GB2069932A

GB2069932A - Reversible printing press

Info

Publication number: GB2069932A
Application number: GB8113292A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-04-18
Filing date: 1979-04-10
Publication date: 1981-09-03
Also published as: SE7903167L; SE442104B; IT1188754B; DD143060A5; GB2069932B; GB2019317A; IT7909396A0; JPS54143307A; CA1138711A; GB2019317B; DE2916048A1; FR2423337A1; FR2423337B1; WO1980000144A1

Description

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SPECIFICATION Reversible printing press

This invention relates to a printing press wherein ink is applied to printing plates which 5 transfer the image to liquid receptive material such as a web. This invention also discloses a method of converting a pair of printing couples of a printing press to print on two sides of a web into a pair of printing couples to print twice on one 10 side of the web.

Inkers for printing plates of a printing press which have achieved commercial acceptance generally comprise from two to four form rollers which are positioned in rolling engagement with a 15 printing plate. Each of the form rollers is usually in rolling engagement with one or more vibrator rollers to which ink is applied by a multitude of rollers in a train of rollers of varying diameters arranged in pyramid fashion. Ink is delivered to the 20 train of rollers over a ductor roller which oscillates into and out of engagement with a film of ink formed by a flexible doctor blade urged into engagement with the hard surface of an ink fountain roller by a multiplicity of ink keys. 25 The ink film formed on the ink fountain roller has been too thick and too irregular for application directly to a printing plate for quality printing. These inkers which include a multiplicity of rollers are intended to reduce the thickness of the ink film 30 and to deliver a film of uniform thickness to the printing plate. However, since the ink film of each of the rollers is not totally replenished on each revolution of the form roller image ghosting and ink accumulation or starvation is not completely 35 eliminated. Thus, stripes and uneven ink distribution are produced on the product being printed e.g. a paper due to the ghosting and ink accumulation.

The conventional inkers, having multiple form 40 rollers require complex drive trains and are relatively expensive to purchase initially and to maintain thereafter.

Other types of inkers which have attempted to meter ink from a transfer roller to a form roller 45 have utilized a doctor blade to remove all of the film of feedback ink from the form roller prior to replenishing the ink film. Since most form rollers are resilient, the contact of the doctor blade with the form roller scores the form roller surface and 50 wears the blade and roller, and this can cause an uneven film of ink.

Devices of the type disclosed in U.S. Patent No. 3,926,114 were devised to remove all the unused portion of ink and dampening fluid from the form 55 roller prior to forming a new film of ink by metering the ink through a gap between the form roller and a transfer roller. There is considerable wear on the ink removal blade and the roller in this type of device. Also, it is extremely difficult to form 60 an ink film which is sufficiently thin by using a doctor blade wherein metering newsprint ink.

Inking devices of the type disclosed in U.S. Patent No. 2,240,762 employ rollers having surface cavities to meter ink onto a form roller for

65 application to a printing plate.

One problem the present invention addresses itself to is that of forming a thin film of newsprint type printing ink of low viscosity having substantially uniform thickness on a form roller 70 and moving the film of ink into engagement with the image area on a printing plate while eliminating from the inking system trains of rollers such as are provided in conventional inking systems, reducing the consumption of power, and 75 minimising or eliminating areas of ghosting and ink accumulation which produce undesirable variations on the web being printed.

A printing press generally comprises two printing couples for applying ink to the web. If it is 80 desired to print on both sides of the web in a single printing press, the web is routed through the unit such that ink is applied to both sides. However, if it is desired to print two colours in the same unit on one side of the web, one of the 85 printing couples must be reversed, from the direction used to print on both sides of the web, and the web is routed to print on one side. The reversal of the printing couple requires reversal of the rollers in the couple.

90 With the foregoing in view the present invention provides a printing press, wherein ink is applied to printing plates which transfer an image to liquid receptive material such as a web, comprising a pair of printing couples, each printing 95 couple consisting of a printing plate, a single form roller having an ink receptive surface; means rotatably supporting said form roller in pressure indented relation with the printing plate; positive drive means connected to said form roller; an ink 100 transfer roller having an oleophillic ink receptive surface; means rotatably supporting said ink transfer roller in pressure indented relation with said form roller; means forming a film of ink on said transfer roller; a pair of ink storage rollers; the ink 105 transfer roller of at least one of the printing couples being provided with reversible drive means, said reversible drive means being adapted to permit reversing the direction of rotation of said ink transfer roller upon reversing the direction of 110 the form roller and the printing plate so that the liquid receptive material can be run through the press once for printing on one side or printing on both sides; and means rotatably supporting said ink storage rollers such that the surface of the 115 form roller which is moving from pressure indented relation with the printing plate moves adjacent to one of said ink storage rollers before moving in pressure indented relation with said ink transfer roller upon rotation of the form roller in a 120 clockwise or a counter-clockwise direction.

