US2683414A

US2683414A - Arrangement to insure complete detonation of explosive charges

Info

Publication number: US2683414A
Application number: US746578A
Authority: US
Inventors: Jr Robert L Klotz
Original assignee: Seismograph Service Corp
Current assignee: Seismograph Service Corp
Priority date: 1947-05-07
Filing date: 1947-05-07
Publication date: 1954-07-13
Anticipated expiration: 1971-07-13

Description

July 13, 1954 2,683,414

R. L. KLOTZ, JR ARRANGEMENT TO INSURE COMPLETE DETONATION OF EXPLOSIVE CHARGES Filed May 7, 1947 IN VEN TOR.

Robert L. Klolz Jr. BY WEMMW Patented July 13, 1954 UNITED OFFICE 0 IN SURE COMPLETE ARRANGEMENT T DETONATION OF E XPLOSIVE CHARGES Application May 7, 1947, Serial No. 746,578

6 Claims.

The present invention relates to a method and arrangement for insuring complete detonation of explosive charges particularly of the type in which a plurality of cartridges or sticks of explosive material are fastened or positioned together by suitable means to form an elongated charge or column of explosive material for use in seismic prospecting, well shooting, and blast hole operations in general.

Since the introduction and rapid extension of seismic methods of prospecting wherein the charges are placed in shot holes, there has been created a demand for specially adapted explosives. It has become common practice in connection with loading such shot holes to connect a plurality of individual cartridges together into a long column or string of charges which can be easily handled when inserted into a shot hole. Initially, the cartridges of explosives were suitably fastened together into an elongated charge by various means referred to by rather descriptive terms as stringing, lathing, or taping, and pegging. More recently the companies manufacturing explosives have provided specially constructed arrangements whereby the cartridges are adapted to be connected together to provide a strong rigid column of explosives or" any desired length.

In one common method of seismic prospecting such columns or charges formed of a plurality of explosive cartridges connected together are detonated in shot holes in the earth at depths of fifty to several hundred feet by a single cap located at a suitable point in the charge. Suitable tamping is usually provided, generally with water, and much difficulty has heretofore been encountered in obtaining detonation from one stick to another. Detonation will propagate throughout the length of a single stick or cartridge but often will not carry through the gap between the cartridges. This gap is formed where the cartridges are placed together and consists partially of air and partially of folded and crimped paper and in certain cases metal, which paper or metal retains the ends of the dynamite cartridge. It is common practice for several sticks of a charge to fail to explode and to be blown from the hole with the water tamping thus creating an operating hazard as well as decreasing the effectiveness of the shooting operation by loss of energy through loss of part of the charge. Experience has indicated further that many of these specially constructed cartridges, which are provided with means for fastening them together in a longcolummoften fail to detonate from cartridge to cartridge. It would be desirable to provide simple and inexpensive means which would insure detonation oi the entire charge regardless of how many sticks or cartridges were connected together.

In a similar fashion, containers or torpedoes of explosives for use in well shooting are positioned end to end in the well in shooting position often building up columnar char es of such length and under such fluid pressures that complete detonation is not assured, and dangerous and costly misfires sometimes ensue. A. simple and inexpensive means to insure detonation of the entire charge is also very desirable for such operations.

Also for the various blasthole operations involved in mining, quarrying, and construction in general excessively long explosive columns in relation to column diameter are often desire ie. This increases the hazards of expensive, dangerous misfires also. Here too, the desirability of simple means to insure detonation of the entire column is desirable.

Accordingly it is an object of the present vention to provide an explosive charge comprising a plurality of cartridges or the like positioned in end to end relationship with a cavitation provided in the ends of some or all of the sticks or cartridges to insure complete detonation oi the entire charge.

It is another object of the present invention to provide an arrangement for obtaining positive detonation from stick to stick or cartridge in an explosive charge comprising plurality of cartridges arranged in end to end relationship before or after insertion. into a shot hole.

A further object of the present invention is to provide a new and improved arrang in seismic shooting to insure complete d of the entire seismic charge.

It is another object of the present invention to provide a column of explosives in which complete detonation occurs even when less sensitive and consequently less expensive explosives are employed.

Further objects and advantages of the present invention will become apparent as the following description proceeds, and the features of not which characterize this invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the present invention, reference may be had to the accompanying drawing in which:

Fig. 1 is a view of a charge formed of a plurality of cartridges embodying the present invention connected in end to end relationship about to be inserted into a shot hole for seismic shooting, and

Fig. 2 is an enlarged sectional view taken on line 2-2 of Fig. 1.

It should be understood that the present invention is equally applicable to seismic operations, well shooting and other blasting operations in general. To simplify the disclosure the invention is described in detail in connection with a seismic application but this is only by way of example since it is intended by the appended claims to cover all applications falling within the spirit and scope of the present invention.

