BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to a method of forming a flare comprising an extrudable
igniter composition.
2. Background Information
[0002] Igniter compositions ought to satisfy a number of design criteria. The igniter composition,
when formed, should be sufficiently robust to remain in operable form prior to deployment
of the device to be ignited, such as a flare or other device.
[0003] One of the commonly proposed igniter systems uses solid particles consisting of B/KNO
3 which, when ignited, initiate combustion of the specified gas generant composition.
[0004] Other recent efforts in the civilian market have focused on developing alternative
cost-effective igniter compositions or igniter compositions which are more easily
manufactured. These efforts have included proposals to use a hot-melt thermoplastic
resin matrix together with a particular igniter composition, such as KNO
3. This effort sought to marry a commercially available hot melt adhesive, such as
one designed for so-called "glue-guns" with a common alkali metal oxidizer. This effort
to improve performance was less than satisfactory. Extrudability and igniter performance
proved difficult to control, and the repeatable ballistic performance desired has
not yet been demonstrated.
[0005] Accordingly, despite these and still other efforts, relevant objectives remain unattained.
A simpler, more cost-effective igniter composition for flares and decoys or other
devices remains desired. In particular, efforts are still on-going towards providing
an igniter composition which avoids the need for hot melting so-called adhesives,
and thus the consequent risks associated with processing a pyrotechnic material at
an elevated temperature, but which is facile to manufacture and would be sufficiently
robust.
[0006] It would, therefore, be a significant advance to provide igniter compositions capable
of being used as an igniter which satisfactorily address these concerns in the industry.
SUMMARY AND OBJECTS OF THE PRESENT INVENTION
[0007] The present invention offers a method of forming flares incorporating one or more
of the herein disclosed igniter sticks.
[0008] The extrudable igniter is readily manufactured at low cost to obtain a physically
robust product. The igniter can be manufactured without the use of a thermopiastic
melt or hot-melt mixing equipment, and thus avoids the potential hazards associated
with processing at such elevated temperatures. The extrudable Igniter composition
from which the igniter stick can be formed is suitably processed at ambient temperatures
into robust products which have sufficiently relatively selectable ignition characteristics.
The igniter stick can have other configurations, provided the configuration is consistent
with the objectives herein disclosed. The extrudable Igniter composition can be used
to form a solid. or hollow igniter "stick" capable of igniting a flare or propellant
composition in a flare or other pyrotechnic device.
BRIEF DESCRIPTION OF THE DRAWING
[0009]
Figure 1 illustrates an exemplary flare device (a XM212 type flare) in longitudinal
cross-section which includes an igniter stick formed from the extrudable igniter composition.
Figures 2, 3, 4 and 5 illustrate diameter cross-sectional views of flares provided
with igniter sticks fabricated from the disclosed extrudable igniter composition.
DETAILED DESCRIPTION OF THE INVENTION
[0010] The extruded igniter sticks formed by the method of the invention can be characterized
as having a configuration designed for rapid deflagration at a high temperature upon
ignition. Upon ignition an igniter stick is capable of igniting another pyrotechnic
composition, In flares, such as the XM212 flare, the igniter sticks are sized to be
capable of complete end to end ignition, e.g., complete flame transition, in a short
time, such as less than 10 miliseconds.
[0011] The igniter compositions which are capable of being extruded comprise a combination
of a water-soluble binder, water-soluble or dispersable oxidizing agent, water-soluble
or dispersable fuel, and a selected amount of water. By preference, the extrudable
compositions are essentially compositionally homogeneous.
[0012] The binder is a water-soluble binder, comprising at least one member selected from
the group consisting of a water-soluble gum present in an amount of about 2 weight
percent to about 10 weight percent based on the total amount of dry ingredients in
the extrudable igniter composition, poly-N-vinyl pyrolidone, polyvinyl alcohols and
copolymers thereof, polyacrylamide, sodium polyacrylates, copolymers based on acrylamide
or sodium acrylate, and water-soluble gelatin. These water soluble gums include naturally
occurring gums, such as guar gum, acacia gum, modified celluloses and starches. A
detailed discussion of "gums" is provided by C.L. Manteil,
The Water-Soluble Gums, Reinhold Publishing Corp., 1947, which is incorporated herein by reference. it is
presently considered that the water-soluble binders improve mechanical properties
or provide enhanced crush strength. The suitable fuels and oxidizers can be water
soluble or water insoluble. Suitable fuels and oxidizers can be inorganic or organic.
[0013] In the formulation from which the extrudate igniter stick is formed, the binder concentration
is such that a sufficiently mechanically robust extrudate is obtained. The extrudate,
such as an igniter stick, should be capable of retaining its shape, e.g. maintaining
its integrity, prior to ignition. By preference, the extruded igniter stick is capable
of being received (inserted) in a pyrotechnic composition, e.g. a suitably configured
bore (e.g. central bore) in a propellant composition, and of shattering or fracturing
when ignited. In general, the binder can be in a range of, for example, of about 2
% by weight to about 10
% by weight, and more particularly about 3% by weight to about 7% by weight, relative
to the dry ingredients in the formulation. The binder can be comprised of more than
one binder material.
