Inertia damper using ferrofluid

A viscous-fluid inertia damper, which damper comprises:

• (a) a housing composed of a nonferromagnetic material and having a chamber therein;
• (b) a seismic mass containing a permanent magnet disposed in the housing chamber and in a closely spaced-apart relationship with the internal wall surface of the chamber;
• (c) means to couple the housing to a dynamic element whose energy is to be dampened;
• and
• (d) a ferrofluid of selected viscosity in the remaining volume of the chamber, the ferrofluid distributed generally uniformly in the volume, the magnetic saturation of the ferrofluid by the magnetic field of the permanent magnet levitating the seismic mass in the damper, and the viscosity of the ferrofluid in the magnetic field providing a means to dissipate energy from the dynamic system through viscous shear forces in the ferrofluid disposed between the wall surface of the chamber and the seismic mass.

A method of dampening the rotational energy of a rotating shaft by a damper coupled to the shaft, the damper comprising a housing having a chamber therein, a seismic mass within the housing and in a closely spaced-apart relationship with the internal wall surface of the housing and a viscous dampening fluid, which method comprises:

• (a) employing, as the dampening fluid in the damper, a ferrofluid of selected viscosity and magnetic susceptibility;
• (b) subjecting the ferrofluid to a constant strength magnetic field by a permanent magnet to provide for magnetic saturation by the field of the ferrofluid, and to suspend the seismic mass in the ferrofluid;
• and
• (c) dampening the rotational energy of the shaft coupled to the damper by the viscous shear forces of the ferrofluid in the damper.