Attenuator for protecting an electroexplosive device from inadvertent RF energy or electrostatic energy induced firing

• US 5,279,225 A
• Filed: 09/18/1990
• Issued: 01/18/1994
• Est. Priority Date: 02/13/1990
• Status: Expired due to Fees

• Current Assignee: Dow, Robert L., Paul W. Proctor
• Original Assignee: Dow, Robert L., Paul W. Proctor
• Inventors: Dow, Robert L., Proctor, Paul W.
• Primary Examiner(s): Jordan, Charles T.
• Application Number:
  US07/584,045
• Time in Patent Office: 1,218 Days
• Field of Search: 102/202.1, 102/202.2, 102/202.3, 102/202.4
• US Class Current: 102/202.2
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: F42B 3/188 having radio-frequency filters , e.g. containing ferrite cores or inductances F42B3/185 takes precedence

Abstract

A device for preventing an electroexplosive device from inadvertent RF energy or electrostatic energy induced firing, even if that device is exposed to high RF power levels or high RF frequencies or to high electrostatic potentials, includes an impedance element in the firing input line between a source of dc power and a bridgewire which has an impedance that exceeds an impedance between the input leads and ground. When RF energy levels and frequencies exceed certain values, arcing occurs between one input lead and the other or between the input leads and a conductive case to cause energy to flow to the conductive case instead of to the bridgewire. One form of the device includes a Ferrite element in electrical and thermal contact with both of the firing input leads and with the thermally and electrically conductive case. The Ferrite element has a dc resistance in excess of the dc resistance of the bridgewire so short circuiting the firing current does not occur.

Claims

1. A device for protecting an EED from inadvertent RF energy induced firing comprising:

A) an input lead for connecting a bridgewire to a dc power source to pass heating current through said bridgewire;

B) a ground element electrically separated from said input lead by a first impedance; and

C) an impedance in said input lead between said dc power source and said bridgewire which is greater than said first impedance when exposed to RF energy.

2. The device defined in claim 1 wherein said input lead is non-magnetic wire.

3. The device defined in claim 1 wherein said input lead is a high magnetic permeability alloy.

4. The device defined in claim 3 wherein said input lead is an iron-cobalt alloy.

5. A device for protecting an EED from undesired effects of RF energy comprising:

A) an input lead for connecting a first element of a device to a dc power source to pass dc current through said first element;

B) a ground element electrically separated from said input lead by a first impedance; and

C) an impedance element electrically connected to said input lead between said dc power source and said first element, said impedance element having an impedance greater than said first impedance when exposed to RF energy.

6. The device defined in claim 5 wherein said impedance element is thermally connected to said input lead.

7. The device defined in claim 5 wherein said ground element includes an conductive case for the EED.

8. The device defined in claim 7 wherein said impedance element is electrically connected to said ground element.

9. The device defined in claim 7 wherein said impedance element has a length measured along said conductive case and said impedance element is connected to said conductive case over essentially the entire length of said impedance element.

10. The device defined in claim 9 wherein said impedance element includes a Ferrite element.

11. The device defined in claim 5 wherein said impedance element includes a Ferrite element.

12. The device defined in claim 11 wherein said Ferrite element includes MN-67 Ferrite.

13. The device defined in claim 11 wherein said Ferrite element has an elemental formulation of MnO₀.45 ZnO₀.3 FeO₀.25 Fe₂ O₄.

14. The device defined in claim 11 wherein said Ferrite element is in the form of a bead device.

15. The device defined in claim 11 wherein said Ferrite element is in the form of a balun device.

16. The device defined in claim 11 wherein said Ferrite element is in the form of a choke device.

17. The device defined in claim 11 wherein said Ferrite element is in the form of an iron-rich, manganese-zinc ferrite formulation.

18. The device defined in claim 11 wherein said Ferrite element has a Curie temperature in excess of 250°

C.

19. The device defined in claim 11 wherein said Ferrite element has a length measured along said input lead and said Ferrite element is connected to said input lead over essentially the entire length of said Ferrite element.

20. The device defined in claim 11 wherein said input lead includes a conductive path through said Ferrite element.

21. The device defined in claim 5 wherein said impedance element is spaced apart from said first element.

22. The device defined in claim 21 further including a shielded cable connecting said first element to said impedance element.

23. The device defined in claim 22 wherein said shielded cable includes a co-axial cable.

24. The device defined in claim 5 further including a second input lead.

25. The device defined in claim 24 wherein said impedance element is spaced apart from said first element.

26. The device defined in claim 25 further including a shielded cable around said first and second input leads.

27. A method for protecting an EED from inadvertent RF energy induced firing comprising:

A) providing an input lead connecting an EED bridgewire to a dc power source;

B) defining an alternative electrical path between the input lead and a ground element, the alternative electrical path having an impedance; and

C) defining an impedance in the input lead to have an impedance to RF energy which is greater than the impedance in the alternative path to that RF energy.

28. A method for protecting an EED from inadvertent RF energy induced firing and from electrostatic induced firing comprising:

A) providing an input lead connecting an EED bridgewire to a dc power source;

B) defining an alternative electrical path between the input lead and a ground element, the alternative electrical path having an impedance; and

C) defining an impedance in the input lead to have an impedance to RF energy which is greater than the impedance in the alternative path to that RF energy.

29. A device for protecting an EED from undesired effects of RF energy comprising:

A) an input lead for connecting a first element of a device to dc power source to pass dc current through said first element;

B) a ground element electrically separated from said input lead by a first impedance; and

C) an impedance element in direct electrical contact with said input lead between said dc power source and said first element, said impedance element having an impedance greater than said first impedance when exposed to RF energy.

30. A device for protecting an EED from inadvertent RF energy induced firing comprising:

A) an input lead for connecting an EED actuating means to a dc power source to pass actuating current through said EED actuating means;

B) a ground element electrically separated from said input lead by a first impedance; and

C) an impedance in said input lead between said dc power source and said EED actuating means which is greater than said first impedance when exposed to RF energy.

31. A device for protecting an EED from inadvertent RF energy or electrostatic energy induced firing comprising:

A) an input lead for connecting a bridgewire to a dc power source to pass heating current through said bridgewire;

B) a ground element electrically separated from said input lead by a first impedance; and

C) an impedance in said input lead between said dc power source and said bridgewire which is greater than said first impedance when exposed to RF energy.