AU2013202099B2

AU2013202099B2 - Device for igniting a pyrotechnic active material

Info

Publication number: AU2013202099B2
Application number: AU2013202099A
Authority: AU
Inventors: Arno Hahma
Original assignee: Diehl Defence GmbH and Co KG
Current assignee: Diehl Defence GmbH and Co KG
Priority date: 2012-03-30
Filing date: 2013-03-27
Publication date: 2016-07-07
Anticipated expiration: 2033-03-27
Also published as: EP2645049A3; EP2645049A2; AU2013202099A1; PL2645049T3; DE102012006429A1; EP2645049B1; DE102012006429B4; ZA201302286B; ES2590456T3

Abstract

Abstract The invention relates to a device for igniting a pyrotechnic active material and for preventing premature ignition of the pyrotechnic active material, wherein the device has an ignition material (12) contained in a housing (10), on a first side (13) of the housing (10) a first opening (14) in the housing (10) for igniting the ignition material (12) by means of a burning propellant charge (16), on a second side (17) of the housing (10) a second opening (18) in the housing (10) for igniting the active material by burning the ignition material (12), and a slide (20) guided in the housing (10), wherein the slide (20) can assume a closed position and an open position, wherein in the closed position the second opening (18) is closed by the slide (20) in order to prevent premature ignition of the pyrotechnic active material, and in the open position it is open in order to ignite the pyrotechnic active material, wherein the slide (20) is mounted in the housing (10) in such a way that it has to at least partially exit the housing (10) on a third side (24) of the housing (10) in order to assume the open position, and as a result cannot assume the open position as long as the partial exiting from the housing (10) on the third side (24) is prevented by a wall (25), bearing against the third side (24), of a projectile casing (26), wherein the ignition material (12) is contained in a compartment (28) in the housing (10), wherein the first opening (14) and the second opening (18) each lead into the compartment (28), wherein the slide (20) forms a piston-like closure of the compartment (28), which closure is driven into the open position by an excess pressure in the compartment (28) which comes about during the burning of the ignition material (12). Fig. 4 Fig. 4

Description

Device for igniting a pyrotechnic active material

The invention relates to a device for igniting a pyrotechnic active material and for preventing premature ignition of the pyrotechnic active material, as well as to a use of this device.

It is known to use what are referred to as ignition pellets to ignite active materials in pyrotechnic decoys which comprise a propellant charge and an active material. For this purpose, an ignition pellet is usually installed in a housing with a sliding securing means. The housing is arranged between the propellant charge and the active material. After the propellant charge has been ignited, the burning propellant charge ignites the ignition pellet through a first opening in the housing. Arranged opposite the first opening in the housing is a second opening which is aligned with an opening in the sliding securing means. The sliding securing means is usually composed of a slide which is subjected to a spring force and which closes the second opening in the housing and as a result prevents a flame, which is passing through the second opening, of the burning ignition pellet from igniting the active material prematurely. The slide does not clear the second opening in the housing until the burning propellant charge has ejected the active material with the housing which serves as propulsion base from the casing of the decoy. This prevents the active material from being prematurely ignited and reacting, for example, while it is still in the aircraft shooting the decoy or in the firing tube. After the ejection from the casing, the flame of the burning ignition pellet ignites the active material through the second opening in the housing, which is then cleared by the slide.

The spring-activated slide has many disadvantages. It requires a complex design with a relatively large number of parts. For example, springs and guides for the springs are necessary, and the slide itself must be guided in such a way that it has sufficient play to be able to be easily and therefore quickly pushed on by the springs. In order to keep the delay during the ignition process as short as possible, the distance which has to be travelled by the slide to open the second opening is kept as short as possible. The distance is typically 5 to 7 mm. This leads to a situation in which the distance from one edge of the second openings to an edge of the surface of the slide which closes the second opening is relatively short and the flame which originates from the ignition pellet can blow past the slide and through the second opening. As a result, the safety of the tube is not ensured, i.e. premature ignition of the active material, for example in the firing tube, is possible. This is the case, in particular, when, in order to bring about rapid ignition of the active material, the ignition pellet is configured in such a way that it burns with a relatively hot flame. If, for the purpose of increasing safety, the ignition pellet is configured in such a way that the ignition flame is relatively cool, the ignition of the active material takes too long. The basic problem of the sliding mechanism is that the slide cannot be completely sealed because it must always have a certain amount of play in order not to stick during the triggering process. In this context, it is basically possible for the ignition flame to blow through a gap which is present and thereby ignite the active material.

