US3064573A - Blasting assembly - Google Patents

Description

Nov. 20, 1962 D. R. BLAIR. JR, ETAL BLASTING ASSEMBLY Filed July 15', 1956 lOa I III ll 2 Sheets-Sheet 1 DAVID R. BLAIR JR.

HOMER W. COLEMAN JOHN RJ'RYAN 'lNVEN-TORS BY M @16 AGENT Nov. 20, 1962 D. R. BLAIR, JR., ETAL 3,064,573

' BLASTING ASSEMBLY Filed July 13, 1956 2 Sheets-Sheet 2 DAVID R. BLAIR JR HOMER W COLEMAN JOHN R. RYAN INVENTOR.

AGENT 3,%4,573 Patented Nov. 20,, 1962,

3,064,573 BLASTING ASSEMBLY David R. Blair, J12, Homer W. Coleman, and John R. Ryan, Wilmington, Del, assignors to Hercules Powder Company, Wilmington, Del., a corporation of Delaware Filed July 13, 1956, Ser. No. 597,678 12 Claims. (Cl. 102-44) This invention relates to new blasting assemblies. In one aspect this invention relates to new booster units. In one aspect this invention relates to watertight primer units for use in an explosive column, particularly as applied to explosives of the nitrocarbonitrate type. In another aspect this invention relates to watertight metal primer cans containing means for supporting an initiator outside the can in indirect detonating contact with a solid unitary booster body fastened inside the can to the initiator support, the said initiator being protected from damage often incurred during operation in a borehole. In another aspect this invention relates to a new blasting method. In still another aspect this invention relates to an improved method for loading a primer can.

The use of an initiator or detonator in conjunction with a booster charge to detonate a relatively insensitive main explosive charge, i.e., insensitive to commercial lasting caps, has been practiced in the art for some time. Dynamites and nitrocarbonitrate compositions have been those relatively insensitive charges generally employed, a nitrocarbonitrate comprising mainly ammonium nitrate and come carbonaceous material with or without additional sensitizer.

In view of the hygroscopic nature of amomnium nitrate, it is important that it be kept dry at all times for use as an explosive. The art has therefore used watertight metal containers for such compositions. Various means have been employed for detonating such cap-insensitive charges. Often a column of such containers is employed in which is disposed one or more primer cans at predetermined points to eifect the necessary detonation. contains a main cap-insensitive charge with a booster charge in propagating relationship therewith and an initiator or detonator in detonating relationship with the booster.

In accordance with one practice an elongated metal booster can assembly comprises a layer of main charge, a layer of booster charge superposed on the initially disposed layer and a top layer of main charge on the layer of booster or primer charge, and a detonating fuse led along the length and outside of the can and held against the can wall in detonating relationship with the layer of booster or primer charge in the can. Other primer cans of similar design have been employed. For example, a metal plate with protruding portions forming channels with the can has been utilized to hold a detonating fuse against the outside of the can. In all instances, the booster charge has been disposed as a layer and has been unduly voluminous in order to fill the requisite space for its support in the can. There has always been the potential danger of the layer settling out of detonating relationship with the detonating fuse with concomitant failure. Further, the packing of the booster or priming charge in the primer can has always involved an interruption of the packing procedure requiring thereby a separate step in the packing operation.

Primer can assemblies of the prior art in which the detonator element is held against the can side wall have been disadvantageous from the standpoint of utilization in a borehole inasmuch as the borehole diameter is only slightly greater than that of the can with the result that any assembly structure on the outside of the can wall is The primer canv very likely to become lodged in the irregular borehole wall surfaces to hang up" the assembly, so as to preclude contact with the remainder of the blast hole charge and impair blasting operations. In some instances the primer can. containing the detonator on its outer wall as a unit of an explosive column has been made of a diameter smaller than that of the other can units in an effort to reduce the likelihood of a hang up of the can in the borehole. Even in such instances the problem of hang up of the assembly in the borehole has not been eliminated inasmuch as the detonator support assembly still protrudes from the outer wall of the can.

