CA1089708A - Explosive energy-initiatable blasting caps containing a porous ignition and detonation system and method - Google Patents

Abstract

EXPLOSIVE ENERGY-INITIATABLE BLASTING CAPS
CONTAINING A POROUS IGNITION AND DETONATION
SYSTEM AND METHOD

Abstract of the Disclosure A non-electrically initiated blasting cap containing a porous ignition charge which is permeable for flow of a gas stream therethrough and initiatable in response to explosive energy of an explosive gas mixture, including conduit means for emplacing a confined stream of the explosive gas in position with-in the blasting cap for the responsive initiation.
Also provided is a system, including a plurality of the above blasting caps spaced apart for detonation of one or more main charges, together with additional conduit means for con-veying the explosive gas to the plurality of blasting caps for the emplacement, and means for ignition of the thus emplaced explosive gas.
Method is provided for making a blasting cap containing a porous ignition charge, making a porous ignition charge and initiating a non-electric blasting cap for the initiation of a main explosive charge.

Description

~ 9 7~8 Hopler Case 8 This invention relates to non-electri.c ~lasting caps ini.tiated by the heat produced by the ignition of an explosive gas mixture. In one aspect, this invention relates t~ non-electric blasting caps Containing a porous ignition charge, initiatable in response to action of explosive energy of an explosive ~as mixture together with conduit means in contact with the porous ignition charge for emplacing a confined stream of the explosive gas in ignition position within the blasting cap for the respon-sive initiation. A further aspect of this invention relates to a detonator system, including a plurality of blasting caps above de-scribed, together with means for emplacing an explosive gas mixture in ignition relationship with a responsively initiatable ignition charge~s) for the detonation of one or more main charges.
A sti.ll further aspect of this invention relates to methods for making a porous ignition charge, making a non-electrically initi-ated blasting cap and initiating a non-electrically ini.tiated blasting cap for the initiation of a main charge. Other aspects will be apparent in light of the accompanying disclosure and the appended claims.
Non-electric blasting caps initiatable by explosive energy from the detonation of an explosive gas mixture are dis-closed and claimed in U.S. Patent No. 3,885,499 to Hurley. These blasting caps contain an open space adjacent the ignition charge, a first conduit extending from outside the blasting cap into the open space in open communication with the ignition charge so as to conveY the explosive gas as a confinea stream into the open space for responsive ignition of the ignition charge and a sec-ond conduit extending from the open space to the outsi.de of the shell so that a stream of the explosive gas mixture can be continuously passed from the first conduit through the open space and through the second conduit to purge and charge the system for the detonation and responsive ignition of the ignition charge.
In the embodiments illustrated in the above patent, the cap shell is elongated and closed, including at one end a plug

