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

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

[0001] Combustible charges adhering to the inner wall of a combustible structure containing a propellant charge

[0002] Field of invention

[0003] The technical field is that of additional combustible charges to a propellant charge of powder of a munition of the shell or mortar type. These additional combustible charges ensure the function of ignition relay, delivery of functional additives (for example an anti-glow, anti-copper or anti-erosion additive), or supply of propulsive energy. According to the present invention, these combustible charges are arranged in adherence to 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 propellant charge, of the arrow shell type.

[0004] State of the art

[0005] The propellant charge of a munition is initiated by combustion by an ignition device. This ignition device, which initiates the combustion of the munition, 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.

[0006] On a first level, the prior art describes ignition relays inserted into the case containing the propellant charge of an arrow shell. These ignition relays make it possible to optimize the ignition for modern munitions which have a significant length and / or a volume of powder which 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 low-vulnerability composite propellant powders which are difficult to ignite, for example of the LOVA or HE LOVA type.

[0007] These ignition relays are connected to the TPA and they ensure better distributed ignition of the propellant charge.

[0008] According to a first technology, these ignition relays are packaged in a support, for example a plastic tube, in the form of cords. They comprise 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.

[0009] 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 throughout the mass of the propellant charge. Patent US5129324 also describes this type of architecture using ignition cords in a single munition and also in a staged munition.

[0010] 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 stuck with adhesive tape on the internal wall of the case and on the tail of the projectile.

[0011] In standard 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 charge. The finned arrow (projectile) equipped with the cage on its tail is secured to the upper part of the case by means of a connecting piece. The upper part of the case then contains, above the first part of the charge, the tail and its cage enclosing the second part of the propellant charge. The connecting piece, made of plastic or fibrous fuel material, is riveted and / or glued to the upper part of the case. The ammunition is therefore made of 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-made munition with its case and projectile. The base of the munition is then put in place and ensures the closing of the loading orifices. For this type of munition for example, it is understood that the ignition relays made up of cords, proposed by the prior art, make the operations of assembling the munition complex. It is necessary to take precautions so as to avoid moving / damaging the cords arranged 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 munition is composed of two assembled parts, the part of the munition supporting the cords is limited to the case and does not cover the area of ​​the connecting piece.Generally speaking, the cords distribute the ignition of the propellant charge locally on their operating line and / or in only a part of the height of the charge. The distribution of the ignition of the propellant charge is therefore not homogeneous and is likely to generate pressure waves on ignition between the rear and the front of the munition. The modularity of the cords in positioning and number is also limited. Their installation requires complex adaptations to each new munition architecture.

[0012] Patent application WO 2009 / 043876 describes an ignition relay consisting of at least one ring (ref. 4) integral with the internal face of the case. This ring has a flexible surface supporting a firing pin (ref. 4e) on the propellant charge side. This ring contains a charge of priming composition (ref. 8) capable of igniting by impact of the firing pin (following the deformation of the flexible surface during pressurization of the ammunition). The ignition of the propellant charge takes place in two stages:

[0013] - partial ignition of the propellant charge and rapid pressurization of the ammunition following operation of the main ignition device (ref.6),

[0014] - 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.

[0015] This embodiment therefore requires annular relays comprising a charge in priming composition with a firing pin inducing safety and handling constraints, particularly during the installation of the load. The two-stage ignition of the propellant charge lengthens the pressurization time of the ammunition. The reproducibility of the operation of the firing pins may depend on the arrangement of the bulk propellant charge in the case. Finally, the additional ignition effects are localized in the areas where the rings are arranged in the charge.

[0016] The person skilled in the art is therefore always looking for a device acting as an ignition relay in an ammunition case, easily positioned in the case (even with an ammunition fin flush with the ignition device), not requiring an additional fixing or connecting member, not interfering with the installation of the propellant charge consisting of loose powder grains, with positioning and quantity that can be adjusted depending on the type of ammunition and leading to distributed and homogeneous ignition over the entire propellant charge.

[0017] On a second level, 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 via bags / sleeves arranged in the structure of the ammunition. Patent application FR2374278 describes a weapon powder composed of grains containing the anti-glow additive K2SO4. Patent US1963116 describes powder grains coated with a tin-based compound as an anti-copper additive. Patent application FR2802918 presents a propellant 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 combustible sleeve incorporating an anti-erosion agent.In all cases, these methods of incorporating additives degrade the overall propellant performance of the ammunition. Their incorporation into the matrix of the combustible case or into bags / sleeves placed in the case does not allow for optimal delivery during operation of the ammunition. In addition, the positioning of bags or sleeves in large ammunition is impossible or adds a complex operation to the constitution of the ammunition.

