US20050066835A1

US20050066835A1 - Propellant powder charge for barrel weapon

Info

Publication number: US20050066835A1
Application number: US10/471,457
Authority: US
Inventors: Anders Hafstrand
Original assignee: Individual
Current assignee: Eurenco Bofors AB
Priority date: 2001-03-14
Filing date: 2002-03-01
Publication date: 2005-03-31
Also published as: JP2004531441A; AU2002233907B2; ZA200307163B; CZ20032483A3; EP1379482A1; EP1379482B1; NO20034050D0; CZ300130B6; CA2440629C; ES2289077T3; PT1379482E; IL157888A0; SE0100863D0; ATE369326T1; NO328476B1; SE0100863L; CY1106907T1; SE518660C2; NO20034050L; DK1379482T3

Abstract

The present invention relates to a method for producing propellant powder charges intended for heavy barrel weapons, such as canons and howitzers, and with a high degree of filling and a high energy content, and also to propellant powder charges produced in accordance with this method. The charges according to the invention are distinguished by the fact that 70 to 95% of their weight consists of a more coarsely grained powder and 30 to 5% consists of a granular powder with a smaller grain size. These two powders have the same of different chemical composition, and one or more of them can be surface-inhibited.

Description

The present invention relates to a propellant powder charge with high progressivity and an extremely high degree of filling or loading density, intended primarily for large-bore barrel weapons.
In what today is the most common way of producing progressive propellant powder charges intended for large-bore barrel weapons, use is made primarily of what is known as granular holed powder, i.e. powder produced by extrusion in a matrix, cut up into short rods or cylinders, with one, seven, nineteen or thirty seven longitudinal priming channels. Because of its geometric configurations throughout its burn time, except during the absolutely final stage, multiple-hole powder of this kind has good progressive burn properties by virtue of the fact that as they are primed they burn from all the surfaces available for priming, i.e. from the outsides of the grains and from the insides of the priming channels, and, from these surfaces thereby primed, the powder will burn towards other primed surfaces during a successive increase of the burn area, and the gas release thereby also increases.
In order to launch a defined missile from a defined barrel weapon with a predetermined Vo, i.e. with a defined launch velocity immediately outside the barrel mouth, the propellant powder has to be able to deliver a certain additional amount of energy. This additional energy, which can be calculated theoretically with great accuracy, must be delivered during the missile's travel through the barrel. This in turn means that the propellant powder must have time to burn out during the time the missile is on its way through the barrel. The period of time which the propellant powder should then have to burn out and which is thus the same as the time the missile has to pass through the barrel can be called the “burn time”.
If at the same time the length which a powder with the chemical composition in question is able to burn is also called the “burn time”, this means that the distance between two adjacent priming channels in a multiple-hole powder which has the desired burn time will correspond to twice the burn length which the burn time in question permits. The distance from respective priming channels to the outer side of the granular powder in which the priming channel is formed must be the same size, provided that the powder grains have not been surface-treated with a burn inhibitor, which is sometimes done in order to increase the powder's progressivity. In summary, it is readily possible to produce multiple-hole powders with different progressivity using different numbers of priming channels, the individual powder grains being given a greater inherent volume depending on the number of priming channels. The progressivity of the powder can then in turn be accentuated by surface treatment with a suitable substance which is more difficult to ignite, but burnable.
The main trends in modern-day arterillery technology are to attempt by all possible means to increase the artillery's range of fire and its firing speed. In view of the refined methods which have been developed in recent years, and which allow an opponent to determine quickly and with very great accuracy from where he has been shot at, it is thus also necessary to rapidly change the site of firing each time the barrel has been opened.
Increased firing speed is mainly achieved by the introduction of mechanized loading systems, and these will not be discussed in any detail here, nor will the tactical need for rapidly changing the firing positions. By contrast, it has been found that older artillery pieces too which are in good condition can be given much longer ranges of fire by means of newly developed and high-energy powder charges and possibly also newly developed shells. However, a problem in this context, which is often more serious than the strength limits of barrel and mechanism, is that the space in the rear part of the barrel, i.e. its chamber position, which is available for the actual propellant charge is too small to accommodate a conventionally configured propellant powder charge with sufficient energy content for this desired increase in the range of fire.
The present invention now relates to a method using holed or unholed granular powder to produce progressive propellant powder charges with a higher degree of filling or loading density and thus also loading weights than has previously been possible. The invention also includes propellant powder charges produced in accordance with said method.
The starting point for the method according to the invention is that, between the grains of a granular powder introduced into a container without any kind of organized order, there will automatically be a very large number of greater or lesser empty volumes which are many but small in the case of a finely grained powder and which are fewer but also larger in a coarser-grained powder.
Our solution to the problem now is so simple that it is astonishing that it has not been done earlier. According to the underlying principle of the present invention, we in fact mix two or more different sorts of granular powder in proportions adapted for the particular purpose, where the more finely grained powder is able to fill the otherwise empty space between the larger powder grains. By suitable choice of powder types and suitable proportions between them, it is thus possible to produce charges which have loading densities lying very near to or higher than those one would have obtained if the powder grains had been rammed in manually for the best degree of packing, and the latter method is entirely excluded for practical use. The only additional measure which may be required in connection with the present invention is that the charges are vibrated during powder filling, which is also preferably done simultaneously with the two powder types. One or more of the powder types used can additionally be surface-treated or surface-inhibited in order to further control the progressivity.
The present invention thus makes it possible to produce propellant powder charges with a high loading density and exactly the high energy content which is required for the case in question. A propellant powder charge produced according to the invention can thus contain 70-95% by weight of a coarsely grained multiple-hole powder, for example a 19-hole or 37-hole powder, and 30-5% by weight of a smaller multiple-hole powder, for example a 1-hole powder or 7-holed powder, and, in view of the desired final result, the powders can each have the same or different chemcial composition and be surface-inhibited (surface-treated with suitable burn inhibitors) or not surface-inhibited. The percentages shown above apply to the outer limits characterizing the invention, whereas, when in practice calculating the charges of the type characterizing the invention, they will in most cases be in the range of 75-85% by weight for the coarser multiple-hole powder and 25-15% by weight for the multiple-hole and more finely grained powder or powders.
The nearest prior art we are aware of is the charge which is described in U.S. Pat. No. 4,519,855 which describes a propellant powder charge for ballistic ammunition comprising a first powder component consisting of large balls or spheres easily fragmentable into small grains of a first powder component surrounded by a second powder component in the form of a conventionally granular powder which fills the space between the large spheres of powder. Here too the aim has been to produce a powder charge with the highest possible degree of filling taking into consideration the powder types used, but the progressivity of the charges obtained by this method will be based primarily on the large spheres of powder bursting apart during combustion of the powder and thereafter burning like conventionally granular powder, whereas the progressivity for our specific charge is based entirely on the original geometrical shape of the powder grains used.
The present invention thus relates to a method in which granular powder is used to produce propellant powder charges with high degree of filling or loading density and a high energy content per charge. The invention also covers the charge produced by this method. The invention also makes it possible to produce charges with precisely controlled progressive characteristics by virtue of the fact that it can be built up from different quantities of different powders which have radically different progressive characteristics.
The invention is thus based entirely on combining two or more types of granular powder having such geometric external shapes and grain sizes that the powder with the smaller grain size will in the best possible way fill the empty space between the larger grains.
The invention has in all its features been defined in the attached patent claims and it can be illustrated by the following example.

