Ignition unit for a propellant charge

Abstract

In an ignition unit for a propellant charge (8), comprising an elongated ignition transfer charge (2) made of propellant powder, through which a free ignition channel (5) runs in its longitudinal direction, and a combustible support tube (3) that surrounds the ignition transfer charge (2) perpendicular to the free ignition channel (5), the ignition transfer charge (2) is formed from a first material which has a glass transition point below -40°C in an observed temperature range of -51°C to +71°C, and the support tube (3) is formed from a second material which does not have a glass transition point below +72°C.

Description

[0001] The invention relates to an ignition unit for a propellant charge according to the preamble of claim 1.

[0002] Such an ignition unit is known from EP 0 306 616 A2. It has an ignition transfer charge formed from a mixture of nitrocellulose (NC) with 20% to 50% nitroglycerin (NGL), and a support tube formed from mono- or polybasic propellant powder without solvent.

[0003] WO 2020 / 109732 A1 describes an ignition unit in which an ignition charge is discontinuously distributed on one side of a film, i.e., applied in a specific pattern—for example, in stripes. The film material is cellulose ester-based and may contain, for example, approximately 70–90 wt% cellulose ester, 1–20 wt% plasticizer, and approximately 0.5–5 wt% stabilizer. The ignition charge contains approximately 88–92 wt% ignition powder and approximately 7–10 wt% cellulose ester and may additionally contain plasticizers, additives, and solvents. The finished film with the patterned ignition charge is cut to size according to the requirements of the intended application and rolled into a cylinder. The cylinder can be inserted into a tube whose material consists of 69% guncotton, 25% cellulose, 5% binding resin and 1% stabilizers.

[0004] From DE 196 04 655 A1 a flame guide tube made of combustible material with external propellant powder rods is known.

[0005] WO 2005 / 057123 A1 describes a propellant charge with high charge density, comprising two nested or successive perforated tubes which are surface-treated or surface-coated to delay the ignition progress so that a maximum gas pressure is built up behind a projectile.

[0006] WO 2021 / 144539 A1 and WO 2021 / 144538 A1 describe devices with which a paste can be applied to the inner surface of a tube, in particular an ignition charge to the inner surface of a combustible tube. The ignition charge is composed of nitrocellulose, plasticizers, stabilizers, additives, water, and solvents, and the tube is formed from nitrocellulose, cellulose, synthetic resin, and a stabilizer.

[0007] The present invention is based on the objective of improving an ignition unit of the type mentioned above in such a way that it is suitable for propellant charges with increased range and at the same time is more weather-resistant and cost-effective.

[0008] The invention is based on the finding that ignition units, as their size increases, are no longer mechanically stable enough to withstand all transport stresses and the so-called "rough handling" (drop tests inside and outside the packaging prescribed by STANAG). Furthermore, it has been found that material with an NC / NGL formulation becomes brittle at -19°C, and therefore ignition units break during drop tests below -19°C and cannot be used.

[0009] The measures according to the invention allow the ignition units to be made larger, in particular longer, and thus more powerful, and can therefore also be used with propellant charges with increased range, without increasing damage during transport. Because the material of the ignition transfer charge only exhibits a glass transition point below -40°C and the material of the support tube does not exhibit a glass transition point below +72°C, the ignition transfer charge and the support tube are less brittle and consequently less prone to breakage, especially at temperatures in the range of below -20°C to -40°C.

[0010] Furthermore, the inventive measure, in that the support tube is formed from a material that does not exhibit a glass transition point below +72°C, precludes support tubes made of propellant powder, since all propellant powder has a glass transition point below +72°C. A propellant powder tube used as a support tube can only be extruded, which, firstly, makes the production of a propellant powder tube considerably more complex than the production of a tube not made of propellant powder, and secondly, limits the diameter to a single size along its entire length. In contrast, the inventive material for the support tube allows for shapes such as a cup at the end of the support tube, which permit a simple and mechanically stable connection to the cartridge case cap and case body of a propellant charge into which the ignition unit is to be inserted.The assembly of the propellant charge with a support tube made of a material according to the invention is faster and more stable, since such a support tube can have shapes at its ends that are specifically adapted to the given connection requirements. This results in simpler manufacturing combined with better mechanical stability.

