# US 2014/0150879 A1 · Apparatus for adjusting shape memory alloy transition temperatures to track slowly changing ambient temperature > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0150879 A1 - Document ID: US20140150879A1 - Status: Published application - Kind: A1 - Application number: 13/691,240 - Filed: 2012-11-30 - Published: 2014-06-05 - Earliest claimed: 2012-11-30 - Assignees: Massachusetts Institute of Technology; Chevron U.S.A. Inc. - Applicants: Chevron U.S.A. Inc.; Massachusetts Institute of Technology - Inventors: Eric Wright Gilbertson; Changkuan Yu; Franz Hover; Dennis Harris; Jose Arellano - Web page: https://patentgrep.com/patent/US20140150879A1 ## CPC - F16K 31/002: {actuated by temperature variation (thermo-electric F16K31/025)} - Y10T 137/0324: With control of flow by a condition or characteristic of a fluid - Y10T 137/7737: Thermal responsive - F16K: VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING {(devices for emptying and evacuating the excess liquid in valves or conduits F16L55/07)} - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract A valve actuator, valve, and method of actuation of a valve are disclosed. The valve actuator includes a shape memory alloy element attachable to a valve body, capable of use with a valve to cause movement of the valve between first and second positions at a predetermined temperature and responsive to at least a threshold amount of temperature change of the shape memory alloy element. The valve actuator further includes an expansion element attached to the shape memory alloy element, the expansion element responsive to temperature changes at a rate lower than a rate of change of temperature indicative of a valve leak, the expansion element adjusting tension on the shape memory alloy element, thereby changing the predetermined temperature. ## Claims ### Claim 1 A valve actuator comprising: a shape memory alloy element attachable to a valve body, the shape memory alloy element capable of use with a valve to cause movement of the valve between first and second positions at a predetermined temperature and responsive to at least a threshold amount of temperature change of the shape memory alloy element; and an expansion element attached to the shape memory alloy element, the expansion element responsive to temperature changes at a rate lower than a rate of change of temperature indicative of a valve leak, the expansion element adjusting tension on the shape memory alloy element, thereby changing the predetermined temperature. ### Claim 2 (depends on 1) The valve actuator of claim 1, further comprising a negative-differential spring applied to the shape memory alloy element, thereby reducing the threshold amount of temperature change needed to cause movement of the valve between the first and second positions. ### Claim 3 (depends on 1) The valve actuator of claim 1, further comprising a torque axle, wherein the expansion element is attached to the shape memory alloy element via the torque axle. ### Claim 4 (depends on 3) The valve actuator of claim 3, wherein the expansion element is connected to an inner radius of the torque axle, and the shape memory alloy element is connected to an outer radius of the torque axle. ### Claim 5 (depends on 1) The valve actuator of claim 1, wherein the expansion element comprises an aluminum rod surrounded by a thermal insulator. ### Claim 6 (depends on 5) The valve actuator of claim 5, wherein the thermal insulator comprises an aerogel coating. ### Claim 7 (depends on 1) The valve actuator of claim 1, wherein the shape memory alloy element contracts from a first length to a second length when heated from a first temperature to a second temperature. ### Claim 8 (depends on 7) The valve actuator of claim 7, wherein the first temperature is an Austenitic start temperature, and wherein the second temperature is an Austenitic finish temperature. ### Claim 9 (depends on 8) The valve actuator of claim 8, wherein the Austenitic start temperature corresponds to the predetermined temperature. ### Claim 10 (depends on 1) The valve actuator of claim 1, wherein the first and second positions correspond to open and closed valve positions. ### Claim 11 (depends on 1) The valve actuator of claim 1, wherein the valve actuator fully actuates over a temperature change of less than about 6° C. within a predetermined amount of time. ### Claim 12 (depends on 11) The valve actuator of claim 11, wherein the predetermined amount of time is approximately an hour. ### Claim 13 (depends on 1) The valve actuator of claim 1, wherein the valve actuator remains unactuated over a temperature change of greater than at least 1° C. if the temperature change occurs over a time period greater than a rate of temperature change of the expansion element. ### Claim 14 A valve, comprising: a valve body; an orifice within the valve body; a fluid flow restraining member located at a first location of the orifice, the fluid flow restraining member movable between a closed position and an open position; a shape memory alloy element connected to the fluid flow restraining member, the shape memory alloy element causing pivotal movement of the fluid flow restraining member between open and closed positions responsive to at least a threshold amount of temperature change of the shape memory alloy element; and an expansion element attached to the shape memory alloy element, the expansion element responsive to temperature changes at a rate lower than a rate of change of temperature indicative of a valve leak, the expansion element adjusting tension on the shape memory alloy element, thereby changing the threshold amount of temperature change. ### Claim 15 (depends on 14) The valve of claim 14, wherein the fluid flow restraining member is pivotable between the closed position and the open position. ### Claim 16 (depends on 14) The valve of claim 14, further comprising a torque axle, wherein the expansion element is attached to the shape memory alloy element via the torque axle. ### Claim 17 (depends on 14) The valve of claim 14, wherein the expansion element comprises an aluminum rod surrounded by a thermal insulator. ### Claim 18 (depends on 17) The valve of claim 17, wherein changes in length of the expansion element apply varying tensile stresses on the shape memory alloy element, thereby adjusting an Austenitic start temperature of the shape memory alloy element based on gradual changes in temperature. ### Claim 19 A method of actuating a valve from an open position to a closed position, the method comprising: experiencing a first temperature change from a first temperature to a second temperature at the valve over a first amount of time; adjusting a tensile stress on a shape memory alloy element used to actuate the valve in response to the first temperature change, thereby adjusting a threshold temperature at which the shape memory alloy element actuates; experiencing a second temperature change at a valve actuator including the shape memory alloy element over a second amount of time; actuating the valve between the open position and the closed position in response to the second temperature change, wherein the second temperature change is greater than the threshold temperature and the second amount of time is shorter than the first amount of time. ### Claim 20 (depends on 19) The method of claim 19, wherein the second amount of time is faster than an expected change in environmental temperature at the valve.