High travel shape memory alloy actuator

Abstract

A shape memory alloy actuator includes a first spool defining a first longitudinal axis and a second spool defining a second longitudinal axis that is parallel to the first longitudinal axis, and a slider assembly disposed between the first spool and the second spool. The slider assembly can move in a direction perpendicular to the first longitudinal axis and the second longitudinal axis. The shape memory alloy actuator further includes a SMA wire wrapped around the first spool, the second spool, and the slider assembly. The SMA wire changes between an extended state and a contracted state in response to heat being applied to the SMA wire. The slider assembly moves from a first position corresponding to the SMA wire being in the extended state to a second position corresponding to the SMA wire being in the contracted state.

Description

HIGH TRAVEL SHAPE MEMORY ALLOY ACTUATORCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit to prior-filed U.S. Provisional Patent Application No. 63 / 710, 447, filed on October 22, 2024, and U.S. Provisional Patent Application No. 63 / 627,453, filed on January 31, 2024, the contents of which are incorporated by reference herein.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 first spool defining a first longitudinal axis and a second spool defining a second longitudinal axis that is parallel to the first longitudinal axis; a slider assembly disposed between the first spool and the second spool, the slider assembly configured to move in a direction perpendicular to the first longitudinal axis and the second longitudinal axis; and a SMA wire wrapped around the first spool, the second spool, and the slider assembly, wherein the SMA wire changes between an extended state and a contracted state in response to heat being applied to the SMA wire, and wherein the slider assembly moves from a first position corresponding to the SMA wire being in the extended state to a second position corresponding to the SMA wire being in the contracted state.

[0005] In some aspects, the techniques described herein relate to a SMA actuator, wherein the SMA wire is a first SMA wire that is wrapped around the first spool, the second spool, and a first side of the slider assembly, and wherein the SMA wire further includes a second SMA wire that is wrapped around the first spool, the second spool, and a second side of the slider assembly opposite the first side.

[0006] In some aspects, the techniques described herein relate to a SMA actuator, wherein when heat is applied to the first SMA wire initially in the extended state, the first SMA wire changes to the contracted state and moves the slider assembly to exert a force on the second SMA wire, thereby changing the second SMA wire from the contracted state to the extended state.

[0007] In some aspects, the techniques described herein relate to a SMA actuator, wherein when heat is applied to the second SMA wire initially in the extended state, the second SMA wire changes to the contracted state and moves the slider to exert a force on the first SMA wire, thereby changing the first SMA wire from the contracted state to the extended state.

[0008] In some aspects, the techniques described herein relate to a SMA actuator, wherein the slider assembly is movable to the first position in response to heat being applied to the first SMA wire and to the second position in response to heat being applied to the second SMA wire, and wherein the slider assembly is movable to a desired position among an infinite number of possible positions between the first position and the second position by heating either the first SMA wire or the second SMA wire and stopping the slider assembly in response to a sensor being triggered.

[0009] In some aspects, the techniques described herein relate to a SMA actuator, wherein the first spool and the second spool each includes a shaft and a plurality of bearings disposed along the shaft, wherein the plurality of bearings is configured to rotate about the shaft, and wherein the plurality of bearings supports the SMA wire.

[0010] In some aspects, the techniques described herein relate to a SMA actuator, further including a carrier frame disposed between the first spool and the second spool, the carrier frameincluding an elongated slot that guides the slider assembly while moving between the first position and the second position.

[0011] In some aspects, the techniques described herein relate to a SMA actuator, wherein the carrier frame defines a carrier axis that is parallel to the elongated slot, and wherein the slider assembly translates in a direction along the carrier axis between the first position and the second position.

[0012] In some aspects, the techniques described herein relate to a SMA actuator, wherein the first spool and the second spool each includes a shaft rigidly mounted to the carrier frame, such that each shaft remains stationary as the SMA wire changes between the extended state and the contracted state.

[0013] In some aspects, the techniques described herein relate to a SMA actuator, wherein the slider assembly includes a shaft that is configured to interface with and actuate another mechanism when moving between the first position and the second position.

[0014] In some aspects, the techniques described herein relate to a shape memory alloy (SMA) actuator including: a first spool and a second spool; a slider assembly disposed between the first spool and the second spool; a first SMA wire wrapped around the first spool, the second spool, and the slider assembly; and a second SMA wire wrapped around the first spool, the second spool, and the slider assembly, wherein the slider assembly is configured to move in a first direction in response to heating of the first SMA wire, and wherein the slider assembly is configured to move in a second direction opposite the first direction in response to heating of the second SMA wire.

[0015] In some aspects, the techniques described herein relate to a SMA actuator, wherein the first SMA wire is wrapped around the slider assembly on a first side of the slider assembly, and wherein the second SMA wire is wrapped around the slider assembly on a second side of the slider assembly opposite the first side.

