US3185092A

US3185092A - Explosive container with yieldable seal

Info

Publication number: US3185092A
Application number: US337090A
Authority: US
Inventors: John F Hamilton
Original assignee: Hercules Powder Co
Current assignee: Hercules Powder Co
Priority date: 1964-01-10
Filing date: 1964-01-10
Publication date: 1965-05-25
Anticipated expiration: 1982-05-25
Also published as: US3376816A; US3395642A; FR94118E; BE658015A; ES344711A2; NL6500284A; GB1031129A; US3186340A; DE1446960A1

Description

y 5, 1965 J. F. HAMILTON 3,185,092

EXPLOSIVE CONTAINER WITH YIELDABLE SEAL Filed Jan. 10, 1964 2 JOHN F. HAMILTON INVENTOR.

United States Patent This invention relates to an explosive column assembly especially adapted for use in seismiooperations and more particularly to an improved explosive column assembly and plastic explosive containers therefor.

The explosives industry has for many years packaged explosives in paper, metal and plastic containers, all of which have been provided with various types of coupling means for forming an explosive column. On a commercial basis, only the paper and metal containers have found wide acceptance primarily due to the economic factors involved when using plastic. Paper containers have been most Widely accepted in view of their versatility for handling both sensitive and insensitive explosives, although paper containers require a considerable amount of water-proofing and wall thickness to insure a substantially rigid explosive column. Metal containers have been widely accepted in view of their strength, waterproofness and ease of providing coupling means therefor; however, they have been limited to the packaging of relatively insensitive explosives in view of the hazards involved in packaging and sealing sensitive explosives in metal. Plastic containers have not heretofore been appreciably accepted in view of the economic factors mentioned although it has long been realized that the material possessed many advantages, particularly in respect to waterproofness and safety for the packaging of sensitive as well as insensitive explosives.

Therefore, it is a principal object of the present invention to provide plastic containers which may be manufactured in an efficient and economical manner and which containers may be assembled in a facile, efficient and economical manner. Moreover, a further object is to provide additional desirable features heretofore not available to the art such as placing the packaged explosive under compressive force during assembly where if the container is not properly filled or if the column tends to elongate, improved contact between adjacent explosive charges is insured with attendant consistency of propagation rate.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

Generally described, the present invention comprises an explosive column assembly having a plurality of substantially cylindrical blown plastic containers charged with explosive, each of said container having a threaded male coupling and end closure at one end and a threaded female coupling and yieldable seal adjacent the explosive at the other end, and said containers being threadedly interconnected by said male and female couplings and having the end closures of the male couplings exerting cornpressive force on the yieldable seals and adjacent explosive of the female couplings. In a more specific aspect in accordance with the present invention, there is provided a container for explosives, adapted for interconnection with like containers to form an explosive column assembly, which comprises a thin-wall elongated substantially cylindrical blown plastic container having explosive disposed therein throughout the major length of the container and having a yieldable seal within the container adjacent the explosive, an externally threaded male coupling and end closure in the thin wall on one end of the container, an internally threaded female cou- 3,185,92 Fatented May 25, 1965 pling in the thin wall on the other end of the container, the female coupling extending beyond the yieldable seal the remaining length of the container, and the male coupling having a reduced external diameter relative to the internal diameter of the female coupling whereby like containers of explosive may be threadedly interconnected by the male and female couplings to form an explosive column assembly having the end closures of the male couplings exerting compressive force on the yieldable seals and adjacent explosive of the female couplings.

A preferred embodiment of the invention has been chosen for purposes of illustration and description and is shown in the accompanying drawings where reference symbols refer to like parts Wherever they occur.

FIG. 1 is an elevational view of a container in accordance with the invention with a part thereof in section showing the yieldable seal and adjacent explosive within the container;

FIG. 2 is a sectional view taken along line 22 of FIG. 1; and

FIG. 3 is a fragmentary part elevational and part sectional view showing the interconnection of the containers of FIG. 1 to form an explosive column assembly.

