IGNITION TUBE FOR PROPULSIVE LOADING

Abstract

The invention relates to an igniter tube consisting of a combustible tube on the inner face of which an ignition charge is deposited along the length of said combustible tube. The invention also relates to a method for preparing the igniter tube.

Description

Title of the invention: Igniter tube for propellant loading Scope of the invention

[0001] The technical field of the invention is that of igniter tubes for propellant charges having a central (cylindrical) channel. State of the art

[0002] The propellant charges equipping shells and missiles are ignited by means of an igniter associated with a firing tube. The firing tube consists of a fuel tube enclosing 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 fuel tube. The igniter tube thus formed is placed in the channel of the propellant charge.

[0003] The composition of the ignition powder is most frequently black powder (BP) consisting of a mixture of potassium nitrate (saltpeter), charcoal, and sulfur. Other ignition powder compositions also exist, notably of the type: Boron / KNO3, generally in a ratio of 70 / 30 (% by mass), a metal (e.g., iron, aluminum, zinc), a perchlorate-type oxidizer (e.g., potassium perchlorate) or a fluorinated polymer (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.

[0004] French patent application FR-A-2 593 905 describes an ignition charge arranged in a fuel tube consisting of a stack of agglomerated ignition powder tablets. These assemblies for ignition tubes require, on the one hand, the manufacture of agglomerated powder tablets, and on the other hand, their placement in the fuel tube.

[0005] It is therefore understood that the ignition charge, placed in the fuel tube, is made of a pyrotechnic material based on an agglomerated powder.

[0006] To prevent the fuel tube (which burns at a lower rate than the ignition charge) from blocking the combustion gases of the ignition powder, combustible seals are distributed along the length of the tube. These combustible seals, approximately ten microns thick, rupture as the pressure increases. in the tube generated by the combustion of the ignition charge. Thus the hot gases generated by the ignition powder can reach, from the beginning of ignition, the parts of the propellant charge located near the openings resulting from the rupture of the seals.

[0007] Prior art powder tablet-based ignition loads (familiar to a person skilled in the art) have several disadvantages (which such a person skilled in the art is aware of).

[0008] First, the operation of filling the fuel tube with the ignition charge is a delicate operation, both in terms of the handling technique and the pyrotechnic risk (ignition powder is classified as hazard division 1.1 according to the UN GHS classification (Globally Harmonized System of Classification and Labelling of Chemicals (UN)). This operation requires special equipment to be automated. Furthermore, when the ignition charge is introduced into the tube mixed with collodion to obtain (in situ) tablets, the evaporation time of the collodion solvent is long due to the confinement of the loaded collodion within the tube.

[0009] Next, the fuel tube has a length equivalent to that of the propellant channel, but the ignition charge occupies a volume proportional to its mass. The mass of the charge can vary depending on the ignition specifications and / or the nature of the propellant. The volume of the ignition charge specified for ignition may be less than that of the propellant channel. Therefore, the ignition of the propellant charge is not always homogeneous within the tube, and thus not always synchronous along the length of the channel. This deviates from the ideal conditions of near-instantaneous ignition of the entire (internal) surface of the propellant charge.

[0010] Finally, it is sometimes necessary to remove the igniter tube from a propellant charge, for example, when disposing of or neutralizing a munition. Removing the igniter tube involves extracting the ignition charge contained within the propellant tube. This extraction, through direct contact with the agglomerated powder, creates a pyrotechnic hazard.

[0011] French patent application FR-A-2 725 781 proposes replacing agglomerated powder tablets with an ignition material comprising a powdered ignition composition (typically black powder) deposited on a flexible support sheet, which is then advantageously rolled up for insertion into a combustible tube to form an igniter tube. To prevent the powder (which is simply placed on the flexible support) from falling to the bottom of the igniter tube, it is essential to coat the powdered composition with another flexible sheet (called a screen sheet), at least one of the screen and support sheets being coated. glue.

[0012] This process allows for better distribution of the powder charge within the ammunition channel and facilitates the removal of the ignition material compared to agglomerated powder ignition material. The ignition material described in patent application FR-A-2 725 781 therefore offers a technical solution to the problems posed by powder tablet-based ignition materials.

