Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F31/00—Inking arrangements or devices
  • B41F31/002—Heating or cooling of ink or ink rollers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F31/00—Inking arrangements or devices
  • B41F31/005—Ink viscosity control means
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F31/00—Inking arrangements or devices
  • B41F31/26—Construction of inking rollers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F33/00—Indicating, counting, warning, control or safety devices
  • B41F33/0036—Devices for scanning or checking the printed matter for quality control
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F33/00—Indicating, counting, warning, control or safety devices
  • B41F33/0063—Devices for measuring the thickness of liquid films on rollers or cylinders
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41F—PRINTING MACHINES OR PRESSES
  • B41F5/00—Rotary letterpress machines
  • B41F5/24—Rotary letterpress machines for flexographic printing

Definitions

• the present invention concerns an engraved printing roller and a relative method for controlling and adjusting printing parameters such as printing density and colorimetric parameters in printing machines, in particular, flexographic printing machines.
• printing machines such as flexographic printing machines comprise a roller unit with mutually tangent and counter-rotating rollers that make for the transfer of the ink to a printing support.
• these rollers comprise a roller with an engraved coating, the so-called anilox, a roller for supporting the printing plate, and a counter-pressure roller (or counter-roller for the sake of brevity).
• the anilox is in direct contact with an ink feeding module (such as an ink storage tank or chamber with its doctor blade) of the machine and transfers the ink to the printing plate that in turn carries out the actual printing step, that is the transfer of the ink on the printing support, held by the counter-roller.
• an ink feeding module such as an ink storage tank or chamber with its doctor blade
• the anilox is an engraved roller, that is with an outer surface in which cells or channels are formed, aimed at containing the ink transferred thereon by the ink-feeding module.
• This engraved outer surface can be the surface of a unitary roller body or, as in a presently more common solution, the anilox can be in the form of a tubular sleeve having the engraved outer surface, inserted by sliding over a sleeve-bearing core or mandrel. This is the so-called anilox sleeve.
• a seriously felt drawback in these type of machines is that as the printing speed increases (that is, as the rotation speed of the printing rollers increases), the effectiveness of the ink transfer to the printing support is affected so that the quality of the print is eventually worsened. More specifically, as the quality of the ink transfer varies, there is a rampant and unpredictable decay of the printing parameters, in terms e.g. of printing density and colorimetric parameters (Lab). These comprise Lightness (Z.) expressed as a percentage (0 for black and 100 for white) whereas with a and b tit is meant two color ranges respectively from green to red and from blue to yellow with values from -120 to +120.
• This device comprises detection means for detecting the printing parameters, actually consisting of video cameras and radiating means affecting a determined portion of the roller to assist the image capture of the cameras. Depending on the values detected by this detection means, the two rollers are mutually displaced. The ink transfer effectiveness remains thus constant as a result of the change of mutual pressure between the rollers.
• this solution has drawbacks deriving mainly by the constructive complication that ensues from the provision of a control system that has to take care of the change of mutual distance between the rollers.
• the heating of the anilox can be obtained by a heat carrier fluid that is made to flow inside the anilox, underneath the engraved surface; the fluid is heated in a controlled manner by a heating surface inside or outside the anilox.
• these systems are structurally complex and costly.
• printing parameters such as printing density and colorimetric parameters
• a particular object of the present invention is to overcome all the limitations of the known devices and provide an advantageous technical alternative with respect to such devices.
• a further object of the present invention is to provide an anilox roller and a method for controlling and adjusting printing parameters in flexographic printing machines making use of such a roller, that can also be implemented as a revamping of pre-existing printing units.
• FIG. 1 is a longitudinal sectional view of an anilox roller provided with magnetic induction means
• an anilox roller 1 has an elongated development according to a longitudinal axis X and comprises an engraved outer surface 10 centered around the longitudinal axis.
• the anilox 1 is adapted to be rotatably supported around the longitudinal axis X in a printing unit (generally indicated with the numeral 2) of a printing machine, namely a flexographic printing machine.
• the rotatable support means are represented only schematically in figure 1 , indicated by the reference numeral 20.
• the anilox according to the invention comprises, underneath the engraved outer surface 10, an annulus tubular gap 1 1 , in turn centered around the longitudinal axis X and extending lengthwise substantially over the entire elongation of the anilox.
