Note: Descriptions are shown in the official language in which they were submitted.
!,I 201q,~23
'i A HIGH TEMPERATURE STABLE, LOW INPUT ENERGY PRIMER/DETONATOR
~I Backuround of the Invention
The invention relates to a method of manufacturing
primers/detonators stable at high temperatures up to 1o0°C or
better, having an all-fire impact sensitivity of 1.0 inch-oz or
less, and high degree of reliability.
The invention more particularly relates to the development
of a primer/detonator, which can function with a very high degree
of reliability at temperatures as low as -40°C, as high as 100°C
or better, and function equally well at ambient temperatures, and
~ should have an all-fire sensitivity to impact of 1 inch-oz or
less in the aforementioned temperature range.
i
The explosive industry uses a variety of primers/detonators.
~i Basically these devices consist of a primary explosive component
I
initiated by stab (friction) or impact, an intermediate explosive
;I composition to be set-off by the primer composition, and a base
i~ charge of secondary explosive like RDX or HMX to give the desired
output to perform work, which may be to set off another explosive
I
device in the ignition train. One of the common low input energy
primers/detonators is an M55 Detonator, which is extensively used
in ordnance for anti-personnel and anti-vehicular munition
systems. The make up of these detonators consist of:
i
(a) A primary explosive composition containing basic lead
i styphnate, dextrinated lead azide, antimony sulfide, barium
~,~ nitrate, and tetracene.
(b) An intermediate explosive charge of RD 1333 lead azide.
i; (c) RDX as secondary explosive.
! These detonators/primers are set-off by stab action with a
~~ firing pin and show a sensitivity of about 0.80 inch-oz at 99.99%
reliability and 95% confidence level. In this detonator system,
while basic lead styphnate and dextrinated lead azide fill their
~~ role as the main primary explosives, barium nitrate fills the
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~0 14 1 23
I role as a supplier of oxygen to the system and the antimony
II sulfide as a fuel cum mechanical sensitizes, because of its high
melting point. But it is tetracene that plays a unique and
important role. It is a chemical sensitizes with the unique
property that makes the system function at an input sensitivity
or energy below 1 inch-oz.
While tetracene is an excellent sensitizes and one of the
best which explosive chemists have developed, its inherent
weakness is that when temperatures higher than 85°C are
encountered, the primers begin to fail. With heat aging above
85°C, the tetracene begins to decompose and leak out from the
i primer. Sensitivity starts to decrease at 95°C, after 100 hours,
i
the impact energy required will be increased by at least a factor
I~ of 3.
i
While there are many applications for primers/detonators
',~~ that would function reliably at temperatures of 100°C or higher
~I (like high cycle firing machine guns), a civilian application is
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!I in the automobile crash air bags used in motor vehicles for
~~ protecting occupants in crashes. In self-contained air bag
j modules involving mechanical sensors, the primers are used to
ignite the propellant system, which then generates the gas to
inflate the air bag. The industry standards demand that air bag
i~ systems function reliably at as high a temperature as 100°C; and
at the same time function equally reliably at -40°C. Also,
;~ industry standards demand that they function with a high degree
I~ of reliability and have a long shelf life.
The operating parameters expected for primers/detonators to
!~ fulfill the aforesaid, as well as similar requirements can be
I~
~i summed up as follows:
(i) The composition used in the primer should be easy
v to manufacture and capable of loading in automatic industry
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CA 02014123 2000-03-21
machines used for manufacture of primers/detonators.
(ii) They should be safe for handling, particularly in
systems using lead styphnate, where protection against
static electricity may be an important safety factor.
(iii) They should be thoroughly stable at
temperatures as high as 100°C and should function
reliably at temperatures as low as -40°C.
(iv) In Systems using stab action energy to set off
the system, the all-fire energy required for setting
off the system should be 1 inch-oz or less, similar to
those required for primers using tetracene as the
sensitizer, where the all-fire sensitivity value is
calculated statistically to 99.99% reliability and 95%
confidence level for the entire population.
umm~ry of the Invention
A principal object of an aspect of the present
invention is to provide conditions of assembly and, make up
of detonators for the production of primers/detonators,
with a high sensitivity to stab action and a high degree of
reliability.
