Printing unit for selective indirect intaglio and flexographic printing

Abstract

A printing unit operative alternatively for either indirect intaglio printing or for flexographic printing which includes a printing unit frame with a relatively fixed position impression cylinder thereon. A first cylinder support is mounted on said frame for supporting alternatively a transfer cylinder or a flexographic plate cylinder so as to be vertically adjustable on the frame, while a second cylinder support is mounted on said frame for supporting alternatively an intaglio plate cylinder or a fountain cylinder to be horizontally adjustable on the frame. With this arrangement, the apparatus can be converted between indirect intaglio and flexographic printing operation by a simple exchange of cylinders in each of the horizontally and vertically adjustable supports with subsequent simple vertical and horizontal adjustment of the supports to accommodate the changed diameter cylinders for the respective printing operation to be performed. Fixed and adjustable stops are arranged for the horizontally adjustable support so as to accommodate rapid adjustment for standard printing operations as well as for providing controlled small adjustments for printing of material of varying thickness.

Description

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to a printing unit usable alternatively for indirect intaglio printing and for flexographic printing, comprising an impression cylinder; an exchangeable cylinder constructed as a transfer cylinder for indirect intaglio printing or as a plate cylinder for flexographic printing; a likewise exchangeable cylinder constructed as an intaglio plate cylinder or as a fountain cylinder disposed in a common horizontal plane with the impression cylinder and provided with an oscillating wiper, which cylinder can be displaced on a slide in the horizontal, direction; and an ink fountain.

U.S. Pat. No. 2,988,989 discloses a printing unit of this general type which has a total of four cylinders, i.e. an impression cylinder, a transfer cylinder, an intaglio plate cylinder, and a fountain roller dipping into the ink fountain. The impression cylinder, the transfer cylinder, and the intaglio plate cylinder are disposed in one common horizontal plane. In order to prevent a continued transport of the ink when the printing operation is interrupted, the transfer cylinder and the printing plate cylinder are arranged on horizontally displaceable slides, making it possible to move the individual cylinders away from each other.

In this conventional printing unit, the transfer cylinder can be replaced by a plate cylinder for flexographic printing. A rapid disengagement of all cylinders from one another during operation, i.e. during an actually continuous printing proces, is impossible by means of this conventional printing unit, because for this purpose at least two slides must be displaced with respect to the machine frame and with respect to each other. Furthermore, in this conventional printing machine, the path of the ink on the transfer cylinder or plate cylinder always corresponds approximately to one-half the circumference thereof, so that, with increasing cylinder diameters, there is an ever-growing danger of drying of the ink.

German Pat. No. 671,789 discloses a flexographic printing unit consisting of four cylinders, wherein an impression cylinder and a form roller having the same diameter are disposed in a common horizontal plane, and wherein a plate cylinder can be adjusted vertically from above with respect to the impression cylinder and the form roller. The form roller is inked by a fountain roller dipping into an ink fountain. The form roller is fixedly mounted.

This conventional printing unit is well suitable for flexographic printing, since for printing and inking of the plate cylinder, only the latter itself need be displaced. Furthermore, this plate cylinder can readily be exchanged for another plate cylinder having a larger or smaller diameter. Besides, in order to briefly interrupt the operation of this printing unit, it is merely necessary to lift the plate cylinder from the impression cylinder and simultaneously from the form cylinder.

This printing machine is unsuitable for indirect intaglio printing and cannot be converted for such operation, either. Also, this printing unit cannot be used for web-used materials of varying thicknesses since, when thicknesses of material are employed which go beyond that taken into account during the manufacture of the unit, either the ink transfer from the form roller to the plate cylinder is no longer ensured, or the web of material or the cliche (plate) mounted on the plate cylinder is squeezed.

U.S. Pat. No. 2,310,788 discloses a flexographic printing unit consisting of an impression cylinder, a plate cylinder, and a form roller dipping into an ink fountain, wherein the form roller has a screen surface from which the ink is wiped off by means of a doctor blade.

The present invention is based on the problem of providing, starting with the aforementioned conventional machine, a machine which can be simply and rapidly converted from flexographic printing to indirect intaglio printing, and vice versa.