[0013] However, its implementation is complex due to the handling of the explosive ignition powder, classified as hazard division 1.1, the control of the consistency of the quantities of powder deposited in piles on the flexible sheet and the geometries of the piles, and the step of covering the powder piles deposited on the flexible sheet with the adhesive screen sheet. To the applicant's knowledge, the described process has not been developed and industrialized since the publication of the application in 1994.

[0014] In terms of the materials used, the flexible foil and the screen foil are made of paper, nitrided 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 achieved solely through the distribution and volume of the powder piles. Varying the composition of the ignition material to optimize the spatial distribution of the ignition charge's energy is not envisaged. Therefore, the configuration possibilities in terms of level and the spatial energy distribution of the pyrotechnic devices described in French patent application FR-A-2 725 781 are limited and governed solely by the mass and spatial distribution of the powder piles.

[0015] It would therefore be useful to have an ignition charge that can be easily produced on an industrial scale and that allows for a high degree of modularity in the level and spatial distribution of the ignition energy. The present invention aims to meet these requirements. Summary of the invention

[0016] The present invention relates to a central channel (cylindrical) propellant loading igniter tube, a method for preparing said igniter tube, and a propellant loading comprising the igniter tube. The igniter tube comprises a combustible tube on the inner face of which an ignition loading is deposited. Brief description of the figures

[0017] [fig. 1] Fig. 1 represents a first variant of the method of depositing an ignition charge inside a fuel tube.

[0018] [fig.2] Fig.2 represents a second variant of the deposition process of a ignition charge inside a combustible tube.

[0019] [fig.3A] Fig.3A illustrates the circular, triangular-section deposit of a load ignition in a combustible tube.

[0020] [fig.3B] Fig.3B illustrates the linear triangular section deposition of an ignition charge in a fuel tube.

[0021] [fig.3C] Fig.3C illustrates the triangular helical deposition of an ignition charge in a fuel tube.

[0022] [fig.4] Fig.4 represents an ignition charge in the form of a helical pattern Licoidal arranged in a combustible tube.

[0023] [fig.5] Fig.5 illustrates a combustible tube provided, on its inner face, with a ignition charge in the form of a helical ribbon. Description of the invention

[0024] The present invention relates, according to a first aspect, to a central channel (cylindrical) propellant loading igniter tube, said igniter tube comprising (consisting of) a combustible tube, made of a nitrocellulosic combustible material (having the appearance of a felt), on the inner face of which an ignition charge is deposited and adheres.

[0025] The ignition charge is deposited (adherently) on the inner surface of the fuel tube, in the form of geometric patterns spaced along the length of said tube. The ignition charge comprises, as its main constituent, at least one ignition powder agglomerated with a cellulose binder (not all patterns necessarily contain the same powder). It is obtained by drying a collodion loaded with ignition powder deposited on the inner surface of the tube.

[0026] To ensure easy insertion and extraction of the fuel tube within the propellant charge (during disassembly for example), the ignition charge does not conveniently cover the axial ends of the inner face of the tube, thus leaving a free height to grasp the tube without contact with the ignition charge.

[0027] Conventionally, the tube is fitted at each end with a lid (commonly called a stopper) acting as a plug. The lids (plugs) are made of a combustible material generally identical to that of the tube.

[0028] The combustible materials constituting the fuel tube and the ignition charge must be chemically compatible and have the property of adhering to one another. To this end, they share a common cellulosic ester base, such as cellulose nitrate, cellulose acetate, or nitrocellulose. Nitrocellulose is the preferred common base and is retained, without limitation, in the remainder of this description.

[0029] In one embodiment, the fuel tube, such as those marketed by Eurenco, is composed of 60% to 80% by mass of cellulosic ester, 17% to 37% by mass of cellulose, 3% to 7% by mass of resin and 0% to 2% by mass of additive Stabilizer (the sum of these different constituents being equal to 100%). Its mass is approximately 15 g to 25 g. The combustible tube has a height of approximately 120 mm to 140 mm, with an internal diameter of 25 mm to 30 mm and a thickness of 1.5 to 2.5 mm.

[0030] Advantageously, the combustible tube has the composition given in Table 1 and the dimensions given below.

