Memory element

• US 4,777,799 A
• Filed: 10/02/1987
• Issued: 10/18/1988
• Est. Priority Date: 10/02/1987
• Status: Expired due to Fees

• Current Assignee: Catheter Research Incorporated
• Original Assignee: Catheter Research Incorporated
• Inventors: Cole, Gregory A., Small, James E., McCoy, William C., Wang, Frederick E.
• Primary Examiner(s): Ostrager, Allen M.
• Application Number:
  US07/104,641
• Time in Patent Office: 382 Days
• Field of Search: 60/527, 60/528, 60/529
• US Class Current: 60/528
• CPC Class Codes: C21D 10/00 Modifying the physical properties by methods other than heat treatment or deformation
• CPC Class Codes: C21D 2201/01 Shape memory effect
• CPC Class Codes: C22F 1/006 Resulting in heat recoverable alloys with a memory effect
• CPC Class Codes: C22F 3/00 Changing the physical structure of non-ferrous metals or alloys by special physical methods, e.g. treatment with neutrons

Abstract

A memory element made of a shape-memory alloy includes lead-attachment and shape-memory portions and a partition interconnecting such portions. The lead-attachment and shape-memory portions are comprised of characteristic internal structures, while the partition is comprised of an internal structure dissimilar to the characteristic internal structure of at least one of the lead-attachment and shape-memory portions. Shape-memory effect characteristics of the shape-memory portion are preserved to maintain the memory function of the memory element by configuring the dissimilar internal structure to block transmigration from the lead-attachment to the shape-memory portions of selected contaminant material existing in the lead-attachment portion. The partition functions as a contaminant filter to control the concentration of contaminant material in the shape-memory portion, thereby enhancing the durability of the memory element. A method is disclosed of altering the first crystalline structure of an uncontaminated memory element to provide the dissimilar, contaminant migration-blocking, internal structure.

Claims

1. A memory element made of a shape-memory alloy, the memory element comprising

first and second portions, each portion having a characteristic crystalline structure, and

partition means for interconnecting the first and second portions, the partition means having an amorphous structure different than the characteristic crystalline structure of at least one of the first and second portions.

2. The memory element of claim 1, further comprising an electrically conductive lead connected to the first portion, the amorphous structure providing means for blocking transmigration between the first and second portions of selected ions indigenous to the electrically conductive lead to control the concentration of said selected ions in the second portion.

3. The memory element of claim 2, wherein the electrically conductive lead is one of soldered and welded to the first portion.

4. The memory element of claim 2, wherein the electrically conductive lead is silver.

5. The memory element of claim 4, wherein said selected ions consist essentially of silver ions.

6. The memory element of claim 2, wherein at least the second portion moves to assume predetermined shape when heated to a predetermined temperature and the amorphous structure is configured also to provide transmission means for communicating power between the first and second portions without permitting transmigration of said selected ions therebetween so that at least the second portion moves to assume its predetermined shape upon being heated to its predetermined temperature by the transmission means.

7. A memory element made of a shape-memory alloy, the memory element comprising

first and second portions, each portion having a characteristic internal structure, and

partition means for interconnecting the first and second portions, the partition means having a dissimilar internal structure.

8. The memory element of claim 7, wherein each characteristic internal structure is a crystalline structure and the dissimilar internal structure is an amorphous structure.

9. The memory element of claim 7, wherein the dissimilar second internal structure is configured to block transmigration of selected ions between the first and second portions.

10. The memory element of claim 7, further comprising an electrically conductive silver lead welded to the first portion, the dissimilar internal structure providing means for blocking transmigration between the first and second portions of silver ions to control the concentration of silver in the second portion.

11. The memory element of claim 10, wherein at least the second portion moves to assume a predetermined shape when heated to a predetermined temperature and the dissimilar internal structure is also configured to Provide means for communicating energy from the first portion to the second portion to its predetermined temperature so that at least the second portion assumes its predetermined shape.

12. The memory element of claim 7, further comprising an electrically conductive lead and connection means for coupling the electrically conductive lead to the first portion, the dissimilar internal structure being configured to provide means for blocking transmigration between the first and second portions of selected ions communicated from at least one of the connection means and the electrically conductive lead to control the concentration of selected ions indigenous to at least one of the electrically conductive lead and the connection means in the second portion.

