US2622528A - Explosive cartridge - Google Patents

Description

Dec. 23, 1952 R. w. LAWRENCE EXPLOSIVE CARTRIDGE 2 SHEETS-SHEET 1 Filed April '7, 1945 FIG-.2

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BY 694MB). Qhm -F ATTORNEY 1952 R. w. LAWRENCE EXPLOSIVE CARTRIDGE 2 Sl-lEETS-SX-IEET 2 Filed April 7, 1945 INVENTUR.

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ATTORNEY Patented Dec. 23, i952 UNITED STATES ATENT OFFICE EXPLOSIVE CARTRIDGE Robert W. Lawrence, Wilmington, Del., assignor to Hercules Powder Company,

Wilmington,

3 Claims.

This invention relates to a new and improved explosive charge and, in particular, to high explosive charges with enhanced detonation velocity.

In the past, explosive charges containing cylindrical and conical cavities in one end have been prepared to produce an intensified action of the explosive. The intensified action resulted from the'concentration of the shock wave and hot gases from the end of the explosive column on a very small area. The intensified action was limited to a small area at the base of the charge.

It is known that the detonation velocity of high explosive depends upon its density and the amount of energy available from its decomposition. The mechanical effects of the explosive upon surrounding materials depend, in part, upon the detonation velocity and energy produced per unit volume. The detonation velocity of an explosive is generally a linear function of the density, and, in most cases, the maximum velocity is obtained at the maximum density. In present explosive charges it is difficult to obtain values approaching crystal density of the explosive.

It is an object of this invention to produce an explosive of high detonation velocity having an increased brisance and shattering power. A further object is the production of an improved explosive for blasting hard rock or for military explosive charges. It is a still further object to produce an explosive with a detonation velocity equivalent to or greater than that achieved at the maximum density of the explosive. Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

These objects are accomplished in accordance with the present invention by the provision of annular space within an explosive cartridge which causes the solid section thereof to be initiated by the shock wave traveling through the annular space rather than by the detonation wave traveling through the solid section.

Preferred embodiments of the invention have been chosen for purposes of illustration and description and are shown in the accompanying drawings forming a part of the specification wherein reference symbols refer to like parts wherever they occur.

Fig. 1 is a longitudinal sectional view of a cartridge having solid sections and an annular section representing one form for the embodiment of the invention,

Fig. 2 is a fragmentary, part-sectional, partelevational view of a cartridge having solid sec tions and an annular section with a priming charge representing another form of this invention.

Fig. 3 is a fragmentary, longitudinal sectional view of a cartridge having a plurality of solid sections and annular sections representing another form of the embodiment of this invention.

Fig. 4 is a fragmentary, longitudinal sectional view of a cartridge having a plurality of solid sections and annular sections with priming charges representing another form of the embodiment of this invention.

Fig. 5 is a fragmentary, longitudinal sectional view of a cartridge having a longitudinal perforation with a plurality of priming charges disposed therein,.thereby forming a plurality of solid sections and annular sections, representing still another form of the embodiment of this invention.

In the drawings, a cartridge 1 of high explosive, having a detonation velocity of at least '5000 in. per sec., is contained in the usual wrapper 2. Cylindrical cavities 3 are positioned as shown, or, in other words, the column is made up of alternating solid sections 4 and annular sections 5.

In Fig. 1, an explosive cartridge I has a conventional wrapper 2 which contains an explosive charge 6. The explosive charge 6 is a high explosive having a sensitivity equivalent to or greater than pentaerythritol tetranitrate, nitrolactose, or nitromannite. A longitudinal, cylindrical cavity 3 is disposed concentrically within the explosive charge 6, thereby forming solid sections and an annular section as represented by 4 and 5, respectively. In detonating a cartridge of this type, the detonation wave travels through the solid explosive as represented by 4 at a speed dependent upon the characteristic of the solid explosive as to kind and density. However, upon reaching the cavity 3 the detonation wave is translated into a shock wave and an accelerated speed is developed throughout the annular section of the explosive as represented by 5. The shock wave in turn initiates the next solid section of explosive and the overall detonation velocity of the explosive cartridge and, accordingly, an explosive column built up of such cartridges is enhanced.

