Lithographic press dampening device

Abstract

 A pneumatically-pulsed dampening device that allows precise variations in the amount of water transferred to selected regions (zones) on a vibrator roller (21) and ultimately to a lithographic printing plate, blows independently operable and adjustable flat air streams (17) over the upper surface of an open-celled sponge (15) whose lower portion rests in a reservoir of water (11). This results in a linear carburezation of the water on the surface of the sponge into a fine atomic mist which is sprayed on the vibrator roller. Capillary tubes can be mounted before the sponge to insure continued wetting of its surface. A shroud (52) open at one end for allowing spraying of the roller, may also be formed with a baffle to further assure the horizontal contour of the air stream and with a Bernoulli effect capturing device to suck in fugitive mist.

Description

[0001] This invention relates to dampening devices for lithographic presses and the like, and more particularly, to a dampening device providing improved water control that virtually eliminates "ghosting".

[0002] Lithographic plates require that non-printing areas be moistened to repel ink; in the process, the printing areas are wet, too. When too much water is deposited on the printing areas (over-dampening), an emulsion is formed thereon when the ink is applied. The emulsion reduces the brilliance of the printing. If too little water is applied to the non-printing areas, (under-dampening), the later applied ink runs thereinto.

[0003] Existing technology in the lithographic industry utilizes several different methods of applying dampening fluid to the lithographic plate. A common method in use is to apply the fluid directly to the plate by means of a rubber roller which runs in contact with a water absorbent cloth sleeve. The cloth sleeve is continuously wetted with the dampening fluid by another roller which runs in a pan of the fluid. This method, although effective in dampening the plate, has three distinct disadvantages. One, it is not capable of applying varying amounts of the fluid to various points across the width of the lithographic plate, and hence can only supply an average overall volume of fluid. This results in over-­dampening in some areas, and under-dampening in other places. Two, since the source of dampening fluid is in physical contact via the roller train at all points from source to plate, a reverse flow of contaminants from the plate back to the source of fluid is possible. When the contaminant is ink, the effectiveness of the fluid feed is adversely affected and demands constant attention. Three, wear and contamination of the cloth roller requires frequent replacement of the cloth sleeve.

[0004] Another method in common usage is to apply the dampening fluid via a series of roller directly to one of the inking form rollers. This method, again lends itself to feed-back of contaminants back to the source of fluid, and does not have the capability of applying controlled amounts of fluid across the width of the plate.

[0005] Another method utilizes a brush rotating against a roller which "flicks" the dampening fluid across a space from one roller to another. This system requires periodic maintenance of the brush due to wear. Also, it is not capable of applying varying amounts of fluid across the width of the plate to properly dampen the printing plate with the correct amount of fluid.

[0006] Another method utilizes spray nozzles which spray the fluid directly through an orifice. This method employs devices which are easily clogged, and plumbing systems which require frequent maintenance to keep them functioning properly. Another method utilizes a series of air jets which blow the fluid from disks which rotate in a pan of the fluid. This method eliminates most of the objections to the present systems, but requires frequent maintenance and critical mechanical adjustments. It also results in considerable difficulty in controlling the path of the fluid as it traverses the space from the source to the point of application of the fluid.

[0007] Various other methods have been employed over the years, but all methods known to exist are variants of the above basic concepts. No system to date allows application of remotely controlled amounts, without feed back of contaminants, or the use of complex mechanical devices or nozzles which spray the fluid directly. The system which blows the fluid from rotating disk addresses most of these objections, but it is not possible therein to precisely control the direction of the fluid, does not thoroughly atomize the fluid, and requires complex mechanical equipment to rotate the disks and to keep them clean and clear.

[0008] Particular examples of the prior art include U.S. Patents no 4,270,451; 4,000,695; 1,719,017; 2,689,523; 3,139,028; 3,776,133; and 4,232,603. Patent 4,270,451 (Perretta) shows the use of grooved rotatable disks to transfer water from a reservoir and the use of nozzles to blow water from the disk grooves onto an oscillating transfer roller. Patent 4,000695 (Perretta) shows an ink fountain blade assembly for transferring ink to a roller 12, through the use of blades having curved ends. patent 1,719,017 (Moe) shows the use of air jets to create vacuums in the upper ends of tubes to draw water from a reservoir and blast it in a circular form directly onto a plate cylinder. Patent 2,689,523 (Koch) shows the use of a single wide nozzle to blow water from the inside of a perforated cylinder that rotates through a reservoir. Patent 3, 139,028 (Huebner) utilizes mutliple nozzles that deliver circular, overlapping sprays by drawing water through tubes into the air jet and breaking it up. Patent 3,776,133 (Ritzerfeld) shows the use of an absorbent applicator consisting of a felt made of wool fibers and the like, to wet duplicator sheets. Patent 4,232,603 shows the use of a pick-­up roll having means on its surface for carrying water spaced from its surface, and of a gaseous blow means for blowing the water such that it contacts other portions of the pick-up roll from where it rebounds to impinge onto the surface of a transfer roll.

