EP0949224A1 - Process for making an object from granular material and an igniter tube and propellant charge obtained by such a process - Google Patents

Abstract

An object is produced by pouring a liquid binder onto coarse granules (16) in a mold (2) and removing excess binder by suction. An object is produced from coarse granules (e.g. of ≥ 0.1 mm size) by pouring a liquid binder onto the granules (16) in a mold (2) having an evacuation opening (6) of size less than that of the granules, through which excess binder is withdrawn by suction (11). Independent claims are also included for: (i) an ignition tube, especially for artillery munitions, produced by the above process; and (ii) a propellant charge, especially for artillery munitions, produced by the above process.

Description

The technical field of the invention is that of methods of making objects from a material granular and in particular methods of manufacturing objects in energetic materials.

It is known from patent EP754927 to produce a tube igniter for an artillery propellant charge which includes several layers of black powder granulometry grains strong (greater than or equal to 0.1 mm) agglomerated with a binder.

This document also describes a method of making of such an igniter tube, process in which a binder layer such as collodion on an interior wall of a tubular support, then we distribute on this binder grains of black powder so as to achieve a first layer. We repeat the operations of removing binder and black powder to obtain the desired tube.

This process has the disadvantage of being too slow to authorize manufacturing on an industrial scale. Moreover it does not sufficiently control the thickness of the black powder deposit, so the ignition properties of the tube igniter. Finally the mechanical characteristics of this tube are insufficient and the use of a support tubular is essential when it risks disturbing combustion of the igniter.

We also know, especially by GB888858 patents and US3926697, a method for manufacturing propellants for rockets or missiles, process in which the propellant powder in a mold then a binder is introduced under pressure at a lower part of the mold.

The binder progresses to the upper part of the mold and ensures the coating of the powder grains without leaving remain of air bubbles or porosities.

This process is well suited for making blocks propellants for propellants for which it is essential to avoid porosities which cause random modifications of the combustion regime therefore disruption of propulsive performance or even regime change that could lead to the detonation of the loading.

It is however unsuitable for making a tube igniter since for such a component we seek to contrary to obtaining a certain porosity which allows facilitate the radial diffusion of the flame produced by the igniter tube.

In addition with such a method, the compression of grains of pyrotechnic composition may cause grain breaks, settlements or even segregation particle size along the mold height which will lead to degraded ignition performance and decreased reliability.

Finally, we know, in particular from patent WO8601584, ignition charge which consists of a stack of annular tablets of compressed black powder. Each tablet is produced by compression which requires the use of a powder of small particle size (less than 0.1mm) to obtain cohesion and hold correct mechanics. However, an ignition signal must have an application time to be effective long enough. We know that when the composition is compacted or compressed, the reaction is lively but has a much too short duration, which harms the effectiveness of such an igniter.

In addition the density of the annular pellets is too important which leads to incorporating spacers in combustible material between the pellets to respect a functional mass ratio between ignition charge and propellant charge.

We also know for example from patent EP306616 an artillery propellant charge consisting of a combustible envelope inside which is disposed a load of loose powder. The charge is initiated by an extruded igniter tube formed of a tube of a composition energy glued to a support tube.

The downside to bulk loads is that the porosity of the propellant charge is not evenly distributed homogeneously. Pressure waves can result in the weapon chamber that disrupt ballistics interior of the projectile. In addition the structure of such propellant charge module is complex and expensive to achieve. Indeed it requires on the one hand the realization a combustible envelope which also ensures mechanical of the module and secondly that of an igniter tube. Then it is necessary to ensure the assembly of the envelope and tube as well as powder loading.

We also know propellant charges agglomerates in which the grains of powder are coated with a binder then the whole is compressed to ensure the holding of the loading. Such a method of making a load does not not allow to control the porosity of the load obtained, the more it requires the establishment of a coating step for grains of powder which complicates the process and increases its cost of implementation.

It is the object of the invention to propose a method of manufacturing an igniter tube or propellant charge does not with no such disadvantages.

The method according to the invention also makes it possible to carry out easily and quickly all types of material objects granular, whether these materials are energetic or inert.

The method according to the invention makes it possible in particular to carry out at low cost a propellant charge module or a block of energetic material (for example gas generator) whose porosity is uniform and evenly distributed. This module can advantageously and thanks to the method according to the invention also include an igniter tube integral with the block propellant or energetic.

The process according to the invention is particularly economical since it uses neither cooking nor compression. It allows to obtain objects of shapes complex, even devoid of rotation symmetry, objects can also include inserts and / or combine several layers of materials of different natures.

The method according to the invention also makes it possible, equivalent ignition performance, saving material first used to make an igniter tube. Besides the resulting cost reduction, such savings also reduces the fouling of weapon tubes.

It is also the aim of the invention to propose a igniter tube and propellant charge produced by process according to the invention, tube and load easy to carry out industrially while having (concerning the igniter tube) improved ignition properties compared to tubes known.

• on met en place le ou les matériaux granulaires dans un moule aux dimensions de l'objet à réaliser et comportant au moins une ouverture d'évacuation, ouverture de dimensions inférieures à la granulométrie du matériau,
• on verse dans le moule un liant en phase liquide,
• on fait diffuser le liant entre les grains de matériau et on évacue le trop plein de liant au travers de l'ouverture d'évacuation à l'aide de moyens d'aspiration.

