Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
A PERFORATING BLADE AND SIGNATURE
This application is a divisional of Canadian patent application Serial
No. 2,199,118 filed internationally on September 7, 1995 and entered
Nationally on
March 4, 1997.
BACKGROUND OF THE INVENTION
This invention relates to an improved perforating blade and signature for
use in cutting sheet material which is to be folded and joined together.
It has been known in the printing industry of the difficulties in folding
paper
without creases or wrinkles forming on the inside page of a chopper folded
signature.
Because of the wide variety of types, sizes, and weights of paper used, the
problem
faced by the press-person is the selection of a perforating blade that matches
the
requirement of the paper being used. Some of those problems are gusseting
caused
by trying to fold multi-web sheets of paper; difficulty in adjusting a variety
of blades
used with different types of paper, which causes excessive down time; and the
inability
to bundle the resultant signatures, the folded stacks of papers which are
assembled
into a book, because the perforations caused by prior blades result in jagged
edges
which catch on each other. As a result, the modern press person usually has on
hand
a large collection of a variety of blades carefully selected from trial and
error that are
selected and utilized depending upon the type of paper, size of book and so
forth.
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A number of patents have issued in the art for perforating blades. The
Michalik patent, U.S, Patent 4,951,967, is representative. This blade comes in
three
embodiments, each comprised of a pair of blade sections joined together to
form a
single blade from which teeth have previously been ground in a variety of
configurations. The three configurations noted in Michalik are a "U" shape, an
"H"
shape, and a "Crank" shape. Each of these teeth shapes are formed by teeth
with a
straight edge from which extends a lateral edge in order to form the above-
mentioned
shapes. Each of these shapes perforate the paper on both sides of the fold
line and
are formed with straight edges at 90 degree angles, preferably. This multi-
edged,
intricate blade formed of two individually ground sections is very expensive
to create
and operate compared to the blade of the present invention.
In general, prior art blades, including Michalik and others, still fail to
solve
all of the aforementioned problems and there was still, until the present
invention, no
single blade that solved all of the aforementioned troubles. In particular,
serrated
blades known in the art, damage the ties that hold the paper together in
between cuts
because, in order to operate, they have to cut deeply. As a result, they also
damage
the opposing perforating rubber which is typically soft so as to enable the
serrated
blades to penetrate, but which results in the ties being damaged by pushing
and
spreading the tie within the soft rubber. A harder, opposing, perforating
rubber simply
does not work with the standard perforating blade. Further, the major problem,
simply
put, is that when the paper is folded, the ties binding the paper together
normally
(unless the correct blade for the correct paper is used) will result in
wrinkles.
Thus, there is a need in the art for providing a perforating blade and
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signature that enhances the twisting ability of the ties and that results in
ties that do
not lose strength during processing and for a single blade that can be used
with many
different stock weights and so that the resulting perforated signatures are
easily
bundled without unwanted gussets or wrinkles. It, therefore, is an object of
this
invention to provide an improved perforating blade and signature for use in
the printing
industry with a variety of different
stock papers and book sizes.
SHORT STATEMENT OF THE INVENTION
Accordingly, the invention provides a foldable signature foldable along an
elongated fold-line, the fold line having a number of space perforations
extending
through the plurality of sheets. The space perforations may comprise a
combination
of straight cuts and angled, straight or curved cuts. The angled cuts are
angled away
from the elongated fold line and all on a single side of the elongated fold
line. Each
of the perforations is spaced from adjacent perforations by a tie.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the present invention will
become more fully apparent from the following detailed description of the
preferred
embodiment, the appended claims, and the accompanying drawings in which:
FIGURE 1 is a perspective view of a portion of a preferred embodiment
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of the perforating blade of the present invention and showing the straight and
angled
perforating sections;
FIGURE 2 is a side elevation view of the perforating blade of FIGURE 1;
FIGURE 3 is a top plan view of a perforated signature fold line made by
the perforating blade of the present invention showing straight and angled,
curved and
straight perforations;
FIGURE 4 is a perspective view of a signature being formed after a
chopper fold and illustrating the signature fold line formed by the
perforating blade of
the present invention; and
FIGURE 5 is a cross-sectional view of a perforating cylinder and showing
a blade block and perforating blade.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment of the present invention is illustrated by way
of example in FIGURES 1 - 5. With specific reference to FIGURES 1 & 2, a
perforating
blade 10 includes unitary blade body 12 that is very narrow in width compared
to its
length. One longitudinal edge 14 is used for the formation of a single
longitudinal
straight cutting edge 16 located generally at the approximate center mid-point
18 of
unitary blade body 12. Depending on printing needs, the center mid-point 18
can be
several inches from the mathematical center of blade body 12. A series of
angled,
curved in this figure, teeth 20 and straight teeth 22 extend outward from mid-
point 18
on both sides of single, long, straight cutting edge 16. The curved teeth 20
and the
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straight teeth 22 are spaced apart from each other by gaps 24. These gaps 24
result
in uncut sections of paper, called ties, that vary in width according to the
gap 24. The
gap 24 in a preferred embodiment varies from between 1I8 of an inch to 1I32 of
an
inch throughout the fold line after each curved tooth 20. Importantly, the gap
24 after
each straight section is less than the gap 24 after each curved section so
that the tie
following the straight cut is the narrowest tie on the fold line. Tie width is
critical to the
twisting action and tinsel strength of the ties. The center portion of the
fold being the
most critical area has the minimum width tie. The outer portions have the
maximum
tie width. This also allows for a different twisting action and tinsel
strength needed
from printing press to printing press.