The object of the present invention is to specify a device for igniting a pyrotechnic active material and for preventing premature ignition of the pyrotechnic active material, which device comprises a high level of protection against premature ignition of the active material and at the same time a brief ignition delay. Furthermore, the use of this device is to be disclosed.

The object is achieved by means of the features of Claims 1 and 11. Expedient refinements of the invention can result from the features of Claims 2 to 10 and 12.

According to the invention, a device for igniting a pyrotechnic active material and for preventing premature ignition of the pyrotechnic active material is provided, wherein the device has an ignition material contained in a housing, on a first side of the housing a first opening in the housing for igniting the ignition material by means of a burning propellant charge, on a second side of the housing a second opening in the housing for igniting the active material by burning the ignition material, and a slide guided in the housing. The slide can assume a closed position and an open position, wherein in the closed position the second opening is closed by the slide in order to prevent premature ignition of the pyrotechnic active material, and in the open position it is open in order to ignite the pyrotechnic active material. The slide is mounted in the housing in such a way that it has to at least partially exit the housing on a third side of the housing in order to assume the open position, and as result cannot assume the open position as long as the partial exiting from the housing on the third side is prevented by a wall, bearing against the third side, of a projectile casing or tube. In the device according to the invention, the ignition material is contained in a compartment in the housing, wherein the first opening and the second opening each lead into the compartment, wherein the slide forms a piston-like closure of the compartment, which closure is driven into the open position by an excess pressure in the compartment which comes about during the burning of the ignition material.

In the device according to the invention, the gas pressure which forms when the ignition material burns and, if appropriate, also the gas pressure which forms as a result of burning of the propellant charge of the pulse cartridge is used to drive the slide. The closure is designed here in the manner of a piston in such a way that the slide is moved in a working stroke like the piston of an internal combustion engine when said slide is driven into the open position. A spring for driving the slide is not necessary. As a result, the device according to the invention can be constructed with fewer parts and therefore more cost-effectively than the known device with a slide which is actuated by spring force.

Since the force acting on the slide as a result of the gas pressure can be significantly higher than the force applied by a spring, the slide can be sealed with little play significantly better with respect to the active material, with the result that the possibility of the flame which is formed during the burning of the ignition material blowing past can be virtually ruled out. As a result of the large force which occurs as a result of the excess pressure, the slide can also be completely sealed in order to reliably prevent the flame from blowing past, without, however, preventing the slide from being ejected. As a result of the relatively large force acting on the slide, the slide in the device according to the invention also reacts significantly more quickly than a conventional slide actuated by spring force, with the result that the ignition delay is significantly shorter than in the case of a conventional slide. Since there is no need to provide any space for a spring, the distance which has to be travelled by the slide in order to clear the second opening by assuming the open position can also be significantly longer than in conventional slides. As a result, the probability of an ignition flame blowing past is also reduced. The device according to the invention is significantly safer in a tube than conventional devices, i.e. unintended ignition of the active material in a projectile, provided with the device according to the invention, with a projectile casing is virtually ruled out.