[0014] The igniter composition includes at least one oxidizer, which is preferably water
soluble or at least water dispersable. The oxidizer can therefore be organic or inorganic,
although inorganic oxidizers are presently preferred. Organic oxidizers which are
dispersable in a binder so that a sufficiently homogeneous igniter composition is
obtainable include amine nitrate salts, nitro compounds, nitramine, nitrate esters,
and amine perchlorates, of which methyl ammonium nitrate, methyl ammonium perchlorate
are are exemplary. Other canditates include RDX and HMX, CL-20 and PETN. Inorganic
oxidizers include oxidizing ionic species such as nitrates, nitrites, chlorates, perchlorates,
peroxides, and superoxides. Typifying these inorganic oxidizers are metal nitrates
such as potassium nitrate or strontium nitrate, ammonium nitrate, meta) perchlorates
such as potassium perchlorate, and metal peroxides such as strontium peroxide. In
general, the oxidizer is ordinarily present in an amount effective to ensure oxidation
of at least the fuel in the igniter and can be in a range of, for example, of about
40% by weight to about 90% by weight, and more particularly about 70% by weight to
about 85% by weight, rotative to the dry ingredients in the formulation.
[0015] The igniter composition can be formulated with an additional fuel, assuming that
the binder may be capable of functioning as a secondary, not primary, fuel for the
igniter composition. These additional fuels include powdered metals, such as powdered
aluminum, zirconium, magnesium and/or titanium, among others; metal hydrides such
as zirconium or titanium hydride; and so-called metalloids, such as silicon and boron
which are capable of being sufficiently "dispersable" in the binder. Water-soluble
or water-dispersable fuels include, e.g., guanidine nitrate, cyano compounds, nitramines
(RDX and/or HMX), CL-20, tetranitrocarbazoles, organic nitro compounds, and may, if
desired, be "multi-modal" in particle size distribution. Water dispersable materials
can be added in substantially even particle size distribution or in multi-modal distributions
depending on the ignition characteristics desired.
[0016] Water dispersable fuels are, by present preference, used in fine particulate form,
such as powder or ground to sufficient fine particles, to ensure adequate distribution
during the manufacturing process. By preference, an at least substantially even distribution
in the resultant extrudable igniter composition is desired. In general, the fuel is
in pulverulent form, such as 100 µ or less, such as, for example, from about 1 µ to
30µ. Metals in powder form may have, if desired, a smaller particle size range, such
as from about 1 to 20µ, or even smaller such as 1 to about 5µ. The amount of fuel
-- other than the binder -- can be in a range of, for example, of about 5 to about
30% by weight, and more particularly about 10% by weight to about 20% by weight, rotative
to the dry ingredients in the formulation.
[0017] The present igniter sticks and related grains can incorporate, if desired, a reinforcement.
Suitable reinforcement can be achieved with fibers, such as combustible fibers, which
can serve to both strengthen the extruded igniter stick, and, upon appropriate selection
of the reinforcement, improve igniter performance. The fibers are preferably generally
shorter in length (low aspect ratio). Fibers incorporated into extrudable igniter
formulations include, for instance, polyolefin fibers, polyamide fibers, polyester
fibers and poly (2,2-(m-phenylene)-5,5-bisbenzimidazole ("PBI") fibers. Polyolefin
fibers include polyethylene ("PE") fibers, such as PE fibers having an outer diameter
of about 0.005 mm and higher, such as to about 0.8 mm, and a length in a range of
0.1 mm to about 3.2 mm, of which the Spectra 900 brand of polyethylene fiber from
Allied-Signal is illustrative. Suitable polyamide fibers, such as Nylon 6 fibers,
can have a suitably selected diameter, such as 19 microns, and a length of 1.5 mm
to about 6.4 mm. Suitable polyester fibers include high tenacity polyester fibers
having lengths of about 1.5 mm to about 6.4 mm, and a suitable diameter of about 25
microns. PBI fibers include those having lengths on the order of 0.8 mm to 3.2 mm.
Representative reinforced igniter sticks and the formulations therefor are reported
in the Examples.
[0018] The composition in extrudable form for use In the method of the invention is readily
obtainable, for instance, by mixing binder, fuel, oxidizer and the selected amount
of water for such a period of time to achieve an at least substantially even distribution
of the fuel and oxidizer throughout the binder. The method involves mixing a water-soluble
binder and a selected amount of water to form a pre-mix, and admixing the pre-mix
with (a) first the fuel and then the oxidizer, or (b) the oxidizer and then the fuel,
or (c) a combination of the oxidizer and fuel. The amount of water is generally such
that the resultant product has a consistency which is extrudable, but. by preference,
is not runny. In principle greater amounts of water can be used but some manufacturing
concerns may arise, including an increase in waste water laden with varying amounts
of pyrotechnic species (fuel, oxidizer etc.).
[0019] The igniter composition thus formed is capable of being extruded to the desired physical
geometry.
[0020] Among the suitable flares are those known to those skilled in the art as thrusted
flares of which the MJU-10 flare is exemplary. Other flares such as M-206 flares (which
may or may not be spectrally matched) or a near IR flare, such as a M-278 type flare,
are also suitably combined with one or more igniter sticks. The suitable flares are
not restricted to the aforementioned MJU-10, M-206 or M-278 flares. For instance,
a so-called standard 6.99 cm (2.75 inch) (cross-section diameter) flare, including
visible illuminating flares, are suitably provided with at least one igniter stick.
Non-commercial flare variants of the standard flare, such as the M-257 type flare,
are also suitably provided with one or more igniter sticks. Advantagesously, the igniter
stick decreases the costs, decreases the fabrication time, and simplifies the design
of flares, including the ignition system for a thrusted flare such as the MJU-10 flare.
Igniter sticks can be used in a great number of decoy devices which include decoy
flares which are deployed to defend against an incoming threats, and particularly
against heat-seeking missiles. The igniter sticks) improve the reliability of flare
ignition by decreasing out-of-place first fire, and the safety of manufacturing flares
by eliminating the use of flammable solvents commonly used when applying traditional
first fires. Suitable flares and/or flare compositions for combination with at least-one
igniter stick are described in Encylopedia of Chemical Technology,
20:680-697 (4th ed, 1996), including the references cited therein, the complete disclosure
of which is incorporated herein by reference.