This invention is concerned with a primer can assembly adaptable as a unit of an explosive column in a borehole which utilizes a much smaller volume of booster charge than heretofore with use of a concomitantly larger amount of main charge, and with such an assembly which supports the detonator device in a manner that it does not protrude from the borehole walls and is protected therefrom, whereby hang up in the hole due to the posi'-- tion of the detonator support means is substantially eliminated and the primer can assembly of an explosive column need not be limited to one of diameter smaller than that of other can units joined therewith. The invention is further concerned with a method for packing primer cans wherein .the packing is accomplished in a single operation uninterrupted by steps ordinarily required for packing the booster charge.

An object of this invention is to provide a new primer can assembly. Another object is to provide for use of a markedly reduced volume of a booster charge in a primer can assembly with a concomitant increase in the amount of main charge available. Another object is to provide a primer can assembly for use as a unit in a cap-insensitive explosive column. Another object is to provide improved booster units. Another object is to provide an explosive column containing such a primer can as a unit. Another object is to provide a primer can assembly adapted to support a smaller volume of booster charge than used heretofore in a primer can in fastened indirect contact and detonating relationship with an initia- .tor, an to support the said initiator protected from damagev often incurred when operated in a borehole. Another object is to provide a method for manufacture of primer can assemblies. Still another object is to provide for a blasting method. Other objects and aspects will be apparent in light of the accompanying disclosure and the appended claims.

In accordance with this invention a blasting assembly is provided which comprises a closed metal container; means for supporting a detonator device in indirect contact with the interior of the container so as to be in detonating relationship with a booster charge therein, said booster charge being a solid unitary body and fastened in contact with the said detonator support means so as to be adapted to said detonating relation, and a main explosive charge in said container positioned in propagating relationship with said booster charge. Also in accordance with this invention is provided a booster device comprising an explosive composition detonatable by a commercial blasting cap disposed as a unitary solid body, and means associated with said body adapted to fasten said body in indirect contact and detonating relationship with an initiator. Further in accordance with this invention is provided a blasting method employing a blasting assembly such as above described. Still in accordance with this invention is provided an improvement in the manufacture of primer can assemblies wherein packing of the main. charge is uninterrupted, which comprises fastening a unitary mass of a booster charge to an inner side wall of the said can, the said booster having an over-all dimension less than that of the diameter of the primer can, and then initiating packing of the main charge and continuing said packing until said can is completely charged.

Our invention is illustrated with reference to the drawings of which FIG. 1 shows a now preferred form of our primer can assembly, alone and as a primer unit of an explosive column; FIG. 2 shows a plan view of a solid unitary booster charge that can be used in the said assembly of FIG. 1; FIGS. 3-7 illustrate another embodiment of primer can assembly and various aspects thereof; FIG. 8 illustrates a wedged fit of booster to detonator support that can be utilized in the assembly of FIGS. 3-7; FIG. 9, in perspective, further illustrates a rolled end portion 31 of FIGS. 5 and 6; FIG. 10 is a plan view further illustrative of the wedge fit of booster and detonator support of FIG. 8 and illustrates an eccentric fixed position of booster to the primer can wall when supported in detonating relation with a detonator device; FIG. 11 illustrates use of an electric blasting cap in lieu of a detonating fuse in an assembly of this invention; and FIGS. 12 and 13 illustrate still another embodiment of our primer can assembly and various aspects thereof.

With reference to FIG. 1, container 10' is preferably elongated, cylindrical and watertight and contains a main explosive charge 11 such as a dynamite or a cap-insensitive ammonium nitrate, i.e., a nitrocarbonitrate. Conduit 12 is disposed in container 10 and of sufiicient size to contain a detonator device, generally a detonating fuse 13, and connects with points outside container 10 through the side wall 14. Preferably the ends of conduit 12 are sealed at openings 16 and 17 in a side Wall of container 10 in sealed relation therewith so as to maintain container 10 watertight as at points 18 and 19. Sealing of tube 12 in the side Wall can be carried out in any suitable manner. Thus, openings 16 and 17 can be indentations as shown terminating in ends of appropriate size for accepting tube 12 in snug fit for sealing.

