KR20050061472A - Multi-stage gas generator and gas generants - Google Patents

Abstract

A gas generator is described that may have two or more compartments, each with a separate initiator. One compartment may discharge before another. Each compartment may have the same propellant. The propellants may have different geometries in each compartment, producing different rates of gas evolution from each compartment. The gas generator may produce a rapid initial inflation, followed by a more gradual inflation rate in subsequent stages. One propellant used may include ammonium nitrate as an oxidizer, a fuel such as CL-20, and a binder such as polycaprolactone. A second propellant may include approximately 70-95% energetic nitramine fuel, 5-25% energetic polymer binder, and 0.1-5% flash suppressant, respectively, by weight. An inflation rate of an airbag may be controlled by connecting a gas generator to the airbag, causing each of the chambers to discharge at a different, predetermined time, and causing the effluent of each chamber to flow into the airbag.

Description

MULTI-STAGE GAS GENERATOR AND GAS GENERANTS}

The present invention relates to a two-stage or multi-stage gas generator using improved gas generative formulation (s). Gas generators, also known as inflators, have numerous commercial and military applications. For example, gas generators are used to deploy airbags used in automobiles, to inflate floating devices, and may be used in oxygen generating devices. Also, for example, gas generators may be used to inflate airbags used to deploy and aim submunitions.

The gas generator operates by burning the propellant contained therein very quickly, usually in the millisecond range. To date, gas generators have typically combusted propellants in airbags in one stage, providing control that is less than optimal throughout deployment.

Propellants used in airbags generally contain sodium azide, which forms corrosion products with particulates, including hot metal oxides, when ignited, resulting in expensive filtration systems that do not damage these munitions or related equipment. It was necessary. Alternative propellants have required systems that produce high temperature emissions and / or gases, including various nitrogen oxides (NO _x ), and also protect the equipment. Such airbag systems also required various protective coatings to prevent damage to the airbags caused by harmful combustion byproducts.

Up to now, uniform and reliable gas generation for the above described systems has been difficult to achieve mechanically in terms of gas generation rate or slope, as well as in terms of control of solid particulates and emissions due to propellant combustion. To date, at least one or more components of the gas generant, such as the oxidant, have been metal based, leading to the formation of hot metal solids or particulates as by-products of combustion. Major airbag manufacturers continue to use sodium azide (NaN ₃ ) as the main fuel component in gas generative formulations and metal oxides such as copper oxide, iron oxide, molybdenum trioxide as the main oxidant component in the formulation. have. Upon combustion, these gas generant formulations produce very hot copper-based, iron-based or molybdenum-based solid by-products as well as NO, NO ₂ , SO ₂ , CO and CO ₂ . Such by-products can often be out of control. Some of these combustion byproducts are extremely toxic to humans and can be very concerned if only a small amount of such gas generous byproducts are produced.

Some airbag systems are based on propellants other than sodium azide, see for example US Pat. No. 5,482,579 which uses cellulose acetate, perchlorate and metal oxides. However, these systems still generate toxic or hot gases that require a filtration system to prevent damage to hot metal particles or airbags.

Another variation of the airbag was studied. For example, some use mechanical means to control the airflow in the airbag. See, eg, US Pat. No. 6,050,601. However, mechanical means are relatively slow compared to the very fast expansion required for airbags. In other cases, a system that depends on the stored expansion gas was used. See, eg, US Pat. No. 6,089,597. Due to the difficulty in maintaining the stored gas for a long time, these systems have not been widely used.

US Pat. No. 5,876,062 relies on the use of resistance wires to ignite propellant. Vibration of the airbag system can cause the ignition wire to break, leading to system failure. Moreover, a filtration system is also needed. US Pat. No. 6,199,906 relies on electronic logic to determine the extent to which airbags are deployed. However, the system still generates harmful emissions and attempts to remove them through certain gas ports. Moreover, the system recognizes that part of the system may be accidentally ignited when exposed to heat or fire.

1 shows a two-stage gas generator. Parts of one embodiment are identified in FIG. 1A and typical dimensions are shown in FIG. 1B. Components for a smaller design are shown in FIG. 1C, the dimensions of which are shown in FIG. 1D.

2 shows the development of a two-stage gas generator compared to a one-stage gas generator.

3 illustrates a typical single stage gas generator of the prior art.

FIG. 4 shows an airbag that deploys several subgun bullets S in a weapon system including a gas generator 40 in the ledge 41.

5, including FIGS. 5A-5C, illustrates an airbag that deploys a parachute to slow down a small gun and control its speed and trajectory.

FIG. 6 shows propellant particle morphology, FIG. 6A shows medium combustion, FIG. 6B gradual combustion, and FIG. 6C shows uniform combustion.

7 shows a logarithmic plot of burn rate versus pressure at various temperatures.

8 shows a representative ignition train.

9 shows various ignition systems in FIGS. 9A-9F.

10 illustrates an electrically actuated initiator.

11 shows ignition initiation for different shapes cut into the particle face of the propellant.

The present invention relates to a gas generator having two or more compartments each having a separate initiator, wherein one compartment is released before the other, ie the compartments are sequentially released.

It is an object of the present invention to provide a gas generator which is reduced in weight and size and has low geometrical constraints from design perspective. It is also an object of the present invention to eliminate the need for a filtration system. It is also an object of the present invention to provide a pressure vessel, ie a gas generating expander, which has eliminated or at least reduced its structural inner member of the combustion chamber. It is also an object of the present invention to provide a gas generator that is less expensive in terms of fewer parts and less process manufacturing operations.

One embodiment may include a gas generator including two or more chambers. Each chamber can release gas at different volumes at different times, and each chamber can contain the initiator and the same propellant as is in the other chamber (s).

The gas generator consists of approximately (a) 84-95% oxidant, (b) 3.4-13.4% fuel and (c) 1.5-2.6% binder based on weight. The combustion product of the propellant may be a harmless gas. Propellant fuel may be selected from CL-20, RDX, HMX, GAP, NGU, TATB, LLM-105, EDNA and mixtures thereof. The binder can be selected from PCL, PIB, GAP, polyvinylpyrrolidone and mixtures thereof. The oxidant may be ammonium nitrate. The propellant may comprise approximately 70-95% active nitramine fuel, 5-25% active polymer binder and 0.1-5% flash inhibitor based on weight.

