Patent Grant
7669529
The invention relates to methods and apparatuses for loading sheet materials on drums such as those employed in plate-setting machines in the printing industry.
In the printing industry, the inclusion of a computer-to-plate (CTP) system in a printing operation suggests a great extent of automation. A full CTP process can automate, through the use of computers and special equipment, the transfer of information from the original layout to the press plate. A computer-to-plate (CTP) system accepts input jobs/pages written in a page description language, for example, Postscript, and the jobs are sent through a raster image processor to a platemaker for exposure. The platemaker engine images the raster data on a plate, which is later mounted on a press, inked and made ready for printing.
Also included in the automation of a CTP system is the media handling. It is necessary to supply plates individually from a plate supply area to the platemaker engine and it is desirable to reduce the amount of operator handling involved. Unexposed plates are normally supplied in packages of 10 to 100 plates, with interleaf paper-sheets between the plates for protecting the emulsion side of the plates, which is extremely sensitive to scratches. The stack of plates is loaded into a supply area of a platemaker in a manner that keeps the stack of plates aligned with automation mechanisms for removing a plate from the stack, and for discarding the interleaf sheets from the stack.
While smaller plates can be loaded by hand, the advent of large printing plates has necessitated the automatic loading of plates onto the sheet materials drum or imaging drum of the CTP platesetter apparatus. While medium-sized platemaking machines with imaging drums of a few feet in length are common-place and printing plates are comparatively easy to load onto or unload from such machines, the same cannot be said for larger machines. The printing industry requires placement of plates with great accuracy when moving over distances of a meter or more. Under pressure from the printing industry for ever greater throughput, the latest generation of extra large format platemaking machines being developed at this time has imaging drums of more than 3 meters in length. At the same time there is no quarter to be sacrificed in quality and precision. It is therefore necessary to be able to load and unload extremely large and heavy materials sheets of the order of 3.15×1.60 meters in size automatically with great accuracy and precision.
One of the proven ways of securing a printing plate for imaging to an imaging drum is to employ spring loaded clamps to clamp the leading edge of the plate to the drum, to then wrap the plate around the drum and to then secure the trailing edge of the plate. In view of the larger and heavier plates being employed, one of the mechanisms developed to automatically open the clamps is to have a push rod, movably attached to a backbone that typically runs the length of the drum, that is moved down towards the clamp to push upon it in such a way as to compress the spring providing the clamping force, thereby opening the clamp and allowing the edge of the plate to be removed from the clamp.
While this was a relatively simple matter in the case of smaller machines, it becomes a rather more complex matter in systems with long imaging drums. In such large systems the sheer length of the backbone carrying the push rods, together with the greater pushing forces required to release large heavy plates from more substantial clamps, can cause the very backbone itself to flex in reaction. This complicates the loading and unloading of the printing plate involved. The same challenge translates to the presses used for printing with such large plates. Both kinds of machines have a drum, the platemaking machine and imaging drum and the press having a drum for mounting the plate imaged by a platemaking machine.
Thus, there remains a need for a simple, flexible and efficient method to load very large printing plates automatically with accuracy and precision onto a sheet materials drum for imaging, and to unload the imaged plates from the drum.
Briefly, according to one aspect of the present invention a method and apparatus provides for mounting and demounting a materials sheet onto and from a sheet materials drum such as those used in the printing industry. A drum has at least one clamp pivotably arranged upon it. The clamp has a first region and a second region, and the second region clamps the materials sheet to the cylindrical surface of the drum. The pivot axis of the clamp is between the first region and the second region of the clamp, allowing the second region to clamp the materials sheet to the cylindrical surface when the first region of the clamp rises and allowing the second region to release the materials sheet when the first region is depressed by a push rod. The push rod is mounted movably on a backbone that extends along the length of the sheet materials drum proximate the cylindrical surface. In order to prevent the backbone flexing and thereby impeding the mounting and demounting of the materials sheet, the backbone is removably attached to the sheet materials drum prior to the pushing by the push rod. The pushrod is then pushed against the second region of the clamp to thereby raise the first region. This makes it possible to either remove a materials sheet that was clasped by the second region of the clamp, or to position a materials sheet in that location. In the case of the latter, the second region of the clamp then clasps the materials sheet to the cylindrical surface when the push rod is operated to not push on the second region of the clamp.
In one embodiment of the present invention the removably attaching is accomplished by attaching the backbone to the sheet materials drum using a latching arrangement. The latching arrangement comprises a latch that is pivotably arranged on the backbone and which engages with a slot in the sheet materials drum. More specifically, a protrusion on the latch engages with a ledge of the slot. A plurality of clamps, push rods and latches may be arranged along the length of the backbone and sheet materials drum to thereby reduce flexing of the backbone and improve the handling of materials sheets. Before removably attaching the backbone to the sheet materials drum, the backbone can be positioned proximate the cylindrical surface of sheet materials drum. After detaching the backbone from the sheet materials drum, the backbone can be relocated away from the cylindrical surface of the sheet materials drum.
