US2422043A - Compound detonator - Google Patents

Description

June 10, 1947. F, ROLLAND 2,422,643

COMPOUND DETONATOR Filed March 25, 1941 Fig. 1' v Fig-2 Fig.3 Fig.4

Guy F. Rolland INVENTOR ATTORNEY Patented June 10, 1947 COIVLPOUND DETONATOR Guy F. Rolland, McKeansburg, Pa., assignor to Atlas Powder Company, Wilmington, Del., a

corporation of Delaware Application March 25, 1941, Serial No. 385,088

4 Claims.

This invention relates to improved detonators intended primarily for detonating charges of explosives. More particularly, it is directed to improved explosive charge combinations for both electric and fuse type detonators wherein pentaerythritoltetranitrate charges are employed.

An object of the present invention is the production of practical and efficient pentaerythritoltetranitrate type detonators which have improved and unusual safety characteristics from the standpoint of both manufacture and use.

Another object of the invention is the production of a pentaerythritoltetranitrate type detonator of improved safety characteristics, said detonator having a relatively low overall weight and volume of explosive for a given detonating value as compared with previously known detonators having safety characteristics comparable to the detonators of the present invention.

A still further object of the invention is the production of pentaerythritoltetranitrate type detonators wherein the pentaerythritoltetranitrate is initiated by relatively small initiating charges. 7

Other objects of the invention will hereinafter more fully appear.

While the construction of a detonator in accordance with the invention, insofar as its mechanical features are concerned, so closely resembles known constructions as to make a drawing of doubtful necessity, yet in order that the invention may be clearly understood, I have illustrated several non-limiting forms of the invention in the accompanying drawings wherein Figs. 1 and 2 represent vertical sections of electric type detonators and Figs. 3 and 4 are similar sections of open shell fuse type detonators.

It has been previously recognized that pentaerythritoltetranitrate is suitable for use as a base charge in detonators, as, for example, in Large Patent No. 1,928,208 and Crater Patent No. 2,214,721. On the other hand, pentaerythritoltetranitrate alone is unsuitable for use as a primary charge because it is incapable of consistently advancing from ignition to detonation when merely ignited by a suitable non-detonating flash composition. Thus, while pentaerythritoltetranitrate has been recognized as having certain advantages as an explosive charge in detonators, its use has heretofore been limited to its association with initiating charges which were either of such a hazardous nature that they offset or overshadowed any safety advantages attributable to the pentaerythritoltetranitrate, or which were the safety types of primary detonator compositions requiring special types of ignition media such as those described in Large Patent No, 1,928,-

208. Moreover, detonators containing an explosive charge of pentaerythritoltetranitrate have heretofore been considered to require an initiating charge present in an amount comparable to the amount present in a conventional primary charge, as for example, that required to detonate tetryl. In fact, many of the initiating charges heretofore proposed for pentaerythritoltetranitrate have been conventional primary charges for tetryl.

In accordance with the present invention, I provide a practical and efficient detonator which may be either of the electric or fuse type, said detonator having an explosive charge consisting essentially of pentaerythritoltetranitrate and an initiating charge superimposed directly thereon and comprising diazodinitrophenol admixed with a solid explosive organic nitrate which becomes coherent when subjected to pressure. The diazodinitrophenol-solid explosive organic nitrate composition is positioned to become ignited by a source of heat, such as that of a superimposed flash charge, the end spit of a safety fuse, the spit of a delay element in a delay-type detonator, the heat of an electrically heated bridge wire embedded therein, the fiash of a preformed fuse head, the heat of an electric spark across electric terminals adjacent to or embedded therein, etc., and to subsequently initiate the explosive charge of pentaerythritoltetranitrate. The diazodinitrophenol-solid explosive organic nitrate composition provides an excellent initiating charge for the pentaerythritoltetranitrate. The more sensitive diazodinitrophenol of the initiating charge is diluted with the less sensitive organic nitrate so that the initiating charge as a whole is less sensitive than straight charges of diazodinitrophenol. The solid organic nitrate com ponent serves to cushion and tends to coat the particles of diazodinitrophenol so as to render it less hazardous in manufacture and use. I have found that this dilution of the diazodinitrophenol may be accomplished without decrease in efliciency of the composition as an initiator for pentaerythritoltetranitrate. In fact, the use of the diazodinitrophenol-solid explosive organic nitrate initiating composition results (in addition to the general safety due to the aforesaid dilution) in other unexpected advantages. For example, it enables the production of efficient and reliable detonators having pentaerythritoltetranitrate charges which are. initiated by much smaller-charges than have heretofore been propresent in an amount which wouldbe insufficient to detonate tetryl.

