EP0648997B1 - High energy fuse - Google Patents

Description

The present invention relates to a firing device of the high energy type.

A privileged field of application of the invention relates to high energy detonators grouping, on the one hand devices with projected element or DEP, and on the other hand, devices with exploded wire or EBW (EBW being the initials English- Saxons put for Exploding Bridge Wire). Such devices can be used in particular as detonators to trigger the operation of military charges, rocket propellants, missiles, or even gas generators (in this case, we speak rather of igniters).

Figure 1 illustrates the electrical diagram of a conventional high energy firing device.

It is presented as the placing in series, in a looped-back circuit, of a storage capacitor 1, of means 2 for controlling the discharge of the capacitor 1, and of a high energy detonator 3. The means 2 are for example made up of: 'a spark gap. The capacitor 1 is used to store the quantity of energy necessary for the operation of the ignition. It is charged under a high voltage V _HT , and must have a relatively large capacity, typically around 0.15 µF. To trigger the actual firing, an electric pulse V _G is delivered on the trigger of the spark gap 2, so that the capacitor can discharge as quickly as possible. The discharge of the capacitor will cause, in the case of a DEP, the cutting and the projection of a pellet on a secondary explosive, or, in the case of an detonator with exploded wire, the explosion of a placed wire in an explosive.

One of the major problems encountered in the production of firing devices operating according to the diagram in FIG. 1, resides in the small volume generally allocated to these devices.

The Applicant has already partially solved this space problem by proposing a DEP type detonator, having a coaxial structure. This detonator was the subject of a French patent application FR-A-26 69725 and shows the characteristics of the preamble of independent claim 1. The appended FIG. 2 briefly illustrates the coaxial structure of the DEP, without going into detail of the operation of the DEP itself:

The detonator 4 with a coaxial structure essentially comprises a cylindrical metallized anvil 40 carrying a fuse bridge 41, a socket of revolution 42 made of dielectric material, and a substantially cylindrical confinement 43 placed on the fuse bridge along the longitudinal axis of symmetry XX ′ of the detonator, and kept in contact with the internal walls of the sleeve 42. This confinement 43 comprises in particular a secondary explosive and a barrel (not visible) positioned between the explosive and the fuse bridge 41 for cutting and guiding the element projected onto the explosive. The socket 42 is connected to the anvil 40 by means of a cylindrical ring with flange 44. Around the body of the socket 42 and the cylindrical ring 44, there is a flexible cylindrical contact piece 45 comprising a cylindrical part 46 in contact with the ring 44, and folded flexible tabs 47. These flexible tabs 47 perform the role of first electrical connection of the detonator. They are in fact electrically connected to one end of the fuse bridge 41 via the cylindrical ring 44 and a conductive surface not visible in FIG. 2 located on the periphery of the upper face of the anvil 40 in electrical contact with one end of the fuse bridge 41. The other end of the fuse bridge is electrically connected to a second connection 48 of the detonator located on the opposite face of the anvil 40, by means of an electrical bushing 49 produced in the anvil. The second connection 48 is for example a metal disc centered on the longitudinal axis XX 'of the detonator 4.

The structure of the detonator, as just described, is said to be coaxial due to the position of the two connections 47 and 48 placed coaxially on the longitudinal axis XX 'of the detonator. From an electrical point of view, the only existing asymmetry comes from the electrical bushing 49 which is eccentric with respect to the longitudinal axis XX '. Thus, the coaxial structure by its connections, also behaves almost like a coaxial element, and therefore has a very low equivalent inductance.

The above coaxial structure is advantageous in that it has a reduced bulk.

The fact remains that, to make a firing device, it is necessary to add to the previous detonator, a spark gap and a storage capacitor, which capacitor, by the large value of its capacity, remains large.

At present, a capacitor with armatures of parallelepiped shape, having two connection tabs and mounted on an electronic card, is used.

The high-energy spark gap and detonator are located on this card as close as possible to the capacitor in order to reduce, as far as possible, the equivalent resistance R _e and the equivalent inductance L _e of the firing device, and be therefore best suited to the operation of the detonator.

