Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1999-04-06
2001-05-15
Yockey, David F. (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S248000, C347S116000, C346S044000
Reexamination Certificate
active
06232998
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a double side printing apparatus for printing on double sides of a recording medium and, more particularly, to a double side printing apparatus for minimizing a printing positional deviation between right and reverse sides thereof.
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 (perfecting) apparatus for printing on double 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. 9
is an explanatory view showing the prior art.
The perfecting apparatus includes a printing unit
9
b
for printing on the right side of a sheet of recording paper PP(which is hereafter simply referred to as the sheet PP), and a printing unit
9
a
for printing on the reverse side of the sheet PP. The reverse side printing mechanism
9
a
has a photosensitive drum
90
. The photosensitive drum
90
is charged by a pre-charger
91
and thereafter exposed to a light image by an exposing unit
92
. The exposing unit
92
serves to scan one line on the photosensitive drum
90
. An electrostatic latent image corresponding to the light image is thereby formed on the photosensitive drum
90
. The latent image on the photosensitive drum
90
is developed by a developing unit
93
. Then, the developed image on the photosensitive drum
90
is transferred onto the sheet PP by a transferring unit
94
. Thus, the image is printed on the reverse side of the sheet PP.
The printing on the right side of the sheet PP is likewise performed. To be specific, the right side printing mechanism
9
b
has a photosensitive drum
95
. The photosensitive drum
95
is charged by a pre-charger
96
and thereafter exposed to a light image by an exposing unit
97
. An electrostatic latent image corresponding to the light image is thereby formed on the photosensitive drum
95
. The latent image on the photosensitive drum
95
is developed by a developing unit
98
. Subsequently, the developed image on the photosensitive drum
95
is transferred onto the sheet PP by a transferring unit
99
. Thus, the image is printed on the right side of the sheet PP.
The perfecting apparatus has the two printing mechanisms which each prints on the single side of the sheet PP. It is required that a printing control unit for controlling the printing mechanism be provided for the printing mechanism. The printing control unit performs the control so that the exposing unit of the printing mechanism executes a one-line exposure in accordance with a printing start timing.
The printing apparatus has one printing control unit and therefore is, it has hitherto been practiced, provided with the printing control units for controlling the two printing mechanisms.
There arise, however, the following problems inherent in the prior art.
First, a method of providing a common control unit for controlling the two print mechanisms involves desinging a common print control unit different from a print control unit of a one-side printing apparatus for printing on one side. Therefore, the print control unit of the perfecting apparatus can not be used for the print control unit of the one-side printing apparatus, resulting in such a problem that the costs light increase.
Second, according to a method of providing each individual printing mechanism with the print control unit, the above print control unit can be used for the print control unit of the one-side printing apparatus, which is advantageous in terms of the costs. However, the two print control units are independently controlled, and therefore the print start timing for the right side is asynchronous with the print start timing for the reverse side, which conduces to such a problem that a print position on the right side deviates from a print position on the reverse side.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a perfecting apparatus capable of preventing a deviation in print position between a right side and a reverse side of a recording medium even by using print control units for the right side and the reverse side, individually.
It is another object of the present invention to provide a perfecting apparatus capable of preventing the deviation in the print position between the right side and the reverse side even by controlling the right side and the reverse side, independently.
It is a further object of the present invention to provide a perfecting apparatus capable of controlling independently the print positions on the right side and the reverse side even by controlling in synchronization the right side and the reverse side.
To accomplish the above objects, according to a first aspect of the present invention, a perfecting apparatus for executing prints on double-sides of a recording medium, comprises a first image forming unit for forming an image on one surface of the recording medium by exposing an image on one line to the light from a first exposure source, a second image forming unit for forming an image on the other surface of the recording medium by exposing an image on one line to the light from a second exposure source, a first print control unit for controlling the one-line image exposure by the first exposure source in accordance with a horizontal synchronous signal, and a second print control unit for controlling the one-line image exposure by the second exposure source, synchronizing with the horizontal synchronous signal.
According to the present invention, the perfecting apparatus is provided with the first print control unit for controlling the one-line exposure for the right side or the reverse side in accordance with the horizontal synchronous signal, and the second print control unit for controlling the one-line exposure for the reverse side or the right side by use of this horizontal synchronous signal. Thus, a print start timing on the right side is synchronized with a print start timing on the reverse side, and it is therefore feasible to prevent a deviation in print position between the right side and the reverse side even by providing the print control units for the right side and the reverse side. Further, since the horizontal synchronous signal is used, this can be easily attained.
According to a second aspect of the present invention, the perfecting apparatus further comprises a delay circuit for generating a second horizontal synchronous signal obtained by delaying the former horizontal synchronous signal, and the second print control unit operates synchronizing with the second horizontal synchronous signal.
According to a third aspect of the present invention, the delay circuit is constructed of a delay circuit capable of making a delay quantity variable. The delay quantity is variable, and hence it is possible to adjust start-of-print positions on the right and reverse sides in accordance with a distance between a reverse-side transfer position and a right-side transfer position and with positions where exposing units are disposed.
According to a fourth aspect of the present invention, the first print control unit includes a first generation circuit for generating the horizontal synchronous signal, a first select circuit for selecting any one of the horizontal synchronous signal generated and a horizontal synchronous signal given from outside, and a first control circuit for controlling an exposure of an image on one line to the light from the first exposure source in accordance with the selected horizontal synchronous signal. The second print control unit includes a second generation circuit for generating the horizontal synchrono
Chihara Amiko
Tokairin Motohiro
Wada Yoshinori
Armstrong Westerman Hattori McLeland & Naughton LLP
Fujitsu Limited
Yockey David F.
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