[0011] In particular, the support tube, cartridge cap, and cartridge case can have similar material properties, which facilitates the connection. Connecting a support tube to a cartridge cap and cartridge case made of a similar or even the same material as the support tube can be achieved, for example, by simple gluing. This bond is extremely strong and can be stronger than the material of the components themselves; that is, the material of the components will tear in such a case before the bond fails. While a propellant powder tube can also be glued, due to the significant difference in elasticity between the propellant tube and the cartridge case material, the bond is subjected to higher stresses under mechanical conditions such as compression. Furthermore, the two different materials cannot be bonded with the same strength as two similar or even identical materials.

[0012] Preferably, the material of the support tube (the second material) is composed of 20–80 wt% nitrocellulose (NC), 20–80 wt% cellulose, 0–20 wt% binder resin, and 0.4–3 wt% stabilizer. With these components, the support tube can be manufactured cost-effectively.

[0013] In an alternative embodiment, the second material contains cellulose. Cellulose gives the support tube greater mechanical stability because cellulose forms strong fiber-to-fiber bonds via hydrogen bonds.

[0014] Preferably, the support tube extends over the entire length of the ignition transfer charge. This measure provides the best possible protection for the ignition transfer charge against external influences, such as environmental factors, and also mechanically reinforces it.

[0015] In a further advantageous embodiment of the invention, the support tube is additionally coated on its outer surface with a pyrotechnic mixture. This coating can be, for example, nitrocellulose lacquer with or without black powder, also known as pyrolac. This enhances or supports the rapid propagation of the ignition, further promotes homogeneous ignition, and reliably prevents the formation of gas pressure waves.

[0016] Preferably, the pyrotechnic coating contains a proportion of black powder in the range of > 50% to < 95% by weight, as well as nitrocellulose or cellulose acetate butyrate as a binder (remainder). Additionally, a stabilizer or inert plasticizer may be present in a percentage concentration.

[0017] Advantageously, the support tube is perforated. Preferably, the perforations have a diameter in the range of 2 mm to 8 mm, most preferably a diameter of 4 mm. The perforations further accelerate and intensify or support the propagation of the ignition.

[0018] Preferably, the perforations are distributed around the circumference of the support tube in several rows of holes, extending in the circumferential direction and having a predetermined distance to each other in the longitudinal direction of the support tube.

[0019] In an advantageous embodiment of the invention, the outer diameter of the support tube is in the range of 26 mm to 35 mm, and the outer diameter of the propellant tube is in the range of 20 mm to 30 mm, with a wall thickness of approximately 1.5 mm. The number of perforations is preferably 8 to 20. For example, a row of holes can have four holes spaced evenly apart circumferentially – i.e., arranged at a 90° interval – and, with an effective support tube length of 96 cm, four rows of holes can be arranged at a distance of approximately 24 cm. The effective support tube length is the length remaining after subtracting the length required at both ends of the support tube for a plug connection with the cartridge case and cartridge case cap of the propellant charge. For longer tubes due to longer charges, a distance of 50 cm should not be exceeded.

[0020] Another arrangement of perforations could, for example, have two rows of holes, each with four holes evenly spaced from each other in the circumferential direction, and two rows of holes, each with three holes evenly spaced from each other in the circumferential direction - i.e., arranged at a mutual distance of 120°.

[0021] According to an advantageous embodiment of the invention, the support tube has a widening at at least one end for fixing it to a counterpart. This facilitates the attachment of the ignition unit to other components, for example to the cartridge case cap and the cartridge case body, for the manufacture of ammunition.

[0022] In an advantageous embodiment of the invention, the material of the ignition transfer charge (the first material) is composed of 20-80 wt% nitrocellulose (NC), 20-50 wt% nitroglycerin (NGL) and / or diethylene glycol dinitrate (DEGN) and / or alkyl nitratoethylnitramine (alkyl-NENA) and / or triethylene glycol dinitrate (TEGN) and / or other energetic plasticizers, 0.4-3 wt% stabilizer, as well as 0.5-5 wt% non-energetic plasticizers and other additives.

