Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
2002-02-01
2004-03-30
Walsh, Donald P. (Department: 3653)
Sheet feeding or delivering
Feeding
Separators
Reexamination Certificate
active
06712350
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a sheet feeding apparatus for separating and feeding sheets such as stacked originals and recording mediums one by one, and an image forming apparatus provided with the sheet feeding apparatus.
2. Description of Related Art
There are known an image forming apparatus of the ink jet type for discharging ink to a recording medium such as recording paper to thereby form an image thereon, and an image forming apparatus of the electrophotographic type for forming an image on a recording medium by the use of a developer (toner), and these image forming apparatuses are provided with a sheet feeding apparatus for supplying the recording medium to an image forming portion.
Now, in some printers, as a sheet feeding apparatus for supplying a recording medium (hereinafter referred to as the sheet) to image forming means, provision is made of a multisheet feeding apparatus of a construction in which sheets set on a tray by a user are fed out, besides a sheet feeding apparatus of a construction in which sheets are fed out from a sheet feeding cassette containing the sheets therein. The multisheet feeding apparatus can set and feed sheets of various sizes and sheets of various kinds, and is efficient for the feeding of a small quantity of sheets, and the feeding of spatial paper such as thick paper or film paper.
An example of the conventional multisheet feeding apparatus will hereinafter be described with reference to
FIGS. 6
to
8
of the accompanying drawings.
FIG. 6
is a longitudinal cross-sectional view of the multisheet feeding apparatus,
FIG. 7
is a perspective view of a separating pad, and
FIG. 8
is an enlarged view showing a state in which a sheet is being separated by a sheet feeding roller and the separating pad.
The multisheet feeding apparatus
50
is provided with an intermediate plate
54
on which a plurality of sheets P are stacked, a side regulating plate
82
for regulating the widthwise position of the sheets P stacked on the intermediate plate
54
, and an intermediate plate spring
56
for upwardly biasing the leading edge side end portion of the intermediate plate
54
in the sheet feeding direction. Above the intermediate plate spring
56
, there is disposed a sheet feeding roller
58
for contacting with the sheets P stacked on the intermediate plate
54
to thereby feed out the sheets P one by one in the sheet feeding direction (the direction indicated by the arrow C).
Downstream of the sheet feeding roller
58
in the sheet feeding direction, there is disposed a sheet feeding guide
60
for guiding the sheet P fed out by the sheet feeding roller
58
to a pair of registration rollers
38
disposed on the downstream side in the sheet feeding direction. A pair of U-shaped grooves
62
(shown in
FIG. 8
) are formed at the right and left of the sheet feeding guide
60
as viewed in a direction orthogonal to the sheet feeding direction on the upstream side in the sheet feeding direction, and the opening
62
a
of each groove
62
faces downwardly.
A separating pad
70
is disposed adjacent to and upstream of the sheet feeding guide
60
in the sheet feeding direction. The separating pad
70
is comprised of a plate-shaped separating pad holder
70
a
provided with two pivot shafts
72
orthogonal to the sheet feeding direction on the downstream side in the sheet feeding direction, and a rectangular separating pad member
74
stuck on the upstream side surface of the separating pad holder
70
a
in the sheet feeding direction and formed of urethane rubber containing cork or the like. The two pivot shafts
72
of the separating pad holder
70
a
fit into the grooves
62
, whereby the separating pad
70
is supported for pivotal movement.
Below the separating pad holder
70
a,
there is disposed a separating spring
76
comprising a coil spring for upwardly biasing the separating pad holder
70
a.
Since the separating spring
76
pushes up that portion of the separating pad holder
70
a
which is opposite to the pivot shaft
72
from below it, the separating pad holder
70
a
is pivotally moved about the pivot shaft
72
. As the result, the separating pad member
74
is urged against the sheet feeding roller
58
. Accordingly, the sheet feeding roller
58
is rotated in the direction indicated by the arrow D, whereby the stacked sheet is fed out from the intermediate plate
54
, and when two or more sheets are fed out, they are separated one by one between the separating pad member
74
and the sheet feeding roller
58
.
Now, to feed the sheet P smoothly in the sheet feeding direction, it is necessary that the surface of the separating pad member
74
be urged against the outer peripheral surface of the sheet feeding roller
58
with uniform contact pressure, and if the contact pressure is non-uniform, the sheet P may not be fed smoothly. When for example, greater contact pressure acts on one of the portions of the separating pad member
74
in the left to right direction thereof (the direction orthogonal to the direction indicated by the arrow C) than on the other portion, the sheet P being separated may be skew-fed or the sheet P may not be separated but may be jammed near the separating pad member
74
.
In order that as described above, the surface of the separating pad member
74
may be urged against the outer peripheral surface of the sheet feeding roller
58
with uniform contact pressure, it is necessary that the line of contact
74
a
(shown in
FIG. 7
) when the separating pad member
74
contacts with the sheet feeding roller
58
and the center line of pivotal movement
72
a
(shown in
FIG. 7
) of the pivot shafts
72
of the separating pad holder
70
a
be parallel to each other. However, the accuracy of the position at which the sheet feeding guide
60
is fixed to the main body of the printer
10
or the accuracy of the shape thereof is sometimes bad due to the deformation or the like of the separating pad holder
70
a
and therefore, the line of contact
74
a
and the center line of pivotal movement
72
a
sometimes do not become parallel to each other.
Accordingly, when the pivot shafts
72
are fitted into the grooves
62
without any gap to such a degree that the pivot shafts
72
can freely pivotally move in the grooves
62
, it is difficult due to the above-mentioned accuracy for the line of contact
74
a
and the center line of pivotal movement
72
a
to become parallel to each other. So, the grooves
62
are formed relatively larger than the outer diameter of the pivot shafts
72
so that irrespective of the above-mentioned accuracy, the line of contact
74
a
and the center line of pivotal movement
72
a
may become parallel to each other. By so constructing, the surface of the separating pad member
74
is urged against the outer peripheral surface of the sheet feeding roller
58
with uniform contact pressure.
Now, the coefficient of friction of the sheet feeding roller
58
and the coefficient of friction of the separating pad member
74
with respect to the sheet P differ from each other. Also, as described above, the grooves
62
are larger than the outer diameter of the pivot shafts
72
and therefore, there is more or less play or slop between these two. Therefore, when the sheet P nipped by and between the separating pad member
74
and the sheet feeding roller
58
is fed, the sheet P and the separating pad member
74
may rub against each other to thereby cause stick-slip motion. Due to the stick-slip motion, there occurs vibration and occurs an abnormal sound called pad chatter (squeak).
So, as techniques for preventing the pad chatter, the following techniques (1) to (4) are under consideration:
(1) The technique of disposing a member for contacting with the front side or the backside of the sheet P on the downstream side of the position, in which the sheet feeding roller
58
and the separating pad member
74
nip the sheet P therebetween, in the sheet feeding direction, and stopping the vibration of the sheet P;
(2) The technique of weakening the
Bower Kenneth W.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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