Sheet feeding or delivering – Feeding – With means to align sheet
Reexamination Certificate
2001-06-05
2004-05-11
Walsh, Donald P. (Department: 3653)
Sheet feeding or delivering
Feeding
With means to align sheet
Reexamination Certificate
active
06733008
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet conveying apparatus, and an image reading apparatus and image forming apparatus having the sheet conveying apparatus and, more particularly, to a structure for correcting skew feed of a sheet.
2. Related Background Art
Some conventional image reading apparatuses or image forming apparatuses have a sheet feeding apparatus which corrects skew feed of a sheet by pressing the sheet conveyed by a conveying means against a registration roller pair to form a loop in the sheet and then conveys the sheet by rotating the registration rollers.
FIG. 10
is a view showing the structure of such a conventional sheet feeding apparatus. Referring to
FIG. 10
, a sheet stocking tray
60
stocks a sheet of paper (not shown). A pickup roller
61
picks up the sheet. A shutter
62
restrains the leading ends of the sheets set on the sheet stocking tray
60
and is released at a predetermined timing. A weight
63
is arranged at a position opposite to the pickup roller
61
and, in feeding the sheet, moves downward and clamps (a batch of) sheets to apply a sheet feeding force to them.
A sheet presence/absence sensor lever
64
is arranged upstream of the shutter
62
to detect the presence/absence of a sheet. When a sheet is abutted against the shutter
62
and set, the sheet presence/absence sensor lever
64
is pressed by the sheet and pivots to shield light to a photointerrupter (not shown). When the light to the photointerrupter is shielded, a signal representing that the light is shielded is input to a control section (not shown). On the basis of the signal, the control section detects that the sheet is set.
A lower guide plate
65
guides the sheet. An upper guide plate
66
guides the sheet. A feed roller
67
feeds the sheet. A separation belt section
68
separates the stocked sheets one by one. A loop formation space
69
allows the sheet to loop to correct skew feed of the sheet. A sheet lower guide plate
70
defines the lower surface of the loop formation space
69
. A sheet upper guide plate
75
defines the upper surface of the loop formation space
69
.
An ante-registration sensor lever
71
detects the leading end of the sheet separated one by one and conveyed by the feed roller
67
and the separation belt section
68
. The ante-registration sensor lever
71
is pressed by the conveyed sheet and pivots to shield light to a photointerrupter (not shown). When the light to the photointerrupter is shielded, a signal representing that the light is shielded is input to a control section. On the basis of the signal, the control section detects that the sheet is conveyed.
A registration roller pair
72
,
73
temporarily stop the leading end of the sheet separated one by one and conveyed by the feed roller
67
and the separation belt section
68
and forms a loop in the sheet, thereby correcting skew feed of the sheet. A sheet leading end detection lever
74
detects the leading end of the sheet conveyed by the registration roller pair
72
,
73
after the skew feed of the sheet is corrected. The sheet leading end detection lever
74
has the same structure as that of the above-described sheet presence/absence sensor lever
64
or the ante-registration sensor lever
71
.
The feed operation of the sheet feeding apparatus having the above arrangement will be described next.
When a user stocks sheets on the sheet stocking tray
60
and sets them by abutting the leading ends of the sheets against the shutter
62
, the sheet presence/absence sensor lever
64
is pressed by the sheets and pivots, and the control section detects that the sheets are set. Upon detecting that the sheets are set, the control section makes the shutter
62
pivot downward and the weight
63
move downward and clamp the sheets with the pickup roller
61
.
Next, the pickup roller
61
is rotated at a predetermined timing. Each batch of sheets is guided by the lower guide plate
65
and the upper guide plate
66
and conveyed to a feed separation section constituted by the feed roller
67
and the separation belt section
68
. After that, the conveyed batch of sheets is separated one by one and conveyed to the registration roller pair
72
,
73
by the feed roller
67
.
Each conveyed sheet reaches the registration roller pair
72
,
73
while making the ante-registration sensor lever
71
pivot. At this time, the registration roller pair
72
,
73
are kept in a stop state. The conveyed sheet abuts against the registration roller pair
72
,
73
, and the leading end of the sheet stops.
Even when the leading end of the sheet stops, the feed roller
67
continuously feeds the sheet for a predetermined time from a time when the leading end of the sheet is detected by the ante-registration sensor lever
71
. Hence, a loop is formed in the loop formation space
69
between the registration roller pair
72
,
73
and the feed roller
67
to correct skew feed of the sheet.
After the skew feed of the sheet is corrected by forming the loop, the control section rotates the registration roller pair
72
,
73
. At this time, since the feed roller
67
is kept stopped, the sheet is conveyed only by the registration roller pair
72
,
73
. As a result, the sheet is conveyed to the next process by the registration roller pair
72
,
73
while attenuating the loop.
In such a conventional sheet feeding apparatus, however, a loop is formed in a different manner depending on the type of sheet. For a certain type of sheet, a loop is abruptly formed, and the sheet strongly abuts against the sheet upper guide plate
75
in the loop formation space
69
to generate large noise. If such large noise is generated every time a sheet is fed, the noise level of the apparatus becomes considerably high.
When the registration roller pair
72
,
73
rotate after loop formation, the loop of sheet disappears. If the loop abruptly disappears, the sheet strongly abuts against the sheet lower guide plate
70
, resulting in larger noise.
A cardboard, a thick sheet of paper, or a strongly rigid sheet remains straight without forming a loop because of its rigidity even when the sheet abuts against the registration roller pair
72
,
73
that stand still, and no sufficient loop can be formed. In this case, skew feed of the sheet cannot be sufficiently corrected.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a sheet feeding apparatus capable of reducing noise and reliably correcting skew feed of a sheet, and an image reading apparatus and an image forming apparatus having the sheet feeding apparatus.
According to the present invention, there is provided a sheet conveying apparatus which corrects skew feed of a sheet by pressing the sheet conveyed by conveying means against a stationary registration roller pair so as to form a loop in the sheet and then rotates the registration roller pair to convey the sheet, comprising a loop formation space provided between the conveying means and the registration roller pair, in which the sheet forms the loop, an upper member for defining an upper surface of the loop formation space, the upper member extending in a direction of the registration roller pair which is to abut against the sheet when the sheet forms the loop, and a lower member for defining a lower surface of the loop formation space, wherein the lower member is designed to move the sheet conveyed by the conveying means toward the registration roller pair along the upper member and move downward when pressed by the sheet conveyed by the registration roller pair while attenuating the loop.
According to the present invention, preferably, the conveying means comprises a conveying member and separation means for separating the sheet upon abutting against the conveying member, and the lower member has an apex which projects upwardly with respect to a line that connects a nip of the registration roller pair and a nip of the conveying member and the separation means.
According to the present invention, the apparatus may preferably include one or
Hayakawa Yasuyoshi
Ogata Atsushi
Waragai Tsuyoshi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Rodriguez Joseph
Walsh Donald P.
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