[0018] The person skilled in the art therefore seeks to incorporate functional additives into the ammunition:

[0019] - without degrading the energy performance of the ammunition,

[0020] - by ensuring their delivery progressively according to the combustion gas flow rate of the propellant charge, and

[0021] - according to an installation compatible with munitions with large internal dimensions.

[0022] On a third level, the person skilled in the art knows that the rate of energetic charges (of the octogen or hexogen type for example) in a powder grain is limited (typically < 75% by mass) in order to maintain sufficient mechanical resistance properties, particularly at low temperature. Too high a charge rate also leads to low combustion speeds at low pressure which also degrade the ignition properties of the charge.

[0023] The person skilled in the art therefore seeks to increase the mass rate of energetic charges in the munition above conventional values ​​without degrading the mechanical or ignition properties of the propellant charge, while maintaining a progressive delivery of this added charge during operation of the munition.

[0024] The present invention relates to combustible loads providing 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 munition with a large internal bulk, thus overcoming the limitations and constraints of the prior art. Summary of the invention

[0025] 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 loose powder grains) and an ignition device for initiating combustion. Said combustible charges can provide an ignition relay function and / or a function of delivering one or more functional additives and / or a function of providing additional energy (doping) to that of the propellant charge. The combustible structure, in particular a combustible case, can therefore receive one or more combustible charges of the same function or different functions. Although mainly relating to the combustible case of the munition, the invention also finds its application to any additional combustible element of the structure containing the propellant charge of the munition.The subject of the invention is more particularly devoted to munitions of the 120 mm tank shell type, explosive shell or large bulk shell for example an arrow shell, but can also be implemented in any type of munition with a combustible structure, for example munitions of other calibers such as a large caliber 155 mm munition with monolithic loading or modular loading, or mortar munitions in particular those of caliber 60 mm, 81 mm or 120 mm.

[0026] Brief description of the figures

[0027] Figure 1 shows different types of patterns of a combustible load on a combustible case.

[0028] Figure 2a shows the rear part of an arrow-type ammunition with a combustible charge on its combustible structure formed by the case.

[0029] Figure 2b shows the front part of an arrow shell type munition having a combustible charge on its combustible structure formed by the connecting piece.

[0030] Figure 3a shows the assembly of the rear and front parts of an arrow shell type munition with a combustible charge on their combustible structure.

[0031] Figure 3b shows an assembled arrow shell type ammunition with a combustible charge on its combustible structure.

[0032] Description of the invention

[0033] It will be noted that within the scope of the present disclosure, the different embodiments described may be combined with each other.

[0034] According to one aspect, the invention relates to a munition containing, in a cellulose ester-based combustible structure, a propellant charge of powder grains and an ignition device for initiating combustion, at least one cellulose ester-based combustible charge being deposited in the form of a solid geometric volume pattern adhering to the internal wall of the combustible structure.

[0035] The above-mentioned combustible load can perform the following functions:

[0036] - it can serve as an ignition relay for the propellant charge (said combustible charge is then also called relay charge in the rest of the document),

[0037] - it can allow the delivery of functional additives (said combustible loading is then also called in the remainder of the document additive loading),

[0038] - it can contribute to a doping energy supply (said combustible loading is then also called energy loading in the rest of the document).

[0039] The cellulose ester-based combustible charge has the advantage of being able to be implanted directly on a combustible structure containing the propellant charge, independently of the propellant charge. Said combustible structure containing the propellant charge includes in particular a combustible case but also any other additional combustible structures, such as connecting or closing elements of the munition. It is also entirely possible to implant said combustible charge on any other combustible structure subsequently added constituting the architecture of the munition.

[0040] The cellulose ester-based fuel charge is obtained from a cellulose ester-based collodion loaded with either ignition powder for relay charging, or at least one functional additive for additive charging, or with at least one energetic charge for energetic charging. The collodion, in the form of a paste, is deposited on the surface of the fuel structure and then dried.

[0041] In some embodiments, the geometric volume pattern formed by deposition of the collodion is a linear, helical, curvilinear pattern, or a pattern of shapes combined to obtain a mesh.

[0042] 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 mass) and generally additionally contains, conventionally, at least one plasticizer (approximately 1% to approximately 20% by mass, preferably approximately 10% by mass) and at least one stabilizer of the cellulose ester (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 major 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%.