Thus, the subject of the invention is a process for manufacturing an object from at least one granular material with a large particle size, for example greater than or equal to 0.1 mm, a process characterized by the following steps:

• the granular material or materials are placed in a mold with the dimensions of the object to be produced and comprising at least one discharge opening, opening of dimensions smaller than the particle size of the material,
• a binder in the liquid phase is poured into the mold,
• the binder is made to diffuse between the grains of material and the overflow of binder is removed through the discharge opening using suction means.

According to an essential characteristic of the invention, the granular material comprises at least one energetic material such as propellant powder, explosive, black powder or a pyrotechnic composition.

The binder may be a solid binder dissolved in a solvent.

The solid binder may in particular be chosen from among the following compounds: polyvinyl nitrate, nitrocellulose, rubber, polyvinyl chloride or its copolymer, acetate polyvinyl or its copolymer, copolymer of chlorofluoroethylene.

The binder may be a polymerizable liquid binder and will then proceed, after diffusion of the solvent at a stage of polymerization of the binder.

The polymerizable binder can thus be chosen from among the following compounds: polybutadiene, polyurethane, resin acrylic, polyester resin, epoxy resin.

According to a particular embodiment of the invention, we can have in the mold at least one insert for be included or in solidarity with the object produced.

The insert may consist of a protective film intended to coat the object.

When the process is carried out with at least one energetic material, at least one insert can be consisting of an energetic material ignition cord.

According to another particular embodiment, at least an insert could be constituted by another object obtained by the method according to the invention.

According to another embodiment, at least one insert could be constituted by a wire crossing the object.

According to a variant of the method according to the invention, will place at least two materials in the mold granular before pouring the binder.

The different granular materials can be arranged in the form of successive horizontal layers.

The different granular materials can be arranged in the form of successive vertical layers, means being provided to at least temporarily isolate the different layers from each other when setting places materials in the mold.

Advantageously, the mold may be coated with a non-stick material.

The subject of the invention is also an igniter tube, especially for artillery ammunition, produced by such process.

This igniter tube may in particular comprise a body tubular formed by stacking at least two layers annulars of pyrotechnic materials of natures different.

In this case and according to a particular example, at least one layer may be formed by a composition combining Boron and potassium nitrate and another layer may be constituted by a composition associating Aluminum and Oxide of copper (CuO).

More specifically, the igniter tube may be formed by stacking of a first annular layer combining: Boron (5% to 35% by mass), Potassium nitrate (65% to 95% in mass), Nitrocellulose (0.5% to 5% by mass), and a second annular layer combining: Aluminum (5% to 35% in mass), Copper oxide (CuO) (65% to 95% by mass).

Or the first annular layer may have for composition: Boron (19% by mass), Potassium nitrate (80% by mass), Nitrocellulose (1% by mass), and the second annular layer have for composition: Aluminum (20% in mass), Copper oxide (CuO) (80% by mass).

According to a variant, from the two previous examples, the tube igniter may include a third annular layer combining: Boron (65% to 95% by mass), Potassium nitrate (5% to 25% by mass), Nitrocellulose (1% to 10% by mass).

Or, the composition of the third layer annular may be: Boron (80% by mass), Nitrate of potassium (14% by mass), Nitrocellulose (6% by mass).

According to another embodiment, the igniter tube according to the invention may include a tubular body formed at least two concentric cylindrical layers of pyrotechnic materials of a different nature.

As a particular example, the igniter tube may have an internal layer combining: Boron (5% to 35% in mass), Potassium nitrate (65% to 95% by mass), Nitrocellulose (0.5% to 5% by mass), and an outer layer combining: Boron (15% to 35% by mass), Potassium nitrate (65% to 85% by mass).

Also as an example, the igniter tube may have an internal layer combining: Boron (19% by mass), Potassium nitrate (80% by mass), Nitrocellulose (1% by mass), and an outer layer combining: Boron (25% in mass), Potassium nitrate (75% by mass).

According to another example, the igniter tube will include a internal layer combining: Boron (5% to 25% by mass), Nitrate potassium (65% to 85% by mass), collodion (0.5% to 8% in mass), and an outer layer combining: Boron (5% to 25% in mass), Potassium nitrate (65% to 85% by mass), chloride polyvinyl (0.5% to 8% by mass).

According to another example, the internal layer will associate: Boron (19% by mass), Potassium nitrate (76% by mass), collodion (5% by mass), and the outer layer will combine: Boron (19% by mass), Potassium nitrate (76% by mass), polyvinyl chloride (5% by mass).

According to another embodiment of the invention, the igniter tube may include at least one composition wire pyrotechnic extending over substantially its entire length.

The pyrotechnic composition of the wire may combine: Magnesium (45% to 65% by mass), polytetrafluoroethylene (20% to 40% by mass), chlorofluoroethylene copolymer (5% to 25% en masse).

Alternatively, the pyrotechnic composition of the wire may combine: Magnesium (54% by mass), polytetrafluoroethylene (30% by mass), copolymer of chlorofluoroethylene (16% by mass).

The invention finally relates to a propellant charge in particular for ammunition produced by such a process.

This propellant charge will for example include a body tubular formed of at least two annular layers of pyrotechnic materials of a different nature, one layer external agglomerated propellant powder and an internal layer made of an ignition material.

