FR2650586A1 - IGNITION COMPOSITION FOR PYROTECHNIC RETARDATION - Google Patents

Abstract

The invention relates to an ignition composition that can be initiated by percussion for pyrotechnic retardation. It comprises a first percussion initiation composition and a second composition consisting of a mixture of titanium and boron powders. The first composition is a tablet of potassium chlorate, lead thyocyanate, antimony sulphide and lead styphnate. The second composition comprises 80% by mass of titanium powder and 20% by mass of boron powder. The first composition is compressed at a pressure between 0.5.10 ** 8 and 2.10 ** 8 Pa and the second composition at a pressure between 0.5.10 ** 8 and 2.5.10 ** 8 Pa. Application of the composition ignition at the initiation of a delay cord integrated in a metal sheath with an outside diameter less than or equal to 3 mm, containing a pyrotechnic composition burning at a speed less than or equal to 4 mm / s.

Description

"- 2650586

  - 1 The technical sector. of the present invention is that of ignition compositions for pyrotechnic delays

  incorporated in a munition or in a

cur-ity and armament (DSA).

  The pyrotechnic delays, of the cordeau-retard type,

  comprise an ignition composition, a pyrolysis composition

  retardant technique confined in a metal sheath, and

  possibly an explosive relay output. They are used

  in a pyrotechnic chain to induce a temporisa-

tion.

  Many pyrotechnic delays have been proposed.

  to obtain a burning rate of the order of a few centimeters per second. In this respect, mention may be made of US-A-4,144,814 and FR-A-2,464,932, which particularly describe delay compositions. However, these compositions are always initiated electrically by

  wire and not by percussion, which renders them inapplicable

  cables in ammunition or in security and weapons devices. On the other hand, it is impossible to date

  to initiate delay compositions when they have a diameter

be less than 3 mm.

  When designing a munition or a DSA, it is often advantageous to use a pyrotechnic delay delay. The solution usually adopted

  consists in defining a delay specific to the studied system, gen -

  a tube containing a retarding composition

  by compression. Such a delay is reliable and accurate, but relatively bulky. So, when a setting of the duration

  time is necessary (as for some

  mortar projectiles), the congestion constraints lead to the possibility of initiating the

  retarding composition compressed more or less close to the

  lais d'amorgage, by mechanical movement of one of the elements

  the rocket (delay carrier or relay carrier). Such a solution

  tion is unsatisfactory because it entails a certain inaccuracy. Thus, at present, many delaying problems do not have a pyrotechnic solution, and one must resort to more complex timing techniques (watchmakers, for example), which are often more cumbersome and more

costly.

  The object of the present invention is therefore to

  to be an ignition composition for pyrotechnic delay amorgable by percussion, suitable for integration into a munition or in a device of armament and security, of diameter

reduced and low cost.

  The subject of the invention is therefore a composition

  percussion ignition device for pyrotechnic delay

  characterized in that it comprises a first component

  percussion boot and a second composition

  consisting of a mixture of titanium powders and boron.

  The first composition may be a tablet of potassium chlorate, lead thyocyanate, sulfide

  antimony and lead styphnate.

  The second composition can comprise 80% by weight

  of titanium powder and 20% by weight of boron powder.

  The first composition may be compressed at a pressure of between 0.5 × 10 8 and 2.10 8 Pa and the second composition at a pressure of between 0.5 × 10 8 and 2.5 × 10 8 Pa. The invention also relates to the application of the ignition composition. to the achievement of a delay line,

  integrated in a metallic sheath with an external diameter

  less than or equal to 3 mm, containing a pyrotech composition

  burning at a speed less than or equal to 4 mm / s.

  An advantage of the present invention lies in

  obtaining a low-dimensional ignition composition

  sions, simple to implement and to manufacture.

  Another advantage lies in the fact that the composition

  The initiating phase initiates long delays of low dia-

  meter, that is to say less than or equal to 3 mm. We can therefore take advantage of the properties of late compositions

  known in devices in which it was impossible to

to use them until then.

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  Another advantage lies in the fact that the composition

  delay is initiated without disorganization or destruction of the cell which encloses it, thus avoiding a disturbance

of the pyrotechnic chalne.

  Other advantages of the invention will become apparent

  reading of the additional description given below.

  The delay composition itself is well known to those skilled in the art. It consists of tungsten, barium chromate and potassium perchlorate at the following respective mass percentages and at

  For example: 28, 62, and 10. We take advantage of

  Examples of this composition are: - a weakly gaseous combustion with an attenuated risk of ejection of residues and disorganization of any of the constituents of the pyrotechnic chain, or even damage to the DSA, - a safety of use and storage because of low sensitivity, - excellent aging behavior (shelf life) 20 years at 20 C, largely exceeding the average storage period of most ammunition and therefore not imposing

visit during this same period.

  However, it is well known that this composition has the disadvantage of being difficult to light because it

  requires a lot of heat.

  It was therefore necessary to define a specific ignition composition with all the guarantees of reliability and safety and having a high calorific value during a lapse of time.

  relatively long time of a few milliseconds.

  This igniter comprises a percussion initiation composition combined with a titanium-boron composition. These two compositions are known in themselves, but they have never been associated and moreover, we know nothing about them.

  industrial use of the titanium-boron composition in py-

rotechnie.

  The titanium-boron composition has certain

  lites that make it particularly suitable for the intended use: -4- high calorific value, - combustion strictly without gas and therefore without

  risks of spillage of residues, disorganization of the com-

  titanium-boron, which may lead to poor contact with

  be this same composition and the retarding composition, and thus prevent the transmission of combustion,

  - non-pyrotechnic raw materials (titanium and boron)

  easy and safe implementation, which improves the

  curity in manufacture, - production of an ignition of the delay composition

by combustion front.

