WO2021144538A1

WO2021144538A1 - Igniter tube for a propellant charge

Info

Publication number: WO2021144538A1
Application number: PCT/FR2021/050066
Authority: WO
Inventors: Sébastien CUVELIER; Arnaud Fontaine; Romain LEGLISE; Serge Lecume
Original assignee: Eurenco
Priority date: 2020-01-17
Filing date: 2021-01-14
Publication date: 2021-07-22
Also published as: US20230100596A1; IL294747A; FR3106401A1; KR20230009356A; EP4090644A1

Abstract

The invention relates to an igniter tube consisting of a fuel tube, on the inner face of which an ignition charge is laid along the length of said fuel tube. The invention also relates to a method for producing the igniter tube.

Description

Igniter tube for propellant charging

Field of the invention

The technical field of the invention is that of igniter tubes for propellant charges having a central (cylindrical) channel.

State of the art

The propellant charges fitted to shells and missiles are put into combustion by means of an igniter associated with an igniter tube. The igniter tube is formed of a fuel tube closing off an ignition charge in the form of tablets and / or blocks arranged in the channel of the fuel tube; these tablets or blocks are removable and do not adhere to the combustible tube. The igniter tube thus formed is placed in the channel of the propellant charge.

The composition of the ignition powder is most often black powder (PN) consisting of a mixture of potassium nitrate (saltpeter), charcoal and sulfur. There are also other ignition powder compositions, in particular of the type: Boron / KN0, in a ratio generally of 70/30 (% by mass), a metal (for example iron, aluminum, zinc ), a perchlorate-type oxidizer (e.g., potassium perchlorate) or a fluoropolymer (e.g. PTFE (Teflon ^®) or Viton ^®). The ignition charges (tablets and / or block (s)) described in the prior art consist of an agglomerated ignition powder, optionally with a cellulose binder. In the latter case, the ignition charge is obtained by mixing the constituents of the ignition powder with a collodion (solvent + binder), followed by the evaporation of the solvent from the collodion. The ignition charge usually called Bénite is black powder agglomerated with a nitrocellulose binder.

Patent application FR-A-2 593 905 describes an ignition charge placed in a fuel tube consisting of a stack of tablets of agglomerated ignition powder. These igniter tube assemblies require on the one hand the production of agglomerated powder tablets, and on the other hand their installation in the fuel tube.

It is therefore understood that the ignition charge, placed in the fuel tube, is made of a pyrotechnic material based on an agglomerated powder.

So that the fuel tube (at a lower combustion speed than the ignition charge) does not shield the combustion gases from the ignition powder, fuel covers are distributed over the length of said tube. These combustible lids, about ten microns thick, break with the rise in pressure in the tube generated by the combustion of the ignition charge. Thus, the hot gases generated by the ignition powder can reach, from the start of ignition, the parts of the propellant charge located in the vicinity of the openings resulting from the rupture of the lids.

The ignition charges based on powder tablets of the prior art (familiar to a person skilled in the art) have several drawbacks (which the said person skilled in the art is aware of).

First of all, the operation of filling the fuel tube with the ignition charge is a delicate operation, with reference both to the handling technique and to the pyrotechnic risk (the ignition powder is classified in risk division 1.1 within the meaning of within the meaning of the UN GHS classification (Globally Harmonized System of Classification and Labeling of Chemicals (UN)). This operation requires special tools to be automated. In addition, when the ignition charge is introduced into the tube mixed with a collodion to obtain (in situ) tablets, the evaporation time of the collodion solvent is long due to the confinement of the loaded collodion in the tube.

Then, the fuel tube has a length equivalent to that of the channel of the propellant charge, but the ignition charge occupies a volume in relation to its mass. The mass of the charge may vary depending on the ignition specifications and / or the nature of the powder. The ignition charge volume specified for ignition may be less than that of the propellant charge channel. The ignition of the propellant charge is therefore not always homogeneous in the tube, and therefore synchronous over the length of the channel. This deviates from the ideal conditions for almost instantaneous ignition of the entire (internal) surface of the propellant charge.

Finally, it is sometimes necessary to dismantle the igniter tube of a propellant charge, for example during the scrapping of a munition or its neutralization. This disassembly of the igniter tube involves extraction of the ignition charge arranged in the fuel tube. This extraction by direct contact with the agglomerated powder generates a pyrotechnic danger.