[0016] In some aspects, the techniques described herein relate to a SMA actuator, wherein the first SMA wire and the second SMA wire are configured to be heated by electrical current flowing through the first SMA wire and the second SMA wire.

[0017] In some aspects, the techniques described herein relate to a SMA actuator, further including a carrier frame disposed between the first spool and the second spool, the carrier frame including an elongated slot that guides the slider assembly while moving in the first direction and the second direction.

[0018] In some aspects, the techniques described herein relate to a shape memory alloy (SMA) actuator assembly including at least two 11, wherein the at least two SMA actuators are configured to operate together in unison.

[0019] In some aspects, the techniques described herein relate to a SMA actuator assembly, wherein the at least two SMA actuators are configured to operate together in unison together as either a single two-position actuator or a continuous adjustment actuator.

[0020] In some aspects, the techniques described herein relate to a SMA actuator assembly, wherein the at least two SMA actuators are configured to operate together in unison together as a single two-position actuator such that heat is applied simultaneously in each of the at least two SMA actuators to only one of the first SMA wire or the second SMA wire at a time, and wherein the slider assembly is movable to a first position in response to heat being applied to the first SMA wire and to a second position in response to heat being applied to the second SMA wire.

[0021] In some aspects, the techniques described herein relate to a SMA actuator assembly, wherein the at least two SMA actuators are configured to operate together in unison together as a continuous adjustment actuator such that heat is applied simultaneously in each of the at least two SMA actuators to one of the SMA wires for a period of time until the slider assembly reaches a desired position among an infinite number of possible positions between and including a first position and a second position, and wherein the slider assembly is movable in a first position in response to heat being applied to the first SMA wire and in a second direction in response to heat being applied to the second SMA wire.

[0022] In some aspects, the techniques described herein relate to a SMA actuator assembly, wherein the at least two SMA actuators are stacked on each other.

[0023] In some aspects, the techniques described herein relate to a SMA actuator assembly, wherein the slider assembly of each of the at least two SMA actuators includes a shaft, andwherein each shaft is configured to interface with a shaft of an adjacent stacked SMA actuator to operate as a single unit and actuate another mechanism when moving between a first position and a second position.

[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 partially exploded, front perspective view of a shape memory alloy (SMA) actuator in accordance with an embodiment of the disclosure, illustrating two SMA wires looped around a pair of spools.

[0026] FIG. 2 is a partially exploded, rear perspective view of the SMA actuator of FIG. 1, illustrating a plurality of bearings exploded from one of the spools.

[0027] FIG. 3 is a front perspective view of a shape memory alloy (SMA) actuator in accordance with another embodiment of the disclosure.

[0028] FIG. 4 is a front perspective view of the SMA actuator of FIG. 1, illustrating the pair of spools encased within a housing.

[0029] FIG. 5 is a cross-sectional view of the SMA actuator along line 5 — 5 of FIG. 4, illustrating a slider assembly and a carrier frame disposed between the pair of spools.

[0030] FIG. 6 is a plan view of a shape memory alloy (SMA) actuator in accordance with another embodiment of the disclosure, illustrating two SMA wires looped around a pair of spools.

[0031] FIG. 7 is a perspective view of the SMA actuator of FIG. 6 being stacked and combined with each other.

[0032] 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 thefollowing 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.

[0033] 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. When used in this specification and claims, the terms “comprises” and “comprising” and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.DETAILED DESCRIPTION

[0034] 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.

[0035] 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” in the martensite phase to a pre-deformed or “contracted state” in 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. When the electric currentis turned off, the SMA wire 104 cools and returns to its original state (i.e., from the contracted state to the extended state).

[0036] In the illustrated embodiment, the SMA wire 104 is composed of a Nickel -Titanium (NiTi) alloy — e.g., a binary NiTi alloy. 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.

[0037] With reference to FIGS. 1 and 2, the illustrated SMA actuator 100 further includes a housing 200, a pair of spools 300 fixedly mounted to the housing 200, a carrier frame 400 disposed between the spools 300, and a slider assembly 500 slidably coupled to the carrier frame 400. A controller 600 and a power source 700 (FIG. 4) may also be provided to initiate and manage the electrical current supplied to the SMA actuator 100.

[0038] The housing 200 is a clamshell-type housing including a first housing portion 204 and a second housing portion 208 that is coupled to the first housing portion 204. The first housing portion 204 and the second housing portion 208 each include a series of protrusions 212 and a series of recesses 216, such that the series of recesses 216 receive the series of protrusions 212 when the first and second housing portions 204, 208 are coupled together. That is, the series of protrusions 212 mesh with the series of recesses 216 to ensure proper alignment and coupling of the housing 200. As explained in further detail below, opposite distal ends (i.e., 108a, 108b, 112a, 112b) of the SMA wire 104 are clamped between the first housing portion 204 and the second housing portion 208 (best illustrated in FIG. 4), such that an amount of the SMA wire 104 does not change.

