EP0198885A1

EP0198885A1 - Dampening unit for printing press

Info

Publication number: EP0198885A1
Application number: EP85905281A
Authority: EP
Inventors: Charles L. Marcum
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-10-11
Filing date: 1985-10-09
Publication date: 1986-10-29
Also published as: JPS61501765A; WO1986002319A1; EP0198885A4

Abstract

Un appareil (21) est destiné à l'amortissement d'une plaque lithographique sur le cylindre de plaques (13) d'une presse d'impression lithographique (11). L'appareil d'amortissement possède un rouleau d'alimentation en fluide (22) monté en rotation sur un premier axe en rotation à une vitesse prédéterminée mais réglable. De l'eau est fournie aux rouleaux d'alimentation en fluide (22) par plusieurs jets d'eau disposés sur sa longueur. Un rouleau d'introduction (23) est monté en rotation autour d'un second axe parallèle au premier axe et est disposé en engagement rotatif avec le rouleau d'alimentation en fluide (22). Le rouleau d'introduction (23) est entraîné en rotation à une vitesse différente de celle du rouleau d'alimentation en fluide (22). Un rouleau de forme (24) est monté en rotation autour d'un troisième axe parallèle et est alimenté uniformément en encre. Le rouleau de forme (24) est également entraîné à une vitesse de rotation différente de celle du rouleau d'alimentation en fluide (22). Le rouleau de forme (24) est monté sur un châssis suspenseur mobile (51) qui est construit et disposé pour déplacer le rouleau de forme (24) d'abord en engagement avec le rouleau d'alimentation en fluide (22) puis en engagement avec le cylindre de plaques (13).An apparatus (21) is intended for damping a lithographic plate on the plate cylinder (13) of a lithographic printing press (11). The damping apparatus has a fluid supply roller (22) rotatably mounted on a first axis rotating at a predetermined but adjustable speed. Water is supplied to the fluid supply rollers (22) by several water jets arranged along its length. An introduction roller (23) is rotatably mounted about a second axis parallel to the first axis and is disposed in rotational engagement with the fluid supply roller (22). The introduction roller (23) is rotated at a speed different from that of the fluid supply roller (22). A form roller (24) is rotatably mounted about a third parallel axis and is uniformly supplied with ink. The form roller (24) is also driven at a rotational speed different from that of the fluid supply roller (22). The form roller (24) is mounted on a movable suspension frame (51) which is constructed and arranged to move the form roller (24) first in engagement with the fluid supply roller (22) and then in engagement with the plate cylinder (13).

Description

DAMPENING UNIT FOR PRINTING PRESS

The invention broadly relates to printing presses and is specifically directed to an improved apparatus for applying dampening fluid to a lithographic printing plate.

Lithographic plates used in offset printing are constructed in such a way that one portion of the lithographic plate (e.g., the portion which is to pro¬ duce the desired image) is made attractive to ink, while the remaining portion is made ink repellent. A dam¬ pening fluid such as water, with or without additives such as alcohol, is applied to the lithographic plate to dampen its nonprinting areas and assist in repelling ink. The application of dampening fluid to the lithographic plate must be precisely controlled to pro¬ duce optimum results, since excessive or insu ficient dampening fluid results in inferior printing.

U.S. Patent No. 3,163,037, which issued to Harold P. Dahlgren on February 2, 1965, discloses an apparatus for dampening lithographic offset printing plates in which physical contact between the litho- graphic plate and the dampening source is avoided. This permits the dampening fluid to be applied uniformly to the inked lithographic plate without transfer of the ink back to the dampening mechanism. The system utilizes a fluid supply roller which has a metallic, smoothly polished outer surface and is chemically treated to make it water attractive (hydrophilic) . This hydrophilic roller rotatably engages one of the ink form rollers of the press in a manner so that the film of dampening fluid on the hydrophilic roller is split, with a portion picked up by the layer of ink on the ink form roller and transferred to the lithographic plate. The other por¬ tion of the dampening fluid is retained on the hydro¬ philic roller to repel ink, preventing the transfer of ink back into the dampening system. The subject invention is an improvement of the dampening apparatus disclosed in U.S. Patent No. 3,168,037, and provides a number of structural and func¬ tional improvements and features that significantly enhance the dampening operation and thereby improve the quality of printing.

