초록 ▼

Linear actuators including coupled elongate members formed of shape memory alloys are provided. Members that lengthen when heated are coupled to members that shorten when heated such that stroke amplification gains are derived from each member. The members may be tubular and may be coaxially arrange

Linear actuators including coupled elongate members formed of shape memory alloys are provided. Members that lengthen when heated are coupled to members that shorten when heated such that stroke amplification gains are derived from each member. The members may be tubular and may be coaxially arranged for telescopic extension and collapse. Sections of a modular structure such as a space vehicle may be latched and clamped together for assembly or for docking by utilizing linear actuators having shape memory alloys that are actuated thermally.

대표청구항 ▼

That which is claimed: 1. A stroke-amplifying linear actuator comprising: an elongate first member comprising a proximal end and a first shape memory alloy, the first member configured to shorten by a first distance when the first shape memory alloy is heated; and an elongate second member having t

That which is claimed: 1. A stroke-amplifying linear actuator comprising: an elongate first member comprising a proximal end and a first shape memory alloy, the first member configured to shorten by a first distance when the first shape memory alloy is heated; and an elongate second member having two opposing ends and comprising a second shape memory alloy, the second member configured to lengthen by a second distance when the second shape memory alloy is heated; wherein the second member is coupled to the first member such that at least one end of the second member travels an amplified distance relative to the proximal end of the first member at a time when the first member is shortened by the first distance and the second member is lengthened by the second distance, the amplified distance being greater than either of the first distance and the second distance. 2. A linear actuator according to claim 1, wherein: the second member travels in a first direction relative to the proximal end of the first member when the first member shortens; and the second member comprises a proximal end that travels in the first direction relative to the proximal end of the first member when the second member lengthens. 3. A linear actuator according to claim 1, wherein the amplified distance is at least as great as the sum of the first distance and the second distance. 4. A linear actuator according to claim 1, wherein: the first shape memory alloy has a first transition temperature; and the first member is configured to shorten when the first shape memory alloy is heated from below the first transition temperature to above the first transition temperature. 5. A linear actuator according to claim 4, wherein: the first shape memory alloy obtains a martensitic state such that the first member obtains a first length when the temperature of the first shape memory alloy is below the first transition temperature; the first shape memory alloy obtains an austenitic state such that the first member obtains a second length when the temperature of the first shape memory alloy is above the first transition temperature; and the first length is greater than the second length. 6. A linear actuator according to claim 4, wherein the first member is configured to lengthen when the first shape memory alloy cools from above the first transition temperature to below the first transition temperature. 7. A linear actuator according to claim 4, wherein: the second shape memory alloy has a second transition temperature; and the second member is configured to lengthen when the second shape memory alloy is heated from below the second transition temperature to above the second transition temperature. 8. A linear actuator according to claim 7, wherein the first transition temperature is approximately the same as the second transition temperature. 9. A linear actuator according to claim 1, further comprising a thermal element for causing a temperature change in at least the first shape memory alloy. 10. A linear actuator according to claim 1, further comprising a heating element for heating at least the first shape memory alloy or the second shape memory alloy. 11. A linear actuator according to claim 1, wherein the first member comprises a tubular portion, and, wherein at least a portion of the second member is surrounded by the tubular portion of the first member. 12. A linear actuator according to claim 1 further comprising an elongate third member that comprises a proximal portion, and a third shape memory alloy, the third member configured to shorten when the third shape memory alloy is heated, wherein: the first member comprises a distal tubular portion; the second member comprises a proximal portion surrounded by the distal tubular portion of the first member, and a tubular distal portion surrounding at least the proximal portion of the third member. 13. A linear actuator according to claim 1, further comprising: a telescoping sub-assembly of tubular members, the sub-assembly comprising an outer tubular member, at least one inner tubular member and at least one shape memory alloy; wherein the second member comprises a tubular distal portion that at least partially surrounds the outer tubular member of the telescoping sub-assembly. 