Patent Application
20160046536
The invention relates to an electrically ignitable caseless propellant charge (for example for bolt-driving tools or other devices and purposes as described in detail below) in the form of a caseless propellant tablet, or furthermore a tablet-like ignition charge.
Offenlegungsschrift DE 2417967 describes nitrocellulose-based propellant charges suitable for driving-in for fastening purposes, which are provided in cases having two open ends, at one end of which ignition can be effected by means of a spark or a hot wire. Alternatively, ignition can be effected by means of a current through a specially shaped current-conducting case-like metal coating, as described in Auslegeschrift DE 1 300 845.
A disadvantage of such devices is the necessity for relatively complicated cases.
On the other hand, U.S. Pat. No. 3,854,400 describes caseless propellants having a porosity achieved by dissolving out a binder (for example potassium nitrate or toluene), especially for firearms, which can be ignited by means of additional ignition charges. Further ingredients are nitrocellulose having a nitrogen content of from 13.2 to 13.5% (“guncotton”), diphenylamine as stabiliser, and further additives. Apparently they are mechanically ignitable (for example by means of firing pins).
DE-OS 2 245 510 also describes propellant compositions for caseless propellant charges as a power source for projectiles and percussion tools. They comprise a mixture of nitrocellulose having a high nitrogen content (from 13.2 to 13.4%) and nitrocellulose having a low nitrogen content (for example from 11.6 to 11.8%) and also potassium nitrate, which are formed into grains, then converted into porous form by dissolving out the potassium nitrate and extruded in the form of a 1.4 mm thick “cord” which is then cut into 0.32 mm thick discs. The discs are then tumbled in a pan with fine graphite in order to provide a coating to improve flow properties and introduction into a mould, and the particles are then compacted in a mould to form cylindrical propellant charges. In this case additional priming compositions are always introduced into an indentation. Electrical ignition is not mentioned.
DE-OS 1 906 573 finally relates to caseless explosive charges which can be ignited by means of power sources such as torch batteries or capacitor discharge circuits. For ignition, single-strand or multi-strand wires or graphite rods are introduced into the composition.
Known tablets or propellant charges of similar form accordingly have relatively complex structures.
In particular, their structure is relatively elaborate insofar as current-conducting wires or rods need to pass through or surround the ignitable propellant material in order to make electrical ignition possible.
DE 37 07 694 C2 describes electrically primable priming charges for caseless ammunition and propellant cartridges, which comprise inter alia nitrocellulose having a nitrogen content of 13.5%, zinc peroxide and carbon fibres. They are used for priming the actual propellant charges. DE 33 46 739 also describes priming charges (primary explosive) to which in this case there is added from 0.8 to 2.0% by weight furnace black or lamp black to increase the conductivity. US 2003/0034103 describes ignition means for propellant powders, which can be used as coatings for such powders.
Against this background, the problem of the invention is to provide simplified propellant charges which can be ignited by means of power sources, without the need for a priming charge.
It has now been found that it is possible to provide caseless electrically ignitable propellant charges (especially in tablet form) which comprise conductive material in finely divided form in their matrix.
In a first embodiment, the invention therefore relates to an electrically ignitable caseless propellant charge (provided without an additional ignition charge or current-conductive wires or rods) in the form of a caseless propellant tablet (compact), characterised in that it is obtainable by mixing together of at least one current-conductive material in dissolved or dispersed form or powder form (apart from, that is to say in addition to, graphite) and graphite in powder form, together with nitrocellulose, with or without addition of further additives, and subsequent compaction to form a propellant tablet, or preferably by one of the processes described below.
The dissolved, dispersed or powder form of the current-conductive material used (unlike implementation in the form of wires or rods or ignition from an outer side) brings about the “finely divided form” and allows rapid and homogeneous ignition.
“Powder form” always includes powder having elongate particles (such as carbon chips or carbon fibres) and/or particles of a rather roundish (approximately spherical) shape.
For further improvement of current conductivity, carbon fibres can have been added or they can be added in the following process.
