Spiral shape memory alloy actuator

Abstract

A shape memory alloy (SMA) actuator (100) may include a main body (200) defining an axis (212) and a shape memory alloy (SMA) wire (104) coupled to the main body in the form of a spiral about the axis. The SMA wire is configured to change between an extended state and a contracted state in response to heat being applied to the SMA wire. The main body rotates about the axis in a first direction when the SMA wire is changing from the extended state to the contracted state and in a second direction opposite the first direction when the SMA wire is changing from the contracted state to the extended state.

Description

SPIRAL SHAPE MEMORY ALLOY ACTUATORCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Provisional Patent Application No. 63 / 637,822, filed April 23, 2024, the entire content of which is incorporated herein by reference.FIELD OF THE DISCLOSURE

[0002] The present disclosure relates to electronically operated actuators, and more specifically to shape memory alloy actuators.BACKGROUND OF THE DISCLOSURE

[0003] Various products in the automotive, aviation, marine, industrial, and domestic applications employ electronically operated actuators. One such type of electronically operated actuator is a shape memory alloy actuator. A typical shape memory alloy actuator includes a metal element that changes form in response to heat being applied to the metal element. The metal element is often coupled to a mechanism, which is actuated when the metal element changes form.SUMMARY OF THE DISCLOSURE

[0004] In some aspects, the techniques described herein relate to a shape memory alloy (SMA) actuator including: a main body defining an axis; and a shape memory alloy (SMA) wire coupled to the main body in the form of a spiral about the axis, wherein the SMA wire is configured to change between an extended state and a contracted state in response to heat being applied to the SMA wire, wherein the main body rotates about the axis in a first direction when the SMA wire is changing from the extended state to the contracted state and in a second direction opposite the first direction when the SMA wire is changing from the contracted state to the extended state.

[0005] In some aspects, the techniques described herein relate to a SMA actuator, wherein the main body includes a first face and a second face opposite the first face.

[0006] In some aspects, the techniques described herein relate to a SMA actuator, further including a plurality of bearing surfaces disposed on the main body, wherein the plurality of bearing surfaces supports and maintains the SMA wire in the spiral form, and wherein the plurality of bearing surfaces are distributed about the main body in a manner that collectively forms a spiral-shape pattern.

[0007] In some aspects, the techniques described herein relate to a SMA actuator, wherein the plurality of bearing surfaces includes a first set of bearings on the first face and a second set of bearings on the second face.

[0008] In some aspects, the techniques described herein relate to a SMA actuator, wherein the SMA wire is a first SMA wire that tautly engages the first set of bearings on the first face, and wherein the SMA actuator further includes a second SMA wire that tautly engages the second set of bearings on the second face.

[0009] In some aspects, the techniques described herein relate to a SMA actuator, wherein the SMA wire is a first SMA wire extending along the first face of the main body, and wherein the SMA actuator further includes a second SMA wire extending along the second face of the main body.

[0010] In some aspects, the techniques described herein relate to a SMA actuator, wherein each of the first SMA wire and the second SMA wire spirals radially inward from a first end to a second end, and wherein one of the first end or the second end of each of the first SMA wire and the second SMA wire is fixed to the main body at a location offset from the axis.

[0011] In some aspects, the techniques described herein relate to a SMA actuator, wherein the SMA wire spirals radially inward from a first end to a second end, and wherein one of the first end or the second end of the SMA wire is fixed to the main body at a location offset from the axis.

[0012] In some aspects, the techniques described herein relate to a SMA actuator, wherein when heat is applied to the first SMA wire in the extended state, the main body rotates in the first direction in response to the first SMA wire changing to the contracted state which, in turn, pulls and deforms the second SMA wire from the contracted state to the extended state.

[0013] In some aspects, the techniques described herein relate to a SMA actuator, wherein when heat is applied to the second SMA wire in the extended state, the main body rotates in the second direction in response to the second SMA wire changing to the contracted state which, in turn, pulls and deforms the first SMA wire from the contracted state to the extended state.

[0014] In some aspects, the techniques described herein relate to a SMA actuator, wherein the plurality of bearing surfaces collectively define a series of concentric circles.

[0015] In some aspects, the techniques described herein relate to a SMA actuator, wherein the main body is one of a plurality of main bodies coupled together for co-rotation about the axis.

[0016] In some aspects, the techniques described herein relate to a shape memory alloy (SMA) actuator including: a shaft disposed along an axis; a plurality of main bodies coupled to the shaft, the plurality of main bodies coupled together for co-rotation about the axis; and a plurality of shape memory alloy (SMA) wires, each SMA wire of the plurality of SMA wires coupled to a respective one of the plurality of main bodies in the form of a spiral about the axis, wherein the plurality of SMA wires is configured to change between an extended state and a contracted state in response to heat being applied to the plurality of SMA wires, wherein the plurality of main bodies rotates in unison about the axis in a first direction when the plurality of SMA wires changes from the extended state to the contracted state and in a second direction opposite the first direction when the plurality of SMA wires changes from the contracted state to the extended state.

[0017] In some aspects, the techniques described herein relate to a SMA actuator, wherein each main body of the plurality of main bodies includes a plurality of bearings arranged in a spiral shape, and wherein each SMA wire of the plurality of SMA wires tautly engages the plurality of bearings of the respective one of the plurality of main bodies.