[0023] The addition of DEGN and / or alkyl-NENA and / or TEGN to the ignition transfer charge material significantly lowers its glass transition point. Thus, according to this embodiment, propellant powders are used for an ignition transfer charge according to the invention that contain either DEGN and / or alkyl-NENA and / or TEGN and / or other energetic plasticizers in addition to NC and NGL. Alternatively, propellant powders containing no NGL, but only NC and additionally DEGN and / or alkyl-NENA and / or TEGN and / or other energetic plasticizers, can also be used for an ignition transfer charge according to the invention. With these components, the first material can also be produced relatively cost-effectively.

[0024] Non-energetic plasticizers such as dioctyl sebacate, dioctyl adipate, Citroflex and others can be used.

[0025] Preferably, the first material contains butyl nitratoethylnitramine as an energetic plasticizer, and particularly preferably, the first material contains 0.5–1.5 wt% butyl nitratoethylnitramine. Butyl nitratoethylnitramine (Butyl-NENA) significantly lowers the glass transition temperature of the first material. In particular, in combination with DEGN and / or alkyl-NENA and / or TEGN, Butyl-NENA reduces the glass transition temperature to below -52°C. Drop tests at -52°C, as prescribed by STANAG for rough handling, have shown that ignition units designed in this way survive these drop tests undamaged. Thus, Butyl-NENA gives the ignition transfer charge even greater flexibility, which considerably reduces the risk of brittle fracture.

[0026] In a preferred embodiment of the invention, the ignition transfer charge is tubular in shape, and the interior of the tube forms the ignition channel. In this way, the ignition transfer charge can be manufactured extremely cost-effectively.

[0027] The tubular design enables simple and robust ignition on the surface. Ignition is initiated by a primer. Subsequently, the combustion of the tubular ignition transfer charge produces a large quantity of hot gases, vapors, and / or particles, which intensify the ignition and promote its propagation within the ignition unit. This results in rapid ignition and, consequently, homogeneous ignition of the entire propellant charge.

[0028] In a favorable embodiment of the invention, the walls of the ignition channel are at least partially coated with a pyrotechnic mixture. This measure increases the burning rate of the ignition transfer charge, so that the flame spreads even faster in the ignition channel.

[0029] Preferably, the ignition transfer charge is profiled on its outer and / or inner surface. The profiling can, for example, have a star shape. Equally preferably, the ignition transfer charge has a longitudinal slot. These measures further promote the rapid and uniform propagation of the ignition.

[0030] Particularly preferably, a longitudinal slot extends over the entire length of a tubular ignition transfer charge and further preferably has a width of no more than 1 mm. The tubular ignition transfer charge is formed into a sleeve by the longitudinal slot, which makes the tubular ignition transfer charge more flexible and easier to insert into the support tube.

[0031] Advantageously, the ignition transfer charge is designed in multiple parts along its length. This further reduces the risk of breakage in very long ignition units.

[0032] Preferably, the ignition transfer charge rests with its outer surface against the inner surface of the support tube. This further promotes rapid ignition and thus also homogeneous ignition of the entire propellant charge.

[0033] In an advantageous embodiment of the invention, the ignition transfer charge is bonded to the support tube. This creates a secure mechanical connection between the ignition transfer charge and the support tube, thereby increasing the reliability of a homogeneous ignition of the propellant charge.

[0034] The invention will be explained in more detail below with reference to the drawings, which show: Figure 1 shows a longitudinal section through a first embodiment of an ignition unit according to the invention; Figure 2 shows a longitudinal section through a second embodiment of an ignition unit according to the invention; and Figure 3 shows a longitudinal section through a third embodiment of an ignition unit according to the invention, installed in a propellant charge module.

[0035] The embodiments of an ignition unit 1 according to the invention shown in the figures have a tubular ignition transfer charge 2 and a support tube 3.

[0036] The ignition transfer charge 2 is made from a first material that exhibits a glass transition point below -40°C within an observed temperature range of -51°C to +71°C. This first material is a propellant powder composed of 20 - 80% by weight Nitrocellulose (NC), 20-50% by weight Nitroglycerin (NGL) and / or diethylene glycol dinitrate (DEGN) and / or alkyl nitratoethylnitramine (alkyl-NENA) and / or triethylene glycol dinitrate (TEGN) and / or other energetic plasticizers, 0.4 - 3 wt% Stabilizer, 0.5 - 5% by weight Non-energetic plasticizers and other additives.