[0039] With continued reference to FIGS. 1 and 2, the housing 200 further includes apertures 220, 224 that receive the spools 300. Specifically, the apertures 220 receive one of the spools 300 and the apertures 224 receive the other one of the spools 300. The apertures 220, 224 are located on a top face 228 and a bottom face 232 of the housing 200. In some embodiments, the apertures 220, 224 are snug-fit around the spools 300 to inhibit rotation of the spools 300, while in other embodiments, the apertures 220, 224 provide clearance around the spools 300 to enable rotation of the spools 300. The housing 200 also includes a pair of elongated slots 236that are located on a front face 240 and a rear face 244 of the housing 200. A portion of the slider assembly 500 (i.e., an actuator) extends outward from the elongated slot 236 to allow the slider assembly 500 to interface with and actuate latches, valves, gear trains, linkages, or other various mechanisms that may be connected to the SMA actuator 100.

[0040] FIG. 3 illustrates another embodiment of the SMA actuator 100 without the housing 200. Instead, the SMA actuator 100 may include mounts 1200 having a top mount 1204 and a bottom mount 1208. In this embodiment, the spools 300 are connected to and received between the top mount 1204 and the bottom mount 1208. As shown in FIG. 3, the SMA wire 104 is exposed to its immediate surroundings (e.g., ambient air, fluid, etc.) rather than being encased in the housing 200. 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 fed through) the SMA wire 104.

[0041] With continued reference to FIGS. 1 and 2, each spool 300 includes a shaft 304 defining a longitudinal axis 308, a plurality of bearings 312, and a plurality of washers 316. The shafts 304, and therefore the longitudinal axes 308, are parallel and offset to each other. Each shaft 304 is rigidly mounted to the carrier frame 400, such that each shaft 304 remains stationary as the SMA wire 104 changes in length. The bearings 312 are disposed along the shaft 304 and one of the washers 316 is disposed between each pair of adjacent bearings 312. As such, the washers 316 separate the bearings 312 to facilitate rotation of the bearings 312 relative to one another. The washers 316 and bearings 312 also provide separation of adjacent lengths of the SMA wire 104, which may facilitate more rapid cooling of the SMA wire 104 when the heat (e.g., electrical current) is removed. In some embodiments, the plurality of washers 316 may be press-fit or otherwise fixed onto the shaft 304 to maintain the position of each bearing 312 along the shaft 304. As such, the washers 316 may inhibit the bearings 312 from moving in a direction along the longitudinal axis 308.

[0042] The bearings 312 are able to rotate about the shaft 304, thereby facilitating movement of the SMA wire 104 as its length changes due to varying temperatures and / or mechanical forces being exerted on the SMA wire 104. The bearings 312 rotate relative to each other, such that adjacent bearings 312 may independently rotate at different times and at differentspeeds depending on a rotational force being exerted on the bearings 312 via the SMA wire 104 as the SMA wire 104 moves between the contracted state and the extended state. In such an embodiment, friction between the spools 300 and the SMA wire 104 is decreased and the longevity of the SMA wire 104 is increased. In other embodiments, the bearings 312 may not rotate about the shaft 304, but the shaft 304 may rotate within the apertures 220, 224. Still, in other embodiments, the bearings 312 may not rotate about the shaft 304, thereby allowing the SMA wire 104 to slide along the bearings 312 as the length of the SMA wire 104 changes. In such embodiments, the bearings 312 may be made of a low friction material. Although the SMA actuator 100 is described as having a plurality of bearings 312, in some embodiments, the plurality of bearings 312 on each spool 300 may alternatively form a single bearing or pair of bearings.

[0043] With reference to FIG. 1, the SMA wire 104 wraps around the spools 300. Specifically, a first SMA wire 104a is wrapped around and supported by the bearings 312 between the spools 300 above the carrier frame 400 and the slider assembly 500, and a second SMA wire 104b is wrapped around and supported by the bearings 312 between the spools 300 below the carrier frame 400 and the slider assembly 500.

[0044] With reference to FIG. 2, the first SMA wire 104a includes a first end 108a that is adjacent the bearings 312 and coupled to a first side of the housing 200 (FIG. 4; or some other rigid body) to inhibit movement of the first end 108a. The first SMA wire 104a also includes a second end 108b that is adjacent the slider assembly 500 and coupled to the first side of the housing 200 (FIG. 4; or some other rigid body) to inhibit movement of the second end 108b. Between the first end 108a and the second end 108b, the first SMA wire 104a is looped around the bearings 312 above the slider assembly 500 in a helical-type pattern. The second end 108b of the first SMA wire 104a is also looped around the slider assembly 500. The amount of material of the first SMA wire 104a between the first end 108a and the second end 108b does not change, but the length of the first SMA wire 104a may change as mentioned above. Specifically, when heat (e.g., an 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 slider assembly 500 to move the slider assembly 500 toward the first side of the housing. When the first SMA wire 104a cools (i.e., returns to ambient temperature when no electrical current isapplied), the first SMA wire 104a is allowed to deform and increase in length (i.e., change to the extended state) when a sufficient force is applied to the first SMA wire 104a.

