US2609751A - Safety blasting operation and blasting assembly for use therein - Google Patents

Description

Sept. 9, 1952 J. TAYLOR ETAL SAFETY BLASTING OPERATION AND BLASTING ASSEMBLY FOR USE THEREIN Filed Jun e 10, 1947 2 SHEETS-SHEET 1 F/Gl.

- ventors .JJRM S TAYJ- THO S THO N Alwmey 2 Sl-lEETS--SHEET 2 FIG. 3.

J. TAYLOR ET AL Sept. 9, 1952 SAFETY BLASTING OPERATION AND BLASTING ASSEMBLY FOR USE THEREIN Filed June 10, 1947 Inventors JAMES TAYJJDR V THOMFSBS TfiOMSCDN w 4 MM Attorney Patented Sept. 9, 1952 SAFETY BLAS'TING OPERATION AND BLAST- ING ASSEMBLY FOR USE THEREIN James Taylor, Saltcoats, and Thomas Thomson, Kilmarnock, Scotland, assignors to Imperial Chemical Industries Limited, a corporation of Great Britain Application June 10, 1947, Serial No. 753,618

In Great Britain July 26, 1946 l 7 Claims. 1

proposed blasting devices of the kind embodying a pressure resisting steel container separated from a perforated discharge head by a closure adapted to yield at a predetermined internal gas pressure produced rapidly but without detonation from a charge of material within the container. The charge is of such nature that the gases emerging through the discharge head into the borehole after the closure has yielded and thereby causing a blasting effect are unaccompanied by flame. The present invention relates more particularly to blasting assemblies embodying blasting devicesof the kind described.

Two of these devices have come into practical use,- namely the Cardox blasting device, in which the gas producing charge comprises a heating charge of a composition capable of strong exothermic decomposition when ignited and a contiguous charge of liquefied carbon dioxide which is gasified by the heating charge and quenches the flame from it; and the Hydrox blasting device in which the charge comprises essentially a solid powder mixture of sodium nitrite and ammonium chloride, which when locally heated at atmospheric pressure is capable of sustaining its own decomposition at a visible rate with the evolution of nitrogen and steam. Under the rising pressure conditions in the pressure resisting container the pressure required to cause the closure to yield is built up in a fraction of a second and without flame. Hydrox blasting assemblies and compositions are described and claimed for instance in British Patent Specifications Nos. 431,935 and 461,647. Other gas producing charges capable of selfsustained decomposition for use in blasting devices of the aforementioned kind have also been proposed.

Whereas in the case of detonating explosives the gas pressure in the borehole is instantaneously developed, in blasting devices of the aforementioned kind the discharge of the gases from the container into the borehole takes a sensible time, and the blast obtained has the general 2 character of a gentle heaving action that favours the production of lump coal rather than the pulverisation of the material in the neighbourhood of the borehole. This is an especially attractive feature of these blasting devices.

The fact that the compositions employed in thes devices are not explosive is an advantage from the point of view of handling and storage. It is also a cognate advantage that the necessary decomposition can be started without the use of detonators, and it is'usual to employ as the electrical initiating device an electric powder fuse. The electric powder fuse comprises essentially a paper package containing a charge of blackpowder in direct ignition relationship with an electric fusehead. Terminals are provided on the pressure resisting container to which the leadin wires from the electric powder fuse within the container and the cables from a. battery or exploder outside the device are attached.

In many cases it would be desirable to arrange that a plurality of shots laid in a single circuit in different boreholes should take effect at short intervals of time one after the other, for instance so that shots containing/charges suitable for cutting, easing and trimming could all be fired after a single shot-laying operation and consequently so that the operations of cutting, easing and trimming could be carried out without the delays incidental to the successive layin experienced when single shot-firing is carried out.

Hitherto, however, it has only been known to do this in the case of detonating explosives and in the case of non-detonating cartridges that cannot be used in fiery or dusty atmospheres; and it is an object of the invention to provide means whereby series firing may be carried out in fiery or dusty atmospheres without the use of detonating explosives.

