SMA actuator assembly

Patent metadata

Field	Value
Publication number	US-12228113-B2
Application number	US-202218569309-A
Country	US
Kind code	B2
Filing date	Jun 17, 2022
Priority date	Jun 17, 2021
Publication date	Feb 18, 2025
Grant date	Feb 18, 2025

Abstract

An SMA actuator assembly ( 1 a ) for driving or rotating a movable part ( 20 ) in a predetermined direction or sense by a plurality of repeated incremental steps is provided. The SMA actuator assembly comprises the movable part; a first engagement portion ( 31 ) for engaging the movable part; two SMA wires ( 41, 42 ) arranged to move the first engagement portion such that the first engagement portion repeatedly, for each of said incremental steps, is configured to do the following: engage with the movable part from a starting position, exert a force or torque on the movable part in the predetermined direction and disengage from the movable part and return to the starting position. The exertion of the force or torque on the movable part and the engaging or disengaging with the movable part are caused by contraction or relaxation of the two SMA wires.

First claim

The invention claimed is:

1. A shape memory alloy (SMA) actuator assembly for driving or rotating a movable part in a predetermined direction or sense by a plurality of repeated incremental steps, the SMA actuator assembly comprising:
the movable part;
a first engagement portion for engaging the movable part;
a second engagement portion for engaging the movable part;
two SMA wires arranged to move the first engagement portion such that the first engagement portion repeatedly, for each of said incremental steps, is configured to:
engage with the movable part from a starting position;
exert a force or torque on the movable part in the predetermined direction; and
disengage from the movable part and return to the starting position,

wherein:
the exertion of the force or torque on the movable part and the engaging and disengaging with the movable part are caused by contraction or relaxation of the two SMA wires,
the two SMA wires together are arranged to control the engagement and/or disengagement of the first engagement portion,
a first SMA wire of the two SMA wires is arranged, on contraction, to cause the first engagement portion to exert a force or torque on the movable part in the predetermined direction or sense,
a second of the two SMA wires is arranged, on contraction, to cause the first engagement portion to exert a force or torque on the movable part in a second direction or sense that is opposite to the predetermined direction or sense, and
at least one SMA wire is arranged to move the second engagement portion to engage with the movable part to control the position of the movable part during at least a part of the time when the first engagement portion is disengaged from the movable part.

2. The SMA actuator assembly of claim 1 , wherein the two SMA wires are arranged to move the first engagement portion to cause driving or rotating of the movable part in the second direction or sense by a plurality of repeated incremental steps, such that the first engagement portion repeatedly is configured to:
engage with the movable part from a starting position;
exert a force or torque on the movable part in the second direction or sense; and
disengage from the movable part and return to the starting position, wherein the exertion of the force or torque on the movable part and/or the engaging or disengaging with the movable part are caused by contraction or relaxation of the two SMA wires.

3. The SMA actuator assembly of claim 1 , wherein the first and second SMA wires are angled with respect to each other.

4. The SMA actuator assembly of claim 1 , wherein the at least one SMA wire is arranged to move the second engagement portion such that the second engagement portion repeatedly, for each of said incremental steps, is configured to:
engage with the movable part from a starting position;
exert a force or torque on the movable part in the predetermined direction or sense; and
disengage from the movable part and return to the starting position,
wherein the exertion of the force or torque on the movable part and/or the engaging with or disengaging from the movable part are caused by contraction or relaxation of the at least one SMA wire.

5. The SMA actuator assembly of claim 4 , wherein:
the at least one SMA wire comprises two further SMA wires;
the two further SMA wires together are arranged to control the engagement and/or disengagement of the second engagement portion;
a first SMA wire of the two further SMA wires is arranged, on contraction, to cause the second engagement portion to exert a force or torque on the movable part in the predetermined direction or sense; and

a second of the two further SMA wires is arranged, on contraction, to cause the second engagement portion to exert a force or torque on the movable part in the second direction or sense.

6. The SMA actuator assembly of claim 1 , wherein:
the second engagement portion exerts a force or torque on the movable part during at least part of the time when the first engagement portion is disengaged from the movable part; and
the second engagement portion exerts a force or torque on the movable part during the time when the first engagement portion is disengaged from the movable part such that a force or torque is continuously applied to the movable part either by the first or by the second engagement portion.

7. The SMA actuator assembly of claim 1 , wherein:
the second engagement portion is configured to engage the movable part before the first engagement portion disengages from the movable part; and
the first engagement portion is configured to engage the movable part before the second engagement portion disengages from the movable part.

8. The SMA actuator assembly of claim 1 , wherein:
the first and/or second engagement portions have a series of first teeth and the movable part has a series of second teeth, wherein teeth of the series of first and second teeth are arranged to engage with each other when an engagement portion engages with the movable part, or
the first and/or second engagement portions are arranged to transfer force exerted by an SMA wire to the movable part by friction.

9. The SMA actuator assembly of claim 1 , further comprising:
a support structure; and
a biasing element arranged to bias the first engagement portion into or out of engagement with the movable part, wherein the biasing element is in sliding or rolling contact with the support structure such that as the first engagement portion exerts a force or torque on the movable part, the biasing element slides or rolls relative to the support structure.

10. The SMA actuator assembly of claim 1 , wherein:
the first engagement portion is mounted on a housing, the housing being pivotable relative to the movable part; and
the pivoting of the housing is arranged to amplify the contraction or relaxation of the first and/or second SMA wire of the two SMA wires to cause a greater extent of movement of the first engagement portion in the predetermined direction.

11. The SMA actuator assembly of claim 1 , further comprising an iris mechanism arranged to control the size of an aperture in an iris, wherein the movable part is coupled to the iris mechanism so that motion of the movable part in the predetermined direction causes the aperture to open or close.

Assignees

• Cambridge Mechatronics Ltd

Inventors

• Howarth James
• Brown Andrew Benjamin Simpson
• Kist René
• Bunting Stephen Matthew
• Doust Alexander

Classifications

• F03G7/0645

  Clamping, fixing or crimping parts · CPC title

• G03B9/06

  Two or more co-operating pivoted blades, e.g. iris type (shutters functioning as diaphragms by limiting extent of opening movement G03B9/08) · CPC title

• F03G7/0641

  Motors; Energy harvesting or waste energy recovery · CPC title

• F03G7/06143 Primary

  Wires · CPC title