Fail-safe actuation system

A fail-safe fluid-based actuation system comprising:

• a control element having a first chamber, a second chamber, a third chamber and a safety position;
• a working circuit having a motor/pump device and configured and arranged to, in an operative state, selectively communicate fluid to the second chamber and the third chamber to actuate the control element;
• a safety circuit having a tank that holds pressurized fluid, an on-off valve for flow between the tank and the first chamber, and a drain valve for flow from the second chamber;
• the safety circuit configured and arranged to, in a failure state, automatically move the on-off valve to a through-flow position to connect the tank to the first chamber, move the drain valve to a through-flow position to drain fluid out of the second chamber, and to thereby move the control element into the safety position;
• the working circuit and the safety circuit configured and arranged such that, in the failure state, flow from the tank into the first chamber is provided by the safety circuit in a manner that is decoupled from the working circuit motor/pump device;
• the working circuit and the safety circuit configured and arranged such that, in the operative state, flow into the third chamber is provided by the working circuit in a manner that is decoupled from the tank;
• a filling line and a first valve element between the working circuit and the tank;
• and
• the filling line and first valve element configured and arranged such that fluid from the working circuit can be selectively fed into the tank and such that the tank is decoupled from the working circuit by the first valve element so as to prevent fluid from flowing back into the working circuit.