EP1741690B1 - Process for continuous production of pyrotechnical objects - Google Patents

Description

The present invention relates to a continuous manufacturing process of a pyrotechnic object.

The present invention provides an improvement to existing processes to date.

• des pâtes de propergol, notamment utiles à la propulsion des moteurs-fusées, des intercepteurs ...
• des explosifs, et
• des objets pyrotechniques à structure bifonctionnelle du type tête explosive montée sur un corps de propulsion ...

It is particularly applicable in the field of manufacturing:

• propellant pastes, particularly useful for the propulsion of rocket engines, interceptors ...
• explosives, and
• pyrotechnic objects with bifunctional structure of the explosive head type mounted on a propulsion body ...

It relates more particularly to the manufacture of large pyrotechnic objects (whose mass m is such that 100 kg ≤ m <500 tons).

The process currently used to manufacture this type of product is a batch process (called "batch"), which consists of preparing a certain amount of product in one (several) kneaded (s), to cast the (the) said (s) kneaded (s) in one or more loads, to cook (s) said (s) load (s).

In a first step, the various ingredients, weighed beforehand, are introduced into a kneader in an appropriate order where they are carefully and extensively kneaded, under pressure conditions (generally vacuum) and very precise temperature.

In a second step, the mixture, which is then in the form of a very viscous paste, is cast in a mold, with shaping tools. The casting is done either by gravity, under vacuum, through a grid; either in source, at atmospheric pressure, via a cannula (pipe) sealing or not. For some large loads, it is necessary to chain several kneaded / poured in the same mold.

The set - casting paste + mold - is baked to ensure the hardening of the dough. The mold is in some cases the same envelope of the prepared pyrotechnic object, envelope that is properly prepared for carrying out the loading.

Some shipments must be made with several different formulations, to meet different constraints, ballistic, vulnerability, for example. In such cases, several successive operations are carried out, batchwise, with said different formulations and the multi-composition loadings are thus obtained after several successive casting and firing operations. Obtaining, with a change of formulation, such loadings. (variable composition), is revealed, in the context of a batch process, a particularly heavy and expensive implementation.

To propose a continuous process, which allows efficient formulation changes and easy implementation, is therefore the technical problem that the inventors have faced.

• par Eric Giraud, Jean-Michel Tauzia, G. Lacroix et Constance M. Murphy, Richard S. Muscato, William F. Newton, Frederick M. Gallant, Mark A. Michienzi, Sharperson G. Johnson, dans v 44 de ICT (Institut Chemische Technologie) 1998 - 29th International Annual Conference ;
• par Hugh A. Bruck, Frederick M. Gallant et Swami Gowrisankaran dans Proceedings of IMECE 2003, 2003 ASME International Mechanical Engineering Congress and R & D Expo, Washington, DC, November 15-21, 2003 .

Methods of continuous manufacture of pyrotechnic objects have already been described, in particular:

• by Eric Giraud, Jean-Michel Tauzia, G. Lacroix and Constance M. Murphy, Richard S. Muscato, William F. Newton, Frederick M. Gallant, Mark A. Michienzi, Sharperson G. Johnson, in v 44 of ICT (Chemische Institute Technology) 1998 - 29th International Annual Conference ;
• by Hugh A. Bruck, Frederick M. Gallant and Swami Gowrisankaran in Proceedings of IMECE 2003, 2003 ASME International Mechanical Engineering Congress and R & D Expo, Washington, DC, November 15-21, 2003 .

In the first of these publications, results of studies on the continuous manufacture of solid propellants are presented. A French team has studied a process of kneading and continuous casting, a US team a process of kneading and continuous extrusion. These two techniques are considered, by the person skilled in the art, as very different. This document also provides no teaching on compositional changes during the process ...

In the second of these publications, the technology in question is that of continuous mixing and extrusion ("TSE = Twin Screw Extrusion") It is shown that composite materials can be obtained with an axial and / or radial composition gradient.

The outlets of the extrusion process are more limited than those of the casting process, with reference to the size of the objects that can be made. Industrially, this process is used for the manufacture of objects from a few tens of grams (a few millimeters in diameter) to a dozen kilograms (about ten centimeters in diameter), in large series.

However, the continuous composition change has only been described in this context of extrusion (in which the object, which has a sufficient viscosity, is shaped as soon as it leaves the die), where it is certainly more easily controlled than during a casting. During a casting, one is particularly confronted with jet interpenetration problems.

• ni l'existence de réticences sérieuses pour renoncer au procédé traditionnel en discontinu ;
• ni l'existence de préjugés certains à l'encontre de la mise en oeuvre d'un changement de composition dans le cadre d'un procédé de malaxage et coulée en continu.

