Electrophotography – Image formation – Photoconductive member
Reexamination Certificate
1999-12-07
2001-06-19
Chen, Sophia S. (Department: 2852)
Electrophotography
Image formation
Photoconductive member
C399S038000, C399S116000
Reexamination Certificate
active
06249662
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a printing apparatus, such as a printer or photocopier, and more particularly, to a device for adjusting the tension applied to a photoreceptor belt that rotates along a predetermined track.
2. Description of the Related Art
In printing apparatuses which are used to form a desired image on a printing paper, a latent electrostatic image is formed on a photoreceptor such as a photosensitive drum or a photoreceptor belt, and developed by a toner of a predetermined color. Then, the developed image is transferred to a print paper.
FIG. 1
is a schematic view of major elements of a conventional printing apparatus. Referring to
FIG. 1
, the conventional printing apparatus includes a photoreceptor belt
10
, and a driving roller
20
, a backup roller
30
, and a tension roller
40
, which circulate the photoreceptor belt
10
along a given track.
A major charging station
50
for charging the photoreceptor belt
10
is placed over a part of the photoreceptor belt
10
. A laser scanning unit (LSU)
60
for emitting a laser beam onto the photoreceptor belt
10
according to an image signal, to form a latent electrostatic image thereon, and a development unit
70
for developing the latent electrostatic image with a developer containing a toner of a predetermined color and a liquid carrier, are installed below the photoreceptor belt
10
. In general, color printers include a plurality of LSU's
60
and a plurality of development units
70
which contain different color developer.
The liquid carrier is removed from the developer which is applied to the photoreceptor belt
10
, by a drying roller
81
and a heating roller
82
, thereby drying the surface of the photoreceptor belt
10
. As a result, a toner image formed by the toner remains on the latent electrostatic image of the photoreceptor belt
10
. The toner image is transferred onto a printing paper
93
by a transfer roller
91
, which is installed parallel to the backup roller
30
, with the photoreceptor belt
10
is interposed therebetween. The printing paper
93
is supplied between the transfer roller
91
and a pressure roller
92
, and the toner transferred onto the printing paper
93
is heated and pressed by the pressure roller
92
, so that the toner is fixed onto the printing paper
93
.
Also, the printing apparatus includes a tension adjusting device
100
for adjusting the tension of the photoreceptor belt
10
. The tension adjusting device
100
adjusts the tension applied to the photoreceptor belt
10
by applying pressure to the tension roller
40
or releasing pressure therefrom.
FIG. 2
is a perspective view of the tension adjusting device of FIG.
1
. The tension adjusting device
100
of
FIG. 2
uses a spring
142
and an eccentric cam
150
. In detail, the conventional tension adjusting device
100
includes an auxiliary frame
110
, which is slidably installed in a main frame
1
and supports the tension roller
40
rotatably, a fixed frame
120
fixed to the main frame
1
, and a guide bar
130
for connecting the auxiliary frame
110
and the fixed frame
120
.
The auxiliary frame
110
has grooves
111
to which a rotary shaft
41
of the tension roller
40
is coupled, and a part
112
which covers the grooves
111
to press the rotary shaft
41
of the tension roller
40
. The fixed frame
120
has a hole
121
at the center portion, through which the guide bar
130
passes. The guide bar
130
is inserted into the hole
121
to be movable, and one end of the guide bar
130
is coupled to the auxiliary frame
110
by a coupling pin
113
. A screw part
131
is formed at the middle portion of the guide bar
130
, and is screw-coupled with a nut
141
. A spring
142
is installed around the guide bar
130
. The eccentric cam
150
that rotates by a driving motor
160
, is installed at the other end of the guide bar
130
, to control the elastic force applied to the spring
142
. Also, a pressing ring
143
is slidably installed around the guide bar
130
such that it can press the spring
142
as the eccentric cam
150
rotates.
In the operation of the tension adjusting device
100
having the above structure, in a normal print mode where the printing apparatus normally operates for printing, the eccentric cam
150
presses the pressing ring
143
, so that the guide bar
130
is pushed toward a direction A. Accordingly, the tension roller
40
is moved in the direction A, so that the tension is applied to the photoreceptor belt
10
. In the case when a worn belt needs to be replaced (referred to as belt replace mode), the pressure applied to the spring
142
is released by the rotation of the eccentric cam
150
, so that the tension roller
40
moves in a direction B. Accordingly, the tension applied to the photoreceptor belt
10
is released.
As described above, the conventional tension adjusting device
100
is designed to operate in two modes: the normal print mode and the belt replace mode. Thus, even when the printing operation stops due to reasons other than the replacement of the photoreceptor belt
10
, the tension applied to the photoreceptor belt
10
remains. Also, if the tension applied to the photoreceptor belt
10
is released by switching the normal print mode into the belt replace mode, in this case, the photoreceptor belt
10
is loosened and falls down, contacting other units such as the LSU
60
(see
FIG. 1
) or the development unit
70
(see FIG.
1
), installed below the photoreceptor belt
10
, causing contamination or damage to the surface of the photoreceptor belt
10
.
Meanwhile, in the case where the operation of the printing apparatus stops, if the photoreceptor belt
10
is left for a long time while the tension is applied thereto, three bent portions of the photoreceptor belt
10
, contacting the driving roller
20
, the backup roller
30
and the tension roller
40
, are partially stiffened, resulting in folds on the photoreceptor belt
10
. Such folds in the photoreceptor belt
10
distort the image developed thereon during a printing process, thereby deteriorating the quality of development, and shortening the life of the photoreceptor belt
10
.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a device for adjusting the tension of a photoreceptor belt in a printing apparatus, which is capable of appropriately letting loose the tension applied to the photoreceptor belt during suspension of a printing operation, thereby preventing generation of folds due to a partial stiffening of the photoreceptor belt.
To achieve the object of the present invention, there is provided a tension adjusting device for printing apparatuses, including: means for rotatably supporting a tension roller; means for adjusting the tension applied to a photoreceptor belt by pushing the tension roller in a direction to apply tension to the photoreceptor belt, or by releasing the tension from the photoreceptor belt; a driving motor for driving the tension adjusting means; and means for controlling the operation of the driving motor such that the tension adjusting means operates in three modes, including: a normal print mode where the tension is applied to the photoreceptor belt for a normal printing, a loosened tension mode where the tension to the photoreceptor belt is loosened due to the suspension of the printing operation, and a belt replace mode where the tension to the photoreceptor belt is released to replace the photoreceptor belt.
Preferably, the control means includes means for sensing the position of the tension adjusting means, and the control means recognizes the modes according to the position of the tension adjusting means, detected by the sensing means as the driving motor operates, and controls the driving motor according to the detected mode.
Preferably, the control means recognizes the modes according to the load which is applied to the driving motor as the driving motor operates to shift the mode, and controls the driving motor according to the detected mode.
Theref
Chen Sophia S.
Samsung Electronics Co,. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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