Abstract
A method for initiating a thermal battery including: releasing an engagement between an element and a striker mass upon an acceleration time and magnitude greater than a first threshold; and moving at least one member into a path of the element to prevent the element from releasing the striker mass only where the acceleration time and magnitude is greater than a second threshold, the second threshold being greater than the first threshold.
Claims
1. A method for initiating a thermal battery, the method comprising: releasing an engagement between an element and a striker mass upon an acceleration time and magnitude greater than a first threshold such that the striker mass is movable towards one of a percussion cap or pyrotechnic material; and moving at least one member into a path of the element to prevent the element from releasing the striker mass only where the acceleration time and magnitude is greater than a second threshold, the second threshold being greater than the first threshold.
2. The method of claim 1, wherein the moving comprises translating the at least one member into the path.
3. The method of claim 1, wherein the moving comprises rotating the at least one member into the path.
4. The method of claim 1, further comprising returning the at least one member from the path when the acceleration time and magnitude lowers from the second threshold.
5. The method of claim 1, further comprising maintaining the at least one member in the path after the acceleration time and magnitude reaches the second threshold.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) These and other features, aspects, and advantages of the apparatus of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:
(2) FIG. 1 illustrates a schematic of a cross-section of a thermal battery and inertial igniter assembly.
(3) FIG. 2 illustrates a schematic of a cross-section of an inertial igniter for thermal battery described in the prior art.
(4) FIG. 3 illustrates a schematic of the isometric drawing of the inertial igniter for thermal battery of FIG. 2.
(5) FIG. 4a illustrates a schematic of a cross-section of a thermal battery with an inertial igniter positioned on the top portion of the thermal battery and in which the ignition generated flame to be directed downwards into the thermal battery compartment.
(6) FIG. 4b illustrates a schematic of a cross-section of a thermal battery with an inertial igniter positioned on the bottom portion of the thermal battery and in which the ignition generated flame to be directed upwards into the thermal battery compartment.
(7) FIG. 5 illustrates a schematic of cross-section of an inertial igniter for thermal battery described in prior art with an outer housing.
(8) FIG. 6 illustrates a schematic of the basic components used to describe the operation of currently available mechanical inertial igniters with 7 feet drop safety mechanism.
(9) FIG. 7 illustrates a schematic of the basic inertial igniter design of FIG. 6 as the all-fire condition is reached and the striker mass is released.
(10) FIG. 8 illustrates a schematic of the basic components used to describe the operation of currently available mechanical inertial igniters with 7 feet drop safety mechanism with the added “deployable locking mechanism” for providing for safety (no initiation) for high-height drops from up to 40 feet.
(11) FIG. 9 illustrates a schematic of the basic inertial igniter of FIG. 8 following a high-height drop with deployed initiation blocking “deployable locking mechanism”.
(12) FIG. 10 illustrates a schematic of the basic inertial igniter of FIG. 8 with a modified high-height drop with deployed initiation blocking “deployable locking mechanism” that would prevent inertial igniter initiation once a high-height drop event has occurred.
(13) FIG. 11 illustrates a schematic of the state of the inertial igniter of FIG. 10 following a high-height drop event.
(14) FIG. 12 illustrates a schematic of the basic components used to describe the operation of currently available mechanical inertial igniters with 7 feet drop safety mechanism with an added “toggle” type deployable locking mechanism for providing for safety (no initiation) for high-height drops from up to 40 feet.
(15) FIG. 13 illustrates a schematic of the basic components used to describe the operation of currently available mechanical inertial igniters with 7 feet drop safety mechanism with an added deforming deployable locking mechanism for providing for safety (no initiation) for high-height drops from up to 40 feet.
(16) FIG. 14 illustrates a schematic of the basic inertial igniter of FIG. 13 following a high-height drop with deployed initiation blocking “deployable locking mechanism”.
(17) FIG. 15 illustrates a schematic of a deforming multi-deployable-locking-mechanism that is constructed as a complete ring for positioning around the inertial igniter as shown in FIG. 17.
(18) FIG. 16 illustrates the cross-sectional view A-A of one of the deployable locking mechanisms of the embodiment of FIG. 15.
