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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F31/00—Inking arrangements or devices
  • B41F31/007—Removing water from ink trains
• • 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
  • B41F7/36—Inking-rollers serving also to apply ink repellants
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M1/00—Inking and printing with a printer's forme
  • B41M1/06—Lithographic printing

Definitions

• Printing plates for lithographic printing presses require application of dampening fluid to render hydrophilic non-image areas ink rejecting so that ink will adhere only to image areas which are oleo ⁇ philic.
• Da peners of the type disclosed in Dahlgren U nited States Patent No. 3,937,141 applied a film of dampening fluid to a film of ink on an ink coated roller which in turn carried a composite film of ink and dampening fluid to the lithographic printing plate.
• Dahlgren Patent No. 4,088,074 disclosed an inker comprising a single resilient form roller which both ink and dampening fluid are applied therewith.
• an air bar was employed for evaporating excess dampening fluid from the surface of the single form roller.
• the dampening fluid removal device disclosed herein relates to improvements in dampening fluid removal devices of the type disclosed in the afore ⁇ mentioned Dahlgren and Corse patents.
• a primary object of the invention is to provide a dampening fluid removal device which is capable of selectively removing dampening fluid from ink to eliminate or reduce scumming, water streaking and plugging of lithographic printing plates.
• Another object is to provide a dampening fluid removal device to enhance color density.
• a further object is to provide a doctor blade and an ink metering member on a single ink coated form roller to selectively -meter components of a composite film of ink and dampening fluid.
• the improved dampening fluid removal device disclosed herein is employed in combination with a printing press applying ink and dampening fluid to a lithographic plate wherein dampening fluid having a viscosity of less than about one poise, is applied to the printing plate to render hydrophilic, non- image, areas on the printing plate ink rejecting; and wherein ink, having a viscosity significantly greater than about.one poise, is applied by an inker roller to oleophilic image ares on the printing plate.
• the dampening fluid removal device comprises a doctor blade positioned in pressure indented rela ⁇ tion with an inking roller to engage ink and dampen ⁇ ing fluid on the portion of the surface of the roller which has applied ink to the printing plate and before fresh ink is applied. The metering portion of the doctor blade is positioned at an angle relative to a
• OMPI line tangent to the roller surface to remove fluid having a viscosity less than a predetermined viscosity from the surface of the inker roller and to leave fluid having a viscosity greater than the predeter ⁇ mined viscosity on the surface of the roller.
• An oscillating idler roller forms a matte finish on the surface of any fluid left on the form roller to increase the adhesion of fresh ink to the film of fluid.
• the fresh ink may be contacted by a material conditioning roller to form a matte, dampen ⁇ ing fluid receptive finish on the surface of the fresh ink before dampening fluid is contacted thereby.
• the fresh film of ink and dampening fluid are then carried by the lithographic printing plate where both ink and dampening fluid are printed ultimately to a printing substrate. Excess dampening fluid attached to the ink on the form roller is removed by the ink removal device after the form roll has printed ink to the plate.
• Adjustments are provided for adjusting the enden- tation of the doctor blade into the resilient roller surface and for adjusting the angle of the metering surface on the doctor blade relative to a line tan ⁇ gent to the roller for changing the efficiency of the doctor blade and causing a fluid of a smaller viscosity to be selectively removed from the fluid of a larger viscosity carried by the resilient sur ⁇ face of the form roller.
• FIG. 1 is a fragmentary front elevational view of a lithographic printing press having the dampen ⁇ ing fluid removal device mounted thereon;
• FIG. 2 is a cross sectional view taken along line 2-2 of FIG.l;
• FIG. 3 is a fragmentary perspective view of the doctor blade and holder
• FIG. 4 is a cross sectional view similar to FIG. 2 of a second embodiment of the dampening fluid removal device and;
• FIGS. 5 and 6 are enlarged details of the blade/ roller interface in operation.
• the numeral 10 generally designates the dampening fluid removing device mounted on a conventional offset lithographic printing press having a conventional plate cylinder P, blanket cylinder B, and impression cylinder I mounted therein for printing on a sheet or web of paper W.
• the printing press is equipped with an inker 20 comprising a single inking form roller 22 having a resilient outer cover to provide a resilient surface which is engaged by an ink metering member generally designated by the numeral 23.
• Inker 20 will be more hereinafter fully described.
