US2412581A - Sheathing for explosives - Google Patents

Description

. Dec# 17 1946. D. D. HUYETT `ET A1. 2,412,581

SHEATHING FOR EXPLOSI-VES l Filed Jan. 22, 1940 2 Sheets-Sheet 1 Dec- 17, 946 D. D. HUYETT ET AL SHEATHING- FOR EXPLOSIVES Filed Jan. 22, 19.40 2 Sheets-Sheet 2 Patented Dec. 17, i946 SHEATHIN G FOR EXPLOSIVES Daniel D. Huyett and Frank S'. Pollock, Wilmington, Del., assignors to Atlas Powder Company, Wilmington, Del., a corporation of Delaware Application January 22, 1940, Serial No. 315,094

2 Claims.

l This invention relates to a. sheathing for ex.- plosives, which sheath is of the type that. isA em;- ployed to modify the normal properties of cartridged explosives in various` ways; as for ex.n

ample: the suppression of flame, the reduction of poisonous fumes, the reduction of smoke,v the reduction of shattering effects, etc. It contemplates the provision, as an article of manufacture, of an improved unit sheathing structure and the method of making the same.

The useof explosives such` as dynamite, blasting powder and thelike in mine operations, particularly in coa-l mining, is attended by considerable danger due to the presence of methane orv fire damp in the passages and chambers of subterranean mines. Many minedisasters have resulted from ignition of nre damp under the pressure and flame conditions accompanying the firing of such explosives. has been proposed to use with the explosive a flame suppressing substance such as a mixture of calcium fluoride and sodium chloride; Heretofore such flame-suppressingr substances have been utilized either by mixing them with the explosive composition, in which case the mixture including the salts is formed directly into` explosive cartridges, or by applying the salts asv aprotective covering abouta separately fabricatedexplosive cartridge.

strength to resist the handling to which they are subjected. Since the salts that are suitable for usel as llame-suppressing substances are usually markedly hygroscopic in character, any struc-VA ture formed of these salts will disintegrate when As a consequence, it

The present invention relates tothislatter type of covering which is' gen-- the salts are exposed to the moisture normally present in the atmosphere. Thus, molded, agglomerated sheathing units having no inner or outer carrier or casingl are entirely impractical and worthless for use With almost all of the desired flame-suppressing compositions which comprise hygroscopic and/or water-soluble ingredients.

Proposed methods which effect the direct formation of the llame-suppressing unit about the explosive cartridge or thepacking of the loose explosive composition directly within the sheathing unitV are. more. or less subject to accidental explosion, particularly When carried out by automatic machinery and are therefore undesirable;v Furthermore` separate sheathing manufacturing units. required to be installed and maintained at each ofA such explosive plants tremendously increases the cost of manufacturing.

sheathed explosive structures which are separatelyv fabricated from the explosives by utilizing a rigid metal sleeve or cylinder as the interior physical support for the sheath insteadof an explosive cartridge are-very expensive to manufactureA and involveconsiderable hazard' inasmuch. as their use would require the insertion` and. tamping of the metal into the borehole along' with the explosive.

The foregoing and other disadvantages inherent inthe explosive sheathings heretofore proposed have preventedtheir adoption to any, great extentin this country.

It is a' primary object of our invention to provide a flame-suppressing unit for explosivesk which is more effective than units heretofore known and in use.

It is also an object of our invention to provide" a flame-suppressing unit for explosives whichis not affected by atmospheric conditions during@ shipment and storage.

Conversely. it is. an object of.l our invention to Vvprovide a hermetically-sealed flame-suppressing.'

unit for explosives which permits the use of extremely hygroscopi'c: substances: otherwise not susceptible. of' successfulA employment. as flame'- suppressing media.

It is also an object of our invention to provide a dama-suppressing uniti for explosives which is simple construction, permitting manufacture at extremely low costfby automatic high-speed:

Further objects and objects relatingy to details of constructionand advantages of use will more definitely appear from the -detailed description to follow. In general, however, weA accomplish the objectsV of our' invention by using'. a: cylindrical shellbody'of any'sutabl'e material adapted to be:`

as to protect the said sheathing composition l (which is usually of a, hygroscopic nature) against moisture damage, at least until the time for use arrives. The said sheathing composition may be any suitable non-explosive material or materials capable of being packed or molded l within said shell as a cohesive lining of sufficient strength to resist damage by shocks incidental to normal handling and shipment, prior to its ultimate assembly with a cartridge of explosive. The said end closing means are of such de- 2O sign as to provide easy insertion of an explosive cartridge into the sheath, without physical damage to the sheath body.

