Method for printing on a material web

EP4532210A1Pending Publication Date: 2025-04-09DURST GROUP AG
View PDF 0 Cites 0 Cited by

Patent Information

Application Number
EP2023777133
Authority / Receiving Office
EP · EP
Patent Type
Applications
Current Assignee / Owner
Priority Date
2022-05-27
Filing Date
2023-03-21
Publication Date
2025-04-09

AI Technical Summary

Technical Problem

Conventional methods for guiding material webs with pressure-susceptible guide surfaces, especially those made of elastomeric plastics or rubber, face challenges in preventing undesirable wrinkling, particularly as these surfaces age and accumulate ink or dust, leading to ineffective fold distribution during printing.

Method used

The method involves temporarily adjusting the pressure on the edge regions of the material web, allowing the central region to be subjected to negative pressure synchronously with the guide surface, with edge regions being 20-40% or 10-30% of the total width, to prevent wrinkling and ensure smooth transport and printing.

Benefits of technology

This approach effectively suppresses wrinkling in both new and used guide surfaces, ensuring high-quality print images by allowing edge regions to slip and move synchronously with the guide surface, enhancing the distribution of folds and preventing accumulation, even with aged surfaces.

✦ Generated by Eureka AI based on patent content.
Patent Text Reader

Abstract

The invention relates to a method for printing on a material web, comprising the steps of: unwinding the material web from a first reel; attaching and fixing the unwound parts of the material web to a guiding surface of an endless transport belt, which revolves between two rollers, by subjecting the material web to negative pressure via the guiding surface, and moving the guiding surface with the parts in the transport direction into the region of action of a print head arrangement and out of the region of action again and printing on the parts with the print head arrangement by emission of ink drops; detaching the unwound, printed parts from the guiding surface and preferably winding up said parts to form a second reel; wherein the unwound parts of the material web can be divided into two edge regions which extend opposite each other in the longitudinal direction of the web and enclose a central region, wherein the side of the respective edge region which faces the guiding surface is not subjected to negative pressure at least temporarily during the intervals of time in which the side of the corresponding edge region facing away from the guiding surface is not being printed, and the side of the central region which faces the guiding surface is subjected to negative pressure in such a manner that the central region is moved in the transport direction synchronously with the guiding surface, the width of each edge region being predetermined at 20% - 40% of the overall width of the material web.
Need to check novelty before this filing date? Find Prior Art

Description

[0001] Method for printing a material web

[0002] The present invention relates to a method for printing a material web according to the preamble of claim 1 or claim 2.

[0003] Methods are known from the prior art for transporting material webs into and out of the effective area of ​​a print head arrangement using a guide surface subjected to negative pressure via a guide device, in which the guide surface has suction openings across its entire working width transverse to the transport direction in order to always suction the material webs over their entire surface.

[0004] In order to achieve a high-quality print image on a material web within the effective range of a print head arrangement, it is essential that no disturbing wrinkling of the material web occurs in the said area.

[0005] In EP2631079A1, for example, the prevention of wrinkling in a paper web is achieved which is brought into the area of ​​a print head arrangement by means of a suction roller subjected to negative pressure by rotating the suction roller, in that the web is subjected to a negative pressure via the roller, which gradually decreases from the center in the width direction of the paper web to both ends in the width direction of the web, but is still present at both ends of the web.

[0006] This prevents the ends of the paper webs from rising up against the roller shell. The use of such a material web with negative pressure can enable the web to be transported through the effective area of ​​the print head assembly without disruptive wrinkles when the cylindrical guide surface is new, because any wrinkles that form in this area are distributed across the width, preventing the accumulation of wrinkles at the rear end of the paper web.

[0007] Nevertheless, undesirable wrinkling can occur in guide surfaces of various shapes, for example flat, elliptical or cylindrical, if the guide surface subjected to negative pressure, in particular the respective edge region of the guide surface, increasingly ages until the resulting increase in static and / or sliding friction between the guide surface and the material web reaches a value above which a distribution of the wrinkling in the said effective area is no longer possible or no longer sufficiently possible. This is particularly the case when guide surfaces comprise an elastomeric plastic, preferably rubber, or are made of an elastomeric plastic, preferably rubber. With such guide surfaces, the guide surface often ages irreversibly. The corresponding aging occurs in particular through the effect and / or adhesion of ink and / or dust to or on the material.on the guide surface and / or due to the effect of unsuitable cleaning agents on the guide surface. Aging or contamination of the respective edge areas of the guide surface typically occurs when ink drops are applied to the edges of material webs of varying widths and unintentionally beyond them.