Thus there may be produced. in accordance with the present invention a pentaerythritol- In the preferred embodiments of the present invention the initiating charge is Y 4 by a source of heat, as for example, an electric match-head 8.

In Fig. 3 the open shell fuse type detonator illustrated comprises an explosive charge of pentaerythritoltetranitrate 9 Which is introduced into the base of the shell and an initiating charge l comprising diazodinitrophenol and a solid explosive organic nitrate, the latter charge being su perirnposed upon the pentaerythritoltetranitrate.

Another modification of the open shell fuse type detonator is shown in Fig. 4 wherein a charge .of tetryl i3 is initially introduced into the shell 5. Positioned directly above this tetryl charge is an'explosive charge of pentaerythritoltetranitrate tetranitrate type detonator having an initiating charg the composition of which is relatively safe and its amount much smaller than previously proposed diazodinitrophenol-containing charges for pentaerythritoltetranitrate.v This is for the reasonthat in accordance with the present invention the diazodinitrophenol is diluted with the. less sensitive organic nitrate which serves to cushion and coat the diazodinitroph'eno'l; and; secondary, the present invention enables the use f rnuch smaller initiating charges comprising dia zodinitrophenol, than have been hitherto thought possible for pentaerythritoltetranitrate.

Moreover, volume for volume, pentaerythritol- 'tetranitrate is as strong as tetryl (when pressed to the same degree) and somewhat stronger than many other detonator charges heretofore pro posed, as, for example, nitromannite. Also, weight for weight, pehtaerythritoltetranitrate is a somewhat stronger detonating agent than either tetryl or nitromannite. Consequently, with a pentaerythritoltetranitrate charge of relatively small weight and volume, detonators of high detonating strength may be provided in accordance with the present invention. Since the pentaerythritoltetranitrate charge is combined, in accordance withth'e present invention, with an initiating charge'whichmay be reducedin volumean'djweightas compared-with initiating charges heretofore proposed forpentaerythritoltetranitrate, there. may, be produced for the first time a practical, efficient, and relatively safe pentaerythritoltetranitrate type detonator having a relatively low overall weight. andvolume of explosive' for'its detonating strength.

Referring nowtothe drawings wherein similar reference characters ar used to indicate corresponding parts'lf'ig. 1 illustrates a detonator. comprising a shell 5, lead wires. 8.. and l, a conventional type of electricmatch-head 8, the lead wires being. connectedwith the electric matchhead. Into-the base of the shell is introduced anexplosive'charge of pentaery-thritoltetranitrate designatedby numeral'S and superimposed upon the pentaerythritoltetranitrate charge is an initiating charge lllgcomprising diazodinitroph'enol and. a solid explosive organic nitratewhich becomes coherent when subjected to pressure. The detonator is closed, as for example, by means of a waterproofing composition I I and a sulfur seal Fig. 2 discloses anotherembodiment of anelectric type detonator wherein a charge of tetryl I3 is introducedintothe base of the shell 5. Superimposed, upon the tetryl charge is a charge of pentaerythritoltetranitrate 9 and'directly above the pentaerythritolte'tranitrate charge is thein itiating charge [0 positioned to become initiated initiating by. weight of diazodinitrophenol.

eiw'hich has an initiating charge l0, superimposed thereon and so positioned as to become ignited by a-source of heat, as for example, the end-spit of a safety fuse.

