US3122096A - Expansible explosive package - Google Patents

Description

Feb. 25, 1964 A. E. WICK EXPANSIBLE EXPLOSIVE PACKAGE Filed March 16, 1962 //V VE N TOR.

ALFRED E. WICK BUCKHORN, CHEATHAM a BLORE AT TORNE YS United States Patent Ofiice 3,lZZ,% Patented Feb. 25, 1954 3,122,096 EXPANSHBLE EXPLQSEVE PACKAGE Alfred E. Wick, @2226 Rio Vista Ave, Milwauhie, Greg. Filed Mar. 16, 1962, Ser. No. 186,233 1 Claim. (@l. li)2-24) The present invention relates to an explosive cartridge and more particularly to an expansible, waterproof explosive cartridge.

The present invention is particularly concerned with providing explosive cartridges which may be used to give efiicient explosive effects in wet locations. It is desirable that an explosive charge completely fill a bore hole and that a minimum of space exist between the cartridge and the walls of the bore hole. When a bore hole is loaded with rigid cylindrical cartridges the cartridges must be of a diameter substantially less than the diameter of the hole to enable the cartridge to clear wall irregularities. Accordingly, there will be considerable space between the cartridge and the bore hole wall which is not desirable since the air space causes a decrease in the efficiency of the explosive effect and, furthermore, the capacity of the bore hole is not completely utilized if such space is not filled with a charge. Heretofore, waterproofed or gelatinized explosives have generally been used in wet locations and which can be in and of themselves expanded upon ramming home to fill the bore hole. However, such explosives are generally relatively expensive and are not in some instances as eilicient as unwaterproofed granular explosives. For example, if maint ined dry a particularly effective explosive for many purposes comprises ammonium nitrate mixed with up to about nitroglycerine and the usual additive such as wood flour and carbonaceous material. Such a mixture has low brisance and very high performance but is not eflective if wet. By increasing the amount of nitroglycerine, detonation of a wet charge can be secured but such a mixture has a high brisance which is undesirable for some purposes. in many types of work the extreme shock which is gencrated by a high brisance explosive contributes very little essentialperfonnance to the explosive. High brisance, where it is not needed, simply wastes costly explosive energy. High brisance also increases the hazard of transmitting earth shock and vibration over a wide area that may damage foundations, structures and terrain relatively far away from the blast. Low brisance, controlled moisture content, granular explosives thus have a distinct advantage where blasting is being done in congested areas.

High brisance explosives are usually desired at the very bottom of a bore hole where the shock and explosive requirement is greatest. However, the energy requirements nearer the surface are considerably less. To restrict the energy release so-called deck loading is sometimes used with high brisance explosives. In a deck load a few feet of a bore hole are loaded with explosive, the next few feet with stemming, that is, an inert material, then more explosive, and so forth, alternating the explosive and stemming until the hole is filled. Deck loading with high brisance explosive is inherently ineificient for many obvious reasons. For one thing the cost of the explosive itself is relatively high. Secondly, the loading costs are high because detonators must be provided for each separate charge. Also, the explosive is not evenly distributed, as is preferred, and the resulting shock from the high brisance charges near the surface may cause damage as indicated previously.

Another problem exists in connection with inserting cartridges in vertical holes which are filled with water in that obviously a cartridge must somehow be anchored in place to hold it in position in the bore hole. Rigid cartridges utilizing a charge having a specific gravity less than 1.0 obviously are unsatisfactory for they are apt to float upwardly. Dense, gelatinized powder charges having a. specific gravity greater than 1.0 are available, and which cartridges would, or course, stay in place within the bore hole. Dense gelatins have a high brisance and when used it has been the practice to load the bottom few feet of a bore hole with the gelatin cartridges and then deck load the remainder of the hole to lower the explosive load factor in the upper part of the hole. The disadvantages of this practice have been mentioned previously.

Gelatinized charges are supplied in non-expansible wrappers. It is the practice in many instances to slit the wrappers prior to loading so that the charge may be expanded when rammed into a bore hole. Slitting of the package releases nitroglycerine fumes which cause discomfort and severe headaches to the handlers.

it is an object of the present invention to provide a new and improved explosive cartridge that may be expanded when rammed home so as to fill the bore hole thus utilizing all available space and at the same time anchoring the cartridge in position.

