A SHAPE MEMORY ALLOY APPARATUS

Abstract

A shape memory alloy apparatus (1) comprising: a member (3) comprising a first end portion (5) and a second end portion (7); and a shape memory alloy component (9) connected to the member (3). The shape memory alloy component (9) being configured to, on contraction, change the separation between the first end portion (5) and the second end portion (7) of the member (3), the member (3) being configured to be in tension during contraction of the shape memory alloy component (9), wherein the said separation changes in a direction that is angled to the direction of contraction.

Claims

1. A shape memory alloy apparatus comprising: a member comprising a first end portion and a second end portion; and a shape memory alloy component connected to the member and being configured to, on contraction, change the separation between the first end portion and the second end portion of the member, the member being configured to be in tension during contraction of the shape memory alloy component, wherein the said separation changes in a direction that is angled to the direction of contraction.

2. The shape memory alloy apparatus according to claim 1, wherein the said separation changes in a direction that is substantially perpendicular to the direction of contraction.

3. The shape memory alloy apparatus according to claim 1, further comprising: a support structure, the first end portion of the member being connected to the support structure; and a moveable element, the second end portion of the member being connected to the moveable element such that the changing of the separation between the first end portion and the second end portion of the member is configured to drive movement of the moveable element relative to the support structure along a movement axis in a first direction and/or to drive, in a first rotational direction, rotational movement of the moveable element about a first axis that is perpendicular to the movement axis.

4. The shape memory alloy apparatus according to claim 3, further comprising a second member comprising a first end portion and a second end portion, the member and the second member forming a pair of members, the shape memory alloy component being arranged between the members of the pair of members and being configured to, on contraction, change the separation between the first end portion and the second end portion of each of the members.

5. The shape memory alloy apparatus according to claim 4 wherein the pair of members is a first pair of members and the shape memory alloy apparatus further comprises: a second pair of members, each member of the second pair of members comprising a first end portion and a second end portion, the first portion of each member being connected to the support structure and the second portion of each member being connected to the moveable element; and a second shape memory alloy component arranged between the members of the second pair of members and being configured to, on contraction, change the separation between the first end portion and the second end portion of each of the members of the second pair of members to drive movement of the moveable element relative to the support structure along the movement axis in the first direction or in a second direction and/or to drive, in a second rotational direction, rotational movement of the moveable element about the first axis, the second direction being opposite to the first direction and the second rotational direction being opposite to the first rotational direction.

6. (canceled)

7. (canceled)

8. (canceled)

9. The shape memory alloy apparatus according to claim 5 further comprising: a third pair of members and a fourth pair of members, each member of the third and fourth pairs of members comprising a first end portion and a second end portion, the first end portion of each member being connected to the support structure and the second end portion of each member being connected to the moveable element; and third and fourth shape memory alloy components arranged between the members of the third and fourth pairs of members respectively and being configured to, on contraction, change the separation between the first end portion and the second end portion of each of the members of the third and fourth pairs of members respectively to drive movement of the moveable element relative to the support structure along the movement axis in the first and second direction respectively, or drive, in respective first and second rotational directions, rotational movement of the moveable element about the first axis.

10. The shape memory alloy apparatus according to claim 9 wherein each pair of members is arranged on a respective one of four sides of the moveable element around the movement axis, wherein the first and third pairs of members are arranged on opposing sides of the moveable element to the second and fourth pairs of members with respect to a plane perpendicular to the movement axis, the first and third shape memory alloy components being configured to, on contraction, increase the separation between the first end portion and the second end portion of each of the members of the first and third pairs of members respectively; and the second and fourth shape memory alloy components being configured to, on contraction, increase the separation between the first end portion and the second end portion of each of the members of the second and fourth pairs of members respectively.

