US3405636A

US3405636A - Lithographic moisture supply

Info

Publication number: US3405636A
Application number: US560697A
Authority: US
Inventors: Raymond J Schmidlin
Original assignee: Multigraphics Inc
Current assignee: AB Dick Co
Priority date: 1966-06-27
Filing date: 1966-06-27
Publication date: 1968-10-15
Anticipated expiration: 1985-10-15
Also published as: NL6703152A; GB1131674A

Description

0d. 15,, 1968 R. J. SCHMIDLIN 3 LITHOGRAPHIC MOISTURE SUPPLY Filed June 27, 1966 ATTORNEY United States Patent 3,405,636 LITHOGRAPHIC MOISTURE SUPPLY Raymond J. Schmidlin, Lyndhurst, Ohio, assignor to Addressograph Multigraph Corporation, Cleveland, Ohio, a corporation of Delaware Filed June 27, 1966, Ser. No. 560,697 2 Claims. (Cl. 101148) ABSTRACT OF THE DISCLOSURE Hence, this invention contemplates avoiding the build-up of incrustation by this concept of filling the supply fountain only as needed.

Background of the invention In the lithographic printing process, ink is applied to selected areas on the face of a master from a roller which is uniformly coated with ink. A preferential rejection phenomena is employed to cause the ink to apply to the master only in the desired area.

The procedure employed is to use an ink which is rejected by a moist surface, and to apply moisture to the surface of the master in all areas Where ink is not to be applied.

. The lithographic process requires the master to be treated in a step called conversion. This is often done on a table by hand application of fluid. The operator scrubs the surface with a pad Wet with a conversion solution. The conversion process causes a change in composition in the areas of the master surrounding the ink accepting image.

Development of the lithographic process has brought about the placing of dry masters on the master cylinder of the machine, and holding a mechanically applied conversion solution applicator against the revolving master surface. Such machine treating is used, for example, in duplicating machines which self-feed the masters to the printing cylinder for rapid change of masters.

The lithography art has progressed to the pointwhere far less operator attention is required. This invention relates to equipment which will make a master from an original document and immediately apply that master to the cylinder.

In order to prepare the master, it is caused to pass through a conversion bath. The solution employed is substantially the same material which was employed in hand conversion.

Itis necessary to keep the master, while on the cylinder, in a properly moistened condition, whether it has been hand prepared or machine prepared. The moisture originally supplied is lost through a combination of factors, such as evaporation and absorption by the sheets of paper which are being printed.

Ink is supplied to the master cylinder by a series of rollers. The first roller is one which picks ink out of a fountain and accomplishes a rough distribution of the ink across its surface. A series of rollers then work together for dividing the ink and distributing it such that it is finally presented to the master cylinder by a form roller. The ink is exceedingly thin on the surface of the form c CC roller and uniformly distributed. This phenomena is well known in lithographic art.

There are two known methods of applying the necessary moisture used in the lithographic offset printing process. One of these methods is to use separate moisture supply and ink supply roller systems wherein the moisture is kept separate from the ink system. A final roller of the moisture system is caused to contact the surface of the master cylinder at a rotary position prior tothe approach of the master to the inking roller. In this way, the master is first supplied with moisture before it is exposed to the ink roller, there-by assuring the presence of suflicient moisture to reject ink in those areas which are not to be supplied with ink.

This separate supply of moisture and ink enables the operator to control the lithographic process more precisely, and gives a freedom of selection of inks with less regard to the compatibility of moisture and ink.

However, a higher degree of skill is required than by a later developed system as shown in such prior art patents as Goedike 2,103,254, and Curtis 2,689,522.

Goedike, as an example of a second known system, teaches a method of inking and dampening print-ing surfaces of planographic and analogous printing members, which consists of transmitting moisture from a source of supply to a roller of an inking mechanism, the water together with a film of ink being transmitted to the printing member through the ink distributing system, whereby an ink repelling coating of water will be applied to the nondesign portions of a printing surface and ink will be applied to the design portions of the surface.

The combined system of the second type requires less operator skill and knowledge, but also has limitations in that there is less flexibility in selecting of types of ink.

The invent-ion is applicable to either of these systems, in that evaporation of water will leave a chemical deposit around the moistening structure, which is undesirable, and excess moisture applied while the machine is running idle is undesirable, whether it is applied through the ink system in the second type, or directly to the master cylinder as in the first example.

