Patent ID: 7497146

Claim:
A method for filtering out rotational vibrations transmitted by a drive shaft ( 11 , 111 ) to an output shaft ( 19 , 119 , 219 ); the method comprising the steps of: providing a filtering device including a drive shaft damper ( 20 , 120 , 220 ) mounted to the output shaft ( 19 ) and an electromagnetic modulating device provided for matching a frequency of rotational vibration of the damper ( 20 , 120 , 220 ) to a frequency of rotational vibrations transmitted by the drive shaft ( 11 , 111 ) which is inside the range of frequencies of the rotational vibrations to be damped out; measuring a frequency of a rotational vibration transmitted by the drive shaft ( 11 , 111 ); and matching the frequency of the rotational vibration of the drive shaft damper ( 20 , 120 , 220 ) to the frequency of the rotational vibrations transmitted by the drive shaft ( 11 , 111 ).