The present invention also provides a method of converting a pair of printing couples of a printing press to print on two sides of a web into a pair of printing couples to print twice on one side 125 of the web, wherein each printing couple comprising a printing plate and a form roller driven a substantially equal surface speeds; an ink metering roller and an ink transfer roller urged together to form a flooded ink metering nip having

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an excess of ink on one side of the ink metering nip, the ink transfer roller being urged into pressure indented relation with the form roller and driven at a surface speed less than the surface 5 speed of the form roller; and a dampening fluid metering roller and a dampening fluid transfer roller urged together to form a flooded dampening fluid metering nip having an excess of dampening fluid on one side of the dampening fluid metering 10 nip, the dampening fluid transfer roller being urged into pressure idented relation with the form roller and driven at a surface speed less than the surface speed of the form roller, the improved method comprising the steps of: reversing the direction of 15 rotation of the printing plate and the form roller in one of the printing couples; reversing the direction of rotation of the ink metering roller and the ink transfer roller to move the excess of ink to the opposite side of the ink metering nip and to 20 move the surfaces of the ink transfer roller and the form roller in the same direction at different surface speeds; and reversing the direction of rotation of the dampening fluid metering roller and the dampening fluid transfer roller to move the 25 excess dampening fluid to the opposite side of the dampening fluid metering nip and to move the surfaces of the dampening fluid transfer roller and the form roller in the same direction at different surface speeds, and such that dampening fluid is 30 applied at the dampening fluid transfer nip to the surface of the form roller which is moving toward the ink transfer nip.

As an irrregular film of ink moves from the printing plate on the form roller, it marries with a 35 fresh uniform of ink on the transfer roller to form a substantially uniform film of ink on the form roller by removing ink from the transfer roller to replenish the depleted area on the form roller. The transfer roller continuously furnishes a uniform 40 film of ink to the form roller and the irregular feedback film, formed as the form roller removes ink from the transfer roller, moves back to the flooded nip between the transfer roller and metering roller to be remetered.

45 The film of ink on the form roller is further conditioned by a material conditioning roller to produce a smooth matte finish thereon. The material conditioning roller has essentially the same affinity for ink as does the form roller and 50 thus splits the film causing a matte finish on the ink layer.

The matte finish is readily adapted to accepting dampening fluid for use in a lithographic printing system. A dampening system having a transfer 55 roller with a hydrophillic surface and a metering roller transfer dampening fluid to the matte finish of the ink on the form roller prior to movement of the ink and dampening fluid layer into engagement with the printing plate. The ink and 60 water film is transferred to image areas on the printing plate and the dampening fluid to non-image areas such that lithographic printing may be performed.

After the layer of ink on the form roll moves 65 away from the printing plate there will be ghosted or depleted areas of ink which are reduced by an ink storage roller which accumulates the ink and supplies it to the ghosted or areas starved of ink prior to the layer of ink moving the nip between the form roller and the transfer roller to replenish the depleted film of ink.

The inking and dampening units are particularly adapted to be reversed, such that dampening fluid' is applied to the form roller and then ink applied there over. This permits reversal of the entire unit when desired.

This type of inker is particularly adapted for applying newsprint type ink processes such as Di-Litho (registered trademark of Americal Newspaper Publishers Associated/Research Institute) for printing direct on a lithographic plate with water, printing offset from a blanket with water, letterpress stereotype, dry offset, and letterpress direct printing with a letterpress plastic relief plate.

The inking system affords precision control of the thickness of the ink film to eliminate ghosting and a resulting colour variation of printing images.

The invention will be described further, by way of example, with reference to the accompanying drawings which illustrate a preferred embodiment of the printing press conforming to the invention. In the drawings, which correspond to those of my co-pending application No. 7912656 (Serial No.

to the claims of which attention is drawn and from the former of which the present application is divded:—

Fig. 1 is a diagrammatic illustration of a preferred inking system of the invention illustrating the various films of ink and dampening fluid;

Fig. 2 is a front elevational view illustrating the metering and transfer rollers and support structure;

Fig. 3 is a cross sectional view taken along line 3—3 of Fig. 2;

Fig. 4 is a diagrammatic view of a standard printing unit-

Fig. 5 is a diagrammatic view of a reversed printing unit;

Fig. 6 is a diagrammatic view of the electrical hook-up of the motors of dampening and inking units.

Numeral references are employed to designate like parts through the various figures of the drawing.

In Fig. 1 of the drawings, the numeral 1 generally designates a preferred embodiment of inker apparatus for applying ink and dampening fluid to a lithographic printing plate of a printing press. The dampening fluid applicator is a dampener 200 of the type disclosed in United States Patent No, 3,937,141, entitled "Dampener For Lithographic Printing Plates" which issued February 10th, 1976 to Harold P. Dahlgren. The disclosure of Patent No, 3,937,141 is incorporated herein by reference in its entirety for all purposes.

As best illustrated in Fig. 2, the inker apparatus 1 comprises spaced side frames 2 and 4 joined by

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tie bars (not shown) forming a strong rigid structure for supporting form roller 90, ink transfer roller 10, ink metering roller 12 and ink pan 14. Side frames 2 and 4 may be the side frames of a 5 press or may comprise inker side frames connectable to side frames of a printing press.

