Patent Document

CROSS REFERENCE RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional Application Ser. No. 60/184,137 filed on Feb. 22, 2000. Also, this application is related to U.S. patent applications Ser. No. 09/192,805 filed Nov. 5, 1999 entitled “ULTRA-MINIATURE, MONOLITHIC, MECHANICAL SAFETY-AND-ARMING (S&amp;A) DEVICE FOR PROJECTED MUNITIONS,” and U.S. patent applications entitled, “Microelectromechanical Systems (MEMS)-Type Devices Having Latch, Release and Output Mechanisms” and “Ultra-Miniature Mechanically Enabled Detonator With Safety and Arming Device,” filed herewith, the contents of which are expressly incorporated in their entirety herein. 
    
    
     U.S. GOVERNMENT INTEREST 
     The invention described herein may be manufactured, used, and licensed by or for the U.S. Government for U.S. Government purposes. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to microelectromechanical systems (MEMS)-type devices and, more particularly, to microelectromechanical safety-and-arming (S&amp;A) devices used in fuzing applications. 
     DESCRIPTION OF THE PRIOR ART 
     Explosive projectiles, such as mortar shells, artillery shells and other similar projectiles, normally have an S&amp;A device, which operates to permit detonation of the explosive only after the projectile has been fired or launched. Thus, mechanical arming delay mechanisms for such projectiles or explosives are well known in the art. 
     For example, three-dimensional rotary or linear zigzag delay (that is, inertial delay) devices on the scale of millimeters or centimeters, fashioned by precision machining, casting, sintering or other such “macro” means, have previously been used to provide a mechanical delay before closing a switch, or removing a lock on a detonator slider in a fuze S&amp;A device. Such devices are disclosed, by way of example, in U.S. Pat. Nos. 4,284,862 and 4,815,381. However, fabrication of such devices is costly since such devices are constructed from extremely precision components, often requiring time-consuming component sorting, thus limiting their use. 
     Other mechanical arming delay mechanisms include sequential falling leaf-spring mechanisms and escapement mechanisms. The technology surrounding such devices also includes rotors or sliders which, as arming proceeds, move out-of-line fire-train components toward and into an in-line position. Typically, the out-of-line element is a detonator or squib (propellant initiator). In such devices, the rotor or slider can remove an explosive barrier that has blocked function of the fire train, thereby arming the device. 
     Finally, such devices also include arrangements wherein mechanical sequential interlocks control motion of a slider/rotor mechanism such that out-of-sequence actuation of the interlocks leads to a fail-safe condition. An example of out-of-sequence actuation includes a spin lock releasing an arming slider before a setback lock has functioned to release the arming slider. 
     Overall, prior art arrangements are such that mechanical fuze S&amp;A devices comprise complicated, three-dimensional assemblies of piece-parts working together inside of a frame, collar or support housing. The piece-parts interact to provide dual-environment, out-of sequence safety and arming functions. Complexity comes from the need for pins, screws, bushings, specialty springs, lubrication, dissimilar materials, and assembly, as well as a need for maintaining small tolerances on all parts for trouble-free operation. 
     In summary, there is need in the fuze arts, as similarly discussed in my related U.S. patent applications referenced above, for ultra-miniature, monolithic, mechanical fuze S&amp;A devices for munitions. More particularly, there is need for fuze mechanical S&amp;A device designs that are significantly smaller and more reliable, which have varied electrical control switching action, thereby providing more space in the munitions for payload or electronics. In addition, there is need for development of a fuze S&amp;A device fabrication techniques that can replace or reduce dependence on a disappearing, domestic precision small-parts manufacturing base. Furthermore, there is need for development of fuze S&amp;A device designs that allows fuze developers and manufacturers to make changes to design thereof involving non-complex exposure-mask and process-parameter changes to the MEMS micromachining process, compared to expensive factory retooling currently used to achieve the same goal when using conventional mechanical components. Additionally, there is need for improvement in how these S&amp;A devices are interfaced and integrated with increasingly electronics-intensive fuze designs. Moreover, there is a need for the development of improvements in potential shelf-life of mechanical S&amp;A devices, taking advantage of inherent characteristics of microscale moving parts that do not require lubrication that degrades with time in conventional mechanisms. Finally, there is need for improved safety and reliability of fuzing devices by incorporating redundant functions that can be built and tested by high-rate micromachining production processes. 
