Patent Grant
10337848
The present invention relates generally to simultaneous linear and rotary acceleration (deceleration) operated mechanical mechanisms, and more particularly for inertial igniters for reserve batteries used in gun-fired munitions and other similar applications or electrical switches to open (close) a normally closed (open) circuit upon the device experiencing a prescribed simultaneous linear and rotary acceleration profile threshold.
Reserve batteries of the electrochemical type are well known in the art for a variety of uses where storage time before use can be extremely long and on the order of several decades. Reserve batteries are in use in applications such as batteries for gun-fired munitions including guided and smart, mortars, fusing mines, missiles, and many other military and commercial applications. The electrochemical reserve-type batteries can in general be divided into two different basic types.
The first type includes the so-called thermal batteries, which are to operate at high temperatures. Unlike liquid reserve batteries, in thermal batteries the electrolyte is already in the cells and therefore does not require a release and distribution mechanism such as spinning. The electrolyte is dry, solid and non-conductive, thereby leaving the battery in a non-operational and inert condition. These batteries incorporate pyrotechnic heat sources to melt the electrolyte just prior to use in order to make them electrically conductive and thereby making the battery active. The most common internal pyrotechnic is a blend of Fe and KClO4. Thermal batteries utilize a molten salt to serve as the electrolyte upon activation. The electrolytes are usually mixtures of alkali-halide salts and are used with the Li(Si)/FeS2 or Li(Si)/CoS2 couples. Some batteries also employ anodes of Li(Al) in place of the Li(Si) anodes. Insulation and internal heat sinks are used to maintain the electrolyte in its molten and conductive condition during the time of use.
Thermal batteries have long been used in munitions and other similar applications to provide a relatively large amount of power during a relatively short period of time, mainly during the munitions flight. Thermal batteries have high power density and can provide a large amount of power as long as the electrolyte of the thermal battery stays liquid, thereby conductive. The process of manufacturing thermal batteries is highly labor intensive and requires relatively expensive facilities. Fabrication usually involves costly batch processes, including pressing electrodes and electrolytes into rigid wafers, and assembling batteries by hand. The batteries are encased in a hermetically-sealed metal container that is usually cylindrical in shape.
The second type includes the so-called liquid reserve batteries in which the electrodes are fully assembled for cooperation, but the liquid electrolyte is held in reserve in a separate container until the batteries are desired to be activated. In these types of batteries, by keeping the electrolyte separated from the battery cell, the shelf life of the batteries is essentially unlimited. The battery is activated by transferring the electrolyte from its container to the battery electrode compartment.
A typical liquid reserve battery is kept inert during storage by keeping the aqueous electrolyte separate in a glass or metal ampoule or in a separate compartment inside the battery case. The electrolyte compartment may also be separated from the electrode compartment by a membrane or the like. Prior to use, the battery is activated by breaking the ampoule or puncturing the membrane allowing the electrolyte to flood the electrodes. The breaking of the ampoule or the puncturing of the membrane is achieved either mechanically using certain mechanisms usually activated by the firing setback acceleration or by the initiation of certain pyrotechnic material. In these batteries, the projectile spin or a wicking action is generally used to transport the electrolyte into the battery cells.
Reserve batteries are inactive and inert when manufactured and become active and begin to produce power only when they are activated. Reserve batteries have the advantage of very long shelf life of up to 20 years that is required for munitions applications.
Thermal batteries generally use some type of initiation device (igniter) to provide a controlled pyrotechnic reaction to produce output gas, flame or hot particles to ignite the heating elements (pyrotechnic materials) of the thermal battery. There are currently two distinct classes of igniters that are available for use in thermal batteries. The first class of igniter operates based on electrical energy. Such electrical igniters, however, require electrical energy, thereby requiring an onboard battery or other power sources with related shelf life and/or complexity and volume requirements to operate and initiate the thermal battery. The second class of igniters, commonly called “inertial igniters”, operates based on the firing acceleration. The inertial igniters do not require onboard batteries for their operation and are thereby often used in munitions applications such as in gun-fired munitions and mortars.
Inertial igniters are also used to activate liquid reserve batteries through the rupture of the electrolyte storage container or membrane separating it from the battery core. The inertial igniter mechanisms may also be used to directly rupture the electrolyte storage container or membrane.
Inertial igniters used in munitions must be capable of activating only when subjected to the prescribed setback acceleration levels and not when subjected to all so-called no-fire conditions such as accidental drops or transportation vibration or the like. This means that safety in terms of prevention of accidental ignition is one of the main concerns in inertial igniters.
