Multifilament nickel-titanium alloy drawn superelastic wire

• US 6,215,073 B1
• Filed: 03/17/1998
• Issued: 04/10/2001
• Est. Priority Date: 05/02/1997
• Status: Expired due to Fees

• Current Assignee: General Science Technology Corporation
• Original Assignee: General Science Technology Corporation
• Inventors: Avellanet, Francisco J., Bales, Thomas O. Jr.
• Primary Examiner(s): Kincaid, Kristine
• Assistant Examiner(s): Mayo, III, William H
• Application Number:
  US09/043,341
• Time in Patent Office: 1,120 Days
• Field of Search: 174/126.1, 174/128.1, 174/94.R, 174/90, 174/128.2
• US Class Current: 174/128.1
• CPC Class Codes: A61M 2025/09075 having a core without a coil possibly combined with a sheath
• CPC Class Codes: A61M 2025/09091 where a sheath surrounds the coil at the distal part
• CPC Class Codes: A61M 2025/09175 having specific characteristics at the distal tip
• CPC Class Codes: A61M 2025/09191 made of twisted wires
• CPC Class Codes: A61M 25/09 Guide wires
• CPC Class Codes: B21C 37/045 Manufacture of wire or bars with particular section or properties
• CPC Class Codes: H01B 13/0292 After-treatment
• CPC Class Codes: H01B 5/10 stranded around a space, insulating material, or dissimilar conducting material
• CPC Class Codes: H01B 7/0009 Details relating to the conductive cores

Abstract

A highly flexible cable includes two, and preferably three or more strands of nickel-titanium alloy wire which are twined (twisted) to form a wire rope. The nickel-titanium alloy wire rope is drawn through successive dies to reduce its diameter until the outer surface of the cable is substantially smooth, the cross section of the cable is substantially circular, and the overall diameter of the wire rope is reduced by 20-50%. The cable is then annealed to remove the effects of cold working. The resulting cable has been found to have an improved flexibility (i.e., a lower modulus of elasticity) relative to single strand nickel-titanium wires of the same diameter.

Claims

1. A nickel-titanium cable, comprising:

at least two twined nickel-titanium wires drawn through a die to form a flexible cable having a substantially circular cross section having a desired final diameter, wherein none of said at least two twined nickel-titanium wires forms a central core wire of said nickel-titanium cable, and further wherein said die has a diameter smaller than said desired final diameter of said cable.

2. A nickel-titanium cable according to claim 1, wherein:

said at least two twined nickel-titanium wires comprise at least three nickel-titanium wires.

3. A nickel-titanium cable according to claim 2, wherein:

the cross sectional diameter of said nickel-titanium cable is approximately 20-50% smaller than the overall cross sectional diameter of said at least three twined nickel-titanium wires.

4. A nickel-titanium cable according to claim 3, wherein:

said flexible cable having a substantially circular cross section has a cross section of between 0.008 inch and 0.044 inch.

5. A nickel-titanium cable according to claim 2, wherein:

said at least three twined nickel-titanium wires comprise exactly three helically twisted nickel-titanium wires.

6. A nickel-titanium cable according to claim 2, wherein:

said at least three twined nickel-titanium wires comprise wires of between 0.005 inch and 0.028 inch diameter.

7. A nickel-titanium cable according to claim 1, wherein:

said at least two twined nickel-titanium wires comprise exactly four wires.

8. A nickel-titanium cable according to claim 7, wherein:

each of said four wires is of the same diameter.

9. A nickel-titanium cable according to claim 7, wherein:

a first two of said four wires have a first diameter, and a second two of said four wires have a second diameter different than said first diameter.

10. A method of making a nickel-titanium cable, comprising:

a) twining at least two strands of nickel-titanium wire to form a nickel-titanium wire rope, wherein none of said at least two strands forms a central core wire of said nickel-titanium wire rope; and

b) drawing the wire rope through at least one die to form a cable having a substantially circular cross section with a desired diameter, wherein said die has a diameter smaller than said desired final diameter.

11. A method according to claim 10, wherein:

said at least two strands comprises at least three strands.

12. A method according to claim 11, further comprising:

c) annealing the cable to remove the effects of cold-working.

13. A method according to claim 11, wherein:

said drawing step reduces the overall cross sectional diameter of said wire rope by approximately 20-50%.

14. A method according to claim 13, wherein:

said drawing step reduces the overall cross sectional diameter of said wire rope by approximately 30-40%.

15. A method according to claim 14, wherein:

said cable has a cross section of between 0.008 inch and 0.044 inch.

16. A method according to claim 13, wherein:

said at least three strands comprise strands of between 0.005 inch and 0.028 inch diameter.

17. A method according to claim 11, wherein:

said drawing step includes successive drawing through a plurality of dies of decreasing diameter, wherein said at least die having a diameter smaller than said desired final diameter is a last of said plurality of dies of decreasing diameter.

18. A method according to claim 11, wherein:

said twining at least three strands comprises helically twisting exactly three strands.

19. A method according to claim 10, wherein:

said twining at least two strands comprises helically twisting exactly four strands.

20. A method according to claim 19, wherein:

each of said four strands is of the same diameter.

21. A method according to claim 19, wherein:

a first two of said four strands have a first diameter, and a second two of said four strands have a second diameter different than said first diameter.