The inventive dampening apparatus utilizes a hydrophilic fluid supply roller that is direct driven by a variable speed motor, and which acts as a pivot point for movement of other rollers in the system. The pre- ferred embodiment utilizes a metering roller that is driven by the hydrophilic roller at a slightly greater rotational speed, but which is- in continuous engagement with the hydrophilic roller so that relative slippage or wiping takes place. This results in maintaining a pre- cisely controlled uniform layer or film of water on the hydrophilic roller.

The metering roller is carried in a main hanger frame that pivots about the rotational axis of the hydrophilic roller, permitting the metering roller to move through a limited range of arcuate movement while maintaining driving and roller engagement with the hydrophilic roller.

A dampening form roller is disposed for selec¬ tive engagement with the hydrophilic roller and litho- graphic plate cylinder. This is accomplished by mounting the form roller eccentrically on a form roller hanger which is pivotally connected to the main hanger frame. The pivotal connection of the form roller hanger is spaced from the rotational axis of the form roller so that pivotal swinging movement of the form roller hanger effects limited arcuate movement of the form roller bet¬ ween positions of nonengagement and engagement with the hydrophilic roller. An adjustable limit stop precisely determines the engagement between these two rolls.

An actuator taking the form of a pneumatic cylinder, lever arms and toggle mechanism operates to first move the roller hanger frame to cause engagement of the form roller with the hydrophilic roller. The actuator thereafter causes movement of the main hanger frame to move the form roller into engagement with the lithographic plate cylinder. This engagement is also precisely controlled by an adjustable stop. A bridge roller is disposed in continuous engagement between an ink roller and the dampening form roller to continuously apply a layer of ink to the form roller. The form roller is rotatably driven by the bridge roller and by the lithographic plate cylinder upon engagement at a speed which is less than the selected rotational speed of the hydrophilic roller.

As constructed, the form roller does not engage either the hydrophilic roller or the lithographic plate cylinder when the printing press is inoperative. Operation of the actuator initially causes the form roller to engage the hydrophilic roller, and the rela¬ tive rotational velocities result in the "milling" of a precisely controlled layer or film of water onto the form roller. It will be recalled that the layer or film of water on the hydrophilic roller is split, with a por¬ tion being retained to repel ink and thus prevent ink from entering the dampening fluid supply. Further actuation of the actuator causes the form roller to engage the lithographic plate cylinder to apply the precisely controlled water film to the litho¬ graphic plate. The water is retained by the nonprinting areas, resulting in optimum printing results.

Causing all motions of the dampening apparatus to be concentric around the fixed hydrophilic roller permits the various rollers to be adjusted much more easily, and at the same time adjustment of one roller will not affect the settings of other rollers. Driving the hydrophilic roller on a fixed rotational axis with a variable speed motor avoids the setting of gears, which is common in prior art structures.

Another significant improvement with the inventive dampening apparatus is the requirement of a single adjustment to set the form roller to the hydrophilic roller in a precise manner, and a single adjustment for setting the form roller to the lithographic plate cylinder in a precise manner. The toggle mechanism used in the actuator moves to an over center position when the system is operative, thus avoiding problems resulting from fluc¬ tuations in air pressure supplied to the pneumatic actuator. In addition, the bridge roller in the pre¬ ferred embodiment is mounted by eccentric bushings to insure a proper setting of the bridge roller to the form roller, whether the form roller is in the operative or inoperative position. Last, water is applied to the hydrophilic roller through a plurality of water jets, rather than the conventional approach of running the roller in a pan of water. This insures that all lint and other debris which might be lifted from the pan is flushed off the hydrophilic roller before such debris can enter the press.