Inertia-based igniters must provide two basic functions. The first function is to provide the capability to differentiate the aforementioned accidental events such as drops over hard surfaces or transportation vibration or the like, i.e., all no-fire events, from the prescribed firing setback acceleration (all-fire) event. In inertial igniters, this function is performed by keeping the device striker fixed to the device structure during all aforementioned no-fire events until the prescribed firing setback acceleration event is detected. At which time, the device striker is released. The second function of an inertia-based igniter is to provide the means of accelerating the device striker to the kinetic energy that is needed to initiate the device pyrotechnic material as it (hammer element) strikes an inertial igniter body provided “anvil” over which the pyrotechnic material is provided. In general, the striker is provided with a relatively sharp point which strikes the pyrotechnic material covering a raised surface over the anvil, thereby allowing a relatively thin pyrotechnic layer to be pinched to achieve a reliable ignition mechanism. Alternatively, the anvil with the covered pyrotechnic material may be provided on the striker element and the sharp point on the device base structure.
In many applications, percussion primers are directly mounted on the anvil (striker) side of the device and the required initiation pin is machined or attached to the striker (anvil) to impact and initiate the primer.
In either design, exit holes are provided on the inertial igniter to allow the reserve battery activating flames and sparks to exit.
Two basic methods are currently available for accelerating the device striker to the aforementioned needed velocity (kinetic energy) level. The first method is based on allowing the setback acceleration to accelerate the striker mass following its release. This method requires the setback acceleration to have long enough duration to allow for the time that it takes for the striker mass to be released and for the striker mass to be accelerated to the required velocity before pyrotechnic impact. Thus, this method is applicable to larger caliber and mortar munitions and rockets in which the setback acceleration duration is relatively long and in the order of several milliseconds, sometimes even longer than 10-15 milliseconds. This method is also suitable for impact induced initiations in which the impact induced decelerations have relatively long duration.
The second method relies on potential energy stored in a spring (elastic) element, which is then released upon the detection of the prescribed all-fire conditions. This method is suitable for use in munitions that are subjected to very short setback accelerations, such as those of the order of 1-2 milliseconds. This method is also suitable for impact induced initiations in which the impact induced decelerations could have relatively short durations.
Inertia-based igniters must therefore comprise two components so that together they provide the aforementioned mechanical safety (the capability to differentiate the prescribed all-fire condition from all aforementioned no-fire conditions) and to provide the required striking action to achieve ignition of the pyrotechnic elements. The function of the safety system is to keep the striker element in a relatively fixed position in the direction of initiation strike until the prescribed all-fire condition (or the prescribed impact induced deceleration event) is detected, at which time the striker element is to be released, allowing it to accelerate toward its target under the influence of the remaining portion of the setback acceleration or by the force generated by the aforementioned potential energy stored in a spring (elastic) element. The ignition itself may take place as a result of striker impact, or simply contact or proximity. For example, the striker may be akin to a firing pin and the target akin to a standard percussion cap primer. Alternately, the striker-target pair may bring together one or more chemical compounds whose combination with or without impact will set off a reaction resulting in the desired ignition.
Currently available technology (see e.g., U.S. Pat. Nos. 7,437,995; 7,587,979; and 7,587,980; U.S. Application Publication No. 2009/0013891 and U.S. application Ser. Nos. 61/239,048; 12/079,164; 12/234,698; 12/623,442; 12/774,324; and 12/794,763 the entire contents of each of which are incorporated herein by reference) has provided solution to the requirement of differentiating accidental drops during assembly, transportation and the like (generally for drops from up to 7 feet over concrete floors that can result in impact deceleration levels of up to 2000 G over up to 0.5 milli-seconds). The available technology differentiates the above accidental and initiation (all-fire) events by both the resulting impact induced inertial igniter (essentially the inertial igniter structure) deceleration and its duration with the firing (setback) acceleration level that is experienced by the inertial igniter and its duration, thereby allowing initiation of the inertial igniter only when the initiation (all-fire) setback acceleration level as well as its designed duration (which in gun-fired munitions of interest such as artillery rounds or mortars or the like is significantly longer than drop impact duration) are reached. This mode of differentiating the “combined” effects of accidental drop induced deceleration and all-fire initiation acceleration levels as well as their time durations (both of which would similarly tend to affect the start of the process of initiation by releasing a striker mass that upon impact with certain pyrotechnic material(s) or the like would start the ignition process) is possible since the aforementioned up to 2000 G impact deceleration level is applied over only 0.5 milli-seconds (msec), while the (even lower level) firing (setback) acceleration (generally not much lower than 900 G) is applied over significantly longer durations (generally over at least 8-10 msec).
