EP3218331B1 - Pyrotechnical retarding element - Google Patents

Description

The invention relates to a pyrotechnic delay element for use in pyrotechnic ignition chains and in particular to a delay set therein. The delay element is characterized by a flexible and simple adjustment of the burning speed over a wide range.

In the case of pyrotechnic ammunition, they are triggered by firing chains, which can consist of several firing devices. The task of this ignition chain is to convert an external trigger pulse into a pyrotechnic reaction and to make the active charge react at the desired time. It is often necessary to adhere to a certain time interval between the external trigger and the reaction of the active charge. Since the times for external triggering and reaction of the active charge are usually uninfluenced, a so-called delay element within the ignition chain must ensure the necessary time interval (delay time). This delay time can range from a few milliseconds to several seconds, depending on the application.

A typical embodiment of a delay element (also called ignition retarder) shows illustration 1 , The ignition retarder (1) consists of a cylindrical metal tube (2) and usually contains three pyrotechnic sentences. The cylindrical metal tube (2) is preferably made of steel, brass or aluminum. On the input side is the flame-sensitive firing set (3), which is ignited by the upstream igniter and has the task of safely igniting the subsequent, usually less sensitive, delay set (4). On the output side, after the delay set, there is the firing set (5), which ensures the transfer of the reaction to the next kindling. The pyrotechnic reaction runs linearly through the ignition retarder therethrough. All sets are introduced into the metal body by single or multi-part loading and pressing processes. From the design point of view of the ammunition, it is desirable to implement the different delay times with a fixed length of the ignition retarder. Since the quantity of the firing set (5) must be kept constant (ensuring an even output) and the length of the firing can only be varied to a limited extent, the delay time can preferably be controlled by the set composition. A delay rate system is therefore necessary that enables the desired delay time to be set by fine-tuning its composition.

Pyrotechnic delay sets have been known for decades and are also used in civilian blasting technology with so-called detonator detonators. They usually consist of a mixture of fuel and oxidizing agent. Compared to civilian applications, there are additional requirements when used in pyrotechnic ammunition. The burning capacity (i.e. the reliable linear erosion of the deceleration set) must be given over a wide temperature range (at least -54 ° C to +71 ° C) and largely independent of the pressure conditions. Ideally, the burning rate should have little or no dependence on temperature and external pressure. A distinction is made between ignition retarders in "closed" and "open" construction. When the construction is closed, a triggering element (for example a primer) and a cover for the firing kit are integrated. The surfaces of the firing and firing are exposed in an open construction. The open design requires the pyrotechnic kits to be largely independent of the burning speed from the external pressure. In addition, a high stability of the delay sets and compatibility with the contact materials is necessary to ensure the long lifespan between 12 and 20 years. The burning speed should not change during this period. Pyrotechnic delay sets can be used as a dry mix of the starting materials or in a wet process with the addition of a binder as granules of the starting materials.

A pyrotechnic delay element is used in the EP 0847972 A1 disclosed. Among other things, the delay element can consist of black powder, silicon, ferric oxide and binder.

An alternative to this delay rate is in the European application EP 0304973 A1 called. Among other things, a delay set with a long delay period containing tungsten, lead chromate, nitrocellulose, Ferozen and polytetrafluoroethylene is mentioned.

At present, pyrotechnic delay sets are often used in open ignition retarders for military applications, which contain SVHC substances (Substances of Very High Concern) on the one hand and on the other hand have a comparatively clear temperature response of the burning time. A typical representative of these delay sets is a system consisting of potassium perchlorate, lead chromate, antimony and a binder such as nitrocellulose. With lead chromate, this delay rate contains an SVHC substance that has been subject to approval since May 2015 in accordance with Regulation (EC) No. 1907/2006 REACH. In addition, the temperature response in the processed state in the ignition retarder is approx. 10 to 20% of the nominal value of the delay time (temperature range: -54 ° C to +71 ° C). In order to increase the precision of the pyrotechnic ammunition, a significant improvement is desirable here.

• eine Einstellmöglichkeit der Verzögerungszeit von 0,5 bis 5 s innerhalb einer Rahmenzusammensetzung des Verzögerungssatzes bei vorgegebener Geometrie und Ausführung des Anzündverzögerers gestatten,
• die Funktionsfähigkeit im Temperaturbereich zwischen -54°C und +71 °C sicherstellen,
• eine geringe Abhängigkeit der Verzögerungszeit von der Umgebungstemperatur und vom äußeren Druck aufweisen sowie
• die Einhaltung der Verzögerungszeit über einen Zeitraum von mindestens 12 Jahren gewährleisten.

The present invention has for its object to provide a pyrotechnic delay element for pyrotechnic ignition chains. This should:

• allow the delay time to be set from 0.5 to 5 s within a frame composition of the delay set for a given geometry and design of the ignition retarder,
• ensure functionality in the temperature range between -54 ° C and +71 ° C,
• have a slight dependence of the delay time on the ambient temperature and on the external pressure and
• ensure compliance with the delay time over a period of at least 12 years.

The aforementioned objectives are achieved by a delay element which contains a firing kit, a delay kit and a firing kit mixture in a metal sleeve, wherein in the firing and firing kit mixture at least 35 parts by weight of boron, at least 15 parts by weight of iron (III) oxide and at least 5 parts by weight of potassium perchlorate are contained in addition to 100% by weight and the mixture of the retardation sentence contains at least 5 parts by weight of potassium perchlorate, at least 10 parts by weight of titanium (IV) oxide, at least 25 parts by weight of tungsten and at least 1 part by weight of aluminum. Components listed in the mixtures with a minimum content and optionally at least one further component add up to 100 parts by weight.