With reference to the drawings, a thin-wall elongated blown plastic container 1 has an explosive 2 disposed therein throughout the major length of the container. A yieldable seal 3 is provided within the container 1 adjacent the explosive 2. A double lead externally threaded male coupling 4 with a rounded thread and standard pitch of 29 and a convex end closure 5 are formed as a unitary structure in the thin wall at one end of the container 1 and the explosive 2 extends throughout the length of the coupling. An internally threaded female coupling 6 with threads compatible to the male coupling is formed in the thin wall on the other end of the container 1 and extends substantially beyond the yieldable seal 3 and the explosive 2 positioned adjacent thereto. The male coupling 4 has a reduced external diameter relative to the internal diameter of the female coupling 6 with a transition taper 7 being provided in the thin wall of the container 1 to accomplish this. The relationship between the diameters of the couplings is such as to insure a snug and yet easily rotatable threading. The threaded female coupling 6 has double lead internal threads 8 positioned in the midportion of the coupling. This arrangement facilitates the insertion of the male coupling of a like container since the unthreaded extending portion of the coupling 6 serves as a guiding sleeve for proper engagement of the threaded couplings and adds rigidity to the explosive column assembly. The arrangement also reduces the number of turns required for interconnection of like containers.

Referring now more particularly to FIG. 3, it will be appreciated that a considerable bending moment can occur in the coupling 6 particularly when several containers are interconnected in a horizontal position and then lifted for insertion in a vertical borehole. Accordingly, four equally spaced reinforcing fillets 9 are provided which extend across the threads 8. For the same reason and to counteract unusual bending moments imparted to the body of the thin-wall container 1, a plurality of longitudinal reinforcing ribs Ill is spaced circumferentially about and substantially coextensive with that portion of the body of the container lying between the male coupling l and the female coupling 6. Additionally, a plurality of girth reinforcing ribs 11 is spaced along the length of the longitudinal ribs 19 to insure overall integrity of the body structure of the container 1 against deformation under various conditions of manufacture and field handling. It has been found that the longitudinal reinforcing ribs ll) should have a width of not more than the width of the areas 12 lying therebetween and that :3 ordinarily. three to five of the girth reinforcing ribs 11 spaced along the length of the longitudinal ribs give very satisfactory results for the average size of most commercial cartridges. Furthermore, the threaded portion of the male coupling 4 is greater than the threaded portion of the female coupling 6 to insure that in threadedly assembling a column of the containers 1, the convex end closure of the male coupling exerts a positive compressive force on the yieldable seal 3 and adjacent explosive 2 of the female coupling of a like container. If the packaged exposive is soft,. the yieldable seal 3 will be depressed therein as illustrated particularly in FIG. 3 depicting the interconnection of two like containers where 1a and its like parts represent a superjacent container and 1 and its like parts represent the subjacent container. If the packaged explosive is hard, there will be very little depression, if any, of the yieldable seal 3. In any event, regardless of the exact height to which the container is filled including vagaries in filling height during manufacture and possible subsequent shrinkage, a compensating adjustment insuring minimum proximity of explosive charges is actually made in the field during assembly of the containers of this invention by the exertion ofthe compressive force heretofore discussed. This insures a consistent propagating relationship with consistency of rate and quite advantageously is accomplished in the field at the time the explosive column is being readied for use. Moreover, a tight seal is effected as between adjacent containers as the female coupling being slightly elastic has its end maintained in tension as it is forced to accommodate the unthreaded portion of the male coupling. Since the internal diameter of the female coupling is less than the unthreaded external diameter of the male coupling, upon engagement of the two coupling's, the unthreaded outer portion of the female coupling is slightly expanded over the male coupling as it is completely threaded thereinto. Accordingly, since the expansion is small and the elastic limit or yield point of the plastic not exceeded, the upper portion of the female coupling remains under tension to insure and maintain a tight water-resistant seal between the couplings upon complete assembly; This tight seal as depicted in FIG. 3 is substantially effortlessly obtained due to the mechanical advantage imparted by the inclined plane of the screw coupling means.