The second embodiment may include a method of controlling the inflation rate of an airbag. Gas generators having two or more chambers each capable of releasing at different rates can be connected to the airbag. Each chamber may release the gas at different predetermined times. The method may include causing the discharge of each chamber to flow into an airbag.

The gas generator may be located in a vehicle and operated in response to a collision of the vehicle. The airbag is used to inject one or more subgun bullets from the weapon and the gas generator can be operated in response to the trigger signal. The trajectory of the small gun can be controlled by the deployment of the airbag.

The third embodiment is a method using a multi-stage gas generator, comprising about 70-95% active nitramine fuel, 5-25% active polymer binder and 0.1-5% flash inhibitor, based on weight. Promote small, medium and large caliber bullets from weapon systems. The gas generator can be inserted into the barrel of the weapon system and a bullet can be inserted. The gas generator is operated so that the gas released from the gas generator can be used to propel the bullet.

The fourth embodiment may include an environmentally friendly gas generant propellant. The environmentally friendly gas generant propellant may be comprised of (a) 84-95 weight percent oxidant, (b) 3.4-13.4 weight percent fuel, and (c) 1.5-2.6 weight percent binder. The combustion product of the propellant may be a harmless gas.

Green gas general propellants may be selected from CL-20, RDX, HMX, GAP, NGU, TATB, LLM-105, EDNA and mixtures thereof. The environmentally friendly gas generant propellant binder can be selected from PCL, PIB, GAP, polyvinylpyrrolidone and mixtures thereof. The oxidant of the environmentally friendly gas generant propellant may be ammonium nitrate.

In certain embodiments, the same propellant may be used in each compartment or chamber. The propellant may have a different form within each compartment, resulting in different rates of gas release from each compartment. The gas generator of the present invention can be designed to reach maximum expansion or full deployment in the same amount of time as current single stage gas generators. However, compared to previously known gas generators, the generators of the present invention may have a faster initial expansion by means of more innovative propellant forms, after which the expansion speed may be slower at the next stage. Sequential inflation speeds can improve safety for vehicle occupants and / or improve final speed control for injection of bullets and subgun bullets.

In a particular embodiment, one propellant or gas generant used in the gas generator according to the invention is (1) ammonium nitrate as a harmless and noncorrosive oxidant as opposed to a conventional airbag propellant formulation, and (2) CL- A fuel having high energy density and stability, such as 20, or other suitable fuel (characteristics described later), and (3) polycaprolactone (PCL), polyisobutylene (PIB), or glycidyl azide polymer (GAP) Binders, such as these may be included. Fuels that can be used as an alternative or in combination with the CL-20 for fuels of the present invention have similar or larger physical properties of density, heat of formation and heat of decomposition. Examples of such suitable fuels include, but are not limited to, tri-amino-trinitro-benzene (TATB) and 2,6-diamino-3,5-initropyrazine-1-oxide (LLM-105).

In certain embodiments, the second propellant may comprise approximately 70-95% active nitramine fuel, 5-25% active polymer binder and 0.1-5% flash inhibitor.

In certain embodiments, the generation of hot metal particles, such as copper oxide (CuO), is prevented and expensive filtration systems used in current airbag systems may be unnecessary. The use of coated airbags can be avoided.

The present invention relates to a novel type of gas generator. This new type of gas generator can be used for various military applications such as, for example, airbags used for deploying small guns, aiming warheads, automotive airbag systems, inflation devices, airbags used to generate oxygen in oxygen generators, and other applications. Can be used for commercial applications. These gas generators have two or more chambers whose conditions allow each gas volume to be produced under different conditions, ie the time versus pressure profile of the gas volume produced by each chamber may be different.

In this way, by designing multiple chambers differently, the gas generator can be adapted to the requirements of a particular application. For example, to improve the control of ballistics, a dual chamber gas generator can be used, one chamber being designed to partially deploy the airbag very quickly initially as compared to previously known gas generators. The second chamber can be designed to provide a much slower second expansion of the airbag as compared to previously known gas generators.

In a particular embodiment, a two-stage gas generator can be used in an automotive airbag system designed to be activated during rapid deceleration of a vehicle, for example, which occurs in a collision between a vehicle and an object. An inertial switch can trigger the gas generator to deploy the airbag of the system.

In certain embodiments, the sequential release of gas from each chamber of the gas generator and the sequential and gradual inflation of the airbag can improve control of the trajectory of the ammunition or subgun bullets, for example, during horizontal and transition paths and their downward free fall. .

A dual stage or two stage generator according to one embodiment of the invention is shown in FIG. Gas generator 10A is shown in FIG. 1. In this design, two combustion chambers 1 are present in the housing closure 2 and are separated by a 3.00 mm thick wall 3. Each combustion chamber contains a propellant 4, both propellants having the same formulation but different geometries. The type of propellant is chosen to produce the desired single and two stage performance.

Two igniters may be present, one in each combustion chamber. The two igniters can be designed to work with a 5-20 ms difference between a gradual or fast or high R _Q combustion propellant and a medium or slow or low R _Q combustion propellant. The igniter may include an ignition enhancer 5 designed to surround the initiator 6 and to increase the power of the propellant upon ignition. The bursting disc 7 allows the released gas to pass through the gas port 8, where the gas is released. A particular embodiment, for example a compact design such as used for side airbags, may include a slag filter 9. The slag filter 9 is advantageously used as a heat sink so that no special filter is necessary. The hot gas produced by the gas generator passes through the slag filter and loses heat to the slag filter by the conductive heat transfer.

In an exemplary embodiment, the slag filter is coated with zeolites such as sodium aluminosilicate powder known as zeolite CVB-100. This is the case when the gas generant comprises CL-20, GAP and KNO ₃ . In such embodiments, the zeolite coating acts to reduce the gas temperature, thereby reducing the likelihood of combustion damage to the equipment as well as premature explosion of the explosives. Zeolite coatings can also trap harmful gases such as NO _x and CO. In other words, zeolites can act as molecular traps for opposite- and biatomic and multiatomic gases. The proportion of zeolite used in the slag filter may amount to 1 to 10% by weight, more preferably 3 to 7% by weight and most preferably 5% by weight of the filter. Alternatively, a suitable high cross sectional material can be used to produce the same result.