Booster 22 is a solid unitary mass of any suitable booster composition such as a polymeric material containing a suitable crystalline explosive dispersed therethrough. Such an explosive material is disclosed and claimed in the copending application of Alpheus M. Ball, Serial No. 538,788, filed October 5, 1955, and now abandoned. Booster 22 is shaped so that it can be inserted in container 10 in direct fixed contact with conduit 12 such as concentrically, as illustrated. Booster 22 can be a bare plastic mass or it can be packaged in a suitable wrapper, in any event, being disposed as a unitary solid body adapted to be aflixed to conduit 12.

FIG. 1 also illustrates the primer assembly of our invention as a primer unit of an explosive column in a borehole 9 containing unprimed explosive cartridges 10a, generally of the nitrocarbonitrate type. As illustrated in FIG. 1, the detonating fuse 13 is supported within the conduit 12 with booster 22 also fixed in its position rela-' tive to conduit 12, the detonating fuse being thereby in secured detonating relationship with the booster so that hang-up of the fuse on the wall of borehole 9, with concomitant removal of the fuse from detonating relationship with the booster, cannot take place.

As illustrated with reference to FIG. 2, booster 22 in a preferred form as applied in the assembly of FIG. 1 is an elongated block 22a with a groove 22b extending longitudinally therethrough and having a depth to permit substantially concentric positioning of unit 22 on tube 12. Groove 2212 is dimensioned to permit a snug fit of unit 22 on tube 12.

Conduit 12 can be disposed through container 10 in any suitable manner, it being important in any event that unit 22 be at all times in fastened contact with conduit 12. Conduit 12 can extend across container 10 transversely or angularly as desired, it being important only that it extend through at least a portion of the said container in direct communication with points outside the said container and that it form a seal with the container side walls to render the container watertight. If desired, one or more of the ends of conduit 12 can be extended beyond the side wall of container 10 although that is generally not preferred in view of difiiculty that would generally be encountered in the borehole with such projecting portions.

Initiator 13 is ordinarily a detonating cord, for example, Primacord, and extends from the outside of container 10 into and through conduit 12 and then to the outside of container 10. Any suitable means for supporting cord 13 in conduit 12 can be employed as, for example, a knot formed in the cord at a point below the end of conduit 12 below point 18 so that cord 13 will not be pulled out of conduit 12; or one end of conduit 12 can be flared and the tail end of the detonating cord forced into it, causing sufficient obstruction and making it impossible for detonating cord to be pulled through the conduit.

When a blasting cap is employed in place of a detonating fuse 13, unit 22 is positioned on conduit 12 substantially opposite the said cap to assure detonation. Booster 22 is always disposed in container 10 in propagating relationship with main charge 12 and generally being substantially surrounded by the main charge except for the portion that may be in direct contact with the inner wall 14.

With reference to FIG. 3, side wall 14 of a can 10' is drawn to form a passageway or indent 12' and a recess 23, the latter to accept a plate 24 (FIG. 6) positioned flush with the outer surface of the side wall 14 to form conduit 12a for accepting a detonator such as detonator 13 of FIG. 1. Recess 23 is shown in more detail with reference to FIG. 4. Draw or recess 23 and indent 12 can be made in a single step. Conduit 12a formed by indent 12 and plate 24, the latter disposed in recess 23, is shown with reference to FIGS. 5 and 6. Indent 12 is shaped along its side within container 10 to form a supporting surface for booster 22, in container 10, to firmly support booster 22 in fastened relation therewith. Thus, in one form, the innermost side of indent 12 in container 10 is progressively increased in width along its length 27 to form wedge 28 of FIG. 5, 6 or 8 on which booster charge 22 (FIG. 7), wedge shaped to conform to fit the indent 12 inner surface, can be supported. FIG. 8 is further illustrative of the wedge shape support of booster 22, in container 10, on indent 12. Conduit 12a together with the wedge-shaped surface of indent 12', from which it is formed and which supports booster 22 along groove 220, is shown in side view in FIG. 6.

