EP0626555B1 - Practice projectile and method for fabrication - Google Patents

Description

The technical field of the present invention is that of ammunition and exercise projectiles and more particularly that of projectiles which disintegrate at the exit of the barrel of a weapon.

Among the ammunition of exercise one distinguishes generally those which are intended to reproduce the real ballistics of a war projectile, but on a reduced distance and those which are intended to reproduce only the environment suitable for shooting (noise, recoil, fumes ...).

The first type of ammunition for practice can be illustrated by the patents FR2509457, on which the preambles of independent claims 1 and 11 are based, and DE734429, which both describe a projectile comprising a body formed by the assembly of several segments. This projectile is intended to reproduce the actual ballistics of a war projectile over a certain distance. It thus comprises means which make it possible to secure the joining of the different segments over part of the trajectory. It requires the installation of a shooting safety template and cannot be used to reproduce only the shooting environment.

If we now consider the ammunition intended to reproduce the environment of a shooting, we know the so-called "blank" ammunition which does not comprise a projectile. The disadvantage of these munitions is that they require the addition of auxiliary devices to the weapon, in particular to enable rearming.

We also know the so-called "break up" munitions which fire a projectile comprising a load of steel or tungsten powder placed inside a fragile envelope. This projectile bursts at the exit of the tube under the effect of centrifugal forces of inertia. The patents US3338167 and CH445341 describe such ammunition, which has the advantage of being able to be fired without modifying the weapon.

However, a "break up" projectile has drawbacks. First of all, it is of significant cost, because it requires the production of a metal powder charge having well defined mechanical characteristics.

This charge must in particular be sufficiently dense and compact to ensure the mechanical strength of the projectile, but it must still be easily dispersed at the exit of the barrel of the weapon.

The storage behavior of such a load is random and it happens that the metal powders oxidize, which affects the behavior of the projectile in the tube and at the exit of the latter.

In addition, it is frequently observed that these projectiles burst inside the barrel of the weapon, thus causing rapid deterioration of the latter.

Finally, the dense powder which is dispersed in the vicinity of the muzzle of the weapon risks damaging the sighting optics, or even injuring personnel.

The document DE3819251 describes a bullet whose body is formed from several bonded metal sectors which remain integral on the trajectory and only separate on impact on a target.

It is the object of the invention to provide an exercise projectile disintegrating at the outlet of the barrel of the weapon but not having the drawbacks of "break up" projectiles according to the state of the art.

Thus the projectile according to the invention is inexpensive and does not degrade the barrel of the weapon. It also has excellent storage behavior even in the harshest climatic environments.

The invention also relates to a particularly advantageous manufacturing method for such an exercise projectile.

Thus the subject of the invention is an exercise projectile comprising a body formed by the assembly of several sectors and a base having a housing intended to receive the different sectors, projectile characterized in that the sectors are made of a material of the type thermoplastic and in that it comprises means ensuring maintenance of the assembly of the sectors during the handling phases, means designed so as to release the sectors at the exit of the barrel of a weapon when the projectile is fired.

According to various embodiments, the holding means can comprise a cap surrounding a front part of the projectile.

The cap can carry a bead which penetrates into an annular groove arranged on the sectors and ensures the fixing of the cap on the latter.

• un manchon entourant une partie avant du projectile, manchon réalisé en un matériau thermorétractable,
• au moins un point de soudure entre deux secteurs contigus,
• au moins une saillie solidaire d'un secteur et coopérant avec une rainure aménagée sur un secteur contigu au précédent, rainure ayant une forme complémentaire de celle de la saillie,
• une zone centrale formée d'une seule pièce avec au moins deux secteurs régulièrement répartis angulairement et formant un premier groupe de secteurs.

According to various embodiments, the holding means can comprise:

• a sleeve surrounding a front part of the projectile, sleeve made of a heat-shrinkable material,
• at least one weld point between two contiguous sectors,
• at least one projection integral with a sector and cooperating with a groove arranged on a sector contiguous to the previous one, groove having a shape complementary to that of the projection,
• a central zone formed in one piece with at least two sectors regularly distributed angularly and forming a first group of sectors.

In the latter case, the first group of sectors delimits dwellings in which the other sectors are arranged, and the latter which constitute a second group of sectors are held together with the previous ones by a cover.

The second group of sectors can be formed in one piece with the cover.

According to a particular embodiment, the sectors are welded two by two along their external contact edges.

