Patent ID: 8261896

Claim:
A tuned mass damper for use with a structure that vibrates at a first axial surge mode and a second axial surge mode, when exposed to a predetermined frequency range, the tuned mass damper comprising: a housing defining a cavity and including an end; an endcap disposed over the end of the housing, the endcap including a chamber and an aperture that provides fluid communication between the cavity and the chamber; a first ring-shaped mass disposed in the cavity; a second ring-shaped mass disposed in the cavity; a first tuned mass damper spring disposed in the cavity coupling the first mass and the endcap; and a second tuned mass damper spring disposed in the cavity coupling the first mass and the second mass; a shaft extending from the endcap and through the first mass, the first tuned mass damper spring, the second mass, and the second tuned mass damper spring, wherein: the tuned mass damper has a first resonant frequency that is in the predetermined frequency range to damp the first axial surge mode, the tuned mass damper has a second resonant frequency that is in the predetermined frequency range to damp the second axial surge mode, and the second mass resonates at an amplitude that is greater than an amplitude at which the first mass resonates, when the first mass and the second mass are subjected to the second axial surge mode.