Patent ID: 7130245
Filing Date: 2006-10-31
Classification: B65H,G01N

Abstract:
1. A double feed detecting apparatus comprising: ultrasonic transmitting means installed on one side of a transport path for a sheet material for transmitting an ultrasonic wave toward the sheet material; ultrasonic receiving means installed on the other side of the transport path for the sheet material for receiving the ultrasonic wave transmitted by said ultrasonic transmitting means and outputting a received ultrasonic signal; first double feed determining means for determining whether double feed is arising or not in accordance with an amplitude of the received ultrasonic signal output by said ultrasonic receiving means; and second double feed determining means for determining whether double feed is arising or not in accordance with a phase of the received ultrasonic signal output by said ultrasonic receiving means, wherein said first double feed determining means calculates an amplitude of a noise signal received by said ultrasonic receiving means while said ultrasonic transmitting means does not transmit the ultrasonic wave, and determines whether a double feed is occurring or not on the basis of a change in the amplitude of the received ultrasonic signal and a change in the calculated amplitude of the noise signal.