GB2138111A

GB2138111A - Initiating explosive charges

Info

Publication number: GB2138111A
Application number: GB08212021A
Authority: GB
Inventors: Dr Manfred Held
Original assignee: Messerschmitt Bolkow Blohm AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1981-04-29
Filing date: 1982-04-28
Publication date: 1984-10-17
Also published as: GB2138111B; DE3116930A1; DE3116930C2; FR2547909A1; FR2547909B1

Abstract

Primer means for an explosive charge include a primer charge 8, for accelerating a primer layer 9 of inert material towards the explosive charge 3, and having a recess 7 which serves to accommodate the explosive charge. In this arrangement the primer charge recess 7 extends a sufficient distance in the transversal direction to ensure that when the explosive charge is centrally positioned therein, between the explosive charge periphery and the primer layer, a free acceleration space 10 for the latter is provided. This space may be determined by an inert spacer 11. <IMAGE>

Description

SPECIFICATION Priming explosive charges This invention relates to a primer means for initiating an explosive charge, particularly one having a penetratorforming lining, penetratorforming coating or projectile-forming, with a primerchargefor accelerating a primer layer of inert material towards the explosive charge.

In a prior unpublished German application there is described an arrangement wherein a rotationally symmetrical explosive charge is provided, for the purpose of priming from a forward end, with a priming charge having a priming layer, in such away thatthe latter has a preselected airgap, opposite to the relevantfront end of the explosive charge.

The purpose ofthis invention isto provide a primer meanswherebythe space requirement is reduced and the explosive chargeto be primed can be dynamically blocked to a degree which has hitherto not proved possible.

According to this invention there is provided primer means for initiating an explosive charge having a primercharge for accelerating a primer layer of inert material towards the explosive charge, wherein the primer charge has a charge recess delimited by the primer layer and serving to accommodate the explosive charge either completely or over a certain zone, the primer charge recess extending transversallyto a distance which is such that when the explosive charge is situated centrallytherein, it leaves between the periphery of the explosive charge and the primer layer afreeacceleration spaceforsaid layer.

The arrangement according to this invention does not involve especial difficulties and offersthe advantage of providing a compact primerwhich is suitabie for any kind of explosive charge to provide dynamic blocking of maxitnum efficiency for whatever type of charge isto be primed.As regardsthe primer charge which is decisive the recess provided for it and the primer layer presenttherein, the ranges of variation are sufficientto ensure that even the explosive charge can be in the form of a hollow charge with a rotationally symmetrical penetratorforming lining or layer, our a projectile-forming layer or of a cutting charge with a planisymmetrical penetratorlining or layerthe penetrator-forming or projectile-forming process can be influenced by the dynamic blocking of the said liner or layer, this being done by means of the phase velocity atwhich the primer layer makes impact on the hollow charge or cutting charge and also by means ofthe contour and size ofthe surfaces taking part in the impact.

In this connection it is found of advantage if the recess of the primer charge contains in that zone ofthe primer layer which is nearertothe apex, a spacer of inert material which serves to determine the free acceleration space between the said layer and the explosive charge and whch takes the form of an insert tapering conically towards the said charge. In the first place, this accurately determines the free acceleration space in which the energy ofthe priming charge is concentratedforthe acceleration ofthe primer layer.

In the second place it renders it impossible for a spike, which could impede the further process, to form from that zone ofthe primer layer which is closetothe apex.

One example ofthe consequences ofthis would be an undesirable advance priming of the hollow charge or cutting charge in the zone closetothe axis.

Forthe phase velocity vph already mentioned an angles, with which the priming coating encounters the explosive charge to be primed, is of importance. If the explosive charge is provided, on the side ofthe free acceleration space, with a conical boundary surface having an aperture angle of 2 '3,while the primer layer is provided, on the side ofthe free acceleration space, with a boundary surface tapering conically in the same direction and having an aperture angle of 2 y, then the foilowing reiationship applies between the angles , ss, y and 25,-with 25 as the deviation angle which the primer layer assumes, after initial acceleration, in respectofits initial position: S 25-(13-y).

