Ammunition comprising a base and an insert

Abstract

Munition comprising a base and an insert. The present invention relates to ammunition comprising a projectile (1), a propellant charge (3), and a priming device (5) held together by a case, the case forming a nozzle, a nozzle throat, a combustion chamber (4j), and a primer channel. The ammunition is characterized in that the case consists of at least two parts: a base (4b) and an insert (4a), said parts being assembled together after the propellant charge (3) has been inserted into the combustion chamber (4j). Figure for the abstract: Figure 2

Description

Title of the invention: Ammunition comprising a base and an insert FIELD OF INVENTION

[0001] The present invention relates to ammunition comprising a base and an insert. Such ammunition is particularly suitable for use in firearms. STATE OF THE ART

[0002] In the firearms industry, regardless of caliber or application, there is always a strong preference for solutions that facilitate the handling of consumable components with each shot. This issue is paramount in the field of weaponry, as it impacts both operator safety and weapon performance. This explains why pre-assembled ammunition has become widespread in the vast majority of applications.

[0003] According to a prior art example, as shown in [Fig. 1], an assembled cartridge consists of a casing 4, a primer 5, a propellant charge 3a, 3b, and a projectile 1. The role of the casing 4 is to maintain the integrity of all the components necessary for firing into a compact unit. The shape of the casing 4 also fulfills a number of functions, including: allowing the cartridge to be positioned in the barrel before firing, ensuring the barrel is sealed during firing, providing protection to the propellant charge 3a, 3b from the environment during storage or handling, and guaranteeing the possibility of extracting the cartridge or firing debris after firing. Consequently, the shape of a casing 4 is relatively fixed, as these constraints have been known and resolved for over a century.

[0004] Generally, a high-pressure ammunition case 4 is made from a single piece of brass or steel by multi-stage stamping. However, weight constraints for new ammunition are such that multi-part, permanently assembled case 4 solutions are gradually emerging, as demonstrated by True Velocity's US patent 9,518,810 and Sig Sauer's US patents 10,866,072 and 11,067,370. It is important to note that both of these solutions were proposed in response to the US Army's NGSAR and NGSW requests for proposals, which aimed to provide a significant performance increase for a weapon and ammunition combination compared to solutions already in service.

[0005] The solutions proposed in these calls for tenders clearly demonstrated the limitations of the approach of improving the performance of a weapon couple and munition by a simple increase in service pressure, it was necessary to conduct further internal ballistics studies which led to the discovery of the solutions protected by patents FR 22 04 908 and FR 22 04 909. The general principle of these solutions can also be illustrated by [Fig. 1].

[0006] With reference to this [Fig. 1], patents FR 22 04908 and FR 22 04909 highlight a sub-caliber ammunition solution particularly suited to the constraints and needs specific to small and medium caliber weapons. Indeed, this solution incorporates the combination of the two distinctive elements of the innovations, namely:

[0007] - The presence of a nozzle 4k, separating the combustion chamber 4j from the barrel, consisting of a convergent section, a 4 o'clock nozzle throat, and a divergent section, designed to allow a substantial increase in the velocity of the propellant gases inside the barrel as soon as the 4 o'clock nozzle throat is primed. This reduces the pressure on the internal walls of the barrel while maximizing the thrust of the propellant gases onto the projectile 1, even though it is close to the muzzle despite the barrel's length.

[0008] - The use of a degradable sabot 2 which, combined with the use of a barrel The conical shape maximizes the thrust surface area at the beginning of the internal ballistics while allowing direct guidance of projectile 1 inside the barrel near its muzzle. This increases the acceleration of projectile 1 by maintaining moderate propellant gas pressure in the first part of the barrel, while retaining the use of rifling in the barrel near the muzzle to stabilize projectile 1.

[0009] However, this same figure also presents two design difficulties:

[0010] - A 4-gauge socket has the disadvantage of being relatively heavy in addition to being particularly complex (and therefore costly) to achieve.

[0011] - The filling of the combustion chamber 4j by the propellant charge 3a, 3b requires the propellant to pass through the throat of the nozzle 4h or through the channel of the primer 4f. This would imply that the propellant charge 3a, 3b would be loaded in the form of very small granules in order to be able to enter despite the restricted section of each of these passages, or flowed through the throat of the nozzle 4h in the form of a liquid (more or less viscous) so that the propellant charge 3a, 3b can fill the volume of the chamber.

