Paper multi-feed detection apparatus and paper multi-feed detection method

Abstract

A paper multi-feed detection apparatus and a paper multi-feed detection method are provided for preventing the detection capability from being deteriorated by a noise factor and improving the detection precision even where an area around the feeding path has no extra space in terms of the shape and there are many noise-generating factors because of a demand for a smaller size of the device. An ultrasonic transmission opening formed in one of two feeding guide plates is large so as to discharge outside a reflected wave which returns through the ultrasonic transmission opening, and an ultrasonic receiving opening formed in the other feeding guide plate is smaller than a receiving face area of a receiver for receiving the ultrasonic wave.

1 . A paper multi-feed detection apparatus, comprising:
 a feeding path covered with one feeding guide plate and another feeding guide plate facing each other while having therebetween a feeding space for feeding a paper sheet two-dimensionally; and   a transmitter of an ultrasonic sensor provided on one of two sides facing each other while having the feeding space therebetween, and a receiver of the ultrasonic sensor provided on the other of the two sides;   wherein:   an ultrasonic wave is incident on the feeding space from the transmitter via an entrance opening formed in the one feeding guide plate;   the ultrasonic wave output via an exit opening formed in the another feeding guide plate is received by the receiver;   paper multi-feed is detected by comparing attenuation information on the ultrasonic wave when the paper sheet passes between the transmitter and the receiver, against a threshold value for multi-feed detection;   the entrance opening is formed to be large so as to discharge outside the ultrasonic wave incident thereon and then reflected, without making the reflected wave a noise component; and   the exit opening is formed to be smaller than a receiving face area of the receiver for receiving the ultrasonic wave.   
   
   
       2 . A paper multi-feed detection apparatus, comprising:
 a feeding path covered with one feeding guide plate and another feeding guide plate facing each other while having therebetween a feeding space for feeding a paper sheet two-dimensionally; and   a transmitter of an ultrasonic sensor provided on one of two sides facing each other while having the feeding space therebetween, and a receiver of the ultrasonic sensor provided on the other of the two sides;   wherein:   an ultrasonic wave is incident on the feeding space from the transmitter via an entrance opening formed in the one feeding guide plate;   the ultrasonic wave output via an exit opening formed in the another feeding guide plate is received by the receiver;   paper multi-feed is detected by comparing attenuation information on the ultrasonic wave when the paper sheet passes between the transmitter and the receiver, against a threshold value for multi-feed detection;   an ultrasonic wave transmission area from the transmitter to the entrance opening is in a open state; and   an ultrasonic wave receiving area from the exit opening to the receiver is enclosed by a noise shielding wall.   
   
   
       3 . A paper multi-feed detection method, wherein where a transmitter and a receiver are provided to face each other while having a feeding path for a paper sheet therebetween, an entrance opening, on which an ultrasonic wave transmitted from the transmitter toward the receiver is incident via a feeding guide plate which covers an ultrasonic wave transmission side of the feeding path, is formed to be large so as to discharge a reflected wave outside; and an exit opening, for outputting the ultrasonic wave via a feeding guide plate which covers an ultrasonic receiving side of the feeding path facing the ultrasonic transmission side, is formed to be smaller than a receiving face area of the receiver.