• la figure 1 est une vue schématique en coupe d'un outillage mis en oeuvre avec le procédé selon l'invention,
• la figure 2 représente plusieurs étapes successives du procédé selon l'invention,
• les figures 3, 4 et 5 sont des représentations en coupes longitudinales de trois modes de réalisation de tubes allumeurs selon l'invention,
• la figure 6 est une vue en coupe d'un premier outillage mis en oeuvre pour réaliser le tube allumeur selon la figure 5,
• la figure 7 est une vue en coupe d'un deuxième outillage mis en oeuvre pour réaliser le tube allumeur selon la figure 5,
• la figure 8 est une vue en coupe d'un troisième outillage permettant l'inclusion d'inserts,
• la figure 9a est une vue en coupe d'un quatrième outillage permettant la réalisation d'inserts,
• la figure 9b est une vue en perspective d'un tube allumeur réalisé avec l'outillage selon la figure 9a.
• la figure 10 est une vue en coupe longitudinale d'une charge propulsive selon l'invention.

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

• FIG. 1 is a schematic sectional view of a tool used with the method according to the invention,
• FIG. 2 represents several successive stages of the method according to the invention,
• FIGS. 3, 4 and 5 are representations in longitudinal sections of three embodiments of igniter tubes according to the invention,
• FIG. 6 is a sectional view of a first tool used to produce the igniter tube according to FIG. 5,
• FIG. 7 is a sectional view of a second tool used to produce the igniter tube according to FIG. 5,
• FIG. 8 is a sectional view of a third tool allowing the inclusion of inserts,
• FIG. 9a is a sectional view of a fourth tool allowing the production of inserts,
• FIG. 9b is a perspective view of an igniter tube produced with the tool according to FIG. 9a.
• Figure 10 is a longitudinal sectional view of a propellant charge according to the invention.

Referring to Figure 1, a tool 1 required to the implementation of the method according to the invention comprises a mold 2, which here delimits an internal volume substantially cylindrical with axis 3, and whose internal cylindrical surface 4 is chosen equal to the desired diameter for the object to to manufacture.

The mold is closed at a lower end by a grid 5, which is constituted here by a plate perforated by holes 6 regularly distributed.

The holes will be chosen with a diameter less than the granulometry of a granular material which is intended for the manufacture of the object.

The mold 2, closed by the grid 5, is placed on a suction support 7 comprising a cavity 8. Means seals (not shown), such as seals, are arranged between the support 7 and the mold 8. The fixing of the support mold is secured by means of flanges (not represented).

The cavity 8 internal to the support 7 is connected by a opening 9 to a pipe 10, itself connected to a suction means 11 (such as a vacuum pump actuated by a electric motor). The discharge nozzle 12 of the pump 11 is connected to a recovery tank 13. A valve 14 will advantageously be placed on the line 10 between the pump 11 and cavity 7.

Mold 2, grid 5 and support 7 will be produced in materials chemically inert to the material granular and retaining good characteristics dimensional despite the constraints generated by aspiration. We will for example make these elements in Teflon (registered trademark for polytetra-fluorethylene), we could also make them in steel or polyamide 6-6 (more known under the registered trademark Nylon).

To facilitate demolding, the mold can be produced (as well as the possible nucleus (s)) made of a material non-stick (such as polytetra-fluorethylene or Teflon) or cover the walls of the mold with such a material non-stick. The surface finish will also be chosen sufficiently smooth to facilitate demolding.

Figure 2 shows this tool during the different steps for making an object 15, which is here a tube igniter for artillery ammunition.

During a first step A we put in place a material granular 16 in mold 2.

In the example described here, the mold 2 receives (before placing granular material) a cylindrical core 17 which is coaxial with mold 2 and made of non-stick material (or covered with such material). Means (no shown), for example holding spacers, ensure positioning of the coaxial core on the surface internal cylindrical 4 of the mold 2.

We also have a first film in the mold cylindrical 18 having the same diameter as the cylindrical surface internal 4 of the mold and a second cylindrical film 19 having same diameter as core 17. Films 18 and 19 are intended to be fixed respectively to the surface external cylindrical of the igniter tube and the surface internal cylindrical of its axial bore. They will ensure protection function of the igniter tube against humidity.

The granular material will have a large particle size, for example greater than or equal to 0.1 mm. Indeed a too small a grain size may prevent the diffusion of a binder between the grains of the material as will be specified further.

Here the material used is a black powder of particle size between 1.4 and 3.2 mm (PN3). It is dumped through a hopper 20.

When the mold is completely filled (end of step A), a binder 21 is poured into the mold in the liquid phase (step B). The binder is distributed by means of a container doser 22. Due to the particle size of the material 16, the binder 21 diffuses uniformly by gravity between the grains and wets all the granular material placed in the mold as well as the inserts formed by the protective films 18 and 19.

Simultaneously with this distribution of the binder, the suction means 11 which have the effect of part of accelerating the diffusion of the binder through the grid 5, and on the other hand to evacuate the excess of binder, which flows through holes 6 and is discharged to the recovery basin 13.

When the binder used is a solid binder dissolved in solvent, this suction operation also promotes drying the binder.

For the example described here, the binder used to coat grains of black powder is a nitrocellulose glue obtained by dissolving 13 g of nitrocellulosic powder in 100 cubic centimeters of a suitable solvent (e.g. a mixture of 60% by volume of ethyl acetate, of 15% by volume acetone, 10% by volume of ethanol and 15% by volume Butyl acetate).

With such a process it was possible to produce an igniter tube of 100 mm high and 24 mm in diameter, with a bore 17mm axial. The whole of phase B of dissemination and suction lasts less than 2 minutes.

After step B, the igniter tube is removed from the mold 15. The igniter tube may possibly be passed through oven to improve drying.