[0018] In some aspects, the techniques described herein relate to a SMA actuator, wherein each bearing of the plurality of bearings is rotatable relative to the main body.

[0019] In some aspects, the techniques described herein relate to a SMA actuator, wherein each main body of the plurality of main bodies includes a first face and a second face opposite the first face.

[0020] In some aspects, the techniques described herein relate to a SMA actuator, wherein the plurality of bearings includes a first set of bearings on the first face and a second set of bearings on the second face.

[0021] In some aspects, the techniques described herein relate to a SMA actuator, wherein the plurality of SMA wires is a first plurality of SMA wires that tautly engages the first set of bearings on the first face of each main body of the plurality of main bodies, and wherein the SMA actuator further includes a second plurality of SMA wires that tautly engages the second set of bearings on the second face of each main body of the plurality of main bodies.

[0022] In some aspects, the techniques described herein relate to a SMA actuator, wherein when heat is applied to the first plurality of SMA wires in the extended state, the plurality of main bodies rotates in the first direction in response to the first plurality of SMA wires changing to the contracted state which, in turn, pulls and deforms the second plurality of SMA wires from the contracted state to the extended state; and wherein when heat is applied to the second plurality of SMA wires in the extended state, the plurality of main bodies rotates in the second direction in response to the second plurality of SMA wires changing to the contracted state which, in turn, pulls and deforms the first plurality of SMA wires from the contracted state to the extended state.

[0023] In some aspects, the techniques described herein relate to a shape memory alloy (SMA) actuator including: a plurality of shape memory alloy (SMA) wires, each SMA wire of the plurality of SMA wires forming a spiral shape; and a main body coupled to a first end of each SMA wire of the plurality of SMA wires, wherein the plurality of SMA wires is configured to change between an extended state and a contracted state to rotate the main body in response to heat being applied to the plurality of SMA wires.

[0024] Other features and aspects of the disclosure will become apparent by consideration of the following detailed description and accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a plan view of a shape memory alloy (SMA) actuator in accordance with an embodiment of the disclosure, illustrating a first side of the SMA actuator.

[0026] FIG. 2 is a plan view of the SMA actuator of FIG. 1, illustrating a second side of the SMA actuator.

[0027] FIG. 3 is a perspective view of the SMA actuator of FIG. 1.

[0028] FIG. 4 is a perspective view of a shape memory alloy (SMA) actuator in accordance with another embodiment of the disclosure.

[0029] FIG. 5 is a perspective view of a shape memory alloy (SMA) actuator in accordance with another embodiment of the disclosure.

[0030] Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

[0031] Various terms and / or phrases describing a positional or directional reference, such as “top”, “bottom”, “front”, “rear”, “left”, “right”, “above”, “below”, “vertical”, “horizontal”, etc. are for purposes of describing the disclosure to one skilled in the art as it pertains to the frame of reference of the drawings, but should not be interpreted as limiting.DETAILED DESCRIPTION

[0032] FIG. 1 illustrates a shape memory alloy (SMA) actuator 100 that may be employed to actuate various latches, valves, gear trains, linkages, or other various mechanisms. Once actuated, the SMA actuator 100 may, for example, unlock / lock a door or adjust the translational / rotational position of an object. The SMA actuator 100 includes an SMA wire 104 that can change length depending on its temperature.

[0033] In general, the SMA wire 104 may exist in two different solid-state phases — a martensite phase at a first, lower temperature and an austenite phase at a second, higher temperature. The SMA wire 104 is configured to change its shape in response to thermal activation from a deformed or “extended state” during the martensite phase to a pre-deformed or“contracted state” during the austenite phase. Typically, the phase transformation is reversible and independent of time. An electric current is applied to flow through the SMA wire 104 to thermally activate the SMA wire 104. Due to the electrical current flowing through the SMA wire 104 and the wire’s resistance to the current, the SMA wire 104 is heated. The change in temperature causes the length change (i.e., from the extended state to the contracted state). In other embodiments, external heating elements arranged adjacent to the SMA wire 104 may alternatively be employed to heat the SMA wire 104, e.g., separate current-carrying wires, proximate heating element, radiator, heat exchange fluid system, etc.

[0034] In the illustrated embodiment, the SMA wire 104 is composed of a Nickel -Titanium (NiTi) alloy — e.g., binary NiTi alloys. In some embodiments, ternary or quaternary elements (e g., carbon, oxide, copper, chromium, etc.) may be added to the NiTi alloy SMA wire 104. In other embodiments, the SMA wire 104 may be composed of copper-based alloys, such as CuZnAl, CuAlNi, or the like.

[0035] With reference to FIGS. 1-3, the SMA actuator 100 further includes a main body 200, a plurality of bearings 300 mounted to the main body 200, and two pairs of actuators 400 disposed on the main body 200. A controller 600 and a power source 700 (FIG. 3) may also be provided to initiate and manage the electrical current supplied to the SMA actuator 100.

[0036] In the illustrated embodiment, the main body 200 is a flat plate and defines a first face 204 and a second face 208 opposite the first face 204. The main body 200 may be rotatable about an axis 212. For example, the illustrated main body 200 includes an aperture 216 that is configured to receive a shaft or axle 218 of another body 219 (e.g., a fixed support), such that the main body 200 is configured to rotate about the shaft or axle 218 relative to the body 219. The faces 204, 208 extend perpendicularly relative to the axis 212, but the main body 200 may have other shapes in other embodiments. Although not illustrated, the SMA actuator 100 may include a housing that encases components such as the main body 200 and the controller 600. Instead, in the illustrated embodiment, the SMA wire 104 is exposed to its immediate surroundings (e.g., ambient air, fluid, etc.) rather than being encased in a housing. This may be advantageous for purposes of efficient heat dissipation and rapid cooling of the SMA wire 104 after being heated (e.g., via electrical current being applied).