Patent application FR-A-2 725 781 proposes to replace the tablets of agglomerated powder by an ignition material comprising an ignition composition in powder form (typically black powder) deposited on a flexible support sheet, which is then advantageously wound on itself so as to be inserted into a fuel tube to form an igniter tube. So that the powder (which is just placed on the flexible support) does not fall to the bottom of the igniter tube, it is imperative to coating the powder composition with another flexible sheet (called a screen sheet), at least one of the screen and support sheets being coated with adhesive.

This method makes it possible to better distribute the powder charge in the channel of the munition and facilitates the dismantling of the ignition material from the agglomerated powder ignition material. The ignition material described in patent application FR-A-2 725 781 therefore provides a technical solution to the problems posed by ignition materials based on powder tablets.

However, its implementation is complex due to the handling of the explosive ignition powder classified in risk division 1.1, the control of the regularity of the quantities of powders deposited in a heap on the flexible sheet and the geometries of the heaps, the step of covering the piles of powders deposited on the flexible sheet by the sticky screen sheet. To the knowledge of the applicant, the process described has not been developed and industrialized since the publication of the application in 1994.

In terms of the materials used, the flexible sheet and the screen sheet are made of paper, nitro paper, fabric, plastic or aluminum. These materials do not contribute significantly to the energy input of the ignition charge. The spatial distribution of the ignition energy of the charge is only obtained by the distribution and the volume of the piles of powder. It is not intended to vary the composition of the ignition material to optimize the spatial distribution of the energy of the ignition charge. The configuration possibilities in terms of level and the spatial energy distribution of the pyrotechnic objects of patent application FR-A-2 725 781 are therefore limited and controlled only by the mass and the spatial distribution of the piles of powdered powder.

It would therefore be useful to be able to have an ignition charge capable of being produced in a simple manner on an industrial scale and allowing great modularity in the level and spatial distribution of the ignition energy. The present invention proposes to meet these specifications.

Summary of the invention

The present invention relates to a propellant charge igniter tube with a central channel (cylindrical), a method of preparing said igniter tube, and a propellant charge comprising the igniter tube. The igniter tube comprises a fuel tube on the inner face of which is deposited an ignition charge.

Brief Description of the Figures FIG. 1 represents a first variant of the method for depositing an ignition charge inside a fuel tube. FIG. 2 represents a second variant of the method for depositing an ignition charge inside a fuel tube.

FIG. 3A illustrates the circular deposition with a triangular section of an ignition charge in a fuel tube.

FIG. 3B illustrates the linear deposition with a triangular section of an ignition charge in a fuel tube.

Figure 3C illustrates the triangular cross-sectional helical deposition of an ignition charge in a fuel tube.

Figure 4 shows an ignition charge in the form of a helical pattern disposed in a fuel tube.

FIG. 5 illustrates a fuel tube provided, on its internal face, with an ignition charge in the form of a helical ribbon.

Description of the Invention The present invention relates, in a first aspect, to a central channel (cylindrical) propellant charging igniter tube, said igniter tube comprising (consisting of) a fuel tube, of a combustible material (having the appearance of 'a felt), comprising a cellulose ester, preferably nitrocellulose, on the inner face of which is deposited and adheres an ignition charge.

The ignition charge is deposited (adherently) on the internal face of the fuel tube, in the form of geometric patterns spaced along the length of said tube. The ignition charge contains as main constituent at least one ignition powder agglomerated with a cellulose binder (all the patterns do not necessarily contain the same powder). It is obtained by drying a collodion loaded with ignition powder deposited on the internal face of the tube.

To ensure easier insertion and extraction of the fuel tube within the propellant charge (during dismantling, for example), the ignition charge does not suitably cover the axial ends of the internal face of the tube, which thus leaves a free height to grip the tube without contact with the ignition charge.

Conventionally, the tube receives at each of its ends a cover (commonly called a straw) acting as a stopper. The lids (plugs) are made of a combustible material generally identical to that of the tube.

