Low observable aircraft fastener treatment

• US 6,315,485 B1
• Filed: 08/13/1999
• Issued: 11/13/2001
• Est. Priority Date: 08/13/1999
• Status: Expired due to Fees

• Current Assignee: Northrop Grumman Corporation
• Original Assignee: Northrop Grumman Corporation
• Inventors: Otto, Paul E., Speck, William S.
• Primary Examiner(s): KIM, HARRY CHONG HYUN
• Application Number:
  US09/373,956
• Time in Patent Office: 823 Days
• Field of Search: 403/6, 403/7, 403/23, 403/24, 403/404, 403/408.1, 411/371, 411/373, 244/132, 244/133
• US Class Current: 403/7
• CPC Class Codes: F16B 37/14 Cap nuts; Nut caps or bolt caps

Abstract

In accordance with the present invention, there is provided a low observable fastener for use with a panel structure having a panel bore formed therein. The panel structure has a RAM panel layer formed thereon. The RAM panel layer has a RAM panel layer bore formed therethrough aligned with the panel bore. The RAM panel layer bore defines an inner surface. The fastener is provided with a fastener head disposable within the panel bore. The fastener head has a tool engagement recess formed therein. The fastener is further provided with a RAM treatment layer disposed upon the fastener head. The RAM treatment layer has a fastener access bore aligned with the tool engagement recess of the fastener head. The RAM treatment layer further has a cylindrical outer surface sized and configured to be concentrically received by the inner surface of the RAM panel layer. The cylindrical outer surface is sized and configured to absorb electromagnetic energy radiating from the inner surface of the RAM panel layer for mitigating radar emissions formed adjacent thereto.

Claims

1. A low observable fastener for use with a panel structure having a panel bore formed therein, the panel structure having a RAM panel layer formed thereon, the RAM panel layer having a RAM panel layer bore formed therethrough aligned with the panel bore, the RAM panel layer bore defining an inner surface, the fastener comprising:

a fastener head disposable within the panel bore, the fastener head having a tool engagement recess formed therein; and

a RAM treatment layer disposed upon the fastener head and comprising;

a fastener access bore aligned with the tool engagement recess of the fastener head; and

a cylindrical outer surface sized and configured to be concentrically received by the inner surface of the RAM panel layer, the cylindrical outer surface being sized and configured to absorb electromagnetic energy radiating from the inner surface of the RAM panel layer for mitigating radar emissions formed adjacent thereto.

2. The low observable fastener of claim 1 wherein the inner surface of the RAM panel layer is cylindrically shaped and has an inner surface diameter, the cylindrical outer surface of the RAM treatment layer has an outer surface diameter less than the inner surface diameter for mitigating abrasive contact between the inner surface of the RAM panel layer and the cylindrical outer surface of the RAM treatment layer during insertion/removal of the fastener into and out of the panel structure.

3. The low observable fastener of claim 1 wherein the inner surface of the RAM panel layer is conically shaped.

4. The low observable fastener of claim 1 wherein the fastener head has a fastener head diameter, the cylindrical outer surface of the RAM treatment layer has an outer surface diameter substantially the same size as the fastener head diameter.

5. The low observable fastener of claim 1 wherein the fastener head has a fastener head diameter, the cylindrical outer surface of the RAM treatment layer has an outer surface diameter sized less than the fastener head diameter for mitigating abrasive contact between the inner surface of the RAM panel layer and the cylindrical outer surface of the RAM treatment layer during insertion/removal of the fastener into and out of the panel structure.

6. The low observable fastener of claim 1 wherein the cylindrical outer surface of the RAM treatment layer is sized and configured to form a gap between the inner surface of the RAM panel layer for mitigating abrasive contact between the inner surface of the RAM panel layer and the cylindrical outer surface of the RAM treatment layer during insertion/removal of the fastener into and out of the panel structure.

7. The low observable fastener of claim 1 wherein the RAM treatment layer and the RAM panel layer are formed of substantially the same material.

8. The low observable fastener of claim 1 wherein the RAM treatment layer and the RAM panel layer have similar electromagnetic properties.

9. The low observable fastener of claim 1 wherein the RAM treatment layer is generally toroid shaped.

10. The low observable fastener of claim 1 wherein the RAM panel layer and the RAM treatment layer are formed to have similar thickness.

11. The low observable fastener of claim 1 wherein the RAM panel layer having a RAM panel layer surface, the RAM treatment layer having a RAM treatment layer surface substantially aligned with the RAM panel layer surface.

12. The low observable fastener of claim 1 wherein the panel structure having a panel structure surface, the fastener head having a fastener head surface substantially aligned with the panel structure surface.

