US2972944A - Dampening device and method for lithographic offset printing plate - Google Patents

Description

Feb. 28, 1961 H. P. DAHLGREN DAMPENING DEV Filed April 9, 1956 2 Sheets-Sheet 1 INVENTOR m M H Li.

ATTORNEYS Feb. 28, 1961 H. P. DAHLGREN 2,972,944

DAMPENING DEVICE AND METHOD FOR LITHOGRAPHIC OFFSET PRINTING PLATE 2 Sheets-Sheet 2 Filed April 9. 1956 INVENTOR Hero/d A? Dab/grew D 0 0 3 BY k m ATTORNEY s DAMPENING DEVICE AND METHOD FOR LITHO- GRAPHIC OFFSET PRINTING PLATE Harold P. Dahlgren, Mobile, Ala. (6919 Blackwood, Dallas 31, Tex.)

Filed Apr. 9', 1956, Ser. No. 577,031

11 Claims. c1. 101 -148 This invention is concerned with an improvement in dampening devices for lithographic offset printing plates and it is particularly concerned with a dampening device wherein water or other liquid is atomized and propelled against, and deposited on, an ink applying form roller or other intermediate roller from whence it is deposited on the plate.

A lithographic offset printing plate is chemically treated so that the printing or image area thereon has an afinity for the relatively greasy ink and the non-printing area thereon has an afiinity for moisture. It is necessary to apply moisture to the non-printing area of the plate in order to keep it from receiving ink.

Various means have been employed in the past for applying moisture to the printing plate, none of which have been entirely satisfactory.

Such means of applying moisture to the plate have included wicks or swabs which wiped against the plate as it rotates, individual spray heads spaced along the length of the plate drum, air jets which blew moisture from a fabric belt or screen, the mixing of water with the ink supply and applying it directly to the inking rollers, and the application of moisture to the plate by means of fabric covered rollers which dip into awater pan and roll directly against the plate to deposit moisture thereon. The latter means is the most common type of dampening device presently employed.

All of these plate moistening systems have proven deficient for one reason or another. Use of swabs or wicks bearing directly against the plate damage the plate by friction, thus decreasing the life of the plate, and they do not provide uniform distribution of moisture. The use of spray heads is unsatisfactory because of the difiiculty of adjusting the spray heads to apply the correct amount of moisture, and they usually supply more moisture than is needed or is desirable.

The use of air jets to blow moisture onto the plate also presents the problem of proper adjustment to supply the desired amount of moisture to the plate.

Furthermore the use of spray heads and air jets presents the problem of proper lateral distribution of moisture to the plate, in that more moisture would be applied at some points than others.

The mixing of water with the ink supply causes the ink to emulsify. The emulsified fluid becomes unevenly distributed on the ink rollers, resulting in poor quality of the printed material.

Another means of applying moisture to the printing plate was the condensation of steam on the plate. Such means was found deficient because the plate became heated by the steam to such an extent as to prevent condensation. It was attempted to solve this problem by cooling the plate cylinder by artificial means as the steam was applied, but this required complicated and clumsy mechanisms which were difficult to adjust to apply the proper amount of moisture to the plate and to maintain even distribution thereof.

' 2,972,944 7 atented Feb. 2%, 1961 directly to the offset printing plate, which is the dampening means most universally employed at this time, has proven inadequate because the fabric soon becomes impregnated and encrusted with ink by direct contact with the plate, resulting in .the necessity for repeated changing of the rollers, which results in costly down time of the press and unnecessary labor. It is also a laborious task to change the fabric on the rollers.

Excess water accumulates in the fabric covered dampener rolls which often necessitates the stopping of 'thepress to allow the rolls to dry.

Furthermore, when the press is started sufiicient time must be allowed to cause'the. rolls to be evenly saturated with water, thus resulting in lost production.

After a time the fabric covered dampener rolls become worn by frictional contact with the plate causing lint from the fabric to be deposited on the printing area of the plate. The water saturated lint causes white specks on the printed matter.

The frictional contact of the dampener rollers causes deterioration and wear on the plate, resulting'in distortion and loss of printed images.

When ink color is changed dampener covers. must usually be changed, so that impregnated pigment from prior color does notcontaminate new color.

