Patent ID: 7438165

Claim:
A damper for mitigating torsional vibrations of a shaft rotating with an angular velocity, said damper comprising: a generally circular ring surrounding said shaft and rotatable therewith; and at least two generally diametrically opposite spring and mass arrangements, each of said spring and mass arrangements comprising: a first spring coupled at one end to said ring and being radially inwardly oriented toward said shaft; and a mass coupled to said shaft via a second radially oriented spring, said mass oscillating in a direction generally perpendicular to the axes of said first and second springs, wherein oscillation of said masses dampens torsional vibrations of said shaft corresponding to a frequency of said oscillation, the mass of each spring and mass arrangement being moveable radially along the first spring of the same spring and mass arrangement in response to changes in the angular velocity of said shaft thereby to adjust the spring constant of that first spring.