[0009] A main object of the invention is to provide a lithographic press dampening device that provides improved water control.

[0010] A related object of the invention is to provide such a dampening device which also enables incremental zone control across the width of the plate.

[0011] Another object of the invention is to provide such a dampening device which is subject to precise, push button control.

[0012] Still another object of the invention is to provide such a dampening device which can be computer controlled and can have its dampening profile displayed; additionally one having complete manual over-ride and that allows by-passing of the computer control on a zone by zone basis.

[0013] A further object of the invention is to provide such a dampening device which is more trouble free in operation and of low and easy of maintenance. Included in this object is the prevention of dampener contamination by ink feed-back.

[0014] Yet another object of the invention is to provide such a dampening device which has a low mechanical profile and thus can be readily fitted to all presses, web or sheet-fed, new or existing.

[0015] These objects of the invention are achieved by the blowing of thin air streams individually adjustable in real time, over an open-celled sponge to spray a fine mist onto a printing press roller to leave a vapor residue on it. The lower portion of the sponge rests in a reservoir of dampening fluid, which fluid flows to the top surface of the sponge by capillary action. Wetting of the top surface of the sponge is assured by mounting capillary tubes on the air stream source side of the sponge to blow water from the top of the tubes onto the sponge.

[0016] A feature of the invention is that the wetting of various zones of the printing press can be differentially adjusted during printing press operation as called for by monitoring its operation.

[0017] The above and other objects, advantages and features of the invention will be apparent from a consideration of the following description of a preferred embodiment of the invention when taken together with the accompanying drawings wherein:

Fig. 1 is a schematic profile of a printing press having the dampening device of the invention.

Fig. 2 is an exploded isometric view of the dampening device, per se, of Fig. 1.

Fig. 3 is a detailed vertical sectional view of a slightly modified dampening device.

Fig. 4 is an exploded isometric view of the tray contents of Fig. 3.

Fig. 5 is a schematic profile of a printing press having a dampening device that includes a shroud for further controlling mist.

Fig. 6 is an enlarged view in perspective of the shroud in Fig. 5.

[0018] Referring now particularly to Fig. 1 of the drawings, a printing press is shown as including a transfer roller having a surface 25 and adapted to carry vapor residue 23 from a spraying roller having a surface 21. The transfer roller having a surface 25 would normally also be interacting with a lithographic plate (not shown) to transfer the vapor residue to the plate surface to wet the non-printing and printing areas thereof properly. The spraying roller having the surface 21 receives its uniform vapor residue from the dampening device of the invention.

[0019] The dampening device includes an air manifold 1 having a series of exhaust ports 3 in its bottom. A tray 11 is mounted below and in front of the manifold and is secured to the underside thereof by a plate 5 formed integral with it. Tray 11 contains a conventional dampening fluid 13 (mostly water) and a corrugated member 9 of approximately 2mm thickness and having capillary tubes and so bonded to a sponge 15 (of one-­half inch thickness) that the upper ends of the capillary tubes terminate flush with the upper surface of the sponge; a fluted rubber member 35 (Figs. 3 and 4) spaces the corrugated member 9 and sponge from the bottom of the tray to facilitate water flow underneath the sponge and to the capillary tubes and so that their upper surface lies just below jet ports 7 formed just below the front edge of the manifold 1.