[0021] The well-known Jane's Handbook describes flares and other solid propellant devices
suitably used in combination with the igniter sticks.
[0022] Extrusion and extruders are described generally in Encyclopedia of Polymer Science
and Engineering,
16.570-631 (2nd Edition 1996), including references cited therein, the complete disclosures
of which are incorporated herein by reference.
[0023] Figure 1 illustrates, in cross-section, a type of flare known as a XM212 flare, in
the longitudinal cross section view, the casing is a suitable pressure enclosure fabricated
from steel or other material capable of being used for a flare application. The cartridge
case 18 can have a vented housing 17. One closed end Is defined by the forward closure
19. The opposing end of the XM212 flare includes an aft closure 12, spacers 13, an
ignition system with igniter 15, protective cap 10 and a piston 11. In a preferred
embodiment, a solidified (extruded) igniter stick 16, which may be solid or hollow,
extends lengthwise (completely or partially) through the propellant grain as shown
in Figure 1. The igniter stick is formed by extruding the hereinabove described extrudable
igniter composition, allowing the extrudate to solidify, and inserting it into the
propellant grain (preferably before its cured.) A selected propellant composition
14 surrounds the igniter stick. A so-called rapid deflagration cord, if desired, can
be disposed lengthwise, e.g., such as loosely sleeved, within a hollow igniter stick.
Although not illustrated, more than one igniter stick can, if desired, be used.
[0024] Cross sectional "diameter" views of flare casings with propellant and igniter sticks
are shown in Figures 2-5. in the diameter cross-sectional view of Figure 2, the flare
case 28 can, if desired, have a foam layer 22 (e.g. a foamed nitrocellulose liner)
sprayed on its interior surface before propellant 24 is loaded. A center bore having
a pre-selected geometry 26 sleeves a hollow igniter stick 20 (in end view such as
quargum binder/B/KNO
3).
[0025] In the diameter cross-sectional view of Figure 3, the flare case 38 has been loaded
with propellant 34 and provided with a centrally positioned hollow igniter stick 36.
Optionally, additional solid or hollow igniter sticks 32 can be provided.
[0026] In the diameter cross-sectional view of Figure 4, flare case 48 is loaded with propellant
44, and a centrally positioned shaped bore of pre-selected geometry. The centrally
positioned bore may have an igniter stick 42 with igniter sticks 46 (in strip form)
disposed radially in the slots from the bore. The igniter sticks are fitted within
the slots, and preferably are not loosly fitted.
[0027] In the diameter cross-sectional view of Figure 5, the flare case 58 is shown loaded
with propellant 54 and a centrally positioned igniter stick having multiple axial
bores therein.
[0028] The igniter stick can, if desired, be fitted with a peelable glove/sleeve prior to
its insertion into the propellant grain. This can protect an igniter stick during
the manufacturing process or during storage before use.
[0029] The igniter sticks are preferably inserted into the propellant grain before the latter
is cured.
[0030] The invention is further described with reference to the following non-limiting Examples.
Examples
Example 1
[0031] To a 3.8 l (one gallon) Baker-Perkins planetary mixer, 1170 g (78%) of 35 micron
potassium nitrate and 105 g (7%) of Cytec Cyanamer® N-300 brand polyacrylamide (15
million MW) were added. These ingredients were then blended remotely in the dry state
for one minute. To this blend, 217.5 g (14.5 parts per 100 of igniter formulation)
of water were added and mixed for five minutes. The mix blades and inner surface of
the mix bowl were scraped with Velostat (conductive plastic) spatulas followed by
15 additional minutes of mixing. To the resulting thick white paste, 225 g (15%) of
amorphous boron powder (90-92% purity) were added and mixed remotely for five minutes.
While wearing approved protective clothing, the blades and bowl were again "scraped
down" manually and the formulation was mixed for ten additional minutes. The resulting
brown, dough-like material was granulated to -4 mesh and fed into a Haake 25 mm single-screw
extruder. The igniter formulation was extruded through a 12 point star die with a
maximum diameter of 0.84 cm (0.33") and a minimum diameter of 0.76 cm (0.30"). The
die included a central 0.203 cm (0.080") diameter pin, thus producing a hollow rod-like
configuration. The extruded igniter formulation was cut into 17.8 cm (7") lengths.
Before drying, a 19.1 cm (7.5") length of 0.18 cm (0.07") diameter Teledyne RDC (rapidly
deflagrating cord) was inserted into the 0.20 cm (0.08") diameter perforation. The
igniter sticks were dried at 74°C (165°F) overnight. The igniter sticks were tested
to evaluate their performance as an igniter in an inflator which was designed for
passenger side automotive safety bags. The igniter sticks performed satisfactorily.
Example 2
[0032] A series of extruded igniter stick formulations containing boron, potassium nitrate,
a water-soluble binder, and optionally, fibers for reinforcement were prepared. These
formulations are reported in Table I. The formulations were first mixed on a 10 g
and then a 30 g scale to determine their sensitivity towards stimuli including impact.
friction, electrostatic discharge, and heat (Table II). In general, carbohydrate-based
binders exhibited the greatest sensitivity with respect to ABL friction. Formulations
containing methyl cellulose, guar gum, and locust bean gum as the binder were also
used to prepare igniter sticks.