[0012] Certain constraints, however, justify this manufacturing complexity.

[0013] In particular, the need for good coaxiality between the projectile 1, the sabot 2, and the barrel during the forcing of the assembly consisting of the projectile 1 and the sabot 2 into the barrel, that is, during the transition between the guidance of the sabot 2 by the socket 4 and the guidance of the sabot 2 by the barrel at the very beginning of the internal ballistic phase. This step is crucial when using a degradable sabot 2 insofar as where a second forcing operation takes place when projectile 1 engages the rifling of the barrel.

[0014] Furthermore, during firing, the lateral walls of the combustion chamber 4j are subjected to tension by the pressure of the gases on the nozzle converging 4k and on the base of the cartridge case 4. This stress is also present in ammunition with a conical cartridge case 4 or when the headspace is created by a shoulder (generally conical) between the large-diameter portion of the cartridge case 4, which serves as a reservoir for the propellant charge 3a, 3b, and the neck retaining the projectile 1. It should be noted, however, that this stress is even more pronounced when the diameter of the neck of the cartridge case 4 is small. Beyond the problem of longitudinal deformation of the cartridge case 4 during firing, it is indeed a problem of tearing of the cartridge case 4, and therefore a breach of the chamber seal, that can result from improper system design. Summary of the invention

[0015] The present invention aims to solve the aforementioned problems of the prior art.

[0016] To this end, the invention relates to a munition comprising a projectile, a propellant charge and a priming device held together by a casing, the casing forming a nozzle, a nozzle throat, a combustion chamber and a primer channel, characterized in that the casing is made up of at least two parts: a base and an insert, said parts being assembled together after the integration of the propellant charge inside the combustion chamber.

[0017] The problems raised in the prior art have indeed been solved by splitting the casing into two pieces (a base and an insert) which are permanently assembled after the propellant charge has been placed in the munition.

[0018] According to other advantageous aspects of the invention, the munition comprises one or more of the following features taken individually or in all technically possible combinations:

[0019] - the side wall of the combustion chamber is formed by an extended part of the base, the combustion chamber being closed by the insert;

[0020] - the crimping of the base onto the insert is achieved by deforming a collar of the base inside a groove of the insert by means of a crimping die, the insert being pressed against the base by means of an insert positioner;

[0021] - an external seal is placed in the groove of the insert following crimping, said seal external support taking hold in a chamber of the cannon during firing;

[0022] - the side wall of the combustion chamber is formed by an extended part of the insert, the combustion chamber being closed by the base by means of the interlocking of two complementary portions;

[0023] - the assembly of the base onto the insert is secured by the presence of an internal lock put in place by means of a spreader deforming the internal lock during its extraction through the primer channel;

[0024] - the insert is made by assembling the nozzle inside a socket body;

[0025] - the projectile and its sabot are positioned inside a barrel by means of cylindrical or slightly conical bearing surfaces forming front and rear contacts between the insert and the barrel;

[0026] - the ammunition is positioned longitudinally in the barrel;

[0027] - the longitudinal positioning of the ammunition in the barrel is ensured by a conicity of the front or rear contact and compression of the link between the insert and the base by a cylinder head;

[0028] - the ammunition is positioned longitudinally in the barrel;

[0029] - the longitudinal positioning of the ammunition inside the barrel is achieved at by means of a rebate contact between the base and the barrel.

[0030] In addition, the invention relates to a method for manufacturing ammunition comprising an internal nozzle separating the combustion chamber from the barrel where the thrust on the projectile occurs. This particular configuration offers advantages in terms of barrel operating pressure, but poses certain problems with regard to ammunition manufacturing. Indeed, the presence of a nozzle throat, separating the combustion chamber from the barrel, makes filling the cartridge case with propellant, to form the propellant charge, particularly complex.

[0031] In addition, to maximize the effects of the nozzle, the use of an undersized projectile is recommended. This implies that the projectile's guidance by the barrel is achieved through an intermediate component or, at a minimum, the use of a projectile with deformation properties that allow its diameter to decrease as it travels through the barrel. In both cases, the projectile's position relative to the barrel prior to firing is an important parameter dictating the accuracy of the barrel-ammunition assembly, especially when the projectile is stabilized by its rotation using rifling in the barrel.

