Ammunition and explosives – Igniting devices and systems – Arming devices
Reexamination Certificate
2000-04-24
2001-11-13
Jordan, Charles T. (Department: 3641)
Ammunition and explosives
Igniting devices and systems
Arming devices
Reexamination Certificate
active
06314887
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to microelectromechanical systems (MEMS)-type devices and, more particularly, to microelectromechanical safety-and-arming (S&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&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&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&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&A devices for munitions. More particularly, there is need for fuze mechanical S&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&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&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&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&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&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&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&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&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
Beam Robert C.
Jordan Charles T.
Lofdahl Jordan M
Moran John F.
Sachs Michael C.
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