Brief Description of the Drawings Figure 1 is a view in end elevation of dam- pening apparatus for a printing press which embodies the invent:on;

Figure 2 is an enlarged fragmentary sectional view taken along the line 2-2 of Figure 1 showing the apparatus in a first mode of operation; Figure 3 is an enlarged fragmentary sectional view taken along the line 3-3 of Figure 1 with the apparatus in the first mode of operation;

Figure 4 is an enlarged fragmentary sectional view taken along the line 4-4 of Figure 1 with the apparatus in the first mode of operation;

Figure 5 is a view similar to Figure 3 with the apparatus in a second mode of operation; and

Figure 6 is a view similar to Figure 4 with the apparatus in a second mode of operation. Description of the Preferred Embodiment

With initial reference to Figures 1-4, a printing press utilizing the inventive dampening appara¬ tus is represented generally by the numeral 11.

Printing press 11 comprises a frame 12 formed from a number of separate components all of which bear the reference numeral 12. A large plate cylinder 13 is mounted to the frame 12 for rotation about a horizontal axis, and is adapted to receive a lithographic plate (not shown). Ink is fed to the lithographic plate on cylinder 13 through a series of rollers 14-16 that are also rotatably mounted to the frame. The rollers 14-16 are in rotatable engagement with each other and the plate cylinder 13 to distribute ink which is fed from a conventional supply source (not shown) onto the lithographic plate as the plate cylinder 13 is rotated.

With specific reference to Figures 2-4, apparatus for providing a dampening fluid to the litho- graphic plate is represented generally by the numeral

21. Dampening apparatus 21 comprises a fluid supply or transfer roller 22 the function of which is to receive dampening fluid from a fluid source and to transfer it in metered quantities, a metering roller 23 the function of which is to meter the amount of dampening fluid on supply roller 22, a form roller 24 the function of which is to transfer dampening fluid to the surface of the plate cylinder 13, and a bridge roller 25 the purpose of which is to transfer ink from the ink roller 15 to the form roller 24.

With reference to Figures 1 and 2, fluid supply roller 22 is rotatably mounted about a fixed axis within the frame 12. As such, the position of supply roller 22 within the frame 12 is stationary, although it is capable of rotation. Supply roller 22 is driven by a variable speed motor 20 through a gear reduction box 26, coupling 27 and drive shaft 28 at a desired rotational speed.

Fluid supply roller 22 is generally of the type disclosed in U.S. Patent No. 3,168,037, which issued to Harold P. Dahlgren on February 2, 1965; viz., it is a metallic roller having a smoothly polished sur¬ face and is chemically treated so that it is hydrophilic (has an affinity to water). With reference to Figures 2 and 6, metering roller 23 is rotatably mounted in a main hanger frame bearing the general reference numeral 31. Main hanger frame 31 comprises an upright section 32 and a generally horizontal section 33, the sections 32, 33 being rela¬ tively slidable about the drive shaft 28 and secured in a fixed relative position by a nut and bolt 34 disposed in an arcuate slot 35.

The upright section 32 of main hanger frame 31 has spaced legs 32a that slidably receive a rectangular bearing block 36 therebetween. The bearing block 36 has a bearing 36a in which one end of the shaft 23a of metering roller 23 is carried.

A bridge member 32b interconnects the legs 32a and carries an adjustment bolt 37 that projects through and acts as an upper limit stop to the bearing block 36. The bearing block 36 is urged upwardly into engagement with the adjustment bolt 37 by a pair of springs 38 dis¬ posed in recesses formed in the hanger section 32. A main hanger frame 31a which is symmetrically identical to the hanger frame 31 is disposed at the opposite side of printing press 11 to support the other end of the metering roller 23, as well as form roller 24. However, of the two hanger frames 31, 31a, only frame 31 includes the arcuate slot 35 and nut and bolt assembly 34 and portions 32, 33 of frame 31a are of one- piece construction. This permits the relative position of the hanger sections 32, 33 to be adjusted, and accor¬ dingly, to skew one end of the metering roller 23 to insure a proper rotational relationship between the rollers 22, 23.