(19) FIG. 17 illustrates a schematic of the isometric drawing of a possible modification of the striker mass locking collar of the inertial igniter of FIGS. 2 and 3 to allow for integration of a deployable locking mechanism.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
(20) Referring now to the schematic of FIG. 6, which is used to describe basic mechanism used in currently available mechanical inertial igniters to satisfy safety (no initiation) requirement for drops from heights of up to 7 feet over a concrete floor (resulting in up to 2,000 G of impact deceleration of the inertial igniter structure over up to 0.5 msec). The basic mechanical inertial igniters are provided with a striker mass 301, which when free, can slide down against the surface 303 of the inertial igniter structure 302. Before being activated, the striker mass 301 is held fixed to the inertial igniter structure 302 by the mechanically interfering element (in the schematic of FIG. 6, the ball) 304, which engages the striker mass 301 in the provided dimple 305. In this state, the ball 304 rests against the surface 306 of the element 307, thereby it is prevented from disengaging the element 301, i.e., to move to the right and out of the dimple 305. The element 307 is free to slide along the surface 308 of the inertial igniter structure 302. The element 307 is also attached to the inertial igniter structure 302 via the spring element 309, which is attached to the element 307 on one side and to the inertial igniter structure 302 on the other side. The direction of the firing acceleration (setback) is considered to be as indicated by the arrow 310. If the inertial igniter is dropped from a certain height, e.g., from the aforementioned 7 feet over a concrete floor and strike the floor while vertically oriented as shown in FIG. 6, the resulting impact causes the inertial igniter to be decelerated (accelerated in the direction of the arrow 310). Following impact, the element 307 is decelerated from its initial (downward) velocity at the time of impact at a rate proportional to the ratio of the (instantaneous upward) force applied to the element 307 by the spring element 309 (neglecting friction and other usually incidental forces) and the mass of the element 307. Considering the fact that the spring element 309 may be preloaded in compression, the motion of the element 307 relative to the structure of the inertial igniter is determined by the net (external) force acting on the element 307. If the level of said deceleration stays high enough and act over long enough period of time, then the element 307 moves down enough to allow the locking ball 304 to be pushed out of the dimple 305 by the dynamic force acting on the inertial of the striker mass 301 as shown in FIG. 7. The striker mass 301 is then accelerated downward, causing the pyrotechnic elements 311 and 312 (alternatively one part pyrotechnic material 312 and the striker tip 311) to impact and initiate the igniter. Otherwise, if the inertial igniter impact induced deceleration ends before the striker mass 301 is released, the element 307 is pushed back up to its pre-impact position by the spring element 309, securing the striker mass 301 via the locking ball 304. Similar excursions of the element 307 may occur during transportation induced movements (acceleration/deceleration cycles applied to the inertial igniter) without causing the striker mass 301 to be released. The safety requirements for inertial igniter transportation and drops from heights of up to 7 feet over concrete floor are designed to be satisfied as previously discussed by selecting appropriate values for the mass of the element 307, the level of preloading of the spring element 309 and its rate, and the distance that the element 307 has to travel down before the locking ball 304 is released.
(21) It is noted that in practice, the upward motion of the element 307 is usually constrained (preferably mechanically) so that the spring element 309 could be preloaded in compression.
(22) The present exemplary devices and methods set forth below can be used to design inertial igniters and the like that can overcome the shortcomings of the prior art, i.e., that can satisfy the safety (no initiation) requirement of drops from heights of up to 40 feet (which can generate impact deceleration levels of up to 18,000 Gs with durations of up to 1 msec) for gun-fired munitions, mortars and the like with relatively low firing (setback) acceleration levels (for example, in the range of 900-3000 Gs—usually lasting around 8-15 msec).
(23) The basic inertial igniter device design shown in the schematic of FIGS. 6 and 7 is used in this illustration (FIG. 8) with added mechanisms (hereinafter called “deployable locking mechanisms”) to be described to arrive at inertial igniters that in addition to satisfying the aforementioned requirements of safety (no initiation) when dropped from 7 feet to concrete floors and safety (no initiation) in response to low levels of relatively long term acceleration and deceleration cycles during transportation or the like, would also satisfy the requirement of safety (no initiation) when dropped from high-heights such as up to 40 feet which could result in up to 18,000 Gs of impact induced deceleration of the inertial igniter structure (FIGS. 7 and 8) with up to 1 msec of duration.
(24) As can be seen in the schematic of FIG. 8, the element 307 is provided with a protruding step 321. It is noted that as it was previously described, that the element 307 serves to prevent the release of the striker mass 301 by preventing the locking ball 304 from moving out of the dimple 305 of the striker mass 301. In the present device and method, a “deployable locking mechanism” is provided that engages the provided step 321 (or other similarly provided motion constraining surface on the element 307) and prevents it from moving down far enough to allow the release of the locking ball 304 when the inertial igniter is subjected to impact induced (or explosion or the like) in the direction parallel to that of the arrow 320 corresponding to drops from high-heights of up to 40 feet (which can generate impact deceleration levels of up to 18,000 Gs with durations of up to 1 msec).
(25) It is appreciated by those skilled in the art that numerous types and designs of mechanical mechanisms may be used for the aforementioned deployable locking mechanism. The only operational requirement for such deployable locking mechanism is that up to a predetermined acceleration threshold it should not deploy, but once the predetermined acceleration threshold has been reached, it should deploy and provide a mechanical stop in the downward path of motion of the element 307 such that it is prevented from moving down far enough to allow the locking ball 304 to disengage the striker mass 301.
(26) It is also appreciated by those skilled in the art that the aforementioned embodiment of the deployment mechanism shown in the schematic of FIG. 8 is exemplary and provided mainly to describe the disclosed method of providing the aforementioned high-drop safety requirements for mechanical inertial igniters.
(27) It is appreciated by those skilled in the art that such “deployable locking mechanisms” may be designed to deploy as a result of other events, such as lateral impact (perpendicular to the direction of the arrow 320). In addition, the inertial igniter may be provided with more than one type of “deployable locking mechanisms” that operate independently and deploy if either one of the considered events occurs.
