US3431842A - Wetting mechanism for offset printing machines - Google Patents

Description

WETTING MECHANISM FOR OFFSET PRINTING MACHINES Sheet Filed Aug. 28, 196'? Inventors Fig.2

TORNEBS March 11, 1969 R. WINKLER .ETAL 3,431,842

WETTING MECHANISM FOR OFFSET PRINTING MACHINES Filed Aug. 28, 1967 Sheet 2 of 2 7 Q Fig.3

Inventors R. WL n/der w: Ounneber A TTOVLN 595' United States Patent 3,431,842 WETTING MECHANISM FOR OFFSET PRINTING MAQHINES Richard Winkler, Rengsdorf, and Kurt Dunnebier, Gladbach, Germany, assignors to Winkler & Dunnebier Machinenfabrik und Eisengiesserei KG, Neuwied am Rhein, Germany, a corporation of Germany Filed Aug. 28, 1967, Ser. No. 663,622 Claims priority, application Germany, Dec. 5, 1966,

US. c1.101-142 3 Claims Int. (:1. B41f 9/00; B411 23/00, 25/00 ABSTRACT OF THE DISCLOSURE A wetting mechanism is intended for use with an offset printing machine having at least three form rollers and at least two vibrator rolls engaging the form rollers. The wetting mechanism includes a transfer roller engaging a squeezer roller which engages a scoop roller mounted in a trough for the wetting liquid. The transfer roller is in engagement either directly with one of the vibrator rolls or with a rubber roller which engages the vibrator rolls. The scoop roller may be moved in and out of contact with the transfer roller during the operation of the printing machine. Additional squeezer rollers may be located around the scoop roller and a blower may be provided between the squeezer roller and the transfer roller.

This invention refers to a wetting mechanism for offset printing machines. More particularly the invention relates to a wetting mechanism which applies wetting liquid together with ink, distributed as evenly as possible over a plurality of form rollers, upon the printing plate of an offset printing machine, more particularly an offset printing machine having three or four form rollers for each inking mechanism and two or more vibrator rolls running in contact with the form rollers.

German Patent No. 678,543 describes a wetting mechanism in which one or more rollers of the inking mechanism is in contact with a water-receiving roller to which the necessary quantity of water is directly or indirectly fed. It is furthermore known, for example from German Patent No. 1,127,369, to regulate the quantity of the wetting medium fed to the form cylinder by providing a transfer roller between the wetting roller which dips into the wetting medium storage tank and the subsequent distributor roller, the transfer roller being mounted so as to oscillate by itself or together with the entire wetting mechanism, bearing on the distributor roller for variable periods for time.

Extensive experiments with inking mechanisms having, for example, fifteen inking rollers following the vibrator have shown that the wetting liquid is imperfectly accepted and unevenly distributed by an inking mechanism roller, the surface of which is still covered with a relatively thick and as yet unevenly distributed coating of ink and which is close to the vibrator of the inking mechanism, resulting in reduced printing quality. The quality of printing is substantially improved if the wetting liquid is fed to the vibrator rolls running in contact with the foam rollers from the inking mechanism.

It has been also found that, with periodic supply of wetting liquid at the last-mentioned location, by means of an oscillatingly mounted transfer roller, an even wetting of the printing form cannot be achieved. Furthermore, a roller of this type which feeds wetting liquid periodically requires a particular drive running at the peripheral speed of the printing form, as otherwise the ink is unevenly distributed over the cover of the inking mechanism roller.

3,431,842 Patented Mar. 11, 1969 It has also been found that the so-called stencil phenomena, which are caused by the fact that the coating of ink at those parts of the form rollers which have supplied ink to the printing form does not receive the same thickness as at the other places until the next delivery of ink, take place infrequently if the wetting liquid is applied to the printing formas evenly as possible 'by all the inking rollers of an inking mechanism. If only one single form roller also applies the wetting liquid to the printing form, the quantity of ink delivered by it tothe printing plate is thereby obviously considerably reduced.

An object of the present invention is to eliminate these drawbacks of prior art constnuctions.

Another object of the invention is toprovide a simple wetting mechanism at such a location of the train of rollers of the inking mechanism of an offset printing machine, that the above-mentioned drawbacks are reduced to a minimum and, furthermore, that regulation of the quantity of wetting medium supplied to the inking mechanism is readily possible during operation of the printing machine.

Other objects will become apparent in the course of the following specification.

These objectives were accomplished in the case of an offset printing machine of the above-described type by a wetting mechanism having a trough for the wetting liquid, a scoop roller rotating therein, a squeezer roller rotating at regula-ble pressure against the scoop roller, and a transfer roller disposed on the downstream side of this squeezer roller and revolving at regulable pressure against the scoop roller, the transfer roller bearing on a friction cylinder which is first when viewed in the direction of motion of the plate cylinders, and which drives the form rollers, or on an intermediate roller connecting the first and second friction cylinders with each other, in either case with sufficient pressure to ensure a friction drive effect.