The inventors, confronted with the technical problem mentioned above, did not ignore:

• nor the existence of serious reluctance to abandon the traditional batch process;
• or the existence of certain prejudices against the implementation of a change of composition in the context of a process of kneading and continuous casting.

They have developed the present invention despite said reluctance and prejudices and have shown the feasibility of a kneading and continuous casting process to obtain a pyrotechnic object with several compositions.

• d'alimentation d'un organe de mélange en les différents constituants dudit objet ; ledit organe de mélange étant du type monovis ou bivis corotative ou contrarotative,
• de mélange desdits différents constituants dans ledit organe de mélange, avec progression au sein de la structure dudit organe de mélange,
• de coulée du mélange obtenu en sortie dudit organe de mélange, ledit mélange présentant une viscosité comprise entre 200 et 3 000 Pa.s.

According to its first object, the present invention therefore relates to a continuous process for manufacturing a pyrotechnic object, which comprises the following phases, implemented continuously:

• feeding a mixing member into the different constituents of said object; said mixing member being of the monovis or twin-screw corotative or counter-rotating type,
• mixing said different constituents in said mixing member, with progression within the structure of said mixing member,
• pouring the mixture obtained at the outlet of said mixing member, said mixture having a viscosity of between 200 and 3000 Pa.s.

Typically, in the context of said process, the feed phase is carried out with at least one variation of at least one of its parameters, so that the composition of said cast mixture is modified during manufacture. This produces a pyrotechnic object, which has a variable composition.

The continuous process of the invention is particularly well suited to the manufacture of large pyrotechnic objects (whose mass m is such that 100 kg ≤ m <500 tonnes).

The pyrotechnic objects in question are in particular of the types specified above: propellant loadings, explosives, bifunctional pyrotechnic objects ... It is advantageously large pyrotechnic objects, from a hundred kilograms to a few hundred tons (see above). It can include objects of about 200 tons.

The manufacturing process of said objects in question is a process of kneading and continuous casting of the type for example those described in the first part of the first publication identified above.

Said process is carried out with a paste (castable) which has a viscosity of between 200 and 3000 Pa.s, generally between 400 and 2000 Pa.s. In general, the viscosity of the dough must not be an obstacle to its flow (hence η <3,000 Pa.s) nor to its degassing, which can be implemented during mixing, at least in the end said mixing (hence η≥200 Pa.s).

The pastes in question, which have a viscosity between 200 and 3000 Pa.s, advantageously between 400 and 2000 Pa.s, are of the type of those kneaded and cast according to the prior art.

Typically, in the context of the process of the invention, the composition of said pasta is continuously modified. The feed phase in the various constituents is implemented with at least one variation of one of its parameters. Only one parameter may vary, one time, during the manufacturing operation. In the same way, at least two parameters may vary, at least once, during said manufacturing operation.

The variation (s) in question can be brutal (s) or not. The person skilled in the art knows the notion of residence time (the residence time (DTS) of a continuous process is the average time required for a particle to cross the device where said process is implemented. introduced at the input of said device at the same time, do not come out at the same time The residence time is a statistical bell curve (Gaussian) which gives the number of outgoing particles as a function of time. continuous has a clean residence time, sometimes modifiable). Thus, a sudden change in the flow rate of an input ingredient necessarily takes a certain time before being effective output of a continuous process of mixing with transport. There is always, in the final object, a composition gradient. Such a gradient is of a magnitude that is lower when the (the) set (s) of (the) metering (s) is (are) changed (s) brutally; an amplitude all the more consistent that the (said) (s) instruction (s) is (are) changed (s) more gradually. In such and such a context, it is possible to aim at obtaining a gradient of small amplitude, and care is then taken to implement a sudden change in composition. In such or such other context, one can, on the contrary, aim at obtaining a consequent amplitude gradient. This can be an advantage from a mechanical or ballistic point of view.

• le nombre de constituants intervenants,
• la nature desdits constituants intervenants, et
• les débits d'alimentation en lesdits constituants intervenants.

The parameters of the feed that may vary to cause a variation in the composition of the cast mixture include:

• the number of constituents involved,
• the nature of the said intervening constituents, and
• the feed rates of said intervening constituents.

Those skilled in the art are aware that the constituents in question are often macro-components (ie a (pre) mixture of several ingredients of the basic formulation, in order to limit the number of dosers around the organ mixtures), which consist mainly of active fillers, binders, crosslinking agents and premixes.

In the context of the implementation of the process of the invention, it is therefore possible to vary, advantageously, the nature and / or the amount of said active binders, binders, crosslinking agents and premixes involved in the diet of the organ mixture.