Still another object of the invention is to provide a cartridge which has suilicient rigidity in its initial condition to permit it to be inserted and positioned within a bore hole but which may be expanded when desired so as completely to till the bore hole.

A further object of the invention is to provide a cartridge having an expansible, Waterproofed sheath so that the charge is protected from moisture after the cartridge has been expanded.

A still further object of the invention is to provide a waterproof cartridge of a low density, low cost explosive that may be utilized as a continuous load in a bore hole.

A further object of the invention is to provide a cartridge of the type described that may be easily loaded.

A still further object of the invention is to provide a cartridge having an expansible, waterproof sheath which is protected from rupture or cutting as the cartridge is inserted in a bore hole.

Still another object is to provide an inexpensive cartridge of an explosive of low brisance and low density that is adapted to be utilized in wet locations.

Another object is to provide a cartridge that prevents the escape of nitroglycerine fumes during handling and loading.

Still other objects and advantages of the invention will become more apparent hereinafter.

In accordance with the illustrated embodiment the present invention comprises a cartridge including a cylindrical powder charge encased within a tubular sheath formed of wax impregnated, frangible paper. Surrounding the inner sheath is a sealed tubular plastic sheath which has a normal diameter substantially greater than that of the inner sheath so that upon collapsing of the cartridge endwise the cartridge may expand radially outwardly. Surrounding the plastic sheath and holding the same snugly against the walls of the inner sheath is an outer frangible paper sheath which may be ruptured permitting the cartridge to expand when endwise pressure is placed upon the same by ramming in a bore hole.

For a more detailed description of the invention reference is made to the accompanying drawings and the following specification.

In the drawings:

FIG. 1 is a perspective view partly broken away of a cartridge made in accordance with the invention;

PEG. 2 is a view of the cartridge encased in the innermost sheath;

FIG. 3 is a view of the cartridge in the waterproof sheath; and

FIG. 4 is an enlarged sectional view taken substantially along line 4=-d of RIG. 1.

Referring now to the drawing, indicated at it is the explosive charge which may, in accordance with the invention, comprise a granular mixture of ammonium nitrate and a small amount of nitroglycerine, the latter being present in amounts of less than along with the usual carbonaceous material and wood flour. A specific example of a desirable explosive having low brisance is the following:

Percent Ammonium nitrate 64 Sodium nitrate 18.4 Nitroglycerine, etc. 8.8 Absorbents and carbonaceous material 5.4 Antacid 0.2 Sulfur 2.2 Moisture .96

It will be obvious that such an explosive mixture is of advantage because of its relatively low cost and low brisance. Low brisance, it will be recognized, is desirable because of the greater effectiveness of the explosion. On the other hand, it will be recognized that the charge of low nitroglycerine content must be kept dry' in order to secure satisfactory performance of the explosive.

The charge ltl is contained immediately within an inner, tubular Wrapper or sheath 12 which is preferably formed of relatively heavy kraft paper such as fifty pound paper and which preferably is waxed in order to prevent migration of liquid nitroglyccrine through the wmls of the sheath. The charge 1ft is loaded within the sheath 12 in the usual manner and the ends of the tubular sheath overfolded and sealed in the conventional manner to form a tubular package as shown in FIG. 2.

Surrounding the inner sheath 12 is an intermediate tubular sheath 14 formed of a flexible, waterproof material inert to nitroglycerine fumes. The sheath 14 may, for example, be formed of polyethylene film, a film thickness of about three mils having been found satisfactory though thinner or thicker film may be used as desired.

The sheath 14 has a normal diameter substantially greater than the sheath 12 so that the sheath 14% may be expanded a substantial amount without rupturing.

In assembling the cartridge of the invention the inner sheath 12 may be loaded with the powder charge which is tamped to compact the same. The sheath is then sealed and this package then slipped within the sheath 14 which may' be presealed at one end in any conventional manner, the top or open end thereafter being closed to provide a completely water tight package. The open end may be closed by a ring clip 16 or other suitable means. Of course, prior to the sealing of the open end the walls of the sheath 14 are pressed against the sides of the inner sheath 12 so as to exclude as much air as possible. The unit thus assembled and indicated at 18 in FIG. 3 is inserted within an outer sheath 29 which preferably comprises a duplex wrapper including an inner tubular wrapper formed of wax impregnated kraft paper 22 and an outer unimpregnated kraft paper 24. The wrapper 242 may, for example, be formed of forty pound kraft paper impregnated with eight pounds of wax whereas the outer layer 24 may be formed of fifty pound kraft paper. If desired the assembly within the sheath 14- may be inserted into the outer sheath 2% prior to scaling the open end of the plastic sheath. The sheath 14 will be compressed against the inner package as this is done.

