WO2024062199A1

WO2024062199A1 - Combustible charges adhering to the inner wall of a combustible structure containing a propellant charge

Info

Publication number: WO2024062199A1
Application number: PCT/FR2023/051446
Authority: WO
Inventors: Sébastien CUVELIER; Alain Tronche
Original assignee: Eurenco France Sas
Priority date: 2022-09-21
Filing date: 2023-09-21
Publication date: 2024-03-28
Also published as: FR3139818A1

Abstract

The invention relates to ammunition containing, in a combustible structure based on a cellulose ester, a propellant charge of powder grains and an ignition device, wherein in said ammunition at least one combustible charge based on cellulose ester is deposited in the form of a solid geometric volumetric pattern adhering to the inner wall of the combustible, cellulose ester-based structure.

Description

Combustible charges adhering to the internal wall of a combustible structure containing a propellant charge

Field of the invention

The technical field is that of additional combustible loads to a propulsive powder load of a shell or mortar type ammunition. These additional combustible loads provide the function of ignition relay, delivery of functional additives (for example an anti-glow, anti-copper or anti-erosion additive), or propulsive energy supply. According to the present invention, these combustible charges are arranged in adhesion on the internal wall of the combustible structure, in particular the combustible case, containing the propellant charge of a munition. These combustible charges are particularly suitable for munitions with large internal dimensions, for example those in which the tail of the projectile is integrated into the heart of the propulsive charge, of the arrow shell type.

State of the art

The propellant charge of an ammunition is initiated into combustion by an ignition device. This ignition device, which initiates the combustion of the ammunition, is composed of a primer and possibly a pyrotechnic charge. This ignition device can be coupled with one or more ignition relays ensuring uniform ignition of the propellant charge.

On a first level, the prior art describes ignition relays inserted in the case containing the propellant charge of an arrow shell. These ignition relays make it possible to optimize ignition for modern munitions which have a significant length and/or a volume of powder that is difficult to access by the flame of a conventional ignition device, composed of a primer, an igniter and an igniter tube forming the primer tube (TPA). Increasing the performance of the ignition means is also sought due to the use of composite propellant powders with low vulnerability that are difficult to ignite, for example of the LOVA or HE LOVA type.

These ignition relays are connected to the TPA and they ensure better distributed ignition of the propellant charge.

According to a first technology, these ignition relays are packaged in a support, for example a plastic tube, in the form of cords. They include for example a pyrotechnic composition, such as black powder or a composition combining boron/potassium nitrate or aluminum/potassium perchlorate or even Magnesium I Teflon® or Viton®. Depending on the ammunition, the ignition cords are arranged in the mass of the load and/or are fixed on the internal surface of the case and/or on a rear part of the projectile inserted in the load.

Patent application WO 93/12400 describes for example this type of device. The ignition cords [figures 10 and 11, ref. 32], connected to the igniter, are distributed in the mass of the propellant charge. Patent US5129324 also describes this type of architecture using ignition cords in a simple ammunition and also in a stepped ammunition.

Patent application FR2799832 describes a device of the same type as that of patent application W093/12400 but also including ignition cords (ref 8a) glued or plated with adhesive tape on the internal wall of the case and on the tail of the projectile.

In usual ammunition of the arrow shell type (see the principle representation of Figures 3a and 3b below), a first part of the propellant charge is first placed in the case equipped with its base supporting the TPA. A space is left free in the upper part of the case. This space has the function of receiving the tail of the arrow supporting around it a cylindrical cage enclosing a second part of the load. The fletched arrow (projectile) fitted with the cage on its fletching is secured to the upper part of the case by means of a connecting part. The upper part of the case then contains, above the first loading part, the empennage and its cage containing the second part of the propulsive loading. The connecting part, made of plastic or fibrous combustible material, is riveted and/or glued to the upper part of the case. The ammunition is therefore made in two assembled parts, each including a part of the propellant charge. It is also possible, according to another method, to load the powder grains via orifices on the rear bottom of the pre-constituted ammunition with its case and projectile. The base of the ammunition is then put in place and ensures the closure of the loading ports. For this type of ammunition for example, we understand that the ignition relays made up of cords, proposed by the prior art, make the operations of mounting the ammunition complex. It is necessary to take precautions to avoid moving/damaging the cords placed in the heart of the case and/or on the wall of the case and/or the tail as well as their connection to the ignition device . When the ammunition is made up of two assembled parts, the part of the ammunition supporting the lines is limited to the case and does not cover the area of the connecting part. Generally speaking, the cords distribute the ignition of the propellant charge locally on their operating line and/or in only part of the height of the charge. There distribution of the ignition of the propellant charge is therefore not homogeneous and is likely to generate pressure waves upon ignition between the rear and the front of the munition. The modularity of the cords in positioning and number is also limited. Their implementation requires complex adaptations to each new ammunition architecture.