By reason of the change in the absorptive character dampening device which is not in physical contact with the plate and in one with non-changing mechanical aspects'. This would assure consistency and uniformity of moisture supply and distribution. This invention is intended to solve that problem.

In my co-pending application for patent, Serial No. 458,226, filed September 24, 1954, now Patent No. 2,868,-

' 118, issued J anuary' 13, 1959, therewas disclosed a dampening' device wherein atomized moisture was applied directlyito the face of the lithographic offset printing plate bymeans of a rotary brush which flicked water from the surface of a rotary waterconveyor roller as the brush and roller rotated in contact. i V 1 The advantages of this system, as set forth in said copending application, are that moisture is conveyed to the plate without physical contact therewith; it is evenly distributed laterally across the face of the plate as it rotates; there is no wear or abrasion to the plate by friction; and it is possible to accurately adjust the amount of moisture applied to the plate by adjusting the speed of rotation of the water'conveyor roller. By using such system it is possible to accurately adjust the amount of moisture to be applied to the plate for each job, and it is unnecessary to readjust same during the operation of the press. No foreign matter, such as lint, is deposited on the plate.

The moisture applying brush is durable' an'd long lasting,

thus resulting in a great savings in labor and down time of the press.

Although the system of applying moisture directly to the plate "by such brush, as disclosed in' said co-pending application, has the advantage hereinbefore stated and would have particular use in a web-fed ofiset press, wherein there is no gap in the plate cylinder, it has been found that in applying moisture directly to the plate in a lithographic ofiset press, wherein there is'a gap in the cylinder for attaching the ends of the plate, it is desirable to apply the moisture to the plate indirectly by depositing it on one of the inking form rollers from whence it is deposited on the plate. of moisture in the gap which would, in some instances, .cause the accumulation of excessive moisture on the plate at the edges of the gap. a

In said co-pending application a cam arrangement was provided for lifting the brush away from the water conveyor roller as the brush passed the gap in order to pre- .vent deposit of moisture in the gap. The improvement, forming the basis of this application, eliminates the necessity of such cam arrangement and also prevents the deposit of moisture in the gap.

The present invention includes the basic advantages of the employment of the said brush to atomize, propel, distributeand deposit moisture on the plate and at the same time offers an improvement which makes it universally applicable to all types of lithographic offset printing wherein moisture must be applied to the plate, and at the same time simplifies the system and provides for more even distribution of moisture on the non-image area of the plate.

It is therefore a primary object of this invention to provide means for applying moisture to lithographic offset printing plates wherein the moisture may be applied in regulated quantities, and evenly and uniformly distributed on the plate without repeated adjustment.

Another object is to provide a dampening means for lithographic offset printing plates wherein lateral distribution of the moisture is attained and maintained without repeated adjustment.

A still further object is to provide dampening means for lithographic offset printing plates which is durable and long-lived and results in the reduction to a minimum of down time of the press. i

Still another object is to provide a dampening device for a lithographic ofiset printing plate which is simple to operate and relatively inexpensive-to manufacture, and is easy to adjust, install and remove.

A further object is to provide av dampening means for lithographic offset printing plates wherein moisture is applied uniformly and evenly to an inking form roll or other intermediate roller in rotative contact withthe plate from whence it is deposited on the plate, thus preventing moisture from collecting in the plate cylinder p Another object of this invention is to provide a dampening device for lithographic oflset printing plates which employs a brush rotated against a wet surface to flick moisture off the surface in atomizedparticles and projects or propels the atomized particles in a controlled stream of moisture against the face-of an inking form roller or other roller from whence it is deposited on the face of the plate as the roller rolls thereagainst.

Other and further objects of my invention will become apparent upon reading the ensuing specification and by referring to the drawings annexed hereto.

. A suitable embodiment of my invention is shown in the attached drawings,-in which;

Fig. I is a fragmentary cross-sectional elevational view of a lithographic offset printing press having attached thereto the plate dampening mechanism comprising the improvements with which this invention is concerned. In said view the plate dampening mechanism is shown in operative position, wherein moisture is being applied This eliminates the accumulation 1 to the surface of a form roller which is in rotative contact with the plate cylinder. In said view only such portions of the lithographic offset press are shown, as will show the connection of said dampening device to said the offset press, which permits the retraction of the tion of the said improved dampening device.