[0033] The remaining formulations were mixed on a 325 g scale in a one pint Baker-Perkins
planetary mixer. Potassium nitrate and the respective water-soluble binder were blended
remotely in the dry state for one minute. To this blend, the respective amount of
water (Table III) was added and the slurry was mixed for five minutes. As in Example
1, the bowl and blades were "scraped down". At this point, fibers were added to fiber-containing
formulations and the dough was mixed for an additional 5 minutes. All formulations
were mixed for 10 additional minutes before adding boron. One half of the boron was
added at this point followed by five minutes of mixing. The rest of the boron was
then added followed by an additional five minutes of mixing. After a final "scrape
down", the formulation was mixed for an additional ten minutes. The resulting brown,
dough-like material was granulated to -4 mesh and fed into a Haake 25 mm single-screw
extruder. The igniter formulation was extruded through a 12 point star die with a
maximum diameter of 0.84 cm (0.33") and a minimum diameter of 0.775 cm (0.305"). The
die included a centrally located 0.20 cm (0.80") diameter pin. The extruded igniter
formulation was cut into 17.8 cm (7") lengths. Before drying, a 19.1 cm (7.5") length
of 0.18 cm (0.07") diameter Teledyne RDC (rapidly deflagrating cord) was inserted.
Ten additional 5.1 cm (2") lengths were extruded. The igniter sticks were dried at
74°C (165 F) overnight.
[0034] important factors in determining useful formulation include quality of the grain
after drying, actual performance as an igniter, and drying rate. Leaching of a mixture
of KNO
3 and binder to the surface of the grain may occur for some formulations during drying.
Leaching in the perforation is not desired. Leaching was found to be least important
in formulations containing tragacanth gum, Cyanamer® A-370 and Cyanamer® P-21 (Table
III). igniter sticks from the formulations containing Cyanamer® A-370 and Cyanamer®
P-21 were evaluated in content with an inflator device. Relative drying rates of 10
:1.7 : 1 were calculated for formulations containing Cyanamer® N-300, Cyanamer® P-21
and Cyanamer® A-370, respectively. Thus, the formulation containing Gyanamer® A-370
was shown to dry quickly, with minimal KNO
3 leaching producing a grain that ignites gas generant with minimal ignition delays.
[0035] It is important to develop an extruded igniter stick for flares and other solid propellant
devices that will withstand decades of jolts and vibrations while in service prior
to deployment. Thus, a durability test method was developed for the extruded igniter
sticks. Durability tests were performed in 3-point bending, with the load applied
at mid-span. Bending was selected since tensile, compressive, and shear stresses are
all present. Also, the sample configuration lends itself to this type of loading.
A span of 3.8 cm (1.5 inches) was used, with the loads applied using 0.32 to 0.64
cm (⅛- to ¼-inch) diameter dowel pins. A nominal preload of 0.32 kg (0.7 pounds) was
applied. The sample was then subjected to 1,000 loading cycles with the following
conditions: cyclic amplitude 0.076 mm (0.003 inch), frequency 10 Hertz. After the
cydic loading, the samples were tested to failure at a displacement rate of 0.51 cm
(0.2 inches) per minute. The durability of each sample is reported as the area under
the load-displacement curve. For simplicity, the units are maintained as calibrated
(load in 4.4 N (pounds-force), displacement in 2.54 x 10
-3 cm (milli-inches)). Therefore, the reported durability has units of 2.54 x 10
-3cm - 4.4 N (milli-inch-pounds). All testing was performed at lab ambient temperature
(24 ± 2.8°C) (75° ± 5°F). Durability test results indicated enhanced durability of
extruded igniter formulations containing fibers, e.g., formulation #13 and #15 in
Table III.
Example 3
[0036] A series of igniters containing fibers were formulated with the goal of enhancing
durability of the extruded igniter sticks as seen from Table IV. All formulations
exhibited favorable safety characteristics. Samples (325 g) of each formulation were
mixed in a Baker-Perkins pint mixer with 13.5 parts/100 of water. After dry blending
the KNO
3 and Cyanamer® A-370 for one minute, the water was added followed by five minutes
of mixing. The fiber was then added in two increments and the boron in three increments
with three minutes of mixing after each addition. After a final "scrape down", the
formulation was mixed for an additional ten minutes. The resulting brown, dough-like
material was granulated to -4 mesh and fed into a Haake 25 mm single-screw extruder.
The igniter formulation was extruded through a 12 point star die with a maximum diameter
of 0.84 cm (0.33") and a minimum diameter of 0.775 cm (0.305"). The die included a
centrally located 0.38 cm (0.15") diameter pin. The extruded igniter formulation was
cut into 17.8 cm (7") lengths. Ten additional 5.1 cm (2") lengths were extruded. The
igniter sticks were dried at 74°C (165 F) overnight.
[0037] There were no signs of KNO
3/binder leaching outside of the igniter grains after drying. Grains were ignited with
the ignition plume of an ES013 squib directed into the 0.38 cm (0.15") ID perforation
in the grain. The igniter grain was held in a 1.0 cm (0.4") ID, 1.2 cm (0.49") wall,
cylindrical fixture with approximately 95 evenly distributed 0.277 cm (0.109") ID
holes drilled along its length and diameter. The times required for the flame front
to reach the opposite end of the grain after ignition by the squib are reported in
Table V. The times were determined from 1000 frames/second video. Generally, only
a few milliseconds were required. Durability of 5.1 cm (2") long grains was determined
as described in Example 2. The results are reported in Table V. By far, the formulation
containing 2% polyethylene fibers exhibited the greatest durability. Firings were
conducted using igniter grains from formulations #3 and #19 with RDC inserted into
the 0.38 cm (0.15") perforation. Formulation #19 with polyethylene fibers produced
the least amount of delay before the pyrotechnic composition was ignited.