     Such needs are addressed by further research and development of LIGA (LIthographie, Galvanoformung, Abformung, for “lithography, electroplating, molding”) micromachining processing methods that use metals, polymers and even ceramics for the production of varied microstructured devices having extreme precision. These collective microstructures are implemented as microelectromechanical systems (MEMS) that are alternatives for conventional discrete electromechanical devices such as relays, actuators, and sensors. When properly designed, MEMS-type actuators produce useful forces and displacement, while consuming reasonable amounts of power. MEMS-type devices are low cost devices, due to using microelectronic fabrication techniques. 
     Using MEMS micromachining methods, I previously disclosed a miniature, planar, inertially-damped, inertially actuated delay slider actuator micromachined on a substrate, which included a slider in cooperation with a zig-zag or stair-step-like pattern on side edges for a time delay mechanism for a S&amp;A device in U.S. Pat. No. 5,705,767, as discussed below. The present invention provides additional MEMS-type switching devices for use with S&amp;A devices in view of the above mentioned needs in the fuze arts. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is a primary object of the present invention to provide MEMS-type inertial switching (G-switch) devices, in a threshold non-enabled type, an enabled electromechanical-type and an enabled mechanical-type switching device, for relatively high electrical current capacity switching applications, which resolves problems related to fuzing applications as discussed above. 
     It is another object of the present invention to provide novel MEMS-type inertial switch (G-switch) devices, which incur lower production cost compared to conventional devices now used. 
     It is yet another object of the present invention to provide a MEMS-type inertial switch (G-switch) device particularly adapted for use in S&amp;A devices forming part of a fuze in projected munitions. 
     Briefly, various high-aspect-ratio MEMS-type inertial switching (G-switch) devices are provided that can electrically switch up to about an ampere of current when subjected to a threshold acceleration (for example, an impact or gun launch of a projection munition). These switching (G-switch) devices are typically used with safety and arming (S&amp;A) devices for projected munitions. The two embodiments of the invention can be a passive threshold G-switch without an enable capability. Both embodiments of the invention either by mechanical or electromechanical enable capability allow switching to occur. Either of these embodiments can also incorporate a shuttle time-delay capability. Both embodiments of the invention can be one of multiple designs for a switching assembly. These switching assembly designs can be a latching single-throw switch having a configuration of either a normally-open, double pole, single-throw switch or a normally open, single pole, single-throw switch. Switching action occurs when the shuttle member experiences inertial loading and penetrates the anvil closure member. 
     The G-switching devices of the invention can be used in various military applications by providing a mechanically-enabled, latching mechanical inertial switch (G-switch) device; an electromechanically enabled latching mechanical G-switch device; a miniature unpowered inertial t-zero or power switch device to enable electronic circuits within either gun-launched or tube-launched based weapons or instrumentation packages (for example, flight recorders or telemetry packages). The environments in which the invention can be used include sea- and water-vehicles, space borne instrumentation packages, and safety and emergency response systems. The G-switch devices can function in non-lethal weapons, by virtue of the small size and weight. The MEMS-type device is smaller, thus less massive, and can be considered “frangible” in association with an electromechanical assembly that it forms part of. 
     The above remarks, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same element and functional type of assembly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows an exemplary sectional plan view of a first embodiment of a MEMS unpowered G-switch with electromechanical enable capability. 
     FIG. 2 a  shows an exemplary sectional plan view of a second embodiment of a MEMS unpowered G-switch with mechanical enable capability. 
     FIG. 2 b  shows a sectional plan view of the device of FIG. 2 a,  wherein a linchpin is retracted, and allowing during inertial loading of the switching device, a shuttle member to close and cause switching action. 
     FIG. 3 shows a sectional plan view of incipient closure of one design of a switching assembly shown in FIG.  1 . 
     FIG. 4 shows a sectional plan view of a contact hammer standoff feature of the switching assembly shown in FIG.  1 . 
     FIG. 5 is a sectional plan view showing breakaway type standoffs that separate contact anvils of the device in FIG.  1 . 
     FIG. 6 is a sectional plan view showing sprung-type standoffs that separate contact anvils of the device in FIG.  1 . 
