PRIMER FOR A PROPELLANT CHARGE

Abstract: The disclosure relates to an apparatus in a primer (5) of the type which is disposed in the cartridge case (3) of a shell, projectile or the like for igniting the propellant charge (4) of the cartridge case. The primer comprises a sleeve-shaped portion (6) disposed in the rear plane (7) of the cartridge case, and an elongate tube (8) which extends centrally through the propellant charge (4) of the cartridge case forwardly towards the rear plane (15) of the shell. The forward portion of the primer tube adjacent the rear plane (15) of the shell is provided with an extension sleeve (12) which extends forwardly towards the rear plane (15) of the shell such that the forward portion (14) of the sleeve will surround a tracer cartridge (2) disposed at the rear plane of the shell. The point of collision in the event of a jolt against the rear plane (7) of the cartridge case will instead hereby be located between the extension sleeve and the rear plane (15) of the shell, such that damage to and unintentional ignition of the tracer cartridge (2) may be avoided.

Description: The present invention relates to an apparatus in primers of the type which are disposed in the cartridge case of a shell, projectile or the like for igniting the propellant charge of the cartridge case. A tracer cartridge is located at the rear plane of the shell, projectile or the like. The apparatus comprises a sleeve-shaped portion disposed in the base plane of the cartridge case and an elongate primer tube which extends centrally through the propellant charge of the cartridge case forwardly towards the rear plane. The forward portion of the elongate tube is provided with an extension sleeve which extends forwardly towards the rear plane. A primer of the above type is previously known from, for instance, EP-A- 0 237 711. In drop tests against the rear plane of the cartridge case in ammunition units of the above-disclosed type, it has proved that the shell shows a marked tendency to slide into the cartridge case. Neither the crimp-and-groove union nor the bourrelet of the shell is capable of resisting the shell. The risk of collision between a tracer cartridge mounted on the rear plane of the shell and the primer is obvious. Such a collision will result in ignition of the tracer cartridge, which may have serious consequences in connection with ammunition handling. The object of the present invention is to realize an apparatus which prevents collision between the primer and a tracer cartridge disposed on the rear plane of the shell. In such instance, the present invention is characterized in that the forward portion of the extension sleeve is arranged to surround the tracer cartridge adjacent to the rear plane. The point of collision in the event of a jolt against the rear plane of the cartridge case will then instead be located between the above-mentioned extension sleeve and the rear plane of the shell so that the tracer cartridge remains undamaged. According to one advantageous embodiment of the present invention, the extension sleeve is slightly conical with its broader portion facing towards the rear plane of the shell and provided with a number of apertures or slots which serve as ports for the gas flow from the powder in the propellant charge towards the tracer cartridge. The nature of the present invention and its aspects will be more readily understood from the following brief description of the accompanying Drawings, and discussion relating thereto. In the accompanying Drawings: Fig. 1 shows a complete round in the form of a shell with tracer cartridge and cartridge case; Fig. 2 shows, on a larger scale, a portion of the round; Fig. 3 shows a first variant of the extension sleeve; Fig. 4 shows an alternative design of the sleeve; and Fig. 5 shows the forward region of the primer tube in detail. Referring to the Drawings, Fig. 1 shows an ammunition unit in the form of a complete round which comprises a fin-stabilized armour-piercing shell 1 with tracer cartridge 2 and cartridge case 3. These parts are per se known in the art and will not, therefore, be described in greater detail here. For igniting the propellant charge 4 of the cartridge case 5, a primer 5 is disposed in the cartridge case 3. The primer 5 consists of two main parts: a primer sleeve 6 disposed in the rear plane 7 of the cartridge case and an elongate tube 8 which extends centrally through the propellant charge 4. The primer sleeve carries ignition devices, for example a conventional percussion cap and ignition charge, and the elongate tube 8 forms a combustion chamber which is provided with a number of outlet apertures 9 throughout its entire length, through which a simultaneous and rapid ignition may be effected at a plurality of points of the surrounding propellant charge. In this respect, the primer is wholly conventional and will not be described in greater detail here. As was mentioned by way of introduction, it has proved in drop tests against the rear plane of cartridge cases of the above-described type that the shell shows a marked tendency to slide into the cartridge case. While the shell is connected, by the intermediary of a crimp and groove union 10, to the cartridge case, neither this union nor the bourrelet 11 of the shell is capable of resisting the shell in the event of powerful jolts against the rear plane. The risk of collision between the tracer cartridge 2 and the forward region of the primer tube is obvious. The risk of accidents is extremely high, since the tracer cartridge may be ignited as a result of this collision, which could lead to dire consequences. To prevent collision between the tracer cartridge 2 and the primer 5, an extension sleeve 12 is disposed on the forward region of the primer tube. The forward region of the primer tube is provided with an external thread on which the rear portion 13 of the sleeve is fixedly threaded. The forward region 14 of the sleeve extends up to the rear plane 15 of the shell proper and surrounds the tracer cartridge 2. Ideally, the sleeve is disposed such that a narrow gap 16 is left between the forward edge 17 of the sleeve and the rear plane 15. The sleeve is slightly conical, tapering rearwardly, and merges forwardly in a cylindrical portion about the tracer cartridge. The extension sleeve 12 is provided with a partition 18 which separates the rear portion of the sleeve which surrounds the end region of the primer tube, and the forward portion of the sleeve. The partition is provided with a central through aperture 19. At least in the region, between the rear plane 20 of the tracer cartridge and the partition, the wall of the extension sleeve is perforated with a number of holes 20 which allow the gas flow from the powder of the propellant charge to impinge upon the tracer cartridge such that this is ignited. Instead of being provided with a number of holes 21, the sleeve may be provided with through-slots 22, see Fig. 4. In such instance, the gas flow from the powder is aimed directly towards the seal of the tracer cartridge and makes for a more efficient ignition of the tracer cartridge. The forward edge 23 of the primer tube abuts against the partition which thereby prevents the sleeve from being displaced in relation to the primer, see Fig. 5. The forward region of the primer is provided with a cardboard case 24 (a diaphragm) for sealing purposes. The cardboard case is provided with a weakened portion 25 so as to realize an area of fracture. In this instance, a certain assistance may be obtained from the primer in that combustion gases are allowed to flow through the weakened portion 25 and the opening 19 of the partition to the tracer cartridge and ignite it. The weakened portion 25 is normally covered by a thin aluminium foil 26 or the like. On ignition, an earlier occurrence which has happened in this art is that the cardboard case 24 was thrown forwards towards the tracer cartridge and deposited itself over the tracer as a cap, thereby impeding complete ignition. According to the present invention, the cardboard case is entrapped by the partition of the extension sleeve and is prevented from depositing itself on the tracer cartridge. In the embodiment according to Fig. 4, the central through-opening 19 is therefore of slightly smaller diameter than in the embodiment illustrated in Fig. 3.