It is to be understood that the initiating charge employed in the detonators of the present invention maybe either a loose charge surrounding, for example, the electric bridge wires of electric detonators;- acompressed charge as preferred for open f-useca-ps; or a charge initially'charged into the detonator'in a wet paste form and subsequently dried; etc. Regardless of the form in which the initiating charge is employed, 1- employ a solid explosive organic nit-rate which becomes coherent when subjected to pressure admixed with diazodinitrophenol, since I find such admixtures to be reliable and advantageous as initiating charges for pentaerythritoltetranitrate. In the production of pressed charges, which must be resistant to rumbling out, such as for example in an open ended fuse cap, the organic nitrate has the special advantage of serving as a binder for the diazodinitrophenol, thereby permitting the use of relatively low seating pressure. Prefer ably, the initiating charges of the present invention are lightly compressed, that is, formed under a pressure below 50 pounds total pressure in a .222" diametershell; or below 1365 pounds per square inch of press pin cross-section area. In general, I have found those lightly compressed initiating ch'arges to be much more effective in initiating pentaeiythritoltetranitrate than are the more highly compressed initiating charges comprising diazodinitrophenol. In fact, smaller amounts are possible and the reliability and safety'advant-a'ges are such that I have been able to produce commercially practical pentaerythritoltetranitrate type fuse caps which will pass the so-called flash-off test hereinafter more fully described.

In additiomthe low pressureswhich may be employed provide unusual and valuable advantagesfrom the manufacturing standpoint. For example, incases where the pentaerythritoltetranitrate is first pressed into the cap and the initiating charge pressed in a separate operation, there isless danger of over-pressing the underlying charge ofv pentaerythritoltetranitrate even though no inner capsule be employed. Or, if so desired, the pentaerythritoltetranitrate and the initiating charge superimposed thereon may be pressed in,a'single operation. It Will be understood, of course, that where low pressures are employed the hazards of manufacture are also greatly reduced.

The initiating composition of the detonators of the present invention comprises at least 50% The solid'explosive organic nitrate which becomes coherent when subjected'to pressure is present in the initi'ating composition in an amount effective to reduce the sensitivity of the diazodinitrophenol. Generally, I employ an initiating composition comprising at least by weight of said solid explosive organic nitrate and preferably about 25%. Non-limiting eXamples of mixtures found to function quite satisfactorily are organic nitrate consisting of nitromannite and/or nitrodulcite mixed in proportions up to 50% with diazodinitrophenol; and nitrolactose mixed in proportions up to 35% with diazodinitrophenol. Other solid explosive organic nitrates, one or more of which may be employed in the initiating charge composition, are nitrostarch, pentaerythritoltetranitrate, nitroerythrite and nitroinositol.

Although in the following examples I show detonators of the present invention employing as little as .05 gram of initiating charge, it is to be understood that the amount selected for use will, of course, vary over a considerable range depending upon the composition of the initiating charge, the type and diameter of detonator involved, etc. Preferably, the initiating charge is present in an amount which would be insufficient to detonate tetryl, and at least .08 gram. The height of the initiating charge is an important criterion in selecting the amount of the charge to be used; for example, in fuse caps it is desirable to employ sufficient initiating charge to provide enough of the material to form a pressed charge that will inhibit its rumbling out of the shell and this should generally be of a height of at least .05 inch after pressing. For electric detonators havin a bridge wire embedded in the initiating charge it is desirable to employ sufiicient material to adequately cover the bridge wire used, the height of material required generally ranging from about .12 to about .20 inch. For example, an electric detonator having an inside diameter of about .260 inch would require from about .075 to about .125 gram of loose initiating charge to adequately cover the bridge wire. In order to maintain these heights within detonators having larger diameters than those recited above, it will be evident that larger amounts of initiating charge may be employed without departing from the spirit of the invention.

The underlying pentaerythritoltetranitrate charge employed in the detonators of the present invention is present in an amount which when initiated by the initiating charge superimposed thereon will provide positive detonation and it may be employed either as the sole base charge or it may be superimposed upon other explosive base charges, as, for example, tetryl, trinitrotoluene, picric acid, nitrocellulose, nitrostarch, trinitrobenzene, etc.

The solid explosive organic nitrate employed in the initiating charge and the pentaerythritoltetranitrate underlying charge may be the ordinary class of impure product usually produced, for example, by the nitration of commercial forms of material to be nitrated, the said nitrated products being prone to contain certain impure isomers, lower nitric esters, etc. They may, however, also be the chemically pure compounds as obtained, for example, by recrystallization of impure forms from a suitable solvent or solvents. For example, nitromannite may refer either to the chemically pure hexanitrate or it may contain portions of the lower nitric esters mixed therewith. The initiating charge and the underlying charge may be stabilized in any suitable manner by means of minor quantities of one or more stabilizing materials. Moreover, minor proportions of various other admixed materials may be employed in the initiating and underlying charges so long as these charges function in a satisfactory manner and do not have the sensitivity increased to an appreciably hazardous degree. I contemplate, for example, the possible use of such substances as graining agents, diluents, oxygen carriers such as potassium chlorate, potassium perchlorate, ammonium perchlorate, barium nitrate, barium peroxide, lead oxides and the like, as minor ingredients of the initiating and underlyin charge compositions. Additive ingredients as exemplified above may be precipitated or otherwise suitably admixed with the principal ingredients of the initiating and main charge compositions.

