US3143065A

US3143065A - Moistening apparatus and method for offset printing presses

Info

Publication number: US3143065A
Application number: US34528A
Authority: US
Inventors: Russell C Warczak
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-06-07
Filing date: 1960-06-07
Publication date: 1964-08-04
Anticipated expiration: 1981-08-04

Description

Aug. 4, 1964 R. c. WARCZAK 3,143,065

MOISTENING APPARATUS AND METHOD FOR OFFSET PRINTING PRESSES Filed June 7, 1960 2 Sheets-Sheet 1 17 INVENTOR. 3 RUSSELL c. WARCZAK ATTORNEYS 1.964 R. c. WARCZAK 3,143,065

MQISTENING APPARATUS AND METHOD FOR OFFSET PRINTING PRESSES Filed June 7, 1960 2 Sheets-Sheet 2 INVENTOR. I

FIG? RUSSELL CEWARCZAK ATTORNEYS United States Patent 3,143,065 MGIS'IENBLNG AFPARATUS AND METHOD FOR FFET PRWTING PRESSES Russell C. Warczair, 518 W. Barry Ave, Chicago, Ill. Filed June 7, 1960, Ser. No. 34,528 16 Claims. (Cl. 101-147) The present invention is directed to improvements in dampening systems for offset printing presses and is particularly concerned with simplified and improved facilities for controlling the application of moisture to the printing plate.

In offset lithography, it is customary to utilize some means for applying a fine film of moisture to a plate which is carried by the cylinder in the printing press. By applying the moisture to the plate, ink is applied only to the areas of the plate intended for printing contact with the so-called' blanket cylinder which transfers the image to the paper. It is customary to utilize a plate which may have greasy areas in the form of the desired printing image. For example, a copper plate may be used. The copper tends to be greasy and does not pick up the water from the dampening unit, whereas the other areas of the plate will pick up the water. The wetted areas will not take up ink from the inking rollers that apply ink to the printing areas of the plate. It is customary in this form of printing process to apply moisture through the use of rollers which may or may not have covers of paper or other material. These moisture applying rollers or the covers wear and become dirty and consequently require replacement from time to time. In large units, special precautions must be taken to prevent the extremely long rollers from sagging. Furthermore, any contact between the plate and these rollers (or the covers) causes wear of the plate. Some attempts have been made to utilize some form of spray for applying this moisture but for some reason or another these spray systems, which in some instances have involved the use of nozzles for directing compressed air through a perforated plate which carries moisture, have not gone into commercial use of any consequence.

The present invention is concerned with simplified and efficient means for applying moisture to the plate in the form of a fine mist and in such a fashion that the amount of moisture which is applied to the plate may be easily varied through a relatively wide range and which at the same time utilizes simple and inexpensive instrumentalities for producing the desired spray.

Another purpose of the invention is to provide a simple and efficient system for varying the amount of moisture applied to a plate over different areas of the plate.

Another purpose of the present invention is to provide a simple mechanism for controlling the application of moisture to a plate cylinder in the form of a fine mist spray. 7

Other purposes will appear from time to time in the course of the ensuing specification and claims when taken with the accompanying drawing in which:

FIGURE 1 is a diagrammatic view of an off-set lithographing press with the present invention applied thereto;

FIGURE 2 is an enlarged view of certain portions of the assembly illustrated in FIGURE 1;

ice

FIGURE 3 is a detailed view, in partial sections for purposes of clarity, of a cylindrical screen, manifold, and fountain solution reservoir assembly utilized in the invention;

FIGURE 4 is a sectional view of the manifold illustrated in FIGURES 1, 2 and 3;

FIGURE 5 is a side view of the assembly similar to FIGURE 2 but illustrating certain additional features of the invention;

FIGURE 6 is a front view of certain stop elements illustrated in FIGURE 5;

FIGURE 7 is a side diagrammatic view of the invention as utilized with a mechanism for controlling and intermittently stopping the application of the fine mist of moisture to the plate.