Claims: An apparatus in primers of the type which are disposed in the cartridge case (3) of a shell, projectile or the like for igniting the propellant charge (4) of the cartridge case, a tracer cartridge (2) being located at the rear plane (15) of the shell, projectile or the like, the apparatus comprising a sleeve-shaped portion disposed in the base plane of the cartridge case (6), and an elongate primer tube (8) which extends centrally through the propellant charge of the cartridge case forwardly towards the rear plane (15), the forward portion of the elongate tube being provided with an extension sleeve (12) which extends forwardly towards the rear plane (15), characterized in that the forward portion (14) of the extension sleeve (12) is arranged to surround the tracer cartridge (2) adjacent to the rear plane (15). The apparatus as claimed in Claim 1, characterized in that the extension sleeve (12) is slightly conical with its broader portion facing towards the rear plane (15) of the shell, and its forward edge (17) abutting against the rear plane (15) of the shell or being adjacent thereto by the intermediary of a narrow gap (16). The apparatus as claimed in Claim 2, characterized in that the extension sleeve (12) is provided with a partition (18) which separates the rear portion (13) of the sleeve, which, for example via a thread, is mounted on the forward end portion of the primer tube, from the forward portion (14) of the sleeve, the partition (18) being also provided with a central through-opening (19). The apparatus as claimed in Claim 3, characterized in that the forward portion (14) of the extension sleeve is, at least in the region between the partition (18) and the rear plane (20) of the tracer cartridge, perforated by a number of holes (21) or slots (22) for allowing combustion gases from the surrounding propellant charge (4) to reach the tracer cartridge (2). The apparatus as claimed in Claim 3, characterized in that the forward edge (23) of the primer tube abuts against the partition (18). The apparatus as claimed in Claim 3, characterized in that the forward portion of the primer tube is provided with a sealing case (24) of cardboard or similar material, said case being provided with a weakened portion (25) for realizing an area of fracture and permitting combustion gases from the primer to reach the tracer cartridge (2) via the opening (19) in the partition.

Inventors: HELLMAN, ULF, SUNDELL, CHRISTER
Applicants: AB BOFORS
Application year: 1990
Main classification: F42C19
IPC codes: F42C19