• Dampening fluid removal device 10 comprises a doctor blade 60, which may comprise for example a flat strip of metallic material, such as stainless steel having a thickness of 0.020 inches. Blade 60 is sufficiently flexible to be deformed when urged into pressure indented relation with the resilient cover on form roller 22 to maintain substantially uniform pressure along the length of form roller 22 and along the edge of doctor blade 60.
• Doctor blade 60 in the illustrated embodiment is disposed at an angle "X" of 30 to tangent line L.
• Doctor blade 60 is secured by a clamp bar 62 to a mounting bar 64 having opposite ends rotatably secured between hangers 70 which are rotatably secured to the press side frames.
• opposite ends of mounting bar 64 are secured by connector plates 65 and screws 66 to journal blocks 67 having a journal 68 extending outwardly therefrom.
• Journals 68 are mounted in bearings 69 in hanger 70.
• Bearings 69 comprise split bearing blocks including semicircular bearing segments 69A and 69B and are secured together by screws 69C.
• journals 68 and doctor blade 60 can be rotated in bearing block segments 69A and 69B for adjusting the angular relationship between doctor blade 60 and a line L tangent to form roller 22.
• hangers 70 are pivotally mounted on journals extending out ⁇ wardly from opposite ends of an oscillating idler roller 80.
• Idler 80 is adjustable radially to the ' cover of form roller 22.
• Each hanger 70 is equipped with an externally threaded adjustment screw 72 for adjusting indentation of the doctor blade 60 into the resilient surface of the form roller 22.
• Exter ⁇ nally threaded screw 72 extends through an internally threaded anchor nut pivotally secured to the press side frame and the end of each adjustment screw 72 is rotatably secured in an anchor member 73 pivotally secured to the lower end of hanger 70.
• rotation of adjustment screw 72 causes hanger 70 and doctor blade 60 to rotate about the axis 81 of vibrator roller 80.
• a lock nut 74 is moved into engagement with the anchor nut and secured in position by a set screw 74A to assure that the edge of doctor blade 60 will be repositioned in the same indented position with the surface of resilient form roller after doctor blade 60 has been moved out of indentation with the resilient roller surface for cleaning.
• doctor blade 60 As will be hereinafter more fully explained, the pressure and angular relationship of doctor blade 60 relative to the surface of form roller 22 is main ⁇ tained to prevent passage of low viscosity dampening fluid and an emulsion of ink and dampening fluid, comprising primarily dampening fluid, while leaving higher viscosity ink on the surface of form roller 22.
• Dampening fluid removed from the surface of form roller 22 by doctor blade 60 flows by gravity downwardly into a dampening fluid collection tray 75 having downwardly inclined bottom walls.
• a drain pipe 76 communicates with the inside of tray 75 and dampening fluid collected therein is discharged through a hose 78 to waste or filtered and reused.
• Vibrator roller 80 has a cam follower 82 secured to one end thereof which rides in a groove in cam disc 83 on form roller 22. If it is deemed expedient to do so, doctor blade 60 may oscillate with roller 80 by connecting hangers 70 to prevent movement of the hangers 70 longitudinally relative to vibrator roller 80.
• Vibrator roller 70 forms a matte finish on the surface of any fluid left on the surface of form roller 22 to render the film of fluid more receptive to fresh ink.
• a pair of material conditioning rollers 80 and 91 are urged into pressure indented relation with the film of fresh ink formed on the form roller 22 by the inker 20. Rollers 90 and 91 form a matte finish of the freshly metered film of ink to make the film of fresh ink more receptive to dampening fluid.
• the dampener 95 is of the type disclosed in Dahlgren U. S. Patent No. 3,343,484, the disclosure of which is incorporated herein by reference, and includes a hydrophilic transfer roller 96 and a resil ⁇ ient covered metering roller 97 urged into pressure indented relation. Transfer roller 96 and form roller 22 are driven at different surface speeds.
• the resilient surfaced ink form roller 22 com ⁇ prises a hollow, rigid, tubular metallic core 42 having a resilient non-absorbent cover 44 secured thereto, the cover having a uniformly smooth, uni- formly textured, and resilient outer surface 45.
• the cover 44 on applicator roller 22, while being resilient, is relatively firm, for example, in a range between 30 and 70 Shore A durometer.
• the cover 44 on resilient surfaced ink form roller 22 is preferably formed of a resilent ure- thane, polyurethane, rubber or rubber-like material attached to a "metallic core 42.