13. The memory element of claim 12, wherein at least the second portion moves to assume a predetermined shape when heated to a predetermined temperature and the dissimilar internal structure is also configured to provide means for communicating energy from the first portion to the second portion to its predetermined temperature so that at least the second portion assumes its predetermined shape.

14. The memory element of claim 7, wherein the partition means is configured to provide filter means for substantially blocking transmigration of selected ions between the first and second portions.

15. The memory element of claim 14, wherein the partition means is also configured to provide conductor means for conducting an electrical current between the first and second portions.

16. The memory element of claim 15, further comprising an electrically conductive silver lead connected to the first portion, and wherein said selected ions consist essentially of silver ions extant in the first portion and the filter means is configured to provide means for controlling the concentration of silver in the second portion.

17. The memory element of claim 15, further comprising an electrically conductive lead and connection means for attaching the electrically conductive lead to the first portion, the selected ions blocked by the filter means being communicated from the electrically conductive lead to the first portion via the connection means.

18. The memory element or claim 7, wherein each of the first and second portions moved to assume a predetermined shape when heated to a predetermined temperature, and the dissimilar internal structure is configured to provide transmission means for communicating power between the first and second portions without permitting transmigration of selected ions therebetween so that at least one of the first and second portions moves to assume its predetermined shape upon being heated to its predetermined temperature by the transmission means.

19. A memory element made of a shape-memory alloy, the memory element comprising

a lead-attachment portion,

a shape-memory portion, and

barrier means interconnecting the lead-attachment and shape-memory portions for blocking transmigration of selected ions from the lead-attachment portion to the shape-memory portion so that reverse martensitic transformation of the shape-memory portion at temperatures in excess of a threshold transformation temperature is not impaired due to the presence of said selected ions in the shape-memory portion.

20. The memory element of claim 19, wherein each of the lead-attachment and shape-memory portions have a characteristic internal structure and the barrier means has a dissimilar structure.

22. The memory element of claim 19, further comprising an electrically conductive silver lead connected to the first portion, and wherein said selected ions consist essentially of silver ions extant in the first portion and the barrier means is configured to provide means for controlling the concentration of silver in the second portion.

23. The memory element of claim 19, further comprising an electrically conductive lead and connection means for coupling the electrically conductive lead to the lead-attachment portion, said selected ions being communicated to the lead-attachment portion from at least one of the electrically conductive lead and the connection means.

24. The memory element of claim 23, wherein at least the shape-memory portion moves to assume a predetermined shape when heated to a predetermined temperature and the barrier means includes means for communicating energy from the lead-attachment portion to heat the shape-memory portion to its predetermined temperature so that at least the shape-memory portion assumes its predetermined shape.

25. The memory element of claim 23, wherein each of the lead-attachment and shape-memory portions have a characteristic internal structure and the barrier means has a dissimilar internal structure configured to block transmigration of said selected ions from the lead-attachment portion to the shape-memory portion without substantially impeding electric current flow from the lead-attachment portion to the shape-memory portion.

26. The memory element of claim 25, wherein each characteristic internal structure is a crystalline structure and the dissimilar internal structure is an amorphous structure.

27. A memory element made of a shape-memory alloy having a first internal structure, the memory element comprising

a first portion having said first internal structure,

a second portion having said first internal structure, and

partition means for interconnecting the first and second portions, the partition means having a dissimilar second internal structure, the partition means being formed by exposing a selected portion of the first internal structure between the first and second portions to an energy source.

21. The memory element of claim 29, wherein each characteristic internal structure is a crystalline structure and the dissimilar structure is an amorphous structure.

28. The memory element of claim 27, wherein the first internal structure is a crystalline structure and the dissimilar internal structure is an amorphous structure.

29. The memory element of claim 27, wherein the energy source is a laser.

30. The memory element of claim 27, wherein the exposing step continues for a predetermined period of time to alter the first internal structure to provide the dissimilar second internal structure.

31. The memory element of claim 27, wherein the energy source includes means for generating energy having a magnitude sufficient to disrupt the internal structure of the selected portion to provide the dissimilar second internal structure.

32. A memory assembly comprising

a memory element made of a shape-memory alloy, the memory element including a lead-attachment portion and a shape-memory portion, each of said portions having a characteristic internal structure, and

an electrically conductive lead connected to the lead-attachment portion, the memory element further including partition means for interconnecting the lead-attachment and shape-memory portions, the partition means defining a thermally-stressed zone having an internal structure dissimilar to at least one of the characteristic internal structures of the memory element induced by exposure to thermal stress before the lead is connected to the lead-attachment Portion.

