FR2840978A1 - MASKING AMMUNITION - Google Patents

Abstract

The invention relates to a masking ammunition (1) comprising an instantaneous masking means effective in the infrared and / or millimeter range which is arranged in an envelope (2) and dispersible using a dispersion means (8, 16). This munition is characterized in that the masking means comprises at least one wafer (13) of conductive fibers and at least one layer (14) of a masking powder.

Description

includes at least one self deployable reflector (50).

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  The technical field of the invention is that of

masking ammunition.

  Such ammunition ensures the protection of a vehicle or a fixed platform against a threat,

  It’s like a projectile with target detection means.

  The patent FR2612287 thus describes an ammunition dispersing, on the one hand a brass powder ensuring an almost instantaneous masking, and on the other hand pots comprising a fumigant pyrotechnic composition and which allow

to ensure lasting masking.

  However, protection is insufficient for threats that use a working radar seeker

in the millimeter band.

  The patent US5337671 describes a multispectral munition which disperses a powder or particles ensuring masking both in the infrared range and in the

millimetric domain.

  This munition thus comprises an annular compartment inside which is disposed an aluminum, bronze or brass powder associated with an anti-caking agent, powder which is chosen with a particle size suitable for

mask infrared radiation.

  This powder is mixed in the same compartment with another powder, or with particles such as fibers, which are chosen to be of dimensions such as to ensure effective masking in the millimeter range. These fibers are cut for example to lengths of 1, 5mm or 4, lmm

  depending on the wavelength to be masked.

  This munition has drawbacks.

  The materials thus mixed will separate or decant inside their compartment and over the storage periods. This will result in a risk of agglomeration of the masking materials therefore difficulties in obtaining a

  masking cloud of sufficient size.

  Furthermore, the distribution of the masking particles will no longer be homogeneous at the end of the settling. Their

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  the distribution in the masking cloud will therefore be random from one munition to another, which will adversely affect the masking performance. It is the aim of the invention to propose a munition which does not have such drawbacks and which guarantees reproducibility of the masking performance from one munition to another after more or less long storage periods. Thus, the subject of the invention is a masking munition comprising an instantaneous masking means effective in the infrared and / or millimetric range, disposed in an envelope and dispersible using a dispersing means, ammunition characterized in that the masking means comprises at least one wafer of conductive fibers and at least one

layer of masking powder.

  The masking munition may comprise a stack arranged in the envelope and alternating one or more wafers of conductive fibers with one or more layers

masking powder.

  The dispersing means may include a piston pushed by an ejection means and pushing the masking means out of the envelope as well as a disposable explosive cane

  axially through the stack.

  The conductive fibers forming the wafers may be carbon fibers or aluminized glass fibers. The fibers may have a length of between 3

mm and 10 mm.

  The masking powder may include a powder

metallic or organic.

  The masking powder may have a particle size distribution whose median diameter will be smaller or

equal to 25 micrometers.

  According to a particular embodiment, the ammunition may include at least two layers of masking powder

  of different nature and / or particle size.

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  If there is another particular mode of rea l i sat ion the ammunition may include at least two wafers of fibers of

different nature and / or length.

  The invention will be better understood on reading the scripting script which will follow in particular modes of

  realization, description made with reference to the drawings

  annexes and in which: - Figure 1 is a longitudinal sectional view of a munition according to a first embodiment, - Figure 2 is a longitudinal sectional view of an ammunition according to a second embodiment of real i sat ion , - Figures 3a, 3b and 3c show variants of

  realization of a stack of masking materials.

  Figure l shows a munition 1 according to a first mode

of realization of the invention.

  This ammunition is intended to be placed in a unrepresented launching tube and secured to a fixed platform or a vehicle (such a tube is for example described

in patent FR2765869).

  The ammunition comprises a casing 2 in the form of a tube at the rear part of which there is a base 3, screwed thereon, and which carries a radial lug 4 allowing the ammunition to be fixed by means of a bayonet mounting on a launcher not shown. The base 3 carries a 2s axial contact 5 electrically insulates from the base by a

insulating cylinder 6.

  The base contains a pyrotechnic ejection charge 7 (a propellant powder for example) and an igniter 8 which is electrically connected, on the one hand to the contact 5 and on the other hand to the metallic body of the base 3. The envelope 2 contains a piston 9 on which is applied a cylindrical case 10 which

  delimits a cylindrical housing 11.

