| 摘要 |
Disclosed are a method and an apparatus for easily, sensitively and reliably detecting the presence of a magnetic substance in a non-magnetic product, and even a minuted magnetized material such as a broken needle erroneously included in a sewn product. Magnetic sensors as a sensing unit are disposed at a prescribed position between a pair of opposed magnetic shielding members made of a soft magnetic material as a magnetic flux converging unit. A non-magnetic product including a magnetic substance is passed through between the pair of magnetic shielding members. A magnetic flux generated by the magnetic substance mingled in the product is converged to the magnetic shielding members, while shutting off a magnetic field due to external disturbance, and residual magnetization of the magnetic substance is detected by the magnetic sensors. Preferably, each of the magnetic shielding members has a curved surface projecting inwardly in the form curved along the conveyance direction of the non-magnetic product, and a plurality of magnetic sensors are disposed on each of the curved surfaces at intervals of a prescribed size in the lateral direction thereof.
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