The function of the device according to the invention is as follows:

The device is arranged in a projectile casing, in front of the propellant charge and behind the active material, in the direction of flight of the projectile. After the ignition of the propellant charge, it ignites the ignition material (ignition pellet) through the first opening and at the same time drives the housing out of the casing. However, as long as the housing is still moving within the casing, the slide cannot partially exit the housing and as a result cannot assume the open position. The burning ignition material and the burning propellant charge then develop a high pressure in the compartment. As soon as the housing exits the projectile casing, the slide is no longer prevented from assuming the open position by the wall of the projectile casing. The slide is catapulted into the open position under the high pressure. The flame which starts from the burning ignition material can then ignite the pyrotechnic active material through the second opening.

In one refinement of the active material according to the invention, a stop is present which prevents the situation in which after the slide has reached the open position it carries out a further movement causing it to exit the compartment. As a result, the exiting of the slide from the compartment is prevented from bringing about a relief opening from which the hot gases which are formed during the burning of the ignition material and the ignition flame which starts from the ignition material can escape. As a result, a relatively high pressure is reached in the compartment, with the result that the gases with a relatively high pressure flow through the second opening. This increases the safety of the ignition of the active material and reduces the ignition delay. The stop can be made available, for example, by a securing pin or a latching projection.

The device according to the invention is particularly efficient if the slide is configured in such a way that during its movement for assuming the open position it exits the first opening. This causes a very high pressure to be built up in the compartment after the ignition of the ignition material because the gas which is formed can then no longer escape through the first opening but only still through the second opening when the open position is assumed. As a result, a ignition flame which is formed with high energy is blown out in the direction of the active material. The ignition safety is thereby increased greatly and the ignition delay greatly reduced. As a result, reliable ignition with a smaller quantity of ignition material than hitherto customary can be achieved.

In one refinement of the device according to the invention, the slide is configured in such a way that during the movement of said slide to assume the open position, said slide closes the first opening before or even significantly before the second opening opens. This ensures that the ignition material burns briefly in an enclosed space and generates an even higher gas pressure, which catapults the slide even more quickly into the open position. When the open position is reached, the built-up pressure is relieved suddenly through the second opening in the direction of the active material. As a result, even more reliable ignition with a still small ignition delay is achieved.

Furthermore, the closing of the first opening prevents the ignition flame from exiting the first opening. This occurs, in particular, with projectiles which move at high speeds because an underpressure arises behind the securing element in the direction of flight, which underpressure pulls the flame towards the rear out of the housing through the first opening. As a result, the flame which passes through the second opening on the side of the active material is weakened and an ignition delay occurs. The problem is amplified to a greater extent by a drop in atmospheric pressure. Given customary flight altitudes of decoys which are shot over 10 km, this effect is therefore extremely relevant. It can even cause the ignition of the active material to be prevented. A further advantage which is associated with the closing of the first opening, in particular in the case of decoys, is that the closure of the first opening means that no radiation penetrates to the outside from the flame which is produced during the burning of the ignition material. This is important in particular in the case of spectral decoys because customary ignition materials are strong one with black bodies during the burning, and the spectrum of the burning ignition material differs significantly from the spectrum of the active decoy material. As a result of the radiation which is emitted by the burning ignition material, detection systems can discover that this is just a decoy and not an aircraft. The avoidance of outward penetration of detectable radiation which results from burning of the ignition material is a significant advantage of the device according to the invention and is not ensured by ignition devices which have been known hitherto.

The slide can have an, in particular cup-like, recess which is open towards the compartment and in which the ignition material is contained, wherein the recess has a first breakthrough and a second breakthrough, wherein in the closed position the first breakthrough is aligned with the first opening, and in the open position the second breakthrough is aligned with the second opening. As a result of the recess in the slide, it is possible to ensure that the force acting on the slide during the burning of the ignition material acts virtually exclusively in the direction of its movement in order to assume the open position. As a result, a further reduction in the ignition delay can be achieved. The ignition material can be in the form of an ignition pellet, i.e. as a moulded pellet which is formed from the ignition material. The ignition material can be composed of any desired pyrotechnic firing charge, for example from boron potassium nitrate, barium peroxide magnesium or barium peroxide zirconium boron. A clamping means, in particular a clamping strip, which is introduced into the housing can be formed between the housing and the slide, or a guide for the slide can be formed in the housing, or the slide itself can be formed, in such a way that, when the slide is inserted into the closed position the clamping means or a component of the housing or of the slide is deformed in such a way that as a result the slide is clamped tight in the closed position in such a way that it can be released from this closed position by the excess pressure. The component of the housing or of the slide can be a fold or a bellows. This avoids a situation in which the slide has play in a direction of movement. As a result, the slide cannot shake free through vibrations and thereby, for example, damage the ignition material.

