 9,   characterized in that it comprises means (136) of elastic biasing of the thrust body (133) from its rest position to its activation position.   Apparatus according to any one of claims 1 to 10,   characterized in that it comprises means (27, 29, 38, 39, 40, 41, 50) of electrical safety to prevent accidental creation of said spark in case of accidental application of said stress of   piezoelectric body compression (16).   Device according to claim 11 in combination with   any one of claims 2 to 5 or with any one of   Claims 7 to 10, characterized in that the security means   electrical (27, 29, 39, 40, 41, 50) comprise in said electrical connection circuit (20, 21, 68, 69, 81, 82) a switch mechanically coupled to the thrust body (46) so as to be open when the thrust body (46) is in the rest position and closed when the body of   thrust is in the activation position.   Apparatus according to claim 11 in combination with   any one of claims 2 to 5 or with any one of   Claims 7 to 10, or according to Claim 12, characterized in that   the electrical safety means (27, 29, 38, 39, 40, 41, 50) 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) to be closed when the thrust body (46) is in the rest position and open when the thrust body (46) is in activation position.   Device according to claim 11, in combination with   any one of claims 2 to 5 or with any one of   claims 7 to 10, or according to any one of claims 12 and   13, characterized in that the electrical safety means (27, 29, 38, 39, 41, 50) comprise means (38) for guiding one (31), at least,   electrodes with respect to a movement of approximation or distance   with respect to the other electrode (30, 36), and means (39, 48) for coupling between the thrust body (46) and said electrode (31) guided so that the electrodes ( 30, 31, 36) are mutually spaced a distance (D) greater than said determined distance (d) and too large to allow the creation of an electric spark between them, through said area of the load (37), in case of accidental application of said compressive stress to the piezoelectric body (16), while the thrust body (46) is in the rest position, and spaced from said determined distance (d) when the thrust body (46) is in the activation position.   Apparatus according to any one of claims 1 to 14,   characterized in that it forms a unit of structure (9, 94) comprising the piezoelectric body (16, 95), the actuating means (44, 104, 108), the electrodes (30, 31, 36, 111, 112), the load (37, 110) and the connection (20, 21, 113, 114).   Device according to any one of claims 1 to 13,   characterized in that it forms two disjoint structure units (9a, 9b, 123a, 123b), one of which (9a, 123a) groups the piezoelectric body (16, 124) and the means actuation (44, 135, 136, 138, 140), the other (9 b, 123 b) including the electrodes (84, 85, 130, 131) and the load (80, 132), and   which are connected to each other by the electrical connection circuit that (68, 69, 128, 129).   Pyrotechnic device such as a firecracker or a signaling torch (1, 117), a smoke device (89), a mine, a pyrotechnic projectile, comprising a useful pyrotechnic charge (8, 78, 92, 180) chosen in a group consisting of explosion charges (8), illuminating charges (120), smoke loads (92), military charges with a thermal, explosive or detonating effect, and an ignition device (9, 9 a, 9 b, 94 , 123a, 123b), characterized in that the ignition device (9, 9a, 9b, 94, 123a, 123b) is an electric ignition device according to any one of   Claims 1 to 17, including the pyrotechnic charge (37, 80, 110, 132)   is in pyrotechnic connection with the payload (8, 78, 92, 120).   18 Device according to claim 17, characterized in that it constitutes a signaling firecracker (1, 66, 67) or a mine, respectively intended to deflag or explode at the appearance of a charge and in that, according to the claim 4, the thrust body (46) constitutes a pedal   (48) for detecting the occurrence of a charge.   19 Device according to claim 18, constituting a signal firecracker, characterized in that it forms two disjoint structure units (66, 67), one of which, according to claim 16, groups the piezoelectric body (16) and the actuating means (44, 135, 136, 138, 140) and the other of which includes the electrodes (24, 25), the pyrotechnic charge (80) flammable by flash, and the payload (78), and are connected to each other by an electrical connection cable   part of the electrical connection circuit (68, 69).   Device according to Claim 17, characterized in that it constitutes a signaling torch (117) or a smoke device (89) intended to emit a signal respectively light or defined in a deliberately controlled manner, and in that, according to the claim 4, the body   push button (104) is a manually operated push button.   21 Device according to claim 17, characterized in that it constitutes a signaling torch (117) or a smoke device (89), intended to emit respectively a light signal or a smoke voluntarily controlled, and in that, according to any of   4 and 5, the thrust body (133) constitutes a mass   inertial. Device according to claim 21, characterized in that,   according to claims 9 and 10 in combination, said mass (133) is   elastically biased from the rest position to the activation position and in that there is provided a trigger (138) for retaining said mass (133) in the rest position and a trigger (140) in operative connection with the trigger (138) and manually operable to release at will mass (133) of said retainer.   23 Apparatus according to claim 17, characterized in that it constitutes a pyrotechnic projectile and in that, according to claim 4, the thrust body (104) forms a pusher disposed in the ogive along the axis of the projectile, is arranged in before the piezoelectric body (95) and forms a protrusion forward with respect to the warhead, with reference to a normal direction progress of the projectile.   24 Device according to claim 17, characterized in that it constitutes a pyrotechnic projectile and in that, according to claim 5, the thrust body (104) constitutes an inertial mass placed behind of the piezoelectric body (24).