Explosive and thermic compositions or charges – Containing inorganic oxygen-halogen salt – Ammonium perchlorate
Reexamination Certificate
2002-04-23
2004-04-20
Carone, Michael J. (Department: 3641)
Explosive and thermic compositions or charges
Containing inorganic oxygen-halogen salt
Ammonium perchlorate
Reexamination Certificate
active
06723191
ABSTRACT:
BACKGROUND OF THE INVENTION
The technical scope of the present invention is that of pyrotechnic compositions intended to make pyrotechnic delays that are to be integrated into a piece of ammunition, in a safety and arming device or in a safety fuse.
When a piece of ammunition or pyrotechnic system is to be designed incorporating a long duration timer device (from several seconds to several minutes), a clock or electronic timing device may be implemented, or else a chemical reaction may be used.
These solutions are both costly and bulky. Ammunition designers therefore prefer to use pyrotechnic delays (rigid column or cord) since such solutions are compact, reliable, robust and inexpensive.
However, a particularly long timing in a small sized ammunition is extremely difficult to produce using a pyrotechnic composition.
Thus, patent FR-2 464 932 proposes a composition for a delay cord comprising tungsten powder (W), barium chromate (BaCrO
4
), and potassium perchlorate (KClO
4
). This composition has a combustion rate of 4 mm/s in a sheath of 3 mm external diameter (the thickness of tin sheaths is generally of around 0.5 mm).
Patent FR-A-2 706 449 in the name of the applicant proposes an improvement to the composition described in the previous patent by incorporating nanometric silica powder. Such a composition allows a combustion rate of 2 to 2.5 mm/s to be obtained in a sheath of 3.1 mm external diameter. The silica thus introduced prevents the cord from bursting but is in proportions that are too low to substantially modify the combustion rate of the composition.
Reference may further be made to patents U.S. Pat. No. 3,028,229 and EP-0 332 986 that describe compositions essentially comprising metallic powder.
Known tungsten, barium chromate, potassium perchlorate and possibly silica-based compositions generally have a combustion rate of around or over 2 mm/s. These compositions have the particularity of generating almost no gases whilst burning.
The cord technology is well suited to the manufacture of delays for ammunition. This technology allows longer delay columns to be made and allows complex shapes to be made that may be adapted to a reduced available volume. Thus, timing of 15 s may easily be obtained by implementing a cord length of 35 mm enclosing a composition such as that described in patent FR-2 706 449.
However, if a longer timing is required (for example 30 s) without requiring the implementation of a longer (and therefore bulkier) cord, a composition having a combustion rate of around 1 mm/s must be used.
SUMMARY OF THE INVENTION
The aim of the present invention is to supply a new composition with a slow combustion rate, of around 1 mm/s, intended to be incorporated into a piece of ammunition or one of its components, for example a safety and arming device.
The invention thus relates to a slow combustion pyrotechnic composition notably intended to manufacture pyrotechnic delays, said composition wherein it comprises an oxidant of the perchlorate type according to a percentage in mass of between 75 and 91%, a reductant selected from among the aromatics according to a percentage in mass of between 5 and 20%, 0 to 6% in mass of a binder and 0 to 5% in mass of a nanometric silica powder.
Advantageously, the oxidant may be ammonium perchlorate.
Advantageously, the reductant may be constituted by anthracene, phenanthrene, naphthalene or a mixture of these.
According to a first embodiment, the composition may comprise a binder that is constituted by a wax.
The composition may, in this case, be constituted in mass by 75 to 91% of perchlorate, 5 to 20% of aromatics and 1 to 6% of binder.
According to different examples, it may notably be constituted in mass by:
91% of ammonium perchlorate, 7% of anthracene and 2% of wax, or
88% of ammonium perchlorate, 7% of anthracene and 5% of wax, or
88% of ammonium perchlorate, 7% of phenanthrene and 5% of wax, or
88% of ammonium perchlorate, 7% of naphthalene and 5% of wax.
According to a second embodiment, the composition may be constituted in mass by 80% of ammonium perchlorate and 20% of anthracene.
According to a third embodiment, the composition may be constituted in mass by: 75 to 91% of perchlorate, 5 to 20% of aromatics and 0.5 to 5% of a nanometric silica powder.
According to different examples it may notably be constituted in mass by:
85% of ammonium perchlorate, 10% of anthracene and 5% of nanometric silica powder, or
84.5% of ammonium perchlorate, 12.5% of anthracene and 3% of nanometric silica powder.
According to a fourth embodiment, the composition may be constituted in mass by 75 to 91% of perchlorate, 5 to 20% of aromatics, 1 to 6% of binder and 1 to 5% of a nanometric silica powder.
According to different examples it may notably be constituted in mass by:
81.5% of ammonium perchlorate, 12.5% of anthracene, 5% of wax and 1% of nanometric silica powder, or
82.5% of ammonium perchlorate, 7.5% of anthracene, 5% of wax and 5% of nanometric silica powder, or
87% of ammonium perchlorate, 7.5% of anthracene, 2.5% of wax and 3% of nanometric silica powder, or
89% of ammonium perchlorate, 7% of anthracene, 2% of wax and 2% of nanometric silica powder.
A first advantage of the pyrotechnic composition according to the invention lies in that it may be used either in the form of a traditional tubular delay column or in that of a delay cord or even be used to make safety fuses.
Another advantage lies in the fact that the combustion rate of the composition may be adjusted whilst guaranteeing stable pyrotechnic behaviour without undesirable gaseous projection.
Another advantage lies in the fact that the composition allows pyrotechnic delays to be made of several seconds to several minutes.
Other characteristics, particulars and advantages of the invention will become more apparent after reading the additional description given hereafter by way of illustration.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Thus, the composition according to the invention is mainly constituted by an oxidizing salt, such as ammonium perchlorate and an organic reductant component of the aromatics type, such as anthracene, phenanthrene or naphthalene. A binder, for example a wax of the wax-ester or polyethylene wax type, may also be incorporated.
In a known manner the binder or wax coats the composition grains thereby improving the homogeneity of the composition and the mechanical strength of the delay produced. The age-resistance of the delay is also thereby improved, in fact the binder prevents the sedimentation of the different constituents of the composition thereby ensuring its continued homogeneity through time (and thus also its delay performances).
The binder also participates in the pyrotechnic reaction. The quantity of binder that may be used thus enabling the delay's combustion rate to be regulated.
It is also possible to incorporate a nanometric silica powder to the composition according to the invention, whether said composition comprises a binder or not.
A nanometric silica is silica whose mean grain diameter lies between 7 and 40 nanometers. Such silica is sold, for example, under the trade name AEROSIL.
Such silica ensures that the prepared composition is easy to cast, thereby facilitating the loading and implementation operations when a delay column is being produced. It also enables the combustion to be regulated. It does not directly participate in the combustion but the combustion rate may be regulated by acting on the quantity of silica used.
Naturally, the proportions of the constituents must be precisely adjusted so as to obtain a reproducible combustion regime guaranteeing a stable pyrotechnic behaviour without undesirable gaseous projection. In fact, the combustion rate and regime vary depending on the proportion of the components. They also vary according to the nature of the aromatics used.
A binderless composition is implemented by dry process as follows:
To prepare 1 kg of composition, the reductant and the oxidant are introduced into the mixing vessel of a mixer known under the trade name TURBULA. The composition is mi
Espagnacq Andre
Morand Philippe
Carone Michael J.
Felton Aileen B.
Giat Industries
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