The following example will serve to illustrate a commercially sized preferred embodiment of this invention. It is to be understood, however, that the scope of the invention is not limited thereby with respect to the specific structure or to the explosive charges utilized.

- A series of thin-wall containers was formed by blowmolding high-density polyethylene having a density of 0.962 and a nominal melt index of 0.8 (I at 190 C.). These containers were molded in a split mold designed to yield the structure heretofore described and illustrated as a preferred embodiment of the invention. Dimensions of the containers were 22%" overall length, 2 body diameter, sixteen reinforcing ribs wide raised 2" around 2 diameter, male coupling 4%" long, threaded portion of male coupling 2 /2" with convex end closure extending and with one rounded thread per 1" with double lead, said thread having a root diameter of 2 /s. and external diameter of 2 /2", a female coupling 4%" long, threaded midportion of female coupling /z c. to c. of split double lead thread wide and 7 deep with two filled each side, and a ribbed body portion. The ribbed body portion had five girth ribs 75 wide equally spaced with the exception of a midportion 4" long wherein three longitudinal ribs were omitted to provide a smooth area for labeling. The wall thickness of the body of the container including the female coupling, was approximately 40 mils, and the wall thickness of the male coupling was approximately 55 mils. Programming was used during the blow-molding process dto obtain female couplings that were uniform in thickness and strength.

Each of these containers was charged with approximately 5 pounds of explosive composition consisting of 49.0% nitroglycerin, 1.5% nitrocotton, 36.0% sodium nitrate, 7.0% pulp, 3.0% coated cob meal, 2.0% starch, 0.5% bagasse and 1.0% chalk. This charge filled each container to a height approximately level with the girth rib adjacent the female coupling. A cupped polyethylene sealing disk approximately 25 mils thick was then placed over the explosive and snugly fitted into the annular girth rib adjacent the female coupling. The containers thus manufactured were tested and initiated under conventionalt field conditions as explosive column assemblies containing from two to ten containers in each assembly. The tests were satisfactory in all respects with additional advantages hereinafter set forth. 2

With reference to the foregoing, it will be appreciated that the containers of this invention may be formed from many of the plastic materials capable of being blown but that the economy of the material will largely dictate its use. Thus, although linear polyethylene is preferred and has been found highly satisfactory, polyolefins generally, and copolymers and alloys thereof and other materials such as ABS terpolymer, plasticized vinyl chloride, plasticized vinyl chloride-vinyl acetate copolymer and the like may be used. Also, it will be appreciated that in addition to the specific seismic explosive used in the example, other explosives of various types suitable for various other blasting purposes may be used such as generally, gelatins, dynamites, permissibles, safety explosives, slurry explosives and the like. Moreover, distinct advantages inure when employing the present invention for aqueous slurry explosives which show a one inch or two inch propagation gap under water, and for gelatin dynamites Where under very high water pressure, the propagation gap is markedly reduced as compared to that observed under low water pressure. Furthermore, in addition to the polyethylene yieldable seal used in the example, other plastics such as those set forth for the container and nonplastic seals may be used including treated paper board, waxes, resins, waterproofing compounds, and the like. Also, the seal can be a plastic cup sealed around its lip and the shell body with a hot melt adhesive, or a wax such as paraffin, or resins or asphaltic compounds or the like where extreme water proofness is desired. The essential thing is that the seals should be yieldable in respect to deflection or in respect to sliding along the wall of the container or otherwise yielding so that compressive force is gently but firmly developed with close proximity assured as between adjacent container explosive charges. Still further, although continuous male and female threads have been depicted for the couplings, the term threaded is meant to include interrupted threads, the essential feature being that suificient thread pitch be utilized to function with for ward progression to insure compression as the couplings herein described. Moreover, although the reinforcing ribs have been described as raised, they may be obtained also by providing a constant body diameter with the areas such as 12 depressed, thus forming ribs such as 10 and 11. Ordinarily, the explosive containers of this invention are made available in sizes from about 6 to about inches in length and from about 1 to about 8 inches in diameter with the number of interconnected units dependent upon the specific service desired. Generally, for seismic Work, not more than about 10 units are used, and the 2 /2" x 22%" container herein specifically described has been found a popular size. In progressing to the larger sizes, an increase in the wall thickness of the plastic is ofcourse necessary but, nevertheless, due to the blown feature and other structural features introduced by this invention, the wall thickness need be only slightly increased, not exceeding about 10 to 25%, thus retaining efficient and economical manufacture.

