Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F7/00—Rotary lithographic machines
  • B41F7/20—Details
  • B41F7/24—Damping devices
  • B41F7/26—Damping devices using transfer rollers

Definitions

• 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 ⁇ quiz 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 ⁇ Jerusalem 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• Figure 6 is a view similar to Figure 4 with the apparatus in a second mode of operation. Description of the Preferred Embodiment
• 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.
• apparatus for providing a dampening fluid to the litho- graphic plate is represented generally by the numeral
• 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.
• 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).
• 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.
• 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.
• 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.
• 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.
• the outer surface of metering roller 23 is formed from a layer of rubber or an alternate resilient material suitable for the intended purpose.
• 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 -
• 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 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).
• 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.
• 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.
• 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-
• 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.
• 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.
• 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) .
• 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.
• 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.
• form roller 24 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.
• 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.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Rotary Presses (AREA)
• Inking, Control Or Cleaning Of Printing Machines (AREA)

Applications Claiming Priority (2)

Publications (2)

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Citations (2)

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• 1985
  • 1985-10-09 WO PCT/US1985/001971 patent/WO1986002319A1/en not_active Ceased
  • 1985-10-09 JP JP60504646A patent/JPS61501765A/ja active Pending
  • 1985-10-09 EP EP19850905281 patent/EP0198885A4/de not_active Withdrawn

Patent Citations (2)

Non-Patent Citations (1)

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