It will be here noted that in the interest of brevity only those components associated with frame 31 on the left side of Figure 1 will hereinafter be described and that similar components associated with frame 31a on the right side of Figure 1 for mounting the other end of rollers 23, 24 will carry similar reference numerals where possible.

With specific reference to Figure 2, a gear 29 is mounted on the drive shaft 28 of hydrophilic roller 22. A slightly smaller gear 39 is mounted on the shaft 23a of metering roller 23, and the two gears 29, 39 meshably engage so that the metering roller 23 is rotated at a slightly faster rotational speed than hydrophilic roller 22. However, and as best shown in Figure 3, the outer cylindrical surfaces of both the rollers 22, 23 engage, and there is a slight wiping action between these surfaces as the metering roller 23 rotates slightly faster.

In the preferred embodiment, the outer surface of metering roller 23 is formed from a layer of rubber or an alternate resilient material suitable for the intended purpose.

With reference to Figures 1 and 5, a longitu¬ dinal drip pan 41 is carried by the frame 12 below the hydrophilic roller 23 over its entire length. A dam¬ pening fluid, which is preferably water, is applied to the nip between hydrophilic roller 22 and metering roller 23 by a plurality of water jets emanating from a water supply pipe 42 having a plurality of apertures sized and spaced in a desired manner. A pump 43 pumps water into the supply pipe 42 at a desired pressure, and a pump 44 in a drain pipe 45 assists in positively draining water from the drip pan 41 into a waste reser¬ voir 46. It is imperative that the water supplied to hydrophilic roller 22 be clean for optimum printing - 10 -

the extent to which form roller hanger 51 may move in a clockwise direction, and hence determines the specific point at which form roller 24 engages hydrophilic roller 22, as described in further detail below. With reference to Figures 3-6, a horizontal pivot shaft 64 is carried between opposite sides of the frame 12. A long lever arm 65 is secured to the pivot shaft 64 for rotation therewith externally of the frame 12. A pivot link 66 connects the lever arm 65 with the 0 extensible rod 67 of a pneumatic actuator 68. Actuator 68 is pivotally connected to the frame 12 as shown at 71 and includes air supply and exhaust lines 68a, 68b.

A short lever arm 72 is secured to the pivot shaft 64 for rotation therewith, such rotation being 5 substantially coplanar with the limited rotational move¬ ment of the form roller hanger 51. A tie rod 73, the length of which is adjustable by threaded end couplings, has one end pivotally connected to the short lever arm 72 by a pivot bolt 74. The opposite end of the tie rod 0 73 is pivotally connected to the arm member 53 of form roller hanger 51 by a pivot bolt 75.

Short lever arm 72 is angularly positioned on the pivot shaft 64 in a manner so that the tie ror* 73 moves through an over center position as the pneur, atic 5 actuator 68 moves from a retracted position ( Figui e 5) to an extended position (Figure 3). In the fully extended position of Figure 3, the tie rod 73 has moved just slightly over center relative to the pivotal con¬ nection between the tie rod 73 and hanger arm member 53, '0 and these respective components are therefore locked in the position of Figure 3 even though pressure fluc¬ tuations in the air supply to pneumatic actuator 68 may occur. -9-

results, and the water is recycled through a filter (not shown) .