• soit par modification d'au moins un débit de constituant (généralement de macro-composant) initial, alimentant l'organe de mélange en entrée et/ou le long de son axe ;
• soit par ajout et/ou suppression d'au moins un constituant (généralement d'au moins un macro-composant), en entrée et/ou le long de l'axe de l'organe de mélange ;
• soit par modification d'au moins un débit de constituant initial et ajout et/ou suppression d'au moins un constituant, en entrée et/ou le long de l'axe de l'organe de mélange ...

In general, the management of the feed of the mixing member, which is therefore, according to the invention, with at least one variation of one of the parameters, can be manual or at least partly electronically controlled. by means of a suitable programmer. In any case, the cast formulation is modified, manually and / or by programming, continuously and simultaneously with its casting phase:

• or by modifying at least one initial component (usually macro-component) flow rate, feeding the input mixing member and / or along its axis;
• either by adding and / or deleting at least one constituent (generally at least one macro-component), at the inlet and / or along the axis of the mixing member;
• either by modifying at least one initial constituent flow rate and adding and / or deleting at least one constituent, at the inlet and / or along the axis of the mixing member ...

Whatever the exact variant of implementation of the casting and more particularly in a source casting context (see below), it is desirable that the casting mixture arrives at the outlet of the mixing member, free from defects. ; ie degassed. It is therefore advantageous for the mixture to be used under high vacuum, at least at the end of its progression within the structure of the mixing member. By high vacuum is meant in this context a pressure less than 150 mbar, preferably less than 100 mbar.

According to a first variant of implementation, the continuous casting of the process of the invention is a gravity casting under vacuum, via a degassing gate. In the context of this variant, upstream degassing is less critical since the casting per is ensured with degassing (under vacuum, through a degassing gate). The implementation of such gravitational casting, in the context of the method of the invention, is limited to contexts of low height of fall. During compositional changes with large drop heights, jet penetration problems may occur.

According to a second variant of implementation, the continuous casting of the process of the invention is a source casting, at atmospheric pressure, through at least one cannula, sealing or not. Said casting is carried out on a mixture which contains no or very little gas, generally on a dough degassed upstream (very generally degassed within the structure of the mixing member). Advantageously, such a source casting is implemented with slaving of the relative movement, cannula / mold for receiving the cast mixture, at the casting rate, so that a small distance (of the order of a few centimeters: do not create a winding of the dough net by increasing this distance too much ... or to immerse the cannula (s) in the dough), stable, between the outlet of said at least one cannula and the level of the mixture cast in said mold.

• de couler à pression atmosphérique,
• d'éviter le mélange des différentes formulations par interpénétration du jet à l'impact.

Such a source casting system with cannula (s) allows, even for the filling of objects of great height:

• to sink at atmospheric pressure,
• to avoid mixing the different formulations by interpenetration of the jet on impact.

Such a system with cannula (s) is used, taking care of the problems of its initiation. If the casting of the dough is in fillets, the filling is incorrect, since there is imprisonment of air. The flow of the dough must be a piston flow. Either we take care to use a properly sized cannula or is associated with the cannula a plug or sacrificed the volume of the cannula at first filling ...

• soit en excédent de volume du moule rempli,
• soit en défaut de volume pour le moule suivant à remplir (cas des petits chargements coulés en série),
• soit en égoutture continue (salissure avec risque pyrotechnique et nettoyage à prévoir).

It also uses such a system with cannula (s), ensuring the problems of its end of use. When stopping feeding of the cannula (s), the paste contained in the cannula flows by gravity and comes:

• either in excess of volume of the filled mold,
• in the absence of volume for the next mold to be filled (in the case of small loads cast in series),
• or in continuous dripping (soiling with pyrotechnic hazard and cleaning to provide).

It is therefore highly desirable to ensure perfect closure of the end of the cannula at the end of the dispensing of the dose.

In the context of the present invention, the specificities of implementation of these two casting variants have proved usable for the implementation of a continuous process with variation of the composition of the cast paste.

• simplification de la géométrie (en particulier interne : voir les figures 3A et 3B annexées) d'objets préparés : il est en effet possible de jouer sur la composition du propergol et non plus uniquement sur la géométrie interne du chargement pour répondre à des spécificités balistiques et mécaniques particulières ;
• obtention de chargements multi-compositions (notamment bi-compositions) sans cuisson intermédiaire.

Compared to the batch process widely used to date, the continuous process of the invention, in a context of formulation change, reduces the costs of production, by:

• simplification of the geometry (in particular internal: see Figures 3A and 3B annexed) of prepared objects: it is indeed possible to play on the composition of the propellant and no longer solely on the internal geometry of the load to meet specific ballistic and mechanical specificities;
• obtaining multi-composition loads (especially bi-compositions) without intermediate firing.

