Pyrotechnic Initiator device

Abstract

The invention proposes the design of a pyrotechnic initiator applied in the aerospace field, including three main components: the housing, the burning bridge and the pyrotechnic dose. The housing has a protective effect and increases the power of the pyrotechnic dose, in which the number of threads and the thread length are calculated to ensure to withstand the fire pressure. The burning bridge generates heat to ignite the ignition dose, the diameter of the bridge is calculated to ensure the resistance of the burning bridge. The pyrotechnic dose consists of 3 ingredient doses, which are the ignition dose, the intermediate dose, and the fire-boosting dose. In which, the mass, composition and density of the doses are calculated to ensure that the required working pressure is created.

Claims

1. A pyrotechnic initiator comprising three main components, including: a housing, a burning bridge and a pyrotechnic dose, as follows: the housing is a part that protects and increases power of the pyrotechnic dose, so it should not to react to the pyrotechnic dose, withstand the pressure of stuffing, and resistant to corrosion; the housing is connected by one or more threads with other parts; stainless alloy steel 09Cr16Ni4 comprises the housing of the initiator; the number of threads is determined from tensile strength (n.sub.k) and shear strength (n.sub.c) by the formula: $n_k=\frac{P.Math.d}{k_k.Math.s.Math.\left[{\sigma }_k\right]};n_c=\frac{P.Math.d}{k_c.Math.s.Math.\left[\tau \right]}$ In which: σ.sub.k, τ is a tensile and shear strength of the material (σ.sub.k=6750 kG/cm.sup.2; τ=5200 kG/cm.sup.2 with stainless alloy steel 09Cr16Ni4); k.sub.k, k.sub.c is a safety coefficients (when calculated by tensile strength k.sub.k=1,57; by shear strength k.sub.c=2); s is the pitch, s=0.15 cm; d is the mean diameter of the thread (˜2.1 cm); P is the average pressure, P=693 kG/cm.sup.2, n.sub.k is the tensile strength, n.sub.c is the shear strength of the housing; the number of the threads is:
n=1,5.Math.n.sub.max(n.sub.k;n.sub.c)+4 therefore, the number of the threads on the housing is 6; thread length (l.sub.r):
l.sub.r=n.Math.s In which: n—number of the threads; s—pitch; Therefore: l.sub.r=6.Math.0,15=0,9≈1 cm; the burning bridge is a part with a function of generating heat to ignite the ignition dose, requiring a large resistivity and not being greatly changed when activated; the burning bridge must ensure mechanical durability and must not react to the dose; the burning bridge can be made of several alloys such as platinum-iridium, Ni—Cu alloy, Ni—Cr alloy; the diameter of the burning bridge is determined by the formula: $R=\rho \frac{l}{S}=\rho \frac{4l}{\pi d^2}$ in which: R—Resistance of the pyrotechnic initiator (average value—0,952); ρ—The resistivity of the burning bridge; l—Length of the burning bridge (2,4.Math.10.sup.−3m); d—Diameter of the burning bridge; from there, the optimal calculated burning bridge diameter is 0.04 mm; the pyrotechnic dose of the initiator includes: ignition class: oxidizing agent CuO.sub.2—60%; ignition substances Zr—40%; cotton binder powder based NO.sub.3—2%; the mass is 0.12 g; density 2.5 g/cm.sup.3; intermediate class: potassium perchlorate KClO.sub.4—50%; lead rodanite Pb(CNS).sub.2—47%; barium chromate BaCrO.sub.4—3%; NC glue (C.sub.24H.sub.31N.sub.9O.sub.38)—1%; the mass is 0.25 g; density 1.45 g/cm.sup.3. fire-boosting class: potassium perchlorate KClO.sub.4—64%; aluminum powder—31%; NC glue (C.sub.24H.sub.31N.sub.9O.sub.38)—5%; the mass is 0.4 g; density 1.23 g/cm.sup.3.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0021] FIG. 1 illustrates the structure of the pyrotechnic initiator.