Like elements are designated by like characters throughout the specification and drawings.

With particular reference to the drawings and in the first instance to FIGURE 1, the numeral 10 designates the plate cylinder which may have the customary plate 11 aflixed to the peripheral surface thereof. In plate and cylinder assemblies of this type, the ends of the plate are clamped into a recessed portion of the cylinder as is designated generally at 12.

A series of rollers, diagrammatically represented at 13, are adapted to apply ink to the printing surface of the plate 11 in more or less conventional fashion and by means that are well known to this art. 14 designates a blanket cylinder which may receive the printed image from the plate 11 during rotation of the

cylinders

10 and 14 and then transfer the image received to the paper or substance upon which the image is printed.

In accordance with the present invention a dampening unit designated generally at 15 is located in close proximity to the plate cylinder. The dampening unit includes a cylindrical screen 16 which has a length corresponding generally to the width of the plate 11 (taken longitudinally of cylinder 10). The cylindrical screen 16 is adapted to dip into a reservoir 17 for a fountain solution or moistening liquid. The reservoir 17 is supported beneath the screen 16. It is preferable that the screen 16 be located with its surface closely adjacent to the surface of the plate 11. It may be approximately 4 inch away from the surface of the plate 11. It should be understood that the cylinder 16 may be spaced more closely than this and at greater distances from the plate 11 than this spacing, although as the distance from the plate 11 increases the control of the moisture applied to the plate 11 becomes more difficult.

The dampening unit is preferably located at one side of cylinder 19, with the axis of screen 16 at or near a horizontal plane passed through the axis of cylinder 10.

The screen 16 may be unitarily formed as a cylinder without any seams although the screen 16 may be formed with a spiral seam thereby enabling the use of flat screen stock in the formation of the cylinder. It is preferred to use screen of between 35 mesh and mesh. The screen can be smaller although as the openings or interstitial spaces in the screen decrease in size the unit becomes less efiicient.

As is particularly seen in FIGURE 3, the screen 16 is supported by

end discs

18 and 19, which discs are journaled for rotation in suitable bearings (not shown).

a 3 These

end plates

18 and 19 have driven

gears

20 and 21 fixed thereto for rotation therewith.

A manifold, which may conveniently take the form of a cylinder 22 is positioned Within the screen 16 and has a length corresponding generally to that of the screen 16. The manifold has an air inlet tube 23 which extends through an opening in one end casting; 19, which inlet 23 provides support for one end of the manifold. The other end of the manifold may be rotatably supported in a bearing in the other end casting 18, if the length of the manifold makes such support necessary. It should be understood that Whereas the manifold 22 is shown as having a single air inlet 23, the manifold 22 may be supplied with air from an inlet in each end thereof.

The manifold 22, as is seen best in FIGURES 2 and 4, has an air discharge orifice 24 which is positioned closely adjacent to the inner peripheral surface of the screen 16. The orifice 24 takes the form of a slot which extends through a distance generally equal to the length of the manifold and substantially equal to the length of the screen. It extends in a direction generally parallel with the axis of the screen cylinder 16 and axis of the cylinder 10. It is important that the orifice 24 be formed so as to direct a flow of air at an angle to the surface of the screen 16. The orifice has a direction such that, as seen in FIGURE 4, it is inclined to a radius of the manifold and also inclined to a radius of the screen that passes through the orifice or a radius that passes through the screen at the mid point of contact with the air flow from orifice 24. Similarly as seen in FIGURE 2 the orifice 24 is inclined to the surface of the plate cylinder and inclined toward the direction of the rotation of the plate cylinder. It has been found that an angle of 20 degrees between the diameter of the manifold and the axis of the slot, as is seen in FIGURE 4, is satisfactory in the present invention. The actual angle may vary from this 20 degree figure. It may for example vary between approximately degrees and 30 degrees. The angle should be such that the fiow of the air from the orifice can pass substantially unobstructed through the spaces between the screen wires. If the angle is much greater than this range, then the air tends to impinge upon the screen wires with the result that very little air goes through the screen wires without deflection. Similarly the angle must not be so small as to cause water carried by the screen to be forced downwardly towards the reservoir 17. For example, if the axis of orifice 24 is directed along a radial towards the screen then the air directed through the orifice tends to .cause the water entrapped in the interstitial spaces of the screen to run back down the screen towards the reservoir 17. The inclination of the orifice 24 with respect to the plate cylinder also is important since this inclination in the direction of rotation of the plate cylinder tends to direct moisture carried from the screen in the general direction of rotation whereas if the moisture contacts the plate cylinder in a radial direction then it tends to spread in the opposite direction which is disadvantageous.

