Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
2000-05-12
2002-05-07
Ellis, Christopher P. (Department: 3651)
Sheet feeding or delivering
Feeding
Separators
C221S167000
Reexamination Certificate
active
06382622
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a sheet feeding apparatus for feeding sheets sheet by sheet by a retard separation method and to an image forming apparatus and an image reading apparatus such as a photocopier or printer having the sheet feeding apparatus.
2. Description of Related Art
FIG.
19
and
FIG. 20
show a schematic cross section and a drive portion illustration of sheet feeding apparatuses of two types, respectively, capable of feeding sheets successively using representative retard separation methods that have been used conventionally. First, as the first prior art, a retard separation sheet feeding apparatus having a pickup roller is described in reference to FIG.
19
.
A feeding motor M for driving the apparatus has a route to transmit the drive force to a feeding roller
203
and a pickup roller
202
, and a route to transmit the drive force to a separating roller
204
.
An one-way clutch
211
for limiting rotation in a direction opposite to the sheet feeding direction is formed at a feeding roller shaft
213
.
The separating roller
204
formed in contact with the feeding roller
203
with a prescribed pressure is supported rotatively via a torque limiter
212
to a separating roller shaft
214
rotating in a direction opposite to the sheet feeding direction.
The pickup roller
202
feeds one sheet only out, and where the sheet is nipped at a nipping portion formed at a pressurized contact portion between the feeding roller
203
and the separating roller
204
, the separating roller
204
rotates in association with the rotation of the feeding roller
203
in the sheet feeding direction, but where plural sheets come into the nipping portion between the feeding roller
203
and the separating roller
204
(hereinafter, this situation is referred to as “double feeding”), the torque limiter operates to render the separating roller
204
rotates in the direction opposite to the sheet feeding direction, thereby leaving the topmost one sheet only and returning other doubly fed sheets to a stacking plate
201
.
The pickup roller
202
is controlled to feed the sheets stacked on the stacking plate
201
sheet by sheet in a direction of the feeding roller
203
and to escape from the sheet surface upon operation of a pickup solenoid
206
after the sheet fed reaches the nipping portion between the feeding roller
203
and the separating roller
204
.
This is for avoiding operation by the separating roller
204
to return the sheets in the direction of the stacking plate
201
from being disturbed when plural sheets are fed to the nipping portion.
In this prior art, the pickup roller
202
is rotatively supported around the feeding roller shaft
213
by a pickup supporting plate
215
. According to whether a pickup lever
208
moving in association with the pickup solenoid
206
is pushing up the pickup supporting plate
215
or not, the pickup roller
202
switches the pickup roller's position for pressing to and escaping from the sheet S.
When a user sets a sheet bundle to this sheet feeding apparatus, the pickup roller
202
is structured to escape by the pickup solenoid
206
during non-operation period of the apparatus so as not to interfere the pickup roller
202
with the setting operation.
Where one sheet fed by the feeding operation and separated by the separating roller
204
is transferred to the nipping portion of the pulling-out roller pair
205
formed on a downstream side in the sheet feeding direction, a controlling means, not shown, stops drive of the feeding motor M
1
until the sheet rear end passes the nipping portion between the feeding roller
203
and the separating roller
204
. Where the feeding motor M
1
stops drive, a stepping motor or the like is used which does not rotate in a direction opposite to the drive direction.
The reason that the drive of the feeding motor M
1
is stopped is to prevent a sheet subsequent to the forgoing sheet from being fed together where the leading end of the sheet subsequent to the sheet being fed is conveyed right before the nipping portion between the feeding roller
203
and the separating roller
204
.
The one-way clutch
111
is so formed that the feeding roller
203
can rotate along with the sheet until the sheet rear end passes the nipping portion even after the feeding motor M
1
stops its drive.
In addition, when the user sets the sheet bundle, a shutter
210
is provided to give the user setting feeling to prevent the sheet bundle from reaching the nipping portion by mistaken control of the user, or to prevent pickup failure due to mistaken setting made by the user. The shutter
210
moves to a position to hit the sheet bundle during the non-operation period of the apparatus by a shutter solenoid
207
, and during feeding operation, can escape to a position not disturbing the feeding operation.
Next, as a second prior art, a sheet feeding apparatus of a retard separation method not using any pickup roller is described using a schematic cross section shown as FIG.
20
.
As shown in
FIG. 20
, sheets S stacked on an intermediate plate
306
in a cassette
307
are lifted together with the intermediate plate
306
by a pressing arm
308
and a sheet pressing spring
305
and is normally in pressurized contact with the feeding roller
301
to receive feeding pressure.
A separating roller
302
provides the feeding roller
301
retard pressure (separating roller pressure). In this state, if the feeding roller
301
rotates in a direction for feeding sheets, the sheet S in pressurized contact with the feeding roller
301
is fed out and reaches the nipping portion formed between the feeding roller
301
and the separating roller
302
.
At that time, if the sheet S is solely nipped at the nipping portion, the separating roller
302
rotates together with the feeding roller
301
in a direction for feeding sheet by operation of a torque limiter
303
formed in a united body with the feeding roller
301
, thereby feeding the sheet S.
However, if plural sheets are nipped at the nipping portion, the separation rotates in a direction to return the doubly fed sheets with a prescribed torque by operation of the torque limiter
303
, thereby preventing the sheets from being doubly fed.
The two sheet feeding apparatuses using major retard separation methods are described above, but those sheet feeding apparatus suffer from the following problems.
With the sheet feeding apparatus of the first prior art, to use the retard separation feeding method, the pickup roller is necessary to feed the sheet from the sheet bundle sheet by sheet, and a escaping mechanism such as the shutter solenoid
207
and the like is required to escape the pickup roller
202
.
Moreover, since the apparatus requires the mechanism made of the shutter
210
and the shutter solenoid
207
, the apparatus also requires an installation space for the mechanism, and this compelled the apparatus to be larger. The mechanism further requires larger number of parts, makes the structure complicated, and renders the manufacturing costs higher.
In a meantime, there is a problem relating to paper jamming handling. Since one-way clutch
211
for limiting the rotation in the direction opposite to the sheet feeding direction is formed at the feeding roller
203
, the feeding roller
203
does not rotate in the direction opposite to the sheet feeding direction. The sheets jammed at the nipping portion between the feeding roller
203
and the separating roller
204
can be pulled only on a side of the sheet feeding direction, so that it is required to do work such as removal of the apparatus to handle the paper jamming and that such a removal imposes a duty on the user. In addition, when the user forcibly pulls sheets in the direction opposition to the sheet feeding direction, the sheets may be broken, and the sheets left within the apparatus may cause further problems.
To solve the problems relating to the first prior art, the second prior art has been conceived as a retard separation method as a type not using s
Takada Hideaki
Yano Takashi
Bower Kenneth W
Canon Kabushiki Kaisha
Ellis Christopher P.
Fitzpatrick ,Cella, Harper & Scinto
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