The need to differentiate accidental and initiation accelerations by the resulting shock loading level of the event necessitates the employment of a safety system which is capable of allowing initiation of the igniter only during high total impulse levels, i.e., when the prescribed all-fire acceleration level is detected over long enough duration to differentiate event from accidental events, which are either low in acceleration level such as vibration duration transportation or are short in duration such as accidental drop over a hard surface.
Inertial igniters that are used in munitions that are loaded into ships by cranes for transportation are highly desirable to satisfy another no-fire requirement arising from accidental dropping of the munitions from heights reached during ship loading. This requirement generally demands no-fire (no initiation) due to drops from up to 40 feet that can result in impact induced deceleration levels (of the inertial igniter structure) of up to 18,000 Gs acting over up to 1 msec time intervals. Currently, inertial igniters that can satisfy this no-fire requirement when the all-fire (setback) acceleration levels are relatively low (for example, as low as around 900 G and up to around 3000 Gs) are not available. In addition, the currently known methods of constructing inertial igniters for satisfying 7 feet drop safety (resulting in up to 2,000 Gs of impact induced deceleration levels for up to 0.5 msec impulse) requirement cannot be used to achieve safety (no-initiation) for very high impact induced decelerations resulting from high-height drops of up to 40 feet (up to 18,000 Gs of impact induced decelerations lasting up to 1 msec). This is the case for several reasons. Firstly, impacts following drops occur at significantly higher impact speeds for drops from higher heights. For example, considering free drops and for the sake of simplicity assuming no drag to be acting on the object, impact velocities for a drop from a height of 40 feet can reach approximately 15.4 m/sec as compared to a drop from a height of 7 feet is of approximately 6.4 m/sec, or about 2.3 times higher for 40 feet drops.
Secondly, the 7 foot drops over a concrete floor lasts only up to 0.5 seconds, whereas 40 feet drop induced inertial igniter deceleration levels of up to 18,000 Gs can have durations of up to 1 msec. As a result, as it is shown later in this disclosure the distance travelled by the inertial igniter striker mass releasing element is so much higher for the aforementioned 40 feet drops as compared to 7 foot drops that it has made the development of inertial igniters that are safe (no-initiation occurring) as a result of such 40 feet drops impractical.
Thus, it is shown that it is not possible to use the methods used in the design of currently available inertial igniters to provide no-fire safety for accidental drops from height of up to 7 feet (such as those described in the aforementioned patents and patent applications and the prior art indicated therein) to design inertial igniters that provide no-fire safety for the aforementioned drops from heights of up to 40 feet.
In the case of munitions that are fired by rifled gun barrels or are provided with other means of being spin accelerated during firing to certain barrel exit linear velocity as well as spin rate, or the so-called spin-stabilized munitions, the munitions is subjected simultaneously to both a linear setback acceleration profile as well as a spin acceleration profile. However, when munitions are subjected to accidental drops, even from great heights, or nearby explosions or the like, it is impossible for them to be subjected simultaneously to both high firing setback induced linear as well as spin accelerations. In the present invention, this characteristic of spin stabilized munitions of various kinds is used to develop methods to design inertial igniters and to construct inertial igniters that require to detect the prescribed all-fire setback induced spin acceleration as well as linear accelerations for initiation.
A schematic of a cross-section of a conventional thermal battery and inertial igniter assembly is shown in
The basic design of the currently available inertial igniters for satisfying the safety (no initiation) requirement when dropped from heights of up to 7 feet (up to 2,000 G impact deceleration with a duration of up to 0.5 msec) is described below using one such embodiment disclosed in U.S. Pat. No. 8,550,001, the contents of which is incorporated herein by reference. An isometric cross-sectional view of this embodiment 200 of the inertia igniter is shown in
A striker mass 205 is shown in its locked position in
In its illustrated position in
The collar 211 can ride up and down the posts 203 as can be seen in
In this embodiment, a one part pyrotechnics compound 215 (preferably lead styphnate base pyrotechnic material or some other similar compound) is used as shown in
Alternatively, a two-part pyrotechnics compound, e.g., potassium chlorate and red phosphorous, may be used. When using such a two-part pyrotechnics compound, the first part, in this case the potassium chlorate, is preferably provided on the interior side of the base in a provided recess, and the second part of the pyrotechnics compound, in this case the red phosphorous, is provided on the lower surface of the striker mass surface facing the first part of the pyrotechnics compound. In general, various combinations of pyrotechnic materials may be used for this purpose and with an appropriate binder to firmly adhere the materials to the inertial igniter (metal) surfaces.