It is oftentimes desirable to vary the amount of moisture delivered to different areas of the plate taken widthwise (or axially) of the plate. To this end, a series of stops of varying widths and varying densities may be positioned widthwise of the plate (or lengthwise of the screen 16 as is seen in FIGURES 5 and 6). These stops 25 are held by clamps 26 which are clamped to the supporting bar 27 which extends above the screen cylinder 16 and in a direction generally parallel to the axis of the screen cylinder. These stops may have varying densities, as, for example, varying from a solid plate which stops the flow of moisture altogether to a screen of relatively large mesh which only slightly reduces the flow of moisutre to the plate cylinder. For example, in FIGURE 6 the stop 25a is illustrated as a stop of solid formation, whereas the stop 25b is illustrated as a stop of fine mesh. The stop 25c is illustrated as a screen of relatively large mesh.

These stops preferably have an arcuate configuration as seen in FIGURE 5 with their lower ends positioned above or within the reservoir 17. Thus moisture entrapped by these stops may run down the stops and back to the reservoir. In this way, varying amounts of moisture may be applied to varying areas taken widthwise of the plate 11.

FIGURE 7 illustrates a mechanism for driving the screen cylinder at varying speeds and for controlling the movement of the screen cylinder 16 in timed relation to the rotation of the plate cylinder. Drive gears 28 are in engagement with the driven gears 20 and 21 and are adapted to be rotated through partial revolutions by means of a crank 29 which is interconnected with the drive gears 28 through a pawl and ratchet type of clutch, so that upon movement of the crank 29 to the left the drive gear is rotated while upon reverse movement the drive gear is stationary. A cam 3% is driven in timed relation to the rotation of the plate cylinder 16 and may be, for example, interconnected with the plate cylinder drive so as to rotate through one revolution for every revolution of the plate cylinder. A follower link 31 is pivoted to a fixed support as at 32 and is interconnected with the crank 22 through a lever 33, which lever may be pivoted to the link 31 at an adjustable position designated at 34 along the length of the link 31. The pivot block for the pivot 34 may be adjustably positioned by means of a threaded connection with a screw 36, which screw may be rotated by means of a handle 37.

The cam 35) is adapted for contact with a cam follower roller 33 carried by the link 31. Cam 30 has a configuration such that it causes forward movement, or movement to the left as seen in FIGURE 7, of the link 31 when the forward edge of the plate 11 approaches a position generally aligned with the flow from the nozzle 24. When the end of the plate approaches a position aligned with the nozzle 24, follower 58 moves from the high point to the low point of the cam, allowing the spring 39 to Withdraw the actuating linkage, and thus stopping movement of the screen 16.

Only a partial revolution of the screen cylinder is used for each revolution of the plate cylinder 10 in the form of the invention illustrated in FIGURE 7. For example, one-fourth of an inch of circumferential area of the screen cylinder may be used to supply moisture to one foot of circumferential area of the plate. The rotation of the screen cylinder 16 is stopped when the opening between the ends of the plate passes the nozzle 24. By varying the pivot point 34 between the lever 33 and link 31 the amount of throw of the crank 22 may be varied and thereby the amount of rotation of the drive gear 28 may be varied. The variance in the rotation of the drive gears 28 produces an attendant variation in the amount of travel of the screen 16 during any one revoluation of the plate cylinder 10. Small amounts of rotation of the screen cylinder 16 result in relatively small amounts of moisture being applied to the plate cylinder during the rotation thereof, whereas relatively large amounts of rotation of the screen cylinder 16 result in more moisture being applied, per unit area, to the plate.

