Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Patent
1992-07-01
1994-08-23
Green, Anthony
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
106403, 106404, 106425, 106426, 106431, 106453, 106472, 106475, 106477, 106480, 106481, 106483, 106489, 106499, 106285, 102208, 102334, 2503381, 252305, 428403, 428404, 428406, 428407, C09C 100, F42B 1248, C06D 300
Patent
active
053403959
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with the field of powdered materials which are intended to be scattered by dispersion means in order to produce a camouflaging cloud.
Smoke-producing compositions which have an effective action in the visible region of the spectrum (from 0.4 .mu.m to 0.8 .mu.m) have already been known for a long time. In the majority of instances, these compositions include an oxidizing agent associated with a reducing agent and with a sublimable compound. Reference will be made, for example, to patent U.S. Pat. No. 2,939,779 which describes a composition having a base of hexachloroethane and zinc oxide.
The reaction between these two compounds produces a grey smoke screen which is not capable, however, of masking the transmission of infrared radiation (wavelength of 0.8 .mu.m to 14 .mu.m). In addition, the compound obtained is highly corrosive and toxic.
Statutory Invention Registration USH769 proposes to carry out masking in the optical field by means of titanium dioxide particles having a particle size of the order of 0.3 micrometer. These particles are coated with siloxane with a view to preventing detonation of the cloud which is formed. The masking effect thus obtained fails to prevent transmission of infrared radiation.
It is also known to produce mists of fine droplets by vaporizing oils by means of gas compressors but these mists are also transparent in the infrared region.
Patent FR2396265 proposes to disperse the solid particles of a mineral powder by means of a propellant gas.
When the mean particle size of the powder is uniform and close to the wavelength of the radiation to be occulted, infrared masking can in fact be obtained but it has been found that, when the particles described in this patent were dispersed in the cold state, agglomeration of the particles occurred and had an adverse effect on the requisite opacity.
It has also been sought to obtain masking both in the visible and infrared regions by vaporizing an oil charged with a mineral powder.
For example, patent U.S. Pat. No. 4,484,195 describes a smoke-producing device in which a turbine is employed for dispersing aluminum particles mixed with gas oil.
A device of this type is very disappointing since the aluminum particles undergo considerable degradation at the time of dispersion.
Statutory Invention Registration USH360 describes a smoke-producing grenade which is effective in the infrared region and involves the use of fine particles of brass or aluminum placed in a volatile liquid. This arrangement makes it possible to reduce the dispersion energy and prevents agglomeration of the particles.
In point of fact, prevention of particle agglomeration is not sufficiently effective and the infrared masking performances obtained are unsatisfactory. Furthermore, a grenade of this type is capable of masking only small areas over a limited period of time.
SUMMARY OF THE INVENTION
A primary aim of the invention is to provide a powdered material having the intended function of producing smokes which achieve better infrared masking than materials employed in the prior art.
The invention also proposes a smoke-generating device which is adapted to this type of material.
Thus the invention is concerned with powdered material which is intended to be scattered by dispersion means in order to produce a camouflaging cloud which is effective in the infrared region. The distinctive feature of this material is that it includes at least one powder having grains provided with a coating which is chemically inert with respect to the grain, which is resistant to temperatures lower than or equal to the dispersion temperature and which does not oxidize in free air.
BRIEF DESCRIPTION OF THE DRAWING
The drawing figure shows a device according to the invention for dispersing the powdered material to form a smoke screen.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The coating considered can be a compound of silica and alumina and the mean particle size selected for the coated powder will be within the range of 1 .mu.m to 15 .mu.m.
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REFERENCES:
patent: H360 (1987-11-01), Shukis et al.
patent: H769 (1990-04-01), Rouse et al.
patent: 2408429 (1946-10-01), Levey
patent: 2913419 (1956-04-01), Alexander
patent: 2939779 (1960-06-01), Brock
patent: 3849152 (1974-11-01), Mimeault
patent: 4484195 (1984-11-01), Shaffer
patent: 4568820 (1986-02-01), Swiatosz
patent: 4808230 (1989-02-01), Bugnon et al.
Lacreuse Gilles F.
Larmignat Daniel
Morand Phillippe C.
Prieur Christian H.
Giat Industries
Green Anthony
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