Another object of an aspect is to eliminate tetracene
with its inherent limitation of decomposing at temperatures
higher than 85°C~ and provide a method to use mechanical
sensitizers like sand, glass powder, or carborundum in
primer mixes to improve both sensitivity to impact and
temperature aging.
~1 further object of an~aspect is to provide a method
of the foregoing with a method to co-precipitate the
mechanical sensitizer with an explosive to improve
homogeneity and sensitivity.
Still another object of an aspect is to provide a
composition using a powerful oxidizer like potassium
chlorate as a sensitizer.
Still another object of an aspect is to provide a
composition, eliminating primary explosives like azide and
styphnate and using oxidizers and fuels like potassium
chlorate, and antimony sulfide, in combination with a
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CA 02014123 2000-10-24
mechanical and chemical sensitizer, to achieve a high
degree of sensitivity, reliability, and temperature aging
properties.
Another important object of an aspect is to improve
the primers of the foregoing type to withstand very high
temperature by using high energy fuels like selenium and
titanium.
Still another important object of an aspect is to
provide a method of manufacturing detonators with a high
degree of reliability at 90%-99.99% reliability and 95%
confidence level, and achieve primers/detonators of
sensitivity 0.8 inch-oz to 3.0 inch-oz, having temperature
aging properties that would retain sensitivity from -40°C
to 200°C and capable of standing temperature cycling and
humidity from 95% RH at 95°C to -40°C.
The above operating parameters could be achieved by
eliminating tetracene with its inherent limitation of
decomposing at temperatures higher than 85 C, and replacing
it with mechanical sensitizers, or by developing an
entirely different composition system, using ingredients
which are highly stable at the temperatures for which the
system is being designed.
According to an aspect of the invention, there is
provided a consolidated mixture of a primer initiating
composition omitting tetrazene as a sensitizer yet capable
of withstanding aging and providing a relatively high
degree of sensitivity, reliability, and confidence level
within a wide temperature range consisting essentially of:
from 40 to 42 weight percent of basic lead styphnate;
from 20 to 22 weight percent of lead azide;
from 15 to 20 weight of barium nitrate; and
from 1 to 3 weight percent of a sensitizer selected
from the group consisting of silicon carbide, fused
alumina, ground glass powder, and pure silica sand.
According to an aspect of the invention, A method of
forming an explosive primer capable of withstanding aging
within the temperature ranging from -40 C to 200 C and
providing sensitivity of 0.80 inch-oz at 99.99% reliability
and 95% confidence level, which comprises forming a mixture
consisting of:
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CA 02014123 2000-10-24
(a)from 40 to 42 percent by weight of basic lead
styphnate;
(b) from 20 to 22 percent by weight of lead azide;
(c) from 15 to 20 percent by weight of antimony
sulfide;
(d) from 15 to 25 percent by weight of an oxidizer
selected from the group consisting of Chlorate and barium
nitrate; and
(e) from 1 to 3 percent by weight of a mechanical
sensitizer selected from the group consisting of glass
powder, and sand; and
taking from 15 to 25 mg of the mixture formed; and
consolidating the taken mixture under a pressure of from 70
to 100 kpsi.
Other objectives and advantages of the invention will
become more apparent to those skilled in the art, as the
invention is
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2014123
disclosed in the examples given below:
Detailed Description
EXAMPLE 1
Primer Initiating Composition
Basis Lead Styphnate - 40 - 42% )use 15-25
Lead Azide - 20 - 22% )milligrams and
Antimony Sulfide - 15 - 20% )consolidate at
Barium Nitrate - 15 - 20% ) 70-100 Kpsi
Carborundum - 1 - 3% )
y
Intermediate charges and the base charge could be varied
i
~) from the standard intermediate lead azide and base charges like
j PETN, RDX, or HMX to less powerful output charges, like a mixture
~~ of basic lead styphnate, barium nitrate and antimony sulfide or
i
titanium-potassium perchlorate or zirconium-potassium
perchlorate.
Detonators assembled as above and initiated by a standard
firing pin would stand aging at 100°C and would give a
sensitivity of 2-3 inch-oz at 99% reliability and 95% confidence
level.
