Printing – Rolling contact machines – Rotary
Reexamination Certificate
1999-11-16
2001-07-31
Yan, Ren (Department: 2854)
Printing
Rolling contact machines
Rotary
Reexamination Certificate
active
06267053
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to lithograph offset printing presses and, more particularly, to an improved shell for use in place of a standard rubber blanket when applying a perf, score or slit to a substrate in an offset printing press.
As shown in
FIG. 1
, a typical offset press printing group includes a plate cylinder
20
, an impression cylinder
22
and a blanket cylinder
24
. The blanket cylinder
24
is covered with a rubber blanket
26
and contacts the impression cylinder
22
. A printing plate
28
featuring text or images is attached to the plate cylinder
20
. Ink is supplied to the plate cylinder
20
so that the text or images of the printing plate are transferred onto the blanket cylinder
24
and ultimately onto a substrate, such as paper
32
.
As illustrated in
FIG. 1
, perforating material
34
may be placed about the impression cylinder
22
so that the printing group applies perforations to the substrate
32
instead of printed text or images. Slitting or scoring material may be substituted for, or used in addition to, perforating material
34
. As illustrated in
FIG. 2
, typical perforating material includes spaced teeth
40
with pointed or curved tips
42
that dig into the rubber blanket
26
of the blanket cylinder
24
(FIG.
1
).
The perforating arrangement of
FIGS. 1 and 2
have two significant disadvantages. First, the process damages the rubber blanket of the blanket cylinder over time so that reuse of the blanket is prevented. Second, a quality defect called a “shoulder” is produced on the substrate due to the flexibility of the rubber blanket. A shoulder, illustrated at
46
in
FIG. 3
, is a raised area on the substrate
32
that runs parallel to the perforation
48
(or score). In some instances, the shoulders may become severe enough that sheets of the substrate cannot be stacked for ease of subsequent processing.
In an attempt to overcome the above problems, shells or foils that are substituted for the rubber blanket of the blanket cylinder during perforating, slitting or scoring operations have been introduced. An example of such an arrangement is presented in U.S. Pat. No. 5,623,874 to Ruprecht. While the prior art arrangements have been effective, their performances have been less than optimal. In addition, installation of the prior art devices could be facilitated.
Accordingly, it as object of the present invention to provide a perf/score shell for presses that enables perforations, slits and scores to be formed in a substrate without creating shoulder defects.
It is a further object of the present invention to provide a perf/score shell for presses that may be used repeatedly.
It is a further object of the present invention to provide a perf/score shell for presses that enables perforations, slits and scores to be formed in a substrate going around the cylinders of the presses and across the cylinders of the presses with equal quality.
It is still a further object of the invention to provide a perf/score shell for presses that is easy to install using existing cylinder lock-ups.
It is still a further object of the invention to provide a perf/score shell that may be used on sheet-fed offset presses and the perf units of web offset presses.
SUMMARY OF THE INVENTION
The present invention is directed to a system for perforating, scoring or slitting a substrate passing between the impression and blanket cylinders of a sheet-fed offset press or the plate and blanket cylinders of a perf unit of a web offset press. The shell includes a main body constructed of a hard and flexible sheet-like substance such as stainless steel.
In the case of a sheet-fed offset press, flexible sheets constructed of rubber are attached to the end portions of the main body by rivets. Blanket bars are attached to the flexible sheets by bolts or are compressed on with adhesive. Stability strips constructed of self-adhesive foam are attached to the surface of the main body. The shell is substituted for the rubber blanket typically used on the blanket cylinder. The blanket bars engage the lock-up of the blanket cylinder. Perforation material featuring spaced teeth with flat edges are mounted onto the impression cylinder. The flat edges of the spaced teeth lightly contact or “kiss” the main body of the shell on the blanket cylinder so that perforations are formed without shoulder defects. Slitting or scoring material may be used in place of or in addition to the perforating material.
The shell may also be utilized on the perf unit of a web offset press. The end portions of the main body are folded so that borders are formed for engaging the blanket cylinder.
REFERENCES:
patent: 737052 (1903-08-01), Allen
patent: 1414104 (1922-04-01), Strawn
patent: 2199973 (1940-05-01), Sheeler et al.
patent: 3012498 (1961-12-01), Gurin
patent: 3765329 (1973-10-01), Kirkpatrick et al.
patent: 3926118 (1975-12-01), Preuss
patent: 3995555 (1976-12-01), Stewart
patent: 4006686 (1977-02-01), Ackerman
patent: 4337700 (1982-07-01), Etchell et al.
patent: 4402265 (1983-09-01), Pickard
patent: 4598641 (1986-07-01), Fischer
patent: 4951568 (1990-08-01), Tsukamoto et al.
patent: 5052120 (1991-10-01), Lubberts
patent: 5088408 (1992-02-01), Philpot
patent: 5623874 (1997-04-01), Ruprecht
patent: 5918542 (1999-07-01), Ruprecht
Hatcher Billy D.
Miske Michael T.
Environmental Specialties Inc.
Piper Marbury Rudnick & Wolfe
Yan Ren
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