US3777662A

US3777662A - Effect of the shock pressure of explosive charges

Info

Publication number: US3777662A
Application number: US00166013A
Authority: US
Inventors: P Lingens; G Martin
Original assignee: Dynamit Nobel AG
Current assignee: Dynamit Nobel AG
Priority date: 1970-07-24
Filing date: 1971-07-26
Publication date: 1973-12-11
Anticipated expiration: 1990-12-11
Also published as: FR2103285A5; DE2036726A1; BE770335A

Abstract

An explosive charge and method for increasing detonative percussion in which the explosive is provided with cavities, gas or fissures which permit the ''''advance ignition'''' of the explosive. Preferably, the explosive is cylindrically shaped with a through-axial core. The bore may include explosive or inert baffles. Also the bore may be provided with a fuze train of explosives.

Description

United :States Patent [191 Lingens et al.

[ Dec. 11, 1973 EFFECT OF THE SHOCK PRESSURE OF EXPLOSIVE CHARGES [75] Inventors: Paul Lingens, Leverkusen; Gerhard Martin, Troisdorf, both of Germany [73] Assignee: Dynamit Nobel Aktiengesellschaft,

Troisdorf, Germany [22] Filed: July 26, 1971 [21] Appl. N0.: 166,013

[30] Foreign Application Priority Data July 24, 1970 Germany P 20 36 726.4

[52] US. Cl. 102/23, 102/24 R [51] Int. Cl. F42d 1/00 [58] Field of Search ..l02l2224, 28 R, 28 EB [56] References Cited UNITED STATES PATENTS 2,622,528 12/1952 Lawrence ..102/24R 2,697,399 12/1954 McAdams 102/24 R 3,457,859 6/1969 Guenter........ 102/28 X 1,406,844 2/1922 Gelm 102/24 R Primary Examiner-verlin R. Pendegrass AttorneyCraig, Antonelli & Hill [5 7] 7 ABSTRACT An explosive charge and method for increasing detonative percussion in which the explosive is provided with cavities, gas or fissures which permit the advance ignition of the explosive. Preferably, the explosive is cylindrically shaped with a through-axial core. The bore may include explosive or inert baffles. Also the bore may be provided with a fuzc train of explosives.

14 Claims, 4 Drawing Figures PAIENIEBHEc n ma 3377.662

INVENTORS PAUL LINGENS GERHARD MARTIN 0,14 mm amp ATTORNEYS EFFECT OF THE SHOCK PRESSURE F EXPLOSIVE CHARGES This invention relates to a process for improving the effect of the shock or percussion pressure of explosive charges, which improvement is attained with the aid of a high velocity flow of large energy density in predetermined cavities, fissures or gaps of the explosive charge or with the aid of a fuze train of explosive wires.

It is known that short-time pressure shocks of a high energy resulting from a high concentration of explosive, e.g., in so-called demolition charges, are effective for the destruction of objects. Naturally, the higher the shock pressure the earlier the destruction occurs.

It is proposed that explosive charges be provided with a bore to produce gas currents of a high velocity and intrinsic energy during the detonative reaction therein. In this connection, the velocity of the gas flow can be considerably higher than the detonating velocity of the explosive. When the bore is subdivided by partitions, e.g., of explosive or an inert material, into individual chambers of a specific length, ignitions can occur in advance of the detonating front.

According to German Patent Application P 16 46 348.2, (a counterpart to U.S. Pat. application Ser. No. 780,202, filed Nov. 29, 1968, by Gehard Martin) it is possible to ignite explosive charges by means of fuze trains of explosive wires.

lthas now surprisingly been found that a considerable increase in the shock pressure outside of an explosive charge is obtained if either the gas flow of high velocity and energy density formed in bores and/or gaps is utilized for the advance ignition of a charge, and thus for the accelerated reaction of the explosive of such charges, or the abovementioned fuze train of exploding wires is utilized.

The effect of the pressure shock of an explosive charge ,on the surroundings depends, first of all, on the magnitude of the detonating pressure at the phase interface between the explosive and the surrounding medium. The detonation velocity of the typical charges and thus the detonating pressure are dependent, in the explosive, on the chemical structure and the density of the explosive, rather than on the fact whether an explosive charge is ignited within short intervals of time at several places.

With the use of an explosive cloumn having an axial bore according to the present invention, wherein the latter is subdivided by partitions of explosive into chambers of a specific length, a considerable increase in the shock pressure outside of the column is obtained. As will subsequently become apparent, the same effect can. also be accomplished by the use of the explosive train of exploding wires. The idea of increasing the shock pressure according to this invention can be applied to almost any type of explosive charges in order to obtain advance ignitions and thus an accelerated reaction.

