Image forming apparatus and controlling method thereof

Photocopying – Projection printing and copying cameras – Photographing on both sides of photo-sensitive paper

Reexamination Certificate

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Details

C355S040000, C355S024000

Reexamination Certificate

active

06177977

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus such as a laser printer capable of forming images on a front surface and a back surface of a sheet and a controlling method of this image forming apparatus, and particularly relates to an image forming apparatus having a both-face conveying portion for reversing surfaces of a sheet on one surface of which an image is formed and conveying the sheet to an image forming portion.
2. Related Background Art
There is a conventional image forming apparatus in which surfaces of a sheet on one surface of which an image is formed by an image forming portion is reversed and the sheet is again conveyed to the image forming portion and an image is formed on a back surface of the sheet.
For example, in an image recorder such as a laser printer as one example of the conventional image forming apparatus, a both-face conveying portion having a both-face conveying path for conveying the sheet to the image forming portion by reversing the surfaces of the sheet is optionally mounted to a relatively large-sized device operated at high speed and high in cost, and images are recorded to both surfaces of the sheet. Recently, a tendency to the requirement of a function for recording images to both surfaces of the sheet is increasing to save resources, etc. even in a laser printer, etc. made compact and operated at low speed and low in cost.
The conventional image recorder having such a both-face conveying portion has a one-face mode for forming an image on one surface of the sheet and a both-face mode for reversing by the both-face conveying portion the surfaces of the sheet on one surface of which an image is formed and conveying this reversed sheet to the image forming portion and forming an image on a back surface of the sheet.
Further, for example, a face-up tray is openably and closably arranged in an apparatus body to face-up-discharge the sheet on one surface of which the image is formed. In the one-face mode, the sheet is stored in a face-up state by opening this face-up tray.
When the sheet is stored in a face-down state in the one-face mode, the face-up tray is closed to form a sheet discharge path for conveying the sheet to a face-down storing portion arranged on an upper face of the apparatus body. Further, this face-up tray is closed in the both-face mode to form the sheet discharge path for conveying the sheet forming images on both surfaces thereof to the face-down storing portion and a conveying path to the both-face conveying portion.
However, when the sheet discharge path is formed by the face-up tray in this way, there is a case in which the sheet on one surface of which the image is formed is not conveyed to the both-face conveying portion but the sheet discharge path is jammed with the sheet when the face-up tray is opened in error particularly in the both-face mode.
SUMMARY OF THE INVENTION
Therefore, the present invention has been made in view of such a situation, and therefore has an object to provide an image recorder (image forming apparatus) able to be constructed such that no image recorder is jammed with a sheet even when a face-up tray is opened during a both-face mode.
The present invention resides in an image forming apparatus having a one-face mode for forming an image on one surface of a sheet and a both-face mode in which the sheet on one surface of which the image is formed is reversed and is again conveyed to an image forming portion through a both-face conveying portion and an image is formed on a back surface of the sheet, the image forming apparatus comprising:
a first sheet discharge portion for storing the sheet discharged after the image is formed on one surface or both surfaces of the sheet;
a second sheet discharge portion arranged openably and closably in the image forming apparatus for forming a sheet discharge path communicated with the first sheet discharge portion when the second sheet discharge portion is closed and for storing the sheet when the second sheet discharge portion is opened;
second sheet discharge portion open and close detecting means for detecting an opening and closing of the second sheet discharge portion;
conveying means arranged between the image forming portion and the second sheet discharge portion and conveying the sheet on which the image is formed;
forward and reverse rotatable conveying means which is arranged in the sheet discharge path so as to be rotatable forwardly and reversely and nips the sheet, on one surface of which the image is formed, conveyed by the conveying means and is forwardly rotated for a predetermined time period and is then reversely rotated and conveys the sheet to the both-face conveying portion;
means for detecting a position of the sheet in the sheet discharge path; and
control means for controlling an operation of at least one of the forward and reverse rotatable conveying means and the conveying means so as to convey the sheet to one of the first sheet discharge portion, the second sheet discharge portion and the both-face conveying portion in accordance with the position of the sheet in the sheet discharge path when the sheet on one surface of which the image is formed is located in the sheet discharge path in the both-face mode and when the opening of the second sheet discharge portion is detected by the second sheet discharge portion open and close detecting means.
The control means preferably controls the operation of the conveying means so as to discharge the sheet to the second sheet discharge portion when the second sheet discharge portion is opened before the sheet reaches the forward and reverse rotatable conveying means.
The control means preferably performs a control operation for forwardly rotating the forward and reverse rotatable conveying means for a predetermined time period so as to discharge the sheet to the first sheet discharge portion when the second sheet discharge portion is opened after the forward and reverse rotatable conveying means nips the sheet having reached the forward and reverse rotatable conveying means and is forwardly rotated and before the forward and reverse rotatable conveying means is stopped for the reverse rotation.
The control means preferably performs a control operation for forwardly rotating the forward and reverse rotatable conveying means for a predetermined time period so as to discharge the sheet to the first sheet discharge portion when the second sheet discharge portion is opened while the forward and reverse rotatable conveying means is stopped in a nipping state of the sheet.
The both-face conveying portion preferably has a both-face conveying path for conveying the sheet conveyed from the forward and reverse rotatable conveying means to the image forming portion, and also has reversed sheet inducing means for inducing the sheet to the both-face conveying path, and
the control means preferably performs a control operation for forwardly rotating the forward and reverse rotatable conveying means for a predetermined time period so as to discharge the sheet to the first sheet discharge portion when the second sheet discharge portion is opened before the sheet conveyed by the reverse rotation of the forward and reverse rotatable conveying means reaches the reversed sheet inducing means.
The both-face conveying portion preferably has a both-face conveying path for conveying the sheet conveyed from the forward and reverse rotatable conveying means to the image forming portion, and also has reversed sheet inducing means for inducing the sheet to the both-face conveying path, and
the control means preferably performs a control operation for reversely rotating the forward and reverse rotatable conveying means for a predetermined time period so as to convey the sheet to the both-face conveying portion when the second sheet discharge portion is opened after the sheet conveyed by the reverse rotation of the forward and reverse rotatable conveying means reaches the reversed sheet inducing means.
The both-face mode is preferably stopped when the sh

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