The mechanism of FIGURE 7 is particularly applicable to printing presses having an opening between the ends of the printing plate as is found in many installations. In some cases, as for example with a roll fed or web fed olfset press, where the ends of the plate are quite close to one another, the driven gears 21 and the screen 16 may be continuously rotated by means of any suitable electric motor drive or by a drive connected to the drive for the plate cylinder 10. A variable speed transmission is preferable in these installations in that it allows a variance in the speed of rotation of the screen 16 with an attendant variation in the amount of moisture supplied to the plate 11 during rotation thereof.

In operation, a centrifugal type of blower or fan is used to supply a large volume of low pressure air to the manifold 22, which acts as a plenum chamber. The discharge slot 24, which may have a width of approximately a fiftieth of an inch, has a size such the manifold is kept under low pressure throughout the length thereof. It is desirable to keep the width of the slot 24 as small as possible so as to minimize the volume of air necessary while still being sufficient to dislodge the water from the screen. In a typical installation the blower 22a may supply on the order of 1.25 to 2.18 cubic feet of air per minute per lineal inch of orifice length, which is entirely adequate in providing the fine mist desired in the invention. Pressures in the range of 4 to 12 ounces per square inch (above atmospheric) are entirely adequate for the invention. Higher pressures are used with screens of fine mesh while lower pressures are used with screens of larger mesh. The phrase low pressure, high volume air flow, as used herein, is intended to apply to those low pressure air flows produced by a fan or blower, as distinguished from compressed air delivered from an air compresser.

In operation, as the forward end of the plate 11 moves to a position approaching alignment with the flow from discharge orifice 24, the screen rotating mechanism causes rotation of the screen through a partial revolution, thereby bringing moisture entrapped in the interstices of the screen into alignment with the discharge orifice 24. During this rotation of the screen 16 the air discharged through the orifice 24 tends to blow Water from one row of screen spaces at a time, which moisture is dispersed as is shown by the dotted lines in FIGURES 2 and 5, The dispersal is in the form of a fine mist and due to rotation of the plate cylinder this dispersal is over a relatively large circumferential area of the plate. When the end of the plate 11 approaches the point of alignment with the discharge from orifice 24, the cam actuating linkage retracts and stops rotation of the screen 16 until the forward end of the plate again approaches alignment with the discharge orifice, at which time the cam actuating linkage again produces a partial rotation of the screen 16 so as to properly moisten the plate.

If relatively large amounts of moisture are required on the plate, the pivot point 34 is moved upwards on the link 31 so as to increase the throw of the crank 29 and thereby increase the travel of the screen 16 for each revolution of the plate cylinder it if the amount of moisture should be decreased the pivot point 34 is moved downwardly on the link 31 so as to decrease the throw of the crank 29 and decrease the amount of travel of the screen per revolution of the plate cylinder in.

On roll fed or Web fed offset presses the variable speed transmission may be used to vary the amount of moisture delivered to the plate through varying the speed of rotation of the screen 16.

It should be noted that the rotation of the screen 16 is such, with relation to the position of the discharge slot 24, that a relatively small area of the screen above the fountain solution carries entrapped Water at one time, the spaces in the upper portion of the screen being open. In this connection, it should be noted that the surface of screen 16 moves in the same direction as the surface of plate 11 adjacent orifice 24, even though cylinder 15) is shown as rotating counterclockwise and screen 16 is shown as rotating clockwise. It should also be noted that screen 16 travels in a direction from reservoir 17 immediately toward the side of the manifold in which the slot 24 is located. By so relating the direction of rotation of the screen 16 to the position of the orifice, the system avoids a pressure build-up within the screen.