In Fig. 2, an explosive cartridge I has a conventional wrapper 2 which contains an explosive charge I. The explosive charge 1 is a high explosive having a detonation velocity of at least 5000 m. per sec., such as pentaerythritol tetranitrate, vnitrolactose, nitromannite, cyclonite, tetryl, or 40 to straight dynamite. A longitudinal cylindrical cavity 3 is disposed concentrically within the explosive charge I, thereby forming solid sections and an annular section as represented by 4 and 5, respectively. A wafer 8 of priming explosive, such as lead azide, mercury fulminate, diazodinitrophenol and the like, is disposed across the end of the cavity 3 in abutting relationship with the explosive charge I. In detonating a cartridge of this type, or an explosive column built up of such cartridges, the wave traversal is the same as that described for Fig. 1, with the exception that the impact of the shock wave instantly initiates the wafer 8 of priming explosive which in turn initiates the next solid section of explosive. It will be seen that this embodiment of the invention provides for the use of less sensitive explosives, such as cyclonite, tetryl, or 40 to 60% straight dynamite as the explosive charge 1. However, this embodiment may be employed in conjunction with the more sensitive explosives, such as pentaerythritol tetranitrate, nitrolactose or 'nitr'omannite as the explosive charge, particularly when it is desired to utilize long annular sections or thick solid sections, or in any such combination where the shock wave is'liable to be rendered inefiective.

In Fig. 3, an explosive cartridge I has a conventional wrapper 2 which contains an explosive charge 6. The explosive charge 5 is a high explosive such as the high explosive set forth for Fig. l.' A plurality of longitudinal, cylindrical cavities 3 is disposed concentrically within the explosive charge 6, withthe exception of the cavity 3a. This cavity is disposed at one end of the cartridge I to facilitate insertion of a blasting cap therein. A disc 9 of paper or equivalent material is inserted between the explosive charge 6 and the wrapper 2 to assist in confining the explosive charge surrounding the cavity. With this embodiment, a plurality of solid sections and annular sections, as represented by 4 and 5 respectively, is formed and the wave traversed is substantially the same as that described for Fig. -1, with the exception that a plurality of solid sections and annular sections is utilized instead of two solid sections and one annular section as described concerning Fig. 1.

In Fig. 4, an explosive cartridge I has a conventional wrapper 2 which contains an explosive charge'l. The explosive charge I is a high explosive similar to the high explosives set forth for Fig. 2. A plurality of longitudinal, cylindrical cavities 3 is disposed concentrically within the explosive charge 1, thereby forming a, plurality of solid sections and annular sections as represented by 4 and 5, respectively. A plurality of wafers 8 of priming explosive, such as the explosive described in connection with Fig. 2, is disposed in tubular members I0 of paper or equivalent material. Each of the wafers 8 is disposed across the end of its respective tubular member II] in abutting relationship to the explosive charge I. With this embodiment, a plurality of solid sections and annular sections, as represented by 4 and 5, respectively, is formed and the wave traversal is substantially the same as that described for Fig. 2, with the exception that a plurality of solid sections and annular sections is utilized instead of two solid section and one annular section as described concerning Fig. 2.

In Fig. 5, an explosive cartridge I 'has a conventional wrapper 2 which contains an explosive charge I. The explosive charge I is a high explosive such as the high explosive set forth for Fig. 1. A plurality of longitudinal, cylindrical cavities 3 is disposed concentrically within the '4 explosive charge I, with the exception of thecavities 3b and to. each disposed at opposite ends of the cartridge I and either of these cavities may be utilized for insertion of a blasting cap therein. A disc 9 of paper or equivalent material is inserted at each end of the cartridge I in the position and for the equidistant throughout the perforation, thereby forming a plurality of solid and annular sections as represented by 4 and 5, respectively. The wafers 8 are of priming explosive such as the explosive described in connection with Fig. 2. With this embodiment, the shock wave initiates the wafers 8 sequentially and, accordingly, the explosive I in juxtaposition thereto in advance of the detonation wave progressing through a respective portion of the solid explosive, thereby giving an enhanced detonation velocity to the cartridge. 7

