IL137467A - Mechanical explosive breakaway element - Google Patents

Abstract

A safe/ arm system, particularly for warheads, penetrators or safe demolition of explosive charges, which comprises, in combination with a main charge explosive; (a) a firing detonator (10) for generating a detonation signal; (b) a first trail (11) for transmitting said detonation signal as a firing signal to said main charge explosive; (c) a second trail (12) for conveying said detonation signal to a point of said first 1937 ז' באב התשס" ד - July 25, 2004 trail, whereby to interfere with said firing signal and prevent it from reaching said main charge explosive; (d) an arming detonator for generating an arming signal; and (e) a mechanical breakaway device (14) installed on said second trail and actuated by said arming signal to interrupt said second trail, whereby to permit said firing signal to reach said main charge explosive through said first trail.

Description

Υ ΙΏΏ ]ΏΌΏ ΡΠ3Τ3Π "ΊΏΏ ΪΠΐΤ7Ν MECHANICAL EXPLOSIVE BREAKAWAY ELEMENT 8386/99 -1- MECHANICAL EXPLOSIVE BREAKAWAY ELEMENT Field of the Invention This invention relates to a logic detonating transfer device, which comprises a mechanical explosive breakaway element and which can be produced in small sizes, for use in safe/arm devices, particularly for warheads, penetrators or safe demolition of explosive charges.

Background of the Invention Conventional mechanical safe/arm systems interpose a physical barrier between the detonator explosive charge and the main charge of the warhead. This barrier is essential, as the detonator comprises a primary explosive charge which may be undesirably activated when exposed to external hazards, such as fire, mechanical shock or excessive heat. Safe/arm systems known today include mechanical, electrical and detonating logic networks. The operating principles of these systems are compared in Table I. 8386/99 -2- Table I Comparison Between S/A Devices in Detonation Systems Explosive logic networks are well known in the literature. They are used as components of safe/arms systems and can also serve as safe/arm systems, based on logic alone, by themselves. Explosive trails which generate OR, AND and DIODE logic elements have been known for the last twenty years.

In U.S. Patent No. 5,009,162 (Silvia), an explosive logic resolver network is disclosed for determining which detonator in a plurality of detonators will be the first to detonate. The resolver network is interposed between a plurality of detonators and the explosive logic clock of a safe/arm network. Each detonator is provided with a resolver network explosive trail which intersects the resolver network explosive trails of the remaining detonators to form a plurality of explosive logic switches. 8386/99 -3- Another explosive logic network is described in U.S. Patent No. 5,311,819 (Silvia), including a first explosive path which is crossed by second explosive paths such that a detonation propagating along the second path in either direction cuts and opens a first end of the first path and will be propagated at an opposite second end of the first path. The two paths are connected by explosive logic elements such that a detonation propagating from the first end to the second end of the first path will also be propagated in both directions along the second path, and a detonation propagating from the second end to the first end of the first path will cut and open both ends of the second path.

An explosive AND/NAND logic element is disclosed in U.S. Patent No. 3,753,402 (Menz et al.).

An explosive safety junction is described in U.S. Patent No. 4,974,514 (Silvia). In this patent, an explosive logic device is disclosed, having an inlet trail which diverges into one or more tiers of safety trails and converges to form an outlet trail. The safety trails are crossed by a control trail which propagates a control detonation wave which severs the safety trails and prevents an input detonation wave from proceeding from the inlet trail to the outlet trail to detonate the weapon.

Yet another explosive logic safety device is disclosed in U.S. Patent No. 4,412,493 (Silvia), provided with an inlet explosive trail which conveys an inlet detonation signal to an outlet explosive charge. A control explosive trail connects the inlet explosive trail and the outlet explosive trail. A failure explosive trail is connected between the control explosive trail to 8386/99 the outlet explosive trail when a plurahty of detonators are properly initiated.

A safe rocket motor igniter using sequenced initiation to an explosive logic network is described in U.S. Patent No. 3,973,499 (Anderson et al.).

A pyrotechnic delay element comprising explosive logic network is described in copending Israeli patent application No. 118964, the whole contents of which are incorporated herein by reference. More particularly, said application relates to an explosive logic delay element for providing an additional pyrotechnic delay to a safe/arm system without using an extra safe/arm device.