With reference to Figure 4, a form roller hanger for rotatably carrying the form roller 24 is represented generally by the numeral 51. Form roller hanger 51 is of irregular shape, including a somewhat circular body 52 from which an arm member 53 upwardly projects. Planar abutment surfaces 54, 55 are machined into the body 52 at a right angle. Roller hanger 51 is pivotally mounted to the horizontal section 33 of main hanger frame 31 for free pivotal movement about a pivot axis 56. Form roller 24 has a rotatable shaft 24a mounted in a suitable bearing 57 in the roller hanger body 52. It should be noted that the rotational axis of the roller shaft 24a is spaced from the pivot axis 56, and as such, pivotal movement of the form roller hanger 51 causes the form roller 24 to move eccentrically relative to the pivot axis 56. With continued reference to Figure 4, a limit stop block 61 is mounted to the upright section 32 of main hanger frame 31. Block 61 carries adjustable limit stop screws 62, 63, which are respectively engageable with the planar abutment surfaces 54, 55. Lock nuts 62a, 63a serve to respectively lock the limit stop screws 62, 63 in desired limit stop positions. The two operational positions of form roller hanger 51, as determined by stop screws 62, 63, are shown in Figures 4 and 6. The function of limit screw 62 is to prevent counterclockwise rotation of hanger 51 beyond a pre¬ determined limit which defines the inoperational posi¬ tion of form roller 24. Limit stop screw 63 determines -12-

With reference to Figure 3, the horizontal arm of L-shaped member 82 carries an Allen screw 86 the lower end of which abuts the frame 12 with the pneumatic actuator 68 in its fully extended position. The Allen screw 86 may be adjusted to determine the precise engaging position of the form roller 24 on the plate cylinder 13, and a lock nut 86a secures the Allen screw 86 in the desired position.

With reference to Figures 2 and 3, bridge roller 25 is carried by a bridge roller hanger 91 at each end, the hanger 91 being pivotally carried for swinging movement about the rotational ^ is of ink roller 15. The hanger 91 carries an eccentric mount 92 having a set screw 93 permitting adjustment of the rota- tional axis of bridge roller 25 to insure that it uni¬ formly engages the form roller 24 as well as the ink roller 15.

The bridge roller hanger 91 pivots freely about the axis of ink roller 15, permitting the bridge roller 25 to engageably follow the form roller 24 through its range of movement, while also maintaining proper contact with the ink roller 15. As such, bridge roller 25 is in continuous proper engagement with both the ink roller 15 and the form roller 24 notwithstan ing extension and retraction of the pneumatic actuator 68.

The bridge roller 25 is oscillated longitudi¬ nally (i.e., it moves back and forth along its longi¬ tudinal axis of rotation) in a conventional manner by means not shown to better distribute ink on the form roller 24.

In operation, with the pneumatic actuator 68 retracted, the respective components are as shown in Figures 5 and 6. Water is continuously sprayed onto hydrophilic roller 22 by the water supply pipe 42, and -11-

With the respective components constructed and arranged as shown in the figures, retraction of the pneumatic actuator 68 causes the rollers 22, 23 and 24 to be in the position shown in Figure 5. Hydrophilic roller 22 and metering roller 23 are in rotatable enga¬ gement (as they are in all positions of the apparatus), and dampening form roller 24 is in a position of non- engagement with both the plate cylinder 13 and the hydrophilic roller 22. As the pneumatic actuator 68 is extended, the lever arms 65, 72 and tie rod 73 are ini¬ tially moved from one limit position (Figure 5) to the other limit position (Figure 3), at which time the form roller 24 engages the hydrophilic roller 22. The degree of engagement is precisely determined by the limit stop screw 63.

