Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
2000-10-27
2003-05-20
Ellis, Christopher P. (Department: 3651)
Sheet feeding or delivering
Feeding
Separators
C271S121000
Reexamination Certificate
active
06565079
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to document feeders, document feed methods, and image capture or reading devices, and more particularly to an automatic document feeder (ADF) and automatic document feed method in which feed a sheet from a stack of papers one by one. The document feeder and document feed method of the present invention are suitable for use with an ADF for in an image scanner, a photocopier, a facsimile unit, and other image capture devices.
Document feeders for use with image capture devices are classified into manual document feeders (MDFs) that require user's sheet-by-sheet placement of sheet to be captured on a specified table, and automatic document feeders that automatically feed in a sheet to be captured from one or more sheets which have been placed by a user on a specified table. Thus, whereas the MDFs that require a user to separate sheets to be captured into a single one, the ADFs need include separation/feed means for separating a sheet to be captured from a plurality of sheets, and feeding the same to an image capture device.
A conventional ADF
1
, as shown in
FIGS. 32 and 33
, typically includes a pick roller
2
, a separation roller
4
, a separation belt
6
, a torque limiter
8
, a leaf spring
10
, a separation pad
12
, and a transmission type sensor
14
. Hereupon,
FIG. 32
is a schematic sectional view of principal part of the conventional ADF
1
.
FIG. 33
is a schematic front view of a separation belt unit
5
in the ADF
1
.
The pick roller
2
, generally referred to as a feed roller, a pull-in roller, a dispense roller, or the like, is driven by a driving device (not shown) to rotate in an arrow direction in the drawing. The pick roller
2
touches a top of stacked papers placed on a hopper (not shown), and feeds one or more sheets from the top between the separation roller
4
and the separation pad
12
. The pick roller
2
is located above of the hopper in the width direction of and in the middle of the hopper, so that the pick roller
2
and the hopper may move relative to each other. The separation belt
6
and the separation pad
12
are disposed opposite to the separation roller
4
, and separate sheets into a single sheet in cooperation with the separation roller
4
if the pick roller
2
carries a plurality of sheets.
The separation belt
6
is an endless belt that moves depending upon the separation roller
4
, and looped over a pair of rollers
7
a
and
7
b
that are spaced in a sheet feed direction. A torque of a specified value is fixed by the torque limiter
8
and applied to the separation belt
6
. A compression force (separation load) of the separation belt
6
is applied to the separation roller
4
through the leaf spring
10
, and this force determines a frictional force (driving force), which the separation belt
6
receives from the sheet. Thus, the separation belt
6
does not rotate unless a driving force larger than a braking force determined by the set torque and a size (diameter) of the separation belt
6
is applied to the separation belt
6
. Normally, the compression force and the torque are determined in such a manner: (1) that if one sheet is inserted between the separation roller
4
and the separation belt
6
, the sheet is held and carried without slippage by the separation belt
6
; and (2) that if two sheets are inserted between the separation roller
4
and the separation belt
6
, one of the sheets in contact with the separation belt
6
is held and stopped by the separation belt
6
while only the other sheet at the side of the separation roller
4
is carried to the next stage. The separation belt
6
and the torque limiter
8
are integrated to form a replaceable separation belt unit
5
.
The transmission type sensor
14
detects a sheet at a downstream of the separation roller
4
and the separation belt
6
. An output of the transmission type sensor
14
is connected with a timer means such as a counter (not shown) and a controller, whereby the controller may work out a sheet travel time using the timer means and an output from the transmission type sensor as a trigger. As a result, if a current sheet travel time is longer than a reference value, the controller determines that the sheet (i.e., sheet travel time) is longer than usual, assuming, for example, that two or more partially overlapped sheets are being carried.
However, the conventional ADF has several disadvantages. First, the conventional ADF cannot separate sheets stably (or cannot pick up only one sheet reliably). This is contrary to a recent demand on ADFs for quick feeding of various types of sheets with distinctive properties. In addition, even the same type of sheets may differ in separating condition according to temperature and humidity. An excessively low torque would cause double feeding, then resulting in jamming and poor-quality capturing, or the like. An excessively high torque would not feed any sheet, thereby slipping and jamming sheets on the separation belt
6
. Worse yet, a user cannot easily adjust such an improper torque. For example, some experience is required to adjust the torque by the torque limiter
8
and the pressing force by the leaf spring
10
. An inappropriate adjustment would make unstable the separation belt unit
5
and other neighboring members, causing a vibration associated with a feed action, and thereby rendering unstable the sheet separating action.
In addition, the conventional ADF
1
has no means for easily identifying a cause of unsuccessful sheet separation. For example, the ADF
1
has no means for checking whether the exchangeable separation belt unit
5
is properly installed. An improperly installed or uninstalled separation belt unit
5
would sometimes enable the ADF
1
to separate and feed a highly rigid sheet (e.g., cardboard) by virtue of the separation roller
2
and the separation pad
12
. However, an unsuccessful sheet separation occurs when a user uses a low rigid sheet such as a thin sheet of paper in this condition. Thus, the user cannot easily ascribe the unsuccessful sheet separation to an improperly installed or uninstalled separation belt unit
5
. Similarly, the conventional ADF
1
has no means for checking whether the separation belt
6
is worn out, and thus a user cannot easily ascribe the unsuccessful sheet separation to the worn separation belt
6
.
Still disadvantageously, the conventional ADF
1
cannot detect double feeding reliably using the transmission type sensor
14
. because an output of the transmission type sensor
14
varies with sheet's property (such as color, thickness, type, material. and the like). In other words, the transmission type sensor
14
typically uses light-emitting and light-sensitive elements, but they do not exhibit such a high performance as to detect the double sheet feeding with transmittance. In particular, the transmission type sensor
14
can hardly detect the double feeding where different types of sheets are being fed.
Moreover, the separation belt
6
and the torque limiter
8
are both consumable in the separation belt unit
5
, and the replacement of the unit costs much.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is a general and exemplified object of the present invention to provide a novel and useful document feeder, document feed method, and image capture device, in which the above disadvantages are eliminated.
Another exemplified and more specific object of the present invention is to provide a document feeder, document feed method, and image capture device that deliver high performance in sheet separation.
Another exemplified object of the present invention is to provide a document feeder, document feed method, and image capture device that serve to identify a failed component in a sheet separation mechanism.
Another exemplified object of the present invention is to provide a document feeder, document feed method, and image capture device that can reliably detect the double sheet feeding.
In order to achieve the above objects, a document feeder as one aspect of
Amagai Tamio
Kakegawa Hirotoshi
Tabata Yoshio
Yamazaki Noriaki
Armstrong Westerman & Hattori, LLP
Deuble Mark A.
Ellis Christopher P.
PFU Limited
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