Coupling arrangement for coupling rock drill shank

A coupling arrangement for coupling a drill shank of a rock drill unrotatably but axially movably with respect to a rotation bushing locating around the drill shank while the shank is mounted in place in the rock drill and rotating the drill shank, in which arrangement the rotation bushing comprises, in relation to the direction of rotation, at least one power transmission surface substantially in the direction of the rotation axis, transverse to the direction of rotation and facing the direction of rotation, and correspondingly, the drill shank comprises an equal number of power reception surfaces substantially in the same direction from the power transmission surfaces to the direction of rotation, and power transmission members, whereby the rotation torque is transferred during rotation from the rotation bushing through the power transmission surfaces, the transmissions members and power reception surfaces to the drill shank, wherein power transmission members are mounted rotatably between the power transmission surface and the corresponding power reception surface such that as the drill shank moves in relation to the rotation bushing in the longitudinal direction of the reception and power transmission surfaces, the transmission members rotate along the power transmission surface and correspondingly along the power reception surface.