The additional advantages previously referred to' in connection with the example and field tests are as follows relative to prior art paper containers since metal containers cannot be used for this type explosive: 15% more explosive energy obtained through using plastic shells; an increased overall specific gravity, which, coupled with the gplastic surface features, results in improved sinking rats, in drill mud, consequently reducing the need or poling; of charges; shorter shell length per given weight of charge provides a more compact charge; the charges in Soft containers are easier to prime for the shooter by conventional means; a screw type, positive coupling featitre making assembly and disassembly a simpler task; in-

,creased protection to.,the powder charge because the plastic is impervious to water; improved loading in boreholes due to flexibility as the plastic assembly will yield and slide by obstructions; a plastic unit susceptible for use wherever paper containers or metallic containers formerly were preferred and in some instances unalterably necessary; and a general purpose plastic unit which does not tend to disintegrate or rust internally in the presence of moisture or water containing explosives and does not tend to disintegrate or rust in the presence of moisture or water as externally encountered in water-containing boreholes and unsheltered storage.

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

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

1. A container for explosives adapted for interconnection with like containers to form an explosive column assembly, which comprises:

(a) la thin-wa1l elongated substantially cylindrical blown plastic container having explosive disposed therein throughout the major length of the container and having a yieldable seal within the container adjacent the explosive,

(b) an externally threaded male coupling and end closure in the thin wall on one end of the container,

(c) an internally threaded female coupling in the thin wall on the other end of the container, .the female coupling extending beyond the yieldable seal the remaining length of the container, and

(d) the male coupling having a reduced external diameter relative to the internal diameter of the female coupling and the end closure of said male coupling having protrusion means to contact and to force the yieldable seal of a like container into the explosive adjacent thereto so that like containers of explosive threadedly interconnected by the male and female couplings to form an explosive column. assembly have the end closures of the male cou plings exerting compressive force on the yieldable seals and adjacent explosive of the female couplings.

2. A container for explosives adapted for interconnection with like containers to form an explosive column assembly, which comprises:

(a) a thin-'wall elongated substantially cylindrical blown plastic container having explosive disposed therein throughout the major length of the container and having .a yieldable seal within the container adjacent the explosive,

(c) an internally threaded female coupling in the thin Wall on the other end of the container, the female coupling extending beyond the yieldable seal the remaining length of the container, said female coupling having a threaded midportion only, and

(d) the male coupling having a reduced external diameter relative to the internal diameter of the female coupling and the end closure of said male coupling having protrusion means to contact and to force the yieldable seal of a like container into the explosive adjacent thereto so that like containers of explosive threadedly interconnected by the male and female couplings to form an explosive column assembly have the end closures of the male couplings exerting compressive force on the yieldable seals and adjacent explosive of the female couplings. 3. A container for explosives adapted for interconnection with like containers to form an explosive column assembly, which comprises:

(a) a thin-wall elongated substantially cylindrical blown plastic container having explosivenisposed' therein throughout the major length. of the container and having a yieldable seal within the container adjacent the explosive,

(0) an internally threaded female coupling inthe thin wall on the other end of the container, the female coupling extending beyond the yieldable seal the remaining length of the container, said female coupling having a threaded midpo-rtion only, and said threaded midportion having at least four equally spaced reinforcing fillets for each complete turn thereof extending across the threads, and

(d) the male coupling having a reduced external diameter relative to the internal diameter of the female coupling and the end closure of said male coupling having protrusion means to contact and to force the yieldable seal of a like container into the explosive adjacent thereto so that like containers of explosive threadedly interconnected by the male and female couplings to form an explosive column assembly have the end closures of the male couplings exerting compressive force on the yieldable seals and adjacent explosive of the female couplings.

