Shape memory alloy actuation apparatus

Patent metadata

Field	Value
Publication number	US-12554177-B2
Application number	US-201917253696-A
Country	US
Kind code	B2
Filing date	Jun 21, 2019
Priority date	Jun 21, 2018
Publication date	Feb 17, 2026
Grant date	Feb 17, 2026

Abstract

A shape memory alloy actuation apparatus comprises a support structure ( 2 ) and a movable element ( 10 ). A helical bearing arrangement ( 20 ) supporting the movable element on the support structure guides helical movement of the movable element with respect to the support structure around a helical axis (H). At least one shape memory alloy actuator wire ( 60 ) is connected between the support structure and the movable element in, or at an acute angle to, a plane normal to the helical axis, so as to drive rotation of the movable element around the helical axis which the helical bearing arrangement converts into said helical movement.

First claim

The invention claimed is:

1 . A shape memory alloy actuation apparatus comprising:
a support structure; a movable element; a helical bearing arrangement supporting the movable element on the support structure and defining a helical bearing surface arranged to guide helical movement of the movable element, with respect to the support structure, around a helical axis; and at least one shape memory alloy actuator wire connected between the support structure and the movable element, wherein:
the shape memory alloy actuator wire extends (i) in a plane normal to the helical axis or (ii) in a plane at an acute angle to a plane normal to the helical axis;
the shape memory alloy actuator wire is arranged, on contraction, to drive rotation of the movable element relative to the support structure around the helical axis; and
wherein the helical bearing surface of the helical bearing arrangement converts the driven rotation of the movable element into the helical movement such that the moveable element translates relative to the support structure along the helical axis;
wherein the helical bearing arrangement comprises at least one helical bearing that is a rolling bearing comprising bearing surfaces on the support structure and the movable element, the bearing surfaces including the helical bearing surface, the helical bearing arrangement further comprising at least one rolling bearing element disposed between the bearing surfaces.

2 . The shape memory alloy actuation apparatus according to claim 1 , wherein the helical bearing arrangement comprises a plurality of helical bearings that are rolling bearings.

3 . The shape memory alloy actuation apparatus according to claim 2 , wherein at least one helical bearing comprises a plurality of rolling bearing elements.

4 . The shape memory alloy actuation apparatus according to claim 1 , wherein the bearing arrangement comprises two helical bearings only.

5 . The shape memory alloy actuation apparatus according to claim 4 , wherein:
the bearing surfaces of a first helical bearing comprise grooves on each of the support structure and the movable element; and the bearing surfaces of a second helical bearing comprise either (i) a groove on the support structures; and a planar surface on the movable element; or (ii) a groove on the movable element; and a planar surface on the support structure.

6 . The shape memory alloy actuation apparatus according to claim 2 , wherein the bearing arrangement comprises three helical bearings.

7 . The shape memory alloy actuation apparatus according to claim 6 , wherein:
the bearing surfaces of first and second helical bearings each comprise grooves on each of the support structure and the movable element; and the bearing surfaces of a third helical bearing comprise either (i) a groove on the support structures; and a planar surface on the movable element; or (ii) a groove on the movable element; and a planar surface on the support structure.

8 . The shape memory alloy actuation apparatus according to claim 7 , wherein the first, second, and third helical bearings each comprise a single rolling element only.

9 . The shape memory alloy actuation apparatus according to claim 6 , wherein:
first and second helical bearings are arranged so that the bearing surfaces on the movable element are respectively above and below the bearing surfaces on the support structure, as viewed along the helical axis; and a third helical bearings is arranged so that the bearing surfaces on the movable element is above the bearing surfaces on the support structure, as viewed along the helical axis.

10 . The shape memory alloy actuation apparatus according to claim 1 , wherein the shape memory alloy actuation apparatus further comprises a loading arrangement that loads at least one of the bearing surfaces against the rolling bearing element.

11 . The shape memory alloy actuation apparatus according to claim 10 , wherein the loading arrangement is a resilient loading arrangement that resiliently loads at least one of the bearing surfaces against the rolling bearing element.

12 . The shape memory alloy actuation apparatus according to claim 10 , wherein the loading arrangement comprises a resilient element connected between the support structure and the movable element.

13 . The shape memory alloy actuation apparatus according to claim 10 , wherein the loading arrangement is a magnetic loading arrangement.

14 . A shape memory alloy actuation apparatus, comprising:
a support structure; a movable element; a helical bearing arrangement supporting the movable element on the support structure and defining a helical bearing surface arranged to guide helical movement of the movable element, with respect to the support structure, around a helical axis; and at least one shape memory alloy actuator wire connected between the support structure and the movable element, wherein:
the shape memory alloy actuator wire extends (i) in a plane normal to the helical axis or (ii) in a plane at an acute angle to a plane normal to the helical axis;
the shape memory alloy actuator wire is arranged, on contraction, to drive rotation of the movable element relative to the support structure around the helical axis; and
wherein the helical bearing surface of the helical bearing arrangement converts the driven rotation of the movable element into the helical movement such that the moveable element translates relative to the support structure along the helical axis;
wherein the helical bearing arrangement comprises at least one flexure extending between the support structure and the movable element.

15 . The shape memory alloy actuation apparatus according to claim 14 , wherein the at least one flexure extends in an arc around the helical axis and is pre deflected along the helical axis.

16 . The shape memory alloy actuation apparatus according to claim 14 , wherein the at least one flexure comprises a plurality of flexures that extend along the helical axis and are inclined with respect to a plane perpendicular to the helical axis with rotational symmetry around the helical axis.

17 . The shape memory alloy actuation apparatus according to claim 14 , wherein the helical bearing arrangement further comprises a support plate mounted on the support structure and a movable plate mounted on movable element, the at least one flexure being integrally formed with the support plate and the movable plate.

18 . The shape memory alloy actuation apparatus according to claim 1 , wherein, projected along the helical axis, the extent of the shape memory alloy actuator wire is no greater than the extent of the helical bearing arrangement.

19 . The shape memory alloy actuation apparatus according to claim 2 , wherein the at least one shape memory alloy actuator wire is arranged to apply a force to the movable element that loads the helical bearing arrangement.

20 . The shape memory alloy actuation apparatus according to claim 1 , wherein the at least one shape memory alloy actuator wire comprises at least two shape memory alloy actuator wires arranged to apply a couple to the movable element that loads the helical bearing arrangement.

21 . The shape memory alloy actuation apparatus according to claim 1 , wherein the at least one shape memory alloy actuator wire is perpendicular to the helical axis.

22 . The shape memory alloy actuation apparatus according to claim 1 , wherein the at least one shape memory alloy actuator

Assignees

• Cambridge Mechatronics Ltd

Inventors

• Brown Andrew
• Bunting Stephen
• Burbridge Daniel
• Hart Oliver
• Heijne Nicholas
• Howarth James
• Scholz Marc-Sebastian

Classifications

• F03G7/0665

  controlled displacement, e.g. by using a lens positioning actuator · CPC title

• F03G7/0636

  with several elements connected in parallel · CPC title

• F03G7/0633

  performing a rotary movement · CPC title

• G03B3/10 Primary

  Power-operated focusing · CPC title

• F03G7/06143 Primary

  Wires · CPC title