Table IV
Igniter Formulations containing Cyanamer® A-370 and Selected Fibers. |
Form |
%KNO3 |
%Boron |
%Cyanamer® A-370 |
Fiber ID |
%Fiber |
3 |
76.30 |
16.70 |
7.00 |
none |
0.00 |
16 |
76.70 |
14.30 |
7.00 |
Pyrograph™ III, Micro |
2.00 |
17 |
74.80 |
16.20 |
7.00 |
Saffil®, Type 590, Micro |
2.00 |
18 |
74.80 |
16.20 |
7.00 |
Nextel®, 1/8" Ceramic |
2.00 |
19 |
77.20 |
13.80 |
7.00 |
Allied, Spectra 900, 1/8" |
2.00 |
20 |
76.50 |
14.50 |
7.00 |
Celanese 1/8" PBI |
2.00 |
(1/8" = 0.32 cm) |
Table V
Test Result Summary for Potential Extruded Igniters Containing Fibers. |
Form |
Fiber ID |
Ignition2 |
Ignition2 |
Durability3,4 |
Coefficien |
3 |
none |
2 |
2 |
96 |
39 |
31 |
none, 0.318cm (0.125") ID |
9 |
8 |
101 |
25 |
16 |
Pyrograph™ III, Micro |
5 |
|
65 |
39 |
17 |
Saffil®, Type 590, Micro |
1 |
|
107 |
4 |
18 |
Nextel®, 1/8" Ceramic |
3 |
|
76 |
69 |
19 |
Allied, Spectra 900, 1/8" |
17 |
1 |
357 |
17 |
20 |
Celanese 1/8" PBI |
13 |
|
126 |
22 |
1Formulation 3 with grains having a 0.318 cm (0.125") ID instead of the nominal 0.38
(0.15'') ID. |
2Time required for the flame front on a 17.8 cm (7") grain ignited on one end to reach
the opposite end. The time is in milliseconds. The data were acquired as described
in Example 3. |
3The same as in footnote 1 but cured epoxy blocking the 0.38 cm (.15") ID perforation
at the opposite end from where ignition was intiated. |
4Units are in milli-inch-pounds (2.54 x 10-3 cm - 4.4 N).
(⅛" = 0.32 cm) |
[0038] In formulations 16, 17, 18, 19 and 20, respectively, the "fiber ID" can be characterized
as carbon fiber, alumina fiber, aluminosilicate, polyethylene, and polybenzimidizole.
Example 4
[0039] An extrudable igniter composition was obtained by forming a pre-mix of guar gum (5.0
wt%, 0.25 gram) and water (deionized 15.0 wt%, 1.75 grams); combining the pre-mix
with potassium nitrate (average particle size of about 26 microns, 75 wt%, 3.75 grams);
and adding thereto fuel, boron (amorphous; 20.0 wt%, 1.00 gram).
Example 5
[0040] An extrudable igniter composition was obtained as in Example 4, but 20.0 wt% of water
was used.
Example 6
[0041] An extrudable igniter composition was prepared as in Example 4, except that the amount
of fuel, boron, was increased to 22.0 wt% (1.10 grams) and the amount of binder, guar
gum, was reduced to 3.0 wt% (0.15 gram).
Example 7
[0042] An extrudable igniter composition was prepared according to the procedure of Example
4, except that the binder was polyacrylamide (cyanamer "N-300" from American Cyanamid,
5.0 wt%, 0.25 gram).
Example 8
[0043] An extrudable igniter mixture is prepared by adding potassium nitrate (210 grams)
and a polyacrylamide (14 gram; cyanamer "N-300" from American Cyanamid) to a bowl;
adding water (44.8 grams), to the bowl and mixing for 1 minute; and adding boron (amorphous;
56.0 grams) thereto followed by mixing for about four minutes.
Example 9
[0044] An extrudable igniter composition was prepared as in Example 8, except that the amount
of water is 50.4 grams, the potassium nitrate and binder are first dry-blended together
before adding the water and mixing 1 minute. The powdered boron is then added and
the mixing is continued for four minutes.
Example 10
[0045] The igniter composition prepared according to Example 8 was granulated, dried and
pressed into 1.3 cm (½ inch) diameter by 2.5 cm (1 inch) long pellets. The pellets
were then inhibited on all but one face and combusted in a closed pressurized vessel
at 6.9 x 10
6, 13.8 x 10
6, and 20.7 x 10
6 N/m
2 (1000, 2000 and 3000 psi) via ignition of the uninhibited face. Burning rates of
10.6 cm/s (4.16 ips), 10.97 cm/s (4.32 ips) and 11.23 cm/s (4.42 ips) respectively,
were observed.
Example 11
[0046] A portion of the wet igniter composition prepared as described in Example 9 was placed
in a 5.1 cm (2 in) diameter ram extruder and forced through an appropriate die so
as to provide a center perforated cylindrical extrudate of approx 0.8 cm (0.3 in)
diameter with a perforation diameter of approx 0.15 cm (0.06 in). This extrudate was
partially dried and cut into 17.8 cm (7 in) lengths prior to final drying. The resulting
igniter sticks were then tested in a gas generating device consisting of a tubular
metal cylinder approx 20.3 cm (8 in) long by approx 5.1 cm (2 in) diameter dosed at
both ends and provided with radial ports. One of the end closures was further provided
with an initiating squib. The igniter stick was retained in the center of the tube
and a 17.8 cm (7 in) length of rapid deflagration cord (RDC) placed in the center
perforation of the stick. The gas generating device was then filled with a charge
of gas generant pellets and tested in a closed tank. Comparable results were obtained
with the igniter stick in contrast to those obtained with a conventional ignition
train in which a perforated metal tube filled with a like quantity of ignition powder
and the RDC replaces the igniter stick/RDC combination. In all cases ignition of the
gas generant pellets was observed to occur within 8 msec.
