SHAPE MEMORY ALLOY ACTUATION APPARATUS

• US 20110179786A1
• Filed: 07/24/2009
• Published: 07/28/2011
• Est. Priority Date: 07/30/2008
• Status: Active Grant

• Current Assignee: Cambridge Mechatronics Limited
• Original Assignee: Cambridge Mechatronics Limited
• Inventors: Topliss, Richard, Brown, Andrew Benjamin David
• Granted Patent: US 8,588,598 B2
• Time in Patent Office: Days
• US Class Current: 60/527
• CPC Class Codes: F03G 7/065 using a shape memory element
• CPC Class Codes: G02B 7/08 adapted to co-operate with a remote control mechanism
• CPC Class Codes: G03B 3/10 Power-operated focusing

Abstract

A shape memory alloy actuation apparatus comprises a movable element suspended on a support structure by a plurality of flexures which are non-uniformly configured to apply forces having differing components perpendicular to the movement axis generating a net moment around the centre of mass of the movable element in an opposite sense from the moment generated by the actuation force. A shape memory alloy wire is coupled between the support structure and an intermediate body engaging the movable element through a pivotal contact to avoid lateral force transfer. Also coupled between the support structure and the intermediate body is a resilient biassing flexure plastically deformed in a partial region thereof. The shape memory alloy wire is crimped by a crimping member fixed to the support structure holding the shape memory alloy wire against a curved surface from which the shape alloy memory wire extends to the movable element.

Claims

1. An apparatus comprising:

a support structure;

a movable element;

a suspension system comprising a plurality of flexures coupled between the support structure and the movable element to support the movable element on the support structure and to guide movement of the movable element along a movement axis by deflection of the flexures;

an actuator arrangement arranged to apply an actuation force to the movable element along the movement axis, the actuation force also generating a moment around the centre of mass of the movable element,

wherein the flexures are non-uniformly configured such that the flexures, on movement of the movable element along the movable axis without rotation, apply forces having differing components perpendicular to the movement axis, which components generate a net moment around the centre of mass of the movable element in an opposite sense from the moment generated by the actuation force.

2. An apparatus according to claim 1, wherein the flexures include at least one first flexure and at least one second flexure arranged at different positions along the movement axis

3. An apparatus according to claim 2, wherein the at least one first flexure and the at least one second flexure are non-uniformly configured to apply said forces by:

having different lengths; and

/or

being deflected, at a given position of the movable element, by different amounts from their respective non-deflected positions.

4. An apparatus according to claim 2, wherein the at least one first flexure comprises at least one pair of flexures arranged with mirror symmetry about a notional plane perpendicular to said moment around the centre of mass generated by the actuation force, and the at least one second flexure also comprises at least one pair of flexures arranged with mirror symmetry about said notional plane.

5. An apparatus according to claim 1, wherein said moment generated by said flexures balances said moment generated by the actuation force, thereby preventing rotation of the movable element.

6. An apparatus according to claim 1, wherein said flexures extend around the movement axis.

7. An apparatus according to claim 1, wherein the actuator arrangement comprises a shape memory alloy actuator.

8. An apparatus according to claim 7, wherein

the shape memory alloy actuator is arranged to apply said actuation force to the movable element in a first direction along the movement axis, on contraction of the shape memory alloy actuator, and

the actuator arrangement further comprises a biassing element arranged to bias the movable element relative to the support structure in a second direction along the movement axis, opposite to the first direction.

9. An apparatus according to claim 8, wherein the apparatus further comprises an end-stop arranged to limit the movement of the movable element in a second direction along the movement axis, opposite to the first direction, the apparatus being arranged such that, when the moveable element is held against the end-stop, the force applied by the biassing element in said second direction is greater than the force applied by the flexures of the suspension system.

10. An apparatus according to claim 1, wherein the shape memory alloy actuator comprises shape memory alloy wire coupled between the support structure and the movable element.

11. An apparatus according to claim 10, wherein the shape memory alloy wire extends at an acute angle to the movement direction of the movable element.

12. An apparatus according to claim 11, wherein the shape memory alloy wire comprises two portions arranged with mirror symmetry about a notional plane perpendicular to said moment around the centre of mass generated by the actuation force.

13. An apparatus according to claim 12, wherein the shape memory wire is a continuous piece hooked over the movable element to form the two portions on either side thereof.

14. An apparatus according to claim 1, wherein the movable element is a camera lens element, the movement axis being the optical axis of the camera lens element.

15. An apparatus according to claim 14, wherein the camera lens element comprises one or more lenses having a diameter of at most 10 mm.

16. A shape memory alloy actuation apparatus comprising:

a support structure;

a movable element;

a suspension system comprising a plurality of resilient flexures coupled between the support structure and the movable element to support the movable element on the support structure and to guide movement of the movable element along a movement axis by deflection of the flexures;

an intermediate body engaging the movable element in a manner providing transfer of force from the intermediate body to the movable element in a first direction along the movement axis whilst allowing pivoting of the intermediate body with respect to the movable element;

a shape memory alloy actuator coupled between the support structure and the intermediate body and arranged to apply an actuation force to the intermediate body in the first direction along the movement axis, on contraction of the shape memory alloy actuator; and

a biassing element coupled between the support structure and the intermediate body and arranged to bias the intermediate body relative to the support structure in a second direction along the movement axis, opposite to the first direction.

17-43. -43. (canceled)

44. A shape memory alloy actuation apparatus comprising:

a support structure;

a movable element;

a suspension system arranged to support the movable element on the support structure and to guide movement of the movable element along a movement axis;

a shape memory alloy wire coupled between the support structure and the movable element and arranged to apply an actuation force to the movable element in a first direction along the movement axis on contraction of the shape memory alloy wire,

the shape memory alloy wire being coupled to the support structure by a crimping member and a curved surface, the crimping member crimping the shape memory alloy wire and being fixed to the support structure holding the shape memory alloy wire against the curved surface from which the shape alloy memory wire extends to the movable element.

45-49. -49. (canceled)