[0037] With continued reference to FIGS. 1-3, the bearings 300 extend away from the main body 200 in directions parallel to the axis 212. The illustrated plurality of bearings 300 includes a first set of bearings 304 on the first face 204 and a second set of bearings 308 on the second face 208. The first and second sets of bearings 304, 308 are collectively distributed across the first face 204 (FIG. 1) and the second face 208 (FIG. 2), respectively, such that the first set of bearings 304 and the second set of bearings 304, 308 each defines a spiral shape. The first and second sets of bearings 304, 308 may have mirror symmetry across a mid-plane extending parallel to the first and second faces 204, 208 in some embodiments. The SMA wire 104 is guided tautly around and engaged with bearing surfaces of the plurality of bearings 300, such that the SMA wire 104 also generally forms the shape of a spiral and the bearing surfaces support and maintain the SMA wire 104 in its spiral form. In the illustrated embodiment, a first SMA wire 104a is wrapped around the first set of bearings 304 on the first face 204 (FIG. 1), and a second SMA wire 104b is wrapped around the second set of bearings 308 on the second face 208 (FIG. 2).

[0038] The bearings 300 are configured to rotate relative to the first face 204 and the second face 208, thereby facilitating movement of the first SMA wire 104a and the second SMA wire 104b, respectively, as the lengths of the wires 104a, 104b change due to varying temperatures. Also, the bearings 300 may rotate relative to each other, such that adjacent bearings 300 may rotate independently at different times and at different speeds depending on a rotational force being exerted on the bearings 300 via the SMA wire 104 in response to the SMA wire 104 changing between the contracted state and the extended state. In such an embodiment, friction between the bearings 300 and the SMA wire 104 is decreased and the longevity of the SMA wire 104 is increased. In other embodiments, the bearings 300 may be fixed to the first face 204 and the second face 208, such that the bearings 300 are not configured to rotate. In such embodiments, the SMA wire 104 slides along the bearings 300 as the length of the SMA wire 104 changes. In such embodiments, the bearings 300 may be made of a low-friction material to facilitate sliding of the SMA wire 104.

[0039] With reference to FIG. 1, the first SMA wire 104a includes a first end 108a that is rigidly fixed to the other body 219 (i.e., not the main body 200) via a first anchor 220. That is, the first end 108a is inhibited from moving. The first end 108a is also fixed to a location radiallyoffset from the axis 212. The first SMA wire 104a also includes a second end 108b that is rigidly fixed to the first face 204 of the main body 200 via a second anchor 224. That is, the second end 108b is inhibited from moving relative to the main body 200. The second end 108b is also fixed to a location that is radially offset from the axis 212. The first end 108a is radially offset from the axis 212 a greater distance than the radial offset of the second end 108b relative to the axis 212. As previously mentioned, between the first end 108a and the second end 108b, the first SMA wire 104a is looped around the first set of bearings 304 in a spiral-type pattern. Therefore, the first SMA wire 104a tautly bears against a portion of the outer periphery of each one of the first set of bearings 304 as the first SMA wire 104a is looped around the bearings 304 in a spiral -type pattern. Since the first and second ends 108a, 108b of the first SMA wire 104a are rigidly fixed, the amount of the first SMA wire 104a does not change.

[0040] With reference to FIG. 2, the second SMA wire 104b includes a first end 112a that is rigidly fixed to the other body 219 (i.e., not the main body 200) via a third anchor 228. That is, the first end 112a is inhibited from moving. The first end 112a is also fixed to a location radially offset from the axis 212. The second SMA wire 104b also includes a second end 112b that is rigidly fixed to the second face 208 of the main body 200 via a fourth anchor 232. That is, the second end 112b is inhibited from moving relative to the main body 200. The second end 112b is also fixed to a location that is radially offset from the axis 212. The first end 112a is radially offset from the axis 212 a greater distance than the radial offset of the second end 1 12b relative to the axis 212. As previously mentioned, between the first end 112a and the second end 112b, the second SMA wire 104b is looped around the second set of bearings 308 in a spiral-type pattern. Therefore, the second SMA wire 104b tautly bears against a portion of the outer periphery of each one of the second set of bearings 308 as the second SMA wire 104b is looped around bearings 308 in a spiral -type pattern. Since the first and second ends 112a, 112b of the second SMA wire 104b are rigidly fixed, the amount of the second SMA wire 104b does not change.

[0041] With reference to FIGS. 1-3, each face 204, 208 includes a pair of actuators 400. Each pair of actuators 400 is disposed adjacent an outer periphery of the main body 200, such that the actuators 400 are radially offset from the axis 212. The radial offset of the actuators 400 relative to the axis 212 is greater than the radial offset of the fixed ends 108b, 112b from the axis212. This, in turn, enables the pair of actuators 400 to travel a greater distance when the main body 200 rotates about the axis 212. One pair of actuators 400 extend upward from the main body 200 along a direction parallel to the axis 212 and one or both actuators 400 may interface with and actuate various latches, valves, gear trains, linkages, or other various mechanisms connected to the SMA actuator 100 when the main body 200 is rotated. The rotational motion of the actuators 400 may result in rotational motion of various latches, valves, gear trains, linkages, etc., or may be converted to translate the various mechanisms connected to the SMA actuator 100.