DETAILED DESCRIPTION OF THE INVENTION

[0022] As shown in FIG. 1, the FIGURE illustrates the main mechanisms of the pyrotechnic initiator. It includes housing 1, burning bridge 2, pyrotechnic dose 3. In which:

[0023] The housing 1 has the effect of protecting and increasing the power of the pyrotechnic dose, so it must satisfy the following requirements: not to react to the pyrotechnic dose; withstand stuffing pressure; resistant to corrosion; must be precision machined and have the required mechanical strength. From there we choose the stainless alloy steel 09Cr16Ni4 which is a high-tech and mechanical steel, the steel is heated to temperature at 1052° C. and the next aging at 482° C. to secrete the dispersion phases to make the durability of steel can reach 1654 MPa. Steel is used for applications requiring high strength, resistance to corrosion, typically in aircraft structures.

[0024] The housing is connected by thread with other parts so the calculation of the number of threads to ensure maximum allowable effect to the thread when the device operates, the thread must be durable.

[0025] Maximum permissible force applied to the thread (Fmax):

[00003]$F_{\max }=\frac{\pi d^2}{4}P$

[0026] In which: d—Diameter of the thread (˜2.1 cm); P—Average (693 kG/cm.sup.2).

[0027] Pitch: s=0.15 cm.

[0028] The number of threads is determined from the tensile strength (n.sub.k) and shear strength (n.sub.c):

[00004]$n_k=\frac{P.Math.d}{k_k.Math.s.Math.\left[{\sigma }_k\right]};n_c=\frac{P.Math.d}{k_c.Math.s.Math.\left[\tau \right]}$

[0029] In which: σ.sub.k, τ is the tensile and shear strength of the material (σ.sub.k=6750 kG/cm.sup.2; τ=5200 kG/cm.sup.2 with stainless alloy steel 09Cr16Ni4); k.sub.k, k.sub.c is the safety coefficients (when calculated by tensile strength k.sub.k=1,57; by shear strength k.sub.c=2); s is the pitch, s=0.15 cm; d is the mean diameter of the thread (˜2.1 cm); P is the average pressure, P=693 kG/cm.sup.2, n.sub.k is the tensile strength, n.sub.c is the shear strength of the housing.

[0030] The actual selected number of the threads is:

n=1,5.Math.n.sub.max(n.sub.k;n.sub.c)+4

[0031] Therefore, the number of the threads on the housing is 6.

[0032] Thread length (10:

l.sub.r=n.Math.s

[0033] In which: n—number of the threads; s—pitch.

[0034] Therefore: l.sub.r=6.Math.0,15=0,9≈1 cm.

[0035] The burning bridge 2 generates heat to ignite the Ignition class. The accumulation process begins with the conversion of electricity into heat. The burning bridge must satisfy the following requirements: having high resistivity; must not melt; resistant to corrosion; ensure mechanical strength; do not react to the dose; there is no major resistance changed when activated.

TABLE-US-00001 TABLE 3 Main parameters of some alloys used as burning bridge. ρ (300° C.) C γ T.sub.nc Material (Ω .Math. mm.sup.2/m) (Cal/g .Math. ° C.) (g/cm.sup.3) Cγ/ρ (° C.) Platinum - Iridium 0.36 0.032 21.6 1.92 1800 (85% Pt + 15% Ir) Ni—Cu Alloy 0.485 0.098 8.9 1.80 1260 Ni—Cr Alloy 1.19 0.11 8.4 0.78 1410 (80% Ni + 20% Cr)

[0036] The resistance of pyrotechnic initiator is determined by the formula:

[00005]$R=\rho \frac{l}{S}=\rho \frac{4l}{\pi d^2}$

[0037] In which: R—Resistance of the pyrotechnic initiator (average value—0,9Ω); ρ—The resistivity of the burning bridge; 1—Length of the burning bridge (2,4.Math.10.sup.−3m); d—Diameter of the burning bridge.

[0038] According to the sensitivity and economy of the pyrotechnic initiator, we choose Ni—Cu alloy as the burning bridge wire, the wire size is calculated by the formula:

[00006]$d=\sqrt{\frac{4\rho l}{\pi R}}=\sqrt{\frac{4.Math.0.49.Math.\text{2.4}.Math.{10}^{-3}}{\text{3.14}.Math.0,9}}=0.040\mathrm{mm}$

[0039] Principle of operation: The device works when voltage is applied to the burning bridge, the current will heat up the burning bridge and burn the combustible component in the Ignition class, burning the intermediate class and fire-boosting class, fire-boosting dose will generate heat and pressure to work.