[0008] There is therefore a need for a method which enables the guiding of a material web synchronously to a guide surface subjected to negative pressure, both in new and used condition, with a more effective suppression of undesirable wrinkling than with conventional methods.

[0009] The present invention is therefore based on the object of providing a method for printing a material web, which enables the guiding of a material web synchronously to a guide surface subjected to negative pressure, both in new and used states, with a more effective suppression of undesired wrinkling than in conventional methods, and thus enables the production of high-quality printed images.

[0010] According to the invention, the object is achieved by a method comprising the features of claim 1 or claim 2. The respective subclaims relate to further advantageous and possibly additionally inventive embodiments.

[0011] The first invention is based on the idea that the side of the respective edge region of an unwound material web facing the guide surface is not subjected to negative pressure at least temporarily during the time intervals in which the side of the corresponding edge region facing away from the guide surface is not printed, but the side of the central region facing the guide surface is subjected to negative pressure in such a way that the central region is moved synchronously with the guide surface in the transport direction, wherein the width of each edge region is specified as 20% - 40% of the total width of the material web.

[0012] The unwound parts of a material web can be divided into two edge regions running opposite one another in the longitudinal direction of the web and enclosing a central region. The method according to the invention for printing a material web comprises the steps of: unwinding the material web from a first roll; applying and fixing the unwound parts of the material web to a guide surface of an endless conveyor belt circulating between two rollers by applying negative pressure to the material web via the guide surface, and moving the guide surface with the parts in the transport direction into the effective area of ​​a print head arrangement and out of the effective area again and printing the parts with the print head arrangement by ejecting ink droplets; detaching the unwound printed parts from the guide surface and preferably winding them up into a second roll.

[0013] Accordingly, the first alternative of the method according to the invention is a method for printing a material web, comprising the steps:

[0014] Unwinding the material web from a first roll;

[0015] Attaching and fixing the unwound parts of the material web to a guide surface of an endless conveyor belt circulating between two rollers by applying negative pressure to the material web via the guide surface, and moving the guide surface with the parts in the transport direction into the effective area of ​​a print head arrangement and out of the effective area again and printing the parts with the print head arrangement by ejecting ink drops,

[0016] Detaching the unwound printed parts from the guide surface and preferably winding them up into a second roll;

[0017] According to the invention, the unwound parts of the material web can be divided into two edge regions which run opposite one another in the longitudinal direction of the web and which enclose a central region, wherein the side of the respective edge region facing the guide surface is not subjected to negative pressure at least temporarily during the time intervals in which the side of the corresponding edge region facing away from the guide surface is not printed, but the side of the central region facing the guide surface is subjected to negative pressure in such a way that the central region is moved synchronously with the guide surface in the transport direction, wherein the width of each edge region is specified as 20% - 40% of the total width of the material web.

[0018] Each side of the edge regions of the material web facing the guide surface that is not subjected to negative pressure behaves, even with aged edge regions of the guide surface, in such a way that an effective distribution of wrinkles is possible both in the width direction and in the transport direction of the material web if the edge regions of the material web are slightly longer in the longitudinal direction of the material web than the central region of the material web, whereby the edge regions of the material web can be moved towards the guide surface in a way that allows slippage and is essentially synchronous with the guide surface. When reference is made in this description to a width of the material web or a width of the edge region, this means a width of the material web or edge region oriented transversely to the transport direction.

[0019] According to a preferred embodiment of the first invention, the width of each edge region is specified as 25% - 35% of the total width of the material web.

[0020] The second invention is based on the idea that the side of the central region facing the guide surface is not subjected to negative pressure, but the sides of the edge regions facing the guide surface are subjected to negative pressure in such a way that the edge regions are moved synchronously to the guide surface in the transport direction, whereby the width of each edge region is specified as 10% - 30% of the total width of the material web.

[0021] Accordingly, the second alternative of the method according to the invention is a method for printing a material web, comprising the steps:

[0022] - Unwinding the material web from a first roll;

[0023] - Attaching and fixing the unwound parts of the material web to a guide surface of an endless conveyor belt circulating between two rollers by applying negative pressure to the material web via the guide surface, and moving the guide surface with the parts in the transport direction into the effective area of ​​a print head arrangement and out of the effective area again and printing the parts with the print head arrangement by ejecting ink drops,

[0024] - Detaching the unwound printed parts from the guide surface and preferably winding them up into a second roll.