     FIGS. 7 a,    7   b,    7   c,    7   d,    7   e  and  7   f  are diagrams showing various types of switching assemblies that can be used in the embodiments of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIRST EMBODIMENT OF INVENTION: Referring now to FIG. 1, a first embodiment of the invention is shown in a sectional plan view of a MEMS-type unpowered G-switch device  100  with electromechanical enable capability. This switching device comprises an actuator component  52  that provides enablement of the switch device  100 , a shuttle member  50 , an anchor assembly  51  that includes the following members of anchor legs  51   a,  anchor feet  51   b  that are attached to the shuttle member and are shaped to bear laterally against constriction members  51   c;  and one of several designs of a switching assembly  75 . Each constriction member  51   c  has a cam face that is attached to the substrate  70  and forming part of a raised structural upper section of the MEMS-type device and shown as just one of many “land” structures  72  that form this raised section. After the anchor feet are unpinned by upward movement of a linchpin  53  and out from between the feet  51   b,  the anchor feet can slide past these constriction members allowing the shuttle  50  to be pulled downwards by inertia when subjected to a threshold accelerating event, resulting in switching action by the switch assembly  75  when a shuttle head member  55  attached to the shuttle  50  makes contact with contact hammers  57   a  and  57   b.    
     In particular, when the linchpin  53  is removed, the gap between the left and right anchor feet  51   b  is sufficient for the feet to be deflected towards each other without interference to exit the constriction  51   c,  which is a symmetrical throat area that traps the anchor feet  51   b.  The angle of the cam face partially determines the force and stroke necessary to pull the feet through the constriction. A more vertical angle makes it easier to pull the feet through the constriction, but means a longer pullout stroke for a given amount of lateral deflection of the anchor feet. The linchpin  53  spaces the anchor feet apart and prevents them from clearing the constriction  51   c.  The linchpin can be pulled out of the lock by some applied upwards force to allow the anchor feet to pull through the constriction. 
     To enable the switch device  100  as shown in FIG. 1, the electromechanical actuator  52  effectuates removal of the movable linchpin  53  from the shuttle&#39;s anchor feet  51   b  upon electrical signal command from a controller (not shown) that is connected to the actuator  52  via bond pads  71   a  and  71   b,  thus causing the switch device  100  to be enabled and armed. 
     The enable and arming function is accomplished by removal of the linchpin  52  from between the shuttle anchor feet. Removal of the linchpin is electromechanically effectuated by either magnetic or thermal mechanisms characterized by low-force, small-stroke action that is applied to the linchpin. An example of such the actuator  52 , is taught in U.S. Pat. No. 5,994,816 entitled, “Thermal arched beam microelectromechanical devices and associated fabrication methods.” The electromechanical actuator  52  requires a low power input signal for control compared to much greater power handling capabilities of the switching assembly  75 . 
     So long as the actuator  52  keeps the linchpin inserted in the anchor feet  51   b,  the shuttle cannot move even though an inertial loading (acceleration) is applied that would make the shuttle move, and if the actuator removes the linchpin from the anchor feet, the shuttle will then be free to respond to an acceleration along its axis. Thus the electromechanical actuator  52  provides the function of a time-gated enablement of the G-switch device  100 , so the G-switch can be enabled, disabled, or re-enabled for different “windows” of time, based on an electrical input to the actuator  52  by a controller (not shown), that controls the movement of the linchpin  53 . 
     When the switch device  100  is enabled and armed, the shuttle  50  can move down the slide track  56  due to inertia when the device  100  is subjected to inertial loading, thus providing switch closure of the switch assembly  75 , by inserting shuttle head  55  between the contact hammers  57   a  and  57   b.  The shuttle  50  must have sufficient mass to respond to a predetermined threshold inertial forces acting upon the switch device  100 . A tapered shuttle head  55  is attached the shuttle member that can insert between the contact hammers  57   a  and  57   b,  thus causing switch closure of any one of the designs of the switch assembly  75 ; the shuttle head  55  has catch members  58  that engage with catch engagement features  59  on contact hammers  57   a  and  57   b;  and flat sides for sliding in slide track  56 . 