In this respect five different sets of circumstances can be distinguished: Case1:s > 2owìthy > gi' Case 2: E = 2 8 with y = B Case3: e > O with ss > yand2di > (ss-y) Case 4: = 0 with 2 = (ss - y) Case 5: s < 0 with 13 > yand25 < (13-y) Each of these cases is subjectto a different phase velocity Vph. If the detonation is led into the primer charge with a glancing angle of incidence the angle 6 is obtainablefrom the Taylor equation: sin B = v0/2D, wherein v0 is the velocity ofthe primer layer and D the detonation velocity ofthe priming charge.Taking this into account and using the sine lawfordetermining the phase velocity, we obtain the foilowing formula: sin 2 i Vph = D - sin e This enables us to derive, forthefive different "E cases" mentionedthefollowing phasevelocities: Case 1 :Vph < D Case 2: Vph = D Case 3: vph > D Case 4: Vph = 00 Case 5: Vph inverse All these cases are of importance. The explanation forthisisasfollows: I Vph < D.

In this case the result obtainable depends on the relation borne bythe detonation velocity D' ofthe explosive charge to be primed to the detonation velocity D ofthe primer charge and to the phase velocity ofthe primer layer.

If D is noticeably greaterthan D' and D' smaller thanvph,the impactofthe primer layer on the explosive charge results in the priming of the latter.

Where D' > Vph applies, the primer layer, in addition, constitutes a certain "dynamic" damping, by which the expansion ofthe gases of the explosive charge is delayed or the gas is compressed.

Vph = D.

If detonation velocity D' of the explosive charge coincides with the phase velocity Vph ofthe primer layer,the latter represents a purelydynamicdamping and not a means for guiding the detonation wave in addition.

'rphD.

Underthese circumstances the impact ofthe primer layer on the explosive layer causes a certain detonation profile in the latter. In other words, the primer layer in this case represents both a dynamic damping and a means for guiding the detonation wave.

Vph =00.

This extreme case is of interest because the explosive charge is primed by the incident primer layer over the entire impact surface simultaneously.

Vph inversely.

Inthis casethe explosive charge is primed bythe primer layer from the base side ofthe latter, which is tantamountto a very noticeably influenced detonation wave guiding action.

For cases in which the explosive charge to be primed takes the form of a hollow charge our a cutting charge, with a static lining angle or layer angle o, the following considerations are to be added: In Cases 1 to 3 discussed in the foregoing the dynamic angle of collapse of the liner and layer making impact is generally greaterthattheir static angles.

In Case 4 discussed in the foregoing, however, the dynamic collapse angle and the static angle a are equal, provided the angle ss ofthe hollow charge or cutting charge coincides with the static angle oc.

Finally, Case 5 is characterized by a dynamic collapse angle smallerthan the static angle a.

Further preferred features of this invention and technical advantages are described with reference to the accompanying drawings which show embodiments bywayofexamples, in the drawings: Figure 1 shows a shaped hollow charge with a priming system, and Figures 2to 6 showfurtherembodiments of charges with priming systems.

Referring to the drawings, Figure 1 shows, by way of example, a rotationally symmetrical hollow charge f with a housing 2, explosive charge 3 and penetrator forming liner 4. The lining 4 may comprise a liner with a conical shape and an included angle of 2 or. The explosive charge 3 has a peripheral boundary surface 5 adapted to the contour of the liner and having an included angleof2 ss. In this case itis highlydesirable forthe boundary surface 5to be covered with a foil 6 of aluminium our a similarsubstance.

The aforementioned hollow charge 1 is situated concentrically in a recess or cavity 7 of a primer charge 8, the cavity being preferably conical. Between boundary surface 5 and a primer layer 9 of inert (non-reactive) material with an included angle of 2y and delimiting the priming charge cavity 7 is a free zone forming an acceleration space 1 Oforthe layer.

The free width ofthe space is determined by a spacer 11 of inert material completely filling in the zone of the primer layer 9 in the vicinity of the apex, that part ofthe recess which is thus divided.