Alternatively, instead of using the pyrotechnics compound 215,
Alternatively, the percussion primer or the directly loaded pyrotechnic material may be applied to the striker element and the inertial igniter base be provided with the appropriately shaped tip to initiate ignition as previously described.
The basic operation of the embodiment 200 of the inertial igniter of
If the acceleration time profile is at or higher than its specified all-fire magnitude and duration thresholds, the collar 211 will have translated down passed the locking balls 207, allowing the striker mass 205 to accelerate down towards the base 202. In such a situation, since the locking balls 207 are no longer constrained by the collar 211, the downward force that the striker mass 205 has been exerting on the locking balls 207 will force the locking balls 207 to move outward in the radial direction. Once the locking balls 207 are out of the way of the dimples 209, the downward motion of the striker mass 205 is no longer impeded. As a result, the striker mass 205 accelerates downward, causing the tip 216 of the striker mass 205 to strike the pyrotechnic compound 215 on the surface of the protrusion 217 with the requisite energy to initiate ignition.
In the embodiment 200 of the inertial igniter shown in
In the embodiment 200 of
Alternatively, as described in the aforementioned previous art, side ports may be provided to allow the flame to exit from the side of the igniter to initiate the pyrotechnic materials (or the like) of a thermal battery or the like that is positioned around the body of the inertial igniter. Other alternatives known in the art may also be used.
In
The inertial igniter 200,
It will be appreciated by those skilled in the art that by varying the mass of the striker 205, the mass of the collar 211, the spring rate of the setback spring 210, the distance that the collar 211 has to travel downward to release the locking balls 207 and thereby release the striker mass 205, and the distance between the tip 216 of the striker mass 205 and the pyrotechnic compound 215 (and the tip of the protrusion 217), the designer of the inertial igniter 200 can try to match the all-fire and no-fire impulse level requirements for various applications as well as the safety (delay or dwell action) protection against accidental dropping from relatively short distances such as from 5-7 feet of the inertial igniter and/or the munitions or the like within which it is assembled.
Briefly, the safety system parameters, i.e., the mass of the collar 211, the spring rate of the setback spring 210 and the dwell stroke (the distance that the collar 210 must travel downward to release the locking balls 207 and thereby release the striker mass 205) must be tuned to provide the required actuation performance characteristics. Similarly, to provide the requisite impact energy, the mass of the striker 205 and the separation distance between the tip 216 of the striker mass and the pyrotechnic compound 215 (and the tip of the protrusion 217) must work together to provide the specified impact energy to initiate the pyrotechnic compound when subjected to the remaining portion of the prescribed initiation acceleration profile after the safety system has been actuated.
The currently available inertial igniters, including the prior art inertial igniters of
In the case of munitions that are fired by rifled gun barrels or are provided with other means of being spin accelerated during firing to certain barrel exit linear velocity as well as spin rate, or the so-called spin-stabilized munitions, the munitions is subjected simultaneously to both a linear setback acceleration profile as well as a spin acceleration profile. However, when munitions are subjected to accidental drops, even from great heights, or nearby explosions or the like, it is impossible for them to be subjected simultaneously to both high firing setback induced linear as well as spin accelerations. This characteristics of the firing of spin stabilized munitions of various kinds is used to develop the following methods for the design of inertial igniters and electrical switches and for the construction of inertial igniters and electrical switches that are required to detect the prescribed all-fire setback induced and simultaneous spin acceleration as well as linear accelerations for initiation, thereby also making then satisfy the required no-fire 40 feet drops, which could subject the inertial igniters and electrical switches to acceleration of up to 18,000 Gs in the direction of their activation for up to and possibly over 1 millisecond.
In the following inertial igniter and electrical switch embodiments of the present invention, the methods used for the development of the inertial igniter and electrical switch mechanisms are based on using either the firing setback induced linear or spin acceleration event to arming the device (enabling the device for activation) and use the other to initiate the device. That is, if setback induced linear acceleration is used to arm (enable) the device (either the inertial igniter or the electrical switch), then the spin acceleration is used for initiation (activation). On the other hand, if setback induced spin acceleration is used to arm (enable) the device (either the inertial igniter or the electrical switch), then the linear acceleration is used for initiation (activation).
A need therefore exists for methods to design mechanical inertial igniters that could satisfy high-height drop safety (no-fire) requirements while satisfying relatively low all-fire firing (setback) acceleration requirement.
