FR2840401A1 - SAFETY PRIMING COMPONENT WITH PLASMA TORCH - Google Patents

Abstract

The safety detonator comprises electrodes (5a, 5b) connected by a fuse (6), a barrel (16) separating the fuse from an explosive (3), and an insulating tube (7) separating the electrodes so that the electrodes and insulating tube form a plasma torch separated from the explosive by the barrel. The fuse is made of a plasmagenic material that generates a gas with a temperature above 15000 K and an electron density above 1018/cm3 when a current of at least 5000 A is passed through it.

Description

with 30% to 10% by mass of polyurethane.

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  The technical field of the invention is that of safety initiating components comprising at least two

electrodes connected by a fuse.

  Safety ignition components for explosives are known, components which are said to be "with a projected layer" (and more commonly known as "slappers"). These components include a resistive bridge on which is placed a tube (or "gun") made for example of ceramic. An insulating disc is placed between the tube and the resistive bridge. The passage of electric current in the bridge causes the vaporization of this one / which entails the cutting of the insulating disc which is projected through the tube. This disc comes to impact a

explosive receiver that it initiates.

  The advantage of "slappers" is that they can only initiate an explosive when the supply current applies

  at the electrodes is important (higher than 500 volts).

  Concretely, the wind operating voltages of the order of 3000 volts for a current intensity of the order of 5000 amperes. A voltage lower than 500 volts is insufficient to project the disc and therefore cannot ensure

an initiation.

  Such parameters of use entail an important level of safety which authorizes an alignment of the pyrotechnic chain between the component and the receiving explosive, which

  is usually a relay in HNS (hexanitrostilbene).

  These initiators, however, have drawbacks.

  First of all, they operate with a high operating voltage (3000 volts). This results in problems of electrical insulation which complicate the assemblies as well as

connectivity.

  In addition, in order to reduce the level of energy used, the resistive bridge is generally of reduced size as well as the ceramic tube (the latter most often has a diameter less than a millimeter). This results in significant production costs which limit the use of such

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  components in clvile applications such as

  initiators for automobile safety.

  It is the aim of the invention to provide a priming component, a safety cage not presenting such drawbacks. Thus the component according to the invention can operate with a reduced voltage (less than or equal to 1000 volts).

  while having a satisfactory level of security.

  Thus, the subject of the invention is a priming component, safety cage comprising at least two electrodes connected by a fuse and an orifice or barrel separating the fuse from a receiving explosive to be initiated, a component characterized in that the two electrodes wind separated by an insulating tube delimiting an internal volume, electrodes and insulating tube thus forming a plasma torch whose internal volume is separated from the receiving explosive by the barrel, and in that the fuse is made of a plasmagene material it ie a material providing gases at high temperature (greater than 15000 K) and having a high electronic density (greater than 1018 electrons / cm3) when it is traversed

  by an electric current of at least 5000 amperes.

  Concretely the dimensions of the torch will be such that it generates a plasma when it receives, receives a prime voltage, cage lower or equal to 600 volts and that it is supplied with an electrical energy lower or equal to 5000 Joules. According to an essential characteristic of the invention, the fuse material comprises at least one conductive material associated with at least one energetic material or capable of

react with the conductive material.

  The conductive material may be constituted by

carbon or a metal.

  The energetic material or material capable of reacting with the conductive material may be chosen from the following compounds or compositions:

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  Copper oxide, polytetrafluorethylene, copolymer of chlorofluoroethylene; polytetrafluorethylene / chlorofluoroethylene copolymer; Magneslum / polytetrafluorethylene / chlorofluoro-ethylene copolymer; Boron / Potassium nitrate; plasticized nitrocellulose film or film; polyvinyl nitrate; polyoxymethylene; Trifluoroethylene polychloride; polyvinyl chloride; Polychloride

  trifluoroethylene; polysulfone; polyvinylidene fluoride.

  According to a mode of real i sat ion, the fuse can be formed by a homogeneous mixture associating from 85% to 95% by mass of particles of conductive material and from 5% to 15% by mass of an energetic material or very susceptible to react with

the conductive material.