[0045] With continued reference to FIG. 2, the second SMA wire 104b includes a first end 112a that is adjacent the bearings 312 and coupled to a second side of the housing 200 opposite the first side (FIG. 4; or some other rigid body) to inhibit movement of the first end 112a. The second SMA wire 104b also includes a second end 112b that is adjacent the slider assembly 500 and coupled to the second side of the housing 200 (FIG. 4; or some other rigid body) to inhibit movement of the second end 112b. Between the first end 112a and the second end 112b, the second SMA wire 104b is looped around the bearings 312 below the slider assembly 500 in a helical-type pattern. The second end 112b of the second SMA wire 104b is also looped around the slider assembly 500. The amount of material of the second SMA wire 104b between the first end 112a and the second end 112b does not change, but the length of the second SMA wire 104b may change as mentioned above. Specifically, 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 slider assembly 500 to move the slider assembly 500 toward the second side of the housing. When the second SMA wire 104b is cooled (i.e., no electrical current applied), the second SMA wire 104b is allowed to deform and increase in length (i.e., change to the extended state) when a sufficient force is applied to the second SMA wire 104b.

[0046] With reference to FIGS. 1-5, the carrier frame 400 is coupled between the spools 300. The carrier frame 400 includes a first frame body 404 and a second frame body 408 that are formed in a clamshell-type manner. When coupled together, the first frame body 404 and the second frame body 408 encase a portion of the spools 300 to further inhibit movement of the spools 300 in any direction (e.g., towards each other). The first frame body 404 couples to the second frame body 408 via a series of interconnecting teeth 412, while in other embodiments, various other techniques may be used to couple the first frame body 404 to the second frame body 408, such as fasteners 414 (FIG. 3), snap-fit, adhesive, and other similar ways. The carrier frame 400 defines a carrier axis 416 and includes an elongated slot 420 that is parallel to the carrier axis 416. The carrier axis 416 is perpendicular to the longitudinal axes 308 of the spools 300. The elongated slot 420 guides the slider assembly 500 as the slider assembly 500 moves ina direction along the carrier axis 416 between a first position (shown in phantom lines in FIG. 4) and a second position (shown in solid lines in FIG. 4).

[0047] With continued reference to FIGS. 1-5, the slider assembly 500 includes an actuator or shaft 504, a first bearing 508, and a second bearing 512. The shaft 504 defines a shaft axis 516 extending along the shaft 504 that is perpendicular to the longitudinal axes 308 of the spools 300. The shaft 504 is an actuator that may be ultimately coupled to and configured to actuate various latches, valves, gear trains, linkages, or other various mechanisms. The shaft axis 516 is also perpendicular to the carrier axis 416.

[0048] The shaft 504 includes an enlarged-diameter section 520 located between two opposing ends 524, 528 of the shaft 504. The enlarged-diameter section 520 has a diameter greater than the width of the elongated slot 420 and is disposed between the first frame body 404 and the second frame body 408 of the carrier frame 400, thereby inhibiting movement of the shaft 504 in a direction along the shaft axis 516. However, the shaft 504 is configured to move (i.e., slide, translate, etc.) within the elongated slot 420 of the carrier frame 400, in which the shaft axis 516 remains perpendicular to the longitudinal axes 308 of the spools 300. In other words, the enlarged-diameter section 520, and therefore the shaft 504, is configured to move along the carrier axis 416.

[0049] The first SMA wire 104a is wrapped around a portion of the first bearing 508 and the second SMA wire 104b is wrapped around a portion of the second bearing 512. As such, the slider assembly 500 moves to the first position when the first SMA wire 104a changes to the contracted state via exerting a biasing force on the first bearing 508. Similarly, the slider assembly 500 moves to the second position when the second SMA wire 104b changes to the contracted state via exerting a biasing force on the second bearing 512. The slider assembly 500 is also movable to an infinite number of positions between the first position and the second position, as explained in further detail below.

[0050] Although the shaft axis 516 of the slider assembly 500 is perpendicular to the carrier axis 416, in other embodiments, the shaft axis 516 may be oriented parallel to the carrier axis 416 such that the shaft 504 moves in a direction along the shaft axis 516 and the carrier axis 416.