The method according to the invention has made it possible during these three steps to make an igniter tube 15 to the dimensions definitive desired and comprising, thanks to the core 17, a axial ignition channel 23 (see Figure 3). The process has also allowed to obtain an igniter tube carrying a film of protection 18.19 on each cylindrical surface. The films of protection being made integral with the tube thanks to the binder.

This igniter tube has a certain porosity due to the spontaneous arrangement of the grains during the placement of granular material. Distributing, like the proposes the invention, the binder by gravimetric diffusion and with a suction allows to distribute the quantity of binder just sufficient to agglomerate the grains, while maintaining the natural porosity of the unbound load.

The porosity can be adjusted by the choice of the particle size range of the material. So by way of example, for a particle size between 0.1 and 0.5 mm the porosity is about 40% and for a particle size between 0.3 and 0.8mm the porosity is around 60%.

We can also modify the porosity by associating with minus two materials with different particle sizes.

The porosity of the tube obtained in the previous example (ratio of vacuum volume to total volume) is around from 30 to 50% by volume (approximately 16 cm3 of vacuum for a volume 38 cm3).

The black powder igniter tube thus produced in the previous example has a density of around lg / cm3 (the density of the black powder is 1.76 g / cm3), its porosity is therefore about 40%. For exemple comparative, a classic igniter tube produced by the stack of rings of compressed black powder has a mass volume of 1.75 g / cm3 (and its porosity is less than 1%).

We carried out comparative shots on a simulation bench between an igniter tube obtained according to the process according to the invention (described above) and a similar igniter tube external dimensions and formed from the stack of 6 tablets black powder. We observed :

With a classic compressed black powder igniter tube (prior art), the appearance of the pressure rise signal (start of ignition) occurs 22 milliseconds after ignition tube initiation, maximum pressure appearing 24.55 milliseconds after initiation, i.e. effective ignition time of approximately 2.55 milliseconds.

With an igniter tube according to the invention, the rise in pressure appears 34 milliseconds after initiation, and the maximum pressure appears 38.28 milliseconds after initiation, i.e. an effective ignition duration of approximately 4.28 milliseconds.

In both cases the ignition is carried out with a temperature of about 1500 ° C and with reaction heat of the order of 450 cal / g. However, with the igniter tube according to the invention, this energy is applied during twice as long, better results ignition performance.

The progressiveness of the ignition is much better with the igniter according to the invention and such a result is due to the greater porosity of the igniter obtained according to the process according to the invention.

On the other hand, the total mass of the igniter according to the invention thus tested is 38 g while that of the black powder tablet igniter is 51 g. The igniter according to the invention therefore ensures better ignition while having a lower mass, which reduces costs, clogging of the barrel, and risks pyrotechnics during the storage and handling by reducing the amount of material active.

As a variant, other types of binders, whether pyrotechnically active or inert.

Liquid binders such as (non-exhaustive list): polyurethanes, acrylics, polyesters.

Binders formed from a solid compound dissolved in a suitable solvent, such as (non-exhaustive list): polyvinyl chloride (PVC), polyvinyl acetate (PVA), nitrocellulose or polyvinyl nitrate (NPV).

Certain binders may require a phase of polymerization to solidify (for example a resin polyurethane or epoxy). In this case we will proceed to the end from step B and before demolding to a crosslinking phase by heating. The durations and temperatures of such a phase heating will be chosen by the skilled person in depending on the characteristics of the binder used.

The method according to the invention also makes it possible to carry out other objects with controlled porosity than igniter tubes. Just give mold 2 the external geometric shape desired for the object. This form may or may not have a symmetry of revolution. We could for example have a mold whose internal volume has a rectangular section, or a mold whose section varies axially between the opening upper and grid 5.

From an industrial point of view it is possible to define a mold comprising several parallel cylindrical cavities between them and therefore to simultaneously realize several tubes igniters.

The method according to the invention also makes it possible to carry out other types of igniter tubes.

FIG. 4 thus shows an igniter tube 15 having also a generally cylindrical shape and an axial channel 23. This igniter tube is formed by the stack of several annular layers 15a, 15b and 15c, the compositions are different.

• la couche 15a avec une composition associant Bore, Nitrate de potassium et de la nitrocellulose comme liant (B/KNO3/NC), cette composition permet de délivrer des produits de réaction gazeux et condensables favorisant un allumage convectif,
• la couche 15b avec une composition associant Aluminium et Oxyde de cuivre (Al/CuO), composition qui permet de délivrer des produits de réaction essentiellement condensés ayant une température de réaction supérieure à 3200 °K, favorisant ainsi un allumage radiatif,
• la couche 15c avec une autre composition associant Bore, Nitrate de Potassium et nitrocellulose. Cette composition permet de délivrer des produits de réaction gazeux et condensables, mais elle sera formulée de façon à avoir une vitesse de réaction plus grande que celle décrite pour la couche 15a. Un tel allumeur permet de maítriser la fonction d'allumage en délivrant des produits de réaction spécifiques.

We can thus achieve:

• layer 15a with a composition combining boron, potassium nitrate and nitrocellulose as a binder (B / KNO3 / NC), this composition makes it possible to deliver gaseous and condensable reaction products favoring a convective ignition,
• layer 15b with a composition combining aluminum and copper oxide (Al / CuO), a composition which makes it possible to deliver essentially condensed reaction products having a reaction temperature above 3200 ° K, thus promoting radiative ignition,
• layer 15c with another composition combining boron, potassium nitrate and nitrocellulose. This composition makes it possible to deliver gaseous and condensable reaction products, but it will be formulated so as to have a reaction rate greater than that described for layer 15a. Such an igniter makes it possible to control the ignition function by delivering specific reaction products.