• the cover is made from Buna Nitrile rubber which pro ⁇ vides a natural surface having microscropic pores to receive and hold ink therein to enable metering a thin ink film suitable for lithographic printing applications.
• the cover 44 on resilient surfaced ink form roller 22 should have high tensile strength, excellent tear and abrasion resistance, and resis ⁇ tance to oils, solvents and chemicals.
• the cover should, furthermore, have low compression set, good recovery, and uniform ink receptivity.
• a suitable cover can be formed using urethane or rubber to form a resilient cover preferably of about 60 Shore A durometer.
• a suitable urethane cover may be made from a blocked, pre-catalized material which is commercially
• OMPI available from Arnco in South Gale, California, under the trademark "Catapol”. The material is pre-heated at 160°F for five hours, poured into a mold around the roller core, and then heated to 280 ⁇ F for 8-1/2 hours, and allowed to cool prior to grinding and polish ⁇ ing.
• a suitable rubber cover may be obtained from Mid- America Roller Company, Arlington, Texas, and specified as Buna-Nitrile which is conventionally formed over the core and ground with a high-speed grinder prior to polish ⁇ ing.
• the roller may have a slick glazed outer skin or film over the surface thereof which is removed by grinding.
• the surface of resilient cover 44 if constructed of ure ⁇ thane, is sanded by using 180 grit sandpaper to form a surface of uniform smoothness over the surface 45 of the resilient cover 44.
• the surface of resilient cover 44 if construct ⁇ ed of rubber is sanded with 400 grit sandpaper to insure a velvet smooth, uniformly textured surface, free of "orange peel" or other surface irregularities.
• Microscopic reservoirs into which ink is attached help to assure that a continuous unbroken film of ink is maintained on the surface 45 of resilient surfaced ink form roller 22.
• a Shore A durometer test is generally used to indicate the hardness of a resilient roller cover by measuring resistance to penetration at a constant temperature of, about 76°F while the resilient cover is stationary.
• the apparent hardness of a resilient surface under dynamic conditions deviates radically from the hardness indicated by the durometer test under static conditions.
• the spring constant of a resilient material so increases slightly as deformation increases.
• the surface 45 of cover 44 on roller 40 is preferably in pressure indented relation with the surface of a plate cylinder, the plate cylinder having a gap extending longitudinally thereof, this cyclic loading will result in generation of heat at an irregular rate circumferentially of the surface 45.
• Such temperature differences over surface 45 may cause an appreciable varia tion in the radial distance from the axis of the roller 22 to points over the surface 45, because the co-efficient of thermal expansion of elasto eric materials employed
• O PI for forming resilient roller covers is several times the co-efficient of thermal expansion, of e.g. steel.
• Roller 22 can be different in diameter than the plate cylinder P without adversely affecting printing of the film 130 to the web W, or sheet, since member 10 produces a continuous ribbon of ink on the applicator roller surfac regardless of the prior impression and regardless of therma changes within the roller cover 44.
• a second embodiment of ink removal member 60' is illustrated in Figures 4 and 6 of the drawings.
• the ink metering member 60' has a smooth, polished, highly developed, precision metering edge 25 which is formed at the juncture of metering surface 24 and support surface 26.
• Edge 25 is defined by the intersection of the polished surfaces 24 and 26. Polished surfaces 24 and 26 meet at an obtuse angle to form a wedge having an included edge bevel angle "A ⁇ "which is approxi ⁇ mately 150° or greater.
• the edge 25 is preferably formed on relatively hard metallic material having a hardness of about Rockwell C48-50 or higher. It is important that the polished edge 25, surface 24, support surface -26, trailing surface 28a and edge 28b be wear resistant since they are indented into the resilient surface 45 of form roller 22 during normal operating conditions.
• Member 60' is preferably a resilient, i.e., flexible, metallic, material having a modulus of elasticity of approximately 30 x 10 6 psi, or less, to provide what might be termed a "stylus effect" to the metering edge 25 as the form roller 22 rotates.
• the strip of stainless steel was selected for its hardness, flatness, resilience, grain structure and fine surface finish to provide high wear resistance and good fatigue properties.
• the stainless steel strip had a thickness of 0.070 inches and a width of approximately 3.000 inches.
• the strip of material had been heat treated and had a bright polished surface finish, extra accurate flatness and norm straightness.
• the tolerance of the width was + o.016 M and the tolerance of the thickness was + 0.00181 inches.