Patent application WO 2009/043876 describes an ignition relay consisting of at least one ring secured (ref. 4) to the internal face of the case. This ring has a flexible surface supporting a striker (ref. 4e) on the propulsive loading side. This ring contains a charge in priming composition (ref.8) likely to ignite by impact of the striker (following the deformation of the flexible surface during pressurization of the ammunition). The ignition of the propellant charge takes place in two stages:

- partial ignition of the propellant charge and rapid pressurization of the ammunition following operation of the main ignition device (ref.6),

- the rapid deformation of the flexible surface (ref. 4d) of the rings causing the percussion and ignition of the charge in the priming composition of the ring. The operation of the annular ignition relays thus contributes to accelerating and completing the ignition of the propellant charge.

This embodiment therefore requires annular relays comprising a charge in priming composition with striker inducing safety and handling constraints, particularly when placing the charge. The two-stage ignition of the propellant charge lengthens the pressurization time of the ammunition. The reproducibility of firing pin operation may depend on the arrangement of the bulk propellant charge in the case. Finally, the complementary ignition effects are localized in the areas where the rings are placed in the load.

Those skilled in the art are therefore always looking for a device acting as an ignition relay in an ammunition case, easily positioned in the case (even with an ammunition tail flush with the ignition device), not requiring no additional fixing or connecting member, not interfering with the installation of the propellant charge consisting of grains of powder in bulk, with adjustable positioning and quantity depending on the type of ammunition and leading to distributed ignition and homogeneous over the entire propellant load.

On a second level, the functional additives, for example anti-glow or anti-copper or anti-erosion, are incorporated into the propellant powder or into the fibrous matrix of the combustible case of the ammunition. They can also be provided through sachets/sleeves placed in the structure of the ammunition. Patent application FR2374278 thus describes a weapon powder composed of grains containing the anti-glow additive K ₂ SO ₄ . Patent US1963116 describes powder grains coated with a tin-based compound as an anti-copper additive. Patent application FR2802918 presents a propulsive charge of ammunition or a combustible case incorporating a charge comprising a metal oxide with a wax, polyurethane or cellulose binder as an anti-erosion additive. Patent US4098193 incorporates between the case and the propellant charge a textile fuel sleeve incorporating an anti-erosion agent. In all cases, these modes of incorporating additives degrade the overall propulsive performance of the ammunition. Their incorporation in the matrix of the combustible case or in bags/sleeves placed in the case does not allow optimal delivery during operation of the ammunition. In addition, the positioning of bags or sleeves in bulky ammunition is impossible or adds a complex operation to the constitution of the ammunition.

Those skilled in the art therefore seek to incorporate functional additives into the ammunition:

- without degrading the energy performance of the ammunition,

- by ensuring their delivery progressively following the flow of combustion gases of the propellant charge, and

- according to an installation compatible with munitions with large internal dimensions.

On a third level, those skilled in the art know that the rate of energetic charges (of the octogen or hexogen type for example) in a grain of powder is limited (typically <75% by mass) in order to maintain sufficient mechanical resistance properties. especially at low temperatures. Too high a charge rate also leads to low combustion rates at low pressure which also degrade the ignition properties of the charge.

Those skilled in the art therefore seek to increase above conventional values the mass rate of energy charges in the ammunition without degrading the mechanical or ignition properties of the propellant charge, while maintaining progressive delivery of this added charge during the operation of the ammunition.