This is particularly useful in the case of switching on the composite powders that require ignition materials complex because they are both sensitive to ignition convective and radiative ignition.

The complex igniter tube thus produced will again have porosity characteristics that the process according to the invention allows to master.

1. couche 15a

Bore : 5% à 35% en masse (de préférence 19%),

Nitrate de potassium: 65% à 95% en masse (de préférence 80%),

Nitrocellulose : 0,5% à 5% en masse (de préférence 1%).

2. couche 15b

Aluminium : 5% à 35% en masse (de préférence 20%),

Oxyde de cuivre (CuO): 65% à 95% en masse (de préférence 80%).

3. couche 15c

Bore : 65% à 95% en masse (de préférence 80%),

Nitrate de potassium: 5% à 25% en masse (de préférence 14%),

Nitrocellulose : 1% à 10% en masse (de préférence 6%).

By way of example, the following compositions can be combined:

1. layer 15a

Boron: 5% to 35% by mass (preferably 19%),

Potassium nitrate: 65% to 95% by mass (preferably 80%),

Nitrocellulose: 0.5% to 5% by mass (preferably 1%).

2. layer 15b

Aluminum: 5% to 35% by mass (preferably 20%),

Copper oxide (CuO): 65% to 95% by mass (preferably 80%).

3. layer 15c

Boron: 65% to 95% by mass (preferably 80%),

Potassium nitrate: 5% to 25% by mass (preferably 14%),

Nitrocellulose: 1% to 10% by mass (preferably 6%).

This igniter tube can easily and inexpensively be carried out with the method according to the invention.

It suffices to provide several different hoppers 20, each hopper bringing the quantity of material necessary for making a single annular layer.

The granular material is thus placed in the mold (step A) by several successive fillings of way to make the different layers. The binder is then poured into the mold in a single step B. It ensures the wetting of all the grains whatever their nature which will allow an intimate solidarity of each of the layers. This gives an igniter tube complex but having a mechanical behavior similar to that of a homogeneous igniter tube.

It is also possible to make an igniter tube formed by the stack of two layers: a layer 15a and a layer 15b with the compositions given above for these two layers (15a: B / KNO3 / NC, 15b: AlCuO).

FIG. 5 shows another type of igniter tube 15 which also has a generally cylindrical shape and a axial channel 23. This igniter tube consists of two concentric cylindrical layers 150a and 150b whose compositions are different.

It will thus be possible to produce the internal layer 150a with a composition Boron / Potassium Nitrate (B / KNO3) formulated from so as to have a reaction speed close to 15 mm / s. This layer provides a transmission time of the reaction over the entire length of the igniter tube relatively short (axial progression of the reaction). The outer layer 150b will be produced with a composition B / KNO3 formulated with so as to have a reaction speed close to 8 mm / s. This layer promotes ignition of the propellant charge ammunition in the vicinity of its grains (radial ignition).

1.couche interne 150a

Bore : 5% à 35% en masse (de préférence 19%),

Nitrate de potassium: 65% à 95% en masse (de préférence 80%),

Nitrocellulose : 0,5% à 5% en masse (de préférence 1%).

2. couche externe 150b

Bore : 15% à 35% en masse (de préférence 25%),

Nitrate de potassium: 65% à 85% en masse (de préférence 75%).

We could for example associate:

1.internal layer 150a

Boron: 5% to 35% by mass (preferably 19%),

Potassium nitrate: 65% to 95% by mass (preferably 80%),

Nitrocellulose: 0.5% to 5% by mass (preferably 1%).

2. 150b outer layer

Boron: 15% to 35% by mass (preferably 25%),

Potassium nitrate: 65% to 85% by mass (preferably 75%).

Figure 6 shows a first tool for make such an igniter tube.

To simplify the drawing, the tool is shown here configured so as to produce an igniter tube not comprising than two concentric cylindrical layers.

In addition, the suction means (11) and the support suction (7) on which the mold is fixed so waterproof are not shown. These means are identical to those described with reference to Figures 1 and 2 which can refer.

The mold 2 receives as in the embodiment according to Figure 2 an axial core 17. An intermediate screen tubular 24 is arranged coaxially with the core 17 and the internal cylindrical surface 4 of the mold 2. Means of support (not shown), for example spacers, will ensure the positioning of the core 17 and the screen 24 coaxially with the cylindrical surface 4.

The screen 24 has the function of materializing the separation between two concentric cylindrical layers of the tube igniter. It will be constituted for example by a sheet of paper or thin cardboard (a few hundredths of a mm thick).

A first hopper 20a will ensure the filling of the annular space between the core 17 and the screen 24 at using a first granular material 16a.

A second hopper 20b will ensure (simultaneously or no) filling the annular space between the screen 24 and the cylindrical surface 4 of the mold by means of a second granular material 16b.

Once the two materials are in place in the mold, screen 24 can be removed before filling with the binder.

The binder will evenly coat and secure all grains of granular materials and will ensure in the same time the joining of the two annular layers.

It is of course possible to make an igniter tube comprising more than two coaxial cylindrical layers in having several concentric screens and pouring into each annular space arranged between two consecutive screens a different granular material.

Alternatively, screen 24 can be made in one energetic or combustible material (nitrofilm) that will remain in place between the two layers.

It will then be necessary to pour the share binder and on the other side of the screen 24 in order to ensure that the grains constituting each cylindrical layer of the tube igniter. The binder will also ensure the joining of each layer with the screen, so the joining of different layers between them.