4. A container for explosives adapted. for interconnection with like containers to form an explosive column assembly, which comprises:

(a) a thin-wall elongated substantially cylindrical :blown plastic container having explosive dis-posed therein throughout the major length of the container and having a yieldable seal within the container adjacent the explosive,

(0) an internally threaded female coupling in thethin wall on the other end of the container, the female coupling extending beyond the yield-able seal the remaining length of the container, said female coupling having a threaded midportion only, and said threaded midportion having at least four equally spaced reinforcing fillets for each complete turn there-of extending across the threads,

(d) a plurality of longitudinal reinforcing ribs spaced circumferentially about and substantially coextensive with that portion of the body of the container lying between the male coupling and the female coupling, and

(e) the male coupling having a reduced external diameter relative to the internal diameter of the female coupling and the and closure of said male coupling having protrusion means to contact and to force the yieldable seal of a like container into the explosive adjacent thereto so that like containers of explosive threadedly interconnected by the male and female couplings to form an explosive column assembly have the end closures of the male coupl-rngs exerting compressive force on the yieldable seals and adjacent explosive of the female couplings.

5. A container for explosives adapted for interconnectron with like containers to form an explosive column assembly, which comprises:

(a) a thin-wall elongated substantially cylindrical blown plastic container having explosive disposed therein throughout the major length of the container and having a yielda-ble seal within the container adjacent the explosive,

(b)-|an'externallythreaded male coupling and end closure in the thin wall on one end of the container,

() an internally threaded female coupling in the thin wall on the other end of the container, the female coupling extending beyond the yieldable seal the remaining length of the container, said female coupling having a threaded midportion only, and said threaded midportion having at least four equally spaced reinforcing fillets for each complete turn thereof extending across the threads, and

(d) a plurality of longitudinal reinforcing ribs spaced circumferentially about and substantlally coextensive with that portion of the body of the container lying between the male coupling and [the female coupling,

(e) 'a plurality of girth reinforcing ribs spaced along the length of the longitudinal reinforcing ribs, and (f)'the male coupling having a reduced external diameter relative to the internal diameter of the female coupling and the end closure of said male coupling having protrusion means to contact and to force the yieldable seal of a like container into the explosive adjacent thereto so that like containers of explosive thrcadedly interconnected by the male and female couplings to form an explosive column assembly have the-end closures of the male couplings exerting compressive force on the yieldab'le seals and adjacent explosive of the female couplings. 6. A container for explosives adapted for interconnection with like containers to form an explosive column assembly, which comprises:

(a) la thin-wall elongated iblown polyethylene plastic container'having explosive material disposed therein throughout the major length of the container and having a yieldable seal within the container adjacent the explosive material, (b) -an externally threaded male coupling and end closure blown asa unitary structure in the thin wall on one end of the container, (c)-aninternal1y threaded fem-ale coupling blown in the thin wall on the other end of the container, the female coupling extending beyond the yield-able seal theremaining length of the container, said female coupling having a threaded midportion only, and said threaded midportion having at least four equally spaced rein-forcing fillets for each complete t-urn thereof extending across the threads, and (d) a' plunality of longitudinally reinforcing ribs spaced circumferentia'lly about and substantially coextensive with that port-ion of the body of the container lying between the male coupling and the female coupling, e) a plurality of girth reinforcing ribs spaced along the length of the longitudinal reinforcing ribs, and (j) the male coupling having a reduced external diameter relative to the internal diameter of the female coupling'and the end closure of said male i coupling havin-g protrusion means to contact and to force the yieldable seal of a like container into the explosive adjacent thereto so that like containers of explosive threadedly interconnected by the male and female couplings to form an explosive column assembly have the end closures of the male {couplings exerting compressive force on the yield ible seals and adjacent explosive of the female couplings.