At the time that the planar abutment surface 55 engages the limit stop screw 63, the pneumatic actuator 68 is only partially extended. Further exten¬ sion imparts counterclockwise rotational movement of the entire main hanger frame 31 about its pivot axis (the rotational axis of hydrophilic roller 22), and this movement causes the form roller 24 to engage the plate cylinder 13 due to the presence of a limit stop 81 ' described below. With reference to Figures 1-3, limit stop 81 specifically comprises an L-shaped member 82 the upr ight leg of which is secured to the side of main hanger frame 31 by a suitable fastener 83 ( Figure 1 only) . With reference to Figure 2, the horizontal arm of the member 82 carries a threaded bolt 84 having adjustable lock nuts 84a. A coil spring 85 extends between the end of bolt 84 and a recess in the frame 12. metering roller 23 is in rotatable and wiping engagement with the hydrophilic roller 22 to uniformly control the thickness of the water layer or film on the surface of roller 22. In this position, the form roller 24 is out of engagement with hydrophilic roller 22, but remains in engagement with bridge roller 25. Ink roller 15 is not in contact with plate cylinder 13, as is the conven¬ tional practice. As such, the printing press 11 is ino¬ perative. With a lithographic plate (not shown) mounted on the plate cylinder 13, operation of the press 11 is initiated by causing the pneumatic actuator 68 to move to its extended position. In so doing, form roller 24 initially engages hydrophilic roller 22 as described above, with contact properly established by adjustment of the limit stop screw 63.

Prior to engagement with the hydrophilic roller 22, form roller 24 has been rotatably driven by its engagement with oscillating bridge roller 25, and as a result has a uniform layer of ink over its surface.

Upon engagement with the hydrophilic roller 22, a layer or film of water is "milled" onto the form roller 24 by the hydrophilic roller 22, which rotates at a greater speed. Having received a layer of water from hydro- philic roller 22, the form roller 24 is now ready for engagement with the plate cylinder 13. Further exten¬ sion of the pneumatic actuator 68 causes the form roller 24 to engage the plate cylinder 13 as described above, with precise contact determined by setting of the Allen screw 86. At this time, the form roller 24 immediately applies water to the lithographic plate on plate cylinder 13 in a precisely controller proper amount. This engagement is shown in Figures 1-4, which also show the ink roller in rolling engagement with the litho¬ graphic plate of plate cylinder 13.

When the pneumatic actuator 68 is retracted to the inoperative position, form roller 24 first leaves engagement with the plate cylinder 13, and thereafter leaves engagement with the hydrophilic roller 22.

As described, the dampening apparatus is capable of uniformly applying water to the lithographic plate in precisely controlled quantities, which produces optimum printing results, while at the same time avoiding undesirable inter iv-ture of excessive quan¬ tities of ink and water, which results in emulsification and poorer printing results.

Claims

What is claimed is:

1. Apparatus for dampening a lithographic plate on a printing press plate cylinder, comprising: frame means; first hanger means mounted to the frame means for pivotal movement between first and second positions about a first pivot axis; a fluid supply roller carried by the first hanger means for rotation about a first axis coinciding with said first pivot axis; first drive means for driving the fluid supply roller at a selected rotational speed; means for supplying dampening fluid to the fluid supply roller over substantially its entire 1ength; a metering roller carried by the first hanger means for rotation about a second axis in rotating enga¬ gement with the fluid supply roller; second drive means for driving the metering roller at a rotational speed different than that of the fluid supply roller; second hanger means mounted to the first hanger means for pivotal movement between first and second positions about a second pivot axis; a dampening form roller carried by the second hanger means for rotation about a third axis spaced from said second pivot axis; third drive means for driving the dampening form roller at a rotational speed different than that of the fluid supply roller; the fluid supply and form rollers and said first and second hanger means being constructed and arranged so that the dampening form roller moves into rotational engagement with the fluid supply roller when the second hanger means is moved from its first position to its second position, and for moving the form roller into engagement with the plate cylinder when the first hanger means is moved from its first position to its second position; and actuator means for sequentially moving the second hanger means from its first to its second posi¬ tion, and the first hanger means from its first position to its second position, whereby the dampening form roller first engages the fluid supply roller and then engages the printing press plate cylinder.

2. The apparatus defined by claim 1, which further comprises adjustable stop means for adjustably limiting movement of the first hanger means beyond its second position, whereby engagement of the form roller with the plate cylinder is precisely controlled.