This problem is solved, in accordance with this invention, by providing that the cylinder fashioned as a transfer cylinder or plate cylinder can be adjusted vertically with respect to the impression cylinder and with respect to the cylinder which can be displaced in a horizontally adjustable manner and which dips into the ink fountain, and that this cylinder has a patterned (screen) surface provided with nubs. An important advantage of the arrangement of the present invention resides in that it is possible to effect an extremely simple, accurate, and rapid adjustment of the cylinder, serving as the plate cylinder in flexographic printing and as the transfer cylinder in intaglio printing, with respect to the impression cylinder and the cylinder dipping into the ink fountain. In this type of adjustment of the cylinder vertically from above, coupled with the horizontal adjustability of the cylinder dipping into the ink fountain, the advantage is obtained that the conversion from flexographic printing to indirect intaglio printing and vice versa, and a conversion during flexographic printing operation to various format sizes, take place in a very simple manner. This is so, because the cylinder which is adjustable from above need only be adjusted, completely independently of its diameter, only with respect to the two other cylinders, and the cylinder dipping into the ink fountain can be placed into its new operating position by a simple horizontal adjustment. Furthermore, the adjustability of the horizontally displaceable cylinder dipping into the ink fountain has the result that it is possible to adjust the cylinders exactly with respect to one another in a simple manner in case of varying thicknesses of the material, and this can be done in both types of operation. Since the three cylinders are arranged in an approximately isosceles triangular relationship according to the present invention the ink paths on the cylinder adjustable from above become very short and substantially less than one-half the circumference thereof. Consequently, the danger of drying of weak color hues, i.e. so-called halftones, on this cylinder is extensively avoided, which is of great significance especially when operating the printing unit for indirect intaglio printing. Due to the fact that, according to the preferred embodiment of the present invention, always only three cylinders are provided, of which the cylinder dipping into the ink fountain is always fashioned as a pattern cylinder with an oscillating doctor blade, an extremely uniform ink transfer is ensured especially also during flexographic printing operation.

In a further development of the invention, the fountain cylinder and the impression cylinder have the same diameter for flexograhic printing. This has the result that, in flexographic printing operations, an exchange of the plate cylinder against a plate cylinder of different diameter does not necessitate a change in the adjustment of the fountain cylinder. Furthermore, the conversion of the machine of this invention from indirect intaglio printing operation to flexographic printing is facilitated furthermore by providing that the slide, in the mode of operation for flexographic printing, abuts against a stop. Since the geometry of the printing unit -- presupposing approximately uniform thicknesses of web of material -- does not change during flexographic printing operation, such a stop can fixedly determine in each case the exact position of the cylinder dipping into the ink fountain. In order to be able to take differing thicknesses of the web-shaped material into account, a further advantageous feature of this invention is that a stop is displaceably arranged and is coupled with a meter. In order to be able to change over rapidly and simply during flexographic printing from a prdetermined material thickness range, for which the fixed stop determines the position of the fountain cylinder dipping into the ink fountain to a different thickness of material, another advantageous feature of the present invention provides that the displaceably arranged stop can be pivoted from an ineffective position into an effective position.

The present invention makes it possible, in multicolor printing machines constructed from the printing units of the invention, to operate any desired number of printing units in a flexographic operation and the remainder in indirect intaglio operation, and to change the sequence of the printing units operating in one or the other mode of operation, without exchanging the entire printing unit, because actually only two cylinders have to be exchanged for varying the mode of operation. This results in an extraordinary versatility in the usefulness of such a printing machine.

BRIEF DESCRIPTION OF THE DRAWINGS

These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a single embodiment in accordance with the present invention, and wherein

FIG. 1 is a side, partially cross-sectional view of a printing unit in accordance with the present invention which shows the printing unit in the mode of operation for indirect intaglio printing;

FIG. 2 is a view similar to FIG. 1 which shows the same printing unit in the mode of operation for flexographic printing;

FIG. 3 is a schematic partial view showing details of nubs on a cylinder surface of cylinders arranged at ink fountains; and

FIG. 4 is a sectional view taken along line IV--IV of FIG. 3.

DETAILED DESCRIPTION OF THE DRAWINGS

In FIG. 1, the printing unit is shown as equipped for indirect intaglio printing.

On a machine frame 1, two vertical supports 2 disposed oppositely to one another in pairs are arranged. A fixedly mounted impression cylinder 3 and a vertically adjustable transfer cylinder 4 for indirect intaglio printing are disposed in these supports 2. A horizontal guide 5, connected to form a unit with the supports 2, is furthermore mounted on the machine frame 1. A slide 8, carrying an ink fountain 6 and an intaglio plate cylinder 7 dipping into the ink fountain 6 and being constructed as a screen cylinder (with nubs on the surface), is guided on this guide means 5 and can be moved horizontally in the direction toward the impression cylinder 3 and away therefrom.

