Ammunition and explosives – Igniting devices and systems – Ignition or detonation circuit
Patent
1991-10-21
1992-11-24
Brown, David H.
Ammunition and explosives
Igniting devices and systems
Ignition or detonation circuit
102204, 102308, 102476, F42B 1218, F42C 1102
Patent
active
051664690
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a delay fuse for placing between two shaped charges mounted in tandem in a warhead.
French patent FR 2 559 896 describes a delay fuse including an inter-charge protective screen.
On detonation of the front charge in the warhead, the protective screen moves rearwards and causes an electrical circuit to be closed.
Such a configuration makes it possible to obtain considerable delays (of 0.5 milliseconds (ms) to 3 ms) while avoiding the need to use a conventional solution with coils of great lengths of fuse cord.
However, when using this solution, even the slightest change in the required time delay requires a change in the total mass of the screen, or in the distance the screen is to travel.
Such geometrical modifications are particularly difficult to perform since they give rise to changes in the dimensions of the warhead and also in the distribution of its total mass.
In addition, long delays require long travel distances thus degrading the compactness of the warhead.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a delay fuse between two shaped charges mounted in tandem that enables time delay changes without disturbing the geometrical and ballistic characteristics of the warhead.
Another object of the present invention is to make it possible to reduce the distance between shaped charges that are to be detonated in sequence without thereby reducing the firing time delay between these charges.
The invention thus provides a delay fuse for a warhead including at least two charges for sequential detonation disposed inside a casing, the delay fuse comprising a screen which is axially movable inside the casing under the effect of the first charge detonating, from a starting position to a destination position wherein it acts on control means for firing a second charge, which fuse is characterized in that it includes a component of compressible material disposed inside the casing between the screen and the control means.
The screen may be fixed to the casing by shearable fixing means. The crushing strength of the compressible material is such that its volume reduces by less than 5% when it is subjected to a pressure equal to the quotient of the inertia, from warhead launch, of the assembly constituted by the first charge and the screen divided by the cross-sectional area of the first charge.
The crushing strength of the compressible material is preferably such that its volume reduces by less than 5% under a pressure of 10.sup.6 pascals, and that it reduces by at least 90% under a pressure of 10.sup.8 pascals.
Advantageously, the compressible material is an organic foam having a density of not more than 250 kg/m.sup.3, e.g. a polyethylene foam or a polyurethane foam.
The screen may be constituted by a safety and arming device for the first charge, and the screen may be separated from the first charge by a shock-absorbing block.
The shock-absorbing block is partly made of a sintered metal material of density lying in the range 1500 kg/m.sup.3 to 3000 kg/m.sup.3.
The means for controlling firing of the second charge may include a piezoelectric generator.
Other advantages of the invention appear from reading the following description of a particular embodiment, which description is made with reference to the accompanying drawing which is a diagram of a delay fuse in accordance with the invention.
BRIEF DESCRIPTION OF THE DRAWING
With reference to the accompanying figure, a fragment of a warhead 1 is shown diagrammatically.
It includes two shaped charges mounted in tandem inside a casing 2 for sequential firing.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
The front charge 3 is fired first in convention manner and comprises a covering 4 and an explosive filler 5. A detection system (not shown) fires it by means of a safety and arming device 6.
FIG. 1 shows a partial cross-section of a warhead according to the present invention.
A shock-absorbing block 7 is disposed between the filler 5 and the safety and arming device 6.
REFERENCES:
patent: 2894457 (1959-07-01), Severance
patent: 3349709 (1967-10-01), Vilbajo
patent: 3356026 (1967-12-01), Lubig
patent: 3967141 (1976-06-01), Gawlick et al.
patent: 4714022 (1987-12-01), Chaumeau et al.
patent: 4793256 (1988-12-01), Webb
patent: 4803928 (1989-02-01), Kramer et al.
patent: 4854240 (1989-08-01), Hirsch et al.
patent: 5003879 (1991-04-01), Jones
Durand Richard J. C.
Kerdraon Alain L.
Brown David H.
Giat Industries
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