• regroupement des secteurs de façon à constituer le corps de projectile,
• positionnement d'au moins une zone avant du corps de projectile dans un outillage destiné à chauffer sa surface externe à une température suffisante pour faire fondre localement le matériau des secteurs et les souder le long de leurs arêtes de contact externe,
• refroidissement du corps,
• assemblage du corps de projectile et du culot.

The subject of the invention is also a method of manufacturing a projectile comprising the following steps:

• regrouping of the sectors so as to constitute the projectile body,
• positioning of at least one front zone of the projectile body in a tool intended to heat its external surface to a temperature sufficient to locally melt the material of the sectors and weld them along their edges of external contact,
• body cooling,
• assembly of the projectile body and the base.

According to an advantageous variant, the different sectors are produced by a single molding operation, all of them connected in a star by their tapered ends.

• les figures 1a et 1b représentent un projectile suivant un premier mode de réalisation de l'invention, la figure 1a étant une coupe longitudinale axiale et la figure 1b une coupe transversale suivant le plan AA de la figure 1a,
• les figures 2a et 2b représentent un projectile suivant un deuxième mode de réalisation de l'invention, la figure 2b étant une coupe transversale suivant le plan BB de la figure 2a,
• les figures 3a et 3b représentent un projectile suivant un troisième mode de réalisation de l'invention, la figure 3b étant une coupe transversale suivant le plan CC de la figure 3a,
• les figures 4a et 4b représentent un projectile suivant un quatrième mode de réalisation de l'invention, la figure 4b étant une coupe transversale suivant le plan DD de la figure 4a et la figure 4a étant une coupe suivant le plan EE de la figure 4b,
• les figures 5a et 5b représentent un projectile suivant un cinquième mode de réalisation de l'invention, la figure 5b étant une coupe transversale suivant le plan FF de la figure 5a et la figure 5a étant une coupe suivant le plan GG de la figure 5b,
• les figures 6a et 6b représentent un projectile suivant un sixième mode de réalisation de l'invention, la figure 6b étant une coupe transversale suivant le plan HH de la figure 6a et la figure 6a étant une coupe suivant le plan II de la figure 6b.
• les figures 7a et 7b représentent un projectile suivant un septième mode de réalisation de l'invention, la figure 7b étant une coupe transversale suivant le plan JJ de la figure 7a et la figure 7a étant une coupe suivant le plan KK de la figure 7b.
• la figure 8 schématise les différentes étapes d'un procédé de fabrication du projectile selon les figures 7a et 7b.

The invention will be better understood on reading the description which follows of various embodiments, description made with reference to the appended drawings and in which:

• FIGS. 1a and 1b represent a projectile according to a first embodiment of the invention, FIG. 1a being an axial longitudinal section and FIG. 1b a transverse section along the plane AA of FIG. 1a,
• FIGS. 2a and 2b represent a projectile according to a second embodiment of the invention, FIG. 2b being a cross section along the plane BB of FIG. 2a,
• FIGS. 3a and 3b represent a projectile according to a third embodiment of the invention, FIG. 3b being a cross section along the plane CC of FIG. 3a,
• FIGS. 4a and 4b represent a projectile according to a fourth embodiment of the invention, FIG. 4b being a cross section along the plane DD of FIG. 4a and FIG. 4a being a section along the plane EE of FIG. 4b,
• FIGS. 5a and 5b represent a projectile according to a fifth embodiment of the invention, FIG. 5b being a cross section along the plane FF of FIG. 5a and FIG. 5a being a section along the plane GG of FIG. 5b,
• Figures 6a and 6b show a projectile according to a sixth embodiment of the invention, Figure 6b being a cross section along the plane HH of Figure 6a and Figure 6a being a section along the plane II of Figure 6b.
• Figures 7a and 7b show a projectile according to a seventh embodiment of the invention, Figure 7b being a cross section along the plane JJ of Figure 7a and Figure 7a being a section along the plane KK of Figure 7b.
• FIG. 8 schematizes the different stages of a method of manufacturing the projectile according to FIGS. 7a and 7b.

Referring to Figures 1a and 1b, an exercise projectile 1 according to a first embodiment of the invention comprises a body 2 formed by the assembly of six identical sectors 3a, 3b, 3c, 3d, 3e and 3f.

Each sector is delimited by two intersecting planes 4a, 4b which form an angle of 60 °. Thus, after assembly, each sector is in contact with two neighboring sectors at its intersecting planes. The absence of empty space between the sectors ensures excellent rigidity of the projectile.