Conduit or tunnel 12a formed by plate 24 and indent 12 is of sufficient size as to accept a detonator, generally a detonating fuse such as fuse 13 of FIG. 1, although a blasting cap 13a can be supported therein, if desired, as shown in FIG. 11.

With reference to FIG. 10, booster 22 is fastened to the wall portion of conduit 12a in container 10' by support by way of wedge-shaped groove 22c (FIG. 7) against the inner wedged surface of conduit 12a, i.e., the innermost side of indent 12' in container 10. Plate 24 is rolled back along a portion of its terminal edge, as also shown with reference to FIGS. 6 and 9, to provide a smooth surface 31 over which the detonating fuse can move into and out of conduit 12a without danger of being cut or damaged in any way.

With reference to FIGS. 12 and 13, metal container 10a, closed and cylindrical, contains indentation 12b the: same as indent 12 of FIG. 3. Plate 14b is fastened to the outside of container 10a, of a dimension less than the length of indent 12b, and placed over indent 12b to form conduit 12'a of size and shape to contain a detonating element, such as conduit 12a of FIGS. 5 or 11..

Plate 141) is generally fastened to container 10a by weld Indentation 12b is shaped along its side Wall, in direct communication with the interior of container a, so as to support a booster unit such as unit 22 of FIG. 7, for example, as illustrated with reference to FIG. 8 showing booster 22 supported on wedge shape element 12'.

The assembly of FIG. 12 is further illustrated with reference to FIG. 13 in which T-shaped metal sheet 24 contains members 140 and 14b and indent 12b. Sheet 24' can be rolled to form container 10a with indent 121) on its outside surface as shown with reference to FIG. 12. Preferably, the roll is made so that the edge C-C abuts edge A and a weld can be made along the resulting line of abutment C-C of FIG. 12 including that portion under member 14b, to render the container 10a watertight. Member 14b, covering a portion of indentation 12b, is then welded to the outer surface of container 19a along the line bb. In lieu of an abutting relationship to form line C-C of FIG. 12, any desired amount of overlap can be employed, with a weld along the line of contact of either edge CC or AA, or both, with metal container Etta and with additional weld when necessary to render container 14in watertight.

Indent 12b of FIG. 13 is dished in the appropriate direction to face from container 16a, depending on the direction of roll of sheet 24'.

Any suitable booster composition can be employed so long as it can be fastened as a unitary body to the detonator support means. Exemplary of suitable boosters are tetryl, pentaerythrite tetranitrate, picric acid and the like. These materials are generally packaged in a suitable wrapper for fastening to the detonator support element.

Preferred booster compositions are those produced by the formation of the polymerization product of a uniform mixture of polymerizable vinyl material through which is dispersed a nonaromatic explosive material selected from the group consisting of azides, organic nitrates and organic nitramines. Such vinyl-type polymerizable materials are exemplified by the acrylics such as methyl, ethyl and butyl acryl-ate or methacrylate; styrene, styrene-polyesters, acrylonitrile, diallyl phthalate and the like. The acrylics and the styrene-polyesters are preferred. Exemplary nonaro-matic explosive components we ethylene dinitramine, methylene dinitramine, cyclotrimethylenetrinitramine, diethanolnitramine dini'trate, pentaerythritol tetranitrate, lead azide, silver azide, nitrolactose, succrose octanitrate, manni-tol hexanitrate. Nitrocellulose in fibrous or filament form or in solution may also be employed. When it it is desired to incorporate a liquid explosive in the composition, nitroglycerin or other liquid nitric ester may be employed. These compositions are set forth in application Serial No. 538,788, above referred to. Our preferred booster charge is a polymerization product of the type described above containing pentaerythritol tetranitrate as the dispersed explosive component, polybutylmethacrylate-PETN being now preferred.

