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...

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