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Патент USA US2127603

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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.
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