US2652775A - Percussion initiated detonator - Google Patents

Description

Sept. 22, 1953 M. E. SWANSON PERCUSSION INITIATED DETONATOR Filed June 6, 1951 INVENTOR. MTTZZZESll/(ULSOJL %0- WM /-w Patented Sept. 22, 1953 PERCUS SION INITIATED DETONATOR Merrill E. Swanson, Woodbury Heights, N. J

assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Dela- Ware Application June 6, 1951, Serial No. 230,165

8 Claims.

The present invention relates to blasting detonators adapted to be initiated by percussion means, and, more particularly, to impact ignitable detonators suitable for use in well shooting.

In the shooting of wells, it is customary to lower a charge of high-strength explosive into the well to the desired depth, and then initiate the charge by means of a detonator. Failure of the detonator to initiate the main charge is extremely serious, since it frequently becomes necessary to raise the charge where this is possible, or to attempt to initiate the charge with a newly lowered detonator. Either course is both expensive and dangerous, since the explosive may be discharged at an undesired time.

For many shots, particularly where the well is deep, it is inconvenient to use electrically fired detonators due to the necessity of leading the leg wires the entire distance, and the likelihood of their being severed or short-circuited. A number of mechanical devices for initiating the main charge are known, and all consist essentially of a, firing pin in striking arrangement with a percussion cap which in turn ignites a primer charge. The firing pin may be actuated in a number of ways, such as by a weight dropped from the surface and guided by the lowering lines, a spring mechanism released from the surface or by clockwork lowered with the charge, etc.

A serious disadvantage of the present mechanical firing devices lies in the fact that under the extreme pressures encountered in deep wells, the detonator sometimes fails to ignite the primer charge due either to the collapse of the holding means or the entrance of fluid into the container. A further disadvantage is that the detonator and primer have to be handled and installed separately, thereby increasing the hazard as well as the possibility of improper installation. It has been found that it is very difficult toobtain a fluid proof arrangement utilizing the prior art assembly.

An object of the present invention is to provide a unitary detonator for well shooting which is adapted to be ignited by percussion means. A further object is to provide a percussion ignited detonator for a main charge which will withstand great pressures. A still further object of the present invention is to produce a fluid-resistant percussion initiator for well shooting. Additional objects will become apparent as the invention is further described.

I have found that the foregoing objects are achieved when I provide a tubular metal shell having one end closed and integral with the sides, said end being flat and of relatively small thickness, a thin layer of an impact-ignitable explosive composition pressed against the inside of the flat end, a metal anvil interposed between a priming charge of explosive and said impact ignitable charge, a pressed main charge adjacent t0 the priming charge, and a sealing plug closing the remaining end of the tubular shell. I find it preferable to completely fill the interior of the shell so that no voids are present. The sealing plug may be crimped into place to completely seal the opening, and to prevent it from being dislocated, or it may be provided with a gasket or the like.

In order to more fully describe the present invention, reference is made to the accompanying drawings, in which:

Figure 1 is a sectional elevation of a detonator in accordance with the present invention; and

Figure 2 is a view representing one arrangement of a firing pin and two percussion detonators with respect to a well charge.

In Figure 1, I is a metallic tubular shell having one end thereof closed and integral with the sides, the end being flat; 2 is a thin layer of an impact-sensitive ignition material, 3 is a metal anvil having a flat surface of reduced diameter on the portion adjacent to the end of the shell, 4 is a priming charge of a flash-ignitable con position, 5 is the main detonator charge and 6 is a resilient plug closing the remaining end of the shell I, and held in position by crimping the shell I. The outer end of the plug 5 is flush with the end of shell I.

In Figure 2, the detonator assembly is indicated by the same numbers as in Figure 1. I is a double-pointed firing pin, 8 is a striker rod, 9 is a charge of high-strength explosive, and I0 is a metallic support for the detonators.

In operation, the striker rod 8 is struck sharply,

for example, by a weight dropped thereon. The resulting impact causes the firing pin I to depress the ends of the shells l, thereby squeezing the ignition charge 2 between the shell I and the anvil 3, and igniting it. The resulting flash is transmitted between the sides of shell I and the anvil 3 to the priming charge 4, igniting it, and the main detonator charge 5 is detonated thereby, setting oil the blasting charge 9.

' In Figure 2, two detonators are shown, since this is a practice followed in the field to reduce the chance of a mis-fire due to a defective detonator. Obviously, this arrangement is subject to many variations, and is not a part of the present invention.