     Alternatively, instead of using the substantially straight edges for the track  56 , a zig-zag track  54  (shown on one side only, but would be on both sides if used) can be used in place thereof that can attach to the sides of the slide track  56  to provide time-of-travel delay of a downward moving shuttle  50  when activated. This feature is taught in U.S. Pat. No. 5,705,767, entitled “Miniature, planar, inertially-damped, inertially-actuated delay slider actuator,” which is hereby incorporated by reference. In particular, this patent teaches of a miniature, planar, inertially-damped, inertially-actuated delay slider actuator that is micromachined on a substrate that includes a “slider member” (a member that slides in a similar manner as the shuttle member  50  herein), with zig-zag or stair-step-like patterns on the side edges (as shown on only one side of the track  56  in FIG. 1) interacting with similar vertical-edged zig-zag patterns “teeth” on “racks” that are positioned across a small gap on each side of the “slider.” In the present invention, as the shuttle  50  is drawn along the track such that the right edge of the slider engages with teeth on the right rack. The zig-zag rack and track member  54  causes the shuttle  50  to move back and forth as it slides down the faces on the both racks, until it is thrown clear of both racks. In this way, the shuttle zig-zags under inertial forces as it moves axially down the track toward the end thereof to actuate the electrical switch assembly  75 , thus effectuating a required mechanical programmed time delay feature. An example of a need for this feature would be where there is need for delay for turning on a projectile&#39;s test instrumentation package until the munition has nearly exited a gun fired from. This feature can be used with the second embodiment of the invention discussed below. 
     In operation, the switch device  100  is initially enabled by the actuator  52  that effectuates a relatively small force to remove the linchpin  53  from the anchor feet  51   b.  Then, when sufficient acceleration of the device  100  occurs, the shuttle  50  is free to move and exert its inertial force upon the switch assembly  75 . Thus, the device  100  requires relatively low power input signals to enable and arm the device  100  so that the shuttle  50  can respond to a predetermined threshold inertial loading of the switch device  100 . Although the actuation of the actuator  52  requires an external electrical power input, the shuttle member is unpowered and operated by inertial loading of the device  100 . 
     The electromechanical actuator  52  is powered through the two bond pads  71   a  and  71   b.  There may be more bond pads, as necessary, to operate the electromechanical actuator (for example, two pads for power and one for control, (not shown)). When the switch device  100  is not enabled, the preferred initial state of the switch is with the linchpin  53  situated between the two anchor feet  51   b,  which prevents the feet from pulling through the constriction  51   c  when loaded by anchor legs  51   a  as a result of an applied acceleration to the device. In this state, the shuttle is anchored and cannot move along its vertical track toward the switch assembly  75 . The electrical path between pads  63 A and  63 B is open because the contact anvils  61  and  62  are not touching. The voltage standoff is determined by the gap between the anvils and the dielectric constant in the gap. Neither the substrate  70  nor the cover plate of the device  100  is conductive. Thus the “pole” between electrical contacts  63 A and  63 B is open. The case is similar with the other pole between contact pads  63 C and  63 D, and anvils  76  and  77 . This is shown in FIG. 7 a.    
     In FIG. 1, the switch device  100  is enabled and armed when the electromechanical actuator  52  receives a command from a controller (not shown) or circuit logic telling it to energize and pull the linchpin out from between the anchor feet. Once enabled, the shuttle  50  can now respond to a subsequent inertial loading state that pulls it downward with sufficient force to exceed a pull-out threshold force of the anchor feet  51   b  through the constriction  51   c.  Once this acceleration is reached, the shuttle pulls free and under continuing acceleration moves down the slide track  56  toward the switch assembly  75  and engages therewith. A mechanical delay function can be added to the shuttle travel process by including a zig-zag inertial delay feature as discussed above. Then, when subjected to inertial loading, the shuttle gains speed and thrusts the shuttle head  55  between the contact hammers. Because of the significant taper of the head and angle of the accepting “jaws” formed by the contact hammers, considerable lateral force develops so that contact anvil pairs  61  and  62  and  76  and  77  are pressed together. This closes the electrical contacts of the two poles of the switch, so that bond pad  63 A is now connected to  63 B and bond pad  63 C is now connected to  63 D. The anvils and anvil arms are electrically conductive. This is discussed and shown in FIG.7 b.    
