US3048098A - Printing press and method - Google Patents

Description

1962 c. o. SIEBKE 3,048,098

PRINTING PRESS AND METHOD Filed Jan. 12, 1960 INVENTOR Carl 0. Siebke Unite States This invention relates to a printing press and method. It relates particularly to a method and means for improving the printing quality of a printing press in which ink is applied to the form accompanied by the application of water which becomes admixed or emulsified with the ink, as in lithographic offset printing.

As is Well known to those skilled in the art, ink and water are applied to the form or printing plate in lithographic offset printing, the ink and water forming an emulsion. The water is applied to keep the printing form or plate sufficiently wet in the non-printing areas so that the ink, which has an oily base, will not be deposited in those areas. The water unavoidably forms an emulsion with the ink. Formation of the emulsion is not desired but is one of the necessary evils of the process. In lithographic printing the best results are obtained by using a minimum amount of water. However, enough water must be kept in the non-printing areas of the plate to prevent those areas from drying up; otherwise the plate will pick up ink and start printing. For uniform tone reproduction a constant ink-water balance or ratio should ire maintained.

While my invention is applicable to any printing process in which ink and water are used, its principal application is inthe lithographic offset printing art, and for purposes of explanation and illustration the invention will be. described as embodied in a lithographic offset printing press and method.

In a lithographic offset printing press the so-called plate cylinder has a printing form or plate applied to its surface which extends throughout less than the full circumference of the cylinder. I herein use the generic term form which is to be understood to include any form for printing in a press of the type to which the invention is applicable; the form in a lithographic offset printing press is commonly termed a printing plate and is normally of flexible sheet metal such as Zinc or aluminum and-is applied to the surface of the cylinder and stretched and fastened in place thereon.

Since the printing plate or form extends throughout less than the full circumference of the cylinder there is a gap between the trailing and leading-edges of the form. As well known to those skilled in the art, the form in lithographic offset printing is hydrophylic. Ink is supplied to the form through an inker having ink form rollers and which for present purposes may be deemed to be of conventional construction. Water is also supplied to the form through a system of water supplying rollers and which for present purposes may be deemed to be of conventional construction.

The system of water supplying rollers employed in presses of the type above referred to includes water form roller means which may, for example, constitute two water form rollers adapted to directly engage and deliver water to the form or printing plate. Other rollers deliver water to the water form rollers in conventional manner well known to those skilled in the art. The rollers are driven constantly at constant speed so water is delivered to the Water form rollers at a fixed (although adjust-able) rate of feed.

When the water form rollers are in engagement with the form they deliver water thereto. When they are not in engagement with the form, i.e., when they are opposite the gap in the cylinder between the trailing and leading when water is being applied to the form. 7

3,048,098 Patented Aug. 7, 1962 edges of the form, they do not deliver water to the form. But the rollers which deliver water to the water form rollers operate continuously and hence the water form rollers are receiving a constant supply of water at all times regardless of whether or not they are delivering water to the form. The result is that during the time when the water form rollers are opposite the gap between the trailing and leading edges of the form the quantity of water carried thereby builds up so that when they engage the form at the leading portion thereof they deliver to that portion of the form a relatively great quantity of water and after that excess of water has been delivered to the leading portion of the form the water form rollers deliver a lesser quantity of water to the remainder of the form.

When the ink form rollers are traversing the gap between the trailing and leading edges of the form the ink on those rollers tends to lose some of its water content, increasing the intensity of the tone produced in printing. Regardless of how much water is on the form the ink applied to the form will have a more intense tone for the first revolution of the ink form rollers. The water picked up from the form does not affect the ink during the first revolution of the ink form rollers. It is, however, picked up by the ink form rollers and carried to the other rollers of the inker such as distributing rollers and vibrating rollers well known to those skilled in the art which cause the ink to be spread in a film of uniform thickness. The ink is also thereby emulsified and when a form roller starts its second revolution on the form it deposits thereon the emulsified ink which is lighter in tone than unemulsified ink.

' Therefore the ink form rollers on their first revolution deposit ink of a relatively intense tone while on the second revolution of the ink form rollers a lighter tone is produced because the form rollers have picked up more water from the leading edge of the form and worked it into the ink on the first revolution of the ink form rollers and deposit it on the second revolution. While depositing ink on the form during the second revolution the ink form rollers also pick up water from the form. However, the amount of water thus picked up is less than that picked up on the first revolution of the ink form rollers on the form and so the tone of the ink applied to the form during the third revolution of the ink form rollers is more dense than that of the ink applied during the second revolution but less dense than that of the ink applied during the first revolution. This is caused primarily by the fact that the water form rollers store up water while passing through the gap and during the first revolution on the form deposit an excess of water. During their second revolution they deposit less water than on the tfirst and during their third revolution probably a little less than on the second.

