Field

The present application relates to a shape memory alloy (SMA) actuator assembly.

Summary

According to an aspect of the present invention, there is provided a shape memory alloy (SMA) actuator assembly comprising: a first part; a second part; an SMA element configured to (e.g. upon actuation) drive relative movement between the first and second parts; wherein the SMA element is coupled to the first part via a first coupling component which is encapsulated within the first part.

Optionally, the SMA element is coupled to the second part via a second coupling component which is encapsulated within the second part. Alternatively, the SMA element may be further coupled to the first part via a second coupling component which is encapsulated within the first part, wherein the SMA element engages the second part (e.g. is wrapped/hooked around a component of the second part) so as to drive the relative movement.

Optionally, the first coupling component is integrally formed, and/or the second coupling component is integrally formed.

Optionally, the first coupling component comprises a crimp, and/or the second coupling component comprises a crimp.

Optionally, the first coupling component further comprises an element extending from the crimp, and/or the second coupling component further comprises an element extending from the crimp.

Optionally, the first part is a support structure of the SMA actuator assembly. Optionally, the second part is a movable part of the SMA actuator assembly. The movable part may comprise an electronic component such as an image sensor, a display, or an emitter. The movable part may comprise a lens assembly.

Optionally, the first coupling component is encapsulated within the first part by way of the first part being moulded at least partly around the first coupling component or at least partly additively manufactured so as to hold the first coupling component; and/or the second coupling component is encapsulated within the second part by way of the second part being moulded at least partly around the second coupling component or at least partly additively manufactured so as to hold the second coupling component.

Optionally, the SMA actuator assembly comprises at least one further SMA element coupled to the first part via a third coupling component which is encapsulated within the first part, and the third coupling component is separate from (e.g. not integrally formed with) the first coupling component. This further SMA element may be coupled to the first and second parts, and configured to (e.g. upon actuation) drive relative movement between the first and second parts.

According to another aspect of the present invention, there is provided a method of manufacturing an SMA actuator assembly comprising a first and a second part that are movable relative to each other (such as the ones described above); the method comprising: coupling an SMA element to a first coupling component; and (e.g. subsequently) encapsulating the first coupling component within the first part.

Optionally, the SMA element is coupled to the first coupling component before the first coupling component is encapsulated.

Optionally, the method further comprises: coupling the SMA element to a second coupling component; and (e.g. subsequently) encapsulating the second coupling component within the second part.

Alternatively, (e.g. where the SMA element is wrapped/hooked around a component of the second part) the method may further comprise: coupling the SMA element to a second coupling component; and (e.g. subsequently) encapsulating the second coupling component within the first part. The first and second coupling components may be encapsulated within the first part simultaneously.

Optionally, the SMA element is coupled to the second coupling component before the second coupling component is encapsulated.

Optionally, the SMA element is coupled to both the first and second coupling components before the first and/or second coupling components are encapsulated.

Optionally, the first and second coupling components are held apart by a sacrificial strut body (during at least part of the encapsulation).

Optionally, the method comprises: removing the sacrificial strut body holding apart the first and second coupling components after the first and/or second coupling components are encapsulated. Optionally, encapsulating the first coupling component within the first part comprises moulding the first part at least partly around the first coupling component. Optionally, encapsulating the second coupling component within the second part comprises moulding the second part at least partly around the second coupling component. Optionally, encapsulating the second coupling component within the first part comprises moulding the first part at least partly around the second coupling component.

Optionally, encapsulating the first coupling component within the first part comprises additively manufacturing at least part of the first part so as to hold the first coupling component. Optionally, encapsulating the second coupling component within the second part comprises additively manufacturing at least part of the second part so as to hold the first coupling component. Optionally, encapsulating the second coupling component within the first part comprises additively manufacturing at least part of the first part so as to hold the first coupling component.

Optionally, additively manufacturing at least part of the first part so as to hold the first coupling component (and/or the second coupling component) comprises: additively manufacturing the first part up to and including a pocket (or pockets) shaped to fit the first coupling component (and/or the second coupling component) within it (or them); placing the first coupling component (and/or the second coupling component) into the pocket(s);

(subsequently) additively manufacturing the rest of the at least part of the first part so as to (at least partly) enclose the first coupling component (and/or the second coupling component) within the pocket(s).

Optionally, additively manufacturing at least part of the second part so as to hold the second coupling component comprises: additively manufacturing the second part up to and including a pocket shaped to fit the second coupling component within it;

(subsequently) placing the second coupling component into the pocket;

(subsequently) additively manufacturing the rest of the at least part of the second part so as to (at least partly) enclose the second coupling component within the pocket.

The pockets may also be referred to as cavities.