The present invention relates to combustible loads ensuring an ignition relay, and/or the delivery of functional additives and/or a doping energy supply, said combustible loads being capable of being implanted with a large latitude of positioning in a high-energy munition. internal bulk thus freeing itself from the limitations and constraints of the prior art. Summary of the invention

The invention relates to combustible charges adhering to the internal wall of a combustible structure of a shell-type munition containing a propellant charge (composed of bulk powder grains) and an ignition device to initiate combustion. Said combustible loads can provide an ignition relay function and/or a delivery function of one or more functional additives and/or an additional energy supply function (doping) to that of the propulsive load. The combustible structure, in particular a combustible case, can therefore receive one or more combustible loads with the same function or different functions. Although mainly concerning the combustible case of the ammunition, the invention also finds its application to any additional combustible element of the structure containing the propellant charge of the ammunition. The object of the invention is more particularly devoted to ammunition of the 120 mm tank shell type, explosive or bulky shell for example an arrow shell, but can also be used in any type of ammunition with a combustible structure, for example ammunition of other calibers such as large caliber ammunition of 155 mm with monolithic loading or modular loading, or mortar ammunition in particular those of caliber 60 mm, 81 mm or 120 mm.

Brief description of the figures

Figure 1 shows different types of patterns of a combustible charge on a combustible case.

Figure 2a shows the rear part of an arrow shell type ammunition comprising a combustible charge on its combustible structure formed by the case.

Figure 2b shows the front part of an arrow shell type ammunition comprising a combustible charge on its combustible structure formed by the connecting part.

Figure 3a shows the assembly of the rear part and the front part of an arrow shell type ammunition comprising a combustible load on their combustible structure.

Figure 3b shows an assembled arrow shell type ammunition comprising a combustible charge on its combustible structure.

Description of the invention

It will be noted that in the context of the present disclosure, the different embodiments described can be combined with each other.

According to one aspect the invention relates to a munition containing, in a combustible structure based on cellulose ester, a propellant charge of powder grains and an ignition device for initiating combustion, at least one combustible charge at cellulose ester base being deposited in the form of a solid geometric volume pattern adhering to the internal wall of the combustible structure.

The aforementioned combustible cargo can perform the following functions:

- it can serve as an ignition relay for the propulsive charge (said combustible charge is then also called relay loading in the remainder of the document),

- it can allow the delivery of functional additives (said combustible loading is then also called additive loading in the remainder of the document),

- it can contribute to a doping energy supply (said combustible loading is then also called energy loading in the remainder of the document).

The combustible charge based on cellulose ester has the advantage of being able to be installed directly on a combustible structure containing the propellant charge, independently of the propellant charge. Said combustible structure enclosing the propellant charge comprises in particular a combustible case but also any other additional combustible structures, such as connecting or closing elements of the ammunition. It is also entirely possible to install said combustible load on any other combustible structure subsequently added constituting the architecture of the ammunition.

The combustible loading based on cellulose ester is obtained from a collodion based on cellulose ester loaded with either ignition powder for relay loading, or at least one functional additive for additive loading, or with at least one energy charge for the energy charge. The collodion, in the form of a paste, is deposited on the surface of the combustible structure then dried.

In certain embodiments, the geometric volume pattern formed by deposition of the collodion is a linear, helical, curvilinear pattern, or shapes combined so as to obtain a mesh.

The collodion used in the context of the invention is of the cellulose ester base + solvent(s) type. In one embodiment, the base of the collodion consists of a cellulose ester (for approximately 70% to approximately 90% by weight) and generally additionally contains, conventionally, at least one plasticizer (approximately 1% to approximately 20% by weight). mass, preferably approximately 10% by mass) and at least one cellulose ester stabilizer (approximately 0.5% to approximately 5% by mass). It is likely to contain a residual quantity of solvent(s), in particular phlegmatization solvent(s) or (and) solvent(s) for dissolving the cellulose ester used during its manufacture. Advantageously, the cellulose ester used as the majority component is chosen from cellulose nitrate, cellulose acetate or nitrocellulose, the latter being preferred. The nitrogen mass content of nitrocellulose is conveniently 10.5% to 13.5%, an example being grade E nitrocellulose with a nitrogen mass content of 11.8% to 12.3%, advantageously equal to 12 %.

The plasticizer used to prepare the collodion may in particular be a ketone (such as camphor), a vinyl ether (such as poly(ethyl vinyl ether) sold under the name LUTA 50-50%® by the company East Harbor Group), a polyurethane (such as NEP-PLAST 2001 marketed by the company Hagedorn-NC), an adipate (such as dioctyl adipate) or a citrate (such as triethyl 2-acetyl citrate).