[0043] The plasticizer used to prepare the collodion may include a ketone (such as camphor), a vinyl ether (such as poly(ethyl vinyl ether) marketed under the name LUTA 50-50%® by the East Harbour Group company), a polyurethane (such as NEP-PLAST 2001 marketed by the Hagedorn-NC company), an adipate (such as dioctyl adipate) or a citrate (such as triethyl 2-acetyl citrate).

[0044] The stabilizer used to prepare the collodion may be, in particular, a compound whose chemical formula includes aromatic nuclei (opportunely two aromatic nuclei), capable of fixing nitrogen oxides from the decomposition of nitric esters (presently nitrocellulose). Examples of stabilizers include 2-nitrodiphenylamine (2-NDPA), 1,3-diethyl-1,3-diphenyl urea (centrality I), 1,3-dimethyl-1,3-diphenyl urea (centrality II), and 1-methyl-3-ethyl-1,3-diphenyl urea (centrality III).

[0045] The solvent(s) is(are) chosen from acetic esters (e.g. ethyl acetate, butyl acetate), carbonic esters (e.g. methyl carbonate, ethyl carbonate), propylene glycol ethers (e.g. Dowanol® PM), acetates (e.g. 1,3-dioxolane), ethyl esters (e.g. ethyl lactate).

[0046] The solvent is for example a double solvent of the acetone / butyl acetate (AB) type at 50% / 50% by mass or a double solvent of the ethyl lactate type for 35% to 60% by mass and butyl acetate for 40% to 65% by mass for a total of 100%.

[0047] Collodion is advantageously formulated to result in a dry extract (after evaporation of the solvent) of 10% to 40% by mass.

[0048] The composition of the cellulose ester base to form collodion is for example that of Table 1:

[0049] Table 1 Table 2 below shows a formulation of collodion at 14% dry extract by mass using the cellulose base from Table 1.

[0050] Table 2

[0051] In certain embodiments, the combustible charge (relay charge) is obtained after deposition and then drying of a paste (adhering to the surface of the combustible structure of the munition) consisting of a cellulose ester-based collodion loaded with ignition powder (classified in risk division 1.1 within the meaning of the UN GHS classification (UN Globally Harmonized System of Classification and Labeling of Chemicals)) or with the ingredients forming the ignition powder.

[0052] The composition of the ignition powder is most frequently black powder (NP) 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 / KNO3, 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®).

[0053] In one embodiment, the collodion loaded with ignition powder(s) comprises about 50% to about 70% by mass of ignition powder(s), and the balance to 100% (i.e., about 30% to about 50% by mass) of collodion. Conventionally, the ignition powder(s), previously constituted, is (are) added to the collodion.

[0054] Table 3 below gives an example of collodion composition from Table 2, loaded with ignition powder to form the relay charge. Table 3

[0055] Collodion charged with ignition powder is classified in hazard division 1.3 according to the UN GHS classification (UN Globally Harmonized System of Classification and Labeling of Chemicals). The hazard zones to be taken into account when handling charged collodion are therefore reduced, which facilitates the operations of depositing the collodion on the tube.

[0056] After drying, a combustible charge 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 remainder to 100% 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 combustible charge. As an indication, the dry combustible charge obtained after drying (evaporation of the solvent) of the collodion of table 3 contains the mass ratios indicated in table 4 below.

[0057] Table 4

[0058] In certain embodiments, the combustible charge (additive charge) is obtained after deposition and then drying of a paste (adhering to the surface of the combustible structure of the munition) consisting of a cellulose ester-based collodion loaded with at least one functional additive. These additives are either inert (for example calcium carbonate) or low-energy (for example potassium nitrate) and to guarantee the absence of residues after combustion, the paste may also, in addition, contain in small mass proportion (< 10%) a combustible charge in order to adjust the combustion properties of the additive charge after drying of the paste. This combustible charge may be an ignition powder or a propellant powder.

[0059] As functional additives that may be used in the context of the invention, examples that may be mentioned are anti-glare additives, anti-erosion additives, anti-copper additives, and mixtures of one or more of these additives.

[0060] The anti-glare additive is, for example, chosen from potassium nitrate, potassium or sodium sulfate, potassium nitrate, potassium or sodium cryolite, sodium oxalate, sodium bicarbonate, potassium or sodium carbonate, potassium or sodium cobalt nitrite, sodium nitrite, preferably potassium sulfate.

[0061] 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 already possibly contained in very small quantities in the collodion as a stabilizer.

[0062] The anti-copper additive is, for example, chosen from tin, tin oxide, lead oxide, preferably tin oxide.