The combustible materials constituting the combustible tube and the ignition charge must be chemically compatible and have the property of adhesion to each other. For this, they have a common cellulose ester base, such as cellulose nitrate, cellulose acetate or nitrocellulose. Nitrocellulose is the preferred common base and is used, without limitation, in the remainder of the description.

In one embodiment, the fuel tube, such as those marketed by the company Eurenco, consists of 60% to 80% by weight of cellulose ester, 17% to 37% by weight of cellulose, 3% to 7% by weight of cellulose. mass of resin and 0% to 2% by mass of stabilizing additive (the sum of these various constituents being equal to 100%). Its mass is about 15 g to 25 g. The fuel tube has a height of about 120 mm to 140 mm, for an internal diameter of 25 mm to 30 mm and a thickness of 1.5 to 2.5 mm.

Advantageously, the fuel tube has the composition given in Table 1 and the dimensions given below.

Table 1

The mass of the fuel tube is 18 g +/- 3g. The tube has a height of 126 mm, for an internal diameter of 28 mm and a thickness of 1.8 mm.

In one embodiment, the ignition charge is obtained by drying a collodion (solvent + binder) charged with an ignition powder. Ignition powder is a conventional ignition powder used for the ignition of propellant charging. Ignition powder is a powdery granular material classified in risk division 1.1 within the meaning of the UN GHS classification (Globally Harmonized System of Classification and Labeling of Chemicals (UN). ignition comprises an inorganic oxidizing compound such as KN0 or KCI0 ₄ , and typically consist of such an inorganic oxidizing compound and a reducing compound forming an agglomerated mixture. therefore not cellulose materials such as a dried composite material based on nitrocellulose and nitroglycerin Examples of ignition powder compositions are given in Table 2 below. Table 2

The powder used is preferably black powder (PN) of mass composition: - potassium nitrate (saltpeter): ~ 75%

- charcoal: ~ 15%

- sulfur: ~ 10%.

Black powder (PN) is conventionally classified according to an index relating to its particle size (see Table 3 below). Table 3

The fine particle size powders, of the PN5, PN6 or PN7 type, are the best suited within the framework of the invention. A fine particle size in fact ensures better dispersion of the powder in the collodion.

The collodion used in the context of the invention is of the cellulose ester base + solvent (s) type. In one embodiment, the cellulose ester base of the collodion consists of a cellulose ester (from about 70% to about 90% by weight) and generally contains in addition, conventionally, at least one plasticizer (about 1% to about 20%). % by mass, preferably approximately 10% by mass) and at least one stabilizer for the cellulose ester (approximately 0.5% to approximately 5% by mass). It also generally contains at least one additive (> 0% to approximately 1% by mass), for example chosen from anti-adhesion agents, anti-glare agents and antioxidants. It is likely to contain a residual amount of solvent (s), in particular of phlegmatization solvent (s) or (and) of solvent (s) for dissolving the cellulose ester used during its manufacture.

Advantageously, the cellulose ester used as the major component is chosen from cellulose nitrate, cellulose acetate or nitrocellulose, the latter being preferred. The nitrogen mass content of nitrocellulose is suitably 10.5% to 13.5%, an example being grade E nitrocellulose with a nitrogen mass content of 11.8% to 12.3%, advantageously equal to 12. %.

The plasticizer used to prepare the collodion may in particular be a ketone (such as camphor), a vinyl ether (such as LUTONAL ^® A50 marketed by BASF), polyurethane (such as NEP-PLAST 2001 sold by Hagedorn-NC society ), an adipate (such as dioctyl adipate) or a citrate (such as triethyl 2-acetyl citrate).

The stabilizer used to prepare the collodion can in particular be a compound whose chemical formula comprises aromatic rings (suitably two aromatic rings), capable of fixing nitrogen oxides from the decomposition of nitric esters (presently nitrocellulose). By way of example of a stabilizer, mention may be made of 2-nitrodiphenylamine (2NDPA), l, 3-diethyl-l, 3-diphenyl urea (centrality I), 1,3-dimethyl-l, 3-diphenyl urea ( centrality II), and 1-methyl-3-ethyl-1,3-diphenyl urea (centrality III).

The optional additive used to prepare the collodion can in particular be chosen from non-stick agents, such as silicone-type non-stick agents, anti-glare agents, antioxidants, dyes, surfactants, anti-agglomeration agents and hydrophobic agents. . The solvent can be a double solvent of the acetone / butyl acetate (AB) type at 50% / 50% by mass.