The stabilizer used to prepare the collodion may in particular be a compound whose chemical formula includes aromatic nuclei (opportunity two aromatic nuclei), capable of fixing the nitrogen oxides from the decomposition of nitric esters (currently nitrocellulose). As an example of a stabilizer, mention may be made of 2-nitrodiphenylamine (2-NDPA), 1,3-diethyl-1,3-diphenyl urea (centrality I), 1,3-dimethyl-1,3-diphenyl urea (centrality II), and l-methyl-3-ethyl-1,3-diphenyl urea (centrality III).

The solvent(s) is(are) chosen from acetic esters (for example ethyl acetate, butyl acetate), carbonic esters (for example methyl carbonate, ethyl carbonate), propylene glycol ethers (for example Dowanol® PM), acetates (for example 1,3-dioxolane), ethyl esters (for example ethyl lactate).

The solvent is for example a double solvent of the acetone/butyl acetate (AB) type at 50%/50% by weight or a double solvent of the ethyl lactate type for 35% to 60% by weight and butyl acetate for 40% by weight. % to 65% by mass for a total of 100%.

The collodion is advantageously formulated to produce a dry extract (after evaporation of the solvent) of 10% to 40% by mass.

The composition of the cellulose ester base to form the collodion is for example that of table 1:

Table 1

Table 2 below presents a formulation of the collodion at 14% dry extract by mass using the cellulose base from Table 1.

Table 2

In certain embodiments, the combustible loading (relay loading) is obtained after deposition and then drying of a paste (adherent to the surface of the combustible structure of the ammunition) consisting of a collodion based on cellulose ester loaded with the ignition powder (classified in risk division 1.1 within the meaning of the UN GHS classification (UN General Harmonized System of Classification and Labeling of Chemicals)) or with the ingredients forming the ignition powder.

The composition of the ignition powder is most frequently black powder (PN) consisting of an agglomerated mixture of potassium nitrate (saltpeter), charcoal and sulfur. There are also other compositions of agglomerated ignition powder, in particular of the type: Boron/KNO ₃ , in a ratio generally of 70/30 (% by mass), a metal (for example iron, aluminum, zinc, magnesium), an oxidant of the perchlorate type (for example potassium perchlorate) or of the fluoropolymer type (for example PTFE such as Teflon®).

In one embodiment, the collodion loaded with ignition powder(s) comprises approximately 50% to approximately 70% by mass of ignition powder(s), and the remainder at 100% (i.e. approximately 30% to approximately 50% by mass) of collodion. Conventionally, the ignition powder(s), previously constituted, is(are) added to the collodion.

Table 3 below gives an example of the collodion composition from Table 2, loaded with ignition powder to form the relay loading. Table 3

Collodion loaded with ignition powder is classified in risk division 1.3 within the meaning of the UN GHS classification (UN General Harmonized System of Classification and Labeling of Chemicals). The danger zones to be taken into account for handling the charged collodion are therefore reduced, which facilitates the operations of depositing the collodion on the tube.

After drying, a combustible load useful as an ignition relay is formed, which adheres to the internal surface of the combustible structure and comprises approximately 88% to approximately 92% by mass of ignition powder(s), approximately 7% to approximately 10 % by mass of cellulose ester, the 100% complement being provided by the plasticizer, the stabilizer and the residual solvent from the collodion. The residual solvent from the collodion generally represents less than 1% by mass of the total mass of the fuel load. As an indication, the dry fuel loading obtained after drying (evaporation of the solvent) of the collodion in Table 3 contains the mass ratios indicated in Table 4 below.

Table 4

In certain embodiments, the combustible loading (additive loading) is obtained after deposition then drying of a paste (adherent to the surface of the combustible structure of the ammunition) consisting of a collodion based on cellulose ester loaded with least one functional additive. These additives are either inert (for example calcium carbonate) or low in energy (for example potassium nitrate) and to guarantee the absence of residues after combustion, the paste can also, in addition, contain a low mass proportion (< 10%) of a combustible filler in order to regulate the combustion properties of the additive filler after drying of the paste. This combustible charge can be an ignition powder or a propellant powder.

As a functional additive capable of being used in the context of the invention, mention may be made, for example, of anti-glow additives, anti-erosion additives, anti-copper additives, and mixtures of one or more of these additives.

The antiglow additive is, for example, chosen from potassium nitrate, potassium or sodium sulfate, potassium nitrate, potassium or sodium cryolite, sodium oxalate, sodium bicarbonate, carbonate potassium or sodium, potassium or sodium cobaltnitrite, sodium nitrite, preferably potassium sulfate.