All three cylinders 3, 4, 7 are disposed axially parallel with respect to one another, wherein the impression cylinder 3 and the intaglio plate cylinder 7 are disposed in a common horizontal plane passing through their axes. The transfer cylinder 4 is vertically adjustable with respect to the impression cylinder 3 and the intaglio plate cylinder 7 at right angles to this horizontal plane. For this purpose, the transfer cylinder 4 is supported in holding arms 9 horizontally projecting from the supports 2. These holding arms are displaceable together vertically in the supports 2 in dovetail guides 10. The vertical adjustment of the holding arms 9 and thus of the transfer cylinder 4 is effected by means of spindles actuated by way of a common handwheel 11. Since details of the spindles interconnected between the handwheel 11 and the holding arms could be readily constructed by those skilled in the art using the present disclosure and known mechanisms, these details have not been included herein. In order to be able to raise the transfer cylinder 4 quickly in case of operational disturbances, a hydraulic quick-action shutoff device can be provided in addition to the spindles, which device lifts the transfer cylinder 4 off the impression cylinder 3 and off the intaglio plate cylinder 7 by several millimeters, so that simultaneously the ink transfer from the intaglio plate cylinder 7 to the transfer cylinder 4 and the transfer of the picture from the transfer cylinder 4 to a web of material 12 passing between the transfer cylinder 4 and the impression cylinder 3 are interrupted. The details of such a hydraulic quick-action shutoff device have also not been illustrated and described because one skilled in the art could readily construct same from known mechanisms and the present disclosure.

The transfer cylinder 4 is mounted in the holding arms 9 in split bearings 13, the upper halves of which, denoted by 14, are tiltable by means of pivot pins 15 and which can be locked at their ends by means of radily releasable setscrews 16. The construction of the bearing for the intaglio plate cylinder 7 is similar. The bearing blocks 17 are likewise split, so that their upper halves 18 can be swung away about pivot pins 19. These upper halves 18 can likewise be clamped into position at their other ends by means of radily releasable setscrews 20. By this construction of the bearings, the intaglio plate cylinder 7 and the transfer cylinder 4 can readily be exchanged for other cylinders. Furthermore-- and this is especially important-- the intaglio plate cylinder 7 can be exchanged for a fountain cylinder, and the transfer cylinder 4 can be exchanged for a plate cylinder, so that, after these simple rearrangements, the printing unit can be further utilized for flexographic printing instead of indirect intaglio printing as previously.

The slide 8 can be displaced horizontally by means of spindles 21 engaging the two outer ends, (it is to be understood that one end is illustrated, the other end being spaced therefrom in a direction perpendicular to the plane of the figures) of the slide; the spindles can be operated via a worm gear 22 by means of a handwheel, not shown. For the rapid disengagement of the intaglio plate cylinder 7 from the transfer cylinder 4, the housing 23 carrying the worm gear 22 and the spindle 21 can be shifted by means of a rotatable eccentric 24 by the stroke of this eccentric, so that, when the eccentric is operated or rotated, the entire slide, including the elements carried thereby, is moved toward the right as seen in the drawing.

The printing unit as illustrated in FIG. 1 is constructed for indirect intaglio printing, so that the intaglio plate cylinder 7 and the transfer cylinder 4 have the same diameter resulting respectively from the length of the format.

In the modification of the same printing unit shown in FIG. 2 for use in flexographic printing, a fountain cylinder 7' has taken the place of the intaglio plate cylinder 7, and a plate cylinder 4' has taken the place of the transfer cylinder 4. In the last-mentioned case as illustrated in FIG. 2, the impression cylinder 3 and the fountain cylinder 7' have the same diameter. In the case shown in FIG. 2 wherein the unit operates as a flexographic printing mechanism, a device 25, shown in FIG. 1, (many parts of which are also illustrated in FIG. 2) is used for the rapid and accurate adjustment of the slide and thus of the fountain cylinder 7', so that, upon the vertical setting of the plate cylinder 4', the latter is in accurate contact with the fountain cylinder 7' and with the impression cylinder 3 or the passing web 12 of material. Such an exact vertical adjustment of the plate cylinder 4' is made possible due to the fact that this cylinder is mounted on both sides and guided in the supports 2.

The device 25 has a stop pin 27 abutting against an end face 26 of the slide 8; this pin is mounted to be axially adjustable in a pivotable bushing 28. The slide 8 carrying the fountain or inking cylinder 7' for flexographic printing is pushed against this stop pin 27, if the printing unit is to be operated as a flexographic printing machine. In this case, the slide is exactly disposed in such a position relatively to the impression cylinder 3 and the plate cylinder 4' that the latter, with a vertical adjustment, contacts the impression cylinder 3 and/or the web 12 of material guided therearound and the fountain cylinder 7' without any additional adjusting measures. This fixed adjustment is sufficient for thicknesses of material up to about 40 microns.