[0031] [Tables 1] Composition % by mass: Nitrocellulose powder cotton 69%, Cellulose 25%, Resin 5%, Stabilizing additive 1%

[0032] The mass of the fuel tube is 18 g + / - 3 g. The tube has a height of 126 mm, an inner diameter of 28 mm and a thickness of 1.8 mm.

[0033] In one embodiment, the ignition charge is obtained by drying a collodion (solvent + binder) loaded with an ignition powder. The ignition powder is a conventional ignition powder used for propellant charge ignition. Examples of ignition powder compositions are given in Table 2 below.

[0034] [Tables2] Ignition Powder: Constituents Chemical Formulas Boron / Potassium Nitrate b / KNO3 Aluminum / Potassium Perchlorate Al / KClO4 Magnesium / Teflon®-Viton® Mg / PTFE-TV Zirconium / Barium Chromate Zr / BaCrO4 Aluminum / Copper Oxide Al / CuO Black Powder S / Charcoal / KNO3 Magnesium / Sodium Nitrate / Potassium Nitrate Mg / NaNO3 / KNO3 Zirconium / Lead Chromate Zr / PbCrO4 Zirconium-Nickel / Potassium Perchlorate-Barium Nitrate ZrNi / KClO4-Ba(NO3)2 Cesium Decahydroborate / Potassium Nitrate Cs2B10H10 / KNO3

[0035] The powder used is preferably black powder (PN) with the following mass composition:

[0036] - potassium nitrate (saltpeter): ~ 75% - charcoal: ~ 15% - sulfur: ~ 10%.

[0037] Black powder (BP) is conventionally classified according to an index relating to its particle size (see table 3 below).

[0038] [Tables3] Index Refusal <3% Refusal >95% Sifting Through a sieve Sifting Through a sieve PN1 7.10 mm 10.00 mm 4.00 mm 5.00 mm PN2 4.50 mm 5.75 mm 2.50 mm 3.00 mm PN3 2.80 mm 3.20 mm 1.00 mm 1.40 mm PN4 1.25 mm 1.6 mm 0.71 mm 1.00 mm PN5 1.00 mm 1.25 mm 0.63 mm 0.80 mm PN6 0.80 mm 1.00 mm 0.45 mm 0.50 mm PN7 0.50 mm 0.60 mm 0.10 mm 0.10 mm

[0039] Fine-grained powders, such as PN5, PN6, or PN7, are best suited for the purposes of this invention. A fine grain size ensures better dispersion of the powder in the collodion.

[0040] The collodion used in the context of the invention is of the nitrocellulose base + solvent(s) type. In one embodiment, the nitrocellulose base of the collodion consists of a cellulose ester (approximately 70% to approximately 90% by mass) and generally also contains, conventionally, at least one plasticizer (approximately 1% to approximately 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, selected from among anti-adhesion agents, anti-glare agents, and antioxidants. It is likely to contain a residual amount of solvent(s), in particular phlegmatizing solvent(s) and / or solvent(s) for dissolving the cellulosic ester used during its manufacture.

[0041] Advantageously, the cellulosic 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 conveniently from 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%.

[0042] The plasticizer used to prepare the collodion may be, in particular, a ketone (such as camphor), a vinyl ether (such as LUTONAL® A50 marketed by BASF), a polyurethane (such as NEP-PLAST 2001 marketed by Hagedom-NC), an adipate (such as dioctyl adipate) or a citrate (such as triethyl 2-acetyl citrate).

[0043] The stabilizer used to prepare the collodion may be, in particular, a compound whose chemical formula includes aromatic rings (opportunity two aromatic rings), capable of binding the nitrogen oxides from the decomposition of nitric esters (presently nitrocellulose). Examples of stabilizers include 2-nitrodiphenylamine (2NDPA), 1,3-diethyl-1,3-diphenyl urea (centrality I), 1,3-dimethyl-1,3-diphenyl urea (centrality II), and 1-methyl-3-ethyl-1,3-diphenyl urea (centrality III).

[0044] The optional additive used to prepare the collodion can be chosen in particular from among the anti-stick agents, such as silicone-type anti-stick agents, anti-glare agents, antioxidants, colorants, surfactants, anti-caking agents and hydrophobic agents.

