GB2065840A

GB2065840A - Detonator

Info

Publication number: GB2065840A
Application number: GB8040068A
Authority: GB
Original assignee: Messerschmitt Bolkow Blohm AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1979-12-19
Filing date: 1980-12-15
Publication date: 1981-07-01
Also published as: FR2474157A1; DE2951113C2; FR2474157B1; GB2065840B; DE2951113A1

Abstract

An electrical detonator unit for a shaped charge 302 comprises electrical ignition means 304b, 304a at respective ends of a tube 307 containing a detonator charge 306. At least one propagation charge 305 or 310 is located at a defined point along the tube and the means 304b, 304a are fired with appropriate time delay, if any, to produce coincidence of shock waves at the selected propagation charge 305 or 310 whereby the said charge is detonated by the Dautriche effect. Spurious ignition of one or other ignition means does not detonate the charge 310, 305. The use of two propagation charges permits the hollow charge to be fired either symmetrically or assymetrically. <IMAGE>

Description

SPECIFICATION An Electrical Detonator Unit This invention relates to an electrical detonator unit.

Many detonator units are known but these require safety devices except systems such as socalled exploding bridge-wire (EB\N) or exploding-foil detonators (EFD).

Safety units need a complicated mechanical system for interruption of the detonation chain, in order to separate the primer explosive from the main explosive charge to enable the apparatus to be stored, and transported without risk of detonation. Such interruption is necessary in practice in order to obviate risk of detonation from the variety of stresses to which the sensitive primary explosives may be subject As mentioned mechanical safety devices can be dispensed with if so-called EBW or EFD systems are used requiring only secondary explosives but such systems suffer from a disadvantage as voltages of about 2 kV are required with a 1F capacitance that is an energy of 2J, and this necessitates large and complex electronic units. Systems of this kind are therefore only suitable for comparatively large weapons.

This invention seeks to provide a detonator unit which does not require additional mechanical safety devices or EBW or EFD systems and which is secure in itseif against accidental detonation.

According to this invention there is provided an electrical detonator unit with an explosive detonator charge, wherein the detonator charge is an elongate unit with ignition primers at each end which initiate detonation from opposite directions, a propagating charge being located at a point alony the detonator charge, the propagator charge being detonated on coincidence of shock waves generated in the detonator charge from each primer.

Preferably the primers are arranged to ignite simultaneously. The propagator charge may be offset with respect to the centre of the detonator so that simultaneous ignition of the primers does not cause detonation. The primers are ignited with a time difference selected to detonate one of a plurality of propagator charges.

The detonator may be associated with a hollow charge which can be detonated by one of two or more propagator charges positioned centrally for high penetration or off-centre for maximum cross sectional area effect.

In an embodiment the propagator charge extends continuously over a length of the detonator charge, the time difference between ignition of the two electrical detonators being arranged to detonate the required point of the propagator charge Preferably the detonator charge is contained within a tube with electrical detonating means at each end comprising primers each with an electrical ignition means, the propagating charge being offset with respect to the centre of symmetry of the tube. The detonator unit to which the invention relates, owing to its smaller structure, can be made relatively compact and light in weight and furthermore a sensitive detonating means can be employed without difficulty.Safety is provided by a certain order of firing in the detonation chain of two different detonating means which are to be detonated a certain interval apart or simultaneously within microseconds or shorter intervals apart. With such detonation whether simultaneously or in succession at a time delay detonation from stresses arising from environmental effect can be regarded as practically impossible and the detonation apparatus offers a very high degree of safety.

The invention is further described and illustrated in conjunction with the accompanying drawings showing exemplary embodiments and wherein: Figure 1 shows a cross section through one example of detonator, Figure 2 shows a section on the line A-A of Figure 1, Figure 3 shows a cross section through a hollow shaped charge system.

Figure 4 shows a plan view of the charge of Figure 3, Figure 5 shows a further embodiment of a detonator unit, in part-section, and Figures 6 to 9 show block circuit diagrams of various detonating devices.

The detonator unit of Figure 1 has a tube 1 containing an explosive charge 2. Electrical ignition means 3a and 3b are provided at each respective end of the tube with primers 4a and 4b. In place of the detonating chain comprising the ignition means 3a, 3b, and primers 4a, 4b, electric detonators can be built in as complete assemblies.