  The fusible sheet may have the composition: 85% to 95% by mass of aluminum or magnesium powder,% to 15% by mass of a composition combining

  polytetrafluorethylene and chlorofluoroethylene copolymer.

  The fusible sheet may in particular have the composition: 90% by mass of aluminum powder,% by mass of a composition combining polytetra

  fluorethylene and chlorofluoroethylene copolymer.

  The fusible sheet may also have the composition: 90% by mass of magnesium powder,% by mass of a composition combining polytetra

  fluorethylene and chlorofluoroethylene copolymer.

  According to another embodiment, the fuse may comprise at least one layer of energetic material or else capable of reacting with the conductive material deposited on

  at least part of a layer of conductive material.

  The fuse may comprise at least one conductive layer of aluminum or magnesium on which is deposited at least one reactive layer of polytetra fluorethylene, or of nitrocellulose or polyvinyl nitrate, or of copper oxide or of copolymer of

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  chlorofluoroethylene or polyoxymethylene or trifluoroethylene polychloride or polysulfone or polyvinylidene fluoride en masse of the material (s) of the or

reactive layers.

  The fuse may include at least one layer of aluminum or magnesium and at least one layer of

chlorofluoroethylene copolymer.

  The fuse may include at least one layer of

  magnesium and at least one layer of polytetrafluorethylene.

  According to another embodiment, the safety initiating component comprises a spray pad which

  is clamped between the torch and the barrel.

  The patch can be made of an insulating material

  electric or covered with an electrical insulating layer.

  The tablet may have a diameter between 1 mm and 4 mm and a thickness between 20 and 200

micrometers.

  The invention will be better understood on reading the description which will follow from different embodiments,

  description made with reference to the accompanying drawings and in

  which: - Figure 1 is a sectional view of a priming component according to a first embodiment, - Figure 2 is a sectional view of a priming component according to a second embodiment, - the Figure 3 is a sectional view of a component

  initiation according to a third embodiment.

  Referring to Figure 1, a safety ignition component 1 according to the invention is fixed by appropriate means (not shown) to an explosive charge 2

  comprising an explosive 3 is placed in an envelope 4.

  The explosive charge will for example be a detonating hexogen detonator in the pulverulent state or else compressed.

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  As a variant, we could initiate directly without

  relay the explosive charge of a munition.

  Component 1 comprises at least two electrodes 5a and 5b which are connected by a conductive fuse 6 and separated by an insulating tube 7 comprising an axial bore 14. A first electrode 5a, or peripheral electrode, comprises a cylindrical wall 8 and a bottom 9 drilled with an axial hole lOo Wile delimits an internal cylindrical housing 11 a

  the interior of which is placed the insulating tube 7.

  The insulating tube 7 has, at an upper face, a counterbore 12 inside which the

  second electrode 5b, or axial electrode.

  The insulating tube 7 delimits an internal volume 13 which receives the fuse 6. This here has the form of a tube which is applied against the internal surface of the bore 14 of the insulating tube 7 and which is wedged between the axial electrode 5b

  and the bottom 9 of the peripheral electrode 5a.

  The peripheral electrode 5a is placed in a support 15 which can be made of an insulating material, for example polyamide. This support has an axial hole 16, or barrel, arranged in the extension of the axial hole 10 of the electrode a and whose diameter is less than or equal to that of the hole 10. According to an essential characteristic of the invention, the fuse 6 is made of a plasma material, that is to say a material providing gases at high temperature (greater than 15000 K) and having a high electronic density (greater than 1018 electrons / cm3) when it is

  traversed by an electric current of at least 5000 amperes.

  The electrodes 5a, 5b and the insulating tube 7 thus form a plasma torch whose internal volume 13 is separated from

  the explosive receiver 3 by the barrel 16.

  The barrel 16 is disposed opposite another hole 17 feed into the casing 4 of the explosive charge 2O

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  Component 1 is a plasma torch of reduced size (or "micro torch"). Wile has dimensions which are chosen to be small enough for it to generate a plasma when it receives a priming voltage less than or equal to 600 volts and when it is supplied with an electrical energy less than or equal to 5000 Joules. Such a micro torch is described as an ignition component in patent EP905470 to which reference may be made. Wile has dimensions of the order of 6 to 10 mm long for 5 to 10 mm in

diameter.