Optionally, additively manufacturing at least part of the first part so as to hold the first coupling component (and/or the second coupling component) comprises: additively manufacturing a portion of the first part comprising a main body, a pocket (or pockets) shaped to fit the first coupling component (and/or the second coupling component) within it (or them), and a lid (or lids) connected to the main body via a living hinge (or living hinges);

(subsequently) placing the first coupling component (and/or the second coupling component) into the pocket(s);

(subsequently) closing the lid(s) so as to (at least partly) enclose the first coupling component (and/or the second coupling component) within the pocket(s);

(subsequently) additively manufacturing the rest of the at least part of the first part so as to seal the first coupling component (and/or the second coupling component) within the pocket(s).

Optionally, additively manufacturing at least part of the second part so as to hold the second coupling component comprises: additively manufacturing a portion of the second part comprising a main body, a pocket shaped to fit the second coupling component within it, and a lid connected to the main body via a living hinge;

(subsequently) placing the second coupling component into the pocket;

(subsequently) closing the lid so as to (at least partly) enclose the second coupling component within the pocket;

(subsequently) additively manufacturing the rest of the at least part of the second part so as to seal the second coupling component within the pocket.

Optionally, the method comprises locally cooling the SMA element during at least part of the encapsulation, for example during the moulding or the additive manufacturing of the first and/or the second parts.

Optionally, the method comprises providing a sealing around the SMA element so as to protect the SMA element from being damaged (e.g. from high temperatures) during at least part of the encapsulation, for example during the moulding or the additive manufacturing of the first and/or the second parts.

Brief description of the drawings

Certain embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 is a schematic view of an SMA actuator assembly.

Detailed description The present invention describes ways of manufacturing the shape memory alloy (SMA) actuator assembly 1 shown in Fig. 1. The SMA actuator assembly 1 comprises a first part 3 (which may be a support structure) and a second part 4 (which may be a movable part). A first coupling component 31 (which may be or may include a crimp) is held within and encapsulated within the first part 3. A second coupling component 41 (which may be or may include a crimp) is held within and encapsulated within the second part 4. The first and second coupling components 31, 41 are coupled to an SMA element 2, which is an SMA wire 2 in Fig. 1. The SMA wire 2 is configured to move the first part 3 and the second part 4 relative to each other when actuated by being contracted. The SMA wire 2 contracts when heated. The SMA wire 2 may be heated by passing a current through the SMA wire 2.

The SMA actuator assembly 1 may be manufactured using an insert moulding process comprising:

1) Placing inside a mould the first coupling component 31 and/or the second coupling component 41 holding the SMA wire 2.

2) Closing the mould.

3) Injecting molten material (e.g. plastic) into the mould and over the coupling component(s) provided inside the mould, to form the first part 3 and/or the second part 4.

During this manufacturing process, the first and second coupling components 31, 41 may be connected via a disposable fret (herein also referred to as a sacrificial strut body) holding apart the two coupling components 31, 41. Where this is the case, the manufacturing process could also involve:

4) Removing the disposable fret (i.e. the sacrificial strut body) from the first and second coupling components 31, 41.

One of the issues with the above methods of manufacturing is that the SMA wire 2 may be damaged by the temperatures of the injection moulding process. To mitigate this risk, one may provide:

• local cooling around the SMA wire 2;

• sealing around the SMA wire 2 without damaging the wire.

The latter may be done by providing flexibility in the crimps so that the crimps mount on a reference surface in the tool and there is a wire sealing surface at the crimp thickness above.

Alternatively, the SMA actuator assembly 1 may be manufactured using an additive manufacturing process (e.g. a 3D printing process) comprising:

1) Additively manufacturing (e.g. 3D printing) the first part 3 up to and including a pocket (e.g. a cavity, a space) shaped to hold the first coupling component 31 and/or additively manufacturing the second part 4 up to and including a pocket shaped to hold the second coupling component 41. ) (Optionally) Pausing the additive manufacturing 3) Placing the first coupling component 31 within the pocket of the first part 3 and/or placing the second coupling component 41 within the pocket of the second part 4.

4) Additively manufacturing (e.g. 3D printing) over the first coupling component 31 and/or the second coupling component 41 so as to (at least partly) enclose it/them within the pocket(s). In other words, restarting the additive manufacturing (e.g. the print) at the layer that rests on top of the inserted coupling component(s) so as to seal the inserted coupling component(s) within the pocket(s).

During this manufacturing process, the first and second coupling components 31, 41 may be connected via a disposable fret (herein also referred to as a sacrificial strut body) holding apart the two coupling components 31, 41. Where this is the case, the manufacturing process would also involve:

5) Removing the disposable fret (i.e. the sacrificial strut body) from the first and second coupling components 31, 41.

