EP2426455A1 - Method for compressing an explosive material in the body of a projectile and tool for implementing such a method - Google Patents

Abstract

The method involves implementing a compression punch (14.1) for compressing an explosive material (18.1) in a military head or projectile body through a rear opening of the body. A punch guide (13.1) is interposed between the compression punch and the body. Length of the punch guide is defined such that the punch guide is in contact on a circular internal bead (12a) of the body or in immediate proximity of the internal bead, where internal diameter of the punch guide is lower or equal to diameter of the internal bead. An independent claim is also included for a tool for compressing an explosive material in a military head or projectile body through a rear opening of the body.

Description

The technical field of the invention is that of methods for compressing explosive materials in the projectile bodies as well as tools associated with such processes.

It is conventional to perform a loading of a projectile body by compression. This is more particularly used to carry out the projectiles of medium caliber (caliber between 20mm and 75mm) or to load military heads.

For larger shells, casting is the preferred method.

The advantage of explosive compression processes is that they allow the projectiles to be loaded relatively quickly. Indeed, the explosive is set up by dosing the material in the powdered and non-liquid state and it is not necessary, when the compression is carried out at ambient temperature, to carry out heat treatments for cooling the load such as the usual casting processes impose it.

With the known compression methods, the explosive material in powder form is compressed by means of a compression punch directly into the projectile body and through a rear opening of this body.

Such an operation is facilitated by the fact that the inner surface of the projectile bodies is generally cylindrical over substantially the entire height of the projectile. A compression punch can therefore be guided on part of the body of the projectile during compression.

However, it is sometimes necessary to make projectile bodies or military heads with circular inner beads more or less long, for example to strengthen the projectile body or give it particular fragmentation characteristics.

In this case it is no longer possible to load the explosive by compression and only the casting can completely fill the internal volume of the projectile body with the explosive material. Heat treatments or cooling cycles are then necessary to ensure the homogeneity of the loading (avoid the shrinkage).

The object of the invention is to propose a method, and the associated tooling, for compressively loading a projectile body or military head having one or more internal circular beads.

Thus, the subject of the invention is a method of compressing an explosive material in a projectile body or military head through a rear opening of this body, a method employing at least one compression punch, characterized in that the compression is carried out in several successive steps, each compression step being carried out by using a particular tooling associating a compression punch and a punch guide, guide interposed between the punch and the body, at minus a first punch guide having a defined length such that this guide can come into contact with an internal bead of the body or at least in the immediate vicinity of this bead, the internal diameter of the guide being less than or equal to the diameter of the bead .

It is advantageous to fix before each compression step a head at the end of the punch, head having a profile adapted to the internal profile of the body against which the compression is performed.

It may optionally provide at least a second guide, second guide longer than the first guide and thus to guide a compression punch beyond an inner bead.

The second guide may be disposed within the bore of the first guide.

The invention also relates to a tool for compressing an explosive material in a projectile body or military head through a rear opening of the body, a tool comprising a support for holding the body and at least one punch of compression mounted sliding relative to the support, tooling which is characterized in that it comprises at least one cylindrical guide for the sliding punch, guide interposed between the body and the punch, the guide having a length such that it can come into contact on an internal bead of the body or at least in the immediate vicinity of this bead, the inner diameter of the guide being less than or equal to the diameter of the bead.

This compression tooling may comprise a set of at least two punch guides of different lengths, the punch may also be equipped with at least two different compression heads.

The compression tool may comprise at least a second guide longer than the first guide and thus to guide a compression punch beyond the inner bead.

The second guide may be disposed within the bore of the first guide.

According to an alternative embodiment, the punch head may include an end shoulder for scraping the inner surface of the guide.

The punch may also include at least one circular groove behind the head.

• la figure 1 montre un exemple de réalisation du support de l'outillage selon l'invention, support sur lequel est positionné un corps de projectile,
• la figure 2 montre le même support après positionnement du guide ainsi que d'un poinçon de compression,
• les figures 3a, 3b et 3c montrent trois étapes successives du procédé de compression selon l'invention, et
• la figure 4 montre un autre mode de réalisation de l'outillage selon l'invention, mode dans lequel un deuxième guide est disposé dans le premier guide.

The invention will be better understood on reading the additional description which will follow of different embodiments, description made with reference to the accompanying drawings and in which:

• the figure 1 shows an exemplary embodiment of the support of the tool according to the invention, support on which is positioned a projectile body,
• the figure 2 shows the same support after positioning the guide as well as a compression punch,
• the figures 3a , 3b and 3c show three successive steps of the compression process according to the invention, and
• the figure 4 shows another embodiment of the tool according to the invention, wherein a second guide is disposed in the first guide.