Example 12
[0047] Two fifty gram mixes formulated from 20 percent boron, 75 percent potassium nitrate,
5 percent Cytec Cyanamer
® N-300 brand polyacrylamide (15 million molecular weight), and 17.5 weight percent
of water were produced. The mixes were combined and then loaded into a 5.1 cm (2.0
inch) diameter RAM extruder. The RAM was pressurized to 2.1 x 10
6 N/m
2 (300 psi) to extrude the ignitor sticks. The igniter composition was originally extruded
into 0.254 cm (0.100 inch) diameter solid sticks and also into 0.254 cm (0.100 inch)
diameter with a 0.076 cm (0.030 inch) diameter center perforation. The igniter sticks
were cut into 15.2 cm (6 inch) lengths and dried at 57°C (135°F) overnight prior to
use. The center perforated ignitor sticks were successfully demonstrated in an XM-212
decoy flare. Two XM 212 grains were fabricated. One with the traditional slurry first
fire and the other with three center perforated igniter sticks. A flare configuration
with an igniter stick is shown in Figure 1.
Example 13
[0048] The igniter sticks were also incorporated in the main ignition system of a MJU-10
decoy flare. The MJU-10 flare requires a larger igniter than the XM-212 flare. Therefore,
the igniter formulation was extruded through a 12 point star die that has a 0.84 cm
(0.33 inch) maximum diameter a 0.76 cm (0.30 inch) minium diameter. The extrusion
die also included a 0.20 cm (0.80 inch) diameter pin used to produce a center perforated
grain. The extruded igniter sticks were cut to 12.7 cm (5.0 inch) lengths and then
dried at 57°C (135°F) for 24 hours. The igniter sticks were then inserted into the
center perforation of the MJU-10 flare grain. The MJU-10 flare was successfully ignited
with the igniter stick.
[0049] In view of the foregoing, the igniter stick will decrease the cost, decrease the
fabrication time, and simplify the design of an ignition system for the thrusted MJU-10
flare.
[0050] In view of the Examples, igniter sticks can be used in a great number of decoy flare
devices. They will aid in improving the reliability of flare ignition by decreasing
out-of-place first fire, and also improve the safety of manufacturing flares by eliminating
the use of flammable solvents commonly used when applying traditional first fires.
1. A method of forming a flare comprising a case propellant contained within the case,
and an igniter system comprising an extruded dry igniter element deflagrating upon
ignition for igniting the propellant of the flare, the extruded dry igniter element
being formed from an extrudable igniter composition, said method comprising:
dissolving at least one water-soluble binder into an aqueous solvent,
mixing the dissolved binder with at least one oxidizer agent and at least one fuel
to form the extrudable igniter composition, and
extruding and drying the extrudable igniter composition,
wherein the water-soluble binder comprises at least one member selected from the
group consisting of a water-soluble gum present in an amount of about 2 weight percent
to about 10 weight percent based on the total amount of dry ingredients in the extrudable
igniter composition, water-soluble gelatin, poly-N-vinyl pyrrolidone, polyvinylalcohol,
a copolymer of poly-N-vinyl pyrrolidone and polyvinylalcohol, polyacrylamide, sodium
polyacrylates, and a copolymer of polyacrylamide and polyacrylate.
2. The method of claim 1, wherein the water-soluble binder comprises poly-N-vinyl pyrrolidone.
3. The method of claim 1, wherein the water-soluble binder comprises polyvinylalcohol.
4. The method of claim 1, wherein the water-soluble binder comprises gum.
5. The method of claim 1, wherein the water-soluble polymeric binder comprises polyacrylamide.
6. The method of any of claims 1 to 5, wherein the oxidizer is present in an amount of
from about 40 weight percent to about 90 weight percent relative to the dry ingredients
used in formulating the extrudable igniter composition.
7. The method of any of claims 1 to 6, wherein the oxidizer comprises an organic oxidizer.
8. The method of any of claims 1 to 6, wherein the oxidizer comprises at least one ionic
species selected from the group consisting of nitrates, nitrites, chlorates, perchlorates,
peroxides, and superoxides.
9. The method of any of claims 1 to 8, wherein the extrudable igniter composition further
comprises fibers.
10. The method of claim 9, wherein the fibers comprise at least one of polyolefin fibers,
polyamide fibers, polyester fibers, and poly(2,2'-(m-phenylene)-5,5-bisbenzimidazole
fibers.
11. The method of claim 1, wherein:
the binder comprises at least one member selected from the group consisting of poly-N-vinyl
pyrrolidone, polyvinylalcohol, copolymers thereof, and gum;
the oxidizer is present in an amount of about 40 weight percent to about 90 weight
percent relative to the dry ingredients used in formulating the extrudable igniter
composition, and the oxidizer contains at least one ionic species selected from the
group consisting of nitrates, nitrites, chlorates, perchlorates, peroxides, and superoxides;
and
the extrudable igniter composition contains low-aspect ratio fibers, the fibers comprising
at least one of polyolefin fibers, polyamide fibers, polyester fibers, and poly(2,2'-(m-phenylene)-5,5-bisbenzimidazole
fibers.
12. The method of any of claims 1 to 11, wherein the extruded igniter element is configured
as an igniter stick.
13. The method of claim 1, wherein the fuel comprises boron and the oxidizer comprises
potassium nitrate.