• la réduction des zones de danger, de par la faible quantité de matière mise en oeuvre ;
• la réduction de l'emprise au sol : les opérations de malaxage et coulée sont réalisées au même endroit,
• la diminution des coûts de fabrication : procédé d'une mise en oeuvre rapide, sans transport de cuve, sans séquence successive de malaxage et coulée ;
• une bonne reproductibilité ;
• une bonne flexibilité : il est possible de formuler un grand nombre de formulations différentes.

In addition, the use of a continuous process allows:

• the reduction of the danger zones, because of the small quantity of material used;
• the reduction of the footprint: the mixing and casting operations are performed in the same place,
• the reduction in manufacturing costs: a method of rapid implementation, without tank transport, without sequential mixing sequence and casting;
• good reproducibility;
• good flexibility: it is possible to formulate a large number of different formulations.

• le vide n'est pas indispensable lors de la coulée,
• les temps de coulée sont réduits (par l'absence de mise sous vide mais aussi grâce à la possibilité de remplir à grande vitesse),
• les outillages nécessaires sont simples et peu nombreux,
• on peut obtenir un remplissage sans création de cavités, sans interpénétration, avec des gradients de compositions plans, assez bien délimités entre les différentes formulations ...

Finally, the advantages of the preferred embodiment of the method of the invention, variant with source casting, are emphasized:

• the vacuum is not essential during casting,
• the casting times are reduced (by the absence of evacuation but also thanks to the possibility of filling at high speed),
• the necessary tools are simple and few,
• it is possible to obtain a filling without creating cavities, without interpenetration, with gradients of planar compositions, fairly well delimited between the different formulations ...

The interest of the method of the invention and the many fields of application of said method have not escaped the skilled person.

• pour obtenir une structure de l'objet pyrotechnique avec variation de composition selon son axe longitudinal, avec au moins une variation, par exemple brutale, de la composition du mélange coulé. On peut ainsi couler une composition moins dense après une composition plus dense, voire l'inverse ; les débits de coulée étant, en tout état de cause, adaptés ;
• pour obtenir une structure de l'objet pyrotechnique avec variation de composition selon son axe radial, avec une variation brutale de la composition du mélange coulé. On peut ainsi couler une composition plus dense après une composition moins dense, voire l'inverse ; les débits de coulée, étant, en tout état de cause, adaptés.

It can in particular be implemented:

• to obtain a structure of the pyrotechnic object with variation of composition along its longitudinal axis, with at least one variation, for example sudden, of the composition of the cast mixture. It is thus possible to cast a less dense composition after a denser composition, or even the opposite; the flow rates being, in any case, adapted;
• to obtain a structure of the pyrotechnic object with composition variation along its radial axis, with a sudden change in the composition of the cast mixture. We can thus sink a composition more dense after a less dense composition, even the opposite; the flow rates, being, in any case, suitable.

The parameters, flow rate, viscosity, density, are to be adjusted to obtain the expected result.

• dans la réalisation de chargements de très grande taille (100 kg à moins de 500 tonnes (par exemple, environ 200 tonnes) de propergol), multi-compositions, substituts de chargements à géométrie de noyau complexe (voir les figures 3A et 3B annexées) ... ;
• dans la réalisation d'explosifs présentant des parties peu sensibles, plus exposées et des parties très sensibles, moins exposées (voir la figure 4 annexée)...,
• dans la réalisation d'objets pyrotechniques à structure bifonctionnelle (voir la figure 5 annexée)... ;
• dans la réalisation d'intercepteurs ...

The process of the invention in particular has outlets:

• in the production of very large loads (100 kg to less than 500 tons (for example, about 200 tons) of propellant), multi-compositions, load substitutes with complex core geometry (see Figures 3A and 3B annexed) ...;
• in the production of explosives with insensitive, more exposed parts and very sensitive, less exposed parts (see figure 4 attached) ...
• in the production of pyrotechnic objects with a bifunctional structure (see figure 5 annexed) ...;
• in the realization of interceptors ...

We now come to the description of a device suitable for manufacture of the type kneading and continuous casting, with variation in the feed of the kneading member, particularly suitable for carrying out the method described above. .

• un organe de mélange (ou malaxage), du type monovis ou bivis corotative ou contrarotative, qui convient pour assurer le mélange avec transport des différents constituants de l'objet pyrotechnique en fabrication ; ledit organe de mélange comportant au moins une ouverture de récupération desdits constituants mélangés (une ouverture pour la délivrance desdits constituants mélangés),
• un ensemble de dispositifs d'alimentation dudit organe de mélange en lesdits constituants (un ensemble de doseurs aptes à délivrer les différents constituants, liquides et/ou solides ...), et
• un dispositif de coulée, agencé au niveau de ladite au moins une ouverture de récupération dudit organe de mélange, qui convient pour la coulée du mélange obtenu dans un moule.

