DESCRIPTION OF THE DRAWINGS
The invention has been defined in its entirety in the following Patent Claims, and it will only be described here in slightly more detail in conjunction with the following Figures. Of these,
FIG. 1 shows a greatly magnified view of a small part of a perforated propellant block;
FIG. 2 shows a part of a longitudinal section of an essential three-tube propellant charge;
FIG. 3 shows a cross section through the charge in accordance with FIG. 2;
FIG. 4 shows a partially sectioned complete round;
FIG. 5 shows a cut-away enlargement from FIG. 4 in accordance with the marking in FIG. 4;
FIG. 6 shows a general pressure/time graph which, for a charge of the type shown in FIGS. 3 to 5, indicates the pressure in the barrel behind a projectile on its path along the barrel; while
FIGS. 7
a-c show, by way of cross sections through a number of charges, different ignition propagation possibilities for these; and
FIG. 8 shows a longitudinal section through a charge consisting of a plurality of perforated propellant tubes arranged both inside one another and after one another.
DETAILED EMBODIMENT DESCRIPTION
FIG. 1 accordingly shows a greatly magnified view of a small part of a perforated propellant block 1 with a very large number of perforation or ignition channels 2. The outer configuration of the propellant block 1 can be cube-shaped or tube-shaped or can exhibit any other form. The principal task of FIG. 1, which shows the part of the propellant block 1 as a view transversely across the perforation or ignition channels of the block, is to clarify the combustion sequence for a highly perforated propellant. The starting point in this case is the theoretical combustion circles 3-9, which together form an imaginary seven-perforation propellant, which, since it constitutes an inner part of the propellant block 1, can be regarded after its ignition as burning only via its respective perforation or ignition channels 2. Combustion of the propellant then takes place from the respective propellant channel 2 and radially outwards in the direction r of the arrows. It can thus be appreciated from the Figure that the combustion area of the propellant increases successively with the combustion time, i.e. combustion of the propellant is progressive until the combustion processes come together at the mutual points of contact of the combustion circles 3-9 drawn in the Figure. As can be appreciated from the Figure, a number of small quantities of propellant x, which are illustrated in the Figure with dashed lines, also remain in the corners between the combustion circles, and these quantities of propellant burn degressively together with the outer surfaces of the propellant block. This degressive contribution can be regarded as negligible, however, relative to the progressive contribution.
The e-dimension of the propellant is thus represented in FIG. 1 by the edge-to-edge distance between two adjacent ignition channels 2 or the combined radii of two contiguous circles 3-9 minus the diameter of one ignition channel. Bearing in mind the intrinsic rate of combustion of a propellant and the requirement for the propellant charge in barrel weapons to have delivered its energy to the projectile fired from the weapon before the projectile has left the barrel, the e-dimension lies between 0.5 mm and 10 mm as a rule, but preferably between 1 mm and 4 mm.
The actual invention is illustrated in FIGS. 2 and 3 in the form of a propellant charge intended for barrel weapons consisting of three propellant tubes 10, 11 and 12 inserted into one another, where each outer propellant tube is inhibited, surface treated with a substance to delay the propagation of ignition or surface coated with a layer of a propellant to delay the propagation of ignition, on both its own outside and inside and on the ends. In the Figures, these combustion-modifying layers have been given the designations 13, 14, 15 and 16, with 17 and 18 being given for the respective ends, where the latter designations apply to all ends of the propellant tubes 10-12. The inhibition, surface treatment or surface coating of at least some of the propellant tubes that is necessary for the control of combustion can also be combined with, or partially replaced by, ensuring that these propellant tubes are executed so that they are not perforated all the way through to the insides of the tubes. If it is envisaged that propagation of the ignition of the propellant tubes is to take place from the inside outwards, a relatively small quantity of propellant would accordingly require to be burned off in this variant before the combustion channels or the perforations become accessible for the propagation of the ignition. Another way of delaying propagation of the ignition between the different perforated propellant tubes, and which is illustrated in FIG. 8, is based on the principle of separating the different propellant tubes from one another with a separation layer consisting of a propellant which, in a similar fashion, must first be burned away before ignition can be propagated to the next propellant tube.
