US1578998A

US1578998A - Shot-firing system

Info

Publication number: US1578998A
Application number: US13745A
Authority: US
Inventors: John J Jakosky
Original assignee: EDWARD STEIDLE
Current assignee: EDWARD STEIDLE
Priority date: 1925-03-07
Filing date: 1925-03-07
Publication date: 1926-03-30
Anticipated expiration: 1943-03-30

Description

March so 192s. 1,578,998

J. J. JAKOSKY SHOT FIRING SYSTEM Filed March '7 1925 F'IELI.

Fll3'-Z.

/7 m W Q W/TNESSES UNITED J'OHN'J. JAKOSKY, or PITTSBURGH. PENNSYLVANIA, Assrenon or ONE-THIRD T0 7 PATENT. OFFIC.

EDWARD STEIDLE, OF PITTSBURGH, PENNSYLVANIA.

SHOT-FIRING SYSTEM.

Application filed March 7, 1925.' Serial No. 13,745;

To all whom it may concern:

Be it known that 1, JOHN J. JAKOSKY, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Shot-Firing Systems, of which the following is a specification.

. The invention relates to shot firing, by which is meant the detonating, igniting or exploding of charges of detonative or explosive material used for blasting in coal andmetal mines, open pit mining, rock excavations, stone quarries, etc.

In the customary practice of firing shots, a detonator having short lead wires connected to it is properly positioned in a charge, and its lead wires are electrically connected to lead conductors which are of suflicient are electrically connected to a shot firing apparatus, which usually comprises a blasting machine, power circuit or battery, and a i switch for closing a circuit through one or the other and the long lead conductors. When the switch is closed, adirect of alternating current flows through the conductors to fire or prime the detonator.

In the use of this apparatus, premature blasts occasionally occur resulting in serious, and sometimes fatal, accidents to workmen. It has been found that such premature blasts are due largely to various stray and leakage currents that gain access to the long lead conductors, which frequently have faulty or insuflicient insulation at splices, and at other places where the insulation is abraded or otherwise injured. The conditions of serv ice are such that, from a practical point of view. it is impossible to assure adequate insulation throughout the entire length of the lead conductors.

The currents which may gain access to these conductors and cause premature firing of shots are either alternating currents of frequencies the same as those of commercial power or supply lines. or are direct currents.

For example, if insufiicicntly insulated portions of the long lead conductors happen to' 'contact with electric track rails, or signal mines and quarries makes favorable conditions for the conduction of stray currents from grounded conductors or from leakage points of supposedly insulated conductors. I have found from extensive experiments that the resistanceof different earth strata maybe such as toafford very favorable conditions for the development of high potentials between two'exposed or insufficiently insulated portions of the long lead conductors used in shot firing apparatus, and when leakage currents are present in such strata there are afforded extensiveareas for such currents to gain access to the long lead conductors and cause premature firing.

A further characteristic of shot firing apparatus of the character explained is that the long lead conductors must be quite large in order to carry the relatively low voltage and high amperage currents generated by a battery or blasting machine, and because of this there is so much resistance to the flow of current and so much loss of voltage at splices andjoints that not infrequently there is not sufficient electroinotive force available to send a current of sufficient magnitude to fire a shot when the circuit is closed through the battery or blasting machine.

The object of this invention is to provide an economic shot firing system whereby such stray and leakage currents as may be found in the conditions of service cannot under any'circumstances effect a premature blast, and in which the prejudicial effect of loss of shot firing currents is eliminated.

The shot. firing system provided accordii-i'g to this invention comprises two essential elements, first, a generator for generatorder to have premature firing take place, because the dampness which prevails 'in' at least to any iug an alternating current of high voltage and low amperage, and of a frequency much greater than that of commercial currents, and second, a transformer for transforn'iing the current so generated into one of low voltage and highamperage fur firing ashot or shots, the generator and transformer being connected by long lead conductors so that the former may be placed at a safe distance from a charge to be fired, and the latter placed close tothe charge.