(28) In the embodiment of FIG. 8, the “deployable locking mechanism” consists of a solid element 331 which is fixed to the inertial igniter 302. The element 331 is provided with an inclined surface 322. A second solid movable element 323 with a matching inclined surface 324 is positioned as shown over the element 331. The inclined surfaces 322 and 324 of the elements 331 and 323 are held in contact, allowing the element 323 to slide up or down along this inclined surface of contact. The element 323 is held in place and is prevented from sliding down along the inclined surfaces of contact by a spring (elastic) element 326, which is attached to the element 323 at one end (such as through a rotary joint 327 or the like) and to the structure of the inertial igniter 302 at the other end (such as through a second rotary joint 328 or the like). The spring element 326 can be preloaded in tension, while the upward movement of element 323 is constrained by the stop 329, which is fixed to the structure of the inertial igniter 302.
(29) The “deployable locking mechanism” works as follows. If the inertial igniter is dropped such that it impacts a solid surface vertically (in a direction parallel to the arrow 320), during the impact, the element 323 is decelerated in the direction the arrow 320 from its initial velocity at the time of impact. The level of deceleration is obviously proportional to the net force acting on the inertia of the element 323. The net decelerating force is due mainly to the components of the force applied by the spring element 326 and the contact (reaction) force between the contacting surfaces 322 and 324 and other (usually incidental) forces such as those generated by friction, in a direction parallel to the direction of the arrow 320. The resisting force offered by the spring element 326 is generated since the spring element 326 is preloaded in tension. As a result, the spring element 326 resists downwards motion of the element 323 due to the presence of inclined surfaces of contact 324 and 322, FIG. 8. Thus, if the aforementioned initial velocity of the element 323 at the time of inertial igniter drop induced impact is high enough (given the slope of the surfaces 324 and 322, the tensile preloading level of the spring 326 and its rate and the level of friction and other said forces acting on the element 323), the resistance of the spring element 326 (and friction between the surfaces 324 and 322) is overcome, and the element 323 begins to slide down the surface 322 of the element 331, causing the element 323 to move down as well as to move towards the left. If the impact induced deceleration level of the inertial igniter is high enough and its duration is long enough, then the element 323 travels down until its bottom surface 330 comes into contact with the surface of the inertial igniter structure 302. By this time, the top surface 325 of the element 323 is positioned under the bottom surface 332 of the protruding portion (step) 321, thereby preventing the element 307 from moving down enough to cause the locking ball 304 to be disengaged from the striker mass 301 as shown in FIG. 9. This scenario obviously assumes that the locking element 323 of the “deployable locking mechanism” moves far enough to the left and under the protruding element 321 by the time the element 307 has moved down enough to interfere with the movement of the locking element 323.
(30) As described above, with the addition of the aforementioned “deployable locking mechanism” as shown in FIGS. 8 and 9, mechanical inertial igniters can be designed to satisfy the safety (no initiation) requirement of drops from heights of up to 40 feet (which can generate impact deceleration levels of up to 18,000 Gs with durations of up to 1 msec) for gun-fired munitions, mortars and the like, when the firing (setback) acceleration levels are relatively low (for example, in the range of 900-3000 Gs—usually lasting around 8-15 msec). It is noted that the design parameters provided by the aforementioned “deployable locking mechanism” include the geometries of the elements 323, 331 and the protrusion 321; the inertia of the element 323 and its distance 333 (FIG. 8) from the inertial igniter structure 302; and the attachment points, length and rate of the spring element 326. A few examples showing how a wide range of all-fire and no-fire requirements as well as the above high-height drop requirements can be satisfied are provided below.
(31) As an example, consider a typical situation in which the firing (setback) acceleration is around 3,000 Gs and lasts up to 4 msec, which constitutes the all-fire acceleration requirement for the inertial igniter; and the no-fire requirements (in addition to the low G accelerations and decelerations due to transportation and other similar events) to be 2,000 Gs with a duration of 0.5 msec (for drops from up to 7 feet over concrete surfaces) and 18,000 Gs with a duration of 1 msec (for drops from up to 40 feet). The basic embodiment shown in FIGS. 8 and 9 can readily satisfy these all-fire and no-fire requirements with the following design parameters, noting that these parameter values are provided only for the sole purpose of illustrating how the disclosed method can be used to design inertial igniters that can satisfy a wide range of present all-fire and no-fire requirements and noting that the selected parameters do not represent their optimal values. The spring element 309 of the striker mass 301 release element 307 (FIGS. 8 and 9) is provided with a compressive preload corresponding to a force acting on the element 307 that is generated when an acceleration of 2,500 Gs acts on the inertia of the element 307. This means that for inertial igniter accelerations of up to 2,500 Gs acting in the direction of the arrow 320, the net force acting on the element 307 is upwards, i.e., does not cause the element 307 to begin to translate downwards relative to the inertial igniter structure (in the direction of releasing the locking ball 304). In addition, the spring element 326 of the deployable locking mechanism is preloaded in tension corresponding to a force acting on the element 323 that is generated when an acceleration of 3,000 Gs acts on the inertia of the element 323 and causing it to begin to slide down on the surface 322 of the fixed element 331. This means that for inertial igniter accelerations of up to 3,000 Gs acting in the direction of the arrow 320, the net force acting on the element 323 in the lateral direction is positive towards the right (as observed in FIGS. 8 and 9), i.e., the direction of preventing the element 323 from beginning to move to the left (in the direction of blocking full downward translation of the element 307 to release the locking ball 304).
