Патент USA US2127603код для вставки
Aug. 23, 1938. 2,127,603 E. JONES GASLESS IGNITER Filéd Dec. 19, 1934 Elwyn Jones INVENTOR. BY AT TORNE Y. 2,127,603 Patented Aug. 23, 1938 UNITED STATES PATENT OFFICE 2,127,603 GASLESS IGNITER. Elwyn Jones, Saltscoats, Scotland, assignor to Imperial Chemical Industries Limited, a cor poration of Great Britain " Application December 19,' 1934, Serial No. 758,317 ‘In Great Britain December 20, 1933 v10 Claims. (Cl. 102-—10) This invention relates to a device suitable in particular for igniting explosives of the burning or nondetonating type, for example gunpowder, and has for its object the provision of an im 5 provedigniter which may be used with safety in ?ery or dusty mines. More particularly an ob ject of the invention is the provision of an im proved igniter suitable for use with blasting cartridges which comprise an explosive of the 10 kind described, the said cartridges having been rendered safe for use in ?ery or dusty mines, for example by means of a sheath of borax. Explosives of the burning or non-detonating type are customarily ignited by means of safety 15 fuze, or by an electric powder fuze which con tains a charge of combustible material ignited by means of an electric fuzehead. In each case terials are used itis desirable to leave a consider able free space above the combustible composi tion in order to minimize any rise in pressure which may occur as a result of the incidental amounts of gas usually generated. The fuzehead may suitably comprise mixtures of ?nely divided zirconium with an oxidizing agent and in particular may comprise a mixture of ?nely divided zirconium and lead mono-nitro 10 resorcinate. The combustible material may, for example, comprise a ?nely divided metal together with an oxidizing agent and the following mixtures are suitable in particular for use in the invention. In each of the following combustible mixtures the ingredients are ?nely divided, e. g. to pass a 200 mesh sieve and‘ uniformly mixed:-— the ?ame or spit from the'combustible material comes into direct contact with the explosive. 20 The ‘?ame or spit from these devices is capable of igniting dangerous mixtures of methane and air or suspensions of coal dust, and hence the functioning of these devices when exposed in a mine is a source of danger which has hitherto 25 hindered the development of safety explosives comprising black powder and the like. According to the present invention a safety igniter suitable in particular for igniting ex plosives of the burning or non-detonating type, Percent Red lead _______________________________ __ 87 Ferrosilican ____________________________ __ 13 Lead chromate _________________________ __ Calcium silicate ________________________ __ 90 10 Zinc ___________________________________ __ 60 Potassium permanganate ________________ __ 40 Iron ___________________________________ -_ 30 Potassium permanganate ________________ __ '70 Tin ____________________________________ __ 35 30 comprises an electric fuzehead and a quantity of Lead peroxide __________________________ __ 65 combustible material sealed together'within a Tin ____________________________________ __ 40 metal container, the arrangement being so adapt ed that the products of‘combustion of ‘the said fuzehead and/or combustible material cannot 35 escape therefrom, the temperature of a portion Potassium permanganate ________________ __ 60 Magnesium _____________________________ __ Barium peroxide ______________ __‘_ ______ __ 94 Calcium silicide ________________________ __ 30 Red lead _______________________________ __ 70 at least of the external surface of the metal con tainer being raised, however, to a temperature suf?cient to ignite a blasting charge but insu?i cient to ignite mixtures of air with methane or 40 coal-dust. The attainment of a surface tem perature of 300° C. is su?icient to ignite a black powder explosive, whereas a surface temperature of about 650° C. is required to ignite a methane air or coal-dust air mixture. 45 50 In the igniters ‘of the present invention the products of combustion can come into contact neither with the explosive to be ignited nor with ignitable mixtures of air with methane or coal dust which may be present. The fuzehead and combustible material em ployed are suitably of the kind yielding little or no gas on combustion. The metal container must be so adapted as to be capable of withstand ing the pressure developed by any gas which is 55 evolved, and even when substantially gasless ma 20 25 30 6 35 It will readily be understood by those skilled in the art that maximum temperature attained by 40 the external surface of the container is influenced by a number of factors and that by suitable varia tion of these factors any temperature within reasonable limits may be arrived at. Thus, for example in igniters having a constant 45 ratio between thevolume of the heating charge and the surface in contact therewith, the maxi mum external surface temperature will tend to be increased by increasing (1) the calori?c value of the combustible ma 50 terlal; (2) the