Throw-off links 16 and 18 are pivotally secured by stub shafts 20 and 22 to the respective side frames 2 and 4. Throw-off cylinders 24 and 26 are 10 pivotally connected between side frames 2 and 4 and throw-off links 16 and 18, respectively, for pivoting throw-off links 16 and 18 about stub shafts 20 and 22 for moving ink transfer roller 10 into position, as will be hereinafter more fully 15 explained, for delivering ink to a form roller 90 in a lithographic printing system.

A skew arm 28 is mounted for pivotal movement of one end of metering roller 12 about the axis of ink transfer roller 10. As diagrammatically 20 illustrated in Fig. 2, skew arm 28 is rotatably secured to stub shaft 30 extending between link 18 and skew arm 28 adjacent an end of ink transfer roller 10.

Skew arm 28 and throw-off link 16 has grooves 25 28a and 16a, respectively, formed in the inner surfaces thereof in which blocks 36, carrying self-aligning bearings 38, are slidably disposed. Blocks

35 are rigidly secured in the upper portion of grooves 28a and 16a by screws 37 to provide

30 suitable support for shafts 31 and 32 of the ink transfer roller 10. Suitable means such as resilient springs 40 between blocks 35 and 36 urge blocks

36 longitudinally of skew arm 28 and throw-off link 16 in a direction away from the longitudinal

35 axis of transfer roller 10. A pressure adjustment screw 42 urges block 36 longitudinally of skew arm 28 and throw-off link 16 against the bias of spring 40. Stub shafts 44 and 46, extending outwardly from opposite ends of metering roller 40 12, are received in self-aligning bearings 38 to rotatably secure metering roller 12 in pressure indented relation with transfer roller 10. Stub shafts 31 and 32, extending outwardly from opposite ends of transfer roller 10, are received in 45 bearings 39 in blocks 35.

It should be readily apparent that rotation of pressure adjustment screws 42 will move opposite ends of metering roller 12 relative to the axis of transfer roller 10 for controlling pressure 50 between transfer roller 10 and metering roller 12.

As illustrated in Fig. 3, suitable means is provided for establishing and maintaining a desired angular relationship between throw-off link 18 and skew arm 28. In the form of the 55 invention illustrated in Fig. 3, an adjusting screw 50 is rotatably secured to skew arm 28 and extends through threaded apertures in pivotal blocks 52a and 526. Block 52a and 526 are pivotally secured to lug 54 on arm 28 and lug 56 60 on link 18. By adjusting screw 50, the spacing between lugs 54 and 56 is adjusted to move skew arm 28 relative to link 18 about shaft 30.

Side frames 2 and 4 have suitable adjustable stop means such as stop blocks 5 having set 65 screws 5a extending therethrough for engaging throw-off links 16 and 18 when rods of throw-off cylinders 24 and 26 are extended for establishing a desired pressure relationship between the transfer cylinder 10 and ink coated form roller 90 arranged to transfer ink to a lithographic or relief printing plate 112 on plate cylinder P, as will be hereinafter more fully explained. Stop means such a stop blocks 6 having set screws 6a secured thereto provide an off-impression limit when piston rods of throw-off cylinders 24 and 26 are retracted to move the transfer roller 10 away from the surface of form roller 90. Stud shaft 32 has a brake disc 51 secured thereto and friction pads 53 are pivotally secured to support 55 secured to arm 28 to control the speed of transfer roller 10 when it is driven by frictional engagement with form roller 90.

Stib-shaft 31, extending outwardly from the ends of transfer roller 10, has a gear 60 rigidly secured thereto by screws 61 which is in meshing relation with a gear 62 rotatably secured by a bearing 45 disposed on shaft 44.

Gear 62 is secured in meshing relation with gear 64 on shaft 58 rotatably secured to side frame 2 through a clutch assembly 66 of a type such as a Morse (registered trade mark) one-way clutch. Shaft 58 is secured to the shaft of a reversible variable speed drive means such as a reversible variable speed electric gear-motor 69. It should be appreciated that gear-motor 69 may be replaced by other drive means such as gears, sprockets, or pulleys arranged to be driven from the printing press drive, preferably through a gear box or similar variable speed control apparatus.

Shaft 44, extending outwardly from the end of metering roller 12, has a gear 70 secured thereto in meshing relation with a gear 71 secured to and driven by shaft 58.

Power supply line 80 is connected through a variable rheostat 84 to the terminals of motor 69 so that motor 69 may run at variable speeds to control the speed of rotation, and consequently, surface speeds of transfer roller 10 and metering roller 12 independently of the press drive. If it is deemed expedient to do so motor 60 could be replaced by a speed-variable coupling which connects shaft 58 to the press drive means, as hereinbefore described.

Clutch assembly 66 allows transfer roller 10 to be driven by gear-motor 69 at a minimum speed ratio relative to metering roller 12, for example 1:1, and allows transfer roller 10 to be over-driven by form roller 90 at higher speeds without driving the metering roller 12 at a faster speed which may tend to sling ink 14a out of pan 14.