  The fuse is here produced in the form of a layer

  tubular, and clamped between the two electrodes 5a and 5b.

  The plasma material will comprise at least one conductive material associated with at least one energetic material or

  likely to react with the conductive material.

  By energetic material is meant a material capable of supplying chemical energy in the form of a flame when it is initiated by the joule effect generated by the passage of current in the material.

  driver with whom he is intimately associated.

  By reactive material or capable of reacting with the conductive material is meant a material, inert in isolation, but capable of reacting chemically with the conductive material during the heating thereof by the Joule effect. Chemical energy is then supplied by

  this reaction in the form of a flame.

  The conductive material may be constituted by carbon or by a metal such as copper, aluminum,

silver or magnesium.

  The energetic material or likely to react with the conductive material may be chosen from the following compounds or compositions: Copper oxide polytetrafluorethylenei chlorofluoroethylene copolymer polytetrafluorethylene / chlorofluoroethylene copolymer Magnesium / polytetrafluorethylene / chlorofluoro-ethylene copolymer Bore / Nitrate

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  potassium; plasticized nitrocellulose film or film; polyvinyl nitrate, polyoxymethylenei Trifluoroethylene polyvinyl chloride polychloride; Polychloride

  -trifluoroethylene; polysulfone; polyvinylidene fluoride.

  In this list the energetic materials wind the compositions Magnesium / polytetrafluorethylene / copolymer of chlorofluoro-ethylene; Boron / potassium nitrate) plasticized nitrocellulose film or film;

polyvinyl nitrate.

  Reactive materials with a wind conductive material: Copper oxide, polytetrafluorethylene, copolymer of chlorofluoroethylene; polytetrafluorethylene / chlorofluoroethylene copolymer; polyoxymethylene; Trifluoroethylene polychloridei Vinyl polychloridei Polysulfone;

1S Polyvinylidene fluoride.

  According to the particular embodiment of FIG. 1, the fuse tube 6 is formed by a homogeneous mixture associating 85 to 95% by mass of conductive material and 5 to% by mass of an energetic material or else capable of

react with the conductive material.

  We could for example make a fusible tube with the following compositions:

Example 1

  2s 85 to 95% by mass of aluminum powder and preferably%,% to 5% by mass of a composition combining polytetrafluorethylene and chlorofluoroethylene copolymer,

and preferably 10%.

Example 2

  % to 95% by mass of magnesium powder and preferably 90%,% to 15% by mass of a mixture associating polytetrafluorethylene and chlorofluoroethylene copolymer,

and preferably 10%.

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  We can concretely real i ser the leaf by mixing the metal (aluminum or magnesium) with a solution of

  polytetrafluorethylene and chlorofluoro copolymer

  ethylene in a suitable solvent, for example a ketone: s cyclohexyl ketone (cyclohexane) or acetone. The mixture thus produced will be applied like a paint to the internal surface of the bore 14 of the insulating tube 7. Then the solvent will be evaporated before placing the insulating tube 7 in the peripheral electrode 5a and placing the electrode axial 5b. In order to ensure good quality of contact, the parts of the insulating tube which wind in contact with the electrodes 5a and b may be covered with the material of the fuse tube (counterbore 12 and lower face of the tube 7). Component 1 is connected by conductors 18 and 19 to an electric generator 20. This generator is designed to be able to deliver energy from 10 kJ to 1 megaJoule under

  form of voltage pulses from 1000 volts to 20 kilo Volts.

  Such a generator is conventional and includes for example capacitors, an inductor, thyristors and a power supply.

stabilized.

  A small fraction of the energy supplied by the generator is used to initiate the fuse tube 6 by the Joule effect. The energetic material is then initiated or the reaction between the conductive material and the reactive material is initiated. A combustion flame fills the

room 13.

  This flame is naturally formed from ionized atoms and molecules. Wile ensures an electrical conduction of reduced resistance between the electrodes 5a and 5b which allows

  maintaining an electric arc between the electrodes.

