Electrophotography – Control of electrophotography process
Reexamination Certificate
1999-06-11
2001-02-13
Chen, Sophia S. (Department: 2852)
Electrophotography
Control of electrophotography process
C399S306000, C399S364000, C399S384000
Reexamination Certificate
active
06188853
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a double side printing apparatus for printing on opposite sides of a recording medium and, more particularly, to a double side printing apparatus for making one-side printing feasible.
2. Related Background Art
A printing apparatus has been widely utilized as an output apparatus of a computer. An electrophotographic apparatus capable of printing on an ordinary sheet of paper has been utilized as the printing apparatus. In response to a demand for saving natural resources in recent years, a double side printing apparatus for printing on opposite sides of the sheet has been required. Then, an apparatus provided with both a mechanism for printing on the right side of the recording medium and a mechanism for a printing mechanism for printing on the reverse side of the recording medium, is required for increasing a printing speed.
FIG. 12
is an explanatory view showing the prior art.
The perfecting (double side printing) apparatus includes a printing unit
9
b
for printing on the right side of a sheet of recording paper P(which is hereafter simply referred to as the sheet P), and a printing unit
9
a
for printing on the reverse side of the sheet P. The sheet P is classified as a continuous sheet perforated per page. The printing unit
9
a
for printing on the reverse side has a photosensitive drum
90
. The photosensitive drum
90
is charged by an unillustrated pre-charger and thereafter exposed to a light image by an exposing unit (not shown). An electrostatic latent image corresponding to the light image is formed on the photosensitive drum
90
. The latent image on the photosensitive drum
90
is developed by an unillustrated developing unit. Then, the developed image on the photosensitive drum
90
is transferred onto the sheet P by a transferring unit
91
. Thus, the image is printed on the reverse side of the sheet P.
The printing on the right side of the sheet P is likewise performed. To be specific, the printing unit
9
b
for printing on the right side has a photosensitive drum
92
. The photosensitive drum
92
is charged by an unillustrated pre-charger and thereafter exposed to a light image by the exposing unit (not shown). An electrostatic latent image corresponding to the light image is formed on the photosensitive drum
92
. The latent image on the photosensitive drum
92
is developed by the unillustrated developing unit. Subsequently, the developed image on the photosensitive drum
92
is transferred onto the sheet P by a transferring unit
93
. Thus, the image is printed on the right side of the sheet P.
Toner images are fixed onto both sides of the sheet P by a fixing unit
94
. The thus constructed perfecting apparatus for printing on the continuous sheet is disclosed in Japanese Patent Application Laid-Open Publication Nos.7-77851 and 8-211664.
There arise, however, the following problems inherent in the prior art perfecting apparatus.
With a diversification of printing modes, there is a mode for printing on only one side of the recording sheet. With this demand, the perfecting apparatus is required to print on only one side of the recording sheet. In this case, a problem is that the prior art perfecting apparatus does not have a one-side printing mode, and hence the one-side printing is difficult to perform.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a perfecting apparatus capable of executing one-side printing in addition to double-side printing.
It is another object of the present invention to provide a perfecting apparatus capable of minimizing a blank space on a recording medium even when effecting the one-side printing.
It is a further object of the present invention to provide a perfecting apparatus constructed to minimize a back-feed quantity when in the one-side printing mode.
To accomplish the above objects, according to a first aspect of the present invention, a perfecting apparatus comprises a feeding unit for feeding a recording medium, a first image-forming unit disposed downstream in a feeding direction of the recording medium for forming a toner image on one surface of the recording medium, a second image-forming unit disposed upstream in the feeding direction of the recording medium from the first image forming unit for forming the toner image on the other surface of the recording medium, a fixing unit for fixing the toner images on the double surfaces of the recording medium, and a control unit for controlling the first and second image forming units when in a double-side printing mode. Then, the control unit, when in the one-side printing mode, controls the first image forming unit disposed downstream in the feeding direction in order for the first image-forming unit to form the toner image on one surface of the recording medium.
According to the present invention, first, one-side printing is conducted by use of one of the two image-forming units. Second, in the perfecting apparatus, the toner image on the image-forming unit is fixed thereto by the fixing unit. Therefore, a printing last page is at the fixing unit. The recording medium positioned between this fixing unit and the image-forming unit comes to an unused space when starting the print. Hence, it is required that this unused space be minimized. For this requirement, when performing one-side printing, the printing is executed by using the first image-forming unit disposed downstream in the feeding direction.
The first image-forming unit is more proximal to the fixing unit than the second image-forming unit, and hence a distance between the fixing unit and the first image-forming unit is short. With this contrivance, it is feasible to decrease the number of pages of the recording medium between the fixing unit and the image-forming unit when in the one-side printing mode. The unused blank space can be thereby minimized.
Further, at the start of the one-side printing, when performing the control of positioning the printing start page of the recording medium at the first image-forming unit by feeding the recording medium back thereto, this back-feed quantity can be reduced. Consequently, the time until the one-side printing mode is started can be reduced.
According to a second aspect of the present invention, the control unit, when in the one-side printing mode controls the first image forming unit after feeding a printing start page of the recording medium back to the first image forming unit. Since the printing start page is fed back, even when performing the one-side printing, the pages turning out to be the blank spaces can be minimized.
According to a third aspect of the present invention, a perfecting apparatus may further comprise a guide roller, provided between the first image-forming unit and the fixing unit, for giving a tension to the recording medium by its coming into contact with the other surface of the recording medium. Because of the guide roller being provided between the first image forming unit and the fixing unit, the tension can be imparted to the recording medium, thereby preventing a jam in feeding.
According to a fourth aspect of the present invention, the control unit, when in the double-side printing mode, controls the first and second image forming units after feeding the printing start page of the recording medium back to the second image forming unit. When in the double-side printing mode, the printing start page of the recording medium is fed back to the second image forming unit, and therefore the pages turning out to be the blank spaces can be minimized also when in the double-side printing mode.
According to a fifth aspect of the present invention, the control unit, when in the one-side printing mode, controls the second image forming unit so as to stop an operation of the second image forming unit. Under this control, the image forming unit unused is not allowed to operate, whereby a longer life-span of the apparatus can be attained.
According to a sixth aspect of the present invention, the fixing unit is const
Chinzei Kiyoshi
Ishida Shigeo
Armstrong, Westerman Hattori, McLeland & Naughton
Chen Sophia S.
Fujitsu Limited
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