14. A stroke-amplifying thermally actuatable telescoping assembly comprising: an elongate tubular first member comprising a first shape memory alloy; and an elongate second member comprising a second shape memory alloy; the second member at least partially surrounded by the tubular first member; wherein either the first member and the second member are both configured to lengthen by respective distances when thermally actuated or they are both configured to shorten by respective distances when thermally actuated; wherein the second member is operably coupled to the first member such that a portion of the second member moves linearly relative to a portion the first member by an amplified distance at a time when the first member and the second member are both thermally actuated; and wherein the amplified distance is greater than any one said respective distance. 15. An assembly according to claim 14, wherein: the first member comprises a proximal end and a distal portion; the second member comprises a proximal portion and a distal end; the telescoping assembly further comprises a third member at least partially surrounded by the tubular first member; and the proximal portion of the second member is operably coupled to the distal portion of the first member by the third member such that the distal end of the second member moves linearly relative to the proximal end of the first member when the assembly is thermally actuated. 16. An assembly according to claim 15, wherein, when the assembly is thermally actuated: the distal portion of the first member moves by a first distance relative to the proximal end of the first member; the distal end of the second member moves by a second distance relative to the proximal portion of the second member; and the distal end of the second member moves by the amplified distance, which is more than the first distance and more than the second distance. 17. An assembly according to claim 16, wherein the amplified distance is at least as great as the sum of the first distance and the second distance. 18. An assembly according to claim 16, wherein: the third member comprises a distal portion, a proximal portion, and a third shape memory alloy; the proximal portion of the third member moves a third distance relative to the distal portion of the third member when the assembly is thermally actuated; and the amplified distance is more than the third distance. 19. An assembly according to claim 18, wherein the amplified distance is at least as great as the sum of the first distance, the second distance, and the third distance. 20. An assembly according to claim 16, wherein: the first member is configured to shorten when the first shape memory alloy is heated; the second member is configured to shorten when the second shape memory alloy is heated; and the third member is configured to lengthen when the third shape memory alloy is heated. 21. An assembly according to claim 14, wherein: the first member is configured to shorten when the first shape memory alloy is heated; and the second member is figured to shorten when the second shape memory alloy is heated. 22. A telescoping actuator according to claim 14, wherein: the telescoping assembly further comprises a telescoping sub-assembly of tubular members, the sub-assembly comprising an outer member at least partially surrounded by the tubular first member, an inner member at least partially surrounding the second member, and at least one shape memory alloy; and the second member is operably coupled to the first member by way of the sub-assembly such that the portion of the second member moves linearly relative to the first member when the telescoping assembly is thermally actuated. 23. A stroke-amplifying thermally actuatable coaxial assembly comprising: an elongate first member disposed along an axis, the first member comprising a first proximal portion, a first distal portion, and a first shape memory alloy configured to forcibly change the distance between the first proximal portion and the first distal portion by a first distance when thermally actuated; an elongate second member disposed along the axis, the second member comprising a second proximal portion, a second distal portion, and a second shape memory alloy configured to forcibly change the distance between the second proximal portion and the second distal portion by a second distance when thermally actuated; and an intervening member disposed along the axis, the intervening member operably coupling the first distal portion to the second proximal portion such that the second proximal portion is moved forcibly along the axis by the intervening member relative to the first proximal portion when the first shape memory alloy is thermally actuated, and such that the second distal portion is moved forcibly along the axis relative to the first proximal portion by an amplified distance that is greater than the first distance and greater than the second distance at a time when the first shape memory alloy and the second shape memory alloy are both thermally actuated. 24. An assembly according to claim 23, wherein: the first distal portion is tubular; at least a portion of the intervening member is disposed within the tubular first distal portion; at least a portion of the intervening member is tubular; and at least a portion of the second member is disposed within the tubular portion of the intervening member. 25. An assembly according to claim 23, wherein: the first shape memory alloy has a first transition temperature about which the alloy is configured to forcibly change the distance between the first proximal portion and the first distal portion; the second shape memory alloy has a second transition temperature about which the alloy is configured to forcibly change the distance between the second proximal portion and the second distal portion.