It should be appreciated that clutch 66 can be omitted and replaced by a gear to allow drive of the transfer roller 10 positively from the gear-motor 69 or clutch 66 may be locked to permit reversing of inker transfer roller 10. Clutch 66 may be reversed by removing same and reversing it on shaft 58 if so desired.

Ink storage rollers 82 and 82', illustrated in Fig. 1, are preferably vibrator rollers. Ink storage rollers 82 and 82' are adapted to equalize areas of

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excess ink on transfer roller 10 in a manner to be more fully explained hereinafter. Rollers 82 and 82' are preferably driven positively by roller 10, i.e. by gears driven by a gear on roller 10.

5 Suitable means is provided for delivering an abundant supply of ink to the ink metering nip N between adjacent surfaces of transfer roller 10 and metering roller 12. In the particular embodiment of the invention illustrated in Fig. 1, a 10 portion of the surface of metering roller 12 is submerged in ink 14a in ink pan 14.

Ink 14a preferably comprises a low viscosity ink such as the type employed for inking raised image areas in letterpress printing or the type used in 15 direct or offset lithographic printing such a type ink.

The transfer roller 10 is preferably hard and has an exterior surface which may be smooth or textured and which is ink receptive or oleophillic. 20 Ink transfer roller 10 may, therefore, have an exterior surface of materials such as copper, or plastic. The surface of transfer roller 10 may be either hard or resilient, depending upon the characteristics of the surface of form roller 90. If 25 form roller 90 has a hard surface, the surface of transfer roller 90 is preferably hard.

Metering roller 12 preferably comprises a hotlow tubular sleeve having stub shafts 44 and 46 formed thereon. A resilient cover 12c is 30 secured about the outer surface of the sleeve. The material of metering roller 12 is selected so as to be oleophillic and the surface may be smooth or textured.

To reduce the tendency of ink to accumulate 35 adjacent the ends of transfer roller 10, metering roller 12 is longer than transfer roller 10 such that ends of the metering roller 12 extend beyond the ends of the transfer roller 10. The transfer roller 10 is preferably longer than form roller 90 to 40 minimize accumulation of excess ink adjacent ends of form roller 90.

It should be readily apparent that, if desired, the material of transfer roller 10 and metering roller 12 may be reversed such that metering roller 12 45 has a hard surface and transfer roller 10 has a resilient cover, or both could be resilient.

Form roller 90 is preferably cut to be the same length as the printing plate to also eliminate accumulation of excess ink which will tend to 50 build up on the form roll if longer than the printing plate.

Referring to Fig. 1 of the drawing, transfer roller 10 is preferably positioned in pressure indented relation with a form roller 90, having a metal 55 tubular core 91 to the ends of which are secured stub shafts extending outwardly therefrom and rotatably journaled in bearings 92 carried by the side frames 2 and 4.

Form roller 90 has a smooth outer cover 96 60 which may be non-absorbent or absorbent, hard or soft, depending upon the nature and construction of printing plate 112.

In one embodiment, form roller 90 may have a resilient non-absorbent surface and a molleton 65 type cover which absorbs ink and will reject dampening fluid. However, if plate 112 has raised image areas and is constructed of resilient material, form roller 90 could be provided with a hard surface of, for example, copper or a hard thin, plastic covering.

An ink storage roller 94, preferably a vibrator roller, is adapted to remove ink from areas 128" from ink film 128 on the surface of form roller 90 and add the ink to the depleted areas 128' thereby creating a more uniform film of ink on the surface of roller 90 moving from nip 120 toward nip 106.

A second ink storage roller 94', similar to roller 94, is positioned between plate cylinder P and dampener 200 to smooth the ink film upon reversal of form roller 90 as will be more fully explained hereinafter.

A material conditioning roller 86, preferably a vibrator roller, is rotatably supported on shaft 86a in blocks 86d and is adapted to condition and smooth the surface of ink film 100 to make the film more receptive to accepting dampening fluid. Screws 866 and 86c are adapted to urge blocks 86(/and roller 86 into pressure indented relation with form roller 90. The surface of material conditioning roller 86 is preferably of similar material to that of form roller 90 such that the surface has the same affinity for ink as does the surface of form roller 90.

As the ink film 100 emerges from the nip 106 between form roller 90 and transfer roller 10, it is slick, and calendared. A slick film of ink is not particularly receptive to dampening fluid since the surface tension of the molecules of ink may reject the thin layer dampening fluid to be applied by dampener 200. Material conditioning roller 86 will receive a portion of the film 100 of ink thus splitting the film 100 of ink and producing a film 100' on roller 86 thus leaving film 100a with a matte finish having microscopic indentations. The matte finish on film 100a will more readily accept the thin layer of dampening fluid due to molecular attraction which is now greater than the surface tension of the dampening fluid forming a film 217.

Material conditioning roller 86 and ink storage rollers 94 and 82 are preferably constructed of diameter such that as they rotate ink will be properly applied or extracted and redistributed on the surface of roller 90.