The size of the booster body is small as compared with the interior of the metal container as is clear from the foregoing, being in any event sufiiciently small that when fastened in detonating relation with the initiator, it cannot seriously obstruct flow of main charge into the container during the packing operation. Booster bodies of this invention, by way of example, are often say from M2 by 2 inches up to about 2 /2 by 4 inches.

Although We have illustrated a conduit or tunnel as our preferred detonator support means, any suitable sup port means can be employed, it being preferred that the entire support means does not extend from the outer wall of the metal can to thereby obstruct handling of the can in a borehole. Thus, a draw can be made in the wall of the metal can and the detonating fuse can be supported therein in indirect contact with the booster by brackets. An electric blasting cap can be similarly lactose octanitrate and 6 supported in detonating relationship with the booster.

An important feature of the invention is the single step packing operation that can be employed in loading the blasting assembly. In loading the prior art devices, the packing step must be interrupted to permit loading the booster layer, and then be resumed to complete the charge. Thus, it is in accordance with this invention only necessary that the unitary booster body he fastened to the support means in the uncharged can prior to packing the main charge, after which packing is initiated and continued until the container is completely charged. This improvement is of major importance, particularly with reference to assembly line packing where considerable time has been consumed in the past in terminating the packing operation, moving the container to a position for packing a layer of booster charge in position for detonation by the initiator, packing the booster charge, and then moving the container from the booster charging step to a position for completing charge of the main explosive. Thus, in accordance with our invention, we can pack the container with one composition rather than using various increments in the cans such as is necessary in packing the primer cans of the prior art.

The metal container is of any suitable size, say from 3 inches to 11 inches in diameter and of a length in the order of from about 10 to 24 inches. Metal containers of size outside these ranges can, of course, be em ployed.

Although any cap-insensitive main explosive charge is preferably employed in the practice of this invention, the invention is not limited thereby, as any type of main explosive charge can be employed as desired.

Nitrocarbonitrate explosive compositions which constitute our new preferred main charge are sufiiciently insensitive so that they will consistently fail, when unconfined, to prop-agate when initiated by the strongest commercial detonator in general use, namely, a No. 8 cap. The composition, furthermore, will fail to detonate With several No. 8 blasting caps fired simultaneously or with from 0.540 grams TNT primed with a single blasting cap. Thus, the sensitivity of the composition is far below that necessary to detonate consistently with a single commercial blast-ing cap of maximum strength.

The No. 8 blasting cap is defined as one containing the standard charge of 2 grams of mercury fulrninate or fulminate composition and the No. 6 cap is defined as one containing 1 gram of mercury fulminate or fulminate composition, both as set forth in Bulletin No. 39 of the US. Bureau of Mines.

The nitrocarbonitrate is not, however, less sensitive than a uniform composition comprising 94.5 percent ammonium nitrate and 5.5 percent paraffin, providing the ammonium nitrate has a certain fineness and the finished explosive has a density not exceeding 1.15.

Sensitivity of nitrocarbonitrate explosives can be regulated by utilizing a more efficient sensitizer such as a nitroaromatic compound or mixture thereof, preferably one or more of the nitrotoluenes. Preferably, a fuel is utilized with the nitrocompound which iscapable of utilizing the excess oxygen of the ammonium nitrate with generation of heat. Hydrocarbons of the olefin, paraflin or aromatic series, parafiin, and carbon as coal, are advantageously employed, although many other suitable carbonaceous materials have been utilized, such as amyl alcohol, ethylene glycol, starch, cellulose and the like.

Exemplary of other sensitizers that can be employed are Mg, Al, Se, S, inorganic sulfides and carbides.