- 2 -1 ~9~7~ 8 type closure member spaced from the ignition charge to form the requisite open space. Both conduits are p~astic and thin walled for flexi~llity purposes.- The first conduit extenas into the sh~ll through the end alosure member and the second conduit ex-tends ~rom the open spaCe either through the plug end closure or through the side of the cap shel~.
This invention is concerned with non-electric blasting caps essentially of the type above described but ~hich do not require an open spaCe between the ignition charge and the plug closure member.
In accordance with the invention, a non-electrically initiated blasting cap is provided which comprises: a closed shell, including a plug closure therefor; an ignition charge in said shell substantially contiguous with said plug closure and initiatable in response to action of explosive energy of an ex-plosive gas mixture, and sufficiently porous and permeable for flow of a gas stream through the interstices thereof; a first con-duit means extending from outside said shell through said plug closure and opening into contiguous contact with said ignition charge so as to convey an explosive gas mixture as a confined stream into initiating position in said interstices for respon-sive initiation of said ignition charge; and a second conduit means extending from contiguous contact with said ignition charge to the outside of said shell, whereby a stream of said explosive gas can be continuously passed from said first conduit means through the interstices of said ignition charge and through said second conduit means to purge and charge said porous ignition charge and thereafter explosive gas in said first conduit means can be ignited for propagation of resulting explosive energy within the interstices of said porous ignition charge for initiation of same.
In a preferred embodiment, the closed shell is elongated, having a base charge in the integrally closed end of the sh~ll, a primer charge in direct operativ~ communication with the base ~Q~97(~8 charge, a porous ig~ition charge in operative contact with the primer charge, with or without a deIay charge intermediate the primer and i~nition charges, wherein the plug closure substanti-ally fills the cross-section of the 5hell and has a first and a second passageway therethrough to allow gas to be introduced into and to exit from the closed she~l. Further, and in preferred practice, the porous ignition charge alone or together with a delay charge substantially fills the cross-section of the closea shell between the primer charge and the plug closure, has inter-connnected pores and is initiatable in response to action ofexplosive energy of an explosive gas mixture, wherein, in turn, the primer charae is detonatable in operative r~sponse to the heat produced by the ig.nition charge or the ignition charge and delay charge, and the base charge is detonatable in response to the detonation of the primer charge, and wherein a delay charge might be included intermediate to the primer and ignition charges, said delay charge would be detonatable in operative response to the heat produced by the ignition charge.
Further, in accordance with the invention, a detonator system is provided for detonation of one or more main charges comprising a plurality of spaced apart non-electrically initiated blasting caps above described, wherein the first passageway of the first of said plurality is connected with a source of explo-sive gas mixture and means for igniting said explosive gas mix-ture, and the second passageway of the first of said plurality is connected with the first passageway of the second of said plurality and thereby in series to provide for purging and charging action of the porous ignition charge in each of said blasting caps by flow of the explosive gas mixture in series flow therethrough and subsequently f~r ignition of said explosive gas mixture to propagate an explosive reaction front in series through each of said blasting caps in said plurality. In addition, the invention includes a method for making a porous i.gnition charge, a method for making a blasting cap containing a porous ignition charge, l(t~971~8 and a method for initiating a non-eIectric blasting cap for the initiation of a mai~ explosive charge.
The invention is illustrated with reference to the draw-ings of which:
FIG. 1 illustrates a zero delay type blasting cap of the invention, including a pair of conduits supported in an igni-tion plug end clo~ure for ingress ana egress of the explosive gas mixture during the purging and charging operation, and thereafter for ingress o~ explosive energy from ignition of the explosive gas mixture FIG. 2 is a delay type blasting cap otherwise the same as that of FIG. l;
FIG. 3 is the same as FIGS. 1 or 2 except that in lieu of the egress conduit, an open passageway is disposed in the side wall of the shell for egress of the explosive gas mixture during the purging and charging operation;
FIG. 4 illustrates a plurality of any of the blasting caps of Figs. 1 and 2 as elements of a detonator system of the invention;
FIG. 5 is the same as FIG. 4 except that it illustrates a plurality of blasting caps of FIG. 3;
FIG. 6 illustrates an embodiment of the blasting system of the invention including a plurality of blasting caps of either or both of FIGS. 1 and 2 supported for detonation of a series of separate main explosive charges. Like parts in the drawings are designated by like numbers.
FIGS. 4-6 are particularly illustrative of the method for initiating non-electric blasting caps for the initiation of main explosive charges.
Referring to FIG. 1, elongated cup-shaped shell lQ of zero delay type blasting cap g is integrally closed at bottom end 11 and is closed at the opposite end 12 by ;gnition plug end closure 13. Base explosive charge 14, primer charge 1~ and porous ignition charge 17 extend in that order in shell 10 from bottom 1(~897(~8 end 11 toward closure plug 13, and face 18 of porous ignition charge 17 is in substantial contiguous contact with face 13' of plug 13. Although charge 17 can be referred to as an initiator or ignition charge, herein-after, it will be described as porous ignition charge 17.
A first tube 19 extends from outside shell 10 through plug closure 13 into communication with por~us ignition charge 17. A second tube 21 extends through plug 13 from a point in communication with porous ignition charge 17 to a point outside shell 10.
Base charge 14 is detonatable in response to detonation of primer charge 16 and primer charge 16 is detonatable in response to the heat output of porous ignition charge 17. Base charge 14 is any suitable high explosive charge such as PETN, RDX, Tetryl, OT the like, with adequate explosive energy output to produce detonation of a main explosive charge in detonating relationship therewith. Exemplary of primer charge 16 is diazodinitrophenol, often a diazodinitrophenol system of the wèll known type incluting a top layer for ignition in response to ignition of the pOI0uS ignition charge 17 and an underlying higher_density layer detonat-able in response to ignition of the top layer. Further exemplary primer chasges 16 are tiazotinitrophenol/potassium chlorate, lead azide, mercuTy ~ulminate, leat styphnate, barium styphnate, potassium dinitrobenzfuroxyl and nannitol hexanitrate tetracene.
POTOUS ignition charge 17 may be a pOTOUS agglomeration of ; partîcles made from an ignition powder; a permeable mat-like pad of fibrous particles of ignition ~aterial; a pellet of minute spheres of ignition material, attachet to one another at their contact surfaces, preferably ; by coating with a binder material, to prevent transport of the spheres into the gas conduits during charging or handling; or a sponge-like pellet of ignition material, with connected porosity to protuce pe$me ability. Porous ignition charge 17 must be pe~eable for flow of a gas stream therethrough, preferably it shoult have an effective cross-sectional ~6~
~,' -1(~897(~8 area ~o~ gas flow at least substantially equal to the cross-sectional area said irst or second condduit means~ Porous ignition charge 17 must also be initiatable in response to action of explosive energy of an explosive gas mixture. Examples of materials which can be used for porous ignition charge 17 are -6a-B

