Ammunition and explosives – Igniting devices and systems – Arming devices
Utility Patent
1998-11-05
2001-01-02
Price, Thomas (Department: 3643)
Ammunition and explosives
Igniting devices and systems
Arming devices
Utility Patent
active
06167809
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an ultra-miniature, monolithic, mechanical safety-and-arming (S&A) device for projected munitions. More specifically, the invention relates to an ultra-miniature, mechanical, artillery-fuze S&A device based on commercial microelectromechanical systems (MEMS) technology.
2. 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 zig-zag delay (i.e., inertial delay) devices on the scale of millimeters or centimeters, fashioned by precision machining, casting, sintering or other such “macro” means, have served the purpose of providing 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. No. 4,284,862 and U.S. Pat. No. 4,815,381.
However, the fabrication of such devices is costly in that the devices are required to be constructed of extremely precision components, often requiring time-consuming sorting of components, which limits the use of these types of devices. In recent years, the LIGA (Lithographie, Galvanoformung, Abformung, for “lithography, electroplating, molding”) micromachining technique has evolved as a basic fabrication process for the production of a large variety of microstructure products utilizing metals, polymers and even ceramics. The extreme precision of the microstructure products resulting from this technique, in combination with other advantages of the technique, has opened a broad field of application for the fabrication of sensors, actuators, micromechanical components, microoptical systems, and electrical and optical microconnectors.
With the latter considerations in mind, a miniature, planar, inertially-damped, inertially-actuated delay slider actuator micromachined on a substrate and consisting of a slider with a zig-zag or stair-step-like pattern on the side edges was developed. That device was disclosed in U.S. Pat. No. 5,705,767, which is assigned to the assignee of the present invention.
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 the necessity to maintain tight tolerances on all parts for trouble-free operation.
In summary, there is a need in the prior art for the development of an ultra-miniature, monolithic, mechanical S&A device for projected munitions, and more particularly there is a need to design and manufacture fuze mechanical S&A devices which are significantly smaller, thereby providing more space in the munitions for payload or electronics. In addition, there is a need for the development of a fuze S&A fabrication technique that can replace or reduce dependence on a dwindling, and even disappearing, domestic precision small-parts manufacturing base. Furthermore, there is a need for the development of a theory, approach and design for a flexible fuze S&A fabrication technique that enables fuze developers/manufacturers to make changes to a fuze S&A design involving relatively simple exposure-mask and process-parameter changes to the LIGA-MEMS (or other micromachining) process, compared to the large cost and delay of retooling a factory line to achieve the same goal.
In the latter regard, there is a 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 the fact that microscale moving parts do not require lubrication to function. Finally, there is a need for an increase in safety and reliability in fuzing and safety devices by taking advantage of the ease with which redundant functions may be built and tested in high-rate micromachining production processes.
The following additional U.S. patents are considered to be representative of the prior art relative to the invention, and are burdened by the disadvantages set forth herein: U.S. Pat. Nos. 2,475,730; 2,710,578; 4,195,575; 4,770,096; 4,793,257; and 4,891,255.
SUMMARY OF THE INVENTION
The invention generally relates to an ultra-miniature, monolithic, mechanical S&A device for projecting munitions. The invention accomplishes the functions of a mechanical S&A device for projected munitions, but does so in a smaller package, using a new and growing industrial base (MEMS) with characteristics of the technique and technology to make the invention architecture able to be tailored and flexible to meet the needs of whole “families” of munitions. The functions of the device, therefore, are such as to provide a dual-environment S&A for munitions fuzing. Physical inputs corresponding to proper arming sequences result in a minimum of two independent mechanical locks being removed from an arming slider so that the slider is free to remove a barrier in the explosive train or to move out-of-line elements of the explosive train into line in order to arm the fuze or to mechanically close switches that enable the fire circuit to operate. The mechanical locks or “detents” respond only to specific physical inputs corresponding to valid launch or deployment conditions, and must be operated in a specific order in order to unlock the arming slider. Physical inputs received in an incorrect order will not result in arming of the fuze, and instead will result in a fail-safe condition. With respect to the latter information, a “detent” is defined as “a device, such as a catch or a spring-operated ball, for positioning and holding one mechanical part in relation to another so that the device can be released by force applied to one of its parts” (Webster's Ninth New Collegiate Dictionary, 1985). Thus, the term “detent” is used herein to denote a class of environmentally-driven mechanical catches or locks which are used to secure actuating sliders and rotors in a mechanical S&A device. The term “detent” is also sometimes used in the literature as synonymous with “safety-lock”.
In view of the objective that the S&A device of the present invention be based on MEMS technology, a LIGA-MEMS S&A module design has been conceived so as to incorporate the dual-safety-environment, multiple-mechanical-interlock approach used in many fielded mechanical S&A devices, although the inventive design generally results in the reduction of the mechanical S&A to a one-chip module. More specifically, an objective of the present invention is to incorporate the “heart” of the S&A module onto a single chi
Robinson Charles H.
Wood Robert
Clohan, Jr. Paul S.
Kelly Mark D.
Price Thomas
The United States of America as represented by the Secretary of
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