Patent ID: 7677863

Claim:
Overspeed safety device for a pneumatic rotation motor including a cylinder ( 10 ), a pressure air inlet opening ( 21 ), and a rotor ( 13 ), comprising an actuator ( 18 ) co-rotating with the rotor ( 13 ) and responsive to centrifugal action, and a valve element ( 20 ) arranged to control the air flow through the inlet opening ( 21 ), said valve element ( 20 ) is arranged to be engaged by the actuator ( 18 ) for initiating a shifting movement of the valve element ( 20 ) from an open position to closed position as the rotor speed exceeds a predetermined maximum speed level, said valve element ( 20 ) is formed by a lid which is tiltable about a pivot axis (C) between the open position and the closed position, and said pivot axis (C) extends substantially along a chord related to the centre of the rotor ( 13 ), and the actuator ( 18 ) is formed with a cam surface ( 25 ) for caming engagement with said lid ( 20 ) for accomplishing tilting of said lid ( 20 ) about said pivot axis (C), wherein said inlet opening ( 21 ) is surrounded by a flat seat surface ( 32 ) for sealing engagement by the lid ( 20 ) in the closed position of the latter, said lid ( 20 ) is formed with at least one ridge portion ( 33 , 34 ) for resting on said seat surface ( 32 ), a spring ( 26 ) is arranged to retain and bias said lid ( 20 ) toward said seat surface ( 32 ) such that when shifted between the open position and the closed position the lid ( 20 ) is made to perform a bi-stable over-centre movement by the ridge portion or portions.