The transformer, to the secondary of which the short lead wires of one or more detonators may be attached, is so designed or tuned that it is capable of transforming substantial extent, only currents of the high frequency generated by the generator element of the system. Be cause direct current passing through the primary of a transformer will not induce any current in its secondary, no direct cur-- rent which may gain access to the long lead conductors will have any effect upon a detonator in circuit with the secondary. Furthermore, because the transformer is tuned to transform onlycurrentsof a much higher frequency than those of commercial alternating currents, any alternating current which, under the conditions of service, may gain access to the long lead conductors, will not be of such frequency as to cause the transformer to induce sufiicie'nt current in its secondar to prime orfire a detonator. Therefore, t eshot-firing effect of stray currents is entirely eliminated, and a shot may be fired only by the very highfrequency current generated by the generator element of the system, and to which the transformer is tuned.

The invention is illustrated inthe accompanying drawings of which Fig. 1 is a wiring diagram of the preferred system; Fig. 2 a wiring diagram of a "modification; and Fig. 3 a perspective bodying the system.

In the embodiment of theinvention illustrated in Fig. 1, the generator element of the system comprises a battery 1, which may consist of a plurality ofdryo'r storage battery cells, a battery circuit 2 3, a.- transformer having a primary 4 and a. secondary 5, and a circuit interrupterfor causinga rapidly pulsating current to flow through the battery circuit and primary of the'transformer which forms apart of-such circuit. The circuit interrupter may comprise a leaf spring 6 of conducting material electrically supported at one end and connected by a wire 7 to the battery circuit. At its free end spring 6 is provided with an armature 1 1 which is attracted by the magnetic flux threading core 12 when current flows in primary 4, and with a contactor 8 adapted to make and break contact with a contact element which may take the form of an adview of apparatus em just-able Set screw 5) mounted in an arm 10 of conducting n'iatcrial, which armis separated from spring 6 by a body of insulation 11. Ina manner well known inthe art, the armature 14 and contact element 8 vibrates between the end of the transformer core 12 and contactor 9 causing a pulsating nating current being of the same frequency.

as the rate of interruption of the direct current. The high voltage low amperage alternating current thus generated may be of different frequencies providing its frequency is much higher than that of commercial currents. By way of example, and not of limitation, the induced alternating current may have a frequency of 500.

The current thus generated is conducted through long lead conductors 15 to the primary 16 of a transformer which forms the second element of the system, and which, as

already stated, is tuned to transform only currents of the same,'or substantially the same, frequency as that generated by the generator. The secondary'17 of the transformer is provided with. suitable contact terminals 18 for making electrical connection to the small wires attached to shot priming detonators.

To avoid injury to the secondary 5 of the generator and to the primary 16 of the transformer by stray currents which may leak into the long lead conductors 15, protecting devices such as

fuses

19 and 20 may be placed in the circuit adjacent to these elements, as is clearly indicated.

Instead of using a generator of the type explained with reference to Fig. 1, a high frequency alternating current having {a high voltage and low amperage may be generated by a magneto or alternating current generator 21, as illustrated in Fig. 2,

the magneto being adapted to be operated manually in any desired or well known manner. When a magneto is thus used, its armature brushes may be directly connected to. the long lead conductors 15, the transformer element of the system, the primary of which is connected to the other end of these conductors, may be the same as that explained with reference to Fig. 1. In place of the

fuses

19 and 20 of Fig. 1, blocking condensers 31 and .32 may be placed in the circuit adjacent to the magneto 21 and primary 16 to protect them against becoming burned out by leakage currents which may gain access to the long lead conductors 15.

