FR2496252A1 - Multiple stage hollow charge - has conical stages of differing sizes and taper acting in forward and rear directions - Google Patents

Abstract

The hollow charge has a cover shape formed by revolution of an opposed conical section solid (10-14). The slope may be regular and define several perforation stages. The thickness of all parts of the revolution elements can be the same or varied. Each element of the generated shape forms one stage of working of the hollow charge. From rear to front, the first rear stage (J1 N1) acting forward, is followed by a first intermediate stage (J13) acting rearwards and so on.

Description

 This invention relates to improvements made to shaped charges. It is known that the known shaped charges generally comprise a coating of revolution in copper of simple geometric shape: for example, cane (straight generator), or of curvilinear profile (for example, ogival coating or "tulip").

In order to increase the efficiency of these charges, it has been imagined to add effects of charges arranged one behind the other, for example as described and claimed by the Applicant in its French patents
- No. 75 14 091, of May 6, 1975
- No 77 35 320 of 24 November 1977 and its first Addition,
- No 80 23 444, of 3 November 1980.

 These provisions require having two or more charges, separate coatings and delay systems between the initiation of successive charges (pyrotechnic or electronic delays).

 The present invention brings a new progress, by increasing the mass of the jet produced without increasing the caliber.

 According to the invention, the mass of the jet is increased by providing a single coating of revolution, said coating being generated by a broken or curved line composed of rectilinear elements with several maxima and minima, of revolution around the longitudinal axis of the projectile , defining the perforating operating stages of the assembly.

 The number of elements of the broken or curved line generator coating according to the invention is not limited; it can be more than 2.

 The various characteristics and advantages of the invention will emerge from the examples described below.

 It is clearly stated that these are only examples, and that all other modes of construction, arrangement, shapes, proportions, can be used without departing from the scope of the invention.

In the course of this description, reference is made to the appended drawings, in which
- Figure 1 is a schematic view, in elevation, of a first embodiment of a hollow charge according to the invention;
- Figures 2 and 3 are partial schematic views, in elevation, illustrating two variants of the coating of the shaped charge according to the invention; and,
- Figure 4 is a schematic view, in elevation, of a variant of the coating comprising curved elements.

 Referring to Figure 1, there is shown schematically a hollow charge head comprising three perforating stages (non-limiting example) according to the invention. It comprises a coating 1 in a broken line according to the invention, main explosives 2, 2 ′ and 2 ″ from the three successive perforating stages 10, 11 and 12. The rear stage 10 further comprises a screen 4 and a priming 5. An envelope 6 and a warhead 7 complete the construction.

 The coating 1 in broken line according to the invention comprises five rectilinear elements P1 to P5 (this number not being limiting), and four discontinuities d to d4 (this number not being limiting).

 This coating 1 defines the three aforementioned perforating stages 10, 11 and 12 of operation according to the invention (not limiting).

We see, in Figure 1, that after initiation of the priming 5, an O-wave is formed in the explosive 2 by the screen 4, and attacks the fraction
P1 of the first stage 10 perforating the coating according to the invention.

 The part P1 of the coating 1 according to the invention produces a first jet J1 and a core N1.

 The second perforating stage 11 of the coating 1 according to the invention functions like the first perforating stage 10. This perforating stage 11 comprises the fraction P3 of said coating 1, a main explosive 2 ', and it forms a jet J2 (+ core N2) which must complete, according to the invention, the jet J1 of the previous stage 10.

According to the invention, an annular charge 3 of explosive slower than explosives 2 and 2 ′ of said perforating stages 10 and 11 is interposed between these two perforating stages 10 and 1 1. This charging 3 surrounds the part
P2 of the coating with a broken line generator according to the invention. This produces an intermediate assembly 13 (explosive 3 and fraction P2 of the coating 1) which, according to the invention, forms on the one hand a hollow charge with an effect directed towards the 'rear, and which, on the other hand, ensures the excitation of the second perforating stage 1 1 (P3 coating and explosive 2') via said explosive
3 3 of said explosive intermediate stage or assembly 1 3 according to the invention, slower, hence, intrinsically, taking into account the dimensions (length e) of said assembly or stage 13, an operating delay of the second perforating stage 11 relative to the first perforating stage 10.

 Thus, and according to the invention, this device of a “retro” jet J13, acting in the opposite direction, brakes the core N1 of the first perforating stage 10 and prevents it from generating the addition of the jets J1 and J2 of the two stages perforators 10 and 11 (J1 passing naturally before J2, even by the timing of the operation of the load according to the invention).