(32) Now if the no-fire condition of 7 feet drops over concrete floors (2,500 Gs) occurs, the aforementioned 2,500 G level of preloading of the spring element 309 prevents the element 307 from beginning to move and thereby rendering the inertial igniter safe to the said required 7 feet drops over concrete floors. On the other hand, if the all-fire acceleration of 3,000 G is experienced by the inertial igniter, at the 2,500 G level, the element 307 begins to move down (acted upon by a net equivalent acceleration level of 500 Gs (i.e., 3,000−2,500=500 Gs), thereby if the 3,000 G firing (setback) acceleration is applied over long enough period of time, then the element 307 travels down enough to release the striker mass 301 by allowing the locking ball 304 to move out of the dimple 305. The striker mass is then accelerated down, causing the pyrotechnics components 311 and 312 (FIG. 6) to impact and thereby initiate the thermal battery. It is noted that the aforementioned firing acceleration duration of 4 msec can be readily shown to be well beyond the firing acceleration (setback) duration needed allow the above process to be completed.
(33) Now consider the event in which a munitions containing the inertial igniter described in FIGS. 8 and 9 is dropped from a height of 40 feet (resulting in an impact induced deceleration of the inertial igniter of the around 18,000 Gs for a duration of 1 msec). In this situation, the striker mass releasing element 307 and the deployable locking mechanism element 323 are decelerated from the same initial velocities. In addition, both elements begins their downward translation nearly at the same time and very quickly following the impact time since the 18,000 G of impact induced acceleration is generally reached in a very small fraction of the total acceleration duration of up to 1 msec. As a result, both elements 307 and 323 translate downward with nearly the same velocity profiles. However, since the element 323 requires only a small downward translation to move under the protruding portion 321 of the element 307 to prevent it from moving down enough to release the locking ball 304, therefore it would always move to the latter “locking” position and prevent the striker mass from being released and initiate the thermal battery. In fact, noting that the downward acceleration of the element 307 is approximately 500 Gs (3,000−2,500=500 Gs) higher than the downward acceleration of the element 323, thereby the element 307 closes its distance to the element 323 (indicated here as distance d.sub.o) over the time t described by the relationship
d.sub.o=(½)(500 G×9.8m/s.sup.2/G)t.sup.2 (1)
and for a maximum duration of t=1 msec for the aforementioned impact induced acceleration level of 18,000 Gs, the above distance d.sub.o is reduced by d.sub.o=2.45 mm. Thus, for example, if the element 323 has to move downwards less than 2.45 mm before being positioned below the bottom surface of the protrusion 321 of the element 307, the deployable locking mechanism illustrated in the schematics of FIGS. 8 and 9 would block the element 323 from releasing the striker mass 301, i.e., from initiating the inertial igniter. And considering the fact that the inertial igniter can be readily designed such that the element 323 has to translate down a relatively small distance before it is positioned below the protruding portion 321 of the element 307, it is seen that by selecting proper parameters for the aforementioned components of the inertial igniter and the present deployable locking mechanism, the inertial igniter can be rendered safe to the aforementioned high-height drops of up to 40 feet.
(34) It is appreciated by those skilled in the art that in the above example, the aforementioned equivalent preloading level of the element 323 only needs to be higher than that of the equivalent preloading level of the element 307 and does not have to be as high as 500 Gs. However, in practice, this difference can be selected to be high enough to ensure reliability of the operation of the high-height drop mechanism.
(35) It is also appreciated by those skilled in the art that as long as the equivalent preloading level of the element 323 is higher than that of the equivalent preloading level of the element 307, the high-height drop mechanism would operate properly to prevent initiation of the inertial igniter and in turn the thermal battery irrespective of the firing (setback) acceleration level and its duration (i.e., the all-fire condition). For example, the all-fire acceleration level may be 900 G, 2500 G, or 8,000 Gs, etc., with durations in the range of 4-16 msec and the inertial igniter will still be high-height drop safe (it is noted that when the all-fire setback acceleration is below 2,000 Gs with relatively long duration—usually over 8 msec—then the safety requirement for 7 feet drop over concrete floor, which results in up to 2,000 Gs of acceleration over up to 0.5 msec duration, is satisfied by the longer time (i.e., more than 0.5 msec) that the element 307 would require to translate down enough to allow the locking balls 304 to move and allow the striker mass 301 to be released—as described in the above-listed patents and patent applications.