Said device comprises:

• a mixing member (or kneading), of the monovis or twin-screw corotative or counter-rotating type, which is suitable for mixing with transport the various constituents of the pyrotechnic object in production; said mixing member having at least one recovery opening of said mixed components (an opening for delivery of said mixed components),
• a set of devices for supplying said mixing member with said constituents (a set of metering devices capable of delivering the various constituents, liquid and / or solid, etc.), and
• a casting device, arranged at said at least one recovery opening of said mixing member, which is suitable for casting the mixture obtained in a mold.

The set of feeding devices is suitable for continuously ensuring variations in the feed of the mixing member.

• l'un au moins desdits dispositifs est-il susceptible d'assurer sa fonction d'alimentation (partielle) à différents débits ...
• ledit ensemble des dispositifs d'alimentation convient-il pour assurer au moins une variation d'au moins l'un des paramètres de l'alimentation, de sorte que la composition du mélange coulé est modifiée en cours de fabrication.

Thus, at least one of said devices is likely to be stopped and / or started during operation; and or

• at least one of said devices is capable of performing its (partial) feed function at different flow rates ...
• is said set of feeders suitable for providing at least a variation of at least one of the feeding parameters so that the composition of the cast mixture is changed during manufacture.

The device advantageously comprises, in addition, electronic control means for at least one of its supply devices.

Said device advantageously comprises means for maintaining a high vacuum in its mixing member, at least in the portion of said mixing member adjoining its at least one recovery opening.

Regarding the casting device, its structure is obviously adapted to the targeted casting type.

According to a first variant, said casting device comprises a gravity casting system with at least one pipe opening through a degassing gate in a vacuum casting cabinet.

According to a second variant, said casting device comprises a source casting system, operating at atmospheric pressure, with at least one cannula, sealing or not. Such a system advantageously comprises means for controlling the relative movement of the cannula (s) / mold (s) of reception, at the casting rate, so that a small, stable distance is maintained between the emergent outlet of the said at least one cannula and the level of mixture poured into the corresponding mold. With such a system, it is possible to flow, without interpenetration, at atmospheric pressure, formulations of different compositions, with large drop heights. The intervention of such a system is particularly appropriate in a context of manufacturing large objects.

The intervening mixing device is a continuous kneading machine: a twin-screw, co-or counter-rotating or a single-screw machine.

The feed devices are generally arranged in the upstream part of the mixing member and the recovery opening (s) is (are) generally arranged in the downstream part. said mixing member. The organization of the supply devices at the periphery of said metering member is generally such that the energy charges "fall" into liquid components, introduced slightly upstream; this, for obvious reasons of security.

Said supply devices in principle comprise feed hoppers equipped with metering devices, advantageously of the type dosing powder, metering pumps or syringe type pumps.

• La figure 1 est un schéma de principe du procédé de l'invention.
• La figure 2A est un schéma de principe d'une variante de mise en oeuvre, avec coulée gravitaire, du procédé de l'invention.
• La figure 2B est un schéma de principe d'une variante de mise en oeuvre, avec coulée en source, du procédé de l'invention.
• La figure 3A montre un chargement à iso-composition de l'art antérieur (nécessitant un noyau à géométrie complexe, pour répondre au cahier des charges) tandis que la figure 3B montre un chargement bi-composition de l'invention (à noyau simplifié, répondant au même cahier des charges).
• La figure 4 montre l'obtention, selon l'invention, avec variation brutale de la composition du mélange coulé, d'un objet pyrotechnique présentant une variation de composition selon son axe radial.
• La figure 5 est un schéma de principe du procédé de l'invention mis en oeuvre pour obtenir un objet pyrotechnique bifonctionnel (tête et moteur intégré).

It is now proposed to describe the invention, in no way limiting, with reference to the appended figures.

• The figure 1 is a schematic diagram of the method of the invention.
• The Figure 2A is a block diagram of an implementation variant, with gravitational casting, of the method of the invention.
• The Figure 2B is a block diagram of an implementation variant, with source casting, of the method of the invention.
• The figure 3A shows an iso-composition loading of the prior art (requiring a core with complex geometry, to meet the specifications) while the figure 3B shows a bi-composition loading of the invention (simplified core, meeting the same specification).
• The figure 4 shows the obtaining, according to the invention, with sudden variation in the composition of the cast mixture, a pyrotechnic object having a composition variation along its radial axis.
• The figure 5 is a schematic diagram of the method of the invention used to obtain a bifunctional pyrotechnic object (head and integrated motor).