However, the combination system of the second type has been employed as an illustration of the present invention, because it is exceptionally desirable in a system wherein a rapid change of masters takes place and only a few copies are printed from each master. In such a rapid turnover, the ratio of cylinder revolutions in preparation for printing, to revolutions for printing, is quite low. In such a situation, the moisture is not taken away in the printing process as fast as it is normally supplied, if the water system is constantly present. The system disclosed herein is intended primarily for use with a controlled printing apparatus wherein the master is used for relatively few copies, and is intended for a minimum of operator attention. Thus, the illustration is made in connection with the type of inking system originally disclosed by Goedike.

The ink is of a type which is moisture repelling, but the fountain rollers will pick up a rough film of moisture over the ink, and this film will distribute itself along the roller series as fine droplets dispersed throughout the ink. In all probability, the moisture is carried in surface irregularities of the ink because the ink is in place upon the rollers before moisture is applied.

A supply of moisture droplets is thus made available along with the ink for application to the surface of a master on the master cylinder. However, if there is no master on the cyilnder, the moisture is not used and will gradually accumulate and being to emulsify the ink. Emulsified ink will fall away from the rollers in chunks and will not properly ink a master which is later applied. Therefore, moisture emulsification is to be prevented.

It is the concept of this invention that the amount of moisture may be related to the need by supplying moisture to the fountain rollers of the moisture series only when a master is actually in place on the master cylinder to use the moisture. Hence, a closed reservoir sump, with a pump which is responsive to sensing means detecting the presence of a master, will fill a moisture fountain only at the properly desired time.

Further, in order to supply a proper amount of the liquid, a double trough system is contemplated by this invention wherein an excess of fluid is supplied to a first trough in which the fountain roller operates, and the excess is permitted to overflow into a catch basin for return to source, thus maintaining a uniform supply in the basin in which the fountain roller Operates.

In accordance with these and other objects which will become apparent hereinafter, the best mode contemplated for the present invention is disclosed in the accompanying drawing.

Description of the invention FIGURE 1 is a schematic representation of a master cylinder and its associated paper carrying cylinder, together with a symbolic illustration of an ink supply and moisture supply roller series.

FIGURE 2 is a partial top plan view of the liquid holding pan depicting the large catch basin with a smaller retainer basin therein.

In a mechanically fed and loaded master cylinder systern of a lithography device, a prepared master is fed along a guide track 10, and fed into the area wherein the clamping mechanism of the master cylinder takes over the master by grasping the edge thereof and pulling the lead edge into a working relationship on the cylinder. A switch 12 is actuated by a master being fed along the track 10, and switch 12 signals for the supply of moisture to begin. The means for attaching the master to the cylinder is not illustrated, this being a known construction. The master cylinder is, therefore, represented by a large circle 14 in the drawing, and circle 16 represents a mated cylinder which carries paper in a known manner into direct contact with the master. However, the circle 16 could also represent the offset blanket in an offset printing process. These features of lithography are sufficiently known to the art that further illustration and discussion is believed unnecessary.

An ink supply fountain is indicated symbolically by the symbol bearing reference character 18. A fountain roller 20 accepts ink from the fountain 18 and divides and distributes that ink with roller 22. The ink is then further divided and distributed to roller 24 which is referred to as the form roller. Form roller 24 applies ink and moisture to the face of the master carried by the cylinder 14.

Moisture is supplied as a chemical solution well known to the lithography art. For the purpose of this discussion, it will be referred to only as liquid or moisture, without designating any particular type.

A fountain roller 26 operates in a bath 28 of the liquid. Thus, a relatively heavy film of the liquid is carried on the surface of roller 26 and is rolled out upon the surface of an intermediate roller 30, which causes a more even distribution. By reason of the fact that the two rollers operate in contact, the amount of moisture carried to the bite between

rollers

26 and 30 is divided between the two rollers. Thus, the available quantity is reduced when it is deposited upon the roller 30.

The roller 30 in turn operates in conjunction with another intermediate roller 32 and again available moisture is divided and uniformly distributed. Because the quantity of liquid is reduced from the original supply by roller 26, it may more properly be considered as moisture on roller 32. Finally, the roller 32 operates against the intermediate ink train roller 22, and deposits the portion of moisture along with the portion of ink carried by the roller 22 from the fountain roller 20.