Referring now to FIGURE 3, the gaps 24 can be seen along the fold line
26. FIGURE 3 also demonstrates two important advantages of the present
invention
over prior art-perforating blades. To begin with, the ability of the signature
to fold has
been determined to be dependent upon the ability of the ties 28 to twist. By
means
of the present invention, the curved teeth 20 result in curved cuts 21 that
enable
twisting better than prior art straight or straight angled cuts. Angled
straight cuts 23
all to the same one side only of center cut 19 are also shown in FIGURE 3.
These
function well also, so long as the cuts are all to the same side of center
line 26 on both
sides of center cut 19, as required by the invention.
Additionally, FIGURE 3 illustrates another significant advantage of the
present invention in that the curved teeth 20 are arranged so that the
resultant curved
cuts 21 curve inwardly toward center point 18 from both sides of center point
18.
Thereby, the inventors have found, facilitating a gussetless fold. Important,
too, is that
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the fold line 26 has perforations, whether straight or curved, that extend
only on one
side 29 of the fold line 26 and not on the opposite side 30 of the fold line
26. As more
clearly shown in FIGURE 4, too, when the signature is folded along chopper
fold 34,
the elongated fold line 26 has perforations on the inside 36 of signature 32
only and
not on the outside 38 of signature 32. This means that there are no loose
edges or
flaps of paper which extend exteriorly of the fold and this enables the easy
stacking
of signatures 32 for binding without the signatures catching on each other, as
is
common with prior art perforating blades and resulting signatures. Again, the
cuts to
the inside of the fold benefit the inside portion of the folded signatures in
the
prevention of gussets and wrinkles. It also keeps the outer portion of the
signatures
free of any jagged edges that would interfere with delivery on the press,
bundling
tables and the binding process.
Referring now to FIGURE 5, there may be seen a portion of a folding
mechanism of a rotary printing press which includes a perforating cylinder 40
and
cooperating counter perforating cylinder 42. The perforating cylinder 40 has a
blade
block 44 and a pair of cheek rubbers 46 which encompass perforating blade 10.
Perforating blade 10 is located at or very near the top of blade cheek rubbers
46 so
when the signature 32 is cut by perforating blade 10 the cheek rubbers 46 help
push
the perforated paper off the blade.
An additional advantage of the perforating blade of the present invention
is that the elastic bar 48 can be much harder because the sharp narrow blade
12 of
the present invention does not have to extend so far from the cheek rubbers 46
to cut
the signature 32 as required by most blades known in the art. Again, as a
result, the
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elastic bar 48 can be much harder. As a further result, the signature 32 is
not
captured within a groove that forms early in the soft elastic bars of prior
art blades .
Therefore, the perforations of the present perforating blade are clean and
sharp and
the ties are not stretched or broken by the action of the blade being removed
from a
deep groove as normally occurs, again, with soft elastic bars of the prior
art.
A further advantage of the thin, narrow blade 12 of the present invention
is that , because it is able to be located at or below the cheek rubber level,
it reduces
blade flick, the action of the blade flicking against the elastic bar as it
rotates out of the
channel normally formed in the elastic bar. This minimizes wear and tear on
the blade
and minimizes stress on the ties. The curvature of the curved edge, when used,
is
designed to prevent damage to the cutting surface by having the same
circumference
as the counter part cutting surface with a minimum depth requirement.
Importantly,
the curved and straight edges all to the same side enhance the twisting action
of the
ties during chopper fold. They also allow for a wider range of chopper and
delivery
adjustments.
In general, the perforating blade 10 of the present invention) enables
signatures to be folded more advantageously than prior art perforating blades
because
perforating blade 10 results in the creation of ties 28 that twist
mechanically and
easily. This is the result of the straight andlor curved teeth 20 that are, in
the preferred
embodiment, angled generally at 22 degrees. In general, however, the best
results
are achieved in straight andlor curved teeth that are angled from 10 to 40
degrees.
The blade may have all curved cuts with the exception of straight cutting edge
16.
Further, a preferred embodiment of the present invention includes a repeating
pattern
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of three angled, straight or curved teeth 20 followed by a straight tooth 22.
The
purpose of the intermittent straight tooth is to provide a signature that has
straight
cuts, interspersed with the angled cuts, that help the signature hold the fold
line 26
when folded. It should be recognized that curved teeth 20 could be "U" shaped
or
straight angled so long as the pattern and placement is as described herein.
Again, the perforating blade 10 of the present invention results in a
signature with a fold line comprised of a succession of angled, straight
andlor curved
cuts and straight cuts. A series of ties, 28, result with the outside of the
angled cut
pointing toward the chopper fold line 34 starting from the outer edges of the
folded
signature, as shown in FIGURE 4. This results in opposite angled cut ties 28
facing
toward the center from the two sides of the chopper fold 38. That is, all of
the angled
cut ties start generally at the outer edge and angle toward the inside of the
folded
signature as shown in FIGURE 3. The inventors have found that this direction
gives
the tie 28 its best twisting action during the chopper fold sequence. One
reason is that
the angled cut cuts across the grain of the paper and weakens it thereby
enabling it
to twist more easily.
The present invention provides an improved perforating blade and
signature which eliminates the need for press operators to collect an
expensive array
of blades for use with various weights, sizes and types of paper and finishes.
A single
blade of the present invention can be utilized with the complete range of
papers seen
by press-persons, is economical and simple in design, and has the important
advantage of providing a blade that is versatile and easy to use.
While the present invention has been disclosed in connection with the
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preferred embodiment thereof, it should be understood that there may be other
embodiments which fall within the spirit and scope of the invention as defined
by the
following claims.