The projectile also includes a base 5 which has a housing 6 intended to receive the sectors 3. The base 5 carries an annular bulge 7 which constitutes a belt intended to come to seal the propellant gases in the barrel of the weapon. The base also carries an annular groove 8 intended to allow the projectile to be secured to a propellant charge case (not shown).

The base 5 has an internal rim 9 which penetrates into a groove 10 arranged on the body 2. This rim secures the base and the body.

The main function of the base is to seal the propellant gases in the barrel, on the one hand thanks to the belt 7, and on the other hand thanks to the bottom wall 11 of the base which prevents gases from entering between the different sectors.

The sectors and the base are made of a plastic material of the thermoplastic type. These elements are obtained for example by injection. This material allows the projectile to withstand the various temperature and humidity constraints encountered during storage.

Different thermoplastic materials can be considered. We can for example choose from the following materials: Polyethylene, Polyamide, Polypropylene, Polystyrene, Polycarbonate, Polyphenylene Oxide and Acrylonitrile Butadiene Styrene.

The projectile comprises means ensuring maintenance of the assembly of the sectors during the transport and handling phases.

These means make it possible to guarantee the resistance of the projectile to vibrations and other mechanical stresses encountered during transport or loading of the weapon.

According to the first embodiment described here, these means comprise a welding point 12 which secures the various sectors at a front part 13 of the projectile.

This welding can be carried out by locally heating the front part 13 of the projectile.

The holding means are designed so as to free the sectors at the outlet of the barrel of a weapon when the projectile is fired. The mechanical strength of the weld is not sufficient to withstand the stresses developed during firing.

After rupture of the weld the sectors can deviate, they remain however maintained by the barrel of the weapon, but they deviate at the exit of this last owing to the aerodynamic forces which are exerted on the projectile (forces to which centrifugal force will be added in the case of shooting from a rifle with a rifled tube).

It is thus seen that by an appropriate dimensioning of the holding means, it is possible to design an exercise projectile intended for shooting in a smooth tube. On the contrary, the known “break up” type projectiles, which are mentioned in the preamble, can only be broken when firing in a striped tube.

Due to the lightness of the plastic, the sectors are quickly braked after their separation at the outlet of the tube. They will be dispersed a short distance from the weapon (of the order of 50 m for a caliber of 20 millimeters).

We therefore see the advantages provided by the invention on the known ammunition of the "Break up" type: the holding in the tube is excellent because the sectors constitute a rigid projectile body, the bursting at the exit of the barrel of the weapon is guaranteed because the holding means are sized for this purpose. The barrel of the weapon is not deteriorated by the sectors and the energy of the latter after dispersion is insufficient to deteriorate the optics or to injure the servants of the weapon.

• les secteurs sont assemblés de façon à constituer le corps 2, qui est ensuite disposé dans un outillage présentant une forme complémentaire,
• le culot est mis en place sur la partie arrière du corps par déformation élastique,
• le projectile est retiré de l'outillage et la soudure 12 est réalisée par chauffage de la partie avant 13.

The assembly of the projectile is carried out as follows:

• the sectors are assembled so as to constitute the body 2, which is then placed in a tool having a complementary shape,
• the base is placed on the rear part of the body by elastic deformation,
• the projectile is removed from the tool and the welding 12 is carried out by heating the front part 13.

Such a projectile is inexpensive to produce.

As a variant, the holding means can be constituted solely by the base itself which will then have a sufficient length to ensure the maintenance of the sectors.

In the other embodiments which will now be described with reference to Figures 2 to 6, some constituent elements of the projectile will bear the same numbers as those described with reference to FIGS. 1a and 1b.

These elements will not be described in more detail when they are structurally identical to those described above.

FIGS. 2a and 2b show a second embodiment in which the holding means comprise a sleeve 14 made of a plastic material of the heat-shrinkable type. Such a material is known to those skilled in the art. It is thus possible to set up a sleeve with a diameter greater than that of the body 2, then to heat this sleeve to reduce its diameter so that it comes to bear tightly on the body 2.

With this variant, it is possible to precisely modulate the resistance of the connecting means by varying the length of the sleeve 14.

Figures 3a and 3b show a third embodiment in which the holding means comprise a cap 15 made of plastic (for example of the same type as that constituting the body).

The cap 15 completely surrounds the front part of the projectile. It has at its rear part a bead 16 which enters an annular groove 17 arranged on the sectors 3. The bead ensures the fixing of the cap 15 on the sectors constituting the projectile body. The cap is assembled by elastic deformation of the latter.

