Mechanical protection device

1. A mechanical protection device comprising:

a transmission shaft including a frangible element that is breakable under a torsional overload;

a movable member secured to the transmission shaft to rotate about a main axis and configured to move radially outwards relative to the main axis from a first position to a second position;

a spring urging the movable member towards the first position; and

a tangential abutment configured to stop rotation of the movable member about the main axis when the movable member is in the second position; and

wherein the movable member and the spring are calibrated so that, from a predetermined trigger angular speed, the movable member moves from the first position to the second position under effect of centrifugal force greater than prestress of the spring such that the tangential abutment stops rotation of the transmission shaft causing said torsional overload to break the frangible element.

2. A mechanical protection device according to claim 1 , wherein the movable member is configured to move from the first position to the second position in translation.

3. A mechanical protection device according to claim 1 , wherein the movable member is configured to move from the first position to the second position in pivoting.

4. A machine comprising a drive shaft, a feed pump, and a mechanical protection device according to claim 1 , wherein the transmission shaft connects the drive shaft to the feed pump to actuate the feed pump.

5. A machine according to claim 4 , wherein the feed pump is a fuel feed pump.

6. A machine according to claim 5 , wherein the drive shaft is coupled to a turbine configured to be actuated by expansion of a fluid heated by combustion of the fuel.

7. A mechanical protection device according to claim 1 , wherein said predetermined trigger angular speed is in a drive direction of the transmission shaft.

8. A mechanical protection method comprising:

at a certain angular speed of a transmission shaft, triggering a movement of a movable member from a first position to a second position that is radially further out relative to the transmission shaft under effect of a centrifugal force and against a resilient prestress from a spring urging the movable member in the direction opposite to the centrifugal force, the movable member rotating with the transmission shaft;

in the second position, causing the rotating movable member to make contact against one or more tangential abutments; and

breaking a frangible element of the transmission shaft under a torsional overload caused by the movable member making contact against the tangential abutment.

9. A mechanical protection method according to claim 8 , wherein the transmission shaft transmits rotation from a drive shaft to a feed pump.

10. A mechanical protection method according to claim 9 , wherein the feed pump feeds fuel to combustion delivering heat energy suitable for causing the drive shaft to rotate.

11. A mechanical protection method according to claim 10 , wherein the drive shaft is actuated by a turbine, the turbine being actuated in turn by expansion of a fluid heated by the combustion.

12. A mechanical protection method according to claim 8 , wherein said certain angular speed is in a drive direction of the transmission shaft.