A need also exists for methods to design mechanical inertial igniters that would initiate only when subjected simultaneously to firing setback induced spin and linear acceleration and do not initiate when subjected any of the aforementioned no-fire events.
A need also exists for mechanical inertial igniters that are developed based on the above methods and that can satisfy the safety requirement of drops from high-heights of up to 40 feet that could generate impact induced deceleration rates of up to 18,000 Gs or even higher over a duration of 1 millisecond or higher.
Accordingly, methods are provided that can be used to design fully mechanical inertial igniters that can satisfy high-height drop safety (no-fire) requirements for munitions fired from rifled gun barrels, i.e., munitions that are spin accelerated during firing, while satisfying relatively low all-fire firing (setback) acceleration level requirement. In addition, several embodiments are also provided for the design of such high-height-drop-safe inertial igniters for use in gun-fired munitions, mortars and the like.
An inertial igniter that combines such a safety system with an impact based initiation system and its alternative embodiments are described herein together with alternative methods of pyrotechnics initiation.
Such inertial igniters may be used to initiate reserve batteries such as thermal batteries and liquid reserve batteries as well as various initiation trains.
The methods to design fully mechanical mechanisms are particularly suitable for inertial igniters, but may also be used in other similar applications, for example as so-called electrical G-switches that open (or close) an electrical circuit only when the device is subjected the prescribed simultaneous setback induced linear and spin acceleration profile threshold. Here, it is appreciated that the setback acceleration profile threshold to for inertial igniter and G-switch activation consists of a prescribed acceleration magnitude threshold as well as a prescribed duration threshold of the prescribed acceleration magnitude threshold. It is therefore appreciated by those skilled in the art that the electrical switch embodiments of the present invention activate upon sensing of the setback acceleration induced impulse and not just its acceleration magnitude and a more appropriate name for them being “impulse-Switch”. However, hereinafter and for the sake of avoiding confusion by current users of, the terms “G-switch” is used to also indicate the “Impulse-Switch”.
Also disclosed are several inertial igniter embodiments that combine such mechanical mechanisms (safety systems) with impact based initiation systems. Also disclosed are several electrical G-switches that open (or close) an electrical circuit only when the device is subjected the prescribed simultaneous setback induced linear and spin acceleration profile threshold.
A need also therefore exists for the development of novel methods and resulting mechanical G-switches for use in gun fired munitions, small rockets or other similar applications that can be used to open (close) a normally closed (open) electrical circuitry or the like upon the device using such G-switch experiencing a prescribed simultaneous setback induced linear and spin acceleration profile threshold. Such G-switches must occupy relatively small volumes and do not require external power sources for their operation.
In many gun-fired munitions and other similar applications, such G-switches must not operate when dropped, e.g., from up to 40 feet onto a hard ground (generally corresponding to acceleration levels of up to 2,000 G for a duration of up to 0.5 msec) for certain applications, and from up to 40 feet (generally corresponding to acceleration levels of up to 18,000 G for a duration of up to 1 msec) for certain other applications.
Accordingly, methods are provided that can be used to design fully mechanical G-switches that can satisfy high-height drop safety (no-fire) requirements for munitions fired from rifled gun barrels, i.e., munitions that are spin accelerated during firing, while satisfying relatively low all-fire firing (setback) acceleration level requirement. In addition, several embodiments are also provided for the design of such high-height-drop-safe inertial igniters for use in gun-fired munitions, mortars and the like.
It is, therefore, highly desirable to develop inertial igniters that are smaller in height and also preferably in volume for thermal batteries in general and for small thermal batteries in particular. This is particularly the case for inertia igniters for gun-fired munitions that experience high G firing setback accelerations levels, e.g., setback acceleration levels of 10-30,000 Gs or even higher, since such thermal batteries would have significantly higher no-fire and all-fire acceleration requirements, which should allow the development of inertial igniters that are smaller in height and possibly even in volume.