In one refinement of the device according to the invention, there is no spring present for moving the slide by spring force.

In a further refinement of the device according to the invention, said device is embodied as a propulsion base. This can be ensured by the presence of a sealing lip or of a sealing ring which is formed by the housing or is separate. The sealing lip or the sealing ring prevents the situation in which gases which are formed during the burning of the propellant charge can flow past between the wall of the projectile casing and the housing and as a result cannot contribute to driving the device with the active material arranged in front of it out of the projectile casing. The sealing lip or the sealing ring can be composed, for example, of polyethylene or polyamide or from some other suitable material.

In order to increase the safety of the device with respect to the forces which occur during the use thereof, the housing and/or the slide can be composed of a plastic, in particular polycarbonate or polyamide, which is reinforced with fibres, in particular glass fibres or carbon fibres. The proportion of fibres is approximately 30% in one refinement.

According to the invention, the use of a device according to the invention for igniting a pyrotechnic active material is furthermore provided. The device can for this purpose be arranged in a projectile casing and serve to ignite the active material during or after the exiting of the projectile casing. The active material may be an active decoy material.

The invention is explained below with reference to an exemplary embodiment and the figures. In the drawings:

Figs 1 to 3 show a device for igniting a pyrotechnic active material and for preventing premature ignition of the pyrotechnic active material according to the prior art,

Fig. 4 shows a schematic cross-sectional illustration of the device according to the invention with a slide in the closed position,

Fig. 5 shows a schematic perspective illustration of the device according to the invention with the slide in the closed position,

Fig. 6 shows a schematic perspective cross-sectional illustration of the device according to the invention with the slide in an open position,

Fig. 7 shows a schematic perspective illustration of the device according to the invention in a cross section along the line A-A' in Fig. 6,

Fig. 8 shows a schematic cross-sectional illustration of the device according to the invention with the slide in the closed position in a casing with a propellant charge before the ignition of the propellant charge,

Fig. 9 shows a schematic perspective cross-sectional illustration of the device according to the invention after the ignition of the propellant charge and during the exiting of the device from the casing with the slide in open position, and

Fig. 10 shows a schematic cross-sectional illustration of the individual parts of the device according to the invention.

The schematic, perspective illustration of the ignition device according to the prior art, illustrated in Fig. 1, shows a housing 10 with a slide 20, actuated by springs 22, in the closed position. The slide 20 has a breakthrough 6 for the ignition of an active material, and a further breakthrough 5 for a stop 30 in the form of a securing pin to engage through. Fig. 2 shows a cross section through the device according to Fig. 1 along the line A-A' , and Fig. 3 shows a cross section through the device according to Fig. 1 along the line B-B'. The cross sections show, in the centre, a receptacle 8 for an ignition material 12 in the form of an ignition pellet. The receptacle 8 has an opening 9 which is closed off by the slide 20. In the figures 1 to 3, the slide 20 is closed, but it can also be opened by the force of the springs 22. As long as the housing 10 is still inserted in a projectile casing (not illustrated here), the slide 20 can, however, not exit the housing 10. If the slide 20 is opened by the force of the springs 22 after the projectile casing is exited, the breakthrough 6 for the ignition enters a position of congruency with the opening 9, with the result that the flame coming from the burning ignition material 12 can pass through the opening 9 and the breakthrough 6 for the ignition and can ignite an active material (not illustrated here) which is arranged above it.