[0025] According to the invention, the unwound parts of the material web can be divided into two edge regions running opposite one another in the longitudinal direction of the web and enclosing a central region, wherein the side of the central region facing the guide surface is not subjected to negative pressure, but the sides of the edge regions facing the guide surface are subjected to negative pressure in such a way that the edge regions are moved synchronously with the guide surface in the transport direction, wherein the width of each edge region is specified as 10% - 30% of the total width of the material web.

[0026] A side of the central region of the material web facing the guide surface, which is not subjected to negative pressure, behaves even with respect to an aged central region of the guide surface in such a way that an effective distribution of wrinkles is possible both in the width direction and in the transport direction of the material web if the central region of the material web is slightly longer in the longitudinal direction of the material web than the respective edge regions of the material web, whereby the central region of the material web can be moved towards the guide surface in a way that allows slippage and is essentially synchronous to the guide surface.

[0027] At this point, it should be noted that the respective edge regions of most commercially available material webs are slightly longer in the longitudinal direction of the web than the central region. While a person skilled in the art cannot tell with the naked eye whether the central region or the edge regions are longer in the longitudinal direction of the web, there is a simple way to select the correct method. For example, in a series of tests, the person skilled in the art can first apply the first variant of the inventive method and then the second variant of the inventive method. This will enable them to determine relatively quickly which of the two methods effectively suppresses unwanted wrinkling or perhaps increases wrinkling.

[0028] According to a preferred embodiment of the second invention, the width of each edge region is specified as 25% - 35% of the total width of the material web.

[0029] According to a preferred embodiment of the first or second alternative of the method according to the invention, the guide surface is flat, at least in the effective area of ​​the print head arrangement. This development has the advantage of increasing the reliability of the distribution of unwanted wrinkles in the transport direction of the material web, for example, compared to a cylindrical guide surface.

[0030] Furthermore, it is possible for the guide surface of the conveyor belt to comprise an elastomeric plastic, preferably rubber, or to consist of an elastomeric plastic, preferably rubber. Furthermore, it is possible for the guide surface to comprise fabric layers embedded in an elastomeric plastic, preferably rubber. The conveyor belt itself typically comprises fabric layers embedded in an elastomeric plastic, preferably rubber.

[0031] In a further preferred embodiment, the width of each of the opposing edge regions of the material web is specified to be the same. These developments offer the advantage of achieving a homogeneous distribution of unwanted wrinkles. The material web can have a width of 1 meter to 5 meters, preferably a width of 1 meter to 3.3 meters. Furthermore, the material web can have a thickness of 0.05 mm to 3 mm.

[0032] According to a preferred embodiment, the material web is a paper web, a composite web, or a plastic web, preferably a thermoplastic web, in particular a polyvinyl chloride or vinyl web. Accordingly, the material web can generally be a substantially or completely air-impermeable material web.

[0033] According to a preferred embodiment, the guide surface is a guide surface of a guide device, wherein the guide device comprises means for adjusting the suction width of the material web, which are designed to adapt the suction width to the width of the unwound parts of the material web transversely to the transport direction in such a way that the central region and / or the respective edge regions are or are subjected to pressure accordingly.

[0034] The means for adjusting the suction width transversely to the transport direction of the material web can comprise a suction chamber arrangement with a plurality of independent chambers which are arranged along a width direction oriented transversely to the transport direction T and which can be individually switched on or off and, in the switched-on state, define a single suction width for acting on the central region or two spaced-apart suction widths for acting on the respective edge regions.

[0035] According to a preferred embodiment of the first variant, the respective edge region of the sucked-in, unwound parts of the material web facing the guide surface is not subjected to negative pressure at all times during the time intervals in which it is not printed.

[0036] Furthermore, it is possible that unwound parts of the material web are brought into the effective area of ​​the print head arrangement and then the print head arrangement is moved transversely to the transport direction over the entire width of the material web and at the same time parts of the material web are printed, whereupon the print head arrangement is moved at least once more transversely to the transport direction over the entire width of the material web in order to print parts of the material web again or the material web is moved forward by a predetermined length in the transport direction and that the unwound parts of the material web are alternately intermittently advanced or printed until the end of a printed image and / or the material web is reached, wherein the respective edge region of the sucked unwound parts facing the guide surface is subjected to negative pressure during the time intervals in which the respective edge region is printed, in such a way thatthat the edge region subjected to negative pressure is also moved synchronously with the guide surface. This refinement has the advantage that edges of certain material webs that tend to stand up do not stand up against the guide surface during the time intervals in which they are printed, but nevertheless enables more effective suppression of unwanted wrinkling than with conventional methods. According to a preferred embodiment of the first or second variant, the edge regions of the unwound parts of the material web are guided in a grazing manner over or under a respective spreader element before being applied to the guide surface, which generates a tensile stress in the width direction in the respective edge regions. According to a particularly preferred embodiment, the method is provided for printing at least two webs guided parallel to one another.