• the strip of stainless steel material was resistant to corrosion in the presence of air, water and most organic acid in dilute form at room temperature. The tensile strength was about 249,000 psi corresponding to the hard ⁇ ness of Rockwell C 49.
• edges 24 and 26 were ground at a specified obtuse angle, then finished with a fine-grit stone as will be hereinafter more fully explained, as a first step in forming polished edge 25.
• the strip was then clamped in a special fixture. Surface 24 on the strip was superfinished at the specific angle by hand with a fine grit stone and then hand polished with 600 grit sandpaper.
• the stainless steel strip was posi ⁇ tioned on a flat horizontal surface.
• Surface 26 was then superfinished by hand with a stone having a fine grit and hand polished with 600 grit sandpaper.
• a feather edge forms on the member while portions of surfaces 24 and 26 are being superfinished and polished the feather edge should be removed with leather or a polis ing material.
• a smooth, continuous, uniform, blemish- free edge is formed on the strip.
• the acuteness of the edge may be altered somewhat to form a non-cutting, non-film-piercing edge. This process produces a fine, continuous, smooth, straight, polished, highly developed, uniform, super- finished, edge 25, having minimal surface irregulari ⁇ ties. There should be no small notches or protrusions in the edge.
• the developed edge 25, formed by polished sur ⁇ faces 24 and 26, is an extremely fine edge which has been polished to bring it to a highly developed finish, and as nearly perfect condition as possible.
• Surfaces 24 and..26 are preferably finished to an RMS reading not exceeding RMS 4.
• the term "superfinishing" as used herein applies to a surface which has been ground and polished such that the peaks of the surface have been removed to form flat bearing surfaces, yet still having minute valleys or reservoirs for accepting and carrying the lubricant dampening fluid and ink.
• Edge 25 is finished to a surface finish approximat ⁇ ing that of the edge of a razor blade.
• the obtuse angle "A ⁇ " between sur ⁇ faces 24 and 26 is significantly greater than the bevel angle on a razor blade and thus an obtuse, blunt, non- cutting and non-piercing edge is formed.
• sur ⁇ face 24 blends into surface 26 through edge 25 to form a continuous polished surface adjacent each side of edge 25.
• edge 25 must not only be hard and capable of being formed to provide a blunt, fine, polished, unbroken, edge, but the material must also be dense yet flexible along the length of the edge 25.
• the edge 25 must be quite flexible in a lengthwise direction so that when urged into pressure indented relation with the resilient surface of resilient surfaced ink form roller 22, the edge 25 will be flexed, yielding to the influence of the surface of roller 22, to conform the edge 25 and the surface of roller 22 to form a substantially uniform indented area along the length of roller 22.
• the resilient cover 44 on roller 22 has a thickness in the range of approximately 3/8 to 5/8 inches, preferably 1/2 inch, and a resilience of about 30 to 70 Shore A durometer, preferably 60 durometer. Shore A. This loading of edge 25 to obtain conformation with the surface of roller 22 should be possible without excessively indenting the surface of the roller when in a dynamic, running condition.
• the edge 25 on member 60' should be mounted so that it is resiliently urged toward the surface of the resili ⁇ ent surfaced ink form roller 22 and is free for movement along its entire length in a direction radial to the , applicator roller. Also, the edge 25 must be rigidly supported in a direction substantially tangent to the applicator roller surface.
• the ideal support for the edge 25 is a flexible can ⁇ tilever beam which supports the edge 25 and provides the required bias and rigidity.
• the edge 25 may be a part of a separate trapezoidal like element, which is functionally associated with a cantilever beam, it is preferable to form the edge 25 of the trapezoidal portion 10 on the beam so that the two are an integral unit.
• the beam must be flexible in two direc ⁇ tions; namely, along the length of the edge 25 and also along the width of the strip, ie., the length of the can ⁇ tilever beam.
• Support surface 26 lies substantially in the plane of surface 29, when the cantilever beam is in a non-flexed condition.
• Surface 24 and support surface 26 intersect forming an obtuse angle "A]_" and intersect at an apex 25, which is substantially a straight line.
• the cantilever beam which includes the obtuse edge 25 may be formed from a thin, flexible, elon- gated stainless steel strip or band, as hereinbefore des ⁇ cribed, having a thickness of 0.070 inches and a width of 3.0 inches, or less.