The pivotable bushing 28 carrying the stop pin 27 is fixedly disposed on a rotatable axle 29 arranged eccentrically to the stop pin 27, so that the bushing rotates with the axle. This axle can be pivoted by a certain angle by means of a handle, not shown. Upon such a pivoting motion, the stop pin 27 is brought into a position wherein it can enter a bore 29a (FIG. 1) provided in the end face 26 of the slide 8, so that the pin no longer serves as an abutment. Axially in parallel to the axle 29 an axially displaceable rod 30 is disposed in a support 2, contacting with one end a meter 31. This rod 30 carries, likewise eccentrically with respect to its axis, a stop pin 32 at its other end facing the same direction as the stop pin 27. The stop pin 32 is provided in an arm 33 to be longitudinally or horizontally adjustable. The arm 33 is affixed to the rod 30 in a non-rotatable and non-displaceable manner. The stop pin 32 has a stud-like projection 34 at its rear end, engaging a recess 35 in the bushing 28, which recess is arranged eccentrically with respect to the axle 29. Thereby, upon a rotation of the axle 29 and the concomitant pivoting of the stop pin 27 from an inoperable position, the stop pin 32 can be pivoted into an effective position wherein it can abut against an abutment surface in the end face 26 of the slide 8. If, in this case, the slide 8 is furthermore displaced in the direction toward the impression cylinder 3, the meter 31 indicates quite accurately the additional adjustment. Such an additional adjustment is necessary in a case where the web of material has a thickness of more than 40 microns. Thus, it is possible by this construction to imprint in the printing unit material up to the thickness of cardboard (of a thickness on the order of .8mm), because the adjustment can still be executed in a maximally simple manner. A return of the stop pin 32 into a respective starting position is effected by a compression spring 36.

Upon an opposite pivoting of the axle 29 the stop pin 32 and the stop pin 27 are pivoted into a position wherein they are disposed in alignment with two associated bores 38, of which only the one associated with the stop pin 32 is shown, in the end face 26 of the slide 8. The stop pins 27 and 32 can then slide into bores 38 so that damage to the adjustment device 25 is prevented for certain printing operations with appropriately dimensioned cylinders, whereby the flexibility of the machine is enhanced.

The excess printing ink is stripped off from the intaglio plate cylinder 7 and/or the fountain roller 7', by means of an oscillating doctor blade 37.

The unit is driven in such a manner that the impression cylinder 3 is driven directly. The impression cylinder 3 drives the vertically adjustable cylinder 4 or 4' and, by the latter, the cylinder 7 or 7' dipping into the ink fountain 6 is driven. In front of the impression cylinder 3, a free-wheeling mechanism is disposed, so that the cylinder is arrested when the printing unit operates in a self-sustaining manner.

FIGS. 3 and 4 illustrate the nub patterns for the cylinders 7, 7' with cylinder axle 39. The nubs 38 have a generally quadrangular cross-section with a ridge length of about 30 .mu. m and are arranged in rows alongside a circumferential line of the cylinder with neighboring rows displaced by half a division with respect to one another. As best shown in FIG. 4 the nubs have a pyramid shaped cross-section and have a depth of approximately 30 .mu.m. Cross-pieces 40 remain between neighboring nubs, where no nubs have been inserted into the polished surface of the cylinders 7, 7'. The cylinder 7' for flexographic printing is covered over the whole surface in the manner illustrated in FIGS. 3 and 4 while cylinder 7 for intaglio printing is provided with such nubs only at places where dye or ink is to be absorbed for the printed picture. Width, form and depth of the nubs depend on the particular dye to be used.

While we have shown and described only one embodiment in accordance with the present invention, it is understood that the same is not limited thereto but also contemplates numerous changes and modifications as would be known to those skilled in the art given the present disclosure of the invention, and we therefore do not wish to be limited to the details shown and described herein only schematically but intend to cover all such changes and modifications.

