Sheet-material associating – Associating and folding – Stapling or stitching
Reexamination Certificate
1999-08-04
2002-05-28
Ellis, Christopher P. (Department: 3651)
Sheet-material associating
Associating and folding
Stapling or stitching
C493S469000, C493S424000, C493S442000, C493S454000
Reexamination Certificate
active
06394441
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to paper handling. More specifically, the invention relates to folding and manipulation of stapled documents.
BACKGROUND OF THE INVENTION
One commonly used method of permanently fixing multiple pages is stapling of the pages. When print jobs are produced by laser printing, photocopying and other short-run processes, it may be desired to fold or otherwise manipulate assembled documents. In the prior art, this was either done by hand, or by the use of paper handling equipment, such as sheet folders.
One of the aspects of sheet folders is that it was necessary to separately align individual documents. This increased the expense of paper folding equipment. In addition, the staples present alignment problems, particularly if staples are to be in alignment with the fold. Generally, the fold should occur along a staple line.
In the case of documents which are produced by the use of laser printers or photocopiers, any additional procedures involved in producing a final product, such as folding equipment, require the use of additional equipment. This additional equipment would be either within the printer or external to the printer, but in either case requiring additional expense and bulk. That means that the ability of providing office printers which are capable of providing assembled booklets or other multi-page brochures is limited. It would be desired to provide a printer arrangement which allows assembly of multiple sheets of paper or other sheet media, but does not require a substantial investment in additional equipment for folding and other paper handling purposes. It is desired that the additional features be provided without making the printer or copier substantially more complicated or less economical to operate. It is therefore desired to provide a simplified automatic paper folder for such equipment.
In providing such a paper folder, it is important that the staples be aligned when using a folding blade or other creasing device. If the staples are not aligned, the folding line will occur at the wrong position on the document. While having the staples in a staple line collinear to a fold is a minor inconvenience; an angular misalignment creates an unsightly appearance and is also objectionable to readers of the document. Angular misalignment is more critical and can result in the staples being skewed, as well as the folded document itself being skewed with respect to itself. Thus, if an 11″×17″ ledger or (double letter size, 27.94×43.18 cm) document is folded to form two letter size halves per sheet, a 1° misalignment will result in an offset in the x and y directions of 4.8 mm and 3.8 mm, respectively.
FIG. 1
shows the results of misalignment of such a job in millimeters of offset versus angular alignment when using ledger size sheets.
In the prior art, mechanical force is used to transmit motion to a “feeding blade” or to create a “buckle” in the sheets. This requires either a motor or additional mechanism to cause this mechanical force. The feeding blade can get stuck between folding rollers, especially when folding documents having large numbers of sheets. At that point, a high force is needed to release the feeding blade and causes the document to be marked by the exertion of the release force. It is also necessary to position the job extremely accurately; otherwise, the folding line will not be centered or will not be perpendicular, causing an unacceptable booklet quality.
In addition, the paper folding mechanism must, prior to folding the documents, transport the documents to an appropriate location for folding. This means that, often after the documents are assembled or otherwise sorted at a discharge end of a printer, these documents must again be handled. This can result in mishandling of the documents and of course results in increased complexity of the equipment.
In describing the invention, the term “paper” is used to describe paper, as well as other forms of sheet media. “Document” is intended to describe one or more sheets which may be in the form of a booklet. A “print job” may include multiple copies of a document. A document can take a number of forms, but is often an assembly of sheets of paper or other sheet media. In this invention, the documents are generally bound by a row of staples. Typically, this is a “booklet,” sometimes called “saddle stitch and fold.” A booklet has more than one page, usually two to five or more pages. It has one or more staples that hold the pages together. The staples are located along a line, approximately at the middle of the page. Unless portions of the booklet are intentionally offset, and after the pages are stapled, the pages are folded along a staple line, meaning a line defined by the staples.
Typically, the process to make a booklet is to add a set of staples, usually in the middle of the sheet, as shown in FIG.
2
. Once the document is stapled, it is folded at the center line so that it has a book appearance, as shown in FIG.
3
. In a “feeding blade” approach, a document is positioned extremely accurately, so that the staples are nearly exactly above a feeding blade and below a nip defined by a pair of folding rollers. The feeding blade is then shifted toward the nip in order to feed the stack of papers toward the nip of the folding rollers. By friction, the folding rollers grab the stack. At this time, the blade retracts back to its original position away from the nip, thereby avoiding the feeding blade being trapped by the feeding rollers. This procedure is shown in
FIGS. 4 and 5
.
There are two key points in the process in which accuracy is essential. The first is when the blade initiates the feeding movement. At that time, the staples must be precisely aligned with the blade. If this does not occur, the folding line will be at the wrong position, or diagonal to the edge of the stack. This would make the booklet unacceptable. This misalignment is shown in
FIG. 6
, and is important in order to achieve a proper print job. The misalignment can be characterized, referring to
FIG. 6
, by the following equations:
FIG.
6
. Impact of the Alignment of the Job
a
+
b
=
l
sin
θ
=
y
b
tan
θ
=
(
b
-
a
)
2
h
2
=
b
-
a
h
sin
θ
=
2
y
h
tan
θ
+
1
tan
θ
=
2
b
-
1
h
y
=
h
sin
θ
tan
θ
+
1
sin
θ
2
b
=
h
tan
θ
+
1
2
cos
θ
=
x
+
a
b
=
x
+
1
-
b
b
1
+
cos
θ
=
2
(
x
+
1
)
h
tan
θ
+
1
(
1
+
cos
θ
)
(
h
tan
θ
+
1
)
2
-
1
=
x
x
=
h
(
sin
θ
+
tan
θ
)
+
(
1
+
cos
θ
)
2
1
According to these equations, a 1° misalignment when folding an 11″×17″ (ledger size or double letter size sheet) would represent an offset of
x=4.8 mm
y=3.8 mm
FIG. 1
shows the behavior of the variables x and y, when the angle varies from 0° to 20° in a ledger size booklet. The steep slope of these lines is notable.
In another prior art technique, a “buckle approach” is used. This is schematically shown in FIGS.
7
. In
FIGS. 7A and B
, a stack of sheets is fed until the leading edges of the sheet find a stop. As the feeding process continues, the stack is forced to deform upwards, as shown in
FIGS. 7C and D
, creating a buckle. When the buckle is high enough, it contacts a pair of folding rollers, which by friction grabs the stack and creates the folding line, as shown in
FIGS. 7D-F
. This method has the disadvantage of being hard to control with respect to accuracy of the alignment of the folding line. This is particularly
Cruz Israel
Guerrero Marco A.
Obregon Roberto
Ellis Christopher P.
Mackey Patrick
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