A satisfactory nitrocarbonitrate composition is one containing, for example, 92-95 percent ammonium nitrate and 5-8 parts of coal. When employing a nitroaromatic hydrocarbon as a sensitizer, from about 0.5 to 10 percent of each nitrocompound is employed, the composition preferably containing about pcrcent or more ammonium nitrate. If less than 85 percent ammonium nitrate is em- Composition 1 2 3 4 5 Weight percent Ammonium nitrate Sodium nitrate Dinitrotoluene N1trobenzene Paraflin Fuel oil. Coal 1 A now preferred composition.

Our invention relates also to metal containers per se for explosives, as described herein, which are accordingly an object of our invention. Thus, in accordance with such an embodiment, we provide a closed metal can; means for supporting a detonating device in indirect contact with the interior of said can so as to be in detonating relation with a booster therein; and means in said can for supporting a solid unitary body of a booster charge in fastened position in said detonating relation.

Although we prefer to fasten the booster charge in the container directly to the detonator support means as described, it is to be understood that it is within the scope of our invention to fasten the said booster within the container in any suitable manner, it being only required that the booster charge be a unitary solid body fastened in the container in indirect contact and detonating relation with the detonator. Thus, a detonating fuse can be supported adjacent the outside wall of the container and the solid booster unit can be attached directly to the inside wall of the container in close proximity to the detonator in detonating relation therewith. By way of further illustration, a conduit 12 of FIG. 1 need not always be the supporting means for the booster charge. The booster charge can be supported in the container of FIG. 1 in any suitable manner in detonating relation with detonator 13, such as by any suitable means for connecting the booster unit with an inner wall of the container; for example, a bracket or clamp device on the inner wall of the container for engaging the booster and holding same in detonating relation, or means associated with the booster for so supporting it, as described herein.

Any suitable means associated with the solid booster unit for fastening it in the container in indirect contact and detonating relation with the detonator can be employed. Thus, any suitable fastening device as a ring or clamp around the booster unit, adapted to engage the detonator support or the inner wall of the container to hold the booster in the said detonating relation, can be employed.

In another embodiment we provide as an explosive assembly a closed watertight metal can equipped with a conventional conduit-well for containing a blasting cap, and having a unitary solid booster body fastened inside the container to the said conduit.

As will be evident to those skilled in the art, various modifications can be made or followed in light of the foregoing disclosure and discussion without departing from the spirit or scope of the disclosure or from the scope of the claims.

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

l. A blasting assembly comprising a cylindrical metal container, watertight except that its side wall contains a pair of openings disposed on a line substantially parallel 8 with'its longitudinal axis and adapted to accept a detonating fuse; a conduit in said container adapted to accept a detonating fuse and of length about the same as the distance between said openings, said conduit at each end connecting with said side wall to close one of said openings in sealed relation therewith to render said container watertight; a main explosive charge, insensitive to detonating action of a commercial blasting cap within said container; a solid plastic body, as a booster charge, within said coutainer and imbedded, in at least major proportion, in said main charge and containing a crystalline explosive dispersed therethrough; means for securing said solid plastic booster body, in said container, directly to, and about at least a portion of, the said conduit, and said plastic body being supported by said means in said contact with said conduit.

2. In the assembly of claim 1, a groove disposed along a side of said plastic body and shaped to accept said conduit for support of said body on said conduit.

3. An assembly of claim 1 wherein said plastic booster body contains pentaerythritol tetranitrate dispersed therein.

4. A blasting assembly comprising a closed elongated water-tight metal container; a main explosive charge, insensitive to detonating action of a commercial blasting cap, in said container; a conduit longitudinally extending adjacent at least a portion of a side wall of said container and within the contour of the said side wall, and at least a portion of the wall of said conduit being in direct communication with the interior of said container; said conduit being connected at its ends, with the said side wall of said container, in direct communication with the exterior of said container in sealed relationship therewith to maintain said container water-tight; a solid body, as a booster charge, within said container and imbedded, in at least major proportion, in said main charge and comprising a crystalline explosive; said conduit being adapted to contain a detonator for initiating said booster charge; means for securing said solid booster body in said container directly to, and about at least part of, the said conduit wall portion in direct communication with the interior of said container as described; and said solid booster body being secured by said means in said contact with said conduit.