Vibrator rollers 82, 86 and 94 are preferably provided with drive means (not shown) to oscillate the rollers in a longitudinal direction. Suitable oscillator drive means is well known to persons skilled in the printing art and further description is not deemed necessary. Rotation is provided through friction contact with adjacent surfaces.

Dampener 200 is diagrammatically illustrated in Fig. 1 and comprises a hydrophillic transfer roller 210 on shaft 210a and a resilient metering roller 212 on shaft 212a, mounted in a similar manner to inker 1, as described in United States Patent No. 3,937,141. Metering roller 112 meters dampening fluid 214a from pan 214 onto transfer roller 210 through flooded nip Na. Water film controlled by pressure between rollers 210 and 212 forms a thin layer of dampening fluid 204

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which is metered through dampening fluid transfer nip 106a onto the matte finish of ink film 100a on the surface of form roller 90.

Dampener metering roller 212 is driven by a 5 variable speed reversible motor 269. As illustrated in Fig. 6, rheostats 84 and 284 are connected to a suitable electrical supply and are connected to a pair of gained double pole, double throw switches 81a* and 816 to control the direction of motors 69 10 and 269.

The operation and function of the apparatus hereinbefore described is as follows:

Pressure between ends of transfer roller 10 and metering roller 12 is adjusted by rotating pressure 15 adjustment screws 42.

Since long rollers urged together in pressure relation tend to deflect or bend, pressure adjacent centres of such rollers is less than pressure adjacent ends thereof. Pressure longitudinally of 20 rollers 10 and 12 is adjusted by rotating screw 50 and rotating skew arm 28 about the axis of transfer roller 10 to a position wherein a desired pressure distribution longitudinally of rollers 10 and 12 is obtained.

25 Adjustment screw 5a is positioned to engage throw-off links 16 and 18 for establishing a desired pressure between transfer roller 10 and form roller 90.

The surface speeds of rollers 10 and 12 are 30 regulatable by manipulating rheostat 84 as has been hereinbefore explained.

Dampener 220 is adjusted in a similar manner as inker 1.

For the purpose of graphically illustrating the 35 novel function and results of the process of the mechanism hereinbefore illustrated and described, a diagrammatic view of the metering roller 12, the transfer roller 10 and the form roller 90 is shown in Fig. 1. Ink and water films shown are 40 exaggerated for clarity.

As shown in Fig. 1, metering roller 12, when employed to deliver ink to a printing plate 112, is preferably a resilient surface 12c thereon and has the lower side thereof immersed in ink 14a and 45 pan 14. The metering roller 12 is rotatably mounted in pressure indented relation with transfer roller 10, and the pressure between adjacent roller surfaces is adjusted by screw 42, as hereinbefore described, so that the surface of 50 transfer roller 10 is actually impressed into the surface of roller 12 at ink metering nip N.

As the surface of roller 12 rotates towards the ink metering nip N between rollers 10 and 12, a relatively heavy layer 101 of ink is packed up and 55 lifted on the surface of roller 12. At the point of tangency, or cusp area at the ink metering nip N, between the rollers 10 and 12, a bead 102 of ink is piled up forming an excess of ink. The size of the excess of ink bead 102 is regulated by virtue of 60 the fact that excess of ink will fall back into the pan by gravity, thus, virtually creating a waterfall, and by the surface speed of metering roller 12. The bead 102 becomes a reservoir from which ink is drawn by transfer roller 10. As roller 10 and 12 65 rotate in pressure indented relation, a layer of ink is sheared and/or metered between adjacent surfaces of the two rollers separated by a thin lubricating layer of ink 103. Since the transfer roller 10 has a smooth, oleophillic surface thereon, a portion of the film 103 adheres to the surface of roller 10 to form a film 104a, the remaining portion 105 thereof being rotated back or fed-back in the pan 14. The film of ink 104a is distributed on the surface of roller 10 by reason of the rotating, squeezing action between rollers 10 and 12 at their tangent point at ink metering nip N. Ink storage roller 82 splits ink film 104a and receives a film 104' which is added to film 104a again to further assure smooth uniform thickness of film 104 on transfer roller 10.

The film of ink 104 rides on the surface of roller 10 and comes in contact with the film 130 of ink on form roller 90 at the tangent point or ink transfer nip 100 between transfer roller 10 and form roller 90.

At ink transfer nip 106, it will be observed that transfer roller 10 is impressed into the resilient surface of form roller 90 and that the film of ink 104 has an outer surface 108, contacting ink film 130, and an inner surface 110 adhering to the surface of the roller 10. The outer surface 108 of the film 104 and the outer surface 131 of the film of ink 130 on form roller 90 are urged together to create a hydraulic connection between roller 10 and 90 as they rotate in close relationship, but there is no physical contact between the roller surfaces.

It is an important fact to note that the relative thick film of ink 104 permits rollers 10 and 90 to be rotated at different surface speeds as will be hereinafter explained. Preferably, the form roller 90, which is normally rotated at the same surface speed as the printing plate 112, and press driven, is rotated at a greater surface speed than the surface speed of roller 10. By regulating the differential surface speed between transfer roller 10 and applicator roller 90 the amount of ink applied to the plate 112 may he regulated.