• de dosage des macro-composants : deux macro-composants "charges", référencés C1 et C2, sont susceptibles d'être délivrés via les deux doseurs 1, indépendants ; un macro-composant "liant", référencé L1, est susceptible d'être délivré via le doseur 2 ; deux macro-composants "réticulants", référencés R1 et R2, sont susceptibles d'être délivrés via les deux doseurs 3, indépendants ;
• de malaxage et transport dans l'organe de mélange 4 ;
• de coulée, en aval de l'ouverture de récupération 4' dudit organe de mélange 4 ;
• d'obtention de l'objet pyrotechnique 10 à composition variable le long de son axe longitudinal. Ledit objet présente successivement quatre zones de compositions différentes, par exemple :
  • composition 1 : C1 + L1 + R1
  • composition 2 : C1 + C2+ L1 + R1
  • composition 3 : C1 + C2 + L1 + R2
  • composition 4 : C1 + C2' + L1 + R2 (débit de C'2 inférieur à celui de C2) ;

séparées chacune par une zone 11 de gradient de composition.The principle of the method of the invention is illustrated on the figure 1 , where are represented, from left to right, the steps:

• macrocomponent dosing system: two "charge" macro-components, referenced C1 and C2, are capable of being delivered via the two independent dosers 1; a macro-component "binder", referenced L1, is capable of being delivered via the metering device 2; two "crosslinking" macro-components, referenced R1 and R2, are capable of being delivered via the two independent dosers 3;
• mixing and transport in the mixing member 4;
• casting, downstream of the recovery opening 4 'of said mixing member 4;
• for obtaining the pyrotechnic object 10 with a variable composition along its longitudinal axis. Said object successively has four zones of different compositions, for example:
  • composition 1: C1 + L1 + R1
  • composition 2: C1 + C2 + L1 + R1
  • composition 3: C1 + C2 + L1 + R2
  • composition 4: C1 + C2 '+ L1 + R2 (flow rate of C'2 less than that of C2);

each separated by a composition gradient zone 11.

On the Figures 2A and 2B two variants of the method of the invention are illustrated. In said figures, the various elements of the device in question have been better schematized.

In 1, 2 and 3 are always represented dosers suitable for feeding the mixing member 4a or 4b to, respectively,
C1 and C2 charges,
binders L1 and L2,
a crosslinker R1.

The mixing element, schematized on the Figure 2A , is a single screw machine 4a. At its emergent end 4a ', it is coupled to a gravity casting device which comprises a pipe 6 with a degassing gate 6'. Said pipe 6 opens via its degassing gate 6 'in the vacuum casting cabinet 8. Within said cabinet 8, there is the mold 7 for receiving the cast paste.

The mixing element, schematized on the Figure 2B , is a 4b corotative twin machine. At its emergent end 4b ', it is coupled to a source casting device which comprises the cannula 5. It delivers the paste via its emergent end 5' into the mold 7. Said mold 7 is stabilized on the plate of a device 9 able to move it vertically. At the beginning of casting, the cannula 5 penetrates into the mold 7 and as and when said casting, the mold 7 is lowered via said device 9.

To the consideration of said Figures 2A and 2B the results obtainable are realized.

The figure 3B shows, as specified above, a pyrotechnic object 20, obtained according to the invention, meeting the same specifications as that of the figure 3A . Said pyrotechnic object 20 is bi-component; its structure comprises propellant A and propellant B separated by a composition gradient 21.

Propellant A is cast in the first phase of the process by a first dosage of its various constituents. Then, the dosing instructions are modified, without stopping the mixing member, to obtain a second dosage which corresponds to the propellant B. Said propellant B is poured into the second phase of the process. The formulation change can take place in a very short time and therefore end up on a low composition gradient height.

• la première 31, "fluide", moins sensible,
• la seconde 32, "visqueuse", plus sensible.

The figure 4 Continuously illustrates the casting of two explosive compositions:

• the first 31, "fluid", less sensitive,
• the second 32, "viscous", more sensitive.

A two-component pyrotechnic object is obtained, within whose structure the composition 32, the most sensitive, is protected by the composition 31.

The figure 5 illustrates the manufacture according to the invention (continuously) of a bifunctional pyrotechnic object 40. Said object comprises an explosive head 40a (cast first), mounted on a body 40b, suitable for propulsion (cast second).

It is now proposed to illustrate the invention by the example below, to be considered with the Figure 2B attached.

Example

There are five feeders (two, referenced 1, each suitable for the delivery of fillers, two, referenced 2, each suitable for the delivery of a binder and a referenced 3, suitable for the delivery of a crosslinking agent) arranged around a laboratory 4b double screw. In this twin-screw 4b, an inert composite propellant, representative of a real propellant, is prepared. This eliminates the safety instructions.

The screw profile, adapted to the type of composition, allows the homogenization, at 50 ° C and 100 mbar, of the propellant, with an overall flow rate of 4 kg / h.