In the drawings which illustrate non-limiting embodiments of the invention:
a shows the arrangement and working of the clamp and pushrod of
b shows the arrangement and working of the clamp and pushrod of
Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense.
At least one clamp 40 is arranged on cylindrical surface 20 of drum 10 to pivot about pivot axis 60, thereby to clamp the leading edge of materials sheet 50 by means of clamp proximal end 70. Pivot axis 60 and distal end 80 of clamp 40 can optionally be recessed below cylindrical surface 20 of drum 10. Proximal end 70 of clamp 40, however, is arranged to allow materials sheet 50 to be clamped to cylindrical surface 20 by clamp proximal end 70 and therefore proximal end 70 at least partially protrudes outside of cylindrical surface 20. In this arrangement clamp proximal end 70 rises with respect to drum 10 when clamp distal end 80 is depressed toward cylindrical axis 30. Conversely, clamp proximal end 70 closes down towards cylindrical surface 20 when clamp distal end 80 rises away from drum 10. Clamp distal end 80 is spring loaded (shown in more detail in
Push rod 90 is movably arranged on backbone 120 and latch 130 is rotatably arranged on backbone 120. Latch 130, having latch protrusion 160, can be rotated in direction 140 about latch rotation axis 150. Push rod 90 can be moved in direction 100 to press upon distal end 80. When push rod 90 pushes against clamp distal end 80, materials sheet 50 is no longer clamped by clamp 40 and can be removed.
a and
a shows clamp 40 in its closed position, clamping materials sheet 50 to cylindrical surface 20 of drum 10 by means of proximal end 70. Springs 190 provide the force on distal end 80 of clamp 40 to thereby close clamp 40 by pivoting it about pivot axis 60. Push rod 90 is in its retracted position on backbone 120, having been moved along direction 100.
b shows clamp 40 in its open position, releasing materials sheet 50 from cylindrical surface 20 of drum 10 by proximal end 70 being in a raised orientation. Springs 190 are compressed by the action of push rod 90 on backbone 120 pushing on distal end 80 of clamp 40 along direction 100. Clamp 40 is pivoted about pivot axis 60.
The apparatus of the present invention may have a plurality of clamps 40 and may have a plurality of push rods 90 and a plurality of latches 130, a plurality of sets of these devices being required to attach large materials sheets to extra large format drums, 3.15×1.6 meter plates having to be attached to drums of length greater than 3.15 meters in some cases. In a further embodiment of the present invention backbone 120 is capable of being relocated closer to or further away from cylindrical surface 20 of drum 10.
In operation, as shown in the flow diagram of
In operation, as shown in the flow diagram of
In a further embodiment of the present invention, backbone 120 is maintained in a fixed position proximate cylindrical surface 20, but with suitable clearance for drum 10 and any clamps 40 to safely rotate past it. In this embodiment neither the method for clasping materials sheet 50 to cylindrical surface 20 of drum 10, as shown in the flow diagram of
In both the method of clasping and the method of releasing described herein backbone 120 may be removably attached onto drum 10 by a number of different alternative mechanisms, including but not limited to that of a latch 130 having a protrusion 160 that engages a ledge 180 of a slot 170 in drum 10.
Furthermore, slot 170 is not limited to being parallel to cylindrical axis 30 and may have any other orientation that allows a part of latch 130 to engage with it or any part of it, including but not limited to slot 170 being aligned perpendicular to cylindrical axis 30. Latch 130 can correspondingly be arranged on backbone 120 in any orientation that allows it to engage with slot 170 or any part of it.
The arrangement as described here prevents backbone 120 from flexing when a plurality of push rods push against a plurality of distal ends 80 of a plurality of clamps 40 arranged along the length of a long sheet materials drum 10. The invention thereby ensures smooth functioning of automated sheet materials loading and unloading operations.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the invention.
| Number | Name | Date | Kind |
|---|---|---|---|
| 6260482 | Halup et al. | Jul 2001 | B1 |
| 6752080 | Fukui | Jun 2004 | B2 |
| 20010032561 | Halup et al. | Oct 2001 | A1 |
| 20030037688 | Fukui | Feb 2003 | A1 |
| 20030051621 | Fukui | Mar 2003 | A1 |
| 20050193913 | Toledo | Sep 2005 | A1 |
| Number | Date | Country |
|---|---|---|
| 1 364 779 | Nov 2003 | EP |
| Number | Date | Country | |
|---|---|---|---|
| 20090151580 A1 | Jun 2009 | US |