Non-limitin examples (wherein percentages are by weight) of detonators produced in accordance with the present invention are:

Example 1 An electric detonator comprising a .260" inside diameter shell, a .29 gram charge of tetryl in the base of the shell, superimposed thereon a charge of .12 gram pentaerythritoltetranitrate, superimposed upon the pentaerythritoltetranitrate charge an initiating charge of .05 gram of a composition consisting of 75% diazodinitrophenol and 25% nitromannite, all charges being positioned under an inner capsule which is pressed at a total pressure of 1'75 lbs. (3481 lbs. per sq. in.); over the pressed charge is then assembled an electric match head in the usual well known manner.

Example 2 An electric detonator comprising a .260" inside diameter shell, a .29 gram charge of tetryl in the base of the shell. superimposed thereon a charge of .12 gram pentaerythritoltetranitrate positioned I under an inner capsule, the said tetryl and pentaerythritoltetranitrate charges being pressed in one operation at lbs. total pressure (2486 lbs. per sq. in.); superimposed upon the pentaerythritoltetranitrate charge an initiating charge of .125 gram of a composition consisting of 75% diazodinitrophenol and 25% nitromannite, the said initiating charge being pressed at a total pressure of 25 lbs. (497 lbs. per sq. in.) over the pressed charge is then assembled an electric match head in the usual well known manner.

Example 3 An electric detonator comprising a .260" inside diameter shell and a .29 gram charge of tetryl pressed into the base of the shell at about lbs. total pressure; 0.12 gram charge of pentaprythritoltetranitrate positioned above the tetryl;

superimposed upon the pentaerythritoltetranitrate charge an initiating charge of .15 gram of a composition consisting of 75% diazodinitrophenol and 25% nitromannite; the said pentaerythritoltetranitrate and initiating charges being pressed in one operation at 30 lbs. total pressure (597 lbs. per sq. in.) over the pressed charge is then assembled an electric match head in the usual well known manner.

7 Emample A fuse cap comprising'a .222" inside diameter shell, a .29 gram charge of tetryl in the base of the shell; superimposed thereon a charge of .12 gram pentaerythritoltetranitrate positioned under an inner capsule, the said tetryl and pentaerythritoltetram'trate charges being pressed in one operation at 100 lbs. total pressure (2729 lbs. per sq. in); superimposed upon the pentaery= thritoltetranitrate charge an initiating charge of .075 gram of a composition consisting of 75% diazodinitrophenol and 25% nitromannite; the said initiating charge being pressed at a total pressure of 25 lbs. (682 lbs. per sq. in.)

Example 6 A fuse cap similar to Example 5 but with the saidinitiating charge consisting of. .125 gram of a composition consisting of 75% diazodinitrophenol and 25% pentaerythritoltetranitrate.

Example 7 A fuse cap comprising a .222" inside diameter shell, a .29 gram charge of tetryl pressed into the base of the shell at about 150 lbs. total pressure; a .12 gram charge of pentaerythritoltetranitrate positioned above the tetryl, and superimposed upon the pentaerythritoltetranitrate charge an initiating charge of .10 gram of a composition consisting of 75% diazodinitrophenol and 25% nitromannite; the said pentaerythritoltetranitrate and initiating charges being pressed in one operation at 25 lbs. total pressure (682 lbs. per sq. in.)

Example 8 Example 9 A fuse cap comprising a .222" inside diameter shell, a .29 gram charge of tetryl pressed into the base of the shell at about 150 lbs. total pressure; a .16 gram charge of pentaerythritoltetranitrate positioned above the tetryl, and superimposed upon the pentaerythritoltetranitrate charge an initiating charge of .15 gram of a composition consisting of 75% diazodinitrophenol and 25% nitrolactose; the said pentaerythritoltetranitrate and initiating charges being pressed in one operation at 25 lbs. total pressure (682 lbs, per sq. in.).

