ELECTRONIC SAFE, ARM, AND FIRE DEVICE CONFIGURED TO REJECT SIGNALS BELOW A PREDETERMINED 'ALL-FIRE' VOLTAGE

Abstract

An electronic ignition safety device configured to reject signals below a predetermined ‘all-fire’ voltage includes an exploding foil initiator having an electrical input and an output end, and an electronic fireset electrically connected to the electrical input of the exploding foil initiator. The device also includes a through bulkhead initiator (TBI) body, a donor charge disposed adjacent the output end of the exploding foil initiator, and an acceptor charge. The device further includes an integral barrier disposed between the donor charge and the acceptor charge, and one or more of the donor charge, the acceptor charge, and/or the integral barrier being disposed within a component part that is assembled to the TBI body. The device also includes an output charge disposed adjacent the acceptor charge.

Description

FIELD OF THE INVENTION

The present invention relates primarily to the field of electronic ignition safety devices, and more particularly, to an electronic safe, arm, and fire device configured to reject signals below a predetermined ‘all-fire’ voltage.

BACKGROUND OF THE INVENTION

While various electronic ignition safety devices exist, there is a need for an electronic ignition safety device that is suitable for use in applications such as rocket motors, but that can be configured to meet applicable U.S. military standards (e .g., MIL-STD-1316 and MIL-STD-1901) without requiring a safety mechanism that relies upon moving parts.

SUMMARY OF THE INVENTION

According to various embodiments of the present invention, an electronic ignition safety device configured to reject signals below a predetermined ‘all-fire’ voltage includes an exploding foil initiator having an electrical input and an output end, and an electronic fireset electrically connected to the electrical input of the exploding foil initiator. The device also includes a through bulkhead initiator (TBI) body, a donor charge disposed adjacent the output end of the exploding foil initiator, and an acceptor charge. The device further includes an integral barrier disposed between the donor charge and the acceptor charge, and one or more of the donor charge, the acceptor charge, and/or the integral barrier being disposed within a component part that is assembled to the TBI body. The device also includes an output charge disposed adjacent the acceptor charge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of an electronic ignition safety device configured to reject signals below a predetermined ‘all-fire’ voltage according to the present invention;

FIG. 2 is a longitudinal sectional view of the embodiment shown in FIG. 1;

FIG. 3 is a close-up view of the ‘pickup’ section shown in FIG. 2;

FIG. 4 is a longitudinal sectional view of an alternative embodiment of the safety device shown in FIG. 1;

FIG. 5 is a longitudinal sectional view of another alternative embodiment of the safety device shown in FIG. 1;

FIG. 6 is a longitudinal sectional view of yet another alternative embodiment of the safety device shown in FIG. 1; and

FIG. 7 is a longitudinal sectional view of still another embodiment of the safety device shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1-3 depict a embodiment of an electronic ignition safety device configured to reject signals below a predetermined ‘all-fire’ voltage—more particularly, an electronic safe, arm, and fire device (“ESAF device”) 20—according to the present invention. As seen in FIG. 1, the ESAF device 20 (having a 2.051″ length in the illustrated embodiment) includes a standard electrical connector 26 at one end. As seen in FIG. 2, the electrical connector 26 is secured to a housing endpiece 25, and electrical attachments 48 extend from the electrical connector 26 to a fireset 22 (the internal contents of which are not illustrated for simplicity). The fireset 22 accepts power, ground, ARM signal, and FIRE signal from weapon control electronics (not shown) connected to the ESAF device 20, and provides a SAFE-ARM electrical indication based on the voltage on a firing capacitor within the fireset 22. The fireset 22 also preferably includes a DC-DC converter that steps up the input voltage (normally in the 28V DC range) to a predetermined voltage preferably greater than 500V, and includes electronic switches that maintain a zero voltage on the fireset's firing capacitor until a proper ARM signal is received. The fireset 22 is configured to charge the firing capacitor to a minimum of a predetermined ‘all-fire’ voltage in response to receipt of a proper ARM signal, and to close an electronic switch discharging the firing capacitor into the EFI 30 (described below) within a predetermined delay after subsequent receipt of a proper FIRE signal.

A housing receiver 24 is joined at a circumferential weld 28 to the housing endpiece 25, over the fireset 22, and is provided internally with female threads 36. The housing endpiece 25 and housing receiver 24 are machined from stainless steel, although other materials might be used such as aluminum. Secured atop and electrically connected to output terminals (not shown) of the fireset 22 is an exploding foil initiator (EFI) 30. The EFI 30 comprises (details not illustrated) a miniature circuit board made from an epoxy/fiberglass base, a copper bridge, a kapton layer that serves as a flyer plate, and a barrel and explosive charge (a secondary explosive such as HNS-IV) attached to the kapton layer and contained within a thin-walled drawn stainless steel cup. When the fireset 22 applies an adequate voltage of suitable waveform to the EFI 30, the copper bridge explodes, shearing and accelerating the kapton flyer plate along the barrel and into the explosive charge, causing it to detonate.