  The chamber 13 ensures confinement of the arc and the rise in pressure thus allowing the development of the plasma generated by the fuse tube 6. The plasma is ejected at a

speed of the order of 3500 m / s.

  The result is an ounce of very intense shock (pressure of the order of Giga Pascal) which impacts the explosive charge 3

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  through holes or cannons 16 and 17 and ensures the initiation of that cf. The shock will be all the more intense than the volume of the

room 13 will be reduced.

  By way of example, an ignition component has been produced associating a plasma micro torch delimiting a chamber 13 having a volume of approximately 15 mm 3 and comprising a fusible tube 2 mm in diameter, 0.1 mm thick and having as composition one or the other of the compositions according to

examples 1 and 2.

  Such a component, supplied under a voltage pulse of 800 to 1000 Volts with a maximum intensity of 10000 Amperes, ensures the detonation of an explosive relay of 11.5mm in diameter and 11 / 5mm high made of hexagonal Is / wax / graphite (proportions by relative masses: 98/2/1). The gas pressure obtained at the outlet of the component

  is around 1 GPa (1 gigapascal).

  We see that the component according to the invention is simpler to manufacture than that of known safety components or "slappers" since it does not require the creation of a resistive bridge and it does not operate

  of pastille to project of reduced size.

  The diameter of the chamber 13 (2 mm) is greater than that of the guns used in known "slappers" (donations

  diameter is generally less than mm).

  The supply voltage is also lower (of the order of 1000 volts against almost 3000 Volts for known "slappers"). This greatly reduces the insulation problems and therefore facilitates the integration of the component.

  in ammunition or automotive safety systems.

  The electrical power consumed is of the same order as for the known "slappers" (10 Mega Watts), the maximum intensity being also higher (about 10 kilo Amperes). The component according to the invention is a safety component since the level of energy necessary for its

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  initiation meets the requirements given by the standards no pyrotechnic reaction for an impulse of less than 500 volts. It can therefore be used in a priming device, cage devoid of chain misalignment means

s pyrotechnics.

  It is possible according to the needs to play on the different dimensions of the component to define a component operating with a voltage lower than 1000 volts. We can thus reduce the volume of the chamber 13 to change the plasma pressure generates, therefore the power of the component. Figure 2 shows a primer component, cage according to a second embodiment of the invention. For the simplification of the figure, component 1 has been represented

  alone without the explosive charge he must initiate.

  This component differs from the previous one by the structure of the

fuse 6.

  The fuse 6 thus comprises a layer 6a of conductive material on which is deposited at least one layer 6b of an energetic material or material capable of reacting with

the conductive material.

  To make such a fuse, it is possible, for example, to wind a metal sheet on itself, onto which a mixture of glue and material has been previously projected.

  energetic or capable of reacting with the conductive material.

  Concretely we can realize a fuse comprising a sheet wrapped in aluminum or magnesium on which has been deposited a layer of pol yt and ra fluorethyl ene or

polyvinyl chloride.

  The thickness of the metal layer will be of the order of micrometres. The thickness of the layer (s) of

  energetic material will be of the order of 100 micrometers.

  It is also possible to combine a layer of aluminum or magnesium with a layer of nitrocellulose or nitrate of

Polyvinyl.

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  We can make a deposit of copper oxide or chlorofluoroethylene copolymer on a sheet

aluminum or magnesium.

  We can also realize a polyoxymethylene depat

s on a layer of aluminum.

  In all cases / the dimensions of the different layers will be such that they will combine from 85 to 95% by mass of the material of the conductive layer to 5 to 15% by mass of the

  materials of the reactive layer or layers.

  According to a preferred embodiment, a fuse will be produced by winding an aluminum sheet on which is deposited at least one layer of copolymer of

  chlorofluoroethylene (known under the trademark Viton).

  The relative mass proportions will be 90% for aluminum and 10% for the chlorofluoroethylene copolymer. The fuse 6 is arranged so that the metal layer 6a is on the side of the insulating tube 7 and in

  contact with the two electrodes 5a and 5b.

  The passage of the current can thus be done through the conductive layer 6a which will ensure by Joule effect the initiation of the reaction with the energetic layer 6b.

therefore the generation of plasma.