Detonator shells are, for the most part, produced by cold-drawing of aluminum, copper, and alloys thereof. In the manufacture of the shells, the closed end is, therefore, usually rounded and considerably thicker than the sides. Since the impact required to ignite the highly sensitive ignition composition is directly proportional to the thickness of the end, I prefer to grind oiT the excess at the end to produce a relatively thin bottom. By flattening the bottom, a better striking surface is also presented, thus reducing the likelihood of the firing pin being deflected. Preferably, the bottom thickness should not exceed .020 inch. Also, the inside of the shell irequently contains a raised portion at the juncture of the end and the sides, therefore, the anvil 2' is desirably made with a flat surface of smaller A drawn aluminum shell similar to that illustrated in Figure 1 having a diameter of 0.281 inch, a length of 3.3125 inches, and a wall thickness of 0.010 inch, was loaded in the following manner: 075 grain of fulminate of mercury was inserted, followed by a steel anvil 0.25 inch in height and .25 inch diameter, and the assembly was then pressed at 250 pounds per square inch. 3 to 4 grains of lead azide were then introduced, and the assembly again pressed at 250 pounds per square inch. The main detonator charge of 50 grains of cyclonite was introduced, and pressed at 250 pounds per square inch, and a rubber plug inserted as far as possible, and crimped into the shell. The plug was then trimmed off flush with the top of the shell.

This cap was detonatable by the impact of a three pound weight falling seven inches onto a pointed firing pin.

Example II A shell similar to that described in Example I was loaded in the same manner, except that the fulminate of mercury was replaced by a mixture consisting of 37.5% fulminate of mercury, 37.5% potassium chlorate, and 25% antimony sulfide.

The sensitivity of this cap was identical with that described in Example I.

Example I II Using a procedure and shell similar to that described in Example I, except that the fulminate of mercury was replaced with an equal amount of lead azide, it was found that a thirteen inch drop of the three pound weight was required to detonate the assembly.

Detonators prepared in accordance with the present invention were subjected to twenty-four hours immersion in water under a pressure of 5000 pounds per square inch. There was no noticeable collapse of the shell, and no appreciable impairment in the sensitivity to impact.

Any of the well-known impact-sensitive ignition compositions normally used in percussion devices may be used in the present detonators. Fulminate of mercury is the most widely used compound, others include lead azide, tetrazene in admixture with smokeless powder, red lead, or nitromannite, mixtures including fulminate of mercury, etc. Any of the ignition charges will also be suitable for use as the priming charge, or a less sensitive compound such as diazodinitrophenol may be substituted. For the main detonator charge, I may use cyclonite, tetryl, P. E. T. N., pentolite, or similar detonating explosives.

The shell can best be sealed by means of a sealing plug. A plug of a resilient material such as natural rubber, synthetic rubber, neoprene, and the like is particularly suitable. Such a plug can be fastened in the upper end of the shell by means of crimping, or it may be of such dimensions in relation to the shell that a force fit is obtained. It is also possible to use closely fitting metal plugs provided with gaskets or with recessed grooves filled with sealing material. The shell may be of any metal or alloy, although consideration must be given to non-reactivity toward the explosive charges used. While I prefer that the bottom be flat, it is not essential. if the bottom is not flat, the anvil must correspond in contour with that of the bottom in order to provide the proper impact surface. Also, the sensitivity of the ignition charge is considerably greater in the form of an extremely thin layer, therefore it is essential that the anvil fit the bottom of the shell closely.

The present invention has been fully described in the foregoing, and distinct embodiments of the invention illustrated. Obviously many details may be changed without departing from the spirit of the invention. I intend to be limited only by the appended claims.

I claim:

I 1. A detonator assembly comprising in combination a tubular metal shell having one end thereof closed integrally with the sides, an impact-sensitive explosion ignition charge in contact with said end, a metal anvil adjacent to said impact-sensitive charge, an explosive priming charge adjacent to said anvil, a main detonator charge adjacent to said priming charge, and a plug sealing the said metal shell.

2. A detonator assembly as claimed in claim 1, wherein the said integral end is of less than 0.020 inch in thickness.

3. A detonator assembly comprising in combination a tubular metal shell having one end thereof fiat and closed integrally with the sides, an impact-sensitive explosive ignition charge in contact with said end, a metal anvil adjacent to said ignition charge, an explosive priming charge adjacent to said anvil, a main detonator charge adjacent to said priming charge, all of said charges being pressed, and a plug sealing the said metal shell.

4. A detonator assembly as claimed in claim 3, wherein the charges are pressed at about 250 pounds per square inch.

5. A detonator assembly as claimed in claim 3, wherein the ignition charge is fulminate of mer-v cury.

6. A detonator assembly as claimed in claim 3, wherein the priming charge is lead azide.

7. A detonator assembly as claimed in claim 3, wherein the main detonator charge is cyclonite.

8. A detonator assembly comprising in combination a tubular metal shell having one end integral with the sides, said end being fiat and of less than 0.020 inch thickness, a thin layer of an impact-sensitive explosive ignition charge in contact with said end, a metal anvil pressed on said ignition charge, an explosive priming charge pressed on said anvil, a main detonator charge pressed on said priming charge, and a tightlyfitting resilient plug crimped at the remaining end of said shell.

MERRILL E. SWANSON.

References Cited in the file of this patent FOREIGN PATENTS Number Country Date 16,405 Great Britain 1914 251,874 Great Britain May 13, 1926 541,687 Great Britain Dec. 8, 1941

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