7. The explosive cartridge according to claim 6 wherein the threaded portion of the male coupling ismore than twice the length of the threaded'rnidportion of the female coupling.

8. The explosive cartridge according to claim 6 where in the end closure is convex and the threaded portion of the male coupling and the threaded midportion of the female coupling have double lead threads.

9. The explosive cartridge according to claim 6 wherein the longitudinal reinforcing ribs have a width of not more than the width of the areas lying therebetween.

10. The explosive cartridge according to claim 6 wherein the blown polyethylene plastic is high-density polyethylene characterized 'by a density of 0.962 and a nominal melt index of 0.8.

11. An explosive column assembly comprising:

(a) a plurality of substantially cylindrical blown plastic containers charged with explosive,

(b) each of said containers having a threaded male coupling and a projected end closure having protrusion means atone end and a threaded female coupling' and yieldable 'seal adjacent the explosive at the other end, and

' (c) said containers being threadedly interconnected I by said male and female couplings and having the protrusion means of the end closures of the male couplings exerting compressive (force on the yield- ;able seals and-adjacent explosive of thefemale couplings. I

12. The explosive column assembly according to claim 11 wherein the plastic is high density polyethylene charagterized by a density of 0.962 and a nominal melt index 0 0.8.

13. The explosive column assembly according to claim 11 wherein the upper portion of the female couplings is in tension about the upper portion of the male couplings said upper portion of the female couplings being of slightly less diameter than said upper port-ion of the male couplings so that said tens on is effected upon complete interconnection of the couplings.

References Citedby the Examiner UNITED STATES PATENTS 1,037,709 9/12 Zieg 285-401 1,940,657 12/33 Wood'fond 102--'43 2,345,887 4/44 'R-othrock 102-24 2,383,542 8/45 Godfrey l02-24 2,500,276 3/50 Church 285402 2,755,735 7/56 Hatter 10224 3,013,492 12/6'1 Sexton l02--24 BENJAMIN A. BORCHELT, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,185,092 May 25, 1965 John F. Hamilton It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 11, for "exposive" read explosive column 8, line 27, strike out "a projected'h Signed and sealed this 7th day of December 1965.,

(SEAL) Altest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims

1. A CONTAINER FOR EXPLOSIVES ADAPTED FOR INTERCONNECTION WITH LIKE CONTAINERS TO FORM AN EXPLOSIVE COLUMN ASSEMBLY, WHICH COMPRISES: (A) A THIN-WALL ELONGATED SUBSTANTIALLY CYLINDRICAL BLOWN PLASTIC CONTAINER HAVING EXPLOSIVE DISPOSED THEREIN THROUGHOUT THE MAJOR LENGTH OF THE CONTAINER AND HAVING A YIELDABLE SEAL WITHIN THE CONTAINER ADJACENT THE EXPLOSIVE, (B) AN EXTERNALLY THREADED MALE COUPLING AND END CLOSURE IN THE THIN WALL ON ONE END OF THE CONTAINER, (C) AN INTERNALLY THREADED FEMALE COUPLING IN THE THIN WALL ON THE OTHER END OF THE CONTAINER, THE FEMALE COUPLING EXTENDING BEYOND THE YIELDABLE SEAL THE REMAINING LENGTH OF THE CONTAINER, AND (D) THE MALE COUPLING HAVING A REDUCED EXTERNAL DIAMETER RELATIVE TO THE INTERNAL DIAMETER OF THE FEMALE COUPLING AN THE END CLOSURE OF SAID MALE COUPLING HAVING PROTRUSION MEANS TO CONTACT AND TO FORCE THE YIELDABLE SEAL OF A LIKE CONTAINER INTO