Overspeed safety device

An overspeed safety device for a pneumatic rotation motor with a stator with an air inlet passage, a rotor comprising a speed responsive actuator connected to the rotor for co-rotation therewith, and a valve shiftable by said actuator from an open position to a closed position,

• wherein said actuator comprises a contact element which is radially movable by centrifugal action between an inactive position and an active position, and a spring means arranged to maintain said contact element in said inactive position at motor speed levels below a predetermined maximum speed level and to permit said contact element to be displaced radially to said active position at motor speed levels above said maximum speed level to thereby accomplish shifting of said valve from said open position to said closed position;
• wherein said valve comprises a disc-shaped valve element which is rotatable about a pivot axis for movement between said open position and said closed position, and wherein said valve element in said open position is located substantially in parallel with the inlet passage, and in said closed position said valve element is located transversely to the inlet passage;
• wherein said pivot axis extends transversely to the inlet passage and is located in a laterally off-set position in relation to the rotation axis of the rotor in such a way that said valve element in said open position is out of reach by said contact element when said contact element occupies said inactive position, whereas said contact element in said active position reaches out radially to hit said valve element making said valve element shift from said open position to said closed position;
• and
• further comprising a retaining device for releasably holding said valve element in said open position.