[0032] To allow the integration of a neck and a nozzle inside a cartridge case, it may be advantageous for the latter to be made in the form of an insert made of relatively resistant and refractory material, and taking place, at least partially, inside the base.

[0033] According to one embodiment, the short insert is placed from the front of the long base and is crimped to the long base after the latter has received the propellant charge. Ideally, to ensure the projectile is centered in the barrel prior to firing, the headspace of the cartridge should pass through the short insert. This configuration also offers the advantage of allowing the force resulting from the pressure inside the chamber The combustion chamber is designed to bear directly against the barrel during firing. The seal between the short insert and the long base is achieved by energizing the combustion chamber, which will tend to push and crush the front part of the long base against the internal walls of the barrel chamber. If any concern remains regarding the strength of the assembly between the short insert and the long base, an external locking mechanism can be integrated into the assembly to make it geometrically impossible for the short insert to separate from the long base inside the barrel chamber.

[0034] In another embodiment, a cartridge case open at both ends has an internal shoulder allowing the placement of a short insert from the rear end. The projectile is then placed inside the short insert, and the sabot is cast between the short insert, optionally the cartridge case, and the projectile, thus closing the front part of the ammunition. The propellant charge is placed inside the combustion chamber before the latter is closed by a short base that receives the primer.

[0035] The combustion chamber is closed from the rear by means of a short metal base surrounding the outside of the cartridge case body and secured by crimping. Ideally, an internal locking mechanism in the form of a conical spring washer can be placed inside the cartridge case body above the propellant charge. When the short base is installed, it pushes on the internal locking mechanism until the conical shape of the washer reverses.

[0036] By extension of this latter method of manufacture, it is possibly possible to fuse the short insert and the socket body into a long insert provided that the material used is the same and that the process of obtaining this part is plastic or metal injection.

[0037] It is however important to note that: while it remains possible to adapt the external closing and locking technique to a short base and a long insert, and conversely, the internal closing and locking technique to a long base on a short insert, these two configurations are governed by additional constraints.

[0038] Indeed, when the external locking pin is positioned very close to the case base, contact between the external locking pin and the chamber is quickly lost during cartridge extraction. This means that the crimp must be able to withstand greater tensile stresses between the case base and the insert. One solution to mitigate this problem is to adopt a sufficiently tapered overall shape for the cartridge to limit the phenomenon of the case sticking in the chamber during firing.

[0039] Conversely, if the internal lock is located on the nozzle side, it is important to consider that the nozzle geometry must incorporate a convergent section as well as a throat and a divergent section. To accommodate these two aspects, two solutions can be implemented: At a minimum, the functions The convergent and neck sections are positioned on the internal locking mechanism, not on the insert, allowing for installation using a spreader. Alternatively, the internal locking mechanism relies on reversing the conicity of the internal locking mechanism during crimping, with the constraint that the internal diameter of the locking mechanism must be greater than the maximum diameter of the convergent section of the nozzle. DESCRIPTION OF THE FIGURES

[0040] The invention will become clearer upon reading the following description, given solely by way of non-limiting example and with reference to the drawings in which:

[0041] - [Fig. 1] [Fig. 1] is a schematic view of a munition according to the state of the technique;

[0042] - [Fig.2] [Fig.3] [Fig.4] [Fig.5] Figures 2 to 5 are different views of a munition according to a first embodiment of the invention; and

[0043] - [Fig.6] [Fig.7] [Fig.8] [Fig.9][Fig.10] Figures 6 to 10 are different views of a ammunition according to a second embodiment of the invention.

[0044] - [Fig. 11] [Fig. 11] is a schematic view of a munition according to a mode of design adapted to the architecture of large caliber munitions. Description of the implementation methods

[0045] As illustrated in the various attached figures, the munition according to the invention has a two-piece casing 4: a base 4b, 4d and an insert 4a, 4b. These parts are permanently assembled after the propellant charge 3 has been placed in the munition.

