EP0350569B1 - Press inking system - Google Patents

Description

Background of the Invention
• This invention relates to inking systems for printing presses and more especially to an inking system in which the supply of ink is controlled as a function of the amount of ink coverage required by a given column of printed matter.
• Ink is normally supplied to web fed printing presses from an ink fountain onto a fountain roller that is in operative contact with a ductor roller which forwards the ink to the remaining ink train rollers. The feeding of ink into a press, particularly one using the lithographic process, is a demanding operation, yet one which is vital to successful printing. The oil base inks which are used in offset lithography are very viscous, in many cases being more plastic than fluid. This physical property of these inks is one reason why ink is supplied to the plate roller through a train, i.e., so that the viscous nature can be reduced and a uniform film of ink presented to the plate.
• The application of ink to the fountain roller has been commonly regulated by means of a blade which forms one wall of the ink fountain. The free end of this blade is adjustable by means of a manually or motor operated adjusting screw. This type of system is generally referred to as being a keyed inker and it is capable of controlling the amount of ink that is presented to each column of print across the width of the plate roll.
• A more recent development is that of supplying ink to an ink rail by means of individual gear pumps that are mounted directly on the rail; one for each column of print. This type of ink supply which is shown in U.S. Patent No. 4,281,597, regulates the amount of ink supplied to each column by varying the speed of the drive motor operating the gear pump associated with each print column. Adjustment in the speed of the motors can be performed either manually or automatically. Additional types of keyed inkers where generally a pump or a piston is used to deliver the ink through suitable dispensing nozzles onto the ink roll are 2,981,182, 2,081,906, 3,207,070 and 2,130,659.
• It is a principal object of this invention to provide a press inking system that provides greater ink control than has heretofore been possible.
• It is an additional object of this invention to provide a press inking system that has fewer parts.
• It is a further object of this invention to provide a press inking system that provides a pulsed ink injection onto the ink roller in amounts satisfying ink requirements for each print column.
• Other objects and advantages of this invention will be in part obvious and in part explained by reference to the accompanying specification and drawings in which:
• Fig. 1 is a schematic drawing showing the elements of the present inking system; and
• Fig. 2 is a graph illustrating the nature of ink coverage effect by the inking system as a function of ink flow "on and off" rates.
Description of the Preferred Embodiment
• For a more complete understanding of the inking system of this invention, reference is made initially to Fig. 1 of the drawings. In this figure, the numeral 10 indicates the inking roll which would normally be found as the initial roll in the train of inking rollers. The system itself which is indicated generally by the numeral 11 comprises a supply of ink 12 which enters into a supply manifold 13. From the manifold 13 a supply pipe 14 directs the ink into positive displacement ink pump means 15 at an inlet side 16. The pump 15 is shown here as being a gear pump, which is a type of pump well suited for the purpose of moving the highly viscous printing ink. Normally, in the printing of articles such as daily newspapers, there are a plurality of columns of print, the exact number depending upon the size of the newspapers and whether the press is of single or double width.
• Thus, the manifold 13 is used to supply ink to a plurality of pumping means that are lined in series parallel with the manifold 13. From the outlet side 17 of pump means 15 a conduit or pipe 18 directs the ink into valve means 20. Valve means 20 is operable by means of a suitable actuating mechanism which in the present case is shown as being a solenoid 21. From the valve means 20 there is an ink bypass means, hereshown as a conduit 25 that returns ink to the manifold 13 when the valve is in what is considered as the "off" position for purposes of this explanation. In the other position, the "on" condition, the valve directs ink through ink conduit means 26 into the ink rail 30. Ink rail 30 provides the ink to the plurality of columns that are to be printed by the plate roll.
• The operation of this inking system is such that ink from supply 12 is made available to the series of gear pumps 15 which continuously pumps ink into the conduit 18. The individual valving means 20, one for each column, are controlled from the block that is labeled Input From Press Control System. This system can be one that is manually controlled so that each valve will permit ink to pass into the ink rail for a pre-selected time or it can be controlled by means of an optical reader which recognizes the amount of ink that will be necessary to print a column of a known print density.
• As mentioned, each valve means 20 basically operates between two positions, these being one in which ink is permitted to go through the rail and the other being the position illustrated in Fig. 1 where the ink flow is sent through the bypass 25 to return to the supply manifold. Depending upon the setting that is initially made, the valving means will pulse between the two positions at a given frequency for selected durations of time. For example, if the printing is of high density that requires a great deal of ink then the control system (or the initial manual setting) will cause the valve means 20 to be opened a length of time that will supply more ink to the ink rail in the given column than it would for a column that is of light print density. It is apparent that the method of portion of this inking system is basically a digital control operation that supplies the ink to the ink roll 10 in a series of bursts. The system at start up is initially set or programmed to arrange for the bursts of supplied ink to be at a frequency that will result in an overall even dispersion of the ink on the ink roll. This is in contradistinction to leaving the valve means 20 open for a long period of time to supply all of the necessary ink for a given print density.
• Fig. 2 illustrates the manner in which ink is supplied to the ink rail as a factor of the percent coverage. This percent coverage being indicated by the numeral N. For coverages of greater than 50%, the time in which a valve must remain in a position permitting to flow through to the ink rail is given by the equation:

  

  
  where:
  
  ${\text{T}}_{\text{MIN}}\text{= a pre-selected time when said valve means is open;}$

  

  
  $\text{N = percent ink coverage > = 50\%}$

  

  
  
     On the other hand if the percentage of coverage is 50% or less, then the amount of time that the valve must remain off is indicated by the equation:

  

  
  where:
  
  ${\text{T}}_{\text{MIN}}\text{= a pre-selected time when said valve means is open;}$

  

  
  $\text{N = percent ink coverage < = 50\%}$

  

  
  
     The two curves shown in Fig. 2 indicate the manner in which ink would be applied for a percent coverage from ten percent up to total ink coverage for a valve open time of .5 second. The following table shows how the curve is derived and indicates the time in which the valving means 20 is on in the time in which it is off to produce 50% coverage factor. TABLE

  % COVER	IMPRESS/INK OFF	TIME OFF	TIME ON	TIME OFF	TIME ON	CYCLE/MIN
  1	0	0		0		0
  .9	8.5	.5	4.5	.5	4.5	12
  .8	8.5	"	2.0	.5	2.0	24
  .7	8.5	"	1.17	.5	1.17	36
  .6	8.5	"	.75	.5	.75	48
  .5	8.5	"	.50	.5	.5	60
  .4	12.75	"	.33	.75	.5	48
  .3	19.89	"	.21	1.17	.5	36
  .2	34.00	"	.12	2.0	.5	24
  .1	76.50	"	.05	4.5	.5	12

• By use of the inking system of this device it is possible to vary the time the valve will be open and increase the pulse rate so that a distribution of the ink around the ink roll can be accomplished through cycle variation rather than through utilizing a larger fixed time to supply the amount of ink required. It is to be understood that as the ink progresses from discrete quantities on the ink roll on through the ink train, it will be mulled into a smooth pattern during its travel through the remainder of the inking train and various changes and modifications may be made within the scope of the inventive concept.

Claims (4)

1. An inking apparatus for supplying ink to a press having a roll with a plurality of columns to be inked simultaneously, said apparatus, comprising:

   a. a supply of ink;

   b. positive displacement ink pump means having an inlet side and an outlet side, said inlet side being connected to said supply of ink;

   c. an ink rail positioned adjacent said plate roll and having an ink outlet orifice positioned to supply ink to each print column;

   d. ink conduit means connecting the outlet side of said pump means with each outlet orifice in said ink rail;

   e. valve means connected in said ink conduit means between said pump means and said ink rail to permit the flow of ink from said ink pumping means to said rail in timed discharges;

   f. ink by-pass means to conduct ink from said valve means to a site upstream from the inlet of said pumping means; and

   g. control means for regulating the operation of said valve means to deliver ink to said ink conduit means and to said by-pass means at a selected ratio.
2. An apparatus as defined in claim 1 wherein said control means includes optical reading means for initiating a signal representative of print density in a column and a solenoid actuator to said valve means which is responsive to the signal from said optical reading means to pulse the flow of ink.
3. A method for operating the apparatus according to claims 1 or 2, wherein said control means causes said valve means to open to permit ink to flow to said ink rail for periods of time determined from the equation:

   

   where:
   
   ${\text{T}}_{\text{MIN}}\text{= a pre-selected time when said valve means is open;}$

   

   
   $\text{N = percent ink coverage ≧ 50\%}$

   
4. A method for operating the apparatus according to claims 1 or 2, wherein said control means causes said valve means to close to permit ink to flow to said ink rail for periods of time determined from the equation:

   

   where:
   
   ${\text{T}}_{\text{MIN}}\text{= a pre-selected time when said valve means is open;}$

   

   
   $\text{N = percent ink coverage ≦ 50\%}$

   

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