[0037] Preferably, butyl nitratoethylnitramine (Butyl-NENA) is used as an "alternative" energetic plasticizer because Butyl-NENA is extremely effective at further lowering the glass transition point to below -52°C.

[0038] For example, an NC / NGL / DEGN formulation can be composed of 54.0% by weight NC, 25.0% by weight NGL, 19.0% by weight DEGN, 1.0% by weight Acardite (stabilizer), 1.0% by weight other additives or -without NGL- an NC / DEGN formulation from 61.4% by weight NC, 36.0% by weight DEGN, 1.5% by weight Acardite (stabilizer), 0.55% by weight non-energetic plasticizer, 0.55% by weight further additives, where DEGN can be used in combination with 0.5-1.5 wt% Butyl-NENA, and the wt% of DEGN is then reduced accordingly.

[0039] The support tube 3 is made of a second material that is combustible and does not exhibit a glass transition point below +72°C. This second material can be composed of 20 - 80% by weight Nitrocellulose (NC), 20 - 80% by weight Cellulose, 0 - 20% by weight Binding resin 0.4 - 3 wt% Stabilizer.

[0040] For example, the second material could be composed of 74.0% by weight + / - 1.5% NC with ≥ 13.3% nitrogen content (N 2 ), 15.0% by weight + / - 2.0% Cellulose, 10.0% by weight + / - 2.0% Binder resin 0.75 - 1.6 wt% stabilizer or from 65.0% by weight + / - 1.5% NC with ≥ 13.3% nitrogen content (N 2 ), 24.0% by weight + / - 1.5% Cellulose, 10.0% by weight + / - 2.0% Binder resin 0.75 - 1.6 wt% stabilizer or from 65.0% by weight + / - 2.0% NC with ≥ 13.3% nitrogen content (N 2 ), 15.0% by weight + / - 2.0% Cellulose, 10.0% by weight + / - 2.0% Binder resin 0.75 - 1.6 wt% Stabilizer.

[0041] In another embodiment, cellulose can also be used as a material for the support tube 3.

[0042] In Figure 1The structure of an ignition unit 1 according to the invention with tubular ignition transfer charge 2 and support tube 3 is shown in general terms.

[0043] The interior of the tubular ignition charge 2 forms a free ignition channel 5 and can be coated with a pyrotechnic mixture 6. The coating is preferably applied over the entire surface; however, partial coating is also possible.

[0044] The coating 6 can contain black powder with or without sulfur. The coating can also be made with nitrocellulose lacquer. The proportion of black powder is preferably in the range of >50% by weight to <95% by weight. Suitable additives include, for example, titanium, calcium silicide, aluminum, antimony sulfide, bismuth sulfide, zirconium, nitrocellulose, potassium nitrates, and barium nitrate. The nitrocellulose lacquer ensures very good adhesion of the black powder to the ignition transfer charge 2.

[0045] The tubular ignition transfer charge 2 rests with its outer surface against the inner surface of the support tube 3 and is bonded to it.

[0046] The support tube 3 extends over the entire length of the ignition transfer charge 2 and completely encloses it perpendicular to the ignition channel 5.

[0047] At the in Figure 2 In the illustrated embodiment, the support tube 3 extends beyond the tubular ignition transfer charge 2 at one end of the ignition unit 1 and has a widening 7 there. This widening 7 serves for fixing to a counterpart, for example to a pin-shaped protrusion of a cartridge cap 9 and a cartridge jacket 10 of a propellant charge module 8 ( Figure 3 ).

[0048] For very long ignition units 1, the ignition transfer charge 2 can be made in multiple parts to further reduce the risk of breakage during transport and / or rough handling.

[0049] Figure 3 Figure 1 shows a cross-section of a tubular ignition unit 1 installed in a propellant module 8. The perforations 11 shown are for illustrative purposes.

[0050] The propellant charge module 8 has a cartridge cover 9 and a cartridge jacket 10, each of which in turn has a pin-shaped projection 9a, 10a that engages in the corresponding ends of the support tube 3 for fastening cartridge cover 9 and cartridge jacket 10.