  The case 10 is in the form of two half

  shells lOa, lOb. The envelope 2 is closed at its other end by a cover 12 connected to the latter by a

  radial shear pin (not shown).

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  The housing 11 contains a masking means in the

  infra ouge and / or millimtique domain.

  According to the invention, this masking means comprises at least one wafer 13 of conductive fibers having a masking efficiency in the millimeter range (frequency of 35 94 GHz) and at least one layer 14 of a masking powder having an efficiency in the infrared domain (spectral domains of 3 5 micrometers and 8 12 micrometers). Wafers 13 and layers 14 form a stack in which alternate wafers 13 of conductive fibers and

layers 14 of masking powder.

  Pes galettes 13 (here ten galettes) are made of carbon fibers or aluminized glass fibers. All fibers are stored parallel to each other and

  parallel to the axis 15 of the ammunition.

  Each wafer 13 thus has the thickness of the fiber length, ie from 3mm to 6mm. A process allowing to realize

  such pancakes is described in patent ER2797044.

  [a masking powder forming the layers 14 (here ten layers 14) is a metallic or organic powder (for example aluminum, bronze, carbon or brass), the particle size of which is chosen according to the length

wave mask.

  Concretely, the average diameter of the paticles of the layers 14 is chosen to be less than or equal to 25 micrometers. It is also possible to use particles in the form of lamellae or

sheets.

  [ammunition 1 also includes means for dispersing

masking materials.

  This means comprises the piston 9 which receives the pressure of the gases generated by the injection charge 7 and an explosive cane 16 which is arranged axially through

  the stack of pancakes 13 and layers 14.

  This cane 16 is produced for example in the form of a cardboard tube containing a pyrotechnic composition of s 2840978 dispersion, for example a composition combining aluminum

and potassium perchlorate.

  The pyrotechnic composition of the cane 16 is initiated by a delay igniter 17 which is integral with the piston 9 and which is initiated by the gases of the ejection charge 7 at

through an orifice 18.

  The igniter 17 incorporates a delay pyrotechnic composition which will ensure the initiation of the cane 16 after

  ejection of the masking means from the case 12.

  Such delay compositions are well known to those skilled in the art. It will be dimensioned so as to ensure a delay of the order of ten milliseconds between the initiation of the delay and that of the dispersion composition.

  The operation of the ammunition is as follows.

  The igniter 8 initiates the ejection charge 7. In the same

  time the delay of the igniter 17 is initiated.

  The pressure of the gases generated by the ejection charge 7 pushes the piston 9 which causes, through the case 10, the shearing of the pins retaining the

  cover 12 and [ejection of the latter.

  The case 10 and its contents are therefore ejected out of the envelope 2. The two half-shells 10a, 10b of the case separate outside of the envelope 2 thus releasing the

content.

  At the end of the planned pyrotechnic delay, the igniter 17 initiates the dispersion pipe 16. The radial effect of this causes the simultaneous dispersion of the fibers of the wafers 13 as well as of the metal powder of the layers 14. This results in a effective masking cloud both in the

  millimeter range and in the infrared range.

  Due to the stacking structure proposed by the invention, there is no decantation over the storage periods between the millimetric masking fibers and the

infrared masking powder.

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  In addition, the alternation of conductive fiber wafers 13 and layers 14 of masking powder ensures a good distribution of the fibers and powder particles in the cloud generates. The mixture of fibers and particles is more homogeneous and the masking performance is therefore better. From the manufacturing and assembly point of view, the wafers are produced according to the method described by patent FR2797044. The wafers obtained with this process have an axial bore delimited by a cardboard tube and a peripheral holding case (for example steel from 20 to 140 micrometers thick). This tube and this holding case are not shown in the figures so as not to harm their clarity. We can therefore handle and stack the pancakes 13 easily. We therefore have on a holding tool (not shown) the case 10 and the cane 16 (not loaded by its dispersion composition). A first wafer 13 is then introduced into the case, then the quantity of masking powder desired is metered to produce a first layer 14. The powder is packed by vibration or compression and

  a second pancake 13 is positioned.

  We reiterate the operations to realize

stacking wishes.

  2s After making the stack, the cane is loaded with its pyrotechnic dispersion composition and the case 10 is positioned in the casing 2 carrying the piston 9 and the load

ejection 7.

