Sheet feeding or delivering – Feeding and delivering – Separator and conveyor
Reexamination Certificate
2000-03-21
2002-02-12
Ellis, Christopher P. (Department: 3651)
Sheet feeding or delivering
Feeding and delivering
Separator and conveyor
C271S111000, C271S243000, C271S270000
Reexamination Certificate
active
06345817
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a sheet separator, and more particularly, to a document sheet separator adapted for use in an optical document reader.
2. Description of the Related Art
Generally, an optical document reader is an apparatus in which documents are sent or fed one sheet at a time from the top of a stack of document sheets set in the hopper of the optical document reader to an optical document reader unit that optically reads information printed on the document. Typically, such optical document readers include a document separator for separating sheets of documents into single sheets whenever two sheets are fed from the hopper at the same time, that is, whenever a double-feed occurs. Obviously, such a double-feed is undesirable and should be avoided wherever possible.
At present the range of types of materials from which documents are made is very large. In some cases, these materials from which documents are made are such that single sheets of such documents tend to stick together, making a double-feed more likely to occur. As a result, a sheet separator with an improved ability to separate such double-fed sheets of documents into single sheets is needed.
FIGS. 1A and 1B
show an example of the prior art, that is, a conventional sheet separator. As shown in
FIGS. 1A and 1B
, the conventional sheet separator
10
A consists of one separating roller
11
, one torque roller
12
, a pulse motor
13
that rotates the separating roller
11
and a separation force application mechanism
14
that imparts a separation force F to the torque roller
12
, with the torque roller
12
being pressed against the separating roller
11
. The torque roller
12
is coupled to a torque limiter not shown in the diagram so that the torque roller
12
remains stopped even if a certain amount of torque is applied and begins to rotate only when a predetermined amount of torque is applied. The separation force application mechanism
14
can be used to adjust the separation force F.
The above-described conventional sheet separator
10
typically remains inactive unless a double-feed occurs, that is, when the first document sheet
21
-
1
is fed onward by a pick-up roller
22
and a second document sheet
21
-
2
sticks to the back of a first document sheet
21
-
1
and is dragged together with the first document sheet
21
-
1
, the first sheet
21
-
1
being the sheet positioned at the top of a stack
21
of multiple document sheets set in a hopper
20
.
In the event of a double-feed like that described above, a forward longitudinal edge of the second sheet
21
-
2
, which is on the bottom, is braked by the stopped torque roller
12
and the forward advance of the second sheet
21
-
2
is retarded thereby. At the same time, the first sheet
21
-
1
, which is on the top and against which a feed force is exerted by the separating roller
11
, slides over and separates from the second sheet
21
-
2
so that only the first sheet
21
-
1
is fed onward to the feed roller
23
by the separating roller
11
. After the first sheet
21
-
1
is fed onward the second sheet, which had been braked by the torque roller
12
and any forward progress retarded thereby, is fed onward by the separating roller
11
, with the torque roller
12
being rotated by the force of frictional contact with the second sheet
21
-
2
.
It should be noted that, for clarity of illustration only, in
FIG. 1B
the second sheet
21
-
2
on the bottom is shown slightly smaller than the first sheet
21
-
1
on the top. A similar approach is taken with respect to
FIGS. 7B
,
8
C and
8
E.
However, a problem arises with the conventional sheet separator
10
like that described above insofar as the conventional sheet separator
10
is not fully capable of separating double-fed sheets. As a result, when the coefficient of friction between sheets is large, that is, when it is hard to separate the sheets set in the hopper
20
, double-fed sheets are not separated but might pass through the document sheet separator
10
in that double-fed state.
Typically, the coefficient of friction between two documents stuck together differs depending on the type of documents in question, so the separation force application mechanism
14
described above is used to adjust the separation force F downward, that is, to reduce the separation force F in order to make it easier to separate the sheets. However, even with this adjustment of the separation force F depending on the type of paper used to make the document sheets it sometimes happens that document sheets are double-fed through the sheet separator
10
.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an improved and useful document sheet separator in which the above-described disadvantage is eliminated.
The above-described object of the present invention is achieved by a sheet separator that separates sheets of documents supplied as a stack into single sheets, the sheet separator comprising:
a first separating mechanism having a first separating roller; and
a second separating mechanism having second separating rollers,
the second separating mechanism provided at a position downstream from a position of the first separating mechanism.
According to the invention described above, the second separating mechanism separates those sheets that are fed onward without being separated by the first separating mechanism.
Additionally, the above-described object of the present invention is also achieved by the sheet separator as described above, wherein a peripheral velocity of the second separating rollers is set lower than a peripheral velocity of the first separating roller.
According to the invention described above, setting the peripheral speed of the second separating rollers slower than the peripheral speed of the first separating roller causes a compressive force to act on the top sheet of two sheets double-fed onward without being separated by the first separating mechanism, causing such a top sheet to form an upward bulge.
Additionally, the above-described object of the present invention is also achieved by the sheet separator as described above, wherein the first separating roller is positioned so as to act upon a central portion in a lateral direction of a sheet transported thereto and the second separating rollers are positioned so as to act upon edge surface portions in the lateral direction of the sheet transported thereto.
According to the invention described above, positioning the second separating rollers so as to act upon edge portions of the sheet transported thereto causes the separation force to act on locations near the corners of the top sheet of two double-fed sheets, at which locations the top sheet is more easily separated from the bottom sheet.
Additionally, the above-described object of the present invention is also achieved by the sheet separator as described above, wherein:
a peripheral velocity of the second separating roller is set lower than a peripheral velocity of the first separating roller;
the first separating roller is positioned so as to act upon a central portion in a lateral direction of a sheet transported thereto; and
the second separating rollers are positioned so as to act upon edge surface portions in the lateral direction of the sheet transported thereto.
According to the invention described above, setting the peripheral speed of the second separating rollers slower than the peripheral speed of the first separating roller causes a compressive force to act on a portion of the top sheet of two sheets double-fed onward without being separated by the first separating mechanism that lies between the first separating roller and the second separating rollers, causing such a top sheet to form an upward bulge.
Additionally, as described above, positioning the second separating rollers so as to act upon edge portions of the sheet transported thereto causes the separation force to act on locations near the corners of the top sheet of two double-fed sheets, at which
Kakegawa Hirotoshi
Kanemitsu Norio
Armstrong Westerman Hattori McLeland & Naughton LLP
Bower Kenneth W
Ellis Christopher P.
Fujitsu Limited
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