EXAMPLE

From a nitrocellulose powder of standard quality which we have used for many years for producing artillery powder, we produced on the one hand a 19-hole powder with grain size of 17×17 mm and a 1-hole powder with a grain size of 5×5 mm. Of these powders, we mixed 2.3 kg of the 19-hole powder with 0.5 kg of the 1-hole powder and thus obtained a charge with an energy content corresponding to 122% of the energy content in a standard charge which we had previously produced and which was made only from 19-hole powder. Both the charge types are held in the same volume. The invention thus makes it possible to achieve considerable advantages by very small means.

Claims

1-7. (Cancelled).

8. A method for producing progressive propellant powder charges suitable for use in barrel weapons having a high degree of filling or loading density and thus also a high energy content at which the charge is produced, the method comprising:

mixing at least two types of granular powder of different grain size, of which at least one of the at least two powder types with a largest grain size and a larger number of internal priming channels has a progressive burn characteristic,

wherein, as subsidiary components of an actual charge, granular powders are chosen having size, geometric shape, and quantities adapted to give a smallest possible empty spaces between the powder grains.

9. The method of claim 1, wherein a starting material chosen for the charge comprises at least two types of powder whose mutual progressivity has been optimized for a particular purpose.

10. The method of claim 1, wherein a starting material chosen for the charge comprises granular powder having a same or different chemical composition, but with different grain size and a different number of internal priming channels.

11. The method of claim 1, wherein, when choosing a starting material, powder types are chosen of which one or more are surface-inhibited.

12. The method of claim 1, wherein, of the powder types included in a finished charge, all the types are introduced contemporaneously with each other and, at the same time a casing or cartridge to which the powder is added and in which the charge is to be stored prior to use is subjected to vibrations which improve a degree of packing of the charge.

13. Propellant powder charge suitable for use in barrel weapons and having a high degree of filling or loading density and with a high energy content, the power charge comprising:

at least two different types of granular powder of which at least one type has a progressive burn characteristic and in which one or more of these powders is surface-inhibited,

wherein burn characteristics of each of these different powders are adapted to one another while their mutual grain sizes and quantities of each powder included in a charge are adapted to one another such that an empty space remaining between the powder grains is minimized.

14. The propellant powder charge of claim 13, wherein between 70-95% of a powder charge weight comprises relatively coarsely grained powder, and

wherein 30-5% of the weight comprises a relatively more finely grained powder,

wherein these two powders have a same or different chemical composition and at least one of the two powders is progressive and one or more of the two powders is surface-inhibited.

15. The propellant powder charge of claim 14, wherein between 75 to 85% of of a powder charge weight comprises relatively coarsely grained powder.

16. The propellant powder charge of claim 14, wherein the coarsely grained powder is either 19-hole or 37-hole powder cut into short sections.

17. The propellant powder charge of claim 14, wherein the finely grained powder is either 1-hole or 7-hole powder.