Atop the fireset 22 and EFI 30, a through-bulkhead initiator (TBI) body 32 (having a 0.75″ outermost diameter in the illustrated embodiment) is secured to housing receiver 24 by circumferential welding after fully engaging male threads 34 on the TBI body 32 into the female threads 36 of the housing receiver 24, and hermetically seals a rocket motor firing chamber to which it attaches (through external features not shown). The TBI body 32 is precision—machined of stainless steel, with a pickup section that includes an integral barrier configured to propagate a shock wave. Referring to FIG. 3, the pickup section includes a donor charge 38 (having a 0.111″ diameter and 0.14″ length in the illustrated embodiment) that is set within a first cavity in the TBI body 32 aligned with the output end of the EFI 30 and hermetically covered with a foil seal 50, an integral barrier 52 (having a 0.043″ length in the illustrated embodiment), and an acceptor charge 40 (having a 0.093″ diameter and 0.147″ length in the illustrated embodiment) that is set within a second cavity in the TBI body 32 and hermetically covered with another foil seal. The donor charge 38 and acceptor charge 40 are made from compressed secondary explosives such as CH-6, RDX or PBXN-5, and the pickup section is designed so as to allow a shock wave sufficient to detonate the acceptor charge while maintaining structural integrity, as is known in the art. Likewise, the TBI body 32 is configured such that there is a small gap 54 (primarily based upon the particular EFI chosen—e.g., approximately 0.010″ in the embodiment illustrated) between the output end of the EFI 30 and the foil seal 50, in order to facilitate reliable propagation of the detonating output from the EFI 30 to the donor charge 38.

Atop the foil seal overlaying the acceptor charge 40 is an output charge 42 (formed, e.g., as pellets, powder, granules, etc.) made of an igniter material such as BKNO3 and covered by a thin metallic sealing closure 44. Atop the sealing closure 44, an output port 46 is screwed into the end of the TBI body 32. Propagation from the acceptor charge 40 ignites the output charge 42, and the resulting output can be used to ignite, e.g., a rocket motor propellant either directly or through a booster igniter.

The EFI 30 only produces a high-order detonation in response to voltage at or above a high “all-fire” voltage, for example, in excess of 500V. In the event of an inadvertent low voltage signal from the fireset 22, the EFI 30 would at most produce a low energy or low-order deflagrating output; even if that deflagration causes the donor charge 38 (which is a secondary explosive) to burn, a shock wave of sufficient energy would not be produced to initiate the acceptor charge 40, so the output charge 42 would not be initiated. Thus, the combination of an EFI in line with a TBI pickup/barrier results in a device that cannot produce an output below the EFI's ‘all-fire’ voltage, yet does not require a safety mechanism that relies upon moving parts.

In alternative embodiments of the present invention, the TBI body 32 may comprise one or more of the donor charge 38, the acceptor charge 40, and/or the bulkhead or integral barrier 52. For example, each of these components 38, 40, 52 can be configured to be “integral” within the TBI body 32 as in the embodiment described above with respect to FIG. 2. That is, in the embodiment of FIG. 2 the donor charge 38 and the acceptor charge 40 are each disposed within their own cavity in the TBI body 32. In the case of the two charges 38, 40, “integral” refers to the charge cavity (i.e., the volume into which the charges 38, 40 are pressed or otherwise formed and not the charge itself).

Alternatively, as described in the various embodiments herein after, one or more of the donor charge 38, the acceptor charge 40, and/or the bulkhead or integral barrier 52 may be implemented in different component parts that may then be assembled together from any combination of these three separate component parts (i.e., the component parts for the donor charge 38, the acceptor charge 40, and the bulkhead or integral barrier 52) into a structure that is somewhat similar, but not identical, to the “one-piece” TBI body 32 configuration of the embodiment of FIG. 2.

Referring to FIG. 4, in an alternative embodiment of the present invention, the one-piece TBI body 32 of FIG. 2 is replaced by three separate parts; a bushing 32A that holds the donor charge 38, a barrier 52 that replaces the integral barrier 52 in the one-piece design of FIG. 2, and the TBI body 32 that holds the acceptor charge 40, the bushing 32A, and the barrier 52.

Referring to FIG. 5, in another alternative embodiment of the present invention, the one-piece TBI body 32 of FIG. 2 is replaced by three separate parts; a bushing 32A that holds the donor charge 38, a washer 32B that holds the acceptor charge 40, and the TBI body 32 that holds the bushing 32A, the washer 32B, and that also contains the integral bulkhead or barrier 52.