(36) It is also appreciated by those skilled in the art that the “two sliding block” (blocks 323 and 331) mechanism used in the embodiment 320 of FIGS. 7 and 8) is only one out of numerous possible mechanical mechanism types that can be used to achieve the required aforementioned functionality of a “deployable locking mechanism”. In general, these mechanism types can be classified as follows, and with each class of such “deployable locking mechanisms” providing the indicated unique operational characteristics that make them advantageous to the indicated operational requirements: 1. A first class of deployable locking mechanisms in which once the predetermined high-height drop level induced (impact) acceleration threshold is reached, the locking mechanism (which is intended to block the release of the striker mass—in the embodiment of FIGS. 8 and 9, the element 307) is deployed and stays deployed even after the said high-height drop induced acceleration event has ended. Such a class of deployable locking mechanisms has the advantage of providing the means of preventing subsequent thermal battery initiation since high-height impacts may have damaged other components of the munitions or the like and render them unsafe if a power source (the thermal battery using the present inertial igniter) could eventually be activated as a result of certain event (for example, the shock of transportation or loading into a gun or even drops from even less than 7 feet heights). 2. A second class of deployable locking mechanisms in which once the predetermined high-height drop level induced (impact) acceleration threshold is reached, the locking mechanism is deployed. However, in contrast with the above first class of deployable locking mechanisms, when the impact induced acceleration drops below a predetermined threshold (which might be different from the aforementioned deployment acceleration threshold), the deployable locking mechanism returns substantially to its pre-deployment (i.e., pre high-drop) state. This class of deployable locking mechanisms has the advantage of providing safety against high-drop impacts, which allowing the munitions and the like to stay operational. This class of deployable locking mechanisms are appropriate for use in inertial igniters that are employed in munitions or the like that are designed not to be substantially damaged following drops from the aforementioned high-heights, thereby posing no safety and/or operational issues following such drops.
(37) In addition, the deployable locking mechanisms corresponding to either one of the above two classes may be provided with the means to allow the user of the thermal battery or the like to determine if the high-impact drop (or any other similar events) has deployed the locking mechanism without the need to disassemble or radiate the thermal battery, and possibly without the need to disassemble the munitions or the like in which the thermal battery is used.
(38) The deployable locking mechanism of the embodiment illustrated in the schematics of FIGS. 8 and 9 belongs to the above second class of mechanisms. In this embodiment, once the impact induced inertial igniter deceleration has ended, the aforementioned dynamic force acting on the element 323 (being in the deployed position shown in FIG. 9) is essentially ended. The element 323 is then pulled back to its original (not deployed) position shown in FIG. 8. This embodiment may, however, be modified such that once the element 323 is fully deployed as shown in FIG. 9, it is then prevented from moving back to its pre-deployment position of FIG. 8. This return motion prevention task can be performed using many different mechanisms, an example of which is in the schematic of FIG. 10. In this schematic, only the elements required to illustrate the said return motion prevention functionality of this embodiment of the present invention are shown.
(39) As can be seen in the schematic of FIG. 10, the element 341 (element 323 in the embodiment of FIGS. 8 and 9) is provided with a protruding portion 342. The element 343 (element 331 in the embodiment of FIGS. 8 and 9) is in turn provided with a recess 344 for receiving the protruding portion 342 of the element 341 as described below. In addition the position of the stop 348 (element 329 in the embodiment of FIGS. 8 and 9) is also adjusted to properly constrain the motion of the element 341 as was previously described for the element 329 for the embodiment of FIGS. 8 and 9.
(40) When a high-height drop event occurs and the element 341 is decelerated from its initial velocity at the time of impact, if the aforementioned net force (dynamic—due to the inertia of the element 341—and spring element 326, etc.) acting on the element 341 is high enough, then as was previously described for the element 323 of the embodiment of FIGS. 8 and 9, the element 341 would similarly slide down the inclined surface 345 of the element 343 (noting that for the case of element 341, the frontal surface of the protruding portion 342 and upper tip 346 of the surface 347 of the element 341 will be sliding down the inclined surface 345 of the element 343). The downward slide of the element 341 will then continue until it touches the bottom surface 302 of the inertial igniter structure. The element 341 is then pulled to the right by the tensile force of the spring element 326, causing the protruding portion 342 of the element 314 to engage the recess 344 of the fixed element 343. As a result, once the high-height drop impact induced acceleration has ceased, the element 341 is securely locked to the element 343 as can be seen in the schematic of FIG. 11 and can no longer return to its original (pre high-height drop) position shown in FIG. 10. As a result, the inertial igniter can no longer be initiated by the firing (setback) acceleration or the like events.
(41) In another embodiment, “toggle” type of mechanisms are used in the deployable locking mechanism portion of the inertial igniters. Hereinafter, by “toggle” type of mechanisms it is meant those mechanisms (of linkage or non-linkage type) in which the mechanism has at least one elastic element and at least two stable minimum potential energy positions that it would tend to move to when released depending on its current position if no external load is applied to the mechanism. Such “toggle” type of deployable locking mechanisms belong to the aforementioned first class of deployable locking mechanisms. An example of such a “toggle” mechanism type of deployable locking mechanism is shown in the schematic of FIG. 12.
