US3295445A - Method of blasting - Google Patents

Description

Jan. 3, 1967 T. z.BA1 ETAL METHOD OF BLASTING .v

Filed July 2l, 1965 zot d@ ZQEE ,Tsw @Emi mozoumj ooo@ wmzowj @com wnomzzw mozmnomw msi m 050m@ N 505 m505 llwmjo NIV $.61 N|Y L $.51 wm Teoow @55mg wsoomm @50mg Tem eoom smv 350002 350%: Eem@ 268B @ENE @soos 25mg A260; www m6 wm@ w m5 wm@ mm@ m@ @o no 253mg 758mm@ Tsomwwu Tsooom. wsom $628 .29 :E032 eooo: me om@ 320mm@ @55S meco@ Econ; w59 i@ m5 m6 8 m0 u H2552 @22 memt Engl @CSE 352m@ eomt Gem 3&3.: 25ms @SMS2 39000@ E508 @soos GEOS mm@ Q mm@ 5 m3 Nm@ m0 m@ No INVENTORS Thomas Z. Boll United States Patent Oiice Patented `Fain. 3, 1967 3,295,445 METHOD F BLASTING Thomas Z. Ball, New Ringgold, and Edwin G. Brown, Thornton, Pa., assignors to Atlas Chemical Industries, Inc., Wilmington, Del., a corporation of Delaware Filed July 21, 1965, Ser. No. 473,597 3 Claims. (Cl. 102-23) This invention relates to a method of detonating a large number of explosive charges in a desired sequence. More particularly, it relates to a method of blasting utilizing a multiplicity of charges arranged in a plurality of groups which are denoted sequentially by means of delay detonators in such la manner so that groups of charges not yet red are initiated before proximate charges in adjacent groups are tired.

In blasting oper-ations utilized in mining it is often desirable to re a large number of shots along a face o-r wall being mined in .a -denite sequence at very close intervals. Generally, this technique is desired 'because it usually results in blastin-g in which Ibetter breaking of the tace is `achieved than whe-n larger but less numerous explosive charges are used or when all of the charges placed in the face are caused to fire at the same instant.

In the long wall method 4of mining a typical face to be blasted may be several hundred feet long. To satisfactorily break-up such a face the explosive charges to be used are placed in holes arranged in rows running along the length of the face. For example, holes may be arranged in vertical rows so that each hole in a given row is approximately three feet from the next hole and the vertical rows are spaced approximately three feet apart. Thus with a face of about 300 feet long and six feet high there will be about 300 blasting holes containing an equal number of explosive charges. In blasting such a face it is advantageous to detonate the entire face as a single round but it is desirable to have a minimum number of detonations (preferably one) occurring `at any given instant in order to minimize damage to surrounding roofs due to iiying material and/or vibrations and to produce a good breaking of the face being blasted. Therefore, in essence, it is desirable to have a method of shooting a large number of charges over a relatively short period in such a manner so that only one charge or a few charges is shot at any given instant but such that all of the charges are shot Within a period of a few seconds or longer in a desired sequence. It is important in the blasting of a face, as ydescribed above, that the various charges be arranged and tired in a manner so that the leads running to charges adjacent to those fired a-re not broken by flying material from charges previously fired.

An object of this invention is t-o provide a method of detonating a large number of explosive charges in close order in a desired sequence.

Another object of this invention is to p-rovide a method of blasting with a large number of explosive charges through the use of delay tiring detonators arranged in groups whereby only one explosive charge is fired at any given instant and whereby the groups of charges not yetA fired are initiated sequentially before proximate charges in adjacent groups are tired.

Other objects of this invention will be obvious to those skilled in the art in view of the following description.

The method of the present invention involves blasting wherein a multiplicity of changes is detonated in a desired sequence by delay detonators. The present method comprises initiating del-ay tiring detonators in separate groups so that the charges in a first group are initiated at one time while charges in adjacent groups are initiated at a later time, but prior to detonation of any charge in said rst group which has a field of execution inclusive of any charge of said adjacent group. However, according to the present method, the delay between initiation -and ring of Iany charge of any such adjacent group within such iield of execution is such that said charge of such adjacent group detonates after ldetonation of the charges having such a field ofexecution.

In the present invention, the desired firing sequence is achieved -by utilizing a series `of varying delay firing detonators. Suitably, either the fuse or electric type of blasting cap may be used in the present method. The delay tiring electric blasting cap-s which lare used in accordance with the present invention are such that can be initiated and will lire over a period of time. -Delay tiring electric lblasting caps are known to be comprised of the various customary elements of conventional electric blasting caps, 'and in addition a train of Ideilagrating material located bet-Ween the ignition element and the detonating charges in the blasting caps. The train of defagrating material in the cap produces the desired delay in the firing of the cap after its ignition. The period of dela-y after ignition and before firing is varied according to the length and speed of burning of the delay train in the yblasting cap. In the utilization of the p-referred embodiment of this invention it is desirable to use delay tiring electric blasting caps which possess delay periods of from a fraction of one second to about 7.5 seconds or longer and which vary between each other at intervals between about 5 and about 125 milliseconds.

The delay iiring of the lfuse-type caps is obtained and varied by using varying types and lengths of safety fuses. In roperation such fuses are properly connected to a trunk line of ignition cord, such as sold under the trademark Ignitacord `and manufactured by the Ensign-Bickford Co. of Simsbury, Connecticut, which in turn is ignited by means of an electric starter which is initiated Iby means of an electric multiple circuit switch located in an area remote from the blasting site.