lead/selenium, lead-tin/selenium, tin/selenium, red lead/boron, lead monoxide/boron, lead oxide/manganese, lead monoxide/silicon, and lead/tel~urium By the term "explosive energy" is meant the heat and flame produced by the detonation or deflagration of an explosive gas mixture~ -Tube 19 is generally a plastic tube, as for example,0.103 inch OD by 0.0~0 inch ID and formed from polyethylene; and confines a stream of the explosive gas mixture for flow into porous ignition charge 17, and tube 21 is the same, or similar in design and composition to tube 19. Tube 21, in direct contact with porous ignition charge 17, serves to convey a stream of ex-plosive gas mi~ture from porous ignition charge 17, during the purging and charging operation and, as an element of the initia-tion system of the invention, to direct propagating explosive energy to the succeeding blasting cap in the system.
In the operation of blasting cap assembly 9, a stream of an explosive gas mixture such as a mixture of oxygen with a fuel such as manufactured gas, acetylene, hydrogen, or hydrogen/
methane, is passed through tube 19 into porous ignition charge 17 and is thus emplaced so that, upon ignition, the resulting explosive energy propagates into initiation relationship wïth porous ignition charge 17~ Prior to initiation of porous igni-tion charge 17, enough of the gas, which is initially present in the interconnected pores of charge 17, must be replaced by the explosive gas mixture from tube 19 to insure reliable initiation.
This is accomplished by passing a stream of the explosive gas through tube 19, porous ignltion charge 17 and then tube 21 to purge the pores of charge 17 free from such initially present gas.
FIG. 2 illustrates another embodiment, which is the same as that of FIG. 1 except that the blasting cap 9' is of the delay type and contains a delay charge 22 intermediate the porous igni-tion charge 17 and primer ch~rge 16. Often p~rous ignïtion charge ~ (?i~'37(~8 17 of FIG, 2 dif~ers in composition from that of FIG. 1 to the extent necessary to a~sure a sufficiently hot ignition for delay fuse 23, which is conventionally disposea as a core in a swaged metal tube 24 in ignitable relationship with porous ignition charge 17 and in detonating relationship with primer 16. Often, in a delay cap system such as that of FIG. 2, a wafer type charge (not specifically shown) which has a higher heat of reaction than that of porous ignition charge ~7 and serves as a supplemental source of heat for ignition of the delay fuse, is positioned sub-jacent porous ignition charge 17. Such wafer type charges aregenerally utilized in combination with longer burning and hence less ignition-sensitive delay charges, as disclosed in U.S.
Patent No. 3,776,135.
FIG. 3 illustrates a blasting cap 8 which is similar to the blasting caps of FIGS. 1 and 2 except that in lieu of the tube 21, a conduit or passageway 26, extends from open communication with porous ignition charge 17 through a side wall of shell 10.
Referring to FIG. 4, a series of five blasting caps A-E
inclusive, which can be any of blasting caps 9 and 9' of FIGS. 1 and 2, each for being disposed in detonating relationship with a booster or main explosive charge (neither shown), are in series with the discharge line fro~ a gas mixing and ignition system 27.
Gas mixing and ignition system 27 comprises fuel gas supply 28, connecting through line 29, gas flow control meter 31, and line 30, with gas mixing/ignition chamber 32 and oxidizer gas supply 33, connecting through line 34, flow control meter 36, and line 37 with gas mixing/ignition chamber 32.
In operation of the system 27, a suitable fuel gas, gen-erally a manufactured gas, or a mixture of hydrogen and methane, is passed from supply 28 via line 29, through flow meter 31 which in turn controls the requisite rate of flow and pressure of fuel gas through line 30 to mixing chamber 32 for mixing therein with oxidizer gas from supply 33. Similarly th~ oxidizing gas is passed from supply 33 via line 34, through flow meter 36 wl~ich in turn 1~389'7~

