US2027208A - Ignition composition - Google Patents

Description

Jan. 7, 1936. c. E. sossoN IGNI'TION COMPOSITION Filed Nov. 19, 1934 INVENTOR.

C/mr/ej josson ATTORNEY.

Patented Jan. 7, 1936 UNITED STATES PATENT OFFICE IGNITION COMPOSITION V Application November 19, 1934, Serial No. 753,778 In Great Britain November 21, 1933 10 Claims.

This invention relates to ignition compositions and more particularly to a new and improved. ignition mixture which gives rise to little or'no gas on combustion.

Ignition mixtures which have heretofore been widely employed in the arthave been unsatisfactory for many purposes because of the large volume of gases generated during combustion. These gases were particularly objectionable in delay detonators, since the hot gases were known to produce premature detonations and at times to cause the undesirable burning of the dynamite. Various attempts have been made, therefore, to develop gasless ignition mixtures or compositions giving off relatively small volumes of gas which would be satisfactory for use in electric blasting devices. The present invention proposes a more satisfactory solution to the problem.

The object of myinvention is an improved ignition mixture. A further object is an ignition mixture which produces little or no gas on combustion and which is particularly advantageous for use in delay detonators. Other'objects will appear as the invention is hereinafter disclosed.

I have found that these objects may be accomplished by the following invention, which consists essentially in the employment of an ignition composition comprising zirconium and an easily ignitable lead salt of a nitrophenol.

According to my invention, the material directly ignitable by the passage of the electric current consists of a quantity of finely divided zirconium together with basic lead 2-mono-nitro resorcinate, basic lead picrate or other easily ignitable lead salt of a nitrophenol having a suitably low firing current, preferably below 0.5 amps. when the current is applied for a period of 50 milliseconds. While previous low tension ignition compositions containing basic lead 2-mono-nitro resorcinate have shown considerable advantage, those made in accordance with the present invention provide an even greater degree of certainty in ignition.

The zirconium is advantageously employed in a fine state of division, e. g. having a particle size not greater than 0.005 mm., and preferably substantially less. i

The proportion of zirconium to basic lead 2- mono-nitro resorcinate or other lead salt of a nitrophenol may vary within wide limits. I prefer, however, that'the ratio should be high, since the compositions containing the higher proportions of zirconium yield a more powerful flash. Beneficial results are obtained with compositions in which the ratio of zirconum to lead salt is 50/50 but preferably the ratio lies between 35/65 and 95/5. It is not, however, advisable to exceed the last mentioned proportion since the firing current then becomes unduly high. In general, the best results are obtained as regards firing and freedom from gas when the proportion of zirconium to lead salt is at least 70 to 30. Various types of electric ignition devices may be employed in carrying out my invention, such as for example the well known concave plug, the bridge plug type, or a form of match head. When necessary the mixture of zirconium and lead salt may be made into a coherent form with the aid of a small quantity of a suitable cementing material such as nitrocellulose.

The fact that the compositions comprising finely divided zirconium and lead salts of the kind described produce little or no gas on combustion, together with the fact that they produce a powerful flash, renders the invention especially advantageous for use in delay action dentonators of the ventless type. Since the compositions employed in the delay elements of such detonators are usually less easily ignited than ordinary delay fuse compositions, I prefer to use fairly high proportions of zirconium to lead salt, forexample 70 to 'or higher. In theconstruction of the fir- :in'g devices intended for'such uses, the diameter of the bridge wires may be somewhat reduced in order to prevent the increase in the firing current which would otherwise be necessary when the proportion of zirconium to lead salt rose'above Moreover, the presence of other materials yielding gases should be avoided when the herein described invention is used in ventless delays. In all other types of detonators, various materials customarily employed to give a better flash may be used, if desired, but this is quite unnecessary according to the present invention.

In order to illustrate the use of my invention more fully, I may cite the following examples which are diagrammatically represented in the attached drawing. Figure 1 represents a vertical section of an electric blasting cap using the bridge plug type of ignition, Figure 2 represents a delay electric blasting cap having a match head igniter, while Figure 3 represents a similar section of a delay detonator having a concave plug type igniter.

