US2771033A - Ventless delay electric initiators - Google Patents

Ventless delay electric initiators Download PDF

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Publication number
US2771033A
US2771033A US305906A US30590652A US2771033A US 2771033 A US2771033 A US 2771033A US 305906 A US305906 A US 305906A US 30590652 A US30590652 A US 30590652A US 2771033 A US2771033 A US 2771033A
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US
United States
Prior art keywords
delay
ventless
silicon
weight
red lead
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US305906A
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English (en)
Inventor
Idwal O Lewis
Robert D J Owens
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Imperial Chemical Industries Ltd
Original Assignee
Imperial Chemical Industries Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB2741951A external-priority patent/GB711815A/en
Application filed by Imperial Chemical Industries Ltd filed Critical Imperial Chemical Industries Ltd
Application granted granted Critical
Publication of US2771033A publication Critical patent/US2771033A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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

Definitions

  • the object of the present invention is to provide series of ventless short delay electric detonators having delay intervals between successive delay numbers for example of the order 25 or 50 milliseconds which, when the ventless container consists at least essentially of copper, have the advantage that single detonators of any such practical series when fired freely suspended in an inflammable gas mixture, for example, 9% methane/ air mixture, show no tendency to cause ignition of the gas mixture, and which when the ventless container is of aluminium or copper or copper alloys are cheaper to produce than has heretofore been possible.
  • the ventless short delay electric detonator comprising an electrically actuated igniting charge, an initiating charge, and an interposed short delay element enclosed in a ventless container
  • the said short delay element comprises a cut-ofi length of fuse comprising a flexible envelope surrounding a core comprising a preferably graphite-glazed, nitrocellulose bonded granular rmxture of silicon and red lead.
  • ventless container consists essentially of copper.
  • the bonded granular mixture of the core of the delay fuse element may contain red lead in an amount from 65 to 95 percent by weight, silicon in amount from to 35 percent by Weight and nitrocellulose in amount up to 5 percent by weight of the red lead plus silicon. It is preferred, however, generally for the compositions to consist of 70 parts red lead, 30 parts silicon and 0.25 part nitrocellulose by weight.
  • mixtures are preferably made by first dry nnxing the red lead and silicon, then mixing the resulting mixture with a solution of nitrocellulose in a suitable solvent, for example, amyl acetate, in sufiicient amount to give a dry crumbly mass which is then sieved, for example, through a 25 B. S. S. mesh sieve and dried to give the bonded granular mixture.
  • a suitable solvent for example, amyl acetate
  • the bonded granular mixture is preferably glazed by tumbling with graphite in a drum or other suitable container, for example, for a time of the order of eight hours to give a final composition containing less than 1 percent of graphite.
  • the step of glazing enables the granular compositions to be incorporated into fuse more easily than the same compositions unglazed.
  • the flexible envelope may be formed of glass or textile yarns and may be provided with an outer coating which may consist of an organic thermoplastic material such as, for example, polyethylene, polyvinyl chloride or polystyrene.
  • the textile covering may be spun around a core of the glazed material and compressed against it by passage through a die and the fuse thereafter finished in the manner known in the manufacture of safety fuse.
  • Delay elements of differing delay periods can be obtained either by using different lengths containing the same composition or by varying the composition.
  • the delay element be secured in position by pressing an inverted perforated metal cup over the end thereof remote from the initiating composi- I 2,711,033 Patented Nov. 20, 1956 'ice tion, instead of relying on a friction fit between the outer envelope and the wall of the tubular container.
  • the use of such a cup also prevents the envelope, if ignitible, from being ignited by the igniting charge.
  • the soft and somewhat compressible nature of the envelope renders the attainment of the necessary tight fit easy without the application of loading pressures so high as to damage the structure of the delay element. An expansion space should be left between the end of the delay element and the igniting charge.
  • a small supplementary charge of, preferably gasless, igniting composition may be interposed between the end of the delay element and the initiating charge. It is also sometimes desirable to press a small charge of a gasless igniting composition directly on top of the delay element in order to ensure its ignition from the electrically actuated igniting charge, which will usually be spaced from it.
  • the electrically actuated igniting charge may take the form of an electric fusehead.
  • 1 is an aluminium detonator tube
  • 2 is a detonating explosive charge of tetryl compressed into the end of the tube
  • 3 is a more sensitive detonating charge compressed on top of charge 2 and consisting essentially of a mixture of aluminium, lead azide and lead 'styphnate and constituting the initiating charge
  • 4 is the flexible envelope
  • 5 is a covering of polyethylene
  • 6 is a core of a glazed bonded granular mixture.
  • 7 and 8 are layers of gasless igniting composition consisting of silicon and red lead in the weight ratio 30 to 70
  • 9 is an inverted perforated metal cup pressed over the composition 8 and over the top of the delay element so as to secure the delay element longitudinally in the tube
  • 10 is an electric fusehead
  • 11 is an axially perforated sealing plug of rubber-like material crimped between the aluminium tube 1 and the insulated electric leading wires 12 and 12' as shown at 13 whereby there is attained a seal capable of withstanding an internal pressure greater than the maximum pressure that can be produced as a result of the combustion of the contents of the detonator tube with the exception of the detonating explosive charges 2 and 3.
  • the space 14 between the end of the plug 11 and the inverted cup 9 and hence the length of the tube 1 is accordingly made sufficient to ensure that the maximum pressure that can even temporarily be developed in the initiator by the successive consumption of the compositions of the electric fusehead 10, the igniting charge 8, the delay composition 6, and the igniting charge 7 will not unseal the tube.
  • the invention is also illustrated by the following examples in Table 1 in which are recorded lengths of delay elements, mean delay times, and the number of ignitions given when single detonators are fired freely suspended in a 9 percent methane/ air mixture.
  • the delay composition consists of 70 parts red lead, 30 parts silicon and 0.25 nitrocellulose.
  • the detonators are commercial lead azide/lead styphnate/aluminium/tetryl delay detonators in copper tubes without any supplementary igniting charges top and bottom.
  • the invention is further illustrated by the following examples in Tables 2 and 3 in which are recorded delay periods of delay fuse elements ofthe lengths shown made from fuse whose core consists of a nitrocellulose bonded granular mixture having the composition given when used in commercial lead azide/lead styphnate/aluminium delay detonators without any supplementary igniting charges top and bottom.
  • a ventless short delay electric detonator comprising an electrically actuated igniting charge, an initiating charge and an interposed short delay element enclosed in a ventless container essentially of copper wherein the said short delay element comprises a cut-ofi length of fuse comprising a flexible textile envelope around a core comprising a dry crumbly graphite-glazednitrocellulose bonded granular mixture of silicon and red lead, said red lead being in amount of from about 65% to 95% by weight, the silicon in amount of from about 5% to 35% by weight, and the nitrocellulose in amount up to about 5% by weight of the red lead andsilicon.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Air Bags (AREA)
US305906A 1951-11-22 1952-08-22 Ventless delay electric initiators Expired - Lifetime US2771033A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB2771033X 1951-11-22
GB2741951A GB711815A (en) 1952-07-16 1952-07-16 Improvements in or relating to ventless delay electric initiators

