US2894452A - Moistening system for rotary offset machine - Google Patents

Description

1959 N w. TRISLER 9 5 MOISTENING SYSTEM FOR ROTARY OFFSET MACHINE Filed May 2, 195a Anwmw: Maison WV. Frasier Witness )3 m M dHorn y United States Patent MOISTENING SYSTEM FOR ROTARY OFFSET MACHINE Nelson W. Trisler, Des Moines, Iowa Application May 2, 1956, Serial No. 582,122

6 Claims. (Cl.-101-136) This invention is a novel plate moistening system for offset printing presses and one that is particularly useful in multicolor, single impression work. It features a fountain roller in the moistening system the surface of which is rotated so as to have a moistened surface portion brought by the shortest route to a position to be contacted by the ductor roller. The ductor roller is arranged in relation to the fountain so that the surface of the roller therein has moved only a limited number of degrees of rotation from the fountain liquid when the ductor roller contacts the fountain roller. This cooperation between the ductor and fountain rollers provides extremely consistent and uniform moistening of the plate surface with resulting excellent printing and with less attention required of the operator. Once the proper balance between ink and moisture has been established for the particular printing problem involved, the system will operate for long periods without getting out of adjustment.

This application claims in part structure shown but not claimed in my copending application Ser, No. 551,559, filed December 7, 1955.

In use on multi-color presses of the single impression type, the moistening system also features a reverse order of application of ink and moisture to all plates after the first one to contact the blanket after an impression is made. By reversing the order in which ink and moisture are applied, etching is minimized on plates after the first one. Additional plates after the first one are insulated from etching by a film of moisture laid onto the plate just before it contacts the blanket. In this manner, wearing or etching of the additional plates by ink on the blanket from the first plate is minimized. As it is as a result of such etching that inks are carried from one systeminto another, minimizing this etching minimizes color distortion or tinting. It has also been found that plates used on presses incorporating my novel moistening system makes it possible to print up to twenty-five percent more images before the plate is worn out than is true when conventional ratchet drive roller moistening systems are used.

Accordingly it is the principal object of this invention to-provide a novel moistening system; one that:

(1) provides uniform moistening of a plate surface.

(2) provides consistent moistening of plates during a printing run.

(3) increases plate life.

(4) requires less skill of the operator to get satisfactory results in printing.

(5) minimizes color distortion when multi-color single impression printing is done.

While the foregoing specifically listed objects are the main ones of this invention, it is my intention to include as objects hereof any such as may be clear to a skilled, offset printing press operator-mechanic after he has read this specification, including the claims, and examined the accompanying drawings which. are briefly described as follows:

Fig. l is a diagrammatic view of a multi-color, single impression, offset printing press incorporating my novel moistening system;

Fig. 2 is a fragmentary, perspective, diagrammatic view of my novel moistening system; and

Fig. 3 is a fragmentary, diagrammatic view of an offset press equipped with a modified form of my novel moistening system.

Referring to the drawings there is shown in Fig. 1 a multicolor, single impress, offset printing press having the usual impression or platen cylinder 10 which cooperates with blanket cylinder 12 in applying printed impressions to paper 14 which is fed between the cylinders by conventional mechanism which, therefore, is not shown. Blanket cylinder 12 is provided with the usual blanket 16 which carries the impression from the inked plates on the first plate cylinder 18 and the second plate cylinder 20. Cylinder 18 is called the first plate cylinder, because it is the first of the plate cylinders to contact the blanket 16 after it has transferred its impression to a sheet of the paper 14. Another way of stating this is that plate cylinder 18 is the first to apply fresh ink to the blanket in each printing cycle. An ink fountain 22, ink fountain roller 24, ink ductor roller 26, ink transfer and spreading rollers 28 and form rollers 30 provide ink for the plate cylinder 18. This same plate cylinder has a moistening system associated with it which system comprises a fountain 32 containing liquid 33, fountain roller 34, ductor roller 36, hard surface transfer roller 38 and molleton or cloth covered roller 46. An appropriate structure is provided to drive the fountain roller such as ratchet mechanism 41. A control 43 determines the amount of rotation that the ratchet is allowed to impart. Ratchet system 41 and control 43 are of the type described in United States Patent No. 2,065,535 (The elements 111l25). This moistening system is unconventional in that the fountain roller 34 is rotated by appropriate ratchet mechanism in the direction shown by the arrow in it. With the exception of the direction of rotation, the ratchet drive is conventional. The surface of fountain roller 34 moves up, by the shortest route, out of liquid 33 to a position to be contacted by the ductor roller 36. Ductor roller 36 is conventional and is moved back and forth as shown by the double headed arrow on pivoted arms, as suggested by the element 42, to take moisture from the fountain roller 34 and carry it to transfer roller 38. These arms and the ductor roller are preferably constructed and arranged to barely clear the fountain 32 so that ductor roller 36 contacts the surface of the fountain roller 34 as near to the surface of liquid 33 as possible and certainly within ninety degrees of rotation of the surface of the fountain roller from the surface of the liquid 33 in the fountain. This combination of relative location of the ductor roller and fountain roller and the direction in which the latter rotates is one that provides both consistent moistening of plates during a printing run and uniform moistening over the face of the plate for each impression. The consistency and uniformity of the moistening achieved with this system illustrated in Fig. 2 where it can be seen that a film of moisture, represented by the stipling at 35, extends entirely along the length of the ratchet driven fountain roller 34. If this film is contacted soon after the fountain roller emerges from the liquid in the fountain, it remains evenly spread on the roller. Surface tension will not yet have separated the liquid into patches on the surface of the [fountain roller. When fountain roller 34 is contacted by ductor roller 36, the latter is evenly moistened along its entire length and to the extent determined by the setting of the ratchet drive of the fountain roller. As the degrees of rotation of the. fountain roller surface after it emerges from the liquid before it is contacted by the ductor increases, the efiiciency of the moistening system decreases rapidly. The longer the delay at this point in the operation, the greater is the likelihood that surface tension will separate the liquid film into patches. When the liquid is not evenly distributed, the plates are less uniformly moistened which results in ink being carried back into the moistening system. As the ink used is greasey in nature, it will accentuate the surface tension problem when it is carried back into the moistening system. Surface tension operates more readily on a greasey surface than on one that is free from grease. Conversely, when moistening is uniform and consistent, little or no ink is carried back. Conditions favorable to uniform moistening are maintained for extended periods. As the ductor roller 36 contacts the rapidly rotating transfer roller 33, moisture is transferred evenly along the transfer roller at several locations. Similarly, moisture is evenly placed on the molleton roller 40 when it rotates in contact with the transfer roller 38.