  A component was thus produced comprising a fuse having a layer of 80 micrometers thick of aluminum carrying a layer of 11 micrometers of chlorofluoroethylene copolymer (known under the trademark Viton). The fuse is placed in a room 13 of

volume about 15mm3.

  This component could initiate an explosive tablet as described above in response to a voltage pulse of

  1000 volts for a maximum intensity of 10 kA.

  We also made a geometric component identical to that of the previous one but whose fusible sheet has a layer of 80 micrometers thick.

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  Magnesium carry a layer of 11 micrometers of chlorofluoroethylene copolymer We finally made a geometric component identical to that of the previous ones but whose fusible sheet comprises a layer of 80 micrometers thick Magnesium carry a layer of 11 micrometers of polytetrafluorethylene (known

under the Teflon trademark).

  These components have also successfully initiated the

  explosive tablet described above.

  In order to initiate less sensitive explosives or to configure more precisely the initiation performance of the component according to the invention, it is possible to define a component also comprising (as in the

  classic slapper components) a projectable tablet.

  Figure 3 shows such a component 1.

  As in the embodiment of FIG. 2, the component 1 comprises two electrodes 5a and 5b which are connected by a fuse 6 associating a conductive layer 6a

and an energy layer 6b.

  This component differs from that of FIG. 2 in that a patch 21 is interposed between the annular rim 9 of the electrode 5a and the insulating support 15. This patch therefore separates the chamber 13 of the plasma torch and the barrel 16. The pad 21 will be made of an electrical insulating material or covered with an electrical insulating layer. Such an arrangement makes it possible to avoid priming, cages of electrical areas directly between the axial electrode 5b and the pellet 21. One could for example make the pellet in a plastic material such as a polyimide (material known under the registered trademark Kapton). We can also make the tablet in mica or in metal (aluminum, titanium or steel). In the case of a metal patch, it will be covered on both sides with an insulating material, for example a layer of insulating adhesive tape ensuring a level of electrical insulation of at least 1000 volts (such

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  insulators generally use an insulating layer of

  rubber or polyvinyl chloride or PVC).

  Projectable steel pellets of 120 micrometers thick were thus produced. During the passage of current through the fuse, the pressure generated by the reaction between the conductive material and the energetic material causes the cutting of the pastel and its

projection through the barrel 16.

  It is therefore not necessary as in known slappers to provide a specific "canon" component (such as a

  ceramic tube of the order of a mm in diameter).

  The diameter of the barrel 16 may vary between 1 and 4 mm, which is greater than the diameters of the barrels used

  usually in ['slappers ".

  The skilled person will easily choose the appropriate dimensions to ensure the desired effect. We can especially play on the thickness' therefore the mass of the pellet, to modify the energy received by the explosive to initiate. By way of example, components have been made incorporating a fuse associating a layer of aluminum and a layer of chlorofluoroethylene copolymer (known under the registered trademark Viton) with the proportions in respective masses of% and 10% (total thickness of the fuse 100 micrometers). Each component has a pastille to be sprayed associated with a 2 or 4mm diameter cannon, a pastille having a thickness of 30 to 120 micrometres for steel or 80 to micrometres for Kapton. All components led to the initiation of an 11.5mm x hexagen tablet

  11.5mm compresses under 160 Mega Pascals.

  The same tests were successfully carried out using a fuse associating a layer of magnesium and a layer of polytetrafluorethylene (known under the trademark Teflon)

  with the respective mass proportions of 90% and 10%.