33. The memory assembly of claim 32, wherein the thermally-stressed zone is configured to provide means for blocking transmigration between the lead-attachment and shape-memory portions of selected ions indigenous to the electrically conductive lead to control the concentration of said selected ions in the shape-memory portion.

34. The memory assembly of claim 33, wherein the electrically conductive lead is silver and said selected ions consist essentially of silver ions.

35. A memory assembly comprising

a memory element made of a shape-memory alloy, the memory element including a lead-attachment portion and a shape-memory portion, and

a silver lead connected to the lead-attachment portion, the lead-attachment portion providing a source of silver ions extant therein and communicated from the silver lead, the memory element further including means interconnecting the lead-attachment and shape-memory portions for regulating transfer of silver ions from the lead-attachment portion to the shape-memory portion to control the concentration of silver in the shape-memory portion.

36. A memory element made of a shape-memory alloy having a crystalline internal structure, the memory element comprising

partition means for dividing the shape-memory alloy into first and second portions, the partition means having a dissimilar internal structure.

37. A memory element made of a shape-memory alloy, the memory element comprising

first and second portions having first internal structures, and

partition means for separating the first and second portions, the partition means having a dissimilar second internal structure.

38. A method of making a temperature-activated memory element, the method comprising the steps of

providing a mechanism made of a shape-memory alloy having a crystalline structure,

exposing a selected portion of the mechanism to an energy source to divide the mechanism into first and second portions interconnected by the selected portion, and

continuing the exposing step for at least a predetermined period of time sufficiently to disrupt the crystalline structure of the selected portion to alter the crystalline structure to provide a dissimilar structure configured to block transmigration of selected ions between the first and second portions.

39. The method of claim 38, wherein the energy source is a laser.

40. The method of claim 38, wherein the dissimilar structure is configured to provide means for conducting an electrical current between the first and second portions.

41. The method of claim 38, further comprising the step of connecting an electrically conductive lead only to the first portion after the exposing and continuing steps to provide means for applying an electric current to the mechanism, the selected portion providing a partition intermediate the first and second portions to isolate in the first portion selected ions communicated from the electrically conductive lead to the first portion.

42. The method of claim 38, wherein the dissimilar structure is configured to provide means for conducting an electrical current between the first and second portions so that an electric current is applicatory to the second portion via the electrically conductive lead, the first portion, and the selected portion without causing said selected ions to transmigrate from the first portion to the second portion.

43. A method of making a temperature-activated memory element, the method comprising the steps of

providing a mechanism made of a shape-memory alloy having a crystalline structure,

thermally stressing a selected portion of the mechanism to divide the mechanism into first and second portions interconnected by the selected portion and alter the crystalline structure to provide a dissimilar structure configured to provide means for blocking transmigration of selected ions between the first and second portions.

44. The method of claim 43, further comprising the step of connecting an electrically conductive lead only to the first portion to provide means for applying an electric current to the mechanism subsequent to the thermally stressing step, said selected ions being indigenous to the electrically conductive lead.

45. A memory element comprising

lead-attachment and shape-memory portions made of a shape-memory alloy, and

barrier means communicating with the lead-attachment and shape-memory portions for blocking transmigration of selected ions from the lead-attachment portion to the shape-memory portion.

46. The memory element of claim 45, further comprising a silver lead connected to the lead-attachment portion, and wherein said selected ions consist essentially of silver ions extant in the lead-attachment portion and the barrier means is configured to provide means for controlling the concentration of silver in the shape-memory portion.

47. The memory element of claim 45, further comprising an electrically conductive lead and means for coupling the electrically conductive lead to the lead-attachment portion, and wherein said selected ions are indigenous to at least one of the electrically conductive lead and the coupling means.

48. A memory assembly comprising

a lead-attachment element made of a shape-memory alloy,

a shape-memory element made of the shape-memory alloy,

an electrically conductive lead,

means for coupling the electrically conductive lead to the lead-attachment element,

barrier means communicating with the lead-attachment and shape-memory elements for regulating transfer of selected ions indigenous to at least one of the electrically conductive lead and the coupling means from the lead-attachment element to the shape-memory element to control the concentration of said selected ions in the shape-memory element.