Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B3/00—Blasting cartridges, i.e. case and explosive
  • F42B3/10—Initiators therefor
  • F42B3/16—Pyrotechnic delay initiators
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B23/00—Compositions characterised by non-explosive or non-thermic constituents
  • C06B23/04—Compositions characterised by non-explosive or non-thermic constituents for cooling the explosion gases including antifouling and flash suppressing agents
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B33/00—Compositions containing particulate metal, alloy, boron, silicon, selenium or tellurium with at least one oxygen supplying material which is either a metal oxide or a salt, organic or inorganic, capable of yielding a metal oxide
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06C—DETONATING OR PRIMING DEVICES; FUSES; CHEMICAL LIGHTERS; PYROPHORIC COMPOSITIONS
  • C06C5/00—Fuses, e.g. fuse cords
  • C06C5/06—Fuse igniting means; Fuse connectors

Definitions

• This invention relates to delay compositions having delayed-action times in the millisecond range. More particularly, it relates to flameproof delay compositons with a delay in the millisecond range which consist essentially of an oxidizable metal, an oxidizing agent, and a metallic ballast material. Even more particularly, the invention relates to flameproof delay compositions having a delay time in the millisecond range which consist essentially of an oxidizable metal, an oxidizing agent, and a metallic ballast material and which, because of the particular metals chosen as the ballast material, will not ignite explosive atmospheres or firedamps when burned because of their relatively low heat and temperature of combustion.
• Delay compositions are used, for example, in delay electric blasting caps which essentially comprise an ignition charge, a detonating charge and a delay element through the medium of which the detonating charge is fired.
• the delay element is customarily a fuse of such length and composition as will afford the desired delay interval between firing of the ignition and detonating charges.
• Such explosive means have found wide use in mining and quarrying operations to provide sequential initiation of the explosive charges in an array of boreholes. By such sequential initiation, an eit'icient blasting action with respect to the amount of material blasted in one operation and to the degree of fragmentation of the material blasted can be achieved.
• the delay compositions of the present invention are those which have become known in the art as delay com positions with short delay periods, i.e., wherein the period of delay is measured in terms of milliseconds.
• compositions are used as delay elements especially for electrical time fuses which are gasless and possess explosive power.
• the present invention is directed to a different solution to the problem of eliminating the danger of igniting firedamp mixtures when using such delay compositions.
• the concept behind the present invention is the recognition that it is more expedient and safe to strip the slag itself, which is formed during the burning of the delay composition, of its capacity to ignite firedamp mixtures, rather than to strive only to prevent, by employing corresponding counter-measures, the disadvantageous consequences which could result from the potential danger inherent in the slag.
• the cause of the ignition of firedamps or other explosive atmospheres during the use of the conventional millisecond delay compositions of silicon and lead oxide lies in the aforementioned high temperature of burning of these delay compositions as well as the very strong afiinity for oxygen of the excess silicon present in these compositions.
• a decrease of the combustion temperature which may be effected, for example, by increasing the silicon content of the delay composition, is possible only to a limited extent because the combustion time then becomes too long if a certain limit is exceeded.
• the use of activated silicon with the object of rendering possible an increased silicon content in the composition, thus maintaining a constant combustion time for the composition may be realized only to a limited extent since excess activated silicon is particularly dangerous with respect to igniting firedamps. 7
• one of the objects of the present invention is to provide a delay composition having a delay-action time in the millisecond range which overcomes the disadvantages and deficiencies of the prior art compositions.
• Another object of the present invention is to provide a delay composition which will not ignite explosive atmospheres or firedamps by virtue of its relatively low heat and temperature of combustion.
• a further object of the invention is to provide a delay composition which will not ignite explosive atmospheres or firedamps because of the properties of the delay composition itself, thus obviating the need for complex-prior preventive measures, as employed with the prior art compositions.
• adifferent approach is chosen in that a delay composition consisting essentially of an oxidizable metal or metalloid and oxidizing agents therefor is provided, wherein the excess oxidizable metal or metalloid present in the composition is replaced by a corresponding amount of a metallic ballast.
• the metallic ballast material added to the delay composition is one which has a thermal conductivity of greater than 0.5 and/or which forms with the oxidizable metal an alloy the eutectic point of which is less than 1300 C. and which has a heat of formation of its oxide of less than 1200 calories per gram.