The invention consists of an assembly of safety blasting devices of the kind embodying a pressure resisting steel container separated from a perforated discharge head bylaclosure adapted to yield at a predetermined gas pressure and a charge of non-detonating material capable of producing a blasting effect unaccompanied by flame in which assembly the said-safety blasting devices are electricallyconnect ed to permit them to be fired simultaneously and some at least of the said chargesof non-detonating material are each in association with a non-detonating delay electric initiatorof a predetermined delay time-interval in initiating relationship with its associated charge.

tween its primary electric ignition element and its main initiating charge in such mannenthat the delay fuse element must be consumed be? fore said main initiating charge can be ignited, and the term non-detonating delay electric initiator will be used hereinafter in thatsenseg The individual delay'fuse elements of the nondetonating delay electric initiators in the set employed in the blasting round are varied in length and/or composition so as to provide the desired differing time intervals, which may for instance range from about second to seconds. In the case of the Cardox blasting device there may be'employe'd as the non-detonating delay electric initiators for instance delay electric powder fuses, which consist essentially of thin metal tubes each containing a blackpowder charge separated from an electric fusehead by a delay fuse element. The delay electric powder fuse may be inserted into the customary heatin charge; advantageously so that it is wholly surroundedby the heater composition. For the firs'tshot there may be used an ordinary elec tric powder fuse. For the "Hydro? blasting device it is important that the main initiating charges of the non-detonating electric initiators should have an effective bulk heating action so that the time taken'for the decomposition of the charge consisting essentially of s'odium nitrite and ammonium chloride within the pressure resisting container, once it has begun, will be negligible in comparison with the shortest of the delay intervals provided by any ofthe delay fuse elements, and for -this purpose a blackpowder charge such as is present as the main initiating charge. in the. electric initiatorsordinarily used for Hydroxi which usually amounts to about 60. grains may he. suitablymodified or replaced or reinforced bya more effective heating compositionx Delay electric, powder fuses maybe used, for instanc i conjunction with charges of a mo e e ec ve h atin composition surround he Thi mo e ef e ti heatin com i i may for instanc heone ad ted o, r c the required heating effect by, chemical reaction between its owncohstituents alone, or between its own constituents and the surrounding charge of Hydrox. In the latter case the said more effective heating composition may for example be based on ammonium perchlorate or potassium perchlorate, For the first shot an electric powder fuse Without a delay element but having its main initiating charge similarly modified, replaced or reinforced may 'be 'us'ed. I

The *electrical connections may be made so that the shots can be 'fired in series or in parallel or in any combination thereo By means of the invention blasting effects not hitherto attainableewith blasting devices of the aforesaid kind may be achieved. A, p

The invention will be further understood by reference 'to the diagrammatic drawings accompanying the specification whereof Figure 1 represents an elevation ofan undercut rock face showing a set of Hydrox blasting devices in a plurality of'shot holes connected up in series, Figure 2 represents a longitudinal view mostly in section of one of the "Hydrox" blasting de-' vices in the set, Figure 3 is a relatively enlarged longitudinal view partly in section of a nondetonating delay electric initiator suitable for use in the Hydrox blasting device of Figure 2, while'Figure 4 is a further enlarged vertical section showing a delay electric fuse forming a portion of the delay electric initiator of Figure 3.

-In Figure 1, C, D, and E are bore holes in the rock 13, which is undercut so as to overhang a coal seams:- The firing ends of three Hydrox" blasting devices H, H and H are seen protrudp ing} from these boreholes.

initiating devices ojf'these blasting devices, which are not visible'in the figure, are connected in The non-detonating series with '9'," battery F by cables G, G, G", and

,G! through a "firing switch K. The non-detonate ing ;i'nitiator for the blasting device I-I comprises no delay fuse element, so that this blasti'ng device fires immediately the circuit is comis a conductor insulated from the metal of the firing head 4, le'ading' from an external terminal socket 6to a plug electrode "1, both insulated from the firing; head 8-. 8; is a socket return terminal. 9 is the non-'det'onating delay electric initiator, the construction ofwhich is seen in greater detail in Figure 3-, this non-detonating delay electric initiator beingyi-n circuit with thefiring heads 'G""'and G. l0 isa charge *of Hydrox' Powder No; 1 which 'fillsthe available spacein thecontainer w r In Figure 3, *H' is-a paper cylinder, I2 is a wooden-plug, I3 is a delayelectric'powder fuse in greaterdetail in-Figure '4' from which the bared end of one of theleading wires is coiled as it enters 'thejr'ece'ss- M, whereit makescontact with the plugelectrode I seen-in Figure 2-. The return leading wire from the delay electric powder fuse is expanded t'o'a' terminal strip 15 which is led between the plug 'I-2 and the tube-t land soldered over a flanged copper ring T6 crimfped aroundsaid plug and tube, thereby forming a'fconne'ction to the terminal 8 through the metal of the firing head A-shoWn-i-n Figure 2, when the latter isserewed home. yl'l' is the main charge ofthe initiating composition and "I 8 is a paper discover which the end of thewall 11- 'ist i vI l f In Figur'e-4, F9j i-s athin metal tube, made of a ductile copper {alloy} within Whichis ioca ted a low tension electric fus'ehea-d 20 'ffhelead-ing; wires from the f usehead areinsulated with re silient tubing as shown at z la d 2i" where they pass through a perforated plug 22galsoof resilient insulating 1 material, which brim-tied between them and 'the wall?! 9, and also where they pass through the -per'f'o'rated lead cup 13' which is crimpedover the plug 22 and the wall 19;; 12 i is a-meta-l delay-sleeve and 25is a delay "fuse.

composition providing the desired] delay p riod in this case "of l ,seccndjcompressed' into the sleeve 24; 26"-'-is' an igniting composition' and ousl'y amouriting'toabout-60 grains. 28 is a metal closure disc over which the end of the wall 19 is turned.