The thickness of the cap will be defined as a function of the resistance desired for the connecting means. It will be possible in particular to provide incipient fractures on the cap, for example longitudinal thinning regularly distributed angularly.

The cap is a connecting means making it possible to provide mechanical resistance to environmental stresses which is better than that of the welding point described above.

The cap also has the advantage of preventing humidity or dust from entering between the sectors.

FIGS. 4a and 4b show a fourth embodiment in which the holding means comprise on the one hand a cover 15 made of plastic material and on the other hand projections 18, integral with the different sectors and which cooperate with grooves 19 arranged on the sectors. The grooves 19 have a shape complementary to those of the projections 18.

The cap is identical to that described with reference to Figures 3a and 3b and will not be described in more detail.

Each sector 3 carries a groove 19 on one of its intersecting planes 4a and a projection 18 on the other intersecting plane 4b.

Grooves and projections extend substantially over the entire length of each sector as can be seen in FIG. 4a.

We can play with both the dimensions of the projections 18 and the thickness of the cap 15 to modulate the resistance of the connecting means.

Grooves and projections also make it possible to improve the mechanical resistance to environmental constraints of the assembly of the sectors.

It is possible, as a variant, not to provide a cover 15 and to ensure the maintenance of the sectors only by means of the projections 18 and the grooves 19.

Figures 5a and 5b show a fifth embodiment in which the holding means comprise on the one hand a cap 15 (identical to that described with reference to Figures 3a and 3b) and on the other hand a central area 20 which is formed in one piece with the three sectors 3a, 3c and 3e and which extends over substantially the entire length of the latter.

These three sectors are regularly distributed angularly, they form what will be called hereinafter the first group of sectors.

The first group of sectors delimits housings 21 in which the sectors 3b, 3d and 3f are arranged (which constitute what will be called hereinafter the second group of sectors).

The cap allows the first and second group of sectors to be joined together.

It is possible to play on the dimensions of the central zone 20, as well as on the thickness of the cap to modulate the resistance of the connecting means.

FIGS. 6a and 6b show a sixth embodiment similar to the previous one but in which the second group of sectors (which is made up of sectors 3b, 3d and 3f) is formed in one piece with the cover 15.

The first group of sectors, consisting of sectors 3a, 3c and 3e connected by the central area 20, is therefore housed inside the cover 15 which carries the second group of sectors.

• mise en place du premier groupe de secteurs dans la coiffe,
• fixation du culot.

This particular embodiment allows a particularly easy mounting of the projectile since only two operations are necessary:

• establishment of the first group of sectors in the cap,
• fixing the base.

The resistance of the connection means will be modulated by varying the dimensions of the central zone 20 and the thickness of the cap 15 opposite the first group of sectors.

It will in particular be possible to arrange on the cap 15 primers for longitudinal breaks arranged in the extension of the intersecting planes 4a and 4b of the sectors of the second group.

• associer soudure 12 et manchon thermorétractable 14,
• associer les saillies 18 et rainures 19 avec une soudure ou un manchon thermorétractable,
• remplacer, dans la variante des figures 5a et 5b, la coiffe par une soudure ou un manchon thermorétractable.

Other variants are possible without departing from the scope of the invention. Thus it is possible to combine together the different holding means described above. For example:

• combine welding 12 and heat-shrinkable sleeve 14,
• associate the projections 18 and grooves 19 with a weld or a heat-shrinkable sleeve,
• replace, in the variant of FIGS. 5a and 5b, the cap with a weld or a heat-shrinkable sleeve.

Figures 7a and 7b show a seventh embodiment of a projectile according to the invention.

This embodiment is a variant of the mode described with reference to Figures 1a and 1b.

The body 2 of the projectile 1 is further formed by the assembly of six identical sectors 3a, 3b, 3c, 3d, 3e and 3f.

The sectors are all joined at their tapered ends by a plastic connection 22 obtained by molding with the sectors.

The sectors are also welded two by two along the external contact edges 23 of the intersecting planes 4a, 4b.

These longitudinal welds 24 extend along the body 2 of the projectile from its front part 13 to the annular bulge 7 of the base 5. They are obtained by heating the body 2 along the external contact edges 23 of the intersecting planes 4a, 4b.

The welds 24 also extend radially over a certain thickness towards the inside of the projectile.

They constitute the means for maintaining the assembly of the sectors and their thickness is chosen by a person skilled in the art as a function of the mechanical strength desired for these holding means.

As in the previous variants, a base 5 receives the sectors 3 in a housing 6.

This variant has the advantage of ensuring good mechanical strength of the assembly of the sectors during transport or loading phases of the weapon.

