| 摘要 |
PROBLEM TO BE SOLVED: To detect metals contained in a test object 1 which is covered with a lid 9, formed of a non-magnetic metal. SOLUTION: The metal detecting device is equipped with a conveyer mechanism 2 which conveys the test object 1, an alternating current magnetizing coil 3 which is placed under the conveyer mechanism and generates alternating-current magnetic field in a three dimensional region, covering from the lower end of test object to the vicinity of upper end; a pair of receiving coils 5 and 6 which is arranged on the mutually spaced positions along conveying direction of the test object beneath the conveying mechanism and detects the magnetic metal and non-magnetic metal contained in the test object passing, through the alternating current magnetic field, a direct-current magnetizing unit 17 which magnetizes in direct current way the magnetic metal contained in the test object under conveyance by conveying mechanism; a magnetic sensor 19 which is installed above the conveying mechanism and detects the magnetized magnetic metal contained in the test object under conveyance by conveyance mechanism, and a decision processing section 16 which decides the presence of metals other than the lid in the object to be tested, based on the combined detection signal, obtained by difference-combining of each detected signal, in a pair of receiving coil and detection signal of magnetic sensor. COPYRIGHT: (C)2005,JPO&NCIPI |