[0040] pyrotechnic dose 3: The doses are the main element to create fire, heat and pressure. Pyrotechnic dose includes ignition dose 31, intermediate dose 32, fire-boosting dose 33. The volume, density, component rate of pyrotechnic dose for device is calculated according to the details below:

[0041] + Calculate fire-boosting dose 33

[0042] a − Calculate the composition of the dose

[0043] The fire-boosting dose needs a relatively short burning time, can create heat and pressure in this time, so we choose the mixture Al—KClO.sub.4—NC as the fire-boosting dose.

TABLE-US-00002 TABLE 1 Properties of fire-boosting dose Al—KCLO.sub.4—NC Ability to Ability to Ignition Burning generate Heat to generate Fire-boosting Density Temperature temperature heat burn performance dose (g/cm.sup.3) (° C.) (° C.) (Cal/g) (Cal/g) (at .Math. cm.sup.3/g) Al—KClO.sub.4—NC 2.46 754 5223 2000 3.45 5396

[0044] Calculate the oxygen balance for each 1 g dose as follows:

[0045] Oxidizing agent (KClO.sub.4): +0,462

[0046] Ignition substance (Al aluminum powder): −0,890

[0047] Binder (adhesive NC C.sub.24H.sub.31N.sub.9O.sub.38): −0,387.

[0048] Assume that the Al ratio is x, the KClO.sub.4 rate is y and the C.sub.24H.sub.31N.sub.9O.sub.38 rate is z (5%)

y=100−5−x=95−x

[0049] The algebraic sum of oxygen at the respective proportions of each component must be zero.

[0050] Therefore: 0,462.Math.(95−x)−0,89x−(0,387.Math.5)=0 [0051] x=31(%); y=64(%); z=5(%)

[0052] Therefore, the composition of the fire-boosting dose is as follows: KClO.sub.4—64%; Al—31%; C.sub.24H.sub.31N.sub.9O.sub.38—5%.

[0053] + Calculate dose density

[0054] With the density and proportion of the given compositions, the density of the dose powder can be calculated by the formula:

[00007]$\begin{array}{cc}{q}_{\max }=\frac{100}{\frac{x_1}{q_1}+\frac{x_2}{q_2}+\mathrm{.Math.}+\frac{x_n}{q_n}}& \left(31\right)\end{array}$

[0055] In which: x.sub.1, x.sub.2, . . . x.sub.n—the proportion of compostions (%); q.sub.1, q.sub.2, . . . q.sub.n—density of compositions (g/cm.sup.3). [0056] q=K.sub.c.Math.q.sub.max; K.sub.c—compression coefficient (40-60% of q.sub.max), take K.sub.c=0,5

[0057] The density of the compositions is as follow: Al—2.72 g/cm.sup.3; KClO.sub.4—2.52 g/cm.sup.3; C.sub.24H.sub.31N.sub.9O.sub.38—1.60 g/cm.sup.3.

[0058] Following the formula (31): q.sub.max=2.46 g/cm.sup.3; q=0,5.Math.2,46=1.23 g/cm.sup.3.

[0059] c—Calculate the mass

[0060] The mass of the fire-boosting dose required co should be sufficient to produce the required pressure P.

[0061] P pressure is calculated by the formula:

[00008]$P=\frac{f}{\left(V/\omega \right)-1}.Math.\mathrm{Do}{o}^{\prime }\text{:}\omega =\frac{V}{1+\frac{f}{P}}$

[0062] In which: ω—mass of the fire-boosting dose (g); P—burning pressure (kG/cm.sup.2); V—volume of combustion chamber (cm.sup.3); f—dose force (at.Math.cm.sup.3/g).

We have P=450 kG/cm.sup.2 (value according to the standards), V=5 cm.sup.3, f=5396 at.Math.cm.sup.3/g then ω=0,4 g.