The end closures of the sheathings are also so designed :that lthey will permit a plurality of sheathed explosive cartridges to fit snugly together end to end, with a minimum of space and/ or inert covering therebetween, and into such juxtaposition that the propagating explosive wave will be eiectively transmitted throughout .the

length of a column of such assemblies.

Further, the end closures are designed so that, if desired, the sheathings may be rendered mois-V ture or Water resistant, after the insertion of .the

explosive cartridge. 3y

More specifically, we accomplish the objects of our invention by the means and methods set forth in the following specification. Non-limiting structures constituting preferred embodiments of our invention as illustrated in the accompanying drawings form a part of this specication in which:

Figure 1 is a longitudinal sectional view of a sheath showing one form, though not necessarily thepreferred form, of the invention;

Figure 2 is a view like Fig. 1, illustrating one of lthe end closures punctured and pushed inwardly preparatory to the insertion of a stick or cartridge of explosive, such as for example dynamite; 5o

Figure 2a is a view of the structure of Fig. 1 showing a cartridge of explosive inserted in the sheath, but with a paper disc cemented to the annular portion of the crimped wad;

Figure 3 is a View of the structure of Fig. 1 55 showing a cartridge of explosive inserted in the sheath, but with a separate paper disc disposed under and cemented to the segments of the original punctured end closure;

Figure 4 is an end view of the closure of Fig. 1, 60

showing the manner of splitting or puncturing the end closure or Wad, as in Fig. 2, preparatory to inserting the explosive cartridge;

Figure 5 is a longitudinal sectional view illustrating a modified form of end closure consisting of a simple cupped, thin paper wad, inserted in the ends of a plain paper cylinder or shell containing the sheath, but not crimped;

Figure 6 is a view like Fig. 5 but illustrating the explosive cartridge in place and a new paper wad cemented in place and supported by the explosive cartridge; and

Figure 7 is a longitudinal sectional view of another form ofV sheath, one end of which is left permanently open, and with the interior surface 7 CII 4 of the sheath covered by a protecting cylinder of waxed paper.

Like numerals designate corresponding parts in all of the figures of .the drawings.

In the drawings, Figs. 1 to 4 and 5 designate a .tubular shell made preferably of paper. Both for reasons of economy and to reduce the quantity of combustible material, the shell 5 is preferably formed of a relatively light paper.

This shell carries a cylindrical lining 6 of a material .that is capable, when surrounding a cartridge of explosives, of modifying certain of its normal characteristics to the extent desired. For example, the lining 6 may consist of a amesuppressing composition comprising such hygroscopic and/or Water soluble inorganic ingredients as for example sodium chloride, sodium bicarbonate, ammonium chloride, magnesium carbonate, sodium carbonate, magnesium sulphate and the like, for the purpose of suppressing the normal flames `of explosives so as to render them less likely to ignite inflammable gases and dusts in mines and tunnels. Y While our invention is not restricted thereto, most of the desirable sheathing compositions, for various purposes, with which we are familiar, are of such a nature .that thelr require a binder ingredient to impart the necessary physical strength. As a binding ingredient for the sheathing composition there may be employed starch, sodium silicate, dextrin, glue, asbestos fiber, Wood pulp, bagasse fiber, etc. Various fillers and/or density lowering ingredients may also be used in the sheathing composition, as well as ingredients for miscellaneous other purposes as, for example, bagasse pith, kieselguhr, chalk, lime, zinc oxide, silica, balsa sawdust, etc.

The sheathing 6 is molded in place in the shell 5 preferably while moist with water, and is tamped to yield a cylindrical body which, when dry has considerable strength. The open ended .tubular shell 5 serves as a mold for the sheathing composition and provides a path for air to pass through and moisture to escape in the drying operation. In the absence of any moisture to cause its disintegration, this cylindrical body of sheathing material, by reason of its arch formation and the support provided by the shell 5, will resist considerable pressure and stress and may be shipped in this form and stored for considerable periods of time Without breaking down.