Gas generators for typical airbags can be very small. The overall dimensions of one air bag can be approximately 85 mm x 44 mm. The dimensions of such a typical gas generator 10B are shown in FIG. 1B.

For airbags that require more power, for example for larger ammunition, a larger weight of propellant is needed so that a larger gas generator can be used. The amount of propellant can be calculated, and the size of the gas generator is adjusted accordingly.

Referring now to FIGS. 1C and 1D, the structure of a smaller or smaller dual stage gas generator is shown. Gas generators 10C and 10D are in principle identical to those shown in FIGS. 1A and 1B, respectively, but small in size and low in mass of propellant. The partition between the two combustion chambers aims to remove unnecessary safety concerns, ie to propagate to adjacent combustion ports. When one propellant is deployed, the heat generated by the reaction heats the propellant in the adjacent chamber, and severely high pressures can cause the airbag to fail when deploying the second propellant.

The gas generants in each chamber of the dual chamber gas generator are generally in the same formulation manner, and the geometry of each generant is different. Practically, the gas generant has a cylindrical, hexagonal or rosette geometry with 37, 19, 7 or 1 perforation or no at all. Depending on the desired application, the gas generant in the second chamber as well as any sequential gas generant in the additional chamber may be less gradual, intermediate or reverse with less perforations compared to the first gas generant. In a preferred two chamber airbag, the gas generating rate of the first chamber relative to the second chamber is greater than the second chamber. For example, for the gas produced by the first chamber, the change in pressure as a function of time may be at least twice as large as the change in pressure as a function of time of gas produced from the second chamber.

The ability to vary the timing of ignition of each chamber in accordance with the change in perforation shape yields a high degree of control over the inflation characteristics of the airbag. That is, the change in pressure with time can be controlled very well. See, eg, FIG. 2 where a two chamber gas generator is used. In the early part of the expansion, the change in pressure versus time is steeper than the control, i.e., the first stage gas generator, and the rate of change in the second stage is more progressive than the control. The use of an airbag with a two-stage gas generator greatly improves the control of inflation rate versus one-stage gas generator.

Solid propellants are often classified into two types: gas generator propellants and rocket motor propellants. This classification is mainly based on its energy content. Gas generator propellants generally contain ammonium nitrate as oxidant and have little or no metal additives. Double base compounds and their containing nitraamines as oxidants, such as RDX, HMX, EDNA, NGU, ammonium salts, etc., can sometimes be contained as gas generators, as in the case of N-5, the US Army's Wide Area Munition's gas generator holds a battery. Ammonium salts are one of the popular oxidants for rocket motor propellants, and metals such as aluminum are often added to increase energy content. The energy content of the propellant is increased to increase the flame or combustion temperature. The flame temperatures of most gas generator propellants range from 1600 ° to 3000 ° F. (870 ° to 1650 ° C.), and rocket propellants generally have a flame temperature of 3000 ° to 6000 ° F. (1650 ° to 3315 ° C.).

In certain embodiments, the solid propellant used has a flame temperature of 1600 ° to 3000 ° F. (870 ° to 1650 ° C.). The fuel used may be synthetic rubber or plastics selected on the basis of chemical structure, mechanical properties and processability. Some materials commonly used are butadiene acrylic acid, butadiene / methylvinylpyridine, cellulose acetate, nitrocellulose, polyisoprene and polyvinylchloride. The most commonly used oxidant in almost all gas generators is ammonium nitrate. All synthetic propellants contain one or another type of additive to achieve the desired combustion rate, temperature sensitivity, flame temperature, gas output and physical properties.

Multibase solid propellants are also used as gas generants. In fact, this is the type of solid propellant formulation used in WAM battery gas generators. As mentioned above, they generally have high flame temperatures of 2300 ° to 3500 ° F. (1260 ° to 1926 ° C.) and more solid particles in the exhaust gas. These homogeneous formulations are unstable chemical compounds such as nitrocellulose and nitroglycerin, which are originally propellants that can burn without the need for all other materials, that is, are very ignitable. The most common propellants of this type are sometimes called "dual" propellants and are primarily colloids of nitroglycerin and nitrocellulose.

Mixing of the dual system propellant components can be carried out by filling the mixer with the original components in a particular order in order to obtain the desired final propellant properties as in the case of N-5 propellants. Mixers of general use are of horizontal type and vertical type, ie the axis of rotation of the mixing blade is vertical or horizontal. The action of the blades can completely disperse, mix and integrate the various components into one homogeneous mixture. This mixing can be tightly controlled in terms of blade rotation rate, ie rotation speed and time. Over mixing and under mixing can produce propellants that do not meet ballistic or physical property requirements.

Solid propellant particles may be formed by extrusion, compression molding or casting as in the case of the N-5 propellant. Since most propellants are limited to one or two methods by their chemistry and some types of particles are more suitable for one treatment method than others, it is rarely possible to form specific particles by all available methods. Not. Thus, it is necessary to determine whether the particular formulation and form desired are suitable for the processing techniques available. Particles can be machined by equipment in most machine shops.

The rate of energy release of the solid propellant gas generator is highly dependent on the particle shape. The possible geometric shapes are practically unlimited. Most applications require relatively constant energy for 20 hours up to 100 seconds or more, or short durations of 1 to 10 seconds at relatively high energy release rates. A typical propellant particle morphology is shown in FIG. 6.

For example, the end burn rate or cigarette burn rate shown in FIG. 6A is limited in diameter and at one end, and the other end remains exposed and cannot be burned uniformly, ie receives intermediate combustion over the entire length. This form is used for longer periods of time, lower energy release rates. The form shown in FIG. 6B has a limiter shown in FIG. 11 and also as 114 or an obstruction is attached to all surfaces of the particle except the inner diameter. When this exposed propellant is ignited, much more propellant is exposed as it burns out and proceeds to the flame front. This form produces a gradual rate of energy release. The particle form shown in FIG. 6C has unlimited inner and outer diameters. When both the inner and outer diameters are ignited, the energy release is at a uniform rate, but the combustion time is significantly shorter than the end burners shown in FIG. 6A. Many other forms and special forms are used to achieve the desired rate of energy release. Commonly used forms may include seven progressive and seventeen perforated cylindrical particles and a plurality of perforated rose-like forms with high efficiency and energy release rates.