The explosive cartridges of the present invention may be prepared in numerous ways. For example, this may be done by placing a solid explosive, such as pentaerythritol tetranitrate, cyclonite, or tetryl, into forms so that part of them are solid cylindrical columns and part of them have coaxial cylindrical cavities running throughout their length. These sections may then be wrapped together, alternating a solid section with an annular section, so that the cartridge contains at least two solid sections and one annular section. It is preferable to have between four and eight sections per cartridge. To prevent crumbling of the explosive charge into the cavity, it is sometimes desirable, depending upon the explosive, to line the annular sections with a thin sheet of material I0, such as paper or cellophane.

Whenan explosive which is not easily shaped into forms, such, as 60% straight, dynamite, is packed, awrapper 2 with the desired outside diameter may be used, and a solid section is tamped in. Then a tubular member ID, such as glassine paper, is inserted into the wrapper. This member may be closed at the top to prevent the explosive from falling into it during the packing operation. The explosive is then tamped into the annular space between .the tubular member and the outer wrapper. This process is repeated until the wrapper is filled and a cartridge of the desired length is obtained. The wrapper is then crimped in the conventional manner to complete the cartridge. The cartridge contains at least two solid sections and one annular section.

The outside diameter of the explosive cartridge may be of any diameter desired but, generally speaking, is in the range of between one inch and eight inches. The length of each of the annular and solid sections may vary from one inch to six or more inches. The annular sections and solid sections may be the same length; however, it is preferable that the annular sections should be relatively long, compared with the solid ones. The diameter of the cavity is dependent upon the diameter of the cartridge and will generally be about 25% of the diameter of the cartridge. In most cases this will be between about one-quarter inch and about one inch in diameter, depending on the diameter of the cartridge.-

The cavities 3b and 3c are This invention is illustrated by the examples shown in the table. In this'table, comparison is made between the detonation velocity observed when normal solid cartridges are used and the :de'tonation velocity observed when the cartridges are made up of alternating solid and annular sections. The detonation velocity was determined by the use of a high-speed rotating drum camera with .a film speed of about 180 meters per second. This is described by R. W. Cairns in Industrial and Engineering Chemistry, 1944, vol. 36, pages '79 to 83. The explosive to-be photographed was-exposed in a vertical column, and its image'was transverse to the long dimension o'f'the photographic-film. The detonation velocity is determined from the slope of the image.

In each of the cartridges of the examples given in the table, the section at the priming end was solid. Electric blasting caps were used in Examples 1 and 2. In Example 3, a pentaerythritol tetranitrate fuse was used, and the base of the cartridge was filled to a height of three-quarter inch with loose pentaerythritol tetranitrate. In Example 4, a pentaerythritol tetranitrate cap weighing 1.6 grams was used.

TABLE "forms than that of a wafer, for example, in the form of a pellet or the like disposed within a solid section and adjacent a cavity.

It will be seen, therefore, that this invention may be carried out by the use of various modifications and changes without departing from its spirit and scope.

When a wafer of priming charge is present, it is necessary to detonate the cartridge in such a manner that the shock wave will travel through the cavity and strike the wafer. Therefore, cartridges of the type illustrated in Fig. 2 and Fig. 4 should be marked to indicate the direction in which the cartridges should be detonated. It is, of course, unnecessary to mark cartridges of the type illustrated in Fig. 5 due to symmetry of the solid and annular sections.

The advantage of the invention lies in the increased detonation velocity giving rise to an increase in brisance and chattering power. This is important in blasting hard rock, and in military explosive charges. By use of this invention, it is possible to achieve a detonation velocity equivalent to that of the maximum. density of Comparison of the detonation velocities of solid cartridges and cartridges made up of solid and annular sections of explosive Cartridge D gy 1011 Example Explosive 2321?" Arrangement Length Diauk 237132 eter Y inches inches ILL/sec.

1 Pentaerythritol tetranitrate 0. 95 S01id. 1 1% 5, 300 pentaerythritol temnitmte ,95 Alternating 2 1n. soll col s a 2 5, 670

lainiiular columns with in. diameter 0 es. Pent-aerythritol tetranitrate80%, 1- 12 Solid 1% 6, 100 2 nitroglyccrin-%.