[0051] 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., the electrical current) is applied to only one of the first SMA wire 104a or the second SMA wire 104b at a time. So, for example, when the slider assembly 500 is in the first position (shown in phantom lines in FIG. 4), the first SMA wire 104a is in the contracted state and the second SMA wire 104b is in the extended state. When heat (e.g., the electrical current) is applied to the second SMA wire 104b (and no heat or electrical current to the first SMA wire 104a), the second SMA wire 104b transitions to the austenite phase, such that the second SMA wire 104b moves from the extended state to the contracted state. During this time, the slider assembly 500 moves from the first position to the second position (shown in solid lines in FIG. 4), thereby exerting a force on the first SMA wire 104a via the shaft 504 sufficient to deform the first SMA wire 104a to the extended state. At this point, the first SMA wire 104a is in the martensite phase. The slider assembly 500 returns to the first position when heat (e.g., the electrical current) is applied to the first SMA wire 104a under the same principles just described. Depending on the application, various latches, valves, gear trains, linkages, and / or other various mechanisms may be coupled to the slider assembly 500, and more particularly to the shaft 504 (i.e., the actuator) to initiate movement.

[0052] As a continuous adjustment actuator, the SMA actuator 100 works in a similar manner as previously explained, but now, heat (e.g., the electrical current) is applied to one of the SMA wires 104a, 104b for a period of time until the slider assembly 500 (i.e., the actuator or shaft 504) reaches a desired position among an infinite number of possible positions between and including the first position and the second position.

[0053] A position sensor 532 may be employed to detect when the slider assembly 500 reaches the desired position between the first position and the second position and relay a signal to the controller 600 indicating to cutoff supply of the heat (e.g., electrical current). In other embodiments, various sensors or timers may be used, such as electrical resistance sensors, limit switches, and other similar sensors. In such an embodiment, the slider assembly 500 moves toward the first position as heat (e.g., the electrical current) is applied to the first SMA wire 104a and the slider assembly 500 is stopped when the sensor 532 or timer is triggered. Similarly, the slider assembly 500 moves toward the second position as heat (e.g., the electrical current) isapplied to the second SMA wire 104b and the slider assembly 500 is stopped when the sensor 532 or timer is triggered.

[0054] Based on the travel distance requirements of the slider assembly 500 and available package space, design parameters such as wire length, number of loops, distance between spool or longitudinal axes 308, wire diameter, voltage, current flow, and other parameters may be adjusted.

[0055] The SMA actuator 100 can vary in size and shape, as shown in FIG. 6. For example, the SMA actuator 2100 of FIG. 6 is generally more compact in size than the SMA actuator 100, but still maintains the same features of the SMA actuator 100. For sake of brevity, like features are given the same reference numerals plus “2000”. For example, the SMA actuator 2100 includes an SMA wire 2104, a housing 2200, a pair of spools 2300 fixedly mounted to the housing 2200, and a slider assembly 2500 slidably coupled to the housing 2200. A controller 2600 and a power source 2700 may also be provided to initiate and manage the electrical current supplied to the SMA actuator 2100.

[0056] Due to its smaller size, the relatively compact SMA actuator 2100 illustrated in FIG. 6 may be stacked (and coupled together) or otherwise combined with similar SMA actuators 2100 to act together in unison with each other and thereby achieve desired enhanced outcome and performance characteristics, preferably within about the same amount of space or, at least, not significantly more space, than would be occupied by a single SMA actuator 100. Specifically, FIG. 7 illustrates one exemplary embodiment in which four individual SMA actuators 2100 are stacked on top of each other and work together in unison. As such, the four stacked SMA actuators 2100 may generate a force that is greater than the force that would be generated by a single SMA actuator 100 that would occupy about the same amount of space as the stacked assembly. Each SMA actuator 2100 in the stack of four actuators includes an SMA wire 2104 that can change length depending on its temperature.

[0057] With continued reference to FIG. 6, each spool 2300 includes a shaft 2304 defining a longitudinal axis 2308, a plurality of bearings 2312, and a plurality of washers 2316. The shafts 2304, and therefore the longitudinal axes 2308, are parallel and offset to each other. The bearings 2312 are disposed along the shaft 2304 and one of the washers 2316 is disposedbetween each pair of adjacent bearings 2312. As such, the washers 2316 separate the bearings 2312 to facilitate rotation of the bearings 2312 relative to one another. The washers 2316 and bearings 2312 also provide separation of adjacent lengths of the SMA wire 2104, which may facilitate more rapid cooling of the SMA wire 2104 when the heat (e.g., electrical current) is removed.

[0058] With reference to FIG. 6, the SMA wire 2104 wraps around the spools 2300. Specifically, a first SMA wire 2104a is wrapped around the bearings 2312 between the spools 2400 and the slider assembly 2500, and a second SMA wire 2104b is wrapped around the bearings 2312 between the spools 2300 and the slider assembly 2500.