A first drawback associated with this parallelepiped capacitor is that it makes the detonator with a coaxial structure as described above lose some interest. Indeed, to ensure the connection of the detonator with a coaxial structure with the parallelepiped capacitor, it is necessary to produce an electrical interface. This interface is produced in the form of a box in which the detonator with a coaxial structure is placed. This box has at its bottom and on its internal lateral face conductive surfaces in contact respectively with the connections 48 and 47 of the detonator. The housing must also have external connections in the form of two tabs located under the housing, which are connected to the capacitor and to the spark gap via conductive tracks made on the electronic card.

The production of such a box is heavy and expensive and the electrical connections are also more difficult to achieve. It is also necessary to place the longitudinal axis of the detonator perpendicular to the plane of the electronic card. As a result, the complete firing device is bulky and difficult to integrate near a pyrotechnic chain to initiate.

Furthermore, current firing devices using a capacitor of the aforementioned type have an equivalent resistance R _e and an equivalent inductance L _e respectively of the order of 150 mΩ and 30 nH, values which should be reduced to optimize firing of the detonator.

Finally, to increase the level of reliability, the volume occupied by the capacitor should be increased. There is therefore an incompatibility between on the one hand, the space constraints and on the other hand, the reliability criteria imposed.

The object of the present invention is to overcome the various aforementioned drawbacks by proposing a high energy firing device occupying a small volume and having connections between elements much simpler to produce than in the prior art, and therefore , more easily industrializable. The device according to the invention does not require any electronic card for mounting the various elements, and has an equivalent impedance and inductance reduced compared to those obtained hitherto.

More specifically, the present invention relates to a high energy firing device as defined in claims 1 to 10.

• la figure 1 est un schéma électrique d'un dispositif de mise à feu ;
• la figure 2 rappelle la constitution d'un détonateur type DEP à structure coaxiale de l'art antérieur ;
• la figure 3 est une coupe d'un premier mode de réalisation possible du dispositif de mise à feu haute énergie selon l'invention ;
• la figure 4 est une coupe d'un second mode de réalisation possible du dispositif de mise à feu haute énergie selon l'invention ;

The invention, as well as the various advantages which it provides, will be better understood in the light of the description below, given with reference to the appended figures:

• Figure 1 is an electrical diagram of a firing device;
• Figure 2 recalls the constitution of a DEP type detonator with coaxial structure of the prior art;
• Figure 3 is a section through a first possible embodiment of the high energy firing device according to the invention;
• Figure 4 is a section of a second possible embodiment of the high energy firing device according to the invention;

Figures 1 and 2 have already been described above.

Before describing the different figures illustrating different particular embodiments of the firing device according to the invention, it is necessary to describe the general characteristics common to these embodiments:

The high energy firing device according to the invention corresponds to the electrical diagram of FIG. 1, and therefore results from the placing in series of a storage capacitor 1, of control means 2 for discharging the capacitor 1, and a high energy detonator 3. The important innovation of the device proposed here lies in the choice of particular structural elements, in particular as regards the capacitor and the detonator, as well as in the relative positioning of these elements. In fact, according to a first important characteristic of the device according to the invention, the capacitor 1 used is produced in the form of a cylinder with a longitudinal axis X ₁ X ′ ₁ , having a hole or axial recess of shape substantially cylindrical. It should be specified here that the terms "cylinders" and "cylindrical" must be taken in the geometric sense of the term, that is to say as defining any solid generated by a straight line which moves parallel to itself in s' pressing on a directing curve, the latter being able to be circular (cylinder of revolution), or not.

The capacitor 1 is preferably a capacitor with armatures produced, in a known manner, by the winding of films on a mandrel having the shape and the dimensions of the desired axial recess. The capacitor 1 has two metal electrodes which can advantageously be located respectively on the upper and lower bases of the cylinder. The dimensions of the axial recess are chosen so that the control means 2 can be placed inside this recess. These for example consist of a spark gap made in the form of a cylinder comprising at each end, a connection electrode and, on one of the two electrodes, a trigger receiving the electric pulse V _G controlling the discharge of the capacitor. The spark gap 2 is advantageously positioned so that the axis joining the two spark gap electrodes is aligned with the longitudinal axis X ₁ X ' ₁ of the capacitor, the trigger being able to come out slightly from the recess.