controls the requisite rate of flow and pressure of oxidizer gas through line 37 in the r~quirea proportions for the mixing step in chamber 32. The ~ela~ive proportions of fuel and oxidizer are predetermined to pro~ide an explosive gas mixture which is then ignited in chamber 32 by a spark generated by action of spark plug 39 operativëly extending into chamber 32 for that purpose.
Conduit 38 extends from chamber 32 and connects through a suitable collar, or sleeve-type connector 38a with inlet tube 19 of a first blasting cap 9 of the series A-E to convey flow of the explosive gas mixture from chamber 32 through the tube member 19, porous ignition charge 17 and exit flow tube 21, and in series through each of the successive caps B-E to thereby purge each p~rous ignition charge ~7 of substantially all gas other than that from line 38 and in turn to charge each porous ignition charge 17 with the explosive gas mixture. Tube 21 of each of blasting caps 4A-D connects with tube 19 of the succeeding blasting cap of the Series B-E by any suitable means, such as by a plastic collar, or sleeve, connector 20, During the purging and charging operation, the stream of explosive gas mixture from line 38 is passed in series through tube 19, porous ignition charge 17 and tube 21 of each of caps A-E; and the flow o explosiv~ gas through the series A-E is main-tained for a time duration sufficient to complete the requisite purging and charging of all blasting cap ignition charges 17, gen-erally for a period of at least about one minute, but often from five to ten minutes, depending upon the flow variables involved.
Upon completion of the purging and charging action and with the flow of the explosive gas mixture in line 38 stopped, the ignitor member 39 is actuat~d, and, by action of the spark, the explosive gas mixture thus smplaced for i~nition and respon-sive initiatioh of the porous ignition charge, is ignited. Check valve syst~m 35 in chamber 32 precludes back pressure flow of explosive energy into the upstream flow and supply stream. The explosive reaction wave front then travels, confined in line 38 _ g _ 97~8 and each of tubes 19 and ~1, through eaah poroug lgnition charge 17 in series A-E.
Occasionally, one'or more of the tubes 19 and 21 may fail to confine the explosive energy, in which ~vent the reaction rate of the particular explosive gas is sufficiently hig~ to per-mit the explosive reaction wave front to travel ahead of the tube breakage so that the latter does not preclude series travel of the wave front through the series of caps.
FIG. S illustrates another embodiment of the detonator system of the invention which is the same as that in FIG. 4 except that blasting caps 8 of FIG. 3 are in lieu of those of FIGS. 1 or 2. In the embodimsnt of FIG. 5, a continuous stream of an explosive gas mixture from chamber 32 is passed through line 38 as a manifold supply connecting by suitable connector means, such as a collar or sleeve ~S, with each of the caps A-E respectively to supply a stream of explosive gas mixture through each tube 19 into each corresponding porous ignition charge 17A-E. InGtead of the series type purging and charging action of FIG. 4, the explosive gas mixture from each porous ignition charge 17 is dis-charged therefrom through the conduit, or opening, 26 in a sidewall of each cap assembly. As in FIG. 4, after the requisite' purging and charging period, the explosive gas mixture in line 38 is ignited by action of spark generation means in chamber 32.
The explosive reaction wave front then travels along line'38 through each tube 19, to, in each instance, emplace the'resulting explosive energy in initiating contact with the ignition charge.
Referring to FIG. ~, each of the separate bore holes 41, in earth formation 40, of FIGS. 6A-C is loaded with any suitable cap-insensitive main exp~esive charge 4~ such as an aqueous gel type explosive, prills/fuel oi~, or the'like. A pair of suita~le boosters 43 is embedd~d i~ each of the màin explosive masses.
Each booster is ~ap-sensitive and is in detonating reIationship with main explosive aharge'42 adjacent thereto, and ïs initiatea le~s7us by action of a blasting cap system of the invention such as that of FIG~ 4.
Thus in each b~re ho~e 41 of FIG. 6, two booster units 43, e.g., each 500 grams of PE~N, tetryl ox the like are embedded and spaced apart, in main explosive Gharge 42 to provide for det-onation of the main explosive charge 42 along its entire length.
Each hooster unit 4~ contains a blasting cap 9 or 9' of FIGS. 1 or 2, respectively. The explosive gas mixture from chamber 32 (not shown) is supplied via line 38 and passed in series through the entire plurality of blasting caps 9 and/or 9' in the separate booster charges in the three bore holes via tubes 19 and 21 of each blasting cap, as illustrated with r~erence to FIG. 4. The flow of explosive gas mixture rom line 38 in series through the en-- tire plurality of blasting caps in the bore holes 41A-C is con-tinued until each porous ignition charge 17 is substantially free from initially present gas, ater which the ~low of the ex-plosive gas mixture stream is terminated or continued as desired, followed by ignition of the gas in chamber 32 and travel of the explosive reaction wave front in series through each of the blast-ing caps in initiation relationship with the main explosive chargetherein. Dependent on whether a main charge is reliably cap-sensitive~ a booster charge(s) may not be required, in which event one or more of the blasting caps are embedded directly in the main charge, and are charged with gas and initiated.
The system of FIG. 6 containing delay caps regulates the burning time of each delay charge and hence, the delay between shots in each bore hole including, when desired, a progressively longer delay time along the entire series of boosters in the bore holes of FIG. 6.

