The present invention relates generally to printing presses and more particularly to a variable cutoff alignment apparatus for a printing press and a method of aligning printing cylinders during a cutoff change.
In order to vary a cutoff length of signatures printed by a printing press, plate cylinders, blanket cylinders and impression cylinders may have to be removed from the printing press and replaced with respective cylinders having circumferences that correspond to a new desired cutoff length. Alternatively, each cylinder may include a sleeve that may be removed and replaced with a sleeve having a circumference that corresponds to the new desired cutoff length. Changing cylinders or sleeves may require the mechanisms supporting the cylinders to be separated from one another. After the change, the new cylinders may need to be brought back into contact with one another at a desired position.
A variable cutoff cylinder alignment apparatus is provided. The variable cutoff cylinder alignment apparatus includes a plate cylinder support box for supporting an exchangeable variable cutoff plate cylinder, the plate cylinder support box including an exchangeable plate cam, a blanket cylinder support box for supporting an exchangeable variable cutoff blanket cylinder, the blanket cylinder support box including an exchangeable blanket cam and an alignment stop for aligning the variable cutoff blanket cylinder and the variable cutoff plate cylinder. The exchangeable plate cam capable of contacting the stop and the exchangeable blanket cam capable of contacting the plate support box to align the variable cutoff blanket cylinder and the variable cutoff plate cylinder for different sized cutoffs.
A method of aligning printing cylinders during a cutoff change is also provided. The method includes the steps of removing a first plate cylinder and a first plate cam from a plate cylinder support box and removing a first blanket cylinder and a first blanket cam from a blanket cylinder support box; mounting a second plate cylinder and a second plate cam on the plate cylinder support box and mounting a second blanket cylinder and a second blanket cam on the blanket cylinder support box; and aligning the second plate cylinder and the second blanket cylinder by contacting an aligning stop with the second plate cam and contacting the plate cylinder support box with the second blanket cam.
A variable cutoff offset printing press is also provided. The variable cutoff offset printing press includes an exchangeable variable cutoff plate cylinder, an exchangeable variable cutoff blanket cylinder, a plate cylinder support box supporting the exchangeable variable cutoff plate cylinder, a blanket cylinder support box supporting the exchangeable variable cutoff blanket cylinder and an alignment stop adapted to align the exchangeable variable cutoff plate cylinder and the exchangeable variable cutoff blanket cylinder. The plate cylinder support box includes an exchangeable plate cam and the blanket cylinder support box includes an exchangeable blanket cam. The exchangeable plate cam is capable of contacting the stop and the exchangeable blanket cam is capable of contacting the plate support box to align the exchangeable variable cutoff blanket cylinder and the exchangeable variable cutoff plate cylinder. The plate cylinder support box and the blanket cylinder support box are capable of aligning cylinders of different sized cutoffs.
Preferred embodiments of the present invention will be elucidated with reference to the drawings, in which:
Printing unit 10 includes an impression cylinder 12, a blanket cylinder 14, a plate cylinder 16 and an inking and dampening apparatus 18. In operation, inking and dampening apparatus 18 provides ink and dampening solution to plate cylinder 16. Plate cylinder 16, which may be provided with an imaged printing plate mounted thereon, transfers inked images to a printing blanket on blanket cylinder 14 at a nip 15. A printing blanket on blanket cylinder 14 then transfers the images to a web passing between blanket cylinder 14 and impression cylinder 12 at a nip 13.
Cylinder alignment apparatus 20 includes an impression cylinder support box 22 supporting impression cylinder 12, a blanket cylinder support box 24 supporting blanket cylinder 14 and a plate cylinder support box 26 supporting plate cylinder 16. Support boxes 22, 24, 26 are coupled to a supporting frame at respective pivot points 23, 25, 27 on a first side. One a second side, impression cylinder support box 22 is coupled to an actuator 33 and plate cylinder support box 26 is coupled to an actuator 37. Actuators 33, 37 may be pneumatic air cylinders or hydraulic cylinders. An impression cam 42 is coupled to support box 22, first and second blanket cams 43, 44 are coupled to support box 24 and first and second plate cams 45, 46 are coupled to support box 26. An alignment stop 40, which may be coupled to the supporting frame, is near inking and dampening apparatus 18. Alignment stop 40 may be eccentrically mounted on the supporting frame and may be movable between a non-aligning position and an aligning position. In
Support box 24 may be locked into a set position for a given cutoff, which may be accomplished by be locking support box 24 to the supporting frame via lock mechanism 50. When support box 24 is in the locked position, support box 24 provides a reference point for support boxes 22, 26. Thus, once blanket support box 24 is locked into a desired position for a given printing cutoff, impression cylinder and plate cylinder and their respective support boxes may be thrown on and off as necessary during the printing process, while the blanket cylinder support box remains stationary.
In situations where some type of maintenance is required, but no change in cutoff is necessary, support box 24 may not need to be moved. If a plate on plate cylinder 116 needs to be replaced, a blanket on blanket cylinder 114 needs to be replaced or impression cylinder 12 needs to be replaced, or any cylinder 12, 114, 116 needs to be repaired, but no cutoff change is required, support box 24 may be left in the locked position. In such an instance, alignment stop 40 may be moved out of the gauging/alignment position and one or more rollers of inking and dampening apparatus 18 may be moved away from plate cylinder 116. Actuator 37 may then move support box 26 away from support box 24 and actuator 33 may move support box 22 away from support box 24. After cylinders 12, 114, 116 are thrown off from one another, the particular maintenance may be performed and it may be unnecessary to gauge the pressure between cylinders 12, 114, 116.
Also, if the web is replaced with web of a different thickness, support box 24 may remain in the locked position and actuator 33 may adjust the position of support box 22 accordingly so that cylinders 12, 114 are correctly positioned with respect to one another.
Blanket cam 144 is sized such that a radius Rbc2 of blanket cam 144 with respect to a center axis of blanket cylinder 114 is equal to the radius Rb of blanket cylinder 114 plus the difference between the radius Rp of plate cylinder 116 and a radius Rpc1 of plate cam 45 with respect to a center axis of plate cylinder 116 (Rbc2=Rb(Rp−Rpc1)).
In alternative embodiments, blanket cams 43, 44 (
In the preceding specification, the invention has been described with reference to specific exemplary embodiments and examples thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense.
Priority is claimed to U.S. Provisional Application No. 61/199,886 filed Nov. 21, 2008, and hereby incorporated by reference herein.
Number | Date | Country | |
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61199886 | Nov 2008 | US |