The rate of energy release of the propellant particles may be based on the start of the ignition cycle up to the end [d (dp / dt) / dt]. This speed may also be called relative rapid (R _q ) or active. Relative speed is controlled by the type of propellant: particle diameter, aperture diameter, web length and number of apertures. Such propellants are called rapid propellants and generate pressure in a closed chamber at a fraction of milliseconds. Rapid propellants almost always require obstructions, i.e. inert materials, to slow their combustion rate to an acceptable safety rate. Such obstacles are attached to the surface of the propellant in one of many coating techniques.

Examples of barrier coatings that may be used include, but are not limited to, polyester plasticizers (paraplex) (hercoat), distyrene glycol dimethacrylate (DEGDMA) and dibutylphthalate (DBP). The first two obstruction coatings have proven to be very effective in reducing the rate of energy release upon ignition of the propellant particles. However, DBP is less desirable, especially since it appears to move over an extended time at a temperature of 140 ° F. (60 ° C.).

If the propellant is coated with an obstruction, the coating generally saturates the particles completely, but remains on the surface at a relatively high concentration. As a result, combustion is slowed at the initial stage of the ballistic cycle, i.e., a reduction / control of the pressure is caused. In the case of DBP, due to the low molecular weight, the coating moves to the center of the particle until equilibrium is achieved if the same distribution of the coating is achieved throughout the particle. As a result, upon ignition of the particles, the rate of energy release is relatively higher than expected, leading to LAT failure or high sigma.

The propellant combustion rate is the rate at which the combustion zone proceeds with a predetermined mass of propellant and may be called the mass combustion rate. Burn rate is a function of the specific propellant formulation, chamber pressure, and propellant temperature. In general, the rate of combustion at a particular propellant temperature is expressed as

r = aP ⁿ or r = a (p / 1000) ⁿ

When the burn rate versus pressure is plotted on a logarithmic sheet, the curve is straight, the slope of the line appears as "n" and "a" as burn rate is blocked at 1 psia or 1000 psia.

Most solid propellants follow this linear function. However, in some propellants the pressure index n is not constant, ie it can be changed to high or low pressure. In a few propellants, the pressure index remains constant over a limited range of pressures. In the latter type of propellant, burn rate data can be derived from experimental data or burn rate plots. Propellant burn rate also depends on ambient propellant temperature. Temperature sensitivity is generally not constant. It varies with ambient temperature decreasing to high and low temperatures, and therefore is generally provided in a specific temperature range, typically 160 to 65 ° F. (71 to 53 ° C.). The temperature sensitivity at constant pressure (σ _p ) is:

P _c = constant within the gas generator

Is provided. The temperature sensitivity of a pressure system with a constant combustion area to nozzle area ratio is:

K _n = constant in the gas generator

Is provided.

In the log plot, this is represented by the intercept of the burn rate versus pressure at various temperatures with 45 ° inclined lines as shown in FIG.

The relationship between σ _p and π _k is:

to be.

Due to the many different applications of gas generators, the requirements put on the ignition system for a particular unit vary widely. Therefore, every state of gas generator operation from the method of initiating the effect of the exhaust gas product must be thoroughly considered. For example, in ignition secondary charges, fast, reliable and reproducible ignition over a given temperature is the goal of any solid propellant gas generator. Some of the ignition parameters most frequently defined by the user are the time required for ignition, i.e. the time interval between the start of combustion signal and the normal combustion of particles, the maximum ignition pressure, the igniter combustion products and the achievement of the temperature range and reliable ignition. The pressure that must be generated.

Ignition systems may be desirable in which solid propellant gas generators allow for rapid and reliable ignition of propellant particles over a wide temperature range. These systems are often somewhat complex and are formed of a number of components, as shown in FIG. 8, which shows the initiator 80, the secondary charge 81, and the initiator combustion surface 82.

Ignition systems that may be used in the present invention may include electrically actuated detonators, pyrotechnics or secondary charges and propellant particles, as described below. The detonator ignites the secondary charge, which ignites the propellant particle surface. The secondary charge must provide energy over an appropriate time to complete ignition of the particle surface and pressurize the gas generator free volume. The term "booster" is frequently used to identify the holding charge of the ignition system.

The energy output of the detonator is small compared to the total energy required for particle ignition because its function is only to ignite a pyrotechnic material that is easily and easily ignitable. Some designs require additional energy during the initial part of the ignition to compensate for heat loss to the inert gas generator component, for which the particle detonated combustion surface is contoured through grooves, slots or holes to provide additional combustion surface. Become This contour burns away the burning surface of the desired hope.

For example, when designing an ignition system to meet defined requirements for use within embodiments of the present invention, certain parameters may be fixed, or they may, for example, vary within a narrow range. The fixed parameters relate to the ignition mechanism of the igniter, the type and structure of the propellant, the chamber design and the nozzle or orifice size. The igniter performance, which can be modified to meet the final product requirements igniter performance under conditions imposed by other design features, can be affected by factors including:

Choice of primary initiator;

Type of ignition train or secondary charge;

Composition of the ignition material;

Density and shape of secondary ignition charges such as, for example, dense, loose; And

Igniter hardware design including electrical connections such as, for example, pigtails, AN connectors, and the like.

For reliable ignition, most gas generator propellants require a normal energy input to first decompose the binder and the oxidant and then allow the combustion process to reach equilibrium. An igniter based on this principle is referred to as a "oiler" igniter. In summary, the ignition system functions or steps can be summarized as follows:

Provide a proportion and amount of thermal energy sufficient to ignite propellant particles;

Pressurize the generator free volume; And

Provide gas and / or heat to supplement particle output until thermal equilibrium is obtained.

Step 3 is a regression requirement because thermal equilibrium is reached asymptotically. Thus, a suitable ignition design should include:

A quick burn charge designed to quickly press the case and burn at pressurization; And

A retainer with an energy output that approximates a right triangle as a function of time.

