EP0082758B1 - Mixed propulsive charge for cartridge ammunition - Google Patents

Description

The present invention relates to the field of mixed propellant charges for ballistic ammunition comprising a combustible or non-combustible cartridge case.

Traditional propellant charges for ballistic ammunition consist of grains of propellant powder in bulk in a combustible or non-combustible cartridge case. These loadings have the drawback of not being progressive, which amounts to saying that if we draw the curve representing the variation of the pressure in the weapon as a function of time at the time of firing, this curve has the general appearance of a peak increasing very rapidly and also decreasing very rapidly. As the maximum pressure developed in the weapon by the propellant charge at the time of firing must in any case remain below the rupture limit of the barrel of the weapon, this type of charge does not generally allow , to obtain a good filling coefficient of the socket.

Various attempts have been made to find more progressive loadings, that is to say loadings leading to a "pressure as a function of time" curve having the general appearance of a plateau rather than a peak, thereby enabling to obtain a better filling coefficient of the casing and consequently a higher initial velocity of the projectile without risk of rupture of the barrel of the weapon.

The choice of propellant powder already constitutes a possibility of solution to this problem. We can indeed improve the progressiveness of the powder by playing on the one hand on the geometry of the grain of powder, this is how a grain of cylindrical powder with 19 holes is more progressive than a grain of powder with 7 holes itself more progressive than a grain of monotubular powder, and on the other hand on the composition of the powder grain thanks to the smoothing operations which make it possible to incorporate a combustion moderator on the surface of the powder grain. Thus the article Ammunition, General published in War Department Technical Manual TM9-1900, US War Department, June 18, 1945, page 37, lines 3 to 6, he describes spherical powders coated with graphite. However, these possibilities are still insufficient for many loads.

We have also proposed progressive loading consisting of a fragmentable cylindrical block of agglomerated powder, having a central channel in which is placed propellant powder in grains. At the time of ignition the propellant powder in grains burns first, causing the fragmentation of the cylindrical block which burns in turn like a loose powder. Such loadings, described for example in French patents 2,374,278, 2,411,817, 2,436,766, in the name of the applicant, make it possible to significantly improve the filling factor of the ammunition and, for the same muqition of a caliber 30 mm allow for example to increase the initial velocity of the projectile from 780 m / s to around 870 m / s. However, these loads have two major drawbacks. On the one hand, in terms of ballistic performance, these loads exhibit poor conservation of temperature performance (whether these are temperature cycles during which the powder remains at different temperatures before being drawn at room temperature or temperature shots) leading to a wide dispersion of results. On the other hand, these loads are poorly suited to collar sockets having a narrowing at the loading orifice. Indeed, for the latter type of bushings, the diameter of the fragmentable cylindrical block, necessarily smaller than the diameter of the body of the bushing due to the narrowing presented by the loading orifice, leaves a far too large dead volume.

Another solution has also been proposed leading to progressive loading which can be used both in ammunition comprising a cylindrical sleeve and in those comprising a collar sleeve. This solution, described in French patent 2 214 672, which has the characteristics of the preamble of independent claims 1 and 2, consists of having a mixed charge consisting of a mixture of a part of propellant charges which can be fragmented in the form of small tablets made of powder. agglomerated and whose dimensions are small compared to those of the sleeve and on the other hand of granular propellant powder. Such a loading makes it possible to improve the filling coefficient of the ammunition but does not make it possible to ensure good reproducibility of the firing results due to the lack of reproducibility in the distribution of the tablets inside the casing, the tablets tending to decant during storage, which can lead to poor combustion of the load. moreover, the industrial production of such a load is not very convenient.

Finally, a solution has been proposed which consists in mixing powders of different natures with a liquid binder, introducing this mixture into the bushing and hardening it by compression or baking according to the nature of the binder. This solution described in French patent 2 422 925, makes it possible to obtain a progressive loading which can be used in all types of socket and makes it possible to improve the filling coefficient but is not easy and perfectly easy to use. reproducible because it involves filling a socket with a mixture of slightly pasty consistency.

The object of the present invention is precisely to propose a progressive loading for ammunition with casings, usable in any type of casing, making it possible to obtain a good coefficient of filling in a reproducible and convenient manner on an industrial scale and having good temperature resistance.