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Claims (13)

  1- Component (1) of amor, safety cage comprising at least two electrodes (5a, 5b) connected by a fuse (6) and S an orifice or barrel (16) separating the fuse from an receiving explosive (3) to initiate, component characterized in that the two electrodes (5a, 5b) are separated by an insulating tube (7) delimiting an internal volume (13), electrodes and insulating tube thus forming a plasma torch whose internal volume (13) is separated from the explosive receiver (3) by the barrel (16) / and in that the fuse (6) is made of a plasma material, that is to say a material supplying gases at high temperature (greater than 15000 K) and having a high electronic density (greater than 1018 electrons / cm3) IS when it is traversed by an electric current of at least 5000 amperes.   2- primer component, safety cage according to claim 1, characterized in that the dimensions of the wind torch such that it generates a plasma when it receives, receives a primer voltage, cage less than or equal to 600 volts and that it is supplied with an electrical energy less than or equal to 5000 JoulesO 3- Amor component, safety cage according to one of the   claims 1 or 2, characterized in that the material of the   fuse (6) comprises at least one conductive material associated with at least one energetic material or capable of reacting with the conductive material.   4- primer component, safety cage according to claim 3, characterized in that the conductive material   is made up of carbon or a metal.   - Component of amor, safety cage according to one of   claims 3 or 4, characterized in that the material   energetic or likely to react with the conductive material is chosen from the following compounds or compositions 3s 2840401   Copper oxide; polytetrafluorethylenei copolymer of chlorofluoroethylene; polytetrafluorethylene / chlorofluoroethylene copolymer; Magnesium / polytetrafluorethylene / chlorofluoroethylene copolymer; Boron / Potassium nitrate; plasticized nitrocellulose film or film; polyvinyl nitrate; Polyoxymethylene; Trifluoroethylene polychloride; polyvinyl chloride; Polychloride   trifluoroethylene; polysulfone, polyvinylidene fluoride.   6- Dlamor component, safety cage according to one of the   Claims 3 to 5, characterized in that the fuse (6)   is formed by a homogeneous mixture associating 85% to 95% by mass of particles of conductive material and 5% to 15% by mass of an energetic material or well likely to react with the conductive material.   7- primer component, safety cage according to claim 6, characterized in that the fusible sheet has the composition o% to 95% by mass of aluminum or magnesium powder,% to 15% by mass of a composition combining   polytetrafluorethylene and chlorofluoroethylene copolymer.   8- primer component, safety cage according to claim 7, characterized in that the fusible sheet has the composition:% by mass of aluminum powder, 10% by mass of a composition combining polytetra   fluorethylene and chlorofluoroethylene copolymer.   9- primer component, safety cage according to claim 7, characterized in that the fusible sheet has the composition: 90% by mass of magnesium powder,% by mass of a composition combining polytetra   fluorethylene and chlorofluoroethylene copolymer.   - Component of amor, safety cage according to one of the   Claims 3 to 5, characterized in that the fuse (6)   has at least one layer (6b) of energetic material or capable of reacting with the conductive material 16 2840401   deposited on at least part of a layer (6a) of conductive materialO 11- Primer component, safety cage according to claim 1OF characterized in that the fuse (6) comprises at least one conductive layer (6a) of aluminum or magnesium on which is deposited at least one reactive layer (6b) of polytetrafluorethylene, or nitrocellulose or polyvinyl nitrate, or of copper oxide or of chlorofluoroethylene copolymer, or of polyoxymethylene, or of trifluoroethylene polychloride, or polysulfone, or polyvinylidene fluoride.   12- diamond component, safety cage according to claim 11, characterized in that the dimensions of the various wind layers such that 85 to 95% by mass of the material of the conductive layer is combined to 5 to 15% by mass   of the material (s) of the reactive layer (s).   13. Damor component, safety cage according to claim 12, characterized in that the fuse comprises at least one layer of aluminum and at least one layer of chlorofluoroethylene copolymer.   14- amor component, safety cage according to claim 12, characterized in that the fuse comprises at least one layer of magnesium and at least one layer of chlorofluoroethylene copolymer.   15- amor component, safety cage according to claim 12, characterized in that the fuse comprises at least one layer of magnesium and at least one layer of polytetrafluoroethylene. 16- Amor component, safety cage according to one of   claims 1 to 15, characterized in that it includes a   tablet (21) to be projected which is clamped between the torch and the Canon 16).   17- primer component, safety cage according to claim 16, characterized in that the patch (21) is made of an electrically insulating material or covered an electrical insulating layer. 17 2840401   18- safety initiating component according to claim 17, characterized in that the pellet (21) has a diameter between 1 mm and 4 mm and a thickness   between 2G and 200 micrometers.