It is desirable to obtain maximum energy output to pressurize the case and start the ignition process. The retainer is detonated by the pressure charge and returns to zero from the maximum detonation output at the point where thermal equilibrium is obtained. This ignition system model serves as the basis for ignition system design with "smooth" pressure-time characteristics, ie rapid pressurization to a working pressure without significant peaks, followed by a neutral pressure-time curve over combustion. An empirical formula has been developed to estimate igniter energy requirements. Final manufacture of the igniter may be carried out through ballistic testing of the gas generator system.

The techniques used to provide model ignition requirements vary widely. Some conventional systems are shown in FIG. However, most ignition systems consist of the following parts: detonator 91, primer 92, booster 93 and retainer 94, where the booster and retainer form a secondary charge. As shown in FIGS. 9C and 9E, type “C” and type “E” ignition systems may be used in certain embodiments. Other ignition systems can also be used.

Referring to FIG. 10, the detonator can be classified into two main categories: electrically operated or mechanically operated. The electrically actuated detonator 100 (shown in FIG. 10) is a high temperature wire or explosion bridge wire detonator. Mechanically actuated detonators are actuated by collisions or impacts. Electrically actuated initiators may be used in the preferred embodiments.

The high temperature wire initiator may have a resistance wire or device mounted between two electrodes 102 and 103. The device can be coated with low ignition temperature pyrotechnic beads. The current flowing through the bridge wire 101 or element raises the temperature of the pyrotechnic above its auto ignition temperature, detonating the rest of the pyrotechnic and pyrotechnic train. The resistance of the wire and the ability of the detonator element to conduct heat away from the pyrotechnic can determine the non-combustion and complete combustion characteristics of the detonator. High current detonators, for example from 1 ampere / 1 watt to 5 ampere / 5 watts have a large heat sink or heat dissipation capacity.

Explosion bridge wire detonators are similar to high temperature wire types except that high energy electric pulses applied across bridge wire 101 vaporize them to convert electrical energy into thermal energy and ignite adjacent pyrotechnic materials. . Although gaps are often used in detonation circuits to provide open circuits that direct current, at high current pulses this gap is bridged and the resistive wire explodes.

11 illustrates the types of saddles that are expected to have various structures. This shows that by the proper use of one or both systems, a certain ignition pressure-time curve can be obtained. To provide a smooth transition between the ignition and propellant combustion equilibrium, an ignition maintainer is often used. One type of ignition retainer may be a small pellet and / or disc 111 of vigorous propellant bonded to the surface of particles 113. Notched grooves 112 in the particle surface provide increased combustion surface and assist in obtaining rapid ignition. If properly provided, the second charge can prevent the "pressure saddle" or instantaneous drop in pressure due to heat loss to the surrounding metal parts.

The choice of initiator can depend on the means available to provide thermal energy to the primary ignition material. Current can be applied through low resistance bridge-wires of, for example, 0.02 to 5.0 ohms embedded in a thermally sensitive pyrotechnic composition. The lower the energy of the solid propellant, the greater the ignition system output required. Physical parameters that affect the design of the ignition charge system are free volume, particle structure and propellant combustion surface. Rapid ignition is very supported by pressurization, but care must be taken to avoid overpressure during the ignition phase. When determining the requirements for a gas generator system, careful consideration should be given to the ignition system before securing any physical structure.

The operation of one embodiment will now be described. Upon receipt of the signal to the initiator (s), the more advanced gas product experiences rapid ignition and ranges from 35 to 85% of its total capacity, preferably 45% to 85% of its capacity, most preferably its total capacity. Sufficient pressure is generated to inflate the airbag to 65 to 85% of the volume. The second gas product in the second chamber is detonated at 45% to 95% of the given time t = t _{pmax (first gas generator)} . That is, the gaseous product in the second chamber can be detonated when 45% to 95% of the gas is produced from the first generator. Preferably, the gas product in the second chamber can be detonated when 65% to 95% of the gas is produced from the first generator. In a preferred embodiment of the invention, the gas product in the second chamber can be detonated when 90% to 95% of the gas is produced from the first generator.

The gaseous product in the second chamber provides residual expansion of the airbag to achieve an overall internal gas pressure equal to the pressure rated for the airbag for this particular subsystem. That is, when gas is produced completely from both chambers of the new system, the final gas pressure in the airbag is equal to the gas pressure from the current one-stage gas generator. The rate of gas evolution of the proposed technique is controlled by providing a propellant that produces different rates of gas emissions. By providing different rates of gas discharge, the pressure versus time curve can have two slopes for a two stage system. One slope, eg, the slope corresponding to the first gas product in the first chamber, can have a very steep slope [(dp) ₁ / (dt) ₁ ], and the second slope of the second gas product has a less steep slope [ (dp) ₂ / (dt) ₂ ]. The effective time for the maximum volume corresponding to the full deployment of the airbag can still be the same, but it can be controlled in such a way as to prevent a strong impact on the airbag.

In commercial or commercial applications, this performance is a serious accident that can occur when the airbag is deployed in a vehicle traveling at speeds in excess of 100 mph (165 km / h), or in children, lightweight passengers or pipe-smoking passengers. And because it is possible to prevent possible disasters.

This performance is advantageous in military applications because it provides improved control over the trajectory while preventing accidents that result in drastic changes in trajectory resulting from current airbag systems.

Embodiments of the present invention allow for much better control of pressure vs. time, and thus can even have a gas generator system with two or more chambers to enable designers to match almost any pressure vs. time profile. have.

Considerations in designing inflators or gas generators for passive airbag confinement systems are the toxicity and hazards of the gas filling the airbag. Inflators for airbags exhaust or filter gases and other materials that can damage portions of the airbag. If the gas generating components are very toxic or unstable, special handling may be required during the manufacturing process, and if any part of the munitions and / or quasi-munitions product (s) system remains, this may create disposal problems at the end of the useful life of the device. have.

As an example, the raw sodium azide used as the gas generating composition of most gas generators (for airbag applications) has a relatively high toxicity, which causes handling problems during the manufacturing process. In addition, where soldiers or citizens are exposed to the remainder of the device, toxic or environmental pollution concerns may need to be considered.

Current airbags are typically coated to prevent damage to the bags. Packaging constraints add additional design considerations in the deployment of passive airbag inflators. By way of example, weight and size are the primary factors in determining the suitability of a vehicle inflator design.