[0059] With reference to FIG. 7, the four SMA actuators 2100 are all identical and stacked along a common shaft axis 2516. Each shaft 2504 of each individual SMA actuator 2100 in stacked assembly is coupled to another shaft 2504 of an adjacent SMA actuator 2100. In other embodiments, there may be fewer or greater than four SMA actuators 2100 stacked together. For each SMA actuator 2100 added to the stacked actuator assembly, the output force generated by the entire stacked assembly as a single unit is incrementally increased.

[0060] During operation of the stacked actuator assembly illustrated in FIG. 7, each SMA actuator 2100 may be operated in unison together with the other stacked SMA actuators 2100 as a single two-position actuator and / or a continuous adjustment actuator. As a two-position actuator, heat (e.g., the electrical current) is applied simultaneously to each of the stacked SMA actuators 2100 to only one of the first SMA wire 2104a or the second SMA wire 2104b at a time.

[0061] So, for example, in each of the stacked SMA actuators 2100, when the slider assembly 2500 is in a first position, the first SMA wire 2104a is in the contracted state and the second SMA wire 2104b is in the extended state. When heat (e.g., the electrical current) is applied to the second SMA wire 2104b (and no heat or electrical current to the first SMA wire 2104a), the second SMA wire 2104b transitions to the austenite phase, such that the second SMA wire 2104b moves from the extended state to the contracted state. During this time, the slider assembly 2500 moves from the first position to the second position in each of the stacked SMA actuators 2100 in unison with the other stacked actuators, thereby exerting a force on the firstSMA wire 2104a via the shaft 2504 sufficient to deform the first SMA wire 2104a to the extended state. At this point, the first SMA wire 2104a is in the martensite phase.

[0062] The slider assembly 2500 in each stacked actuator returns to the first position when heat (e.g., the electrical current) is applied to the first SMA wire 2104a under the same principles just described. Depending on the application, various latches, valves, gear trains, linkages, and / or other various mechanisms may be coupled to and operated by the stacked assembly of actuators 2100 operating in unison as a single actuator , and more particularly, to the unified shaft 2504 (i.e., the actuator) formed from coupling together the individual shafts 2504 of the stacked SMA actuators 2100.

[0063] As a continuous adjustment actuator, each SMA actuator 2100 in the stacked actuator assembly illustrated in FIG. 7 works in unison together with the other stacked SMA actuators 2100 as a single unit in a similar manner as previously explained, but now, heat (e.g., the electrical current) is applied simultaneously in each of the stacked SMA actuators 2100 to one of the SMA wires 2104a, 2104b for a period of time until the slider assembly 2500 (i.e., the actuator or shaft 2504) reaches a desired position among an infinite number of possible positions between and including the first position and the second position. A position sensor 2532 may be employed to detect when the slider assembly 2500 reaches the desired position between the first position and the second position and relay a signal to the controller 2600 indicating to cutoff supply of the heat (e.g., electrical current).

[0064] 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

[0065] 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.

[0066] Clause 1. A shape memory alloy (SMA) actuator comprising: a first spool defining a first longitudinal axis and a second spool defining a second longitudinal axis that is parallel tothe first longitudinal axis; a slider assembly disposed between the first spool and the second spool, the slider assembly configured to move in a direction perpendicular to the first longitudinal axis and the second longitudinal axis; and a SMA wire wrapped around the first spool, the second spool, and the slider assembly, wherein the SMA wire changes between an extended state and a contracted state in response to heat being applied to the SMA wire, and wherein the slider assembly moves from a first position corresponding to the SMA wire being in the extended state to a second position corresponding to the SMA wire being in the contracted state.

[0067] Clause 2. The SMA actuator of clause 1, wherein the SMA wire is a first SMA wire that is wrapped around the first spool, the second spool, and a first side of the slider assembly, and wherein the SMA wire further includes a second SMA wire that is wrapped around the first spool, the second spool, and a second side of the slider assembly opposite the first side.

[0068] Clause 3. The SMA actuator of clause 2, wherein when heat is applied to the first SMA wire initially in the extended state, the first SMA wire changes to the contracted state and moves the slider assembly to exert a force on the second SMA wire, thereby changing the second SMA wire from the contracted state to the extended state.

[0069] Clause 4. The SMA actuator of clause 2 or 3, wherein when heat is applied to the second SMA wire initially in the extended state, the second SMA wire changes to the contracted state and moves the slider to exert a force on the first SMA wire, thereby changing the first SMA wire from the contracted state to the extended state.

[0070] Clause 5. The SMA actuator of any one of clauses 1-4, wherein the slider assembly is movable to the first position in response to heat being applied to the first SMA wire and to the second position in response to heat being applied to the second SMA wire, and wherein the slider assembly is movable to a desired position among an infinite number of possible positions between the first position and the second position by heating either the first SMA wire or the second SMA wire and stopping the slider assembly in response to a sensor being triggered.

