Electrophotography – Document handling – Copy
Reexamination Certificate
2000-10-04
2001-07-10
Grainger, Quana M (Department: 2852)
Electrophotography
Document handling
Copy
C399S394000, C399S397000
Reexamination Certificate
active
06259886
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrophotographic printing apparatus such as a laser printer or copier.
2. Description of the Related Art
In the electrophographic printing apparatus provided with: a timing roller to convey the sheet sent from a sheet hopper at the predetermined timing; a register roller to convey the sheet in timed relationship with the timing at which the toner image formed on the photoreceptor drum surface reaches the transfer device; and a conveying apparatus to convey the sheet passed through the transfer device toward a fixing device, conventionally, the sheet conveying speed of the timing roller, register roller, and conveying apparatus is set to the same as a process speed.
By using
FIG. 1
, the schematic structure of the electrophotographic printing apparatus will be described below. The sheet accommodated in a sheet hopper
10
, is sent out by a pick roller
9
, and one sheet passed through double feeding prevention rollers
8
a
and
8
b
is sent into timing rollers
1
a
and
1
b
by conveying rollers
7
a
and
7
b.
The sheet sent out by the timing rollers
1
a
and
1
b
at the predetermined timing is sent into the stopped register rollers
2
a
and
2
b.
Herein, in the sheet sent into the register rollers
2
a
and
2
b,
because, under the condition that the leading edge of the sheet comes into contact with the register rollers
2
a
and
2
b,
the trailing edge side is sent into the register rollers
2
a
and
2
b
by the timing rollers
1
a
and
1
b,
the deflection is formed between the timing rollers
1
a
and
1
b
and the register rollers
2
a
and
2
b.
By this deflection and the rigidity of the sheet itself, the posture of the sheet is corrected, and the leading edge of the sheet is corrected so that it comes straight into contact with the nip of the register roller
2
a
and the register roller
2
b.
As described above, the sheet whose posture is corrected, is sent from the register rollers
2
a
and
2
b
in timed relationship with the timing at which the toner image (not shown) formed on the photoreceptor drum
3
surface reaches the transfer device
4
.
The sheet holding the toner image which is transferred from the photoreceptor drum
3
and not yet fixed, is sent to the fixing device
6
through the conveying apparatus
5
, and the toner image is thermally fixed onto the sheet by the fixing device
6
.
When the fixed sheet is delivered outside the printing apparatus, the sheet is delivered through conveying rollers
20
a,
20
b,
and conveying rollers
21
a
and
21
b.
Further, when the front and rear sides of the fixed sheet are reversed and the sheet is delivered outside the printing apparatus, the sheet sent from the conveying rollers
20
a
and
20
b
is introduced once into a sheet path side provided with conveying rollers
22
a,
22
b,
23
a
and
23
b,
then, the conveying rollers
22
a,
22
b,
23
a
and
23
b
are reversely rotated, and the sheet is sent to the conveying rollers
21
a
and
21
b,
and delivered. Further, when two-sided printing is conducted, the sheet sent from the conveying rollers
20
a
and
20
b
is introduced into the sheet path side provided with conveying rollers
22
a,
22
b,
23
a
and
23
b,
and then, the sheet is sent again to the timing rollers
1
a
and
1
b
through the two-sides conveying path (the path provided with conveying rollers
24
a,
24
b,
25
a,
25
b,
26
a
and
26
b
) branched from the sheet path, and thereby, two-sided printing is conducted.
However, in the above structure, when the sheet ream weight is large (the thickness of the sheet is large), or when the sheet length is large (A
3
sheet), because, when the trailing edge of the sheet is separated from the timing roller and register roller, the deflection of the sheet is released, the vibration is generated on the sheet, and the vibration is transmitted along the sheet, and there is a disadvantage that the transfer blurring is generated when the toner image is transferred by the transfer device.
SUMMARY OF THE INVENTION
An object of the present invention is to realize an electrophotographic printing apparatus by which the vibration generated when the sheet is separated from the timing roller and register roller is suppressed, and a fine image can be obtained without the transfer blurring.
The above object can be attained by an electrophotographic printing apparatus, which comprising: a timing roller which conveys a sheet sent from a sheet hopper at the predetermined timing; a register roller to convey the sheet in timed relationship with the timing at which a toner image formed on a photoreceptor drum surface reaches a transfer device; and a conveying apparatus to convey the sheet passed through the transfer device toward a fixing device, wherein, when the conveying speed of the timing roller is Vt, the conveying speed of the register roller is Vr, the peripheral speed of the photoreceptor drum is V0, and the conveying speed of the conveying apparatus is Vf, each speed is set to satisfy the relationship of Vf>V0≧Vr>Vt, and when a sheet deflection amount formed when the sheet comes into contact with the register roller, is &dgr;r, the sheet deflection amount at the photoreceptor drum entry section is &dgr;0, and the sheet length is Lp, each value is regulated so that the relationships of &dgr;r≧Lp ((Vr−Vt)/Vt), and &dgr;0≧Lp ((Vf−V0)/V0) are satisfied.
REFERENCES:
patent: 4240739 (1980-12-01), Koumura et al.
Ishii Kenji
Seino Minoru
Grainger Quana M
Hitachi Koki Co,. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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