[0042] During operation, the SMA actuator 100 can be used as a two-position actuator and / or a continuous adjustment actuator. As a two-position actuator, heat (e.g., an electrical current) is applied to either the first SMA wire 104a or the second SMA wire 104b. For example, the main body 200 rotates counterclockwise when heat (e.g., the electrical current) is applied to the first SMA wire 104a and clockwise when heat is applied to the second SMA wire 104b. Specifically, when heat (e.g., the electrical current) is applied to the first SMA wire 104a, the first SMA wire 104a decreases in length (i.e., changes to the contracted state) and exerts a biasing force on the second anchor 224. Since the second anchor 224 is radially offset from the axis 212, the biasing force extends along a direction perpendicular to and radially offset from the axis 212. As a result, the main body 200 rotates in a first direction (i.e., counterclockwise) when the first SMA wire 104a changes to the contracted state. The first SMA wire 104a exerts a sufficient force to deform the second SMA wire 104b when the main body 200 is rotating counterclockwise. In contrast, when the first SMA wire 104a cools (i.e., returns to ambient temperature when no electrical current is applied), the first SMA wire 104a will deform and increase in length (i.e., change to the extended state) when a sufficient force is applied to the first SMA wire 104a by the contraction of the second SMA wire 104b.

[0043] Likewise, when heat (e.g., an electrical current) is applied to the second SMA wire 104b, the second SMA wire 104b decreases in length (i.e., changes to the contracted state) and exerts a biasing force on the fourth anchor 232. Since the fourth anchor 232 is radially offset from the axis 212, the biasing force extends along a direction perpendicular to and radially offset from the axis 212. As a result, the main body 200 rotates in a second direction (i.e., clockwise) when the second SMA wire 104a changes to the contracted state. The second SMA wire 104bexerts a sufficient force to deform the first SMA wire 104a when the main body 200 is rotating clockwise. In contrast, when the second SMA wire 104b cools (i.e., returns to ambient temperature when no electrical current is applied), the second SMA wire 104b will deform and increase in length (i.e., change to the extended state) when a sufficient force is applied to the second SMA wire 104b by the contraction of the first SMA wire 104a. Depending on the application, various latches, valves, gear trains, linkages, and / or other various mechanisms may be coupled to the actuators 400 to initiate movement.

[0044] As a continuous adjustment actuator, the SMA actuator 100 works in a similar manner as previously explained, but now, heat (e.g., an electrical current) is applied to one of the SMA wires 104a, 104b for a period of time until the actuators 400 reach a desired position among an infinite number of possible positions while rotating in the first and second directions.

[0045] A position sensor may be employed to detect when the actuators 400 reach the desired position and relay a signal to the controller 600 indicating to cutoff supply of the heat (e g., electrical current). In other embodiments, various other sensors may be used, such as electrical resistance sensors, limit switches, and other similar sensors. In such an embodiment, the actuators 400 move, for example, in a counterclockwise direction as heat (e.g., electrical current) is applied to the first SMA wire 104a and the actuators 400 stop when the sensor or timer is triggered. Similarly, the actuators 400 move in a clockwise direction as heat (e.g., electrical current) is applied to the second SMA wire 104b and the actuators 400 stop when the sensor or timer is triggered.

[0046] Based on the travel distance requirements of the actuators 400 and available package space, design parameters such as wire length, number of loops, distance between bearings 300, wire diameter, voltage, current flow, and other parameters may be adjusted.

[0047] FIG. 4 illustrates a shape memory alloy (SMA) actuator 1100 according to another embodiment that is similar to the SMA actuator 100 with like components given reference numerals plus “1000”. Specifically, the SMA actuator 1100 essentially includes multiple SMA actuators 100 stacked on top of each other and working in unison. As such, the SMA actuator 1100 may generate a force that is greater than the force generated by the SMA actuator 100 and capable of actuating various latches, valves, gear trains, linkages, or other various mechanisms.Once actuated, the SMA actuator 1 100 may, for example, unlock / lock a door or adjust the translational / rotational position of an object. The SMA actuator 1100 includes an SMA wire 1104 that can change length depending on its temperature.

[0048] The SMA actuator 1100 further includes a plurality of main bodies 1200, a plurality of bearings 1300 mounted to the main bodies 1200, and a pair of actuators 1400 disposed on the main bodies 1200. The controller 600 and the power source 700 (FIG. 3) are also provided to initiate and manage the electrical current supplied to the SMA actuator 1100.

[0049] In the illustrated embodiment, there are three main bodies 1200 that are each identical and stacked along a common axis 1212. Each main body 1200 defines a first face 1204 and a second face 1208 opposite the first face 1204. The main bodies 1200 are rotatable about the axis 1212. Specifically, the main bodies 1200 include an aperture that receives a shaft or axle 1218 such that the main bodies 1200 are configured to rotate about the shaft or axle 1218. The main bodies 1200 rotates together about the axis 1212, as explained in further detail below. The faces 1204, 1208 extend perpendicularly relative to the axis 1212. The SMA actuator 1100 includes a housing 1236 that supports components such as the main bodies 1200 and the anchors 1220, 1228. In other embodiments, there may be fewer or greater than three main bodies 1200, each with their own SMA wire 1104. For each main body 1200 added to the SMA actuator 1100, the force generated by each main body 1200 cumulatively transfers to the actuators 1400, and therefore, the output force of the actuators 1400 to move another mechanism increases as well. Although the illustrated embodiment includes a pair of actuators 1400, in other embodiments, there may be more or less actuators 1400.