After inserting the package 18 within the outer sheath the ends of the layers 22, 24 are overfolded and sealed in any suitable manner so as to form a unitary package which maybe shipped and handled in the normal manner.

Moisture will be absorbed by the outer layer 24 during the loading process to weaken such layer and facilitate rupturing thereof. On the other hand, it will ordinarily' retain sufficient strength during the loading process to help stiffen the cartridge and permit it to be rammed home. It is highly desirable that the layer 22 be wax impregnated so that it will resist wetting and remain intact during loading to protect the sheath 14 which would be likely to be ripped upon contact with the rough surface of a bore hole wall.

In use the package thus described is loaded into a bore hole and pushed into place in the manner of the conventional package. The package is then rammed so as to compress it lengthwise and which will, of course, cause the charge to exert radial pressure upon the wrappers of the package. Upon exertion of sufficient pressure the paper wrappers 12., 20 will rupture permitting the expansible wrapper 14 to expand against the walls of the bore hole. It will be appreciated that ordinarily the bore hole has a normal diameter considerably larger than the overall diameter of the package. The package of the invention may be expanded substantially to fill the outer perimeter of the bore whereupon the charge will be substantially in contact with the rock surfaces defining the bore hole and substantially all air and water will be eliminated from between the explosive package and the wall of the bore hole. After the bore hole has been filled to the desired capacity the charge can be detonated in the usual manner.

It will be appreciated that the several sheath layers making up the cartridge will provide a cartridge sufficiently rigid to permit it to be loaded into a bore hole without buckling. On the other hand, the cartridge may be deformed laterally sufiiciently to permit the cartridge to pass over slight protrusions on the wall of a bore hole upon which an entirely rigid and nondeformable cartridge is apt to hang up. Thus, the cartridge is substantially rigid longitudinally but is deformable laterally to some extent.

The use of the inner sheath .12 is highly desirable in the first instance because loading of the charge directly into a polyethylene sheath 14 would present a problem in the control of static electricity and, furthermore, it would be difficult to load the polyethylene without snagging and tearing the polyethylene.

A common difficulty in handling nitroglycerine containing explosives is that the escape of fumes affects the handlers of the explosives and causes severe headaches. An important advantage of the package of the invention 'is that inasmuch as the sheath 14 is completely sealed,

the escape of nitroglycerine fumes is prevented and iandlers are not subject to headaches.

Having illustrated and described a preferred embodiment of the invention, it should be apparent to those skilled in the art that the invention permits of modification in arrangement and detail. I claim as my invention all such modifications as come Within the true spirit and scope of the appended claim.

I claim:

An explosive cartridge comprising:

a filling of a low brisance ammonium nitrate base explosive,

an inner tubular sheath enclosing said filling, said inner sheath comprising a single layer of a wax-impregnated, frangible kraft paper of about fifty pound weight, said filling being tamped therein,

an intermediate tubular sheath surrounding said inner said outer and inner sheaths being adapted to rupture sheath, said intermediate sheath being formed of whether wet or dry upon endwise ramming of said a flexible, synthetic, waterproof plastic material imcartridge whereby said intermediate wrapper may pervious to vapors and being sealed at its opposite expand to fill said bore hole and provide a waterends, said intermediate sheath being of substantially 5 proof wrapper about the expanded explosive filling. larger diameter than said inner sheath and being longitudinally pleated so as snugly to lie against References Cited in the file Of this Patent f g h th t UNITED STATES PATENTS an an on er u ar s ea surroun mg sai 1n ermediate sheath, said outer sheath being formed of 10 fizg g a {ti frangible paper, said outer sheath being of only 2565380 L A 1951 slightly larger diameter than said inner sheath where- 2887954 e 1959 by it snugly encompasses said inner and interrne- 2966855 1961 diate sheaths to form a relatively rigid cartridge for 2969101 wi inserting in abore hole, 15 lte 1961 3,049,079 E110 Aug. 14, 1962 said outer sheath comprising a single inner layer of wax impregnated forty pound kraft paper and a single outer layer of fifty pound kraft paper,

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