The roller 22 deposits discrete and unemulsified particles of ink and moisture to the surface of the roller 24 for presentation to the surface of the master. Provided the discrete particles do not remain too long on the surface of the roller 24, and further provided that the amount of moisture is not excessive on the roller with respect to the ink, emulsification is avoided within the limits of practical practice. The infinitesimally small amount of emulsification which takes place can be tolerated. However, excessive amounts of moisture in the bite between

rollers

22 and 24 will upset the proper balance and increase the emulsification beyond acceptable limits.

Accordingly, this invention contemplates the provision of a unique fountain 34 supplied with liquid from a sump 36 only when needed in the supply system.

A catch basin 38 has a retainer basin trough portion 39. A motor 40 is employed to drive a centrifugal pump 42 located in the sump 36 and supply liquid through a supply tube 44 directly into the trough 39. The trough 39 is created by a division wall 46 which is substantially as wide as the catch basin 38, but is sufliciently short that a slotted area is open to allow full drainage of trough 39. Thus, the trough 39 is maintained completely full but no chance of stagnate accumulation is provided. Furthermore, the slotted area at the side of the wall 46 will permit complete and rapid draining of the bath 28 as soon as the supply ceases. Hence, an efficient uniform level of fluid is supplied at all times, but is quickly returned to the protective area of the sump wherein excessive evaporation is avoided.

Electrically, the motor 40 is integrated into the associated apparatus in such a way that the master begins the motor cycle as it is placed upon the master cylinder, and finally the ejection of the master from the master cylinder is employed as a signal to end the master operation.

As an illustration of such control, the switch 12 is employed to supply power to a relay 50. Relay 50 has two sets of contacts. The first set is indicated by reference character 52 and the second by reference character 54. A normally closed switch 56 detects the ejection cycle as the master is removed. Switch 56 is connected to supply power to relay 50 through the contacts 52 and, therefore, the contacts 52 and the closed switch 56 serve as a holding cycle. Switch 12 may be actuated for only a brief moment but the relay '50 will continue to receive power until switch 56 is opened to break the circuit.

Contacts 54 are normally open and are closed when the relay 50 is energized. Therefore, the relay 50 will cause power to be supplied to motor 40 through contacts 54 from the time that switch 12 is actuated until the time that switch S6 is actuated.

Whereas the present invention has been shown and described herein in what is conceived to be the best mode contemplated, it is recognized that departures may be made therefrom within the scope of the invention which is, therefore, not to be limited to the details disclosed herein, but is to be afforded the full scope of the invention as hereinafter claimed.

What is claimed is:

1. In a lithography system having:

a master cylinder;

an ink supply roller system from an ink fountain to the master cylinder;

a fountain trough, a moisture supply roller system from said fountain trough to the master cylinder;

a source of fiuid supply for said fountain;

a master supply system means for bringing a master to said master cylinder and mounting said master on said cylinder; and

a master ejection means for removing said master from said cylinder and transporting said master along an ejection path;

5 6 the improvement in moisture supply control, charac- 2. In a lithography system as defined in claim 1, said terized by: moisture supply system further comprising:

a first detector switch means in the master supply a sump;

system for detecting the passage of a master to said trough having drainage openings ofa size to permit said master cylinder, and control means respon- 5 rapid return of all liquid to said sump, and means sive to detection of such master passage by said to supply liquid from said sump to said trough at first detector switch for initiating the filling of a rate greater than the capacity of said openings. said fountain trough to thereby provide moisture through said moisture roller system to said R f r n s C t master cyllnder; 10 UNITED STATES PATENTS said fountain trough having an outlet means which maintains a constant level of fluid in the foun- Algal-{Ian 73 tain as long as a supply at least as great as a 2'633821 4 1953 Sc u tz 1 8 predetermined minimum is maintained, and 581794 19 58 2335 grrlzcllms said fountain upon cessation of supply; 15 2:953:476 9/1960 Armstrong "nu-n; 118 7 a second detector switch means for detecting the 3,094,065 6/1963 Roberts 101 148 fact of ejection of the master from said master 3,145,653 8/1964 Lake 101-148 cylinder, and control means responsive to de- 3 5/1965 Rodman 118-3 tection of master ejection for bringing a ces- 20 sation of said moisture supply from said source ROBERT PULFREY Emmmerto said fountain. C. D. CROWDER, Assistant Examiner.