Patent ID: 9638343
Date: 2017-05-02
CPC Classifications: E21B,F16K,Y10T

Claim:
1. A valve actuator comprising: 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 responsive to at least a specified amount of temperature change of the shape memory alloy element; and a negative-differential spring applied to the shape memory alloy element, thereby reducing the specified amount of temperature change needed to cause movement of the valve between the first and second positions, the transition temperatures of the shape memory alloy element being tuned to the specified amount of temperature change, wherein a lever is connected to the shape memory alloy element and allowed to rotate when the temperature applied to the shape memory alloy element increases, the lever includes a lever arm, wherein angular displacement of the lever arm is associated with the specified amount of temperature change of the shape memory alloy element, wherein the negative-differential spring applies a first stress to the shape memory alloy element when the shape memory alloy element is near the Austenitic start temperature, and a second stress lower than the first stress when the shape memory alloy element is near the Austenitic finish temperature.