Fig. 4 shows a device according to the invention in cross section. A compartment 28, which is closed off by the slide 20, is provided in the housing 10. The ignition material 12 is arranged in a recess 32 in the slide 20 which is open towards the compartment 28. The ignition material 12 is therefore also contained in the compartment 28. The slide 20 has a first breakthrough 34, which in the closed position of the slide 20 illustrated here is aligned with a first opening 14 in the housing 10. The second opening 18 is closed off by the slide 20. The slide also has a second breakthrough 36. The stop 30 is formed by a securing pin. Furthermore, a sealing ring 38 is provided with a sealing lip 11 and a third opening 19 which is aligned with the first opening 14. The sealing ring 38 therefore serves as a propulsion base. The device has a first side 13, a second side 17 and a third side 24, which can be surrounded by the wall 25 of a projectile casing 26.

Fig. 5 shows the device in a perspective illustration from the outside. The housing 10 can be seen here with the inserted slide 20, and the sealing ring 38 can be seen with the third opening 19 and the sealing lip 11.

Fig. 6 shows the device according to the invention with the slide 20 in an open position in cross section, and Fig. 7 shows the same situation in a cross section along the line A-A' illustrated in Fig. 6. The ignition material 12 can be composed of any desired known firing charge, for example boron potassium nitrate, barium peroxide magnesium boron or barium peroxide zirconium boron. The ignition material 12 can be in the form of a pressed pellet which is only inserted into the slide 20 or else bonded into the slide 20. The pellet can become detached during burning. This can favourably influence the function since, as a result, sparks can be thrown through the second opening 18 in the direction of the active material. The sparks can bring about more effective ignition of the active material. According to an advantageous embodiment of the invention, a braking device is provided through which the slide 20 is braked in a protective fashion before the open position is reached, in order to attenuate an impact into the housing. This can prevent an impact, caused by a slide 20 moving at high speed, from damaging the housing 10 or the slide 20. Such protective braking can be implemented by a braking distance which is extended in terms of length compared to the absent braking distance of a hard, unbraked stop. For this purpose, the elongated hole of the further breakthrough 5 preferably tapers in the same end section of the elongated hole which accommodates the stop 30 in the open position of the slide 20. As a result of the fact that at the transition into the open position the stop 30 runs into the wedge-shaped opening of the end section of the elongated hole, the braking of the slide 20 is no longer so abrupt. The softness of the braking can be amplified even further by making the material of the stop 30 and/or of the walls of the wedge-shaped opening of the end section of the elongated hole slightly deformable. Another possible way of implementing a braking distance which can be extended by means of length is to provide a slightly deformable compression material in the same end section of the elongated hole which accommodates the stop 30 in the open position of the slide 20. At the transition into the open position, the compression material is compressed by the stop 30 and the slide 20 is gently braked here.

The device can be inserted with the slide 20 in the closed position into a projectile casing 26, in which the sealing ring 38 is arranged on sides of the propellant charge 16. This is illustrated in Fig. 8. In this arrangement, the wall 25 of the projectile casing 26 prevents the slide 20 from partially exiting the housing 10, even if the ignition material 12 has been ignited.

Fig. 9 shows the situation after the ignition of the propellant charge 16 at the moment at which the device is driven out of the projectile casing 26. The slide 20 is released through the exiting of the projectile casing 26. The burning of the ignition material 12 which is ignited by the burning propellant charge 16 through the first opening 14 and third opening 19 brings about, after the generation of gas, a severe increase in pressure in the compartment 28, which increase drives the slide 20 into the open position as far as the stop 30. In this open position, the burning ignition material 12 can blow an ignition flame through the second opening 18 to the active material (not illustrated here) , and as a result ignite the active material.

Fig. 10 shows the housing 10, the slide 20 which is to inserted therein, with the ignition material 12 and the stop 30 in the form of a securing pin, to be inserted after the insertion of the slide 20, and the sealing ring 38 as individual parts.