Referring to the figure 1 , a compression tool 1 for an explosive material comprises a support 2 ensuring the maintenance of a body 3 of a projectile. This support 2 is secured to a frame (not shown) of a compression machine. The support 2 comprises a cylindrical bore 2a which receives the projectile body 3. The bore 2a is extended by a concave surface 4 which has a shape complementary to that of the nose 3a of the body 3. Thus the body 3 is firmly maintained by the support 2, both radially and axially.

The support 2 is capped at its rear by a sleeve 5 to which it is fixed by screws or radial pins 6. The sleeve has an internal counterbore 7 which constitutes a stop bearing against the rear 3b of the body 3 to level of the opening 8 of the latter. The positioning holes of the pins 6 in the support 2 are arranged on the tool so that when placing these pins 6, the countersink 7 is actually in abutment against the rear 3b of the body.

The sleeve 5 has an axial bore 9 which has the same diameter as the internal bore 3c of the projectile body 3. The axial bore 9 opens into an opening 10 of larger diameter and is threaded to receive a guide as will be described later.

The sleeve 5 finally carries radial vents 11 which allow the evacuation of air during the positioning of the sleeve 5 on the support 2.

We notice on the figure 1 that the body 3 of the projectile has a particular internal profile which here comprises two circular beads 12a, 12b. These beads 12a, 12b are intended to strengthen the structure of the body 3 of the projectile. They oppose against the passage of a compression punch of the explosive which would be the internal diameter of the bore 3c of the body 3.

Considering the figure 2 and according to an essential feature of the invention, a cylindrical tubular guide 13 is disposed in the bore 9 of the sleeve 5. This guide slides when it is placed on the bore 3c of the body 3 of the projectile up to come into contact on the first bead 12a or at least in the immediate vicinity of this bead.

The internal diameter of the bore 13a of the guide 13 is less than or equal to the inner diameter (d) of the bead 12a (here substantially equal). Thus, when a punch 14 is slid inside the guide 13, this punch no longer interferes with the bead 12a.

It has been specified "at least in the immediate vicinity of the bead". Indeed, depending on the sectional shape of the bead 12a (rectangular, trapezoidal or rounded) and taking into account that the guide 13 abuts against the sleeve 5, it is not always possible to bring the guide 13 in contact with the bead 12a. A reduced gap may therefore remain between the end of the guide and the bead.

What is important however is that the punch that slides inside the guide does not interfere with the bead and the length of the guide is sufficient to guide the punch during compression. The end of the guide must also be as close as possible to the bead to limit the risk of introducing explosive between guide and bead during loading.

The guide 13 is secured to the support 2 by means of the sleeve 5 and is interposed between the body 3 of the projectile and the punch 14. The guide 13 thus ensures the guiding of the punch 14 as usually done the body of the projectile when the latter is devoid of bulges. This avoids any risk of buckling of the punch and prevents the rise of the explosive material along the punch body 14.

We notice on the figure 2 that the guide 13 comprises an enlarged rear head 15 which is threaded and is housed in the tapping 10 of the sleeve 5. It is thus ensured a rigid positioning of the guide 13 relative to the assembly formed by the support 2 and the sleeve 5.

Punch 14 is attached at its back to the compression machine (not shown). The latter exerts a force on the punch 14 and the head 16 of the punch 14 is then applied against the explosive charge (not shown in this example). figure 2 ) to achieve its compression in the body 3.

We notice on the figure 2 that the head 16 of the punch 14 comprises a conical portion 16a which terminates in a spherical portion 16b. The shape of the end of the head 16 of the punch is defined so as to ensure a transfer of the axial compression force along non-axial directions towards the wall of the body 3.

Indeed, the compression force that the head 16 provides to the explosive material is oriented perpendicularly to the walls of the head 16.

The shape of the head 16 will therefore be chosen as a function of the maximum depth of penetration of the punch 14 inside the body 3 and in particular the distance maximum then separating the head 16 from the wall of the body 3.

We also notice on the figure 2 that the head 16 of the punch 14 has an end shoulder 16c in the form of a circular ring between the conical portion 16a and the cylindrical body of the punch 14.

This shoulder is a scraper for scraping the inner surface of the guide 13 during the advance of the punch. This scraping makes it possible to push towards the inside of the body 3 the explosive material which could be adhering to the inner wall 13a of the guide 13.

We also notice on the figure 2 that the punch 14 has a circular groove 17 behind the head 16. This groove 17 completes the scraper 16c and makes it possible to trap during the movement of the punch 14 the explosive material that may be on the inner cylindrical surface 13a of the guide 13.

The annular surfaces 17a and 17b delimiting the groove 17 are also scrapers which lead to the groove 17 the explosive material present on the cylindrical surface of the guide.