The anti-erosion additive is, for example, chosen from camphor, 2-4 dinitrotoluene, butyl phthalate, calcium carbonate, titanium dioxide, molybdenum trioxide, tungsten trioxide, silicon oxide , magnesium silicate (talc), preferably titanium dioxide. The additive can also be the centrality possibly already contained in very small quantities in the collodion as a stabilizer.

The anti-copper additive is, for example, chosen from tin, tin oxide, lead oxide, preferably tin oxide.

In certain embodiments, the collodion loaded with functional additive(s) comprises approximately 30% to approximately 50% by mass of collodion and the complement to 100% by mass of at least one functional additive and optionally a combustible filler , for example approximately 40% to approximately 70% by mass of functional additive(s), and 0% to approximately 10% by mass of a combustible filler.

After drying, a combustible filler useful as an additive filler is formed, which adheres to the internal surface of the combustible structure and comprises approximately 70.3% to approximately 92% by mass of additive(s), 0% to approximately 17.6%. of a combustible charge, approximately 7% to approximately 10% by mass of cellulose ester, the remainder to 100% being provided by the plasticizer, the stabilizer and the residual solvent coming from the collodion. The residual solvent from the collodion generally represents less than 1% by mass of the total mass of the fuel load.

An example of the composition of the dry material forming the additive loading after deposition is given in Table 5. This example is obtained with the use of the same collodion as that given in Table 2 and the same ratio between the loading(s). ) added to the collodion than that given in Table 3. In this example, the total of the mass percentage of the filler of at least one functional additive and of the possible combustible filler therefore represents 90.08% of the total of the dry composition.

Table 5

In certain embodiments, the combustible loading (energy loading) is obtained after deposition and then drying of a paste (adherent to the surface of the combustible structure) consisting of a collodion based on cellulose ester loaded with at least one filler energy. Said energetic charge is for example chosen from hexogen (RDX), octogen (HMX), FOX-7 (l,l-diamino-2,2-dinitroethene (DADNE)), FOX-12 (dinitramide of guanylurea, GUDN), or even a composite powder composition (also called LOVA powder) comprising an energetic filler and a crosslinked binder, for example of the polyurethane, polyglycidyl azide (PAG) and/or thermoplastic type, for example PMMA or an ethylene/vinyl acetate copolymer (EAV).

In some embodiments, the collodion charged with energetic charge comprises about 50% to about 70% by mass of energetic charge, and the balance 100% (i.e., about 30% to about 50% by mass) of collodion.

The paste intended to form said energy loading is classified in risk division 1.3 within the meaning of the UN GHS classification (UN General Harmonized System of Classification and Labeling of Chemicals). The danger zones to be taken into account for handling the loaded collodion are therefore reduced, which facilitates the operations of depositing the collodion on the tube.

After drying, a combustible filler useful as an energetic filler is formed, which adheres to the internal surface of the combustible structure and comprises approximately 88% to approximately 92% by mass of the at least one energetic filler, approximately 7% to approximately 10% by mass. of cellulose ester, the 100% complement being provided by the plasticizer, the stabilizer and the residual solvent from the collodion. The residual solvent from the collodion generally represents less than 1% by mass of the total mass of the fuel load.

An example of the composition of the dry material forming the energetic fuel charge after deposition is given in Table 6. This example is obtained with the use of the same collodion as that given in Table 2 and the same ratio between the charge(s). s) added to the collodion than that given in table 3. In this example, the total mass percentage of the energy charge therefore represents 90.08% of the total dry composition.

Table 6

Said paste, containing either an ignition powder, or at least one functional additive, or an energy charge, or a mixture of several of these constituents, is obtained by introducing the constituents into a standard blade mixer or a twin-screw continuous mixer or in a mixer by acoustic resonance. Said paste is then extruded via a press piston or a single screw extended by an extrusion channel and a nozzle to form patterns on a support (the internal surface of the combustible structure of the ammunition for the present invention), for example by means of a device of the type described in patent application WO 2021/144539.

As part of the implementation of the present invention, the nozzle described in patent application WO 2021/144539 is optionally articulated so as to deposit patterns perpendicular to the surface of a curved support not collinear with the axis d extrusion of the press piston or the single screw. It is thus possible to make deposits on a curved support such as the rear bottom of an ammunition case.