When the plates are well moistened, which includes both consistency and uniformity, there are several advantages that follow. As pointed out above continued even moistening for extended periods is one. Another is that ink sticks to the plates only where intended which in turn has two important results. In sticking only to the image formed on the plate, ink is available to be transferred in the pattern intended only. Clear impressions are made therefore. When the plate is not supplied with ade uate quantities of ink on its pattern, it wears more rapidly than it will otherwise. It can be seen that all these advantages are intertwined and correlated and that once a consistent and uniform moistening is accomplished, the other results follow. It seems also that it is easier to establish a proper balance between ink and moisture when my novel moistening system is used than when conventional ratchet driven, roller applied moistening is employed.

Plate 20 is provided with an inking system generally designated 44 like the one for plate 13 the parts of which are numbered in detail. There is one difference between these two inking systems. They apply ink in relation to the application of moisture in reverse order to each other. The system for plate 18 is conventional in respect to the order of application, but the order for plate 20 is reversed. It can be seen from the arrows on cylinder 18 that as a portion of the plate on the cylinder leaves the blanket 16, it will first have moisture applied to it and then be provided with ink. This is the conventional arrangement. In my system as shown in Fig. 1 for the second plate 20, ink is first applied by inking system 44 and then the plate encounters the rollers of the moistening system 46 which, except for this positioning, is like the one 32- 50 for plate is. A ratchet system 47 and control structure 4') are provided for moisture system 46. These units also are of the type described in United States Patent 2,065,535. The prior art has taught introducing moisture with the ink, but to my knowledge I am the first to apply the moisture specifically after the ink as the last step in preparing the plate for contact with the blanket. This statement is also limited to the application of moisture in actual printing which might properly be assumed from the words preparing the plate for contact with the blanket. Even the systems in which the moisture is introduced into the ink and onto the plate with the do so far back in the inking system.

As a result of my order of applying ink and moisture, the plate has been freshly moistened just before the second plate Ztl contacts the blanket. No roller engages the second plate after moisture has been applied and before contact between the plate and the blanket. In short moisture is applied between the application of ink and the contact of the plate and blanket. It is believed that it is for this reason that there is an insulating moisture film on the plate so that there is little, or no mechanical etching of the plate 20 with the image of plate 18 that has been transferred previously to the blanket. There is further evidence supporting the belief that the film of moisture applied as the last step in preparing plates after the first one for contact with the blanket is beneficial in preventing etching and plate wear. When about seventy-five percent of the total moisture needed in a given situation is added with moisture system 46 in Fig. 1 and only twenty-five percent is added with system 3240, less etching and plate'wear occurs than when the moisture added by the two systems is more evenly divided between them or unbalanced in the opposite direction.

If a conventional order of application is used for successive plates after the first one in single impression, multi-color printing as shown here; there is a very noticeable tendency for the image from plate 18, the first plate, to be transferred from the first plate to the blanket and then to the successive plates. If the wear between the successive plates after the first one and the blanket is not minimized, the second plate will become etched mechanically to carry also the image of the first plate. When the second plate becomes etched With the first plate image as well as its own, both images will take ink from inking system 44. Via the blanket the inks from the two inking systems will become mixed which could be called tinting in relation to the lighter color and dilution for the darker color. When overlay work, printing one color directly on top of another, is done; my novel order in applying ink first and then moisture is particularly advantageous. Most of the color distortion that occurs when a conventional system is used is from the first system into successive systems, because much of the ink on the blanket is removed as an impression is made. However, there will be some distortion, either diluting or tinting, from successive inking systems back into the first one also. When my order of ink and moisture application is used for plates after the first one, color distortion is not totally eliminated, but it is reduced to the point that very satisfactory printing for long runs can be accomplished.