Referring now to Fig. l of the drawing, there is illustrated a charge or column ID of explosives about to be inserted into a shot hole H as in seismic work. This charge or column of explosives H] comprises a plurality of individual cartridges generally designated at l2, fastened together in end to end relationship in any suitable manner. As illustrated, these cartridges are fastened together by a process known as taping or lathing in which one or more suitable laths such as 13 are adapted to bridge across the junction points between each two adjacent cartridges l2, and the laths are taped as indicated at M and E5 to produce a rigid or semi-rigid structure. Instead of lathing or taping as illustrated, the cartridges may be fastened together by stringing, pegging, or any one of the special means now produced by various manufacturers of explosives. The particular manner in which the cartridges I2 are fastened together to form the long column of explosives It forms no part of the present invention, and the illustrated embodiment is by way of example only.

It is a well known fact that the detonation or propagation of explosions in a column of explosives tends to become less intense the further the explosive wave travels from the point of initiation. This tendency increases as the diameter of the explosive column decreases. It also increases as the pressure, such as the fluid tamping pressure, increases. It furthermore increases as the sensitivity of the explosive is decreased. To overcome this tendency, in accordance with the present invention, at least some or all of the cartridges !2 are provided with structural elements defining cavities such as is designated at it in the cartridge specifically designated as l2a in Fig. 2 of the drawing which has one end in engagement with the cartridge 12b. Preferably the cartridges each comprise a suitable container such as H within which is disposed the explosive material 18. For the purpose of defining the cavity it there is preferably provided a suitable structural element in the form of a sealed hollow container H! which prevents the explosive [8 in the cartridge [2a from entering the cavity IS. The sealed container is is illustrated in the drawings as having a conical end Ilia and a cylindrical portion 9b. The distance between the lowermost end of the conical member l M and the bottom of the container I? of the cartridge I'Za is generally referred to as the stand-off distance. The cavitated charges such as l2a permit the well-known Munroe effect or directionalized explosive efiect to be obtained. Although a sealed container 19 having a conical end is illustrated, other similar end shapes symmetrical about the axis such as hemispherical or hermispheroidal might be employed. In any case these shapes act to redistribute and concentrate the energy of the portion of the charge nearest the housing of the sealed container 19. The explosive forces on the periphery of the conical portion Hla of the container I9 which presumably act with equal force in all directions will have a resultant force normal to the surface of the conical portion working progressively down from the apex thereof. If the cavity is symmetrical about its axis, these forces will meet at the axis, will be vectorially additive in magnitude and will thus affect the concentration of kinetic energy that would otherwise be spread over a considerable area of the sphere of explosive efiect. It is apparent then that by employing a cavitated cartridge such as l2a the explosive efiect is directed with a jet effect into the next adjacent cartridge in a much more satisfactory manner than would be the case if the cavitated charge were not employed, and by properly choosing the stand-off distance and the shape of the container I 9 which may have a conical or some other shaped end such as semispherical the maximum explosive jet for detonating adjacent cartridges is obtained. It has been found in the case of sealed containers having a conical end such as lfia and probably containers of other shapes that these containers collapse into particles which form an eifective part of the jet. Preferably the container is is formed of metal or the like. Although the cavitation device has been described as a sealed container is which may be inserted into the end of a cartridge, it should be understood that the cavity is could be initially built into the explosive cartridge. When the bullet shaped sealed container is employed the end of cartridge may be cored and the sealed container [9 pressed into the opening point first.

In order to form the cavity is at the end of each cartridge or at least at the ends of a predetermined number of cartridges, it is preferably desirable to employ a sealed container is as mentioned above formed of relatively rigid material whereby the shape of the cavity is can be retained as Well as the proper stand-oil distance. With this arrangement the water used for tamping will not enter the cavity it and reduce the effectiveness of the cavitated charge or nullify it entirely. It will be understood, however, that instead of employing a sealed container a very low density water-impervious material such as cork or one of the so-called foam types of rubber might be employed in place of the cavity It. The cavity might also be defined by a low density but water-impervious paper. The last two alternatives would need to be relatively incompressible or otherwise placed in a rigid container so that the shape would be retained in spite-of tamping or the use of force in loading the charge.

