COMBUSTIBLE CHARGES ADHERING TO THE INNER WALL OF A COMBUSTIBLE STRUCTURE CONTAINING A PROPELLANT CHARGE

Abstract

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

Claims

1. Ammunition containing, in a cellulose ester-based combustible structure, a propellant charge of powder grains and an ignition device, in which ammunition at least one cellulose ester-based combustible charge is deposited in the form of a solid geometric volume pattern adhering to the inner wall of the cellulose ester-based combustible structure.

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

3. Ammunition according to claim 1, wherein the combustible charge comprises at least one functional additive selected from the group consisting of an anti-glow additive, an anti-erosion additive and an anti-copper additive.

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

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

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

7. Ammunition according to claim 2, 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 claim 3, 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 claim 1, which is of the arrow shell or explosive shell type.

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

11. Ammunition according to claim 1, wherein the geometric volume pattern is a linear, helical, curvilinear pattern, or a pattern of shapes combined so as to obtain a mesh.

12. A process for preparing an ammunition combustible structure, the 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 inner wall, which process comprises depositing by extrusion 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 inner face of the combustible structure, and drying the deposited paste, the loaded collodion comprising from 30% to 50% by weight of collodion and the balance to 100% of ignition powder or of at least one functional additive or of at least one energetic charge.

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

14. The process according to claim 13, wherein the cellulose ester is nitrocellulose.

Description

BRIEF DESCRIPTION OF FIGURES

[0023] FIG. 1 shows different types of patterns of combustible charge on a combustible casing.

[0024] FIG. 2a shows the rear part of an ammunition of the arrow shell-type comprising a combustible charge on its combustible structure formed by the case.

[0025] FIG. 2b shows the front part of an ammunition of the arrow shell-type comprising a combustible charge on its combustible structure formed by the connecting part.

[0026] FIG. 3a shows the assembly of the rear and front parts of an ammunition of the arrow shell-type comprising a combustible charge on its combustible structure.

[0027] FIG. 3b shows an ammunition of the assembled arrow shell-type arrow comprising a combustible charge on its combustible structure.

DESCRIPTION OF THE INVENTION

[0028] It will be noted that within the scope of the present disclosure, the various embodiments described may be combined with one another.

[0029] According to one aspect, the invention relates to an ammunition 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 inner wall of the combustible structure.

[0030] The above-mentioned combustible charge can perform the following functions: [0031] it can be used as an ignition relay for the propellant charge (in this case, the combustible charge is also referred to as a relay charge), [0032] it can enable the delivery of functional additives (said combustible charge is then also referred to in the following as additive charge), [0033] it can contribute to a doping energetic supply (the said combustible charge is then also referred to in the remainder of this document as an energetic charge).

[0034] The cellulose ester-based propellant charge has the advantage of being able to be installed directly on a propellant charge-containing combustible structure, independently of the propellant charge. This combustible structure containing the propellant charge includes in particular a combustible case, but also any additional combustible structure, such as connecting or closing elements for the ammunition. It is also conceivable to install said propellant charge on any other combustible structure subsequently added to form the architecture of the munition.

[0035] The cellulose ester-based combustible charge is obtained from a cellulose ester-based collodion loaded with either ignition powder for the relay charge, or at least one functional additive for the additive charge, or at least one energetic charge for the energy charge. The collodion, in the form of a paste, is deposited on the surface of the combustible structure and then dried.

[0036] In some embodiments, the geometric volume pattern formed by collodion deposition is a linear, helical, curvilinear pattern, or shapes combined to form a mesh.

[0037] The collodion used in the invention is of the cellulose ester base+solvent(s) type. In one embodiment, the collodion base consists of a cellulose ester (for about 70% to about 90% by weight) and generally contains in addition, conventionally, at least one plasticizer (about 1% to about 20% by weight, preferably about 10% by weight) and at least one cellulose ester stabilizer (about 0.5% to about 5% by weight). It may contain a residual quantity of solvent(s), in particular phlegmatizing solvent(s) and/or cellulose ester dissolving solvent(s) used in its manufacture.

[0038] Advantageously, the cellulose ester used as the majority component is selected from cellulose nitrate, cellulose acetate or nitrocellulose, the latter being preferred. The nitrogen content by weight of nitrocellulose is suitably 10.5% to 13.5%, an example being grade E nitrocellulose with a nitrogen content by weight of 11.8% to 12.3%, advantageously 12%.

[0039] 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) marketed under the name LUTA 50-50% by the company East Harbour 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).