List of reference numerals 5 Further breakthrough 6 Breakthrough for the ignition 8 Receptacle 9 Opening 10 Housing 11 Sealing lip 12 Ignition material 13 First side 14 First opening 16 Propellant charge 17 Second side 18 Second opening 19 Third opening 20 Slide 22 Spring 24 Third side 25 Wall 26 Projectile casing 28 Compartment 30 Stop 32 Recess 34 First breakthrough 36 Second breakthrough 38 Sealing ring

Claims

Patent Claims

1. Device for igniting a pyrotechnic active material and for preventing premature ignition of the pyrotechnic active material, wherein the device has an ignition material (12) contained in a housing (10), on a first side (13) of the housing (10) a first opening (14) in the housing (10) for igniting the ignition material (12) by means of a burning propellant charge (16), on a second side (17) of the housing (10) a second opening (18) in the housing (10) for igniting the active material by burning the ignition material (12), and a slide (20) guided in the housing (10), wherein the slide (20) can assume a closed position and an open position, wherein in the closed position the second opening (18) is closed by the slide (20) in order to prevent premature ignition of the pyrotechnic active material, and in the open position it is open in order to ignite the pyrotechnic active material, wherein the slide (20) is mounted in the housing (10) in such a way that it has to at least partially exit the housing (10) on a third side (24) of the housing (10) in order to assume the open position, and as a result cannot assume the open position as long as the partial exiting from the housing (10) on the third side (24) is prevented by a wall (25), bearing against the third side (24), of a projectile casing (26), wherein the ignition material (12) is contained in a compartment (28) in the housing (10), wherein the first opening (14) and the second opening (18) each lead into the compartment (28), wherein the slide (20) forms a piston-like closure of the compartment (28), which closure is driven into the open position by an excess pressure in the compartment (28) which comes about during the burning of the ignition material (12).
2. Device according to Claim 1, wherein a stop (30) is present which prevents the situation in which after the slide (20) has reached the open position it carries out a further movement causing it to exit the compartment (28).
3. Device according to one of the preceding claims, wherein the slide (20) is configured in such a way that during the movement of said slide (20) to assume the open position, in particular before the second opening (18) opens, said slide (20) closes the first opening (14).
4. Device according to one of the preceding claims, wherein the slide (20) has an, in particular cup-like, recess (32) which is open towards the compartment (28) and in which the ignition material (12) is contained, wherein the recess (32) has a first breakthrough (34) and a second breakthrough (36) , wherein in the closed position the first breakthrough (34) is aligned with the first opening (14), and in the open position the second breakthrough (36) is aligned with the second opening (18).
5. Device according to one of the preceding claims, wherein the ignition material (12) is in the form of an ignition pellet.
6. Device according to one of the preceding claims, wherein a clamping means, in particular a clamping strip, which is introduced into the housing (10) is formed between the housing (10) and the slide (20), or a guide for the slide (20) is formed in the housing (10), or the slide (20) is formed, in such a way that, when the slide (20) is inserted into the closed position a component of the housing (10) or of the slide (20) or the clamping means is deformed in such a way that as a result the slide (20) is clamped tight in the closed position in such a way that it can be released from this closed position by the excess pressure .
7. Device according to one of the preceding claims, wherein there is no spring (22) present for moving the slide (20) by spring force.
8. Device according to one of the preceding claims, wherein the device is embodied as a propulsion base, in particular through the presence of a sealing lip (11) or of a sealing ring (38) which is formed by the housing (10) or is separate.
9. Device according to Claim 8, wherein the sealing lip (11) or the sealing ring (38) is composed of polyethylene or polyamide.
10. Device according to one of the preceding claims, wherein the housing (10) and/or the slide (20) are/is composed of a plastic, in particular polycarbonate or polyamide, which is reinforced with fibres, in particular glass fibres or carbon fibres.
11. Use of a device according to one of the preceding claims for igniting a pyrotechnic active material.
12. Use according to Claim 11, wherein the active material is an active decoy material.