  It is of course possible to vary the number of wafers 13 of fibers and / or the number of layers 14 of material of my base depending on the characteristics of

  masking desired for the cloud to generate.

  It is also possible to vary the nature and / or the length or grain size of the materials of the pancakes.

  3s fibers and / or layers of masking powder.

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  Figure 2 thus shows a second embodiment of the invention in which the masking means comprises a stack arranged in the case 10 which comprises two different types of fibers, forming wafers 13a or 13b (here five wafers of each type wind represented), and two different types of pulverulent materials, forming layers 14a or

  14b (here five layers of each wind type represented).

  For example, it is possible to combine wafers 13a formed from fibers of the carbon fiber type with or without enzymes with wafers 13b formed from fibers of the glass fiber type.

aluminized (or "chaffs").

  It is also possible to combine carbon fibers approximately 3 mm long with carbon fibers 6 to 8 mm long. We can use to achieve the layers 14a a powdery material with a particle size close to 3 to 5 micrometers and to achieve the layers 14b a material

  pulverulent with a particle size close to 8 to 12 micrometers.

  These powdery materials may be of the same or different nature (aluminum, bronze, brass, carbon, ...). The invention therefore makes it possible to optimize the loading by using the most suitable materials for each wavelength that it is sought to mask. We can eventually add additives to increase the time

cloud suspension.

  Such an embodiment makes it possible to create a homogeneous cloud whose infrared occultation characteristics

and optimal wind millimetric.

  Each layer 14a is arranged between a wafer 13a and

a pancake 13b.

  Each layer 14b is arranged between a wafer 13b and

a pancake 13a.

  There is therefore a perfect separation between the pulverulent layers 14a and the layers 14b. There is therefore no

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  risks of sedimentation of materials and the ammunition keeps

  its performance even after long periods of storage.

  We can also, depending on operational needs, define a munition in which the thicknesses of the different layers of pulverulent materials are

different along the ammunition.

  It is also possible to produce a stack in which at least two wafers of wind fibers arranged one on the other. l0 Figures 3a, 3b and 3c thus show by way of nonlimiting example different types of combinations or structures

  of the stack of wafers / layers which are possible.

  FIG. 3a shows a stack in which the fiber slabs 13 are stacked two by two and a layer of masking powder 14 is placed between each

group of two pancakes 13.

  FIG. 3b shows a stack in which the layers 14a, 14b and 14c of masking powder disposed between two wafers 13 of fibers have a thickness different from one

layer to another.

  FIG. 3c shows a stack in which the layers 14 of wind masking powder are placed between wafers of fibers of different dimensions and characteristics: first wafers 13a of carbon fibers having approximately 3 mm in length and second wafers 13b of fiber fibers

  carbon 6 mm to 8 mm long.

Claims (8)

  1- Masking ammunition (1) comprising an instantaneous effective masking means in the infrared and / or millimetric range disposed in an envelope (2) and dispersible using a dispersing means, ammunition characterized in that the masking means comprises at least one wafer (13) of conductive fibers and at least one   layer (14) of a masking powder.   2- masking ammunition according to claim 1, characterized in that it comprises a stack placed in the envelope (2) and alternating one or more wafers (13) of conductive fibers with one or more layers (14) of masking powder.   3- masking ammunition according to claim 2, characterized in that the dispersing means comprises a piston (9) pushed by an ejection means (7) and pushing the masking means out of the envelope (2) as well as '' an explosive cane (16) arranged axially through stacking.   4- Masking ammunition according to one of claims 1 a   3, characterized in that the conductive fibers forming the wafers (13) wind carbon fibers or fibers aluminized glass.   2s 5- Masking ammunition according to claim 4, characterized in that the fibers have a length included between 3 mm and 10 mm.   6- Masking ammunition according to one of claims 1 a   , characterized in that the masking powder comprises a metallic or organic powder.   7- Masking ammunition according to claim 6, characterized in that the masking powder has a particle size distribution whose median diameter is less than or equal to 25 micrometers.   8- Masking ammunition according to one of claims 2 a   7, characterized in that it comprises at least two layers (14) of masking powder of different nature and / or particle size.   9- Masking ammunition according to one of claims 2 a   8, characterized in that it includes two pancakes in the hand