Fig. II is a view similar to Fig. I, showing the dampening device in retracted position, with the form rollers disengaged from the plate cylinder and the rotatable brush disengaged from the liquid conveying roll.

Fig. III is a fragmentary cross-sectional view taken on the line IIIIII of Fig. I, showing the slidable mounting of the dampening device frame on the end frame of the offset press, which permits the retraction of the dampening device frame when the press is shifted to nonimpression position.

Fig. IV is a fragmentary plan view of the water conveyor roller showing the knurled or roughened surface of the roller. p Numeral references are employed to designate the various parts of the devices shown in the drawings, and like numerals indicate like parts throughout the various figures of the drawings.

The numeral 1 indicates a fragmentary portion of one of the side frames of a conventional lithographic offset printing press. It is believed unnecessary for the purpose of the disclosure of this invention to illustrate a complete lithographic offset printing press, the construction and operation of which are Well-known to those skilled in the art. This invention is specifically addressed to a dampening device for applying moisture to the plate, and only such portions of the press are shown as will illustrate, and provide a proper orientation, for the construction and operation of therdampening device.

It will be understood that there is a side frame l at each side of the lithographic offset press, and that the view shown in Figs. I and II hereof are elevational sectional views taken at a point intermediate the sides of the press and looking toward one of the sides.

The plate cylinder 2 is mounted on a shaft 3, which shaft is journaled at each end to the side frames 1. A lithographic offset plate 4 is arranged about, and secured to, the outer side of the plate cylinder 2 by means of clamp elements 6, whiehare recessed in the gap 5 in the periphery of the plate cylinder 2, and in a manner which is well-known in the art.

A blanket cylinder 7, which has on its outer surface a covering of specially treated and prepared rubber material,.is'mounted on a shaft 8 which is journaled at each end to the end frames 1.

.The impression cylinder 9 is mounted on a shaft 10 which is also journaledat its opposite ends to the end frames 1.

Gears 11, 12 and 13 are secured to the shafts 3, 8 and 10, respectively, at the ends thereof, whereby the cylinders 2, 7 and 9 are rotated in unison from a suitable power source (not shown).

An inking vibrator roller 14, which is usually of metallic construction, is mounted on a shaft 15 which is journaled at each end to the end frames 1. Ink applying form roller 16, which is mounted on a shaft 17, journaled at each end to hanger arms such as shown at 30, is in rotatable contact with the vibrator roller 14, and with the printing plate 4.

Another form roller 18 is mounted on a shaft 19, which is journaled at each end to hanger arms, such as shown at 30, and is in rotative contact with the vibrator roller 14 and the plate 4. The form rollers are usually made of resilient material such as relatively soft rubber. Ink is applied to the vibrator roller 14, which is transferred to the form rollers 16 and 18, and in turn to the printing plate 4, as the said form rollers rotate by frictional contact with the plate. The vibrator roller 14 is rotated through conventional drive means such as a sprocket or gear secured to shaft 15, in a-manner which is well-known in the art. There may be a plurality of sets of co-acting vibrator and form rollers like'those shown at 14, 16 and 18.

Another set of co-acting vibrator and form rollers is shown at 20, 22 and 24, respectively, the said vibrator and form rollers being rotatably mounted upon shafts 21, 24 and 25 respectively. The shaft 21 is journaled at each end to the end frames 1 and the shafts 23 and 25 are journaled between hanger arms, such as shown at 30'. The said vibrator roller 20 is also rotatable by suitable drive means, such as a sprocket or gear secured to the shaft 21 therefor, in a manner which is well-known to those skilled in the art. The form rollers 22 and 24 are rotatable by frictional contact with the plate 4.

The vibrator rollers, form rollers, plate cylinder, blanket cylinder and impression cylinder are shown merely for the purpose of orientation of the dampening device, constituting the subject matter of this invention. The detailed construction, mounting and operation of these conventional elements are well understood by those familiar with the art, constitute no part of the present invention, and it is not thought necessary to illustrate and describe same in more detail.

As is well-known in the art, ink is applied to the image area of the plate 4 by the form rollers in rotative contact therewith. The printing impression is applied from the image area of the plate 4 to the rubber surface of the blanket cylinder 7, which image is in turn transferred from the rubber surface of the blanket cylinder 7 to the paper, which passes between the blanket cylinder and the impression cylinder 9.