     To prevent re-opening of the switch device  100 , catch features  58  on the shuttle head  55  and catch features on the contact hammers  57   a  and  57   b  engage once the shuttle head  55  enters the switch assembly  75 , and hold the shuttle in a closed-switch position. Prior to latching and closing the switch, and to prevent inadvertent closure of the switch poles prior to shuttle movement, standoffs members  64  hold the contact hammers  57   a  and  57   b  in place and to keep the switch poles anvils  61  and  62 , and  76  and  77  separated. The several standoff arms, and the several attachment lands  66 , are structurally and electrically separated from each other so as to prevent shorting of the switch device. 
     Alternatively, the electromechanical enable function of the switching device  100  can be optional by omitting the electromechanical actuator  52  and the linchpin  53  components so that the anchor feet  51   b  are unpinned, resulting in a threshold G-switch device wherein the shuttle  50  pulls the anchor feet away from the constriction  51   c  when a threshold loading is exceeded. 
     SECOND EMBODIMENT OF INVENTION: Now referring to FIGS. 2 a  and  2   b,  a second embodiment of the G-switch device with enable capability is shown in sectional plan views. This embodiment is a switching device  200  that comprises a linchpin lift arm and support assembly  85 , an anchor foot assembly  51  having components  51   a,    51   b  and  51   c , a shuttle member  50 , and another design of the switching assembly  75 . The support assembly  85  includes a movable linchpin  53  connected to lift arm transverse member  95  that is controlled by a linchpin lift arm  94 , which in turn is supported by a support member  93  when the lift arm is flexed over until its top part engages with a capture feature on the end of the linchpin lift arm as shown in FIG. 2 b.  Actuation of the linchpin lift arm is accomplished by an externally coupled actuator such as a pressure switch, a rotatable cam member or a linear actuator. Movement of the linchpin caused by the external actuator (not shown) by mechanical coupling has sufficient stroke and power to control actions of the linchpin  53 . 
     To enable and arm the switching device  200 , a similar anchor foot assembly  51  is provided wherein removal of the linchpin  53  between the anchor feet  51   b  enables and arms the switch device  200 . Enabling of the switch device is by a low-force, small-stroke mechanical force applied to the linchpin member. Once lifted, the linchpin cannot re-enter the anchor assembly  51 . The linchpin and its support arms are released from the device substrate. FIG. 2 b  shows the device  200  when the linchpin  53  is moved upwards, and the shuttle  50  traveled downwards in the slide track  56 , and the shuttle head  55  deflects and contacts the contact arms  92  causing switch-closure of the switch assembly  75 . 
     In operation, the displaced shuttle  50  can move when the anchor feet  51   b  are unpinned. The shuttle, which is released from the substrate, can move downwards in the slide track  56  by inertial forces by an upward acceleration of the entire device  200 . Additionally, the zig-zag track can be included with this embodiment of the invention in a similar manner as discussed above for required time-delay operational characteristics. A certain threshold acceleration level must be exceeded to overcome friction and the spring rate of the anchor legs  51   a,  which must deflect inwards to clear the anchor feet  51   b  of the constriction  51   c.  Under continuing inertial load, the shuttle pulls free of the anchor assembly and travels downward in the slide track  56 , until the shuttle head  55  inserts between the electrode contact arms  92 , electrically connecting the left contact arm to the right contact arm. The head of the shuttle  50 , if not the whole shuttle, is made of or coated with a conductive material, so that it can electrically bridge the gap between the two contact arms  92 , which are also conductive. The contact arms  92  provide switching capability by inserting the shuttle head  55  between the two electrode contact arms  92 , where by spring forces, the contacts and shuttle are kept in contact, and where by virtue of catch features the shuttle head is held captive. The contact arms themselves, which are recognized as cantilever beams, have a spring stiffness determined by such parameters as material, cross sectional dimensions, and length. The contact arms are released from the substrate, but their supported ends are of a piece with the electrode bond pads,  96 A and  96 B, which are not released from the substrate. The spring stiffness of the contact arms are made to assure a good physical pressure is maintained between the interposed shuttle head  55  and the contact arms  92 . 