For the printing of sheets or webs which are narrower than the length of the form rollers, the invention provides the arrangement of squeezer rollers and/0r streams of blown air between the squeezer roller and the transfer roller, so as to prevent the supply of too much wetting liquid where it is not removed by the paper.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawings, showing by way of example, an embodiment of the invention in conjunction with an inking mechanism having three form rollers and two vibrator roll running in contact therewith.

In the drawings:

FIGURE 1 is a cross section taken along the line I-I of FIG. 2 through a wetting mechanism according to the present invention, provided in an approximately horizontal inking mechanism;

FIGURE 2 is a plan view of the inking mechanism according to FIG. 1;

FIGURE 3 is a cross section along the line III-III of FIG. 2, through an inking mechanism according to the invention, but in conjunction with an approximately vertically disposed mechanism;

FIGURE 4 is a cross section along the line IVIV of FIG. 3, through a wetting mechanism according to the invention, having a blower device.

With reference to FIG. 1 of the drawings, the purely diagrammatically indicated inking mechanism of the offset printing machine has a ductor roller 1 with a doctor blade 2, a vibrator 4 oscillating about a pivot point 3, and a steel cylinder 5 with associated rubber rollers 6 and 7. The roller 7 contacts a vibrator roll 8, with which rubber rollers 9 and 10 are associated. The vibrator roll 8 contacts a rubber roller 11 which is followed by a vibrator roll 12 and a form roller 13. The vibrator roll 12 communicates, through a rubber roller 14, with a vibrator roll 15 adjacent to which are form rollers 16 and 17. The ink applicator rollers 13, 16 and 17 contact the printing plate 19 which is stretched over a plate cylinder 18. Also associated with the vibrator roll 15 are two rubber rollers 20, 21. All rollers and cylinders rotate in the direction of the arrows shown in the drawings.

The wetting mechanism has side walls 22 between which, by means of screws 24, a trough 23 is fixed to hold the wetting liquid.

Rotatably mounted in the two side walls 22 is a preferably hollow and externally chromium-plate scoop roller 25. A squeezer roller 26 and a shaft 27 with two squeezer rollers 28 are rotatably mounted in bearings 29 which are adapted to slide in slots 30 in the side walls 22 so that, by means of wing screws 31 which are provided in plates 32 rigid on the side walls 22, they can be brought closer to the scoop roller 25 against the pressure of springs 33. Thus the squeezer roller 26 and/ or squeezer rollers 28 can press to a greater or lesser extent agaisnt the scoop roller 25.

It is intended that the squeezer rollers 28 should further reduce the thicknes sof the film of wetting liquid on the surface of the scoop roller 25 which is determined by the squeezer roller 26 when, as already stated, the paper which is to be printed does not remove the wetting liquid from the printing form or the offset sheet. Its length, therefore, depends upon the extent to which the paper to be printed is narrower than the scoop roller or the form rollers 13, 16 and 17. If, when printing on narrower paper, the same quantity of wetting liquid is fed to the form rollers over their entire length, too much wetting liquid will accumulate at a location from which it is not removed. At such places, then, there is the danger that the ink will emulsify.

According to the embodiment of the invention shown diagrammatically in FIG. 4, it is possible to provide a blower apparatus instead of the squeezer rollers 28 or between the squeezer rollers 28 and the transfer roller 42. The blower apparatus consists of a tube 46 disposed at a certain distance above the scoop roller 25 and attached to the side walls 22 of the damping mechanism; over both ends of the scoop roller 25, nozzles 47 are provided in the tube; they are adapted to blow air obliquely towards the ends of the scoop roller. The nozzles 47 can be opened or closed by rotation of rings 48, in each of which there is a hole 49. A tap 50 makes it possible to adjust the quantity of blowing air which is supplied through a hose (not shown). The blower device can be used instead of or in addition to the squeezer rollers 28.

The entire wetting mechanism is pivotally secured by two bolts 34 to intermediate walls 35 of the printing machine, in which rollers 6, 9, 10, 14, and 21 are also rotatably mounted; it is pressed resiliently (in a manner not shown) against the cylinders 5, 8, 12 and 15. The intermediate walls 35 are secured by bolts 36 to the side walls 45 of the machine in which the vibrator roll and other cylinders are also rotatably mounted in a manner which need not be described in detail (see FIG. 2).