The typical form roller hanger arm 36} is pivotally connected to the shaft 21 for the vibrator roller 20, as indicated at 31. The lower end of hanger arm 39 is rotatably connected to the shaft 25 for the form roller 24, as indicated at 32.

An adjustment screw 33 threadably extends through the outer end of the hanger arm 30, and is secured in adjusted position by means of a set screw 34. The adjustment screw 33 has a head 35 thereon, and the adjustment screw is so adjusted that the head 35 is in slidable contact with the cam shaft 39 when the press and dampening device are in impression position, as shown in Fig. I.

An upwardly extending bracket 36 is secured to the end frame 1 and a compression spring 38 is attached between the bracket 36 and the upper end of the hanger arm 30. Said spring 38 normally urges the upper end of the arm 36 downwardly, and the form roller 24 into contact with the plate 4.

A cam shaft 39 is journaled at each end to the end frames 1. A cam lobe 48 is secured on the cam shaft 39, and is arranged to contact the head 35 on the adjustment screw 33, when the cam shaft is rotated in a clockwise direction.

The crank arm 43 is secured at its lower end to the cam shaft 39, and is pivotally attached at its upper end to a rod 44.

The rod 44 is actuated by a cam, crank or electrically driven mechanism, forming a part of a conventional offset press, and since such actuating mechanism forms no part of this invention, it is not thought necessary to il1ustrate same.

in any event, it will be seen that when the rod 44 is moved to the right in Fig. I, the cam shaft 39 is rotated clockwise by rotation of the crank arm 43, thus bringing the cam lobe 40 into contact with the head 35, thereby raising the upper end of the hanger arm 30, and pivoting it in a counterclockwise direction about the shaft 21, thereby moving the form roller 24 away from the plate 4, as shown in Fig. II. Such motion of the rod 44 will also move the dampening device carriage away from the form roller 24 in the manner which will be hereinafter described.

It will be understood that each of the form rollers 16, 18, 22 and 24 is moved away from the cylinder 2 by means of a hanger arm and cam arrangement, such as illustrated and described immediately hereabove and that the hanger arm 30 and co-acting cam'lobe 40 and head 35 are duplicated at each side of the presss. Such hanger arm and cam arrangement is illustrated only in connection with one of the form rollers as being a typical means for moving the form rollers away from the plate cylinder when the press is in non-printing position. Such arrangement is conventional on printing presses of this type, and constitutes no part of this invention, per se.

When the rod 44 is moved to the left in Fig. I, and the head 35 is released from the cam lobe 40, the compression spring 38 will pivot the arm 30 in a clockwise direction and again bring the form roller 24 into engagement with the plate 4.

The dampening device is mounted on a retractable carriage which includes separate side mounting plate 46 at each side of the lithographic offset printing press. A rack gear 47 is mounted to the side frames 1 at each side of the press by means of Allen screws 47a. A flange 48 is secured to the mounting plate 46 by means of cap screws 49, in position so that the flange 48 overlaps, in slidable contact with, the inner edge of the rack gear 47. The rack gear 47 is also in slidable contact with the mounting plate 46.

A shaft 52 extends through, and is journaled to, the mounting plate 46. A gear 53 is aflixed to the shaft 52, the teeth on said gear being intermeshed with the teeth on the rack gear 47. A crank arm 54 is secured at its lower end to the shaft 52, and is pivotally attached at 56 to the link 55. The link 55 is pivotally attached at its upper end to the rod 44, as indicated at 45.

It will be seen that when the rod 44 is moved to the right in Fig. I, the link 55 also moves to the right, which movement causes the gear 53 to move along the rack 47, carrying with it the side frames 46 for the dampening device, thereby moving the entire dampening device carriage to the right and away from the form roller 24, in non-impression position, as shown in Fig. II. This operation takes place simultaneously when the form rollers are shifted away from the plate 4-, as the movements are initiated through a common actuating rod 44.

A fluid containing pan 59 extends between the side plates 46 at each side of the dampening device frame and is secured at each end to side plates 46. A quantity of fluid 60, which may be water, or some other suitable plate wetting fluid, is disposed in said pan, the level thereof being'sufficient to allow the fluid conveying roller 61 to be partially submerged in said fluid.