     The standoff member  60  in FIGS. 2 a  and  2   b  is separated into two halves to prevent electrical shorting prior to switch closure. When the standoff member  60  is made of an electrical insulator-type material, there is no need for separation into halves, conversely when they are made of an electrically conductive material, the left half must support the left contact arm  92  and the right half must support the right contact arm, while maintaining a space between the standoff member  60 . The standoff member  60  also has stabilizing extension legs  60   b  and a support members  60   a  to support the anvils  57   a  and  57   b  prior to switching action. 
     The second embodiment of the invention can also be used as a threshold G-switching device. In such a design, the linchpin  53  and lift arm assembly  85  are omitted, wherein the anchor foot assembly  51  holds the shuttle  50  in an initial configuration until upward acceleration is applied sufficient enough to pull the anchor feet  51   b  through the constriction  51   c . The accelerating threshold at which the anchor feet pull free is a function of friction, mass of the shuttle, and design of the anchor foot assembly  51 . 
     SWITCHING ASSEMBLIES: Various designs of the switching assembly  75  can be used in either embodiment of the invention. As shown in FIG. 1 (for example) the contact hammers  57   a  and  57   b  interact with the shuttle head  55  to close the switch assembly by acting upon the anvil pair  61  and  62 . The switching assembly  75  can be a latching single-throw switch of a type being either a normally-open, double pole, single-throw switch or a normally-open, single pole, single-throw switch. 
     Referring now to FIGS. 3 and 4, features of the contact hammers  57   a  and  57   b  include: being positionable with space in between to permit insertion of the tapered shuttle head  55 ; being tapered to provide a slanted entryway to guide the shuttle head; being flexibly supported to allow lateral deflection when shuttle head; having catch engagement features  59  that latches in place the inserted shuttle head; having a related contact hammer standoff feature  60  (FIG. 4) that prevents the contact hammers  57   a  and  57   b  from moving laterally under inertial loading prior to forcible insertion of the shuttle head  55  using leg members  57   c  and  57   d  that are attached to the contact hammers and cylinder in groove coupling members  60   a  and  60   b  that couple to standoff feature member  60 ; having sufficient structural strength to transmit relatively large compressive forces caused by wedging action of the inserted shuttle head  55 , to the adjacent anvils; and being electrically non-conductive unless required. 
     The electrical contact-anvil pairs  61 ,  62  and  76 ,  77  are typically made of a conductive material (either by selection of the intrinsic material or by a process of doping, deposition, plating as required by the method of fabrication) and their function is to be forcibly pressed by the contact hammers into contact with one another. When anvil  61  is pressed against anvil  62  to carry current between bond pads  63 A and  63 B, and  76  is pressed against  77 , to carry current between bond pads  63 C and  63 D, switching action occurs. 
     Referring to FIG. 5, the breakaway standoffs  64  are shown in greater detail to show how they maintain anvil pair  76  and  77  separated until lateral force caused by shuttle head  55  insertion into the switch assembly  75  overloads these standoffs  64  causing them to break or bend at a breakaway weak section. The standoffs each have attachment lands  66  on the substrate, and are electrically isolated from one another. These breakaway standoffs separate the anvils under normal dynamic inputs to prevent the switch from inadvertently closing due to self-loading during inertial loading input events. 
     Referring to FIG. 6, sprung standoff arms  65  provide a similar function as the breakaway-type of standoffs. These sprung standoffs separate anvils  61  and  62  until the lateral force from the shuttle head  55  insertion into the switch assembly overloads them. However, instead of having a breaking feature, the sprung standoffs use a “cylinder in groove”  68  geometry such that a lateral force on the associated anvils cause the anvils to move laterally by forcing the spring arms of the standoffs  65  up and over the cam surface of the “groove”  68 A. The standoffs have their own anchor lands  66  that attach to the substrate  70 , and are electrically isolated from one another. 
     The electrical poles and bonding pads  63 A,  63 B,  63 C and  63 D in FIGS. 1 and 3 are shown as the anchor lands for the anvil arms  67  and anvil pairs  61 ,  62  and  76  and  77  but they also serve as electrical bonding pads for the input/output electrical connections of the switching assembly. 
     Referring to FIGS. 7 a-f,  wiring diagrams of the switch device  100  is shown. Movement of the shuttle  50  into one of the designs of the switch assembly  75  simultaneously connects pad  63 A to  63 B and  63 C to  63 D, see FIG. 7 b.  In FIGS. 7 a  and  7   b , the switching assembly comprises a normally open, double-pole, single throw (DPST) switch device. This configuration of the switching assembly can switch power or signal or both, including switching power on one pole (e.g., pole  63 A and  63 B) and switching signal on the other pole (e.g., pole  63 C and  63 D). 
