Nitinol washers

• US 20020187020A1
• Filed: 06/11/2002
• Published: 12/12/2002
• Est. Priority Date: 06/11/2001
• Status: Abandoned Application

• Current Assignee: National Technologies Incorporated (Network Connex)
• Original Assignee: National Technologies Incorporated (Network Connex)
• Inventors: Julien, Gerald J.
• Application Number:
  US10/167,799
• Publication Number:
  US 20020187020A1
• Time in Patent Office: Days
• US Class Current: 411/544
• CPC Class Codes: F16B 2200/77 Use of a shape-memory material
• CPC Class Codes: F16B 39/24 by means of washers, spring washers, or resilient plates that lock against the object locking to the screw-thread F16B39/14 , F16B39/34, F16B39/36
• CPC Class Codes: F16B 43/00 Washers or equivalent devices; Other devices for supporting bolt-heads or nuts circlips F16B21/18; for indicating tensile load F16B31/02; forming a whole with the bolt or nut F16B33/00; locking bolts or nuts by means of a fixed plate or ring, or washer-like resilient plates F16B39/10, F16B39/24

Abstract

A lock washer for locking a threaded fastener from loosening under vibration includes an annular body with a central opening cutting from a sheet or plate of Nitinol, and an integral layer of NiTiOx on at least one face of said body. The lock washer is made of a high transition temperature form of Type 55 Nitinol that remains in its martensitic state in all normal conditions of use. The martensitic Nitinol initially yields during torquing of the nut to allow the nut to indent itself slightly into the lock washer. The resulting cold working of the washer material causes a transformation into stress-induced martensite, which is strong and elastic to resist further deformation and also exerts a preload on the bolt shank. The nut, indented into the lock washer, strongly resists turning under vibration, which effect is further enhanced by the vibration absorbing characteristics of the material. The integral layer of NiTiOx on the surface of the washer provides electrical insulation, minimizing galvanic corrosion.

Claims

1. A method of making a Nitinol washer, comprising:

selecting a sheet or plate of monolithic hot-worked Nitinol; and

cutting an annular body with a central opening from said sheet.

2. A method as defined in claim 1, wherein:

said cutting is by abrasive waterjet.

3. A method as defined in claim 1, wherein:

said Nitinol sheet is Type 55 Nitinol having a transition temperature above about 100°

C. so that it remains in its Martensitic state for all normal conditions of use.

4. A method as defined in claim 1, further comprising:

producing an integral layer of NiTiOx on at least one face of said body by heating said body to an elevated temperature above about 500°

C. and then quenching said body.

5. A fastened assembly, comprising:

two juxtaposed parts having an aligned fastener hole therethrough;

a fastener under tension extending through said aligned hole in said two parts, said fastener having a shank extending through said hole and a securement device, such as a nut or a swaged collar, for maintaining a tensile preload on said shank;

an annular Nitinol washer between a protected item and an impacting force;

whereby said impacting force will deform said Nitinol structure and said Nitinol structure will absorb significant portions of the energy in said impacting force by deforming said Nitinol washer.

6. A fastened assembly as defined in claim 5, wherein:

said Nitinol in said annular Nitinol body is monolithic Type 55 Nitinol in its martensitic state.

7. A fastened assembly as defined in claim 5, further comprising:

a hard, abrasion resistant, electrically insulating, integral NiTiOx layer between said annular Nitinol body and said juxtaposed parts.

8. A fastened assembly as defined in claim 5, wherein:

said Nitinol structure is a corrugated washer.

9. A fastened assembly as defined in claim 8, wherein:

said Nitinol structure includes two layers of different types of Nitinol bonded together, said layers including martensitic Type 55 Nitinol and either superelastic Type 55 Nitinol or ultraelastic Type 60 Nitinol.

10. An article, comprising:

an annular disc having a central opening, said annular disc being made of monolithic Nitinol.

11. An article as defined in claim 10, wherein:

said Nitinol is Type 55 Nitinol heat treated to have shape memory characteristics.

12. An article as defined in claim 10, wherein:

said Nitinol is superelastic Type 55 Nitinol; and

said annular disc is dished to form a Belleville spring that exerts an axial restoring forced when flattened axially.

13. An article as defined in claim 10, wherein:

said Nitinol is ultraelastic Type 60 Nitinol; and

said annular disc is dished to form a Belleville spring that exerts an axial restoring forced when flattened axially.

14. An article as defined in claim 10, further comprising:

said annular disc is dished to form a Belleville spring that exerts an axial restoring forced when flattened axially;

said annular disc is one of multiple Belleville springs disposed in alternating orientation to face each other with wide diameters in contact, and small diameters in contact with adjacent Belleville springs; and

a guide rod through a center hole in each of said Belleville spring to maintain said Belleville springs in an aligned stack.

15. An article as defined in claim 14, wherein:

said stack of Belleville springs exerts an axial force on a projectile in a projectile launcher.

16. An article as defined in claim 14, wherein:

said stack of Belleville springs converts mechanical energy to thermal energy in a fluid heat exchanger.

17. An article as defined in claim 14, wherein:

said Nitinol is ultraelastic Type 60 Nitinol.

18. An article as defined in claim 14, wherein:

said Nitinol is superelastic Type 55 Nitinol.