11. (canceled)

12. The shape memory alloy apparatus according to claim 10 wherein: the first, second, third, and fourth pairs of members are arranged on a same side of the moveable element with respect to a plane perpendicular to the movement axis; the first and third shape memory alloy components being configured to, on contraction, increase the separation between the first end portion and the second end portion of each of the members of the first and third pairs of members respectively; and the second and fourth shape memory alloy components being configured to, on contraction, decrease the separation between the first end portion and the second end portion of each of the members of the second and fourth pair of members respectively.

13. (canceled)

14. (canceled)

15. (canceled)

16. A shape memory alloy apparatus comprising: a support structure; a moveable element; a first pair of members and a second pair of members, each member comprising a first end portion and a second end portion; a first shape memory alloy component arranged between the members of the first pair of members and being configured to, on contraction, change the separation between the first end portion and the second end portion of the members of the first pair of members to drive movement of the moveable element relative to the support structure along a movement axis in a first direction and/or to drive, in a first rotational direction, rotational movement of the moveable element about a first axis that is perpendicular to the movement axis; and a second shape memory alloy component arranged between the members of the second pair of members and being configured to, on contraction, change the separation between the first end portion and the second end portion of the members of the second pair of members to drive movement of the moveable element relative to the support structure along the movement axis in a second direction and/or to drive rotational movement of the moveable element about a second axis perpendicular to both first axis and the movement axis or about the first axis in a second rotational direction; wherein the second direction being opposite to the first direction and the second rotational direction being opposite the first rotational direction.

17. The shape memory alloy apparatus according to claim 16 wherein: the first and second pairs of members are arranged on opposing sides of the moveable element with respect to a plane perpendicular to the movement axis; the first shape memory alloy component being configured to, on contraction, increase the separation between the first end portion and the second end portion of each of the members of the first pair of members; and the second shape memory alloy component being configured to increase the separation between the first end portion and the second end portion of each of the members of the second pair of members.

18. The shape memory alloy apparatus according to claim 16 wherein: the first and second pairs of members are arranged on a same side of the moveable element with respect to a plane perpendicular to the movement axis; the first shape memory alloy component being configured to increase the separation between the first end portion and the second end portion of each of the members of the first pair of members; and the second shape memory alloy component being configured to decrease the separation between the first end portion and the second end portion of each of the members of the second pair of members.

19. The shape memory alloy apparatus according to claim 16 further comprising: a third pair of members and a fourth pair of members, each member of the third and fourth pairs of members comprising a first end portion and a second end portion, the first end portion of each member being connected to the support structure and the second end portion of each member being connected to the moveable element; and third and fourth shape memory alloy components arranged between the members of the third and fourth pairs of members respectively and being configured to change the separation between the first end portion and the second end portion of each of the members of the third and fourth pairs of members respectively to drive movement of the moveable element relative to the support structure along the movement axis in the first and second direction respectively, or drive, in respective first and second rotational directions, rotational movement of the moveable element about the first axis.

20. (canceled)

21. (canceled)

22. (canceled)

23. The shape memory alloy apparatus according to claim 16 wherein: the first and second pairs of members are arranged on adjacent sides of the moveable element with respect to a plane perpendicular to the movement axis; the first shape memory alloy component being configured to drive rotational movement of the moveable element about a first axis that is perpendicular to the movement axis; and the second shape memory alloy component being configured to or to drive rotational movement of the moveable element about a second axis that is perpendicular to the movement axis and the first axis.

24. The shape memory alloy apparatus according to claim 23 wherein: a third and fourth pairs of members are arranged on adjacent sides of the moveable element and respectively opposite to the first and second pairs of members; a third shape memory alloy component being configured to drive rotational movement of the moveable element about the first axis and in an opposite direction to the first shape memory alloy component; and a fourth shape memory alloy component being configured to drive rotational movement of the moveable element about the second axis and in an opposite direction to the second shape memory alloy component.

25. The shape memory alloy apparatus according to claim 23 wherein: a third and fourth pairs of members are arranged on respective sides of the moveable element having the first and second pairs of members; a third shape memory alloy component being configured to drive rotational movement of the moveable element about the first axis and in an opposite direction to the first shape memory alloy component; and a fourth shape memory alloy component being configured to drive rotational movement of the moveable element about the second axis and in an opposite direction to the second shape memory alloy component.

