US2448658A - Method for making explosive assemblies - Google Patents

Description

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Claude H Corey INVENTOR,

Sepo E948. C, H, CAREY 2,448,65

METHOD FOR MAKING EXPLOSIVE ASSEMBLIES I Filed March 2, 1946 2 Sheets-Sheet 2 I la INVENTOR.

Cioude H. Corey Iliff Fig. 5

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Patented Sept. 7, 1948 METHOD FOR MAKING EXPLOSIVE ASSEMBLIES Claude H. Carey, Rush Township, Schuylkill County, Pa., assignor to Atlas Powder Company, Wilmington, Del., a corporation of Dela- Ware Application March Z, 1946, Serial No. 651,563

3 Claims.

The present invention relates to the manufacture of explosive assemblies.

An object of the invention is the provision of a method for the manufacture of cast explosive assemblies.

Another object of the invention is the provision of a method for the manufacture of cast explosive assemblies with reduced cavitation.

A further object of the invention is the provision of a method for the rapid manufacture of cast explosive assemblies.

Other objects of the invention will be apparent from the following description and from the drawings.

Explosive assemblies have been made by pouring melted explosive into shells and then cooling to solidify the explosive. Simple pouring operations have, however, resulted in much undesired cavitation as the cast explosive shrinks on cooling. Since the melted explosive cools and solidies gradually from the outside walls of the shell toward the center, the molten material in the center drops down, leaving a funnel shaped cavity in the upper interior portion of the explosive charge. Also, as local pockets of explosive cool independently, cavities often appear dispersed through the mass and particularly around any objects contained within the casting, such as pellets of primer charge, detonator wells, and so forth.

Cavitation is not only undesirable because it results in incompletely lled shells but also, for one reason, because it is very apt to hinder propagation of detonation in the explosive.

It has been attempted in the past to overcome cavitation by filling shells in a series of steps with a stirring or puddling operation between each step. This method improves cavitation conditions, but it is exceedingly cumbersome and timeconsuming and unless carried out with great care will lnot adequately prevent undesirable cavitation. y

The present invention provides a rapid and convenient method by which shells are lled with reduced resultant cavitation.

According to the present invention, a number of shells provided with exit and entrance ports are arranged in an upstanding communicating series. The series is then filled with melted exvplosive and the series is cooled until the explosive contained in it has solidified. As the cooling/explosive shrinks, melter explosive under a head from the upper members of the series ows down lling cavities as they are formed, and it is usually found that all the cavitation has taken 2 place in the upper member. The upper member of the series which has absorbed the shrinkage and, consequently, is not completely filled with explosive may then be used as the lower member in a subsequent series which is prepared and filled.

The invention will be particularly described in connectionl with the drawings which illustrate a number of constructions which may be used in speciiic embodiments of the invention and in which:

Figure 1 is a. longitudinal sectional view of a completed assembly lled according to the method of the present invention;

Figure 2 is a longitudinal view of the juncture between two shells of the type shown in Figure 1 which are ready for lling with explosive;

Figure 3 is a top view of the end member of the shells shown in Figure 2;

Figure 4 is a longitudinal sectional view of a modied form of juncture of the type shown in Figure 2;

Figure 5 is apartial longitudinal sectional view of the end portion of another modied shell which has been filled in accordance with the invention.

Figure 6 is a longitudinal, sectional view of a sleeve member adapted to link together two shells of the type shown in Figure 5.v

Figure 'I is a partial longitudinall sectional view of two completed assemblies of the type shown in Figure 6 and joined together for use; and

Figure 8 represents a simplified embodiment of the invention and is a longitudinal sectional view of the juncture between two shells ready for filling with explosive.

Referring to Figure 1 of the drawing, I I is an y elongated tubular shell circular in cross section; -I2 and I2' are cartridges containing booster explosive I4 and I4'; I6 and I6' are detonator wells leading into booster explosive I4 and I4; I8 and I8 are end members which will be described more fully below; 20 and 20' are end caps over the ends of the assembly; and 22 isv the cast charge of melted explosive.

While any normally solid meltable explosive may be used in assemblies prepared according to the process of the present invention, it will usually be preferable to use such materials as TNT, amatols, pentolities, tetrytols, TNT and cyclonite mixtures, picric acid, and the like.

The inclusion of booster charges in explosive assemblies made according to the present invention usually depends upon whether or not the main explosive charge is suiiiclently sensitive to take initiation from the initiatingv means employed, such as a detonator or a primer cartridge,-

and to propagate the detonation through the shell, and from shell to shell where the shells are employed in a series. When TNT is used as the explosive charge. it' is usually found preferable to use an internal booster charge as shown in Figure 1. While it is not necessary to employ booster charges in both ends of the shells as shown in Figure 1, this construction is often most convenient since when a booster charge is contained in both ends of a long assembly, theassembly may be initiated at either end; and, also, care does not have to be taken to provide that an end containing a primer charge is located near the point of juncture where one assembly connects with a preceding assembly of a. series as is otherwise sometimes important.

Any convenient sensitive materials may be used for booster charges. Pressed pentaerythritol tetranitrate, tetryl, and cyclonite are highly effective booster materials as are combinations of these with low melting explosives such as TNT and/or with plasticizing materials.

Assemblies of the type shown in Figure 1 may be prepared according to the present invention by pouring the charge into an upstanding endto-end series of shells. Usually from about two to about six shells make a convenient series length. The bottom shell ofthe series is closedl off; the connections between the shells are made tight against leakage; and the column is filled from the top with molten exposive. The whole column may then be permitted to cool, broken apart at the points of shell juncture after solidication, and individual assemblies capped if desired. Practically the entire amount of cavltation will be found to have taken place in the upper shell or so. Then, any unfilled shells may be used as bottom shells in a subsequent series so that they then become completely filled.

