Rotary actuator

A rotary actuator comprising:

• an actuator body having a first end and a second end defining an interior of the actuator body therebetween, an axis X of the body being between the first and second ends, each end provided with a port arranged to receive hydraulic fluid;
• mounting parts extending from the ends into the interior of the actuator body
• a screw mounted to the mounting parts within the actuator body between the first and second ends, the screw mounted to the mounting parts via splines to allow linear axial translation of the screw relative to the mounting parts;
• the screw having one or more walls extending across an inner diameter d of the screw;
• the actuator body, the mounting parts and the one or more walls defining a first chamber in fluid communication with the port at the first end of the actuator body and a second chamber in fluid communication with the port at the second end of the actuator body;
• a first piston having a piston head located within the first chamber;
• a second piston with a piston head located within the second chamber;
• a nut mounted within the actuator body around the screw, the nut having an inner diameter D;
• ball bearings between the screw and the nut such that axial movement of the screw relative to the mounting parts causes rotational movement of the ball bearings which causes rotation of the nut relative to the screw and to the body;
• wherein the splines are provided radially between the nut and the screw and so within the inner diameter D of the nut;
• wherein the axial translation of the screw is caused by the force of hydraulic fluid in the first or second chamber, from the port, pushing against the piston, the piston head of which pushes against the wall or walls defining the chamber;
• wherein each of the mounting parts comprises a pair of flanges separated by a gap (g);
• and
• wherein the screw is mounted, via the splines, in the gap.