Publications (1)

Publication Number Publication Date
US2771033A true US2771033A (en) 1956-11-20

Family

ID=32328129

Family Applications (1)

Application Number Title Priority Date Filing Date
US305906A Expired - Lifetime US2771033A (en) 1951-11-22 1952-08-22 Ventless delay electric initiators

Country Status (4)

Country Link
US (1) US2771033A (en, 2012)
BE (1) BE514360A (en, 2012)
CH (1) CH310832A (en, 2012)
FR (1) FR1062887A (en, 2012)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3041972A (en) * 1958-12-15 1962-07-03 Atlas Chem Ind Arc resistant electric initiator
US3102474A (en) * 1961-04-14 1963-09-03 Du Pont Sonic pulse generating device
US3112699A (en) * 1961-04-14 1963-12-03 Du Pont Sonic pulse generator
US4369708A (en) * 1979-09-21 1983-01-25 E. I. Du Pont De Nemours And Company Delay blasting cap

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1825224A (en) * 1930-02-28 1931-09-29 Ensignbickford Co Safety fuse
US1999820A (en) * 1931-06-24 1935-04-30 Hercules Powder Co Ltd Delay cap
US2079777A (en) * 1934-04-07 1937-05-11 Ici Ltd Safety igniter for blasting explosive devices
US2410801A (en) * 1945-03-13 1946-11-12 Ludwig F Audrieth Igniting composition
US2416639A (en) * 1944-07-08 1947-02-25 Ensign Bickford Co Slow-burning powder composition
US2478501A (en) * 1945-08-01 1949-08-09 Ici Ltd Ignition compositions
US2513391A (en) * 1943-10-06 1950-07-04 Ici Ltd Waterproof fuse
US2586959A (en) * 1949-09-16 1952-02-26 Canadian Ind Delay electric blasting cap
US2619035A (en) * 1947-12-31 1952-11-25 Ici Ltd Production of ventless delay initiators for explosive or other charges capable of exothermic reaction

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1825224A (en) * 1930-02-28 1931-09-29 Ensignbickford Co Safety fuse
US1999820A (en) * 1931-06-24 1935-04-30 Hercules Powder Co Ltd Delay cap
US2079777A (en) * 1934-04-07 1937-05-11 Ici Ltd Safety igniter for blasting explosive devices
US2513391A (en) * 1943-10-06 1950-07-04 Ici Ltd Waterproof fuse
US2416639A (en) * 1944-07-08 1947-02-25 Ensign Bickford Co Slow-burning powder composition
US2410801A (en) * 1945-03-13 1946-11-12 Ludwig F Audrieth Igniting composition
US2478501A (en) * 1945-08-01 1949-08-09 Ici Ltd Ignition compositions
US2619035A (en) * 1947-12-31 1952-11-25 Ici Ltd Production of ventless delay initiators for explosive or other charges capable of exothermic reaction
US2586959A (en) * 1949-09-16 1952-02-26 Canadian Ind Delay electric blasting cap

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3041972A (en) * 1958-12-15 1962-07-03 Atlas Chem Ind Arc resistant electric initiator
US3102474A (en) * 1961-04-14 1963-09-03 Du Pont Sonic pulse generating device
US3112699A (en) * 1961-04-14 1963-12-03 Du Pont Sonic pulse generator
US4369708A (en) * 1979-09-21 1983-01-25 E. I. Du Pont De Nemours And Company Delay blasting cap

Also Published As

Publication number Publication date
BE514360A (en, 2012)
FR1062887A (fr) 1954-04-28
CH310832A (de) 1955-11-15

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