[0063] + Calculate the intermediate dose 32

[0064] a − Calculate the composition of the dose

[0065] Intermediate dose 32 works to increase the ability to reliably ignite the fire-boosting dose from the initial heat pulse generated by the ignition dose. Intermediate dose 32 lies between ignition dose 31 and increased flame dose 33. We choose a mixture of Pb(CNS).sub.2-KCLO.sub.3—BaCrO.sub.4—NC (has good ignition ability and high burning temperature to ensure reliable ignition fire-boosting dose) as an intermediate dose.

TABLE-US-00003 TABLE 2 Properties of intermediate dose Pb(CNS).sub.2—KCLO.sub.3—BaCrO.sub.4—NC Ability to Ignition Burning Heat to generate temperature temperature burn performance Intermediate dose (° C.) (° C.) (Cal/g) (at .Math. cm.sup.3/g) Pb(CNS).sub.2—KCLO.sub.3—BaCrO.sub.4—NC 205 2618 3.87 3824

[0066] Calculate the oxygen balance for each 1 g dose as follows:

[0067] Pb(CNS).sub.2: −0,395

[0068] KCLO.sub.3: +0,392

[0069] BaCrO.sub.4: +0,125

[0070] Assume that the Pb(CNS).sub.2 ratio is x, the KClO.sub.3 rate is y and the BaCrO.sub.4 rate is z (3%).

y=100−3−x=97−x

[0071] The algebraic sum of oxygen at the respective proportions of each component must be zero.

[0072] Therefore: 0,392.Math.(97−x)−0,395x+0,125.3=0 [0073] x=50(%); y=47(%); z=3(%)

[0074] Therefore, the composition of the intermediate dose is as follows: Pb(CNS).sub.2—47%; KCLO.sub.3—50%; BaCrO.sub.4—3%; NC glue (C.sub.24H.sub.31N.sub.9O.sub.38)—1% (external calculation).

[0075] b—Calculate the mass

[0076] The limited mass (G) of the intermediate dose is calculated by the formula:

[00009]$\begin{array}{cc}G=q_{\mathrm{gh}}\frac{\pi d_{ch}^2}{4}& \left(32\right)\end{array}$

[0077] In which: q.sub.gh—Limited mass of intermediate dose per 1 cm.sup.2 surface area; d.sub.ch-diameter of intermediate dose.

[0078] We have: q.sub.gh=0,2 g and d.sub.al=1.25 cm so G=0,25 g.

[0079] c—Calculate the density

[0080] The density of the compositions: KClO.sub.3—2,32 (g/cm.sup.3); Pb(CNS).sub.2—3,82 (g/cm.sup.3); BaCrO.sub.4—4,498 (g/cm.sup.3).

[0081] According to the formula (31): q.sub.max=2,9 (g/cm.sup.3); q=0,5.Math.2,9=1,45 (g/cm.sup.3).

[0082] + Calculation of ignition dose 31

[0083] The ignition dose should be easily burned by the initial heat impulse, has a high fire sensitivity and also has a large heat. We choose the CuO.sub.2—Zr—NO.sub.3 mixture as the ignition dose.

[0084] The composition and rate of the ignition dose are as follows: Oxidizing agent CuO.sub.2—60%; ignition substances Zr—40%, cotton adhesive powder NO.sub.3—2%.

[0085] The limited mass (G) of the ignition dose is calculated by the formula (32):

[0086] In which: q.sub.gh=0.1 g and d.sub.ch=1.25 cm so G=0.12 g.

[0087] Weight, density and size of ignition dose should be selected, ignition dose density is within 2.5 g/cm.sup.3.

[0088] + Calculate the combustion pressure generated in a standard volume chamber

[0089] The pressure when the dose burns in the closed volume is calculated by the formula:

[00010]$\begin{array}{cc}P=\frac{f\Delta }{1-\alpha \Delta }& \left(33\right)\end{array}$

[0090] In which: f—dose force (at.Math.cm.sup.3/g); Δ—dose density (g/cm.sup.3); α—cumulative coefficient (cm.sup.3/g).

[0091] The force of the dose (f) is calculated by the formula:

f=n.R.T  (34)

[0092] In which: n—the number of moles of the gas produced; R—gas constant; T—burning temperature.