[0071] Clause 6. The SMA actuator of any one of clauses 1-5, wherein the first spool and the second spool each includes a shaft and a plurality of bearings disposed along the shaft, whereinthe plurality of bearings is configured to rotate about the shaft, and wherein the plurality of bearings supports the SMA wire.

[0072] Clause 7. The SMA actuator of any one of clauses 1-6, further comprising a carrier frame disposed between the first spool and the second spool, the carrier frame including an elongated slot that guides the slider assembly while moving between the first position and the second position.

[0073] Clause 8. The SMA actuator of clause 7, wherein the carrier frame defines a carrier axis that is parallel to the elongated slot, and wherein the slider assembly translates in a direction along the carrier axis between the first position and the second position.

[0074] Clause 9. The SMA actuator of clause 7 or 8, wherein the first spool and the second spool each includes a shaft rigidly mounted to the carrier frame, such that each shaft remains stationary as the SMA wire changes between the extended state and the contracted state.

[0075] Clause 10. The SMA actuator of any one of clauses 1-9, wherein the slider assembly includes a shaft that is configured to interface with and actuate another mechanism when moving between the first position and the second position.

[0076] Clause 11. A shape memory alloy (SMA) actuator comprising: a first spool and a second spool; a slider assembly disposed between the first spool and the second spool; a first SMA wire wrapped around the first spool, the second spool, and the slider assembly; and a second SMA wire wrapped around the first spool, the second spool, and the slider assembly, wherein the slider assembly is configured to move in a first direction in response to heating of the first SMA wire, and wherein the slider assembly is configured to move in a second direction opposite the first direction in response to heating of the second SMA wire.

[0077] Clause 12. The SMA actuator of clause 11, wherein the first SMA wire is wrapped around the slider assembly on a first side of the slider assembly, and wherein the second SMA wire is wrapped around the slider assembly on a second side of the slider assembly opposite the first side.

[0078] Clause 13. The SMA actuator of clause 11 or 12, wherein the first SMA wire and the second SMA wire are configured to be heated by electrical current flowing through the first SMA wire and the second SMA wire.

[0079] Clause 14. The SMA actuator of any one of clauses 11-13, further comprising a carrier frame disposed between the first spool and the second spool, the carrier frame including an elongated slot that guides the slider assembly while moving in the first direction and the second direction.

[0080] Clause 15. A shape memory alloy (SMA) actuator assembly comprising at least two of the SMA actuator of any one of clauses 1-14, wherein the at least two SMA actuators are configured to operate together in unison.

[0081] Clause 16. The SMA actuator assembly of clause 15, wherein the at least two SMA actuators are configured to operate together in unison together as either a single two-position actuator or a continuous adjustment actuator.

[0082] Clause 17. The SMA actuator assembly of clause 16, wherein the at least two SMA actuators are configured to operate together in unison together as a single two-position actuator such that heat is applied simultaneously in each of the at least two SMA actuators to only one of the first SMA wire or the second SMA wire at a time, and wherein the slider assembly is movable to a first position in response to heat being applied to the first SMA wire and to a second position in response to heat being applied to the second SMA wire.

[0083] Clause 18. The SMA actuator assembly of clause 16, wherein the at least two SMA actuators are configured to operate together in unison together as a continuous adjustment actuator such that heat is applied simultaneously in each of the at least two SMA actuators to one of the SMA wires for a period of time until the slider assembly reaches a desired position among an infinite number of possible positions between and including a first position and a second position, and wherein the slider assembly is movable in a first position in response to heat being applied to the first SMA wire and in a second direction in response to heat being applied to the second SMA wire.

[0084] Clause 19. The SMA actuator assembly of any one of clauses 15-18, wherein the at least two SMA actuators are stacked on each other.

[0085] Clause 20. The SMA actuator assembly of clause 19, wherein the slider assembly of each of the at least two SMA actuators includes a shaft, and wherein each shaft is configured to interface with a shaft of an adjacent stacked SMA actuator to operate as a single unit and actuate another mechanism when moving between a first position and a second position.

[0086] Various features and aspects of the present disclosure are set forth in the following claims.

Claims

CLAIMSWhat is claimed is:

1. A shape memory alloy (SMA) actuator comprising: a first spool defining a first longitudinal axis and a second spool defining a second longitudinal axis that is parallel to the first longitudinal axis; a slider assembly disposed between the first spool and the second spool, the slider assembly configured to move in a direction perpendicular to the first longitudinal axis and the second longitudinal axis; and a SMA wire wrapped around the first spool, the second spool, and the slider assembly, wherein the SMA wire changes between an extended state and a contracted state in response to heat being applied to the SMA wire, and wherein the slider assembly moves from a first position corresponding to the SMA wire being in the extended state to a second position corresponding to the SMA wire being in the contracted state.