The gas flow of high velocity and energy density required for this purpose can be produced in hollow spaces of any desired cross section (for example, circular, elliptical, square, rectangular, stellular, or portions of these geometric configurations). However, the cross sections can also be asymmetrical or exhibit irregular boundaries. Thecross sections can vary over the length ordepth of the cavities or gaps, respectively, in a continuous or discontinuous manner. For reasons of expediency, an explosive charge can optionally also be provided with several parallel or antiparallel cavities and- [or gaps of equal or unequal cross sections and lengths.

If an explosive column consists of two columns, one inserted in the other, the former being solid and the latter hollow, and if an annular air interspace exists between the two columns, an increased effect of the shock pressure outside of the explosive charge is likewise obtained. The increase in the shock pressure is not limited only to the use of annular gaps in the longitudinal direction of explosive charges for the formation of a gas flow of high velocity and energy. Rather, such a flow is also formed in certain explosives in any type and shape of appropriately dimensioned gaps. Also, such an explosive column can consist of several columns, one inserted in the other, with appropriate interspaces.

The partitions which subdivide the cavities and/or gaps into chambers of specific lengths can consist of the explosive of which the explosive charge is made, or of another explosive, or of an inert material, e.g. metal, synthetic resin, ceramic. The thickness of the partitions can be varied within a wide range. The partitions must be adapted to the chamber lengths and the dimensions of the explosive charge. The fuze trains consist of alternating pieces of a thick wire and a thin wire of the same or different length. upon ignition of the train, the thin wire sections undergo an explosive conversion. The surrounding explosive is detonated. By the aforementioned construction of the train, a simultaneous and uniform initiation of the explosive or of the primer charge is ensured over the entire length of the train. The ignition can take place linearly, annularly, in a surface area, or in spatial extension.

Also, in explosive charges including a central primer, reaction can be accelerated by gas flow in predetermined cavities and/or gaps or by a fuze train of exploding wires.

It is possible for example, to arrange any desired number of bores in a ball of explosive starting at the center thereof, i.e. the ignition point, in the radial direction, in a geometric or any desired distribution. The bores are preferably subdivided by partitions into chambers of the required length. By means of appropri' ate arrangements under the guidelines of the present invention, the effect of the shock pressure can be considerably enhanced in these explosive charges.

An increase in the shock pressure is also obtained in explosive lenses similar to the optical lenses, and in explosive charges of a specific shape for the production of directional shock waves, by the introduction of the aforementioned cavities and/or gaps subdivided into chambers, or by the use of a fuze train of explosive wires. (These charges are produced, for example, by sintering in accordance with German Pat. Application P 16 46 2832., a counterpart of U.S. Pat. application Ser. No. 759,501, filed Sept. 12, 1968, by Adolf Berthmann et al.

All in all, the magnitude of the shock pressure can be influenced with respect to its spatial distribution in explosive charges by the introduction of cavities and/or gaps subdivided into chambers or by the use of a fuze train of exploding wires in specific arrangements and directions.

These and other features and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawing, which shows embodiments in accordance with the present invention, wherein:

FIG. 1 is a cross section of one embodiment of an explosive charge according to the present invention;

FIG. 2 is a cross section of a second embodiment of an explosive charge according to the present invention;

FIG. 3 is a cross section of a further embodiment of an explosive charge according to the present invention; and

FIG. 4 is a perspective view of still another embodiment of an explosive charge according to the present invention.

In FIG. 1 cylindrical explosive charge 1 is shown hav ing bore 3 subdivided into chambers by partitions or baffles 4 which can consist of an explosive or of an inert material. Explosive charge 1 is detonated by means of initiator charge 5.

FIG. 2 shows explosive charge 12 consisting of individual cylindrical bodies 2 separated from one another by fissures or gaps 7. Central bore 3 extends through the entire explosive charge. Hereagain, gaps 7 and/or bore 3 can be subdivided into individual chambers, eg as illustrated in FIG. 1.

In FIG. 3, another arrangement is illustrated wherein primer rod 10, containing fuze train 6 of exploding wires, is introduced into central bore 3. The primer rod can furthermore have a casing 11, e.g. sheet metal, cardboard, or a synthetic resin, which casing is provided for the protection of primer rod 10, for example, for storing the primer rod or for separating the explosive of the primer rod from explosive charge 1 in the event of incompatibility between the explosives. Again explosive charge 1 can be provided with gaps and/or cavities.

In FIG. 4 an explosive charge is illustrated consisting of cylindrical explosive charge 8 around which hollow cylindrical explosive charge 9 is arranged, so that gap 12 remains between both charges. Thus, it is possible in a simple manner to introduce into the explosive charge arrangements with cavities and/or fissures and- /or a fuze train of exploding wires.