5. An assembly of claim 4 wherein said conduit is disposed within said container substantially parallel with the longitudinal axis of said container in close proximity to an inner wall thereof, and said booster is secured sub stantially concentrically with said conduit.

6. An assembly of claim 4 wherein said container con tains an elongated indentation in an external side wall thereof, the said indentation laterally extending into said container, and wherein a plate is disposed flush with the said external side wall of said container over a portion of said indentation, to form said conduit.

7. An assembly of claim 6 wherein the wall of said conduit in direct communication with the interior of said container is of progressively increased width; wherein a groove is disposed along an outside wall of said solid booster body and is shaped to fit the contour of said conduit at at least one predetermined point; and wherein said solid booster body is fastened around a portion of the conduit thus formed by contact of the surfaces of said groove fitted on the wall of said conduit at at least one of said predetermined points;

8. An assembly of claim 4 wherein said container contains an elongated indentation in an external side wall thereof, the said indentation extending laterally into said container, and wherein a plate is disposed on said external side Wall over a portion of said indentation to form said conduit.

9. A device of claim 8 wherein said plate is an extended portion of the wall of said container and overlaps said indentation in sealed relation with the outside wall of said container to maintain said container watertight.

10. An assembly of claim 4 wherein said main charge is a nitrocarbonitrate, and wherein the booster charge is a plastic body and comprises the polymerization product of a polymerizable vinyl material containing dispersed therein a nonaromatic explosive material selected from the group of azides, organic nitrates and organic amines.

11. In an assembly of claim 4 said means comprising a groove along a side of said solid booster body parallel to the longitudinal axis of said conduit and shaped to engage said conduit to secure said body to said conduit.

12. An explosive assembly consisting of a plurality of cartridge units disposed in propagating relationship as a column and each said unit containing an explosive insensitive to detonating action of a commercial blasting cap as the sole explosive charge, together with at least one primer unit as a member of said column and in propagating relationship with at least one of said cartridge units, the said primer unit comprising a closed elongated water-tight metal container; 2. main explosive charge, insensitive to detonating action of a commercial blasting cap, in said container; a conduit longitudinally extending adjacent at least a portion of a side Wall of said container and within the contour of the said side Wall, and at least a portion of the wall of said conduit being in direct communication With the interior of said container; said conduit being connected at its ends, with the said side wall of said container, in direct communication with the exterior of said container in sealed relationship therewith to maintain said container Water-tight; a solid body, as a booster charge, within said container and imbedded, in at least major proportion, in said main charge and comprising a crystalline explosive; said conduit being adapted to contain a detonator for 1.0 initiating said booster charge; means for securing said solid booster body in said container directly to, and around at least part of, the said conduit wall portion in direct communication with the interior of said container as described; and said solid booster body being secured by said means in said contact with said conduit.

References Cited in the file of this patent UNITED STATES PATENTS 292,642 Freund I an. 29, 1884 2,171,384 Young Aug. 29, 1929 2,138,581 Kirst Nov. 29, 1938 2,398,071 Barab Apr. 9, 1946 2,425,472 Hodgson et a1 Aug. 12, 1947 2,586,541 Horn et al Feb. 19, 1952 2,669,928 Sweetman Feb. 23, 1954 2,680,406 Austin June 8, 1954 2,733,658 Moat Feb. 7, 1956 2,751,810 Clark et al June 26, 1956 2,754,755 Ruth et al July 17, 1956 2,761,384 Sweetman Sept. 4, 1956 2,775,200 Guenter Dec. 25, 1956 2,782,715 Udry Feb. 26, 1957 2,784,638 Diels et al Mar. 12, 1957 2,913,892 Hayes Nov. 24, 1959 2,944,485 Ely et al July 12, 1960 FOREIGN PATENTS 649,806 Great Britain Jan. 31, 1951 493,862 Canada June 23, 1953

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