26. The shape memory alloy apparatus according to claim 3, wherein: an image sensor is mounted to the support structure; the moveable element is a lens carriage comprising at least one lens; and the movement axis is along an optical axis of the lens element.

27. (canceled)

28. (canceled)

29. (canceled)

30. The shape memory alloy apparatus according to claim 1 wherein the shape memory alloy component being connected to the member at a position between the first end portion and the second end portion.

31. The shape memory alloy apparatus according to claim 1 wherein the members are flexures, wherein the flexures at least define V-shape structures each comprising a pivot, the shape memory alloy component being connected to the pivot.

32. (canceled)

33. The shape memory alloy apparatus according to claim 31 wherein the angle defined between the shape memory alloy components and the first and second end portions of their respective flexures is from 10 degrees to 45 degrees, preferably from 20 degrees to 30 degrees, more preferably from 22 degrees to 26 degrees, and most preferably 23 degrees.

34. (canceled)

35. (canceled)

36. A method of controlling a shape memory alloy apparatus, the method comprising: contracting a shape memory alloy component; placing, by contracting the shape memory alloy component, a member under tension; and changing, by placing the member under tension, the separation between a first end portion and a second end portion of the member, wherein the said separation changes in a direction that is angled to the direction of contraction.

37. (canceled)

38. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Certain embodiments of the presently-claimed invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0061] FIG. 1 is a perspective view of a shape memory alloy apparatus embodying an aspect of the present invention;

[0062] FIG. 2 is a perspective view of a shape memory alloy apparatus embodying an aspect of the present invention;

[0063] FIG. 3 is a plan-view of a shape memory alloy apparatus embodying an aspect of the present invention; and

[0064] FIG. 4 is a perspective view of a shape memory alloy apparatus embodying an aspect of the present invention.

[0065] Like features are denoted by like reference numerals.

DETAILED DESCRIPTION

[0066] Example shape memory alloy apparatuses will now be described with reference to FIGS. 1 to 6.

[0067] FIG. 1 illustrates a shape memory alloy apparatus 1, which comprises a member 3. The member 3 comprises a first end portion 5 and a second end portion 7. In this example, the member is a phosphor bronze flexure 3. The flexure 3 is connected to a shape memory alloy component 9 by a crimp portion 8. In this example, the SMA component is an SMA wire 9. The crimp portion 8 is a crimp head connected to the flexure 3 by, in this example, laser welding. The first end portion 5 of the flexure 3 is connected to a support structure 11. The second end portion 7 of the flexure 3 is connected to a moveable element 13. In this example, the end portions 5,7 are glued to the support structure 5 and the moveable element 13.

[0068] When at rest, the flexure 3 is not under tension. The flexure 3 is only tensioned when the SMA wire 9 is contracted. SMA material has the property that, on heating, undergoes a solid-state phase change which causes the SMA material to contract. At low temperatures the SMA material enters the Martensite phase. At high temperatures the SMA enters the Austenite phase which induces a deformation causing the SMA material to contract. The phase change occurs over a range of temperature due to the statistical spread of transition temperature in the SMA crystal structure. Thus, heating of SMA component or wire 9 causes it to decrease in length.

[0069] During use, a drive signal is provided to the SMA wire 9 by a controller (not shown). The drive signal heats the SMA wire 9 and causes it to contract. This places the flexure 3 under tension. In this example, as the SMA wire 9 contracts, the flexure 3 is pulled and the separation between the first and second end portions 5, 7 is therefore increased. Due to the end portions being connected to the support structure 11 and the moveable element 13, the moveable element 13 is moved relative to the support structure 11 in a first direction along a movement axis 4.

[0070] The gearing achieved by the members depends on the angle of the first and second end portions of the member 5, 7 to the direction of motion and is shown in the following Equation 1.