In addition, according to another important characteristic of the device according to the invention, the detonator 3 used has a coaxial structure of axis XX ', as described with reference to FIG. 2, that is to say comprising a first connection 48 located at its base, and a second connection 47, in the form of flexible tongues positioned on the periphery of the detonator, that is to say in a plane substantially perpendicular to the longitudinal axis XX 'of the detonator. It is placed relative to the capacitor 1 so that its axis XX 'is substantially aligned with the longitudinal axis X ₁ X' ₁ of the capacitor, the first connection 48 being for example on the side of the capacitor. The detonator 3 is then electrically connected to the control means by means of an electrical connection preferably passing partly or completely inside the recess, depending on whether the detonator is more or less distant from the capacitor. Such an arrangement of the different elements with respect to each other allows to obtain a device whose impedance and inductance equivalent are very reduced compared to what one obtained until then.

Advantageously, the two electrodes of the capacitor 1 are metal rings placed respectively on the upper base and on the lower base of the cylinder. In this way, the necessary connections between, on the one hand the capacitor 1 and the detonator 3, and, on the other hand the capacitor 1 and the spark gap 2 can be produced in the form of parts of revolution which are more easily industrializable.

In addition, provision can be made to place the detonator 3 inside the axial recess in order to obtain a very compact complete device.

We will now describe, with reference to FIGS. 3 and 4, two particularly interesting possible embodiments of the device according to the invention:

In FIG. 3, the detonator 3 with a coaxial structure and the spark gap 2 are both located inside the axial recess 10 of the cylindrical capacitor 1 along the axis X ₁ X ′ ₁ of the capacitor 1. The spark gap 2 is for example a cylinder provided at its two ends with electrodes 21 and 22, and with a trigger 23 on which an electric pulse V _G is sent to control the discharge of the capacitor. The detonator 3 with coaxial structure has, as we have seen with reference to FIG. 2, two connections 47 and 48 placed coaxially along the axis XX 'of the detonator. The necessary electrical connection between the detonator and the spark gap can therefore be achieved very simply by direct contact between the electrode 22 of the spark gap and the connection 48.

As we said earlier, the electrodes of the capacitor 1 are preferably made on the upper and lower bases of the cylinder 1, for example by means of metal rings 11 and 12, each being connected to one of the two armatures (not visible ) of the capacitor 1. It is thus possible to optimize on the one hand, the electrical connection 5 between the electrode 11 of the capacitor and the electrode 21 of the spark gap, and on the other hand, the electrical connection 6 between l electrode 12 of the capacitor and the connection tabs 47 of the detonator.

The above-mentioned electrical connection 5 is for example a metal revolution part having a hole 50 to allow passage to the trigger 23 of the spark gap.

The electrical connection 6 shown in FIG. 3 is also a piece of metallic revolution, the shape of which is that of a hollow flared sleeve, consisting of a cylindrical part 60 which fits into the axial recess 10 over a length sufficient to be in contact with the tabs 47 of the detonator, and of a flared portion 61, substantially planar, which comes into contact with the electrode 12 of the capacitor. The cylindrical part 60 simultaneously maintains the detonator and the necessary electrical contact.

The firing device in Figure 3 has many advantages:

It is first of all very compact and satisfies the space constraints satisfactorily. Typically, a cylinder of approximately 35 mm in external diameter, provided with an axial hole of approximately 13 mm by 14 mm in height, makes it possible to produce a capacitor of approximately 0.15 μF of capacity, in which can be accommodated. a detonator and a spark gap. With these values, the volume occupied by the capacitor is approximately 11.6 cm ³ against 13.5 cm ³ of total volume occupied by the ignition device, which increases the level of reliability (good coefficient voltage derating).

In addition, the positioning of the spark gap inside the axial recess makes it possible to protect the spark gap against severe electromagnetic environments which risk unexpectedly triggering the ignition.

In addition, the device of Figure 3 has a coaxial structure whose equivalent resistance and inductance are reduced by 30 to 40 mΩ and 15 to 20 nanohenrys respectively compared to the devices of the prior art. It follows that the voltage V _HT necessary for the operation of the device according to the invention can be lowered compared to that of a conventional device.

Furthermore, the various additional connections 5 and 6 are simple and easily industrializable.

Because of the symmetry of the device with detonator inside the capacitor, the device of FIG. 3 is particularly interesting in all systems where the initiation of a pyrotechnic element is carried out by the center.