The coupling components 31, 41 may be attached/bonded (e.g. glued) into the pockets.

This manufacturing process works best where the inserted coupling component has a flat upper surface and no recessed upper surfaces that would require unsupported layers. There are some methods of optimising the shape of the print to accommodate these types of features but they are limiting and dependant on the additive manufacturing technology/3D printing technology being used.

Where the inserted coupling component does not have a flat upper surface, the following alternative method of additive manufacturing may be more appropriate:

1) Additively manufacturing (e.g. 3D printing) a portion of the first part 3 including: (i) its main body comprising a pocket shaped to hold the first coupling component 31, (ii) a lid, and (iii) a living hinge connecting the lid and the main body; and/or additively manufacturing a portion of the second part 4 including: (i) its main body comprising a pocket shaped to hold the second coupling component 41, (ii) a lid, and (iii) a living hinge connecting the lid and the main body of the second part.

2) Placing the first coupling component 31 within the pocket of the first part 3 and/or placing the second coupling component 41 within the pocket of the second part 4.

3) Closing the lid over the coupling component(s) 31, 41 so as to (at least partly) enclose it (or them) within the pocket(s).

4) Additively manufacturing the rest of the first part 3 so as to seal the first coupling component 31 within the pocket of the first part, and/or the rest of the second part 4 so as to seal the second coupling component 41 within the pocket of the second part. During this manufacturing process, the first and second coupling components 31, 41 may be connected via a disposable fret (herein also referred to as a sacrificial strut body) holding apart the two coupling components 31, 41. Where this is the case, the manufacturing process would also involve:

5) Removing the disposable fret (i.e. the sacrificial strut body) from the first and second coupling components 31, 41.

The coupling components 31, 41 may be attached/glued into the pockets.

SMA element

The term 'shape memory alloy (SMA) element' may refer to any element comprising SMA. The SMA element may be described as an SMA wire. The SMA element may have any shape that is suitable for the purposes described herein. The SMA element may be elongate and may have a round cross section or any other shape cross section. The cross section may vary along the length of the SMA element. The SMA element might have a relatively complex shape such as a helical spring. It is also possible that the length of the SMA element (however defined) may be similar to one or more of its other dimensions. The SMA element may be sheet-like, and such a sheet may be planar or non-planar. The SMA element may be pliant or, in other words, flexible. In some examples, when connected in a straight line between two components, the SMA element can apply only a tensile force which urges the two components together. In other examples, the SMA element may be bent around a component and can apply a force to the component as the SMA element tends to straighten under tension. The SMA element may be beam-like or rigid and may be able to apply different (e.g. non-tensile) forces to elements. The SMA element may or may not include material(s) and/or component(s) that are not SMA. For example, the SMA element may comprise a core of SMA and a coating of non-SMA material. Unless the context requires otherwise, the term 'SMA element' may refer to any configuration of SMA material acting as a single actuating element which, for example, can be individually controlled to produce a force on an element. For example, the SMA element may comprise two or more portions of SMA material that are arranged mechanically in parallel and/or in series. In some arrangements, the SMA element may be part of a larger SMA element. Such a larger SMA element might comprise two or more parts that are individually controllable, thereby forming two or more SMA elements. The SMA element may comprise an SMA wire, SMA foil, SMA film or any other configuration of SMA material. The SMA element may be manufactured using any suitable method, for example by a method involving drawing, rolling or deposition and/or other forming process(es). The SMA element may exhibit any shape memory effect, e.g. a thermal shape memory effect or a magnetic shape memory effect, and may be controlled in any suitable way, e.g. by Joule heating, another heating technique or by applying a magnetic field. Other variations

It will be appreciated that there may be many other variations of the above-described examples.

The coupling components 31, 41 may each comprise a crimp and at least one element which may be integral with (e.g. formed from the same sheet of metal as) the crimp and/or which may extend from the crimp. Such elements may, for example, correspond to electrical connection portions configured to allow the SMA wire 2 to be electrically connected to e.g. a control circuit. Alternatively or additionally, such elements may correspond to portions configured to facilitate coupling of the crimps to the first and/or second parts 3, 4. Such elements may correspond to the static and/or moving mount portions described in WO 2016/189314 Al, which is incorporated herein by reference. In some examples, only part of the coupling component 31, 41 (e.g. only such an element and not the crimp) is encapsulated with the first/second part 3, 4.

The first and second coupling components may be both encapsulated within the first part, and e.g. have the SMA wire hooked to or wrapped around a component of the second part. Alternatively, the first and second coupling components may be both encapsulated within the second part, and e.g. have the SMA wire hooked to or wrapped around a component of the first part.