EP0147314A2 - Base wad of plastics material - Google Patents

Abstract

1. An obturator-base for medium-or large-caliber ammunition made of a non-metallic material with a modulus of elasticity ranging from 1000 to 10 000 MPascals, said base comprising a tubular portion (1) integral with the combustible case (10) of the ammunition, the case being engaged into the tubular portion and a rear disk (2) having an axial bore (4) intended to accommodate a primer-tube, characterized in that the front part of the tubular portion pressenting a bevel (5) slanted from the inside to the outside, without any point of contact with the outer surface of the case, the bevel being applied to the wall of the case, the bevel being applied to the wall of the weapon barrel due to its deformation after the combustion of the case, so as to ensure the tightness of the ammunition at a low level of pressure.

Description

The technical sector of the present invention is that of medium or large caliber ammunition, and more precisely ammunition casings.

Currently, large or medium-caliber ammunition uses either an all-metal cartridge case or a metallic shutter base associated with a combustible case.

These solutions have the common disadvantages of having a high mass, of presenting after firing a residue in the turret and of requiring protection of the chamber of the weapon against corrosion.

In addition, the metal bush constitutes a reservoir of harmful gases which it carries into the turret after ej ec _t ion.

As for the shutter base, it also has two specific drawbacks. In fact, it has been found that the metallic shutter caps have poor leaktightness at low pressure level, which necessitates the provision of additional leaktightness devices to obtain inside the socket sufficient pressure for the proper functioning of the ammunition. .

Thus, patent FR 2365096 presents, for a metal base, a rubber or silicone seal fitted on an annular bead of the base.

Patent FR 2380531 shows a seal having a lip making it possible to use the gas streams by converting them into a radial pressure ensuring tightness.

Patent FR 2218547 shows a base for a fuel socket ensuring a sealing function with respect to the wall of the barrel by means of rubber seals which are expandable under the effect of the gas pressure which is established inside the socket.

As can be seen, all these sealing devices are made up of elements attached to the base, the sealing function of which is not always perfectly fulfilled and which can even create problems of extraction of the base after the projectile fire.

Another drawback of current shutter caps used with combustible cases is that they are very imperfectly bonded with the case because of the difference in the nature of the materials used.

In the field of small caliber ammunition where the pressures developed are low of the order of 800 to 1000 bars, plastic materials have been used to produce the cartridges. Thus the patents wo N ° 8300213 and FR 1294 551 show such sockets. However, this type of device has never been used in ammunition of medium or large caliber because it had never been possible to solve the sealing problems with the developed pressures of the order of 7000 at 10,000 bars in such munitions.

The object of the present invention is to overcome the aforementioned drawbacks by producing obturating caps of reduced mass correctly ensuring a sealing function at low pressure level without additional device or with a device very clearly simplified, using for this purpose the capacities deformation of the material used.

Another object of the invention is to provide a particular embodiment of a shutter base made of non-metallic material for large caliber ammunition making it possible to guarantee leaktightness in the range of pressure levels used in medium and large ammunition. caliber.

Another object of the invention is to produce sockets or obturating caps ensuring better mechanical resistance to environmental stresses than the devices currently used.

Another object is to improve the connection between the shutter base and the combustible case.

Finally, the invention also aims to obtain reduced manufacturing costs in large series.

To achieve all these aims, the invention relates to a shutter base for medium or large caliber ammunition, base having a tubular part integral with the ammunition case and a circular rear flange carrying an axial bore intended for placing in place of a primer holder tube. The cap according to the invention has the particularity of being made of a non-metallic material having a modulus of elasticity of between 1000 and 10,000 HPascal and of having a section from the front of the tubular part bevelled from the inside towards the outside to allow a radial deformation ensuring the tightness of the ammunition in the tube at low pressure level.

When the base is used in combination with a combustible case, it may include between the tubular part and the case a foam gasket loaded with combustible material.

In all the aforementioned cases, the base according to the invention may comprise a metal insert comprising a rear pad and a tubular part of small section.

If the base according to the invention must carry an electrical primer, provision may be made for the non-metallic material of the base to be charged with a material conducting the electric current to ensure the electrical connection between the electrical primer and the obturating base.

• La figure 1 représente un culot selon l'invention, de face (figure 1A) et en coupe AA de la figure 1A (figure 1B).
• La figure ² montre un schéma d'un mode simplifié de réalisation du culot de la figure 1.
• La figure 3 montre un culot selon l'invention muni d'un insert métallique.
• La figure 4 montre l'assemblage par collage d'un culot selon les variantes précédentes avec un étui combustible.
• La figure 5 montre une variante où la liaison avec l'étui combustible est réalisée au moyen d'un joint d'étanchéité combustible.
• Les figures 6 et 7 montrent des douilles réalisées monobloc avec le culot selon l'invention sans insert métallique (figure 6) ou avec insert (figure 7).

Other features of the invention will be described with reference to the description which follows and to drawing boards showing, without limitation, embodiments of the invention.

