Electrophotography – Diagnostics – Document handling
Reexamination Certificate
1999-12-20
2001-02-06
Lee, Susan S.Y. (Department: 2852)
Electrophotography
Diagnostics
Document handling
C399S124000, C399S401000, C271S258010
Reexamination Certificate
active
06185381
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus such as a laser printer capable of two sided printing, that is forming images on the front and back surfaces of a sheet, and particularly to an image forming apparatus to the main body of which is detachably mountable two-sided copy a conveying portion (duplexing portion) for reversing the surfaces of a sheet having an image formed on one surface thereof and conveying it to an image forming portion.
2. Related Background Art
Some of conventional image forming apparatuses are such that a sheet having an image formed on one surface thereof by an image forming portion is reversed and is again conveyed to the image forming portion so that an image may be formed on the back surface of the sheet.
In an image recording apparatus such as a laser printer which is an example of the conventional image forming apparatuses, a two-sided copy conveying portion having a two-sided copy conveying path for reversing the front surface and back surface of a sheet and conveying the sheet to an image forming portion is optionally mounted on a relatively bulky, high-speed and high-cost apparatus so that images may be recorded on the both surfaces of the sheet.
Now, in recent years, even in compact, low-speed and low-cost laser printers, there is a growing trend toward including the function of recording images on the both surfaces of a sheet for the saving of natural resources, but when a two-sided copy conveying portion is to be optionally mounted on such a compact, low-speed and low-cost image recording apparatus, a two-sided copy conveying portion of low cost becomes requisite as a matter of course.
Such two-sided copy conveying portion, however, requires various sensors such as a jam detecting sensor for detecting, for example, the occurrence of jam in a two-sided copy conveying path and a jam clearance detecting sensor for detecting jam clearance being carried out, and the duplex conveying portion becomes high in cost.
Also, in the conventional image recording apparatus, when such a two-sided copy conveying portion is to be mounted, detecting means for detecting whether the two-sided copy conveying portion has been mounted must be newly provided and thus, the total cost of the apparatus becomes high.
SUMMARY OF THE INVENTION
So, the present invention has been made in view of such present situation, and has as its object to provide a low-cost image recording apparatus (image forming apparatus) capable of effecting two-sided copy image formation.
The present invention provides an image forming apparatus for reversing surfaces of a sheet having an image formed on one surface thereof by an image forming portion and then reconveying the sheet to the image forming portion, wherein an image is formed on the back surface of the sheet. The apparatus is provided with a two-sided copy conveying portion having an openable and closable two-sided copy conveying path for conveying the reversed sheet to the image forming portion, and detachably mounted to the image forming apparatus, and a position detecting sensor for detecting that the sheet having come into the two-sided copy conveying path has arrived at a predetermined position, the position detecting sensor being designed to be capable of detecting also the presence or absence of the occurrence of jam in the two-sided copy conveying path, the mounting or dismounting of the two-sided copy conveying portion, and the opening or closing of the two-sided copy conveying path.
Preferably, the position detecting sensor may be provided in the two-sided copy conveying portion, and may detect the mounting or dismounting of the two-sided copy conveying portion on the basis of a signal obtained when the two-sided copy conveying portion is mounted to the image forming apparatus.
Also, preferably, the position detecting sensor may output a signal in response to the opening or closing operation of the two-sided copy conveying path.
Also, preferably, the position detecting sensor may detect the occurrence of jam in the two-sided copy conveying path when the position detecting sensor does not detect the sheet having come into the two-sided copy conveying path within a predetermined time period.
Also, preferably, the position detecting sensor may be designed such that the same detected state is obtained for all of the occurring state of the jam, the unmounted state of the two-sided copy conveying portion and the opened state of the two-sided copy conveying path.
Also, preferably, the present invention may have an indicating portion for indicating one or more the occurrence of the jam, the unmounting of the two-sided copy conveying portion, or the opened state of the two-sided copy conveying path.
Also, preferably, the two-sided copy printing operation may be disabled when at least one of the occurrence of the jam, the unmounting of the two-sided copy conveying portion and the opened state of the two-sided copy conveying path is detected.
Also, preferably, the single sided printing operation may be enabled, but the two-sided copy printing operation may be disabled when at least one of the occurrence of the jam, the unmounting of the two-sided copy conveying portion and the opened state of the two-sided copy conveying path is detected.
REFERENCES:
patent: 4671441 (1987-06-01), Hauslaib
patent: 5031896 (1991-07-01), Winkler
patent: 5582399 (1996-12-01), Sugiura
patent: 5974290 (1987-06-01), Inoue
Fuse Hiroshi
Maeda Kohei
Nakahara Takashi
Tanaka Tomoko
Ueki Hitoshi
Canon Kabushiiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Lee Susan S.Y.
Ngo Hoang
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