By varying the speed of rotation of the screen 16 the amount of moisture delivered to the plate surface may be varied from printing situation to printing situation. Similarly it is possible by changing the speed of rotation of the screen 16, during the time the plate is exgids ed to the flow of moisture, to vary the amount of moisture applied to the plate over different circumferential areas of the plate, or peripherally of the plate.

The amount of moisture may be controlled widthwise of the plate by the use of the different stops 25 of different widths and different densities. It should be noted that the flow of air from the manifold is continuous and that the entire control of the application of moisture itself is controlled by control of screen movement, as by intermittent start ing and stopping of the screen 16 in the case of presses using gaps between the ends of the plate. In other presses, such as web or roll fed presses, the control is still through control of movement of the screen cylinder. By controlling through so controlling the movement of the screen cylinder itself, the invention avoids sudden surges of pressure which result in an unusually large amount of moisture delivered from the screen, which happens if the flow of air is intermittent of if the flow is stopped by placing stops in the path of air.

The mist applied is sufficiently uniform that the use of a moisture spreading or distributing roller is unnecessary.

The use of low presure air requires only blowers or fans that are inexpensive as compared to high pressure air systems or compressors. In addition, low pressure air causes relatively little wear on the manifold, discharge slot, screen and conduit leading to the manifold.

Whereas I have shown and described certain operative forms of the invention it should be understood that this showing and description thereof should be taken in an illustrative or diagrammatic sense only. There are many modifications in and to the invention which will fall within the scope and spirit thereof and which will be apparent to those skilled in the art. The scope of the invention should be limited only by the scope of the here inafter appended claims.

I claim:

1. The method of moistening a rotating printing plate cylinder including the steps of directing a flow of low pressure air against a moving screen having a moistening liquid entrapped therein with the flow being in a direction inclined to the surface of said screen and directed toward the plate cylinder in the general direction of rotation of the plate cylinder, the flow being inclined in the direction of said movement of said screen, the inclination of the air flow in relation to said screen surface being such as to avoid substantial surface reflections of the air flow by said screen and at the same time large enough to avoid forcing the moistening liquid down the surface of said screen.

2. The method of moistening a plate cylinder of a printing press including the steps of rotating a moistening liquid carrying cylindrically formed screen in close proximity to a plate cylinder and directing a flow of low pressure air along the surface of substantially the entire length of said screen and through a small circumferential width of said screen, the direction of flow of said air being inclined to a radius of said screen at the point of contact with the flow at a small angle and being inclined to a radius of the plate cylinder at the area of contact between the flow and plate cylinder in the direction of rotation of said plate cylinder.

3. The method of claim 2 wherein said air flow is directed at an angle of 15 to 30 degrees with relation to a radius of said screen which intersects the screen at the midpoint of contact of the screen with said air flow.

4. A moistening assembly for use with printing plate cylinders including a cylindrical screen and means mounting said screen for rotation, a moistening solution reservoir positioned beneath said screen so that the lower portion of said screen moves within a moistening liquid carried by said reservoir during rotation by said screen, a manifold positioned within said screen and having an air outlet orifice positioned adjacent to the surface of said screen for delivering an air flow to the screen, said orifice being elongated and being inclined to a radius of said screen which intersects the screen at the mid point of contact with said air flow, and means delivering low pressure air to said manifold, the air being delivered in a volume such that the manifold is kept under substantially the same pressure throughout the entire length thereof.

5. A moistening assembly for printing plate cylinders including a reservoir for containing a moistening liquid, a screen and means mounting said screen above said reservoir but such that of a portion of said screen is positinned Within the liquid within said reservoir, means for moving said screen so as to carry moistening liquid within the interstices of said screen, means for directing a flow of air against said screen so as to remove the moistening liquid therefrom, said moving means including means for moving said screen past said air flow means, and a series of moistening controlling members of varying widths positioned longitudinally of said screen and in the path of the flow of moistening liquid from said screen, said controlling members having varying densities so as to vary the amount of liquid delivered therethrough widthwise of the printing plate.