• FIG. 1 represents a base according to the invention, from the front (FIG. 1A) and in section AA of FIG. 1A (FIG. 1B).
• FIG. ² shows a diagram of a simplified embodiment of the base of FIG. 1.
• Figure 3 shows a base according to the invention provided with a metal insert.
• Figure 4 shows the assembly by bonding of a base according to the preceding variants with a combustible case.
• Figure 5 shows a variant where the connection with the combustible case is made by means of a combustible gasket.
• Figures 6 and 7 show sockets made in one piece with the base according to the invention without metal insert (Figure 6) or with insert (Figure 7).

With reference to FIG. 1, the base according to the invention comprises a tubular part 1 intended to allow the base to be secured to the case of the ammunition and to achieve the sealing function fulfilled by the invention, and a circular rear flange. 2 comprising a shoulder 3 intended to come to bear on the rear of the barrel of the weapon.

. The flange 2 has in its center a threaded axial bore 4 intended for the installation of a primer holder tube of conventional type.

According to a fundamental characteristic of the invention, the base is made of a non-metallic material having a modulus of elasticity of between 1000 MPascal and 10,000 MPascal. The base can thus be made of a plastic material such as polyester, polyvinyl chloride or polyethylene. In addition, to use this characteristic of elasticity, the section of the tubular part 1 decreases from the flange 2 to its free front end and, ends with a bevel 5 made from the inside towards the outside, this arrangement allowing a radial deformation towards the outside under the effect of the removal without the shell of the ammunition during firing in order to ensure the tightness of the ammunition at low pressure level.

FIG. 3 shows an alternative embodiment according to which the shutter base made of non-metallic material comprises a metal insert intended to obtain good mechanical strength of the base and to control the radial elastic deformation of the latter during firing. This insert comprises a rear pellet 6 with a diameter slightly greater than the caliber of the ammunition so that the pellet 6 projects beyond the inside of the shoulder 3 to ensure its rigidity. This pellet 6 is integral with a tubular part of small section 7 which penetrates inside the tubular part 1 of the cap and whose free end is located at the base of the bevel 5 of the cap. Obtaining a base comprising such an insert can be achieved by overmolding the non-metallic material on the insert.

In Figures 4 and 5 are shown two means of connecting the base on a possibly combustible case. According to Figure 4, the case is assembled by gluing on the internal part 8 of the tubular part 1 of the base. The internal part 8 has the shape of an annular bowl on which rests an annular rounding 9 of the rear part of the case 10. As can be seen in FIG. 4, the assembly only includes a bonding on the part internal 8 of the base and not on the bevel 5 so as not to oppose the radial deformation of the base during firing.

According to the assembly mode of Figure 5 intended more particularly for the establishment of a combustible case, is introduced between the case 10 and the base a foam 11 comprising a binder loaded with combustible material. The elasticity of the foam is determined by the rate of loading of combustible material, which allows perfect control of the coupling of the base and the case.

Such an assembly is very favorable to the holding of the ammunition; especially during environmental testing.

. In addition, such a very flexible seal 11 ensures excellent tightness at a very low pressure level and disappears entirely during the combustion phase.

Figures 6 and 7 show a variant of ammunition in which the complete socket was made in a single piece of non-metallic material. without metal insert (figure 6) or with insert (figure 7). The sealing problem at low pressure level is solved in the same way as for a base and case munition as shown above, by the radial deformation of the sleeve allowed by the elasticity characteristics of the non-metallic material chosen.

All the variants shown above have a central bore4 intended to receive a primer holder tube, that is to say conventional; be combustible.

In the case of an electrical ignition, the electrical connection can be made, either by a metallic ground connection, or preferably by adding conductive material to the mass of the non-metallic material of the base.

As is apparent from the above, the invention has the advantage of ensuring a more secure connection between the shutter base and the combustible case of the ammunition and of greatly improving the seal at very low pressure level in the gun barrel.

Claims (7)

1 - Sealing cap for medium or large caliber ammunition made of a non-metallic material having a modulus of elasticity of between 1000 and 10,000 MPascal, cap having a tubular part secured to the case of the ammunition and a rear circular flange bearing an axial bore intended for the installation of a primer-carrying tube, characterized in that the section of the front of the tubular outlet is bevelled from the inside towards the outside to allow a deformation ensuring the sealing ammunition in the low pressure tube. 2 - obturating cap according to claim 1, for combustible case characterized in that it comprises between the tubular part and the case a foam gasket loaded with combustible material. 3 - obturating cap according to any one of claims 1 or 2, characterized in that it comprises a metal insert comprising a rear pad and a tubular part of small section. 4 - obturating base according to claim 3, characterized in that the non-metallic material of the base is overmolded on the metal insert. 5 - obturating base according to any one of claims 1 to 4, carrying an electrical primer, characterized in that the non-metallic material of the base is charged with a material conducting the electric current to ensure the electrical connection between the electrical primer and the shutter base. 6 - Socket for ammunition characterized in that it comprises a shutter base according to any one of claims 1 to 5. 7 - Ammunition socket according to claim 6, characterized in that the base and the case are made of the same material.

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