  The granulometry of titanium and boron has no significant influence on the performance of the ignition composition. Titanium powder has an average particle size

  of the order of 15 μm and the boron powder of 1.2 μm.

  The titanium-boron composition being impossible to ignite

  sea by percussion, it is essential to

  boot position. The latter consists of a tablet of potassium chlorate, lead thyocyanate,

  of antimony sulphide and lead styphnate. This composition

  sition is known and is easy to initiate by percussion.

  It is energetic enough to initiate the hot composition of titanium-boron, without disrupting it or destroying the cell. Its percussion energy is of the order of 0.1 Joule and it generates a strong energy of exit, of

  the order of 100 Joules. Finally, the explosion of this compound

  sition is transmitted neither to the titanium-boron composition nor to

  the pyrotechnic delay composition.

  These two compositions make it possible to obtain

  very small size, 4 mm in diameter and 5

mm high.

  A delay is thus realized comprising a head primer set on one end of a metal sheath. This sheath may be for example a lead or tin sheath of about 3 mm internal diameter. The other end of this cord carries an output relay, made in a known manner

  and which will not be the subject of a more detailed description.

  The head primer is constituted by a cell in which the first priming composition and the second composition are compressed. The cell has at its end a passage hole for a firing pin, closed

  by a thin paillet ensuring tightness.

  Industrially, the delay line is obtained at

  from a large diameter tube that is cut to a length

  determined and then filled with a delaying composition. After sealing the ends, this tube is introduced into a machine which will roll it between rollers until the desired diameter is obtained, the length of the cord

  being of course a function of this diameter.

  By way of example, it is possible to obtain cords with tin sheath 3 mm in external diameter, from a

  tube 17 mm in outer diameter. During this opera-

  tion, the delaying composition is subject to compression

  to go up to several hundred Pascal. It is necessary

  note, however, that the compression ratio of this composi-

  tion has virtually no influence on the speed of com-

  as the tests carried out have shown.

  Various operational tests have made it possible

  the reliability of a pyrotechnic delay set,

  finish precisely the pyrotechnic components and of

  optimize the masses. The result is the following compositions

  (% expressed in mass): - first composition: 25 mg, compressed to 168 Pa, potassium chlorate ............ 52% lead thiocyanate .......... .

  . 25% antimony sulphide .............. 13% lead styphnate .......... DTD: ...... 10% - second composition: 80 mg, compressed to 1.5.108 Pa, titanium .......................... 81.6% boron ......... ................... 18.4% - pewter tin 0.05 mm thick, .. DTD: - cord with tin sheath or lead of outside diameter -

  3 mm, - retarding composition: tungsten ........................ 28% barium chromate ............ ... 62% potassium perchlorate ......... 10%

  The particle size of the tungsten is less than 20 μm.

  Some fifty delays made with the pro-

  portions above were fired. No misfire is observed although the percussion energy is of the order of

  0.1 Joule and the following results are obtained on a cor-

  water 10 cm in length: - maximum duration 15,9 s - minimum duration 14,03 s - average duration 14,8 s

- standard deviation 0.45.

  This achievement is satisfactory in terms of performance. The assembly is tested by imposing minimal radii of curvature. There are no ignition spikes and operating times then oscillate between 14.54 and 15.98

  s, values comparable to those obtained with a standard cord

  tiligne. These tests highlight the interest of the use of compositions without gas, which does not cause projections, destruction of the cord sheath, or non-functioning. he

  is also interesting to note a perfect-e trans-

  mission of combustion under such adverse conditions.

  despite the breakages caused by folding at

very weak curvature.

  Another series of tests focused on the functioning of

  at low temperature, the most stringent conditions, four pyrotechnic delays placed in the climatic chamber for 2H30 to -40 C. The operating times vary from 14.90 s to 15.83 s, durations quite comparable with those

obtained at room temperature.

  Finally, the retarding composition has been the subject of aging tests which suggest a duration of

  life above 20 years at 30 C and 10. years at -60 C.

  The delay according to the invention can be used each

  that the following characteristics are desired: very slow combustion (2 mm / s) inducing long time delays for a short string length and therefore a reduced mass, which is important in the case of embedded devices, - ease of integration into a system thanks to the flexibility of the cord and its ability to function despite creases, - good reproducibility of performance that are practically unaffected by the conditions of use, low performance conservation temperature,

- good aging behavior.

  We have successfully tested other compositions

  in which the respective percentages of

  tane and boron varied between 68% and 32% on the one hand, and 81.6% and 18.4% on the other hand. The replacement of titanium by the

  zirconium makes it possible to obtain the same results.

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Claims (4)

  1 - Ignition ignition composition   for pyrotechnic delay, characterized in that   takes a first percussion priming composition and a second composition consisting of a mixture of powders of titanium and boron.   2 - Ignition composition according to claim   1, characterized in that the first composition is a compound   awarded with potassium chlorate, lead thyocyanate,   antimony sulphide and lead styphnate.   3 - ignition composition according to claim 2, characterized in that the second composition comprises 80%   mass of titanium powder and 20% by weight of powder of   re. 4 - Ignition composition according to claim   3, characterized in that the first composition is   at a pressure of between 0.5 × 10 8 and 2 × 10 8 Pa and the second composition at a pressure of between 0.5 × 10 8 and 2.5.108 Pa.   - Application of the ignition composition according to   any one of the preceding claims to the   detonation cord built into a metal sheath with an external diameter of 3 mm or less, containing   a pyrotechnic composition burning at a lower velocity than re or equal to 4 mm / s.