Clamping shaft, printing cylinder unit and method for operating a clamping shaft

A clamping shaft for a rotationally driven part, the clamping shaft comprising:

• a shaft body being rotatable about a shaft axis;
• and
• at least one fluid chamber being located inside the shaft body and being filled with a predetermined amount of fluid,
• wherein the fluid chamber is delimited by a piston surface of a piston being located inside the shaft body and a cylinder part, being movable relative to each other such that a volume of the fluid chamber is adjustable by moving the piston relative to the cylinder part,
• wherein the shaft body comprises at least one elastic clamping region delimiting the fluid chamber,
• wherein the clamping region has a first diameter when the piston and the cylinder part are in a first relative position, and a second diameter when the piston and the cylinder part are in a second relative position, the second diameter being bigger than the first diameter,
• wherein the clamping shaft further comprises a spring assembly applying a preloading force on the piston and/or the cylinder part such that the piston and the cylinder part are biased towards the second relative position,
• wherein the preloading force on the piston and/or the cylinder part is selectively counteracted by an external force from an actuation interface of the piston.