US3782283A

US3782283A - Defined disintegration of the casing of an explosive element

Info

Publication number: US3782283A
Application number: US00169272A
Authority: US
Inventors: P Lingens; G Martin
Original assignee: Dynamit Nobel AG
Current assignee: Dynamit Nobel AG
Priority date: 1970-08-06
Filing date: 1971-08-05
Publication date: 1974-01-01
Anticipated expiration: 1991-01-01
Also published as: FR2104002A5; BE771024A; DE2039131A1

Abstract

An explosive device and processing for causing, upon detonation, the defined disintegration of the casing of the explosive device. This result can be achieved directly by providing cavities in the explosive charge of the device which conduct the high velocity gas flow generated during the reaction of the explosive to predetermined points along the casing. Preferably the explosive charge has a central bore which connects radially extending gaps. Alternatively, a defined disintegration can be obtained indirectly by including cavities in the explosive charge of the device which are subdivided into chambers by either explosive or inert materials. Finally, a fuze trail of explosive wires can be incorporated into the explosive charge to yield the same effect. Moreover, the explosive charge can be employed as a primer charge and disposed inside a main charge which, in turn, is enclosed by a casing.

Description

Lingens et al.

Jan. 1, 1974 DEFINED DISINTEGRATION OF THE CASING OF AN EXPLOSIVE ELEMENT Inventors: Paul Lingens, Leverkusen; Gerhard Martin, Troisdorf, both of Germany Dynamit Nobel Aktiengesellschaft, Troisdorf, Germany Filed: Aug. 5, 1971 Appl. No.: 169,272

Assignee:

Foreign Application Priority Data Aug. 6, 1970 Germany P 20 39 131.5

u.s. c1. 102/23, 102/24 R, 102/28 EB,

[02/67 1111. c1. F42d 1/00, F42d 1/04 Field ofSearch ..102/22-24, 2s, 28 EB, WJ ZI I 21,

References Cited UNITED STATES PATENTS 3,457,859 7/1959 Guenter 102/28 R Primary ExaminerVerlin R. Pendegrass AttorneyCraig, Antonelli & Hill [5 7] ABSTRACT An explosive device and processing for causing, upon detonation, the defined disintegration of the casing of the explosive device. This result can be achieved directly by providing cavities in the explosive charge of the device which conduct the high velocity gas flow generated during the reaction of the explosive to predetermined points along the casing. Preferably the explosive charge has a central bore which connects radially extending gaps. Alternatively, a defined disintegration can be obtained indirectly by including cavities in the explosive charge of the device which are subdivided into chambers by either explosive or inert materials. Finally, a fuze trail of explosive wires can be incorporated into the explosive charge to yield the same effect. Moreover, the explosive charge can be employed as a primer charge and disposed inside a main charge which, in turn, is enclosed by a casing.

29 Claims, 10 Drawing Figures PAIENT JAT 11m SHEET 1 0T 3 FIG. I

FIG. 8

INVENTORS PAUL LINGEN S GERHARD MARTIN ATTORNEYS PATEHTEU 11574 SHEET 2 BF 3 INVENTORS PAUL LINGENS GERHARD MARTIN QM k mm ATTORNEYS PATENTEU H91"? SHEET 3 IF 3 GERH ARD MARTIN ATTORNEYS DEFINED DISINTEGEATION OlF THE CASING OF AN EXPLOSIVE ELEMENT BACKGROUND OF THE INVENTION This invention relates to the defined disintegration or fragmentation of the casing of an explosive element.

In solid explosive elements, the disintegration of the casing is caused by the shock wave and the explosion produced gas pressure associated with progressing detonation front. The disintegration of the casing necessarily occurs in a random manner. In addition to small fragments or splinters, in many cases undesirable, large fragments result. Thus, the mass of the individual fragments varies within a wide range. Attempts have been made to divide the easing into segments or preformed fragments by reducing the wall thickness at specific points, in order to obtain defined fragments upon disintegration of the casing. However, such process has the disadvantage that it unduly complicates the manufacture of the casing. Moreover, the desired strength of the casing is often impaired thereby.

SUMMARY OF THE INVENTION It has now been found, surprisingly, that these disadvantages can be eliminated by providing that the gas flow of high velocity and high energy density occurring during the reaction of the explosive in cavities, chambers, gaps and/or fissures be conducted to the casing and/or to an explosive, and/or that fuze or primer trains of explosive wires be arranged in the explosive element.