     FIGS. 7 c  and  7   d  show the switching device as a variation of the DPST wherein using a shunt connection at the output as a common node between pads  63 B and  63 D so as to enable a common voltage potential at the output of the switching device. 
     FIGS. 7 e  and  7   f  shows a normally open, single-pole, single throw (SPST) switching configuration that is able to carry twice the current that either one of the above double-pole switches can carry given that the size of the pads and connections remain the same. An optional bond pad connector  69  may be fabricated with this design to reduce the number of input/output wire leads by one for the SPST configuration. There has been some rewiring external to the switching assembly to connect the electrical poles in parallel, so that nominally twice the current capability of either pole is available between new external poles E and F. 
     METHOD OF USE AND MAKING: The various designs of the invention, as discussed above, can be used to provide a miniature high-current switching device used in various military applications by providing a mechanically-enabled, latching mechanical inertial switch (G-switch) device; an electromechanically enabled latching mechanical G-switch device; a miniature unpowered inertial t-zero or power switch device to enable electronic circuits within either gun-launched or tube-launched based weapons or instrumentation packages (for example, flight recorders or telemetry packages). Environments in which the invention can be used include sea and water-type vehicles, space borne instrumentation packages, and all types of safety and emergency response systems. The G-switch devices can function in non-lethal weapons, by virtue of the small size and therefore light weight of the MEMS S&amp;A compared to a conventional mechanical G-switch device. The MEMS device is smaller and therefore of less mass, and can be considered “frangible” in association with an electromechanical assembly that it forms a part of. 
     In particular, these embodiments can be used for turning-off or turning-on instrumentation packages upon impact, provide t-zero or t-impact signals; allow for a miniature unpowered threshold impact switch that electronically enables weapon circuits or features upon impact or penetration (note that whole-body acceleration is a safer way to sense impact than using a crush switch, which can be inadvertently activated or damaged in handling, so this invention represents a potential improvement over crush-switches used for impact sensing in weapons); inertially-induced switching of arming energy circuit in a fuze safety and arming device; neutralizing or bleeding down powered circuits on weapons that fail to function in the intended time period (that is, prior to impact or after a programmed delay after impact); impact-induced safety bleed-down of circuit or battery in a system that has suffered an impact (for example, due to cargo or equipment mishandling, accident situations, explosions, vehicle impact, or to intended conditions in test or deployment situation; electronically interrogatable uniaxial threshold-G (acceleration threshold) event recorder, or to use different terminology, an impact telltale that can be examined for evidence of blast or impact long after an incident has occurred; miniature unpowered inertial switch for detection of impact and enablement of an electronic circuit that deploys a response to the impact condition (for example, the invention device could enable an impact-mitigating air bag or a visual or auditory damage warning). 
     Other applications of the invention include, but are not limited to, safety and arming pyrotechnics, flown instrumentation packages, and actuators for or in automotive impact sensing. The features and characteristics of the invention include, but are not limited to, development of a devices that are substantially planar in form, which affords improved size and shape advantages when compared to functionally-comparable and traditional three-dimensional devices such as fuzes, switches, and assemblies that may not require electrical power to function during initial arming stages, as well as other features and characteristics discussed and described herein. 
     In the latter discussion, the term “flown instrument packages” indicates an arrangement in which the device, instead of arming a fuze, closes a switch that initiates data recording aboard a tube-launched instrumentation package. The phrase “actuators for or in automotive impact sensing” indicates an application similar to the above “flown instrumentation packages” application but, in the automotive environment, the shuttle with zig-zag feature responds to crash deceleration to work its way down the zigzag track, and it locks down and closes the switch the switch when a certain minimum velocity change occurs. The device also can act as a mechanical impact switch that closes upon first impact, with the crushing of the vehicle structure, for example. The inertial switch closing constitutes detection that closes a switch at its end of travel, and this fires an airbag or other automotive safety device. Thus, the present invention is not necessarily limited to fuzing S&amp;A applications. 