The collodion is advantageously formulated to lead to a dry extract (after evaporation of the solvent) of 10% to 40%, by mass. Table 4 below shows a formulation of collodion at 14% solids content by mass.

Table 4

In one embodiment, the collodion charged with ignition powder (s) comprises from about 50% to about 70% by weight of powder (s), and the balance at 100% (i.e. about 30% at about 50% by mass) of collodion. Conventionally, the ignition powder (s), previously constituted, is (are) added to the collodion.

The collodion charged with ignition powder is advantageously obtained by adding the ignition powder, previously formed, in the solvent. He was then baptized “Bénite B”. It differs from those of the prior art, designated "Benite", obtained by separate additions in the collodion of the constituents of the ignition powder and without plasticizer.

Table 5 below gives an example of the collodion composition of Table 4, loaded with PN7 ignition powder. Table 5

Collodion charged with ignition powder is classified in risk division 1.4 within the meaning of the UN GHS classification (UN Globally Harmonized System of Classification and Labeling of Chemicals). The danger zones to be taken into account for handling the charged collodion are therefore reduced, which facilitates the operations for depositing the collodion on the tube.

After drying (evaporation of the solvent) of the charged collodion, the ignition charge (dry) adheres to the internal surface of the fuel tube and comprises about 88% to about 92% by mass of ignition powder (s), about 7% to approximately 10% by mass of cellulose ester, the remainder to 100% being provided by at least one compound chosen from a plasticizer, an additive and a residual solvent. As an indication, the dry ignition charge obtained after drying (evaporation of the solvent) of the collodion in Table 5 contains the mass ratios indicated in Table 6 below.

Table 6

According to a second aspect, the present invention relates to a process for preparing an igniter tube by (direct) deposition by extrusion of collodion charged with ignition powder on the internal face of a fuel tube.

In one embodiment, the surface of the tube intended to receive the deposit can be, if necessary, prepared by sanding prior to the deposition of the collodion. Such a step can promote the adhesion of the paste to the tube during the deposition.

In one embodiment, the collodion deposition inside the tube is carried out by means of a telescopic rod 1 provided at its end with at least one nozzle 3. In a reservoir, the collodion is conditioned in temperature. . The collodion passes through a die of determined dimensions. The delivery of the collodion in the die is achieved by means of an application of pressure. This pressure conditions the flow. The die is extended by the rod fitted with one or more extrusion nozzles. Several extrusion nozzles are optionally used on the same manufacturing tool in order to be able to combine successively or simultaneously several formulations within one. same loading. The nozzle (s) can make several passes over the same deposition zone 2 in order to superimpose layers and increase the local thickness and therefore the mass of the ignition charge. According to a first variant (see FIG. 1), the tube is stationary and the collodion deposits on the internal face of the tube are produced by displacement of the nozzle. According to a second variant (see Figure 2), the tube is mounted on a rotary and axial displacement lathe, the nozzle then being stationary. The deposition process according to these two variants can be easily industrialized. Once the collodion is deposited, it is allowed to dry (by evaporation of the solvent) to obtain an igniter tube in which the ignition charge adheres to the internal surface of the fuel tube.

The method according to the invention makes it possible to envisage any geometry and arrangement of the ignition charge on the internal face of the fuel tube, provided that this leads to proper ignition of the ignition charge.

Advantageously, the ignition charge is deposited as spaced point patterns, or circular patterns spaced along the length of the tube, or linear patterns along the length of the tube, or one or more helical patterns in the tube. tube length. The deposits are not all necessarily identical in size and / or in composition and are not all necessarily arranged regularly. The number of deposits, their geometry, their arrangements constituting the ignition charge in the tube are parameters for adjusting the ignition charge.

In one embodiment, each pattern contains a substantially identical amount of ignition powder (s) (on the order of about 90% by weight). In another embodiment, the patterns deposited on the internal face of the fuel tube do not all contain the same amount of ignition powder (s), the amount of ignition powders in each pattern being in the proportions indicated above (about 88% to about 92% by weight).

