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AssigneeThe Secretary of State for Industry in Her Britannic Majesty's Government of the United Kingdom of Great Britain and Northern Ireland
InventorWilliam Bertram Scamaton
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An electrically initiated igniter having good resistance to accidental looltage triggering is disclosed. The igniter comprises a layer of pyrotechnic mixture packed between two initiating electrodes, advantage being taken of the dielectric properties of a selected component of the mixture to provide a high d.c. resistance between the electrodes, which d.c. resistance so limits the current flow through the layer, resulting from an applied electrical stimulus, as to prevent firing of the mixture at all applied voltages which are less than that at which dielectric breakdown of the layer occurs. When fired, the combustion proceeds without shattering and the igniter is particularly suitable for igniting materials requiring non-brisant initiation. A detonator capsule is also disclosed for attachment to the igniter when brisant initiation is required, thus providing an efficient igniter/detonator, the efficiency of which is not impaired by the use of long firing lines, and which may be safely handled and transported because of the separable nature of the two parts.
An electro-explosive igniter comprising two initiating electrodes separated by a layer of a pyrotechnic mixture of metal particles intimately and uniformly intermixed with particles of an oxidising agent for oxidising the metal particles, said mixture including particles of a dielectric material so selected and distributed in said mixture that said layer has a two-stage electrical resistance characteristic, the first stage having the natural high resistivity of said dielectric material of sufficient magnitude to limit the density of a current flow through said layer upon an application of a potential difference across the initiating electrodes to a level which is insufficient to initiate an exothermic reaction between said metal particles and said oxidising agent when said potential difference is less than a breakdown voltage at which the natural resistivity of said dielectric material degenerates, and the second stage, once said breakdown voltage has been exceeded, being the low resistivity of the resulting dielectrically degenerate mixture, the reduced magnitude of the low resistivity thereafter increasing the density of current flow to initiate said exothermic reaction.
Dependencies are inferred from the claim text.