The wall thickness and the material of tube 1 and also the internal diameter and thus the diameter of the explosive charge 2 are selected, together with the type of explosive, in such a way that if only one of the electrical detonating means 3a, 4a or 3b and 4b is fired no radial priming takes place in respect of the propagating charge 5 and thus the intensifying charge 9. The shock wave intensity is possibly capable of destroying the charge 5 as a result of the widening of the intensifying charge tube but is not capable of causing it to detonate. If, however, the detonation shock waves from the two ends of the tube 1 come together within the length 8 of the propagating charge 5 then this results (as is well known) in a greatly increased shock wave pressure (Dautriche effect) which is now capable of detonating the propagating charge 5 and thus the intensifying charge.

For the detonation of the charge 5 in the plane of symmetry 6, that is with the so-called central arrangement of the charges 5 and 9, therefore, simultaneous firing of means 3a, 3b and simultaneous commencement of the detonation in the two priming means 4a, 4b, and at the priming points is necessary. The time spread At must thus not exceed: At=+2 L/2 : D=+ idD L being the length 8 of charge 5 and D the detonation speed of the explosive charge 2. If the length 8 of the charge 5 is 12 mm, for example, and the detonation speed 8 mm/y sec, then the spread of the response of the detonating means including the priming must not exceed + 1 .5y sec.

If the spread is greater than the Deutriche effect occurs outside the position of charge 5, the charge being then no longer detonated. By reducing the length L the requirement of more exact detonation and increased safety can be made still greater, although in this case the reliability is correspondingly reduced. It will thus in every case be necessary to select an optimum between reliability, determined by the detonating means, the time spread of the response of the latter, the primer transmission and the detonation speed, against unintentional detonations arising out of environmental conditions.

Detonation from external events, such as atmospheric discharge and the resulting high voltages may lead to detonation if the arrangement of the conductor lines and the electronic structure of the apparatus are unsuitable. If the charge 5 is positioned off centre by distance 7 from the symmetry line 6 then the Dautriche effect will only occur at the charge 5 when the two detonating means are caused to respond at a time difference At. This measure increases the safety factor because accidental response in both detonators within the time window T is made more improbable by several powers often. The time difference At required between the two detonating means in order to obtain detonation in the eccentrically positioned charge 5 is obtained from the formula 2Le At= D in which Le is the off centre distance and D the detonation speed.If the distance Le is 24 mm and the speed D is 8 mmkt sec, for example, then the time difference required in order to obtain the Dautriche effect at the centre of the charge 5 will be 6,u sec. With a diameter of 12 mm for the charge 5, therefore, the time difference Ayt must not spread by more than + 1 .5,u sec, that is the values must not be below 4.5 or above 7.5 y sec if any detonation at all is to be obtained in the charges. This system provides a detonative safety unit which, despite a very simple structure, has considerable reliability and safety.

Various detonating systems for a detonator unit are shown in Figures 6 to 9. The detonating device shown in Figure 6 for simultaneous detonation of both primers consists of an electronic control system 20 supplied with current from an energy source 21. When the control 22 is closed current is discharged through the two electro-explosive elements 23 and 24 connected in parallel or in series. A similar system is shown in Figure 7. In this case the supply of energy 121 charges up a storage capacitor 126 via a charging resistor 125. The capacitor is discharged by the control contact 122 through the two elements 123 and 124.

Figure 8 shows the block circuit diagram for detonation of the electro-explosive elements with a certain particular time difference. The control contact 222 actuates a pulse generating device 225 which triggers a detonating device 226 which causes the electro-explosive element 223 to respond without delay. Parallel with the triggering of the device 226 a delay generator 227 is actuated and triggers the detonating device 228 after a preselected delay and this stage in turn causes the electro-explosive elements 224 to respond after a delay.

Figure 3 shows an embodiment of the invention with a hollow shaped charge comprising a casing 303 with a conical liner 301 and an explosive charge 302. The propagation charge 305 is positioned centrally on the axis with a detonator unit 100 in accordance with the example already described provided above same.