3~ Although the invention is specifically illustrated with reference to delay and nondelay type blasting caps utilizing a porous ignition charge in combination with primer and base charges, with or without an intermediate delay charge, it is to be under-stood that the invention is applicable to initiation devices in 1(~l3~7Q8 Which the ignition charge is the only charge in the device, or is utili~ed with o~e or more additional charges, exemplary of which initiating devices are those of the deflagrating or squib type.
A non-e~ectric b~asting cap 9 containing a porous ignition charge, as shown in FIG. 1, is made by initially pro-viding ~longated cup-shaped shell 10 which is integrally closed at bottom end 11~ Base explosive charge 14 and primer charge 16 are placed in the shell 10, with base explosive charge 14 in contact with the inner surface of bottom end 11 and primer charge 16 resting thereon. Where a delay type, non-electric blasting cap with porous ignition charge is desired, as shown in FIG. 2, the delay charge or fuse assembly 22 is placed in shell 10 upon and in contact with primer charge 16. The porous ignition charge 17 may be prepared by initially forming a suitable ighition powder into a pellet, i~e., by pressing the powder within a cylindrical press mold, with sufficient pressure to consolidate the ignition powder. The compressed pellet is then removed from the press mold and cut into small fragments. These fragments are then screened to provide a predetermined size range, free of fine par-ticles and dust, preferably with a maximum cross-sectiona~ dimen-sion less tha~ about 0.187 inch, fo~ flow of a fluid therethrough.
The fragments are then placed in shell 10, thereby having a por-tion thereof in direct contact with primer charge 16 or delay charge 22, if present. The charge fragments are placed in shell 10 to a predetermined height, after which, ignition plug end closure 13, containing tubes 19 and 21, is forced into shell 10 through end 12 until contact is made by face 13' of plug 13 with face 18 of porous ignition charge 17. A standardized fluid flow test is then made on each cap to detect any leakage or blockage of the passageways within th~ cap.