Figures 3A, 3B and 3C illustrate different geometries of the aforementioned patterns (circular pattern, linear pattern, helical pattern), said patterns advantageously having a triangular section. An ignition charge in the form of one or more helical patterns is particularly advantageous in terms of ease of deposit and distribution of the load in the tube.

Hereinafter, illustratively (in no way limiting), for an equivalent of a total volume of ignition charge of approximately 10 g in solid block (prior art), the preferred geometry consisting of a pattern is indicated below. helical of an ignition charge deposited in a tube with an internal diameter of 2.8 cm and a length of 12.6 cm according to the invention (see FIG. 4). Helical diameter of the pattern: d = 2.8 cm

Axial length of the motif: h = 10 cm

Propeller pitch: = 2 cm

Number of turns n = 5

Pattern length = 45.1 cm

Geometry of the pattern section: semi-circular

Base section length = 0.6cm

Section radius: 0.3 cm

Pattern section area: 0.14 cm ²

Pattern volume: 0.14 x 45.1 = 6.3 cm ³

Density ~ 1.6 g / cm ³

Pattern mass ~ 10 g.

Tests for the deposition of collodion loaded with ignition powder were carried out on the internal face of a tube (see FIG. 5) by means of a device as described in FIG. 2. The collodion was dried at temperature. room temperature for about 2.5 hours (this time can be greatly reduced by drying in a hot air stream, for example at about 80 ° C). During this drying, the assembly (tube + ignition charge) was easy to handle. The deposit after drying had a mass of about 10 g. It was regular in a helical pattern of 10 cylindrical turns of about 0.3 mm in diameter, and adhered perfectly to the inner surface of the tube.

According to a third aspect, the present invention relates to a propellant charge comprising an igniter tube as defined above.

The present invention has the advantage that, whatever its mass, the ignition charge can be distributed evenly over the internal face of the fuel tube (this ensures ignition in a homogeneous manner in the tube).

Claims

1. Central channel igniter tube made of a fuel tube, of a fuel material comprising a cellulose ester, on the inner face of which an ignition charge is deposited in the form of geometric patterns spaced along the length of said fuel tube, and adheres to said fuel tube, said ignition charge comprising from 88% to 92% by mass of igniter powder (s) and from 7% to 10% by mass of cellulose ester.

2. Igniter tube according to claim 1, wherein the ignition charge further comprises at least one compound selected from a plasticizer, an additive and a residual solvent.

3. An igniter tube according to claim 1 or claim 2, wherein the igniter powder is a powdery granular material comprising an inorganic oxidizing compound.

4. Igniter tube according to any one of claims 1 to 3, wherein the ignition powder is black powder.

5. Igniter tube according to any one of claims 1 to 4, wherein the cellulose ester of the ignition charge is nitrocellulose.

6. Igniter tube according to any one of claims 1 to 5, wherein the fuel tube comprises 60% to 80% by mass of cellulose ester, 17% to 37% by mass of cellulose, 3% to 7% by mass. of resin and 0% to 2% by mass of stabilizing additive.

7. Igniter tube according to any one of claims 1 to 6, wherein the ignition charge is deposited on the internal face of the fuel tube and in the length thereof, in the form of circular patterns.

8. Igniter tube according to any one of claims 1 to 6, wherein the ignition charge is deposited on the internal face of the fuel tube and in the length thereof, in the form of linear patterns.

9. Igniter tube according to any one of claims 1 to 6, wherein the ignition charge is deposited on the internal face of the fuel tube and in the length thereof, in the form of helical patterns.

10. A method of preparing an igniter tube according to any one of claims 1 to 9, which comprises depositing by extrusion of a collodion charged with ignition powder on the internal face of the fuel tube, and drying the collodion. deposited, said collodion charged with ignition powder comprising from 50% to 70% by mass of ignition powder, and from 30% to 50% by mass of collodion.

11. The method of claim 10, wherein the collodion comprises from 70% to 90% by weight of cellulose ester, from 1% to 20% by weight of at least one plasticizer, from 0.5% to 5% by weight. mass of at least one stabilizer for the cellulose ester and optionally up to 1% by mass of at least one additive.

12. The method of claim 11, wherein the cellulose ester is nitrocellulose.

13. A propellant charge comprising an igniter tube according to any one of claims 1 to 9.