GB2200975A - Explosive device - Google Patents

Abstract

A limpet mine has a timing circuit (20), Fig. 2, to produce a first trigger signal on expiration of a preset delay and a sensing circuit (21) including a hydrophone to produce a second trigger signal in response to an acoustic pressure wave produced by detonation of another, nearby limpet mine. Detonation of one of the group mines, on expiration of the respective preset delay, causes near simultaneous detonation of the other mines in the group thereby enhancing the effectiveness of the group. Each mine may be provided with an anti-handling device. The mine comprises a body portion 10, Fig. 1, and a detachable fuze 12. <IMAGE>

Description

EXPLOSIVE DEVICE This invention relates toan explosive device bandit relates particularly to an explosive device including an explosive charge and a fuze provided with timing means arranged to initiate detonation of the charge on expiration of a delay of preset duration.

A known device of this kind, commonly referred to as a limpet mine, is so constructed as to be attachable magnetically or otherwise to a suitable body e.g. the hull of a ship.

Generally, a number of limpet mines are deployed below the waterline and their respective delays set individually.

Clearly, the effectiveness of the group is enhanced , , .

significantly if the mines detonate simultaneously or nearly so; however, because each delay is usually set manually, simultaneous, or near simultaneous, detonation may not be achieved in practice unless physical interconnection between mines is provided. Such interconnection can, however, be undesirable in that it tends to hinder attempts to conceal the mines.

It is an object of the present invention to provide an explosive device whereby the above-described problems are at least alleviated.

Accordingly there is provided an explosive device including an explosive charge and a fuze provided with timing means arranged to initiate detonation of the charge on expiration of a delay of preset duration, wherein said fuze is provided also with further means to initiate detonation of the charge in response to an acoustic pressure wave produced by detonation of another explosive charge.

It will be appreciated that if a number of said explosive devices are deployed in a group, detonation of the explosive charge associated with any one of them, in response to expiration of a respective delay, will cause substantially simultaneous detonation of the charges associated with the other devices in the group, thereby enhancing significantly their effectiveness.

- Said fuze may also include anti-handling means arranged to initiate detonation of the charge if the device is subject to physical dispfäcement.

The explosive device may be a limpet mine.

In order that the invention may be carried readily into effect an embodiment thereof is now described by reference to the accompanying drawings of which, Figure 1 shows a perspective view of a limpet mine, Figure 2 shows, in block schematic form, a fuze employed in the limpet mine of Figure 1, and Figure 3 shows a circuit employed in the fuze of Figure 2.

Referring now to Figure 1, a limpet mine comprises a housing, shown generally at 10, which is adapted, in known manner, to be attachable magnetically or otherwise to a suitable body e.g. the hull of a ship. The housing includes a main portion 11 containing an explosive charge (not shown) and a detachable portion 12 containing a fuze. A suitable explosive connection 13 is provided to couple a firing signal, generated by the fuze, to the charge.

The fuze, which is shown in Figure 2, comprises a timing circuit 20, of conventional form, arranged to produce a first trigger signal TRI on expiration of a delay of preset duration and a sensing circuit, shown generally at 21, arranged to produce a second trigger signal TR2 in response to an acoustic pressure wave as generated by detonation of another limpet mine. Optionally, the fuze may also include an antihandling device 25 arranged to produce a third trigger signal TR3 in response to detection of physical displacement of the mine.

The output locations of circuits 20 21 and 25 are connected electrically to respective input locations of an OR gate 22.

If any one of the circuits generates a trigger signal, indicating either that the delay has expired. or that an acoustic pressure wave has been sensed or that the device has been tampered with, OR gate 22 produces a firing signal FS which is routed, via a safety and arming arrangement 23, to a detonator 24 thereby to initiate the explosive charge.

The sensing circuit is arranged to discriminate between the shock wave produced as a result of detonation of another mine and other acoustic pressure waves due to background effects such as engine noise, for example. As shown in Figure 3 of the drawings the sensing circuit includes a detector (DET) in the form of a hydrophone.

The output of the hydrophone is amplified in a preamplifier and signal conditioning circuit (AMP) and the amplified signal subjected to thresholding in a level and edge detection circuit (LEC). Provided both the rise time and magnitude of the detected signal are consistent with a shock wave produced by detonation of another mine, circuit LEC generates the trigger signal TR2.

In a typical application of the present invention, a plurality of limpet mines are attached to the hull of a ship below the waterline. Detonation of one of the mines, on expiration of the respective delay, produces an acoustic shock wave which is sensed by the other mines and causes their detonation. In this manner substantially simultaneous detonation of the mines is achieved thereby enhancing significantly the effectiveness of the group.

It will be appreciated that although the above-described example relates to a limpet mine the present invention encompasses other explosive devices of the kind which are intended to be attached to, or placed adjacent, a body to be disabled and which include timing circuits to initiate detonation on expiration of a preset delay.

Claims (5)

1. An explosive device including an explosive charge and a fuze provided with timing means arranged to initiate detonation of the charge on expiration of a delay of preset duration wherein said fuze is provided also with further means to initiate detonation of the charge in response to an acoustic pressure wave produced by detonation of another explosive charge.

2. An explosive device wherein output locations of said timing means and said further means are connected to respective input locations of an OR gate arranged to initiate detonation of said explosive charge in response to a trigger signal generated at an output location of one or the other of said timing and further means.

3. An explosive device according to Claim 1 or Claim 2 wherein the fuze includes anti-handling means to initiate detonation of the charge in response to detection of a physical displacement of the device.

Bn explosive device according to Claims 1 to Claim 3 in the form of a limpet mine.

5. An explosive device substantially as hereinbefore described by reference to and as illustrated in the accompanying drawings.

5. An explosive device substantially as hereinbefore described by reference to and as illustrated in the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS 1. An explosive device comprising an explosive charge, means for attaching said explosive charge to a body and a fuze, wherein said fuze comprises timing means arranged to initiate detonation of said explosive charge on expiry of a delay of preset duration and acoustic means arranged to discriminate a characteristic acousti:pressure wave produced by detonation of another said explosive charge of another said exposive device from acoustic pressure waves otherwise produced and to initiate detonation of the associated explosive charge on detection of a said characteristic acoustic pressure wave.

2. An explosive device according to Claim 1 wherein output locations of said timing means and said further means are a connected to respective input locations of an OR gate arranged to initiate detonation of said explosive charge in response to a trigger signal generated at an output location of one or the other of said timing and further means.

3. An explosive device according to Claim 1 or Claim 2 wherein the fuze includes anti-handling means to initiate detonation of the charge in response to detection of a physical displacement of the device.

4. An explosive device according to Claims 1 to Claim 3 in the form of a limpet mine.