[0040] The stabilizer used to prepare the collodion can be, in particular, a compound whose chemical formula includes aromatic rings (appropriately two aromatic rings), capable of fixing the nitrogen oxides from decomposition of nitric esters (currently nitrocellulose). Examples of stabilizers include 2-nitrodiphenylamine (2-NDPA), 1,3-diethyl-1,3-diphenyl urea (centralite I), 1,3-dimethyl-1,3-diphenyl urea (centralite II) and 1-methyl-3-ethyl-1,3-diphenyl urea (centralite III).

[0041] Solvent(s) is (are) selected 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).

[0042] The solvent is, for example, a double solvent of the acetone/butyl acetate (BA) 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% to 65% by weight for a total of 100%.

[0043] The collodion is advantageously formulated to give a dry extract (after evaporation of the solvent) of 10% to 40% by weight.

[0044] The composition of the cellulose ester base to form the collodion is, for example, that shown in Table 1:

TABLE-US-00001 TABLE 1 Cellulose base Nitrocellulose 84 Plasticizer 13 Stabilizer 3 Total 100

[0045] Table 2 below shows a 14% solids by weight collodion formulation using the cellulose base of Table 1.

TABLE-US-00002 TABLE 2 Collodion Composition (% by weight) Cellulose base Nitrocellulose 84 14 Plasticizer 13 Stabilizer 3 Total 100 Solvents Butyl acetate 43 Acetone 43 Total 100

[0046] In some embodiments, the combustible charge (relay charge) is obtained after deposition and subsequent drying of a paste (adhering to the surface of the munition's combustible structure) consisting of a cellulose ester-based collodion loaded with ignition powder (classified in hazard division 1.1 under the UN GHS (UN Globally Harmonized System of Classification and Labeling of Chemicals) classification) or with the ingredients forming the ignition powder.

[0047] The composition of the ignition powder is most frequently black powder (BP), consisting of an agglomerated mixture of potassium nitrate (saltpetre), charcoal and sulphur. There are also other agglomerated ignition powder compositions, such as: Boron/KNO.sub.3, in a ratio generally of 70/30 (% by weight), a metal (e.g. iron, aluminum, zinc, magnesium), a perchlorate-type oxidant (e.g. potassium perchlorate) or a fluoropolymer-type oxidant (e.g. PTFE such as Teflon).

[0048] In one embodiment, the collodion loaded with ignition powder(s) comprises about 50% to about 70% by weight of ignition powder(s), and the balance to 100% (i.e. about 30% to about 50% by weight) of collodion. Conventionally, the ignition powder(s) is (are) added to the collodion.

[0049] Table 3 below shows an example of a collodion composition from Table 2, loaded with ignition powder to form the relay charge.

TABLE-US-00003 TABLE 3 Raw materials Composition (% by weight) Black powder (or equivalent) 59 Collodion 41 Total 100

[0050] Collodion loaded with ignition powder is classified in hazard division 1.3 of the UN GHS (UN Globally Harmonized System of Classification and Labeling of Chemicals). The danger zones to be taken into account when handling the loaded collodion are therefore reduced, making it easier to deposit the collodion on the tube.

[0051] After drying, a combustible charge useful as an ignition relay is formed, which adheres to the inner surface of the combustible structure and comprises about 88% to about 92% by weight of ignition powder(s), about 7% to about 10% by weight of cellulose ester, the remainder to 100% being provided by the plasticizer, stabilizer and residual solvent from the collodion. The residual solvent from the collodion generally represents less than 1% by weight of the total weight of the combustible charge. As an indication, the dry combustible charge obtained after drying (solvent evaporation) of the collodion in Table 3 contains the weight ratios indicated in Table 4 below.

TABLE-US-00004 TABLE 4 Dry composition Weight % Black powder (or equivalent) 90.08 Nitrocellulose 8.35 Plasticizer 0.96 Stabilizer 0.35 Residues (water, solvent, etc.) 0.26 Total 100

[0052] In some embodiments, the combustible charge (additive charge) is obtained after deposition and subsequent drying of a paste (adhering to the surface of the munition's combustible structure) consisting of a cellulose ester-based collodion loaded with at least one functional additive. These additives are either inert (e.g. calcium carbonate) or low-energy (e.g. potassium nitrate), and to guarantee the absence of residues after combustion, the paste can also contain a small proportion by weight (10%) of a combustible charge to regulate the combustion properties of the additive charge after the paste has dried. This combustible charge can be an ignition powder or a propellant powder.

[0053] Examples of functional additives which can be used in the context of the invention are anti-glow additives, anti-erosion additives, anti-copper additives, and mixtures of one or more of these additives.

[0054] The anti-glow additive is, for example, selected 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.