Claims

We claim:

1. Printing unit apparatus operable alternatively for direct intaglio printing and for flexographic printing; said apparatus comprising:

a printing unit frame,

an impression cylinder,

first cylinder supporting means for supporting said impression cylinder for rotation about a first axis of rotation,

first mounting means for mounting said first supporting means on said frame,

a transfer cylinder,

a flexographic plate cylinder,

second cylinder supporting means for selectively and exchangeably supporting one of said transfer cylinder and flexographic plate cylinder for rotation about a second axis of rotation,

second mounting means for mounting said second supporting means on said frame, said second mounting means including vertical adjusting means for adjusting the vertical position of said second axis of rotation at the beginning of each printing operation,

an intaglio plate cylinder,

a fountain cylinder,

third cylinder supporting means for selectively and exchangeably supporting one of said intaglio plate cylinder and said fountain cylinder for rotation about a third axis of rotation disposed in a common horizontal plane passing through the first and third axis of rotation,

third mounting means for mounting said third supporting means on said frame, said third mounting means including horizontal adjusting means for adjusting the horizontal position of said third axis of rotation,

an ink fountain disposed adjacent said third supporting means for supplying ink to one of said intaglio plate and fountain cylinders being supported by said third supporting means,

an oscillating doctor blade means engageable with the one of said intaglio plate and fountain cylinder being supported by said third supporting means,

a patterned surface provided on the intaglio plate cylinder and the fountain cylinder,

said first and third mounting means including means for maintaining said first and third axes of rotation in a common horizontal plane for all adjusted positions of said third axis of rotation,

said impression cylinder and fountain cylinder having the same diameter and said transfer cylinder and intaglio plate cylinder having the same diameter,

whereby flexographic printing operations can be facilitated by placing said flexographic plate cylinder in said second supporting means, by placing said fountain cylinder in said third supporting means, and by appropriately adjusting the position of said second and third axes of rotation with respect to said first axis of rotation,

and whereby indirect intaglio printing operations can be facilitated by placing said transfer cylinder in said second supporting means, by placing said intaglio plate cylinder in said third supporting means, and by appropriately adjusting the position of said second and third axes of rotation with respect to said first axis of rotation.

2. Apparatus according to claim 1 wherein the pattern surface is provided with nubs.

3. Apparatus according to claim 1 wherein the impression cylinder is mounted in a fixed position on said frame.

4. Apparatus according to claim 1, wherein the one of said flexographic plate cylinder and transfer cylinder supported by said second cylinder supporting means directly engages both the one of said fountain cylinder and intaglio plate cylinder supported by said third cylinder supporting means and a strip of material being printed which is passing over said impression cylinder during respective flexographic and indirect intaglio printing operations.

5. Apparatus according to claim 1, wherein means are provided for conversion of said apparatus between flexographic and intaglio printing operations with maintenance of said first axis of rotation in a fixed position, with adjustment of said second axis of rotation only in a vertical direction, and with adjustment of said third axis of rotation only in a horizontal direction.

6. Apparatus according to claim 5, wherein said vertical adjusting means includes slide means for slidably moving said second supporting means in a vertical direction along fixed vertical sliding surfaces of said frame.

7. Apparatus according to claim 5, wherein said horizontal adjusting means includes slide means for slidably moving said third supporting means in a horizontal direction along fixed horizontal sliding surfaces of said frame.

8. Apparatus according to claim 1, further comprising stop means mounted on said frame and abuttingly engageable with a part of said third mounting means when said apparatus is being operated as a flexographic printer.

9. Apparatus according to claim 8, wherein said horizontal adjusting means includes slide means movable with said third supporting means along a horizontal sliding surface of said frame, and wherein said stop means abuttingly engages said slide means when said apparatus is being operated as a flexographic printer.

10. Apparatus according to claim 9, wherein said stop means includes a horizontally fixed stop member positioned at a predetermined position with respect to the relative diameters of the flexographic plate, fountain, and impression cylinders such that horizontal movement of said slide member to abuttingly engage said fixed stop member positions said respective cylinders properly for flexographic printing of relatively thin material.

11. Apparatus according to claim 10, wherein said stop means includes means for moving said fixed stop member such that said fixed stop member is inoperative to limit horizontal movement of said slide member and wherein said stop means includes a horizontally displaceable stop member and meter means including display means for indicating the position of said displaceable stop member, said displaceable stop member being engageable with said slide member, whereby said slide member can be horizontally moved against said stop member closer to said impression cylinder than if said fixed stop member was in operative position for accommodating flexographic printing of thicker materials to be printed.

12. Apparatus according to claim 9, wherein said stop means includes a horizontally displaceable stop member and meter means including display means for indicating the position of said displaceable stop member, said displaceable stop member being engageable with said slide member.

13. Apparatus according to claim 12, wherein means provided for moving said displaceable stop member between a first effective position where it will abuttingly engage said slide member and a second ineffective position where it will not abuttingly engage said slide member when said slide member is moved toward said impression cylinder to accommodate flexographic printing operations.

14. Apparatus according to claim 13, wherein said displaceable stop member is pivotally mounted for movement between said effective and ineffective positions.

15. Apparatus according to claim 1, wherein the impression cylinder and fountain cylinder are smaller than the transfer cylinder and intaglio plate cylinder.