The invention will be explained in greater detail below with reference to subsequent examples which provide the shock pressures realized by detonating various explosive charges of the invention. As an indicator for the effects of the shock pressures, pressure gauges with lead diaphragms were utilized. From the bulging of the diaphragms caused by the shock pressures, conclusions can be drawn to the magnitude of the shocks.

Cylindrical explosive columns (such as denoted by numerals 1 or 12 of the drawing) without casing were employed, lest, during the blasting, the pressure gauges and the diaphragms be damaged by the fragments of the casing. Explosive columns having a small amount and a large amount of explosive were selected.

In the first five examples, the explosive columns were composed of six individual cylindrical bodies (like numetal 2 of FIG. 2) with a 10 mm. in diameter bore, e.g. numeral 3 of sintered TNT (density: 1.2 g/cm, detonating velocity: 5,200 m/sec.) with an outer diameter of 30 mm. and a length of 66 mm., combined to a total length of about 400 mm. (Sintered explosive charges can be manufactured in accordance with German Pat. application P 16 46 283.2.) The weight of the explosive was approximately 420 g. Each of the explosive columns was mounted horizontally at a height of 1,000 mm. above ground and ignited from one side by means of a blasting cap No. 8(an 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) under the interposition of a shaped charge (referenced as numeral 5 in the drawing) of penthrite. On the ground, at a distance of 250 mm. transversely and symmetrically with respect to the center of the explosive column, two pressure gauges with lead diaphragms 1 and 2 ofa thickness of 2 mm. were disposed. Employing the same experimental arrangements, with the modifications of the experimental conditions disclosed in the individual examples, the magnitudes of the bulging, arching or convexity of the lead diaphragms set forth below were measured in the pressure gauges.

EXAMPLE 1 The explosive column included a continuous bore without subdivision into chambers. Upon detonation, diaphragm 1 bulged 11.1 mm. and diaphragm 2, 11.2

EXAMPLE 2 EXAMPLE 3 i The bore of the explosive column was subdivided into four chambers of a length of mm. by partitions of a thickness of 18 mm. made of explosive. The result was a 14.7 mm. bulge in diaphragm 1 and a 14.8 mm. bulge in diaphragm 2.

EXAMPLE 4 An explosive column with a subdivision of the bore into five chambers of a length of 60 mm. by partitions of a thickness of 18 mm. made of explosive. The shock wave caused diaphragm l to bulge 14.2 mm. and diaphragm 1, 13.9 mm.

EXAMPLE 5 In this example, an unsubdivided axial bore of the explosive column was filled with an explosive. The column was detonated, in one instance, by means of a blasting cap Alu No. 8 and, in the other instance, by an inserted fuze train of explosive wires. In the first situation diaphragm 1 exhibited a bulge of 11.8 mm. and diaphragm 2, a bulge of 12.1 mm. With the fuze train, diaphragms 1 and 2 had a 15.3 mm. and 15.6 mm. bulge, respectively.

In Examples 6-9, explosive columns having bores (designated by numeral 3) of a size of 10 mm. without casing, with a length of about 1 mm., composed of respectively seven cylindrical bodies (numeral 2) of a diameter of 80 mm. and a length of mm. were fired in the horizontal position 2,000 mm. above ground. The columns consisted of sintered bodies of the explosive TNT (density 1.2 g./cm detonation velocity 5,000 m./sec.) and of TNT microgranules (mixture ratio TNTzmicrogranules 96:4; density 0.96 g./cm detonating velocity 4,500 m./sec.) (See, in this connection, German Pat. application P 16 46 283.2.) On the ground transversely to the center of the explosive columns, pressure gauges with lead diaphragms were disposed at spacings of 2 m. symmetrically with respect to EXAMPLE 6 The explosive column of sintered TNT had a continuous bore without subdivision into chambers an an explosive weight of about 6,000 g. Upon detonation, diaphragm l bulged 14.8 mm. and diaphragm 2, 15.0 mm.

EXAMPLE 7 An explosive column of sintered was employed with subdivision of the bore into ten chambers of a 1 length of 80 mm. by partitions of a thickness of 18 mm., made of explosive; weight of the explosive about 6,000 g. Diaphragms 1 and 2 exhibited bulges of 18.9 mm. and 18.6 mm., respectively.

EXAMPLE 8 The explosive column of sintered TNT microgranules included a continuous bore subdivided into ten chambers of a length of 80 mm. by partitions of a thickness of 18 mm., made of explosive; weight of the explosive about 4,800 g. The detonation wave created an 18.4 mm. bulge in diaphragm l and an 18.3 mm. bulge in diaphragm 2.