Within limits, as will be hereinafter more fully explained, if the surface speed of transfer roller 10 is increased the ink film 104 is presented at the ink transfer nip 106 at a faster rate and more ink is transferred by the surface of roller 90 to lithographic printing plate 112, and the opposite is true, if the surface speed of roller 10 is decreased.

The film of ink 104, existent between adjacent surfaces of rollers 10 and 90, permits rollers 10 and 90 to be rotated at different surface speeds in sliding relationship, because the film of ink 104 actually provides lubrication which permits slippage between adjacent surfaces of rollers 10 and 90 without frictional deterioration. By reason of the slippage between rollers 10 and 90, the ink film 104 is calendared, smoothed out, metered and distributed by shearing the ink between adjacent surfaces of roller 10 and the ink film 130 on form roller 90, to create ink film 100. The thickness of the ink film 100 is controlled by pressure between metering roller 12 and transfer roller 10 and the speed of transfer roller 10.

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Transfer roller 10 preferably is driven at a surface speed which is within a range of for example, several hundred feet per minute slower than the surface speed of form roller 90. For 5 example, if a printing press has paper travelling therethrough at a surface speed of 1200 feet per minute the surfaces of printing plate 112 and form roller 90 will ordinarily have surface speeds of 1200 feet per minute. The surface speed of 10 transfer roller 10 would preferably rotate at a surface speed in a range between 50 feet per minute and 100 feet per minute.

Ink films 104 and 130 will be combined at ink transfer nip 106 and will split when sheared as 15 rollers 10 and 90 rotate away from ink transfer nip 106. The fresh film 100 of ink adheres to the surface of form roller 90. Ink rejected by form roller 90 forms a feedback film 116 of ink which may be slightly irregular which adheres to the 20 surface of the transfer roller 10 and is conveyed back to the bead 102 of ink adjacent ink metering nip N to be remetered. Feedback film 116 is not uniform because the starved areas on form roller 90, from which ink was removed by image areas 25 on the plate 112, removed different quantities of ink from film 104 in order to remeterfilm 128 on form roller 90. Film 128 has starved areas 128' from ink removed by image areas 122 on plate 112, thus rendering film 128 irregular. 30 As the film 100 of ink on the surface of form roller 90 moves from ink metering nip 106 adjacent transfer roller 10, the film 100 is substantially uniform as non-uniform film 130 is combined with the uniform 104 carried on 35 transfer roller 10. Film 130 accepts ink from film 104 in the starved or depleted areas 128°. The transfer roller 10 is caused to rotate at a speed which satisfies the need for ink by form roller 90 by overriding clutch 66. The depleted portion or 40 feedback film 116 is returned to the abundant or excess supply of ink at bead 102 between metering roller 12 and transfer roller 10 to replenish the ink film 104.

It has already been explained that the ink film 45 130 is smoothed out, distributed, metered, and regulated at the ink transfer nip 106 between transfer roller 10 and form roller 90. Material conditioning roller 86 splits film 100, taking on a film 100' to produce a matte finish on ink film 50 100a. Any irregularities or streaks in film 100 will be spread and equalized to form film 100a of very uniform thickness.

The interface tension between the outer surface of the less viscous dampening fluid film 204, by 55 reason of molecular attraction between the surface of the more viscous ink film 100a, causes a portion 216 of the smooth and regulated film 204 of dampening fluid to be added to the surface of ink film 100a, which in turn is transferred to the 60 plate at the tangent point between the plate 112 and form roller 90 at inking nip 120.

The lithographic printing plate 112 has hydrophillic or water liking, non-image areas 121 formed on the surface thereof. If printing plate 112 65 is provided with raised image areas, the dampener

200 would be required to prevent transfer of ink to non-image areas.

At the nip 120 between applicator roller 90 and printing plate 112, the ink film 100 is split,

forming thin films 125 of ink and water over oleophillic surfaces 122 on the printing plate. The layer 216 of dampening fluid, if dampening fluid is employed, is carried on and in the film 100 of ink" and is also distributed to form a thin layer 226 of dampening fluid over hydrophillic areas 121 of the printing plate.

No appreciable amount of dampening fluid remains on the surface of form roller 90 which is moving away from the nip 120, but such dampening fluid as does remain thereon is transferred with the ink film 128 to the ink film 130a on the ink storage roller 94 where the dampening fluid can be dissipated and/or evaporated to such an extent as to be of no consequence in the inking system.

Ink of film 128 remaining on form roller 90 is combined with film 130a on ink storage roller 94 and split and collected on roller 94. Ink on roller 94 is added to replated areas 128' thus reducing the effect of ghosted and areas in film 128 by forming a more uniform film 130 before reentering nip 106.

The layer of dampening fluid 216 is applied in substantially the same manner. An excess of dampening fluid 210 is supplied to bead 202 to form a film 204 of dampening fluid which is applied to ink films 100a on form roller 90 at nip 106a. The film 217 of dampening fluid is returned to bead 202 to be re-metered at nip Na.