The above described condition has existed since the invention of lithographic offset printing. Those skilled in the art have made many attempts to avoid the unevenness of the tone of the printing but no entirely satisfactory solution to the problem has heretofore been discovered.

I provide a printing press and method obviating the disadvantages above explained and insuring the supplying of water to the form at a fixed rate of feed. I provide a method of improving the printing quality of a printing press in which ink is applied to the form and water is admixed with the ink in the zone of application of ink to the form comprising during operation of the press supplying water at a fixed rate of feed for admixture with the ink. Preferably the water is applied to the form for admixture with the ink and I supply the water to the form at a fixed rate of feed at all times I preferably supply the water to the zone of application thereof to the form at a fixed rate of feed and during intervals while no portion of the form is at said zone remove water from the supply at the same rate as the form removes water from the supply to avoid accumulation of Water during such intervals so that at all times when water is being applied to the form it is applied to the form at a fixed rate of feed. The removal of the water from the supply during the intervals while no portion of the form is at the zone of application of water thereto is preferably accomplished by engaging the water supply with a moving surface which removes water therefrom at the same rate as the form removes water from the supply.

I further provide, in a printing press, a form cylinder, a form on the cylinder extending throughout less than the full circumference of the cylinder and means for supplying ink and water for application to the form, said means including means insuring supplying water for application to the form at a fixed rate of feed during operation of the press. My press preferably comprises means for applying ink to the form, means for applying water to the form and means cooperating with the means for applying water to the form insuring applying water to the form at a fixed rate of feed during operation of the press. I preferably provide means operative during intervals while no portion of the form is in Water receiving relationship to the means for applying water to the form removing water from the means for applying water to the form at the same rate as the form removes water therefrom when in water receiving relationship therewith to obviate accumulation of water by the means for applying water to the form during said intervals, which accumulation would result in application of water to the form at a fluctuating rate of feed, thereby insuring application of water to the form at a fixed rate of feed during operation of the press.

I preferably provide a moving hydrophylic surface engaging the means for supplying water to the form during intervals while no portion of the form is in water receiving relationship to the means for applying water to the form removing water from the means for applying water to the form at the same rate as the form removes water therefrom when in water receiving relationship therewith.

In my preferred structure I provide bridging means applied to the cylinder at the portion of the circumference thereof not covered by the form and having a hydrophylic surface of substantially the same curvature as the form, so that the surfaces of the form and of the bridging means together constitute substantially a full cylindrical hydrophylic surface, said surface of the bridging means removing water from the means for applying water to the form at the same rate as the form receives water therefrom when in water receiving relationship therewith. The means for applying water to the form preferably comprise water form roller means, and water is supplied to the water form roller means at a fixed rate of feed during operation of the press.

Other details, objects and advantages of the invention will become apparent as the following description of a present preferred embodiment thereof and a present preferred method of practicing the same proceeds.

In the accompanying drawings I have shown a present preferred embodiment of the invention and have illustrated a present preferred method of practicing the same in which FIGURE 1 is a diagram showing the form cylinder and the means for applying ink and water to the form in a lithographic offset press;

FIGURE 2 is a diagrammatic view to enlarged scale of the form cylinder having the bridging means of my invention applied thereto;

FIGURE 3 is a plan view of the under side of the bridging means;

FIGURE 4 is an end view of the bridging means; and

FIGURE 5 is a fragmentary cross-sectional View to enlarged scale of the bridging means, taken on the line VV of FIGURE 3.

Referring now more particularly to the drawings and in the first instance to FIGURE 1, the form or plate cylinder of a lithographic offset press is designated by reference numeral 2. Ink is applied to the cylinder 2 by inking means designated generally by reference numeral 3 and which may be conventional. The inking means 3 include four ink form rollers 4. Water is applied to the form by water applying means designated generally by reference numeral 5. The water applying means 5 include two water form rollers 6. Everything shown in FIGURE 1 may be convention except the cylinder 2, and no attempt is made in the small scale drawing constituting FIGURE 1 to illustrate the bridging means, which are illustrated in FIGURES 2-5.