The object of the invention is achieved thanks to the features in independent claims 1 and 2, that is to say a mixed charge for ammunition with cartridge case (2), constituted by a mixture of a part of fragmentable propellant charges constituted by the agglomerated propellant powder and on the other hand, by a granular propellant powder (6), this charge being characterized in that said fragmentable charges are in the form of spheres (5), the diameter of said spheres (5) being such that the spheres (5) are distributed in the sleeve (2) by layers, the number of spheres (5) per layer being between 1 and 4, the said spheres (5) of each layer being staggered relative to the spheres (5) of the neighboring layers when the number of spheres (5) per layer is between 2 and 4. According to a preferred embodiment of the invention, the diameter of said spheres is slightly less than half the diameter of the body of said socket. When the diameter of the spheres (5) is greater than half the diameter of the body of the socket (2), the said spheres (5) are arranged in layers containing only one sphere (5).

• La figure 1 montre, vue en coupe longitudinale, une munition selon une version préférée de l'invention.
• La figure 2 représente une coupe selon 11-11 de la douille et du chargement représentés à la figure 1.
• La figure 3 montre, vue en coupe longitudinale, une autre réalisation de l'invention.
• La figure 4 représente une coupe selon IV-IV de la douille et du chargement représentés à la figure 3.

The invention is described in detail below with reference to Figures 1 to 4 which illustrate particular embodiments of the invention.

• Figure 1 shows, in longitudinal section, a munition according to a preferred version of the invention.
• 2 shows a section on 11-11 of the sleeve and the load shown in FIG. 1.
• Figure 3 shows, in longitudinal section, another embodiment of the invention.
• FIG. 4 represents a section on IV-IV of the sleeve and of the load represented in FIG. 3.

A progressive propellant charge according to the invention therefore consists on the one hand, of fragmentable charges in the form of spheres constituted by agglomerated propellant powder and on the other hand, by a granular propellant powder.

The Applicant has in fact observed that the sphere shape for the fragmentable charge is the shape which makes it possible to obtain both a good filling coefficient and great ease of filling the socket on an industrial level. The spheres according to the invention consist of a propellant powder in grains agglomerated by compression, generally hot. The granular propellant powder intended for making the spheres is essentially chosen as a function of the thermodynamic properties desired for the spheres. for safety reasons, it will however be preferred to use powders which do not contain nitroglycerin. That said, one can use any propellant powder in grains which does not contain an ingredient which can decompose at the compression temperature.

The actual manufacturing of the spheres is done either by compression of the only grains of propellant powder previously treated to be able to be compressed, as described for example in French patents 2 374 278 or 2 436 766, or even by compression of a mixture of grains propellant powder and grains of a thermoplastic binder as described in French patent 2,411,817. The preferred solution of the applicant is rapid compression (approximately two seconds); under a pressure close to 100 bars, at a temperature below 110 ° C. of grains of smokeless nitrocellulose powder coated with a thin film of polyvinyl nitrate, as described in French patent 2,436,766.

It is thus possible to compress the powder either directly in the form of spheres, or in the form of hemispheres, which are then bonded two by two, for example using a collodion, so as to form spheres.

The dimension of said spheres, relative to the socket receiving them, is not unimportant. It is first necessary that the spheres are of a diameter smaller than the diameter of the loading orifice of said socket and, in the case of cylindrical sockets, that it is sufficiently smaller than the latter to allow the introduction of throughout the socket the grains of loose propellant powder next to the. marbles. But, and this contrary to the teaching of French patent 2 214672, the Applicant has also observed that, to obtain the best ballistic performance, the diameter of the spheres is small compared to that of the body of the socket. The Applicant has on the contrary discovered that the best ballistic performance is obtained when the diameter of the spheres is slightly less than half the diameter of the body of the sleeve. In this case, the spheres are naturally distributed in layers of two, the spheres of layer n being staggered relative to the spheres of layers n - 1 and n +

Of course, this is the preferred embodiment of the invention, but the spheres can have other diameters. The diameter of the spheres may be greater than half the diameter of the body of the socket, in which case there will be layers containing only one sphere, it being understood that the diameter of the spheres must in any event remain less than the diameter of the body of the socket so as to allow the addition of loose powder grains. The diameter of the spheres can also be less than half the diameter of the body of the socket and there are cases where it may be advantageous to seek diameters such that there are three or even four spheres per layer. The Applicant has however noted that, as a general rule, it is not advantageous, from a ballistic point of view, to go beyond four spheres per layer, that is to say to use spheres with a diameter smaller than that leading to an arrangement of four spheres per layer.