(42) In the schematic of FIG. 12, a toggle-type deployable locking mechanism is constructed with a link 350 which is attached to the structure of the inertial igniter 302 by a pin joint 351. A relatively rigid element 352 is attached to the free end of the link 350. Hereinafter, the link 350 and the relatively rigid element 352 are jointly referred to as the “toggle element”. In its un-deployed state, the toggle element (shown in solid in the schematic of FIG. 12) rests against the stop 353 (which is fixed to the structure of the inertial igniter 302). A spring element 354 is attached on one end to the link 350 (preferably by a pin joint 355) and at the other end to the structure of the inertial igniter 302 through a pin joint 356. The spring element 354 can be preloaded in tension. The toggle element (elements 350 and 352) is designed such that its center of mass is located on the left side of the pin joint 351. As a result, when the inertial igniter is dropped from a high-height and impacts the ground or other hard surfaces such as that previously described, the toggle element is decelerated from its initial velocity at the time of the impact, the deceleration would act on the inertia of the toggle element and cause the toggle element to apply a dynamic counterclockwise torque against clockwise toque applied to the toggle element by the spring element 354. In which case, if the magnitude of the said dynamic counterclockwise torque is high enough to overcome the clockwise torque that is applied to the toggle element by the spring element 354, then the toggle element will begin to rotate in the counterclockwise direction. Now if the duration of the dynamic counterclockwise torque is also long enough, then the toggle element will begin to rotate counterclockwise, pass through the position of maximum spring force indicated by the dotted line 357 (connecting the pin joints 351 and 356), and comes to rest relative to the structure of the inertial igniter 302 when the relatively rigid element 352 comes into contact with bottom surface of the inertial igniter 302 (as shown in dotted and indicated by the numeral 358 in FIG. 12). In this configuration of the toggle element, the relatively rigid element 352 would block downward motion of the element 307 by being positioned under the protrusion portion 321 of the element 307. As a result, the locking ball 304 and thereby the striker mass 301 of the inertial igniter cannot be released and the inertia igniter cannot be initiated. In addition, noting that the toggle element is in its new (second) stable position as shown in dotted lines in FIG. 12, upon the termination of the aforementioned impact process, the toggle element stays deployed (shown dotted lines and numeral 358—FIG. 12), therefore the inertial igniter stays in the no initiation state. It is also noted that the inertial igniter would not initiate even if it is dropped a second time (even from the aforementioned high-heights of up to 40 feet) since the impact would generate a further dynamic counterclockwise torque on the toggle element (as shown in dotted and indicated by the numeral 358 in FIG. 12), which cannot be turned any further in the counterclockwise direction). It is also noted that by providing a spring element 354 of appropriate rate; preloading it in tension (at its un-deployed state, FIG. 12) to an appropriate level; selecting a proper geometry and size and shape for the toggle element (i.e., the length and inertia of the link 350 and the size, shape and mass of the relatively rigid element 352—which would also determine the overall geometry of the toggle element, location of its center of mass and its inertia characteristics), the present toggle-type deployable locking mechanism can be designed to deploy as a result of drops from high-heights such as the aforementioned up to 40 feet heights that can generate up to 18,000 G of impact induced deceleration levels for the inertial igniter.
(43) It is also noted that as can be seen in the schematic of FIG. 12, during the impact induced counterclockwise rotation of the toggle element (thereby the link 350 and the tensile spring element 354), once the link 350 crosses the position of maximum spring force (dotted line 357), the component of the spring force perpendicular to the direction of the link (or the line connecting the pin joints 355 and 356 if the link 350 is not straight as shown in FIG. 12) would also generate a counterclockwise torque that assists the counterclockwise torque acting on the toggle element in affecting counterclockwise rotation of the toggle element. As a result, by proper selection of the geometrical, inertia and spring rate parameters of the deployable locking mechanism of the toggle mechanism type embodiment of FIG. 12 of the present invention, the time that it would otherwise take for the deployable locking mechanism to deploy is significantly reduced. As a result, for applications such as the one provided in the aforementioned example, the distance d.sub.o, equation (1), that needs to be provided between the bottom surface 332 of the protruding portion 321 of the element 307, FIG. 8, and the top surface 359 of the element 352 of the toggle element can be less than the calculated d.sub.o=2.45 mm. This characteristic of toggle mechanism type of deployable locking mechanisms has the advantage of allowing inertial igniters to be designed with smaller required heights.