14. The method of claim 13, wherein the water-soluble polymeric binder comprises at least
one member selected from the group consisting of polyacrylamide, sodium polyacrylates,
and a copolymer thereof.
15. The method of claim 14, wherein the boron is present in an amount of about 5 weight
percent to about 30 weight percent, the potassium nitrate is present in an amount
of about 40 weight percent to about 90 weight percent, and the binder is present in
an amount of about 2 weight percent to about 10 weight percent.
16. The method of claim 15, wherein the extrudable igniter composition further comprises,
as one of the ingredients, guanidine nitrate.
1. Verfahren zum Bilden eines Leuchtsatzes, umfassend einen Behälter, Treibmittel, das
in dem Behälter enthalten ist und ein Zündsystem, umfassend ein extrudiertes trockenes
Zündmittelelement, das bei Zündung verbrennt, zum Zünden des Treibmittels des Leuchtsatzes,
wobei das extrudierte trockene Zündmittelelement gebildet wird aus einer extrudierbaren
Zündmittelzusammensetzung, wobei das Verfahren umfasst:
Lösen mindestens eines wasserlöslichen Bindemittels in einem wässrigen Lösungsmittel,
Mischen des gelösten Bindemittels mit mindestens einem Oxidationsmittel und mindestens
einem Brennstoff, um die extrudierbare Zündmittelzusammensetzung zu bilden, und Extrudieren
und Trocknen der extrudierbaren Zündmittelzusammensetzung,
worin das wasserlösliche Bindemittel mindestens einen Bestandteil umfasst, ausgewählt
aus der Gruppe, bestehend aus einem wasserlöslichen Gummi, der in einer Menge von
etwa 2 Gewichtsprozent bis etwa 10 Gewichtsprozent, basierend auf der Gesamtmenge
trockener Bestandteile in der extrudierbaren Zündmittelzusammensetzung, vorliegt,
wasserlöslicher Gelatine, Poly-N-vinylpyrrolidon, Polyvinylalkohol, einem Copolymer
aus Poly-N-vinylpyrrolidon und Polyvinylalkohol, Polyacrylamid, Natriumpolyacrylaten
und einem Copolymer aus Polyacrylamid und Polyacrylat.
2. Verfahren nach Anspruch 1, worin das wasserlösliche Bindemittel Poly-N-vinylpyrrolidon
umfasst.
3. Verfahren nach Anspruch 1, worin das wasserlösliche Bindemittel Polyvinylalkohol umfasst.
4. Verfahren nach Anspruch 1, worin das wasserlösliche Bindemittel Gummi umfasst.
5. Verfahren nach Anspruch 1, worin das wasserlösliche Bindemittel Polyacrylamid umfasst.
6. Verfahren nach einem der Ansprüche 1 bis 5, worin das Oxidationsmittel in einer Menge
von etwa 40 Gewichtsprozent bis etwa 90 Gewichtsprozent, bezogen auf die bei der Formulierung
der extrudierbaren Zündmittelzusammensetzung verwendeten trockenen Bestandteile, vorliegt.
7. Verfahren nach einem der Ansprüche 1 bis 6, worin das Oxidationsmittel ein organisches
Oxidationsmittel umfasst.
8. Verfahren nach einem der Ansprüche 1 bis 6, worin das Oxidationsmittel mindestens
eine ionische Spezies umfasst, ausgewählt aus der Gruppe, bestehend aus Nitraten,
Nitriten, Chloraten, Perchloraten, Peroxiden und Superoxiden.
9. Verfahren nach einem der Ansprüche 1 bis 8, worin die extrudierbare Zündmittelzusammensetzung
weiterhin Fasern umfasst.
10. Verfahren nach Anspruch 9, worin die Fasern mindestens eine aus Polyolefinfasem, Polyamidfasem,
Polyesterfasem und Poly(2,2'-(m-phenylen)-5,5-bisbenzimidazolfasem umfassen.
11. Verfahren nach Anspruch 1, worin:
das Bindemittel mindestens einen Bestandteil umfasst, ausgewählt aus der Gruppe, bestehend
aus Poly-N-vinylpyrrolidon, Polyvinylalkohol, Copolymeren davon und Gummi;
das Oxidationsmittel in einer Menge von etwa 40 Gewichtsprozent bis etwa 90 Gewichtsprozent
der trockenen Bestandteile vorliegt, die beim Formulieren der , extrudierbaren Zündmittelzusammensetzung
verwendet werden, und das Oxidationsmittel mindestens eine ionische Spezies enthält,
ausgewählt aus der Gruppe, bestehend aus Nitraten, Nitriten, Chloraten, Perchloraten,
Peroxiden und Superoxiden; und
die extrudierbare Zündmittelzusammensetzung Fasern mit niederem Aspektverhältnis enthält,
wobei die Fasern mindestens eine aus Polyolefinfasem, Polyamidfasern, Polyesterfasem
und Poly(2,2'-(m-phenylen)-5,5-bisbenzimidazolfasem umfassen.
12. Verfahren nach einem der Ansprüche 1 bis 11, worin das extrudierte Zündmittelelement
als ein Zündmittelstab konfiguriert ist.
13. Verfahren nach Anspruch 1, worin der Brennstoff Bor umfasst und das Oxidationsmittel
Kaliumnitrat umfasst.
14. Verfahren nach Anspruch 13, worin das wasserlösliche polymere Bindemittel mindestens
einen Bestandteil umfasst, ausgewählt aus der Gruppe, bestehend aus Polyacrylamid,
Natriumpolyacrylaten und einem Copolymer davon.