Referring to FIG. 6, in yet another alternative embodiment of the present invention, the one-piece TBI body 32 of FIG. 2 is replaced by two separate parts; a washer 32B that holds the acceptor charge 40 and the TBI body 32 that holds the donor charge 38, the washer 32B, and that also contains the integral bulkhead or barrier 52.

Referring to FIG. 7, in still another alternative embodiment of the present invention, the one-piece TBI body 32 of FIG. 2 is replaced by two separate parts; a bushing 32A that holds the donor charge 38 and the TBI body 32 that holds the acceptor charge 40, the bushing 32A, and that also contains the integral bulkhead or barrier 52.

Although the present invention has been described in detail in the context of a preferred embodiment for use in applications such as rocket motors, one skilled in the art will appreciate that numerous variations, modifications, and other applications are also within the scope of the present invention. For example, dual, parallel firesets, EFIs, and pickup sections could be provided in a single housing, for redundancy. Further, although an embodiment of the invention for use with a rocket motor has been described, the invention could be used in other applications such as gas generators, cartridge-actuated devices, and/or propellant-actuated devices. Thus, the foregoing detailed description is not intended to limit the invention in any way, which is limited only by the following claims and their legal equivalents.

Claims

1. An electronic ignition safety device configured to reject signals below a predetermined ‘all-fire’ voltage, comprising: an exploding foil initiator having an electrical input and an output end;an electronic fireset electrically connected to the electrical input of the exploding foil initiator;a through bulkhead initiator (TBI) body;a donor charge disposed adjacent the output end of the exploding foil initiator;an acceptor charge;an integral barrier disposed between the donor charge and the acceptor charge;one or more of the donor charge, the acceptor charge, and/or the integral barrier being disposed within a component part that is assembled to the TBI body; andan output charge disposed adjacent the acceptor charge.

2. The device of claim 1, further comprising a bushing in which is disposed the donor charge, the integral barrier being disposed adjacent to the bushing, wherein the bushing, the acceptor charge, and the integral barrier being disposed within the TBI body.

3. The device of claim 1, further comprising: a bushing in which is disposed the donor charge; anda washer in which is disposed the acceptor charge, wherein the integral barrier, the bushing and the washer being disposed within the TBI body.

4. The device of claim 1, further comprising a washer in which is disposed the acceptor charge, wherein the donor charge, the washer and the integral barrier being disposed within the TBI body.

5. The device of claim 1, further comprising a bushing in which is disposed the donor charge, wherein the bushing, the integral barrier and the acceptor charge being disposed within the TBI body.

6. The device of claim 1, wherein the exploding foil initiator is configured to detonate in response to a signal only if the signal exceeds a predetermined voltage.

7. The device of claim 2, wherein the predetermined voltage is at least 500V.

8. The device of claim 1, further comprising a sealing closure adjacent the output charge, and an output port.

9. The device of claim 1, further comprising a gap between the output end of the exploding foil initiator and the donor charge.

10. The device of claim 1, wherein the device comprises an electronic safe, arm, and fire device.

11. An electronic ignition safety device configured to reject signals below a predetermined ‘all-fire’ voltage, comprising: an exploding foil initiator having an electrical input and an output end;a fireset electrically connected to the electrical input of the exploding foil initiator;an output charge; anda structure having a plurality of components assembled together, wherein the structure being configured to propagate detonation of the exploding foil initiator to the output charge.

12. The device of claim 11, wherein the structure comprises: a through bulkhead initiator (TBI) body;a donor charge disposed adjacent the output end of the exploding foil initiator;an acceptor charge;an integral barrier disposed between the donor charge and the acceptor charge;one or more of the donor charge, the acceptor charge, and/or the integral barrier being disposed within a component part that is assembled to the TBI body.

13. The device of claim 12, further comprising a bushing in which is disposed the donor charge, the integral barrier being disposed adjacent to the bushing, wherein the bushing, the acceptor charge, and the integral barrier being disposed within the TBI body.

14. The device of claim 12, further comprising: a bushing in which is disposed the donor charge; anda washer in which is disposed the acceptor charge, wherein the integral barrier, the bushing and the washer being disposed within the TBI body.

15. The device of claim 12, further comprising a washer in which is disposed the acceptor charge, wherein the donor charge, the washer and the integral barrier being disposed within the TBI body.

16. The device of claim 12, further comprising a bushing in which is disposed the donor charge, wherein the bushing, the integral barrier and the acceptor charge being disposed within the TBI body.

17. The device of claim 11, wherein the exploding foil initiator is configured to detonate in response to a signal only if the signal exceeds a predetermined voltage.

18. The device of claim 17, wherein the predetermined voltage is at least 500V.

19. The device of claim 11, further comprising a sealing closure adjacent the output charge, and an output port.

20. The device of claim 11, further comprising a gap between the output end of the exploding foil initiator and the donor charge.