(44) Another embodiment is shown in the schematic of FIG. 13. This type of deployable locking mechanism belongs to the aforementioned first class of deployable locking mechanisms. In the embodiment, a relatively rigid element 360 is attached to the structure of the inertial igniter 302 at the point 362 by a deforming (such as beam type flexural) element 361. If the inertial igniter is dropped from a high-height (such as from the aforementioned height of up to 40 feet, which could cause the inertial igniter structure to be decelerated at a rate of up to 18,000 Gs), the impact induced deceleration of the inertial igniter structure would cause the relatively rigid element 360 and the “beam” element 361 to be decelerated from their initial velocity at the time of impact. The deceleration acts on the inertia of the relatively rigid element 360 and the beam element 361, resulting in a dynamic force that tends to push the elements down. The relatively rigid element 360 can be more massive than the beam element 361, thereby causing the resultant dynamic force to act closer to the relatively rigid element 360 side of the beam 361. The beam element 361 is preferably designed to deform elastically up to certain level of applied (dynamic) force, and deform plastically above that level of applied force, causing the beam element 361 to be deformed permanently before it comes into full contact with the bottom surface of the inertial igniter 302. If the aforementioned magnitude of downward deceleration applied to the elements 360 and 361 is up to or below the level that of firing (all-fire), i.e., setback acceleration or up to or below the magnitude of the deceleration level reached if the inertial igniter is dropped from up to 7 feet over a concrete floor (i.e., 2,000 Gs or the like according to the no-fire safety requirement), then the beam element 361 is designed to deform elastically downward less than the amount that is required to position the relatively rigid element 360 in the path of downward translation of the element 307 and its protruding portion 321, FIG. 13. On the other hand, when the inertial igniter is dropped from a high-height of up to 40 feet and the inertial igniter impacts the ground such that its structure is decelerated in a direction parallel to the arrow 320 at rates of up to 18,000 Gs, then the aforementioned downward dynamic force acting on the elements 360 and 361 causes the beam 361 to bend beyond its elastic limit and plastically deform until the relatively rigid element 360 comes into contact with the bottom surface of the inertial igniter structure 302 (shown in dotted lines and enumerated as 363), and the beam element 361 deforms and comes to rest as shown in dotted lines and enumerated as 364, FIG. 13. As a result, the relatively rigid element 360 is positioned below the protruding portion 321 of the element 307, preventing the element 307 from moving down enough to release the locking ball 304 and thereby the striker mass 301 as shown in FIG. 14. It is noted that once the drop impact induced downward acceleration of the elements 360 and 361 has ended, the beam element 361 would in general rebound slightly due to certain amount stored elastic potential energy, but the beam element 361 is readily designed such that the amount of rebound would still position the top surface 365 of the relatively rigid element 360 below the bottom surface 332 of the element 307 and/or its protruding portion 321.
(45) It is appreciated by those skilled in the art that the geometry of the beam element 361 can be designed and it could also, for example, be provided with sharp enough notches (not shown) to facilitate its plastic deformation and the final shape of its plastically deformed configuration and even minimize the level of its aforementioned rebound. In addition, certain bulging element(s) 366 shown in FIG. 13 may be provided over the bottom surface of the inertial igniter surface 302 and under the deforming beam element 361 (or on the bottom surface of the beam itself) to force the beam element to deform in a predetermined pattern to better position the relatively rigid element 360 under the bottom surface 332 of the element 307 and/or its protruding portion 321.
(46) It is also appreciated by those skilled in the art that the deployable locking mechanism of the embodiment shown in FIGS. 13 and 14, i.e., the elements 360 and 361, may be biased against deforming downwards to their deployed configuration of FIG. 14, for example by providing preloaded compressive spring (not shown) under element 360 and/or 361 while providing stops to prevent their upward motions (similar to the stop 353 in FIG. 12). By providing such biasing spring elements (or the like), the deployable locking mechanism is prevented from beginning deployment unless the applied downward acceleration is above certain threshold, such as above the all-fire setback acceleration or deceleration experienced when the inertial igniter is dropped from heights of over 7 feet height.
(47) In each one of the schematics of the disclosed embodiments shown in FIGS. 6-14, only one deployable locking mechanism is shown to be used. However, it is appreciated by those skilled in the art that more than one deployable locking mechanism can be used for several reasons, including the following. Firstly, by using more than one deployable locking mechanism, the inertial igniter safety against the aforementioned high-height drops becomes more reliable by providing more than one auxiliary deployable locking mechanisms that operate independently. Secondly, by providing more than one downward translation blocking stops for the element 307 (usually a sleeve with circular cross-section—FIGS. 6-9 and 12-14) by deployable locking mechanisms—such as at least 3 elements that are positioned symmetrically around the element 307—the element 307 is more uniformly supported during high-height drop induced downwards deceleration induced impact with the stops deployed by the deployable locking mechanisms. As a result, the chances that the element (sleeve) 307 becomes jammed along its path of motion are minimized.
(48) When several deployable locking mechanisms are used in the design of an inertial igniter, the fixed component of the mechanism—such as the element 331 of the embodiment of FIGS. 8 and 9, element 343 of the embodiment of FIGS. 10 and 11, or the element 362 in the embodiment of FIG. 13—may be integral, and can be integral to the structure of the inertial igniter. In fact, the inertial igniters can be constructed with as few parts as possible. In addition, all the pin joints used in such deployable locking mechanisms can be living joints. For example, multiple deployable locking mechanisms of the type of embodiment of FIGS. 13 and 14 can be designed to be fabricated as one single piece, such as a symmetrical ring-shaped structure shown schematically in FIGS. 15 and 16.
(49) In the schematics of FIG. 15 and the cross-sectional view A-A shown in FIG. 16, the deployable locking mechanism is shown to consist of more than one “locking elements” 370 which are connected via a (preferably flexural) beam elements 371 to the base (ring) structure 372. The “locking element” and the beam element units (together enumerated as elements 373) are preferably positioned symmetrically around the ring element 372. The ring structure is in turn fixed to the base structure 302 of the inertia igniter (other components of the inertial igniter are not shown). The present embodiment functions as previously described for the embodiment of FIGS. 13 and 14. The present embodiment is preferably fabricated as an integral component.