In a further embodiment, the invention relates to a process for the production of a propellant charge mentioned hereinabove or hereinbelow in the form of a caseless propellant tablet, which process is characterised by mixing together of at least one current-conductive material in dissolved or dispersed form or in powder form, apart from graphite, and graphite in powder form, together with nitrocellulose, with or without addition of further additives, and subsequent compaction to form a propellant tablet.
A preferred embodiment of the production process relates to a process as mentioned above, which is characterised in that a current-conductive material in dissolved or dispersed form or in powder form, apart from graphite, is mixed with nitrocellulose, with or without addition of further additives, (wherein in a special embodiment of the invention granules of the obtainable mixture are produced, preferably by grinding, and those granules are used as the obtainable mixture), and graphite in powder form is added to a largely dry obtainable mixture (especially having not more than 15% by weight, for example having 6-12 or having 8-10% by weight residual moisture) (if necessary obtained or obtainable by a drying step), and then the mixture is compacted to form propellant tablets according to the invention. A possible advantage of such a process is that the at least partly soluble materials (such as nitrocellulose and acrylate granules) are able to penetrate around and into the granules like a paint, which can bring about a reduction in the hydrophilicity and thus contribute to the storage stability and insensitivity to moisture of the propellant charges.
Such processes also allow simple industrial production of propellant charges according to the invention. Depending upon the production, the propellant charges according to the invention that are obtainable have a largely homogeneous structure in the sense of a solid dispersion (solid-solid mixture); in simple terms, in the preferred structure obtainable in accordance with the preferred process the granules, which may be deformed after the pressing, and optionally further particulate constituents are arranged as a discontinuous phase in a kind of three-dimensional lattice structure having a high graphite content. The graphite can therefore bind the granules practically in the form of a three-dimensional lattice, so that even with only a small proportion of graphite it is possible to achieve sufficient conductivity for the ignition current.
The invention relates also to the use of a conductive material in dissolved or dispersed form or in powder form in the production of an electrically ignitable propellant charge.
The use takes place especially with implementation of the steps of one of the production processes mentioned hereinabove and hereinbelow.
A further embodiment of the invention relates also to the use of a propellant charge according to the invention described hereinabove and hereinbelow in a bolt-driving tool for installing bolts, as an explosive charge in a warning shot device, as a gas-generating element in airbags, for driving cutting devices or as a propellant charge in small calibre rifles for sporting purposes.
In addition to the fact that no awkward-to-install current-conductive components, such as metal wires or rods, for example made of graphite or metal, are required for ignition and for that reason alone machine-based production is facilitated, the caseless propellant charges according to the invention also have further advantages of caseless propellant charges, for example scope for any desired shaping, for example cylindrical, ovoid or spherical; no polarity (no difference between a “front” and “rear”, as is the case with cartridges having ignition charges and/or cases), ease of handling, for example even without “cartridge belts” or the like; low weight and low space requirement. In particular, they also allow ignition without special electrical terminals or contacts provided in the propellant charge.
The propellant charges according to the invention are suitable for use especially for bolt-driving tools, but also for warning shot devices (for example for scaring away birds in fruit-growing areas), as gas-generating elements in airbags, for driving cutting devices such as bolt cutters or for cutting tensioning devices in shipping, but they also come into consideration, for example, as propellant charges in small calibre rifles for sporting purposes, for example in the biathlon, or for captive bolt devices for animal slaughtering.
The energy released for the mentioned purposes can advantageously be in the range from 10 to 1200 Joule per propellant charge, for example in the range from 50 to 1000 Joule, for example between 50 and 700 Joule, for example between 150 and 400 Joule. The measurement can be determined, for example by means of a photoelectric barrier, from the mass and the speed of a shot.
Surprisingly, the propellant charges according to the invention are water-proof and, for example, are very dimensionally stable even under sub-tropical conditions (50° C./75 to 80% relative humidity)—in use they can also briefly fall into a puddle, for example, and nevertheless be fully ignitable.
In comparison with propellant charges that have conventional cases and are mechanically ignitable by impact by means of primers, the propellant charges according to the invention additionally have the advantage that they can be supplied directly to the device in question (for example by means of a tube) in the form of a loose product without retaining bands or the like. It is thus possible to achieve, for example, reductions in volume down to an order of magnitude of a tenth and reductions in weight down to an order of magnitude of a fifth of the values for conventional propellant charges (especially those having cases and/or ignition charges).