It also makes it possible, with a reduced number of parts therefore a low manufacturing cost, to prevent humidity or else dust from entering between the sectors. Longitudinal welds thus play the same role that the cap 15 described in the previous embodiments.

FIG. 8 schematizes the different stages of a method of manufacturing the projectile according to this latter embodiment.

Firstly, all the sectors intended to form the projectile body are produced (step A), by a single molding operation in a suitable mold not shown.

The different sectors 3a, 3b, 3c, 3d, 3e and 3f are thus all connected in a star shape by the link 22 at their tapered ends.

The sectors are then grouped together (step B) so as to constitute the projectile body 2.

A front zone 2a of the body 2 is placed inside a tool 26 intended to heat its external surface (step C).

The tool 26 comprises for this purpose a housing of shape complementary to that of the front zone 2a of the projectile body, thus the heat is imparted uniformly over the entire external surface of the front zone 2a.

The tool 26 is defined so as to bring the front zone 2a to a temperature sufficient to locally melt the material of the sectors, which makes it possible to weld them along their edges of external contact 23.

Different technologies can be used for the heating tool 26. We could for example use an electric oven connected to an energy source 25.

One could also use an oven in which a heat transfer fluid would circulate, or alternatively dip tool sleeves 26 carrying the projectile body in a thermostatically controlled bath.

A person skilled in the art will choose the welding temperature and the duration for which the projectile body is maintained at this temperature depending on the one hand on the characteristics of the thermoplastic material used. and on the other hand the thickness desired for the welds 24 (therefore the mechanical strength of the connecting means).

It is in fact noted that for a given heating temperature, the thickness of the weld increases with the duration during which the projectile body is maintained at the temperature considered.

After the body 2 has cooled, it is removed from the tool 26 (step D1).

The sketch D1 no longer represents the separations between sectors on the projectile body, the welds 24 in fact give the front part 2a of the body a smooth external surface.

A base 5 is also produced by molding (step D2).

Finally, the projectile body 2 and the base 5 are assembled (step E).

This manufacturing process is particularly economical and suitable for mass production of the projectiles according to the invention.

Claims (12)

1. A practice projectile (1) comprising a body (2) formed by assembling several segments (3) and a base (5) having a housing (6) designed to accommodate these segments, characterised in that the segments are made of a thermo-plastic type material and in that it comprises means to hold the segment (3) assembly together during the handling phases, means designed so as to free the segments upon exiting from the barrel of a weapon during firing of the projectile.
2. A projectile according to Claim 1, characterised in that the holding means comprise a nose cap (15) surrounding a front part of the projectile (1).
3. A projectile according to Claim 2, characterised in that the nose cap (15) has a flange (16) which penetrates into a ring-shaped groove (17) arranged on the segments (3) thereby fastening the nose cap to the latter.
4. A projectile according to Claim 1, characterised in that the holding means comprise a sleeve (14) surrounding a front part of the projectile (1), a sleeve made of a heat-shrinkable material.
5. A projectile according to one of Claims 1 to 4, characterised in that the holding means comprise at least one protrusion (18) integral with a segment and working in conjunction with a groove (19) arranged on a contiguous segments to the previous one, a groove of a matching shape to that of the protrusion.
6. A projectile according to one of Claims 1 to 5, characterised in that the holding means comprise a central section (20) formed in a single piece with at least t<o segments evenly distributed at an angle and forming a first group of segments.
7. A projectile according to Claim 6, characterised in that the first group of segments marks out housing (21) in which the other segments are placed, the latter, which form a second group of segments, being joined to the former by means of a nose cap (15).
8. A projectile according to Claim 7, characterised in that the second group of segments is formed in a single piece with the nose cap (15).
9. A projectile according to Claim 1, characterised in that the holding means comprise at least one spot weld (12) between two contiguous segments (3).
10. A projectile according to Claim 9, characterised in that the segments (3) are welded two by two along their outer contact edges (23).
11. A production process for a projectile according to Claim 10, characterised by the following steps :

    - the segments (3) are grouped together so as to form the projectile body,

    - at least a front section (2a) of the projectile body is placed in a tooling (26) designed to heat its outer surface to a high enough temperature to make the constitutive material of the segments (3) melt locally and weld them along their outer contact edges (23),

    - the body (2) is cooled,

    - the projectile body (2) and the base (5) are assembled.
12. A production process according to Claim 11, characterised in that the various segments (3) are made in a single operation by casting and are joined together in a star shape by their tips.

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