This variant ensures mechanical properties more important, in particular improves the holding of the tube shock igniter.

Figure 7 shows part of a second tool making it possible to produce an igniter tube according to FIG. 5.

Again, the suction means have not been shown (11) and the suction support (7) on which the mold tightly. These means are identical to those described with reference to Figures 1 and 2 which we can report to.

The tools used here include two molds, one first (not shown) intended to perform a first annular layer 150a of the igniter tube, and a second (shown in Figure 7) for performing a second annular layer 150b around this first layer.

The tool shown in Figure 7 is actually similar to that described with reference to FIGS. 1 and 2. It differs therefrom in that the core 17 is replaced by a cylindrical layer annular 150a of a first agglomerated granular material thanks to the process according to the invention and in another mold (not shown) whose internal cylindrical surface is equal to the external diameter of this first layer.

The second granular material 16b is poured through the hopper 20b in the annular volume separating the layer 150a and the cylindrical surface 4 of the second mold.

Once this volume is filled, we put in place the binder which will both secure the grains of the material granular and the bond of the second annular layer 150b thus produced with the first annular layer 150a.

Again the igniter tube thus produced will have porosity characteristics that the process according to the invention allows to master.

We can use the same binder to make each annular layer of this igniter tube.

We can also use a specific binder each of the layers.

We could for example make an outer layer combining Boron, Potassium Nitrate and agglomerated with a inert binder such as polyvinyl chloride (PVC). We create an internal layer combining Boron, Nitrate Potassium and agglomerated by a collodion. The interest of this variant is again to be able to confer a speed of faster axial spread of ignition at the central part of the tube, the peripheral layer having a lower speed allowing a radial ignition of the propellant charge of the ammunition.

1. couche externe

Bore : 5% à 25% en masse (de préférence 19%),

Nitrate de potassium: 65% à 85% en masse (de préférence 76%),

chlorure de polyvinyle (PVC) : 0,5% à 8% en masse (de préférence 5%).

2. couche interne

Bore : 5% à 25% en masse (de préférence 19%),

Nitrate de potassium: 65% à 85% en masse (de préférence 76%),

collodion : 0,5% à 8% en masse (de préférence 5%).

We will associate for example:

1. outer layer

Boron: 5% to 25% by mass (preferably 19%),

Potassium nitrate: 65% to 85% by mass (preferably 76%),

polyvinyl chloride (PVC): 0.5% to 8% by mass (preferably 5%).

2. inner layer

Boron: 5% to 25% by mass (preferably 19%),

Potassium nitrate: 65% to 85% by mass (preferably 76%),

collodion: 0.5% to 8% by mass (preferably 5%).

It is of course possible to repeat the operation with one or more other molds of suitable dimensions for make an igniter tube with more than two layers coaxial cylindrical.

Another advantage of the process according to the invention is that it allows you to make objects of various shapes and with inserts.

We saw previously that it was thus possible during of manufacturing to make one or more protective films integral with the igniter tube produced (Figures 2 and 3), or again to drown a screen 24 between two layers of material granular.

Figure 8 shows a third tool set up for allow the incorporation of other types of inserts into a igniter tube.

The mold 2 is always closed at its lower part by a grid formed by a plate 5 pierced with holes 6.

Again, the suction means have not been shown (11) and the suction support (7) on which the mold tightly. These means are identical to those described with reference to Figures 1 and 2 which we can report to.

The mold is also closed at the level of its part. upper by a cover 25, fixed to the mold 2 by means (not shown), and carrying an orifice filling 26 intended to allow the material to pass granular 16.

Threads of pyrotechnic composition 27 are stretched between cover 25 and plate 5. They are regularly angularly distributed around the surface axis mold 4 of mold 2.

These wires pass through cover and plate through holes and they are immobilized in translation by means suitable, e.g. locking screws 28 screwed into the cover or plate and each pinching a wire.

The threads will for example be threads of a composition combining Magnesium, polytetrafluoroethylene (known as registered trademark Teflon), chlorofluoroethylene copolymer (known under the trademark Viton). We can place 5 wires 2 mm in diameter distributed over a crown.

Magnésium : 45% à 65% en masse (de préférence 54%),

polytétrafluoréthylène : 20% à 40% en masse (de préférence 30%),

copolymère de chlorofluoroéthylène : 5% à 25% en masse (de préférence 16%).

The wires can be made according to the following composition:

Magnesium: 45% to 65% by mass (preferably 54%),

polytetrafluoroethylene: 20% to 40% by mass (preferably 30%),

chlorofluoroethylene copolymer: 5% to 25% by mass (preferably 16%).

With the tools produced here, the cover 25 maintains also an ignition cord 29 such as an explosion-proof cord one end of which is fixed to the grid 5 by means suitable, for example by clipping onto a clamp 30 carried by grid 5.

The ignition cord is thus coaxial on the surface cylindrical 4 of the mold 2 and it extends longitudinally over the full height of the mold.

To implement the tooling according to FIG. 8, we starts by fixing the cover 25 and the grid 5 to the mold 2 carrying the wires 27 and the cord 29. Then we put in place the granular material 16 through the orifice 26. Finally, when the mold is filled, we pour a binder which will ensure the joining of the different grains of the material granular as well as inserts 27 and 29.

Before demolding, the wire retaining screws are dismantled and we possibly shorten these so that they don't not come out of the igniter tube made.