Furthermore, the propellant charges according to the invention have the advantage that they combust without residue—no residual items, such as, for example, cases, wires or rods or a plurality thereof, are left behind. The person skilled in the art can easily determine the amounts of materials and additives it is necessary to use for residue-free combustion (on the basis of stoichiometric considerations and simple tests).
In addition, the shape of the propellant charges according to the invention can be configured as desired, for example in a spherical shape, a conical shape, in the form of polygonal bodies or, especially, in a cylindrical shape, it being possible in special embodiments also to provide a central through-hole, which can be made, for example, by pressing tools suitably provided with a spike.
An igniter (for example a primer, priming charge) is not required and therefore preferably not provided—the propellant charges according to the invention are therefore scalable as desired; there is no necessity to distinguish between “front” and “rear” (for example with an igniter in the “rear” region) and it is unnecessary to provide indentations or the like for receiving igniters.
Finally, the propellant charges according to the invention also allow the exclusive use of cellulose nitrate (“nitrocellulose”) freely available commercially, as is used, for example, in paint bases. The nitrogen content (% by weight, based on the nitrocellulose itself) of such nitrocellulose is here approximately in the range from 10.7 to 12.5%, for example from 11.8 to 12.3%—unlike guncotton, where it is in the range from 13.2 to 13.5%.
Hereinbelow, unless otherwise indicated or apparent, percentages by weight are based on the total weight of all constituents of a mixture for the production of a propellant charge according to the invention mixed together prior to drying and compaction steps.
Preferably the nitrocellulose used for production in accordance with the invention has been stabilised, for example with a solvent such as a lower alcohol, for example ethanol or isopropanol, it being possible for further stabilisers, such as plasticisers, to have been added, such as epoxidised soybean oil or acetyl tributyl citrate. Walsroder™ nitrocellulose E 330 ethanol (Dow Chemical Co.) is an example of a preferred nitrocellulose. Based on the nitrocellulose component itself, the proportion of solvent and/or stabiliser can be in total from 10 to 50% by weight, for example approximately from 30 to 40% by weight, for example 35% by weight.
The proportion of nitrocellulose (optionally stabilised, that is to say, for example, with solvent) in a propellant charge according to the invention is, for example, advantageously in the range from 18 (for example 18.695) to 50 (for example 49.757) % by weight, especially from 27 to 35% by weight, including any solvent present as mentioned. The nitrocellulose serves as propellant and fuel and can furthermore act as water-resistant binder. For example, the proportion of (optionally stabilised) nitrocellulose is from 27.652 to 33.797 or from 27 to 35% by weight.
As current-conductive material, apart from graphite, in the embodiments of the invention there come into consideration especially carbon, preferably a wood charcoal (such as barbecue charcoal), such as hazel, linden wood, beech, alder or vine charcoal, carbon fibre chips (obtainable, for example, from R&G Faserverbundwerkstoffe GmbH, Waldenbuch, Germany) or medical charcoal (less preferred activated charcoal) or especially a rather hydrophobic charcoal (having, for example, high conductivity and low hygroscopicity) such as alder buckthorn charcoal (which tends to be rather greasy), which is especially preferred, or carbon chips. The charcoal used is preferably finely pulverised, for example homogenised by means of a ball mill (tumbled) (ball mill FP-2012, the steel balls supplied therewith were used, 9.5 or 16 mm); Feuerwerksparadies Wennesheimer, Tuttlingen, Germany). The current-conductive material or the carbon is/has been added advantageously in a proportion of from 2.4 (for example 2.487) to 12.5 (for example to 12.439) % by weight, or, for example, in a proportion of from 3 to 6% by weight. The carbon serves inter alia as fuel source and as current conductor. For example, the current-conductive material can be provided in a proportion of from 7.164 to 8.757% by weight. Advantageously, alternatively or preferably in addition it is possible to add a fibrous conductive material, for example carbon fibres. In that case the proportion of charcoal and/or fibrous material is preferably in the range from 3 to 12, especially from 3.5 to 6% by weight.