Referring now to FIGURE 2, the cylinder 2 has a lithographic oifset printing plate 7 applied thereto in ocnventional manner. The printing plate 7 is a thin flexible sheet metal plate made, for example, of sheet aluminum which is clamped and stretched about the cylinder 2 by clamping and stretching means which may he conventional. The clamping and stretching means are duplicated at the two ends of the printing plate 7, such mechanism being, however, illustrated at only one end of the printing plate and designated generally by reference numeral 8. All structure thus far described may be conventional and hence no detailed description of elements of the structure well known to those skilled in the art is included.

The cylinder 2 rotates in the counte clockwise direction or in the direction of the arrows 9* in FIGURES 1 and 2. The leading edge of the printing plate 7 is at It and the trailing edge is at 11. The printing plate 7 is continuous along the surface of the cylinder 2 from the leading edge 10 to the trailing edge 11. However, from the trailing edge 11 to the leading edge 10 at the right-hand side of FIGURE 2 there is a gap. In conventional lithographic oifset presses as provided prior to the present invention the ink form rollers and the water form rollers made no contact with any means for removing ink or wa'-- ter therefrom while traversing the gap 1110-. As a result, since the water supplying rollers behind the water form rollers 6 operate continuously at constant speed water was delivered to the water form rollers 6 at a fixed rate of feed resulting in a build-up of Water on the water form rollers 6 while they traversed the gap I l-10 with the undesirable results above explained.

I provide bridging means designated generally by reference numeral 12 which I apply to the cylinder 2 to bridge the gap 11-10. The bridging means 12 may be of any suitable material such as steel or aluminum and may comprise a plate-like outer portion 13 having a cylindrically curved outer surface whose curvature is the same as that of the cylindrical surface of the cylinder 2. The bridging means 12 are applied to the cylinder 2 so that the surface 13 thereof forms with the portion of the surface of the cylinder 2 covered by the printing plate 7 substantially a full cylinder. Small discontinuities 14 exist between the ends of the bridging means 12 and the leading and trailing ends 10 and 11 of the plate 7, such discontinuities being exaggerated in FIGURE 2. Actually they are so small that they are negligible in operation of the press.

The bridging means 12 are provided with drilled holes 15 through which screws 16 are applied threading into internally threaded bores *17 in the cylinder to hold the bridging means in place on the cylinder.

The outer cylindrical surface of the bridging means is hydrophylic as is the outer cylindrical surface of the printing plate 7. The outer cylindrical surface of the bridging means may be made hydrophylic in various ways known to those skilled in the art, as, for example, by slightly roughening the surface and coating it with gum arabic.

In operation of the press printing plate 7 and the bridging means 12 considered collectively are engaged substantially continuously by the water form rollers 6 which deliver water thereto at a fixed rate of feed. Thus the provision of the bridging means 12 obviates the former buildup of excess water on the water for-m rollers when traversing the gap between the trailing and leading ends of the printing plate. The result is the maintaining of a uniform proportion of water to ink and consequently a uniform tone in the printed work.

While I have shown and described a present preferred embodiment of the invention and a present preferred method of practicing the same it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced Within the scope of the following claims.

I claim:

1. In a printing press, a form cylinder, a form on the cylinder extending throughout less than the full circumference of the cylinder, means including roller means engaging the form for applying ink to the form, means for applying water to the form and means cooperating with the means for applying water to the form insuring applying water to the form by such roller means at a fixed rate of speed during operation of the press.

2. In a printing press a form cylinder, a form on the cylinder extending throughout less than the full circumference of the cylinder, means for applying ink to the form, means for applying water to the form and means, operative during intervals while no portion of the form is in water receiving relationship to the means for applying water to the form, removing water from the means for applying water to the form at the same rate as the form removes water therefrom when in water receiving relationship therewith to obviate accumulation of water by the means for applying water to the form during said intervals, which accumulation would result in application 'of water to the form at a fluctuating rate of feed, thereby insuring application of water to the form at a fixed rate of feed during operation of the press.

3. In a printing press, a form cylinder, a form on the cylinder extending throughout less than the full circumference of the cylinder, means for applying ink to the form, means for applying water to the form and a moving hydrophylic surface engaging the means for applying water to the form during intervals while no portion of the form is in water receiving relationship to the means for applying water to the form removing water from the means for applying water to the form at the same rate as the form removes water therefrom when in water receiving relationship therewith to obviate accumulation of water by the means for applying water to the form during said intervals, which accumulation would result in application of water to the form at a fluctuating rate of feed, thereby insuring application of Water to the form at a fixed rate of feed during operation of the press.