[0050] The plurality of bearings 1300 extend away from the main bodies 1200 along a direction parallel to the axis 1212. The plurality of bearings 1300 include a first set of bearings 1304 on the first face 1204 and a second set of bearings 1308 on the second face 1208. The first and second set of bearings 1304, 1308 are collectively distributed across the first face 1204 and the second face 1208 (FIG. 2), respectively, in a spiral-type manner. The second set of bearings 1308 are oriented in a mirror-image manner compared to the first set of bearings 1304. The SMA wire 1104 is guided tautly around the plurality of bearings 1300, such that the SMA wire 1104 is generally in the shape of a spiral itself. Specifically, a first SMA wire 1104a is wrappedaround the first set of bearings 1304 on the first face 1204 of each main body 1200, and a second SMA wire 1104b is wrapped around the second set of bearings 1308 on the second face 1208 of each main body 1200.

[0051] FIG. 5 illustrates another embodiment of an SMA actuator 2100 that is similar to the SMA actuator 1100. The differences are that the SMA actuator 2100 has five main bodies 2200 instead of the three main bodies 1200 of the SMA actuator 1100, and the pattern in which the plurality of bearings 2300 are distributed across the faces 1204, 1208. Specifically, the plurality of bearings 2300 are still distributed across the faces 1204, 1208 in a spiral-type manner, but the plurality of bearings 2300 collectively define a series of circles 2312 that are concentric relative to each other. There is a greater number of bearings in the plurality of bearings 2300 than the plurality of bearings 1300, which may be advantageous to reduce the angle at which the SMA wires 1104a, 1104b bend around individual bearings. For example, there are 36 bearings on the first face 1204 in the SMA actuator 2100, whereas there are 22 bearings on the first face 1204 in the SMA actuator 1100. The plurality of bearings 2300 also defines a series of rows 2316, where each row includes an axis 2320 that extends through the axis 1212. As such, the series of rows 2316 are angled relative to each other about the axis 1212. The series of circles 2312 and the series of rows 2316 define the spiral shape of the plurality of bearings 2300. Ultimately, the SMA actuator 2100 includes a greater number of bearings than the SMA actuator 1100, thereby decreasing the change in angle of the SMA wires 1 104a, 1 104b from one bearing to the next and enabling a smoother curvature.

[0052] The plurality of bearings 1300, 2300 are configured to rotate relative to the first face 1204 and the second face 1208, thereby facilitating movement of the first SMA wire 1104a and the second SMA wire 1104b, respectively, as the length changes due to varying temperatures. In such an embodiment, friction between the plurality of bearings 1300, 2300 and the SMA wire 1104 is decreased and the longevity of the SMA wire 1104 is increased. In other embodiments, the SMA wire 1104 slides along the bearings 1300, 2300 as the length of the SMA wire 1104 changes.

[0053] With reference to FIG. 4, the first SMA wire 1104a includes a first end 1108a that is rigidly fixed to a bracket 1219 of the housing 1236 via a first anchor 1220. That is, the firstend 1 108a is inhibited from moving. The first end 1108a is also fixed to a location radially offset from the axis 1212. The first SMA wire 1104a also includes a second end 1108b that is rigidly fixed to the first face 1204 of the main body 1200 via a second anchor 1224. That is, the second end 1108b is inhibited from moving relative to the main body 1200. The second end 1108b is also fixed to a location that is radially offset from the axis 1212. The first end 1108a is radially offset from the axis 1212 a greater distance than the radial offset of the second end 1108b relative to the axis 1212. As previously mentioned, between the first end 1108a and the second end 1108b, the first SMA wire 1104a is looped around the first set of bearings 1304 in a spiral-type pattern. Therefore, the first SMA wire 1104a tautly bears against a portion of the outer periphery of each one of the first set of bearings 1304 as the first SMA wire 1104a is looped around the bearings 1304 in a spiral-type pattern. Since the first and second ends 1108a, 1108b of the first SMA wire 1104a are rigidly fixed, the amount of the first SMA wire 1104a does not change.

[0054] With reference to FIG. 4, the second SMA wire 1104b includes a first end 1112a that is rigidly fixed to the housing 1236 via a third anchor 1228. That is, the first end 1112a is inhibited from moving. The first end 1112a is also fixed to a location radially offset from the axis 1212. The second SMA wire 1104b also includes a second end (similar to 112b of FIG. 2) that is rigidly fixed to the second face 1208 of the main body 1200 via a fourth anchor (similar to 232 of FIG. 2). That is, the second end is inhibited from moving relative to the main body 1200. The second end is also fixed to a location that is radially offset from the axis 1212. The first end 1112a is radially offset from the axis 1212 a greater distance than the radial offset of the second end 1112b relative to the axis 1212. As previously mentioned, between the first end 1112a and the second end 1112b, the second SMA wire 1104b is looped around the second set of bearings 1308 in a spiral-type pattern. Therefore, the second SMA wire 1104b tautly bears against a portion of the outer periphery of each one of the second set of bearings 1308 as the second SMA wire 1104b is looped around bearings 1308 in a spiral-type pattern. Since the first and second ends 1112a, 1112b of the second SMA wire 1104b are rigidly fixed, the amount of the second SMA wire 1104b does not change.

