Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
2001-01-30
2003-02-18
Walsh, Donald P. (Department: 3651)
Sheet feeding or delivering
Feeding
Separators
Reexamination Certificate
active
06520497
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a sheet feeding apparatus for feeding sheets, and an image forming apparatus and an image reading apparatus provided with the same, and particularly to such apparatuses provided with separating and feeding means adapted to separate and feed sheets one by one by the use of a retard separating method.
2. Related Background Art
An image forming apparatus or an image reading apparatus according to the prior art is provided with a sheet feeding apparatus for conveying recording sheets to an image forming portion or an original to an image reading portion.
FIG. 6
of the accompanying drawings shows the construction of such a sheet feeding apparatus according to the prior art, and in
FIG. 6
, the reference numeral
1
designates a sheet feeding apparatus for supplying recording sheets
2
to an image forming portion, not shown.
This sheet feeding apparatus
1
is provided with a pickup roller
5
for feeding out the uppermost recording sheet
2
a
of recording sheets
2
stacked on a stacking plate, not shown, provided on a sheet containing device
3
, a feed roller
6
for conveying the recording sheet
2
a
fed by the pickup roller
5
to an image forming portion, a retard roller
7
brought into pressure contact with the feed roller
6
and rotated in the same direction as or the opposite direction to the direction of rotation of the feed roller
6
, and a pair of conveying rollers
9
provided downstream of the feed roller
6
.
A first guide
10
is disposed between the pickup roller
5
and the combination of the feed roller
6
and the retard roller
7
, a second guide
11
is disposed between the combination of the feed roller
6
and the retard roller
7
and the pair of conveying rollers
9
, and further a third guide
12
is disposed downstream of the pair of conveying rollers
9
, and the recording sheets
2
may be guided and conveyed by these guides
10
to
12
.
Here, the retard roller
7
which is a separating rotary member cooperates with the feed roller
6
which is a feeding rotary member to constitute separating and feeding means for separating and feeding the recording sheets
2
fed out by the pickup roller
5
which is sheet feeding means one by one, and when a plurality of recording sheets
2
are fed from the sheet containing device
3
, the retard roller
7
is adapted to be rotated in the opposite direction to the direction of rotation of the feed roller
6
, as shown in
FIG. 6
, to thereby separate the uppermost recording sheet
2
a
from the other recording sheets
2
.
On the other hand,
FIG. 7
of the accompanying drawings shows the construction of a drive transmitting device for driving the feed roller
6
and the retard roller
7
, and in
FIG. 7
, the reference numeral
13
denotes the drive transmitting device. This drive transmitting device
13
is provided with a feed roller shaft
15
on which the feed roller
6
is mounted, a retard roller shaft
16
on which the retard roller
7
is mounted, and a retard roller driving shaft
17
which is a driving shaft connected to the retard roller shaft
16
. The retard roller shaft
16
and the retard roller driving shaft
17
are provided substantially in parallelism to the feed roller shaft
15
and supported by a pivotally movable supporting member, not shown, and movable toward and away from the feed roller shaft
15
.
Also, the reference numeral
20
designates a torque limiter provided between the retard roller shaft
16
and the retard roller driving shaft
17
, and the reference numeral
22
denotes an electromagnetic clutch provided on the end portion of the feed roller shaft
15
for transmitting a driving force transmitted from the main driving means of the main body of an image forming apparatus, not shown, through a driving input belt
21
to the feed roller shaft
15
.
Also, the reference numeral
23
designates a retard driving belt extended between the feed roller shaft
15
and the retard roller driving shaft
17
for transmitting a rotatively driving force transmitted to the feed roller shaft
15
further to the retard roller driving shaft
17
. The reference numeral
19
denotes a coupling provided between the retard roller shaft
16
and the retard roller driving shaft
17
for transmitting the drive of the retard roller driving shaft
17
to the retard roller shaft
16
.
Description will now be made of the driving of the feed roller
6
and retard roller
7
by the drive transmitting device
13
constructed as described above.
When a rotatively driving force is given from the main driving means, this rotatively driving force is inputted through the driving input belt
21
a pulley
25
provided on the armature portion, not shown, of the electromagnetic clutch
22
ON-OFF-controlled in conformity with sheet feed timing. Here, the feed roller shaft
15
is adapted to rotate with the rotor portion, not shown, of the electromagnetic clutch
22
, and the feed roller shaft
15
and the retard roller driving shaft
17
and the retard roller shaft
16
are connected together by the retard driving belt
23
.
Thus, when the feed roller
15
is rotated, the retard roller driving shaft
17
is rotated in the same direction as the feed roller shaft
15
, and further, when the feed roller
15
and the retard roller driving shaft
17
are thus rotated, the feed roller
6
and the retard roller
7
are rotatively driven in synchronism with the ON of the sheet feed timing.
Now, when the recording sheets
2
are fed one by one in the direction of arrow b in
FIG. 6
, the frictional force between the feed roller
6
and the recording sheet
2
acting on the retard roller
7
is greater than the returning force of the torque limiter
20
and therefore, the retard roller
7
and the retard roller shaft
16
are adapted to be driven to be rotated in the opposite direction to the rotatively driving direction of the retard roller driving shaft
17
while idly rotating the torque limiter
20
.
Also, when a plurality of recording sheets
2
are fed, the frictional force among the plurality of recording sheets
2
is small relative to the frictional force between the retard roller
7
and the recording sheet
2
and therefore, the torque limiter
20
is not idly rotated, whereby the retard roller
7
and the retard roller shaft
16
are rotated in the same direction as the rotatively driving direction of the retard roller driving shaft
17
.
By the retard roller
7
being rotated in such a direction, of the plurality of recording sheets
2
fed, the recording sheet
2
a
which is most adjacent to the feed roller
6
, that is, which is uppermost, comes to be separated from the other recording sheets
2
, whereby the plurality of recording sheets
2
can be prevented from being conveyed to the image forming portion. Hereinafter, the phenomenon that a plurality of recording sheets
2
are fed from the sheet containing device
3
to the retard roller
7
will be referred to as “bundle conveyance”, and the phenomenon that the plurality of recording sheets
2
cannot be separated from one another and are fed will be referred to as “double feeding”.
Description will now be made of theoretical expressions satisfying the feeding and separating conditions for the recording sheet
2
by such a sheet feeding apparatus
1
.
Here, when the coefficient of friction between the feed roller
6
and the recording sheet
2
is defined as &mgr;
BP
and the coefficient of friction between the retard roller
7
and the recording sheet
2
is defined as &mgr;
CP
and the coefficient of friction between the recording sheets is defined as &mgr;
PP
and the pressurizing force (pressure contact force) of the retard roller
7
is defined as N and the idling torque of the torque limiter
20
is defined as T and the effective radius of the retard roller
7
is defined as r and the returning force of the torque limiter
20
is defined as T/r, the feeding condition of the feed roller
6
, the separating condition for the recording sheet
2
and the driven to be r
Bower Kenneth W
Walsh Donald P.
LandOfFree
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