     In summary, the invention generally relates to the field of mechanical S&amp;A devices for projectiles and munition fuze S&amp;A devices using micromachining, microscale device and MEMS technologies. As described above, the invention disclosed herein preferably is used in a mechanical fuze S&amp;A device on a single die. Any solid material or combination of materials can be used to form the shuttle member, anchor assembly and switching assemblies of the present invention. In the preferred embodiment, the invention includes a slider and racks formed of metal (e.g., nickel) using a LIGA-MEMS fabrication process, but other micro-fabrication processes or other materials (including other metals, ceramics or polymers, or even crystalline materials such as silicon or quartz) can be used. The material chosen is not critical to practice the invention, but such material selection should enable one to produce the device to function as taught herein. The device can be sandwiched between one or more other die that act together to enable arming and safety functions for a fuze. 
     In addition, the height (relief) of the features is not critical, given the fact that there is enough material for the shuttle member  50 , slide track  56  and one of the designs of the switching assembly  75  to interact as intended. Current LIGA processes create features whose top surface is about 200-microns above the substrate, but the device may work just as well with only a 25- or 50-micron height. Any technology may be used to form the device, whether a LIGA-type process or a bulk plasma micromachining technique such as RIE (reactive ion etching), or a surface micromachining technique, or some other process yielding the desired configurations. 
     Preferably, each switching device is fabricated on a die approximately one square centimeter or less in area and about 500-microns thick. As mentioned above, preferably, each device is implemented on a single chip or die, but multiple dies also can be used. In a preferred embodiment of the invention, the device is monolithic in its basic configuration, but also, for practical purposes, can be sandwiched or stacked with one or more die. MEMS devices can be readily integrated and interfaced with electronics because they are fabricated much the same way as integrated circuits. The specific MEMS fabrication technique requires only that desired geometries and mechanical and electrical performance characteristics are obtained for an intended application. The moving parts of the embodiments  100  and  200 , that is the shuttle  50 , linchpin  53 , and the moving switch parts of any one of the switch assembly  75  designs are freed from the fabrication substrate  70 , and are held in plane by the substrate  70  and a cover plate for protection and reliability of freedom of moving parts (not shown). The features that are attached to the substrate and form the land structures  72  are shown that include the anchor assembly&#39;s constriction members  51   c , the track  56  and the various electrical bonding pads. There is a working clearance between the moving parts and the substrate/cover plate planes. Preferably, each of the embodiments of the invention when used in fuze applications is stackable such that the G-switch die can be augmented by sandwiching it between other die or cover plates that add more features or provide data pick-off. 
     In addition, each embodiment of the invention is preferably designed and manufactured with high precision using microfabrication technology, based on optical masks. The device brings with it a high degree of precision, with features on a scale ranging from millimeters in dimension to microns in dimension. Also, the required features may be created using any of a variety of micromachining techniques. The most likely fabrication technology for producing copies of the invention is the high-aspect-ratio (HAR) LIGA technique or other HAR bulk micromachining techniques, such as reactive ion etching, (RIE) or the like, to create the intended features on a planar substrate. 
     Packaging of the switching device can be hermetic with a selection of fill gas. Additionally, by varying certain parameters, a particular switching device design can accommodate a variety of threshold levels wherein the g-threshold for pull-out of the anchor is set by selection of parameters such as anchor leg dimensions, required anchor foot deflection as discussed in my other related patent application referenced above. Electrical current carrying capacity, and applications, through relatively simple modifications to the wafer exposure masks and MEMS process parameters, versus retooling an assembly line with conventional G-switches, allows for packaging that is flexible using either a flip-chip, surface mount, or regular chip carrier, according to need. Aspects of the switch assembly  75  performance can be tailored by relatively simple design changes such as for a requisite acceleration threshold, voltage standoff, dwell (plunger travel time as influenced by zig-zag track delay), stroke and/or contact forces. 
     It will be readily apparent to one of ordinary skill in the art that the present invention fulfills the objectives set forth above. After reading the foregoing specification, those skilled in the art will be able to effect various modifications, changes, substitutions of equivalents and various other aspects of the invention as broadly disclosed herein. It is therefore intended that the protection granted hereon be limited only by the scope of the invention as set forth in the appended claims and equivalents thereof.

Technology Category: 2