The graphite used in the embodiments of the invention can perform several functions: firstly it can increase the electrical conductivity inside the propellant charges according to the invention and thus also play a part as current-conductive material in the electrical ignition; furthermore it can contribute to a smooth surface (also having a shiny metallic appearance) and can increase the compressive strength, and finally it can also act as a lubricant which facilitates the production of the propellant charges according to the invention and their handling (insertion etc.). It is/has been added advantageously in a proportion of from 1.2 (for example 1.243) to 24.9 (for example to 24.878) % by weight. For example it can be provided in a proportion of from 2 to 6% by weight, for example from 2.4 to 3.1 or from 4.477 to 5.472% by weight.
As further additives, especially the following come into consideration:
One or more oxygen generators such as especially zinc peroxide or potassium chlorate or potassium perchlorate or mixtures of two (especially the two perchlorates or a perchlorate with zinc peroxide) or all thereof can serve to supply oxygen for the combustion (which allows the use of nitrocellulose having a lower nitrogen content than guncotton) and are present in total advantageously in a proportion of from 12 (for example 12.439) to 50 (for example to 49.757) % by weight. For example, the oxygen generator or the mixture of oxygen generators can be provided in a proportion of from 25.190 to 31.334% by weight or advantageously from 25 to 38% by weight, for example from 30 to 38% by weight.
A catalytically active metal oxide, such as manganese (IV) oxide (for example >90% precipitated, active; CAS No. 1313-13-9, EC No. 215-202-6), can bring about lowering of the ignition temperature, for example from about 550° C. to about 150° C. It can be/have been added advantageously in a proportion of from 0.6 (for example 0.621) to 6.3 (for example to 6.291) % by weight. For example, the catalytically active metal oxide can be provided in a proportion of from 1.3 to 3.2% by weight, for example from 1.3 to 1.8% by weight or from 2.563 to 3.132% by weight.
Iron (III) oxide (for example CAS No. 1309-37-1/EC No. 215-168-2; for example content >97%) can support the combustion and increase the combustion temperature) is/has been added advantageously in a proportion of from 0.000 to 1.3 (for example to 1.243) % by weight and can serve to reduce harmful substances. For example, the iron (III) oxide can be provided in a proportion of from 0.335 to 0.410% by weight. It can also be absent however.
A semi-metallic (such as silicon) or metallic fuel source such as magnesium, fine iron or especially aluminium (preferably having a particle size of 160 μm or less), titanium (for example having a particle size of 40 μm), or zirconium, or a mixture of two or more thereof (supports the combustion and increases the combustion temperature and can likewise be provided as further current-conductive material apart from graphite) can be/have been added in an amount of from 0.000 to 12.5 (for example to 12.439) % by weight. For example, the fuel source can be provided in a proportion of from 3.357 to 4.104% by weight. It can also be absent however.
A binder (which also increases the long-term stability) in the form of a thermoplastic plastics material containing exclusively carbon, hydrogen and oxygen atoms is preferably an acrylate or/or methacrylate, particle size about 200 to 400 μm, preferably of rather low molecular weight, which surprisingly can serve to reduce any harmful substances (such as nitrous gases) that are formed. It is/has been added advantageously in a proportion of from 1.2 (for example 1.243) to 7.5 (for example to 7.463) % by weight. For example, the binder can be provided in a proportion of from 1.5 to 4.2% by weight, for example from 1.5 to 2.0% by weight or from 3.357 to 4.104% by weight.
A hydrocarbon that is liquid at room temperature, such as, for example, pentane and/or isooctane, or a corresponding hydrocarbon mixture (such as petrol, for example automotive petrol or petrol-based cleaner) can be/have been added advantageously in a range from 1.2 (for example 1.243) to 15% by weight, for example from 9 to 15% by weight or from 1.2 to 6.3 (for example to 6.219) % by weight, during mixing of the composition of a propellant charge according to the invention and, for example, prevents the production tools from sticking. The proportion can be, for example, from 9 to 15 or from 3.134 to 3.831% by weight. It can be substantially or entirely removed or evaporated on drying.