[0045] The solvent can be a dual solvent of the type acetone / butyl acetate (BA) at 50% / 50% by mass.

[0046] Collodion is advantageously formulated to lead to a dry extract (after evaporation of the solvent) of 10% to 40%, by mass.

[0047] Table 4 below presents a formulation of collodion with 14% dry extract by mass.

[0048] [Tables4] Collodion Composition (% by mass) Nitrocellulose Base Nitrocellulose 84 14 Plasticizer 10 Stabilizer 3.5 Other (additive(s), water, solvent...) 2.5 Total 100 AB 43 Acetone 43 Total 100

[0049] In one embodiment, the collodion loaded with ignition powder(s) comprises approximately 50% to approximately 70% by mass of powder(s), and the remainder 100% (that is, about 30% to about 50% by mass) of collodion. Conventionally, the ignition powder(s), previously prepared, is / are added to the collodion.

[0050] Collodion loaded with ignition powder is advantageously obtained by adding the ignition powder, previously prepared, to the solvent. It is then called "Bénite B". It differs from those of the prior art, designated "Bénite", obtained by separate additions to collodion of the constituents of the ignition powder and without plasticizer.

[0051] Table 5 below gives an example of the composition of collodion from Table 4, loaded with PN7 ignition powder.

[0052] [Tables5] Raw materials Mass (g) Composition (% by mass) PN7 10.36 56 Collodion 8.14 44 Total 18.5 100

[0053] Collodion loaded with ignition powder is classified in risk division 1.4 according to the UN GHS classification (UN Globally Harmonized System of Classification and Labelling of Chemicals). The hazard zones to be taken into account for handling the loaded collodion are therefore reduced, which facilitates the operations of depositing the collodion onto the tube.

[0054] After drying (solvent evaporation) of the loaded collodion, the (dry) ignition charge adheres to the inner surface of the fuel tube and comprises approximately 88% to approximately 92% by mass of ignition powder(s), approximately 7% to approximately 10% by mass of cellulosic ester, the remainder to 100% being supplied by at least one compound selected from a plasticizer, an additive, and a residual solvent. For illustrative purposes, the dry ignition charge obtained after drying (solvent evaporation) of the collodion in Table 5 contains the mass ratios indicated in Table 6 below.

[0055] [Tableauxô] Composition: Dry Benite B Mass (g) % by mass PN7 10.36 90.08 Nitrocellulose 0.96 8.35 Plasticizer 0.11 0.96 Stabilizer 0.04 0.35 Residues (water, solvent...) 0.03 0.26 Total 11.50 100.00

[0056] According to a second aspect, the present invention relates to a method of preparing an ignition tube by (direct) extrusion deposition of collodion loaded with ignition powder onto the inner face of a combustible tube.

[0057] In one embodiment, the surface of the tube intended to receive the deposit can, if necessary, be prepared by sanding prior to the deposition of the collodion. Such a step can promote the adhesion of the paste to the tube during deposition.

[0058] In one embodiment, the collodion deposition inside the tube is carried out by means of a telescopic rod 1 equipped at its end with at least one nozzle 3. In a reservoir, the collodion is temperature-controlled. The collodion passes through a die of predetermined dimensions. The delivery of the collodion through the die is achieved by means of a pressure application. This pressure determines the flow rate. The die is extended by the rod equipped with one or more extrusion nozzles. Several extrusion nozzles may be used on the same manufacturing tool in order to be able to combine several formulations successively or simultaneously within the same load. The nozzle(s) may make several passes over the same deposition zone 2 to superimpose layers and increase the local thickness and therefore the mass of the ignition load. According to a first embodiment (see [fig.l]), the tube is stationary and the collodion deposits on the inner surface of the tube are made by moving the nozzle. According to a second variant (see [fig.2]), the tube is mounted on a lathe with rotary and axial movement, the nozzle then being stationary. The deposition process according to these two variants is 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 inner surface of the combustible tube.

[0059] The method according to the invention allows for any geometry and arrangement of the ignition charge on the inner face of the fuel tube, provided that this leads to proper ignition of the ignition charge.