[0046] The base 4b, 4d is the rear part of the cartridge case 4 which rests against the breech 9 of the weapon when the ammunition is chambered in the barrel 10 (visible in Figures 5 and 9). Given the pressures involved during firing, the material used for the base 4b, 4d of the ammunition is a metal combining good mechanical strength with a high capacity for deformation without breakage. Historically, bronze has been the preferred material for manufacturing cartridge cases 4 due to its malleability during the manufacturing process as well as during firing. However, it is not uncommon to find steel cartridge cases 4 when the strength requirement for the base 4b, 4d or the walls of the cartridge case 4 is high, or aluminum cartridge cases 4 when the mass requirement for the ammunition is greater (aeronautical applications).

[0047] The insert 4a, 4b is the part forming the front of the sleeve 4 and including the nozzle 4k as described in patent applications FR 22 04909 and FR 22 04908. Although the pressure and temperature internal to the combustion chamber 4j are applied to the internal walls of the insert 4a, 4c, the choice of material for the latter is quite broad insofar as it is a relatively massive part supported by the chamber of the barrel 10. Thus, it is possible to use various metals (steel, bronze, or aluminum), but also certain polymers, either in a simple form or in a composite (with short fibers or ceramic microbeads), or even pure ceramic, depending on the weight constraints of the assembled ammunition and the ease of their production. In the case of using a surface treatment, such as a ceramic paint or a carbon layer in the form of graphite or diamond, on the internal faces of the insert 4a, 4c may be useful to limit abrasion of the nozzle neck 4h during firing. Similarly, a surface treatment on the external walls of the insert 4a, 4c, such as a lacquer, may prove useful to reduce friction with the chamber of the barrel 10 during the loading and ejection of the ammunition into the barrel 10.

[0048] The ammunition designer is under no obligation to choose the same material for the base 4b, 4d and the insert 4a, 4c. However, the designer does not make random combinations but takes into account certain constraints such as chemical and electrochemical compatibility between the materials used for the base 4b, 4d, the insert 4a, 4c, and the propellant used for the propellant charge 3, 3a, and 3b, in particular to avoid corrosion at the interface between the two parts or chemical attack on either part by acidic substances released by the propellant in the case of long-term storage or under poor conditions. Similarly, certain choices are dictated by the compatibility of dimensional stability characteristics with heat, humidity, etc., in order to guarantee the integrity of the ammunition during storage or handling in uncontrolled environments.

[0049] However, it is necessary to resolve the problems that arise, or are amplified, by the adopted modification. To do this, it is necessary to isolate the problems and their associated contributing factors, and thus define the conditions under which the problems are resolved.

[0050] From a safety standpoint, the critical point concerns the risk of tearing due to the deformation stresses of the casing 4 during firing. To address this, the ammunition designer has two options:

[0051] - One possibility, corresponding to the first embodiment illustrated on the figures 2 to 5, would be to combine the use of a long base 4b with a method of assembling the insert 4a onto the long base 4b allowing a relative longitudinal movement between the two parts during firing (dynamic rebate) while ensuring the cohesion of the socket 4 for the ejection operation.

[0052] - Another possibility, corresponding to the second embodiment illustrated on the Figures 6 to 10 and 11, consists of placing the rebate (and therefore the seal) on the base 4d of the socket 4 by adopting a base geometry with a reinforced rim. The advantage of this solution is that the operation of the weapon is not impacted by variability in the length of the cartridge case 4 during firing. This solution is known for applications in weapons whose locking system operates by an orthogonal movement of the bolt relative to the axis of the barrel 10 (falling block locking as well as revolver-type mechanisms).

[0053] The coaxiality constraint of the projectile 1 and its sabot 2 with respect to the barrel 10, before firing, requires the minimization of the number of intermediate parts used to position the projectile 1 in the chamber of the barrel 10. Thus, although it is possible to adopt a socket architecture in which the insert 4a is not directly integrated into the short base 4d by the use of a third intermediate part forming a socket body 4i, it is preferable for the ammunition designer to minimize the number of intermediate components between the projectile 1 and the barrel 10 before firing.