15. Verfahren nach Anspruch 14, worin das Bor in einer Menge von etwa 5 Gewichtsprozent
bis etwa 30 Gewichtsprozent vorliegt, das Kaliumnitrat in einer Menge von etwa 40
Gewichtsprozent bis etwa 90 Gewichtsprozent vorliegt und das Bindemittel in einer
Menge von etwa 2 Gewichtsprozent bis etwa 10 Gewichtsprozent vorliegt.
16. Verfahren nach Anspruch 15, worin die extrudierbare Zündmittelzusammensetzung weiterhin
als einen der Bestandteile Guanidinnitrat umfasst.
1. Procédé d'élaboration d'une fusée lumineuse comprenant un boîtier, un agent propulseur
contenu dans le boîtier et un système d'allumeur comportant un élément d'allumeur
sec extrudé faisant l'objet d'une déflagration lors d'un allumage en vue d'allumer
l'agent propulseur de la fusée lumineuse, l'élément d'allumeur sec extrudé étant formé
d'une composition d'allumeur extrudable, ledit procédé consistant :
à dissoudre dans un solvant aqueux au moins un liant soluble dans l'eau,
à mélanger le liant dissous avec au moins un agent oxydant et au moins un combustible
pour former la composition d'allumeur extrudable, et
à extruder et faire sécher la composition d'allumeur extrudable,
procédé selon lequel le liant soluble dans l'eau comprend au moins un élément choisi
parmi le groupe constitué d'une gomme soluble dans l'eau présente en une quantité
d'environ 2 pour cent en poids à environ 10 pour cent en poids sur la base de la quantité
totale des ingrédients à l'état sec dans la composition d'allumeur extrudable, d'une
gélatine soluble dans l'eau, de poly-N-vinyl pyrrolidone, d'un alcool polyvinylique,
d'un copolymère de poly-N-vinyl pyrrolidone et d'alcool polyvinylique, d'un polyacrylamide,
de polyacrylates de sodium, et d'un copolymère de polyacrylamide et de polyacrylate.
2. Procédé selon la revendication 1, dans lequel le liant soluble dans l'eau comprend
de la poly-N-vinyl pyrrolidone.
3. Procédé selon la revendication 1, dans lequel le liant soluble dans l'eau comprend
un alcool polyvinylique.
4. Procédé selon la revendication 1, dans lequel le liant soluble dans l'eau comprend
une gomme.
5. Procédé selon la revendication 1, dans lequel le liant polymère soluble dans l'eau
comprend un polyacrylamide.
6. Procédé selon l'une quelconque des revendications 1 à 5, dans lequel l'oxydant est
présent en une proportion d'environ 40 pour cent en poids à environ 90 pour cent en
poids par rapport aux ingrédients à l'état sec utilisés pour former la composition
d'allumeur extrudable.
7. Procédé selon l'une quelconque des revendications 1 à 6, dans lequel l'oxydant comprend
un oxydant organique.
8. Procédé selon l'une quelconque des revendications 1 à 6, dans lequel l'oxydant comprend
au moins une espèce ionique choisie parmi le groupe constitué de nitrates, de nitrites,
de chlorates, de perchlorates, de peroxydes et de superoxydes.
9. Procédé selon l'une quelconque des revendications 1 à 8, dans lequel la composition
d'allumeur extrudable comprend en outre des fibres.
10. Procédé selon la revendication 9, dans lequel les fibres comprennent au moins l'un
des éléments constitués par des fibres de polyoléfine, des fibres de polyamide, des
fibres de polyester et des fibres de poly(2,2'-(m-phénylène)-5,5-bisbenzimidazole.
11. Procédé selon la revendication 1, dans lequel.:
le liant comprend au moins un élément choisi dans le groupe constitué d'une poly-N-vinyl
pyrrolidone, d'un alcool polyvinylique, de copolymères de ceux-ci et d'une gomme ;
l'oxydant est présent en une proportion d'environ 40 pour cent en poids à environ
90 pour cent en poids par rapport aux ingrédients à l'état sec utilisés pour former
la composition d'allumeur extrudable, et l'oxydant contient au moins une espèce ionique
choisie parmi le groupe constitué de nitrates, de nitrites, de chlorates, de perchlorates,
de peroxydes et de superoxydes ; et
la composition d'allumeur extrudable contient des fibres à faible rapport d'aspect,
les fibres comprenant au moins l'un des éléments constitués par des fibres de polyoléfine,
des fibres de polyamide, des fibres de polyester et des fibres de poly(2,2'-(m-phénylène)-5,5-bisbenzimidazole.
12. Procédé selon l'une quelconque des revendications 1 à 11, dans lequel l'élément d'allumeur
extrudé est façonné sous forme d'une charge d'allumeur.
13. Procédé selon la revendication 1, dans lequel le combustible comprend du bore et l'oxydant
comprend du nitrate de potassium.
14. Procédé selon la revendication 13, dans lequel le liant polymère soluble dans l'eau
comprend au moins un élément choisi parmi le groupe constitué d'un polyacrylamide,
de polyacrylates de sodium, et d'un copolymère de ceux-ci.
15. Procédé selon la revendication 14, dans lequel le bore est présent en une proportion
d'environ 5 pour cent en poids à environ 30 pour cent en poids, le nitrate de potassium
est présent en une proportion d'environ 40 pour cent en poids à environ 90 pour cent
en poids et le liant est présent en une proportion d'environ 2 pour cent en poids
à environ 10 pour cent en poids.
16. Procédé selon la revendication 15, dans lequel la composition d'allumeur extrudable
comprend en outre, comme constituant l'un des ingrédients, du nitrate de guanidine.