We can thus provide several circular grooves on the punch 14.

The compression method according to the invention will now be described with reference to figures 3a , 3b and 3c .

The figure 3a shows a first step of the method according to the invention.

Before placing the explosive is fixed a first guide 13.1 to the sleeve 5 by screwing. The first guide 13.1 is chosen with a length such that it can come into contact with the first inner bead 12a of the body 3 (or at least in the immediate vicinity of this bead).

A first volume 18.1 of an explosive material in the powdery state is then placed at the bottom of the body 3 of the projectile. The compressible explosives are well known to those skilled in the art. For example, the patent can be consulted FR2801883 which describes a compressible explosive. This explosive is introduced using a metering hopper (not shown) that is positioned in the guide 13.1.

A first punch 14.1 is then introduced into the guide 13.1. This punch is secured to a compression machine (not shown) which exerts on the punch 14.1 an effort F.

When the punch 14.1 is inserted, its scraper 16c will push towards the body 3 the explosive material that may be on the inner wall of the guide 13.1.

The head 16.1 of the punch 14.1 is then applied against the explosive charge to achieve its compression in the body 3. For this first compression step was chosen a head 16.1 having a conical profile at acute apex angle. The axial compression force F will be decomposed into compression forces along directions G perpendicular to the cone walls of the head 16.1. The shape of the head 16.1 will thus ensure compression forces well distributed around the punch 14.1 and to the inner wall of the body 3.

By reaction, the compressive force exerted on the first volume of explosive material 18.1 will also cause it to rise along the punch 14.1 to the first bead 12a (annular zone 18a).

Those skilled in the art will define the geometry of the head 16.1 according to the dimensions of the body 3 and the maximum depth of penetration of the punch 14.1.

The figure 3b shows a second step of the compression process according to the invention.

During this second step, there is disposed in the body 3 of the projectile a second guide 13.2 which is fixed in the same way as the previous one to the sleeve 5 but which is shorter than the first guide and is therefore no longer in abutment against the first bead 12a. This second guide is also the diameter of the bore of the body 3 and is therefore interposed between the punch 14.2 and the body 3.

In addition, a second punch 14.2 is used whose head 16.2 is different from the first head 16.1. This head 16.2 has a conical portion having an obtuse apex angle. Indeed, the second volume of compressed explosive material 18.2 is less for this second compression step and the compression forces must then be distributed either to the nose 3a of the body 3 but rather to the upper interface 18.1a of the first volume of explosive 18.1 tablet.

The second head 16.2 comprises (just like the first head 16.1) an annular scraper 16c.

The figure 3c finally shows a third step of the method according to the invention.

During this step we position a third guide 13.3 shorter than the second guide 13.2. This guide 13.3 is fixed in the same way as the two previous guides. It is also the diameter of the bore of the body 3 and is therefore interposed between a third punch 14.3 and the body 3.

The third punch 14.3 has a head 16.3 having a different profile. Here the profile of the head 16.3 is spherical. The bore of the body at the level of the third layer 18.3 of explosive material is indeed cylindrical without beads and the compression forces can be closer to the axial direction.

The profile of the head 16.3 of the punch 14.3 may change depending on the desired shape for the external surface of the explosive charge.

It can therefore be seen that, thanks to the invention, it is possible to conduct a compression of explosive material inside a projectile body (or military head) 3 comprising internal rolls, regardless of the dimensions of the beads 12a and 12b.

The guides 13.1, 13.2 and 13.3 make it possible to guiding the punches 14.1, 14.2 and 14.3 despite the presence of the beads. The guides also allow to channel the explosive. No interference between the punch and the bead is to be feared because the guide diameter of the punch in the guide is less than or equal to the diameter (d) of the bead.

The lengths of the guides, different from one stage to another, make it possible to progressively fill the body 3 of the projectile with the explosive.

Depending on the geometry of the body 3 and the number of beads 12a and 12b it will be possible to vary the number of guides and punches and the geometry of the heads of the punches.

We have thus previously described ( figure 3a ) a method in which it is sufficient, during the first compression step, to position the first guide directly in contact (or in the immediate vicinity) with the first bead 12a. This is possible if the distance between the end of the head 16.1 of the punch 14.1 and the bottom of the body 3 is not too large relative to the internal diameter of the body 3 (distance between 1 and 2 times the size).

When this distance is greater or the number of beads is greater, it may be necessary to bring the punch 14.1 further forward in the body 3.

The figure 4 shows thus another embodiment of the tool according to the invention, wherein a second guide 13.1b is disposed within the bore of the first guide 13.1a. To receive this second guide, the first guide comprises a tapping 19 arranged in the threaded rear head 15 of the first guide 13.1a.