The blasting method of the present invention will be more readily understood in view of the figure of the accompanying drawing which illustrates an embodiment of the subject invention wherein delay electric blasting caps are used in combination with an ele-ctric timed sequence switch. However, such a switch or timing device is not essential to carry out the present method. Such timing and initiation may be done manually. The igure represents la vertical elevation of a face to be blasted. The C numbers sh-own in the ligure are the identifying numbers of the detonators `as positioned within holes of the face illustrated. Due to the large number ort holes involved, the face as illust-rated in the figure is shown in broken section. The numbers in parenthesis indicate the nominal delay time in millseconds of the various detonators utilized. The numbers in brackets indicate the sum of the delay time in milliseconds of the blasting cap used plus the sequence switch delay in initiating the particular group involved and represents the total time t-o elapse 'between detonation of the charge in Group 1 wherein Cap C1 is positioned and the detonation of the hole under consideration in either Groups 2 or 3. Cap C1 is a standard instantaneous electric blasting cap and not a delay firing blasting cap.

In the ligure, the first 36 holes are connected in an electrical circuit and connected to the iirst pair of terminals of a delay firing sequence switch. The next 24 holes are connected in a second circuit and connected to a second pair of terminals of the same delay firing sequence switch. The 24 holes are connected in a third circuit and connected to a third pair of terminals of the same delay tiring sequence switch. In practice the numbers of explosive charges and corresponding groups could be in creased to a great number and the circuits could be in parallel, in series or in parallel-series. Additionally, the changes in the various gr-oups could be arranged in any suitable pattern. The tiring pattern and times indicated in the gure are achieved by using the delay electric blasting caps indicated with a sequence switch that is designed to furnish current to the successive pairs of terminals indicated above at a time interval of about 3000 milliseconds. However, the `delay time of the sequence ring switch may 'be suitably varied to meet the particular needs in regard to the area to be blasted and the number of blasting caps to tbe utilized.

AIn the illustration of the figure when the sequence ring switch is activated, current is supplied instantaneously to the blasting caps in the first 36 holes making up Group l. These caps will then lire in turn according to the delay train in the cap. Cap C36 in the igure has a firing delay of 3500 milliseconds. While the ydelay blasting caps in the rst 36 holes are in the process of firing, the sequence switch is in motion and at 3000 milliseconds cap C32 `of Group l tires and at the same instant the sequence switoh supplies current to the second group of blasting caps containing 24 blasting caps. Thus all of the caps in Group 2 will be initiated before caps C33, C34, C35, and C36 of Group l fire. Similarly, this same process will Ibe 'repeated in 3000 millisecond intervals With each succeeding group, connected to the sequence switch.

According to the present method, all of the deonators of each succeeding circuit or lgroup Will respectively receive their initiating current prior to the firing of the proximate adjacent charges in each of the respective preceding igroups as shown in the gure. This precaution is taken to insure intiation of the caps in a group before the wires leading to each succeeding group are exposed to breakage by rock movement from nearby holes of the preceding group.

What we claim is:

1. In a method of blasting wherein a multiplicity of charges is detonated at varying times by delay detonators, the improvement which comprises initiating the detonators in separate groups of charges so that the detonators in a rst group are initiated at one time While detonators in an adjacent group are initiated at a later time but prior to detonation of any charge in such rst group which has a iield of execution inclusive of any charge of such adjacent group, the delay between initiation 4 and tiring of a detonator of any charge of such adjacent group Within such field of execution being such that said charge of such adjacent group detonates after detonation of the change having such iield of execution.

2. In a method of :blasting wherein a multiplicity of charges is arranged in a line and detonated sequentially along said line by means of delay detonators, the improvement which comprises grouping said detonators in successive sections in such line of charges in separate groups, initiating a rst suclh group, and then later, but prior to the detonation of any charge in such first group which has a eld of execution inclusive of any charge in the next adjacent group, initiating the said next adjacent group, the delay between initiating and ring of a detonator of any charge of said adjacent group within such eld of execution being such that said charge of said adjacent group detonates after detonation of the charge having such eld of execution.

3. A method of blasting comprising connecting a plurality of varying delay liring electric detonators in a multipilicity `of electrical circuits in a preselected ring order, arranging each of said circuits of detonators in groups of vertical rows in a -face to be blasted, connecting each of said circuits to a time sequence ring switch, initiating a first circuit vby said time sequence firing switch, then initiating the next adjacent circuit by means of said time sequence firing switch so that the next adjacent circuit is initiated before the detonation of any charge in such rst circuit which has a field of execution inclusive of any charge of said next adjacent circuit, the delay between intiation and firing of a detonator of any charge of said adjacent ycircuit within such a eld of execution being such that said charge of said adjacent circuit detonates after detonation of the charges havin-g such eld of execution.

References Cited by the Examiner UNITED STATES PATENTS 12/1955 Colemah 102-23 12/ 1955 Janelid 102-23

Claims (1)

1. IN A METHOD OF BLASTING WHEREIN A MULTIPLICITY OF CHARGES IS DETONATED AT VARYING TIMES BY DELAY DETONATORS, THE IMPROVEMENT WHICH COMPRISES INITIATING THE DETONATORS IN SEPARATE GROUPS OF CHARGES SO THAT THE DETONATORS IN A FIRST GROUP ARE INITIATED AT ONE TIME WHILE DETONATORS IN AN ADJACENT GROUP ARE INITIATED AT A LATER TIME BUT PRIOR TO DETONATION OF ANY CHARGE IN SUCH FIRST

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