6. A moistening assembly for plate cylinders of printing presses including a printing plate cylinder, and a cylindrical moistening screen positioned adjacent to said plate cylinder, a reservoir positioned beneath said screen cylinder so that the lower portion of said screen cylinder is within a moistening liquid carried by said reservoir, a manifold within said screen cylinder and means delivering air to said manifold in large volumes but at low pressures, said manifold having an elongated orifice therein and positioned adjacent to said screen cylinder whereby air from said manifold is delivered through said orifice and against said screen, and means for rotating said screen cylinder such that the screen cylinder carries liquid from said reservoir in the interstices of said cylinder and past the air flow through said orifice, whereby moistening liquid carried by said screen cylinder is carried to said plate cylinder in the form of a fine mist, and means for stopping the rotation of said screen cylinder during instances that the plate clamp opening of said plate cylinder is opposed to the flow from said screen, thereby stopping the flow of liquid during such instances.

7. A moistening assembly for plate cylinders of printing presses including a printing plate cylinder, and a cylindrical mostening screen positioned adjacent to said plate cylinder, a reservoir positioned beneath said screen cylinder so that the lower portion of said screen cylinder is within a mositening liquid carried by said reservoir, a manifold within said screen cylinder and means delivering air to said manifold in large volumes but at low pressures, said manifold having an elongated orifice therein and positioned adjacent to said screen cylinder whereby air from said manifold is delivered through said orifice and against said screen, means for rotating said screen cylinder such that the screen cylinder carries liquid from said reservoir in the interstices of said cylinder and past the air flow through said orifice whereby moistening liquid carried by said screen cylinder is carried to said plate cylinder in the form of a fine mist, said rotating means comprising a driven gear fixed to and rotatable with said cylinder and a drive gear enmeshed therewith, and a mechanism driven in timed relation with said plate cylinder for rotating said drive gear to cause movement of said screen cylinder during instances that the plate is opposed to the liquid of said screen While stopping such movement during instances that the plate opening is opposed to the air fiow.

8. The structure of claim 7 wherein said mechanism includes a cam rotated in timed relation to the rotation of said plate cylinder and a cam follower linkage interconnected between said cam and said drive gear, said cam and said follower linkage being adapted to cause partial rotation of said drive gear and partial rotation of said driven gear when the plate on said cylinder is opposed to the direction of flow from said orifice and said screen.

9. The structure of claim 7 wherein said mechanism includes a cam driven in timed relation to the said plate cylinder and an oscillating cam follower associated with said cam, a lever connected to said link and said drive gear such that movement of said link produces a partial rotation of said gear and thereby produces a partial rotation of said driven gear and said screen, and means for adjusting the point of connection between said link and said lever to thereby adjust the amount of travel of said drive gear during a revolution of said cam and thereby vary the speed of movement of said screen and amount of moistening liquid delivered to said plate cylinder per unit area.

10. A moistening assembly for printing plates and the like including a moistening liquid reservoir and a screen positioned for movement through said reservoir and above said reservoir, means for moving said screen from said reservoir to positions disposed upwardly from said reservoir, an air manifold positioned adjacent said screen, said air manifold having a discharge slot positioned close to said screen, the axis of said slot being directed at an inclination to the surface of said screen and in the same direction as the direction of movement of said screen, the width of the discharge orifice and the spacing from said screen being such that low pressure, high volume air delivered from said orifice contacts at least one horizontal row of screen spaces.

11. The structure of claim 10 wherein said screen has a size of approximately between 35 mesh and 70 mesh.

12. The structure of claim 10 wherein said discharge slot has a width of approximately one-fiftieth or" an inch.

13. A moistening assembly for printing plate cylinders including a reservoir for containing a moistening liquid, a screen and means mounting said screen above said reservoir but such that a portion of said screen is positioned within the liquid within said reservoir, means for moving said screen so as to carry moistening liquid within the interstices of said screen, means for directing a flow of air against said screen so as to remove the moistening liquid therefrom, said moving means including means for moving said screen past said air flow means, and moistening controlling means positioned longitudinally of said screen and in the path of the flow of moistening liquid from said screen, said controlling means having variable densities at different locations lengthwise of said screen as to vary the amount of liquid delivered therethrough width- Wise of the printing plate.