The tapping 19 receives a threaded head 20 secured to the second guide 13.1b. Thus after mounting the two guides 13.1a and 13.1b are secured to one another as well as the sleeve 5.

The first guide 13.1a is positioned in contact (or in the immediate vicinity) with the first bead 12a. It has an internal bore whose diameter is equal to the inner diameter of the bead 12a. The second guide 13.1b has an outer diameter equal to the inner diameter of the first guide 13.1a. This second guide 13.1b is longer than the first guide 13.1a and extends here beyond the second inner bead 12b of the projectile body 3.

The compression punch 14.1 is guided by the second guide 13.1b beyond the first inner bead 12a and also beyond the second inner bead 12b.

With this embodiment, it is therefore possible to compress the explosive without being hindered by the presence of the internal beads.

After a first compression step in which the compressed explosive will go up to the second bead 12b, remove the second guide 13.1b and can proceed to a second explosive compression step with a punch which will then be guided directly by the first guide 13.1a.

The configuration of the tooling during this second stage is practically that of the figure 3a previously described. The subsequent steps will be similar to those described for figures 3b and 3c .

It can thus be seen that this second embodiment of the invention makes it possible to perform compressions in bodies of projectiles or military heads comprising a large number of beads and even adjacent beads of the front end of the body.

As a variant of this second embodiment, it would of course be possible to define a tool in which the guide used in the first step would be in one piece. We can then consider figure 4 considering that guides 13.1a and 13.1b are in the form of one and the same piece.

It will however be necessary to provide a guide in the form of the guide 13.1a for a subsequent compression step.

In all the previous embodiments it is possible to provide a tool in which there is no sleeve 5. The guides are then simply positioned in the projectile body.

Claims (10)

Method for compressing an explosive material (18.1) in a projectile body or head (3) through a rear opening of the body, which method comprises at least one compression punch (14, 14.1, 14.2 , 14.3), characterized in that the compression is carried out in several successive steps, each compression step being carried out using a particular tooling associating a compression punch (14, 14.1, 14.2, 14.3) and a guide Punching guide (13, 13.1, 13.2, 13.3) interposed between the punch (14, 14.1, 14.2, 14.3) and the body (3), at least one first punch guide (13.1) having a defined length of such that this guide can come into contact with an internal bead (12a) of the body (3) or at least in the immediate vicinity of this bead (12a), the internal diameter of the guide (13.1) being less than or equal to the diameter of the bead (12a). Compression method according to Claim 1, characterized in that a head (16, 16.1, 16.2, 16.3) is fixed before each compression step at the end of the punch (14, 14.1, 14.2, 14.3). profile adapted to the internal profile of the body (3) against which compression is achieved. Compression method according to one of Claims 1 or 2, characterized in that at least one second guide (13.1b) is provided, the second guide being longer than the first guide (13.1a) and thus enabling a compression punch ( 14.1) beyond an inner bead (2a). Compression method according to claim 3, characterized in that the second guide (13.1b) is disposed inside the bore of the first guide (13.1a). Tools for compressing an explosive material in a projectile body or head (3) through a rear opening (8) of this body (3), tooling comprising a support (2) for holding the body (3) and at least one compression punch (14) slidably mounted relative to the support, characterized in that it comprises at least one cylindrical guide (13, 13.1) for the sliding punch (14, 14.1), guide interposed between the body (3) and the punch (14, 14.1), a guide having a length such that it can come into contact with an internal bead (12a, 12b) of the body or at least in the immediate vicinity of this bead (12a, 12b), the inner diameter of the guide (13) being less than or equal to the diameter of the bead (12a, 12b). Tool for compressing an explosive material according to claim 5, characterized in that it comprises a set of at least two punch guides (13, 13.1, 13.2, 13.3) of different lengths, the punch (14, 14.1, 14.2, 14.3) can also be equipped with at least two different compression heads (16, 16.1, 16.2, 16.3). Tool for compressing an explosive material according to one of Claims 5 or 6, characterized in that it comprises at least one second guide (13.1b) longer than the first guide (13.1a) and thus making it possible to guide a punch of compression (14.1) beyond the inner bead (12a). Tool for compressing an explosive material according to claim 7, characterized in that the second guide (13.1b) is disposed inside the bore of the first guide (13.1a). Tool for compressing an explosive material according to one of claims 5 to 8, characterized in that the head (16) of the punch (14, 14.1, 14.2, 14.3) has an end shoulder (16c) allowing the scraping of the inner surface of the guide (13). Tool for compressing an explosive material according to one of Claims 5 to 9, characterized in that the punch (14, 14.1, 14.2, 14.3) has at least one circular groove (17) behind the head (16, 16.1, 16.2, 16.3).

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