The fluid conveying roller 61 is mounted on a shaft 63 which is journaled at each end to the side frames 46 for the dampening device.

The peripheral surface of the roller 61 is'preferably knurled or has asimilar irregular surface contour 62 for the purposes which will be hereinafter mentioned. As-the roller 61 is rotated it passes through the wetting fluid 60 and the fluid adheres to the surface thereof and is thusconveyed on the surface of the roller out of the pan 59.

A rotatable brush 64 is mounted on a shaft 66, which is journaled at each end to the pivotal arm 67 (of which there is one at each side of the dampener frame). The arms 67 are pivotally mounted on a shaft 68 which is affixed at each end to the side plates 46.

The rotatable brush 64 has bristles 65 secured thereto which bristles are preferably made of relatively stifl, springy material, such as nylon. However, it will be understood that such bristles could be made of other springy material such as stifi hair, fibre or metal. It has been found, however, that nylon or like synthetic material is more suitable because of its relatively stifi but springy characteristics and the fact that it is durable, long lasting and is impervious to water. In any event the bristles 65 should be of material having the capability of being bent and deformed and of instantly springing back to normal position when released.

It will be noted that when the dampening device is in impression position as shown in Fig. I, the bristles 65 of the brush are pressed against the surface of the roller 61' so that the roller actually enters the bristles and causes them to be bent into unrelaxed position at the contact point.

As indicated by arrows the roller 61 and the brush 64 are preferably rotated in opposite directions but the brush would function to propel moisture against the form roller 24 even though brush 64 and the roller'fil were rotated in the same direction. It will be seen that as the brush 64 is rotated against the surface of the roller 61 the bristles 65 are depressed against the surface of the roller as they pass thereover, thus wiping the wetting fluid from the surface of the roller. As the bristles move out of contact with the roller they quickly spring back to normal relaxed position, thus atomizing and propelling the wetting fluid which they have picked up against the surface of the form roller 24. The fluid which is thus atomized and propelled is in very fine uniform particles. In fact it is so fine that it is invisible to the human eye. The form roller 24 is coated with ink, which has a grease base, and the fine particles of moisture which are propelled'thereagainst adhere to the outer surface of the ink but do not mix therewith. Since the brush 64 extends the length of the form roller, and since it has uniform and even contact with the fluid conveying roller 61 throughout its length, the atomized moisture is propelled against the form roller in a relatively narrow unbroken horizontal stripe parallel to the form roller and is evenly distributed along the surface of the form roller. The moisture adhering to the ink on the form roller is deposited from the form roller directly on the printing plate 4, throughout the Width of the plate, as the form roller rolls in contact therewith. The particles of moisture deposited and received on the form roller, in effect, hitch a ride on the form roller to the plate, where they immediately adhere to the already wetted non-image area of the plate and are pressed against the plate and distributed on the non-printing area of the plate. Since the image area of the plate is covered with ink and is not receptive to moisture, the moisture is squeezed off such area onto the non-image area, and no appreciable amount of moisture collects on the image area.

The knurled or roughened surface 62 on the roller 61 holds the bristles 65 until they are distorted to greater extent than would be the case if the surface of roller 61 were smooth. Therefore, the bristles are released at higher velocity so as to atomize the water and propel it more rapidly against form roller 24. Although a roller 61 with a roughened surface is preferable it will be understood that the device would operate to propel atomized moistur employing a roller 61 with a smooth surface.

, An L-shaped bracket 69 is secured to the side plate 46 at each side of the printing press by means of cap screws 70. A compression spring 71 is attached between the bracket 69 and the arm 67 so as'to urge the arm 67 downward. This presses the brush 64 against the moisture conveyor roller 61 to cause the roller to press the bristles down at the point of contact as shown in Fig. I.

An outwardly extending lug 72 is secured to the end plate 46' at each side of the dampening device frame. An adjustment screw 73 isthreadedly extended through lug 72 and is held in adjusted position by a lock nut 74. The upper end of screw 73 is engageable with the arm 67 to limit its downward movement and to adjust and limit pressure of brush 64 against conveyor roller 61, and to adjust the brush 64 in parallel relationship with the roller 61 and form roller 24.