Two electric ignition means 304a and 304b without primer caps are operatively connected as an assembly with detonator charge 306 and the tube 307 respectively. An electronic firing system 308 is situated on the end face of the explosive charge 302 and extends over the entire cross sectional area being retained by casing 303. The electrical detonator unit according to the invention is accommodated in a slot 309. Owing to the preselected time difference in the response of the two electro-explosive detonators 304a and 304b the Dautriche effect is obtained at the centrally situated transmission charge 305, so that the main charge 302 is detonated centrally.

If an eccentric detonation occurs with a hollow charge then the shaped liner spreads in such 9 manner that there is no longer a penetrating spike formed, but on the other hand a far greater cutting effect is obtained. This effect can be used usefully in combating vehicles, and the like because with such targets what is required is not so much a high penetration effect as an increased penetrative cross sectional area.

This eccentric priming, in the example shown in Figure 3, is obtained by the asymmetrically positioned propagating charge 310. For this purpose all that is required is to select the delay in the response between the two detonators 304a and 304b in such a way that the shock wave coincidence occurs above the charge 310 and which is thereby detonated. For this purpose all that is necessary is a detonating device which enables either of the two possible deiays to be selected between the firings of the electric detonators 304a and 304b in such a way that the shock waves meet, for high penetrating performance of the hollow charge, at the charge 305 and to obtain a high cutting effect in the target at the charge 310.

Figure 5 shows a detonator unit 100 with a propagator charge 405 which extends over a considerable length of the electrical detonator.

The electrical detonators 404a and 404b are at each end of tube 407 housing the explosive charge 406. By appropriate selection of a suitable delay between the detonators 404a and 404b the degree of eccentricity of the priming can be steplessly adjusted, it being possible to select a cutting effect from the right or a cutting effect from the left as well as a penetrative spike producing effect from left or right. The spike formation and the cutting effect always deviate in the hollow charge in an opposition direction to the priming point Figure 9 shows a suitable detonating device for the above example with the firing pulse 522 in this case actuating a pulse forming stage 525 which is connected to a delay generator 529 having a fixed delay time. This latter generator in its turn triggers the detonation stage 526, which causes the explosive element 523 to respond. The pulse former stage 525 simultaneously triggers the delay generator 527, which can be adjusted externally. After the preset delay the generator 527 triggers the detonating stage 528, which in turn causes the element 524 to respond.

The measures described in the foregoing provides a more secure detonator unit which need not have further safety means and which enables units to be constructed which occupy less volume.

Claims

1. An electrical detonator unit with an explosive detonator charge, wherein the detonator charge is an elongate unit with ignition primers at each end which initiate detonation from opposite directions, a propagating charge being located at a point along the detonator charge, the propagator charge being detonated on coincidence of shock waves generated in the detonator charge from each primer.

2. An electrical detonator in accordance with Claim 1, wherein the primers are arranged to ignite simultaneously.

3. An electrical detonator in accordance with Claim 1 or 2, wherein the propagator charge is offset with respect to the line of symmetry of the detonator charge.

4. An electrical detonator in accordance with any one of Claims 1 to 3, wherein the primers are ignited with a time difference selected to detonate one of a plurality of propagator charges.

5. An electrical detonator in accordance with any one of Claims 1 to 4, associated with a hollow charge which can be detonated by one of two or more propagator charges positioned centrally for high penetration or offcentre for maximum cross sectional area effect.

6. An electrical detonator in accordance with amy one of Claims 1 to 5, wherein the propagator charge extends continuously over a length of the detonator charge, the time difference between ignition of the two electrical detonators being arranged to detonate the required point of the propagator charge.

7. An electrical detonator as claimed in any one of Claims 1 to 6, wherein the detonator charge is contained within a tube with electrical detonating means at each end comprising primers each with an electrical ignition means, the propagating charge being offset with respect to the centre of symmetry of the tube.

8. An electrical detonator as claimed in Claim 7, wherein the propagator charge is associated with a tapered intensifying charge serving to ignite the main charge of a warhead.

9. An electrical detonator in accordance with any preceding claim, wherein the electronic assemblies associated with the detonator device are combined with the detonator unit in an integral unit.

10. An electrical detonator constructed and arranged to function substantially as herein described with reference to and as shown in Figures 1 and 2 or 3 and 4 or 5 and Figures 6 to 9 of the accompanying drawings.