A need therefore exists for novel miniature mechanical inertial igniters for reserve batteries such as thermal batteries and liquid reserve batteries and for initiation trains used in gun-fired munitions, mortars, rockets and the like, particularly for small and low power reserve batteries that could be used in fuzing and other similar applications, that are safe (i.e., do not initiate) when dropped from relatively high-heights, such as up to 40 feet. Dropping from heights of up to 40 feet have been shown that can subject the device to impact deceleration levels of up to 18,000 Gs with the duration of up to and sometimes over 1 msec. Such innovative inertial igniters are highly desired to be scalable to reserve batteries and initiation trains of various sizes, in particular to miniaturized inertial igniters for small size thermal batteries. Such inertial igniters are generally also required not to initiate if dropped from heights of up to 7 feet onto a concrete floor, which can result in impact induced inertial igniter decelerations of up to of 2000 G that may last up to 0.5 msec. The inertial igniters are also generally required to withstand high firing accelerations, for example up to 20-50,000 Gs (i.e., not to damage the thermal battery); and should be able to be designed to ignite at specified acceleration levels when subjected to such accelerations for a specified amount of time based on the firing acceleration profile. High reliability is also of much concern in inertial igniters. In addition, the inertial igniters used in munitions are generally required to have a shelf life of better than 20 years and could generally be stored at temperatures of sometimes in the range of −65 to 165 degrees F. This requirement is usually satisfied best if the igniter pyrotechnic is in a sealed compartment. The inertial igniter designs must also consider the manufacturing costs and simplicity in the designs to make them cost effective for munitions applications.
To ensure safety and reliability, inertial igniters should not initiate during acceleration events which may occur during manufacture, assembly, handling, transport, accidental drops, etc. Additionally, once under the influence of an acceleration profile particular to the firing of ordinance from a gun, the device should initiate with high reliability. It is also conceivable that the igniter will experience incidental low but long-duration accelerations, whether accidental or as part of normal handling, which must be guarded against initiation. Again, the impulse given to the miniature inertial igniter will have a great disparity with that given by the initiation acceleration profile because the magnitude of the incidental long-duration acceleration will be quite low.
Those skilled in the art will appreciate that the inertial igniters disclosed herein may provide one or more of the following advantages over prior art inertial igniters:
provide inertial igniters that are safe when dropped from very high-heights of up to 40 feet;
provide inertial igniters that allow the use of standard off-the-shelf percussion cap primers or commonly used one part or two part pyrotechnic components;
provide inertial igniters that can be sealed to simplify storage and increase their shelf life; and
provide inertial igniters that must simultaneously detect firing setback induced spin as well as linear acceleration for activation.
Accordingly, inertial igniters for use with reserve batteries such as thermal batteries and liquid reserve batteries for producing power as well as for igniting initiation trains upon a specified acceleration profile are provided.
These and other features, aspects, and advantages of the apparatus of the present invention will become better understood with regards to the following description, appended claims, and accompanying drawings where:
A schematic of a cross-sectional view of a first embodiment 300 of an inertial igniter is shown in
In the embodiment 300, the inertial igniter body 303, which can be integral to the base element 302, is provided with a cylindrical open compartment 308, which can have a circular cross-section, and which extends to or close to the base element 302, the bottom surface of the open compartment 308 is indicated by numeral 309 in
The striker mass 305 has a main cylindrical body with a top portion 306 with at least one end 307, which are shaped to ride in the guides 304 of the inertial igniter structure body 303 as shown in
In addition, in
The striker mass 305 can be provided with a relatively sharp tip 311 and the cylindrical open compartment 308 bottom surface 309 can be provided with a protruding tip 312, which is covered with a pyrotechnics compound 313, such that as the striker mass 305 is released during an all-fire event and is accelerated down, impact occurs mostly between the surfaces of the tips 311 and 312, thereby pinching the pyrotechnics compound 313, thereby providing the means to obtain a reliable initiation of the pyrotechnics compound 313.
Alternatively, a two-part pyrotechnics compound, e.g., potassium chlorate and red phosphorous, may be used. When using such a two-part pyrotechnics compound, the first part, in this case the potassium chlorate, can be provided on the interior side of the base in a provided recess, and the second part of the pyrotechnics compound, in this case the red phosphorous, can be provided on the lower surface of the striker mass surface facing the first part of the pyrotechnics compound. In general, various combinations of pyrotechnic materials may be used for this purpose and with an appropriate binder to firmly adhere the materials to the inertial igniter (metal) surfaces.
Alternatively, instead of using the pyrotechnics compound 313,
Alternatively, the percussion primer or the directly loaded pyrotechnic material may be applied to the striker element 305 and the bottom surface 309 can be provided with the appropriately shaped tip to initiate ignition as previously described.
