EP2386819B1 - Firing device for an initiator - Google Patents

Description

The present invention relates to a firing device for an initiator. Favorably the initiator, electric, will be a pyrotechnic initiator, a priori pilotable. This may typically be an igniter or detonator. In particular, the firing device will be of the type to enable the ignition of the initiator by the production of heat, in particular by Joule effect or by radiation.

A projected layer detonator is known for initiating a secondary safety explosive. In such a detonator, an electrical conductor produces a plasma that is used to propel at high speed a small projectile delivering the shock wave necessary for the priming of the secondary explosive. Such a detonator requires a voltage greater than or equal to 2000 V and a voltage rise time of less than 1 μs, therefore a complex power supply and a low inductance connection that is very demanding when used.

This particularly high voltage allows the projected layer detonator to meet the safety standards of the STANAG 4560 requiring in particular the initiator not to react when an alternating current of 500 V (with peaks of 710 V) is connected directly to its terminals Otherwise, the initiator must present a mechanical interruption of the pyrotechnic chain downstream of the energetic material.

However, this particularly high voltage has the disadvantage of having a rather cumbersome firing device, consequently limiting the use of the projected layer detonators.

Furthermore, an optical detonator is known in which a laser beam emitted by a laser source (preferably a laser diode) ignites a secondary explosive disposed in a first stage which propels a small projectile delivering the necessary shock wave to the priming the secondary explosive of the second stage.

Such a detonator has many advantages, including that of requiring very little energy (a laser diode requires less than 2 V and less than 1 A to emit light), to be compact (the laser diode is less cumbersome a low voltage / high voltage converter), and to be very sensitive to static electricity (the optical fiber may be several hundred meters long, the laser diode can be integrated in the protected enclosure of the computer).

However, the "laser diode - fiber - opto-pyrotechnic initiator" assembly is assimilated for the first time to an electrical initiator in the third edition of the STANAG 4368 standard because the laser diode is an electrical component. Consequently, since 2 V is sufficient to initiate the laser diode, such a detonator can not remain insensitive to an AC voltage of 500 V and, in order to comply with the security standard of STANAG 4560 mentioned above, it must have an optical line interruption. upstream of the energy material initiated by the laser light.

Or an optical switch disposed on the optical fiber is bulky, has an additional cost and does not support severe environments (mechanical and thermal) experienced by some initiators.

The present invention aims to provide a firing device allowing the initiator with which it is associated to be insensitive to AC voltages of 500 V (and therefore not to require a line interruption), while being of a small footprint.
N02008 / 112235 discloses protecting the heating element of an initiator by an electrical element, which switches from an insulating state to a conductive state, and only from a certain voltage at its terminals. But this electric element does not play the role of a switch: the switch is added in series to the protection element. FR 2408114 and FR 2866703 also refer to the same type of protection as above. In FR 2408114 , which discloses a device according to the preamble of claim 1, it is various electronic components where the thyristor is used as a switch controlled by its trigger. In FR 2866703 , the element is called micro-switch (micro-switch) and is understood as a cleachable insulator or a spark gap.
Thus, it is already known a firing device of an initiator, the device comprising a firing member adapted to generate heat to initiate an energetic material disposed in the initiator, an electric switch arranged in series with the firing member and passing from an open state to a closed state by the application at its terminals of a voltage greater than a closing voltage.
But this does not answer the aforementioned problematic.
A proposed solution provides in this regard that the electrical switch comprises at least one thyristor having an unused trigger and a corresponding overturning voltage (ie equal to) the closing voltage.
Thus, it is the switch itself that will be the protection element.

Also note that in WO2008 / 112235 , it is always mentioned TVS and not thyristor. However, TVS are different components (made of avalanche diodes). They have reversal voltages which are in this case too weak.

In addition, in the documents of the prior art, the thyristor was only mentioned in its normal function of switch controlled by its trigger. It was not used outside of its nominal function and its limits, contrary to the invention.

It is recommended that the firing element be a resistive element (for an electrical initiator) or a laser diode (for an optical initiator).

In order to meet the STANAG 4560 safety standard, the electrical switch is chosen so that its closing voltage is greater than 500 V (AC voltage), which corresponds to peaks of 710 V. In addition, in order to have the smallest possible footprint and a simple implementation, the electrical switch is chosen so that its closing voltage is less than 1000 V.

