Actuator for transfer of forward and backward rotational movement

A fluid-operated actuator comprising a chamber part including chamber walls and at least one chamber which is adapted to be supplied with a pressurized fluid, a carrier which is mounted in the chamber part in such a manner that it can rotate about an axis of rotation, and which is adapted to be connected with an object which has to be rotated, and a plunger piston whose longitudinal axis extends in the form of a circular arc which curves circularly about an axis which is coincident with the carrier's axis of rotation, which plunger pistion is arranged to be rotated about the axis of rotation, and to connect with the carrier, and wherein the plunger piston passes sealingly by way of a sealing device through an opening in the said at least one chamber to extend therein such that there is clearance between a section of the plunger piston which is located in the chamber and the chamber walls, and wherein a section of the plunger piston which is located outside the chamber is slidingly supported along a radial outer surface by a support part which is removably attached to the chamber part.