The ends of the shell 5 are closed by simple thin cupped paper wads or Vwebs 1, and in the form of the invention illustrated in Figs. 1 to 4, the ends of the shell are crimped into engagement with the edges of the wads. A coating of paraffin, indicated at 8, aids in further excluding moisture, and the empty sheathings, consisting of the assembly illustrated in Fig. 1, may be manufactured at one place and shipped to another for the insertion therein of the sticks of explosive, with the assurance that the sheathing composition will be found in good condition whenever the explosive sticks are placed therein, whether thatbe at a factory or Whether it be in the mine immediately prior to the use of the explosive.

When it is desired to insert the stick of ex- I plosive, one of the end closures 'l may be entirely cut out for that purpose, or the end cap may be cut through in any other desired way. For eX- ample, in Fig. 4, we have illustrated the cap slitted radially at 1a. The points 'lb so created may be folded inwardly as in Fig. 2 and the explosive cartridge inserted into the sheathing. The web or cap is radially slit across only that part of its diameter which covers the` bore oithe Thus` when a stick ofi explosive is; thrust into the bore of thesheath the resultant pointed ends Tb willfold inwardly along thezinner sheath. 6.

surface of the. sheath and be bound thereagainst by the presence of the. stick of explosive, leaving.

which. covers the end of the sheathing, thereby to hold the cartridge of explosive in place. This.

disc could be parafned or otherwise madey watertight.

The points 7b may also be turned outwardly, a

stick of' dynamite. 9 inserted, a plain paper disc. lil placed over the end of the stick of dynamite,

as in Fig. 3, and the points 'lli may then be cemented down upon the disc l. This yields a closure having its outer edges still engage-d in the crimp i l, and by dipping the end of the stick in paraine, a closure is then provided which will be water-tight even in the presence of water under pressure. In many instances, it may be more advantageous to bend the points 'lb down against the end of the explosive cartridges, then cement the disc lil over these points rather than under them, and subsequently dip the end of the stick in paraine as hereinbeiore described. If this method were followed, the disc would necessarily be larger in diameter (as disc la in Fig. 2a) to insure a Snug iit inside the crimp.

In the form of the invention illustrated in Figs. 5 and 6, the shell 5a is like the shell 5 except that its ends are not crimped, and the body of sheathing composition 6 is the same as in Fig. l. The end closure 7c in Fig. 5 is a simple paper wad of cup-like formation, cemented in the end of the shell 5a. When the stick of dynamite is to be inserted, the wad 'lc may be punched through, or it may be removed entirely, and after the stick of dynamite 9a has been put in place, a new wad, "id, may be utilized to seal the end of the shell.

It is to be understood that all of the forms shown may be dipped or otherwise coated with a protective material such as paran to improve their water and/or moisture-resistant characteristics.

While means have been shown for re-sealing the sheath after the insertion of the stick of explosive therein, there are many situations where work is being done under suitable dry conditions where such re-sealing of the cartridge is not essential, and it is to be understood that the invention contemplates the use of the sheath consisting of the shell, and its contained, molded body of sheathing material, by rupturing one of the end seals, inserting a stick of explosive therein, and then using the cartridge within such a limited time that absorption of atmospheric moisture by the sheathing material becomes a matter of no moment.

We may also utilize a sheath of the type illustrated in Fig. '7, wherein at least one of the endclosures of Fig. l, indicated 7b, is punctured and folded inwardly, as in Fig, 2, and a cylinder of thin waxed paper I2 is inserted so as to cover and protect from moisture the inner surface of the sheathing material 6 and retain, in a permanently open position, the segments of the punctured wad 1b. The explosive cartridge of the ultimate assembly may then be conveniently inserted into 6, the;` permanent;- open-ing, thus provided. at. any:L time. and location. desired.

While we. have described thef tubev or' web |25 andthe end-Wadi 'lb asv being ofpaper, itis toi-be: understood that any equivalent.material,` such asv paper backed' aluminum foil, chlorinated. rubber, regenerated cellulose, celluloseacetate, orthe like A may be employed.

