Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
2001-05-15
2004-08-03
Walsh, Donald P. (Department: 3653)
Sheet feeding or delivering
Feeding
Separators
Reexamination Certificate
active
06769680
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet feeding apparatus which feeds sheets and an image forming apparatus such as a copier, a facsimile, a printer or a multi function peripheral (MFP) having functions of these apparatuses which is equipped in a main body with the sheet feeding apparatus.
2. Related Background Art
A sheet feeding apparatus is conventionally assembled, for example, in a main body of an image forming apparatus and feeds sheets to image forming means which forms an image. The image forming apparatus forms images on individual sheets. A sheet separating mechanism which separates the sheets one by one is disposed in the sheet feeding apparatus assembled in such an apparatus which carries out any treatment on the individual sheets.
As an example of this sheet separating mechanism, there is a slant surface type sheet separating mechanism which separates sheet by utilizing a slant surface. This slant surface type sheet separating mechanism is configured to stop a leading end of an uppermost sheet fed (sent) by a sheet feeding roller with the slant surface and guide the uppermost sheet along the slant surface. Should a plurality of sheets be sent out following the uppermost sheet sent by the sheet feeding roller, the sheet separating mechanism stops and disposes leading ends of the plurality of sheets with the slant surface, thereby feeding the sheets one by one in a separated condition.
Usable as sheets which can be separated with the sheet separating mechanism are various kinds of articles such as paper, resin sheets, thin paper, thick paper, postal cards, letters and the like.
Referring now to
FIG. 9
, description will be made of a configuration of a sheet feeding apparatus in which the slant surface type sheet separating mechanism is assembled.
A sheet feeding apparatus
101
is composed of a sheet feeding tray unit
102
in which sheets to be fed are mounted, a sheet feeding unit
103
which is to feed the mounted sheets consecutively, a conveying unit
104
which conveys the fed sheets to an image forming unit
3
, for example, of an image forming apparatus
1
shown in FIG.
1
and the like.
The sheet feeding tray unit
102
is composed of a sheet feeding tray
121
on which sheets S are to be mounted, a separating slant surface plate
122
which stops, disposes and separates the sheets at a sheet feeding time while guiding the sheets obliquely, and the like. The separating slant surface plate
122
is the slant surface type sheet separating mechanism.
The sheet feeding unit
103
is composed of a sheet feeding arm
114
which is rotatably attached to a driving shaft
113
, a driving gear
112
which is integrated with the driving shaft
113
, a sheet feeding roller
105
rotatably disposed at a rocking end of the sheet feeding arm
114
, a following gear
123
which is integrated with the sheet feeding roller
105
, a gear train
124
which consists of six idler gears
111
,
110
,
109
,
108
,
107
and
106
which are provided on the sheet feeding arm
114
to transfer the rotation of the driving gear
112
to the following gear
123
, and the like.
The conveying unit
104
is composed of a lower guide
115
which guides a bottom surface of a fed sheet, an upper guide
116
which is integrated with the lower guide
115
and guides a top surface of the fed sheet, a roller holder
119
which is rotatably supported by the upper guide
116
, a conveying roller
117
which is disposed on the lower guide
115
and conveys the fed sheet in a predetermined direction, a conveying roller
118
which is rotatably disposed in the roller holder
119
in opposition to the conveying roller
117
, a conveying spring
120
which urges the roller holder
119
so that the conveying roller
118
is pressed to the conveying roller
117
and the like.
Now, feeding operations of the sheet feeding apparatus will be described on the basis of
FIGS. 9
to
11
.
At a sheet feeding time and a stop time, the driving shaft
113
is rotated and stopped under rotating control with a controllable driving mechanism (not shown). When sheet feeding is to be started, the driving shaft
113
is rotated with a rotating drive force of the driving mechanism (not shown). This rotation is transmitted from the driving gear
112
to the following gear
123
by way of the gear train
124
, whereby the sheet feeding roller
105
starts rotating. By urging means (not shown) and due to weights of the sheet feeding arm
114
, the sheet feeding roller
105
, the gear train
124
and the like, the sheet feeding arm
114
which is holding the sheet feeding roller
105
revolvably around the driving shaft
131
is subjected to a force in a direction to be rotated counterclockwise in the drawings. Due to this force, the sheet feeding roller
105
is in light pressure contact with a top surface of a sheet which is uppermost out of sheets mounted on the sheet feeding tray
121
.
Accordingly, exerted to the sheet is a feeding force which is produced in a sheet feeding direction by a frictional force when the sheet feeding roller
105
starts rotating. At this time, the sheet is pressed to the separating slant surface plate
122
and subjected to a reaction force F. That is, a leading end portion of the sheet is subjected to the feeding force of the sheet feeding roller
105
while being pressed to the separating slant surface plate
122
. As a result, the leading end portion of the sheet is curved. In a condition where the sheet is curved, the leading end of the sheet slides along the separating slant surface plate
122
toward the lower guide
115
. When the sheets are to be sent out in an overlapped condition at this time, leading ends of the overlapped sheets are separated by the separating slant surface plate
122
and only one sheet is sent out. An advancing direction of the sheet is determined by the upper guide
116
and the lower guide
115
, whereby the sheet enters a nip formed between the conveying roller
118
urged toward the carrying roller
117
by the carrying spring
120
and the conveying roller
117
, and further conveyed by the conveying roller
117
in a direction indicated by an arrow A.
When a thick sheet having a high rigidity is to be fed, however, the conventional sheet feeding apparatus
101
may hardly curve the leading end portion of the thick sheet having the high rigidity with the separating slant surface plate
122
, thereby allowing a sheet feeding pressure to be enhanced autonomously by rotations of a motor of the driving mechanism which rotates the driving shaft
113
and increasing a torque which is required for driving the sheet feeding roller
105
.
Accordingly, the conventional sheet feeding apparatus uses a motor which has a large output torque so that even the thick sheet having the high rigidity can be fed by rotating the sheet feeding roller
105
. However, the motor which has the large output torque is expensive and large. Accordingly, the conventional sheet feeding apparatus is expensive and may be large due to a large space required for installing the motor.
Furthermore, a small angle &agr; is formed between the sheet feeding arm
114
and the sheet feeding tray
121
as shown in
FIG. 10
when a large number of sheets are mounted on the sheet feeding trays
121
. The sheet feeding roller
105
is subjected to the reaction force F of the sheet feeding force when rotated. This reaction force F is divided into a component of force N in a direction of the sheet feeding pressure and a component of force T in a direction along a longitudinal direction of the sheet feeding arm
114
. However, the force N in the direction of the sheet feeding pressure is low since the angle &agr; is small. Accordingly, a sheet feeding force remains weak since the sheet feeding pressure is not so high. When the thick sheet having the high rigidity is fed, the sheet feeding apparatus
101
is therefore incapable of advancing the sheet along the separating slant surface plate
122
and may cause improper sheet feeding. The angle &agr; is a
Fukuda Masayuki
Inoue Ryukichi
Kojima Ryuichi
Rodriguez Joseph
Walsh Donald P.
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