Eddy current brake for air driven centrifuge

In an air driven centrifuge having a rotor at least a portion of which is an electrically conductive material, air pressure means supporting the rotor on an air bearing, and air pressure means for rotating the air supported rotor about an axis, improved apparatus for braking the rotor when it is rotating comprising:

• a. a lid having an enclosure therein having a wall thereof disposed adjacent the electrically conductive portion of the rotor when the rotor is rotating, said wall being of a thickness and material whereby magnetic flux can pass from said enclosure through said wall and induce eddy currents in the electrically conductive portion of the rotor sufficient to slow the rotor;
• b. a nonmagnetic carrier disposed within said enclosure and adapted for movement therein between a first position not adjacent said wall and a second position adjacent said wall;
• c. a magnet carried by said nonmagnetic carrier being of a magnetic strength whereby when said nonmagnetic carrier is in said first position the magnetic flux of said magnet will not pass through said wall in sufficient quantity to induce eddy currents in the electrically conductive portion of the rotor sufficient to brake the rotor and when said nonmagnetic carrier is in said second position the magnetic flux of said magnet will pass through said wall in sufficient quantity to induce eddy currents in the electrically conductive portion of the rotor sufficient to brake the rotor;
• and,
• d. means for moving said nonmagnetic carrier from one of said positions to the other.