A manually operated crank arm 75 is secured to a shaft '76 which is rotatably mounted at each end to spaced side plates 46. A cam lobe 77 is secured to the shaft 76 in position to contact the arm 67 and raise the said arm against spring 71 when the shaft 76 is rotated by movement of the hand lever 75, thereby lifting the brush 64 away from roller 61 while the press is in nonimpression position, as shown in Fig. II. This prevents moisture from being propelled against the inking rollers and plate while the press is running in non-impression position.

The pinion shaft 78 is journaled to the side frame 1 of the printing press, and a pinion 79 is secured to shaft 78. The gear 79 meshes with the drive gear 11 for the plate cylinder 2 and is rotated when the plate cylinder is rotated. The plate cylinder 2, blanket cylinder 7 and im-' pression cylinder 9 are rotated by conventional power and drive means, forming a part of the press, and are rotated in unison through theintermeshing gears 11, 12 and 13.

A sprocket wheel 80 is mounted on the pinion shaft 78, and a drive chain 81 is extended about the sprocket wheel 80, and a sprocket wheel 82, mounted on the shaft 66, for the brush 64.

The drive chain 81 is extended about a resiliently mounted idler 83 which is of conventional construction, the said idler being pivotally mounted at 84 to the side frame 46 of the dampening device, and is spring urged against the chain 81, so as to maintain tension of the chain 81 when the dampening device carriage is shifted with relation to the frame 1 of the printing press, as hereinbefore described. The pivoted, spring urged, idler 83 also permits the chain 81 to be lengthened when the brush 64 is pivoted upward out of engagement with the conveyor roller 61, as hereinbefore described.

A pinion shaft 87 is journaled to the side frame 46 of the dampening device. on the shaft 87, which gear meshes with the gear 79 on the shaft 78, to thereby rotate the shaft 87. A sprocket wheel 89 is mounted on the shaft 87, and a chain 90 is extended about the sprocket wheel 89, and a sprocket wheel 91 mounted on the drive shaft 92 of the conventional variable speed transmission 93. The variable speed transmission 93 is mounted on the outer side of the side plate 46 of the dampening device frame by means of cleats 98 extending outwardly from said frame, and the base of the transmission is secured to said cleats by means of suitable bolts 99.

A control wheel 94 is provided for the transmission 93, through which the output speed of the transmission may be varied.

The output sprocket 95 of the transmission 93 has a chain 96 extended thereabout and about a sprocket 97 mounted on the shaft 63 for the conveyor roller 61.

. It will be seen that through the medium of the variable speed transmission, the speed of rotation of the conveyor roller 61 may be adjusted with relation to the speed of rotation of the plate cylinder 2 and the brush 64. The

variance of speed of rotation of the conveyor roller 61 varies the amount of wetting fluid picked up by the roller 61 from the pan 59, and therefore varies the amount of fluid picked up and atomized by the bristles 65 on the brush 64. It therefore varies the amount of moisture applied to the form roller 24 and to the plate 4.

By means of adjustment of the speed of rotation of the conveyor roller 61, the correct amount of moisture applied to the form roller 24 and the plate 4 can be adjusted with relation to the speed of rotation of the plate cylinder 2 and the amount of moisture required by the plate for a particular job or speed. After such adjustment is made, it is unnecessary to change the adjustment, because the characteristics of the fluid atomizing and applying means, consisting of the conveyor roller 61, brush 64 and the form roller 24, do not change to any appreciable extent over a long period of time. The brush 64 has no contact with the form roller 24 or the plate 4, or any other element from which it could pick up, and become impregnated with, undesirable materials, such as ink, grease or lint. Therefore, it will maintain a constant characteristic for a long period of time. Thus it is unnecessary to repeatedly change the brush or the other moisture applying elements in this device, resulting in great saving of labor and down time of the press.

A pinion gear 88 is mounted Although it is convenient and advantageous to employ an inking form roller, such as 24, as the intermediate roller for transferring the dampening fluid to theplate, it will be understood that the intermediate roller need not necessarily be an inking roller. It could be one especially provided forsuch purpose.

It is believed that the operation and function of the plate dampening device herein described is apparent from the foregoing description.