We are aware. ofI the. fact. that` it has been previously proposed to. provide sheaths for exploi-I sive compositions; comprisingA pre-formed'.` bodies: of flame-suppressing material. However,` as' far as we are aware, wee are the rst to utilize a; pre:- formed body' of flame-suppressing; or other' typef of sheathing composition for explosivescontainedz in a moisture resistant and protective: casing and wherein` such body of. sheathing compositi/on` is in such form as: to; be. capable of, maintaining. its; I

sha-pe and initial composition during? handling, transportation and storage, evenin the: absence of the explosive; cartridge or any'other'rigid inner supporting element. in con-junction `with which itis to be ultimately used;

The; sheathing structures. of the present invention are particularly adaptable. for use: iny conjunction with the Slo-called permissible explosives utilized in minesA having; inflammable gasesv and/or dusts which are. likely to become ignited' in the presence of.' flame, but are not restricted; thereto. It will be.` evident that any desired type; of blasting explosive may beV employed; in; the sheaths of our invention and We may employ sheathing compositions to modify properties of the blasting explosives, other than flame, as for example to reduce smoke, to reduce poisonous gas evolution, to lessen shattering effects, etc.

It should therefore be clearly understood that we may use any suitable non-explosive sheathing composition, depending on the explosive property modication desired, without departing from our invention. The sheaths of our invention are also non-restricted as to diameter, thickness or length, but will be largely governed by the sizes of explosive cartridges, with which they are to be used, as well as the extent of the explosive property modification desired. It is preferable, however, in order to produce a sufficiently sturdy and. effective sheath, that the thickness be at least about 1/8-even for small diameter cartridges.

The following non-restricting examples will serve to more fully illustrate suitable sheathing compositions of the name-suppressing type, which may be used in carrying out our invention:

The above exemplary compositions may be successfully used to carry out our invention when thoroughly mixed with 10 to 13% of added water, packed by automatic tamping machinery into sheaths having a thickness of about M1" and outside diameters up to 2" and subsequently dried.

In certain cases, we have found it desirable, though not absolutely necessary to our invention. to dissolve or mix certain of the ingredients in '7 the added water, in order to impart greater dry strength to the finished sheaths. For example, it has been indicated to be beneficial to add at least part of magnesium sulphate and/or starch, etc., in this manner.

It will be understood, however, that we contemplate the use of various means to attain the degree of sheath strength, necessary to carrying out our invention, such as adhesives, fibrous binders, solvents, thermosetting materials, plasters, crystallizing compounds, etc.

Therefore, it is understood that the invention includes within its purview whatever changes fairly come Within either the terms or the spirit of the appended claims.

We claim:

1. The herein described method of preparing an explosive assembly for use, where the assembly comprises a stick of explosive and a tubular structure comprising an outer non-metallic shell, a rigid tubular sheath of an explosive property modifying medium constituting a lining within said shell and the bore of which closely approximates the external diameter of the stick of explosive, and a relatively thin paper cap disposed across the end of the sheath and hermetically sealed at its outer edge to said shell, said method including the step of slitting said end cap in a plurality of directions across that portion of its area which covers the bore of the sheath but noi-l across the remainder of its area, whereby `when the stick of explosive is thrust into said bore of the sheath the cut portions of said cap will fold inward along the inner face of the bore ofY the sheath while the. uncut portion thereof will remain engaged at its outer edge with the shell and will be drawn tightly over and cover and protect the end wall of the sheath.

2. The herein described methodj of preparing an explosive assembly for use, where the assembly comprises a stick of explosive and a tubular structure comprising an outer non-metallic shell, a rigid tubular sheath of an explosive property modifying medium constituting a lining Within said shell and the bore oi which closely approximates the external diameter of the stick of explosive, and a relatively thin paper cap disposed across the end of the sheath and secured at its outer edge to said shell, said method including the step of radially slitting said end cap in a plurality of directions across that portion of its area which covers the bore of the sheath but not across the remainder of its area, whereby when the stick of explosive is thrust into said bore of the sheath the cut portion of said cap will fold inward along the inner face or" the bore of the sheath While the uncut portion thereof will remain engaged at its outer edge with the shell and will be drawn tightly over and cover and protect the end wall of the sheath.

DANIEL D. HUYETT.

FRANK S. POLLOCK.

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