From the foregoing it should be readily apparent that the improved apparatus for applying ink to printing systems offers control of metering at ink metering nip N to provide a film 104 of ink of precisely controlled thickness by adjusting pressure between transfer roller 10 and metering roller 12 and further by controlling surface speeds of the rollers relative to each other. The rate at which the metered film 104 of ink is offered to film 130 of ink on form roller 90 at ink transfer nip N and also the hydraulic force for obtaining the desired film split is controlled.

To eliminate conditions which could cause accumulation of ink rendering it impossible to form a film 104 of precisely controlled thickness the specific roller arrangement provides for elimination of ink which is fed-back in the form of ink film 116 on transfer roller 10 moving away from the ink transfer nip 106. Thus, the effect of the unused depleted film of ink not accepted by form roller 90 if eliminated from the inking system by returning film 116 to the flooded ink metering nip N and is not left to accumulate on transfer roller 10 as in prior art devices.

While a preferred embodiment of the invention has been hereinbefore described and illustrated in the attached drawings it should be appreciated that other and further forms of the apparatus can be devised without departing from the basic concept thereof.

It should further be appreciated that either the

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transfer roller 10 or metering roller 12 could be geared to the press drive, or driven by an independent drive means, for extablishing the conditions hereinbefore described for a specified 5 speed range.

It should be appreciated that transfer roller 10 may be oscillated laterally along its axis to further smooth ink films 130 and 100.

Fig. 4 illustrates a pair of inkers 1 used in the 10 standard configuration to print on both sides of a web W. A printing press U generally has a pair of printing couples C each of which comprise an inker apparatus 1 and dampener unit 200. If it is necessary to print two colours on one side of web 15 W, then right hand couple C as viewed in Fig. 5 must be reversed such that the web W may be routed for printing on a single side. In reversing the direction of the form roller 90, dampening fluid will be applied over the thin ghosted film of ink 20 leaving the plate 112 after ink storage roller 94' evens the ink film to some extent. A fresh supply of ink will be added to the dampening fluid and ink on roller 90 as the roller 90 moves through nip 106. Thus, the couple C may be reversed by simply 25 reversing the drive to the couple and motors 69 and 269.

Since friction on the drive will be altered by reversing the inker 1, brake 51 should be adjusted to control the speed ratio between form roller 90 30 and transfer roller 10.

It should be readily apparent that the films of ink and dampening fluid illustrated in Fig. 1 represent a standard printing couple moving in the normal or standard direction and that their films 35 would change in location from those illustrated should the couple be reversed to apply dampening fluid first and ink on the dampening fluid.

Claims

1. A printing press, wherein ink is applied to 40 printing plates which transfer an image to liquid receptive material such as a web, comprising a pair of printing couples, each printing couple consisting of a printing plate, a single form roller having an ink receptive surface; means rotatably 45 supporting said form roller in pressure indented relation with the printing plate; positive drive means connected to said form roller; an ink transfer roller having an oleophillic ink receptive surface; means rotatably supporting said ink 50 transfer roller in pressure indented relation with said form roller; means forming a film of ink on said transfer roller; a pair of ink strage rollers; the ink transfer roller of at least one of the printing couples being provided with reversible drive 55 means, said reversible drive means being adapted to permit reversing the direction of rotation of said ink transfer roller upon reversing the direction of the form roller and the printing plate so that the liquid receptive material can be run through the 60 press once for printing on one side or printing on both sides; and means rotatably supporting said ink storage rollers such that the surface of the form roller which is moving from pressure indented relation with the printing plate moves

65 adjacent to one of said ink storage rollers before moving in pressure indented relation with said ink transfer roller upon rotation of the form roller in a clockwise or a counter-clockwise direction.

2. A printing press as claimed in claim 1, 70 wherein each printing couple also comprises a dampening fluid transfer roller having a surface; means rotatably supporting said dampening fluid transfer roller in pressure indented relation with said form roller; means forming a film of 75 dampening fluid on said dampening transfer roller; said means supporting said ink storage rollers being adapted to support said ink storage rollers such that the surface of the form roller which is moving from pressure indented relation with the 80 printing plate moves adjacent to one of said ink storage rollers before moving into pressure indented relation with said ink transfer roller or said dampening fluid transfer roller.

3. A printing press as claimed in claim 2 85 wherein at least one printing couple further comprises a second reversible drive means drivingly connected to said dampening fluid transfer roller.