It is clearly apparent from the examples that a marked improvement is obtained in the effect of the shock pressure by an accelerated conversion of the explosive charge, caused by a gas flow of a high velocity and energy and/or by a fuze train of explosive wires according to the invention. However, the bulging of the lead diaphragms produced by the pressure evoked by such a dynamic shock does not occur completely proportional to the stress with increasing depth of bulging but is also a function of time. Therefore, the increase in the shock pressure can only be approximated and ranges between 30 and 40 percent.

The present invention is not limited to the details and embodiments shown and described herein but intended to cover any changes and modifications within the scope of the invention.

We claim:

1. An explosive device comprising an explosive charge, and means for improving the shock pressure effect of said explosive charge, said means including an axially extending bore within said explosive charge, and baffle meansof an inert material filling the cross section of the bore at at least one point therealong, said bore being open along those portions thereof not filled by said baffle means.

2.,An explosive device according to claim 1, wherein a plurality of baffle means are provided within said bore, said plurality of baffle means being spaced from one another along said bore.

3.An explosive device according to claim 2, wherein said means further comprises a plurality of cavities, gaps or fissures extending between said axiallyextending bore and an outer surface of said explosive charge.

4.. An explosive device comprising an explosive charge, and means for improving the shock pressure effect of said explosive charge, said means including an axially extending bore within said explosive charge, and a plurality of cavities, gaps or fissures extending between said axially-extending bore and an outer surface of said explosive charge, said bore and said cavities, gaps or fissures being unlined.

5. An explosive device according to claim 4, wherein said means further include baffle means filling the cross section of said bore and spaced from one another along said bore, said bore being open along those portions not filled by said baffle means.

6. An explosive device comprising an explosive charge, and means for improving the shock pressure effect of said explosive charge, said means including an axially-extending bore within said explosive charge,

and ignition means including a fuse train consisting of explosive wires disposed within said bore along the axial extent thereof, said explosive wires consisting of alternate thin and thick portions.

7. An explosive device according to claim 6, further comprising a casing surrounding said fuse train within said bore.

8. A process for improving the shock pressure effect of an explosive charge comprising the steps of forming an axially-extending bore within the explosive charge, disposing a baffle member of an inert material at at least one point along the bore such that the baffle member fills the cross section of the bore, and maintaining the bore along the portions thereof not filled by the baffle member open, whereby upon ignition of the explosive charge an improved shock pressure effect is provided.

9. A process according to claim 8, wherein a plurality of baffle members of inert material are disposed at spaced points within the bore such that each of the baffle members fills the cross section of the bore, the baffle members being spaced from one another along the bore.

10. A process according to claim 8, further comprising the step of forming a plurality of cavities, gaps or fissures extending between the axially-extending bore and an outer surface of the explosive charge.

11. A process according to claim 9, further comprising the step of forming a plurality of cavities, gaps or fissures extending between the axially-extending bore and an outer surface of the explosive charge.

12. A process for improving the shock pressure effect of an explosive charge comprising the steps of forming an axially extending unlined bore within the explosive charge, and forming a plurality of unlined cavities, gaps or fissures extending between the axially-extending bore and an outer surface of the explosive charge whereby upon ignition of the explosive charge an improved shock pressure effect is provided.

13. A process for improving the shock pressure effect of an explosive charge comprising the steps of forming an axially extending bore within the explosive charge and disposing an ignition means in the form of a fuse train consisting of exploding wires having alternate thick and thin portions along the bore whereby upon ignition of the explosive charge by the ignition means an improved shock pressure effect is provided.

14. A process according to claim 13, further comprising the step of providing a casing surrounding the fuse train within the bore.

Claims

1. An explosive device comprising an explosive charge, and means for improving the shock pressure effect of said explosive charge, said means including an axially extending bore within said explosive charge, and baffle means of an inert material filling the cross section of the bore at at least one point therealong, said bore being open along those portions thereof not filled by said baffle means.

2. An explosive device according to claim 1, wherein a plurality of baffle means are provided within said bore, said plurality of baffle means being spaced from one another along said bore.

3. An explosive device according to claim 2, wherein said means further comprises a plurality of cavities, gaps or fissures extending between said axially-extending bore and an outer surface of said explosive charge.

4. An explosive device comprising an explosive charge, and means for improving the shock pressure effect of said explosive charge, said means including an axially extending bore within said explosive charge, and a plurality of cavities, gaps or fissures extending between said axially-extending bore and an outer surface of said explosive charge, said bore and said cavities, gaps or fissures being unlined.

6. An explosive device comprising an explosive charge, and means for improving the shock pressure effect of said explosive charge, said means including an axially-extending bore within said explosive charge, and ignition means including a fuse train consisting of explosive wires disposed within said bore along the axial extent thereof, said explosive wires consisting of alternate thin and thick portions.