A solvent for (especially for dissolving the fibre structure of) nitrocellulose and the binder in the form of a thermoplastic plastics material containing exclusively carbon, hydrogen and oxygen atoms, such as acetone, methyl ethyl ketone or a different ketone that is liquid at room temperature or an ester such as ethyl acetate, or mixtures of two or more thereof, can be/have been added in the production of a mixture for a propellant charge according to the invention in a proportion of from 3.7 (for example 3.731) to 37.4 (for example to 37.718) % by weight. The proportion can be, for example, from 9 to 16% by weight or from 12.314 to 15.051% by weight. Such a solvent can be substantially or entirely removed or evaporated on drying.
There can advantageously be added as further additive a (preferably hydrophobic or hydrophobised)—for example pyro-genic or precipitated—silicic acid (optionally with contained silicates, such as aluminium and/or calcium silicates), such as, for example, SIPERNAT® D10 from Evonik Industries AG, Hanau, Germany. The proportion can be, for example, from 0.2 to 3% by weight, for example from 0.3 to 1% by weight. This can give rise to a number of advantages, such as, for example, increased storage stability on account of the hydrophobicity, neutralisation of nitrous acids formed on burning off a propellant charge according to the invention in respect of the pH value, improved flow behaviour and improved compressibility in the production process and/or further improved burn-off behaviour of the propellant charges.
The process according to the invention for the production of a propellant charge according to the invention, as described above, can be carried out especially advantageously as follows, which allows especially simple industrial production (also mentioned in the Examples which follow):
The individual substances, apart from the graphite powder, are weighed out, including the nitrocellulose (for example having a content of 35% ethanol), and mixed together without addition of solvent. The liquid substances (solvent and hydrocarbon/-hydrocarbon mixture) are added and the resulting dispersion or solution is mixed. This is followed by drying, for safety reasons advantageously to a residual moisture content of from 5 to 15% by weight, for example from 8 to 10% by weight, residual moisture. The mixture is ground to form granules. Graphite powder is then added and mixed therewith. The granules so obtainable are ready for compaction and are compacted to form tablets in a tabletting machine and dried (for example for 24 hours at 60° C.). The finished propellant charges according to the invention are obtained.
In an embodiment of the invention, the propellant charge according to the invention can have a (for example central) hole which can pass all the way through and, for example, can be made by a corresponding spike in the pressing tool during pressing.
An important embodiment of the invention relates to the combination of nitrocellulose, carbon, graphite and acrylic granules, preferably also carbon fibres and silicic acid as constituents for the production of a propellant charge according to the invention or obtainable propellant charges.
The Examples which follow serve to illustrate the invention but do not limit the scope thereof.
1ELVACITE ® 2008 (Lucite International Inc., Cordova, TN, USA) (a low molecular weight methyl methacrylate)
2Walsroder ™ nitrocellulose E 330 ethanol (Dow Chemical Co.)
The particle size data relate to the result of optical microscopic measurement of the particle size with a stage micrometer and an ocular micrometer.
The individual substances, apart from the graphite powder, are weighed out, including the nitrocellulose having a content of 35% ethanol, and mixed together without addition of solvent. The liquid substances (acetone and isooctane) are added and the resulting dispersion or solution is mixed. This is followed by drying, for safety reasons to a residual moisture content of from 8 to 10% by weight residual moisture (which is also advantageous from the safety aspect). The mixture is ground to form granules. Graphite powder is then added. The granules provided with graphite so obtainable are ready for compaction and are compacted to form cylindrical tablets in a tabletting machine (for example FETTE PERFECTA 1000, FETTE COMPACTING GmbH, Schwarzenbek, Germany) and dried for 24 hours at 60° C.
In the case of a tablet 6×6 mm, the energy released after ignition with 100 to 110 volts was about 300 to 350 J.
Propellant tablets according to the invention were subjected to dry storage at 20° C. and 50% relative humidity until the weight was constant. They could be ignited properly with an ignition voltage of 100-110 volts.
The following water absorption is observed with a propellant charge from Example 1 at the temperatures and relative humidities indicated:
The propellant tablets are therefore stable towards even elevated humidity and can be stored even at sub-tropical humidities.
Propellant charges having the following composition are produced analogously to Example 1:
The invention relates also to the subject matter of the invention mentioned in the claims and in the abstract, which is incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2013 104 170.1 | Apr 2013 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/000994 | 4/14/2014 | WO | 00 |