density of the combustible material when loaded into the container; or (3) the thermal conductance of the walls of the container, 2 2,127,608 or vice versa. The maximum external surface temperature will tend to be decreased by and increase in (1) the thermal capacity of the container; or (2) the thermal capacity of the combustible material or of its solid residue, or vice versa. Any of the above conditions may be varied within suitable limits. In general, however, it ll® is preferred to use a container of such dimensions and of sufficient length to afford a suitable area of maximum temperature to contact with the ex plosive. Caution must also be observed in vary ing the thickness of the metal container since if is the thickness is made too small there is a risk that the walls may be melted with consequent failure of the purpose of the invention. The thickness and other variables of the container should also not be such as to provide an undue delay in the attainment of the maximum exter nal temperature. _ In order to vary the calori?c value of the com bustible material the proportions of the con stituents may be altered, those materials in which the constituents are present in stoichio metric proportions having the greatest calori?c value. Alternatively, the calorific value may be decreased by dilution with a non-volatile inert material. The combustible material is introduced into 30 the metal container under a moderate pressure sufficient to locate the charge securely in posi tion. A common detonator loading pressure, e. g. 150 lbs. per square inch may be used, but P preferably the loading pressures are lower than this and excessive pressures should be avoided, since the sensitiveness to ignition of the charge is thereby reduced. ~ The metal container may suitably be an ordi <10 nary copper detonator tube, but the container may be constructed of other metals or alloys which are non-combustible and of sumciently in the copper tube I, and on assembly it is passed down to make contact with the surface of the combustible material, thus ensuring that the fuzehead is close to the combustible material and at the same time projecting the fuzehead from damage by pressure. The outer tube l and the sleeve fl are preferably crimped together after assembly. In the alternative form illustrated in Figure 2 a shoulder is provided on the plug 6 in order to indicate when the fuzehead has been inserted to the correct distance. The tubes may also be constructed of an alloy or metal other than copper, which does not burn with ?ame nor spark under blasting conditions. Example A copper tube is employed 35 mm. long, 6 mm. internal diameter and having walls 0.2 mm. thick. A suitable charge for such a tube would be 0.75 gm. of a mixture containing 60% ?nely divided zinc and 40% potassium permanganate, pressed into the tube under a pressure of 60 lbs. per square inch. A fuzehead comprising zirconium and lead ,2-mononitroresorcinate is positioned close to the composition, the free space between the top of the composition and the washer ‘I be ing more than twice the internal diameter in length, and advantageously 20 mm. Other combustible compositions may be substi tuted as described above. Considerable latitude in the amount of charge is permissible, amounts ‘from 0.25 to 1.25 gm. being usually suitable in the above tube, but 0.5 to 1.0 gm. is preferred. I claim: 1. A safety igniter for a blasting charge of de ?agrating explosive, said igniter being free from ‘ bursting and detonating charges and comprising an electric fusehead and a substantially gasless combustion charge of predetermined maximum combustion temperature below the ignition tem perature of a ‘mixture of air with methane en closed in a ventless metal container having a high melting point. The constructional mate rial must also be generally serviceable and in‘ fusion temperature above the maximum combus particular must be capable of undergoing the cus " tion temperature of said charge, said charge be ing adapted to heat the outer surface of said con ‘ tomary crimping operation. The igniters of the present invention are par ticularly useful, as already stated, for igniting burning explosives, for example, blackpowder. The said igniters, however, are also useful for initiating blasting devices of the kind compris ing a charge adapted, on initiation, to generate gas, the said charge being enclosed together with the igniter in a pressure-resistant metal vessel adapted to release the generated gases at a suf ?cient pressure to cause a blasting effect in the borehole. The invention is illustrated in the accompany ing drawing, in which Figures 1 and 2 represent 60 central longitudinal sections of two forms of ig niter. In each form the igniter‘ comprises a copper tube i closed at one end and partly ?lled with a charge of combustible material 2. A gas less electric fuzehead 3 with insulated leads 5 is sealed into the tube by means of a plug 6 con structed of lead or other deformable non-com bustible material upon which the tube may be crimped to make a gas tight seal. When a me tallic plug is used, ,the fuzehead may be insu lated therefrom by means of a non-conducting incombustible washer ‘i: In the form of ‘the invention illustrated in Figure 1 the lead plug is secured in a copper sleeve 0 whichv projects slightly beyond the end 75 of the fuzehead. This sleeve is a push ?t with tainer, without rupture of the walls thereof, to a temperature sumcient to ignite said blasting charge indirectly by heat transfer through the walls thereof, but insufficient to ignite a mix ture of air with methane. 