Automatic document feeder having document size detecting device

Abstract

The present invention relates to an automatic document feeder having a document size detecting device. The document size detecting device includes a first paper guide plate, a second paper guide plate, a first elongated perforation, a second elongated perforation, a rack movement mechanism and a plurality of sensing members. The first paper guide plate includes a first paper stopping slice, a first rack and a rib, wherein the rib is disposed on the bottom of the paper input tray. The second paper guide plate includes a second paper stopping slice and a second rack. By moving the first paper guide plate to have the rib located between an optical emitter and an optical receiver of a specified sensing member, the size of the document placed on the paper input tray is realized.

Description

FIELD OF THE INVENTION[0001]The present invention relates to an automatic document feeder, and more particularly to an automatic document feeder having a document size detecting device.BACKGROUND OF THE INVENTION[0002]Generally, an automatic document feeder is used with for example a scanning apparatus for successively feeding many documents at a time. Since A4-sized documents are the most frequently used, the paper input tray and the eject tray of the common automatic document feeder are designed to accommodate A4-sized documents therein. In a case that only A4-sized documents need to be transported by the automatic document feeder, it is not necessary to include a document size detecting device in the automatic document feeder. As known, the automatic document feeder which is able to transport A3-sized documents may be used to transport the A4-sized documents because the area of the A3-sized document is two times as much as the A4-sized document. Under this circumstance, the A4-si...

AI Technical Summary

Benefits of technology

The present invention provides an automatic document feeder with a simplified document size detecting device. The device includes a paper input tray, a first paper guide plate, a second paper guide plate, a first elongated perforation, a second elongated perforation, a rack movement mechanism, and a plurality of sensing members. The first paper guide plate and the second paper guide plate are movable along the first elongated perforation and the second elongated perforation, respectively. The sensing members have optical emitters and optical receivers. The device can detect the size of a document by moving the rib of the first paper guide plate to a specific location between the optical emitter and the optical receiver of a specified sensing member. The technical effects of the invention include simplifying the detection of document size and improving the accuracy of automatic document feeding.

Problems solved by technology

For example, the structure of the document size detecting device 20 is very complicated.

Therefore, the digital circuit of the document size detecting device 20 is also complicated and not cost-effective.

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