[0060] Advantageously, the ignition charge is deposited in the form of spaced point patterns, or spaced circular patterns along the length of the tube, or linear patterns along the length of the tube, or one or more helical patterns along the length of the tube. The deposits are not necessarily all identical in size and / or composition and are not necessarily arranged in a regular pattern. The number of deposits, their geometry, and their arrangement constituting the ignition charge in the tube are parameters for adjusting the ignition charge.

[0061] In one embodiment, each motif contains a substantially identical quantity of ignition powder(s) (on the order of approximately 90% by mass). In another embodiment, the motifs deposited on the inner face of the fuel tube do not all contain the same quantity of ignition powder(s), the quantity of ignition powder(s) in each motif being in the proportions indicated above (approximately 88% to approximately 92% by mass).

[0062] Figures 3A, 3B and 3C illustrate different geometries of the aforementioned motifs (circular motif, linear motif, helical motif), said motifs advantageously having a triangular section. An ignition charge in the form of one or more helical motifs is particularly advantageous in terms of ease of deposition and distribution of the charge in the tube.

[0063] The following is given by way of illustration (in no way limiting), for an equivalent of a total volume of ignition charge of about 10 g in solid block (prior art), the preferred geometry consisting of a helical pattern of an ignition charge deposited in a tube of internal diameter 2.8 cm and length 12.6 cm according to the invention (see [fig.4]).

[0064] Helical diameter of the motif: d = 2.8 cm Axial length of the motif: h = 10 cm Pitch of the helix: 2 cm Number of turns n = 5 Length of motif = 45.1 cm Geometry of the motif cross-section: semi-circular Base length of the cross-section = 0.6 cm Radius of the cross-section: 0.3 cm Pattern cross-sectional area: 0.14 cm2 Volume of the motif: 0.14 x 45.1 = 6.3 cm3 Density ~ 1.6 g / cm3 Mass of the motif ~ 10 g.

[0065] Tests of collodion deposition loaded with ignition powder were carried out on the inner face of a tube (see [Fig. 5]) using a device as described in the [Fig. 2]. The collodion was dried at room temperature for approximately 2.5 hours (this time can be significantly reduced by drying under a stream of hot air, for example at approximately 80°C). During this drying process, the entire assembly (tube + ignition charge) was manageable. The deposit after drying had a mass of approximately 10 g. It was regular, forming a helical pattern of 10 cylindrical turns approximately 0.3 mm in diameter, and adhered perfectly to the inner surface of the tube.

[0066] According to a third aspect, the present invention relates to a propulsive loading comprising an ignition tube as defined above.

[0067] The present invention has the advantage that, regardless of its mass, the ignition charge can be distributed regularly on the inner face of the fuel tube (this ensures homogeneous ignition in the tube).

Claims

Demands

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

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. Igniter tube according to any one of claims 1 to 2, wherein the cellulosic ester of the ignition charge is nitrocellulose.

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

5. Igniter tube according to any one of claims 1 to 4, wherein the ignition charge is deposited, on the inner face of the combustible tube and along its length, in the form of circular patterns.

6. Igniter tube according to any one of claims 1 to 4, wherein the ignition charge is deposited, on the inner face of the fuel tube and along its length, in the form of linear patterns.

7. Igniter tube according to any one of claims 1 to 4, wherein the ignition charge is deposited, on the inner face of the fuel tube and along its length, in the form of helical patterns.

8. A method for preparing an ignition tube according to any one of claims 1 to 7, comprising the extrusion deposition of a collodion loaded with ignition powder onto the inner face of the combustible tube, and drying the deposited collodion, said collodion loaded with ignition powder comprising from 50% to 70% by mass of ignition powder, and from 30% to 50% by mass of collodion.

9. A process according to claim 8, wherein the collodion comprises a nitrocellulosic base consisting of 70% to 90% by mass of cellulose ester, 1% to 20% by mass of at least one plasticizer, 0.5% to 5% by mass of at least one stabilizer of the cellulose ester and possibly up to 1% by mass of at least one additive.

10. A process according to claim 9, wherein the cellulosic ester is nitrocellulose.

11. Propulsive charge comprising an igniter tube according to any one of claims 1 to 7.

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