• a composition for example, one based on a silicon-lead oxide mixture, has a delayed-action time in the millisecond range, while overcoming the disadvantages of the prior art compositions mentioned hereinabove.
• the burning time can be extended to a desired value of, for example, 300 milliseconds if 70% by weight, based on the amount of the mixture, of copper powder is added to the mixture.
• the combustion heat is thereby reduced by almost half, and the comfor the intended purpose of the present invention.
• the delay compositions of the present invention are readily prepared by means well known in the art.
• the components of the delay compositions are generally used in the form of powders and are thoroughly mixed together by well known methods.
• Copper is particularly suitable since it has a thermal conductivity of more than 0.5 and forms an alloy with silicon the eutectic point of which is below 1300 C. and, which, during the formation of its oxide, gives olf a heat of less than 1200 calories per gram. If only the requirement that the ballast material possess a thermal conductivity of more than 0.5 is to be satisfied, aluminum, silver and antimony, for example, are also suitable.
• the thermal conductivity of the metal is to be disregarded and if, for the purpose of reducing the ignition danger posed by the excess silicon present in delay compositions, the only requirement sought to be met is that the ballast material form with the oxidizable metal of the delay compositions alloys whose eutectic points are below 1300 C. and that the ballast material have a heat of formation of its oxide of less than 1200 calories per gram, then nickel and iron, for example, have also been found to be advantageous and fully appropriate
• the silicon-red lead delay compositions of the present invention may contain from to 50% by weight of silicon, from 25 to 75 by weight of red lead and from 50 to 10% by weight of the metallic ballast material. Such delay compositions in the millisecond range are well known in the art.
• the silicon-lead dioxide delay compositions of the present invention may contain from 20 to 70% by weight of silicon, from to 70% by weight of lead dioxide and from 50 to 10% by weight of the metallic ballast material. Such delay compositions in the millisecond range are well known in the art.
• the metallic ballast material has been described as being in the form of a powder.
• a particle size of metallic ballast powder of less than 40p. gives exceptionally good results.
• lead oxides are chiefly lead dioxide and red lead.
• Lead monoxide (PbO) is only of minor importance.
• Delay composition having a delayed-action time in the millisecond range consisting essentially of powdered silicon, an oxidizing agent selected from the group consisting of the oxides of lead, and a pulverulent metallic ballast material, said metallic ballast material being characterized in having a thermal conductivity of greater than 0.5, in forming with said oxidizable metal an alloy the eutectic point of which is less than 1300 C. and in having a heat of formation of its oxide which is less than 1200 calories per gram.
• delay composition of claim 2 wherein said delay composition consists essentially of from 10 to by weight of silicon, from 25 to 75% by weight of red lead and from 50 to 10% by Weight of said metallic ballast material.
• delay composition of claim 4 wherein said delay composition consists essentially of from 20 to 70% by weight of silicon, from 15 to 70% by weight of lead dioxide and from 50 to 10% by Weight of said metallic ballast material.
• a powdered delay composition having a delayedaction time in the millisecond range consisting essentially of approximately 15% by weight of silicon, approximately 44% by weight of red lead, and approximately 41% by weight of copper.
• Delay composition having a delayed-action time in the millisecond range consisting essentially of powdered silicon, an oxidizing agent selected from the group consisting of the oxides of lead and pulverulent silver.
• Delay composition having a delayed-action time in the millisecond range consisting essentially of powdered silicon, an oxidizing agent selected from the group consisting of the oxides of lead and pulverulent antimony.
• Delay com-position having a delayed-action time in the millisecond range consisting essentially of powdered silicon, an oxidizing agent selected from the group consisting of the oxides of lead and pulverulent nickel.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Contacts (AREA)
• Silicon Compounds (AREA)
• Conductive Materials (AREA)

Applications Claiming Priority (1)

Publications (1)

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Citations (8)

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• 1963
  • 1963-09-07 DE DED42428A patent/DE1257650B/de active Pending
• 1964
  • 1964-06-16 CH CH782464A patent/CH424584A/de unknown
  • 1964-06-30 AT AT560964A patent/AT263589B/de active
  • 1964-07-25 CS CS4300A patent/CS150159B2/cs unknown
  • 1964-09-04 GB GB36411/64A patent/GB1074306A/en not_active Expired
  • 1964-09-04 BE BE652682D patent/BE652682A/xx unknown
  • 1964-09-04 NL NL6410309A patent/NL6410309A/xx unknown
  • 1964-09-08 US US395047A patent/US3329539A/en not_active Expired - Lifetime

Patent Citations (8)

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