As illustrated in the drawing, the cavitated charges are arranged with the apex of the coneshaped containers IS pointing upwardly, in which case the explosive column it is detonated from the top as by means of a cap or fuse not shown connected to the fuse wires indicated at 22. With this arrangement a maximum downward action to reduce blowout possibilities is provided. However, under certain conditions it may be desirable to detonate the charge from the bottom in which case the entire column Would be rotated through an angle of one hundred and eighty degrees. It will be understood that the column might be detonated from an intermediate point while still employing the principle of the present invention. The apexes of the sealed containers 1!! having conical ends 19a should all point toward the cap regardless of where in the column it is located. If the cap is disposed in the middle of the explosive column, then the apexes above the cap should point downwardly or toward the cap, and similarly the apexes below the cap should point upwardly toward the cap.

By employing the arrangement described above,

a high intensity detonation jet would be directed into successive sticks or explosive containers which would insure complete detonation of all the sticks or explosive containers in the charge and permit the use of a column of smaller diameter in the charge as well as increased tamping pressure. It will be understood that although every charge or explosive container may be provided with such a cavity, it may merely be necessary to employ such cavitated charges at intervals along the column as illustrated in Fig. 1 of the drawing thereby reconcentrating orre-initiating the explosive waves. Also by employing the present invention, it is possible to use less sensitive explosives which are less expensive. Furthermore much longer columns may be detonated and propagation of the explosive effect is assured even where there is a substantial space between the cartridges which space might be filled with air, water, mud, or the like.

The present invention also lends itself very well to the detonation of lost charges. In placing charges in a shot hole, a pole arrangement is often used, and it sometimes occurs that the charges slip off the spike or other means for holding the charges on the pole whereby these charges are lost in the shot hole. If the location of these charges is not accurately known,

it is difiicult to place a charge close enough to the lost charge to be sure of detonation. By employing the present invention, however, the cavitated charge when disposed somewhere above the lost charge due to the jet efiect of the detonation will greatly increase the possibility of detonating such lost charge. In the same way misfires encountered in well shooting and blast hole oper- 4 ations may be disposed of.

In view of the detailed discussion included above, it will be apparent that with the present invention the possibility of having a portion of a charge blown from the shot hole without 0 detonation thereof is substantially eliminated. Consequently, a more efiicient use of the explosive is obtained, as well as a decrease in the hazard to the operating personnel. The problem of complete detonation of charges in seismic operation, 5 heretofore considered a very important one, is believed to be completely solved by the present invention in a simple and inexpensive manner.

It will be apparent to those skilled in the art that the present invention is not limited to the particular method described and construction shown but that changes and modifications may be made without departing from the spirit and scope of the present invention. It is aimed in the appended claims to cover all such changes and modifications.

What is claimed as new and desired to be secured by Letters Patent of the United States 1. An explosive charge comprising a plurality of explosive cartridges each comprising a body of low sensitivity explosive material, said cartridges being supported in end to end relationship to form a column of cartridges, and detonating means for detonating said charge located at some point in said column, at least a portion of said cartridges comprising structural elements at the ends thereof remote from said detonating means defining shaped jet forming cavities therein for producing a jet explosive effeet in a direction away from said point and into the adjacent end of the next cartridge in said column, thereby to insure complete detonation of all of said cartridges.

2. An explosive charge as claimed in claim 1, wherein means are provided for defining a standoff space adjacent the mouth of each of said jet forming cavities.

3. An explosive charge as claimed in claim 1, wherein each of said structural elements defines a conical cavity in the explosive material of the cartridge in which the element is provided.

4. An explosive charge as claimed in claim 1, wherein each or" said structural elements defines a conical cavity and a cylindrical stand-off space in the explosive material of the cartridge in which the element is provided.

5. An explosive charge as claimed in claim 1, wherein each of said structural elements comprises a closed hollow body extending into the explosive material or the cartridge in which the element is provided from one end of the cartridge.

6. An explosive charge as claimed in claim 1, wherein each of said structural elements comprises a closed hollow body having a conical portion and a cylindrical portion, and said hollow body extends into the explosive material of the cartridge in which the element is provided from one end or" the cartridge with the cylindrical portion of the hollow body being disposed between said one end of the cartridge and the conical portion of the hollow body.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 949,778 Pringle Feb. 22, 1910 1,900,624 Voortmann Mar. 7, 1933 2,238,939 Lewis Apr. 22, 1941 2,396,518 Martin Mar. 12, 1946 2,420,201 Seavey May 6, 1947 2,423,837 Martin July 15, 1947 FOREIGN PATENTS Number Country Date 7,763 Germany Oct. 22, 1879 28,030 Great Britain of 1911 172,914 Great Britain Dec. 22, 1921 437,436 France Apr. 20, 1912 OTHER REFERENCES Publication by M. J. Sukarevsky from Tekhnika i Snabzhenie Krasnoi Armii, vol. 170, pages l3-18, and vol. 177, pages 13-18 (1925).

The Shaped Charge by Torrey in the Explosives Engineer. July-August 1945. Pages through 163.