• the gap 1 1 is open to the outside through an access aperture 12 on a head face 13 of the roller.
• magnetic induction means 3 shown in isolation in figure 2 such as, according to a preferred solution represented in the drawings, a coil inductor or solenoid 3.
• the coil 3 winds in a spiral developing, when arranged in the gap 1 1 , around the longitudinal axis X.
• the coil axially extends substantially for the same elongation of the annulus gap 1 1 .
• a matrix of a non- ferromagnetic material can fill the gap, e.g. a polymeric material matrix 14.
• the coil inductor is connected, via suitable electric wiring 40, to current generating means such as a current generator 4 (shown only schematically in figure 3 3) that supplies alternate current running in the coil and thus generating a magnetic field in its surrounding space
• current generating means such as a current generator 4 (shown only schematically in figure 3 3) that supplies alternate current running in the coil and thus generating a magnetic field in its surrounding space
• This magnetic field induces, in turn, parasitic currents in the ferromagnetic material of which the anilox is made; the currents cause then a heating of the ferromagnetic material.
• connection between the current generator 4 and the coil 3 is obtained via a rotary electrical interface 5 with which the electric wiring 40 is linked; the rotary interface allows for the electrical connection to be maintained during the printing steps, i.e., as the anilox roller turns, being it arranged between the same roller and the structure 20 of the printing unit.
• the anilox roller is associated with an ink-feeding module 21 and is tangent with a plate-carrier roller 22, counter-rotating with respect to the first roller.
• the plate-carrier roller transfers the image to a printing support 23, pushed in abutment against the roller by a counter-roller or pressure roller 24.
• the printing unit further comprises an electronic controller 6 operationally connected to the current generator 4 and to at least a first sensor that measures a measured value of the printing parameters (such as in particular the density and the Lab colorimetric parameters) on the printing support 23. Possibly, a further or second sensor 8 can be provided to detect the temperature of the anilox roller 1 .
• the electronic controller 6, besides controlling the current generator to adjust the frequency and the power of the current circulating in the coil, carries out a comparison between the measured value of the printing parameters, as detected by the first sensor, with a desired target value.
• the printing unit operates as follows.
• the first sensor 7, that can be e.g. (but this indication is not limitative) a spectrophotometer, detects the measured value of the printing parameters and sends this data to the electronic controller 6 that compares this measured value with the target value. If the measured value does not match the desired value, the electronic controller 7 switches the current generator on, to make the electric current run through the coil.
• the current circulating in the coil at a chosen frequency and power determines a controlled heating of the engraved surface of the anilox.
• the ink in the cells of the engraved surface becomes in turn heated, and this affects the viscosity of the ink, or more generally speaking its physical properties improving its capability to be effectively transferred from the anilox roller to the plate-carrier roller.
• the temperature sensor 8 measures the temperature on the engraved outer surface of the anilox and then, in case this measured temperature does not correspond to a desired value, the controller commands the current generator, varying the frequency and power of the current circulating in the coil, until the measured temperature value matched the desired one. Indeed, by varying the frequency and the power of the supplied alternate current running in the coil, a magnetic field variation is obtained, and a consequent change of the induced currents, thereby tuning their penetration depth and their heat generating effect.
• the method therefore obtains the adjustment of the printing parameters, so that they can be unaffected from the printing speed, in a real-time manner, by acting on the transfer capability of the ink.
• the anilox roller according to the invention can be an anilox sleeve or a unitary body; in the case of a sleeve, like the one shown in figures 1 and 2, the anilox comprises an engraved hollow tubular sleeve 10', developing around the longitudinal axis X.
• the engraved tubular sleeve defines, with its outer surface, the engraved surface 10.
• the tubular sleeve is arranged by sliding in a coaxial fashion (according to the longitudinal axis X), over a sleeve-bearing core 15.
• the tubular gap 1 1 is formed within the thickness of the sleeve 10', underneath the outer engraved surface.
• the anilox roller can even, advantageously, be mounted in already existing printing units, with no need of changing the structure of the unit.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Quality & Reliability (AREA)
• Inking, Control Or Cleaning Of Printing Machines (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=56413770

Family Applications (1)

Country Status (3)

Family Cites Families (7)

• 2016
  • 2016-04-07 IT ITUA2016A002391A patent/ITUA20162391A1/it unknown
• 2017
  • 2017-04-06 EP EP17718337.3A patent/EP3439883A1/de not_active Withdrawn
  • 2017-04-06 WO PCT/EP2017/025082 patent/WO2017174218A1/en active Application Filing

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