This invention is directed to swinging bucket rotors and more particularly is directed to a means for reducing the friction between the bucket and the support pins or trunnions when the bucket moves or swings relative to the rotor body.
Presently it is necessary that the swinging buckets as well as the rotor pins or trunnions that support the buckets be made of strong material to withstand the high pressures and forces that are exerted at the bucket pin interface during the centrifugation. Inherent with these high strength materials is a high friction characteristic.
During the operation of the centrifuge, the swinging bucket moves from a generally vertical orientation to a generally horizontal orientation as the rotor moves from the zero speed to operational speed. Further, when the centrifugation operation is completed and the rotor decelerates, the bucket will move from its horizontal orientation down to its vertical or rest position. When the bucket is moving between its vertical and its horizontal orientations, there is constant relative movement between the bucket and the stationary pins. Because of the high friction characteristic of the materials used, this tends to cause galling at the bucket pin interface. The presence of galling will tend to prevent the bucket from returning to a complete vertical orientation, resulting in possible remixing of the centrifuged sample. Further, this galling can also cause a shortening of the life of the bucket by initiating cracks in the bucket material.