The combustible structure of the ammunition is made of combustible material based on cellulose ester (having the appearance of a felt). The combustible materials constituting the combustible structure and said combustible load must be chemically compatible and have the adhesion property on each other. For this, they have a common base of cellulose ester, such as cellulose nitrate, cellulose acetate or nitrocellulose. Nitrocellulose, advantageously containing an average nitrogen level of 12.4% to 13.5%, is the preferred common base and is retained, in a non-limiting manner, in the remainder of the description.

In certain embodiments, the combustible structure is a fibrous structure, such as that marketed by the company Eurenco, consisting of 45% to 81% by mass of cellulose ester (fibers), 3.5% to 33.5% by mass of cellulose (fibers), 4% to 14% by mass of resin (binder), 0% to 1.6% by mass of a stabilizer, and 0% to 15.5% of additional acrylic or polyester fibers (the sum of these different constituents being equal to 100%). An example of the composition of the fuel structure is given in Table 7.

Table 7

The deposition of the paste of said combustible filler in solvent(s) produces a localized dissolution of the surface of the combustible structure ensuring good adhesion of the deposited combustible filler after drying of the paste.

The paste is deposited on the internal wall of the combustible structure of the ammunition in one or more patterns which, after drying, constitute said combustible charge. The patterns deposited can be of linear, helical or curvilinear shapes, or of shapes combined so as to obtain a mesh according to the optimal configuration sought for the ignition of the ammunition or the delivery of at least one additive or an energy supply. (doping). Different patterns can also be placed on the height of the combustible structure.

When the at least one combustible load acts as an ignition relay (relay load), it does not require a specific connection with the ignition device. Said at least one relay loading is for example a linear or curvilinear pattern of which at least one end is coupled (in contact or sufficiently close) with the ignition device to ensure its ignition and thus initiate its combustion. The spatial and mass distributions of the relay loading patterns can be adapted with a wide latitude depending on the characteristics of the propellant charge and the ammunition, thus allowing rapid and homogeneous ignition of the propellant charge. Said at least one relay loading is suitable for munitions with separate stages (for example of the type of those described in patent US5129324), with assembled stages (for example according to the usual assembly mode of the combustible structure of arrow shells, see figure 3b), with large internal dimensions.

When the at least one combustible loading ensures the delivery of at least one functional additive (additive loading) or a doping energy supply (energy loading), the objective sought with the combustible loading is not to provide immediately ignition an almost instantaneous contribution to the propulsive loading, as in the case of relay loading, but to distribute the contribution of additive(s) or energy during the combustion of the loading. For this, the at least one additive or energetic charge is not generally coupled with the ignition device and is ignited by the propulsive charge or a relay charge. Its combustion is therefore generally initiated by that of the propellant charge or by at least one relay charge. However, it is not excluded that said additive loading or said energetic loading is coupled with the ignition device to ensure its ignition. The additive or energetic fuel loads can be deposited in continuous patterns (as previously described for the ignition relays) or semi-continuous or punctual on the wall of the combustible structure according to a geometric and mass distribution ensuring the continuous supply proportional to the gas flow generated by the combustion of the propellant charge. For firing with a tube weapon, this flow rate is intended to increase as the projectile advances in the tube in order to best maintain the constant gas pressure in the tube. The patterns of the additive loadings or the energetic fuel loadings are arranged on the combustible structure in a configuration adapted to the operation of the propulsive loading so as to deliver the at least one additive or the energy supply according to an optimal and continuous mass flow over the duration combustion of the propellant charge. For example, these patterns can be circular or linear or point or combined shapes distributed regularly or not on the combustible structure.

The combustible loading as described above is suitable for different types of ammunition, in particular ammunition of the arrow shell or explosive shell type.

The invention is illustrated by the following examples given without limitation. Examples

Example 1

Figure 1 shows examples of patterns (linear, helical, mesh, combined shapes) that can be retained for fuel loading on a planar view of the internal surface of the fuel structure. The combustible load [1] adhered to the combustible structure [2] is coupled by at least one of the ends of a pattern to the ignition device formed of an igniter [3] and an igniter tube [4] arranged in the rear bottom of the ammunition.