[0054] The ammunition architecture meeting these criteria consists of replacing the projectile 1 of a larger caliber round with an assembly formed by the short insert 4a, the new projectile 1, and the degradable sabot 2. In this case, it is preferable that the positioning of the short insert 4a inside the barrel 10 be achieved through a complementarity between the taper of the barrel chamber 10b and that of the short insert 4a, combined with a compressive stress on the short insert 4a due to its participation in the headspace through the front contact 10a, as illustrated in [Fig. 5]. Accordingly, the method of assembling the short insert 4a onto the long base 4b must take into account the need for elasticity along the axis of the barrel chamber 10 in order to allow for the absorption of the dimensional variability of the ammunition by means of a "crushing" effect.For this purpose, a groove is present on the outer wall of the short insert 4a and serves to receive the front end of the long base 4b during a two-stage crimping, as illustrated in figures 3 and 4. Prior to the crimping of the short insert 4a onto the long base 4b, the front end of the long base 4b consists of a flared rim whose diameter is greater than the maximum diameter of the short insert 4a. The crimping is done by means of a die composed on the one hand of an insert positioner 7c (visible in figures 3 and 4), pushing the short insert 4a against the front face of the long base 4b by means of a spring, and on the other hand of a crimping die 7b whose front face is chamfered so as to impose a plastic deformation of the flared portion of the long base 4b inside the groove of the short insert 4a.At the end of the crimping movement, the long base 4b is axially compressed against the short insert 4a to confirm the plastic deformation of the portion used for crimping the long base 4b onto the short insert 4a. In the case of adopting a long base 4b with a constant cylindrical cross-section, it is possible to reverse the positioning of the crimping die 7b by placing it around the long base 4b and not around the short insert 4a.

[0055] Preferably, the positioning of the long insert 4c relative to the barrel 10 is ensured by distributing the contact along two short, cylindrical or slightly conical bearing surfaces 10c and 10d, positioned as far apart as possible along the axis of the barrel 10. To achieve this, it is advantageous for the walls of the combustion chamber 4j to be formed inside the long insert 4c and not within a long base 4b. In this case, the ammunition production cycle changes: the first step consists of centering the projectile 1 on the long insert 4c by means of a die into which the material forming the degradable sabot 2 will be injected. The second step consists of loading the propellant charge 3 into the combustion chamber 4j through the opening of the long insert 4c at the interface with the short base 4d. The third step consists of closing the combustion chamber 4j with the short base 4d by means of a crimp.The short base 4d may have been fitted with the primer 5 prior to this step, or the primer may be crimped to the short base 4d at the end of the ammunition assembly. A finishing step may be added at the end of the manufacturing process to certify the ammunition's resistance to external moisture by applying lacquer to the crimp connections between the short base 4d and the long insert 4c, as well as between the short base 4d and the primer 5. Ideally, the injection points of the biodegradable sabot 2 are also deburred, followed by the application of a thin layer of lacquer to the front surface of the biodegradable sabot 2 to ensure a certain stability of the ammunition under storage conditions.

[0056] To ensure the connection between the base 4b, 4d and the insert 4a, 4c, it may be advantageous to use an additional safety piece 6 to confirm the locking of the crimp, whether during extraction operations or during firing itself.

[0057] In cases where the chosen ammunition design relies on the external crimping of a long base 4b onto a short insert 4a, the crimping lock confirmation function can be achieved by means of an external seal 6a positioned in the groove formed by the plastic deformation of the flared section of the long base 4b during crimping. During chambering, this external seal 6a is pressed against the inner wall of the chamber of the barrel 10, preventing disassembly between the long base 4b and the short insert 4a during the extraction of a fired or unused round.

[0058] In the case where the chosen ammunition architecture is based on crimping a short base 4d onto a long insert 4c, the crimp locking function can be achieved by means of the permanent deformation of an internal locking 6b in the form of a washer potentially taking the form of a tulip against the short base 4d in the manner of a blind rivet (otherwise known as a pop rivet) through the primer channel 4L. In this case, as illustrated in [Fig. 7], preparing the short base 4d for the crimping operation consists of inserting the lock 6b in the base of the short base 4d and a rod serving as a spreader 8c to the lock 6b passing inside the lock 6b and the channel connecting the primer housing 4g to the combustion chamber 4j. The crimping is carried out by placing the short base 4d on the long insert 4c, previously fitted with the propellant charge 3, by means of a base die 8b while the spreader 8c is held by a clamping device, as shown in [Fig.7]. While the crimping dies 8a,8b hold the short base 4d against the long insert 4c, the spreader 8c is completely withdrawn through the primer channel 4f, causing the lock (6b then 6c) to deform against the short base 4d until contact between the lock 6c and the long insert 4c is established, as shown in [Fig.8], making the connection between the long insert 4c and the short base 4d impossible to break.The pull on the spreader 8c is maintained until the latter has passed through the lock 6c, freeing the passage between the primer pocket 4g and the combustion chamber 4j. The ammunition thus closed can continue its manufacturing process by crimping the primer 5 into the primer pocket 4g at the rear of the short base 4d, and by creating an external seal using lacquer in the gap between the primer 5 and the short base 4d, between the short base 4d and the long insert 4c, and on the degradable sabot 2.