Claims

Claims:

1. Method for printing on a web of material, comprising the steps: - Unwinding the material web from a first roll; - Attaching and fixing the unwound parts of the material web to a guide surface of an endless conveyor belt circulating between two rollers by applying pressure to the material web via the guide surface, and moving the guide surface with the parts in the transport direction into and out of the effective area of ​​a printhead assembly, and printing the parts with the printhead assembly by ejecting ink droplets, - Detaching the unwound printed parts from the guide surface and preferably winding them into a second roll; characterized in that the unwound parts of the material web can be subdivided into two edge areas running opposite each other in the longitudinal direction of the web, which enclose a central area, wherein the side of the respective edge area facing the guide surface is not subjected to pressure at least temporarily during the time intervals in which the side of the corresponding edge area facing away from the guide surface is not printed, and however the side of the central area facing the guide surface is subjected to pressure, such that the central area is moved synchronously with the guide surface in the transport direction, wherein the width of each edge area is specified as 20% - 40% of the total width of the material web.

2. Method for printing on a web of material, comprising the steps: - Unwinding the material web from a first roll; - Attaching and fixing the unwound parts of the material web to a guide surface of an endless conveyor belt circulating between two rollers by applying pressure to the material web via the guide surface, and moving the guide surface with the parts in the transport direction into and out of the effective area of ​​a printhead assembly, and printing the parts with the printhead assembly by ejecting ink droplets, - Detaching the unwound printed parts from the guide surface and preferably winding them into a second roll; characterized in that the unwound parts of the material web can be subdivided into two edge regions running opposite each other in the longitudinal direction of the web, which enclose a central region, wherein the side of the central region facing the guide surface is not subjected to pressure, but the sides of the edge regions facing the guide surface are subjected to pressure, such that that the edge regions are moved synchronously with the guide surface in the transport direction, the width of each edge region being defined as 10% to 30% of the total width of the material web. A method according to claim 1 or 2, characterized in that the guide surface is planar, at least in the effective area of ​​the printhead assembly. A method according to any one of the preceding claims, characterized in that the guide surface of the conveyor belt comprises or consists of an elastomeric plastic, preferably rubber. A method according to any one of the preceding claims, characterized in that the width of each of the opposing edge regions of the material web is defined as the same width.A method according to any one of the preceding claims, characterized in that the material web is a paper web, a composite web, or a plastic web, preferably a thermoplastic plastic web, in particular a polyvinyl chloride or vinyl web. A method according to any one of the preceding claims, characterized in that the guide surface is a guide surface of a guide device, wherein the guide device comprises means for adjusting the suction width of the material web, which are configured to adapt the suction width to the width of the unwound parts of the material web transverse to the transport direction such that the central area and / or the respective edge areas are subjected to pressure accordingly.A method according to claim 7, characterized in that the means for adjusting the suction width transverse to the transport direction of the material web comprise a suction chamber arrangement with several independent chambers, which are arranged along a width direction oriented transverse to the transport direction T and can be individually switched on or off, and in the switched-on state define a single suction width for applying suction to the central region or two spaced-apart suction widths for applying suction to the respective edge regions. A method according to any one of the preceding claims 1 or 3 to 8, relating to claim 1, characterized in that the side of the respective edge region facing the guide surface remains exposed to suction at all times during the time intervals in which the suction is applied. The side of the corresponding edge area facing away from the guide surface is not printed and is not subjected to pressure.

0. A method according to one of the preceding claims 1 or 3 to 9 relating to claim 1, characterized in that unwound parts of the material web are brought into the working area of ​​the printhead assembly, and then the printhead assembly is moved transversely to the transport direction across the entire width of the material web, and parts of the material web are printed simultaneously, whereupon the printhead assembly is moved at least once more transversely to the transport direction across the entire width of the material web in order to print parts of the material web again, or the material web is moved forward by a predetermined length in the transport direction, and that the unwound parts of the material web are alternately advanced or printed intermittently until the end of a printed image and / or the material web is reached.wherein the respective edge region of the suctioned unwound parts facing the guide surface is subjected to negative pressure during the time intervals in which the respective edge region is printed, such that the edge region subjected to negative pressure is also moved synchronously with the guide surface.

1. Method according to one of the preceding claims characterized in that the edge regions of the unwound parts of the material web are guided grazingly over or under a width-holding element before being applied to the guide surface, which generates a tensile stress in the width direction in the respective edge regions.