The primercharge8 has, inthezone oftheprimer layer 9, a peripheral boundary surface 12 adapted to the conical shape of the coating, with an aperture angle of 2 (p and covered buy a damper 13. Forthe purpose of conveying detonation into the primer charge 8 a transmission charge 15 is provided on the end face 14 of the charge which is adjacentto the apex ofthe primer layer 9.

In this example described the aperture angles 2 a, 2 13,2yand2cpareequal.

Figure 2 differs from Figure 1 only in that to lead the detonation accurately into the primer charge 8 in an axial direction the transmission charge 15 is replaced by a so-called pointed transmitter 16 consisting of two charges 1 6a and 1 6b coaxial with the primer charge 8 and the hollow charge 1. In this case the charge 1 6b is provided, on the sidefurthestfrom the primer charge 8, with a central point 17 embedded within the charge 1 6a. The detonation velocity of the charge 16a is in this case lower at least in the zone of the point 1 than the detonation velocity ofthe charge 16b.

Figure 3 differs from Figure 1, in so farasthe angles a, ss, y and cp of the liner 4, the explosive charge 3, the primer layer 9 and the primer charge 8 differ. This variation is asfollows: The angles a and ss, for example, may be identical to figure 1. The angles a and ss are nevertheless greaterthan the angles y and (p, in contrastto the previous embodiment.

The arrangement is such that the value of the angle 25 resulting forthe priming coating 9 will depend on the thickness of the primer layer 9,the thickness of the primer charge 8, the thickness ofthe charge damper 13 and the nature ofthe primer charge.

Figures 3.1, and 3.3 show details of area Shown in Figure 3, as follows: 25 > 13-y(Fig.3.1.) 25 = 13-V (Fig. 3.2.) and ) 28 < P-y(Fig. 3.3.).

ltfollowsfrom the equation s=25-(13-y) that 5 < 25 in the circumstances shown in Figure 3.1, being equal to 0 isthose illustrated in Figure3.2, while s < 0 in those shown in Figure 3.3.

In all three cases the primerlayer9 is given a phase velocity which is greaterthan the detonation velocity D ofthe primer layer 8. Provided thatthe explosive charge 3 at least does not have a greater detonation velocity D' than the primer charge 8 the arrangement is such that a corresponding detonation wave guiding process takes place in the former.

By the selection of a suitable detonation velocity D forthe primer charge 8 and detonation velocity D' and the explosive charge 3,therefore, different detonation wave fronts can be obtained, providing a means of exerting acontrolledeffectontheformation ofthe hollow charge penetratorfromthe lining 4.

Atthispointitshould be noted that the parallelisms shown in the drawings between the explosive charge 3 and the liner 4, resulting in angles cox and ss being equal, only constitute examples. Similariy, the liner 4 may have a wall thickness which increases or decreases from the apex towards the base, and the 5 angle ss ofthe explosive charge 3 may differfrom the angle oc ofthe liner4.The conical shape ofthe liner4 and explosive charge boundary surface 5 is likewise onlyto be regarded as an example. Calotte-shaped, bell-shaped, trumpet-shaped ortulip-shaped con ) tours are equally possible.

What has been stated in the foregoing with regard to the explosive charge 3 and the liner 4 ofthe hollow charge 1 applies similarlytothe primercharge 8 and the primer layer 9 likewise.

Figure 4 shows an embodiment in which a recess 19 is delimited by a primer layer 18 of inert material and is associated with a primer charge 20 containing a hollow charge 22 which is situated concentrically therein and which leaves a free acceleration space 21 for the layer 18 concerned.

The explosive charge 23 and penetratorforming lining 24 of the charge 22, as may be seen by comparison, are shorter than the embodiments already described. This takes account of the fact that the liner and layer elements in the zone of a spke-forming lining which is close to the apex are not presentwhen detonated to form a spike.

