Printing – Print plate feeding or delivering
Reexamination Certificate
2000-06-29
2002-10-22
Evanisko, Leslie J. (Department: 2854)
Printing
Print plate feeding or delivering
C101S415100
Reexamination Certificate
active
06467411
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a printing plate mounting apparatus, and relates in particular to a printing plate mounting apparatus that precisely aligns a printing plate with a plate cylinder and subsequently secures the printing plate to the plate cylinder.
2. Description of the Related Art
Various well known techniques are employed to mount press plates or printing plates (which are materials of the press plates) onto the plate cylinders of printing apparatuses or exposure apparatuses.
But since the sizes of printing lots are steadily becoming smaller, and since there is a continuing growth in the variety of the matter that is being printed, the need is increasing for printing plates (described in this specification as flexible printing plates) that can be produced by depositing layers of photosensitive substances on inexpensive, easily handled supports composed of materials other than metals (e.g., plastic film or paper).
Since a flexible printing plate is less capable of retaining its size and shape than a printing plate for which a metal is used as a support, i.e., it is less rigid, precisely mounting such a flexible printing plate on a plate cylinder is a very complicated process. For this reason, a number of different techniques have been proposed for the mounting of flexible printing plates on plate cylinders.
FIG. 9
is a schematic diagram illustrating one printing plate mounting apparatus
60
for mounting a flexible printing plate on a plate cylinder in a printing apparatus. The printing plate mounting apparatus
60
comprises: a plate cylinder
61
, on which a flexible printing plate
70
composed of a flexible material is to be mounted; a rubber cylinder
65
, which is positioned adjacent to the plate cylinder
61
; and holding mechanism
51
, for holding the flexible printing plate
70
.
The plate cylinder
61
is shaped as a cylinder from which part has been removed, in the axial direction, to provide a substantially flat face (hereinafter referred to as a flat face
61
a
) in which a groove is formed. Provided in the groove are a head clamping mechanism
62
, for engaging a plate head
70
a
(that is, a tip end of the printing plate
70
, the leading end of the flexible printing plate
70
; and a tail clamping mechanism
63
, for engaging a plate tail
70
b,
the trailing end of the flexible printing plate
70
. The clamping mechanisms
62
and
63
respectively include: lower jaws
62
b
and
63
b,
the top face of each of which lies substantially along the same plane as that of the flat face
61
a;
and upper jaws
62
a
and
63
a,
which are supported rotatably, by the lower jaws
62
b
and
63
b
so that the plate head
70
a
and the plate tail
70
b
can be clamped between the upper jaws
62
a
and
63
a
and the lower jaws
62
b
and
63
b.
A top portion
61
c
is formed between the flat face
61
a
and a curved face
61
b
of the plate cylinder
61
. Although not shown, for some cylinders a top portion is formed between the curved face
61
b
and the upper face of the lower jaw
62
b
of the clamping mechanism
62
, instead of the flat face
61
a.
Generally, the portion whereat the flat face
61
a
meets the curved face
61
b
is rounded to form a curved face having a radius of 10 to 20 mm. In this specification, this portion is also called a top portion.
The rubber cylinder
65
can be brought into contact with or separated from the plate cylinder
61
, and when the flexible printing plate
70
is mounted around the plate cylinder
61
, it can be held and pressed between the rubber cylinder
65
and the plate cylinder
61
.
The holding mechanism
51
is provided for the printing plate mounting apparatus
60
because mounting the less rigid flexible printing plate
70
around the plate cylinder
61
would be an extremely difficult and complicated process were it performed by hand. The design of the holding mechanism
51
provides for the positioning of guide rollers
53
at the distal ends of support members
52
projecting outward from a plate member
50
a.
In the printing plate mounting process, first, an operator loads a flexible printing plate
70
into the holding mechanism
51
. Then, as is shown in
FIG. 10
, while supporting the head
70
a
of the flexible printing plate
70
the operator guides it between the upper and lower jaws
62
a
and
62
b
of the head clamping mechanism
62
. The seating of the plate head
70
a
is adjusted by positioning mechanism, such as resister pins or stoppers (not shown) While thus disposed, the plate head
70
a
is secured in place by closing the upper jaw
62
a
in the direction indicated by an arrow A. Thereafter, as the plate cylinder
61
is rotated, the flexible printing plate
70
is wound around the plate cylinder
61
.
However, precisely mounting a flexible printing plate
70
on the plate cylinder
61
is still a difficult task. Even when, as is shown in
FIG. 10
, the head
70
a
of the flexible printing plate
70
is inserted and positioned between the upper and lower jaws
62
a
and
62
b
on the print cylinder
61
, as the upper jaw
62
is closed, the head
70
a
tends to be displaced in the direction (the direction indicated by an arrow B) that causes it to be removed from the head clamping mechanism
62
.
When the plate head
70
a
is displaced, position adjustment mechanism (not shown), provided for the head clamping mechanism
62
, can be used to move the head clamping mechanism
62
, at the bottom of the groove in the plate cylinder
61
, in several directions so as to adjust the position of the plate head
70
a.
However, at this time, the tail clamping mechanism
63
must be simultaneously moved by the position adjustment mechanism (not shown), and since the operation of the position adjustment mechanism is therefore extremely complex and requires a high degree of skill, this procedure is not practical.
As the result of a thorough study, the present inventors had found the following. When, as is shown in
FIG. 10
, the portion of the flexible printing plate
70
that is nearer the tail than is the portion that the rotating tip of the upper jaw
62
a
contacts is bent away from the plate cylinder
61
, because of the weight of the flexible printing plate
70
, a constant force is exerted that removes the plate head
70
a
from a position between the upper and lower jaws
62
a
and
62
b.
Therefore, when the upper jaw
62
is closed in the direction indicated by the arrow A, the flexible printing plate
70
slides across the rotating tip of the upper jaw
62
a,
and is displaced in the direction in which the plate head
70
a
is disengaged from the head clamping mechanism
62
(the direction indicated by the arrow B). That is, since the flexible printing plate
70
is supported by the rotating tip of the upper jaw
62
a,
which acts as a fulcrum as the upper jaw
62
a
is closed and the rotating tip moves toward the plate head
70
a,
the flexible printing plate
70
slides across the rotating tip and is displaced in the direction in which it is removed from the head clamping mechanism
62
.
Further, the present inventors have also found that when there is play in the head clamping mechanism
62
, the upper jaw
62
a
moves spasmodically when the upper and lower jaws
62
a
and
62
b
are closed, and could result in the displacement of the plate head
70
a.
SUMMARY OF THE INVENTION
To resolve the shortcomings, it is one objective of the invention to provide a printing plate mounting apparatus that can precisely and easily mount a printing plate on a plate cylinder.
To achieve this objective, according to the invention, a printing plate mounting apparatus comprises:
a plate cylinder, for which a plate head clamping mechanism having upper and lower jaws is provided to position and secure a plate head of a flexible printing plate; and
a guide member for guiding the flexible printing plate to the plate head clamping mechanism before the plate head is positioned and secured,
wherein the guide member guides the flexible printing plate so
Nakayama Takao
Naniwa Mutsumi
Oishi Chikashi
LandOfFree
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