2. The SMA actuator of claim 1, wherein the SMA wire is a first SMA wire that is wrapped around the first spool, the second spool, and a first side of the slider assembly, and wherein the SMA wire further includes a second SMA wire that is wrapped around the first spool, the second spool, and a second side of the slider assembly opposite the first side.

3. The SMA actuator of claim 2, wherein when heat is applied to the first SMA wire initially in the extended state, the first SMA wire changes to the contracted state and moves the slider assembly to exert a force on the second SMA wire, thereby changing the second SMA wire from the contracted state to the extended state.

4. The SMA actuator of claim 2, wherein when heat is applied to the second SMA wire initially in the extended state, the second SMA wire changes to the contracted state and moves the slider to exert a force on the first SMA wire, thereby changing the first SMA wire from the contracted state to the extended state.

5. The SMA actuator of claim 2, wherein the slider assembly is movable to the first position in response to heat being applied to the first SMA wire and to the second position in response to heat being applied to the second SMA wire, and wherein the slider assembly is movable to a desired position among an infinite number of possible positions between the first position and the second position by heating either the first SMA wire or the second SMA wire and stopping the slider assembly in response to a sensor being triggered.

6. The SMA actuator of claim 1, wherein the first spool and the second spool each includes a shaft and a plurality of bearings disposed along the shaft, wherein the plurality of bearings is configured to rotate about the shaft, and wherein the plurality of bearings supports the SMA wire.

7. The SMA actuator of claim 1, further comprising a carrier frame disposed between the first spool and the second spool, the carrier frame including an elongated slot that guides the slider assembly while moving between the first position and the second position.

8. The SMA actuator of claim 7, wherein the carrier frame defines a carrier axis that is parallel to the elongated slot, and wherein the slider assembly translates in a direction along the carrier axis between the first position and the second position.

9. The SMA actuator of claim 7, wherein the first spool and the second spool each includes a shaft rigidly mounted to the carrier frame, such that each shaft remains stationary as the SMA wire changes between the extended state and the contracted state.

10. The SMA actuator of claim 1, wherein the slider assembly includes a shaft that is configured to interface with and actuate another mechanism when moving between the first position and the second position.

11. A shape memory alloy (SMA) actuator comprising: a first spool and a second spool; a slider assembly disposed between the first spool and the second spool; a first SMA wire wrapped around the first spool, the second spool, and the slider assembly; and a second SMA wire wrapped around the first spool, the second spool, and the slider assembly, wherein the slider assembly is configured to move in a first direction in response to heating of the first SMA wire, and wherein the slider assembly is configured to move in a second direction opposite the first direction in response to heating of the second SMA wire.

12. The SMA actuator of claim 11, wherein the first SMA wire is wrapped around the slider assembly on a first side of the slider assembly, and wherein the second SMA wire is wrapped around the slider assembly on a second side of the slider assembly opposite the first side.

13. The SMA actuator of claim 11, wherein the first SMA wire and the second SMA wire are configured to be heated by electrical current flowing through the first SMA wire and the second SMA wire.

14. The SMA actuator of claim 11, further comprising a carrier frame disposed between the first spool and the second spool, the carrier frame including an elongated slot that guides the slider assembly while moving in the first direction and the second direction.

15. A shape memory alloy (SMA) actuator assembly comprising at least two of the SMA actuator of claim 11, wherein the at least two SMA actuators are configured to operate together in unison.

16. The SMA actuator assembly of claim 15, wherein the at least two SMA actuators are configured to operate together in unison together as either a single two-position actuator or a continuous adjustment actuator.

17. The SMA actuator assembly of claim 16, wherein the at least two SMA actuators are configured to operate together in unison together as a single two-position actuator such that heat is applied simultaneously in each of the at least two SMA actuators to only one of the first SMA wire or the second SMA wire at a time, and wherein the slider assembly is movable to a first position in response to heat being applied to the first SMA wire and to a second position in response to heat being applied to the second SMA wire.

18. The SMA actuator assembly of claim 16, wherein the at least two SMA actuators are configured to operate together in unison together as a continuous adjustment actuator such that heat is applied simultaneously in each of the at least two SMA actuators to one of the SMA wires for a period of time until the slider assembly reaches a desired position among an infinite number of possible positions between and including a first position and a second position, and wherein the slider assembly is movable in a first position in response to heat being applied to the first SMA wire and in a second direction in response to heat being applied to the second SMA wire.

19. The SMA actuator assembly of claim 15, wherein the at least two SMA actuators are stacked on each other.

20. The SMA actuator assembly of claim 19, wherein the slider assembly of each of the at least two SMA actuators includes a shaft, and wherein each shaft is configured to interface with a shaft of an adjacent stacked SMA actuator to operate as a single unit and actuate another mechanism when moving between a first position and a second position.

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