We claim:

1. An assembly of safety blasting devices each of the kind embodying a pressure resisting steel container separated from a perforated discharge head by a closure adapted to yield at a predetermined gas pressure and containing a charge of non-detonating material capable on initiation of undergoing self-sustained reaction yieldin gaseous products whose emergence from said discharge head produces a blasting effect unaccompanied by flame, in which assembly the said safety blasting devices are electrically connected to permit them to be fired simultaneously and at least some of said charges of non-detonating material are each in association with a non-detonating delay electric initiator comprising a shell, containing therein a main initiating charge, a primary electric ignition element, and a delay fuse element positioned for ignition of said main initiating charge, said delay fuse element comprising a second shell containing therein a sleeved first initiating charge, means associated with the electric ignition element for igniting said sleeved first initiating composition, and a second initiating composition positioned for ignition by said first initiating composition, said main initiating charge being separated from said primary electric ignition element by said delay fuse element in such manner that the delay fuse element must be consumed before said main initiating charge can be ignited, thereby providing a predetermined delay time interval between firing and initiating of the main non-detonating blasting charge.

2. An assembly as claimed in claim 1, wherein the non-detonating fuse elements form a set in which the said elements are of varied lengths.

3. An assembly as claimed in claim 1, wherein the non-detonating fuse elements form a set in which the said elements are of varied compositions, said compositions having different combustion speeds.

4. An assembly as claimed in claim 1, wherein the time interval for combustion of said delay fuse elements ranges from second to 5 seconds.

5. An assembly as claimed in claim 1, wherein the charge of non-detonating material capable of producing a blasting effect comprises a composition capable of strong exothermic decomposition and liquid carbon dioxide.

6. An assembly of safety blasting devices of the kind embodying a pressure resisting steel container separated from a perforated discharge head by a closure adapted to yield at a predetermined gas pressure and a charge of solid powder mixture of sodium nitrite and ammonium chloride capable of producing a blasting effect unaccompanied by flame in which assembly the said safety blasting devices are electrically connected to permit them to be fired simultaneously and at least some of said charges are used in association with non-detonating electric initiator comprising a shell, containing therein a main initiating charge, a primary electric ignition element, and a delay fuse element positioned for ignition of said main initiating charge, said delay fuse element comprising a second shell containing therein a sleeved first initiating charge, means associated with the electric inition element for igniting said sleeved first initiating composition, and a second initiating composition positioned for ignition by said first initiating composition, said main initiating charge being separated from said primary electric ignition element by said delay fuse element in such manner that the delay fuse element must be consumed before said main initiating charge can be ignited, thereby providing a predetermined delay time interval between firing and initiation of the main non-detonating blasting charge.

7. A safety blasting device comprising a pressure resisting steel container separated from a perforated discharge head by a closure adapted to yield at a predetermined gas pressure and containing a charge of non-detonating material capable on initiating of undergoing self-sustained reaction yielding gaseous products whose emergence from said discharge head produces'a blasting effect unaccompanied by flame and a nondetonating delay electric initiator in association with said non-detonating material, said nondetonating delay electric initiator comprising a shell, containing therein a main initiating charge, a primary electric ignition element, and a delay fuse element positioned for ignition of said main initiating charge, said delay fuse element comprising a second shell containing therein a sleeved first initiating charge, means associated with the electric ignition element for igniting said sleeved first initiating composition, and a second initiating composition positioned for ignition by said first initiating composition, said main initiating charge being separated from said primary electric ignition element by said delay fuse element in such manner that the delay fuse element must be consumed before said main initiating charge can be ignited.

' JAMES TAYLOR.

THOMAS THOMSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 663,724 Bryant Dec. 11, 1900 821,883 Du Pont May 29, 1906 1,570,733 Eschbach Jan. 26, 1926 1,882,365 Lubelsky Oct. 11, 1932 1,905,863 Harris Apr. 25, 1933 1,950,038 Scott Mar. 6, 1934 2,046,194 Taylor June 30, 1936 2,370,159 Hanley Feb. 27, 1945 FOREIGN PATENTS Number Country Date 380,122 Germany Sept. 3, 1923

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