Positioning table for placing microfiche over light source - uses sequentially activated electromagnets to guide permanent magnets on carrier corners

摘要

To position microfiches over a light source, a moving rectangular carrier with permanent magnets (41,42,43,44) mounted on each corner is placed over a table comprising pole faces of electromagnets. The surface is divided into four quadrants, with the light source (9) at the centre. Each quadrant comprises multiple parallel pole faces (141, 142,---,151,152,---) whose length fills the quadrant and whose breadth is much less than the breadth of the quadrant and determines the minimum motion step of the carrier. Adjacent quadrants have the pole faces oriented at right angles to each other. To move the carrier the table electromagnets are successively energised and the magnets on the carrier corners follow the energised poles. By control of the energisation sequence the motion of the carrier can be controlled in X and Y directions, or a circular motion can rotate the carrier.