Pyrotechnic ignition device

摘要

The pyrotechnic ignition device of this invention comprises a hollow tubular coiled charge of pyrotechnic sheet material defining an ignition initiation position, the internal diameter of the charge decreasing and the wall thickness increasing over at least a portion of the charge extending from the initiation position in the direction of burning. This configuration enhances the reliability of ignition and the rate of flame development. Preferably the adjacent plies of the coiled charge are spaced apart. The preferred coiled charge also has a portion downstream from the initiation position in the direction of burning which decreases in external diameter and wall thickness in a direction extending away from the initiation position, the configuration of this portion being effective to enhance the speed and violence of burning of a main gas-generating propellant charge ignited by the coiled charge. In the preferred device a pyrotechnic sheet comprising a substrate of oxidizing polymeric film coated with an oxidizable metal, for example magnesium, is coiled around a cruciate axial former so that the end edges define helices. Conveniently the coiled charge may be formed by winding the sheet into a right cylindrical tubular coil and pushing out the coil axially from the centre in the direction of burning.