In Figure 1, the shell A contains a base charge B and a primary charge C-covered with a loose ignition mixture D, comprising 70 parts zirconium and 30 parts basic lead 2-mono-nitro resorcinate.

The bridge wire E is connected to the leading ture is positioned a delay element E containing.

any suitable gasless delay ignition mixture F.

The upper end of the delay element is separated by the space G from the match head composition H, which is prepared by dippi'ngthe bridge wire connecting the lead wires I into a suspension 01! a mixture of. 70 parts zirconium powder and 30 parts basic lead 2-mono nitro resorcinate in a sufficient amount of a 5 solution of nitrocellulose in commercial amyl acetate to make a creamy mixture. The bead formed on the bridge wire is then dried, dipped into a waterproofing solution of collodion, and dried again. The leading wires I pass through the plug J held in the detonator by the crimp K. The open end 01" the detonators is then closed with the sealing compound L.

In Figure 3, representing a delay detonator having a concave plug igniter, the shell A contains a base charge B and a primary charge C, covered by a loose ignition mixture D, comprising '70 parts zirconium and 30 parts basic lead 2-mononitro resorcinate. Above this mixture is 'adelay element E containing any suitable gasless delay ignition mixture F. The upper end of the delay element is separated by the space G from a plug H having a concave face and a bridge wire I between two leading wires J. The concave plug is covered with a paste comprising 70 parts'zir conium, 30 parts basic lead 2-mono-nitro resorcinate and suflici'ent 5 amyl acetatesolution' of nitro-cellulose to give the mixture the desired consistency. After this has dried; the? concave mixture is waterproofed; dried again and assembled in thedelay detonator in the usual manner. It is held in place by a waterproofing composition Kand a sulfur" seal L'.

Having now described and illustratedmy'inv'ention in detail, it is apparent'that' many variations can be made without departing from the spirit of the invention. The above examples are illustrative only and are not intended to limit the invention to these particular embodiments. I intend, therefore, to be limited only to the extent indicated by the following patent claims.

I claim:

1. An ignition. composition. comprising zirconium and" an easily ignitable lead salt of a nitrophenol,

2. An ignition composition comprising to 95% zirconium and 50 to 5% of an easily ignitable le'ad' salt of a nitrophenol.

3. An ignition composition comprising 50 to 95% zirconium and 50 to 5% basic lead 2-mononitro. resorcinate. V

4. An ignition composition comprising approximately zirconium and approximately 30% basic'lead 2'-mono-nitro resorcinate.

- 5.. An ignition composition as the firing charge in an electric blasting cap, said composition possessing low firing current requirements andcomprising50 to zirconium and 50 to 5% of an easily ignit'able lead'salt ofa nitrophenol.

6. An ignition composition as the firing charge in a-delaydetonator; said composition comprising 50 to 95% zirconium and 50' to 5% 01 an easily ignitable lead salt of a. nitrophenol.

7. An ignition composition as the firing charge in an electricdelay detonator, said mixture comprising 50 to 95% zirconium and 50-to 5% basic lead 2-mono-nitr'o' resorcinate.

8. An ignition composition as the firing charge in an electric delay detonator; said mixture comprising approximately 70% zirconium and approximately 30% basic lead 2-mono-nitro resorcinate.

9.. A cemented ignition composition asthe firing charge in. a ventlesselectric delay'detonator, said mixture comprising not less than 70% zirconium and notl' m'ore than 30%. basic lead?- mono-nitro resorcinate.

10. Atcemente'd'ignition composition as firing charge inza ventless electric" delay detonatoricomprising 'anignitable' mixturetogether with a small quantity 'ofia' cement,the said mix'ture consisting of not: less than 70% zirconium and not more than 30%" basici-lead.2mono-nitro resorcinate;

CHARLES EDWIN SOSSON;

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