In the case of charges containing a plurality of the propellant tubes that are characteristic of the invention, the intention is thus that the different propellant tubes should be ignited one after the other but before an already ignited propellant tube has had time to burn out. Whether a previously ignited propellant tube is then an outer or an inner propellant tube is of less significance from a purely conceptual point of view. Every propellant tube is also highly perforated in its entirety in accordance with the principles already discussed in the introduction.
As can be appreciated from FIG. 3, where only a few perforations 19, 20 and 21 are consequently shown for the sake of clarity, uniform perforation around a round propellant tube means that the perforations must be directed radially, and that they will thus approach more closely to one another inwards towards the inside of the tube, and bearing in mind the significance of the e-dimension for the combustion characteristic of the propellant that has already been discussed, it is a clear advantage if a tubular charge consists of a plurality of thinner tubes inserted into one another, where the perforation distance for each tube is corrected in order to give the best possible compromise. Additional to this opportunity for controlling the combustion characteristic of the propellant is the basic idea of inhibiting propellant tubes that are lying outside or lying inside, so that these are ignited successively in a predetermined sequence with a certain mutual overlap, at the same time as the combined generation of propellant gas from all of the simultaneously burning propellant tubes is never permitted to generate a combined propellant gas pressure which exceeds the Pmax value of the discharge device in question, i.e. its highest permissible barrel pressure, and yet on the other hand, during the entire discharge sequence, is as close as possible to the maximum pressure as can be allowed during continuous service. The latter pressure is usually referred to as Pmop (maximum operational pressure). The internal cavity 22 of the inner propellant tube 10 provides space, as previously indicated, to accommodate a fuse plus an ignition charge consisting of an optional type of propellant, if required.
The charge illustrated in FIGS. 2 and 3 can in itself be regarded as constituting an example of a so-called modular charge, i.e. a type of standard charge of which a plurality can be combined to form a complete propellant charge. The outer inhibiting layers 16-18 of the charge can be executed in this case so that they also function as protection against the weather, wear and tear and the climate.
When correctly designed, a charge of this kind gives a pressure-path sequence of the type shown in FIG. 6, where a propellant tube, e.g. the inner propellant tube 10, is ignited first and, thanks to its own perforation, produces a progressive combustion sequence in accordance with the part of the curve 10′, which reaches its maximum at 10″, after which the generation of propellant gas from this propellant tube on a level with 10′″ begins to diminish, although since, if the ignition of the propellant tubes is propagated from the inside outwards, the propellant tube 11 will already have been ignited before the propellant tube 10 has reached its maximum, the production of propellant gas from this second propellant tube will, at the same time, begin to provide a significant additional amount of propellant gas while the propellant tube 10 burns out. The curve 12 in FIG. 6 shows the propellant gas pressure available in the barrel behind the fired projectile on each occasion. The propellant tube 11 consequently now contributes with the progressive part 11′ of the curve and thereby restricts the downward trend of the curve, at the same time as the propellant tube 11 provides a maximum contribution at 11 ″. In a similar fashion to that for the propellant tube 10, the diminishing production of propellant gas by the propellant tube 11 will result in a slight decrease in the combined generation of propellant gas at 11′″, at the same time as the addition of propellant gas from the propellant tube 12 makes its contribution in an equivalent fashion in the form of a slight increase at 12′, and a maximum at 12″, after which the entire pressure curve falls rapidly, so that the propellant gas pressure behind the fired projectile as it passes through the muzzle is so low that the laying of the projectile on its intended trajectory is not disturbed. Also shown in FIG. 6, on the one hand, is the maximum permissible barrel pressure Pmax for a single round and, on the other hand, Pmop (maximum operational pressure), which should be approached as closely as possible in continuous service in order to achieve a maximum range of fire. The theoretically optimal curve for a propellant charge has been given the designation Poptimal in the Figure (indicated in the Figure with a cross), and the type of pressure-path curve associated with today's conventional granular propellant has been given the designation Pnormal. Since the granular propellant has a very substantial initial combustion surface, it very quickly gives rise to a maximum pressure which then falls at a far too early stage. On the other hand, as can be appreciated from the Figure, the result obtained in accordance with the invention lies very close to the theoretical optimal value. The pressure-path discussion conducted here is also applicable to the charge in accordance with FIG. 4 and FIG. 5. As can also be appreciated from the curve, there is a requirement that the generation of propellant gas should essentially have ceased entirely immediately before the projectile leaves the muzzle of the barrel.