The function of the wires is to relay the ignition within of the material. The function of these wires is therefore different from those of known wires which are inserted inside the blocks of propellant charge (see for example the patents US3205286 and FR2640259). Known threads have the function of modifying the propagation speed of the combustion front of the block therefore to regulate the combustion regime of this one.

With the igniter tube according to the invention, the wire is made of an ignition material and it relays to both radially and axially the ignition reaction. We thus ensures better ignition performance whatever are the dimensions (axial and radial) of the igniter tube.

In particular, the igniter tube described above allows a multi-point ignition of the material of the igniter tube from a single axial ignition which is given for example by the ignition cord 29. The latter may be a commercial component, for example a cord ITLX (registered trademark).

Figure 9a shows a fourth tool more particularly suitable for making an igniter tube 15 (see Figure 9b) bearing at the level of a lower part a threaded fixing ring 31, for example metallic, and which will facilitate the mounting of the igniter tube on a artillery ammunition base (not shown).

The mold 2 carries a cover 25 fixed to its part upper and a grid 5 linked to its lower part. Of sealing means (not shown) are arranged between the cover and mold.

This tool comprises a cylindrical internal case 32 and an external case 33, also cylindrical and coaxial with the case internal. The two cases are held coaxial by means (not shown), for example spacers integral with the cover 25 of the mold and / or the grid 5.

The cases 32 and 33 are pierced with radial holes 34 of which the diameter is less than the particle size of the material granular which must be implemented.

The outer case 33 has an inner diameter equal to the diameter external wished for the igniter tube and which is also the external diameter of the threaded ring 31.

The threaded ring 31 is positioned in the mold 2 before placement of granular material. It is supported by grid 5 and has a circular flange 31a on which applies the end of the case 33.

The threaded ring is pierced with an axial bore 35 which is equal to the external diameter of the internal case 32.

Finally the ring 31 has an internal radial bead 36 which is intended to allow the joining of the ring and of the igniter tube material.

The granular material 16 is placed by means of the hopper 20 and through hole 26 in space ring separating the cases 32 and 33. Then pour a binder in this same annular space.

The ring 31 occupying the bottom of the annular space, it closes the holes 6 of the grid 5 which are at the bottom of this space.

The suction means are not shown here but are connected as in Figures 1 and 2 to a support on which is positioned in a sealed manner.

Thanks to the holes 6 of the grid 5, the means suction create a depression in the annular space separating the external surface of the case 33 and the surface cylindrical 4 of the mold 2. They also create a depression in the axial cavity internal to the case 32.

Thus the excess of binder is eliminated through radial holes 34 which pass through each case.

As a variant it is possible to replace the case outer 33 by the cylindrical wall 4 of the mold 2. This wall may or may not be pierced with holes to remove the binder.

If the cylindrical wall 4 of the mold is not pierced, the evacuation of the binder will only be done through the case internal 32.

If the cylindrical wall 4 of the mold is pierced with holes to remove the binder, surround the mold with a sleeve allowing to exercise the suction caused by the vacuum 11 all along the external surface of the mold. In this case we can replace the internal case 32 with a solid core, the evacuation of the binder then taking place only through the cylindrical wall 4.

It is of course possible to combine tools described above so as to produce an igniter tube including a threaded fixing ring and several layers (stacked ring or concentric cylindrical) of granular materials of different natures.

It is also possible to insert wires longitudinal or an ignition cord in a tube formed of several layers.

Figure 10 shows another type of object that can be carried out with the method according to the invention. This object is a propellant charge module 37 for ammunition artillery.

The module conventionally comprises a channel axial ignition 38. It consists of two layers in granular materials of different natures and agglomerated by means of a binder (for example polyvinyl nitrate or any other binder described with reference to the previous examples). A inner layer 39 of an ignition composition for example of black powder and an outer layer of propellant charge for example a powder B or GB.

The inner layer can advantageously be produced alone with a mold of the appropriate dimensions (such as that in Figure 2). Then place this layer as a core in a another mold (such as that of FIG. 7) to make the complete propellant charge module.

Thanks to the invention, the distribution of the porosity of the module is controlled and the mechanical strength of the module is insured even in the absence of an external envelope. It results, with lower cost, better reproducibility ballistic performances. In addition, the process according to the invention makes it possible in a simple way to make the igniter tube and propellant charge.

We can adjust the porosity of the load by modifying the arrangement of the propellant powder grains. We will be able to thus achieve a less porous load by arranging in mold a bundle of sprigs of powder in place of grains loose. We can also achieve a less porous load by combining at least two types of particle size different grains of powder.

We can also integrate an igniter tube according to the invention axially within a propellant charge of a propellant charge container as known in the art anterior (loose powder in a cylindrical case combustible).

The igniter tube according to the invention then provides a better ignition since it allows the removal of any barrier (such as known combustible tubes) between the ignition composition and propellant powder.

The invention can also be implemented for realize other types of objects (energetic or not) in which we will seek to control the distribution of porosity, for example blocks of composition generating gases, whether or not integral with their ignition composition.

