Ammunition and explosives – Igniting devices and systems – Arming devices
Reexamination Certificate
2000-04-24
2001-11-27
Jordan, Charles T. (Department: 3644)
Ammunition and explosives
Igniting devices and systems
Arming devices
Reexamination Certificate
active
06321654
ABSTRACT:
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 MEMS-type devices having latch, release and output mechanisms for use in fuze safety and arming devices.
DESCRIPTION OF THE PRIOR ART
Explosive projectiles, such as mortar shells, artillery shells and other similar projectiles, normally have a 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 the motion of the slider/rotor such that an out-of-sequence actuation of the interlocks leads to a fail-safe condition. An example of out-of-sequence actuation is 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 a need in the fuze arts, as similarly discussed in 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 allow 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 the ease with which mechanical S&A devices interface and integrate with increasingly electronics-intensive fuze architectures. Moreover, there is a need for the development of improvements in potential shelf-life of mechanical S&A devices, taking advantage of characteristics of microscale moving parts that do not require lubrication, which can degrade with time, to function. Finally, there is a need for an increase in safety and reliability in fazing using safety and arming devices by taking advantage of the ease with which redundant functions may be built and tested in high-rate micromachining production processes.
Such needs are addressed by further research and development of LIGA (LIthographie, Galvanoformung, Abformung, for “lithography, electroplating, molding”) and other micromachining processing methods that use metals, polymers and even ceramics for the production of varied microstructure-type devices having extreme precision. These microstructures are microelectromechanical systems (MEMS)-type devices that are alternatives for conventional electromechanical devices such as relays, actuators, and sensors. MEMS-type devices are potentially lower in cost to produce, due to the use of microelectronic fabrication techniques and when properly designed, MEMS-type actuators can produce useful forces and displacement, while consuming reasonable amounts of power.
Using MEMS micromachining methods, I previously disclosed a miniature, planar, inertially-damped, inertially actuated delay slider actuator member micromachined on a substrate, which included a slider in cooperation with a zig-zag or stair-step-like pattern on side edges to provide a time delay mechanism for a S&A device, taught in my U.S. Pat. No. 5,705,767, discussed below. The present invention provides additional designs for such devices in view of the above listed needs in the fuze arts.
OBJECTS AND SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide latch, release and output mechanisms for MEMS-type devices, which resolves many of the problems discussed above.
It is another object of the present invention to provide novel MEMS-type latch/release anchor mechanisms and latching output relay mechanisms, which incur lower production cost compared to current macro-sized devices having similar capabilities.
It is yet another object of the present invention to provide a MEMS-type inertial relay device using these mechanisms within a S&A device of a fuze within projected munitions.
Briefly, various designs of latch and release mechanisms and output mechanisms of a MEMS-type device are provided. The invention provides means by which “mechanical logic,” in the form of enforced sequential action of moving components, can be implemented in a planar MEMS-type device. The implementation of this mechanical logic is not limited only to a preferred S&A device of a fuze, but can also be used in many non-fazing applications as well.
A first embodiment of the invention comprises a miniature release and latch anchor assembly that can be fabricated in combination with other moving and fixed elements on a single substrate. Such a release and latch anchor assembly has many applications in MEMS-type devices, particularly those devices whose moving elements react in response to a predetermined inertial loading impetus externally imposed thereupon. Applications of the invention include industrial, commercial, military, or space-type use. In particular, this embodiment provides ways of imposing or enforcing sequential operations of moving parts in a MEMS-type device, a necessity for safe and proper arming of projected munitions. Generally, such munitions must experience a sequence of input conditions prior to arming the fuze. More particularly, this embodiment's release and latch anchor assembly comprises a relatively massive slider member having anchor foot members attached by leg members. The slider member is secured by constriction members attached to a substrate base and a latching linchpin member interposed between the leg members. These components are formed on a single die. When the MEMS-type device experiences an initiating event to enable the release functioning of this embodiment
Jordan Charles T.
Lofdahl J
Moran John F.
The United States of America as represented by the Secretary of
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