Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
2001-02-12
2003-04-29
Skaggs, H. Grant (Department: 3653)
Sheet feeding or delivering
Feeding
Separators
C271S121000
Reexamination Certificate
active
06554270
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet conveying apparatus for separating and feeding sheets one by one to a predetermined position, and more particularly to a sheet conveying apparatus applicable to an image forming apparatus such as a copying machine and a laser beam printer.
2. Related Background Art
There are proposed various types of conventional sheet conveying apparatus for automatically conveying the sheet to an image reading portion of an image forming apparatus such as a copying machine, in which a plurality of sheets resting on a rest stand are separated one by one in a separating portion and conveyed to the image reading portion of the image forming apparatus, and which is provided with a means for reversing a front surface and a back surface of the sheet or the like.
A flow of the original in the separating portion in the conventional sheet conveying apparatus will now be described briefly with reference to
FIGS. 6 and 7
(cross-sectional view and a view as viewed in a direction indicated by the arrow A). First of all, a stack of sheet Sa rested on a rest stand
11
a
is picked up one by one from a top portion of the sheet stack Sa by a feed means such as a feed roller
1
a
that stands by above the sheet stack Sa and is fed toward the separating means downstream thereof. A fixed guide
6
a
for smoothly guiding the sheet to the separating means is provided in a position where it does not interfere with the up-and-down movement of the feed roller
1
a
between the feeding means and the separating means.
The sheets that have been fed without being separated one by one by the feed roller
1
a
(double feed) are separated one by one by the separating means (that is composed of a separating conveying roller
3
a
and a separating pad
4
a
) located downstream of the feed roller
1
a
and conveyed to a predetermined image reading position.
The operation of the feed roller
1
a
and the separating conveying roller
3
a
will now be described.
First of all, the separating conveying roller
3
a
rotates about a shaft
5
a
in a sheet conveying direction (clockwise direction in
FIG. 6
) using a motor Ma as a drive source. The feed roller
1
a
is subjected to the drive transmission through a timing belt
7
a
and rotates about a shaft
13
a
in the sheet conveying direction (clockwise direction in
FIG. 6
) using the same motor Ma as the separating conveying roller
3
a
as a drive source. The up-and-down movement of the feed roller
1
a
is performed by means of the same motor Ma through arms
2
a
rotatable about the above-described shaft
5
a.
When the feed roller
1
a
is brought into contact with the sheet stack and a torque (pressure) equal to or more than a predetermined level in a direction in which the feed roller
1
a
presses the sheet stack is applied, a slide is generated between the shaft
5
a
and the arms
2
a
by spring clutches
12
a
each engaging between the shaft
5
a
and the arm
2
a,
to thereby interrupt the lowering motion of the feed roller
1
a
(see FIG.
12
).
However, if the above-described arrangement is taken as in the conventional case, there is a fear of the generation of the following defects.
Although the fixed guide
6
a
for guiding the sheet from the feed roller
1
a
to the separating conveying roller
3
a
is provided in the position where it does not interfere with the up-and-down movement of the feed roller
1
a,
the same fixed guide could not be provided in the position (space between the arms
2
a
) where it interferes with the up-and-down movement in consideration of the swing (upward and downward movements) of the arms
2
a,
and there is a fear that the sheet could not be guided smoothly between the arms
2
a.
As a result, the sheet is brought into abdominal abutment with the separating conveying roller
3
a
(the phenomenon in which the leading end of the sheet collides against a portion other than the vicinity of the separating nip and is not led to the nip (see FIG.
11
)), the leading end portion of the sheet is raised and damaged in the worst case.
In order to solve such a problem, as shown in
FIGS. 8 and 9
, an arrangement is proposed in which a fixed guide
14
a
(that is a discrete member from the fixed guide
6
a
but integral with the arms
2
a
) is provided between the arms
2
a
to prevent the abdominal abutment to the separating conveying roller
3
a.
However, if such an arrangement is taken, there is a disadvantage that due to the sheet feeding structure of the feed roller
1
a,
in the case where a plurality of sheets are fed toward the separating conveying roller
3
a
at once, the plurality of sheets are constrained by the guide
14
a
so that no sheet could be fed to the separating conveying roller
3
a
(non-feed). Furthermore, in order to avoid the above-described abdominal abutment and non-feed, as shown in
FIG. 10
, it is proposed to provide a structure in which the above-described fixed guide
14
a
is rotatable about a pivot “b” on each of the arms
2
a.
However, even in such a structure, in the case where a plurality of sheets with their leading end folded are introduced to the separating conveying roller
3
a,
there is a fear that it is brought into abdominal abutment and the guide
14
a
is forced up (in a direction indicated by an arrow in FIG.
10
). This is insufficient as a countermeasure.
Moreover, in a practical point of view for shortening a processing time concomitant with the high speed operation, since the stack displacement of the sheets on the feed tray
11
a
and the stack introduction (a state where a number of sheets are introduced to the separating means in the form of a stack) are generated due to the shock upon the up-and-down movement of the feed roller
1
a
by the arms
2
a,
the up-and-down movement is not performed in many cases in the sheet feeding operation (i.e., the feed roller is always pressed to the sheet during the operation). This is the case in the above-described conventional case. Then, in the conventional structure, since the force is applied to the feed roller
1
a
in a direction in which the sheet stack is pressed to thereby keep a conveying force, the force in addition to a self-weight of the feed roller is applied to the feed roller
1
a
by the spring clutch
12
a
that is the force applying means to compensate for the conveying force. Namely, the conveying force is kept by means of the force of the spring clutch
12
a
and the gravitational force (the self-weight) of the feed roller
1
a
upon the forward drive of the motor Ma (in which the feed roller
1
a,
the separating conveying roller
3
a
and the arms
2
a
work in the direction indicated by the arrow in FIG.
6
). However, upon the interruption of the drive of the motor Ma, the force which is applied to the feed roller
1
a
by the spring clutch
12
a
is released and the bias is attained only by means of the gravitational force. Accordingly, in some cases, the feed roller
1
a
is jumped up by the force of restitution of the elastic deformation of the feed roller
1
a
or the restitution force of the elastic deformation of the spring clutch that is larger than the restitution force of the feed roller
1
a
immediately after the interruption of the drive, so that the feed roller
1
a
stays in a position somewhat away from the uppermost surface of the sheet. Then, upon the next sheet feeding operation, the feed roller
1
a
is lowered again downwardly so that the shock is applied to the sheet and the stack displacement and the stack introduction into the separating means would occur. Also, in the case where the separating means is not provided, the stack introduction would occur in the conveying means downstream of the conveying portion so that there is a fear that the faulty sheet conveyance would occur.
SUMMARY OF THE INVENTION
Accordingly, in view of the foregoing problems, an object of the present invention is to stabilize the feed condition of the sheet, and more particularly to prevent the stack displacement on a rest stand a
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Skaggs H. Grant
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