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

[0011]In accordance with an aspect of the present invention, there is provided an automatic document feeder having a document size detecting device. The automatic document feeder further includes a paper input tray for placing a document thereon. 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 for positioning the document on a surface of the paper input tray, a first rack on a bottom of the paper input tray, and a rib on the bottom of the paper input tray. The second paper guide plate includes a second paper stopping slice for positioning the document on the surface of the paper input tray and a second rack on the bottom of the paper input tray. The first elongated perforation is formed in the paper input tray. The first paper guide plate is partially penetrated through the first elongated perforation such that the first paper stopping slice is disposed on the surface of the paper input tray and the first rack and the rib are disposed on the bottom of the paper input tray. The second elongated perforation is formed in the paper input tray. The second paper guide plate is partially penetrated through the second elongated perforation such that the second paper stopping slice is disposed on the surface of the paper input tray and the second rack is disposed on the bottom of the paper input tray. The rack movement mechanism is engaged with the first rack and the second rack such that 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 are disposed under the bottom of the paper input tray and have respective optical emitters and respective optical receivers. The rib is moved with movement of the first paper guide plate to a selected location between the optical emitter and the optical receiver of a specified sensing member, thereby realizing the size of the document.

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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