While the printing press is in impression position, as shown in Fig. I, with the inking form rollers in contact with the printing plate 4, the plate cylinder 2, blanket cylinder 7 and impression cylinder 9, are rotated in unison through suitable power and drive means, thereby rotating the shaft 7S, as described. Through the shaft 78 and gear '79 the brush 64 is rotated by the chain 81. The moisture conveyor roller 61 is rotated through the variable speed transmission 93 and the speed of rotation thereof is adjustable, as described, the conveyor roller speed being proportioned to the speed of rotation of the plate cylinder.

It will be noted that the conveyor roller 61 and the brush 64 are arranged to rotate in suitable directions to cause the brush to propel atomized moisture against the face of the form roller 24. It is desirable that only suflicient moisture be applied to the form roller 24 as is required to moisten the non-image area of the plate 4 to the extent required by the particular job, so that no appreciable amount of the moisture will be conveyed to the vibrator roller 20. The correct amount of moisture applied can be easily adjusted in the manner hereinbefore described, and when once adjusted it need not be changed during the job for which it is adjusted.

It will be noted that the moisture is applied to the form roller immediately before it rotates into contact with the plate 4. Therefore, the moisture is applied directly to the plate, and does not pass between intermediate inking rollers.

As shown in Fig. l the peripheral surface of rotatable brush 64 is positioned in close proximity adjacent the peripheral surface of the applicator roller 24, andthat the roller 24 has a portion which intersects and extends beyond the plane tangent to the brush roller 64 where it contacts conveying roller 61.

It will be further noted in the form of the device shown in Figure I that the applicator roller 24 actually extends into the cusp created by the curved separating surfaces of the brush roller 64 and the fluid conveyor roller 61, thereby providing an enclosed region through which the spray is propelled onto the surface of the roller 24, which region is virtually closed off by the close adjacency between the surface of the brush roller 64 and the roller 24. Thereby the spray emanating from the brush 64 is substantially confined within said area and the particles of spray are effectively prevented from being dispersed between the brush roller 64 and the surface of the roller 24, thereby preventing an excessive loss of moisture. Such arrangement and relationship between the brush and rollers 61 and 24 also assures that the applicator roller 24 is positioned directly in the path of the projected, atomized spray so as to intercept substantially all of the same.

In this connection it will also be noted that the pan roller 61 and the applicator roller 24 are actually physically separated from each other by a space, and that the bristles of the brush 64 actually extend into said space between the opposed curved surfaces of the rollers 61 and 24. It will further be noted that the atomized spray generated by the brush bristles is projected across said space directly upon the surface of the roller 24 and not against the surface of the plate. Therefore, the objectionable results of applying spray directly to the plate, as hereinbefore explained, are eliminated.

Attention is further called to the fact that the space or region between the opposed curved surfaces of the rollers 61 and 24 is non-turbulent and constitutes a rela* tively quiescent body of air thereby assuring that the spray'willnot be scattered'and dissipated, but substantially all of same will be applied directly to the roller 24; It will further be noted that there is a definite geometrical. relationship between the rollers 64,. 61 and 24 in that lines connecting the centers of said rollers would form an acute triangle.

Asthe moisture is applied to the form roller and not directly to the plate, no moisture is deposited in the cylinder gap 5 where it could accumulate and cause over- .transfer roller.

wetting of the plate adjacent to the gap.

It willbe understood that other and further forms and embodiments of my invention may be devised without departing from the spirit andscope ofthe appended claims.

I claim: 1. A plate dampening device for a lithographic offset printing machine comprising, a dampening fluid container disposed on said machine and adapted to contain a quantity of dampening fluid; a fluid supply roller rotatably mounted on the machine and disposed in said container with one side thereof adapted to be immersed in said fluid; fluid transfer means arranged to transfer dampening fluid received thereby to the surface of said plate .by pressure contact application, said fluid transfer means including a fluid transfer roller rotatably disposed on the machine in parallel and spaced relationship to the supply roller; a cylindrical brush rotatably mounted on the machine having springy bristles thereon, with the exposed surface of the supply roller impressed into the bristles of the brush; the peripheral surface of'said brush extending into the region separating the opposed curved surfaces of thetransfer roller and the supply roller; and means to rotate the brush, transfer roller and supply roller, whereby as the supply roller and brush rotate the bristles are released from the roller to atomize and project the fluid from the surface of the supp-1y roller through said' region directly against the surface of the 2. The combination called for in claim 1 with the addition of means to retract the brush, container and supply roller away from the transfer roller when the press is shifted to non-impression position.