The aforementioned goals are also achieved by a delay element in which the firing and firing mixture consists of at least 70 parts by weight of red lead and at least 20 parts by weight of silicon.

The mixtures of the firing and firing rate and the delay rate preferably also contain 0.1-3% by weight of a binder as an additive.

The mixtures of the firing and firing set and the retarding set particularly preferably contain 0.1-3% by weight of cellulose ether (tylose), nitrocellulose or polyvinyl alcohol as an additive.

The high flexibility of the proposed delay rate system can be demonstrated by measuring the delay time in ignition retarders. For this purpose, the delay set as well as the firing and firing set in the ignition retarder are in illustration 1 introduced and compacted. Here, (2) denotes the metal sleeve for receiving the sets, (3) the firing kit, (4) the delay kit and (5) the firing kit.
For example, the length of the metal sleeve is 19 mm with an outside diameter of 6 mm and an inside diameter of 3.6 mm. The height of the deceleration column is 9 mm in all examples. Firing and firing each have a height of 5 mm. The delay time is then defined as the time between the lighting of the firing charge and the reaction of the firing charge ( Figure 2 ).

The invention is explained in more detail by the following exemplary embodiments.

example 1

The preferred delay time of 2.25 s can be achieved, for example, with the following pyrotechnic sentences: Anfeuerungssatz: • Set amount: approx. 100 mg • Composition: boron 65% Iron (III) oxide 25% potassium perchlorate 10% • Set amount: about 320-370 mg • Composition: tungsten 40% Titanium (IV) oxide 45% aluminum 5% potassium perchlorate 10% • Set amount: about 110mg • Composition: boron 45% Iron (III) oxide 45% potassium perchlorate 10%

The desired good burn-through capacity could be verified by testing approx. 1000 ignition retarders of this version. Based on 1000 error-free tests, there is a minimum reliability of 99.7% (level of trust 95%), which clearly exceeds the usual military requirements for such components by 99%.

The dependence of the burning time on the temperature was determined on the basis of the delay time in the ignition retarder in the temperature range between -54 ° C and +71 ° C. In the temperature range under consideration, it is approx. 8% based on the burning rate at room temperature and is therefore significantly below the value of approx. 10 - 20% in conventional batch systems (e.g. potassium perchlorate / lead chromate / antimony).

Long-term stability has been demonstrated by material tests and environmental simulation programs with loaded ignition retarders. The results of these studies allow a positive prognosis for use over more than 12 years.

Example 2

A further preferred delay time of 0.6 s can be set while maintaining the firing and firing as well as the height of the delay kit column of 9 mm with the following composition of the delay kit: • Set amount: about 320-370 mg • Composition: tungsten 50% Titanium (IV) oxide 30% aluminum 10% potassium perchlorate 10%

Example 3

A further preferred delay time of 3.5 s can be set while maintaining the firing and firing and the height of the delay kit column of 9 mm with the following composition of the delay kit: • Set amount: about 320-370 mg • Composition tungsten 44% Titanium (IV) oxide 41.5% aluminum 2% potassium perchlorate 12.5%

Claims (8)

1. Pyrotechnical retarding element characterized in that it has a lighting charge mixture, a retarding charge mixture and a firing charge mixture , the lightning charge mixture and the firing charge mixture containing at least 40% by weight boron, at least 15% by weight iron(III)oxide and at least 5% by weight potassium perchlorate , the percentages adding up to 100% in each mixture, and the retarding charge mixture containing at least 5% by weight potassium perchlorate, at least 10% by weight titanium(IV) oxide, at least 25% by weight tungsten and at least 1% by weight aluminum.
2. Pyrotechnical retarding element, in which the lighting charge mixture and the firing charge mixture consist at least of 70% by weight of read lead and at least 20% by weight of silicon, characterized in that the retarding charge mixture contains at least 5% by weight potassium perchlorate, at least 10% by weight titanium(IV) oxide at least 25% by weight tungsten and at least 1% by weight aluminum.
3. Pyrotechnical retarding element according to claim 1, characterized in that the lightning charge mixture and the firing charge mixture contain 35 to 75% by weight boron, 15% to 55% by weight iron(III)oxide and 5% to 15% by weight potassium perchlorate, and the retarding charge mixture contains 5% to 15% by weight potassium perchlorate, 20 to 55 % by weight titanium(IV) oxide, 25 to 55% by weight tungsten and at least 1 to 10% by weight aluminum.
4. Pyrotechnical retarding element according to claim 1 or 2, characterized in that the retarding charge mixture contains 5 to 15% by weight potassium perchlorate, 20 to 55 % by weight titanium(IV) oxide, 25 to 55% by weight tungsten and at least 1 to 10% by weight aluminum.
5. Pyrotechnical retarding element according to claim 1 or 2, characterized in that the lightning charge mixture and the firing charge mixture and/or the retarding charge mixture contain 0,1 to 3 % by weight of a binding agent.
6. Pyrotechnical retarding element according to claim 5, characterized in that 0,1 to 3 % by weight of polyvinyl alcohol is present as binding agent.
7. Pyrotechnical retarding element according to claim 5, characterized in that the retarding charge mixture contains 0,1 to 3 by weight of cellulose ether as binding agent.
8. Pyrotechnical retarding element according to claim 5, characterized in that 0,1 to 3 % by weight of nitro cellulose is present as binding agent.

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