WO1996041780A1

WO1996041780A1 - Method and arrangement for producing explosive charges

Info

Publication number: WO1996041780A1
Application number: PCT/SE1996/000739
Authority: WO
Inventors: Hans Wallin
Original assignee: Bofors Liab AB
Current assignee: Bofors Liab AB
Priority date: 1995-06-08
Filing date: 1996-06-05
Publication date: 1996-12-27
Anticipated expiration: 1997-12-08
Also published as: SE504994C2; SE9502089D0; SE9502089L

Abstract

The present invention relates to a method and an arrangement for producing explosive charges containing both fusible and non-fusible substances, where the non-fusible substance can be crystalline, for example a crystalline high-energy explosive, while the fusible substance in most cases consists of trotyl. A special feature of the invention is that is can be regarded as constituting a casting process carried out entirely without direct use of a casting pot. The starting material is a particulate material with the same composition as the desired final product. According to the invention, this starting material is heated to the fusion point of the fusible component directly in the desired final mould in which the material is also allowed to solidify.

Description

Method and arrangement for producing explosive charges

The present invention relates to a method and an arrangement for producing explosive charges containing both fusible and non-fusible, particulate substances. The non-fusible components can in this case consist of crystalline substances, such as high-energy explosives, or of metal powder. A special feature of the invention is is that it can be regarded as constituting a casting process which is carried out entirely without direct use of a casting pot in which the components are kept fused and from which the mixture of fused and non-fused substance is drawn up into respective moulds.

The invention offers good possibilities of efficient production of explosive charges with charge weights which are not too high, and at the same time it makes it possible for the person controlling the process to entirely avoid direct handling of fused explosive and the associated safety risks and exposure to explosive vapours. In addition, a production line set up in accordance with the invention can easily be converted for production of charges of different sizes. A further advantage of the method according to the invention is that it involves very good possibilities of controlling the sedimentation between the different phases of the charges. This can be accelerated, for example, by means of a vibration treatment before the charges have fully solidified. By virtue of the fact that the process according to the invention can be run continuously, it also affords a high throughput of material, which results in the manufactured product having a low unit price.

The starting material in the method according to the invention is a solid powder or granular material which contains all the components included in the desired final product and whose average particle size should expediently lie between 0.5 and 5 mm.

There are earlier, previously known processes which have been used for producing explosive articles containing both non-fusible and fusible components, and in which the starting point has been flakes, granules, biscuits or the like containing both the fusible and the non-fusible components, but in which the content of fusible components has been considerably lower in the solid starting material than in the final product. Thus, a common feature of these procedures has been that the mould, shell body, or whatever has been involved, has first been filled with the solid, particulate starting material, which could thus be in the form of flakes, granules, biscuits or the like, and the space between these starting particles has then been successively filled in the solid state with a further amount of fused explosive. In these earlier processes it has therefore been a question of casting solid, partially fusible particles together with separately added fused explosive. However, it has been reported that these methods may be associated with solidification/shrinkage problems which have caused "pipes" and other bubble formations in the finished products. Nor, moreover, is it possible in these processes to get away from the need to have quite large quantities of explosive available in the fused phase.

According to the present invention, the starting point is now a solid, particulate starting material containing fusible explosive in the solid phase, and other non-fusible components which are to be included in the finished product. All these components are in the percentage contents which are wanted in the' finished product. The solid starting material should expediently have a particle size of 0.5 - 5 mm, and matters are made easier if the particle size distribution is such that there is a good degree of compaction right from the outset. Once this starting material has been filled into shells or casings of any chosen type in an amount by weight or amount by volume selected beforehand, the shells or casings filled with explosive are conveyed from the filling zone into a heating zone where they are heated, by means of hot water, hot air, or in some other way, to the fusion point of the fusible explosive, and where the charges are kept until all the fusible substance has been converted to the fused phase. In association with this, a compacting of the starting material occurs as fused explosive from the different original particles together forms a continuous fused phase in which the non-fusible components are distri¬ buted. If so desired, the expulsion of any air and the sedimentation of the solid particles in the fused phase can be accelerated by a vibration treatment. It may be desirable, for example, to have an extra high content of crystalline high-energy explosive at the charge end lying nearest the initiation point. As soon as the above- described fusion and optional vibration have been carried out, the prospective charges are transferred to a cooling zone where the fused explosive is converted to the solid phase.

The procedure described above can then be repeated in two or more sequences, where each sequence comprises a first filling stage, the very first filling stage involving a more or less complete filling of the shell or casing with particulate explosive, while the succeeding filling stage or filling stages has/have been adapted to the lowering of the explosive level in the shell/casing at the preceding heating stage.

