Shape memory actuator with multistable driven element

Patent metadata

Field	Value
Publication number	US-9512829-B2
Application number	US-201414780466-A
Country	US
Kind code	B2
Filing date	Mar 21, 2014
Priority date	Apr 5, 2013
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

A shape memory actuator is described. The shape memory actuator has a supporting body, a driven element slidably mounted on the supporting body for movement between a stable rest position and a stable operative position, a driving element that drives the driven element, the movement of the driving element being determined by a SMA wire and by first resilient return means acting to return the driving element to the rest position upon deactivation of the SMA wire, second resilient return means acting on the driven element in opposition to the SMA wire, engaging means suitable to achieve at the operative position a reversible engagement between the driven element and the supporting body, either directly or indirectly, said engagement being able to resist the action of second resilient return means, and a control system for the engagement and disengagement of the engaging means.

First claim

The invention claimed is:

1. A shape memory actuator, comprising:
a supporting body,
a driven element slidably mounted on said supporting body for movement between a stable rest position and at least one stable operative position,
a driving element, suitable to drive said driven element, moving between a stable rest position and at least one operative position corresponding respectively to said stable rest position and said at least one stable operative position of the driven element,
at least one shape memory alloy (SMA) actuating member suitable to provide the movement of said driving element between its rest position and its operative position(s),
first resilient return means acting in opposition to said SMA actuating member so as to return the driving element to its rest position upon deactivation of the SMA actuating member,
second resilient return means acting on the driven element and suitable to return the driven element to its rest position upon deactivation of the SMA actuating member,
engaging means suitable to achieve at the operative position(s) a reversible engagement between the driven element and the supporting body, either directly or indirectly, said engagement being able to resist the action of said second resilient return means, and
a control system for the engagement and disengagement of said engaging means, said control system including a rotating member pivotally mounted on the supporting body and connected to the driving element through connecting means such that said rotating member can be driven into rotation by the driving element only upon activation of the SMA actuating member but not when the driving element is returned to the rest position upon deactivation of the SMA actuating member, the rotating member being suitable to rotate alternatively clockwise and counter-clockwise at each following activation of the SMA actuating member, a pivoting axis of the rotating member being substantially perpendicular to a sliding axis of the driving element,
wherein the means connecting the driving element to the rotating member consist of a substantially inverted U-shaped bridge having a first end pivotally mounted on the driving element with a pivoting axis substantially parallel to the pivoting axis of the rotating member and a second end slidably engaged in a slot formed in the rotating member and shaped such that ends of the slot are located at different angular positions relative to the pivoting axis of the rotating member in a plane perpendicular thereto.

2. The shape memory actuator according to claim 1 , wherein the rotating member is substantially shaped like a circular sector.

3. The shape memory actuator according to claim 1 wherein the engaging means consist of a first engagement member arranged on the driven element and a second engagement member arranged on the rotating member, such that the rotation of the latter in a first direction brings said engagement members into engagement and the following rotation in the opposite direction causes their disengagement.

4. The shape memory actuator according to claim 3 , wherein the engagement members are substantially L-shaped members arranged with their internal sides facing each other.

5. The shape memory actuator according to claim 1 wherein the driving element is slidably and coaxially mounted on the driven element or slidably mounted parallel thereto.

6. The shape-memory actuator according to claim 5 , wherein the SMA actuating member passes through a transverse sleeve of the driving element, said transverse sleeve being slidably received in a longitudinally extending horizontal slot formed in the driven element.

7. The shape memory actuator according to claim 1 , wherein the first resilient return means consist of one or more coiled springs arranged between the driving element and the driven element.

8. The shape memory actuator according to claim 1 , wherein the second resilient return means consist of one or more coiled springs arranged between the supporting body and the driven element.

9. The shape memory actuator according to claim 1 , wherein at least one of the engaging means is magnetic means.

10. The shape memory actuator according to claim 9 , wherein the engaging means consist of a permanent magnet and a ferromagnetic member or another permanent magnet of opposite polarization.

11. The shape memory actuator according to claim 9 , wherein the engaging means consist of an electro-permanent magnet and a ferromagnetic member, and in that the control system consists of a control unit for the activation and deactivation of said electro-permanent magnet.

12. The shape memory actuator according to claim 9 , wherein the engaging means consist of a reversible magnet and a permanent magnet, and in that the control system consists of a control unit for the reversal of said reversible magnet.

13. The shape memory actuator according to claim 1 , wherein it further includes sensor means suitable to detect the engagement condition of the engaging means or the movement of the driven element, said sensor means being operatively connected to a control unit for the activation and deactivation of the SMA actuating member.

14. The shape memory actuator according to claim 13 , wherein the sensor means include at least one Hall effect sensor.

15. The shape memory actuator according to claim 1 , wherein the SMA actuating member is mounted on the supporting body through resilient means suitable to absorb the contraction of the SMA actuating member in order to serve as a mechanical safety that prevents the rupture of the SMA actuating member in case the driving element and/or the driven element cannot be moved.

16. A valve including a shutter movable between a stable rest position and at least one stable operative position under the action of an actuator wherein said actuator is the shape memory actuator according to claim 1 .

17. The shape memory actuator according to claim 1 , wherein the pivoting axis of the rotating member is coplanar with the sliding axis of the driving element.

18. The shape memory actuator according to claim 1 , wherein the pivoting axis of the means connecting the driving element to the rotating member is coplanar with the pivoting axis of the rotating member.

Assignees

• Getters Spa

Inventors

• Alacqua Stefano
• Butera Francesco
• Mazzoni Matteo

Classifications

• F16K31/44

  Mechanical actuating means · CPC title

• F16K31/025

  actuated by thermo-electric means · CPC title

• F03G7/06143

  Wires · CPC title

• F03G7/0634

  using cam gearings · CPC title

• F03G7/0614 Primary

  using shape memory elements · CPC title