Rotary actuator

A rotary actuator, comprising:

• an output shaft;
• a housing in which a cylinder is defined, the cylinder having a circular arc shape around the output shaft;
• a piston adapted to move inside the cylinder by action of a pressure medium;
• and
• an arm connecting the piston and the output shaft,
• wherein the piston has a through hole that penetrates the piston in an axial direction of the output shaft,
• wherein the arm has a through hole that penetrates the arm in the axial direction of the output shaft,
• wherein the piston is connected to the arm by a bolt inserted into the through hole in the piston and the through hole in the arm so that the piston is rotatable with the bolt as a fulcrum,
• wherein, when viewed in plan from a direction parallel to the output shaft, a top surface of the piston has three equally divided regions divided in a radial direction from a center of the output shaft, a middle one of the three regions being a central region, and
• wherein, when viewed in plan from the direction parallel to the output shaft, a connection point between the piston and the arm is situated on a virtual line that is orthogonal to the top surface and passes through the central region.