GB2158921A - Pyrotechnic device - Google Patents

Abstract

A pyrotechnic device, such as a thunderflash, comprises an explosive charge 4 and a casing. The casing comprises a first part 1 which extends to form a closed handle portion and which is fixedly attached to said explosive charge, and a second part 2 removably connected to said first part, the casing being substantially water resistant and of soft material, such as expanded polystyrene. The two casing parts are connected by a tape 9, removal of which exposes a layer of red phosphorus 7 on part 2. A pyrotechnic composition 11 is ignited by striking against this layer, and connects with charge 4 via a fuse 5. <IMAGE>

Description

SPECIFICATION Pyrotechnic device The present invention relates to a pyrotechnic device, and more particularly to that type of pyrotechnic device known as a thunderflash.

Thunderflashes have long been used for training purposes especially in the armed forces. A thunderflash provides, as its name indicates, a realistic simulation of the sound and appearance of a real explosive device, for example a hand grenade. However, any pyrotechnic device cannot be completely safe.

Thunderflashes are commonly thrown and to protect users against premature explosion the pyrotechnic charge is attached to a relatively long handle which consists of a hollow paper or cardboard tube.

However, the thunderflash is still likely to be hazardous when it detonates. The blast of the explosion may affect people standing in too close proximity. Components, for example: hard paper wads; portions of the handle; pieces of hard plastics material, metal, adhesives and sealants, may be propelled considerable distances, with considerable force, by the blast of the explosion. Pebbles, stones and gravel may enter the hollow hand when the thunderflash hits the ground. On explosion, the hand acts-as a "gun-barrel" and the pebble may be propelled a very great distance.

Another disadvantage of thunderflashes is that they are commonly made with paper as the main component of their bodies. Great care must be taken to prevent absorption of moisture through the paper, which moisture would, of course, render the thunderflash useless or, at best, a damp squib. Thus storage of thunderflashes is critical in that conditions must be dry. Furthermore, care must be taken when using a thunderflash in heavy rain or other damp conditions.

It is an object of the present invention to provide a pyrotechnic device which overcomes the above disadvantages.

According to the present invention, there is provided a pyrotechnic device comprising an explosive charge and a casing, the casing comprising a first part which includes an enclosed handle portion and which is fixedly attached to said explosive charge, and a second part removably connected to said first part, the casing being substantially water resistant and of soft material.

Preferably the casing is of expanded plastics material, for example expanded polystyrene, and the handle portion is solid.

The first and second parts of the casing may be held together by a strip of adhesive material. Preferably the adhesive material, when removed to allow separation of the two parts, exposes a layer of pyrotechnic material on the second part.

The explosive charge may comprise a second pyrotechnic material combinable with said layer of pyrotechnic material to cause ignition of a delay fuse, which in turn causes the charge to explode.

The layer of pyrotechnic material on the second part preferably comprises red phosphorus.

An embodiment of the present invention will now be more particularly described by way of example and with reference to the accompanying drawing, in which there is shown a cross-sectional view of a pyrotechnic device embodying the invention.

Referring now to the drawing, there is shown a pyrotechnic device comprising a waterproof casing formed of a casing 1 and an end cap 2. The material of the casing 1, 2 is a soft waterproof material such as expanded plastics material. A particularly preferred material is expanded polystyrene, although other plastics materials could be used.

The end cap 2 is provided, in the region of its junction with casing 1, with a layer of suitably bound red phophorus 7. This is covered with an inert layer 8 of paper or plastics film. This in turn is covered with a layer of adhesive tape 9. The tape 9 is ideally water repellant and is so positioned as to hold together and seal between the casing 1 and end cap 2. Thus, removal of the tape layer 9 enables separation of the two parts of the casing and simultaneously exposes the layer of red phosphorus 7 on the end cap 2.

The casing 1 is extended, downwardly as shown in the drawing to form a handle portion by which the thunderflash can be held for throwing. The handle portion is "solid" expanded plastics material and there is thus no danger of the "gun-barrel" effect referred to above. The ends of both the handle portion 1 and the end cap are hemispherical. This gives a more pleasing appearance and facilitates manufacture.

The casing 1 is adhered to a tube 3 of soft or frangible material producing no heavy or sharp-edged fragments. The tube 3 is preferably of rolled paper.

The tube 3 is sealed at one end, within the casing 1, by a closure 10 of soft or similarly frangible material. Suitable materials for closure 10 are natural or composite cork or fibrous material, expanded plastics material or paper. The closure is glued in place.

At the other end, the tube 3 is closed by a perforated wad 6 of material similar to that of closure 10. The wad 6 is fixed in place by a thin film of adhesive. The wad 6 accommodates a fuse 5, such as a Bickford fuse which is a reliable burning time pyrotechnic fuse of soft and/or suitably frangible material.

The fuse 5 connects an explosive charge 4 within the tube 3 with a pyrotechnic composition 11 which is sensitive to ignition by friction with red phophorus.

The pyrotechnic device is encased completely by waterproof material in casing 1, end cap 2 and adhesive tape 9 covering the join therebetween. It may thus be stored safely for considerable periods without deterioration in its effectiveness.

To use the pyrotechnic device, the tape 9 is removed exposing the layer 7 of red phophorus and allowing separation of end cap 2 from casing 1. End cap 2 is removed and held. The pyrotechnic composition 11 thus exposed is struck like a match on the layer 7 of red phophorus. Once the fuse 5 is alight, the pyrotechnic device can be delivered toward its chosen explosion site and the end cap 2 discarded.

Methods other than that described of ignition of the explosive charge are possible.

Other materials of the casing 1 than those described are possible. Certain limitations are placed on the material in that it must be substantially waterproof, it must be reasonably light to enable the pyrotechnic device to be thrown, it must not give off large quantities of toxic gas when it burns following an explosion, and it must not break into fragments which are likely to have hard and/or sharp edges.

The casing 1 need not be solid but it is important that the end is so enclosed as to prevent or reduce the aforementioned "gunbarrel" effect.

The explosive charge 4 may be varied in quantity and/or composition to give different simulated effects.

Claims (7)

1. A pyrotechnic device comprising an explosive charge and a casing, the casing comprising a first part which includes an enclosed handle portion and which is fixedly attached to said explosive charge, and a second part removably connected to said first part, the casing being substantially water resistant and of soft material.

2. A pyrotechnic device as claimed in claim 1, wherein the casing is of expanded plastics material, and the hand portion is solid.

3. A pyrotechnic device as claimed in claim 2, wherein the plastics material is polystyrene.

4. A pyrotechnic device as claimed in any one of the preceding claims, wherein the first and second parts of the casing are held together by a strip of adhesive material, which when removed to allow separation of the two parts, exposes a layer of pyrotechnic material on the second part.

5. A pyrotechnic device as claimed in claim 4, wherein the explosive charge comprises a second pyrotechnic material combinable with said layer of pyrotechnic material to cause ignition of a delay fuse, which in turn causes the charge to explode.

6. A pyrotechnic device as claimed in either claim 4 or claim 5, wherein the layer of pyrotechnic material on the second part comprises red phosphorus.

7. A pyrotechnic device substantially as described herein with reference to the accompanying drawing.