Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
2001-03-09
2003-01-07
Skaggs, H. Grant (Department: 3653)
Sheet feeding or delivering
Feeding
Separators
C271S124000, C271S167000
Reexamination Certificate
active
06502816
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet feeding apparatus and an image forming apparatus having such a sheet feeding apparatus, and more particularly, it relates to a sheet feeding apparatus in which sheets are separated by using a separating inclined surface.
2. Related Background Art
In conventional image forming apparatuses such as printers, copying machines, facsimile apparatuses and the like, there is provided a sheet feeding apparatus for feeding a sheet to an image forming portion. Among such sheet feeding apparatuses, there is a sheet feeding apparatus in which sheets are separated one by one by a separating inclined surface to be supplied to the image forming portion.
FIG. 41
is a schematic constructural view of an image forming apparatus having such a conventional sheet feeding apparatus. In
FIG. 41
, the image forming apparatus
100
includes a sheet feeding tray
101
having a horizontal sheet stacking surface
101
a
, and a separating inclined surface
102
disposed at an end of the sheet feeding tray
101
in a sheet feeding direction. The separating inclined surface
102
is inclined with respect to a sheet (stack) S by an angle of &thgr; (obtuse angle). Incidentally, there is further provided a trailing end regulating member
120
for supporting a trailing end of the sheet (stack) S rested on the sheet stacking surface, and a position of such a member can be adjusted.
The sheet feeding apparatus includes a sheet feeding roller
103
to which a gear
103
a
is integrally formed, a sheet feeding roller arm
105
adapted to rotatably support the sheet feeding roller
103
and rotatably held on a driving shaft
104
, a driving gear
106
secured to the driving shaft
104
, and idler gears
107
a
to
107
d
held on the sheet feeding roller arm
105
and serving to transmit a driving force of the driving gear
106
to the sheet feeding roller
103
. Incidentally, the driving shaft
104
is driven by a controllable driving mechanism (not shown) so that start and stop of an sheet feeding operation can be controlled by the driving of the driving shaft
104
.
There are further provided a conveying sub-roller
109
urged against a conveying roller
108
with predetermined pressure by means of biasing means (not shown) (the sheet S fed out by the sheet feeding roller
103
is conveyed by rotations of the conveying roller
108
and the conveying sub-roller
109
), an upper surface conveying guide
111
for guiding an upper surface of the sheet, and a lower surface conveying guide
110
for guiding a lower surface of the sheet. The sheet feeding tray
101
, sheet feeding roller
103
, sheet feeding roller arm
105
and the like constitute the sheet feeding apparatus
100
A.
On the other hand, in
FIG. 41
, there are further provided a photosensitive drum
112
, a toner cartridge
113
for integrally holding the photosensitive drum
112
and image developing means (not shown), a laser scanner
114
for forming a latent image on the photosensitive drum by exposing the surface of the photosensitive drum, and a transfer roller
115
for transferring a toner image (formed on the photosensitive drum by developing the latent image formed on the photosensitive drum in the toner cartridge) onto the sheet S. The photosensitive drum
112
and the transfer roller
115
are parts of an image forming portion
100
B.
There are further provided a fixing device
116
for fixing the toner image transferred by the transfer roller
115
onto the sheet S, a sheet discharging roller pair
117
for conveying the sheet S to which the toner image was fixed, a sheet discharging roller pair
118
for discharging the sheet S out of the image forming apparatus, and a sheet discharge tray
119
on which the sheet S is discharged.
When image formation is effected in the image forming apparatus
100
having the above mentioned construction, first of all, the latent image is formed on the surface of the photosensitive drum
112
by the exposure effected by the laser scanner
114
, and, thereafter, the toner image is formed on the surface of the photosensitive drum by developing the latent image by means of the image developing means provided in the toner cartridge
113
.
On the other hand, in synchronous with the above operation, the driving shaft
104
is rotated by the driving mechanism (not shown), and the rotation of the driving shaft is transmitted to the gear
103
a
of the sheet feeding roller
103
via the idler gears
107
a
to
107
d
born on the sheet feeding roller arm
105
, thereby starting to rotate the sheet feeding roller
103
.
By the way, as shown in
FIG. 42
, since the sheet feeding roller
103
is urged against an upper surface of an uppermost sheet S
1
included in the sheet stack S (referred to as “uppermost sheet” hereinafter) rested on the sheet stacking surface, when the rotation of the sheet feeding roller
103
is started in this way, a feeding force Fp due to a friction force acts on the uppermost sheet S
1
. Further, at the same time, the uppermost sheet S
1
is subjected to a friction force Fs
12
as a resistance force from an underlying next sheet S
2
.
As a result, the uppermost sheet S
1
abuts against the separating inclined surface
102
and is subjected to a reaction force R
1
from the separating inclined surface
102
, with the result that a leading end portion of the uppermost sheet is bent upwardly. Thereafter, when the sheet feeding roller
103
is further rotated, the bent sheet S
1
is further advanced while abutting the leading end thereof against the separating inclined surface. Incidentally, since the next sheet S
2
is subjected to a friction force Fs
23
from an underlying sheet S
3
, the next sheet does not advance together with the uppermost sheet S
1
, thereby preventing double-feeding.
The uppermost sheet S
1
separated and fed by the sheet feeding roller
103
and the separating inclined surface
102
in this way is conveyed by the rotations of the conveying roller
108
and the conveying sub-roller
109
shown in FIG.
41
and is sent to a nip between the photosensitive drum
112
and the transfer roller
115
.
Thereafter, the toner image formed on the photosensitive drum is transferred onto the sheet S
1
(sent to the nip between the photosensitive drum
112
and the transfer roller
115
) by the transfer roller
115
, and the sheet S
1
to which the toner image was transferred in this way is conveyed to the fixing device
116
. After the toner image was fixed in the fixing device
116
, the sheet S
1
is discharged out of a main body
100
C of the image forming apparatus and is rested on the sheet discharge tray
119
.
By the way, in such a conventional sheet feeding apparatus and image forming apparatus having the sheet feeding apparatus, as mentioned above, the prevention of the double-feeding of sheets relies upon deformation resistance of the sheet and the friction force between the sheets.
Thus, for example, when new sheets are replenished before the previously replenished sheets are used up, if coefficient of friction in the interface between the newly replenished sheet and the previously existing sheet is lower than coefficient of friction before other sheets, the sheet separation will be effected only by the deformation resistance of the sheet on the separating inclined surface
102
, with the result that, regarding sheets having low resiliency such as thin sheets, double-feeding may occur frequently in such an interface.
In order to prevent the double-feeding of thin sheets efficiently, for example, although there has been proposed a technique in which a distance between the sheet feeding roller
103
and the separating inclined surface
102
is decreased, if such a technique is used, the double-feeding of thin sheets can be prevented, but, a force required for feeding a thick sheet will become insufficient, thereby causing poor sheet feeding.
SUMMARY OF THE INVENTION
The present invention is made in consideration of the above-mentioned circumstances, and an object of the present inv
Fukuda Masayuki
Inoue Ryukichi
Kojima Ryuichi
Matsuo Yoshihiro
Yamazaki Yoshiyuki
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Skaggs H. Grant
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