The gas flow of high velocity is generated in cavities in the explosive, which cavities have any desired geometric, symmetrical as well as asymmetrical cross sections, or irregular boundaries. The cross sections can vary continuously or discontinuously over the length or depth of the cavities or gaps. For the defined disintegration of the casing, the gas flow of high velocity and high energy content can be utilized, firstly in a direct manner and/or, secondly, in an indirect manner.

In the direct process, the gas flow proper is allowed to be effective on the casing by, for example, providing gaps or fissures in the explosive. Due to the high velocity of the gas flow, a dynamic gas pressure is built up extremely rapidly at the predetermined points of the casing, resulting in a high compressive stress on the easing at the respective points. At these places, there then occurs a preferred rupturing of the casing. If such preferred points are arranged at predetermined intervals in the direction of the progression of the detonation, defined fragments are formed which do not exceed the length of the respective intervals. Thus, the maximum splinter size can be adjusted over a wide range. In the direct use of the gas flow, the gap width can be fixed with the aid of an inert material (metals or nonmetals which do not explode). The cavities in the explosive can also be lined with an inert material (metals or nonmetals).

In the indirect process, gas currents of high velocity and energy density occurring in perforated explosive charges are surprisingly employable for disintegrating the casing into defined splinters. According to this embodiment, a defined disintegration of the casing is unexpectedly obtained primarily by a discontinuity in the chronological stress on the casing. It is unexpected, since disintegration, in addition to being affected by the casing material, depends first of all on the detonation pressure, i.e., on the chemical composition and density of the explosive. In order to attain a discontinuity in the chronological stress (stress per unit time) on the easing, the cavities serving for conducting the gas currents are subdivided into chambers. The chamber walls can consist of an explosive or inert material. The gas flow is dammed up at the chamber wall, which can also form an angle with the direction of propagation of the flow. At the points of dammed-up gas, the surrounding explosive is ignited before the detonation front in the explosive charge arrives. The new detonation front is propagated radially and results, upon striking the casing, in the rupturing thereof before the detonation front within the explosive element has reached this point. The maximum size of the fragments depends on the length of the chamber. In the subdivision of the cavity into chambers, a gas jet (high velocity gas flow) is formed successively in each chamber which again results in the advance ignition of the surrounding explosive. In this manner, a defined disintegration of the casing is obtained. In large cross sectional explosive charges, it is advantageous to arrange several parallel cavities or one cavity with, for example, an annular cross section, subdivided into chambers.

The combination of the direct and indirect utilization of a gas jet of high velocity and high energy density has a very advantageous effect on a defined disintegration of the casing. Various possibilities of the combination will be explained hereinafter in the examples.

It was furthermore found that the use of a fuze train of explosive wires results in a defined disintegration of the casing. The fuze train consists of alternating sections of a thick wire and a thin wire of the same length or of different lengths; see, in this connection, German Pat. No. P 16 46 348.2. By ignition of the train, the thin wire sections undergo an explosive conversion igniting the surrounding explosive. The thick wire sections which do not explode correspond, in this process, to the chamber length in the above-mentioned bores and therefore to the maximum size of the fragments. It is also possible to combine the use of the fuze train with explosive wires with the use of the gas flow of high velocity and energy in predetermined cavities and/or gaps. The utilization of a fuze train thus corresponds to the indirect method.

By the use of the gas jet and/or a fuze train of explosive wires, a defined disintegration of the casing is attained, i.e., the formation of small fragments of high velocity exhibiting great piercing power. The process of the present invention represents a simple and economical way for producing defined splinters of the casing of explosive elements. In the manufacture of large explosive elements, it is often advantageous to provide primer rods (also curved or other shapes) within the explosive charge. Explosives and cavities or fuze trains of explosive wires can be disposed in the primer rods. The ignition of the explosive element by such primer rods, which progresses intermittently in the manner previously indicated, results in the formation of prematurely prodii'ced detonation fronts in the direction toward the casing. Accordingly, defined disintegration of the casings of the explosive elements occurs.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in greater detail below with reference to various embodiments of explosive elements constructed to produce defined disintegration of their casing taken in conjunction with the drawings wherein the same reference numerals are used in different figures to indicate like parts.

FIG. I is a cross-sectional view of an explosive element with a casing and an internal bore according to the invention.

FIGS. 2-6 show cross sections of explosive elements with various arrangements of filled and empty cavities and/or inert partitions according to the invention.

FIG. 7 illustrates an X-ray photograph of a prior art iron pipe during the disintegration into fragments, wherein the iron pipe was completely filled with explosive.

