03.12.2004
Since the coming into force of the new Proof Firing Act (BeschG), launching cups used as additional appliances for the loading of pyrotechnic ammunition in signal weapons must be approved by PTB. As this also applies to old stocks, a large number of gas pressure and velocity tests had to be carried out with simulation bodies.
Since the coming into force of the new Proof Firing Act in April 2003, additional appliances (also called launching cups) used on signal weapons for the launching of pyrotechnic projectiles must be approved by PTB. So far, 64 approvals have been granted after respective testing. Fig. 1 shows such a launching cup. Screwed on the muzzle of the signal weapon, it takes up a pyrotechnic projectile an guides it loosely.
In a signal weapon with launching cup an front-loaded pyrotechnic signal ammunition, first a cartridge is ignited (the calibre of the blank cartridge or detonating ammunition is typically up to 9 mm blank). This yields a detonating noise an results in a hot gas flow which, under pressure, passes through the gas barrel being provided with barriers. The pressure is transmitted to the bottom of the pyrotechnic projectile. Through a bore in the launching cup which (in connection with pressure unloading bores) serves as a nozzle to control the gas pressure, the projectile is then, on the one hand, ignited an, on the other hand, accelerated in the launching cup an guided. The burn-up of the primer of the pyrotechnic projectile then leads - with a delay in time, i.e. after it has reached a certain flight height - to the release of the pyrotechnic effect (lighting up of a flare and/or generation of an acoustic event.)
A prerequisite for a launching cup being approved in conjunction with the signal weapon, as a system, is above all that the dynamic pressure at the primer of the pyrotechnic projectile can be controlled. This gas pressure pulse must never rise so high that the hot gases penetrate the primer an the pyrotechnic effect is already triggered off in the launching cup. If this happens (which is often called breakthrough), a risk to the user of the weapon cannot be ruled out. Also, the pressure must not become so high that when launching the pyrotechnic projectile, a dangerous effect is brought about due to too high a kinetic energy. On the other hand, the pressure must not become too low. The pyrotechnic projectile must be accelerated so strongly that the time-delayed launching of the pyrotechnic effect takes places in sufficient height, and not after the projectile has fallen to the ground.
In cooperation with the Federal Institute of Materials Research and Testing (BAM), which is responsible for the approval of pyrotechnic ammunition. A maximum value of 5 MPa has been laid down for the gas pressure being permitted at the bottom of the projectile, and minimum value of 20 m/s for the projectile velocity to be determined in this measurement.
Both quantities are determined in a joint measurement procedure, in which a cylindrical body with a mass of 8 g serves to simulate a pyrotechnic ammunition. During the system test it is checked whether the maximum pressure pulses, is observed in the launching cup. This is effected by means of a pressure removal boring in the housing using a piezoelectric pressure transducer. The velocity measurement is performed with a light barrier mounted 1 m in front of the launching cup. In addition it must be ensured that the kinetic energy of the pyrotechnic projectiles does not exceed a value of 7.5 J. This is checked in a separate measurement with a shorter cylinder (with a mass of 4 g).
Figure 1: A newly approved and marked launching cup with two pressure unloading borings (right). An emergency signal weapon with launching cup and front-loaded pyrotechnic signal ammunition (left).
Contact person:
Ernst Franke, FB 1.3, AG 1.33, E-mail: ernst.franke@ptb.de