In one embodiment of the novel gas generator described herein, the need for a complex, expensive filter system (to remove high temperature, solid by-products) is eliminated. (A filter is required in current single stage gas generators. See part 11 in Figure 3.) The removal of complex and expensive filter systems means a reduction of at least 4% of the cost of the gas generator.

It is believed that many of the propellants described herein and that can be used in the new gas generators according to the present invention are novel. One includes binders used to hold the oxidant, fuel and components together. Embodiments of the propellant described herein are more environmentally acceptable than current propellants and do not currently require the filtration system required for gas generators.

The oxidant is preferably ammonium nitrate, which may constitute about 89.5 ± 5.5% of the propellant. The oxidant must be phase-stabilized to prevent melting and recrystallization to different particle sizes. An example of a stable phase stabilizer is potassium nitrate (KNO ₃ ), which may be present at a concentration of 0.5% to 7%, may also prevent flash generation, and the preferred concentration of potassium nitrate is 0.5% to 1%. This nitrogen-rich oxidant, when stabilized, is insensitive to shock, impact and electrostatic discharge for manufacturing and packaging, which makes it safe to handle. Phase stabilized ammonium nitrate prevents phase transition of the oxidant during thermal cycling.

The fuel may constitute about 8.4 ± 5.0% of the propellant. Suitable fuels include CL-20 (C ₁₀ H ₂₂ N ₁₂ O ₁₂ ) (Thiokol Corporation), RDX (C ₃ H ₆ N ₆ O ₆ ), HMX (C ₄ H ₈ N ₈ O ₈ ), GAP (C ₃ H ₅ N ₃ O) _n (glycidyl azide polymer or polycyclidyl azide) (3M Corporation, Minnesota), EDNA (ethylene dinitramine), TATB, LLM-105 and mixtures thereof Niramine. Preferred fuel is CL-20.

The binder can make up about 2.1 ± 0.5% of the propellant and acts as a binder to hold (1) the components together, and (2) to prevent rupture of crystals that can cause gas evolution too quickly. Suitable binders include polycaproactone (PCL), polyisobutylene (PIB), polyvinylpyrrolidone and mixtures thereof.

GAP can be used as a combined fuel and binder. However, the combustion byproduct is toxic and an increased amount of ammonium nitrate is required to overcome this disadvantage. Higher concentrations of ammonium nitrate make the composition difficult to process and ignite.

In another embodiment, the gas generator is about 70-95% CL-20 active nitramine fuel, 5-25% active polyglycidyl azide (eg, glycidyl azide polymer or GAP) or active Polymeric binders such as polyisobutylene (Vistanex polymer) or 0.1-5.0% flash inhibitors such as PIB and potassium nitrate. Gas generators may be used in two-stage gas generators and may be particularly useful in propulsion systems for small, medium and large aperture ammunition.

Other ingredients may optionally be added to the composition. They (1) can be used at about 0.1-1.0% to control stability such as, for example, ethyl centralit, Akardite I, Akardite II, diphenyl amine or 2-nitrodiphenyl amine (2) coating materials such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, aryl methacrylate or Hercote polyester, Materials to control ballistic spikes and high initial pressure rises, and (3) examples that can be used at about 0.05-1.0%, include materials for increasing gravity density and dissipating static, such as graphite.

The propellant composition can be treated with either a wet or dry mixture and can be pressed into tablets, disks or other shapes or extruded into particles. M.E. General such as those described in Fayed and L. Otten's Handbook of Powder Science and Technology (1984), and Emil R. Riegel's Chemical Process Machinery (2nd edition, 1960, Wolfgang Pietsch, Size Enlargement by Agglomeration Ch.4 (1991)). The mixing technique used may be used.

Propellants used in different chambers may generally have the same chemical composition, but they often have different shapes, which affects the burn rate of the propellants in each chamber. By way of example, propellants with more penetrations have more surface exposure, which results in faster combustion.

In addition, the density of the propellant is an important indicator of its stability. Good density should be about 92% or more above theoretical density. If the density is too low, large amounts of propellant cannot be filled in the chamber. Secondly, when the density is low, the propellant is more likely to rupture and result in propellants of different shapes, which affects the burn rate, as described above.

The combustion of the propellant is safe and the flame temperature of the gaseous by-product of the reaction is less than 120 ° F. (48 ° C.). Combustion products are generally non-hazardous gases, ie water vapor, nitrogen and carbon dioxide (CO ₂ ). These by-products are not harmful to the environment. In addition, they are not corrosive, which means that uncoated airbags can be used in the system.

The amount of propellant for the new gas generator is much smaller than that required for current generators. Typically, between 70 and 100 gm of propellant are used in the prior art, but new generators with 5 to 8 gm used to deploy submunitions are required.

In order to evaluate the performance of the gas generator, it is possible to use a ballistic tank test. The tank must have a capacity of at least the same size as the airbag in which the gas generator is used. Any commonly used ballistic test procedure can be used to evaluate the performance of the gas generator.

Various design considerations can be considered in developing an airbag system. First, the inflator should be capable of producing and / or releasing a sufficient amount of gas into the airbag within the time limits required for the airbag system. Given the time limits associated with military airbag systems, airbags should deploy within approximately 5 to 100 ms, depending on the size of the airbag. The inflator should generally be able to fill the airbags within these time frames from 15 to 200 liters depending on the intended application.

In this operation, the gas generator receives a signal from an external or internal source and then sends this signal to each initiator. The timing of the inflation of the airbag is incorporated into the gas generator, a sensor such as an infrared (IR) sensor in ammunition that detects a target that meets a specified set of IR requirements, a detector such as a direction sensor that determines a point within a ballistic, a timer, or a weapon. The trigger signal may be triggered by a trigger signal transmitted to data programmed into a computer to be programmed, or by another technique. Detonators function sequentially with delays that can be on the order of milliseconds between ignition or activation of each detonator.

The following examples are intended to further non-limitingly illustrate the invention disclosed herein.

Example 1: two-stage gas generator

A two stage gas generator is shown in FIG. FIG. 1A shows a portion of the generator and FIG. 1B shows representative dimensions. The total weight of the propellant of this system is approximately 5-10 gm. A smaller design is shown in FIG. 1C and a corresponding representative dimension is shown in FIG. 1D. The embodiment shown in FIG. 1 can be used, for example, in an airbag restraint system of an automobile or an airbag system for paramilitary deployment.