Rigid on the side walls 22 of the wetting mechanism are arms 37 into which are screwed screws 38 having counter nuts 39. The screws 38 brace the pivotable wetting mechanism on eccentric members 40 which are keyed upon a shaft 41 which is rotatably mounted in the side walls 45 of the machine. The shaft 41, in a manner not further illustrated, is locked by means of a lever or the like either in the working position shown in FIG. 1 or, in order to lower the wetting mechanism and disengage the scoop roller from the transfer roller 42, it is rotated through approximately 180. The transfer roller 42 is rotatably mounted in eccentric bearings 43 which are secured to intermediate Walls 35. Thus the necessary pressure between the rollers 42 and 14 can be adjusted. On the other hand, this makes it possible for the transfer roller 42, together with the other rollers of the entire inking mechanism, to be cleaned while the wetting mechanism is lowered. The desired pressure between the scoop roller 25 of the wetting mechanism and the transfer roller 42 is adjusted by means of screws 38.

As indicated by arrows in FIG. 1 which denote the direction of rotation, the film of wetting liquid deposited on the upper side of the scoop roller 25 and reduced to minimal thickness by the squeezer roller 26 and possibly squeezer rollers 28 and/or blower nozzles 47, reaches the rubber roller 14 via the transfer roller 42. From the rubber roller 14, the wetting liquid reaches the printing plate 19, partly via the vibrator roll 12 and the form roller 13 which is the first to touch the printing plate, and partly via the vibrator roll 15 and the subsequent form rollers 16 and 17. An even distribution of wetting liquid over all three form rollers 13, 16 and 17 can be achieved by an appropriate adjustment of pressure between the ink applicator rollers and the friction cylinders which precede them.

The wetting mechanism and the inking mechanism in the arrangement shown in FIG. 3 include the same parts as described above, indicated by the same reference numerals. Parts of secondary importance are omitted from FIG. 3. However, there are the following dilferences between the construction shown in FIG. 3 and the previously described construction.

The transfer roller 42 of the wetting mechanism according to FIG. 3 is in direct contact with the vibrator roll 12. In accordance with the arrows indicating direction of rotation, which are the same as those in FIG. 1, the wetting liquid passes from the transfer roller 42 via the vibrator roll 12 partially to the rubber roller 14, partially to the form roller 13 and from this latter onto the printing plate 19. That part of the wetting liquid which is taken by the rubber roller 14 passes over the friction cylinder 15 to the ink applicator rollers 17 and 16 and [from these to the printing plate 19.

According to the space arrangements in the printing machine, it is possible that either the arrangement of wetting mechanism according to FIG. 1 or that according to FIG. 3 may be more expedient. Both arrangements, in conjunction with the wetting mechanism described, oifer the advantages of the present invention.

The lowering of the wetting mechanism by pivoting about the pin members 34 is indicated only as an example. The contact between the scoop roller 25 and the transfer roller 42 can be achieved in any other way, for example, by a parallel displacement of the entire wetting mechanism or by pivoting of the transfer roller 42 about the central point of the friction cylinder which it touches. These and other variations and modifications are to be included within the scope of the present invention.

What is claimed is:

1. In an offset printing machine, in combination, a plate cylinder adapted to rotate in a specific direction, a printing plate extending over said plate cylinder, three spaced form rollers engaging separate portions of said printing plate, two spaced vibrator rolls, said vibrator rolls being so spaced from said said cylinder that in the course of the rotation of said plate cylinder in said specific direction, a portion of the circumference of said plate cylinder first passes adjacent to one of said vibrator rolls and thareafter passes adjacent to the other one of said vibrator rolls, one of said vibrator rolls engaging two of said three form rollers, the other one of said vibrator rolls engaging the third one of said three form rollers, and a wetting mechanism comprising a trough for the wetting liquid, a scoop roller rotatably mounted in said trough, spaced squeezer rollers engaging said scoop roller and rotatable therewith, means connected with said squeezer rollers for varying the pressure exerted by said squeezer rollers upon said scoop roller, a transfer roller located to one side of all of said squeezer rollers and engaging said scoop roller, means connected with said trough for varying the pressure exerted by said transfer roller upon said scoop roller, and means including one roller that directly engages both of the said vibrator rolls for transmitting the wetting liquid from said transfer roller to both vibrator rolls.

2. An offset printing machine in accordance with claim 1, wherein the last-mentioned means comprise a rubber roller engaging the transfer roller and both vibrator rolls.

3. An ofiset printing machine in accordance with claim 1, wherein the last-mentioned means comprise a rubber roller engaging both vibrator rolls, the transfer roller engaging directly one of said vibrator rolls.

References Cited UNITED STATES PATENTS 1,566,800 12/1925 MacArthur 118-63 2,322,533 6/1943 Mayer 11863 5 2,332,385 10/1943 Lauring 118-63 1,364,257 1/1921 Dobbertin 101-148 2,002,815 5/1935 Harrold 101141 2,043,995 6/1936 Goedike 101148 XR 2,689,522 9/1954 Curtis 101148 XR 10 3,038,405 6/1962 Wojciechowski et al. 101-148 EDGAR S. BURR,

Primary Examiner.

U.S. Cl. X.R.

Images