Propellant Charge for the Reduction of Base Eddying

The invention relates to a propellant charge for the reduction of base eddying or drag of an artillery shell and which has a centrally disposed ignition conduit and an ignition device for the charge disposed in the conduit.

Such propellant charges diminish, by pyrotechnical gas production, the base eddying, drag or resistance occurring in a shell in flight and thereby increase the range of the shell. For example, an artillery shell of 155 mm caliber can, with the aid of such a propellant charge (base bleed effect), cover distances of more than 30 km. The propellant charges have ignition means which are activated by hot propellant charge gases during firing of the shell and which in turn ignite the base bleed propellant charge. It was noted in connection with known propellant charges that this ignition process does not occur with a sufficiently high degree of accuracy.

A propellant charge is already known from German patent application DE P No. 34 37 250.4, corresponding to DEOS No. 34 37 250, published Apr. 4th, 1986, in which the wall of the propellant charge which bounds the ignition conduit shows an ignition-enhancing layer or a roughened structure having an increased surface in order to improve the ignition process.

It is an object of the invention to provide an alternate and further improved solution for an assured control of the ignition problem.

The above object is achieved according to the present invention by a propellant charge for the reduction of the base eddying or drag of a projecticle or shell wherein the charge is of the type having a centrally disposed ignition conduit extending axially therethrough and is provided with an ignition means for the charge which is disposed adjacent the front end of the ignition conduit; and wherein the inner surface of the propellant charge defining the ignition conduit conically narrows in the aft direction of the propelling charge.

According to further features of the invention, the conically narrowed inner surface of the propelling charge may additionally be provided with stepped sections and/or the ignition openings provided in the housing for the ignition means may be oriented at an angle to the longitudinal axis of the propellant charge so that they face the inner surface of the propellant charge.

The invention is further explained below with reference to the drawings wherein:

FIG. 1 shows the aft section of a shell in longitudinal section with a first exemplary embodiment of the invention; and

FIG. 2 shows the aft section of a shell in longitudinal section with a further exemplary embodiment of the invention.

FIG. 1 shows the aft end of an artillery shell 12 which can be fired from weapons having gun barrels, such as field howitzers, self-propelled howitzers and mortars. The shell 12 includes a propellant charge 1 for the reduction of base eddying disposed in a screw-on base element 12a with a hollow space serving as a combustion chamber 15. This propellant charge 1 includes an ignition conduit 4 which is disposed central-axially, and is closed, for reasons of safe handling, for the time being by a rupture disk 14 which, when firing the shell 12 from a weapon barrel (not shown), is destroyed by the resultant hot propellant charge gases. Disposed at the front end of the ignition conduit 4 is an ignition means or device 16, including a housing 16a provided with ignition openings 16b and containing an ignition charge 16c. The ignition charge 16c is ignited by the hot propellant charge gases produced in the weapon after the rupture disk 14 has been destroyed and, in turn, provides hot gases for the ignition of the propellant charge 1 to its inner surface 1a via the ignition openings 16b.

To improve the ignition sensitivity of the propellant charge 1, the rim area or inner surface 1a of the propellant charge 1 surrounding and defining the ignition conduit 4 is conically narrowed in the aft direction. This achieves a better ignition of the propellant charge 1 by the hot gases generated by the ignition means 16, since the clouds of gas actually impact on the rim area or inner surface 1a and do not merely tangentially graze same.

In an advantageous embodiment of the invention, stepped sections 1b (FIG. 2) are additionally disposed in the conically narrowed rim area 1a. By means of these stepped sections 1b the ignition readiness of the propellant charge 1 is further increased, since the ignition gases exiting from the ignition openings 16b are caught in the annularly extending edges formed by the stepped sections 1b and thus have a better chance to ignite the propellant charge 1.

In an advantageous improvement of the invention as shown in FIG. 2, at least some of the ignition openings 16b inside the housing 16a of the ignition means 16 are disposed at an angle relative to the longitudinal axis 100 of the propellant charge 1, namely in such a way that they are more or less aligned towards the rim area 1a of the propellant charge 1. This results in a further improvement of the ignition readiness of the propellant charge 1, since now the surface 1a is directly in the flow direction from the ignition openings 16b.

It is, of course, possible to combine the embodiments shown in FIG. 1 and FIG. 2 of the invention with the teachings disclosed in Federal Republic of Germany patent application DE P No. 34 37 250.4, i.e. to provide, for example, the rim area 1a formed in accordance with the invention additionally with a roughened structure or with an ignition-enhancing layer.