[0055] The anti-erosion additive is, for example, selected from camphor, dinitrotoluene 2-4, butyl phthalate, calcium carbonate, titanium dioxide, molybdenum trioxide, tungsten trioxide, silicon oxide, magnesium silicate (talc), preferably titanium dioxide. The additive may also be centralite, which may already be present in very small quantities in the collodion as a stabilizer.

[0056] The anti-copper additive is, for example, selected from tin, tin oxide, lead oxide, preferably tin oxide.

[0057] In some embodiments, the collodion loaded with functional additive(s) comprises about 30% to about 50% by weight of collodion and the balance to 100% by weight of at least one functional additive and optionally a combustible charger, for example about 40% to about 70% by weight of functional additive(s), and 0% to about 10% by weight of a combustible charge.

[0058] After drying, a combustible charge useful as an additive charge is formed, which adheres to the inner surface of the combustible structure and comprises about 70.3% to about 92% by weight of additive(s), 0% to about 17.6% of a combustible charge, about 7% to about 10% by weight of cellulose ester, the balance to 100% being provided by the plasticizer, stabilizer and residual solvent from the collodion. The residual solvent from the collodion generally represents less than 1% by weight of the total weight of the combustible charge.

[0059] 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 weight percentage of the charge of the at least one functional additive and of the optional combustible charge thus represents 90.08% of the total dry composition.

TABLE-US-00005 TABLE 5 Dry composition Weight % Additive(s) charges 74.81 to 90.08 Combustible charge 0 to 15.27 Nitrocellulose 8.35 Plasticizer 0.96 Stabilizer 0.35 Residues (water, solvent, etc.) 0.26 Total 100

[0060] In some embodiments, the combustible charge (energetic charge) is obtained after deposition and subsequent 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, selected from hexogen (RDX), octogen (HMX), FOX-7 (1,1-diamino-2,2-dinitroethene (DADNE)), FOX-12 (guanylurea dinitramide, GUDN), or a composite powder composition (also known as LOVA powder) comprising an energetic charge and a cross-linked binder, for example of the polyurethane, polyglycidyl azide (PGA) and/or thermoplastic type, e.g. PMMA or an ethylene/vinyl acetate (EVA) copolymer.

[0061] In some embodiments, the collodion loaded with an energetic charge comprises about 50% to about 70% by weight of energetic charge, and the balance to 100% (i.e. about 30% to about 50% by weight) of collodion.

[0062] The paste used to form this energetic charge is classified in hazard division 1.3 of the UN GHS (UN Globally Harmonized System of Classification and Labeling of Chemicals). The danger zones to be taken into account when handling the loaded collodion are therefore reduced, making it easier to deposit the collodion on the tube.

[0063] After drying, a combustible charge useful as an energetic charge is formed, which adheres to the inner surface of the combustible structure and comprises about 88% to about 92% by weight of the at least one energetic charge, about 7% to about 10% by weight of cellulose ester, the balance to 100% being provided by the plasticizer, stabilizer and residual solvent from the collodion. The residual solvent from the collodion generally represents less than 1% by weight of the total weight of the combustible charge.

[0064] An example of the composition of the dry material forming the energetic combustible charge after deposition is given in Table 6. 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 weight percentage of energetic charge thus represents 90.08% of the total dry composition

TABLE-US-00006 TABLE 6 Dry composition Weight % Energetic charge 90.08% Nitrocellulose 8.35 Plasticizer 0.96 Stabilizer 0.35 Residues (water, solvent, etc.) 0.26 Total 100

[0065] 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 plunger press or a single screw extended by an extrusion channel and a nozzle to form patterns on a support (the inner surface of the munition's combustible structure for the present invention), for example by means of a device of the type described in patent application WO 2021/144539.

[0066] In implementing 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 co-linear with the extrusion axis of the plunger press or single screw. This makes it possible to deposit patterns on a curved support, such as the rear base of an ammunition case.

[0067] The combustible structure of the ammunition is made of a cellulose ester-based combustible material (having the appearance of a felt). The combustible materials making up the combustible structure and said combustible charge must be chemically compatible and have the property of adhering to one another. To this end, 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 way, in the remainder of the description

[0068] In some embodiments, the combustible structure is a fibrous structure, such as that marketed by the company Eurenco, consisting of 45% to 81% by weight of cellulose ester (fibers), 3.5% to 33.5% by weight of cellulose (fibers), 4% to 14% by weight of resin (binder), 0% to 1.6% by weight of a stabilizer, and 0% to 15.5% by weight of additional acrylic or polyester fibers (the sum of these various constituents being equal to 100%). An example of the composition of the combustible structure is given in Table 7.

