Rotary electrothermal actuator

An electrothermal actuator for converting electrical energy to rotational mechanical motion comprising:

• a housing;
• a flexible diaphragm disposed in the housing and defining a boiler chamber within the housing;
• a working fluid disposed within the boiler chamber, changing phase in response to heating and thereby displacing the diaphragm;
• heating means disposed within the boiler chamber for heating the working fluid in response to an electrical current flowing through the heating means;
• and
• a rotatable shaft assembly partially disposed within the housing and including a rotatable shaft extending outside the housing and rotating between a return position and a rotated position without translational movement of the shaft relative to the housing and a cam driver slidingly disposed within the housing, a cam rotatably disposed within the housing and attached to the shaft, first and second recesses of variable depth respectively disposed in the cam driver and the cam, the respective recesses being disposed opposite each other, a spherical member disposed in the first and second recesses contacting the cam driver and the cam for rotating the cam about an axis in response to sliding of the cam driver whereby displacement of the diaphragm slides the cam driver relative to the housing, thereby rotating the cam and shaft.