Printing – Flexible-sheet-securing devices
Patent
1985-12-03
1987-02-10
Fisher, J. Reed
Printing
Flexible-sheet-securing devices
B41F 2706, B41F 722
Patent
active
046415769
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a clamping device for cylinders on printing machines for flexible printing plates or printing cloths, which at their ends are provided with chamferings or angle stiffeners which can be attached to a slotted shaft, which is biased by means of a torque bar spring.
Known cylinders contain in their interior clamping means for printing plates. These relatively large-sized clamping means, owing to the weakening of the effective cross-section of the cylinder, reduce the rigidity of the cylinder, so that during the printing operation the truth of rotation will be impaired. Known methods for the quick lockup of printing plates to printing cylinders, although indeed permitting a quick lockup, tolerate the lower quality of the prints produced owing to the lower rigidity of the plate cylinder.
When using printing plates consisting of a metal substrate (steel, aluminum or the like) or of an appropriate synthetic material and a photopolymer layer, the printing plate itself is fixed on the saddle plate. Such devices are known (DE-PS 22 07 138).
It may happen that depending from the use of the plate cylinders the rotation of the plate cylinder in the one or the opposite direction is desired. When in such a case printing plates are to be mounted, it will be critical that the tension shafts have the correct position in the recess of the plate cylinder, namely so that the head of a printing plate can be locked in the correct direction. Had the tension shaft not been mounted in this manner the entire unit comprising the torque bar spring and also the tension shaft, must be pulled out and-remounted after a 180.degree. turn.
The invention therefore deals with the problem of avoiding such actually undesirable re-rigging.
The solution of this problem is provided by a plate cylinder assembly according to the claim.
By means of a shaft slotted in two directions it is at all times possible to mount a printing plate in such a manner that the direction of rotation corresponds to the lockup. Simultaneously there can be adjusted the required bias since, as is known, a torque bar spring can be stresses both in the one and the other direction of rotation.
The clamping device according to the invention has the advantage that the printing plates are constantly tensioned during the printing operation in circumferential direction by means of the action of force of the torque bar spring. For the problem as to how the clamping device should be attached to the plate cylinder two alternatives are available. The clamping device could be mounted by means of inner hexagon cap screws being screwed from the outer circumference into the plate cylinder. In this case, however, the countersunk space for the cap of the screw must be filled with a plug of synthetic material. But later, when the unit should be disassembled, it is very cumbersome to remove the plastic plug again. Therefore there is in an embodiment of the clamping device according to the invention the clamping device itself attached on the printing cylinder with a screw which is located in the interior of the clamping device. However, at this position the screw would be inaccessible if the shaft itself were not provided with a through-bore of appropriate size.
The invention is described by way of example with reference to the drawing, in which
FIG. 1 shows a cross-sectional view through a clearance in a plate cylinder assembly with a tension shaft according to the invention.
FIG 2 shows at an enlarged scale a corresponding illustration including printing plates in the lockup position.
FIG. 3 shows a modified embodiment of a clamping device according to the invention.
FIG. 4 shows details of the clamping device shown in FIG. 3.
In the figures, 20 designates the recess in a plate cylinder. Into this recess fits a unit or the device, respectively, designated as a whole as clamping device. The clamping device comprises a shaft 10 and the torque spring 13. The tension shaft according to the invention is provided with two slots 11 and 12, which are disposed symmetrically to
REFERENCES:
patent: 2720673 (1948-11-01), Fischer
patent: 3382799 (1968-05-01), Luehrs
patent: 3771449 (1973-11-01), Hill
patent: 3941055 (1976-03-01), Semmler et al.
patent: 4108069 (1978-08-01), Standiford
Guthling Klaus
Meyer Adolf J.
Miethe Manfred
Fa. Wilhelm Barenschee
Fisher J. Reed
LandOfFree
Clamping device for printing plates and printing cloths on print does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Clamping device for printing plates and printing cloths on print, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Clamping device for printing plates and printing cloths on print will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2358183