Explosive logic network devices are intended to perform logic function using explosive trails. AND gate devices are described in the U.S. patents and Israeli patent described above. In these devices, two or more detonators (arm and fire detonators) are initiated with a prescribed delay. A long delay between the two detonators prohibits the proper functioning of the explosive device. The shock waves generated by the first detonator distort the device and the second detonator can be separated from its explosive trail and unable to initiate it.

Summary of the Invention The safe/arm system according to the invention comprises a mechanical explosive breakaway element (MEBE). 8386/99 -5- More particularly, it comprises, in combination with a main charge explosive: 1) a firing detonator for generating a detonation signal; 2) a first trail for transmitting said detonation signal as a firing signal to said main charge explosive; 3) a second trail for conveying said detonation signal to a point of said first trail, whereby to interfere with said firing signal and prevent it from reaching said main charge explosive; 4) an arming detonator for generating an arming signal; and 5) a mechanical breakaway device installed on said second trail and actuated by said arming signal to interrupt said second trail, whereby to permit said firing signal to reach said main charge explosive through said first trail.

The means for actuating the breakaway device, which is preferably an arm, is a pyrotechnic means.

The first explosive trail is the longer one and the second is the shorter one. With reference to the drawings, they are also called herein the upper and the lower trail respectively. The breakaway or cutting bar is installed on the second, shorter trail. Both trails meet at a junction, which is a point of the first, longer trail spaced from the main charge explosive and connected to it by a final segment of the first trail. The angle at which the two trails meet at their junction is such that no signal can pass from the second trail to the aforesaid final segment of the first trail. Therefore, if both trails transmit to the said junction the same signal, but in opposite directions, the firing signal cannot pass beyond the junction. On the other hand, if the second trail is cut by a breakaway device, e.g. a bar, the firing signal will pass through said junction and along said final segment the first trail, and reach its output point, which is the main charge explosive. 8386/99 -6- The breakaway device can be actuated by a logic electronic circuit with a predetermined, desired delay.

Brief Description of the Drawings In the drawings: Fig. 1 is a schematic representation of the explosive trails and breakaway bar position of the invention; Fig. 2 is a schematic view of the initial part of a device according to an embodiment of the invention; Fig. 3 illustrates the operation of the invention when the breakaway arm is not operative; Fig. 4 illustrates the operation of the device when the breakaway arm is operative; Fig. 5 is a schematic cross-section of a warhead according to an embodiment of the invention; and Fig. 6 schematically illustrates a breakaway bar and it operation according to an embodiment of the invention.

Detailed Description of Preferred Embodiments As seen in Fig. 1, the device of the invention comprises a detonation signal generator 10 (hereinafter briefly "signal generator") which is actuated at the start of the operation of the device. This generates a first signal, that travels along a first, longer trail 11, and a second signal, that travels along a second, shorter trail 12. The first signal is the firing signal; the second one, which is equal to the first signal, but has the purpose of preventing the main charge from being accidentally set off, when the device is not armed, could be called a "negative firing" signal" or a "safety signal", though. The two trails meet at junction 13 at an acute angle. A 8386/99 -7- breakaway bar 14 is installed on trail 12. Beyond junction 13, a final segment 15 of first trail leads to point 16 (hereinafter, "output point") at which the firing signal causes the explosion of the main charge of the warhead.

As illustrated in Fig. 2, the device comprises a metallic or plastic base 20 which supports two channels filled with explosive charge, that can be called explosive trails. These channels are: a first trail 21, corresponding to trail 11 of Fig. 1, and a second trail 22, corresponding to trail 12 of Fig. 1. Since Fig. 2 is a cross-section and part view of the illustrated device from the side, the two trails appear superimposed. The device further comprises a firing detonator 24 for generating a signal to be transmitted by trail 21 and by trail 22, if this latter is not interrupted, and an arming detonator 25 for actuating the metallic cutting or breakaway bar 26, which, when actuated, interrupts said second trail. Trail 21 has an output point, indicated at 23, which corresponds to output point 16 of Fig. 1, at which the firing signal is transmitted to the main charge explosive, if the arming signal has been generated and the cutting bar 26 has cut trail 22.