(50) In one preferred embodiment, one of the aforementioned existing inertial igniters, such as the one shown in FIGS. 2 and 3, is modified to provide it with one of the disclosed “deployable locking mechanisms”. To this end, the following simple modifications are only required to be implemented. Firstly, the collar 211 of the inertial igniter shown in FIG. 2 (which corresponds to the element 307 in FIG. 6), is provided with a flange as shown in FIG. 17. In FIG. 17, the above collar 211 portion of the resulting modified collar 380 is indicated by the numeral 381 and the said provided flange with the numeral 382. It is noted that the flange 382 in the schematic of FIG. 17 corresponds to the protruding portion 321 of the element 307 in the schematic of FIG. 8. With the resulting modification to the element 211 of the inertial igniter of FIGS. 2 and 3, the user may integrate any one of the disclosed deployable locking mechanisms to make the device safe against the aforementioned drops from high-heights. For example, the ring-type multi-deployable-locking-mechanisms element 375 shown in FIG. 15 can be readily fixed to the base 201 (to be extended outwards to provide the required base for attaching the element 375), to provide a high-height-drop-safe inertial igniter for use in various gun-fired munitions, mortars and the like.
(51) In another embodiment, certain means are provided that could be used to examine the thermal battery using the present high-height drop safe inertial igniters to determine whether the deployable locking mechanism has been activated without having to disassemble the thermal battery. In this embodiment, electrical contacts are provided such that once the deployable locking mechanism is deployed (whether stays deployed such as in the aforementioned first class of deployable locking mechanisms or returns to its pre-deployed state such as in the aforementioned second class of deployable locking mechanisms), it becomes possible for the deployment event to be detected. In this embodiment, such a capability is provided by one or more of the following means or the like: 1. Electrically isolated electrical contacts are provided between the contacting elements of the deployable locking mechanisms in which the contacts are lost when the mechanism is deployed, for example, by providing such electrical contacts between the elements 329 and 323 in the embodiment of FIG. 8, or the elements 341 and 348 in the embodiment of FIG. 10, or the elements 352 and 353 of the embodiment of FIG. 12 (none shown in such Figures). 2. Electrically isolated electrical contacts are provided on elements of the deployable locking mechanisms and/or other components of the inertial igniter such that once the said mechanism is deployed, contact is established between the two electrical contacts, for example, by providing such electrical contacts between the elements 323 and the inertial igniter structure 302 of the embodiment of FIG. 8, or between the elements 341 and the inertial igniter structure 302 of the embodiment of FIG. 10, or between the elements 352 and the inertial igniter structure 302 of the embodiment of FIG. 12, or between the elements 360 and the inertial igniter structure 302 of the embodiment of FIG. 13. 3. The means to detect the deployment of the “deployable locking mechanism” such as by providing sensors to detect to motion of the element 323 or the spring element 326 of the embodiment of FIG. 8, or the elements 341 or the spring element 326 of the embodiment of FIG. 10, or the elements 350, 352 or the spring element 354 of the embodiment of FIG. 12, or the elements 360 or 361 of the embodiment of FIG. 13.
(52) In the embodiments of FIGS. 8-16, the disclosed “deployable locking mechanisms” are used to limit the translation of the element (in the above cases the element 307, FIG. 6) that prevents the release of certain striker mass (in the above cases the element 301) that would initiate the inertial igniter. It is appreciated by those skilled in the art that the disclosed deployable locking mechanisms may also be used to block translational, rotational or any other type of motions that components of any other type of inertial igniter must undergo to initiate the inertial igniter initiation process.
(53) It is also appreciated by those skilled in the art that the disclosed deployable locking mechanisms can also be used with the so-called electrical G switches with mechanical time delays similar to the aforementioned inertial igniters such as those disclosed in U.S. patent application Ser. No. 12/623,442 (the entire contents of which is incorporated herein by reference) to provide them with the means to prevent the intended operation of the electrical G switches when similar high-height drop events are encountered.
(54) It is also appreciated by those skilled in the art that more than one such disclosed “deployable locking mechanism” can be provided to the inertial igniters or the electrical G switches and directed in different directions so that if the inertial igniter of the G switch (or the device using these elements) are dropped and impact a relatively hard surface in more than one direction, one of the employed deployable locking elements could deploy and prevent the inertial igniter from initiating or the electrical G switch from being activated. For example, one may provide three such deployable locking mechanisms and form a tri-axial (e.g., oriented in three orthogonal directions) and thereby design them to deploy when the inertial igniter or the device employing it is dropped from relatively high-heights (e.g., from the aforementioned heights of up to 40 feet).
(55) It is also appreciated by those skilled in the art that the disclosed “deployable locking mechanisms” may be designed for different all-fire and no-fire (drops from up to 7 feet heights over concrete floor, drops from heights of around 40 feet causing up to 18,000 Gs of impact deceleration, etc.) by adjusting the parameters of the inertial igniter and/or the deployable locking mechanism.
(56) 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.