• La figure 1 représente un schéma d'un dispositif de mise à feu conforme à un premier mode de réalisation, le dispositif comprenant, en série, un thyristor et une diode, la figure 1 comprenant également un diagramme représentant la tension U et la puissance lumineuse L en fonction de l'intensité I,
• La figure 2 représente un dispositif de mise à feu conforme à un second mode de réalisation, le dispositif comprenant, en série, un thyristor et un élément résistif, la figure 2 comprenant également un diagramme représentant la tension U en fonction de l'intensité I,
• La figure 3 représente l'intensité traversant le dispositif de mise à feu du premier mode de réalisation pour un courant alternatif ayant des pointes de 660 V ;
• La figure 4 représente l'intensité traversant le dispositif de mise à feu du premier mode de réalisation suite à l'application d'une tension de 800 V ;
• La figure 5 représente l'intensité traversant le dispositif de mise à feu du premier mode de réalisation suite à l'application d'une tension de 1000 V, et
• Les figures 6,7 représentent chacune un schéma d'un dispositif de mise à feu conforme à un autre mode de réalisation, le dispositif comprenant, en série, figure 6, un triac et une diode et, figure 7, un triac et un élément résistif.

Other features and advantages will become apparent in the embodiments given as non-limiting examples and illustrated by the appended drawings in which:

• The figure 1 represents a diagram of a firing device according to a first embodiment, the device comprising, in series, a thyristor and a diode, the figure 1 also comprising a diagram representing the voltage U and the light power L as a function of the intensity I,
• The figure 2 represents a firing device according to a second embodiment, the device comprising, in series, a thyristor and a resistive element, the figure 2 also comprising a diagram representing the voltage U as a function of the intensity I,
• The figure 3 represents the intensity through the firing device of the first embodiment for an alternating current having peaks of 660 V;
• The figure 4 represents the intensity passing through the firing device of the first embodiment following the application of a voltage of 800 V;
• The figure 5 represents the intensity passing through the firing device of the first embodiment following the application of a voltage of 1000 V, and
• The figures 6.7 each represent a diagram of a firing device according to another embodiment, the device comprising, in series, figure 6 , a triac and a diode and, figure 7 , a triac and a resistive element.

The invention relates to a firing device 1 for igniting an electric initiator. Such an initiator can be used for firing pyromechanisms or thrusters.

The devices for firing powder or explosive are concerned.

The firing device 1 comprises a firing member 2, 3 which is adapted to generate heat for the initiation of an energetic material disposed in the initiator.

In the first embodiment, the firing member is a laser diode 2 which makes it possible to generate a laser light which, after focusing, makes it possible to ignite the energetic material enclosed in the initiator.

As illustrated in figure 1 , the laser diode 2 begins to conduct the electric current from a threshold of voltage (Udl curve) and, from a minimum intensity therethrough, to emit a light whose power is proportional to this intensity (curve L).

In the second embodiment, the firing member is a resistive element 3 (here, an electrical resistor 3) which generates, by Joule effect, heat for igniting the energetic material enclosed in the initiator.

As illustrated in figure 2 the intensity passing through the resistor 3 is proportional to the voltage at its terminals (curve Ur), and the power delivered is proportional to the square of this intensity.

The firing device 1 also comprises an electric switch 4 which is connected in series with the firing member 2, 3 and which goes from an open state to a closed state by the application of a higher voltage at a closing voltage. More specifically, the electric switch 4 comprises (at least) a thyristor 4 whose trigger is not used, with a reversal voltage equal to the closing voltage. In the embodiments of figures 1,2 , the electric switch 4 is a single thyristor.

typically, such a thyristor, is intended to be used with a voltage lower than its inverting voltage, and to go from its open state to its closed state by the application of an electrical pulse on its trigger. In the present invention, the trigger is not used, the property of the thyristor used is the transition from its open state to its closed state following the application, between its cathode and its anode, of a voltage greater than its voltage. reversal (see curve Ut of Figures 1 and 2 ).

Thus, the firing device 1 according to the present invention does not conduct current as long as the closing voltage of the electric switch 4 is not reached (cf. Figures 3 and 4 where the intensity passing through it remains zero). When this closing voltage is reached, the firing device 1 behaves like the firing member 2, 3 alone with a slightly higher voltage (see U curves of FIG. Figures 1 and 2 ). The figure 5 illustrates the behavior of a firing device 1 following the application of a voltage of 1000 V at its terminals: once the voltage has reached the reversal voltage of the thyristor with electrical switch function 4 ( here, 900 V), an electric current passes through the device, which allows the ignition of the associated initiator.

The electrical switch 4 and the initiation member 2, 3 can be put in the same housing so as to make only one component (with only two connections coming out of the housing - the trigger is not used). The electric switch 4 and the heating element 2, 3 can be placed side by side or fused on the same substrate.

The use of an electrical switch 4 whose closing voltage (the reversing voltage in the case of a thyristor) is greater than the peaks of 710 V of a 500 V AC voltage makes it possible to meet the safety standard STANAG 4560, without line breaks. As a result, such a firing device 1 makes it possible to have an initiator of high reliability and of a high degree of operational safety, handling and implementation. In addition, the costs of electrical switches such as thyristors or triacs are low, which makes it possible to produce very high initiators. security at a much lower price than those currently available on the market.