Exa~le Six non-electric b~asting caps containing porous ignition ch~rges were made in accordancQ with the method of this invention.

7(~8 These six blasting caps were of the delay type containing a base charge, primer charge, de~ay charge and porous ignition charge as shown in FIG, 2. Each cap was made with a cylindrical aluminum shell having a lehgth of 2~01 in., an I.D. of from 0 249 in. to 0.256 in. and ~n O.D. of 0.288 in. A base charge 14, which con-sisted of PETN weighing 0.4 gm., was placed through end 12 into shell 10 in contact with the inher ace of bottom end 11. The PETN was placed in the shell as a loose powder and then pressed in the shell. The primer aharge 16 consisted of a cylindrical pelle~ of dia~odinitrophenol, weighing 0.29 gm., and was placed through end 12 onto and in contact with base charge 14. The com-bined height of base charge 14 and primer charge 16 was approx-imately 0.9 in. The delay charge 22 consisted of a 2 gm. pressed cylindrical pellet of, ~weight basis), lead, 46.9%, tin, 8.3%, selenium, 11.6%, lead oxide, 32.2%, and boron, 1.0~, having a length of 0.4 in. This pellet, designed to provide a delay time of 300-400 milliseconds, was placed through end 12 into cap 10 upon and in contact with primer charge 16, to provide a combined base, primer, and delay charge height of 1.3". The porous igni-tion charge 17 was prepared from an ignition powder consistingof (weight basis) lead, 68.4~, selenium, 26.6%, potassium per-chlorate, 2.2%, aluminum, 1.1%, and snow floss, 1.7%. The igni-tion powder was ~ormed into a .250 in. O.D. 0.25 in. pellet by placing the powder into a cylindrical mold and subjecting said powder to a pressure of 3000 p.s.i. The pellet was then cut with a razor blade into small irregular fragments. The desired size range was obtained by retrieving the fragments which passed through a #4 sieve (U.S.S.S.) and were retained on a ~8 sieve (U.S.S.S.). The fragments were then loosely placed in shell 10 to a total column height of approximatel~ 1.8 ih. for each cap.
The alosure plug assembly 13, which was 0.45 in. long, was then forced into shell ~0 until contact was made by inner face 13' of plug assem~l~ 13 with outer face 18 of porous ignition charge 17.
Closure plug assemb~y 13 contained two 12 in. long tubes 19 and ~ 9708 21 made of low density polyethylene and having an 0.103 in. O.D.
and 0.060 in. I.D., whiah were bonded to plug a8semb1y 13 and had terminal ends 19', within the passageways of plug assembly 13, whioh were in aontact with porous ignition aharge 17. The plug assembly 13 was then affixed to the sheIl 10 by crimping shell 10 around its extQrior along the portion adjacQnt to plug assembly ~ 13.
.: .~
A test for circuit continuity was then separately performed on each of the six caps by passing nitrogen gas at 50 p.s.i.g. through tu~e 19, and measuring the exit flow from tube 21.
~ A stream of gas, comprising, on a volume basis, 50%
; methane and 50% hydrogen, at an approximate rate of 25 liters (S.T.P.) per minute at 40 p.s.i.g., was mixed with a separate stream of oxygen at a rate of 59 liters (S.T.P.~ per minute at 4Q p.s.i.g. through 10 feet of 0.25 in. O.D. by 0.120 in. I.D.
polyethylene tubing to form an explosive gas mixture as the com-bined stream. The oxygen con~tituted approximately 71% of the ; combined stream, which was passed through each individual cap for approximately 0.2~ minute to pUrge and charge the tubing circuit, including porous ignition charge 17, thereby replacing the air which originally filled the tubing circuit, with the explosive gas mixture. After charging, the resulting explosive gas mixture was in each instance ignited upstream rom the individual caps by a spark, whereupon the explosive energy associated with the detonation front, which passed through tube 19 and into porous ignition cha~ge 17, initiated each ignition charge. Each of the six caps fired successfully.
As wiil be evident to those skilled in the art, various modifications can be made in the ~ight of the foregoing disclosure and disc~ssion, without departing from the spirit or scope of the disclosure or from the scop~ of the claims.