In FIGS. 1 to 4, we recognize an ammunition constituted by a shell 1 and by a socket 2 crimped around the shell 1 and closed by a base 3 carrying a primer 4, the mixed load consists on the one hand by fragmentable spheres 5 and on the other hand by grains 6 of a propellant powder. It is observed in Figures 1 and 2 that the spheres whose diameter is slightly less than half the diameter of the body of the sleeve 2 are distributed in layers of two arranged in staggered rows relative to each other. Figures 3 and 4 show a similar loading in which the spheres are distributed by layers of three arranged in staggered rows relative to each other.

A load according to the invention also consists of grains of a propellant powder. The latter may be, with respect to the powder used for making the fragmentable spheres, identical, analogous or of a different nature. This powder will be chosen by the skilled person according to the ammunition and the desired ballistic performance. The only condition imposed is that relating to the dimensions of the grains of the powder. The grains must be able to flow through the interstitial voids existing on the one hand between the spheres and on the other hand between the spheres and the walls of the sleeve. to ensure an easy flow, it is advisable to use grains of dimensions clearly smaller than the so-called interstitial voids which leads in general to prefer monotubular powders.

Although the applicant does not intend to be limited by theoretical considerations, it believes that the operation of the loadings according to the invention is as follows: on ignition, the grains of loose powder ignite first and in increasing the pressure inside the socket causes the spheres to fragment, which then burn like loose powder. The very good progressiveness presented by the loadings according to the invention would be due to the sphere shape of the fragmentable charges, because the spherical shape, is that offering, for a given quantity of material, the minimum surface area which makes it possible to delay the maximum bursting and inflammation of frangmentable charges.

The charges according to the invention can be used in all types of usual sockets such as for example cylindrical sockets or collet sockets, aluminum or brass sockets, combustible or semi-combustible sockets. In all cases, a significant increase in the filling coefficient is observed for a given volume of the sleeve when the sleeve is loaded with a charge according to the invention compared to an identical sleeve loaded in a conventional manner with only powder in loose.

Furthermore, the loadings according to the invention can be carried out industrially very easily and in a very reproducible manner because the spheres are positioned in the socket by the simple play of gravity and allow the same volume to remain in each socket, with the same configuration. geometric, for loose powder.

The implementation of the invention is illustrated with the aid of the examples given below without implied limitation.

Example 1

This example concerns a 30 mm caliber ammunition. The socket is a cylindrical brass socket with a useful length of 77 mm and a diameter of 30 mm, the shell weighs 243 g and the ignition is an electric ignition by primer.

Fragmentable charges were made in the form of spheres with a diameter of 14 mm. These spheres were made from grains of a simple nitrocellulose powder having a potential of 900 cal / g. The grains of powder were coated with a film of polyvinyl nitrate and compressed into hemispheres according to the technique described in French patent 2,436,766. The hemispheres thus obtained were glued two by two by cold pressing in presence of a little nitrocellulose collodion. Fragmentable spheres 14 mm in diameter and 2.4 g in weight were thus obtained. The socket was filled with 14 spheres thus manufactured, that is to say a weight of 33.6 g of energetic material in the form of fragmentable spheres, the spheres being arranged in layers of two arranged in staggered rows relative to each other, as described above . 24.4 g of grains of simple base powder were added to the nitrocellulose having a potential of 980 cal / g. We thus managed to put in the socket 58 g in total of energetic material.

• - vitesse de l'obus à 25 m du canon: 835 m/s.
• - Pression maximale dans la chambre de l'arme = 2590 bars. On a observé par ailleurs que les coefficients de température des chargements selon l'invention sont tout à fait corrects et que sur plusieurs séries de tir on ne constate aucun coup aberrant dans les résultats, ce qui dénote une fiabilité exceptionnelle des chargements selon l'invention.

The firing results were as follows:

• - shell speed 25 m from the cannon: 835 m / s.
• - Maximum pressure in the gun chamber = 2590 bars. It has also been observed that the temperature coefficients of the loadings according to the invention are completely correct and that on several series of shots there is no aberrant hit in the results, which indicates an exceptional reliability of the loadings according to the invention .