[0055] With reference to FIGS. 4, the pair of actuators 1400 are fixedly coupled between each of the main bodies 1200, such that the main bodies 1200 are rotatably locked together. Thatis, the pair of actuators 1400 receive the collective force from each main body 1200 during rotation and transfer the collective force to any latches, valves, gear trains, linkages, or other various mechanisms connected to the SMA actuator 1100. The rotational motion of the actuators 1400 may result in rotational motion of various latches, valves, gear trains, linkages, etc., or may be converted to translate the various mechanisms connected to the SMA actuator 100. The actuators 1400 move through a slot 1238 in the housing 1236. When the main bodies 1200 are rotated, for example, when the first SMA wire 104a is heated (e.g., via electrical current), the pair of actuators 1400 move toward one end of the slot 1238. In contrast, when the main bodies 1200 are rotated, for example, when the second SMA wire 104b is heated (e.g., via electrical current), the pair of actuators 1400 move toward the other, opposite end of the slot 1238.

[0056] During operation, the SMA actuator 1100 can be used as a two-position actuator and / or a continuous adjustment actuator. As a two-position actuator, heat (e.g., an electrical current) is applied to each of the first SMA wires 1104a or the second SMA wires 1104b. For example, the main bodies 1200 rotate counterclockwise when heat (e.g., the electrical current) is applied to each of first SMA wire 1104a and clockwise when heat is applied to each of the second SMA wire 1104b. Specifically, when heat (e.g., the electrical current) is applied to each of the first SMA wire 1104a, each first SMA wires 1104a decreases in length (i.e., changes to the contracted state) and exerts a biasing force on the second anchors 1224. Since the second anchors 1224 is radially offset from the axis 1212, the biasing force extends along a direction perpendicular to and radially offset from the axis 1212. As a result, the main body 1200 rotates in a first direction (i.e., counterclockwise) when each first SMA wires 1104a changes to the contracted state. The first SMA wires 1104a exert a sufficient force to deform the second SMA wires 1104b when the main body 1200 is rotating counterclockwise. In contrast, when the first SMA wires 1104a cool (i.e., returns to ambient temperature when no electrical current is applied), the first SMA wires 1104a will deform and increase in length (i.e., change to the extended state) when a sufficient force is applied to the first SMA wires 1104a by the contraction of each of the second SMA wires 1104b.

[0057] Likewise, when heat (e.g., an electrical current) is applied to each of the second SMA wires 1104b, the second SMA wires 1104b decreases in length (i.e., changes to the contracted state) and exerts a biasing force on the fourth anchor (similar to 232 in FIG. 2). Sinceeach fourth anchor is radially offset from the axis 1212, the biasing force extends along a direction perpendicular to and radially offset from the axis 1212. As a result, the main bodies 1200 rotate in a second direction (i.e., clockwise) when the second SMA wires 1104a change to the contracted state. The second SMA wires 1104b exert a sufficient force to deform each of the first SMA wires 1104a when the main bodies 1200 is rotating clockwise. In contrast, when each of the second SMA wires 1104b cool (i.e., returns to ambient temperature when no electrical current is applied), the second SMA wires 1104b will deform and increase in length (i.e., change to the extended state) when a sufficient force is applied to the second SMA wires 1104b by the contraction of the first SMA wires 1104a. Depending on the application, various latches, valves, gear trains, linkages, and / or other various mechanisms may be coupled to the actuators 1400 to initiate movement.

[0058] As a continuous adjustment actuator, the SMA actuator 1100 works in a similar manner as previously explained, but now, heat (e.g., an electrical current) is applied to one of the SMA wires 1104a, 1104b for a period of time until the actuators 1400 reach a desired position among an infinite number of possible positions while rotating in the first and second directions.

[0059] A position sensor may be employed to detect when the actuators 1400 reach the desired position and relay a signal to the controller 600 indicating to cutoff supply of the heat (e.g., electrical current). In other embodiments, various other sensors may be used, such as electrical resistance sensors, limit switches, and other similar sensors. In such an embodiment, the actuators 1400 move, for example, in a counterclockwise direction as heat (e.g., electrical current) is applied to the first SMA wires 1104a and the actuators 1400 stop when the sensor or timer is triggered. Similarly, the actuators 1400 move in a clockwise direction as heat (e.g., electrical current) is applied to the second SMA wire 1104b and the actuators 1400 stop when the sensor or timer is triggered.

[0060] Although the disclosure has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the disclosure as described.REPRESENTATIVE FEATURES

[0061] Representative features are set out in the following clauses, which stand alone or may be combined, in any combination, with one or more features disclosed in the text and / or drawings of the specification.

[0062] Clause 1. A shape memory alloy (SMA) actuator comprising: a main body defining an axis; and a shape memory alloy (SMA) wire coupled to the main body in the form of a spiral about the axis, wherein the SMA wire is configured to change between an extended state and a contracted state in response to heat being applied to the SMA wire, wherein the main body rotates about the axis in a first direction when the SMA wire is changing from the extended state to the contracted state and in a second direction opposite the first direction when the SMA wire is changing from the contracted state to the extended state.