3. The apprratus defined by claim 1 or 2, which further comprises adjustable stop means for adjustably limiting movement of the second hanger means beyond its second position, whereby engagement of the form roller with the fluid supply roller is precisely controlled.

4. The apparatus defined by claim 1, wherein the first drive means comprises variable speed motor means.

5. The apparatus defined by claim 1, wherein the means for supplying dampening fluid is constructed and arranged to spray dampening fluid on the fluid supply roller in a plurality of fluid jets.

6. The apparatus defined by claim 5, wherein the means for supplying dampening fluid comprises a pipe disposed adjacent to and in substantial parallel rela¬ tionship to the fluid supply roller, the pipe having a plurality of spaced apertures facing the fluid supply roller, and being adapted for connection to a source of dampening fluid under pressure.

7. The apparatus defined by claim 1, wherein the dampening fluid is water.

8. The apparatus defined by claim 1, wherein the external surface of the fluid supply roller is hydrophi¬ lic.

9. The apparatus defined by claim 1 or 8, wherein the external surfaces of the form and metering rollers are resilient.

10. The apparatus defined by claim 1, wherein the second drive means comprises first and second inter- meshing gears respectively mounted on the fluid supply and metering rollers.

11. The apparatus defined by claim 1, wherein the second drive means is constructed and arranged to drive the metering roller at a rotational speed greater than that of the fluid supply roller.

12. The apparatus defined by claim 1, which further comprises means for adjustably skewing one of said fluid supply and metering rollers relative to the other.

13. The apparatus defined by claim 1, which further comprises means for uniformly applying ink to the form roller.

14. The apparatus defined by claim 13, wherein the ink applying means comprises an ink transfer roller mounted for rotation about a fourth axis and disposed in rolling engagement with the form roller.

15. The apparatus defined by claim 14, which further comprises third hanger means for mounting the transfer roller.

16. The apparatus defined by claim 15, which further comprises an ink roller mounted for rotation about a fifth axis and disposed in engagement with the transfer roller, said third hanger means being mounted for piv jtal movement about a third pivot axis that coin¬ cides w.-.th said fifth axis.

17. The apparatus defined by claim 16, wherein the third hanger means comprises adjustable eccentric bearing means for adjusting the rotational axis of the ink transfer roller relative to said fifth axis.

18. The apparatus defined by claim 14, wherein the third drive means comprises said ink transfer roller.

19. The apparatus defined by claim 1, wherein the third drive means comprises said plate cylinder.

20. The apparatus defined by claim 1, wherein the third drive means is constructed and arranged to rotate the form roller at a rotational speed less than that of the fluid supply roller.

21. The apparatus defined by claim 1, wherein the actuator means comprises toggle means for locking the first and second hanger means in said respective second positions.

22. The apparatus defined by claim 21, wherein the actuator means comprises: a fluid cylinder movable between extended and retracted positions; lever means operatively connected to the fluid cylinder; tie rod means pivotally connected between said lever means and said second hanger means; said lever means and said second hanger means being constructed and arranged so that the tie rod means moves to an over center position when the second hanger means is moved from the first position to the second position.

23. Apparatus for dampening a lithographic plate on the plate cylinder of a printing press, comprising: a fluid supply roller mounted for rotation about a first rotational axis; first drive means for driving the fluid supply roller at a predetermined rotational speed; means for supplying dampening fluid to the fluid supply roller; a metering roller mounted.for rotation about a second rotational axis and disposed in rotatable engage¬ ment with the fluid supply roller; second drive means for driving the metering roller at a rotational speed different than that of the fluid supply roller; a form roller mounted for rotation about a third rotational axis; - means for uniformly applying ink to the form roller; third drive means for driving the form roller at a rotational speed different than that of the fluid supply roller; means for carrying the form roller for move¬ ment into and out of engagement with the fluid supply roller, and for movement into and out of engagement with the plate cylinder; and actuator means for moving the form roller first into engagement with the fluid supply roller, and for then moving the form roller into engagement with the plate cylinder.