[0051] The cartridge case cover 9 is stepped with a recess 9b for receiving a projecting section of an adjoining (not shown) propellant charge module. The recess 9b has a circumferential rim in which studs 9c are formed, which are uniformly spaced from each other in the circumferential direction and form a clamping connection with the projecting section of an adjoining (not shown) propellant charge module.

[0052] The part of the shell casing 10 covering the opposite end of the propellant charge module 8 is also stepped and has a projecting section 10b for insertion into the recess of the shell cover of a propellant charge module adjoining it (not shown).

[0053] The space between ignition unit 1, case cover 9 and case jacket 10 is filled with propellant powder 12. Reference symbol list:

[0054] 1Ignition unit 2Ignition transfer charge 3Support tube 4Tube interior 5Ignition channel 6Pyrotechnic coating 7Support tube expansion 3 8Propellant module 9Propellant module cap 8 9Tent-shaped protrusion of the cap 9 9bCrust of the cap 9 9cBump on the cap 9 10Propellant module casing 8 10Tent-shaped protrusion of the casing 10 10bProtruding section of the casing 10 11Perforations 12Propellant powder

Claims

1. Ignition unit for a propellant charge (8), comprising - an elongated ignition transfer charge (2) made of propellant powder, through which a free ignition channel (5) runs in its longitudinal direction, and - a combustible support tube (3) that surrounds the ignition transfer charge (2) perpendicular to the free ignition channel (5), characterized by the fact that - the ignition transfer charge (2) is formed from a first material which has a glass transition point below -40°C in an observed temperature range of -51°C to +71°C, and - the support tube (3) is formed from a second material which does not have a glass transition point below +72°C.

2. Ignition unit according to claim 1, characterized by the fact that The second material is composed of 20 - 80 wt% nitrocellulose, 20 - 80 wt% cellulose, 0 - 20 wt% binder resin, 0.4 - 3 wt% stabilizer.

3. Ignition unit according to claim 1, characterized by the fact that the second material contains cellulose.

4. Ignition unit according to one of the preceding claims, characterized by the fact that the support tube (3) extends over the entire length of the ignition transfer charge (2).

5. Ignition unit according to one of the preceding claims, characterized by the fact that the support tube (3) is additionally coated on its outside with a pyrotechnic mixture (6).

6. Ignition unit according to one of the preceding claims, characterized by the fact that the support tube (3) is perforated.

7. Ignition unit according to one of the preceding claims, characterized by the fact that the support tube (3) has at least one end an expansion (7) for fixing to a counterpart.

8. Ignition unit according to one of the preceding claims, characterized by the fact that the first material is composed of 20 - 80% by weight Nitrocellulose 20-50% by weight Nitroglycerin and / or diethylene glycol dinitrate and / or alkyl nitrateoethylnitramine and / or triethylene glycol dinitrate and / or other energetic plasticizers, 0.4 - 3 wt% Stabilizer, 0.5 - 5% by weight Non-energetic plasticizers and other additives.

9. Ignition unit according to one of the preceding claims, characterized by the fact that the first material contains butyl nitrate ethylnitramine as an energetic plasticizer.

10. Ignition unit according to claim 9, characterized by the fact that The first material contains 0.5-1.5 wt% butyl nitratoethylnitramine.

11. Ignition unit according to one of the preceding claims, characterized by the fact that the ignition transfer charge (2) is tubular in shape and the interior of the tube forms the ignition channel (5).

12. Ignition unit according to one of the preceding claims, characterized by the fact that the walls of the ignition channel (5) are at least partially coated (6) with a pyrotechnic mixture.

13. Ignition unit according to one of the preceding claims, characterized by the fact that the ignition transfer charge (2) is profiled on its outside and / or on its inside.

14. Ignition unit according to one of the preceding claims, characterized by the fact that the ignition transfer charge (2) has a longitudinal slot.

15. Ignition unit according to one of the preceding claims, characterized by the fact thatthe ignition transfer charge (2) is formed in multiple parts in the longitudinal direction.

16. Ignition unit according to one of the preceding claims, characterized by the fact that the ignition transfer charge (2) rests with its outer side against the inner side of the support tube (3).

17. Ignition unit according to one of the preceding claims, characterized by the fact that the ignition transfer charge (2) is bonded to the support tube (3).

Images