On a top surface 314 of the inertial igniter body 303, a support element 315 is provided and to which one end of a tensile spring (elastic) element 316 is attached. The other end of said tensile spring 316 is attached to a U-shaped holding member 318 inside which one end 307 of the top portion 306 of the striker mass 305 is held as shown in
The tensile spring 316 may be preloaded in tension so that it would resist a prescribed level of toque applied to the striker mass 305 in the direction perpendicular to the plane of
In the schematic of
It will be appreciated by those skilled in the art that instead of the tensile spring 316 shown in
It will be appreciated that the inertial igniter 300 is usually packaged in the thermal battery or any other device within a space which provides a rigid stop 319,
The basic operation of the inertial igniter embodiment 300 of
In addition, if the inertial igniter is subjected to a spin acceleration in the clockwise direction about its long axis (perpendicular to the plane of the
However, if the inertial igniter is subjected to a spin acceleration in the counterclockwise direction about its long axis, assuming no friction between the surfaces of the striker mass 305 and the inertial igniter body 303, in the absence of the spring 316 (
However, if the spin acceleration applied to the inertial igniter body in the counterclockwise direction is high enough for the resulting resisting inertial torque of the striker mass 305 to overcome the tensile preloading force of the spring 316, then the tensile spring 316 will begin to extend, thereby allowing the striker mass 305 to rotate in the clockwise direction relative to the inertial igniter body 303. If the spin acceleration magnitude is at or above the prescribed threshold and continues for its prescribed duration threshold, then the tensile spring 316 would be extended long enough to allow counterclockwise rotation of the striker mass 305 relative to the inertial igniter body 303 to position the tips 307 of the striker mass 305 over the guides 304 of the inertial igniter body 303. As can be seen in the top view of
It will be appreciated by those skilled in the art that once the tips 307 of the striker mass 305 are positioned over the guides 304 of the inertial igniter body 303, then the striker mass 305 is free to move down the cylindrical open compartment 308 of the inertial igniter body 303 towards the base 302. The inertial igniter 300 is therefore considered to be armed (enabled) to respond to the linear setback acceleration and ignite the pyrotechnic material 313 as previously described.
Once the inertial igniter 300 is armed (enabled) by the applied spin acceleration of magnitude and duration corresponding to the prescribed all-fire setback induced spin acceleration profile threshold, the setback linear acceleration would accelerate the striker mass 305 downward and cause the tip 311 of the striker mass to impact the pyrotechnic covered protruding tip 312 of the bottom surface 309 of the cylindrical open compartment 308, thereby pinching the pyrotechnics compound 313, thereby initiating the pyrotechnics compound 313. Following ignition of the pyrotechnics compound 313, the generated flames and sparks are designed to exit downward through the opening 324 to initiate the pyrotechnic materials of the thermal battery or any other pyrotechnic or similar material below.
It will be appreciated by those skilled in the art that once the inertial igniter 300 is armed by the spin acceleration of magnitude and duration corresponding to the prescribed all-fire setback induced spin acceleration profile threshold, the magnitude of the linear (setback) acceleration (in the direction of the arrow 320) must be high enough so that as the striker mass 305 is accelerated down towards the base 302 of the inertial igniter it would gain enough speed and thereby kinetic energy to ignite the pyrotechnic compound 313 as the striker mass tip 311 impacts the pyrotechnic compound covering the protruding tip 312 of the bottom surface 309.
It will be appreciated by those skilled in the art that the aforementioned spin acceleration threshold required to arm (enable) the inertial igniter 300 of
In one modified inertial igniter embodiment 300 of
In an alternative modification of the inertial igniter embodiment 300 of
It will be appreciated by those skilled in the art that the springs 325 and 327 shown in
It will also be appreciated by those skilled in the art that as can be seen in the schematic of
In the inertial igniter embodiment 300 of
The schematic of the cross-sectional view of a second embodiment 330 of the inertial igniter which is designed for reliable inertial igniter initiations for munitions with short duration firing setback acceleration profiles is shown in
If a spin acceleration is applied to the inertial igniter body 303 in the counterclockwise direction (as indicated by the direction of the arrows 321 and 322 in
It will be appreciated by those skilled in the art that in cases in which the setback acceleration duration is long enough such that after the inertial igniter embodiment 330 of
The inertial igniter embodiment 300 of
In the above embodiments, following ignition of the pyrotechnics compound 313,
Alternatively, side ports may be provided in the inertial igniter body 303 instead of the opening 324,
The inertial igniter embodiments of
The construction and operation of the resulting electrical “G-switches” is identical to those of the inertial igniter embodiments of
The schematic of one G-switch embodiment 340 constructed based on the design of the inertial igniter embodiment 300 of
The close-up view of the contact element 334 is shown in the schematic of
In applications in which the G-switch 340 is attached, for example, to a printed circuit board, the electrically non-conducting base 339 can be mounted over a provided opening (similar to the opening 324,
The close-up view of the contact element 335 is shown in the schematic of
The electrical G-switch 340 operates in a manner like the inertial igniter 300 of
In addition, if the G-switch embodiment 340 (inertial igniter in
However, if the G-switch is subjected to a spin acceleration in the counterclockwise direction about its long axis, assuming no friction between the surfaces of the striker mass 305 and the inertial igniter body 303, in the absence of the spring 316 (
However, if the spin acceleration applied to the inertial igniter body in the counterclockwise is high enough for the resulting resisting inertial torque of the striker mass 305 to overcome the tensile preloading force of the spring 316, then the tensile spring 316 will begin to extend, thereby allowing the striker mass 305 to rotate in the clockwise direction relative to the G-switch (inertial igniter) body 303. If the spin acceleration magnitude is at or above the prescribed threshold and continues for its prescribed duration threshold, then the tensile spring 316 would be extended long enough to allow counterclockwise rotation of the striker mass 305 relative to the G-switch (inertial igniter) body 303 to position the tips 307 of the striker mass 305 over the guides 304 of the inertial igniter body 303. As can be seen in the top view of
It will be appreciated by those skilled in the art that once the tips 307 of the striker mass 305 are positioned over the guides 304 of the G-switch (inertial igniter) body 303, then the striker mass 305 is free to move down the cylindrical open compartment 308 of the G-switch body 303 towards the base 302. The G-switch 340 is therefore considered to be armed (enabled) to respond to the linear setback acceleration.