As is evident from what has been said above, the processing stages that are needed for carrying out the method according to the invention are relatively simple. An arrangement in accordance with the invention can therefore be easily designed in accordance with fully automatic principles which completely eliminate the need to expose humans to the risk of accidental ignition of fused explosive and to the vapours from the same fused explosive. Examples of explosive mixtures which can be used in accordance with the present invention for producing specific charges are hexotol, pentol and octol. These are in fact military explosives which were previously too expensive for civil application, but as the offloading of earlier military ammunition increases, it can be assumed that the availability of these explosive mixtures will increase, and such explosive, once acquired, will be well suited, after re-granulation, for production of, for example, civil initiation charges intended to be used together with bulk explosives. These are products which are used up in large quantities and which are well suited to being produced in accordance with the present invention. All the abovementioned explosive mixtures contain trotyl as the fusible phase, while the solid, particulate, non-fusible phases consist of the high- energy explosives hexogen, pentyl and octogen.

The method and the arrangement according to the invention have been defined in the following patent claims and they will now be illustrated in conjunction with the attached Figure which shows, in broad outline, a production line in accordance with the invention.

The Figure shows diagrammatically a conveyor track 1 along which a number of casings or containers a are advanced. The direction of conveying of the track is shown by the arrows in the Figure. At a first filling station 2 the casings a are filled with particulate explosive 3 till they are almost full. The explosive mixture can be octol or hexotol, for example. The casings are conveyed onwards from the filling station 2 into a heating zone 4 and down into a water bath 5 which is present in this zone. The trotyl included in both octol and hexotol has a fusion point of approximately 81°C, and so the water bath should be slightly hotter. As is evident from the Figure, the level in the casings a drops as the trotyl fuses and fills all the empty spaces, and the solid crystalline component of the explosive mixtures is compacted. Once the casings leave the heating zone 4 after complete fusion of the trotyl component, they are transferred to a cooling zone 6, here represented by a fan 7. A vibration zone can be arranged, if need be, between the heating zone and the cooling zone. Downstream of the first cooling zone, the casings contain a solid, homogeneous charge which, however, does not completely fill the volume of the casing. They are therefore trans¬ ferred to a new filling station 8 where they are supplied with an amount of particulate explosive of the same type 3 as at the filling station 2, but here in an amount corresponding to the drop in level which occurred during the fusion in the preceding heating zone 4. There then follows a new heating zone 9 with its own water bath 10, and a new cooling zone 11 with the fan 12. If necessary, more than two of these complete sequences can follow one another.

Claims

PATENT CLAIMS

1. Method for producing explosive charges containing both fusible and non-fusible, particulate components, which can be crystalline, from a powder or granular material (3) which is initially solid and in which both the component types are included, characterized in that the starting material (3) chosen is a solid powder or granular material whose particles have a composition which coincides entirely with that of the desired final product, and in that this material is filled into shells or casings (a) which are intended for this purpose, which define the outer shape of the finished charge, and in which the material (3) is exposed in a subsequent stage (4, 9) to heating which fuses the fusible component included therein and thus causes the original particles to fuse together and the fusible component to completely fill the space between the original, non-fusible par¬ ticles and form a continuous phase, after which the charge thus obtained is cooled in a subsequent processing stage (6, 11) so that the fusible component once again solidifies.

2. Method according to Claim 1, characterized in that it is carried out in several successive sequences with filling (2, 8) of further particulate starting material (3) , at the commencement of a new sequence after each cooling stage (6, 11) completing an earlier sequence, as a replacement for the drop which has taken place in the filled part of the respective shell or casing on fusing together of the particles and filling- out of the spaces between them in the earlier sequence.

3. Method according to either Claim 1 or Claim 2, characterized in that the starting material (3) chosen is one with a particle size of 0.5 to 5.0 mm.

4. Arrangement for producing, in accordance with any one of Claims 1 - 3, explosive charges containing both fusible and non-fusible, particulate components, which can be crystalline, from a starting material (3) which is initially particulate and in which both the component types are included, characterized in that it comprises a first filling station (2, 8) for filling into shells or casings (a) intended for this purpose a predetermined amount by weight of a particulate starting material (3) containing both the fusible and non-fusible components, included in the desired final product, in the percentages which are desired in the final product, a second heating station (4, 9) in which the said shells (a) or casings filled with particulate material are heated to the fusion point of the fusible component, and a final cooling station (6, 11) in which the fused explosive is once again cooled to a solid form.

5. Arrangement according to Claim 4, characterized in that it comprises several sets of filling, heating and cooling stages in which each filling stage (8) following the first one (2) is adapted to supply an amount of particulate material (3) corresponding to the drop in level which the preceding heating stage (4) gave rise to when the material from the preceding filling stage (2) fused together.

6. Arrangement according to Claim 4 or Claim 5, characterized in that each heating stage (4, 9) entails each prospective charge in its shell or casing (a) being lowered into a water bath (5, 10) adapted to the fusion point of the explosive.