[0063] Clause 2. The SMA actuator of clause 1, wherein the main body includes a first face and a second face opposite the first face.

[0064] Clause 3. The SMA actuator of clause 2, further comprising a plurality of bearing surfaces disposed on the main body, wherein the plurality of bearing surfaces supports and maintains the SMA wire in the spiral form, and wherein the plurality of bearing surfaces are distributed about the main body in a manner that collectively forms a spiral-shape pattern.

[0065] Clause 4. The SMA actuator of clause 3, wherein the plurality of bearing surfaces includes a first set of bearings on the first face and a second set of bearings on the second face.

[0066] Clause 5. The SMA actuator of clause 4, wherein the SMA wire is a first SMA wire that tautly engages the first set of bearings on the first face, and wherein the SMA actuator further comprises a second SMA wire that tautly engages the second set of bearings on the second face.

[0067] Clause 6. The SMA actuator of clause 2, wherein the SMA wire is a first SMA wire extending along the first face of the main body, and wherein the SMA actuator further comprises a second SMA wire extending along the second face of the main body.

[0068] Clause 7. The SMA actuator of clause 5 or 6, wherein each of the first SMA wire and the second SMA wire spirals radially inward from a first end to a second end, and wherein one of the first end or the second end of each of the first SMA wire and the second SMA wire is fixed to the main body at a location offset from the axis.

[0069] Clause 8. The SMA actuator of any one of clauses 1-4, wherein the SMA wire spirals radially inward from a first end to a second end, and wherein one of the first end or the second end of the SMA wire is fixed to the main body at a location offset from the axis.

[0070] Clause 9. The SMA actuator of any one of clauses 5-7, wherein when heat is applied to the first SMA wire in the extended state, the main body rotates in the first direction in response to the first SMA wire changing to the contracted state which, in turn, pulls and deforms the second SMA wire from the contracted state to the extended state.

[0071] Clause 10. The SMA actuator of any one of clauses 5-7 or 9, wherein when heat is applied to the second SMA wire in the extended state, the main body rotates in the second direction in response to the second SMA wire changing to the contracted state which, in turn, pulls and deforms the first SMA wire from the contracted state to the extended state.

[0072] Clause 11. The SMA actuator of clause 3, wherein the plurality of bearing surfaces collectively define a series of concentric circles.

[0073] Clause 12. The SMA actuator of any preceding clause, wherein the main body is one of a plurality of main bodies coupled together for co-rotation about the axis.

[0074] Clause 13. A shape memory alloy (SMA) actuator comprising: a shaft disposed along an axis; a plurality of main bodies coupled to the shaft, the plurality of main bodies coupled together for co-rotation about the axis; and a plurality of shape memory alloy (SMA) wires, each SMA wire of the plurality of SMA wires coupled to a respective one of the plurality of main bodies in the form of a spiral about the axis, wherein the plurality of SMA wires is configured to change between an extended state and a contracted state in response to heat being applied to the plurality of SMA wires, wherein the plurality of main bodies rotates in unison about the axis in a first direction when the plurality of SMA wires changes from the extendedstate to the contracted state and in a second direction opposite the first direction when the plurality of SMA wires changes from the contracted state to the extended state.

[0075] Clause 14. The SMA actuator of clause 13, wherein each main body of the plurality of main bodies includes a plurality of bearings arranged in a spiral shape, and wherein each SMA wire of the plurality of SMA wires tautly engages the plurality of bearings of the respective one of the plurality of main bodies.

[0076] Clause 15. The SMA actuator of clause 14, wherein each bearing of the plurality of bearings is rotatable relative to the main body.

[0077] Clause 16. The SMA actuator of clause 14 or 15, wherein each main body of the plurality of main bodies includes a first face and a second face opposite the first face.

[0078] Clause 17. The SMA actuator of clause 16, wherein the plurality of bearings includes a first set of bearings on the first face and a second set of bearings on the second face.

[0079] Clause 18. The SMA actuator of clause 17, wherein the plurality of SMA wires is a first plurality of SMA wires that tautly engages the first set of bearings on the first face of each main body of the plurality of main bodies, and wherein the SMA actuator further comprises a second plurality of SMA wires that tautly engages the second set of bearings on the second face of each main body of the plurality of main bodies.

[0080] Clause 19. The SMA actuator of clause 18, wherein when heat is applied to the first plurality of SMA wires in the extended state, the plurality of main bodies rotates in the first direction in response to the first plurality of SMA wires changing to the contracted state which, in turn, pulls and deforms the second plurality of SMA wires from the contracted state to the extended state; and wherein when heat is applied to the second plurality of SMA wires in the extended state, the plurality of main bodies rotates in the second direction in response to the second plurality of SMA wires changing to the contracted state which, in turn, pulls and deforms the first plurality of SMA wires from the contracted state to the extended state.

[0081] Clause 20. A shape memory alloy (SMA) actuator comprising: a plurality of shape memory alloy (SMA) wires, each SMA wire of the plurality of SMA wires forming a spiralshape; and a main body coupled to a first end of each SMA wire of the plurality of SMA wires, wherein the plurality of SMA wires is configured to change between an extended state and a contracted state to rotate the main body in response to heat being applied to the plurality of SMA wires.