Claims (32)

Method for manufacturing an object from at least one granular material with a large particle size, for example greater than or equal to 0.1 mm, characterized by the following steps: the granular material or materials (16) are placed in a mold (2) with the dimensions of the object to be produced and comprising at least one discharge opening (6), opening of dimensions smaller than the particle size of the material, a binder (21) is poured into the mold in the liquid phase, the binder is made to diffuse between the grains of material and the excess of binder is discharged through the discharge opening using suction means (11). Method according to claim 1 characterized in that the granular material comprises at least one material energetic such as a propellant powder, an explosive, black powder or a pyrotechnic composition. Method according to one of claims 1 or 2, characterized in that the binder is a dissolved solid binder in a solvent. Method according to claim 3, characterized in that the binder is chosen from the following compounds: polyvinyl nitrate, nitrocellulose, rubber, polyvinyl chloride or its copolymer, polyvinyl acetate or its copolymer, chlorofluoroethylene copolymer. Method according to one of claims 1 or 2, characterized in that the binder is a liquid binder polymerizable and in that one proceeds after diffusion of the solvent in a polymerization step of the binder. Method according to claim 5, characterized in that the binder is chosen from the following compounds: polybutadiene, polyurethane, acrylic resin, polyester resin, epoxy resin. Method according to one of claims 1 to 6 characterized in that there is at least one insert in the mold intended to be included or integral with the object produced. Method according to claim 7, characterized in that at least one insert is formed by a protective film (18) intended to coat the object. Method according to one of claims 7 or 8 and implemented work with at least one energetic material, characterized in that at least one insert is constituted by a cord ignition (29) of the energetic material. Method according to one of Claims 7 to 9, characterized in that at least one insert is constituted by a another object obtained by the process according to the invention. Method according to one of claims 7 to 10, characterized in that at least one insert is constituted by a wire (27) passing through the object. Method according to one of claims 1 to 11, characterized in that the mold is placed in the at least two different granular materials before pouring the binder. Method according to claim 12 characterized in that that the different granular materials are arranged under form of successive horizontal layers. Method according to claim 12 characterized in that that the different granular materials are arranged under form of successive vertical layers, means being provided for at least temporarily isolating the different layers of each other when setting up materials in the mold. Method according to one of claims 1 to 14 characterized in that the mold is coated with an anti material adherent. Igniter tube, especially for artillery ammunition, characterized in that it is produced by the method according to a of claims 1 to 15. Igniter tube according to claim 16, characterized in that it comprises a tubular body formed of the stack at least two annular layers of material pyrotechnics of different natures. Igniter tube according to claim 17, characterized in that at least one layer is constituted by a composition combining boron and potassium nitrate and a other layer is made up of a composition combining Aluminum and copper oxide (CuO). Igniter tube according to claim 18, characterized in that it comprises a first layer combining: Boron: 5% to 35% by mass, Potassium nitrate: 65% to 95% by mass, Nitrocellulose: 0.5% to 5% by mass, and a second layer combining: Aluminum: 5% to 35% by mass, Copper oxide (CuO): 65% to 95% by mass. Igniter tube according to claim 19, characterized in that the first layer has the composition: Boron: 19% by mass, Potassium nitrate: 80% by mass, Nitrocellulose: 1% by mass, and the second layer has for composition: Aluminum: 20% by mass, Copper oxide (CuO): 80% by mass. Igniter tube according to one of claims 19 or 20, characterized in that it comprises a third layer combining: Boron: 65% to 95% by mass, Potassium nitrate: 5% to 25% by mass, Nitrocellulose: 1% to 10% by mass. Igniter tube according to claim 21, characterized in that the composition of the third layer is: Boron: 80% by mass, Potassium nitrate: 14% by mass, Nitrocellulose: 6% by mass. Igniter tube according to claim 16, characterized in that it comprises a tubular body formed of at least two concentric cylindrical layers of materials pyrotechnics of a different nature. Igniter tube according to claim 23, characterized in that it comprises an internal layer combining: Boron: 5% to 35% by mass, Potassium nitrate: 65% to 95% by mass, Nitrocellulose: 0.5% to 5% by mass, and an outer layer combining: Boron: 15% to 35% by mass, Potassium nitrate: 65% to 85% by mass. Igniter tube according to claim 24, characterized in that it comprises an internal layer combining: Boron: 19% by mass, Potassium nitrate: 80% by mass, Nitrocellulose: 1% by mass, and an outer layer combining: Boron: 25% by mass, Potassium nitrate: 75% by mass. Igniter tube according to claim 23, characterized in that it comprises an internal layer combining: Boron: 5% to 25% by mass, Potassium nitrate: 65% to 85% by mass, collodion: 0.5% to 8% by mass, and an outer layer combining: Boron: 5% to 25% by mass, Potassium nitrate: 65% to 85% by mass, polyvinyl chloride: 0.5% to 8% by mass. Igniter tube according to claim 26, characterized in that it comprises an internal layer combining: Boron: 19% by mass, Potassium nitrate: 76% by mass, collodion: 5% by mass, and an outer layer combining: Boron: 19% by mass, Potassium nitrate: 76% by mass, polyvinyl chloride: 5% by mass. Igniter tube according to one of Claims 16 to 27, characterized in that it comprises at least one wire of pyrotechnic composition spanning substantially all of its length. Igniter tube according to claim 28, characterized in that the pyrotechnic composition of the wire combines: Magnesium: 45% to 65% by mass, polytetrafluoroethylene: 20% to 40% by mass, chlorofluoroethylene copolymer: 5% to 25% by mass. Igniter tube according to claim 29, characterized in that the pyrotechnic composition of the wire combines: Magnesium: 54% by mass, polytetrafluoroethylene: 30% by mass, chlorofluoroethylene copolymer: 16% by mass. Propellant charge, in particular for characterized ammunition in that it is produced by the method according to one of claims 1 to 15. Propellant charge according to claim 31, characterized in that it comprises a tubular body formed at least two annular layers of material pyrotechnics of a different nature, an outer layer of agglomerated propellant powder and an inner layer in one ignition material.

Images