| 摘要 |
PURPOSE:To accurately detect the presence or absence of a can opening tab with high efficiency and without manual operation by measuring vibrational sounds generated when the lids of a can with the fixedly attached tab and of the can without the tab are forcibly vibrated and discriminating which is larger than the other. CONSTITUTION:A hammer 3 momentarily hits the lid of a can 2 by electromagnetic force due to current pulses to generate vibrational sound from the lid. The electric signals of the vibrational sound are inputted to band-path filters 8 and 9. When the can 2 has the normal lid, the electric signals of the vibrational sound pass only to the filter 8 and, when a can opening tab is missed from the can 2, the vibrational sound passes only to the filter 9. An arithmetic circuit 12 conducts subtraction on signals in rectifying circuits 10 and 11 and resultant position or negative sign is fed to a discriminating circuit 13.
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