GB2224560A - Detonators - Google Patents

Abstract

The possible extinction of ignition of a non-disruptive detonating cord 10 is prevented by holding the cord in a hole through a block 14 of material of substantially the same density as the outer sheath of the cord, the detonator 17 being positioned adjacent the hole in the block such that the block partially absorbs the shock wave produced by the detonator when it explodes. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO DETONATORS The present in enticn relates to detonators and more particularly to an ignition system for assisting in igniting a non disruptive detonator cord as described in our co-pending British Patent Application of the same date.

A probl.em which exists with such zoowords ix that if ignited in a powerful detonator the ignit-ion ( an fail because the interrupted by ignition though commenced is interrupted by destruction of the explosive core of the cord by the detonator.

It is an object of the present invention to provide an ignition system for a non disruptive detonator cord to assist in successful ignition of the cord.

The present invention provides an ignition system for a non disruptive detonator cord the system comprising a shock wave absorbing block of material having a hole thererthrough for reception of the cord, means for mounting a detonator in front of the hole for ignition of an explosive charge wit.hin the cord.

Preferably the material of tht block and the outer material of the cord are substantially the same density.

Embodiments of the present inveni i on wi 11 now be described, by wan of example with reference to the accompanying drawings in which Figure 1 shows a perspectiVe view of an ignition stm or a non descriptive detonator cord and Figure 2 shows diagramatically the system of figure 1 in longitudinal cross section illustrating ti,e principle of operation.

With reference now to figure 1, the system comprises a non disruptive detonator cord 10 preferably of small diameter (less than 3mm). The cord is fed through a hole 12 in a shock wave absorbing block 14, (hereinafter referred to as the block 14) a shown in dotted outline, the end of the cord being substantially flush with the end 16 of the block 14. A detonator 17 (of known type) is placed, in the armed condition, adjacent to the end face 16 and against the end of the cord 10. Suitable electrical 18 (or percussive) means is provided to ignite the detonator in known manner.

The operation of the system is shown in figure 2.

When the detonator explodes the ignition process produces an ignition "flame" for the cord 10 iii the direction shown by arrow 20. The centre part of the detonation ignites t explosive in the cord but the surrollnding shock wave produced by the detonator strikes the end 16 of block 14. The shock wave travels through the block as shown at 22, 2-1, 26 anti the detonation explosion travels down the explosive @ore 28 of the cord (see inset ) .

suitable choice of the material nf the block 14 and the outer sheath 30 of the cord the shock wave is slowed by the block 14 thereby allowing the detonation explosion to proceed down the cord without being extinguished by the shock wave produced by the detonator.

Preferably the material of the block is the same or similar density to the material of the cord outer sheath 30 (see inset) this being sufficient to produce the slowing of the shock wave as shown at 22, 24, 26.

The mass of the block is important since the block 14 must be sufficiently large to absorb the shock wave produced by the detonator. The block therefore has to be large relative to the size of the cord. Thus for large cords a larger block is preferable. The block 14 can therefore b as large as possible but within the confines of a practical system. The block size is therefore selected according to the detonator size and type and the cord size.

Claims (3)

1. An ignition system for a non-disruptive detonator cord, the system comprising a shock wave absorbing block of material having a hole therethrough for reception of the cord, and including means for mounting a detonator in front of the hole for ignition of an explosive charge within the cord when fitted within the block.

2. An ignition system for a non disruptive detonator cord as claimed in Claim 1 in which the material is of substantially the same density as the outer sheath material of the cord when fitted.

3. An ignition system for a non-disruptive detonator cord substantially as described with reference to the accompanying drawings.

3. An ignition system for a non-disruptive detonator cord as claimed in Claim 1 or Claim 2 in which the mass of the shock wave absorbing block is substantially greater than the mass of the length of cord to be fitted into the block.

4. An ignition system for a non-disruptive detonator cord substantially as described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows 1. An ignition system for a non-disruptive detonator cord, the system comprising a shock wave absorbing block of material having a hole therethrough for reception of the cord, and including means for mounting a detonator in front of the hole for ignition of an explosive charge within the cord when fitted within the block in which the mass of the shock wave absorbing block is substantially greater than the mass of the length of cord to be fitted into the block in which the mass of the shock wave absorbing block is substantially greater than the mass of th length of cord to be fitted into the block.

2. An ignition system for a non disruptive detonator cord as claimed in Claim 1 in which the material is of substantially the same density as the outer sheath material of the cord when fitted.