Low speed disengageable damper

Abstract

In a damper for a centrifuge for damping the rotor of the centrifuge when the rotor changes rotational velocity through a critical vibrational rotation speed, an improved vibration damper is disclosed. The damper is of the type wherein a conically shaped shaft extension is thrust into engagement with a friction bushing at a circular and central opening to increase shaft section and shift the critical vibrational rotation speed away from the particular critical vibrational rotation speed being traversed. The conical bushing is engaged by a solenoid and translates side-to-side rotor motion to an energy dissipating up and down motion at the solenoid. The improvement disclosed is a conically shaped cone having a negative radius of curvature in section. For small shaft side-to-side excursion (due to small vibration) this conically shaped cone has an initial small slope with respect to the bushing to provide reduced damping of the rotor when small vibration and hence small displacements effect the rotor. For large shaft side-to-side excursion, this same conically shaped cone has a large slope with respect to the low friction bushing which provides for increased displacement of the bushing at large displacements of the rotor. Discontinuities of damping are eliminated. Shaft damping at small excursion is damped with corresponding small damping forces. Shaft damping at large excursion is damped with larger force. Transition of damping between the two extremes is provided with an exponentially increasing damping force having no discontinuities. There results a centrifuge damper that can decelerate a classified sample without appreciable declassification of the sample due to vibration induced diffusion.