In the present case the detonation is fed tothe primer charge 25. The end section 20a of the primer shaft 20, however, can have a different shape. An insert 26 of inert material and of the shape of a truncated cone is adjacent to the said end section on the side corresponding to the recess 19. The insert serves firstly to form a mounting deviceforthe components 18,20,23 and 24 and also prevents dissipation in this zone which would reduce the performance of the detonation gases. In the event of detonation, therefore, the formation of penetrators starts with those elements of the liner 24 which are present at 27, that is the immediate vicinity ofthe insert 26.The spike peakvelocity thus obtained is particularly large, because with the aperture angle selected forthe components 18,20,23 and 24the dynamic collapse angle is relatively small and the primer layer 18 represents,forthe explosive charge 23, a dynamic damping of high phase velocity Vph.

Figure 5 shows an example which only differs from that shown in Figure 4 in the form of the insert 28. The insert 28 in this case is at the sametime used to carry a safety device. This device has a detonator 29 with the remaining components omitted for clarity in the drawing. The purpose of the detonator 29 isto enable a primer charge 30 constructed in accordance with Figure 5to be primed on the axis oftheflat end section 30a, oppositeto the direction of action of a hollow charge 33, the said hollow charge 33 with its spike-forming lining 34 being arranged, as in Figure 4, in a recess 31 of the primer charge 30, in such a way that between the boundary surface 35 and a primer layer 32 of inert material a free acceleration space 36 is leftforthe said iayer.A bevelled part 37, shown by broken lines on the side ofthe base ofthe lining, does not appreciably detract from the performance.

Figure 6 shows a primer charge 38 with a primer layer 39 and a recess 40 serving to accommodate an explosive charge 41 with the penetratorforming lining 42. Between the explosive charge 41 and the primer layer 39 there is a free acceleration space 43 forthe layer.

In the present case the primer charge 38 and the hollow charge 41 and 42 have central bores 44 and 45.

Through these bores a pipe 46 extends from the side ofthe primer charge 38 as far as that side of the penetrator-forming lining 42 which is at a distance from the base. Forthe annular detonation ofthe primer charge 38 a device with a customary detonation means, such as an explosive annularfoil and a voltage source serving to actuate it, is grouped around the pipe 46, at the location 47.

The internal volume ofthe pipe 46 can be used for a numberof purposes, e.g.: -flowtechnique, -the insertion of a stand-off detonator, or - ductfor shells fired from guns.

What has been explained in the foregoing with reference to the examples provided by rotation of symmetrical charges applies similarly to charges of planisymmetrical construction that is so-called "cutting" or"roof" charges.

Claims

1. Primer means for initiating an explosive charge having a primer charge for accelerating a primer layer of inert material towards the explosive charge, wherein the primer charge has a charge recess delimited bythe primer layer and serving to accommodate the explosive charge either complete ly or over a certain zone, the primer charge recess extending transversally to a distance which is such that when the explosive charge is situated centrally therein, it leaves between the periphery of the explosive charge and the primer layer a free acceleration space for said layer.

2. Primer means in accordance with Claim 1, wherein the recess ofthe primer charge contains, in the zone ofthe primer layerwhich is closerthe apex, a spacer of inert material which servestodeterminethe free acceleration space between the said layer and the explosive charge and which takes the form of an insert tapering conically towards the said charge.

3. Primer means in accordance with Claim 1 or 2, for use with an explosive charge constructed as a hollow charge witha rotationally symmetrical lining or layer our a cutting charge with a planisymmetrical lining or layer, wherein the hollow charge or cutting charge and also the primer layer on the side ofthe free acceleration space and possibly the primer charge also on that side which is farther away from the free acceleration space is identical or at least similarinshapetothehollowchargelining or layer and the cutting charge lining or layer respectively.

4. Primer means in accordance with Claim 5, wherein for use with a conical penetratorforming liner, penetratorforming layer or projectile-forming layer with an aperture angle of2 a the explosive charge has on the free acceleration space side a conical boundary surface having an aperture angle of 2 p, while the primer layer has on the side of the free acceleration space a conical boundary surface having an aperture angle of 2 y.

5. Primer means in accordance with Claims 3 and 4, wherein the primer charge is provided, on that side which is farther away from the free accelertion space, with a conical boundary surface having an aperture angle of 2 .

6. Primer means in accordance with Claim 4, wherein the aperture angle 2y ofthe primer layer is greaterthan the aperture angle 2,S ofthe explosive charge.