[0020] Inserted between the bottom of the manifold and the plate 5 is a uniquely shaped mylar gasket 29 (Fig. 4). The gasket is shown as formed with cut-outs 29A. Cut-outs 29A are aligned with the exhaust ports 3 in the bottom of the manifold 1. The gasket may be .0015 inches thick, so the height of the cut-­outs may be deemed .0015 inches high. The width of a cut-out may be once inch. The openings for each of the cut-outs form the jet ports 7 of Fig. 1. The manifold 1, gasket 29, and tray plate 5 may be secured in unitary assembly by a series of machine screws 33a - 33n (Fig. 2) so as to be air-tight, except for the manifold ports 3 communicating with the jet ports 7 via the gasket cut-outs 29A. The manifold ports 3 may each be formed with electrically or hydraulically operated valves 3A of conventional design whereby the size or pulse frequency of the ports may be varied by computer or manual control from remote points. Thus the air flow through a port 3, and hence a port 7, may be adjusted from continuous to over 1000 Hertz. In operation of the printing press, transfer roller having surface 23 and spraying roller having surface 21 would be rotating and requiring the transfer of vapor residue according to the nature of the printing and the speed of operation. Air under pressure would be being delivered to the manifold 1. A conventional dampening fluid 13 would be in tray 11 and wetting the sponge 15 and rising to its top surface by capillary action, and rising by capillary action in the tubes in the corrugated member 9.

[0021] Assuming now that particular ports 7 are not for a zone on a lithographic plate for which no wetting is desired, manifold ports 3 would be delivering air under pressure to jet ports 7 via gasket cut-outs 29A. Air leaving a jet port 7 in a wide stream is blown across the sponge 15 to pick up and atomize moisture therefrom (linear carburization) in the form of mist and spray it on to the surface 21 of the spraying roller where it deposits as a vapor residue. Air leaving a jet port 7 also blows over the upper ends of the capillary tubes in corrugated member 9. In do doing, the air stream picks up the dampening fluid at the upper ends of the capillaries to carry it across the sponge 15 to insure wetness of its surface.

[0022] Turning now Figs. 3 and 4, the tray 11 having a plate 5 is shown as being fastened to a frame 40 having exhaust ports 3 in its bottom, outside of a shim plate 42 and the mylar gasket 29 by machine screws 33. Contrary to Fig. 1 and Fig. 2, the pulsed air is delivered to the ports 3 by tubes 44. The tray 11 is so mounted with respect to the shim plate 42 that the latter extends a slight distance into the tray to form a lip. The cut-outs 29A (Fig. 2) of the gasket 29 terminate flush with the shim plate 42, and thus the jet ports 7 are just above the shim plate.

[0023] Sponge 15 and corrugated member 9 bonded thereto as by adhesive 45 (Fig. 4), is shown in the tray 11 as seated on a fluted rubber member 35. The dimensions of member 35 are such that the member holds the upper end of the corrugated member 9 against the underside of the lip of the shim plate 42 to fix the position of the upper surface of the sponge 15 and of the corrugated member 9 capillary tubes with respect to the jet ports 7.

[0024] The corrugated member 9 and sponge 15 are held in lateral position by a tray divider 46 which also sets the fluid level within the reservoir. The tray divider 46 in cross-section is formed of an inverted U-shaped portion having at the bottom of the longer leg a horizontal portion for welding to the bottom of the tray. The horizontal portion is of such length as to determine the divider spacing to properly hold the sponge 15 and corrugated member 9 in lateral position wherein the upper edge of the member 9 is seated below the shim plate 42. The short leg of the U-shaped portion of tray divider 46 terminates above the fluted rubber member 35 and is formed with holes to accommodate the movement of reservoir fluid into the sponge 15. The upper end of the long leg of the U-shaped portion of the tray divider 46 also is formed with a drain hole to fix the upper level of the reservoir.

[0025] An inlet 46 is provided to supply fluid (water, and various additions such as magnesium nitrate or phosphoric or muriatic acid and gum arabic and glycerine) to the tray reservoir. The fluid fills up in the reservoir to the height determined by the drain hole in the long leg of the U-shaped portion of the tray divider 46. The rubber fluted member 35 enables fluid movement underneath the sponge and the corrugated member, to supply them water. An outlet 50 cooperating with an opening in the horizontal portion of the tray divider, enables drainage of the excess fluid from the tray 11.

[0026] Referring now to Figs. 5 and 6, a shroud 52 is shown for embracing the dampening device of Figs 3 and 4. The shroud includes side plates 54 which are mounted on a pivot 56. The side plates 54 are rigidly connected by a top plate 58, which terminates at one end even with the side plates 52 to determine an opening for spraying the roller surface 21 and at its other end against the frame 40 when in operational position. A slot 60 is formed in the top plate 58 near its frame end to suck in any fugitive mist for reclamation while purifying the environment.

