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.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a paper multi-feed detection apparatus applicable to office equipment such as, for example, copiers and scanners, and more specifically to a paper multi-feed detection apparatus and a paper multi-feed detection method for accurately detecting that sheets of paper such as blank or printed forms, banknotes, gift certificates, book coupons, checks, cards and the like are fed in an overlapped state.[0003]2. Description of the Prior Art[0004]Recently, as an apparatus for detecting multi-feed of sheets of paper which easily tend to be fed in an overlapped state, for example, sheets of thin paper or the like, a paper multi-feed detection apparatus using an ultrasonic sensor is known. When such an ultrasonic sensor is used to detect sheets of paper, the following detection capabilities unique to the ultrasonic sensor are provided.[0005](1) Since detection is performed without any contact with th...

AI Technical Summary

Benefits of technology

[0022]According to the present invention, a stable transmission capability is guaranteed because a noise component is avoided from being generated at the time of the ultrasonic wave transmission, and a receiving capability can be improved by properly blocking a noise component which is likely to enter the receiver at the time of the ultrasonic wave receiving. Especially, the structure of the present invention does not require any new parts, and can be easily obtained even where there is no ample extra space around the feeding path.

Problems solved by technology

Such a noise component may deteriorate the capability of the sensor and thus cause erroneous detection of the paper sheet 41.

However, merely setting the transmitting direction of the ultrasonic wave to be oblique is not sufficient to obtain a sufficient sensor capability.

Such a noise component is likely to have an adverse influence on the performance of the paper multi-feed detection apparatus.

However, such a structure requires the transmission and receiving areas to be enclosed air-tightly by the sound-absorbing material, and thus decreases the level of designing freedom because the arrangement and the shape of the sound-absorbing material are specified.

This structure also has a problem that the ultrasonic sensor itself is costly.

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