Ammunition and explosives – Shells – Focused or directed detonation
Reexamination Certificate
1997-12-11
2001-06-26
Tudor, Harold J. (Department: 3641)
Ammunition and explosives
Shells
Focused or directed detonation
C102S501000
Reexamination Certificate
active
06250229
ABSTRACT:
BACKGROUND OF THE INVENTION
The technical area of this invention is that of charges generating explosively-formed penetrators.
These charges generally comprise an explosive set in a casing and at least one liner having overall the form of a spherical cap.
When the explosive is detonated, the liner is set in motion by the incident pressure wave. It reshapes itself by turning back on itself like a “glove finger”, that is, it transforms itself into a projectile (or slug) whose forward part comprises the central area of the liner while the rear part is a skirt formed by the periphery of the liner. Patent FR2627580 describes such a charge.
The penetrator generating charge is generally initiated at a considerable distance from the target (50 to 100 calibers from the charge). It is thus essential that the projectile's geometry enable it to remain stable along its trajectory.
In fact, destabilization of the projectile will result in the projectile's inability to reach the target at the desired place and will make it insufficiently effective.
To ensure the stabilization, normally, one seeks to give the projectile a geometry comprising a stabilizing skirt in its rear part with its center of gravity as far forward as possible.
Patent FR2654821 thus describes a charge generating an explosively-formed penetrator in which the liner, specifically at its periphery, comprises a layer of less dense material which forms a stabilizing skirt.
This solution is complicated to implement and does not allow for reproducibility of the geometric characteristics of the rear skirting.
The skirting's material comes from the periphery of the liner located near the casing of the charge.
When the charge is initiated, in this peripheral area, reflections of detonating waves are produced which most often result in an accumulation of liner material in the form of skirting of irregular shape whose mass is too great and which destabilizes the projectile.
Control over the skirting is all the more intricate when the liner is made of a material such as Tantalum whose plastic flow stress is essentially constant or decreases as a function of the strain applied to it.
In fact, with such materials, an increase in strain quickly leads to rupture. It is then impossible to elongate the projectile so as to place its center of gravity as far forward as possible while ensuring the formation of skirting of reproducible form.
The goal of this invention is to offer a charge generating an explosively-formed penetrator which is free of these disadvantages.
Thus, the charge according to this invention generates a projectile whose skirt geometry and mass distribution are controlled.
The structure of the charge according to the invention is also very simple and inexpensive to manufacture.
The purpose of the invention is thus a charge generating an explosively-formed penetrator comprising an explosive placed in a casing and at least one liner having the diameter of the casing and which is intended to be set in motion by the detonation of the explosive, with the charge characterized in that it comprises a plate positioned between the explosive and the liner, and this plate's diameter will be equal to that of the casing's internal diameter and this plate will completely cover the surface of the liner placed opposite the explosive and with the material for the plate having a density equal to or lower than the material of the liner and a volumetric compressibility modulus greater than or equal to 100 GPa, with the thickness of the plate being greater than or equal to that of the liner at any point of a central area surrounding the axis of the charge—in order to ensure, at initiation of the charge, a centripetal deformation of the plate which will be less than that of the liner.
Preferably, the diameter of the central area should be greater than or equal to 75% of the diameter of the liner or of the plate (caliber of the charge).
The liner can be made of a material with a plastic flow stress which is essentially constant or which decreases as a function of strain.
The plate's thickness can be essentially constant or, again, increasing from its periphery going toward the axis of the charge.
The liner material can be of any of the following: Tantalum, Molybdenum, Nickel or Copper, and the plate can be made of Aluminum or Magnesium.
In the central area, the thickness of the plate can be greater than or equal to 50% of that of the liner where it forms a right angle with that particular plate.
The external bending radius of the liner can be between 0.7 and 1.5 times its external diameter.
REFERENCES:
patent: 4922825 (1990-05-01), Aubay et al.
patent: 5033387 (1991-07-01), Lips
patent: 5744747 (1998-04-01), Renaud-Bezot et al.
patent: 5792980 (1998-08-01), Weimann
patent: 437992 (1991-07-01), None
patent: 2627580 (1989-08-01), None
patent: 2654821 (1991-05-01), None
patent: 2681677 (1993-03-01), None
Kerdraon Alain
Vives Michel
Giat Industries
Oliff & Berridg,e PLC
Tudor Harold J.
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