• the width of the beam, or the length of the strip of material will preferably be within the range of from 10 to 80 inches, and the beam is supported to be flexible along the length of edge 25 as well as along the length of the cantilever beam.
• the modulus of elasticity E of the beam may be, for example 29 x 10 6 psi, which represents the stiffness of the material; that is, its resistance to deformation. When combined with the moment of inertia I, the El factor represents the stiffness of the cantilever beam.
• Member 60 r also has a groove or relieved area 27 formed in the lower surface 29 of the strip of material from which member 60' is formed.
• the portion of the strip of material which will be polished to form polished edge 25 is masked and the metal ⁇ lic material adjacent thereto is removed by grinding or by chemically milling to remove a portion of the metal without creating stresses that would cause the strip of material to warp.
• Edge 28a adjacent the support surface 26 is smooth ⁇ ed by finish grinding to remove approximately 0.003 inch of rough surface material.
• Surface 28a may then be sand ⁇ ed with 600 grit paper to provide a very smooth surface finish on the surface of 28a.
• Edge 28b is therefore form ⁇ ed as discussed previously for edge 25.
• the depth of the relieved area 27 is preferably greater than 0.020 inches, for example, 0.035 inches, such that the thickness of the material between surface 28' and surf 28 is approximately 0.035 inches.
• Surface 28a intersects the polished surface 26 at angle A' in a range between 30° and 90° as shown.
• the upper portion of surface 24 of metering member 10' may extend to surface 28 or be bevelled as shown at an angle to form surface 22.
• O btuse angle "Al” not only forms a member having a bl obtuse, edge which is not fragile, but, primarily is specifically formed to a particular angle, or configura tion, to enable the doctor of a specific film having a specific viscosity to doctor the film without an immedi ate change in deflection of the roller surface and with out significant indentation of the roller cover which
• polished surface 24 extends upwardly from polished edge 25 a distance approximately equal to the depth of relieved area 27, or greater. It should be * readily apparent that polished surface 26 supports the polished edges 25 and 28b. If surfaces 24 and 28a are parallel, surface 26 can be refinished without changing the load bearing characteristics of the polished edge portion 25 of the metering member 10.
• edges 26 24 and 28a are readily renewable.
• both edges may be resharpened simultan eously; or, surfaces 24 and 26 may also be refinished.
• a small radius or curve may appear at edge 25 to cause changes in doctoring charact istics.
• post-grinding and hand-finishing procedu may be again performed several times before the entire member is replaced. Normally one to three thousandths
• a special fixture or fixtures may be used when re- finishing surfaces 24 and 26 in order to prevent damage to the metering member.
• the fixture should not only hold the member, but also provide guide surfaces for the fine grit stoning and sanding operations to insure that only a minimum amount of material is removed and that the obtuse angle "Ai" and edges 25 and 28b are maintained.
• the relief angle A 1 should be sufficient to cause an ink film carried by the surface of roller 22 to depart and separate from surface 26 without accumulating either on surface 26 or 28a to cause ultimate dripping of the accumulated ink to cause non-uniformity of printing.
• Lithographic printing ink for web-fed, offset presses has a viscosity in a range of about 100 to 200 poises while lithographic printing ink for sheet-fed offset press has a viscosity of about 200 to 265 poises.
• the ink metering member 23 of inker 20 and the doctor member 60* of the illustrated second embodiment are identi except that the angle "X" between tangent line L and meter ing surface 24 of metering surface 24 of metering member 60* is about thirty degress, plus or minus fifteen degrees, while the angel "Y" between the metering surface of meter ⁇ ing member 23 and tangent line T is about forty-five degrees, plus or minus fifteen degrees.
• doctor members 60 or 60' and ink meter ⁇ ing member 23 By selecting doctor members 60 or 60' and ink meter ⁇ ing member 23 with different angles "X" or “Y” relative to a line tangent to the form roller 22, liquids of different viscosities can be selectively metered. If the angle "X" is substantially the same as angle "Y", the metering edge on the ink metering member 23 will be indented a greater distance into the resilient form roller cover than the edge on member 60 or 60'.

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• Printing Plates And Materials Therefor (AREA)

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• 1981
  • 1981-09-08 EP EP19810902689 patent/EP0087416A1/de not_active Withdrawn
  • 1981-09-08 WO PCT/US1981/001213 patent/WO1983000842A1/en unknown

Non-Patent Citations (1)

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