The complete round 23 illustrated in FIG. 4 and partially in FIG. 5 consists of a subcaliber armour-piercing arrow projectile 24 with an associated sabot 25, a case 26 with a base 27 and one of the three propellant tubes 28-30 inserted into one another and the long fuse 31 with its ignition apertures 32 as shown in FIG. 5.
It can also be appreciated from FIG. 5 that the charge (it is in fact partially sectioned in the Figure) consists of three propellant tubes 28-30 inserted into one another, where the two outer propellant tubes 28 and 29 are inhibited on all their outside surfaces 33-36 as well as on the ends that are not included in the Figure. It can also be appreciated from FIG. 4 that the different propellant tubes 28-30, at least with regard to propellant tube 30 in relation to propellant tubes 28 and 29, are of different thickness, and that their perforations, all with the designation 37, are made with different e-dimensions (the perforations 37 have not been drawn in FIG. 4, because this was not permitted by the scale of the Figure). A development of the invention also provides for the different propellant tubes to be made with different types of propellant with different rates of combustion, in conjunction with which a faster-burning propellant is preferably used in propellant tubes that are to be ignited at a later stage, and a rather more slow- burning propellant is used in the propellant tubes that are to be ignited first.
FIGS. 7
a-c show, as already mentioned, a number of different variants for the propagation of ignition between the different propellant tubes. Any other variant that falls within the underlying idea characterizing the invention is also conceivable.
The charge in accordance with FIG. 7a thus comprises three radially perforated propellant tubes 39-41 of the type that is characteristic of the invention. The arrow a denotes that propagation of the ignition of the propellant tubes is intended to take place from inside the centre of the charge and outwards. The outer propellant tubes 40 and 41 are therefore assumed to be inhibited or surface-treated in a previously discussed fashion, so that the desired partially overlapping and mutually delayed propagation of the ignition is achieved.
FIG. 7
b similarly shows a charge consisting of three propellant tubes 42-44 arranged inside one another, where it is envisaged that propagation of the ignition will take place both from the outside inwards in accordance with the arrow b, and from the inside outwards in accordance with the arrow c. In this variant, it is thus the middle propellant tube 43 that has been provided with inhibited or surface-treated outer surfaces to delay propagation of the ignition. Of course, all of the propellant tubes contained in the charge are radially perforated. They can also be made from different types of propellant with different rates of combustion.
FIG. 7
c, finally, shows a two-tube propellant charge consisting of the radially perforated propellant tubes 45 and 46, where the outer surface of the outer propellant tube 46 is prevented from burning, for example by the application of an inhibitor. The aforementioned two propellant tubes 45, 46 are intended to be ignited by propagation from the inside outwards in accordance with the arrow d, although in this illustrative embodiment propagation of the ignition between the propellant tubes 45, 46 is slowed down by a layer 47, which is arranged between the propellant tubes 45, 46, or by a surface coating 47 on the inner surface of the outer propellant tube 46 consisting of a slow-burning propellant 47, which must be burned away before ignition can be propagated to this propellant tube 46.
FIG. 8, in conclusion, shows a longitudinal section of part of a developed variant of the charge in accordance with the invention comprising a plurality of radially perforated propellant tubes arranged after one another and inside one another (as in several of the earlier Figures, the scale of the Figures did not permit the direct illustration of the perforations). The Figure shows four different propellant tubes 48-51, where the propellant tubes 50 and 51 are arranged inside the propellant tubes 48 and 49, respectively. It is envisaged that all of the outside and inside surfaces of the propellant tube 48 are inhibited or surface-treated, while the propellant tube 49 is surface-coated with, or perhaps rather embedded in, a delaying propellant 52. In order to exemplify the flexibility of the invention, it is envisaged that the propellant tubes contained in the charge are made from different types of propellant. Also shown in the Figure are parts of a fuse 53, at the same time as the free space 54 at the centre of the inner propellant tubes 50, 51 is intended to be filled with loose granular initiating propellant.
Patent Application
20080047453