14. A moistening assembly for plate cylinders of printing presses including a printing plate cylinder, a moistening screen positioned adjacent to said plate cylinder, a

reservoir positioned beneath said screen so that the lower portion of said screen is within a moistening liquid carried by said reservoir, a manifold adjacent to said screen and means delivering air to said manifold in large volumes but at low pressures, said manifold having an elongated orifice therein and positioned adjacent to said screen whereby air from said manifold is delivered through said orifice and against said screen, and means for moving said screen such that the screen carries liquid from said reservoir in the interstices thereof and past the air flow through said orifice, whereby moistening liquid carried by said screen is carried to said plate cylinder in the form of a fine mist, and means for stopping the movement of said screen during instances that the plate clamp opening of said plate cylinder is opposed to the flow from said screen, thereby stopping the flow of liquid during such instances.

15. The method of delivering a fine mist of moisture for use in moistening a printing plate cylinder including the steps of directing a flow of low pressure air in large volumes through an elongated orifice and to a moisture carrying screen, the air being delivered at a pressure in the range of 4 to 12 ounces per square inch above at- 9 mospheric pressure, and at a volume on the order of approximately 2.18 cubic feet of air per minute per linear inch of orifice length, said orifice being positioned sufficiently close to said screen as to pick off moisture carried by said screen and deliver the same therefrom in the form of a fine mist.

16. The method of moistening a printing plate cylinder through use of a flow of air directed through the interstices of a moisture-carrying screen including the steps of directing a flow of low pressure air from an elongated orifice, the air being delivered in volumes such that the orifice is kept under substantially the same pressure throughout the entire length thereof, the orifice being positioned closely adjacent to the screen with the direction of the flow and the close positioning of the orifice with 15 3,025,789

10 relation to the screen being such as to substantially avoid forcing moisture along the surface of the screen while substantially avoiding surface reflections of the air flow by the screen whereby moisture is carried from the intersticial spaces of the screen and to the plate cylinder in the form of a fine mist.

References Cited in the file of this patent UNITED STATES PATENTS 841,142 Gramlich Jan. 15, 1907 2,622,520 Hauser et a1 Dec. 23, 1952 2,660,113 Gullixson et a1 Nov. 24, 1953 2,689,523 Koch Sept. 21, 1954 2,791,174 Koch May 7, 1957 Huebner Mar. 20, 1962

Claims

4. A MOISTENING ASSEMBLY FOR USE WITH PRINTING PLATE CYLINDERS INCLUDING A CYLINDRICAL SCREEN AND MEANS MOUNTING SAID SCREEN FOR ROTATION, A MOISTENING SOLUTION RESERVOIR POSITIONED BENEATH SAID SCREEN SO THAT THE LOWER PORTION OF SAID SCREEN MOVES WITHIN A MOISTENING LIQUID CARRIED BY SAID RESERVOIR DURING ROTATION BY SAID SCREEN, A MANIFOLD POSITIONED WITHIN SAID SCREEN AND HAVING AN AIR OUTLET ORIFICE POSITIONED ADJACENT TO THE SURFACE OF SIAD SCREEN FOR DELIVERING AN AIR FLOW TO THE SCREEN, SAID ORIFICE BEING ELONGATED AND BEING INCLINED TO A RADIUS OF SAID SCREEN WHICH INTERSECTS THE SCREEN AT THE MID POINT OF CONTACT WITH SAID AIR FLOW, AND MEANS DELIVERING LOW PRESSURE AIR TO SAID MANIFOLD, THE AIR BEING DELIVERED IN A VOLUME SUCH THAT THE MANIFOLD IS KEPT UNDER SUBSTANTIALLY THE SAME PRESSURE THROUGHOUT THE ENTIRE LENGTH THEREOF.