[00001]$\begin{array}{cc}\mathrm{Gearing}=\frac{\mathrm{InitialZ}-\mathrm{FinalZ}}{\mathrm{SMA}\mathrm{Stroke}}\mathrm{where}:\mathrm{Initial}Z=L_f\mathrm{Sin}\left(\theta \right)\mathrm{and}:\mathrm{Final}Z=\surd (L_f^2-{\left(L_f\mathrm{Cos}\left(\theta \right)+\frac{\mathrm{Wire}\mathrm{Stroke}}{2}\right)}^2& \mathrm{Equation}1\end{array}$

where θ is the exterior angle between horizontal (defined as the plane of the shape memory alloy component) and the first or second portion of the member 5, 7, and L.sub.ƒ is the length of member 5, 7. The gear ratio does not have a linear relationship with the angle. As the angle of the member approaches horizontal, the gear ratio tends towards infinite. The angle may be between 10 degrees and 45 degrees, such as 20 degrees to 30 degrees, such as 22 degrees to 26 degrees, or 23 degrees.

[0071] FIG. 2 illustrates the shape memory alloy apparatus 1 as in FIG. 1, but also includes a second member, which again is a flexure 15 in this example. The flexure 15 comprises a first end portion 17 and a second end portion 19. Connected to the flexure 15 is the SMA wire 9, also connected to the flexure 15 by a crimp head 18. The first end portion 17 and the second end portion 19 are heat staked to the support structure 11 and the moveable element 13 respectively. The member 3 and the second member 15 form a pair of members 21.

[0072] In use, the SMA wire 9 is contracted as above, which places both flexures 3, 15 under tension and causes the separation of the first 5, 15, and second 7, 17 end portions to increase respectively. Due to the connections with the support structure 11 and the moveable element 13, this causes the moveable element 13 to move in a first direction, which in this example is in a direction away from the support structure along the movement axis 4.

[0073] FIG. 2 also illustrates a second pair of members 23, which is similar in many ways to the pair of members 21, but significantly differs in that flexures 25, 27 are arranged such that contraction of the SMA wire 29 moves the moveable element 13 in a second direction relative to the support structure 11. The second direction is opposite to the first direction. So, in this example, the moveable element 13 moves towards the support structure 11 along the movement axis 4 by contraction of the SMA wire 29. The pair of members 21 and the second pair of members 23 therefore act to oppose one another. In this example shown in FIG. 2, the flexures 25, 27 of the pair of flexures 23 are inverted flexures to the flexures 3, 15 of the pair of flexures 21. This allows for the pairs of flexures 21, 23 to be arranged on the same side of the moveable element 13 with respect to a plane perpendicular to the movement axis 4. An alternative arrangement of the pairs of flexures is illustrated in FIG. 4 explained below. By providing opposing pairs of flexures, the moveable element may be tilted.

[0074] The embodiment as shown in FIG. 2 may also be able capable of tilting the movable element 13 about two perpendicular axes that are perpendicular to the movement axis 4, e.g. effecting rotational movement about the x-axis and the y-axis, or tilting. Taking the second pair of members 23 as an example, upon contraction of the SMA wire 29, it may move the respective side of moveable element 13 in a second direction relative to the support structure 11. Thus, if the moveable element 13 is allowed to pivot about the support structure 11, such contraction would cause the moveable element 13 to tilt towards the respective side of shape memory alloy apparatus.

[0075] In some embodiments, a return spring or flexure may be provided such that upon cooling of the SMA wires 9, 29, the return spring or flexure bias the moveable element 13 to return to its default position.

[0076] In some embodiments, the first and second pairs of the members may be placed on the same side (where the two pairs of members acts in opposing directions upon actuation of the SMA wire), or opposite side (where the two pairs of members acts in the direction upon actuation of the SMA wire) to provide bi-directional controlled movement in the moveable element 13.