3. The combination called for in claim 1 with the addition of means to interrupt the propulsion of fluid by the brush when the press is shifted to non-impression position.

4. The combination called for in claim 1 with the addition of means to vary the speed of rotation of the supply roller.

.5. The combination called for in claim 1 with the addition of means to resiliently urge the brush into contact with the supply roller; and means to limit contact between the brush and supply roller.

6. The combination called for in claim 1 with the addition of means to pivot the brush away from contact with the supply roller when the press is shifted to nonimpression position.

7. A plate dampening device for a lithographic offset printing machine comprising, roller means rotatably mounted on the machine and including a roller running in contact with the surface of said plate; an elongate cylindrical brush rotatably mounted on the machine in parallel relationship to the roller means; an elongate fluid retaining tray mounted on the machine and extending parallel to the brush adapted to contain a quantity of plate dampening fluid; an elongate fluid supply roller rotatably mounted on the machine extending parallel to the brush, having one side thereof adapted to be immersed in said fluid and the other side thereof in rotative contact with the brush, with the peripheral surface of the supply roller impressed into the bristles of the brush; said roller means having a portion positioned closely adjacent, but spaced from, the brush, and another portion l1 positioned with relation to the plane'tangent to the brush where the brush contacts the supply roller so as to intercept and confine atomized dampening fiuid projected from the surface of the supply roller by the releaseof the brush bristles; and means to rotate the brush, roller I means and .supply roller, whereby as the supply roller and brush rotate the bristles are released from the roller to atomize and project the fluid from the surface of the supply roller directly against the surface of the roller means for pressure contacting application. to said plate; .8. The combination called for in claim 7 wherein the roller means comprises a fluid transfer rollerhaving a portion extending into the cusp formed by the brush and the supply roller. I 9. The combination called for in claim 7 wherein the roller means comprises a fluid transfer roller against which the atomized fluid is directly projected and wherein lines connecting the centers of the fluid transfer roller, brush and supply roller form an acute triangle.

10. A plate dampening device for a lithographic offset printing machine comprising, roller means rotatably mounted on the machine and running in contact with the surface of said plate; an elongate cylindrical brush having a multiplicity of springy bristles thereon and rotatably mounted on the machine in parallel relationship to said roller means; an elongate liquid supply means mounted on the machine and including a surface extending parallel to said brush; means for supplying said surface of said supply means continuously with a thin film of dampening liquid; means for mounting said brush adjacent said supply means with a narrow band of said surface impressed into the bristles of the brush to cause said bristles to be deflected while in contact with said band and to thereafter be released to flick dampening liquid from said band in finely atomized form through the adjacent relatively quiescent body of air; said roller means having a portion positioned closely adjacent but spaced from said brush and another portion positioned with relation to the plane tangent to said brush at said narrow band so as to intercept and confine the atomized dampening liquid projected from said supply surface by the release of said brush bristles.

11. A method of applying lithographicplate dampening-liquid to the surface of a lithographic plate carried by 'a'rot'ating'cylinder having a gap therein 'by pressure contact with liquid transferring means running in surface contact with said plate for maintaining ink repellent the non-printing areas thereof, comprising the steps of, providing and renewing a thin film of dampening liquid of predetermined thickness on a supporting surface generally parallel to the cylinder, engaging said supporting surface in a narrow band of contact with the ends of a multiplicity of springy brush bristles located closely adjacent but spaced from said liquid transferring means to cause deflection of the bristles, maintaining said liquid transferring means closely adjacent but spaced from said bristles and so related to the plane tangent to said bristles at said narrow band as to intercept and confine atomized liquid flicked by said bristles from said narrow band, moving the bristles and said supporting surface relatively to each other to allow the bristles to spring back to undeflected positions with resultant flicking of the liquid in finely atomized form from said narrow hand through the adjacent relatively quiescent body of air toward and onto the surface of said liquid transferring means, and transferring the liquid received by said transferring means to said lithographic plate by rolling contact under pressure.

References Cited in the file of this patent UNITED STATES PATENTS 734,168 Great Britain July 27, 1955

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