Ammunition and explosives – Igniting devices and systems – Initiating devices
Patent
1992-01-29
1993-06-29
Brown, David H.
Ammunition and explosives
Igniting devices and systems
Initiating devices
1022758, C06C 504
Patent
active
052236641
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to flexible detonating cord containing high explosive useful for linking explosive events when a specific short delay is required between the events.
2. Description of the Prior Art
When detonating cord is to be used in close proximity to a charge of explosive or sensitive material it is important that the cord's detonation energy is contained. In order to overcome this containment problem a detonating delay cord has been proposed in the past which consists of an inner flexible sheath of a ductile metal such as silver which contains a core of high explosive, surrounded by a high strength outer sheath of stainless steel which acts to contain the products of core detonation. In order to allow the shock wave produced by the core detonation to be attenuated sufficiently that the outer sheath can contain the detonation products completely without undergoing any plastic deformation, the sheaths are separated by an annular air gap. The resulting cord has an overall outside diameter in the order of 5 mm and is consequently inflexible and relatively heavy. A support structure is also required in order to support the inner sheath centrally within the outer sheath.
In a weapon system in which a small time delay is required (in the order of 100-500 .mu.s) between detonation events the inflexibility and size of the detonating cord described above is a distinct disadvantage as the delay cannot be achieved by coiling an appropriate length of cord into a confined space. One solution to this problem is to incorporate a short relatively slow burning section of pyrotechnic delay cord into the detonating cord with a sensitive primary initiating composition introduced where the pyrotechnic reaction is to be converted into a detonating regime. Safety considerations however dictate that such conversion systems have to be protected by a relatively bulky and complicated physical shuttering device in order to prevent accidental detonation taking place.
A detonating cord with limited flexibility is disclosed in the U.S. Pat. No. 4,178,853 which comprises an explosive core surrounded by a plurality of braided plastic fibre coverings and an outer braided steel fibre covering. In order to merely prevent rupture of the cord upon detonation between 6 and 12 layers of fibre coverings are required depending on the fibre employed, resulting in the cord having a pre-fired diameter of between 6 mm and 12 mm. The reference to the pre-fired diameter clearly indicates that the cord swells on detonation. Apart from its bulk this cord will presumably be expensive to produce and relatively inflexible due to its multi-braided construction.
A further detonating cord is described in French patent 2166732 which has an inner lead sheath and an outer steel sheath having outer diameters of 3.8 mm and 5.0 mm respectively. The object of the invention is to reduce the scatter of detonation speed of the cord by avoiding complete disintegration of the cord upon detonation. However no claim is made that plastic deformation of the cord will be prevented. The high ductility of lead used for the inner sheath limits the extent to which the explosive is compressed as the sheath is drawn down to a small diameter. This results in a larger core than is desirable being used in the final cord which makes containment of the detonation more difficult and will reduce the flexibility of the cord indeed the specification makes no reference to the cord being easily curvable.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a detonating cord which (a) is sufficiently flexible and narrow to allow it to be coiled in a confined space, (b) confines the products resulting from detonation of the cord, and (c) does not expand when detonated. A combination of these features would enable the cord to be compactly overwound with successive coils tightly wound on top of one another, enabling a long cord with a significant time delay to be coiled into a confined space.
Thus according
REFERENCES:
patent: 2982210 (1961-05-01), Andrew et al.
patent: 3903800 (1975-09-01), Kilmer
patent: 4178853 (1979-12-01), Garrison et al.
patent: 4607573 (1986-08-01), Thoreson et al.
patent: 4991511 (1991-02-01), Simpson
Chemical Abstracts, vol. 98, No. 2, Jan. 1983, Columbus, Oh., p. 84; Nissan Motor Co.
Brown David H.
The Secretary of State for Defence in Her Britannic Majesty's Go
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