EXAMPLE II
Similar to Example I, but replacing carborundum with ground
glass powder or pure silica sand-like Ottawa sand and in the same
sieve size spectrum as for carborundum in Example I and with
output charge as desired. Weight of charge and consolidation
pressures also as in Example I, would give primers with a
sensitivity of 2-3 inch-oz at 90% reliability and 95% confidence
level.
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! ! ~,xAMPLE m
The reliability of mixing mechanical sensitizers like
carborundum, sand and glass powder could be very much improved
i
~ and thus improve the overall reliability by encapsulating the
sensitizer into the primary explosive by co-precipitating the
~ primary explosive and the mechanical sensitizer. As an example,
the lead styphnate and mechanical sensitizer like carborundum,
sand, or glass powder could be co-precipitated in the proportion
i they would be present in the final composition. The method of
Preparation would be as follows:
A solution of magnesium styphnate is prepared by
i
il neutralizing styphnic acid with magnesium oxide, filtering off
I
j the excess magnesium oxide. The mechanical sensitzer
~~ is suspended in the magnesium styphnate solution in the
.proportion it exists in the final mixture. Lead nitrate or lead
il
i acetate solution is run down into the mixture of magnesium
styphnate and mechanical sensitizer, which is kept stirred at
50 C. The co-precipitated lead styphnate mechanical sensitizer
is cooked at 50 C for a further period of 10 minutes, filtered
washed thrice with distilled water, and used in making the primer
composition.
Primer/detonator made up with the above co-precipitated mix
and in a manner similar to that in Example I, improves uniformity,
and gives a primer with a sensitivity of 3-3.5 inch-oz at 99.99%
i reliability and a 95% confidence level.
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2~~4~23
EXAMPLE IV
~i
p The mix in Example I could be sensitized by using a more
powerful oxidizer in place of tetracene. A typical mix made with
the following composition:
Lead Styphnate - 40%
Lead Azide - 20%
Antimony Sulfide - 15%
I Barium Nitrate - 20%
Potassium Chlorate - 5%
i)
j The composition in Example IV can be used in place of the primary
mix in Example I and primers/detonators made as in Example I,
~~ using 25 mgms of the primer composition, consolidated at 100
i
K.psi gives detonators/primers with a sensitivity of 3.1 inch-oz
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~~ at 99.99% reliability and 95% confidence level.
II
EXAMPLE V
A completely new approach is by, going away from the
conventional primary explosives and still achieve a high degree
of sensitivity. This is achieved by using a combination of
mechanical and chemical sensitizers. A typical example of such a
type is:
Potassium Chlorate - 35 - 37%
Antimony Sulfide - 52 - 56%
i
Glass Powder - 2 - 3%
Sulfur - 3 - 4%
i
Lead Thiocyanate - 4 - 6%
The detonator/primer made using the above primary mix, using
15-25 mgms of the mix pressed at 70-100 Kpsi, has an all-fire
I stab sensitivity of 0.80 inch-oz at 99.99% reliability and 95%
confidence level. The base charge could be varied to suit the ,
output desired. Its functionally reliable after aging both at -
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24141 23
't 40 C and 100 C for extended periods, without any significant loss
in sensitivity.
t
EXAMPLE VI
The sulfur in Example V can be substituted with high
energetic fuels like selenium, titanium, or zirconium. They
would maintain the sensitivity and at the same time allow them to
be used up to 200 C without loss in sensitivity.
The scope and ambit of the invention is not limited to the
i
j materials, conditions of processing, and assembly of the
primer/detonator mentioned. As an example, co-precipitating the
il lead azide and lead styphate in the proportion it exists in the
i composition would achieve a higher degree of sensitivity or
replace part of the oxidizer in Examples I to III with a more
powerful oxidizer like potassium chlorate. Judicious combination
I
of the ingredients could lead to higher sensitivity and higher
output. Similarly, newer designs of the firing pin with more
acute included angle from 26 used in standard pin up to 14 and
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also more edges on the pins to develop more hot spots for
initiation would make the system function at lesser impact
energy.
Thus, the several aforementioned objects and advantages are
most effectively attained by the invention which has important
I application in the ordinance, automobile crash air bag and other
i
fields having need for primers/detonators. Although several
'i
embodiments have been disclosed in detail herein, it should be
understood that this invention is in no sense limited thereby and
its scope is to have determined by that of the appended claims.
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