[0063] In some embodiments, the collodion loaded with functional additive(s) comprises about 30% to about 50% by mass of collodion and the balance to 100% by mass of at least one functional additive and optionally a combustible filler, for example about 40% to about 70% by mass of functional additive(s), and 0% to about 10% by mass of a combustible filler.

[0064] After drying, a combustible charge useful as an additive charge is formed, which adheres to the internal surface of the combustible structure and comprises about 70.3% to about 92% by mass of additive(s), 0% to about 17.6% of a combustible charge, about 7% to about 10% by mass of cellulose ester, the balance to 100% 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 combustible charge.

[0065] An example of the composition of the dry material forming the additive charge after deposition is given in Table 5. This example is obtained using the same collodion as that given in Table 2 and the same ratio between the charge(s) added to the collodion as that given in Table 3. In this example, the total of the mass percentage of the charge of at least one functional additive and of the possible combustible charge therefore represents 90.08% of the total of the dry composition.

[0066] Table 5

[0067] In certain embodiments, the combustible charge (energetic charge) is obtained after deposition and then drying of a paste (adhering to the surface of the combustible structure) consisting of a cellulose ester-based collodion loaded with at least one energetic charge. Said energetic charge is for example chosen from hexogen (RDX), octogen (HMX), FOX-7 (1,1-diamino-2,2-dinitroethene (DADNE)), FOX-12 (guanylurea dinitramide, GUDN), or even a composite powder composition (also called LOVA powder) comprising an energetic charge 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).

[0068] In some embodiments, the energetically charged collodion comprises about 50% to about 70% by mass energetic charge, and the balance to 100% (i.e., about 30% to about 50% by mass) collodion.

[0069] The paste intended to form the said energetic charge is classified in hazard division 1.3 within the meaning of the UN GHS classification (UN Globally Harmonized System of Classification and Labeling of Chemicals). The danger zones to be taken into account when handling the charged collodion are therefore reduced, which facilitates the operations of depositing the collodion on the tube.

[0070] After drying, a combustible charge useful as an energetic charge is formed, which adheres to the internal surface of the combustible structure and comprises about 88% to about 92% by mass of the at least one energetic charge, about 7% to about 10% by mass of cellulose ester, the balance to 100% 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 combustible charge.

[0071] 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 using the same collodion as given in Table 2 and the same ratio between the charge(s) added to the collodion as given in Table 3. In this example, the total mass percentage of the energetic charge therefore represents 90.08% of the total dry composition.

[0072] Table 6

[0073] Said paste, containing either an ignition powder, or at least one functional additive, or an energetic charge, or a mixture of several of these constituents, is obtained by introducing the constituents into a standard paddle mixer or a twin-screw continuous mixer or into an acoustic resonance mixer. 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 munition for the present invention), for example by means of a device of the type described in patent application WO 2021 / 144539.

[0074] In the context 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 that is not collinear with the extrusion axis of the press piston or the single-screw. It is thus possible to carry out deposits on a curved support such as, for example, the rear bottom of an ammunition case.

[0075] The combustible structure of the ammunition is made of a cellulose ester-based combustible material (having the appearance of felt). The combustible materials constituting the combustible structure and said combustible charge must be chemically compatible and have the property of adhesion to one another. For this purpose, they have a common cellulose ester base, such as cellulose nitrate, cellulose acetate or nitrocellulose. Nitrocellulose, advantageously containing an average nitrogen content 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.

[0076] 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 combustible structure is given in Table 7.

[0077] Table 7

[0078] The deposition of the paste of said combustible charge in solvent(s) produces a localized dissolution of the surface of the combustible structure ensuring good adhesion of the combustible charge deposited after drying of the paste.

[0079] The paste is deposited on the internal wall of the combustible structure of the munition in one or more patterns which, after drying, constitute(s) said combustible charge. The deposited patterns may be linear, helical or curvilinear, or combined in such a way as to obtain a mesh according to the optimal configuration sought for ignition of the munition or the delivery of at least one additive or an energy supply (dopant). Different patterns may also be deposited over the height of the combustible structure.

[0080] When the at least one combustible charge acts as an ignition relay (relay charge), it does not require a specific connection with the ignition device. Said at least one relay charge 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 patterns of the relay charge can be adapted with great latitude according to the characteristics of the propellant charge and the ammunition, thus allowing rapid and homogeneous ignition of the propellant charge. Said at least one relay charge is suitable for ammunition with separate stages (for example of the type described in patent US5129324), with assembled stages (for example according to the usual assembly method of the combustible structure of arrow shells, see figure 3b), with large internal dimensions.