[0059] Alternatively, as shown in [Fig. 11], and in order to adapt the configuration—short base 4d combined with a long insert 4c—to the ignition requirements of large-diameter ammunition such as tank rounds, it is possible to replace the use of a spacer 8c for locking the case closure assembly 4 with the use of a thread between the internal locking mechanism 6c and the tubular portion of the primer 5 containing the initiating charges 3c. In this case, the ammunition assembly procedure follows these steps:

[0060] - Introduction of the propellant charge 3, in the form of one or more sub- assemblies (monobloc of propellant 3a or fuel-jacketed cartridges containing a grain powder charge 3b) packaged in tubes allowing the passage of the tubular part of the primer 5, inside the combustion chamber 4j formed in the long insert 4c.

[0061] - Separate pre-assembly of the short base 4d with the internal locking 6c not crushed at station, held in place by the thread of the tubular part of the primer 5 containing the initiation charges 3c.

[0062] - Combustion chamber closure 4j by crimping the short base 4d onto the long 4c insert.

[0063] - Locking the assembly by crushing the internal lock 6c against the base short 4d by means of the thread of the primer tube 5 and an indexing between the internal lock 6c and the short base 4d.

[0064] - Sealing the primer 5 in the short base 4d by means of glue or a crimping by punching the short base 4d onto the primer 5.

Claims

Demands

1. Munition comprising a projectile (1), a propellant charge (3) and a priming device (5) held together by a case (4), the case (4) forming a nozzle (4k), a nozzle neck (4h), a combustion chamber (4j) and a primer channel (4f), characterized in that the case (4) is made up of at least two parts: a base (4b; 4d) and an insert (4a; 4c), said parts being assembled together after the integration of the propellant charge (3) inside the combustion chamber (4j).

2. Munition according to claim 1, characterized in that the side wall of the combustion chamber (4j) is formed by an extended part of the base (4b), the combustion chamber (4j) being closed by the insert (4a).

3. Munition according to claim 2, characterized in that the crimping of the base (4b) onto the insert (4a) is obtained by deforming a collar of the base (4b) inside a groove of the insert (4a) by means of a crimping die (7b), the insert (4a) being pressed against the base (4b) by means of an insert positioner (7c).

4. Munition according to claim 3, characterized in that an external seal (6a) is placed in the groove of the insert (4a) following crimping, said external seal (6a) bearing in a chamber of the barrel (10) during firing.

5. Munition according to claim 1, characterized in that the side wall of the combustion chamber (4j) is formed by an extended part of the insert (4c), the combustion chamber (4j) being closed by the base (4d) by means of the interlocking of two complementary portions.

6. Munition according to claim 5, characterized in that the assembly of the base (4d) on the insert (4c) is secured by the presence of an internal lock (6c) put in place by means of a spreader (8c) deforming the internal lock (6b) when it is extracted through the primer channel (4f).

7. Munition according to claim 5 or 6, characterized in that the insert (4c) is made by assembling the nozzle (4k) inside a cartridge case body (4i).

8. Munition according to any one of claims 1 to 7, characterized in that the projectile (1) and its sabot (2) are positioned inside a barrel (10) by means of cylindrical or slightly conical bearings forming front (10a; 10c) and rear (10b; 10d) contacts between the insert (4a; 4c) and the barrel (10).

9. Munition according to claim 8 characterized in that: - the munition is positioned longitudinally in the barrel (10); the longitudinal positioning of the munition in the barrel (10) is ensured by a conicity of the front contact (10a; 10c) or of the rear contact (10b; 10d) and the compression of the link between the insert (4a; 4c) and the base (4b; 4d) by a breech (9).

10. Munition according to claim 8, characterized in that: - the munition is positioned longitudinally in the barrel (10); - the longitudinal positioning of the munition inside the barrel (10) is obtained by means of a rebate contact (lOf) between the base (4b; 4d) and the barrel (10).