Ordnance – Shields – Shape or composition
Patent
1987-11-24
1989-11-21
Kyle, Deborah L.
Ordnance
Shields
Shape or composition
109 26, 109 495, F41H 504
Patent
active
048814482
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to reactive or "dynamic" protective armour arrangements for protection against obliquely impinging hollow explosive charge jets. The armour arrangement comprises two mutually spaced metal plates, which can be penetrated by an impinging hollow explosive charge jet to form a hole in the plates, and further comprises an intermediate layer of non-explosive material located between the plates.
BACKGROUND PRIOR ART
One such reactive armour arrangement is known from U.S. Pat. No. 4,368,660. Incorporated between the plates f this known arrangement is an explosive substance which will detonate when a hollow charge jet or like projectile impinges on the reactive armour arrangement, the subsequent detonation pressure causing the two plates to move away from each other and therewith greatly degrade the hollow charge jet.
The plates of such protective armour arrangement, however, need to be relatively large in order to function effectively, and consequently commensurately large quantities of explosive must be used in order to achieve the effect desired. One drawback in this regard is that the explosive forces generated by such large quantities of explosive are liable to result in damage to the object protected by the arrangement (e.g. an armoured vehicle or tank).
SUMMARY OF THE INVENTION
The object of the present invention is therefore to provide a reactive armour arrangement of the aforesaid kind which does not require the use of an explosive charge to fulfill its protective function.
This object is achieved with a reactive armour arrangement having the inventive features set forth in the characterizing clause of the following claim 1.
Further developments of the invention are set forth in the depending claims.
The invention is based on the discovery that the intrinsic energy of the hollow explosive charge jet in itself can be used to create shockwaves of different pressures in the plates and in an interlayer of the reactive armour arrangement. The pressure differentials created result in two counter-directional forces which tend to move the plates away from one another, in a manner which causes fresh plate material to be moved progressively into the path of the hollow explosive charge jet, thereby reducing the energy of the jet.
Compressible materials such as, e.g. rubber, or gases, e.g air, cannot be used to form the interlayer since almost all of the energy present in the shockwaves is dissipated in dislodging or punching material from the plates. The interlayer material should therefore be incompressible and possess a high dynamic mechanical strength.
The physical explanation of the shockwave effect is that practically total reflection of a shockwave takes place when the shockwave moves from a medium of relatively high density to a medium of lower density. Thus, in the case of the inventive protective arrangement, an impinging hollow charge jet will initiate in the outer plate a first shockwave which is reflected towards the thinner interlayer, this procedure being repeated some microseconds later behind the tip of the jet or thorn in the inner plate. This results in two forces which act in mutually opposite directions and which tend to draw the plates apart. It has optimal shockwave effect is obtained when the interlayer comprises an incompressible material and has a density which is at most 1/3 of the density of the plates.
The hollow charge jet will create in the protective armour arrangement a hole which is inversely proportional to the flow stress of the outer material and which is greater than the diamater of the hollow charge jet. Due to the aforesaid counter-direction forces, the edges around the hole will be lifted to form a bulged or crater-like surround, such that the plate material around the hole will move progressively into the path of the obliquely impinging jet, thereby causing the jet to penetrate further material with a subsequent decrease in jet energy.
The invention can also be explained in terms of shockwave pressure. For example, it has be
REFERENCES:
patent: 3793648 (1974-02-01), Dorre et al.
patent: 3962976 (1976-06-01), Kelsey
patent: 4161125 (1979-07-01), Degnan
patent: 4364300 (1982-12-01), Pagano et al.
patent: 4368660 (1983-01-01), Held
Lundgren Roger
Medin Gunnar
Olsson Erik
Sjoo Lennart
Affarsverket FFV
Johnson Stephen
Kyle Deborah L.
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