4. In a printing press, a form cylinder, a form on the cylinder extending throughout less than the full circumference of the cylinder, means for applying ink to the form, means for applying water to the form and bridging means applied to the cylinder at the portion of the circumference thereof not covered by the form and having a hydrophylic surface of substantially the same curvature as the form, so that the surfaces of the form and of the bridging means together constitute substantially a full cylindrical hydrophylic surface, said surface of the bridging means removing water from the means for applying water to the form at the same rate as the form removes water therefrom when in water receiving relationship therewith to obviate accumulation of water by the means for applying water to the form during intervals while no portion of the form is in water receiving relationship to the means for applying water to the form, which accumulation would result in application of water to the form at a fluctuating rate of feed, thereby insuring application of water to the form at a fixed rate of feed during operation of the press.

' 5. In a printing press, a form cylinder, a form on the cylinder extending throughout less than the full circumference of the cylinder, means for applying ink to the form, water from roller means for applying water to the form, means for supplying water to the water form roller means at a fixed rate of feed during operation of the press and means operative during intervals while no portion of the form is in water receiving relationship to the water form roller means removing water from the water form roller means at the same rate as the form removes water therefrom when in water receiving relationship therewith to obviate accumulation of water on the water form roller means during said intervals, which accumulation would result in application of water to the form at a fluctuating rate of feed, thereby insuring application of water to the form at a fixed rate of feed during operation of the press.

6. In a printing press, a form cylinder, a form on the cylinder extending throughout less than the full circumference of the cylinder, means for applying ink to the form, water form roller means for applying water to the form, means for supplying water to the water form roller means at a fixed rate of feed during operation of the press and bridging means applied to the cylinder at the portion of the circumference thereof not covered by the form and having a hydrophylic surface of substantially the same curvature as the form, so that the surfaces of the form and of the bridging means together constitute substantially a full cylindrical hydrophylic surface, said surface of the bridging means removing water from the water form roller means at the same rate as the form removes Water therefrom when in water receiving relationship therewith to obviate accumulation of water on the water form roller means during intervals while no portion of the form is in water receiving relationship to the water form roller means, which accumulationwould result in application of water to the form at a fluctuating rate of feed, thereby insuring application of water to the form at a fixed rate of feed during operation of the press.

7. A method of improving the printing quality of a printing press of the type having a form cylinder with a form thereon extending throughout less than the full circumference of the cylinder and in which ink is applied to the form and water is applied to the form by rollers engaging the form for admixture with the ink comprising at all times when water is being applied to the form applying the water to the form by such rollers at a fixed rate of feed.

8. A method of improving the printing quality of a printing press of the type having a form cylinder with a form thereon extending throughout less than the full circumference of the cylinder and in which ink is applied to the form and water is applied to the form for admixture with the ink comprising supplying the water to the zone of application thereof to the form at a fixed rate of feed and during intervals while no portion of the form is at said zone removing water from the supply at the same rate as the form removes water from the supply to avoid accumulation of water during such intervals so that at all times when water is being applied to the form it is applied to the form ata fixed rate of feed.

9. A method of improving the printing quality of a printing press of the type having a form cylinder with a form thereon extending throughout less than the full circumference of the cylinder and in which ink is applied to the form and water is applied to the form for admixture with the ink comprising supplying the Water to the zone of application thereof to the form at a fixed rate of feed and during intervals while no portion of the form is at said zone engagingthe water supply with a moving surface which removes water from the supply at the same rate as the form removes Water from the supply to avoid accumulation of Water during such iu- 664,965 Morriss Jan. 1, 1901 Wolff Sept. 19, 1933 Schultz May 15, 1934 Gcedike Mar. 8, 1938 Martin Aug. 30, 1955 Koch .May 7, 1957 Bc-rchers Aug. 23, 1960 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,348,098 August. 7, 1962 Carl 0. Siebke It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, lines 20 and 21, conventional column 5, line 19, after "cylinder," insert means for applying ink to the form, line 20, for "ink" read water lines 20 and 21, strike out means for applying water to the form same column, line 24, for "speed" read feed Signed and sealed this 20th day of November 1962.

for "conventional" read (SEAL) Attest:

DAVID L. LADD ERNEST W. SWIDER Commissioner of Patents Attesting Officer

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