Example 2: performance data

The performance of an example (Table 1A) of one propellant according to the invention comprising 87% CL-20, 12% polyglycidyl arch and 1% potassium nitrate was evaluated by a thermochemical simulation program recorded in Fortran. Shown. The program shows the theoretical thermochemical performance of the gas product. The outputs listed, among other things, list the predicted theoretical density, reaction temperature in the chamber, specific heat ratio (expressed as gamma), and energy or momentum. It also lists the predicted byproducts of combustion in moles, wt%, mol% and volume%. The output shown is based on 100 g of propellant.

Example 3: paramilitary deployment

The munitions system is assembled by enclosing a rocket with a paramilitary. Airbags can be inserted between the rocket and paramilitary. The system also includes a gas generator having two or more chambers. When the system is located in the vicinity of the intended target (s), the gas generator is in operation to inflate the airbag and thus deploy the paramilitary. By having two or more chambers, the gas generator can inflate the airbag in a more predictable manner than the one-chamber gas generator. This means that the paramilitary can be deployed closer to the intended target.

Example 4: Use of Airbags to Control Ballistics of Paramilitary Goods

Once the quasi-munition of Example 3 initiates its downward trajectory, the airbag connected to the para-shoot P of the para-munition is inflated to deploy the para-shoot P. See FIG. 5A. This gas generator 50A has two or more chambers and provides good control over the development of the parachute and thus the trajectory of the quasi-munition for a conventional system comprising only one chamber in the gas generator. Parachute reduces the speed of the paramilitary and also balances it during its horizontal transition path and during its downward free fall.

An alternative to the parachute is the use of the airbag itself to provide buoyancy for paramilitary goods. See FIG. 5B. Air bags are attached to paramilitary goods and act like balloon-like objects when inflated. Rather than the airbag being inflated by the gas from the gas generator 50b and providing the drag provided by the parachute, the airbag also provides buoyancy which affects the trajectory of the submunition. See FIG. 5B where parachute P is replaced with airbag A, shown as a balloon-like object inflated by gas generator 50B.

Example 5: Use of a Gas Generator for Propelled Ammunition

Gas generators can be used for propellant ammunition. Instead of the gunpowder used in the ammunition casing, a gas generator can be used. The gas generator may be embedded in a separate part, for example a plastic or ceramic, which is placed in the muzzle prior to ammunition. Alternatively, the gas generator may be loaded into the barrel of the weapon 59 without the need for a casing with gas generator 50C and projectile 58 as shown in FIG. 5C.

The amount of gas product required for the propellant ammunition can be calculated using known formulas relating to the amount of gas product relative to the production pressure and the rate of the ammunition. for example:

55 to 65 kpsi (379 to 448 MPa) is required to propel any medium caliper round at muzzle velocity equal to or 15% faster than current specifications.

55-65 kpsi (379-448 MPa) is required to propel the M919 medium caliper round at a muzzle velocity of 2000 m / s. The M919 cartridge is 25 mm long, wing stable streak forming peony with tracer.

65 to 75 kpsi (448 to 517 MPa) is required to propel any large caliper round at muzzle velocity at the same or 30% faster current specification.

Example 6: ignition system

Due to the need to ignite the propellant in each chamber of the gas generator at a particular time, it is important that the ignition in one chamber does not accidentally ignite the propellant in the other chamber. Moreover, it is important that the chamber is ignited at a specific time because the rate of gas generation from each chamber controls the rate of inflation of the airbag.

For example, a conventional two-chamber gas generator can generate 8-20% of the total amount of gas needed to inflate the airbag, for example, within 10 ms. The preferred fraction of gas from the first chamber is 10-15%, with the most preferred amount being 15% of the total amount of gas required.

The ignition system of the second chamber should be ignited approximately at the end of gas evolution from the first chamber, and the inflation rate from this chamber should control the final activity in which the airbag is used. For example, a combustion time combination ratio for both the first and second stages, preferably between 60 and 90 ms, is required to deploy the parachute or to discharge the submunition from the ammunition to control the trajectory of the submunition.

Those skilled in the art will recognize that there are other variations of the invention consistent with the invention disclosed herein. Although specific dimensions have been provided in connection with the illustrative embodiments, these embodiments or dimensions do not limit the scope of the invention. The invention may include any sized embodiment, including aspects disclosed herein or equivalents thereof.

The following table is included:

TABLE 1a

Thermochemical code operation

Non-ideal State Equation HEP-100 Propelled Explosives

Polyglycidyl Azide 12.000

Potassium Nitrate 1.000

CL-20 87.000

                                Date Setup 5

OHFP = 21349.29 Density = 1.9101 GM / CC .069008 LBM / IN ** 3E = .0

EFP = 23119.04 Oxygen mean for CO2 = -14.14, 11.02 for CO

OMOX = 1.6337

C 1.5723 H .62178 X .0098905 N 2.7755 O 2.5767 S .1000E-6

Hughner Point 0-Impact Velocity = 2362.98 M / SEC, Particle V = 1088.8

P = 100000.PSI P = 6804.60 ATM T = 4833.3 NG = 3.45327

NT = 3.45327 S = 196.755

CPG = 35.316 CPT = 35.316 Fixed CP Gamma = 1.241 DHDT = 68.4529

Gamma = 1.18404

WT PCT COND = .00000 MW Gas = 28.959 H = 68673 COV = .00000

VSP = 2.01273 Sound Speed = 1251.54

RHO = .49683756 PO = 1.9990 VO = 3.73251 Momentum = 464268

E = 35505.381 DEDT = 54.0953

TABLE 1b

0pressure is less than explosion pressure-impact speed not determined

Hughner Point 0-Impact Speed = .00 M / SEC, Particle V = .0

P = 14.6960 PSI P = 1.00000 ATM T = 3014.1 NG = 3.52045

NT = 3.52045 S = 242.971

CPG = 34.420 CPT = 34.420 Fixed CP Gamma = 1.255 DHDT = 137.180

Gamma = 1.12634

WT PCT COND = .00000 MW Gas = 28.405 H = 10812 COV = .00000

VSP = 8706.95 Sound Speed = 996.843

RHO = .00011485 PO = 1.9990 VO = 3.73251 Momentum = 295154

E = -10273.488 DEDT = 117.968

Claims (38)