As generally illustrated in Fig. 3, the entire generator element may be housed in a small casing 25 which may be readily transferrcd from place to place, and the transforiner element may likewise be housed in a small casing 36 which may be placed near a charge to be tired, the generator being electrically connected to the primary of the transformer by the long lead conductors 15, and the terminals 18 of the secondary of the transformer being connected to short lead wires 27 of a detonator 28. To prevent thesecondurtors from becoming injured by falling coal or rock, they may be protected adjacent the transformer by a suitable magneto 21.

sheath 26 of metal or other material, to which there may be attached a handle 33 for withdrawing casing 36 from beneath blasted coal or rock,

Briefly reviewing the operation of the systern, and having reference first to the embodiment of the invention illustrated in Fig. 1, a rapidly pulsating current may be caused to flow through the battery circuit by closing switches 30 in

conductors

2, 3, which current induces a high voltage low amperage current in the secondary 5 of the transformer of the current generator element. This current is in turn transformed by the

transformer element

16, 17, into a low voltage high amperage current suitable for priming a detonator. In the embodiment of the invention illustrated in Fig. 2, the high voltage low amperage current may be directly generated by suitably operating the Because, for the reasons explained, commercial stray or leakage currents which may gain access to the long lead conductors 15 cannot set up a detonatorpriming current in the secondary 17 of the transformer element of the s stem, premature firing of a shot cannot e effected by stray or leakage currents. Furthermore, because the current generated by the generator element is of high voltage and low amperage, such currcnt suffers but small loss in its transmission through the long lead conductors, and there is little tendency of loss of it due to poor joints in conductors. Accordingly, the system has the additional advantage of minimizing shot failures. Furthermore, the small lead wires make for ease, speed and economy of connecting up a single shot, multiple shots in parallel, series or parallel series.

According to the provisions of the patent statutes, I have explained the principle and operation of my invention and have described and diagrammatically illustrated two embodiments of it. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced by other apparatus than that particularly shown and described.

I claim as my invention:

1. A shot firing system, comprising a generator for generating an alternating electric current of high volt-age and low amperage and a frequency much greater than that of commercial currents, a transformer for transforming said generated current into one of low voltage and high amperage, and lead conductors closing a circuit between said generator and transformer whereby the transformer may be placed close to the charge to be fired and the generator at a safe distance from it.

2. A shot firing system, comprising a gen-' erator for generating an alternating electric current of high voltage and low amperage and of a predetermined frequency much greater than that of commercial currents, a transformer tuned to transform said generated current to one of low voltage and high amperage, and long lead conductors closing a circuit between said generator and transformer whereby the transformer maybe placed close to a charge to be fired and the generator at a safe distance from it, and whereby such commercial currents as may gain access to said conductor are rendered ineffective for firing a shot.

3. A shot firing system, comprising a generator for generating an alternating electric current of high voltage and low amperage and a frequency much greater than that of commercial currents, a transformer for transforming said generated current into one of low voltage and high amperage, and lead conductors closing a circuit between said generator and transformer whereby the transformer may be placed close to the charge to be fired and the generator at a safe distance from it; and protectors in said circuit adjacent to said generator and to the primary of said transformer to prevent their injury by stray currents of large magnitude.

4. A shot firing system, comprising a generator for generating an alternating electric current of high voltage and low amperage and a frequency much greater than that of commercial currents, a transformer for transforming said generated current into one of low voltage and high amperage, and lead conductors closing a circuit between said generator and transformer whereby the transformer may be placed close to the charge to be fired and thegenerator at a safe distance from it; and fuses in said circuit adjacent to said generator and to the primary of said transformer to prevent their injury by stray currents of large magnitude.

5. A shot firing system, comprising a current generating unit consisting of a battery, a battery circuit, means for interrupting the flow of current through said circuit at a rate much higher than the frequency of commercial alternating currents, and a transformer having a primary in said circuitfor inducing in its secondary a high tion of said battery circuit; a second transformer whereby the SGCOHddIMDGd transformer tuned to transform said generated former may be placed close to a charge to alternating current to one of low voltage be fired and said generating unit at a safe 10 and high amperage, and long lead conducdistance from it. Y

5 tors closing a. circuit between said second In testimony whereof, I sign my name.

secondary of said first-named transformer and h Primary of said second-named trans- JOHN J. JAKOSKY.