Pentaerythritol tetranitrate-80%, 1. l2 Alternating 2 in. solid columns and 2 in. 11% 1% 6, 450

nitroglycerin20%. annular columns with 111. die. holes. 3 {Pentaerythritol tetranitrate 1-11 Solid-". 7% 1% 5, 800 Pentaerythritol tetranitrate.. 1.11 Alternating 2 msohd columns and 5% 17% 1 7,200

in. annular columns with A in. holes. Solid columns. except the first, primed with lead azide. 4 dynamite 1. 4 S0 H 5, 400 60% 4 Alternating 2 in. solid columns and 5% ,72

inch annular columns with in. holes. Solid columns, except the first, primed with diazodinitrophenol.

It is noted from the examples, that the detonation velocities of cartridges of this invention are considerably greater than the detonation velocities of corresponding solid cartridges. If a priming charge is included at the base of the solid sections the detonation velocity is enhanced still further. With explosives much less sensitive than pentaerythritol tetranitrate, the addition of a priming charge is essential. It is preferable to have the priming charge in the form of a wafer having a diameter substantially the same as its adjacent cavity and having a minimum thickness depending upon the particular priming explosive utilized. For example, in a 1%" diameter cartridge, a priming explosive such as lead azide would have a minimum thickness in the order of 3 mm., while a priming explosive such as diazodinitrophenol or mercury fulminate would have a minimum thickness in the order of 6 mm. No useful purpose is served by increasing the thickness of the wafer and, accordingly the weight of priming explosive, a substantial amount above the minimum required, although such thick priming charges function entirely satisfactory. The priming explosive may be utilized in other the explosive or even greater than that achieved at the maximum density of the explosive.

By the term priming charge in the claims is meant an easily detonated explosive, such as r pentaerythritol tetranitrate, nitrolactose, nitromannite, lead azide, diazodinitrophenol, mercury fulminate and the like.

What I claim and desire to protect by Letters Patent is:

1. An explosive cartridge of enhanced detonation velocity comprising a charge of detonative high explosive having a detonation velocity of at least 5000* meters per second and having spaced longitudinally thereof a plurality of spaced, concentric, longitudinally extending cavities to form alternate solid and annular sections, each said cavity being radially surrounded and longitudinally separated by said detonative high explosive, and each said cavity having a diameter of about 25% of the diameter of the cartridge.

2. An explosive cartridge in accordance with claim 1 in which the main explosive charge is pentaerythritol tetranitrate.

3. An explosive cartridge in accordance with 7 claim 1 in which the main explosive charge consists of between 40% and 60% straight dynamite and in which water charges of priming explosive are interposed between the cavities.

Number Number Name Date Maxim Jan. 14, 1896 Weber Jan. 12, 1932 Karollus Sept. 18, 1934 Young Aug. 29, 1939 Huber May 29, 1945 Seavey May 6, 1947 Lawrence Aug. 21, 1951 FOREIGN PATENTS Country Date Great Britain Apr. 2, 1898 Great Britain Dec. 13, 1911 France May 12, 1922 Germany Jan. 29, 1927

Claims (1)

1. AN EXPLOSIVE CARTRIDGE OF ENHANCED DETONATION VELOCITY COMPRISING A CHARGE OF DETONATIVE HIGH EXPLOSIVE HAVING A DETONATION VELOCITY OF AT LEAST 5000 METERS PER SECOND AND HAVING SPACED LONGITUDINALLY THEREOF A PLURALITY OF SPACED, CONCENTRIC, LONGITUDINALLY EXTENDING CAVITIES TO FORM ALTERNATE SOLID AND ANNULAR SECTIONS, EACH SAID CAVITY BEING RADIALLY SURROUNDED AND LONGITUDINALLY SEPARATED BY SAID DETONATIVE DIAMETER EXPLOSOVE, AND EACH CAVITY HAVING A DIAMETER OF ABOUT 25% OF THE DIAMETER OF THE CARTRIDGE.

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