A gas generator having two or more chambers, each chamber capable of releasing gas at different times and at different volume fractions, each chamber containing the same propellant and initiator. The propellant of claim 1, wherein the propellant comprises, based on weight, approximately (a) 84-95% oxidant, (b) 3.4-13.4% fuel and (c) 1.5-2.6% binder, wherein The gas generator of which the combustion products of the propellant are harmless gases. 3. The gas generator of Claim 2, wherein the fuel is selected from the group consisting of CL-20, RDX, HMX, GAP, NGU, TATB, LLM-105, EDNA and mixtures thereof. 3. The gas generator of claim 2, wherein the binder is selected from the group consisting of PCL, PIB, GAP, polyvinylpyrrolidone, and mixtures thereof. 3. The gas generator of Claim 2, wherein said oxidant is ammonium nitrate. 3. The gas generator of Claim 2, wherein the oxidant is ammonium nitrate, the fuel is CL-20, and the binder is polycaprolactone. 7. The gas generator of Claim 6, wherein said ammonium nitrate comprises approximately 89.5%, said CL-20 comprises approximately 8.4% and said polycaprolactone comprises approximately 2.1% of said propellant. The gas generator of Claim 1, wherein the shape of the propellant is different from chamber to chamber. The gas generator of claim 1, wherein the propellant comprises approximately 70-95% active nitramine fuel, 5-25% active polymer binder, and 0.1-5% flash inhibitor, based on weight. 10. The gas generator of Claim 9, wherein said nitramine fuel is CL-20. 10. The gas generator of Claim 9, wherein said polymeric binder is GAP or PIB. 10. The gas generator of Claim 9, wherein said flash inhibitor is potassium nitrate. 10. The gas generator of Claim 9, further comprising at least one component selected from the group consisting of components controlling stability, coatings controlling ballistic spikes and high initial pressure rises, and components that increase weight density and dissipation static electricity. 10. The gas generator of Claim 9, wherein the gas generator has two chambers in which the pressure change as a function of time from the first chamber is at least two times greater than the pressure change as a function of time from the second chamber. 10. The method of claim 9, wherein the propellant (a) preparing a mixture of components of the propellant in wet or dry form; (b) forming the mixture into tablets, discs or particles, (c) if wet, drying the tablets, discs or particles, (d) perforating the tablet, disc or particle to obtain the desired form Gas generator manufactured by a method comprising a. 10. The gas generator of Claim 9, wherein the density of said propellant is at least about 92% of the theoretical density. The method of claim 13, wherein the stability controlling component is ethyl centralite (Athyl centralite), Acardite (Akardite I), Acadite II, Diphenyl Amine and 2-nitrodiphenyl Amine (Nitrodiphenyl Amine) Gas generator selected from the group consisting of The method of claim 13, wherein the components controlling the ballistic spike and the high initial pressure rise are Ethylene Glycol Dimethacrylate, Diethylene Glycol Dimethacrylate, Allyl Methacrylate (Allyl). Gas generator selected from the group consisting of Methacrylate) and Hercote Polyester. 14. The gas generator of Claim 13, wherein the component that increases the weight density and dissipation static electricity is graphite. The gas generator of claim 1, further comprising an air bag operable to receive gas discharged from the respective chambers. 21. The gas generator of Claim 20, wherein the airbag is an uncoated airbag. 21. The gas generator of Claim 20, further comprising an inertial switch operable to generate a signal to trigger each of said chambers. 23. The gas generator of claim 22, wherein the inertial switch is an accelerometer of a microelectromechanical system (MEMS). The gas generator of Claim 1, further comprising a third chamber. The gas generator of claim 1, wherein the combustion product of the propellant comprises water, nitrogen, and carbon dioxide. As a method of controlling the inflation speed of an airbag, (a) connecting the gas generator according to claim 1 to an air bag, (b) causing each chamber to be discharged at a different predetermined rate; (c) allowing the discharge of each chamber to flow into the airbag Method of controlling the inflation speed of the airbag comprising a. 27. The method of claim 26, further comprising operating the gas generator in response to a vehicle crash, wherein the gas generator and the airbag are disposed in a vehicle. 27. The method of claim 26, further comprising operating the gas generator in response to a trigger signal, and injecting one or more subgroup coals from the weapon, wherein the gas generator and the airbag are inflated with the airbag connected to the weapon. Control method. 29. The method of claim 28, further comprising firing the weapon. 27. The method of claim 26, further comprising controlling the trajectory of the subgun bullet. 31. The method of claim 30, wherein controlling the trajectory of the small group bullet comprises: (a) operating the gas generator, (b) deploying the parachute of the subgun coal using gas from the gas generator Includes, wherein the deployment is inflated air velocity control method for controlling the ballistics of the subgun bullet. A method of using the gas generator of claim 9 to propel small, medium and large caliber bullets from a weapon system, (a) inserting the gas generator into a barrel of the weapon system, (b) inserting the bullet; (c) operating the gas generator, (d) propagating the bullet using the gas released from the gas generator How to include. As an environmentally friendly gas general propellant, (a) 84-95% by weight of oxidizing agent, (b) 3.4-13.4 weight percent of fuel, (c) 1.5-2.6 wt% binder Wherein the combustion product of the propellant is a harmless gas. 34. The environmentally friendly gas generant propellant of claim 33, wherein the fuel is selected from the group consisting of CL-20, RDX, HMX, GAP, NGU, TATB, LLM-105, EDNA, and mixtures thereof. 34. The environmentally friendly gas generant propellant of claim 33, wherein said binder is selected from the group consisting of PCL, PIB, GAP, polyvinylpyrrolidone and mixtures thereof. 34. The environmentally friendly gas generant propellant of claim 33, wherein said oxidant is ammonium nitrate. 34. The environmentally friendly gas generant propellant of claim 33, wherein said oxidant is ammonium nitrate, said fuel is CL-20, and said binder is polycaprolactone. 38. The environmentally friendly gas generant propellant of claim 37, wherein said ammonium nitrate comprises approximately 89.5%, said CL-20 comprises approximately 8.4%, and said polycaprolactone comprises approximately 2.1% of said propellant.