[0081] When the at least one combustible charge ensures the delivery of at least one functional additive (additive charge) or a doping energy supply (energy charge), the objective sought with the combustible charge is not to provide upon ignition a quasi-instantaneous contribution to the propellant charge, as in the case of relay charging, but to distribute the supply of additive(s) or energy during the combustion of the charge. For this, the at least one additive or energy charge is not generally coupled with the ignition device and is ignited by the propellant 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 charge or said energy charge is coupled with the ignition device to ensure its ignition.The additive or energetic combustible charges can be deposited in continuous patterns (as previously described for the ignition relays) or semi-continuous or punctual patterns on the wall of the combustible structure according to a geometric and mass distribution ensuring the continuous supply proportional to the gas flow rate generated by the combustion of the propellant charge. For firing in 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 charges or energetic combustible charges are themselves arranged on the combustible structure in a configuration adapted to the operation of the propellant charge so as to deliver the at least one additive or the energetic supply according to an optimal and continuous mass flow rate during the combustion time 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.

[0082] The combustible charge as described above is suitable for different types of ammunition, in particular for ammunition of the arrow shell or explosive shell type.

[0083] The invention is illustrated by the following examples given without limitation. Examples

[0084] Example 1

[0085] Figure 1 shows examples of patterns (linear, helical, mesh, combined shapes) that can be retained for a combustible charge on a planar view of the internal surface of the combustible structure. The combustible charge [1] adhered to the combustible structure [2] is coupled by at least one of the ends of a pattern to the ignition device formed by an igniter [3] and an igniter tube [4] arranged in the rear bottom of the munition.

[0086] Example 2

[0087] This example concerns the installation of combustible charges according to the invention in ammunition of the type of a large-sized arrow shell. It is an arrow shell [5] assembled according to the conventional method in two parts (figures 2a and 2b). The first rear part (figure 2a) consists of a case [6] made of fibrous combustible material containing 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

[0010] is left free in the upper part of the combustible case [6]. The second front part (figure 2b) consists of a feathered arrow

[0011] (projectile) equipped with a sabot

[0012] secured to a connecting piece

[0013] and supporting around its rear feathered part a cylindrical cage

[0014] .This cylindrical cage

[0014] contains a second part of the propellant charge [7b]. The upper free part

[0010] of the combustible case is intended to receive the tail of the arrow

[0011] supporting around it the cylindrical cage

[0014] . The tailed arrow

[0011] provided with the cage on its tail is secured to the upper part of the case by means of the combustible connecting piece

[0013] . The connecting piece, also made of fibrous combustible material, is glued to the upper part of the case. The ammunition is therefore made of two assembled parts each including a part of the propellant charge (figures 3a and 3b).

[0088] Relay charge patterns [15a and 15b] have been deposited on the internal face of the connecting piece

[0013] and the case [6], the ends of which become joined after assembly (figures 3a and 3b). This ensures homogeneous ignition over the entire propellant charge (part contained in the case and front part in the area of ​​the connecting piece) of the munition. Similarly, at least one additive charge and / or at least one energetic combustible charge can also be deposited on the internal face of the connecting piece and / or the case, whether or not connected after assembly. The patterns of these combustible charges are adapted to ensure a supply of additive(s) or energy during the combustion of the propellant charge.

Claims

Claims 1. Munition (5) containing, in a cellulose ester-based combustible structure (6), a propellant charge of powder grains (7a, 7b) and an ignition device (8, 9), munition in which at least one cellulose ester-based combustible charge (15a, 15b) is deposited in the form of a solid geometric volume pattern adhering to the internal wall of the cellulose ester-based combustible structure.

2. Ammunition according to claim 1, wherein 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, wherein the combustible charge comprises at least one functional additive chosen from an anti-glow additive, an anti-erosion additive and an anti-coppering 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, wherein 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, wherein 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, wherein 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 piece (13) separately supporting patterns of the at least one combustible load, the patterns of the case and the connecting piece being joined after assembly of the ammunition.

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

12. A method for preparing a combustible munition 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, a method which comprises the deposition by extrusion of a paste consisting of a collodion loaded with an ignition powder, or with at least one functional additive or with at least one energetic charge, on the internal face of the combustible structure, and the drying of the deposited paste, said loaded collodion comprising from 30% to 50% by mass of collodion and the balance to 100% of ignition powder or at least one functional additive or at least one energetic charge.

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

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