Figure 2 shows a construction which may be used for the juncture point of two assemblies in a series so as to permit retention of molten explosive and positioning of the elements of the assembly. Lower shell Il is provided with end portion I8 constructed as shown in Figure 3. It will be noted from that figure that end portion I8 is provided with passages 2B and 28 on either side of a, central hole 30. Referring again to Figure 2, through central hole 30 of endmember I8 extends, in close lit, tubular detonator well former 32 in the form of a tube provided with flanges which rest on end member I8. Detonator well former 32 is inserted, again in close t, into booster shell I2, containing booster eX- lplosive i4. Upper shell IIa is provided, similarly to shell II, with end portion I8a, detonator Well former 32a, booster shell I2a, and booster explosive I4la. Between end portions I8 and I8a lies spacer member 34. Spacer member 34 is provided with passages similar to those in end members I8 and Ia (26 and 28) and also with large central hole 36 into which t the flange portions of detonator well formers 32 and 32a. Spacer 34 serves 'the function of providing a gasket between end members I8 and I8a and leaves room for the anges on detonator well formers 32 and 32a.

The shells are aligned with the passages through the end pieces I8 and I 8a and spacer 34 in registry as shown in Figure 2, and a sleeve 24 is then placed over the juncture point. After the column has been filled and permitted to C001,

sleeve member 24 is slipped of! the juncture point, and the shells are broken apart at the juncture point. Any unevenness in the solidified explosive at the point of breakage is smoothed o, detonator well former 821s pulled out, spacer 84 is removed, and cap members corresponding to cap members 28 and 20 of Figure l are placed over the ends of cartridges. If it is desired to protect detonator wells I8 and I8' an easily frangible member may be placed over them or the cap members may be -made to cover the entire end of the shell and to be themselves easily frangible.

Figure 4 shows a modified construction in accordance with which spacer 84 of Figure 2 is eliminated. As shown in Figure 4, end members I 8 and I8a.,` are made somewhat dished away from one another in the center so as to provide space for the iiange members of detonator weil formers 32 and 82a. Elsewhere on their surfaces end members I8 and I8a directly abut, providing a tight joint between them.

Figure 5 shows a further modification of the invention. According to this modification, end portion I8 is made in the form `of an externally threaded tube, the threaded portion of which extends above shell II. Otherwise, end portion I8 is similar to that shown in Figure 2.

Figure 6 shows an internally threaded sleeve 34 which screws onto the threads on member I8. Sleeve 34 may be used to connect together two shells prior to pouring and also after pouring when in use.

Figure 7 shows two filled cartridges of the type of Figure 5 connected together by the sleeve shown in Figure 6 preparatory to use in a bore hole.

The simplified modication shown in Figure 8 is constructed in somewhat the same form as the embodiment shown in Figure 2. The arrangement shown here, however, provides but one booster charge per cartridge. For this reason, but one end portion I8 is needed. As shown in Figure8, end portion I8 is located inside sleeve 24 and between the ends of shells I I and IIa. To prevent the filling of hollow well former 32 cap 33 is provided.

The shells of the present invention may' be .made of any convenientl materials, though heavy paper is usually to be preferred for the sake of convenience.

For best results the end pieces and any spacer -pieces through which molten explosive is to pass should be made of materials which are poor conductors of heat. Such materials as pressed cardboard, wood, and plastic compositions are useful in this connection. It is found when conductive materials such as metals are used they sometimes tend to conduct heat too rapidly and the explosive material solidifies blocking the passages between shells before they have been properly filled. Also to prevent clogging, the passages through end pieces and spacers which separate the shell should preferably -be made as large as possible. Many variants of the form ofpassage shown in Figure 3 of the drawing are possible, however.

Sleeve members are also preferably made of insulating materials, and it is generally desirable that they be suiiiciently long to cover the shell surfaces adjacent booster charges, in order that they may be of assistance in preventing premature solidification of the explosive in the relatively narrow passages through the assembly where the boosters are located.

Detonator well formers are usually preferably made of metal or other strong material so that they will be suficiently rugged to permit easy extraction after the explosive is solidified.

It will be apparent that according to the present invention a novel and useful manner of manufacturing explosive assemblies is provided which fullls the objects stated above, and it will furthermore be apparent that the speclc embodiments shown. represent only a few of the multitude of modes in which the invention can be performed.

What is claimed is:

1. A process for the manufacture of explosive assemblies which comprises arranging, in an upstanding communicating series, shells having exit and entrance ports, pouring melted explosive into said series, then, after cooling said series until said explosive solidifles, separating a shell not illled with solidified explosive from said series, placing said unfilled shell at the bottom of a subsequent series, and repeating the process.

2. A process for the manufacture of explosive assemblies which comprises placing a plurality of elongated shells having open end walls in endto-end upstanding columnar relation, pouring melted explosive into the column, then, after cooling said column until said explosive solidies therein, separating a shell not iilled with solidiied explosive from the column,vplacing said 11nfilled shell at the bottom of a subsequent series, and repeating the process.

3. A process for the manufacture of explosive assemblies which comprises arranging in upstanding, columnar, communicating relation shells having side walls, end walls provided` with openings, detonator well formers in at least one of said end walls in each shell, and booster explosive assemblies over said detonator well formers, pouring melted explosive into the top of said series, then, after cooling said series until said explosive solidifles. separating a shell not filled with solidied explosive from said column, placing said unlled shell at the bottom of another vertical columnar series of shells, and repeating the process.

CLAUDE H. CAREY.

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