Claims (24)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A non-electrically initiated blasting cap comprising a closed shell, including a plug closure therefor an ignition charge in said shell substantially contiguous with said plug closure and initiatable in response to action of explosive energy of an explosive gas mixture, and sufficiently porous and perme-able for flow of a gas stream through the interstices thereof; a first conduit means extending from outside said shell through said plug closure and opening into contiguous contact with said ignition charge so as to convey an explosive gas mixture as a confined stream into ignition position in said interstices for responsive initiation of said ignition charge; and a second con-duit means extending from contiguous contact with said iginition charge to the outside of the said shell, whereby a stream of said explosive gas can be continuously passed from said first conduit means through the interstices of said ignition charge and through said second conduit means to purge and charge said porous ignition charge and thereafter explosive gas in said first conduit means can be ignited for propagation of resulting explosive energy within the interstices of said porous ignition charge for igni-tion of same.

2. A blasting cap of claim 1, base, primer and said ignition charges, with or without a delay charge intermediate said primer and ignition charges, contiguously extending in that order toward said plug closure.

3. In a blasting cap of claim 2, said second conduit means comprising a passageway in a side wall of said shell.

4. In a blasting cap of claim 2, said second conduit means extending through said plug closure.

5. The blasting cap of claim 1 wherein said ignition charge has an effective cross-sectional area for gas flow at least substantially equal to the cross-sectional area of said first or second conduit means.

6. The blasting cap of claim 1 wherein said ignition charge is a pellet of agglomerated ignition powder particles, comprising, by weight, about 68.4% lead, 26.6% selenium, 2.2 potassium perchlorate, 1.1% aluminum and 1.7% snow floss.

7. The blasting cap of claim 1 wherein said ignition charge is a cohesive agglomerate of individual particles having a multiplicity of interstitial passageways therethrough.

8. The blasting cap of claim 1, wherein said shell is elongated and said first conduit means comprises a tube extending from outside said shell through said plug closure member in sub-stantial closing contact with said ignition charge.

9. The blasting cap of claim 1, wherein said second conduit means is in a side wall of said shell adjacent to said ignition charge.

10. The blasting cap of claim 8, wherein said second conduit means comprises an additional tube extending through said plug closure in substantial closing contact with said ignition charge.

11. A detonator system for detonation of one or more main charges comprising: a plurality of spaced apart non-electrically initiated blasting caps, each cap having; a closed shell, a base charge in the closed end of said shell, a primer charge in direct communication with said base charge, an igni-tion charge in substantial contact with said primer charge, a plug closure member closing the other end of said shell having an end thereof substantially filling the cross-section of said shell and abutting against said ignition charge, said plug having a first and a second passageway therethrough to allow gas to be introduced into and to exit from said ignition charge, said ignition charge substantially filling the cross-section of said shell between said primer charge and said plug closure member, said ignition charge being sufficiently porous and permeable for flow of a gas stream through the interstices thereof and being initiatable in response to action of explosive energy of an explosive gas mixture, wherein said primer charge is detonatable in response to the initiation of said ignition charge; an explosive gas mixture; means for introducing an explosive gas mixture into said plurality of blasting caps; means for igniting said explosive gas mixture; wherein said first passageway of the first of said plurality of blasting caps is connected to means for introducing and means for igniting said explosive gas mixture, said second passageway of the first of said plurality is connected to said first passageway of the second of said plurality and each of said first passageways of the remaining plurality of blasting caps being connected to said second passageway of the preceding blasting cap to first allow said explosive gas mixture to flow through each of said interconnected blasting caps in said plurality to purge and charge with said explosive gas mixture said blasting caps and to allow an explosive reaction wave front in response to ignition of said explosive gas mixture to propagate sequentially through each of said blasting caps in said plurality.