FIG. 8 represents an X-ray flash photograph of the disintegration of an iron pipe according to the invention wherein an explosive column was arranged which was subdivided by partitions into five individual parts, and which had an axial bore.

FIG. 9 shows the splinter impacts in an aluminum plate caused by a prior art iron pipe which was completely filled with explosive.

FIG. 10 shows the various splinter zones produced by fragments stemming from an iron pipe according to the invention which was filled with an explosive column subdivided into sections by partitions.

DETAILED DESCRIPTION The explosive elements illustrated in FIGS. 1-6 having a casing l filled with an explosive 3. This explosive is subdivided by bores 6 (FIGS. 1-5), partitions 4 (FIG. 1) of explosive or partitions 7 of inert material (FIG. 2) inserted in the bore 6, filled or unfilled gaps 8 (FIGS. 3 and 6), or conical flared portions 10 (FIGS. 4 and 5), so that the gas flow of high velocity and energy density is conducted to the casing l or an explosive. Initiator charge 2 is included to ignite explosive 3.

EXAMPLE 1 Three explosive charges (Composition B which is an explosive containing 39.5 percent by weight of trinitrotoluene, 59.5 percent by weight of cyclotrimethylenetrinitramine and I percent by weight of wax) were disposed in a unilaterally sealed iron pipe 1 (length, 450 mm.; inside diameter, 34 mm; outside diameter, 51 mm.). Ignition was effected by means of a blasting cap No. 8 (aluminum cap with primer pellet, a primary charge of 0.3 g. of lead tricinate and a secondary charge of 0.8 g. of tetryl) and a penthrite pressed charge 2 of 36 g. at the open end of the pipe. When the pipe I was filled completely with the explosive 3, i.e., without any cavities or gaps, fragments were produced during the detonative conversion of the explosive 3 which had a length of up to 300 mm. and ranged as low as 50 mm. In contrast thereto, when the charge was provided with an axial bore 6 having a diameter of 10 mm., which was subdivided into chambers 5 of a length of 90 mm. by partitions 4 of explosive having a thickness of 17 mm. (FIG. 1 fragments were obtained upon detonation of only a length of up to 100 mm. The fragment lengths were, in this case, almost uniformly distributed over magnitudes of between 20 100 mm. Also, a reduction in the width of the fragments approximately to one-half the values for the filled pipe occurred. It can thus be seen that the lengths of the fragments at worst barely exceed the lengths of the chambers.

Example 2 In the following experiments, cylindrical explosive columns 3 of Composition B were brought to a detonative conversion in armor steel pipes having inside and outside diameters, 16 mm. and 18.4 mm., respectively, with pipe lengths of 140 and 280 mm., respectively, by means of a pressed penthrite charge 2 of 18 g. with a blasting cap No. 8 inserted therein, at one end. The distribution of the fragments and the size thereof were determined with the aid of the piercing sites produced by the detonation in an aluminum plate disposed at a distance of 250 mm. The manner in which the steel pipes disintegrated was detected by X-ray flash photography.

In order to show the influence of an axial bore 6 in the explosive column 3, explosive columns with or without a bore were fired. The bore 6 was, in some experiments, filled with an inert material (silver steel rods), in order to obtain the same amount of explosive as a basis for the various experimental arrangements.

A further modification of the experiment resided in subdividing the explosive column 3 with or without an axial bore 6, into several adjoining or specifically spaced-apart explosive elements of the same length. In this connection, the bore was also filled with an inert material 7 in a portion of the cases. (See FIG. 2.)

In the arrangements of the explosive columns 3 in the steel pipe 1 according to this example as set forth hereinafter, the maximum fragment sizes were in the following ranges;

a. Continuous explosive column without axial bore:

mm. (reference or control standard).

b. Continuous explosive column with axial bore filled with silver steel: 60 70 mm. (reference standard).

0. Continuous explosive column with an unfilled axial bore: 60 70 mm. (reference standard).

d. Continuous explosive column 3, as shown in FIG.