Fig. 3 shows a modified form of the moistening system for the plates. In that figure, the blanket 48 on the blanket cylinder 50 (shown only in fragment) contacts the plate on plate cylinder 52 in the usual manner. An inking system 54 like those shown in Fig. 1 provides ink and the moisture system 56 provides moisture as the last step again as in Fig. 1. The first cylinder is not shown. This moisture system differs from the system 46 in that the molleton roller 58 does not contact the plate but instead engages a transfer roller 60 which is the same type of roller as the form rollers of the inking system 44 or 54. This roller will take ink from plate cylinder 52 if the quantities of ink on it are excessive and add ink to the cylinder, or more accurately the plate on the cylinder, if the inking system 54 is not applying adequate quantities. For this reason this form of the invention will remain in balance without attention very well. As the ink and moisture will not readily mix, this same roller 60 also serves to transfer moisture to the plate on cylinder 52 as the last step before the plate contacts the blanket 48.

When my improved moistening system is used, the ranges of adjustment on moisture and ink quantities can be substantially greater and still obtain satisfactory results than is true with conventional ratchet driven moisture systems. That is to say much less moisture than in conventional machines will be adequate and more moisture and ink can be used without interfering with the printing of clear copy. Obviously persons only slightly skilled in gaging how to adjust the moisture and ink quantity controls for proper printing will be more apt to be successful with a press equipped with my moisture system than they would be with a conventional ratchet controlled, roller fed moisture system.

The reverse rotation of the fountain roller in the moistening system was first used by me rather accidentally in connection with making a system similar to that shown in Fig. 3. The linkage used to drive the fountain roller ratchet was connected without much thought as to the direction which the fountain roller would turn. As the device was used, however, it was noticed that the control of the balance between ink and moisture was particularly good. This was at first attributed entirely to moving the molleton roller back off the plate and into a position to be contacted by the ductor roller. It was anticipated that there would be perhaps a little more ink than usual picked up by the molleton and ductor rollers. It was expected that they would have to be cleaned a little more often than usualafter a run of fifty thousand impressions say. As a matter of fact, however, the cloth covered rollers (the ductor roller is also cloth covered) were operated extensively with no indication that they were sufficiently ink laden to require Washing. In fact more than three million impressions have been run with some of these rollers without cleaning them. It was then that I gave more attention to all of the details of the way the system was operating. It was soon determined that one of the most advantageous things in my structure for moistening was the direction of rotation of the fountain roller in relation to the position of the ductor roller.

I have disclosed my invention by describing it and showing with drawings practical embodiments thereto, and I now particularly point out and distinctly claim these structures and combinations of structures that I beblieve to be my invention.

I claim:

1. In a multi-color, single impression offset printing press having a blanket cylinder, an impression cylinder cooperating therewith, first and second plate cylinders cooperating with said blanket cylinder, first and second inking systems each comprising, at least an ink fountain, ductor roller, transfer rollers and a form roll for depositing ink on a plate on said plate cylinders; and first and second moistening systems each comprising at least a fountain, a fountain roller, a ductor roller, a transfer roller, and a roller cooperating with the transfer roller and a plate on one of said plate cylinders; the improvement comprising having said second moistening system apply moisture to a plate on said second plate cylinder after the plate is inked and before it deposits ink on a blanket on said blanket cylinder in a normal printing cycle; and said first moisture system applies moisture to a plate on said first plate cylinder before the plate is inked and after it has deposited ink on said blanket cylinder in a normal cycle of printing.

2. The multi-color, single impression, offset printing press of claim 1 in which there is a separate means secured to each said first and second moistening systems for controlling the amount of moisture applied by each of said first and second moistening systems.

3. The multi-color, single impression, offset printing press of claim 2 in which the fountain roller in each of said first and second moistening systems rotates as to bring its surface by the shortest route from the surface of liquid in its fountain to a position to be contacted by its ductor roller.

4. The multi-color, single impression, offset printing press of claim 1 in which the fountain roller in each of said first and second moistening system rotates as to bring its surface by the shortest route from the surface of liquid in its fountain to a position to be contacted by its ductor roller.

5. The multi-color, single impression, offset printing press of claim 1 in which a transfer roller in said second moistening system is a molleton roller that contacts said ductor roller and a roller that cooperates with a plate on said second plate cylinder; said molleton roller remaining out of contact with said second plate cylinder.

6. The multi-color, single impression, offset printing press of claim 1 in which the fountain roller in each of said first and second moistening systems rotates as to bring its surface by the shortest route from the surface of liquid in its fountain to a position to be contacted by its ductor roller; and a transfer roller in said second moistening system is :a molleton roller that contacts said second moistening system ductor roller and a roller that cooperates with a plate on said second plate cylinder; said molleton roller remaining out of contact with a plate on said second plate cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 2,054,830 Osborne Sept. 22, 1936 2,065,535 Morse Dec. 29, 1936 FOREIGN PATENTS 822,735 France Jan. 6, 1938

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