It can therefore be seen that, according to the invention, the coating 1 with a broken line generator and the succession of loading stages generating successive added jets launched forward, with interposition, between two successive perforating stages of this type, d 'a reverse or "retro" stage, allows both, according to the invention: - to delay the disturbing effect of stage of rank n with respect to the stage
of rank n +; - ensure at the same time, with a suitable delay, the detonation of
the stage of row n + 1 after that of the stage of row n.

Continuing the examination of Figure 1, we find continuing to the left, looking at this Figure - an intermediate stage 14 (explosive "slower" 3 ', fraction P4 of the coating-
ment 1, length 1 ,, reverse jet J);
14 - a third perforating stage 12 (faster explosive 2 ", fraction P5 of
coating 1, jet J3 and core N3).

 As described above for the first intermediate stage 13, the second intermediate stage 14 ensures, according to the invention, the excitation of the third perforating stage 12 (by its explosive 3 'slower), and taking into account its length g1, so that the cores N1 and N2 do not disturb the addition to the jet J3 of the third perforating stage 12 of the successive jets J1 and J2 of the two preceding perforating stages 10 and 11.

 This combination of effects makes it possible to obtain, with the coating generated by a broken line according to the invention, a longer jet and of greater mass than a conventional hollow charge jet.

 The slopes o (elements of the broken line generating, by revolution around the axis of the projectile, the coating according to the invention, can be repetitive (Figure 2) or non-repetitive (Figure 3), without departing from the scope of the 'invention.

 In Figure 4, there is shown a variant of the coating according to the invention, the generator of which comprises curved elements, C1 to C5.

The thickness of the coating according to the invention can be constant in its elements in a broken or curved line, or variable, or different, without departing from the scope of the invention
Naturally, depending on the explosives used, pyrotechnic elements can be used, without departing from the scope of the invention, with or without delay, to complete, improve or modify the initiation of the explosive of a stage of rank n + 1 by the intervention of the explosive of an intermediate stage from the explosive of a stage of rank n.

Claims (11)

 1 - Hollow charge comprising a coating of revolution characterized in that it is generated by a broken or curved line generator composed of rectilinear elements or not and with repetitive slopes or not, defining several stages of perforating operation of the assembly .  2 - Hollow charge according to claim 1, characterized in that said coating is generated by a broken line generator with curved elements, at several maxima and minima, defining several stages of perforating operation, whatever the concavities or convexities of the curved elements of the generator.  3 - Hollow charge comprising a coating according to one of the preceding claims, characterized in that the thicknesses of the elements of the generator are constant, or different, or even variable, along each element.  4 - Hollow charge comprising a coating according to any one of the preceding claims, characterized in that each element of the generator corresponds to an operating stage of the hollow charge.  5 - Hollow charge comprising a coating according to any one of the preceding claims, characterized in that by traversing the projectile from rear to front, the first rear perforating stage acting towards the front is followed by a first intermediate stage acting towards the rear, (with so-called "retro" effect), itself followed by a second perforating stage acting also towards the front, and so on.  6 - Hollow charge comprising a coating according to any one of the preceding claims, characterized in that each perforating stage with "retro" effect corresponds to the loading of explosive which is not necessarily identical (detonation speed, power) to that of the stage which precedes or succeeds it.  7 - Hollow charge comprising a coating according to any one of the preceding claims, characterized in that the perforating stages acting towards the front have faster explosive charges, while the intermediate stages, with a "retro" effect acting towards the 'rear, have slower explosive charges.  8 - Hollow charge comprising a coating according to any one of the preceding claims, characterized in that a stage of row n + 1 piercing acting forward, charged with faster explosive, is initiated by the stage, also piercing , acting forwards, of rank n, also charged with faster explosive through the intermediate stage with "retro" effect acting towards the rear, interposed between these two stages n and n + 1, by simple continuity of detonation and direct contact with explosives fast (row n), then slower, intermediate "retro", and finally fast before (row n + 1).  9 - Hollow charge comprising a coating according to any one of the preceding claims, characterized in that the rearward or "retro" effect of the intermediate stage delays the arrival of the core of the stage previous, of rank n, so that the jet of said perforating stage of rank n comes to the front of the jet of the perforating stage of rank n + 1, thus making it possible to add these two jets, and thus close in close for all stages of the load.  10 - Hollow charge comprising a coating according to any one of the preceding claims, characterized in that the timing of the stages, and in particular that of the "retro" retarding effect of an intermediate stage, is regulated by the combination of the lengths of the successive intermediate stages with a "retro" effect and explosive detonation rates of said successive stages.  11 - Hollow charge according to any one of the preceding claims, characterized in that it comprises a particular pyrotechnic element, possibly supplemented by a delay, to ensure, modify, complete the initiation of the loading of a perforating stage of rank n + 1 from the perforating stage of row n, via the loading of the intermediate stage with "retro" effect.