TABLE-US-00007 TABLE 7 Composition Weight % Nitrocellulose 69 Cellulose 25 Resin 5 stabilizer 1

[0069] Depositing the paste of said combustible charge in solvent(s) produces localized dissolution of the surface of the combustible structure, ensuring good adhesion of the deposited combustible charge once the paste has dried.

[0070] The paste is deposited on the inner wall of the ammunition's combustible structure in one or more patterns which, after drying, form the said combustible charge. The deposited patterns may be of linear, helical or curvilinear form, or of a combination of these forms so as to obtain a mesh in the optimum configuration for igniting the munition or delivering at least one additive or energetic input (dopant). Different patterns can also be deposited over the height of the combustible structure.

[0071] When the at least one combustible charge acts as an ignition relay (relay charge), it does not require any specific connection to the ignition device. The at least one relay charge is, for example, a linear or curvilinear pattern, at least one end of which is coupled (in contact or sufficiently close) with the ignition device to ensure its ignition and thus initiate its combustion. The spatial and weight distributions of the relay charge patterns can be adapted with great latitude according to the characteristics of the propellant charge and the munition, thus enabling rapid and homogeneous ignition of the propellant charge. Said at least one relay charge is suitable for ammunition with separate stages (e.g. of the type described in U.S. Pat. No. 5,129,324), with assembled stages (e.g. according to the usual assembly mode of the combustible structure of arrow shells, see FIG. 3b), with large internal footprint.

[0072] When the at least one combustible charge delivers at least one functional additive (additive charge) or a doping energetic contribution (energetic charge), the aim of the combustible charge is not to make an almost instantaneous contribution to the propellant charge on ignition, as in the case of a relay charge, but to distribute the additive(s) or energetic contribution over the course of the charge's combustion. To achieve this, the at least one additive or energetic charge is generally not coupled to 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 possible for the additive or energetic charge to be 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 ignition relays) or in semi-continuous or punctual patterns on the wall of the combustible structure, with a geometric and mass distribution ensuring a continuous supply proportional to the gas flow generated by the combustion of the propellant charge. When firing a tube weapon, this flow rate is designed to increase as the projectile advances through the tube, in order to maintain constant gas pressure in the tube. The patterns of the additive or energetic combustible charges are 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 energetic supply at an optimum and continuous mass flow rate during the combustion time of the propellant charge. For example, these patterns may be of circular or linear or punctual form or of combined forms, distributed regularly or irregularly over the combustible structure.

[0073] The combustible charge as described above is suitable for various types of ammunition, in particular ammunition of the arrow shell or explosive shell type.

[0074] The invention is illustrated by the following non-limiting examples.

EXAMPLES

Example 1

[0075] FIG. 1 shows examples of patterns (linear, helical, meshed, combined shapes) that can be selected for a combustible charge on a planar view of the inner surface of the combustible structure. The combustible charge [1] adhering 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.

Example 2

[0076] This example relates to the installation of combustible charges according to the invention in a munition of the type of a high-capacity arrow shell. This is an arrow shell [5] assembled using the conventional two-part process (FIGS. 2a and 2b). The first, rear part (FIG. 2a) consists of a case [6] made of fibrous combustible material enclosing a first propellant charge [7a] and its ignition device. This ignition device, in the form of a primer tube, comprises an igniter and its primer [8] inserted into the base of the case [6] in conjunction with an igniter tube [9] at the center of the first propellant charge [7a]. A gap [10] is left free at the top of the combustible case [6]. The second front part (FIG. 2b) consists of a feathered arrow [11] (projectile) fitted with a clamp [12] integral with a connecting part [13] and supporting a cylindrical cage [14] around its rear feathered part. This cylindrical cage [14] contains a second part of the propellant charge [7b]. The upper free part [10] of the combustible case is designed to receive the tail of the arrow [11] supporting the cylindrical cage [14] around it. The feathered arrow [11], fitted with the cage on its tail, is secured to the upper part of the case by means of the combustible connecting part [13]. The connecting part, also made of combustible fibrous material, is glued to the upper part of the case. The ammunition is thus made in two assembled parts, each including part of the propellant charge (FIGS. 3a and 3b).

[0077] On the inside of the connecting part [13] and the case [6], relay charge patterns [15a and 15b] have been deposited, the ends of which become contiguous after assembly (FIGS. 3a and 3b). This ensures uniform ignition across the entire propellant charge (the part contained in the case and the front part in the area of the connecting part) of the munition. Similarly, at least one additive charge and/or at least one energetic combustible charge can also be deposited on the inside of the connecting part and/or of the case, in connection or not after assembly. The patterns of these combustible charges are adapted to ensure a supply of additive(s) or energy during combustion of the propellant charge.