Image forming device having common manual and auto sheet input assembly

Abstract

In an image forming apparatus, an automatic paper tray is available for removal and insertion by a user into a housing and has an elastic element to provide a constant lifting force to lift a first sheet of paper. A manual paper tray is located on top of the automatic paper tray and carries a second sheet of paper. A paper feed assembly is disposed within the housing and includes a first roller, a second roller, and a feed roller mounted between the first and second rollers. The outer periphery of the paper-grabbing structure of the feed roller is larger than the outer periphery of the first and second rollers, while the outer periphery of the non-paper-grabbing structure of the feed roller is smaller than the outer periphery of the first and second rollers. This ensures that when the first sheet of paper is lifted and the second sheet of paper is present, after the paper feed assembly is rotated, the paper-grabbing structure preferentially feeds the second sheet of paper rather than the first sheet. The image forming unit prints the second sheet of paper.

Claims

1. An image forming apparatus, comprising at least: a housing; an automatic paper tray for a user to remove and insert into the housing for carrying a first sheet of paper and having an elastic element to provide a constant lifting force to lift the first sheet of paper; a manual paper tray located on the automatic paper tray for carrying a second sheet of paper; a paper feed assembly disposed in the housing, the paper feed assembly including a first roller, a second roller, and a paper feed roller mounted between the first roller and the second roller, the paper feed roller including a non-paper-feeding structure and a paper-feeding structure, the outer periphery of the paper-feeding structure being larger than the outer periphery of the first roller and the second roller, and the outer periphery of the non-paper-feeding structure being smaller than the outer periphery of the first roller and the second roller, such that when the first sheet of paper is lifted and the second sheet of paper is present, after the paper feed assembly is rotated, the paper feed structure preferentially feeds the second sheet of paper instead of the first sheet of paper; and an image forming unit disposed above the automatic paper tray for printing the second sheet of paper.

2. The image forming apparatus of claim 1, wherein a maximum radius of the paper feeding structure is greater than a first radius of the first roller and a second radius of the second roller, and a coefficient of friction of the paper feed roller is greater than the coefficients of friction of the first roller and the second roller.

3. The image forming apparatus as claimed in claim 1, wherein the first roller and the second roller are idler rollers that do not rotate synchronously with the feed roller.

4. The image forming apparatus as claimed in claim 1, wherein the automatic paper tray and the manual paper tray are configured such that the first paper leads the second paper, the leading edge of the first paper contacts the first roller, and the leading edge of the second paper presses against the first paper, and falls within the working range of the paper picking structure.

5. The image forming apparatus as claimed in claim 1, wherein the paper feed assembly further includes a hub on which the first roller, the second roller and the paper feed roller are mounted.

6. The image forming apparatus as claimed in claim 5, wherein the first roller and the second roller are rotatable relative to the hub, and the feed roller rotates synchronously with the hub.

7. The image forming apparatus as claimed in claim 6, wherein the hub is mounted on a rectangular shaft to be driven to rotate by the rectangular shaft.

8. The image forming apparatus as claimed in claim 1 further includes a friction plate flexibly disposed in the housing to press the first paper and the second paper onto the paper-taking structure of the first roller, the second roller and the feed roller at a certain time point, so that the paper-taking structure performs paper-taking and paper-separating actions.

9. The image forming apparatus of claim 1, wherein the automatic paper tray includes a stop structure for stopping a trailing edge of the first paper, and an arcuate profile of the stop structure is in direct contact with the trailing edge.

10. The image forming apparatus as claimed in claim 1, wherein the manual paper tray serves as the cover of the automatic paper tray.

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