Each of the five feeders is able to continuously distribute a macro-component, whose mass composition is specified in the table below: macrocomponents Composition (% by weight) Binder: L1 - PBHT (hydroxytelechelic polybutadiene) 37.65 - Alu (aluminum) 49.64 - Red dye 0.07 - DBTL (tin dibutyldilaurate) 0.1 DMP30 (2,4,6-tri (dimethylaminomethyl) phenol) 0.32 - DOZ (diisooctylazelate) 12.22 Binder: L2 - PBHT 74,80 - Green dye 0.08 - DBTL 0.21 - DMP30 0.65 - DOZ 24.26 Crosslinker: R1 - MDCI (4,4-dicyclohexylmethanediisocyanate) 100 Loads: C1 - Crystallized sugar 342.7 μm 100 Charges: C2 - Crystallized sugar 342.7 μm 76.80 - KCI 10 μm 10.50 - Ice sugar 70 μm 12.65 - Red dye 0.05

Dyes intervene, in order to easily identify changes in composition. The mold 7 is successively filled with a pink composition 1, then a green composition 2 and then a purple composition 3 (see below).

At the outlet of the twin-screw 4b, the paste is poured in source, at atmospheric pressure, directly into the final structure of the object: mold 7. To this end, a flexible hose 5 (Ø = 12 mm and h = 50 cm) was mounted on the die and used as a cannula.

Said mold 7 is placed on the plate of a lifting device 9.

• La machine est mise en route avec une composition 1 du type R1 + L1 + C1.
  R1 est délivré à 73 g/h,
  L1 est délivré à 1 839,5 g/h, et
  C1 est délivré à 1 869,2 g/h ; ce qui correspond à un débit global d'environ 3,8 kg/h.
  Le moule 7 est ainsi rempli sur environ 15 cm, en 40 à 45 min, via la canule 5 qui est remontée au fur et à mesure.
• A l'issue de cette première phase de remplissage, le doseur de liant L1 est arrêté brusquement. Simultanément, le doseur de liant L2 est démarré brusquement. La machine débite alors une composition 2 du type R1 + L2 + C1.
  R1 est délivré à 70,8 g/h,
  L2 est délivré à 900 g/h, et
  C1 est délivré à 2 760 g/h ; ce qui correspond à un débit global d'environ 3,7 kg/h.
  Le remplissage avec ladite composition 2 est mis en oeuvre pendant 40 à 45 min, sur une hauteur d'environ 15 cm, avec remontée de la canule 5.
• A l'issue de cette seconde phase de remplissage, le doseur de charge C1 est arrêté brusquement. Simultanément, le doseur de charge C2 est démarré. La machine débite désormais une composition 3 du type R1+L2+C2
  R1 est délivré à 70,8 g/h,
  L2 est délivré à 900 g/h, et
  C2 est délivré à 2 760 g/h ; ce qui correspond à un débit total d'environ 3,7 kg/h.

At startup, said plate is in the up position, while the cannula 5, more precisely its open end 5 ', is in contact with the bottom of the mold 7.

• The machine is started with a composition 1 of the type R1 + L1 + C1.
  R1 is delivered at 73 g / h,
  L1 is delivered at 1839.5 g / h, and
  C1 is issued at 1,869.2 g / h; which corresponds to an overall flow rate of approximately 3.8 kg / h.
  The mold 7 is thus filled about 15 cm, in 40 to 45 min, via the cannula 5 which is reassembled as and when.
• At the end of this first filling phase, the binder L1 is stopped abruptly. Simultaneously, the binder feeder L2 is started suddenly. The machine then delivers a composition 2 of the type R1 + L2 + C1.
  R1 is delivered at 70.8 g / h,
  L2 is delivered at 900 g / h, and
  C1 is delivered at 2760 g / h; which corresponds to an overall flow rate of approximately 3.7 kg / h.
  The filling with said composition 2 is carried out for 40 to 45 min, over a height of about 15 cm, with raising of the cannula 5.
• At the end of this second filling phase, the load metering C1 is stopped abruptly. At the same time, the load feeder C2 is started. The machine now debits a composition 3 of the type R1 + L2 + C2
  R1 is delivered at 70.8 g / h,
  L2 is delivered at 900 g / h, and
  C2 is delivered at 2760 g / h; which corresponds to a total flow rate of approximately 3.7 kg / h.

The filling with said composition 3 is carried out for 40 to 45 min, over a height of about 15 cm, in fact until the complete filling of the object (with recovery of the cannula as and when).

The resulting model is heat treated.

It then clearly shows the three successive zones of different colors, corresponding to the three compositions 1 (pink), 2 (green), 3 (purple). Said three zones are separated by gradient zones.