[0093] The number of moles of gas produced can be calculated according to the reaction of the fire-boosting dose:

3KClO.sub.4+8Al=3KCl+4Al.sub.2O.sub.3

C.sub.24H.sub.31N.sub.9O.sub.38=4.6CO.sub.2+19.4CO+9.4H.sub.2O+4.5N.sub.2+6.1 H.sub.2

[0094] The number of moles of gas generated when 1 kg of fire-boosting dose is burned is:

[00011]$N=\frac{n^{\prime }.Math.1000}{N_1{M}_1+N_2{M}_2+\mathrm{.Math.}+N_x{M}_x}=\frac{7.950}{3.139+8.27}+\frac{44.50}{1053}=12.6\mathrm{mol}/\mathrm{kg}$

[0095] Burning temperature T=5223° C.

[0096] Gas constant R=0.082 (at/° C.mol).

[0097] From there, according to formula (34) we have: f=5396 (at.Math.cm.sup.3/gf).

[0098] The dose density (Δ) is calculated by the formula:

[00012]$\Delta =\frac{\omega }{V}$

[0099] In which: ω—effective mass of the dose (g); V—volume of the combustion chamber (cm.sup.3).

[0100] Effective mass of the dose (ω): Li{acute over (ê)}u tang lira: 0,4 g (f=5396 at.Math.cm.sup.3/gf); intermediate dose: 0,25 g (f=2500 at.Math.cm.sup.3/gf); ignition dose: 0,12 g (f=4609 at.Math.cm.sup.3/gf).

[0101] From that:

[00013]$\omega =0.4+\text{0.2}5.Math.\frac{2500}{5396}+0.12.Math.\frac{4609}{5396}\approx 0.62g$

[0102] Volume of the combustion chamber: V=5 cm.sup.3.

[0103] So the dose density:

[00014]$\Delta =\frac{0\text{.6}2}{5}=0.124g/{\mathrm{cm}}^3.$

[0104] Cumulative coefficient (α): [0105] α=0,001.Math.γ.sub.0.

[0106] In which: γ.sub.0—Specific volume of ignition dose (cm.sup.3/g)

[00015]${\gamma }_0=\frac{22,4.Math.n^{\prime }.Math.1000}{N_1{M}_1+N_2{M}_2+\mathrm{.Math.}+N_x{M}_x}$${\gamma }_0=2\text{2.4}.Math.12,6=282{\mathrm{cm}}^3/g$$\alpha =0.001.Math.282=\text{0.2}82{\mathrm{cm}}^3/g.$

[0107] Calculate P by the formula (33):

[00016]$P=\frac{5396.Math.\text{0.1}24}{1-0.282.Math.0.124}=693\mathrm{kG}/{\mathrm{cm}}^2$

[0108] Therefore, the actual combustion pressure is greater than the standard pressure (450 kG/cm.sup.2) to ensure that the initiator's working requirements are met.

[0109] In summary, the composition of the doses is as follows:

[0110] + Ignition class: Oxidizing agent CuO.sub.2—60%; ignition substances Zr—40%; NO.sub.3—2% cotton bonding powder. The weight is 0.12 g; density 2.5 g/cm.sup.3.

[0111] + Intermediate class: potassium perchlorate KClO.sub.4—50%; lead rodanite Pb(CNS).sub.2—47%; barium chromate BaCrO.sub.4—3%; NC glue (C.sub.24H.sub.31N.sub.9O.sub.38)—1%. The weight is 0.25 g; density 1.45 g/cm.sup.3.

[0112] + Fire-boosting class: potassium perchlorate KClO.sub.4—64%; aluminum powder—31%; NC glue (C.sub.24H.sub.31N.sub.9O.sub.38)—5%. The weight is 0.4 g; density 1.23 g/cm.sup.3.

[0113] The invention is described in detail as above. However, clearly that to the average person knowledgeable in the field of invention is not limited to the variant described in the invention description. An invention can be made in a modified or altered mode that is not outside the invention scope defined by the points of claim protection. Therefore, what is described in the invention description is for illustrative purposes only, and will not impose any restrictions on the invention.