4. A printing press as claimed in claim 1, 2 or 3 90 wherein each printing couple further comprises an ink metering means; an ink transfer roller having an oleophillic ink receptive surface, a form roller in rotative contact with the printing plate and having an ink receptive surface adapted to be urged into 95 pressure relation with said ink transfer roller to form an ink transfer nip; means supporting said ink metering means and said ink transfer roller in pressure indented relationship to form an ink metering nip between adjacent surfaces of the ink 100 metering means and the ink transfer roller,

means to supply ink to said ink metering nip to produce a smooth, uniform and continuous film of ink on the surface of said ink transfer roller; a dampening fluid transfer roller adapted to apply 105 dampening fluid on the surface of the ink film on the surface of the form roller; means rotatably supporting said dampening fluid transfer roller in pressure indented relationship with said form roller to form a dampening fluid transfer nip; 110 dampening fluid metering means; means to supply dampening fluid to said roller such that the dampening fluid metering means produces a smooth, uniform, continuous film of dampening fluid on the surface of the dampening fluid transfer 115 and drive means associated with said plate cylinder, said form roller, said dampening fluid transfer roller, and said ink transfer roller to move a point on the surface of the form roller sequentially from indented relation with said 120 printing plate where ink and dampening fluid contact the printing plate, to the dampening fluid transfer nip where dampening fluid is applied to said form roller, to the ink transfer nip where ink is applied to said form roller and finally into indented 125 relation with said printing plate, said drive means being adapted to rotate said ink transfer roller such that its surface speed is less than the surface speed of said form roller.

5. A printing press as claimed in claim 4, with

the addition of: a first ink storage roller urged into pressure indented relation with said form roller to engage ink remaining on said form roller which has engaged the printing plate before moving to 5 said ink transfer nip when the form roller is rotating in a first direction; and a second ink storage roller is urged into pressure indented relation with said form roller to engage ink remaining on the surface of said form roller which

10 has engaged the printing plate before moving to said dampening fluid transfer nip when the form roller is rotating in a first direction; and a second ink storage roller urged into pressure indented relation with said form roller to engage ink

15 remaining on the surface of said form roller which has engaged the printing plate before moving to said dampening fluid transfer nip when the form roller is rotating in a second direction.

6. A printing press as claimed in claim 4 with

20 the addition of: an ink storage roller supported in rotative contact with the surface of the film of ink which is just moved from the printing plate, said ink storage roller adapted to equalize the surface of the irregular film of ink.

25 7. A printing press as claimed in claim 4 with the addition of: a material conditioning roller supported in rotative contact with the newly metered film of ink on the surface of said form roller, said material conditioning roller being

30 adapted to produce a matte finish on said film of ink.

8. A printing press as claimed in claim 4 with the addition of: a material conditioning roller supported in rotative contact with the form roller

35 between the ink transfer roller and the dampening fluid transfer roller.

9. A printing press as claimed in claim 4 with the addition of: an ink storage roller having an oleophillic surface; and means supporting said ink

40 storage roller in pressure indented relation with said ink transfer roller, said ink storage roller adapted to remove ink and replenish ink on the surface of the ink transfer roller prior to the ink film moving to said form roller.

45 10. A printing press as claimed in any preceding claim wherein said form roller has a resilient non-absorbent surface formed thereon.

11. A printing press as claimed in any preceding claim wherein said form roller has a

50 resilient absorbent surface formed thereof.

12. A printing press as claimed in claim 3 wherein said ink metering means comprises: an ink metering roller having an oleophillic surface formed thereon and means urging said oleophillic

55 roller into pressure indented relationship with said ink transfer roller.

13. A printing press as claimed in claim 4

GB 2 069 932 A 8

wherein the dampening fluid metering means comprises: a metering roller and means urging 60 said metering roller into pressure indented relationship with said hydrophillic roller.

14. A printing press substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. . 65 15. A method of converting a pair of printing couples of a printing press to print on two side of a web into a pair of printing couples to print twice on one side of the web, wherein each printing couple comprises a printing plate and a form roller 70 driven at substantially equal surface speeds; an ink metering roller and an ink transfer roller urged together to form a flooded ink metering nip having an excess of ink on one side of the ink metering nip, the ink transfer trailer being urged into 75 pressure indented relation with the form roller and driven at a surface speed less than the surface speed of the form roller; and a dampening fluid metering roller and a dampening fluid transfer roller urged together to form a flooded dampening 80 fluid metering nip having an excess of dampening fluid on one side of the dampening fluid metering nip, the dampening fluid transfer roller being urged into pressure indented relation with the form roller and driven at a surface speed less than the surface 85 speed of the form roller, the improved method comprising the steps of: reversing the direction of rotation of the printing plate and the form roller in one of the printing couples; reversing the direction of rotation of the ink metering roller and the ink 90 transfer roller to move the excess of ink to the opposite side of the ink metering nip and to move the surfaces of the ink transfer roller and the form roller in the same direction at different surface speeds; and reversing the direction of rotation of 95 the dampening fluid metering roller and the dampening fluid transfer roller to move the excess dampening fluid to the opposite side of the dampening fluid metering nip and to move the surfaces of the dampening fluid transfer roller and 100 the form roller in the same direction at different surface speeds, and such that dampening fluid is applied at the dampening fluid transfer nip to the surface of the form roller which is moving toward the ink transfer nip.

105 16. A method as claimed in claim 15, with the additional step of: adjusting drive means operably connected to said ink transfer roller to control the speed of the ink transfer roller relative to the form roller. .

110 17. A method of converting a pair of printing couples of a printing press substantially as hereinbefore described with reference to the . accompanying drawings.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1981. Published by the Patent Office. 25 Southampton Buildings, London, WC2A 1AY, from which copies may be obtained.