Abstract: A magnetic levitation conveyor apparatus has levitation electromagnets, linear motors, and displacement sensors which are disposed outside of a tunnel, and a carriage of simple structure which is movable in the tunnel. The carriage is of canned structure for preventing gases from being generated. The carriage of canned structure allows the tunnel to have a reduced cross-sectional area and to be filled with a highly purified atmosphere such as of a high vacuum. The tunnel has substantially orthogonal branches at a branched point. In the branched point, the carriage can move, while being lifted out of contact with the tunnel partition, with a directional change from a main conveyor passage into a branched conveyor passage. The magnetic levitation conveyor apparatus is highly practical as it can control the carriage to be lifted and moved as described above.

Abstract: A two-shaft rotary machine for use in a vacuum pump system includes rotors having a specific profile whereby any vibration and noise generated by the machine is minimized and its efficiency is increased. The number of lobes of each rotor is three or more. The tip and root portions of each rotor are defined by circular arcs, respectively, which are made smoothly continuous with each other through an involute curve. The ratio of the diameter of the tip circle to the diameter of the root circle is selected to fall within a range which is given by a specific expression.