Method to produce pyrotechnical igniting mixtures

Details Method to produce pyrotechnical igniting mixtures Method to produce pyrotechnical igniting mixtures

2000-11-28

2004-08-31

Felton, Aileen B. (Department: 3641)

Explosive and thermic compositions or charges

Structure or arrangement of component or product

Solid particles dispersed in solid solution or matrix

C149S019300, C149S042000, C149S077000, C149S108600, C149S109600

Reexamination Certificate

active

06783616

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a method for producing pyrotechnical igniting mixtures on the basis of metal powders or metal hydrides, potassium perchlorate and binding agents.
Pyrotechnical igniting mixtures are mixtures of solid matter in mostly the powdery state whose components consist mainly of reducing agents and oxidizing agents. When a sufficient quantity of energy is supplied, e.g. in form of an igniting flame, an oxidation-reduction process is initiated: the pyrotechnical mixture will burn away more or less intensely depending on make-up and arrangement.
Pyrotechnical igniting mixtures have numerous uses and are used, for example, as igniting heads of matchsticks, in flare and signal ammunition, in smoke and cloud bodies, in gas generators, e.g. for safety airbags, and in numerous other arrangements in fireworks bodies.
Pyrotechnical igniting mixtures are usually produced by dry mixing of the individual components. If this is performed by hand, the comminuted components are pressed through screens and mixed thoroughly. In the case of mixing by machines, the components of the pyrotechnical mixture are filled in the unmixed state into the receptacle, with optional prior comminution, and mixed in the same by stirrers, rotational movements of the mixing receptacle or devices that apply shearing forces. Suitable mixing devices are asymmetric moved mixers, tetrahedral mixers, planetary mixers or mixing apparatuses derived from or combined with the same.
Pyrotechnical igniting mixtures are often used as granulate, because they can be better poured and apportioned in this form. Granulation is performed by adding a suitable solvent to the dry igniting mixture and mixing in special receptacles. In this process the solvent can already be contained in the binding agent in dissolved form, or the binding agent component which is swellable with the solvent or is soluble in the same is already located in powder form in the pyrotechnical mixture, so that on adding the solvent adhesive forces are able to form which finally lead to the granulate form. Special granulate mixers are provided for the formation of the granulate form. The solvent is removed again by subsequent drying, so that a pourable material is obtained that can be apportioned.
When the components of the pyrotechnical igniting mixture are very fine or the energy stored in the same is very high, measures must be taken in order to keep the hazards manageable during production. The mechanical and thermal sensitivity of these igniting mixtures is often so strong, that handling the same without suitable safety measures is not advisable.
Numerous safety regulations take into account the hazardousness during production. Accordingly, pyrotechnical mixtures are listed according to groups of hazardousness in the accident prevention regulations as issued by the social insurance institutions against occupational accidents. The regulations demand graded safety precautions in the production of the mixtures. The two most hazardous groups may no longer be mixed by hand. They are mixed automatically behind protective walls or in a separated room which is closed off from the control room by a resisting wall. This type of production is usually called “working under security”. This applies primarily for dry powdery components.
If measures are taken during the mixing which reduce the ignitability and the mechanical or thermal sensitivity of the mixtures, reductions in the grading can be made for the above breakdown into groups. One such measure is mixing the components not in the dry state, but together with a liquid.
This method is used particularly during the mixture of pyrotechnical igniting mixtures. By adding solvents such as water, pyrotechnical igniting mixtures can be produced with considerably fewer hazards than in the dry state. The energy stored in the igniting mixtures is still so high, however, that the effects of an ignition caused by an accident prevent the processing by hand even in the wet state. Moreover, the mass of the mixture quantity must be kept low (usually under 100 grams), so that any ignition even during production remains securely manageable.
A further difficulty in this method is the dimensioning of the quantity of the liquid. On the one hand it must be large enough to clearly reduce the hazard of an ignition while mixing the pyrotechnical mixture. On the other hand, any increase in the quantity of liquid also increases the subsequent duration of drying. Moreover, the danger of cracking and shrinkage cavitation increases during drying. Cracks and shrinkage endanger the secure function of the igniting mixture during its ignition.
Since the liquid is included in the mixture which is subsequently dosed in the igniter during the production of the pyrotechnical igniting mixture, but is not involved in the actual conversion of the igniting mixture, the liquid content of the mixture must be precisely definable and must also be kept constant during the dosing. Only in such cases will the igniting mixtures have the same properties during the subsequent drying.
It is further known that liquid paste-like mixtures for pyrotechnical igniting mixtures with components of different density, solubility or electric environment, e.g. the formation of dipoles or charging in the same or opposite direction, are relatively difficult to handle. In the mixtures the various solid components have different sedimentation speeds, so that after a short dwell time the liquid and the solids separate and make the reproducible dosing of the mixture more difficult, which again impairs the quality of the igniter.
SUMMARY OF THE INVENTION
The invention is based on the object of providing a method to produce pyrotechnical igniting mixtures of the kind mentioned above with which the employed components can be mixed homogeneously, the hazard of an ignition can simultaneously be reduced considerably and a reproducible dosing is enabled.
This object, as well as other objects which will become apparent from the discussion that follows, are achieved, in accordance with the present invention, by producing suspensions from the individual components of the pyrotechnical igniting mixture with the help of liquid dispersing agents, with the suspensions, which are not explosive or only marginally so, being mixed by using ultrasonic sound; immediately after the mixing dosing the mixture in this consistency in the desired quantity; and thereafter removing the dispersing agent from the dosed quantity.
Accordingly, several homogenous suspensions are produced from the individual components for the pyrotechnical igniting mixture with the help of suitable liquid dispersing agents, with these suspensions not being explosive or only marginally so. The suspensions are mixed in small quantities with the help of ultrasonic sound. The mixture is dosed in this consistency immediately thereafter for the igniter in the respective, desired quantity; e.g., in igniters or on igniting elements, whereupon the dispersing agents are removed from the dosed quantity.
The application of ultrasonic sound on liquid mixtures made of several components is known, for example from the German Patent Publication No. DE-A1-27 12 603 which discloses a method and an apparatus for modifying the characteristics of a liquid with the several components of the liquid being homogenized by means of ultrasound while flowing through a pipe. It is also known from Soviet patent applications 2050963 and 2056926 to use ultrasonic dispersing mixers in order to thoroughly mix different components, particularly in the foodstuff area. The homogenization or mixing is performed in all these mixing methods in a continuous manner. A respective dosing or drying of the dosed mixture is not provided. Moreover, these methods do not consider any safety measures which need be considered in the mixture of pyrotechnical igniting mixtures.
In accordance with the invention the suspensions which are not explosive, or only marginally so, are mixed in small quantities in batches and dosed immediately after sai

Affiliated with

Also associated with

Rating

Method to produce pyrotechnical igniting mixtures does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method to produce pyrotechnical igniting mixtures, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method to produce pyrotechnical igniting mixtures will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3317281