2, with axial bore 6, wherein the latter was subdivided, by partitions 4 of explosive having a thickness of 9.5 mm, into chambers of a length of 16 mm. (indirect method): 15 20 mm.

e. Experimental arrangement as in ((1) wherein the length of the chamber was 40 mm.: 35 40 mm.

f. Explosive column 3, as shown in FIG. 3, with an axial bore 6 subdivided, by gaps 8 filled with 2 mm. thick inert PVC-ring disks, into adjoining bodies having a length of 25 mm. (direct and indirect method): 15 20 mm.

g. Explosive column as in (f), but with empty gaps 8, wherein the spacing of the individual explosive bodies was 1 mm.: 15 20 mm.

b. Explosive column, as shown in FIG. 3, with a bore 6 subdivided by empty gaps 8 of I mm. between elements ofa length of 15 mm.: IO- 15 mm.

i. Explosive column 3, according to FIGS. 4 and 5, having elements of a length of 25 mm. with an axial bore 6. At the end of each element, the bore was provided with a conically flaring portion 10 (direct and indirect method): 15 20 mm.

j. Explosive column 3 without a bore, as shown in FIG. 6, subdivided by filled gaps 8 of 2 mm. thick inert PVC-ring disks into adjoining explosive elements of 25 mm. (direct method): 25 30 mm.

k. Explosive column as in (j), wherein the spacing of the individual explosive elements from each other was 1 mm.: 20 25 mm.

In experiments ((1) (k) which exhibit various embodiments of the invention, the controlled disintegration of explosive casings into splinters of a defined size is clearly demonstrated. In contrast, reference examples (a) through (c) representative of the prior art, yield splinters having undefined sizes including undesirably large fragments.

Due to the premature rupturing of the casing in certain zones of explosive devices according to the invention, fragments are flung outwardly in defined splinter rings. This premature rupturing is shown by the X-ray flash photograph (FIG. 8). An iron pipe filled with an explosive in the normal fashion (FIG. 7) evidences no such rupturing. The same effect is demonstrated by splinter impacts on aluminum plates. In FIG. 10, which corresponds to FIG. 8, the various splinter zones (delineated by lines 11) are clearly apparent, as well as the smallness of the fragments. By comparison the plate of FIG. 9, which shows the splinters of an explosive-filled iron pipe, includes extremely large fragments distributed over an unzoned area.

Example 3 A steel pipe, having an inside diameter of 160 mm., a wall thickness of 4.5 mm., and a length of 150 mm., was filled with Composition B, including an axial bore of l6 mm. A rod made of Composition B serving as the primer rod, without or with an axial bore of a diameter of 4 mm., was inserted in the bore in various experimental arrangements. The ignition of the rod was effected by a pressed charge of penthrite of 18 g., inserted in front of the rod, with a blasting cap No. 8 included therein. In order to determine the length of the fragments of the casings of the explosive elements during detonative conversions in the various experimental arrangements, the fragments were captured in wooden planks at some distance from the explosive object. The experiments resulted in the following maximum splinter sizes:

a. Primer rod without bore: 100 140 mm. b. Primer rod with continuous bore: 90 130 mm. c. Primer rod with continuous bore, wherein the latter was subdivided by a partition of explosive of a thickness of 10 mm. into two chambers of a length of 65 mm. (indirect method): 50 70 mm. d. Primer rod with a continuous bore, wherein the latter was subdivided by partitions of explosive of a thickness of 10 mm. into three chambers of a.

length of 40 mm. (indirect method): 35 40 mm. This example demonstrates that the idea of this invention of a predetermined disintegration of the casing of an explosive element into fragments of a defined size can also be realized in case of explosive elements of a larger cross section, by the introduction of a primer rod of a certain design into the axial bore of such an explosive element. Such primer rods can also exhibit an envelope consisting of a metal or a nonmetal, the wall thickness of which envelope does not impair the effect on which the present invention is based.

Example 4 Steel armor pipes having an internal diameter of 25.5 mm., an external diameter of 28.4 mm. and a length of 320 mm., filled with Composition B, were axially detonated with primer rods with a diameter of l2 mm. having a primer (or fuze) train of explosive wires incorporated therein. The following fragment lengths were observed a. Six 50 mm. nonexplosive wire sections alternated with five 3 mm. explosive wire sections: fragment lengths, 20 50 mm.

b. Fourteen 20 mm. nonexplosive wire sections alternated with 13 3 mm. explosive wire sections: fragment lengths, 8 20 mm.

The explosive surrounding the fuze train consisted of sintered penthrite (pentaerythritol tetranitrate) of a low density.

This example shows unequivocally that the casing of an explosive element can also be disintegrated into fragments of a defined size of the use of fuze trains of explosive wires within the explosive element.

It is understood that the embodiments disclosed herein are susceptible to numerous changes and modifications, as will be apparent to a person skilled in the art. Accordingly, the present invention is not limited to the details shown and described herein but intended to cover any such changes and modifications within the scope of the invention.