2. A safetyigniter for a blasting charge of de?agrating explosive, said igniter being free from bursting and detonating charges and com prising an electric fusehead and a substantially gasless combustion charge having a maximum combustion temperature lower than 650° C. en closed in a 'ventless metal container having a fusion temperature above the maximum com bustion temperature of said charge, said charge being adapted to heat the outer surface of said container, without rupture thereof, to a tem perature exceeding about 300° C. but substantial ly lower than 650° 0., whereby said blasting charge may be‘ignited indirectly by heat trans fer through the walls thereof without danger of igniting a mixture of air with methane. 3. The igniter of claim 2, in which said com bustible charge comprises a metal ‘forming a solid oxide at its temperature of combustion, and an inorganic salt having a high content of available oxygen. 4. The igniter of claim 2, in which said com bustion composition comprises a metal and po tassium permanganate. 3 2,127,603 5. The igniter of claim_2,_ in which said fuse head comprises zirconium and lead 2-mono nitroresorcinate. ’ ‘ temperature of said charge, said charge being adapted to heat the outer surface of said con _ tainer, without rupture thereof, to a temperature v 6. A blasting. assembly comprising a blasting exceeding about 300° (3. but substantially lower charge of a‘ defiagrating explosive enclosed in a than,650° C., wherebyr said blasting charge may (a be ignited indirectly by heat transfer through the sheath adapted to prevent‘ the ignition of ?re damp, and a safety igniter free _from bursting and walls thereof without danger of igniting a mix detonating charges and comprising a combustion ture of air with methane. ‘ 9. A safety igniter for a blasting charge .of charge of predetermined maximum combustion 10 temperature below the ignition temperature of a "deflagrating explosive said igniter being free from 10 bursting and detonating charges and comprising mixture of air and methane enclosed in a vent less metal container having -a fusion temperature ‘an electric fusehead and a substantially gasless above the maximum combustion temperature of combustion charge comprising zinc and potas said charge, said combustion charge being‘ sium permanganate having a predetermined maximum combustion temperature below the adapted to heat the outer surface of said con F tainer, without rupture of ‘the walls thereof, to ignition temperature of a mixture of 'air with a temperature sufficient to ignite said 'blasting methane, enclosed in a ventless, copper con indirectly by heat transfer through, the walls of tainer having a fusion temperature above the said container, but insu?icient to ignite a mixture 20 of air with methane. ' ' - 7. The blasting assembly of claim 6, in which said de?agrating explosive comprises black pow ‘der enclosed in- a sheath of cooling salts com prising borax. 8. "A safety igniter for‘ a blasting charge ofde -25 ?agrating explosive ,said igniter being free from bursting and detonating charges and comprising an electric fusehead and a substantially gasless (combustion charge comprising zinc and potas 30 sium permanganate having a maximum com bustion temperature lower than 650° C, enclosed in a ventless metal container having a fusion temperature above the maximum combustion maximum combustion temperature of said charge and having walls approximately 0.2 millimeter thick. ' 10. A safety igniter for a blasting charge of deflagrating explosive, said igniter being free from bursting and detonating charges and com prising an electric fusehead and a substantially gasless combustion charge comprising from 0.25 to 1.25 grams of a mixture comprising approxi mately 60% ?nely divided zinc and 40% potas siumj'permanganate having a maximum combus tion temperature lower than 625° C. and enclosed in a ventless copper container having walls ap proximately 0.2 millimeter thick. ELWYN JONES. CERTIFICATE OF CORRECTION. August 2}, 1958-, Patent No. 2,127,603. e . I } Emmi JTONES._ ’ “ _ is hereby certified that error appears in the printed specification of: the above numbered patent requiring correction as follows; Page 3 , first column, line it‘? , claim 6, after the word "blasting" insert charge; and that the said Letters Patent shouldbe read‘ with this correction therein that the same ma'y'conform to.) the recorder the ‘case in the "Patent Office. Signed‘and sealed this 25th day of October, A‘. ID. 1958; ' -\Henry vVan 'Arsdal'e (Seal) Acting Commissioner of Patents.