Claims

CLAIMSWhat is claimed is:

1. A shape memory alloy (SMA) actuator comprising: a main body defining an axis; and a shape memory alloy (SMA) wire coupled to the main body in the form of a spiral about the axis, wherein the SMA wire is configured to change between an extended state and a contracted state in response to heat being applied to the SMA wire, wherein the main body rotates about the axis in a first direction when the SMA wire is changing from the extended state to the contracted state and in a second direction opposite the first direction when the SMA wire is changing from the contracted state to the extended state.

2. The SMA actuator of claim 1, wherein the main body includes a first face and a second face opposite the first face.

3. The SMA actuator of claim 2, further comprising a plurality of bearing surfaces disposed on the main body, wherein the plurality of bearing surfaces supports and maintains the SMA wire in the spiral form, and wherein the plurality of bearing surfaces are distributed about the main body in a manner that collectively forms a spiral-shape pattern.

4. The SMA actuator of claim 3, wherein the plurality of bearing surfaces includes a first set of bearings on the first face and a second set of bearings on the second face.

5. The SMA actuator of claim 4, wherein the SMA wire is a first SMA wire that tautly engages the first set of bearings on the first face, and wherein the SMA actuator further comprises a second SMA wire that tautly engages the second set of bearings on the second face.

6. The SMA actuator of claim 2, wherein the SMA wire is a first SMA wire extending along the first face of the main body, and wherein the SMA actuator further comprises a second SMA wire extending along the second face of the main body.

7. The SMA actuator of claim 5 or 6, wherein each of the first SMA wire and the second SMA wire spirals radially inward from a first end to a second end, and wherein one of the first end or the second end of each of the first SMA wire and the second SMA wire is fixed to the main body at a location offset from the axis.

8. The SMA actuator of any one of claims 1-4, wherein the SMA wire spirals radially inward from a first end to a second end, and wherein one of the first end or the second end of the SMA wire is fixed to the main body at a location offset from the axis.

9. The SMA actuator of any one of claims 5-7, wherein when heat is applied to the first SMA wire in the extended state, the main body rotates in the first direction in response to the first SMA wire changing to the contracted state which, in turn, pulls and deforms the second SMA wire from the contracted state to the extended state.

10. The SMA actuator of any one of claims 5-7 or 9, wherein when heat is applied to the second SMA wire in the extended state, the main body rotates in the second direction in response to the second SMA wire changing to the contracted state which, in turn, pulls and deforms the first SMA wire from the contracted state to the extended state.

11. The SMA actuator of claim 3, wherein the plurality of bearing surfaces collectively define a series of concentric circles.

12. The SMA actuator of any preceding claim, wherein the main body is one of a plurality of main bodies coupled together for co-rotation about the axis.

13. A shape memory alloy (SMA) actuator comprising: a shaft disposed along an axis; a plurality of main bodies coupled to the shaft, the plurality of main bodies coupled together for co-rotation about the axis; and a plurality of shape memory alloy (SMA) wires, each SMA wire of the plurality of SMA wires coupled to a respective one of the plurality of main bodies in the form of a spiral about the axis, wherein the plurality of SMA wires is configured to change between an extended state and a contracted state in response to heat being applied to the plurality of SMA wires, wherein the plurality of main bodies rotates in unison about the axis in a first direction when the plurality of SMA wires changes from the extended state to the contracted state and in a second direction opposite the first direction when the plurality of SMA wires changes from the contracted state to the extended state.

14. The SMA actuator of claim 13, wherein each main body of the plurality of main bodies includes a plurality of bearings arranged in a spiral shape, and wherein each SMA wire of the plurality of SMA wires tautly engages the plurality of bearings of the respective one of the plurality of main bodies.

15. The SMA actuator of claim 14, wherein each bearing of the plurality of bearings is rotatable relative to the main body.

16. The SMA actuator of claim 14 or 15, wherein each main body of the plurality of main bodies includes a first face and a second face opposite the first face.

17. The SMA actuator of claim 16, wherein the plurality of bearings includes a first set of bearings on the first face and a second set of bearings on the second face.

18. The SMA actuator of claim 17, wherein the plurality of SMA wires is a first plurality of SMA wires that tautly engages the first set of bearings on the first face of each main body of the plurality of main bodies, and wherein the SMA actuator further comprises a second plurality of SMA wires that tautly engages the second set of bearings on the second face of each main body of the plurality of main bodies.

19. The SMA actuator of claim 18, wherein when heat is applied to the first plurality of SMA wires in the extended state, the plurality of main bodies rotates in the first direction in response to the first plurality of SMA wires changing to the contracted state which, in turn, pulls and deforms the second plurality of SMA wires from the contracted state to the extended state; and wherein when heat is applied to the second plurality of SMA wires in the extended state, the plurality of main bodies rotates in the second direction in response to the second plurality of SMA wires changing to the contracted state which, in turn, pulls and deforms the first plurality of SMA wires from the contracted state to the extended state.

20. A shape memory alloy (SMA) actuator comprising: a plurality of shape memory alloy (SMA) wires, each SMA wire of the plurality of SMA wires forming a spiral shape; and a main body coupled to a first end of each SMA wire of the plurality of SMA wires, wherein the plurality of SMA wires is configured to change between an extended state and a contracted state to rotate the main body in response to heat being applied to the plurality of SMA wires.

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