Example 2

This example concerns the installation of combustible charges according to the invention in an ammunition of the type of that of a large arrow shell. It is an arrow shell [5] assembled according to the conventional process in two parts (figures 2a and 2b). The first rear part (figure 2a) is made up of a case [6] made of fibrous combustible material enclosing a first propellant charge [7a] and its ignition device. This ignition device forming a primer tube comprises an igniter and its primer inserted [8] in the base of the case [6] in connection with an igniter tube [9] in the center of the first propellant charge [7a]. A space [10] is left free in the upper part of the fuel case [6]. The second front part (figure 2b) consists of a feathered arrow [11] (projectile) provided with a sabot [12] secured to a connecting piece [13] and supporting around its rear feathered part a cylindrical cage [14]. This cylindrical cage [14] contains a second part of the propellant charge [7b]. The upper free part [10] of the fuel case is intended to receive the fletching of the arrow [11] supporting the cylindrical cage [14] around it. The fletched arrow [11] fitted with the cage on its fletching is secured to the upper part of the case by means of the combustible connecting part [13]. The connecting piece, also made of fibrous combustible material, is glued to the upper part of the case. The ammunition is therefore made in two assembled parts, each including a part of the propellant charge (figures 3a and 3b).

Relay loading patterns [15a and 15b] have been deposited on the internal face of the connecting part [13] and the case [6] whose ends become contiguous after assembly (figures 3a and 3b). This ensures uniform ignition over the entire propellant charge (part contained in the case and front part in the area of the connecting part) of the ammunition. Identically, at least one additive loading and/or at least one energetic fuel loading can also be deposited on the internal face of the connecting part and/or the case, in connection or not after assembly. The reasons for these loadings fuels are adapted to ensure a supply of additive(s) or energy during the combustion of the propellant charge.

Claims

1. Ammunition (5) containing, in a combustible structure (6) based on cellulose ester, a propellant charge of powder grains (7a, 7b) and an ignition device (8,9), ammunition in which at less a combustible filler based on cellulose ester (15a, 15b) is deposited in the form of a solid geometric volume pattern in adhesion on the internal wall of the combustible structure based on cellulose ester.

2. Ammunition according to claim 1, in which the combustible charge comprises from 88% to 92% by mass of ignition powder(s) and from 7% to 10% by mass of cellulose ester.

3. Ammunition according to claim 1, in which the combustible charge comprises at least one functional additive chosen from an anti-glow additive, an anti-erosion additive and an anti-copper additive.

4. Ammunition according to claim 3 in which the combustible charge comprises 70.3% to 92% by mass of functional additive(s), 0% to 17.6% of a combustible charge and 7% to 10 % by mass of cellulose ester.

5. Ammunition according to claim 1, wherein the combustible charge comprises at least one energetic charge.

6. Ammunition according to claim 5, in which the combustible charge comprises from 88% to 92% by mass of at least one energetic charge and from 7% to 10% by mass of cellulose ester.

7. Ammunition according to one of claims 2 to 6, in which the at least one combustible charge deposited in the form of a solid geometric volume pattern is coupled with the ignition device.

8. Ammunition according to one of claims 3 to 6, in which the at least one combustible charge deposited in the form of a solid geometric volume pattern is not coupled with the ignition device.

9. Ammunition according to one of claims 1 to 8, which is of the arrow shell or explosive shell type.

10. Ammunition according to claim 9, in which the combustible structure (6) is a case and comprises a connecting part (13) separately supporting patterns of at least one combustible charge, the patterns of the case and of the part of connection being joined after assembly of the ammunition.

11. Ammunition according to one of claims 1 to 10, in which said geometric volume pattern is a linear, helical, curvilinear pattern, or of shapes combined so as to obtain a mesh.

12. Method for preparing a combustible ammunition structure, said combustible structure being based on cellulose ester and comprising at least one combustible charge based on cellulose ester deposited in the form of a solid geometric volume pattern adhering to its internal wall, process which comprises the deposition by extrusion of a paste consisting of a collodion loaded with an ignition powder, or with at least functional additive or with at least one energetic charge, on the internal face of the combustible structure , and drying the deposited paste, said loaded collodion comprising from 30% to 50% by mass of collodion and the 100% complement of ignition powder or at least one functional additive or at least one energetic charge .

13. Method according to claim 12, wherein the collodion comprises a cellulose ester base, said cellulose ester base comprising 70% to 90% by mass of cellulose ester, preferably nitrocellulose, 1% to 20% by weight. mass of at least one plasticizer, and 0.5% to 5% by mass of at least one stabilizer of the cellulose ester.