12. A detonator system for detonation of one or more main charges comprising: a plurality of spaced apart non-electrically initiated blasting caps, each cap having, a cup-shaped shell, a base charge in the closed end of said shell, a primer charge in direct communication with said base charge, a delay charge in direct communication with said primer charge, an ignition charge in substantial contact with said delay charge, a plug closure member closing the other end of said shell having an end thereof substantially filling the cross-section of said shell and abutting against said ignition charge, said plug having a first and a second passageway therethrough, to allow gas to be introduced into and to exit from said igni-tion charge, said ignition charge substantially filling the cross-section of said shell between said delay charge and said plug closure member, said ignition charge being sufficiently por-ous and permeable for flow of a gas stream through the inter-stices thereof and being initiatable in response to action of explosive energy of an explosive gas mixture, wherein said delay charge is detonatable in response to the initiation of said ignition charge an explosive gas mixture; means for introducing said explosive gas mixture into said plurality of blasting caps;
means for igniting said explosive gas mixture; wherein said first passageway of the first of said plurality of blasting caps is connected to means for introducing and means for igniting said explosive gas mixture, said second passageway of the first of said plurality is connected to said first passageway of the second of said plurality and each of said first passageways of the remaining plurality of blasting caps being connected to said second passageway of the preceding blasting cap to first allow said explosive gas mixture to flow through each of said inter-connected blasting caps in said plurality to purge and charge with said explosive gas mixture said blasting caps and to allow an explosive reaction wave front in response to ignition of said explosive gas mixture to propagate sequentially through each of said blasting caps in said plurality.

13. In a detonator system of claim 11, each said blast-ing cap having an elongated shell and said first passageway comprising a tube extending from outside said shell through said plug closure member in substantial closing contact with said ignition charge.

14. In a detonator system of claim 12, each said blast-ing cap having an elongated shell and said first passageway com-prising a tube extending from outside said shell through said plug closure member in substantial closing contact with said ignition charge.

15. In a detonator system of claim 13, each said blast-ing cap having as said second passageway a second tube extending through said plug closure member.

16. In a detonator system of claim 14, each said blast-ing cap having as said second passageway a second tube extending through said plug closure member.

17. A detonator system of claim 15 in detonating rela-tionship with at least one main explosive charge.

18. A detonator system of claim 16 in detonating rela-tionship with at least one main explosive charge.

19. A method of making a non-electrically initiated blasting cap comprising: forming a pellet from an ignition powder; compressing said pellet; cutting said pellet into small fragments; separating said fragments to provide an aggregate fraction having a predetermined size range for flow of fluid therethrough; placing said aggregate fraction within a cap shell such that said aggregate fraction substantially fills the cross-section thereof, to form a porous ignition charge permeable to said fluid flow; and inserting a plug closure member containing passageways for ingress and egress of fluid, into said cap shell, wherein said plug closure member is in substantial closing con-tact with said ignition charge to allow entering explosive gas mixture to penetrate said porous ignition charge for initial purging of air therefrom and subsequent initiation within said ignition charge.

20. The method of claim 19 wherein said pellet is compressed at a pressure of about 3000 pounds per square inch.

21. The method of claim 19 wherein said aggregate frac-tion is provided by retaining fragments that have a maximum cross-sectional dimension less than about 0.187 inch.

22. A method for making an ignition charge comprising:
forming a pellet from an ignition powder; compressing said pellet;
cutting said pellet into small fragments; and forming an ignition charge from said fragments such that the interstices between said fragments will support fluid flow.

23. The method of claim 22 including the additional step of coating said fragments with a binder.

24. A method for initiating a non-electric blasting cap for the initiation of a main explosive charge, wherein said blast-ing cap contains an ignition charge initiatable in response to action of explosive energy of an explosive gas mixture, said method comprising passing an explosive gas mixture into said blasting cap and directly into the interstices of an ignition charge pervious to flow of gas therethrough for ignition and re-sponsive initiation of said ignition charge and then from said interstices to the outside of said blasting cap to purge said ignition charge of gases other than said explosive gas, there-after retaining said explosive gas as a confined stream along the path of said purge and igniting same upstream from said blasting cap, and propagating resulting explosive energy along said path into ignition relationship with said ignition charge.