The residence time of the paste was measured in the case of the test carried out. It is about 3 min 30 s within the single 4b bivis and about 6 min in said bivis 4b coupled with 50 cm of hose: cannula 5.

Claims (13)

1. A continuous process for the production of a pyrotechnical object (10; 20; 30; 40), comprising the phases below, carried out continuously:

   - supplying a mixing member (4; 4a; 4b) with the various components (C1, C2, L1, L2, R1, R2) of said object (10; 20; 30; 40); said mixing member being of the single-screw (4a) type or of the co-rotating dual-screw (4b) type or of the contra-rotating dual-screw type,

   - mixing said various components (C1, C2, L1, L2, R1, R2) in said mixing member (4; 4a; 4b), with progression within the structure of said mixing member (4; 4a; 4b),

   - pouring the mixture obtained at the outlet of said mixing member (4; 4a; 4b), said mixture having a viscosity comprised between 200 and 3000 Pa.s,

   characterized in that said supply phase is carried out with at least one variation of at least one of its parameters, so that the composition of said poured mixture is modified during production.
2. The process according to claim 1, characterized in that said at least one parameter capable of varying is chosen from among:

   - the number of intervening components,

   - the nature of said intervening components, and

   - the supply flow rates of said intervening components.
3. The process according to claim 1 or 2, characterized in that at least one of the components (C1, C2, L1, L2, R1, R2) results from a prior mixing of several ingredients.
4. The process according to claim 3, characterized in that said ingredients are cross-linking agents (Ri), binders (Li), active pre-mixtures or powdered fillers (Ci).
5. The process according to any one of claims 1 to 4, characterized in that the supply of said mixing member (4; 4a; 4b) is at least partially electronically controlled using appropriate programming.
6. The process according to any one of claims 1 to 5, characterized in that said mixing is carried out under high vacuum, at least at the end of its progression within the structure of said mixing member (4; 4a; 4b).
7. The process according to any one of claims 1 to 6, characterized in that the pouring carried out is a gravitational pouring under vacuum via a degassing grid (6').
8. The process according to any one of claims 1 to 6, characterized in that the pouring, carried out on a mixture containing very little or no gas, is a bottom pouring, at atmospheric pressure, through at least one sealing or non-sealing cannula (5).
9. The process according to claim 8, characterized in that said bottom pouring is carried out with slaving of the relative movement, of the cannula(s) (5)/reception mold(s) (7) of the poured mixture, to the pouring flow rate, so that a small, stable distance is maintained between the outlet (5') of said at least one cannula (5) and the level of the mixture poured in said corresponding mold (7).
10. The process according to any one of claims 1 to 9, characterized in that it is carried out in a device for continuous production of a pyrotechnical object (10; 20; 30; 40), comprising:

    - a mixing member (4; 4a; 4b) of the single-screw (4a) type or of the co-rotating dual-screw (4b) type or of the contra-rotating dual-screw type suitable for ensuring mixing with transport of the various components (C1, C2, L1, L2, R1, R2) of said pyrotechnical object (10; 20; 30; 40); said member (4; 4a; 4b) including at least one opening (4'; 4'a; 4'b) for recovering said mixed components,

    - a set of supply devices (1+2+3) for supplying said mixing member (4; 4a; 4b) with said components (C1, C2, L1, L2, R1, R2); said set of supply devices (1+2+3) being suitable for continuously ensuring variations of the supply of said mixing member (4; 4a; 4b), and

    - a pouring device, arranged at said at least one recovery opening (4'; 4'a; 4'b) of said mixing member (4; 4a; 4b), suitable for pouring the obtained mixture into a mold (7); said pouring device comprising a gravitational pouring system with at least one pipe (6) emerging through a degassing grid (6') in a vacuum pouring cabinet (8) or a bottom pouring system at atmospheric pressure with at least one sealing or non-sealing cannula (5).
11. The process according to claim 10, characterized in that at least one of the supply devices (1, 2, 3) is able to perform its supply function at different flow rates.
12. The process according to claim 10 or 11, characterized in that it further includes means for maintaining a high vacuum in said mixing member (4; 4a; 4b), at least in the part of said mixing member (4; 4a; 4b) adjacent at its at least one recovery opening (4'; 4'a; 4'b).
13. The process according to any one of claims 10 to 12, characterized in that said pouring device comprises a bottom pouring system at atmospheric pressure with at least one sealing or non-sealing cannula (5) and in that it further comprises means for slaving the relative movement, of the cannula(s) (5)/reception mold(s) (7), to the pouring flow rate, so that a small, stable distance is maintained between the emerging outlet (5") of said at least one cannula (5) and the level of the mixture poured into said corresponding mold (7).

Images