Electromagnetically floated carrier system with stopping unit

Abstract

A carrier which transports semiconductor chips or the like can run along two rails made of a ferromagnetic material and extending along a running path. The carrier has four supports projecting from its bottom. Four magnets units are supported by the supports, respectively, and each magnet unit includes a permanent magnet and a pair of electromagnets such that the magnet units face the rails. The carrier is held floated with respect to the rails by electromagnetic forces acting between the magnet units and rails. The supports support four gap sensors which detect the gap between the magnet units and rails and produce an output signal corresponding to the gap. Magnetic flux control unit is provided on the underside of the carrier to control the current supplied to the electromagnets in accordance with the outputs of the gap sensors to maintain the gap constant within a predetermined range. A stopping unit is provided at a station at which the carrier is to be stopped, and stops the carrier by means of a electromagnetic forces of attraction acting between the stopping unit and one of the magnet units provided on the carrier.