In the foregoing examples the tetryl base charges may be replaced with other explosivebase charges as indicated above or pentaerythritoltetranitrate may constitute the base charge of the detonator.

I have also found that certain fuse cap embodiments of the present invention will pass what is known as the flash-off test. In other words, they will give a high degree of protection against the firing of the underlying pentaerythritoltetranitrate explosive charge by the superimposed initiating charge when the latter is ignited by the accidental direction of the spit of a fuse or similar flame into the open end of acap; even though the initiating charge will consistently and 8 eifectively fire the underlying pent-aerythritol tetra'nitrate charge, when the said initiating charge is ignited by the spit of a fuse which has been inserted into the open end of the fuse cap. Thus, for example, in detonators having an explosive charge comprising pentaerythritoltetranitrate pressed under an inner capsule into a .222 inside diameter shell at lbs. total pressure, upon which is superimposed an initiatingoharge consisting of from .075 to .10 gram of a composition consisting of 7 5% diazodinitrophenol and-25% nitromannite, the said initiating charge being. pressed at 25 pounds total pressure (682 lbs. per sq. in.) the pentaerythritoltetranitrate charge consistently failed to detonate when the initiating charge was ignited by the spit of a Clover fuse directedinto the open end of the cap from a distance of at least M3" outside the open end of the cap. 0n the other hand, such detonators consistently fired from the spit of a Clover fuse when the fuse was inserted into the open end of the. cap, even though the cap was not crimped upon the fuse. Example 5 above is exemplary of such a cap. The detonators of Examples 7 and 9 are other exemplary embodiments of a fuse cap which will pass this test.

It. should be clearly understood that a perforated inner capsule, for the confinement of the pentaerythritoltetranitrate explosive charge or the confinement of said charge and the initiating charge, may be used or not in carrying out the present invention. Although the use of an inner capsule has certain advantages, as for example: (1') the binding action between the capsule and the shell tends to hold the charge in place in a more positive manner, particularly when very low seating pressures are used; and, (2) it provides added confinement for the charge or charges; nevertheless, I may eliminate the inner capsule for the sake of economy without departing from the invention.

It will therefore be understood that the invention isrbroad in this respect, as long as the initiating charge is positioned between the pentaerythri'toltetranitrate charge and the source of heat (safety fuse end-spit, fuse head, etc.). It has been found preferable, however, to position the initiating charge outside or on top of the confining inner capsule, when and if the latter is used, particularly for fuse caps, in order t present a larger surface area of initiating charge to receive the end spit from the safety fuse when inserted or crimped therein. One advantage of placing the initiating charge under the inner capsule, however, is that the capsule helps to keep the initiating charge in place during handling, shipping, etc., particularly when low seating pressures and/or very thin layers of the initiating charge are employed.

In the specification and claims where I refer to initiating charges present in an amount incapable of directly initiating tetryl I mean that the charge is incapable of consistently, completely detonating an underlying tetryl charge in a commercially practical detonator under corresponding conditions.

Having fully described my invention, What I claim is as follows:

1. In a 'detonator, a charge consisting essentially of pentaerythritcltetranitrate and superimposed directly thereon at least .05 gram of an initiating charge positioned to become ignited by a source of heat and to initiate the pentaerythritoltetranitratecharge, said initiating charge consisting of an admixture comprising pentaerythri 9 toltetranitrate and at least 75% by weight diazodinitrophenol.

2. In a detonator, a charge consisting essentially of pentaerythritoltetranitrate and superimposed directly thereon at least .05 gram of an initiating charge positioned to become ignited by a source of heat and to initiate the pentaerythritoltetranitrate charge, said initiating charge consisting of an admixture comprising pentaerythritoltetranitrate and at least 75% by weight diazodinitrophenol, said initiating charge being present in an amount incapable of directly detonating tetryl.

3. In a detonator, a charge according to claim 1 wherein the initiating charge is in lightly compressed condition.

4. In a detonator, a charge according to claim 1 wherein the initiating charge is a dried paste.

GUY F. ROLLAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 10 Number Name Date 2,186,426 Nash Jan. 9, 1940 2,195,032 Large Mar. 26, 1940 2,214,721 Crater Sept. 10, 1940 1,928,205 Large Sept. 26, 1933 15

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