7. Primer means in accordance with Claim 4, wherein the aperture 2y orthe primer layer is as great as the aperture angle 2 ss ofthe explosive charge.

8. Primer means in accordance with Claim 4, wherein the aperture angle 2 ss ofthe explosive charge is greaterthan the aperture angle 2yofthe primer layer,the angular difference ss-y being smaller than the angle 2 6 which the primer layer assumes, after initial acceleration by the primer charge in respectofthe initial position.

9. Primer means in accordance with Claim 4, wherein the aperture angle 2 ss ofthe explosive charge is greaterthan the aperture angle2yofthe primer layer,the angular difference ss-y being as great as the angle 25 which the primer layer assumed, after initial acceleration bythe primer charge in respect of its initial position.

10. Primer means in accordance with Claim4, wherein the aperture angle 2 ss of the explosive charge is greaterthan the aperture angle 2y ofthe primer layer, the angular difference 13--V being greater than the angle 2 which the primer layer9 assumes, after initial acceleration by the primer charge, in respect of its initial position.

11. An explosive device substantially as described in the Description with reference to and as shown in Figure 1. Figure 2, Figure 3, Figure 4, Figure 5 or Figure 6 ofthe accompanying drawings.

11. Primer means constructed and arranged to function as described herein and with reference to the accompanying drawings.

12. An explosive charge in combination with a primer means according to any preceding claim, or as described and exempliefied herein.

Superseded claims all.

New or amended claims:-

1. An explosive device comprising primer and main explosivecharges,the primer charge having in one end thereof a cavity into which one end of the main charge extends with a space between the charges, the cavity of the primer charge being lined by a transfer plate of inert material which, when the primer charge is detonated, is propelled bodily and substantially without change of shape across said space into contact with the main charge to detonate the latter.

2. A device as claimed in claim 1 wherein the cavity of the primer charge contains, in the region of the transfer platewhich is nearestthe closed end of the cavity, a spacer of inert material which serves to determine the said space between the transfer plate and the main explosive charge, said spacer having the form of an insert which tapers towards the said main charge.

3. A device as claimed in either preceding claim, wherein the main explosive charge is a hollow charge with a rotationally symmetrical lining or a cutting charge with a planisymmetrical lining, and wherein the surfaces ofthe main explosive charge and of the transfer plate presented to said space, and the surface ofthe primer charge remote from said space are similar in shape to the lining of the main explosive charge.

4. A device as claimed in claim 3, wherein the lining ofthe main explosive charge is conical with and apex angle of 2 oc, (as defined herein), the main explosive charge has a conical boundary surface exposed to said space having an apex angle of2 ss, (as defined herein), and the transfer plate has a conical boundarysurface presented to said space having an apex angle of2y, (as defined herein).

5. A device as claimed in claim 3 ordaim 4, wherein the primer charge is provided with a conical boundary surface remote from said space which has an apex angle of 2 cp, (as defined herein).

5. A device as claimed in claim 4, wherein the apex angle 2y ofthetransfer plate is greaterthan the apex angle 2,8 ofthe main explosive charge.

7. A device as claimed in claim 4, wherein the apex angle 2 V ofthe transfer plate is equal to the apex angle 213 ofthe main explosive charge.

8. A device as claimed in claim 4, wherein the apex angle 2 ss ofthe main explosive charge is greater than the apex angle 2 y ofthetransferplate,the angulardifference -^y beingsmallerthanthe angie 2 5 which thetransfer plate assumes, after initial accleration by the primer charge, in relation to its initial position.

9. A device as claimed in claim 4, wherein the apex angle ss ofthe main explosive charge is greater than the apex angle2yofthetransfer plate,the angular difference ,8 -y being equal to the angle 2 which the transfer plate assumes, after initial acceleration by the primer charge in relation to its initial position.

10. A device as claimed in claim 4, wherein the apexangle2,13 ofthe main explosive charge is greater than the apex angle 2 y ofthe transferplate,the angular difference -y being greaterthan the angle 2 5 which the transfer plate assumes, after initial acceleration bythe primer charge, in relation to its initial position.