Information
-
Patent Grant
-
6465154
-
Patent Number
6,465,154
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Date Filed
Tuesday, October 17, 200023 years ago
-
Date Issued
Tuesday, October 15, 200221 years ago
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Inventors
-
Original Assignees
-
Examiners
- Baxter; Janet
- Gilmore; Barbara
Agents
-
CPC
-
US Classifications
Field of Search
US
- 430 302
- 101 141
- 101 212
- 101 216
- 101 219
- 101 224
- 101 225
- 101 226
- 101 227
- 101 228
- 101 4631
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International Classifications
-
Abstract
An elongated web of lithographic printing plate stock is intermittently fed to the drum of an external drum imaging device. The web is then cut to form the trailing end of an individual printing plate either before or after the leading end is clamped to the drum. The drum is then rotated such that the plate is wrapped around the drum and the trailing end is clamped to the drum.
Description
BACKGROUND OF THE INVENTION
The present invention relates to printing plate imaging and particularly to the feeding of an external drum imager with plates directly from a web of printing plate stock.
External drum printing plate imagers have a drum with clamps extending axially along the surface of the drum with one clamp for the leading end of a printing plate and another clamp appropriately spaced for the trailing end of the plate. The printing plate is imaged by clamping it onto the drum and then rotating the drum in the imaging apparatus with the imaging radiation scanning the plate.
In the conventional operation of an external drum imager, there is a stack of printing plates which have been pre-cut to the appropriate size usually with interleaving sheets of paper between adjacent plates to protect the imageable coating on the front faces of the plates from contact with the back faces of the adjacent plates. With automatic operation, each plate is picked up from the stack, usually by vacuum fingers, and loaded into the clamps on the drum. Provision must also be made for removing and disposing of the interleaving paper. This loading process is then repeated for each plate to be imaged.
SUMMARY OF THE INVENTION
The object of the present invention is to simplify the loading of printing plates onto an external drum imager. The invention involves the feeding of a web of printing plate stock to the drum and then cutting the web to form an individual plate of the appropriate length. The drum is then rotated so that the cut plate with the leading end clamped to the drum is wrapped around the drum and the trailing end clamped. The plate is then ready for imaging and unloading from the drum in a conventional manner.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1
is a schematic representation of the invention illustrating a printing plate web processing line feeding to the imaging drum of an external drum imager.
FIG. 2
is a schematic representation similar to
FIG. 1
but illustrating another embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In
FIG. 1
of the drawings, an external drum imaging apparatus is represented at
10
including an imaging head
12
and the drum
14
. The drum includes a printing plate leading end clamp
16
and a trailing end clamp
18
. The clamps
16
and
18
are electrically operated to clamp a printing plate onto the external surface of the drum
14
. Preferably, the clamp
18
may be moved circumferentially around the drum to accommodate various length plates. Such external drum imagers are conventional and commercially available such as from CreoScitex Inc. The operation of the clamps in the context of the present invention will be discussed later.
In the present invention as illustrated in
FIG. 1
, a web
20
of printing plate stock is provided from the roll
22
. The web is preferably continuously fed from the roll
22
by the driven feed rolls
24
. These feed rolls are controlled from the control unit
26
through line
28
. Optionally, a web of interleaving paper is wound on the roll
22
with the printing plate stock for protection and it is merely discarded as the web is unrolled. The web
20
then forms a take-up-loop
30
to compensate for the continuous web feed into the loop and the intermittent web feed downstream from the loop as will be explained.
The web
20
is pulled from the loop
30
by the feed roller device
32
which intermittently or periodically feeds the web
20
a precise distance or length corresponding to the particular plate length desired. This feed roller device
32
is also controlled from the control unit
26
through line
34
. The web
20
is fed from the feed roller device
32
through the shear
36
and over the plate conveyor
38
into the external drum imaging device
10
. The preferred arrangement feeds the web into the leading end clamp
16
before the web is cut but the web may also be cut first and then the cut plate fed some additional distance into the clamp as will be described later. When the drum
14
of the external drum imaging device
10
is at rest and in the loading position, the leading end clamp
16
and the plate conveyor
38
are aligned such that the leading end of the web feeds directly into the leading end clamp.
In the preferred arrangement just mentioned, the leading end of the plate is clamped at
16
which fixes the position of the leading end. The clamp
16
is actuated by the control unit
26
through line
40
so that it closes when the web has been fed into the clamp. The shear
36
is then actuated by the control unit
26
through line
42
to cut a plate to length from the web. For longer plates, the drum
14
can be rotated in coordination with the continued operation of the feed roller device
32
until the desired plate length has been fed and cut from the web by the shear
36
. When the web has been cut, the control unit
26
through line
44
rotates the drum
14
to bring the trailing end of the cut plate into position in the trailing end clamp
18
which is then actuated by the control unit
26
such as through line
46
to close the clamp. The trailing end clamp
18
is moveable around the circumference of the drum
14
so that it can be adjusted to accommodate different length plates as is common in such imagers. The plate is now ready to image and the drum is again rotated but in an imaging mode and the imaging head
12
is actuated through line
48
. After imaging, the imaged plate is released from the drum
14
and fed out of the imaging apparatus
10
in a conventional manner. The system is then ready to repeat the whole process.
As mentioned, an alternate arrangement is for the web to be cut prior to feeding the leading end of the web into the leading end clamp
16
. This arrangement is shown in
FIG. 2
which illustrates an individual plate
50
which has already been cut from the web
20
to form the trailing end
52
before the leading end
54
is positioned in the clamp
16
. This individual plate
50
is fed by the feed roller device
56
into the clamp after which the process continues as previously described.
Claims
- 1. A method of imaging lithographic printing plates comprising the steps of:a. feeding an elongated web of printing plate stock through a shear and feeding the leading end of said web to the drum of an external drum printing plate imager; b. clamping said leading end to said drum and cutting said web with said shear to form a trailing end of an individual printing plate of a desired length; c. rotating said drum and thereby wrapping said individual printing plate around said drum; d. clamping said trailing end of said individual printing plate to said drum; and e. imaging said printing plate.
- 2. A method as recited in claim 1 comprising cutting said web prior to clamping said leading end.
- 3. A method as recited in claim 2 and further including the step of feeding said cut individual printing plate an additional distance such that said leading end is fed into position to be clamped.
- 4. A method as recited in claim 3 and further including the step of adjusting the position of said shear from said leading end a distance corresponding to said desired length of said individual printing plate.
- 5. A method as recited in claim 1 wherein said leading end is fed into position to be clamped and comprising clamping said leading end prior to cutting said web.
- 6. A method as recited in claim 1 wherein said step of feeding said elongated web comprises intermittently feeding said elongated web said desired length of said individual printing plate.
US Referenced Citations (10)