The invention relates generally to initiator systems, and more particularly to an initiator system having a time delay and MEMS-type initiator powered by ballistically-energized piezoelectric materials.
Detonation initiators that rely on the use of a column of a pressed-explosive for the initiator's time delay have a number of drawbacks. In general, pressed-explosive columns do not produce a precise time delay and typically can exhibit errors on the order of 25%. When used in aircraft systems such as aircrew escape systems, fire suppression systems, or ejection seat systems, initiators having a pressed-explosive time delay must be periodically replaced. Still further, pressed-explosive time delay initiators are expensive to manufacture.
Accordingly, it is an object of the present invention is to provide a time-delayed initiator system that avoids the drawbacks associated with pressed-explosive time delays.
Another object of the present invention is to provide a time-delayed initiator system providing a precise time delay over a relatively long useful life.
Yet another object of the present invention is to provide a time-delayed initiator system that is readily adapted to satisfy the form, fit, and function of existing pressed-explosive initiators.
Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings.
In accordance with the present invention, an initiator system includes a firing pin and a piezoelectric-based energy harvester spaced-apart from the firing pin. The energy harvester generates and stores electric energy when impacted by the firing pin. The energy harvester has a first output and a second output where at least a portion of the electric energy is independently available at each of the first output and second output. The system also includes an electronic time delay coupled to the energy harvester's second output for the generation of an electric trigger signal using the electric energy available at the second output. The electric trigger signal is generated at a selected period of time after the electric energy is available at the second output. The system further includes an initiation-energy generator coupled to the energy harvester's first output for the storage of electric energy available thereat. The initiation-energy generator is also coupled to the electronic time delay to receive the electric trigger signal. The initiation-energy generator uses the electric energy stored thereby to generate an initiation explosion when the electric trigger signal is received.
Other objects, features and advantages of the present invention will become apparent upon reference to the following description of the exemplary embodiments and to the drawings, wherein corresponding reference characters indicate corresponding parts throughout the several views of the drawings and wherein:
Referring now to the drawings and more particularly to
Initiator system 10 includes a firing pin 12 that is driven to motion by a ballistic input 100. Depending on the type of device and application that will use initiator system 10, ballistic input 100 may be G-forces (e.g., acceleration generated during the firing or launching of a projectile), expanding-gas forces (e.g., from gas generator, primer charge, etc.), a spring force, and other forces. Accordingly, it is to be understood that the type of ballistic input 100 is not a limitation of the present invention. To prevent unwanted movement of firing pin 12 during normal handling, firing pin 12 may be restrained from movement by, for example, the use of a shear pin 14 that engages/restrains firing pin 12 during normal handling, but fails when ballistic input 100 is present.
When firing pin 12 is driven to movement by ballistic input 100, firing pin 12 travels until it strikes an impact plate 16 of an energy harvester 15. In general, energy harvester 15 generates and stores electric energy when firing pin 12 strikes impact plate 16. More specifically, impact plate 16 is a rigid plate (e.g., metal) having one face opposing firing pin 12 and its opposing face interfacing with piezoelectric crystals 18. The impact force created by firing pin 12 striking impact plate 16 resonates into piezoelectric crystals 18 that, in turn, generate AC electric energy owing to the piezoelectric effect. The generated AC electric energy is coupled to a rectifier and energy storage circuit 20 to convert the AC electric energy to DC electric energy and store the DC electric energy. In particular, circuit 20 provides the DC electric energy (or at least a portion thereof) at two independent outputs 20A and 20B. The electric energy available at output 20A is coupled to a MEMS initiation device 22, and the electric energy available at output 20B is coupled to an electronic time delay 24.
In general, MEMS initiation device 22 generates an initiation explosive output 200 when triggered into operation by electronic time delay 24. Explosive output 200 may be used to initiate a larger charge, propellant, etc., for the particular larger system (not shown) served by initiator system 10. The electric energy at output 20A is used to charge a firing capacitor of MEMS initiation device 22. The electric energy at output 20B is used to generate a time-delayed trigger signal used to trigger operation of MEMS initiation device 22. The time delay is selected to satisfy the charging time required by the firing capacitor of MEMS initiation device 22.
Referring additionally now to
Electronic time delay 24 is any circuit that will generate a time-delayed electric trigger signal using the electric energy at output 20B. The particular design of time delay 24 may be varied without departing from the scope of the present invention. By being electronically generated, the time-delayed trigger signal may be precisely generated once electric energy is available at output 20B. The time-delayed electric trigger signal is indicated by reference numeral 24A.
In operation, the striking of impact plate 16 by firing pin 12 sets off a precise chain of events. The electric energy generated by piezoelectric crystals 18 and made available at independent outputs 20A and 20B sets off parallel operations in device 22 and delay 24. As a result, the electric trigger signal 24A closes switch 222 so that firing capacitor 220 discharges across hot bridgewire 224 to ignite primer charge material 226 and thereby generate explosive output 200.
As mentioned above, initiator system 10 may be configured/constructed in a variety of ways. By way of example,
Although the invention has been described relative to a specific exemplary embodiment thereof, there are numerous variations and modifications that will be readily apparent to those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described.
Finally, any numerical parameters set forth in the specification and attached claims are approximations (for example, by using the term “about”) that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be at least construed in light of the number of significant digits and by applying ordinary rounding.
The invention described herein was made in the performance of official duties by employees of the Department of the Navy and may be manufactured, used, licensed by or for the Government for any governmental purpose without payment of any royalties thereon.
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