We claim:

1. A device for disintegrating a casing into defined splinters comprising a fragmentable casing and means within said casing for producing fragments of a substantially predetermined size range, said means including an explosive charge having at least one cavity or gap arranged within said explosive charge so that, upon detonation of said explosive charge, the high velocity and density gas flow generated therein provides for defined disintegration of said fragmentable casing to producing fragments of said substantially predetermined size range.

2. The explosive device of claim 1 wherein said at least one cavity or gap includes a plurality of dammingup points for said gas flow, spaced at defined intervals.

3. The explosive device of claim 1 wherein said explosive charge includes a bore running therethrough.

4. The explosive device of claim 3 wherein said bore is divided into a plurality of defined chambers by a plurality of partitions.

5. The explosive device of claim 4 wherein said partitions comprise an explosive material.

6. The explosive device of claim 4 wherein said partitions comprise a non-explosive material.

7. The explosive device of claim 3 wherein passageways or gaps are arranged at defined intervals extending outwardly from said bore.

8. The explosive device of claim 7 wherein said enclosing casing is in direct contact with said explosive charge and said passageways or gaps extend between said bore and said casing.

9. The explosive device of claim 8 wherein said passageways or gaps are conically-flared.

10. The explosive device of claim 8 wherein the sides of each of said passageways or gaps are substantially parallel.

11. The explosive device of claim 8 wherein said passageways or gaps are filled by explosively-inert materials.

12. The explosive device of claim 8 wherein said casing is tubular-shaped and said explosive charge comprises a plurality of substantially identical annular elements consecutively spaced from each other.

13. The explosive device of claim 1 wherein said at least one cavity or gap is lined with an explosively-inert material.

14. The explosive device of claim 1 wherein said explosive charge is a primer charge and said explosive device further comprises a main explosive charge positioned between said primer charge and said enclosing casing.

15. The explosive device of claim 14 wherein said at least one cavity or gap is a bore including dammingpoints therein for said gas flow.

16. The explosive device of claim 14 wherein said at least one cavity or gap encloses a fuze train of explosive wires.

17. The explosive device of claim 1 wherein said at least one cavity or gap encloses a fuze train of explosive wires.

18. The explosive device of claim 1 wherein said explosive charge includes a plurality of outwardlyextending gaps spaced at a defined interval.

19. The explosive device of claim 18 wherein said explosive charge comprises a plurality of substantially identical consecutively-spaced explosive elements.

20. The explosive device of claim 19 wherein said gaps are filled by an explosively inert material.

21. The explosive device of claim 1 wherein said device is constructed to produce casing fragments having a maximum dimension of less than about 100 mm.

22. The explosive device of claim 21 wherein said fragments have a maximum dimension of less than about 40 mm.

23. The explosive device of claim 1, wherein the enclosing casing is a pipe having substantially the same wall thickness along the extent thereof and is formed of a material capable of producing fragments for piercing an object.

24. The explosive device of claim 23, wherein said material forming said enclosing casing is one of iron and steel.

25. A device for disintegrating a casing into defined splinters comprising a fragmentable casing and means within said casing for producing fragments of a substantially predetermined size range, said means including an explosive charge and a fuze train of explosive wires disposed within said explosive charge and arranged so that upon detonation of said explosive charge by said fuze train defined disintegration of said fragmentable casing with the production of fragments of substantially the predetermined size range results.

26. A process for disintegrating a fragmentable casing into defined splinters comprising the steps of providing an explosive charge within the fragmentable casing, forming gaps or cavities within the explosive charge in such a manner that upon detonation of the explosive charge the casing is disintegrated into fragments of a substantially predetermined size range.

27. The process of claim 26, including arranging the gaps or cavities to conduct the high velocity and density gas flow occurring during detonation to predetermined points at the casing.

28. The process of claim 26, further comprising the step of positioning a main explosive between the explosive charge and the casing and arranging the gaps or cavities to conduct the high velocity and density gas flow occurring during detonation to predetermined points at the main explosive.

29. The process of claim 26, further comprising the step of disposing a fuze train of explosive wires within at least one of the cavities.

Claims

2. The explosive device of claim 1 wherein said at least one cavity or gap includes a plurality of damming-up points for said gas flow, spaced at defined intervals.

15. The explosive device of claim 14 wherein said at least one cavity or gap is a bore including damming-points therein for said gas flow.

18. The explosive device of claim 1 wherein said explosive charge includes a plurality of outwardly-extending gaps spaced at a defined interval.