The second possible embodiment of the device according to the invention illustrated in FIG. 4 is particularly advantageous in the case where the device is placed in a hermetic case 9, the detonator 3 being outside this case. The device of FIG. 4 is almost identical to that of FIG. 3, except that the detonator 3 is located outside the axial recess 10 of the capacitor 1 and that the connection 7 between the electrode 22 of the 'spark gap 2 and the connection 48 of the detonator on the one hand and the connection 6' between the electrode 12 of the capacitor and the connection 47 of the detonator on the other hand form a hermetic coaxial connection, therefore of low inductance.

In the embodiment shown in FIG. 4, the connection 6 ′ is a coaxial connection comprising a hollow cylindrical and metallic part 60 ′ into which the detonator 3 is inserted, so that the tabs 47 of the detonator are in contact with this part 60 ′, as well as a base in the form of a metal crown 61 which comes into contact with the electrode 12 of the capacitor. The connection 7 is for example made up of an axial metal rod. The connections 6 ′ and 7 are advantageously assembled together by a dielectric 8. This dielectric 8 also provides the connection between the hermetic connection and the housing 9.

The assembly thus produced according to FIG. 4 makes it possible to integrate the electronic part of the device in a hermetic housing, the detonator being outside and easily disconnected. It is then possible to easily test the electronic part.

The high energy firing device as just described in different embodiments, is very flexible to use thanks to its modular nature.

The small volume of the firing module makes it possible to use a single central electronic module supplying in parallel, via high voltage cables, a plurality of firing devices.

Claims (10)

1. High-energy firing device comprising, connected in series in a looped circuit, a capacitor (1) for storing energy at a high voltage V_HT, means (2) for initiating the discharge of the capacitor, and a high-energy detonator (3), the triggering of which results from the said discharge, the device being characterized in that the capacitor (1) is made in the form of a cylinder with a longitudinal axis X₁X'₁ having an axial recess (10) inside which the initiating means (2) are placed, in that the detonator (3) is made in the form of a coaxial structure with an axis XX' approximately aligned with the longitudinal axis X₁X'₁ of the capacitor (1) and in that the detonator (3) is connected to the initiating means (2) via an electrical connection approximately parallel to the longitudinal axis X₁X'₁.
2. High-energy firing device according to Claim 1, characterized in that the capacitor (1) has two metal electrodes (11, 12) placed respectively on the upper and lower bases of the cylinder.
3. High-energy firing device according to Claim 2, characterized in that the electrodes (11, 12) have approximately the shape of rings.
4. High-energy firing device according to any one of the preceding claims, characterized in that the initiating means consist of a spark gap of approximately cylindrical shape arranged axially with respect to the axis X₁X'₁ of the capacitor (1), and having, at each end, a connector electrode (21,22) and, on the connection electrode (21) placed as close as possible to the upper base of the capacitor (1), a trigger (23) which receives an electrical pulse V_G initiating the discharge of the capacitor (1).
5. High-energy firing device according to Claims 3 and 4, characterized in that the electrode (21) of the spark gap located as close as possible to the upper base of the capacitor (1) is connected to the ring-shaped electrode (11) placed on the upper base of the capacitor via an axisymmetric metal piece (5) having a hole (50) for letting the trigger (23) pass through.
6. High-energy firing device according to any one of the preceding claims, characterized in that the detonator (3) is placed inside the axial recess (10).
7. High-energy firing device according to Claim 6, characterized in that the detonator (3) has a connection (48) made in the form of a metal disc centred on the longitudinal axis of the detonator, and in that the electrical connection which connects the detonator (3) to the initiating means (2) is made by direct contact of the metal disc with an electrode (22) of the initiating means.
8. High-energy firing device according to Claims 3 and 7, characterized in that the detonator (3) has a connection (47) comprising bent-over flexible strips and in that the electrical connection which connects the detonator (3) to the capacitor (1) is an axisymmetric piece having the shape of a hollow flared sleeve consisting of a cylindrical part (60), which fits into the axial recess (10) over a length sufficient to be in contact with the strips (47), and of an approximately plane flared part (61) which comes into contact with the metal ring (12) of the capacitor (1) placed on the lower base thereof.
9. High-energy firing device according to any one of Claims 1 to 5, characterized in that the detonator is placed outside the axial recess (10).
10. High-energy firing device according to Claim 9, characterized in that the electrical connection between the detonator (3) and the initiating means (2) consists of a metal rod (7).

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