Once the G-switch 340 is armed (enabled) by the applied spin acceleration of magnitude and duration corresponding to the prescribed all-fire setback induced spin acceleration profile threshold, the setback linear acceleration would accelerate the striker mass 305 downward and cause the electrically conductive contact strip 345 of contact element 335 to come into contact with the at least two contacts 337 and 338 of the contact element 334,
It will be appreciated by those skilled in the art that in the G-switch embodiment 340 of
The schematic of the resulting latching normally open G-switch (in its open state), indicated as the embodiment 350, is shown in
It will be appreciated by those skilled in the art that the level of preloading of the compressive spring 329 must be high enough so that during the firing set-forward and when the munitions or the like is subjected to incidental acceleration and deceleration levels such as due to transportation vibration, contact between the electrically conductive contact strip 345 of contact element 335 and the at least two contacts 337 and 338 of the contact element 334,
It is also appreciated by those skilled in the art that the aforementioned spin acceleration threshold required to arm (enable) the G-switch 340 and 350 of
For the case of the G-switch embodiment 350 of
The For the case of the G-switch embodiment 340 of
It will also be appreciated by those skilled in the art that numerous other return spring designs and configurations are also possible and those illustrated in the schematic of
It will also be appreciated by those skilled in the art that as can be seen in the schematic of
The G-switch embodiments 340 and 350 of
It will be appreciated by those skilled in the art that in the above inertial igniter and G-switch embodiments of the present invention the spin acceleration is considered to be applied about or close to the axis of symmetry of the device (effectively the longitudinal axis of rotation of the striker mass 305 relative to the device body 303). This would obviously occur only when the device axis of symmetry is coincident or close to the spin axis of the munitions. Otherwise the inertial igniter and G-switch will also be subjected to centrifugal force due to centripetal acceleration. The main effect of centrifugal force on the inertial igniter and G-switch embodiments of the present invention would be to press the surface of the striker mass 305 against the surface 310 of the cylindrical open compartment 308,
In general, there are three basic methods that can be used to reduce the level of generated resisting torque. Firstly, the contacting surfaces may be coated or provided by a layer of low friction material such as Teflon or other such materials or lubricants such as graphite. This method can also be used to reduce friction between the top surface 314 of the device body 303,
In the modifications to the above inertial igniter and electrical G-switch embodiments shown in the cross-sectional view of
While there has been shown and described what is considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.
This application claims benefit to U.S. Provisional Patent Application No. 62/438,983 filed on Dec. 23, 2016, the entire contents of which is incorporated herein by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 1956223 | Methlin | Apr 1934 | A |
| 2458474 | Jordan | Jan 1949 | A |
| 4738201 | Holt | Apr 1988 | A |
| 8869700 | Rastegar | Oct 2014 | B2 |
| Number | Date | Country |
|---|---|---|
| 366810 | Oct 1906 | FR |
| 731949 | Sep 1932 | FR |
| 130659 | Aug 1919 | GB |
| Entry |
|---|
| Machine Translation of FR 366,810 (Year: 1906). |
| Number | Date | Country | |
|---|---|---|---|
| 20180180393 A1 | Jun 2018 | US |
| Number | Date | Country | |
|---|---|---|---|
| 62438983 | Dec 2016 | US |
