Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
2003-04-08
2004-08-03
Bollinger, David H. (Department: 3653)
Sheet feeding or delivering
Feeding
Separators
C271S122000, C271S125000, C492S049000, C492S039000
Reexamination Certificate
active
06769679
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a roller for feeding or transporting sheets, such as originals or recording paper, to an image forming apparatus, such as a copying machine, a printer, or a facsimile apparatus. The present invention also relates to a sheet feed apparatus and an image forming apparatus using this roller.
2. Related Background Art
In a sheet feed apparatus for feeding sheets, such as recording paper or originals, it is necessary to supply contained sheets one by one. For this purpose, there is available, for example, a retard separation type sheet feed apparatus
201
shown in
FIG. 11
for feeding sheets one by one.
The sheet feed apparatus
201
shown in
FIG. 11
is equipped with a pick-up roller
205
for feeding a plurality of sheets from a sheet containing device
203
, in which a plurality of sheets are stacked on a stack table (not shown), one by one starting with the uppermost sheet
202
, a feed roller
206
for feeding the sheet
202
, fed from the sheet containing device
203
by the pick-up roller
205
, into an image forming apparatus main body (in the direction indicated by the arrow “b” in the FIG.
11
), a retard roller
207
which is opposed to the feed roller
206
and which, when a plurality of sheets are fed from the sheet containing device
203
, rotates in a rotating direction reverse to the rotating direction for feeding sheets to thereby separate the plurality of sheets into a single sheet
202
, and a transport roller pair
209
for transporting the separated sheet.
Further, in a sheet passage region
210
between the pick-up roller
205
and the roller set consisting of the feed roller
206
and the retard roller
207
, there is arranged a guide
211
. Between the roller set consisting of the feed roller
206
and the retard roller
207
and the transport roller pair
209
, and between the transport roller pair
209
and the image forming apparatus main body, there are arranged guides
212
, each guiding the sheet
202
.
A drive transmission device
213
shown in
FIG. 12
drives the feed roller
206
and the retard roller
207
.
As shown in
FIG. 12
, in the drive transmission device
213
, a feed roller shaft
215
supporting the feed roller
206
, a retard roller shaft
216
supporting the retard roller
207
, and a retard roller driving shaft
217
connected to the retard roller shaft
216
, are arranged substantially parallel to each other. The retard roller shaft
216
is supported by an oscillatable support member (not shown) and capable of moving toward and away from the feed roller shaft
215
so as to be parallel to the same. Further, between the retard roller shaft
216
and the retard roller driving shaft
217
, there are arranged a coupling
219
and a torque limiter
220
. Further, at an end portion of the feed roller shaft
215
, there is provided an electromagnetic clutch
222
for transmitting the driving force transmitted from a main driving unit of the image forming apparatus main body (not shown) to the feed roller shaft
215
through a drive input belt
221
. Further, wrapped around the feed roller shaft
215
and the retard roller driving shaft
217
is a retard driving belt
223
for transmitting to the retard roller driving shaft
217
a rotational driving force transmitted to the feed roller shaft
215
. Note that the coupling
219
serves to transmit a driving force from the retard roller driving shaft
217
to the retard roller shaft
216
even when the retard roller
207
is displaced.
The driving of the feed roller
206
and the retard roller
207
by the drive transmission device
213
will be described. The rotational driving force supplied from the main driving unit of the image forming apparatus main body (not shown) is transmitted to the drive input belt
221
, and input to a pulley
225
provided on the armature portion of the electromagnetic clutch
222
ON/OFF-controlled in accordance with the sheet feed timing. Here, the feed roller shaft
215
rotating integrally with the rotor portion of the electromagnetic clutch
222
is connected to the retard roller driving shaft
217
and the retard roller shaft
216
by the retard driving belt
223
, so that the feed roller shaft
215
, the retard roller shaft
216
, and the retard roller driving shaft
217
rotate in the same direction, and the feed roller
206
and the retard roller
207
are driven to be rotated in synchronism with each other when the sheet feed timing is ON.
When the sheets
202
are fed one by one in the sheet feeding direction (the direction indicated by the arrow “b” in
FIGS. 11 and 12
) by the rollers rotated by the driving force transmitted by the drive transmission unit
213
, the torque limiter
220
makes idle rotation due to the frictional force between the feed roller
206
and the sheet
202
, and the retard roller
207
rotates in the direction reverse to the direction in which the retard roller driving shaft
217
is driven to be rotated.
When a plurality of sheets
202
are fed, the torque limiter
220
makes no idle rotation due to the fact that the frictional force between the plurality of sheets
202
is smaller than the frictional force between the retard roller
207
and the sheets
202
, and the retard roller
207
rotates in the same direction as the retard roller driving shaft
217
. As a result, the sheet
202
nearest to the feed roller
206
side, that is, the uppermost sheet
202
, is separated from the rest of the plurality of sheets
202
, thereby preventing double feed of sheets
202
into the image forming apparatus main body. Note that, in the following, the phenomenon in which a plurality of sheets are fed from the sheet containing device to the retard roller will be referred to as “stack transport”, and the phenomenon in which a plurality of sheets are allowed to be fed into the image forming apparatus main body without being separated by the retard roller will be referred to as “double feed”.
Next, theoretical formulas satisfying the conditions for the feeding and separation of the sheets
202
by the sheet feed apparatus
201
, constructed as described above, will be illustrated.
N>T/r&mgr;BP
+(&mgr;
APP&mgr;AP
)
W/&mgr;BP
(1)
N<T/r&mgr;BPP
2
&mgr;
APPW/&mgr;BPP
(2)
N<T/r&mgr;CP
(3)
where
&mgr;AP: the coefficient of friction between the pick-up roller
205
and the sheets
202
;
&mgr;BP: the coefficient of friction between the feed roller
206
and the sheets
202
;
&mgr;CP: the coefficient of friction between the retard roller
207
and the sheets
202
;
&mgr;APP: the coefficient of friction between the sheets
202
under the pressure portion of the pick-up roller
205
;
&mgr;BPP: the coefficient of friction between the sheets
202
at the nip portion of the feed roller
206
and the retard roller
207
;
N: the pressure force of the retard roller
207
;
T: the idle torque of the torque limiter
220
;
r: the radius of the retard roller
207
; and
W: the pressure force of the pick-up roller
205
.
Formula (1) satisfies the feeding condition, formula (2) satisfies the separating condition, and formula (3) satisfies the retard roller associative rotation condition.
Note that, if the sheets used in the above formulas are the same, there is no great variation in coefficient of friction between the roller pressure portions, so that through the substitution: &mgr;APP≈&mgr;BPP=&mgr;PP, the following formulas (4) and (5) are obtained from formulas (1) and (2):
N >T/r&mgr;BP
+(&mgr;
PP−&mgr;AP
)
W/&mgr;BP
(4)
N<T/r&mgr;PP
−2
W
(5)
FIG. 13
is a graph showing the relationship between the above formulas (3), (4) and (5), using the pressure force N of the retard roller
207
and the idle torque T of the torque limiter
220
as parameters.
In
FIG. 13
, the shaded portion indicates the feed region.
Thus, to enlarge the shaded region, it is necessary either to increase the coefficient of friction between the rollers and sheets or to reduce the pressure forc
Bollinger David H.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
LandOfFree
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