[0027] Depending from the free end of the top plate 58 adjacent the frame 40, as a top plate extension and curving inwards to define a return path for the fugitive mist entering the slot 60, is a plate 62. The plate 62 terminates near the free end of a plate 64 constituting an inwardly turned extension of the spray opening end of the top plate 58. The inward end of the plate 64 is downturned the appropriate amount to aid in shaping the horizontal contour of the spray mist. Drippings from the plate 64 and other droplets are collected in the bottom of the shroud by a plate 66 which interconnects the bottom edges of the side plates 54 and has a "V" shape in longitudinal cross-section. An outlet 68 located in a side plate 54 serves to drain collected fluid.

[0028] It will be evident that the shroud embraces the air stream emanating from the horizontal jet ports defined by the main frame 40, the gasket 29 cut-outs 29A, and the shim plate 42. The air stream flows over the sponge 15 to atomize and entrain moisture therefrom. The air stream bearing the entrained moisture (mist spray) flies out of the open end of the shroud to deposit a vapor residue on the press roller having surface 21. Mist hitting the sides of the shroud is condensed on cosntact and returned. The plate 64 intercepts the upper portion of the spray to help the jets 7 define the horizontalness of the spray. Movement of the air steam past the down turned edge of the plate 64 creates a Bernoulli effect, the low pressure of which is transmitted between the plate 62 and top plate 58 to the outlet 60 to suck in any fugitive mist thereabout.

[0029] The shroud 52 can be swung about pivot 56 to facilitate easy maintenance of the dampening device. New sponge 15 and corrugated member 9 assemblies can be easily inserted by simply pulling out the spent assembly and substituting the new one. Sponges may become spent by choking up on foreign ingredients of the fluid, and after awhile, the supply of fluid from corrugated member 9 capillary tubes may become inadequate to wet the sponge surface sufficiently.

[0030] It will be appreciated that the foregoing is to be considered as illustrative only of principles of the invention, and that while certain novel features of the invention have been shown and described, various omissions, substitutions and changes in the form and details of the device illustrated and in their use and operation can be made by those skilled in the art, without departing from the spirit of the invention.

Claims

1. A dampening device for a printing press or the like, including means for blowing a thin flat stream of air over a fluid source to create a mist.

2. A dampening device according to claim 1, wherein the fluid source is broadly disposed with respect to the air stream.

3. A dampening device according to claim 2, wherein the fluid source includes a sponge.

4. A dampening device according to claim 3, wherein a sponge has an upper surface flush with the upper end of a capillary tube juxtaposed next to the sponge.

5. A dampening device according to claim 4, wherein a tray embraces the capillary tube and sponge and is adapted to hold fluid to a level immersing the lower end of the capillary tube and the lower portion of the sponge.

6. A dampening device according to claim 2, wherein a plurality of means for blowing a thin stream of air are arranged in side by side relationship.

7. A dampening device according to claim 6, wherein capillary tubes are formed in a corrugated member extending across the plurality of means for blowing a thin steam of air.

8. A dampening device according to claim 7, wherein a sponge extends across the plurality of means for blowing a thin stream of air.

9. A dampening device according to claim 8, wherein the various means for blowing a thin stream of air are individually adjustable to vary the strength of the corresponding air stream.

10. A dampening device according to claim 9, wherein the various means for blowing thin streams of air comprises an air manifold, apertures for the respective air streams arranged across the manifold, a gasket for the manifold and having cut-­outs for the respective apertures, and a plate for sealing-off the other side of the gasket but not the open ends of the gasket cut-outs to form thin air stream jet ports.

11. A device for providing thin streams of air for lithographic press dampening devices and the like, comprising an air manifold, apertures for the respective air streams arranged across the manifold, a gasket for the manifold and having cut-­outs for the respective apertures, and a plate for sealing off the other side of the gasket but not the open ends of the gasket cut-outs to form thin air stream jet ports.

12. A dampening device according to claim 10 wherein the plate serves as the mount for the tray.

13. A printing press including a rotatable cylindrical surface able to bear ink, and a dampening device according to any of claims 1 - 10 and 12 to wet the cylindrical surface with mist generated by a thin air stream but spaced therefrom to avoid ink feed-back contamination of the fluid source.

Drawing