As seen in Fig. 4, when the breakaway bar has been activated, no signal is transmitted through the second trail 12/22 and therefore the firing signal proceeds from detonator 24 through trail 11/21 and through the final segment 15 to the output point 16. When the breakaway bar 14/26 has not been activated, the safety signal passes through the second trail 12/22 to the junction 13, as seen in Fig. 3. The firing and the safety signals, that are equal but travel in opposite directions, cancel one another at junction 13, and neither signal passes through final segment 15 to the output 16. No signal can pass from the second trail 12 through the 8386/99 -8- junction 13 to the final segment 15, because a signal can pass from one trail to another only if they meet at an angle at least as large as a critical angle. The angle at which the two trails meet at junction 13 is an acute angle, smaller than the critical angle. Therefore a signal can pass only upwards, meaning from the second and shorter to the first and longer trail.

Fig. 5 schematically illustrates a warhead 30 having a casing 31 and an explosive 32 and carrying at the base thereof a device 33 according to the invention.

Fig. 6 schematically illustrates a breakaway bar and the system of its activation. The arming detonator 25, when activated, pushes the metallic bar 26 to cut a portion of the short explosive channel or trail 22. This inhibits the transmission of the safety signal through this channel.

The explosive trails consist of channels filled with extrudable explosive type TS-20 or XTX-8003, which is a mixture of 80% PETN (Propanediol-Di-Nitrate) and 20% binding material, or equivalent.

An important advantage of the invention is the fact that it does not comprise moving parts in the explosive chain and the explosive are continuous. The device of the invention has been successfully tested and has been proved to achieve all its purposes.

As seen in Fig. 5, MEBE is an integral part of the safe/arming system that initiates the warhead. The actuation of the breakaway bar is the arming 8386/99 -9- action. In the MEBE, the cutting effect of the explosive trail is done by accelerating a bar that makes a hole in the trail without initiating its explosive. The arming detonator is coupled to this bar and does not touch the trail explosive. The fact that the arming detonator is far from the device weakens the shock waves produced by the detonator and thus the shocks cannot damage the device. Therefore, it is possible to fire the second detonator even after a very long delay after the arming detonator. The MEBE of the invention permits the miniaturization of the physical dimensions of the S/A elements and the explosive logic devices that function with two or more detonators with a delay between them.

While an embodiment of the invention has been described by way of illustration, it will be apparent that the invention can be carried out with many modifications, variations and adaptations without departing from its spirit or exceeding the scope of the claims. 8386/99 -10-

Claims (10)

1. A safe/arm system, particularly for warheads, penetrators or safe demolition of explosive charges, which comprises, in combination with a main charge explosive: y ^ a) a firing detonator for generating a detonation signal; b) a first trail for transmitting said detonation signal as a firing signal to said main charge explosive; c) a second trail for conveying said detonation signal to a point of said first trail, whereby to interfere with said firing signal and prevent it from reaching said main charge explosive; d) an arming detonator^for generating an arming signal; and e) a mechanical breakaway device installed on said second trail and actuated by said arming signal to interrupt said second trail, whereby to permit said firing signal to reach said main charge explosive through said first trail.

2. Safe/arm system according to claim 1, wherein the breakaway device is a cutting arm.

3. Safe/arm system according to claim 1, wherein the first trail has an output point at which it is connected to the main charge explosive and said second trail meets said first trail at a junction spaced from and connected to it by a final segment to said output point.

4. Safe/arm system according to claim 1, wherein the angle at which the two trails meet at the junction is such that no signal can pass from the second trail to the final segment of the first trail. 8386/rfl/99 137467/2 -11-

5. Safe/arm system according to claim 1, wherein breakaway device is actuated by a logic electronic circuit with a predetermined, desired delay.

6. Safe/arm system according to claim 1, wherein the first trail is the longer one and the second trail is the shorter one.

7. Safe/arm system according to claim 1, which comprises a base supporting an explosive charge, a first trail, a second trail, a firing detonator for generating a firing signal to be transmitted by said first trail, a cutting bar acting on said second trail, and an arming detonator for actuating said cutting bar to cut off a part of said second trail.

8. Safe/arm system according to claim 1, wherein the detonation signal transmitting trails consist of channels filled with XTX-8003 explosive or equivalent.

9. Safe/arm system according to claim 1, substantially as described and illustrated.

10. A warhead, having a casing and an explosive charge and carrying at the base thereof safe/arm system according to claim 1. LUZZATTO By