[0077] FIG. 3 illustrates a plan view of the arrangement of FIG. 2. As well as the pair of flexures 21 and the second pair of flexures 23, there is also a third pair of flexures 31 and a fourth pair of flexures 33. The third pair of flexures 31 is identical to the pair of flexures 21 in all aspects except its position on the apparatus. The third pair of flexures 31 is arranged on a side opposite to the pair of flexures 21 and on a side of the moveable element 13 perpendicular to the second pair of flexures 23 when viewed along the movement axis 4. The third pair of flexures 31 acts to drive movement of the moveable element 13 relative to the support structure 11 in the first direction. The fourth pair of flexures 33 is identical to the second pair of flexures 23 in all aspects except its position on the apparatus. The fourth pair of flexures 33 acts to drive movement of the moveable element 13 relative to the support structure 11 in the second direction. The fourth pair of flexures 33 is arranged on a side of the moveable element 13 opposite to the second pair of flexures 21 and on a side of the moveable element 13 perpendicular to the pair of flexures 21 and the third pair of flexures 31 when viewed along the movement axis 4. Thus, the four pairs of flexures 21, 23, 31, 33 are arranged on respective one of four sides of the moveable element 13 around the movement axis 4.

[0078] In use, the SMA wires arranged between each of the pairs of flexures may be individually heated and thus contracted. Therefore, the moveable element 13 may be moved both away from and towards the support structure 11, but also the moveable element 13 can be tilted, e.g. rotate about an axis perpendicular to the primary axis 4, by contracting only selected SMA wires. In this example, as in FIG. 2, the pairs of flexures are all arranged on the same side of the moveable element 13 with respect to a plane perpendicular to the movement axis 4, which is achieved by having inverted flexures and non-inverted flexures which act to oppose one another.

[0079] FIG. 4 illustrates an alternative arrangement of a shape memory alloy apparatus. In this example, the moveable element 13 is a lens carriage moveable through an aperture of the support structure 11 in a direction along the movement axis 4. Two pairs of flexures 23a, 23b are arranged on two adjacent sides of the moveable element 13 similarly to the arrangements previously described. In other embodiments, an additional pair of flexures are provided opposite of each pair of flexures 23a, 23b. In contrast to the embodiment as shown in FIG. 2, only inverted flexures pairs 23a, 23b are used. By using the same type of flexures to effect a bi-directional movement, such arrangement may advantageously simplify control, as well as force balance between the flexures.

[0080] As illustrated in FIG. 4, the inverted flexures pairs 23a, 23b are in stack arrangement. As the SMA wires contract, the separation between the end portions of the individual flexures is decreased. For example, a first flexure pair 23a are connected between an upper portion of the moveable element 13 and the support structure 11. As the SMA wire 9a contracts the flexure pair 23a pulls the moveable element 13 in a downward direction. A second flexure pair 23b are connected between a lower portion of the moveable element 13 and the support structure 11. As the SMA wire 9b contracts the flexure pair 23b pulls the moveable element 13 in an upward direction.

[0081] In some embodiments, the flexure pairs 23a, 23b may be replaced by non-inverted flexure pairs 21 as shown in FIG. 2. In such embodiments, upon actuation of the SMA wires, the first flexure pair connected between the upper portion of the moveable element may pull the moveable element in the upward direction, and the second flexure pair connected between the lower portion of the moveable element may pull the moveable element in the downward direction.

[0082] Similar to the embodiment as shown in FIG. 3, the SMA wires arranged between each of the pairs of flexures may be individually heated and thus contracted. Therefore, the moveable element 13 may be tilted, e.g. rotate about an axis perpendicular to the primary axis 4, by contracting only selected SMA wires.

[0083] Combinations of non-inverted and inverted flexures, or flexures placed on the same or opposing sides of the moveable element 13 with respect to a plane perpendicular to the movement axis 4 may be used similarly to the examples described above.

[0084] Embodiments of the present invention have been described. It will be appreciated that variations and modifications may be made to the described embodiments within the scope of the present invention. For example, arrangements, positioning, and types of the various pairs of flexures are not limited to those described above and any combination of position and type of flexures falls within the scope of the present invention.