• - vitesse de l'obus à 25 m du canon: 796 m/s
• - pression maximale dans la chambre de l'arme = 2600 bars.

For comparison, if you fill the socket only with grains of the powder of potential 980 cal / g, you can only put a total of 48 g of energetic material, and the firing results are as follows:

• - shell speed 25 m from the cannon: 796 m / s
• - maximum pressure in the gun chamber = 2600 bars.

The invention therefore allows a gain of 20% of energetic material in the same socket volume, which in the present case results in a gain of nearly 40 m / s on the speed of the shell without appreciable increase in pressure. in the gun room.

Examples 2 to 4

These examples of mixed loading relate to a 30 mm caliber ammunition similar to that of Example 1 and are intended to illustrate the influence of the diameter of the spheres relative to the diameter of the cartridge case.

• - longueur du grain: 1,17 mm
• - diamètre du grain: 1,02 mm
• - diamètre du trou centra1:0,21 mm

The spheres were made from grains of a smokeless nitrocellulose powder of potential 900 cal / g, smoothed with 1.5% by weight of centralite and graphitized with 0.2% of graphite. The grains of powder are in the form of small cylinders with a central hole and have the following dimensions:

• - grain length: 1.17 mm
• - grain diameter: 1.02 mm
• - hole diameter centra1: 0.21 mm

• - température du moule: 110° C,
• - durée de préchauffage des grains: 45 s,
• - pression de compression: 100 bars,
• - durée de compression: 2 s.

These grains of powder were coated with 2% by weight of polyvinyl nitrate and compressed in the form of spheres by a single compression carried out under the following conditions:

• - mold temperature: 110 ° C,
• - grain preheating time: 45 s,
• - compression pressure: 100 bars,
• - compression duration: 2 s.

• - exemple 2: diamètre 14,7 mm, poids moyen: 2,6 g,
• - - exemple 3: diamètre 13,5 mm, poids moyen: 2,0 g,
• - exemple 4: diamètre 12 mm, poids moyen: 1,6 g.

We made 3 types of spheres:

• - example 2: diameter 14.7 mm, average weight: 2.6 g,
• - - example 3: diameter 13.5 mm, average weight: 2.0 g,
• - example 4: diameter 12 mm, average weight: 1.6 g.

• - longueur du grain: 1,76 mm,
• - diamètre du grain: 1,17 mm,
• - diamètre du trou central: 0,22 mm.

Mixed loadings were carried out according to the invention with these three types of spheres and with grains of a smokeless nitrocellulose powder, of potential 900 cal / g, smoothed with 1.7% by weight of camphor and graphitized with 0.25% by weight of graphite and whose grains in the shape of a cylinder with a central hole had the following dimensions:

• - grain length: 1.76 mm,
• - grain diameter: 1.17 mm,
• - diameter of the central hole: 0.22 mm.

The loads had the following characteristics:

1. Zusammengesetzte The firing results were as follows:

These results show on the one hand that it is possible thanks to the invention to obtain mixed loads usable in all types of socket and allowing, in 30 mm caliber, to reach speeds of the order of 870 to 880 m / s for the projectile, and on the other hand that the more the diameter of the sphere decreases and the more the dispersion of the results seems to increase.

Claims (3)

1. Mixed charge for munitions with a casing (2), consisting of a mixture of fragmentable propellant charges consisting of agglomerated propellant powder and a propellant powder in grains (6), characterised in that the said fragmentable charges are in the form of spheres (5) the diameter of which is greater than half the diameter of the body of the casing (2) and which are disposed in layers containing only a single sphere (5).

2. Mixed charge for munitions with a casing (2), consisting of a mixture of fragmentable propellant charges consisting of agglomerated pr.:¡pellant powder and a propellant powder in grains (6), characterised in that the said fragmentable charges are in the form of spheres (5) the diameter of which is such that the spheres (5) distribute themselves in layers in the casing (2), the spheres (5) of each layer being disposed in staggered relationship with respect to the spheres (5) of neighbouring layers and in that the number of spheres (5) per layer is between 2 and 4.

3. Charge according to Claim 2 characterised in that the diameter of said spheres (5) is slightly less than half of the diameter of the body of said casing (2).

Images