IL29794A

IL29794A - Manufacture of electrically conductive igniter charges

Info

Publication number: IL29794A
Application number: IL29794A
Authority: IL
Original assignee: Dynamit Nobel Ag
Priority date: 1967-04-13
Filing date: 1968-04-09
Publication date: 1972-05-30
Also published as: US3476623A; BE713570A; DE1646336B2; CH491060A; GB1189952A; NL6805196A; DE1646336A1; FR1562370A; IL29794A0

Description

Manufacture of electrically conductive igniter charges - - This Invention relates to the manufacture of electrically conductive igniter charges for quick-acting gap igniters* Such igniters are increasingly needed commercially, especially for piezoelectric ignition devices. They are required to be ignitable within a few microseconds at the expense of very small amounts of energy (below 20 μ watts).

Such igniters are conventionally manufactured, for example, as follows: The igniter charge is impressed upo a narrow gap of a few microns width which forms a spark gap. The igniter charge is fired by a spark crossing the gap. Or else, an electrically conducting igniter charge is impressed on a narrow gap. Suoh an igniter charge can rapidly be fired even with low amounts of energy if it has the composition appropriate for the purpose in view, which is within the knowledge of those conversant with this technical field.

Several processes for the manufacture of electrically conductive Igniter charges are known. Thus, by one known process, the priming explosive, e.g. lead azide or silver aside, is admixed with some amount of graphite. It is, however, diffioult to produce a homogeneous mixture. For this purpose, some time is required, as it is in mixing processes generally. It has been found that much time is needed in order to achieve homogeneity of the mixture, and this entails considerable danger, for the priming charge becomes so much sensitive to friction and percussion that detonations readily occur. By another known process some hydrassine is admixed to silver azide I with a view to reducing some of the azide and thereby to produce metallic silver which constitutes the conductive component of the igniter charge. In this process only a few percent of the azide are intended to undergo reduction. Experience has shown, however, that a homogeneous mixture cannot be produced in this manner as the reduction leads as a rule merely to the formation of small, discrete conductive pockets.

By another known process, silver azide is reduced by UV irradiation. This method is not satisfactory either since the top layers are reduced considerably more strongly. No homogeneous mixture is obtained.

It has now surprisingly been found, in accordance with this invention, that eleotrically conductive igniter charges for quick-acting gap igniters, which are free from the drawbacks aforesaid, can be manufactured by a process in which, in a first stage, an electric conductor is mixed with a secondary explosive having a detonation velocity of at least 5000 m sec and this mixture is, in a second stage, mixed with a priming explosive forming at least 30$ by weight of the mixture. ^ The term "secondary explosive" denotes a high-explosive having a detonation velocity higher than 5000 m/sec.

Examples of suitable secondary explosives are pentaerythrityl nitrate, mannityl nitrate, hexogen (oyclonite) and trinitrotoluene.

Examples of suitable electric conductors are graphite and colloidal silver.

Suitable priming explosives are, for example, The invention is illustrated by the following Example to which it is not limited* 55 Parts by weight of pentaerythrltyl nitrate are mixed with 5 parts by weight of graphite until the mixture has become homogeneous. This mixture is then mixed with 40 parts by weight of lead azlde, again until the mixture has become homogeneous. Such a mixture can be fired with certainty over a gap of 0.2 mm width and with an energy of 2 to 10 watts. The time of development of the ignition is 2 to 3 microseconds.

An igniter charge constituted by this mixture has an extremely, high detonation velocity, requires a very small amount of energy for firing, and can safely be handled in manufacture and use.

The process according to the invention can be used for the manufacture of igniter charges which contain the three main components aforesaid in any desired propor'tioi a However, with a view to achieving/sufficient priming effect the proportion of the priming explosive should be at least 30 by weight.

Claims

29794/2 - 0LAIM3

1. A process for the manufacture of electrically conductive igniter charges for quick-acting gap igniters, wherein, in a first stage, an eleotric conductor is mixed with a secondary explosive having a detonation velocity of at least 5000 m/sec and this mixture Is, in a second stage, mixed with a priming explosive forming at least 30$ by weight Of the mixture.

2.,, A process according to Claim 1, wherein pentaerythrityl nitrate, mannityl nitrate, hexogen (oyclonite)or trinitrotoluene is used as a secondary explosive,

3. A process according to Claim 1 or 2, wherein graphite ox* colloidal silver Is used as an electric conductor*

4. process according to Claim 1* 2 or 3, wherein silver azide or lead aside is used as a priming explosive,

5. A process for the manufacture of electrically conductive igniter charges for quick-acting gap igniters, substantially as described herein.

6. Electrically conductive igniter charges when manufactured by the process according to any of the preceding Claims, and gap igniters containing such igniter charges. PARTNERS IS?CB