In addition, the use of an electrical switch 4 whose closing voltage (the inverting voltage in the case of a thyristor) is less than 1000 V makes it possible to have a simple implementation and thus to miniaturize the firing device 1. For example, it is possible to use such a device for firing four impellers embedded in a projectile whose diameter is 30 mm.

Moreover, in order to have the smallest possible circuit, it is preferable to choose an electrical switch 4 whose reversal voltage is barely higher than that authorized by the regulations (typically, from 800 V).

These firing devices for initiators are therefore of the highest security while not being very high energy.

They allow the firing of detonators complying with STANAG 4187 standards and comprising only secondary explosives compliant with STANAG 4170 standards, as well as the ignition of igniters meeting STANAG 4368 standards and loaded with pyrotechnic safety compositions. As a reminder, an igniter is a trigger device that produces a deflagration (burning).

In the case of an optical initiator (igniter or detonator), it may comply with one of the requests EP 1 067 356 , EP 1 067 357 , EP 1 306 643 and EP 1 742 009 .

In the case of an electrical initiator, and more specifically, in the case of a detonator, the resistive element 3 can also be any passive electronic component (resistor or capacitor) or active (diode or transistor) for transmitting its heating to the energy material with good efficiency. Since the Joule effect does not allow a secondary explosive to be detonated, it is therefore necessary to use a two-stage detonator with a deflagration-detonation transition or a shock-detonation transition. For reasons of reliability, shock-detonation operation is preferred.

Thus, the resistive element may be a tantalum capacitor which has the advantages of being of small size, of being able to be easily implemented, and of having two different impedance curves according to its direction of use: this capacitor can be likened to a diac when it is solicited live because it has a negative resistance slope beyond a limit, or diode live when it is invoked in reverse because it has a positive resistance slope beyond a threshold.

Thus, by this invention, the initiator with which the firing device is associated has the following three advantages: reliable operation with less than 1000 V (and therefore simplicity of implementation), holding, with success and without alteration, tests of 500 V AC, and use of insensitive active substances.

Other embodiments are possible. Thus, the electric switch could be a triac.

Figures 6.7 we also see such a triac, "TRIode for Alternating Current" (triode for alternating current).

The Figures 6, 7 correspond to the montages of the figures 1,2 , respectively, except that the thyristor has been replaced by the triac.

The triac is an electronic component equivalent to two thyristors (or semiconductor controlled rectifier (SCR) or SCRs mounted in parallel, but head to tail.A triac is sometimes also called a bidirectional thyristor.It has the same properties than those of such a thyristor, and can be used here in the same way as the thyristor, instead of it, as long as it has the same value of reversal voltage.It can even be considered as more practical in the case of a resistive element initiator, since it can be used indifferently in both directions of current flow and does not require registration.

What was previously presented in relation to the operating mode of the thyristor applies to the triac.

So, Figs. 6.7 , there is the firing device 1 comprising the firing member, respectively 2 and 3, adapted to generate heat for the initiation of an energetic material disposed in the electric initiator. Fig.6 , the firing member is the laser diode 2. Fig.7 , the firing member is the resistive element 3. In both cases, the firing device 1 also comprises the electric switch 4, which here comprises a triac, and which is connected in series with the firing member 2, 3. This triac therefore goes from an open state to a closed state by the application of a voltage greater than a closing voltage.

Claims (12)

1. Firing device (1) of an initiator, the device comprising a firing member (2, 3) suitable for generating heat to initiate an energetic material arranged in the initiator, an electrical switch (4) arranged in series with the firing member (2, 3) and switching from an open state to a closed state by the application to its terminals of a voltage higher than a closure voltage, the electrical switch (4) comprising at least one thyristor, the device being characterized in that the thyristor has an unused gate and a return voltage corresponding to the closure voltage.
2. Firing device according to Claim 1, characterized in that the electrical switch (4) comprises a single thyristor.
3. Firing device according to one of the preceding claims, characterized in that the electrical switch (4) comprises a triac.
4. Firing device according to one of the preceding claims, characterized in that the closure voltage is higher than an alternating voltage of 500 V.
5. Firing device according to one of the preceding claims, characterized in that the closure voltage is lower than a voltage of 1000 V.
6. Firing device according to one of the preceding claims, characterized in that that the firing member (2, 3) comprises a laser diode (2).
7. Firing device according to one of Claims 1 to 5, characterized in that the firing member (2, 3) comprises a resistive element (3).
8. Firing device according to Claim 7, characterized in that the resistive element (3) comprises a resistor.
9. Initiation device according to Claim 7, characterized in that the resistive element (3) comprises a tantalum capacitor.
10. Initiation system of a pyrotechnic chain comprising a firing device (1) conforming to one of the preceding claims, and an initiator to which the firing device (2, 3) is connected.
11. Initiation system according to Claim 10, characterized in that the initiator is a squib.
12. Initiation system according to Claim 10, characterized in that the initiator is a detonator.

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