13. The low observable fastener of claim 1 wherein the fastener head is substantially flat.

14. The low observable fastener of claim 1 wherein the tool engagement recess being sized and configured to engage a driver tool having tool diameter, the fastener access bore having a diameter greater than the tool diameter for mitigating abrasive contact with the driver tool.

15. The low observable fastener of claim 1 wherein the RAM treatment layer is adhesively bonded to the fastener head.

16. The low observable fastener of claim 1 wherein the RAM treatment layer is sprayed onto to the fastener head.

17. The low observable fastener of claim 1 wherein the RAM treatment layer is molded to the fastener head.

18. The low observable fastener of claim 1 wherein the tool engagement recess is formed to have a Allen-head configuration.

19. The low observable fastener of claim 1 wherein the tool engagement recess is formed to have a TORX-head configuration.

20. The low observable fastener of claim 1 wherein the tool engagement recess is formed to have a Phillips-head configuration.

21. The low observable fastener of claim 1 wherein the panel bore having a counter sink portion, the fastener head being sized and configured to engage the counter sink portion of the panel bore.

22. The low observable fastener of claim 1 wherein the fastener head is formed of a conductive material.

23. The low observable fastener of claim 22 wherein the fastener head is formed of metal.

24. The low observable fastener of claim 1 further comprising a shank extending from the fastener head disposable within the panel bore.

25. The low observable fastener of claim 24 wherein the hank is threaded.

26. A low observable fastener treatment for use with a fastener formed to mate with a panel structure, the panel structure having a panel bore formed therein, the fastener having a fastener head disposable within the panel bore and having a tool engagement recess formed therein, the panel structure having a RAM panel layer formed thereon, the RAM panel layer having a RAM panel layer bore formed therethrough aligned with the panel bore, the RAM panel layer bore defining an inner surface, the fastener treatment comprising:

a RAM treatment layer disposable upon the fastener head and comprising;

a fastener access bore aligned with the tool engagement recess of the fastener head; and

a cylindrical outer surface sized and configured to be concentrically received by the inner surface of the RAM panel layer, the cylindrical outer surface being sized and configured to absorb electromagnetic energy radiating from the inner surface of the RAM panel layer for mitigating radar emissions formed adjacent thereto.

27. A low observable fastening system comprising:

a panel structure having a panel bore formed therethrough, the panel structure having a RAM panel layer formed thereon, the RAM panel layer having a RAM panel layer bore formed therethrough aligned with the panel bore, the RAM panel layer bore defining a inner surface;

a fastener head disposable within the panel bore, the fastener head having a tool engagement recess formed therein; and

a RAM treatment layer disposed upon the fastener head and comprising;

a fastener access bore aligned with the tool engagement recess of the fastener head; and

a cylindrical outer surface sized and configured to be concentrically received by the inner surface of the RAM panel layer, the cylindrical outer surface being sized and configured to absorb electromagnetic energy radiating from the inner surface of the RAM panel layer for mitigating radar emissions formed adjacent thereto.

28. A method for reducing the radar signature associated with a fastener for use with a panel structure having a panel bore formed therein, the panel structure having a RAM panel layer formed thereon, the RAM panel layer having a RAM panel layer bore formed therethrough aligned with the panel bore, the RAM panel layer bore defining an inner surface, the fastener head being disposable within the panel bore, the fastener head having a tool engagement recess formed therein, the method comprising the steps of:

a) positioning a RAM treatment layer adjacent the fastener head, the RAM treatment layer having a cylindrical outer surface and a fastener access bore extending therethrough;

b) aligning the fastener access bore of the RAM treatment layer with the tool engagement recess of the fastener head;

c) concentrically receiving the cylindrical outer surface of the RAM treatment layer by the inner surface of the RAM panel layer; and

d) absorbing electromagnetic energy radiating from the inner surface of the RAM panel layer with the cylindrical outer surface of the RAM treatment layer for mitigating radar emissions formed adjacent thereto.

29. The method of claim 28 wherein step (b) further comprises the step of adhesively bonding the RAM treatment layer to the fastener head.

30. The method of claim 28 wherein step (b) further comprises the step of spraying the RAM treatment layer onto the fastener head.

31. The method of claim 28 wherein step (b) further comprises the step of molding the RAM treatment layer to the fastener head.

32. The method of claim 28 wherein step (c) further comprises forming a gap between the inner surface of the RAM panel layer for mitigating abrasive contact between the inner surface of the RAM panel layer and the cylindrical outer surface of the RAM treatment layer during insertion/removal of the fastener into and out of the panel structure.

33. The method of claim 28 wherein the RAM panel layer has a RAM panel layer surface and the RAM treatment layer has a RAM treatment layer surface, wherein step (c) further comprises the step of substantially aligning the RAM treatment layer with the RAM panel layer surface.